Patent Application
20240051833
This disclosure generally relates to the field of nanosize powder advanced materials that can be used in energy-related applications.
Silicon-containing advanced nanosize powder materials have been proposed as a solution to several energy-related applications such as photovoltaics, battery technology and thermoelectrics. In lithium-ion battery applications, silicon-containing advanced powder materials have been proposed as an alternative to state-of-the-art material graphite due to the high lithium storage capacity of silicon (about 10-fold increase by weight compared to graphite), enabling the development of high-capacity anodes. However, a dramatic volume expansion and contraction during lithium storage and release causes bulk silicon to rapidly degrade. It is believed that these variations induce a loss of electronically conductive network contact with the electrode material and/or breaking of electrode material particles. As a result, the battery capacity decreases, resulting in a shorter life span. Nanosized silicon-containing advanced powder materials improves the cycle performance of the resulting anode by helping control changes in volume and stresses, e.g., when the nanosize particles have less than 300 nanometers in average particle size.
Despite the advantageous properties obtained when using nanosized silicon-containing advanced powder materials, the manufacture of high-purity nanosize silicon-containing advanced powder materials for such applications remains costly, inefficient and not scalable.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key aspects or essential aspects of the claimed subject matter.
The present disclosure describes processes and apparatuses for manufacturing advanced nanosize powder materials that address at least some of the known issues of scalability, continuity, and quality inherent in prior art processes and apparatuses. Also described are nanosized powders with advantageous chemical and/or physical properties that can be used in various applications.
As embodied and broadly described herein, the present disclosure relates to nanoparticles, the nanoparticles having a particle size distribution of from 20 nm to 150 nm, with <10 ppm by number of particles having a size which is >1000 nm.
As embodied and broadly described herein, the present disclosure relates to nanoparticles having a substantially uniform doping agent content along a radial distribution of the nanoparticles.
As embodied and broadly described herein, the present disclosure relates to nanoparticles having a core, the nanoparticles having a silicon alloy in the core, the alloy being of silicon and an element, the element having a substantially uniform radial distribution in the core.
As embodied and broadly described herein, the present disclosure relates to nanoparticles of a silicon alloy the alloy being of silicon and an element, the element having a substantially uniform radial distribution in the core.
In some embodiments, the nanoparticles described above may further include one or more of the following features:
As embodied and broadly described herein, the present disclosure relates to an apparatus for producing nanoparticles, comprising a feeding mechanism for feeding a precursor material in fluid form toward a reaction zone along a feed path; a plasma device configured for generating a plasma jet in the reaction zone impinging upon the precursor material at a convergence point between streamlines of the plasma jet and the feed path to produce a reactant gaseous mixture, the plasma jet streamlines being at an angle with respect to the feed path, and a cooling zone receiving the reactant gaseous mixture to cause nucleation and produce the nanoparticles.
As embodied and broadly described herein, the present disclosure relates to an apparatus for producing nanoparticles, comprising a feeding mechanism for feeding a precursor material in fluid form toward a reaction zone along a feed path; a plasma device configured for generating a plasma in the reaction zone, the plasma contacting the precursor material to produce a reactant gaseous mixture, a reaction chamber comprising the reaction zone, the reaction chamber having a longitudinal axis, and the apparatus being configured for injecting a pre-heated gas to generate a radial pre-heated gas flow in the reaction chamber along at least a portion of the longitudinal axis, and a cooling zone receiving the reactant gaseous mixture to cause nucleation and produce the nanoparticles.
As embodied and broadly described herein, the present disclosure relates to a method for producing nanoparticles, comprising feeding a precursor material in fluid form toward a reaction zone along a feed path, generating a plasma jet in the reaction zone and contacting the precursor material with the plasma jet, the plasma jet impinging upon the precursor material at a convergence point between streamlines of the plasma jet and the feed path to produce a reactant gaseous mixture, the plasma jet streamlines being at an angle with respect to the feed path, and cooling the reactant gaseous mixture in a cooling zone to cause nucleation and produce the nanoparticles.
As embodied and broadly described herein, the present disclosure relates to a method for producing nanoparticles, comprising feeding a precursor material in fluid form toward a reaction zone along a feed path, the reaction zone being in a reaction chamber, the reaction chamber having a longitudinal axis, generating a plasma in the reaction zone, the plasma contacting the precursor material to produce a reactant gaseous mixture, injecting a pre-heated gas to generate a radial pre-heated gas flow in the reaction chamber along at least a portion of the longitudinal axis, and cooling the reactant gaseous mixture in a cooling zone to cause nucleation and produce the nanoparticles.
In some embodiments, the method and apparatus described above may further include one or more of the following features:
As embodied and broadly described herein, the present disclosure also relates to a lithium secondary battery including at least an anode, a cathode and an electrolyte, the anode including nano-sized particles of silicon or an alloy thereof, wherein the battery has a charge capacity within the first 50 charge and/or discharge cycles that remains within at least 80% of an initial charge capacity value.
As embodied and broadly described herein, the present disclosure also relates to a lithium secondary battery including at least an anode, a cathode and an electrolyte, the anode including nano-sized particles of silicon or an alloy thereof, wherein the battery has a charge capacity within the first 100 charge and/or discharge cycles that remains within at least 80% of an initial charge capacity value.
As embodied and broadly described herein, the present disclosure also relates to an anode electrode for a lithium secondary battery, the anode electrode including nano-sized particles of silicon or an alloy thereof, and having a charge capacity ≥2000 mAh/g.
All features of exemplary embodiments that are described in this disclosure and are not mutually exclusive can be combined with one another. Elements of one embodiment can be utilized in the other embodiments without further mention. Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying drawings.
A detailed description of specific exemplary embodiments is provided herein below with reference to the accompanying drawings in which:
In the drawings, embodiments are illustrated by way of example. It is to be expressly understood that the description and drawings are only for purposes of illustration and as an aid to understanding and are not intended to be a definition of the limits of the disclosure.
A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of non-limiting examples and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.
The present disclosure describes processes and apparatuses for manufacturing advanced nanosize powder materials that address at least some of the known issues of scalability, continuity, and quality inherent in prior art processes and apparatuses. Also described are nanosized powders with advantageous chemical and/or physical properties that can be used in various applications.
The nanosize powders (also referred herein as “nanoparticles” or “nanopowders”) of the present disclosure have noticeable surprising and unexpected differences compared to powders produced using prior art vaporization processes that make use of micron size precursor materials (e.g., WO 2018/157256, CA 3,024,473 and U.S. Pat. No. 7,572,315 each of which is incorporated by reference herein in their entirety). For example, the nanoparticle powders described herein have more uniform particle sizes and narrower particle size distribution (PSD), while the powders produced using such prior art vaporization processes have much wider PSD with significant portions of large and extra-large micron particles, which is undesirable in a number of applications. The described nanoparticle powders also have a better control/tuning of doping compared to powders produced using prior art vaporization processes. Such control/tuning of doping can allow more flexibility in terms of desired characteristics for the powders in several applications.
In some embodiments, the nanoparticle powders have spherical or near spherical appearance, the powders can be discrete or partially aggregated to various extents, which is essentially dependent on the operating conditions used during the production thereof. The nanoparticle powders can be subjected to surface modification such as oxidation, nitridation, or carburization.
In some embodiments, the PSD can be achieved without the need of implementing a classification step after the plasma processing. Such PSD is, contrary to what is obtained with known processes in the art, tightly controlled such that, for example, the particles have sizes that are skewed towards smaller sizes instead of having sizes skewed towards coarser sizes. There are technical benefits in obtaining such smaller sizes (as discussed elsewhere in this text) as well as economic benefits: when the nanoparticle powders coming out of the manufacturing process have less coarse sizes, there is less wasted material (material that would not make the cut-off classification values) and as such, yields are increased. The powders can have an average PSD where at least 80% of the particles have a size <150 nm, e.g., at least 85%, 90%, 95%, or 99% of the particles have a size <150 nm.
The nanoparticle powders can include one or more of the following particle size features: PSD within the range of 20 nm to 350 nm, 20 nm to 300 nm, or 20 nm to 200 nm, or 20 nm to 150 mm, or any range therein; D90≤200 nm, D90≤150 nm, or D90≤130 nm; median size (D50) of ≤120 nm, median size (D50) of ≤100 nm, median size (D50) of ≤80 nm, or median size (D50) of ≤50 nm; D50 (by number) between 30 nm and 120 nm, or between 40 nm and 100 nm, or between 50 nm and 80 nm, or about 60 nm; particles having a size >350 nm representing less than 100 ppm, less than 10 ppm, less than 1 ppm, or less than 0.5 ppm; D99≤250 nm, or D99≤230 nm; less than 100 ppm of agglomerated particles, less than 50 ppm of agglomerated particles, less than 25 ppm of agglomerated particles, less than 10 ppm of agglomerated particles, less than 1 ppm of agglomerated particles, or in some embodiments, no detectable agglomerated particles.
Particle size features of a composition in particulate form can be determined using techniques known in the art, such as, but not limited to, laser diffraction spectroscopy, transmission electron microscopy, scanning electron microscopy (SEM), and the like. The SEM image is an image of a predetermined area of the composition being analyzed, which will vary depending on at least the D50 of the composition to ensure accuracy and/or statistical significance. For example, a D50 of 120 nm can require a 5 μm per 5 μm area, whereas a D50 of 80 nm can require a 3 μm per 3 μm area and a D50 of 50 nm can require a 2 μm per 2 μm area of the composition. The powders disclosed herein can include features including less than 3 particles having a size >1 μm as determined from an SEM image of 5000× of the composition, less than 2 particles having a size >1 μm as determined from a SEM image of 5000× of the composition, or 1 or no detectable particles having a size >1 μm as determined from a SEM image of 5000× of the composition; less than 3 particles having a size >650 nm in an SEM image of 5000× of the composition, less than 2 particles having a size >1 μm as determined from a SEM image of 5000× of the composition, 1 or no detectable particle having a size >1 μm as determined from a SEM image of 5000× of the composition; less than 3 particles having a size >350 nm in an SEM image of 5000× of the composition, less than 2 particles having a size >1 μm as determined from a SEM image of 5000× of the composition, or 1 or no detectable particle having a size >1 μm as determined from a SEM image of 5000× of the composition.
In some embodiments, the nanoparticle powders can incorporate a doping element in a more controlled manner relative to powders produced using prior art vaporization processes. For example, nanoparticle powders can have a doping agent content that is more flexible and a thickness of the passivation layer that is more consistent since dispersion of the doping agent can also be more homogeneous. The ability to better control the doping of the nanoparticle powders offers more flexibility for tuning the other properties of the nanoparticle powder for specific applications.
In some embodiments, the nanoparticle powders can incorporate no more than 4% of doping agent, e.g., no more than 3%, no more than 1.5%, or no more than 0.75%. Examples of doping agent are further discussed elsewhere in this text.
The nanosize powders described herein can be manufactured using a process that vaporizes and/or reacts precursor materials in fluid form to obtain a reactant gas mixture. Described is a process and apparatus that allows control of the temperature and residence time of the precursor materials in the reaction zone so as to sufficiently vaporize and/or react the precursors to form the desired chemical composition in the resulting nanosize powder. Also described are methods of controlling the cooling rate of the reactant gas mixture to obtain the herein described nanosized powders having the desired particle size features.
The plasma-generating device 120 shown in
The plasma-generating device 120 includes an outer cylindrical torch body 181, an inner cylindrical plasma confinement tube 110, and at least one induction coil 126 in a coaxial arrangement. The outer cylindrical torch body 181 can be made of a moldable composite material, for example a moldable composite ceramic material. The inner cylindrical plasma confinement tube 110 can be made of ceramic material and is coaxial with the torch body 181. The induction coil 126 is coaxial with and embedded in the torch body 181 to produce a RF (radio frequency) electromagnetic field whose energy ignites and sustains the plasma 112 confined in the plasma confinement tube 110.
The plasma is produced from a plasma central gas 20 such as argon and/or helium, and can further include hydrogen, oxygen, nitrogen or any combinations thereof. The plasma central gas 20 is typically supplied within the plasma confinement tube 110 through a head 185 of the plasma-generating device 120 at the upper end of the torch body 181. RF current is supplied to the induction coil(s) 126 via power leads (not shown). The plasma central gas 20 can be inserted in the plasma-generating device 120 so that its flow is coaxial with the torch body 181. Alternatively, the plasma central gas 20 can be inserted in the plasma-generating device 120 so that its flow is at an angle with respect to the torch body 181.
The apparatus 100 can be configured to inject at least one plasma sheath gas 40 at one or more locations downstream or upstream within the plasma confinement tube 110. For example, as shown in
The plasma-generating device 120 is in fluid communication with the reaction chamber 140, through an exit outlet as shown in
The apparatus 100 further includes one or more precursor injectors 1141-114i that inject the precursor material 130 into a reaction zone 128. For example, the reaction zone 128 may be located downstream of the plasma-generating device 120 within the reaction chamber 140 as shown in the figures. Alternatively, at least a portion of the reaction zone 128 may be located within the plasma confinement tube 110 (not shown) such that the one or more precursor injectors 1141-114i may be coaxial with the torch body 181 and configured to inject the precursor material 130 within the plasma 112.
When the reaction zone 128 is located downstream of the plasma-generating device 120, the apparatus 100 may include one or more injectors 1141-114i configured to inject the precursor material 130 into the reaction zone 128 at a convergence point, the convergence point residing downstream from the plasma generating device 120. For example, the apparatus 100 may include two injectors 1141-114i spaced apart one from another by 180° and each being configured to inject the precursor material 130 into the reaction zone 128 at the convergence point. For example, the apparatus 100 may include three injectors 1141-114i spaced apart one from another by 120° and each being configured to inject the precursor material 130 into the reaction zone 128 at a convergence point. In such embodiments, and irrespective of the number of precursor injectors 1141-114i present in the apparatus 100, the injectors are configured such that the precursor material 130 streamlines intersect at the convergence point where the plasma 112 streamlines impinge upon the precursor material 130 streamlines.
In some embodiments, the injectors 1141-114i are located at respective injection points placed sequentially along the longitudinal axis of the apparatus 100. For example, one injector point can be located substantially at the plasma 112 discharge location in the reaction zone 128 and at least another injector point can be located downstream at a distant location within the reaction chamber 140. The composition of the nanosized powder particles can be gradually changed from core to shell by changing the reactant gas composition at the different injection points.
In all of the above configurations of the apparatus 100, the plasma 112 heats the precursor material 130 at a temperature that allows the production of a reactant gaseous mixture. For example, the heating occurs at the point where the impinging takes place. Additionally, the heating can occur along a plasma afterglow 146, which is a portion of the plasma 112 below the plasma-generating device 120 that extends along a longitudinal axis of the apparatus 100. In some embodiments, this portion of the plasma 112 extends within at least a portion of the reaction chamber 140. In other words, the reaction zone 128 can be extended to a point located further downstream from the impinging point. Additionally, the heating can occur further downstream, in a dynamic hot wall region 134, which will be further described below.
The reactant gaseous mixture being produced with the plasma occurs through chemical changes, for example dissociation or decomposition of the precursor material 130. The precursor material 130 is injected into the apparatus 100 via injectors 1141-114i and contains chemical elements that will form at least part of the nanosized powder particles. The nature of the precursors (e.g., chemical composition), their concentrations, and the operating parameters (e.g., temperature) applied can be independently selected such that the process for manufacturing the nanosized powder is more efficient and/or such that the nanosized powder is of higher quality (e.g. the specific properties of the nanosized powder can be improved), as further discussed elsewhere in this text.
In some embodiments, the precursor material 130 can be mixed with a carrier gas prior to, concomitantly with, or after its injection in the apparatus 100 through injectors 1141-114i. The carrier gas is typically a gas that does not react with the precursor material 130. The carrier gas can be the same type of gas as the plasma central gas 20 and/or can include a mixture of gases, and can facilitate transportation of the precursor material 130. The carrier gas relative flow rate can be adjusted over time to allow control of the concentration of the precursor material 130 in the reaction zone 128, thus obtaining a heterogeneous powder composition (e.g., some particles having a first chemical composition and some other particles having a second chemical composition, the first and second chemical compositions being different), for example. The carrier gas can stabilize the precursor material 130 prior to the injection into the apparatus 100. In some embodiments, the carrier gas can reduce a pyrophoric capability of the precursor material 130, thus facilitating handling of the precursor material 130 in industrial settings.
The reactant gaseous mixture can include dissociated or chemically transformed forms of the precursor material 130, e.g., the precursor material 130 can dissociate into a core radical and at least one by-product. For example, when the precursor material 130 includes a silicon or silicon alloy precursor, the apparatus 100 will contain a plasma-generating device 120 generating plasma 112 at a temperature allowing production of a vapor from the precursor material 130 where the vapor may include dissociated silicon atoms.
In conventional single probe plasma systems, the injection of precursor materials is coaxial with the plasma apparatus and parallel to the plasma gas flow, as described in U.S. Pat. No. 9,781,131. In such systems, the injected precursor materials, which are cold relative to the plasma, create a cold region in the core of the plasma afterglow and thus the temperature across the injection streamlines is not uniform. In this relatively cold region of the plasma afterglow, the precursor materials cannot entirely dissociate or chemically transform. This problem with conventional single probe systems can be advantageously mitigated with the apparatus 100 described herein where the injection of the precursor material 130 is configured to be “off-axis” relative to the plasma 112 flow.
In the apparatus 100, the injectors 1141-114i are thus configured to be “off-axis” relative to the plasma 112 flow. In other words, the injectors 1141-114i inject the precursor material 130 in a direction that intersects with a longitudinal direction of the plasma 112 to minimize (or avoid) creating the relatively cold region of the plasma afterglow of prior art plasma apparatuses. For example, as shown in
Without being bound by any particular theory, the use of an “off-axis” configuration for the injectors 1141-114i probes is believed to induce a better mixing of the injected precursor material 130 in the plasma afterglow 146 of the plasma 112, since fluids injected through the injectors 1141-114i impinge at an angle on the plasma 112 streamlines, which induces mixing and a more uniform temperature across the injected fluids. This in turn provides a more uniform energy transfer from the plasma 112 to the injected precursor material 130 and significantly increases the residence time of the reaction species through alteration of their trajectory in the high temperature zone, and thus ensures the dissociation or chemical conversion. It is believed that these benefits can also apply to any doping agent and/or additive gas also injected through the injectors 1141-114i.
For example, in some embodiments, the injectors 1141-114i are configured for injecting the precursor material 130, and optionally an additive gas or doping agent to expose same to such more uniform energy transfer and increased residence time in at least one of the afterglow zone 146, the reaction zone 128, or the dynamic hot wall region 134. This configuration results in increased temperatures and residence times. A person of skill can therefore expose the injected precursor material 130 (and optionally any additive gas/doping agent injected through the injectors 1141-114i) to sufficiently high temperatures and residence time such that at least 60%, e.g., at least 70%, 80%, 85%, 90%, 95%, or at least 100% of the injected precursor material 130 reacts to form the reactant gaseous mixture.
When manufacturing nanosized powders of silicon or silicon alloy, the precursor material 130 and optionally any additive gas/doping agent injected through the injectors 1141-114i is exposed in at least one of the afterglow 146 of the plasma 112, the reaction zone 128, or the dynamic hot wall region 134 to a temperature of at least 400° C., such as any temperature within the range of 400° C. to 1400° C., e.g., approximately 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., 700° C., or 750° C., and the like, and for a residence time of at least 0.2 sec, such as any residence time within the range of 0.2 sec to 1.0 sec. For example, to achieve 60% decomposition of SiH4, the temperature and residence time required can be, for example, 637° C./0.8 sec, or 657° C./0.5 sec, or 690° C./0.2 sec; to achieve 85% decomposition of SiH4, the temperature and residence time required can be, for example, 670° C./0.8 sec, or 690° C./0.5 sec, or 724° C./0.2 sec.
In some embodiments, the precursor material 130 is in fluid form (e.g., a gas or a liquid). For example, in some implementations, when making silicon nanosize particles, the precursor material 130 can include silane (SiH4), trichlorosilane (SiCl3H), or any mixtures thereof.
Those skilled in the art will recognize that the present disclosure can be extended to all possible molecules containing group III, IV or V elements (Mendeleev groups as typically referenced in the periodic table), which can react in at least one of the afterglow 146 of the plasma 112, the reaction zone 128, or the dynamic hot wall region 134 to form the desired reactant gaseous mixture and cooled down to form nanosize powders.
In some embodiments, the precursor material 130 is mixed with the additive gas or doping agent gas or precursor thereof prior to, concomitantly with, or after its injection in the apparatus 100 through injectors 1141-114i so as to generate a powder including alloys of the elements present in the reactant gaseous mixture. The additive gas or doping agent or precursor thereof is typically a fluid (gas or liquid) that can react with the precursor material 130 and/or can react in the high temperatures existing in at least one of the afterglow 146 of the plasma 112, the reaction zone 128, or in the extended dynamic hot wall region 134 (extending downstream of the reaction zone 128), which results in the presence of the doping agent in the powder particles.
In some embodiments, the additive gas or doping agent or precursor thereof can be injected to have a concentration of from 0 to about 5000 ppm, including any value therein. For example, up to 2000 ppm, up to 1000 ppm, up to 500 ppm, up to 200 ppm, up to 100 ppm, and the like. Those skilled in the art will readily recognize that changing the concentration or the location of the injection will modify the profile of the additive/doping concentration with an injection upstream favoring the penetration of the additive/doping to the particle core and an injection downstream causing the additive/doping to remain preferentially close to the particle surface.
In some embodiments, the additive gas or doping agent gas or precursor thereof relative flow rate can be adjusted over time so as to allow control of the concentration of the doping agent or precursor thereof in at least one of the afterglow 146 of the plasma 112, the reaction zone 128, or in the extended dynamic hot wall region 134, thus obtaining a heterogeneous powder composition, for example.
Examples of mixtures of precursor material 130 and optional doping agent may include at least one of the following:
For example, when the nanoparticle powders are silicon or silicon alloy particles doped with nitrogen, the nanoparticle powders have a nitride layer. In some embodiments, the nitride layer can have a thickness of no more than 0.75 nm, e.g., no more than 0.50 nm, 0.25 nm, 0.10 nm, 0.06 nm, and even less.
In some embodiments, the nanoparticle powders include a relatively large amount of doping agent. The doping agent X can be present in the material in a Si:X proportion between 1:0.3 and 1:1, e.g., between 1:0.4 and 1:0.9, between 1:0.5 and 1:0.8, and between 1:0.6 and 1:0.7.
For example, when the Si nanosize particles are doped with nitrogen, the nanosize particles can present a substantially uniform nitrogen content throughout the volume of the nanoparticle so as to form a nearly stoichiometric SiNx alloy.
In some embodiments, the nanoparticle powders have a high degree of purity. For example, the nanoparticle powders can have a degree of purity of at least 99.95%, or at least 99.96%, 99.97%, 99.98%, 99.99%, 99.995%, and even more (e.g., at least 99.998%). For example, when the nanoparticle powders include a silicon or silicon alloy core, the core can include at least 99.95% of the silicon or silicon alloy.
In some embodiments, the precursor material 130 can additionally or alternatively be mixed with an additive gas or doping agent prior to, concomitantly with, or after its injection in the apparatus 100 through injectors 1141-114i. In embodiments where the additive gas or doping agent is mixed with the precursor material 130 concomitantly with, or after its injection in the apparatus 100 through injectors 1141-114i the additive gas or doping agent can be injected into the apparatus 100 through the same injectors 1141-114i as for the precursor material 130 or through different injectors 1141-114i.
In some embodiments, presence of the additive gas or doping agent in at least one of the plasma generating device 120, the reaction chamber 140, and the quench chamber 500 can produce a passivation layer on the nanosize particles, resulting in particles having a core and layer structure.
Chemical Vapor Deposition (CVD), typically carried out in an atomic layer deposition (ALD) reactor, can be used to deposit a passivation layer on conventional nanosize particles after their production. However, in such cases, nanosize particles can be exposed to air during the transfer of the nanosize particles from the plasma apparatus where they are produced to the ALD reactor. In the present disclosure, the nanosize particles can be advantageously covered in situ (within the apparatus 100) with the passivation layer before any potential exposition to oxygen/air and moisture/water, thus avoiding the problem encountered with conventional CVD processes.
In some embodiments, the presence of a passivation layer can reduce the reactivity of the nanosized powder to oxygen/air and/or moisture/water, thereby avoiding, reducing or retarding the formation of an oxide layer. The chemical composition of the passivation layer will depend on the additive gas chosen. For example, using an additive gas such as oxygen will result in an oxide layer, ammonia or nitrogen when making a powder of silicon or silicon alloy will result in a passivation layer made of a nitride of the silicon (Si3N4 or any other stoichiometric or non-stoichiometric Si—N compound SixNy) or silicon alloy, while using an additive gas such as methane or acetylene will result in an amorphous carbon passivation layer.
In some embodiments, presence of the additive gas in the reaction chamber 140 and/or the quench chamber 500 can also act as a particle growth inhibitor. This can be useful in controlling the diameter of the nanosize particles (e.g., the particle size distribution or “PSD”). For example, concentration of gaseous species like oxygen injected in the reaction chamber 140 and/or the quench chamber 500 enables control over the size of the nanosize particles in a size range smaller than the nominal diameter obtained without the growth inhibitor, and the diameter is inversely proportional to the growth inhibitor concentration.
Changing the concentration or the location of the injection of the additive gas will modify its concentration profile. For example, an injection upstream in the apparatus 100 can favor the penetration of the element present in the additive gas into the particle core whereas an injection downstream in the apparatus 100 can cause the element present in the additive gas to remain preferentially close to the particle surface and/or in the passivation layer.
For example, the additive gas can be an oxygen containing species such as H2O or CO2, N containing gases such as N2, NH3, carbon-based gases such as CH4 or C2H2 or any other gas found suitable by those ordinarily skilled in the art. The concentration of the additive gas being injected into the reaction chamber 140 and/or the quench chamber 500 can be from 0 to 5000 ppm, e.g., less than 500 ppm.
Returning to structural features of the apparatus 100,
In operation, the channel 206 carries the sheath gas 201 into the apparatus 100 to allow it to isolate the cooled tip 202 from exposure to precursor material 130 (and/or any carrier gas, additive gas or doping agent) flowing out of the channel 208 and thereby prevent, reduce or minimize condensation of the precursor material 130 onto the external outlet of the injector 1141, including tip 202. An appropriate flow of sheath gas 201 can thus allow for a more continuous operation of the apparatus 100, as there is less risk of downtime that can be required to clean up eventual condensation that would otherwise more often occur at the outlet of the injector 1141.
In conventional plasma reactors, the temperature gradient across the reaction zone is relatively steep, e.g., there can be a radial gradient whereby the temperatures along the axial direction in the reaction chamber are extremely high, while in the large area towards the walls of the reaction chamber the temperatures are relatively lower. Additionally or alternatively, there can be an axial gradient. Additionally, conventional plasma reactors are associated with a significant loading effect when the injection of the precursor occurs. As flow rates of precursor material or sheath gas are increased, temperatures in some areas of the injection zone can drop to the unfavourable territory and, as a result, efficiency of the process is reduced, amorphous nanosize particles are obtained, and the quality of the obtained powder is reduced.
These particular problems with conventional plasma reactors are advantageously mitigated with at least some embodiments where gas pre-heated to a desired temperature is injected into the reaction chamber 140 to form a dynamic hot wall region 134 (shown in
The gas 302 pre-heated to the desired temperature then flows through a diffuser wall 303 disposed within the reaction chamber 140 and sandwiched between an external wall 710 of the reaction chamber 140 and an internal porous wall 305, forming a pre-heated radial gas flow 304. The pre-heated radial gas flow 304 creates a “dynamic hot wall” region 134 that prevents reactive species, e.g., reactive species present in the precursor material 130 and/or any carrier gas, additive gas or doping agent, and/or reactive species present in the gaseous mixture, from reaching the internal wall 305 of the reaction chamber 140. The presence of the dynamic hot wall region 134 thus prevents, reduces or minimizes heterogeneous decomposition and chemical vapor deposition of reactive species on the internal wall 305 while providing enough energy to ensure the complete reaction of the remaining precursor material 130 and/or reactive species, mostly through heterogeneous pyrolysis on the existing seeds 306 (also referred as “nascent particles” or “aerosolized solids”) formed immediately upstream.
As shown in
In operation, the plasma 112 and plasma afterglow 146 provide very rapid heating of the precursor material 130, which then generates the gaseous mixture that flows into the dynamic hot wall region 134 where such high temperature is sustained by the pre-heated radial gas flow 304. This advantageously enables the decomposition and/or vaporization of the precursor material 130 at high temperatures for a much higher throughput. For example, the inventors were able to process precursor material 130 including silane with a throughput of at least at least 1 kg/hour, such as from 1 kg/hour to 3 kg/hour, and in some embodiments even more.
The implementation of the dynamic hot wall region 134 also allows for an adjustable dilution of the aerosolized nascent particles 306 (also referred to as “nanoparticle seeds” or “nascent seeds of the nanoparticles”) and precursor material 130 and/or any doping agent so as to limit particle growth via coagulation of nascent particles 306. More dilute nanosize particles aerosols limit the probability of collisions of nascent particles 306 by increasing the mean free path of the particles. Also, a lower concentration slows the diffusion rate of gases to the surface of nanoparticle seeds. Moreover, the adjustment of the gas temperature in the dynamic hot wall region 134 allows modification of the degree of crystallinity of the nanosize particles formed as a lower temperature favors less crystallinity and vice-versa.
In some embodiments, controlling crystallinity of the nanosize particles can provide a number of advantageous features. For example, in making silicon nanosize particles, amorphous components of the nanosize particles can incorporate hydrogen atoms to form a-Si:H, which are used in the thin-film photovoltaic industry. The processes and apparatuses described herein advantageously allows for the adjustment of the nanosize particles' characteristics for the intended application.
The pre-heated radial gas flow 304 can be of any suitable magnitude. For example, in some embodiments the flow can be in the range of from 50 and 2000 standard litre per minute (“slpm”), e.g., between 50 and 200 slpm, 200 and 500 slpm, 500 and 1000 slpm, 1000 and 2000 slpm, and even more (e.g., at least 2000 slpm).
The thermal energy can be applied to the gas 302 with a heating element 700 as shown in
The dynamic hot wall region 134 can have any suitable length to maximise complete reaction of the precursor material 130, while remaining economically viable and efficient. For example, in some embodiments, the dynamic hot wall region 134 can have a length in the longitudinal direction of the apparatus 100 that is between about 100 mm and 200 mm, e.g., between about 200 mm and 400 mm, 400 mm and 700 mm, 700 mm and 1000 mm, and more (e.g., at least 1000 mm). In a similar fashion, the porous wall 305 of the dynamic hot wall region 134 can have a corresponding length in the longitudinal direction of the apparatus 100 that is between about 100 mm and 200 mm, e.g., about 200 mm and 400 mm, 400 mm and 700 mm, 700 mm and 1000 mm, and more (e.g., at least 1000 mm). In a similar fashion, the diffuser wall 303 of the dynamic hot wall region 134 can have a corresponding length in the longitudinal direction of the apparatus 100 that is between about 100 mm and 200 mm, e.g., between 200 mm and 400 mm, 400 mm and 700 mm, 700 mm and 1000 mm, and more (e.g., at least 1000 mm).
The diffuser wall 303 includes a plurality of apertures 168n to allow passage of the gas 302 therethrough. The plurality of apertures 168n can be dimensioned and disposed in any suitable manner over the gas wall diffuser 303. For example, the plurality of apertures 168n can have at least one of a substantially homogeneous shape, dimension, and disposition over the gas wall diffuser 303. For example, the plurality of apertures 168n can all have a substantially circular shape and be disposed in a substantially homogeneous disposition over the gas wall diffuser 303. In some embodiments, the plurality of apertures 168n can have an elongated shape in a longitudinal direction of the apparatus 100. The plurality of apertures 168n can have an elongated shape in a tangential direction of the apparatus 100. The plurality of apertures 168n can have a dimension that increases downstream, or reduces downstream. There can be more apertures 168n disposed in an upstream portion of the diffuser wall 303 than in a downstream portion thereof, while in other embodiments, there can be more apertures 168n disposed in a downstream portion of the diffuser wall 303 than in an upstream portion thereof. Other examples of implementation are also possible.
As will be apparent to the person of skill, the design and operation of the herein described “dynamic hot wall” differs from prior art designs. In the present disclosure, the apparatus 100 is configured such that the injected gas 302 provides an even, continuous radial gas flow 304 and thus prevents the deposition of powders on the surfaces. Other advantageous features obtained with the present disclosure include but are not limited to: increasing the reaction/conversion rate (supplemental heat); controlling morphology and crystallinity of the nanosize particles (prolonged residence time); controlling particle sizes (dilution effect); avoiding powder deposition, deposits, blockage, and the like.
Several crystalline structures can be obtained with the processes and apparatuses herein described. The process parameters can be controlled to have one or more crystalline structure(s) in the nanosize particles of a given powder batch made in a single run.
The gaseous mixture flowing from the reaction chamber 140 is cooled in the cooling chamber 500 to a temperature where the reaction substantially stops. The cooling chamber 500 includes an injection module 503 configured to inject a longitudinal cooling gas 502 (injected along a longitudinal direction of the cooling chamber 500) or an injection module 505 configured to inject a radial cooling gas 504. In some embodiments, the cooling chamber 500 can include both the injection module 503 and the injection module 505 for injecting the longitudinal cooling gas 502 and the radial cooling gas 504, respectively. In other embodiments, the cooling chamber 500 can include a plurality of injection modules for injecting a corresponding plurality of cooling gases (not shown).
The composition of either or both the longitudinal cooling gas 502 and the radial cooling gas 504 can be selected to carry the growth inhibitor previously discussed. Accordingly, the longitudinal cooling gas 502 and the radial cooling gas 504 can be one and the same, for example.
The chemical composition of the cooling gases may, in some embodiments, be identical to one or more of the other gases injected in the apparatus. In some embodiments, the cooling gas may advantageously be constituted of recycled gas, where the gas being recovered from the apparatus 100 at a lower outlet thereof will be recycled, cooled down to a desired temperature and reinjected into the apparatus 100 as one or both of the herein described cooling gases. For instance, when one injects into the apparatus the gases listed in tables 2A and 2B, namely 30 argon+95 argon+15 H2+50 or 150 argon and 250 N2, one obtain a recycled cooling gas having the following chemical composition 40% argon, 3% H2 and 57% N2 or 51% argon, 3% H2 and 46% N2.
In some embodiments, the additional gas dilution obtained with the injection of one or more cooling gases in the cooling chamber 500 can also help in preventing the coagulation of hot nanosize particles and thus also contribute to controlling the size of the nanosize particles.
The temperature and/or flow rate at which either or both the longitudinal cooling gas 502 and the radial cooling gas 504 is introduced in the cooling chamber 500 can also affect the condensation rate of the reactant gaseous mixture, controlling the size and PSD of the nanosized powder particles and prevent the particles from adhering to the internal walls 506 of the apparatus 100. Specifically, a colder quenching gas will increase the speed at which the reactant gaseous mixture condenses, thereby decreasing the PSD. Conversely, hotter quenching gas will generally result in increased PSD. Similarly, a higher temperature will increase the amount of time the cores react with the additive gas, which can result in a thicker passivation layer, whereas a lower temperature can generally result in a thinner passivation layer. Accordingly, the temperature and/or flow rate at which either or both the longitudinal cooling gas 502 and the radial cooling gas 504 is introduced in the cooling chamber 500 can be controlled to modulate the PSD as well as produce a passivation layer with the desired thickness. The temperature range will naturally depend on the chemical composition of the reactant gaseous mixture. For example, when manufacturing nanosized powders of silicon or a silicon alloy, either or both the longitudinal cooling gas 502 and the radial cooling gas 504 can be injected in the cooling chamber 500 to a temperature where the reaction substantially stops, such as at a temperature selected in the range of from 420 to 600° C., or in the range of from 300 to 420° C., for example at 420° C., or lower.
In some embodiments, the growth and crystallinity properties of the particles obtained in the present disclosure can thus be controlled by adjusting the flow rate, the chemical composition, and temperature of the gases that are injected into the apparatus 100, e.g., those mixed with the precursor material 130, those injected into the reaction chamber 140, and those injected into the cooling chamber 500.
Several variants will become clear to the person of skill in view of this disclosure. For example, in some embodiments, a first additive gas can be introduced along with the precursor material 130, while optionally a second additive gas identical in nature or different from the first additive gas, can be introduced in the dynamic hot wall region 134 in the form of the pre-heated radial gas flow 304, while optionally a third additive gas, identical in nature or different from the first and second additive gases, can be introduced in the cooling section 132 (also referred herein as “quench section”) in the form of either or both the longitudinal cooling gas 502 and the radial cooling gas 504. Such flexibility in the injection point of the additive gas, in the flow rate, and in the temperatures allows the person of skill to control and tailor the overall effect on particle growth and properties.
Without being bound by any particular theory, it is believed that the reaction of the cores of the particles with the additive gas occurs when the cores are in contact with the additive gas at a temperature within a temperature range allowing the reaction. Diffusion through the particle radius can also be important depending on gaseous species/temperatures. This temperature range will depend on the nature of both the cores and the additive gas. In addition, the lower end of this temperature range must be lower than the temperature at which the reactant gaseous mixture condenses and the cores form, otherwise the cores will not be formed at the temperature at which the reaction needs to occur. For example, when the particles are made of silicon or a silicon alloy, and the additive gas is N2, the reaction temperature must be less than about 3265° C. (the vaporization point of silicon), while remaining above the minimum temperature for Si and N2 to react during the available residence time.
Again, without being bound by any particular theory, it is believed that the thickness of the passivation layer can depend on many factors but is ultimately determined by the extent of the reaction of the additive gas (passivating layer gas precursor) on the surface of the core of the particles and by the extent of the diffusivity of the additive gas over the surface of the core of the particles and more generally over the particles. When the reaction occurs to a larger extent, a thicker passivation layer will generally result, and vice versa. Alternatively, when making silicon-based nanoparticles, the silicon itself can diffuse in the passivation layer to the outside face and growth proceeds. Tests have shown that the thickness of the passivation layer is increased by increasing the time spent by the cores in sections of the apparatus where the passivation layer can be formed, for example in the reaction zone 134 or in parts of the quench section 132. For example, in parts of the quench section 132 where the temperature is low enough for vapor condensation to occur, but high enough for the reaction between the particles and the passivating layer gas precursor to occur. This can be increased by one or more of: increasing the volume of this part of the quench section 132; increasing the concentration of the passivating layer gas precursor in the quench section 132; increasing the temperature of the passivating layer gas precursor, and providing auxiliary heating, e.g., as described in U.S. Pat. No. 9,516,734, which is incorporated herein by reference, to increase residence time.
In some embodiments, where preserving diffusivity properties of the nanoparticle layer for electrons and ions is desirable, controlling the thickness of the passivation layer can also offer several advantages. For example, in such applications, the thickness of the passivation layer can be at most about 5 nm, or at most about 3 nanometers. Therefore, one or more of the above factors can be adjusted to produce such a passivation layer, given the composition of the nanosize particles and the passivating gas precursor.
Once formed, the nanosize particles can be separated from the gas flow in a downstream cyclone (not shown) and funneled to a powder collection point 178 and/or in a collection filter 910 in fluid communication with the apparatus 100 and funneled to a powder collection point 188, depending on their PSD. The nanosize particles can be transported to the downstream cyclone and/or collection filter 910 by gravity or can be propelled by a gas or by a vacuum. The nanosize particles can be transported to the downstream cyclone and/or collection filter 910 in a direction other than vertical with respect to the apparatus 100.
Optionally, at least a portion of the effluent gas obtained after separation of the nanosize particles from the gas flow can be recycled and pumped backed into the process with the use of at least one compressor (not shown). Optionally, at least a portion of the effluent gas obtained after separation of the nanosize particles from the gas flow can be processed through an abatement system 920 generating an exhaust. While the assembly 900 is shown in
In this assembly 900, a gaseous precursor is introduced substantially in the hot zone of the apparatus 100 where the hot zone is generated by the thermal plasma where the gaseous precursor starts to decompose into its atomic constituents. The multiple injectors allow for an injection of the gaseous feedstock downstream from the plasma exit to ensure the uniform reaction of the gas or gases. The use of a plurality of injectors allows for a higher feedstock input. Downstream from the torch is also a dynamic hot wall region where a radial flow of hot gas generates a continuously renewed virtual surface that keeps the reactive species away from the solid reactor walls to prevent heterogeneous decomposition and chemical vapor deposition. The dynamic hot wall also provides additional energy to the system to allow the complete decomposition of the feedstock at unseen rates, therefore enabling the economically viable production of nanometric powder.
As a non-restrictive example of a variant, the precursor material in fluid form can be injected directly in the plasma gas of one or a plurality of DC plasma torches. In turn this can be used in combination with multiple injection probes downstream or upstream from the plasma heat source or sources.
The nanoparticle powders described herein can be used in the manufacture of rechargeable electrochemical cells having advantageous properties, particularly when these nanoparticle powders are based on silicon or silicon alloy. Rechargeable electrochemical cells typically are lithium secondary cells constituted by a positive electrode for a lithium secondary cell, a negative electrode and an electrolyte layer.
The positive electrode typically has a positive current collector of, for example, an aluminum foil including expanded metal (such as expanded metal foil available from Exmet, USA), optionally with a carbon-based protective coating (such as current collector available from Exopack® Advanced Coating, USA) and a layer of a positive electrode active material including C-AxM(XO4)y including a binder and generally an electroconductive additive. As a binder contained in the layer of the positive electrode active material, it is possible to use a known resin material routinely used as a binder for the layer of the positive electrode active material for this type of lithium secondary cell. Examples include polyvinylidene fluoride (PVdF), polytetrafluoroethylene, polyvinyl chloride, polyvinylpyrrolidone, styrene-butadiene rubber (SBR), polymethylmethacrylate (PMMA), polyethylene oxide (PEO) and mixtures thereof. Among these, polyvinylidene fluoride and derivatives are typically used for lithium ion type battery, PEO and derivatives are typically used for lithium metal polymer battery. As an electronic conductive additive contained in the layer of the positive electrode active material, it is possible to use a known conductive agent routinely used for this type of secondary lithium cell in, without any limitation, spherical (granular) form, flaky form, a fibrous form and the like. Examples include carbon black, graphite, carbon fiber, nanotube, graphene, vapor growth conductive fiber (VGCF) and mixtures thereof.
Specifically, the negative electrode can contain a collector having coated thereon a material obtained by mixing a negative electrode active substance and a binder. The negative electrode active substance includes the herein described silicon or silicon alloy nanosize particles alone or in combination with any other active substance. Examples include a carbon material, such as natural graphite, artificial graphite, non-graphitizable carbon and graphitizable carbon, a metallic material, such as metallic lithium, a lithium alloy and a tin compound, a lithium-transition metal nitride, a crystalline metallic oxide an amorphous metallic oxide, a titanium oxide, such as TiO2 or carbon-coated TiO2, a lithium titanium oxide such as L4Ti5O12 or carbon-coated L4Ti5O12, and an electroconductive polymer. The binder can be a known organic or inorganic binder such as those shown for the binder that can be used in the positive electrode, such as polyvinylidene fluoride (PVdF). Examples of the collector of the negative electrode include copper and nickel in the form of a mesh, a punching metal, a foamed metal, a foil processed into a plate, or the like.
The electrolyte layer is held with the positive electrode layer and the negative electrode layer and contains an electrolytic solution, a polymer containing an electrolytic salt, a polymer gel electrolyte, or a polymer electrolyte plasticized or not. In the case where an electrolytic solution or a polymer gel electrolyte is used, a separator is typically used in combination. The separator electrically insulates the positive electrode and the negative electrode and retains an electrolytic solution or the like.
The electrolytic solution can be any electrolytic solution that is typically used in a lithium secondary cell, and includes ordinary examples of an organic electrolytic solution, polymer electrolyte, or an ionic liquid and mixtures thereof. Examples of the electrolytic salt include LiPF6, LiBF4, LiClO4, LiAsF6, LiCl, LiBr, LiCF3SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiN(FSO2)2, LiC(FSO2)3, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, Li2B12FxH12-x (10≤x≤12), LiI, LiAlCl4, NaClO4, NaBF4 and NaI, and particularly an inorganic lithium salt, such as LiPF6, LiBF4, LiClO4, and an organic lithium salt represented by LiN(SO2CxF2y+1)(SO2CyF2y+1), wherein x and y each represents independently an integer of 0 or from 1 to 4, provided that x+y is from 2 to 8. Specific examples of the organic lithium salt include LiN(SO2F)2, LiN(SO2CF3)(SO2C2F5), LiN(SO2CF3)(SO2C3F7), LiN(SO2CF3)(SO2C4F9), LiN(SO2C2F5)2, LiN(SO2C2F5)(SO2C3F7) and LiN(SO2C2F5)(SO2C4F9). Among these, LiPF6, LiBF4, LiN(CF3SO2)2, LiN(SO2F)2 and LiN(SO2C2F5)2 are typically used as the electrolyte owing to their excellent electric characteristics. The electrolytic salt can be used solely or as a combination of two or more kinds.
The organic solvent for dissolving the electrolytic salt can be any organic solvent that is ordinarily used in a non-aqueous electrolytic solution of a lithium secondary cell without particular limitation, and examples include a carbonate compound, a lactone compound, an ether compound a sulfolane compound, a dioxolane compound, a ketone compound, a nitrile compound and a halogenated hydrocarbon compound. Specific examples include a carbonate compound, such as dimethyl carbonate, methylethyl carbonate, diethyl carbonate, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, ethylene glycol dimethyl carbonate, propylene glycol dimethyl carbonate, ethylene glycol diethyl carbonate and vinylene carbonate, a lactone compound, such as δ-butyrolactone, an ether compound, such as dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran and 1,4-dioxane, a sulfolane compound, such as sulfolane and 3-methylsulfolane, a dioxolane compound, such as 1,3-dioxolane, a ketone compound, such as 4-methyl-2-pentanone, a nitrile compound, such as acetonitrile, propionitrile, valeronitrile and benzonitrile, a halogenated hydrocarbon compound, such as 1,2-dichloroethane, and an ionic liquid, such as methyl formate, dimethylformamide, diethylformamide, dimethylsulfoxide, an imidazolium salt and a quaternary ammonium salt. The organic solvent can be a mixture of these solvents. Among the organic solvents, at least one non-aqueous solvent selected from the group consisting of carbonate compounds is typically contained since it is excellent in solubility of the electrolyte, dielectric constant and viscosity. Examples of the polymer compound used in the polymer electrolyte or the polymer gel electrolyte include a polymer, a copolymer and a crosslinked product thereof of ether, ester, siloxane, acrylonitrile, vinylidene fluoride, hexafluoropropylene, acrylate, methacrylate, styrene, vinyl acetate, vinyl chloride, oxetane or the like, and the polymer can be used solely or as a combination of two or more kinds of them. The polymer structure is not particularly limited, and the polymer can have an ether structure, such as polyethylene oxide.
In the lithium secondary cell, an electrolytic solution is housed in a cell container for a liquid system cell, a precursor liquid having a polymer dissolved in an electrolytic solution is housed therein for a gel system, or a polymer before crosslinking having an electrolytic salt dissolved therein is housed therein for a solid electrolyte system cell.
The separator can be any separator that is ordinarily used in a lithium secondary cell, such as a porous resin formed of polyethylene, polypropylene, polyolefin, polytetrafluoroethylene or the like, ceramics and nonwoven fabric. The separator can be a dry or plasticized polymer having an ether structure, such as polyethylene oxide for lithium metal polymer batteries.
The batteries tested can be of the “button” type assembled and sealed in a glovebox. For example, such batteries can include a carbon-treated sheet of aluminum carrying a coating including a cathode material (e.g., C—LiFePO4, with a loading of 4.5 mg/cm2), a film containing the herein described anode material (including the silicon or silicon alloy nanosize particles), and a separator having a thickness of 25 μm (supplied by Celgard) impregnated with a 1M solution of LiPF6 in an EC/DEC 3/7 mixture. Other variants of test batteries can be envisioned by the person of skill in view of the herein teachings and as such, for conciseness sake, will not be further described here.
The batteries can be tested in with intensiostatic cycling as per procedures known in the art. For example, one can test the batteries at 25° C. and a rate of C/12, first in oxydation from the rest potential up to 4 V and then in reduction between 4 V and 2.2 V, following charge/discharge cycles in a range of 2.2 and 4 V. Alternatively or additionally, one can test at a temperature of 45° C. and a rate of C/8, and/or at a temperature of 60° C. and a rate of C/8.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. As used herein, and unless stated otherwise or required otherwise by context, each of the following terms shall have the definition set forth below.
As used herein, the term “powder particle” generally relates to particulate matter, including but not limited to micron sized and nanosize particles.
As used herein, the term “plasma” generally relates to a gas in a hot, partially ionized state.
As used herein, the term “plasma torch” generally relates to a device capable of turning a gas into plasma.
As used herein, the term “inductively coupled plasma torch” generally relates to a type of plasma torch using electric current as an energy source to produce electromagnetic induction of the energy into the plasma.
As used herein, the term “injection probe” generally relates to an elongated conduit for insertion or supply of a feed material. In some embodiments, such injection probes can be cooled using a cooling fluid.
The following examples describe some exemplary modes of making and practicing certain compositions that are described herein. It should be understood that these examples are for illustrative purposes only and are not meant to limit the scope of the compositions and methods described herein.
In this example, standard operating conditions for obtaining silicon nanoparticles through silane decomposition are described.
The standard operating conditions include plasma torch operating condition, silane injection method, hot-gas flow rate and temperatures, quench gas flow distribution in the reactor, and the operating pressure in the system. Table 1 includes the operating conditions used in acquiring the experimental data, namely plasma power 77-80 kW, plasma central gas flow 30 liters per minute (1 μm) Argon, plasma sheath gas flow 95 lpm Argon and 15 lpm H2, silane was injected underneath the PN-50 plasma torch using 3 SG1270 probes (120° spaced with downward injection angle of 15-20°). The gases introduced into the reactor are divided into 2 types: 250 lpm fresh N2 in the fishtail module; 8500 lpm recycled mixture gas of (Ar+H2+N2) in various locations in the reactor, among which 1500 lpm was heated up to 500° C. prior to injection to the top reaction zone. The reactor pressure was kept at 14.5 psia.
In this example, alternate operating conditions for obtaining silicon nanoparticles through silane decomposition and nanoparticles obtained therefrom are described.
Table 2 lists some test runs conducted using alternate operating conditions and the analytical results of the powders obtained. The alternate operating conditions were one or more of the following: the total silane injection rate, flow rate of the dilution argon, quench gas flows in the top fishtail modules, and the passivation oxygen flow rate.
Powders were collected from the filter bottom (FB) and reactor wall and bottom (RWB) respectively. The production rates were evaluated based on the powder collected from the filter bottom, and the yield was calculated based on the production rate versus the feed rate (assuming full conversion of SiH4 to Si).
The nanoparticles powders were analysed by BET, Malvern PSD, XRD, FE-SEM, LECO O %, C %, N %, H %, and ICP-MS. The mean particle sizes were evaluated based on the BET specific surface area, while the crystallite sizes were calculated using the Sherrer equation.
The results of these tests show that nano-sized silicon powders of mean particle sizes ranging from 52 to 212 nm can be produced. The production rates varied from around 1 kg/hr to 3.65 kg/hr while the collection yields varied from 41.6 to 97.2 wt %. Oxygen contents and other additives or impurities can be controlled according to the operating conditions. The powders produced are largely spherical or near spherical and have a crystallite size ranging from 24 to 42 nm.
In this example, silicon nanoparticles were obtained through silane decomposition using an embodiment of the apparatus and method described herein.
Table 3 below lists three Si powders with distinct particle sizes. The powders with the mean particle sizes of 212, 113, and 52 nm were produced with the silane injection concentrations of 37.5, 25, and 16.67%, respectively.
In this example, silicon nanoparticles were obtained through silane decomposition using an embodiment of the apparatus and method described herein and compared with silicon nanoparticles (comparative) obtained with an apparatus and method of the prior art that uses micro silicon powder as precursor.
Table 4 is a comparison between the nano-Si powders produced using micro silicon powder as precursor vs. using silane as the precursor.
The comparative powder and the powder in accordance with an embodiment of the present disclosure look generally similar to each other. However, important differences are found in the particle size distribution and purity level. Comparative powders produced from micro silicon have broad size distributions with the inclusion of micro-sized particles in the nanopowder products. These micro-sized particles were from incomplete evaporation in the plasma process and carried over to the powder collector as contaminants. In the nano-Si powders produced from silane precursor, those micro-sized particles were absent. Finally, the purity level of the product powder was directly related to the purity of the precursor. Since the silane was much purer than the micro-sized silicon powders, the nano-Si produced from silane was purer as well.
Different tests were run to investigate the effect of different gas volumes in the system. Table 1 shows the standard operating parameters and Table 2 shows the alternate operating parameters for the test along with some associated data measured on the powders. The parameters of interest were the silane feed-rate, the silane dilution gas volume and the quench volumes. The silane feed-rate simply corresponds to the volume flow of silane injected into the apparatus.
The dilution gas is channeled in the apparatus through the silane injection probe. It is represented as flow 201, in the gap space 209 as shown in
It appears that a higher quench volume, a higher dilution volume and a lower federate all contribute to yield smaller particle sizes. This can be attributed to the inhibition of the nucleation and growth dynamics and the suppression of coagulation through the dilution of the precipitating species.
The powder in accordance to the present disclosure was synthesized according to test #6 conditions in Table 2 with all other parameters set according to Table 1. The comparative powder was synthesized in an induction plasma system according to the process described in U.S. Pat. No. 8,013,269. The silicon powder feed-rate was of 4.5 g/min and the plasma power was 45 kW. The gases used in the torch were 90 slpm Ar and 10 slpm H2.
One will notice the absence of large particles in
The volume distribution for the comparative powders shows a primary and secondary distribution, the latter of which is attributable to the non-vaporized feedstock, consistent with the observations noted earlier. This secondary distribution is not seen in the number distribution, which highlights the disproportionate impact that large particles may have in applications such as energy storage, where mass and volume enter the calculations of energy densities.
The technology disclosed herein enables the mass production of new cell components which are shown to improve the performance of the cell in both storage and charge/discharge characteristics. As such, it is positioned favorably to provide a competitive advantage to the players in “cell components” segment of the value chain for the industry.
The technology provides an improvement of performance simultaneously with a solution for mass production at reasonable costs. This fits into the evolution of both cost and performance of lithium ion cells, as one has evolved opposite to the other in recent years.
All references cited throughout the specification are hereby incorporated by reference in their entirety for all purposes.
Note that titles or subtitles may be used throughout the present disclosure for convenience of a reader, but in no way these should limit the scope of the invention. Moreover, certain theories may be proposed and disclosed herein; however, in no way they, whether they are right or wrong, should limit the scope of the invention so long as the invention is practiced according to the present disclosure without regard for any particular theory or scheme of action.
All references cited throughout the specification are hereby incorporated by reference in their entirety for all purposes.
Reference throughout the specification to “some embodiments”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the invention is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described inventive features may be combined in any suitable manner in the various embodiments.
It will be understood by those of skill in the art that throughout the present specification, the term “a” used before a term encompasses embodiments containing one or more to what the term refers. It will also be understood by those of skill in the art that throughout the present specification, the term “comprising”, which is synonymous with “including,” “containing,” or “characterized by,” is inclusive or open-ended and does not exclude additional, un-recited elements or method steps.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the case of conflict, the present document, including definitions will control.
As used in the present disclosure, the terms “around”, “about” or “approximately” shall generally mean within the error margin generally accepted in the art. Hence, numerical quantities given herein generally include such error margin such that the terms “around”, “about” or “approximately” can be inferred if not expressly stated.
Although various embodiments of the disclosure have been described and illustrated, it will be apparent to those skilled in the art in light of the present description that numerous modifications and variations can be made. The scope of the invention is defined more particularly in the appended claims
The present application claims the benefit of U.S. provisional patent application Ser. No. 63/079,820 filed on Sep. 17, 2020; 62/913,009 filed on Oct. 9, 2019; 62/913,001 filed on Oct. 9, 2019; 62/913,025 filed on Oct. 9, 2019; 62/932,544 filed on Nov. 8, 2019; 62/932,557 filed on Nov. 8, 2019; and 62/932,562 filed on Nov. 8, 2019. The contents of each of the above-referenced documents are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2020/051365 | 10/9/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62913001 | Oct 2019 | US | |
| 62913009 | Oct 2019 | US | |
| 62913025 | Oct 2019 | US | |
| 62932544 | Nov 2019 | US | |
| 62932557 | Nov 2019 | US | |
| 62932562 | Nov 2019 | US | |
| 63079820 | Sep 2020 | US |
