Patent Application
20250158041
The present disclosure belongs to the technical field of anode materials, and particularly relates to an anode material, a method for preparing the anode material, and a lithium ion battery.
Silicon-based anode materials are one of the most key materials for high energy density lithium ion batteries, while existing silicon-based materials have problems such as large expansion and poor rate, which affects the wide application of silicon-based anode materials in lithium batteries. Therefore, inhibiting expansion and improving the cycle rate performance of silicon-based materials is a premise that silicon-based materials can be widely used.
In the process of designing and improving the silicon-based anode material, the design of the material structure is critical for improving the performance of the silicon-based anode material. In the related art, an anode material mainly composed of nano-silicon wires is usually used to prepare a thin film battery. For an anode material of a lithium ion battery, the anode material generally needs to be processed into a powder or granular structure, and the structure of the nano silicon wires cannot be applied, resulting in limited improvement of the conductivity of the material, and further resulting in limited improvement of the rate performance of the anode material. In addition, the existing anode material improves the cycle performance of the material by forming an SEI, but the SEI is generally formed of an insulating material, and the use of the insulating material also causes the rate performance of the material to be reduced.
Therefore, there is an urgent need to improve existing silicon-based anode materials to improve the rate performance of the materials.
The present disclosure provides an anode material, a method for preparing the anode material and a lithium ion battery, which can improve the rate performance of the anode material.
According to a first aspect, an embodiment of the present disclosure provides an anode material, the anode material includes a core and a first coating layer at least partially coating on a surface of the core. The core includes a silicon-based material, the first coating layer includes a carbon material, and at least a part of a surface of the first coating layer is distributed with a fiber material.
The fiber material and the anode material satisfy the formula (I):
In formula (I), Dwire represents a minimum fiber diameter (nm) of the fiber material, D10 represents a corresponding particle size (nm) when the cumulative particle size distribution number of the anode material reaches 10%, and ρ represents a powder conductivity (S/cm) of the anode material.
With reference to the first aspect, in some embodiments, the anode material includes at least one of following features (1) to (7):
With reference to the first aspect, in some embodiments, the anode material includes at least one of following features (1) to (4):
With reference to the first aspect, in some embodiments, the anode material includes at least one of following features (1) to (6):
With reference to the first aspect, in some embodiments, the anode material further includes a second coating layer disposed between the core and the first coating layer and/or a second coating layer disposed on a region of the core surface that is not coated by the first coating layer.
With reference to the first aspect, in some embodiments, the second coating layer includes at least one of following features (1) to (5):
With reference to the first aspect, in some embodiments, the anode material includes at least one of following features (1) to (7):
In a second aspect, an embodiment of the present disclosure provides a method for preparing an anode material, including following steps:
performing a first heat treatment on a mixture containing a silicon-oxygen raw material and at least two salt substances to form a molten salt to obtain a first precursor; and
mixing the first precursor with a carbon source and then performing a second heat treatment to obtain an anode material.
With reference to the second aspect, in some embodiments, the mixture containing a silicon-oxygen raw material and at least two salt substances further includes a metal source.
With reference to the second aspect, in some embodiments, the method includes at least one of following features (1) to (3):
With reference to the second aspect, in some embodiments, the method includes at least one of following features (1) to (10):
With reference to the second aspect, in some embodiments, the method includes at least one of following features (1) to (6):
With reference to the second aspect, in some embodiments, the method includes at least one of following features (1) to (3):
With reference to the second aspect, in some embodiments, after the second heat treatment, the method further includes: a step of washing and drying the material obtained by the second heat treatment with water.
With reference to the second aspect, in some embodiments, the method includes at least one of following features (1) to (5):
With reference to the second aspect, in some embodiments, before washing the material obtained by the second heat treatment with water, the method further includes: a step of soaking and filtering the material obtained by the second heat treatment in water.
With reference to the second aspect, in some embodiments, the method includes at least one of following features (1) to (3):
According to a third aspect, an embodiment of the present disclosure provides a lithium ion battery, the lithium ion battery includes the anode material according to the first aspect or the anode material prepared by the method according to the second aspect.
The technical solution of the present disclosure has at least following beneficial effects.
In the anode material of the present disclosure, the fiber material is coated on the surface of the first coating layer, and the fiber material and the anode material meet the formula (I), indicating that the fiber material of the anode material grows well in the radial direction. The fiber material growing well in the radial direction can effectively reduce the load transfer impedance caused by lithium intercalation, improve the mass transfer efficiency, form a rapid lithium intercalation channel, facilitate the in-situ conduction of the anode material and the lithium source, reduce the interface obstruction, so that the lithium conduction capability of the anode material is improved, and the anode material can quickly receive electrons and lithium ions, thereby improving the conductivity of the anode material, and further improving the cycle performance and the rate performance of the anode material. Further, the anode material is of a core-shell structure, and the shell includes a coating layer containing a carbon material, the conductive contact area of the anode material can be improved, and the rate performance of the anode material is further improved.
In the present disclosure, a mixture containing a silicon-oxygen raw material and at least two salt substances is subjected to first heat treatment, the salt substances can form a liquid mixed salt-molten salt system, a first precursor and a carbon source are mixed and then subjected to second heat treatment, a carbon layer formed by the carbon source coats the surface of the silicon-oxygen raw material, so that the conductive contact area of the anode material can be improved, thereby improving the conductivity. Further, a part of carbon and/or silicon element grows into a fiber material under the catalysis of the mixed salt molten salt system and extends to the surface of the carbon layer, and the presence of fibers on the surface of the carbon layer can improve the mass transfer capacity and load transfer capacity of the anode material, so that the rate performance and the first efficiency of the anode material are improved. The preparation process of the present disclosure is simple and suitable for large-scale industrialization.
The present disclosure is further described below with reference to the accompanying drawings and Examples.
In order to better understand technical solutions of the present disclosure, the embodiments of the present disclosure are described in details with reference to the drawings.
It is to be made clear that the described embodiments are only some rather than all of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure fall within the protection scope of the present disclosure.
The terms used in the embodiments of the present disclosure are only for the purpose of describing specific embodiments, and are not intended to limit the present disclosure. The singular forms of “a”, “the” and “this” used in the embodiments of the present disclosure and the appended claims are also intended to include the plurality form, unless the context clearly indicates other meanings.
It should be understood that the term “and/or” used herein is merely an association relationship describing an associated object, and indicates that there can be three relationships, for example, A and/or B, and can indicate: only A, both A and B, and only B. In addition, the character “/” herein generally means an “or” relationship between the associated objects.
The present disclosure provides an anode material, referring to
The fiber material 4 and the anode material satisfy the formula (I):
In formula (I), Dwire is a minimum fiber diameter (nm) of the fiber material 4, D10 is a corresponding particle size (nm) when the cumulative particle size distribution number of the anode material reaches 10%, and ρ is a powder conductivity (S/cm) of the anode material.
In the above solution, in the anode material of the present disclosure, the fiber material 4 is coated on the surface of the first coating layer 2, and the fiber material and the anode material meet the formula (I), indicating that the fiber material 4 of the anode material grows well in the radial direction. The fiber material 4 growing well in the radial direction can effectively reduce the load transfer impedance caused by lithium intercalation, improve the mass transfer efficiency, form a rapid lithium intercalation channel, facilitate the in-situ conduction of the anode material and the lithium source, reduce the interface obstruction, so that the lithium conduction capability of the anode material is improved, and the anode material can quickly receive electrons and lithium ions, thereby improving the conductivity of the anode material, and further improving the cycle performance and the rate performance of the anode material. Further, the anode material is of a core-shell structure, and the shell includes a coating layer containing a carbon material, the conductive contact area of the anode material can be improved, and the rate performance of the anode material is further improved.
In the present disclosure, a value of AJ can be 0.005, 0.008, 0.04, 0.05, 0.08, 0.1, 0.12 or 0.15, or the like, and can also be other values within the above range, which is not limited herein. According to the present disclosure, whether the fiber material 4 can construct the electron ion mass transfer channel is determined based on the minimum fiber diameter Dwire of the fiber material 4, the particle size D10 of the anode material and the conductivity p of the anode material. In particular, ΔJ is within the range, it is indicated that the fiber material 4 of the anode material grows well in the radial direction, the fiber material 4 can effectively reduce the load transfer impedance caused by lithium intercalation, improve the mass transfer efficiency, form a rapid lithium intercalation channel, improve the load transfer resistance between the material interfaces, and improve the rate performance and the low temperature performance of the anode material. In addition, compared with the powdered material, the fiber material 4 of the present disclosure has a wider mass transfer and load transfer area and a high extensibility, and can effectively combine the battery conductive network, thereby improving the cycle performance of the anode material. If ΔJ is greater than 0.15, the material would deteriorate. According to the present disclosure, the distribution condition of small particles in the anode material is controlled through D10, and the powder of the small particles has a relatively high specific surface area and can generate relatively strong interaction with the fiber material, so that the radial growth and distribution of the fiber material are influenced, thereby further affecting the electrochemical performance of the anode material.
It can be understood that the diameter of the fiber material 4 in a single anode material can vary greatly, for Dwire in the present disclosure, the minimum diameter of the fiber in the measurable sample is taken for substitution calculation, and the minimum diameter of the fiber in the sample is tested with reference to the national standard “GB/T268260-2011 carbon nanotube diameter measurement method”. The fiber diameter (according to the diameter) is quantitatively measured by using an electron microscope SEM/TEM, and the point resolution ratio is better than 0.3 nm. Firstly, a sample is prepared, electron microscope shooting is carried out, a certain number of TEM/SEM effective view field images need to be obtained, then all effective view field images are analyzed, the fiber diameter is measured and counted, finally, a fiber sample diameter distribution diagram is drawn, the average diameter and the standard deviation are calculated, and a limit value is taken as Dwire. It should be noted that selecting a representative effective field of view with no smaller than 10 TEM/SEM images requires that the total number of fibers with measurable diameter in one TEM/SEM image exceeds 200. According to the present disclosure, TEM/SEM measurement analysis is performed on a sample, diameter data of all fibers with identifiable diameters in an image is measured and recorded, and a specific measurement method is as follows: a straight line is made perpendicular to the axial direction of the fiber, the outer diameters are measured respectively, and the measurement result needs to be converted into an actual scale of the fiber diameter according to the TEM/SEM image mark.
Regarding the result calculation, for one anode material powder sample, the fiber diameter distribution is counted and expressed as a fiber fraction column histogram form, one column identifier in the histogram represents the fiber fraction distributed in the interval, that is, the percentage of the fiber number with a diameter within a certain range in the total number of the counted fibers, and the width of the interval of the histogram is the distance between the centers of adjacent columns, and the value of the interval can be determined according to actual requirements. In the present disclosure, the granularity range is divided into 10 intervals for statistical diameter distribution. Finally, according to the above diameter measurement data, the average diameter and standard deviation are calculated according to
and the limit value is adopted, that is, the value of Dwire in the present disclosure.
In some embodiments, when the amount of the fiber material 4 on the surface of the first coating layer 2 is relatively small, the fiber material 4 is dispersed and distributed on the surface of the first coating layer 2, and when the amount of the fiber material 4 on the surface of the first coating layer 2 is relatively large, the fiber material 4 can serve as a coating layer to cover the surface of the first coating layer 2 (the coating layer used is shown by a dashed line in
In some embodiments, referring to
In some embodiments, the fiber material 4 includes at least one of carbon-based fiber and silicon-based fiber.
In some embodiments, the carbon-based fiber includes at least one of carbon fiber, carbon nanotube, and polymer fiber. The polymer fiber includes at least one of polypropylene fiber, polyester fiber, polyamide fiber, polyacrylic fiber, polypolymerase fiber, and polyamine fiber. For example, the polymer fiber includes at least one of polyethylene oxide fiber, polyacrylonitrile fiber, polyvinylidene fluoride fiber, polymethyl methacrylate fiber, polypropylene oxide fiber, and polyvinylidene chloride fiber.
In some embodiments, the silicon-based fiber includes at least one of silicon fiber and silicate fiber.
In the present disclosure, compared with the silicon fiber, the carbon fiber has the smallest fiber diameter, the morphology of the carbon fiber is slender, and the carbon fiber is bent. The diameter of the silicon fiber is relatively large, the fiber diameter of the silicon fiber is medium, the fiber diameter of the silicate is maximum, and the silicon fiber and the silicate fiber are basically upright without bending, so that the anode material can perform SEM/EDS testing, and can be differed according to the fiber diameter and morphology. The anode material is also possible to differ by element composition. It should be understood that the thickness of the fiber material 4 in
In some embodiments, the fiber diameter of the fiber material 4 ranges from 2 nm to 200 nm, the fiber diameter of the fiber material 4 can be 2 nm, 5 nm, 10 nm, 30 nm, 50 nm, 80 nm, 100 nm, 150 nm, 180 nm, or 200 nm, or the like, and can also be other values within the above range, which is not limited herein. If the fiber diameter of the fiber material 4 is greater than 200 nm, a block structure would appear on the surface of the material, which results an increase in the mass transfer resistance of the material. If the fiber diameter of the fiber material 4 is smaller than 2 nm, the influence range of the fiber material 4 is too small, and the fiber ratio needs to be increased to behave high mass transfer performance and load transfer performance, but the material capacity is reduced.
In some embodiments, the carbon material includes at least one of amorphous carbon, graphite, graphene, and diamond-like carbon (DLC), the diamond-like carbon is also referred to as adamas-like carbon, and mainly includes a large amount of sp3 hybrid amorphous carbon, and further includes a small amount of diamond crystallites and graphite crystallites.
In some embodiments, the material of the first coating layer 2 further includes a salt substance. Referring to
In some embodiments, the salt substance includes an inorganic salt and an organic salt.
In some embodiments, the inorganic salt includes at least one of fluoride, lithium salt, carbonate, silicate, phosphate, nitrate, titanate, thioate, and vanadate. For example, the inorganic salt includes lithium fluoride, lithium thiophosphate, lithium vanadate, lithium titanate, lithium carbonate, lithium phosphate, lithium silicate, lithium nitrate, aluminum fluoride, aluminum carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, sodium lithium carbonate, potassium lithium carbonate, potassium fluoride, sodium fluoride, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium hexafluoroarsenate, or the like.
The organic salt includes at least one of a carboxylate, an alkoxide, and an aromatic salt compound. For example, the organic salt includes lithium acetate, aluminum formate, magnesium acetate, aluminum isopropoxide, magnesium ethoxide, and lithium benzenesulfonate, or the like.
In some embodiments, the first coating layer 2 includes a first doping element, and the first doping element includes at least one of N, P, B, S, O, F, Cl, Br, and I. It can be understood that the presence of the first doping element stabilizes the SEI interface and inhibits irreversible expansion of the material.
In some embodiments, the mass ratio of the first doping element in the first coating layer 2 ranges from 0.01% to 5%, e.g., the mass ratio of the first doping element in the first coating layer 2 can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4% and 5%, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the material of the core 1 includes crystalline silicon and silicide. In some embodiments, the silicide includes at least one of silicate, silicon oxide, silicon phosphide, silicon carbide, silicon nitride, and silicon alloy.
In the present disclosure, the silicon oxide is a silicon-oxygen composite including oxygen atoms and silicon atoms, and the molar ratio of oxygen atoms to silicon atoms ranges from 0.5 to 2. The general formula is represented as SiOx (0.5≤x≤2), which can be a material formed by dispersing silicon particles in SiO2, or a material having a tetrahedral structural unit in which silicon atoms are located at the center of the tetrahedral structural unit, and silicon atoms and oxygen atoms are located at four vertices of the tetrahedral structural unit.
In some embodiments, the mass ratio of the metal element in the core 1 ranges from 0% to 15%. The metal element includes at least one of lithium, sodium, magnesium, aluminum, copper, titanium, boron, beryllium, calcium, vanadium, chromium, lanthanum, and selenium. For example, the mass ratio of the metal element in the core 1 can be 0%, 3%, 5%, 8%, 10%, 12% and 15%, or the like, and can be other values within the above range, which is not limited herein.
In some embodiments, referring to
In some embodiments, a second coating layer 3 is disposed on a region of the anode material where the core surface is not coated by the first coating layer 2.
In some embodiments, the fibrous material 4 is also distributed in the second coating layer 3.
In some embodiments, when the first coating layer 2 is a carbon layer, the thickness of the first coating layer 2 ranges from 0.01 μm to 1 μm. In some embodiments, the thickness of the first coating layer 2 can be, for example, 0.01 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm, or the like, and can also be other values within the above range, which is not limited herein. In some embodiments, the thickness of the first coating layer 2 ranges from 0.1 μm to 0.5 μm.
In some embodiments, when the first coating layer 2 is a composite coating layer containing a carbon material and a salt substance, the thickness of the first coating layer 2 ranges from 0.1 μm to 1.2 μm. In some embodiments, the thickness of the first coating layer 2 can be, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm and 1.2 μm, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the thickness of the second coating layer 3 ranges from 0 μm to 1 μm. In some embodiments, the thickness of the second coating layer 3 can be, for example, 0 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm and 1 μm, or the like, and can also be other values within the above range, which is not limited herein. In some embodiments, the thickness of the second coating layer 3 ranges from 0.05 μm to 0.2 μm.
In some embodiments, the mass ratio of the salt substance in the anode material ranges from Owt % to 3.0 wt %, e.g., a mass ratio of the salt substance in the anode material can be 0 wt %, 0.5 wt %, 1.0 wt %, 1.5 wt %, 2.0 wt %, 2.5 wt % and 3.0 wt %, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the mass ratio of the carbon element in the anode material ranges from 0.5 wt % to 10 wt %, e.g., a mass ratio of the carbon element in the anode material can be 0.5 wt %, 1 wt %, 3 wt %, 5 wt %, 7 wt %, 9 wt % or 10 wt %, or the like, and can also be other values within the above range, which is not limited herein. In some embodiments, the mass ratio of the carbon element in the anode material ranges from 2.5 wt % to 6 wt %.
In some embodiments, the median particle size D50 of the anode material ranges from 2.0 μm to 10.0 μm. In some embodiments, a median particle diameter of the anode material can be 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm or 10.0 μm, or the like, and can also be other values within the above range, which is not limited herein. In some embodiments, the median particle size of the anode material ranges from 4.0 μm to 8.0 μm.
In some embodiments, the particle size D10 with a cumulative distribution of 10% in the anode material ranges from 0.5 μm to 4 μm. In some embodiments, the D10 of the anode material can be 0.5 μm, 1 μm, 2 μm, 3 μm, or 4 μm, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the powder conductivity of the anode material ranges from 0.01 S/cm to 500 S/cm, e.g., the powder conductivity of the anode material can be 0.01 S/cm, 0.1 S/cm, 1 S/cm, 5 S/cm, 10 S/cm, 30 S/cm, 50 S/cm, 100 S/cm, 150 S/cm, 200 S/cm, 300 S/cm, 400 S/cm, or 500 S/cm, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the ratio of silicon to oxygen Si/O in the anode material ranges from 0.5 to 3.0, e.g., a ratio of silicon to oxygen Si/O in the anode material can be 0.5, 1.0, 1.5, 2.0, 2.5 or 3.0, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the porosity of the anode material ranges from 0.5% to 15%, e.g., the porosity of the anode material can be 0.5%, 1%, 3%, 5%, 8%, 10%, 12% or 15%, or the like, and can also be other values within the above range, which is not limited herein. It can be understood that due to the presence of the fiber material 4, certain pores present between the core 1 and the coating layer and inside the coating layer, which can improve the anti-swelling capability of the anode material to some extent.
Referring to
performing a first heat treatment on a mixture containing a silicon-oxygen raw material and at least two salt substances to form a molten salt to obtain a first precursor; and
mixing the first precursor with a carbon source and then performing a second heat treatment to obtain an anode material.
According to the above scheme, the mixture containing the silicon-oxygen raw material and at least two salt substances is subjected to the first heat treatment under the sealing condition, the pressure in the sealing condition is increased along with heating treatment of the first heat treatment, the salt substances can form a liquid mixed salt molten salt system, the first precursor and the carbon source are mixed and then subjected to the second heat treatment, the carbon source forms the carbon layer and coats the surface of the silicon-oxygen raw material, the conductive contact area of the anode material can be improved, and the conductivity is improved. In addition, a part of carbon grows into a carbon fiber under the catalysis of the mixed salt molten salt system and extends to the surface of the carbon layer, and the presence of fibers on the surface of the carbon layer can improve the mass transfer capacity of the anode material, so that the rate performance and the first efficiency of the anode material are improved. The preparation process is simple and suitable for large-scale industrialization.
The preparation method of the present disclosure is described below with reference to the embodiments.
Step S100, a first heat treatment is performed on a mixture containing a silicon-oxygen raw material and at least two salt substances to form a molten salt to obtain a first precursor.
In particular, the silicon-oxygen raw material and at least two salt substances are mixed to obtain a mixture, and the first heat treatment is performed on the mixture to obtain a first precursor.
In this step, with the heat treatment of the first heat treatment, at least two salt substances can form a liquid-state mixed salt molten salt system, the liquid-state mixed salt molten salt system further forms a molten salt coating the surface of the silicon-oxygen material under the first heat treatment condition to form a uniformly coated framework layer, and the framework coating layer can facilitate SEI deposition to form a rigid layer, thereby stabilizing the SEI interface and inhibiting irreversible expansion of the material and improving the cycle capacity retention rate and cycle performance of the anode material. It can be understood that the molten salt can be distributed between the silicon-oxygen raw material and the carbon layer to form the second coating layer 3, and/or the molten salt is distributed in the carbon layer to form the composite coating layer. Finally, in the first heat treatment process, a part of the salt substance can enter the core 1 to form doping, thereby improving the conductivity of the material.
In some embodiments, the first heat treatment is performed under the sealing condition, and under the sealing environment, with the heating treatment of the first heat treatment, the pressure in the sealing environment is increased, which is beneficial to the formation of molten salt, and the selectivity of salt substances is enlarged, and some salt substances easy to sublimate can also be applied to the present disclosure.
In some embodiments, the silicon-oxygen raw material includes silicon oxide SiOx, 0.05≤x≤2. The raw material can further include elemental silicon and silicate. The silicate includes lithium silicate, magnesium silicate, aluminum silicate, or binary silicate (such as lithium aluminum silicate and lithium magnesium silicate), or the like.
In some embodiments, the salt material includes an inorganic salt and an organic salt. The salt substance has excellent chemical stability, compactness and adhesion, can form a rigid framework, and is easy for the SEI layer to adhere to the surface of the material.
In some embodiments, the inorganic salt includes at least one of fluoride, lithium salt, carbonate, silicate, phosphate, nitrate, titanate, thioate, and vanadate, for example, the inorganic salt includes lithium fluoride, lithium thiophosphate, lithium vanadate, lithium titanate, lithium carbonate, lithium phosphate, lithium silicate, lithium nitrate, aluminum fluoride, aluminum carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, sodium lithium carbonate, potassium lithium carbonate, potassium fluoride, sodium fluoride, lithium hexafluorophosphate, lithium tetrafluoroborate, or lithium hexafluoroarsenate, or the like.
In some embodiments, the organic salt includes at least one of a carboxylate, an alkoxide, and an aromatic salt compound, e.g., the organic salt includes lithium acetate, aluminum formate, magnesium acetate, aluminum isopropoxide, magnesium ethoxide, and lithium benzenesulfonate, or the like.
In some embodiments, the mass ratio of the salt substance to the first precursor ranges from 1.0 wt % to 20 wt %. In some embodiments, the mass ratio of the salt substance to the first precursor can be, for example, 1 wt %, 5 wt %, 10 wt %, 15 wt % and 20 wt %, or the like, and can also be other values within the above range, which is not limited herein. If the mass ratio of the salt substance to the first precursor is greater than 20 wt %, the capacity of the material is reduced; if the mass ratio of the salt substance to the first precursor is smaller than 1 wt %, a molten salt system is formed too little, and the obtained fiber material 4 is rare or even unavailable.
In some embodiments, the mixing is performed in a protective atmosphere. The protective atmosphere includes at least one of helium and argon.
In some embodiments, the mixing time ranges from 30 min to 360 min, e.g., the mixing time can be 30 min, 60 min, 90 min, 180 min, 210 min, 240 min, 280 min, 300 min, 350 min or 360 min, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the mixing is performed under stirring conditions, and the mixing device can be, for example, a blender or a ball mill.
In some embodiments, the mixture containing the silicon-oxygen raw material and the salt substance further includes a metal source, that is, in step S100, the silicon-oxygen raw material, the metal source and the salt substance are mixed to obtain a mixture, and a first heat treatment is performed on the mixture to obtain a first precursor.
In the process of the first heat treatment, the presence of the mixed salt molten salt system can improve the activity of the doping metal source and the doping depth of the metal source, so that the silicon-oxygen raw material, the molten salt system and the metal source form eutectic activation, and the silicon-oxygen raw material forms silicon fiber (silicon fiber and silicate fiber) under the catalytic action of the doping metal source, thereby improving the conductivity of the anode material and improving the lithium conduction capability of the anode material, so that the anode material can quickly receive electrons and lithium ions, thereby improving the rate performance and the first efficiency of the anode material.
In some embodiments, the metal source includes at least one of lithium metal, magnesium metal, sodium metal, calcium metal, copper metal, and titanium metal. The metal source can further include an active hydride formed by at least one of a lithium source, a magnesium source, a sodium source, a calcium source, a copper source, and a titanium source. In some embodiments, the metal source can be, for example, lithium, magnesium, aluminum, lithium hydride, aluminum hydride, or magnesium hydride, or the like.
In some embodiments, the mass proportion of the metal source in the first precursor ranges from 0 wt % to 15 wt %. In some embodiments, the mass proportion of the metal source in the first precursor can be, for example, 0 wt %, 3 wt %, 5 wt %, 7 wt %, 10 wt %, 12 wt % and 15 wt %, or the like, and can also be other values within the above range, which is not limited herein. The mass ratio of the metal source in the first precursor is greater than 15 wt %, resulting in poor conductivity and reduced capacity of the material.
In some embodiments, a device for the first heat treatment is a high-pressure reactor.
In some embodiments, the temperature of the first heat treatment ranges from 400° C. to 1200° C. In some embodiments, the temperature of the first heat treatment can be, for example, 400° C., 500° C., 600° C., 700° C., 800° C., 900° C., 1000° C., 1100° C. or 1200° C., or the like, and can also be other values within the above range, which is not limited herein. In the above temperature range of the heat treatment, the capacity and cycle of the material are improved.
In some embodiments, the heat preservation time of the first heat treatment ranges from 3 h to 24 h. In some embodiments, the heat preservation time of the first heat treatment can be, for example, 3 h, 5 h, 8 h, 10 h, 15 h, 18 h, 20 h, 24 h, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the heating rate of the first heat treatment ranges from 1° C./min to 10° C./min. In some embodiments, the heating rate of the first heat treatment can be, for example, 1° C./min, 2° C./min, 3° C./min, 4° C./min, 5° C./min, 6° C./min, 7° C./min, 8° C./min, 9° C./min or 10° C./min, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the pressure of the first heat treatment ranges from 0.1 MPa to 0.3 MPa. In some embodiments, the pressure of the first heat treatment is 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa or 0.3 MPa, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the first heat treatment is performed in a first protective atmosphere. The first protective atmosphere includes at least one of nitrogen, helium, and argon.
Step S200, the first precursor is mixed with a carbon source, and then a second heat treatment is performed to obtain an anode material.
In this step, the first precursor and the carbon source are mixed and then subjected to the second heat treatment. Under the catalytic action of the molten salt substance skeleton on the surface of the first precursor, a part of the carbon source generates carbon fiber and grows onto the surface of the material, and the silicon fiber also grow to the surface of the material, that is, the silicon fiber is distributed on the surface of the material, and the carbon fibers are also distributed on the surface of the material. The presence of the fiber material 4 described above improves the electrical conductivity of the anode material and improves the rate performance of the material.
It can be understood that after the first heat treatment and the second heat treatment, a composite coating layer mixed by the salt substance and the coating material can be obtained, or a double-layer coating layer can be obtained. In the double-layer coating layer, the material of the second coating layer 3 in the inner layer includes a salt substance, and the first coating layer 2 in the outer layer includes a carbon material. In addition, when the double-layer coating layer is formed, in the second heat treatment process, a part of the salt-containing substance enters the outer coating layer (i.e., the carbon layer) to form a dopant which can stabilize the SEI interface and inhibit irreversible expansion of the material. The doping elements of the dopant include at least one of N, P, B, S, O, F, Cl, Br, and I.
In some embodiments, the carbon source includes at least one of a solid carbon source and a gaseous carbon source. The solid carbon source includes at least one of asphalt, epoxy resin and phenolic resin. The gaseous carbon source includes at least one of methane, acetylene, ethylene, and propane.
In some embodiments, when the carbon source is a gaseous carbon source, the injection flow rate of the gaseous carbon source is 0.5 L/min to 3 L/min, in some embodiments, the injection flow rate of the gaseous carbon source can be, for example, 0.5 L/min, 1 L/min, 1.5 L/min, 2 L/min, 2.5 L/min and 3 L/min, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, when the carbon source is a gaseous carbon source, the temperature of the second heat treatment ranges from 500° C. to 1000° C., and the temperature of the second heat treatment can be, for example, 500° C., 600° C., 700° C., 800° C., 900° C. or 1000° C., or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, when the carbon source is a gaseous carbon source, the heat preservation time of the second heat treatment ranges from 0.5 h to 5 h, in some embodiments, the heat preservation time of the first heat treatment can be, for example, 0.5 h, 1 h, 2 h, 3 h, 4 h and 5 h, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, when the carbon source is a solid carbon source, the mass ratio of the first precursor to the carbon source is 1:(0.01 to 0.1), for example, the mass ratio of the first precursor to the carbon source can be 1:0.01, 1:0.05, 1:0.1, 1:0.5, 1:0.8 or 1:0.1, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, when the carbon source is a solid carbon source, the temperature of the second heat treatment ranges from 400° C. to 800° C., and the temperature of the second heat treatment can be, for example, 400° C., 500° C., 600° C., 700° C. or 800° C., or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, when the carbon source is a solid carbon source, the heat preservation time of the second heat treatment ranges from 0.5 h to 10 h, in some embodiments, the heat preservation time of the first heat treatment can be, for example, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, when the carbon source is a solid carbon source, the second heat treatment is performed in a second protective atmosphere, the second protective atmosphere includes at least one of nitrogen, helium, and argon.
In some embodiments, the heating rate of the second heat treatment ranges from 1° C./min to 10° C./min, for example, the heating rate of the second heat treatment can be, for example, 1° C./min, 2° C./min, 3° C./min, 5° C./min, 8° C./min or 10° C./min, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the preparation method of the present disclosure further includes: after the second heat treatment, the method further includes a step of washing and drying the material obtained by the second heat treatment with water. Excess water-soluble salt in the material is removed through washing with water, so that the ratio of silicon to oxygen in the material is increased, and the capacity of the anode material is improved.
In some embodiments, before the washing with water, the method further includes: a step of soaking and filtering the material obtained by the second heat treatment in water to fully dissolve the salt and washing the filtered solid with water.
In some embodiments, the soaking time ranges from 10 min to 60 min, in some embodiments, the soaking time can be, for example, 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the soaking is performed under the stirring condition at a stirring speed of 100 r/min to 500 r/min, in some embodiments, the stirring speed can be, for example, 100 r/min, 150 r/min, 200 r/min, 250 r/min, 300 r/min, 350 r/min, 400 r/min or 500 r/min, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the soaking temperature ranges from 25° C. to 80° C., in some embodiments, the soaking temperature is 25° C., 30° C., 40° C., 50° C., 60° C., 70° C. or 80° C., or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the water washing time ranges from 30 min to 90 min, in some embodiments, the water washing time can be, for example, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, or the like, and can also be other values within the above range, which is not limited herein.
In some embodiments, the flow rate of the water washing ranges from 5 L/min to 20 L/min, in some embodiments, the flow rate of the water washing is 5 L/min, 10 L/min, 15 L/min, 20 L/min, or the like, and can also be other values within the above range, which is not limited herein.
In summary, in the present disclosure, a salt substance and a metal source are added in the process for preparing the anode material, so that the core and/or the carbon material can be catalyzed to grow a fibrous substance. Under a molten salt system formed by the salt substance, the metal source can catalyze the core to generate silicon fiber by using the metal source, and the silicon fiber is radially distributed inside the core and the coating layer and mainly distributed on the surface of the anode material. The carbon material can also be catalyzed to generate the carbon fiber under a molten salt system formed by the salt substance, and the carbon fiber is distributed inside and on the surface of the coating layer.
The present disclosure also provides a lithium ion battery including an anode material as described above.
The present disclosure will be further described by using following examples.
The SEM image of the anode material prepared in this example is shown in
An SEM image of the anode material prepared in this example is shown in
An SEM image of the anode material prepared in this example is shown in
In the anode material prepared in this example, the anode material includes a silicon monoxide, a salt coating layer and a carbon layer that sequentially coat the silicon monoxide, and the salt coating material is a solid solution deposit of lithium fluoride, aluminum fluoride, lithium titanate, and aluminum carbonate. The surface of the carbon layer is distributed with carbon fiber, silicon fiber and silicate fiber, mainly silicon fiber.
Different from Example 1, the salt substance “7.5 g lithium fluoride, 7.5 g lithium carbonate and 5 g lithium phosphate” in step (1) was replaced with “5 g lithium titanate, 5 g lithium carbonate, 5 g lithium phosphate and 5 g lithium nitrate”.
In the anode material prepared in this example, the anode material includes a silicon monoxide core to coat a carbon layer on the surface of the silicon monoxide, the molten salt is washed and removed in step (4). The surface of the carbon layer is distributed with carbon fiber, silicon fiber and silicate fiber, mainly carbon fiber.
The anode material prepared in this example includes silicon monoxide, and a salt coating layer and a carbon layer which sequentially coat the silicon oxide. The material of the salt coating layer is a solid solution deposit of lithium fluoride and lithium carbonate. The surface of the carbon layer is distributed with carbon fiber, silicon fiber and silicate fiber, mainly carbon fiber.
In the anode material prepared in this example, the anode material includes a silicon monoxide, a salt substance coated on a surface of the silicon monoxide, and a composite coating layer of amorphous carbon, the salt substance is a solid solution deposit of lithium fluoride, lithium carbonate, and lithium phosphate. A surface of the composite coating layer is distributed with carbon fiber, silicon fiber, and silicate fiber, mainly silicon fiber and silicate fiber.
In the anode material prepared in this example, the anode material includes silicon monoxide, a salt coating layer and a carbon layer that sequentially coat the silicon monoxide, the salt coating layer is made of a solid solution deposit of lithium fluoride, lithium carbonate, and lithium phosphate. The surface of the carbon layer is distributed with carbon fiber.
900 g of silicon monoxide was weighed to prepare a carbon coating layer by chemical vapor deposition, and the preparation process is as follows: the carbon source was methane, the inlet gas flow rate of methane is 2 L/min, the temperature was 800° C., and the deposition time was 0.5 h, the anode material was obtained.
The anode material prepared in the Comparative Example includes a silicon monoxide core and a carbon layer coated on the surface of the silicon monoxide, the carbon layer is smooth, and the SEM image of the anode material is shown in
The anode material prepared in the Comparative Example includes a silicon monoxide core and a carbon layer coated on the surface of the silicon monoxide, the carbon layer is smooth, and the SEM image of the anode material is shown in
Different from Example 1, step (3) was not performed.
The anode material prepared in the Comparative Example includes a silicon monoxide core and a coating layer coated on a surface of the silicon monoxide, and a material of the coating layer is a solid solution deposit of lithium fluoride, lithium carbonate, and lithium phosphate. The SEM image of the anode material is shown in
Different from Example 1, the salt substance “7.5 g lithium fluoride, 7.5 g lithium carbonate and 5 g lithium phosphate” in step (1) was replaced with “20 g lithium carbonate”.
Step (2): the pre-material mixed in step (1) was transferred into a high-pressure reactor, heated to 1000° C. at 10° C./min in an argon atmosphere, reacted for 10 h, and the pressure in the sealed reactor was freely increased.
The test results are shown in Table 1 and Table 2.
As shown in Table 1 and Table 2, the anode material prepared in Examples 1 to 8 of the present disclosure includes a core and a coating layer at least coating the surface of the core, at least part of the surface of the coating layer is distributed with a fiber material, and due to the presence of the fiber material on the surface of the material, and the fiber and the anode material satisfy the formula (I), it indicates that the fiber material 4 of the anode material grows well in the radial direction. The fiber material 4 growing well in the radial direction can effectively reduce the load transfer impedance caused by lithium intercalation, improve the mass transfer efficiency, form a fast lithium intercalation channel, facilitate the in-situ conduction of the material and the lithium source, reduce the interface obstruction, improve the lithium conduction capability of the anode material, enable the anode material to quickly receive electrons and lithium ions, improve the conductivity of the anode material, and improve the rate performance of the anode material. Further, the anode material is of a core-shell structure, the carbon material is used as a coating layer, the conductive contact area of the material can be improved, and the rate performance of the anode material is further improved.
In
The anode material prepared in Example 5, in a molten salt system without salt deposition, can still show high mass transfer and load transfer performance through carbon fiber-carbon coating-core.
In the anode material prepared in Comparative Example 3, although the surface of the material is distributed with the fiber material, the surface of the material lacks a coating layer, resulting in performance deterioration of the anode material.
As shown in
It can be seen from Table 2 that, compared with a conventional anode material with a charging capacity of about 0.5C at normal temperature, the anode active material of the lithium ion battery provided by the examples of the present disclosure can satisfy daily requirements under the condition of 3C rapid charging at normal temperature, and can maintain good performance at low temperature.
The above are merely exemplary embodiments of the present disclosure, which, as mentioned above, are not used to limit the present disclosure. For those skilled in the art, the present disclosure can be subject to various modifications and changes. Whatever within the principles of the present disclosure, including any modification, equivalent substitution, improvement, etc., shall fall into the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202211711132.6 | Dec 2022 | CN | national |
This application is a continuation of International Application No. PCT/CN2023/118419, filed Sep. 13, 2023, which claims priority to Chinese Patent Application No. 202211711132.6, filed Dec. 29, 2022 the entire disclosures of which are hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2023/118419 | Sep 2023 | WO |
| Child | 19020738 | US |
