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CN-116130636-B - Silicon-carbon material, negative plate and battery

CN116130636BCN 116130636 BCN116130636 BCN 116130636BCN-116130636-B

Abstract

The invention relates to the technical field of batteries, in particular to a silicon-carbon material negative plate and a battery. The silicon-carbon material comprises porous carbon as a skeleton structure and a filler filled in pores of the porous carbon, the filler in an inner layer of the silicon-carbon material comprises silicon, and the filler in a surface layer of the silicon-carbon material comprises a material containing F, P, S elements. The silicon-carbon material has the characteristics of high gram capacity, high surface structure and high electrochemical stability, can reduce the occurrence of interfacial side reactions, and greatly improves the cyclic charge and discharge performance, the negative plate comprising the silicon-carbon material has the characteristic of slow thickness growth at high temperature cycle, and the battery comprising the negative plate has the characteristics of high average coulomb efficiency at high temperature cycle and slow thickness growth.

Inventors

  • FAN HONGSHENG
  • Zeng changan
  • WANG HUI
  • LIU CHUNYANG
  • LI SULI

Assignees

  • 珠海冠宇电池股份有限公司

Dates

Publication Date
20260512
Application Date
20230304

Claims (11)

  1. 1. A silicon-carbon material comprising porous carbon as a skeleton structure and a filler filled in pores of the porous carbon, the filler in an inner layer of the silicon-carbon material being silicon, the filler in a surface layer of the silicon-carbon material comprising a material containing F and P and S elements, wherein there is a difference in kinds of elements in the surface layer and the inner layer in the silicon-carbon material, and a weight ratio between F element and P element and S element in the material containing F and P and S element satisfies one or more of the relational expressions (I-1), (II-1), (III-1): 0.04< m P /m F <0.35, formula (I-1); 0.02< m S /m F <0.25, formula (II-1); 0.3< m S /m P <1, formula (III-1).
  2. 2. The silicon-carbon material as claimed in claim 1, wherein the silicon-carbon material comprises C element, si element, F element, P element and S element, wherein the weight content alpha of the C element satisfies 30wt% or less than 80wt% and/or the weight content beta of the Si element satisfies 15wt% or less than 70wt% and/or the sum gamma of the weight contents of the F element, P element and S element satisfies 0.5wt% or less than 9wt% and the sum of alpha, beta and gamma satisfies 93wt% or less than alpha+beta+gamma <100wt%.
  3. 3. The silicon-carbon material as claimed in claim 2, wherein the weight content α of the C element satisfies 40 wt.% or less and 55 wt.% α or less, the weight content β of the Si element satisfies 40 wt.% or less and 55 wt.% β or less, the sum γ of the weight contents of the F element, the P element, and the S element satisfies 2.5 wt.% or less and 5.5 wt.% γ or less, and the sum α, β, γ satisfies 94 wt.% or less and 94 wt.% α+β+γ or less and 97.5 wt.% based on the total weight of the silicon-carbon material.
  4. 4. The silicon-carbon material according to claim 1, wherein Li element is included in the filler in the surface layer of the silicon-carbon material.
  5. 5. The silicon-carbon material according to claim 4, wherein a ratio of the weight of the Li element to the sum of the weights of the F element and the P and S elements satisfies 0.1< m Li /(m F +m P +m S ) <0.45, formula (IV-1).
  6. 6. The silicon-carbon material of claim 1 wherein the porous carbon is porous hard carbon; And/or the porous carbon has an average pore diameter of 0.5nm to 20nm; And/or the porous carbon has a median particle diameter of 1 μm to 15 μm; and/or the specific surface area of the silicon carbon material is <20m 2 /g; and/or the silicon carbon material has a median particle diameter of 1 μm to 15 μm; And/or, in the silicon carbon material, the maximum thickness of the surface layer is 50-1000nm.
  7. 7. The silicon-carbon material as claimed in claim 6, wherein the porous carbon has an average pore diameter of 1nm to 6nm; And/or the porous carbon has a median particle diameter of 5 μm to 12 μm And/or the silicon carbon material has a median particle size of 5 μm to 12 μm; and/or, in the silicon carbon material, the maximum thickness of the surface layer is 100-600nm.
  8. 8. The silicon carbon material as defined in claim 1 wherein the material containing F and P and S elements comprises one or more of lithium difluorooxalato borate, lithium difluorobis-oxalato phosphate, lithium difluorosulfimide, lithium bistrifluoromethylsulfonimide, lithium fluoride, sodium fluoride, lithium hexafluorophosphate, lithium dihydrogen phosphate, lithium phosphate, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, lithium sulfate, sodium sulfate, fluoroethylene carbonate, 1, 3-propane sultone, ethylene sulfate, and the material containing F and P and S elements comprises F element and P element and S element.
  9. 9. A negative electrode sheet, characterized in that the negative electrode sheet comprises the silicon-carbon material as claimed in any one of claims 1 to 8.
  10. 10. The negative electrode sheet according to claim 9, wherein the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer including the silicon carbon material; And/or the silicon carbon material is contained in an amount of 1 to 50wt% based on the total weight of the anode active material layer.
  11. 11. A battery, characterized in that it comprises a silicon-carbon material according to any one of claims 1-8 and/or a negative plate according to claim 9 or 10.

Description

Silicon-carbon material, negative plate and battery Technical Field The invention relates to the technical field of batteries, in particular to a silicon-carbon material, a negative plate comprising the silicon-carbon material and a battery. Background The theoretical gram capacity of silicon is about ten times that of graphite, which is a significant advantage in next generation high energy density lithium ion battery applications. However, the volume change of silicon is large in the process of intercalation and deintercalation, a Solid Electrolyte Interphase (SEI) film which exists on the surface of the silicon and plays a role in protection is extremely easy to break, so that side reactions continuously occur, the capacity retention rate of cyclic charge and discharge is fast in decay, and the thickness expansion rate is increased. This phenomenon is particularly serious at high temperature cycles. At present, a coating mode is generally adopted to enhance the interface stability of a silicon-based material, and the composition materials of the coating layer comprise amorphous carbon, artificial SEI film coating, polymer coating, metal oxide and the like. However, the volume change rate of the silicon-based material is generally greater than 50%, the long-term integrity of the coating layer structure is difficult to maintain, and the high-temperature cycle performance of the silicon-based material cannot meet the application requirements. Therefore, the invention of the silicon-carbon material with high interface stability has important significance for improving the high-temperature cycle performance of the high-energy-density battery. Disclosure of Invention The invention aims to overcome the problems in the prior art and provide a silicon-carbon material, a negative plate comprising the silicon-carbon material and a battery. The silicon-carbon material has the characteristics of high gram capacity, high surface structure and high electrochemical stability, can reduce the occurrence of interfacial side reactions, greatly improves the cyclic charge and discharge performance, has the characteristic of slow thickness growth at high temperature cycle, and has the characteristics of high average coulomb efficiency and slow thickness growth at high temperature cycle. The inventors of the present invention found that the cycling stability of the negative electrode sheet and the battery can be improved by improving the interfacial stability of the silicon carbon material. The inventor of the invention further researches and discovers that in order to improve the interface stability of the silicon-carbon material, the interface structure stability of the silicon-carbon material can be improved by constructing a specific structure, and the interface electrochemical stability of the silicon-carbon material is improved by introducing specific elements, so that the occurrence of side reactions of the interface of the silicon-carbon material is reduced, the high-temperature cycle thickness growth speed of a negative plate is reduced, the high-temperature cycle coulomb efficiency of a battery is improved, and the thickness growth speed is reduced. Through a great deal of intensive research, the inventor screens out specific elements capable of improving the electrochemical stability of the interface of the silicon-carbon material. In order to achieve the above object, a first aspect of the present invention provides a silicon carbon material including porous carbon as a skeleton structure and a filler filled in pores of the porous carbon, the filler in an inner layer of the silicon carbon material being silicon, the filler in a surface layer of the silicon carbon material including a material containing F, P, S elements. The second aspect of the invention provides a negative electrode sheet comprising the silicon-carbon material according to the first aspect of the invention. In one example, the negative electrode sheet includes a negative electrode current collector and an active material layer including the silicon carbon material. A third aspect of the invention provides a battery comprising a silicon carbon material according to the first aspect of the invention and/or a negative electrode sheet according to the second aspect of the invention. Through the technical scheme, compared with the prior art, the invention has at least the following advantages: (1) The silicon-carbon material has high gram capacity and high interface structure stability; (2) The silicon-carbon material has high gram capacity and high electrochemical stability of an interface; (3) The silicon-carbon material has high gram capacity and small occurrence of interface side reaction; (4) The thickness of the negative plate is slowly increased during high-temperature circulation; (5) The battery has high average coulomb efficiency in high-temperature circulation; (6) The thickness of the battery of the invention increases slowly during high te