This disclosure relates to systems, methods, and apparatus for the pretreatment of materials, especially silicon materials, with alkali metal solution for the manufacturing of batteries and capacitors, such a prelithiation.
Current prelithiation methods, such as stabilized lithium metal powder, physical vapor lithium deposition and lithium metal sheet based electrochemical prelithiation are relatively expensive and/or difficult to implement in a compatible manner with existing electrode manufacturing lines. One attempt to provide an improved process was set forth in the article by Jang et al., Molecularly tailored lithium arene complex enables chemical prelithiation of high-capacity lithium-ion battery anodes, Angew. Chem. Int. Ed. 2020, 132, 14581-14588, doi: 10.1002/anie.202002411, the contents of which are incorporated by reference herein in its entirety, which uses immersion of an anode material in a lithium-arene complex solution to perform an uncontrolled lithiation step, followed by a rinsing bath and a high heat drying. However, due to the lack of control and the additional required high energy input step, such proposed process may be problematic or expensive to implement.
A method for pretreatment with an alkali metal, such as prelithiation, that was more efficient, lower in cost, and/or more compatible with existing electrode manufacturing line for high power and high energy batteries and capacitors would be an improvement in the art. Such methods, systems and processes that achieved fast and effective lithium compensation during electrode fabrication and before cell assembly would allow for the development of high energy density cells using lithium deficient electrode materials and thus be a further improvement in the art.
The present disclosure is directed to systems and methods for the pretreatment of materials with an alkali metal solution for the manufacturing of batteries and capacitors. Realizing high energy density and long-term cycling stability of rechargeable batteries and capacitors requires embodied pretreatment methods through that allows alkali metal intercalation/alloying/conversion reaction with positive and negative electrodes, forms stable electrode/electrolyte interphase, mitigates alkali metal loss, increases cell energy density and adapts to any existing electrode manufacturing process. Processes in accordance with the present disclosure address these challenges directly with a liquid alkali metal composition and a corresponding pretreatment procedure for high energy density alkaline-ion batteries and capacitors. In one illustrative embodiment, the alkali metal may be lithium, and the processes generally referred to herein as prelithiation. It will be appreciated that other alkali metals, including sodium and potassium may be used for particular applications. Such processes may utilize reactants that can be oxidized and react with a variety of anode and cathode materials by forming lithiated compound through ion intercalation, alloying and conversion reactions. The reactants may be developed by converting metallic lithium into a liquid solution comprised of lithium ion and coordinating solvent molecules, a film forming agent, and negatively charged organic compounds, which have lower redox potential than the electrode materials. The liquid lithium composition begins lithiation reaction instantly when in contact with target materials and can achieve desired lithiation state in as little time as 5 minutes. Depending on the solvent molecules, film forming agent, and organic species present in the liquid lithium, the decomposition products on the electrode materials forms a low resistance and highly ion conductive interphase, which promotes the battery's cycle life and shortens the time needed for cell formation.
Prelithiation compensates the permanent capacity loss caused by irreversible phase transition and solid-electrolyte-interphase formation of electrode materials, which traps active lithium ion during the initial charge-discharge cycles and thus leads to low Coulombic efficiency. Liquid lithium-based prelithiation method provides at minimum 20% improvement in terms of first cycle Coulombic efficiency for lithium-accepting materials. At least 15% increment of specific energy can be achieved in full cell configuration comprised of lithium-accepting anode and lithium-providing cathode. In some embodiments, treatment of a single electrode material can be used to compensate for both the anode and the cathode in battery cell. The present disclosure also addresses the manufacturing process for both liquid lithium compositions and prelithiation procedures. Large volumes of liquid lithium solution can be prepared under room temperature in a short time and is readily scaled up with larger container size. Prelithiation process involves evenly dispensing liquid lithium containing solution over an electrode substrate and a subsequent drying step. The liquid dispensing system may be accomplished by an add-on equipment to the typical roll-to-roll electrode manufacturing lines between the slot die-casting and electrode drying steps or after electrode calendaring. The lithiation degree may be controlled by the flow rate of the liquid lithium and feeding speed of the electrode sheet.
In one illustrative embodiment, a liquid alkali metal composition, such as a liquid lithium composition, may be formed by dissolving the metallic alkali metal in a solution that includes a suitable organic agent, a suitable solvent and suitable film forming agent. The solvent functions to dissolve the remaining components, the organic agent functions to coordinate the metallic alkali metal and the film forming agent functions to form an ion conductive interphase film following application. Each component of the solution may be present in an effective amount to perform the desired function. Where the alkali metal is lithium, the metallic lithium may be dissolved into the solution to obtain a lithium to organic agent molar ratio of from 1:1 to 10:1 in the liquid lithium composition.
The liquid alkali metal composition may be dispensed onto a suitable substrate material such as a silicon, carbon or composite anode material and allowed to remain thereon for a suitable time for the pretreatment reaction to proceed, followed by the drying of the pretreated substrate. The pretreatment of the substrate with alkali metal (or alkali metallization of the substrate) may take place simultaneously with the formation of the ion conductive interphase film. Dispensing may be performed by spraying on the substrate surface. Drying may be performed at a relatively low temperature and at a reduced pressure. The resulting pretreated substrate may serve as an anode material for a rechargeable battery or capacitor and the method may be compatible with existing electrode manufacturing line equipment or techniques.
It will be appreciated by those of ordinary skill in the art that the various drawings are for illustrative purposes only. The nature of the present disclosure, as well as other embodiments in accordance with this disclosure, may be more clearly understood by reference to the following detailed description, to the appended claims, and to the several drawings.
The present disclosure relates to apparatus, systems, and methods for the pretreatment of materials with alkali metals for the manufacturing of batteries and capacitors. It will be appreciated by those skilled in the art that the embodiments herein described, while illustrative, are not intended to so limit this disclosure or the scope of the appended claims. Those skilled in the art will also understand that various combinations or modifications of the embodiments presented herein can be made without departing from the scope of this disclosure. All such alternate embodiments are within the scope of the present disclosure.
In one illustrative embodiment, a liquid composition of alkali metal, such as lithium, may be formed by dissolving a metallic alkali metal in a solution that includes a suitable organic agent, a suitable solvent and suitable film forming agent. With respect the organic agent where metallic lithium is used, this compound functions to coordinate with the metallic lithium, allowing it to be dissolved into the solution. Some exemplary organic agents may include: Naphthalene, biphenyl, 3,3′-dimethylbiphenyle, 4,4′-dimethyl biphenyl, 2-methylbiphenyl, 3,3,4,4′-tetramethylbiphenyl, and 9,9-dimethyl-9H-fluorene. It will be appreciated that one or more organic agents may be used in a solution and that other organic agents than those listed may be used, so long as the selected organic agent(s) fulfill the function of coordinating with Li ion dissolved into a solution in a form allowing it to be deposited on a suitable substrate in accordance with processes complying with the principles of the present disclosure. It will be further appreciated that where other alkali metals are used, other organic agents may be used.
Some exemplary solvents for the liquid lithium containing composition may include: 1,2-dimethoxyethane, tetrahydrofuran, chloroform, acetonitrile, tetraethylene glycol dimethyl ether dimethylformamide, triethylene glycol dimethyl ether, dimethoxyethane, 2-methyl-tetrahydrofuran, and Methyltetrahydrofuran. It will be appreciated that one or more solvents may be used in the liquid lithium containing solutions and that additional solvents other than those listed may be used, so long as the selected solvents fulfill the function of dissolving the remaining components in solution in a form allowing the prelithiation processes complying with the principles of the present disclosure to be performed. It will be further appreciated that where other alkali metals are used, other solvents may be used.
Some exemplary film forming agents for the liquid lithium containing composition may include: fluoroethylene carbonate, vinylene carbonate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoroproppyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, methoxynonafluorobutane, ethoxynonafluorobutane, tris(2,2,2-trifluoroethyl)orthoformate, pentafluoroethyl 2,2,2-trifluoroethyl ether, 2,2,3,3,4,4,5,5-ocatafluoro-1-pentanol, and 2,2,2-trifluoroethyl nonafluorobutanessulfonate. It will be appreciated that one or more film forming agents may be used in the liquid lithium containing solutions and that additional film-forming agents other than those listed, so long as the selected film forming agents fulfill the function of initiating polymerization to form an ion conductive interphase film on the substrate surface in a process in accordance with the present disclosure. It will be further appreciated that where other alkali metals are used, other film forming agents may be used.
As noted above, in lithium containing solutions in accordance with the present disclosure, the solvent functions to keep the remaining components in solution, the organic agent functions to dissolve the metallic lithium into the solution and the film forming agent functions to form an ion conductive interphase film following application. Each component of the solution may be present in an effective amount to perform the desired function. In a typical solution: (1) the organic agent's concentration in solvent can range from 0.1M to 4M; (2) the film forming additive weight fraction can range from 0-5 wt. %; and (3) the lithium source: organic agent molar ratio can range from 1:1 to 10:1.
In processes in accordance with the present disclosure, the liquid lithium containing composition may be formed by preparing a process solution of the selected solvent, organic agent and film forming agent and then dissolving metallic lithium into the process solution. The mixing of solution and addition of lithium may be carried out a suitable temperature and pressure, for example at a temperature of from about 25° C. to about 50° C. may be suitable for integration into current processes. The liquid lithium containing composition may be maintained by stirring until dispensed. The liquid lithium containing composition may be formed and maintained under an inert gas atmosphere until used.
As depicted in
Some suitable substrate materials on which the pretreatment, including prelithiation, may be performed may include: silicon, tin, antimony, hard carbon, silicon-graphite phosphorus, aluminum, germanium, sulfur, iron fluoride, iron sulfide, copper fluoride, and AxMO2 (0<X<1, A=alkaline metals and M=transition metals), among others. It will be appreciated that a suitable substrate material may include silicon-based substrates that contain silicon with other materials, including graphite, tin, antimony, hard carbon, phosphorus, aluminum, germanium, sulfur, iron fluoride, iron sulfide, copper fluoride, and AxMO2 (0<X<1, A=alkali metals and M=transition metals). In some embodiments, such substrates may contain from 0.1% to 100% silicon and may include graphite-silicon substrates.
The molar ratio of the liquid lithium and substrate material may be from about: 1:1 to about 10:1. The prelithiation reaction may be conducted at a temperature of from about 0° C. to about 100° C. and the reaction may proceed from about 5 minutes to about 1 hour. Upon dispensing onto the substrate, the film forming agent may initiate a polymerization reaction to form an ion conductive interphase layer on the substrate form the liquid lithium containing composition as the prelithiation reaction proceeds.
Drying may be performed at a relatively low temperature and at a reduced pressure. For example, a drying temperature of from about 50° C. to about 120° C. and a vacuum level of from about 500 mbar to about 1000 mbar.
The resulting pretreated substrate may serve as an anode material for a rechargeable battery or capacitor and the method may be compatible with existing electrode manufacturing line equipment or techniques, as depicted in
As depicted in
As the substrate advances, the liquid lithium composition 100B is allowed to remain thereon for a suitable time for a prelithiation reaction to proceed as by forming a film 102B. This may then be followed by the drying of the prelithiated substrate in a subsequent drying step 12B, which may take place in suitable drying chamber 120 for maintaining a suitable temperature and pressure as the substrate SMB is advanced therethrough.
It will be appreciated that in methods in accordance with the present disclosure, the liquid lithium solution dispensing may be performed by spray coating, direct dispensing, or a liquid feeding system. Suitable mixing systems, drying systems, may be used allowing for an integration to roll-to-roll processing for preparation of anode and cathode materials.
Preparation of Liquid Lithium Containing Composition
Step 1: Solution 1 was formed by preparing 1 M 4,4′-dimethyl biphenyl (organic agent) in 1,2-dimethoxyethane (solvent) and then adding 2 weight percent of fluoroethylene carbonate (film forming agent).
Step 2: Metallic lithium (lithium source) was dissolved into Solution 1 under magnetic stirring for 2 hours at 25° C. The obtained liquid lithium containing solution had a molar ratio of lithium:organic agent of 2:1.
A liquid lithium containing composition was prepared as in Example 1 and a hard carbon electrode was prepared using the following protocol:
Step 1: A slurry composed of HC, carbon black and binder (polyvinylidene fluoride) with a mass ratio of 8:1:1 was mixed using a planetary centrifugal mixer. Step 2: The slurry was casted on a Cu foil current collector via dr. blade. Step 3: The electrode was baked at 90° C. for 1 hr and then roll-pressed before overnight drying at 120° C. The mass loading of the HC was controlled at ˜3 mg cm−2.
The prepared hard carbon electrode was treated with the liquid lithium containing composition in the same manner as the electrode of Example 1. Pristine and prelithiated electrode was then electrochemically tested in the same manner as Example 1.
A liquid lithium containing composition was prepared as in Example 1 and hard carbon/silicon electrode was prepared using the following protocol:
Step 1: A slurry composed of HC, silicon, carbon black and binder (polyvinylidene fluoride) with a mass ratio of 5:3:1:1 was mixed using a planetary centrifugal mixer. Step 2: The slurry was casted on a Cu foil current collector via dr. blade. Step 3: The electrode was baked at 90° C. for 1 hr. and then roll-pressed before overnight drying at 120° C. The mass loading of the HC/Si was controlled at ˜3 mg cm−2.
The prepared hard carbon/silicon electrode was treated with the liquid lithium containing composition in the same manner as the electrode of Example 1. Pristine and prelithiated electrode was then electrochemically tested in the same manner as Example 1.
Electrode Preparation
Cathode preparation: a slurry composed of lithium nickel manganese oxide powder (NMC), conductive carbon and binder (polyvinylidene fluoride) with a mass ratio of 9.4:0.3:0.3 was mixed using a planetary centrifugal mixer. (2) The slurry was casted on an Al foil current collector via Dr. blade. (3) The electrode was baked at 90° C. for 1 hr and then roll-pressed before overnight drying at 120° C.
Anode preparation: a slurry composed of graphite-silicon (Gr-Si), conductive carbon and binder (polyvinylidene fluoride) with a mass ratio of 9.4:0.3:0.3 was mixed using a planetary centrifugal mixer. (2) The slurry was casted on a Cu foil current collector via Dr. blade. (3) The electrode was baked at 90° C. for 1 hr and then roll-pressed before overnight drying at 120° C.
Preparation of Liquid Lithium Containing Composition
Step 1: Precursor solution was formed by preparing 1 M 4,4′-dimethyl biphenyl (organic agent) in in 2-methyl-tetrahydrofuran (solvent) and then adding 2 weight percent of fluoroethylene carbonate (film forming agent).
Step 2: Metallic lithium (lithium source) was dissolved into the precursor solution under magnetic stirring for 2 hours at 25° C. The obtained liquid lithium containing solution had a molar ratio of lithium:organic agent of 2:1.
Prelithiation of Graphite-Silicon (Gr-Si) Anode and Manufacturing
The prepared liquid lithium containing solution was dispensed onto the Gr-Si electrode in Ar-filled glove box at room temperature. The formulation of the Gr-Si anode was Si (target material)/binder/carbon additive (mass ratio of 94:3:3). The molar ratio between the dispensed liquid lithium and Gr-Si was 2:1. The direct dispensing was performed by pipetting. The prelithiation reaction was allowed to proceed for 5 minutes, 10 minutes or 30 minutes, followed by vacuum drying at 100° C. for 20 minutes.
Electrochemical Testing
(1) The electrode (pristine or prelithiated) was cut into a 1.76 cm2 laminate.
(2) 2032 coin cells were assembled in an argon-filled glove box using a polyethylene (PE) separator, a Gr-Si anode (treated or untreated) and a cathode.
(3) The cells were rested in an Arbin cycler at 25° C. for 6 hr before electrochemical testing.
(4) Cycling test was carried out with 3 formation cycles at 0.1 C (1 C equals to fully discharge/charge the battery in 1 hour) and continuous cycling at 1 C between 2.5-4.15 V.
(5) Rate testing was carried out at current densities of 0 C/20, C/10, C/5, C/2, 1 C and 2 C between 2.5-4.15 V.
Results
While this disclosure has been described using certain embodiments, it can be further modified while keeping within its spirit and scope. This application is therefore intended to cover any variations, uses, or adaptations of the disclosure using its general principles. This application is intended to cover any and all such departures from the present disclosure as come within known or customary practices in the art to which it pertains, and which fall within the limits of the appended claims.
This application claims the benefit of U.S. Provisional Application No. 63/132,638, filed Dec. 31, 2020, the contents of which are incorporated herein by reference in its entirety, including but not limited to those portions that specifically appear hereinafter.
Number | Date | Country | |
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63132638 | Dec 2020 | US |