CN116598452B

CN116598452B - Silicon-carbon negative electrode material and preparation method and application thereof

Info

Publication number: CN116598452B
Application number: CN202310545727.7A
Authority: CN
Inventors: 吴建华; 简正军; 冯荣标; 吴易华
Original assignee: Jiangmen Hechuang Energy Materials Co ltd
Current assignee: Jiangmen Hechuang Energy Materials Co ltd
Priority date: 2023-05-15
Filing date: 2023-05-15
Publication date: 2024-03-12
Anticipated expiration: 2043-05-15
Also published as: CN116598452A

Abstract

The invention discloses a silicon-carbon anode material, a preparation method and application thereof, and belongs to the technical field of secondary battery materials. The silicon-carbon anode material provided by the invention comprises a core and a shell; the true density of the silicon-carbon anode material is ρ _RD The method comprises the steps of carrying out a first treatment on the surface of the The core comprises a porous carbon skeleton and silicon-based components dispersed therein; the pore volume of the porous carbon skeleton is PV, and the true density is ρ _C The method comprises the steps of carrying out a first treatment on the surface of the The true density of the silicon-based component is ρ _Si The method comprises the steps of carrying out a first treatment on the surface of the The parameters meet the constraint of mathematical relationship, and ρ is not less than 1.5g/cc _RD ≤2.4g/cc；0.45cc/g≤PV≤1.55cc/g；1g/cc≤ρ _Si ≤2.35g/cc；1.2g/cc≤ρ _C Less than or equal to 2.28g/cc. The silicon-carbon anode material provided by the invention can improve the cycle performance, the multiplying power performance and the safety performance on the basis of no obvious volume change. The invention also provides a preparation method and application of the silicon-carbon anode material.

Description

Silicon-carbon negative electrode material and preparation method and application thereof

Technical Field

The invention relates to the technical field of secondary battery materials and preparation methods thereof, in particular to a silicon-carbon negative electrode material and a preparation method and application thereof.

Background

In the current power battery and consumer battery markets, lithium ion batteries become an absolute mainstream energy storage system because of great advantages in terms of voltage, service life, self-discharge, energy density and the like. And also because of the continuous improvement demands of different use scenes on the endurance of the lithium ion battery, improving the Energy Density (ED) (volume energy density VED, mass energy density GED) of the lithium ion battery is a final target on the premise that other basic performances are met.

Both the positive and negative electrode materials affect the energy density of the lithium ion battery. The positive electrode material has reached the limit of capacity exertion in the process use or has low lifting ratio (150/175 mAh/g of lithium iron phosphate, 190/205mAh/g of nickel cobalt manganese ternary positive electrode and 142/148mAh/g of lithium manganate). Graphite is a commonly used commercial negative electrode material due to its high stability and proper voltage, but graphite negative electrodes have also reached a capacity and first efficiency compromise (355/372 mAh/g). In order to break through the bottleneck of energy density, silicon-based negative electrodes are gradually used by consumer batteries and start to develop into power batteries, the main value of the silicon-based negative electrodes is ten times as high as graphite (4200 mAh/g vs 372 mAh/g), but at the same time, because the silicon-based negative electrodes can accommodate a large amount of lithium ions for alloying reaction, the silicon-based negative electrodes can generate volume expansion of more than 300% in the process of lithium deintercalation of battery circulation. The volume expansion can significantly affect the cycling performance of the silicon-based negative electrode material.

The route of the silicon-based negative electrode mainly comprises a silicon-oxygen route, a pre-lithiated silicon-oxygen material and a silicon-carbon material. In the silicon-oxygen route, the first effect of the cathode material is low (76%), which can cause a great deal of loss of active lithium ions of the cathode; the pre-lithiated silica material can compensate the problem of low first effect of the silica material to a certain extent, but the lithium source used in the pre-lithiation process is expensive, and the first effect is improved to be close to the limit (82 percent); most of the traditional silicon-carbon materials are prepared by mixing and grinding a silicon source and a carbon source so as to reduce the particle size of the silicon source, the lower limit of the particle size of silicon particles in the grinding method is very close to that of silicon particles (in the shape of a sheet with the thickness of 20nm and the length of 100 nm), but the obtained silicon-carbon materials still cannot solve the structural impact on a battery cell caused by lithium intercalation expansion.

In summary, the current industrial lead-in verification proves that the common scheme route of the silicon-based negative electrode reaches the design limit of capacity: 390mAh/g, 420mAh/g, 400mAh/g; and the problem of volume expansion of the obtained silicon-based anode material still cannot be well solved, namely, the cycle performance and other electrochemical performances of the battery comprising the silicon-based anode material are still to be further improved.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the silicon-carbon negative electrode material provided by the invention can effectively improve the multiplying power performance and the cycle performance of the silicon-carbon negative electrode material.

The invention also provides a preparation method of the silicon-carbon anode material.

The invention also provides a lithium ion battery comprising the silicon-carbon anode material.

The invention also provides application of the lithium ion battery.

According to an embodiment of the first aspect of the present invention, there is provided a silicon-carbon anode material including a core and a shell wrapped on a surface of the core; the true density of the silicon-carbon anode material is ρ _RD ；

The core comprises a porous carbon skeleton and a silicon-based component dispersed in the porous carbon skeleton; the pore volume of the porous carbon skeleton is PV, and the true density is ρ _C The method comprises the steps of carrying out a first treatment on the surface of the The true density of the silicon-based component is ρ _Si ；

And satisfies formula (I):

wherein: ρ is 1.5g/cc _RD ≤2.4g/cc；0.45cc/g≤PV≤1.55cc/g；1g/cc≤ρ _Si ≤2.35g/cc；1.2g/cc≤ρ _C ≤2.28g/cc。

The silicon-carbon anode material provided by the embodiment of the invention has at least the following beneficial effects:

(1) In the prior art, most of silicon-based materials are crushed by a mechanical method so as to obtain the silicon-based materials with small particle sizes, which can relieve volume expansion, but the effect obtained by the technical means is not obvious.

According to the preparation method provided by the invention, the silicon-based component is limited to be dispersed in the porous carbon skeleton, so that the particle size of the silicon-based component can be limited according to the size of the pores of the porous carbon skeleton, the particle size of the silicon-based component is more convenient to adjust, the range is more, and the electrochemical performance reduction caused by the volume expansion of the silicon-based component in the charge and discharge processes can be avoided as much as possible.

Specifically, the fully embedded expansion of the silicon carbon anode material provided by the invention is reduced by about 50% compared with that of the silicon carbon material by a traditional grinding method.

(2) Compared with the traditional silicon-carbon (Si abrasive particles produced by Samsung and other enterprises are degraded, and are 20nm thin, 100nm long and sheet-shaped), the silicon-carbon negative electrode material provided by the invention has the advantages that the silicon-based components are uniformly dispersed in the porous carbon skeleton, so that the dispersion degree of the silicon-based components is improved to be maximized, the stress distribution of the silicon-carbon negative electrode material is maximized by the lithium intercalation-deintercalation expansion of the silicon-based components, and the impact of the expansion of the silicon-based components on a battery core structure in a lithium ion battery is minimized. In addition, the dispersion distribution mode can obviously promote the synergistic effect between the silicon-based component and the porous carbon skeleton and promote the electronic conductivity and the ionic conductivity of the silicon-carbon anode material. And finally, the cycle performance and the rate capability of the obtained silicon-carbon anode material are improved.

(3) The silicon-carbon anode material provided by the invention is provided with the shell, so that other gases such as hydrogen and the like which are unfavorable for the production of the cell process can be protected after the silicon-carbon anode material is stirred in the water-based binder and eroded and oxidized in the pulping process in the cell preparation process.

(4) The silicon-carbon negative electrode material is high in gram volume density, even though the gram volume density is high, if the true density is too low, the volume density of the silicon-carbon negative electrode material is low, so that the true density is a key index of whether the silicon-carbon negative electrode material can bring about the improvement of the cutting energy density for the battery cell. The invention limits the parameters of the true density of the silicon-carbon negative electrode material, the pore volume of the porous carbon skeleton, the true density of the silicon-based component and the like, and can realize the maximum inhibition of the volume impact of the volume change caused by the lithium intercalation removal of the silicon-based component in the silicon-carbon negative electrode material on the particles of the silicon-carbon negative electrode material per se: finally, a great amount of application and introduction of the silicon-based component in the cell cathode are realized.

(5) The invention selects a porous carbon skeleton with proper parameters according to the grain diameter and crystalline structure which can be achieved by the silicon-based component production process, and regulates and controls the space provided by the porous carbon skeleton for the silicon-based component and the mechanical strength of the porous carbon skeleton, thereby synthesizing the silicon-carbon anode material for the lithium ion battery with low expansion and high compatibility. That is, synergy occurs among the pore structure (pore volume), mechanical strength (pressure bearing capability), graphitization degree (true density), particle size of the silicon-based component (limited by pore diameter), dispersity of distribution (affected by pore distribution), crystalline structure (true density of the silicon-based component), and the like, and the comprehensive performance of the porous carbon skeleton is remarkably improved.

Specifically, on the premise of meeting the current expansion of the battery cell, the composite gram capacity of the silicon-graphite composite negative electrode system can only be about 400 mAh/g. However, the silicon-carbon negative electrode material and graphite provided by the invention are used in a compounding way, so that the negative electrode compound gram capacity is improved from 355mAh/g of graphite to 500mAh/g, and even the upper limit can reach 800mAh/g on the soft package cell volume expansion noninductive layer in different cell structure designs.

According to some embodiments of the invention, in formula (I), ρ _RD 1.75 to 2.25g/cc. For example, it may be about 1.9g/cc, 2.1g/cc or 2.2g/cc.

According to some embodiments of the invention, in formula (I), the PV is from 0.55 to 0.95cc/g. For example, it may be about 0.65cc/g, 0.7cc/g, 0.75cc/g or 0.9cc/g.

According to some embodiments of the invention, in formula (I), ρ _Si 1.25 to 1.75g/cc.

According to some embodiments of the invention, in formula (I), ρ _C 1.5 to 2.2g/cc. For example, it may be about 1.8g/cc or 2.1g/cc.

According to some embodiments of the invention, the silicon-based component comprises W in mass percent of the silicon-carbon anode material _Si The lithium intercalation capacity of the silicon-carbon anode material is CAP; and satisfies formula (II);

180≤CAP-3769×W _Si less than or equal to 680, formula (II);

wherein, W is more than or equal to 30 percent _Si ≤60％。

According to some embodiments of the invention, in formula (II), W _Si The range of the value of (C) is 30-57%.

According to some embodiments of the invention, in formula (II), W _Si The value range of (2) is 35-55%.

According to some embodiments of the invention, in formula (II), W _Si The value range of (2) is 43-47%. For example, it may be about 45%.

According to some embodiments of the invention, the silicon-based component has a particle size D _Si Is defined in the following range: d is less than or equal to 2nm _Si Less than or equal to 10nm. The upper limit of the particle size of the silicon-based component is limited by the pore size in the multi-carbon skeleton. But when the pore diameter is less than or equal to the above pore diameter, D _Si Can be adjusted according to the actual preparation process.

According to some embodiments of the invention, the silicon carbon anode material has a tap density ρ of _TD The range of (2) is: rho of 0.8g/cc _TD ≤1.2g/cc。

According to some embodiments of the invention, the silicon carbon anode material has a tap density ρ of _TD In the range of 0.82 to 1.13g/cc.

According to some embodiments of the invention, the silicon carbon anode material has a tap density ρ of _TD In the range of 0.84 to 1.1g/cc.

According to some embodiments of the invention, the silicon carbon anode material has a tap density ρ of _TD In the range of 0.92 to 0.97g/cc. For example, it may be about 0.95g/cc.

According to some embodiments of the invention, the particle size of the silicon carbon anode material satisfies: d is more than or equal to 0.45 mu m _n10 ≤1μm。

According to some embodiments of the invention, the particle size of the silicon carbon anode material satisfies: d is less than or equal to 1.2 mu m _V10 ≤5.2μm、6μm≤D _V50 ≤9μm、11μm≤D _V90 ≤18μm、19μm≤D _V99 ≤26μm、27μm≤D _VMAX ≤35μm。

According to some embodiments of the invention, the sum of the mass percentages of silicon element and carbon element in the silicon-carbon anode material is >98%.

According to some embodiments of the invention, the shell comprises at least one of carbon, metal oxide, and organic polymer.

According to some embodiments of the invention, the metal oxide comprises at least one of aluminum oxide, iron oxide, magnesium oxide, cobalt oxide, nickel oxide, copper oxide, and zinc oxide.

According to some embodiments of the invention, the organic polymer comprises at least one of a conductive polymer and a non-conductive polymer.

The conductive polymer includes at least one of polyacetylene, polypyrrole, polythiophene, polyphenylacetylene, and polyaniline.

The non-conductive polymer includes at least one of polyethylene, polypropylene, polystyrene, epoxy resin, and phenolic resin.

According to some embodiments of the invention, the shell comprises 0.7-5.3% of the silicon-carbon negative electrode material by mass.

According to some embodiments of the invention, the shell comprises 1.5-2.5% of the silicon carbon negative electrode material by mass. For example, it may be about 1.9%, 2.1% or 2.2%.

According to some embodiments of the invention, the FCE of the silicon-carbon negative electrode material _2.0V The method comprises the following steps: FCE of 84% or less _2.0V ≤94.5％。

According to some embodiments of the invention, the FCE of the silicon-carbon negative electrode material _2.0V The range of (2) is 86 to 94%.

According to some embodiments of the invention, the FCE of the silicon-carbon negative electrode material _2.0V The range of (2) is 87 to 91.5%.

According to some embodiments of the invention, the FCE of the silicon-carbon negative electrode material _2.0V The range of (2) is 88 to 91%. For example, it may be about 89% or 90%.

According to some embodiments of the invention, the FCE of the silicon-carbon negative electrode material _0.8V The method comprises the following steps: FCE of 75% or less _0.8V ≤84.5％。

According to some embodiments of the invention, the FCE of the silicon-carbon negative electrode material _0.8V The range of (2) is 78 to 83%.

According to some embodiments of the invention, the FCE of the silicon-carbon negative electrode material _0.8V The range of (2) is 78 to 82.5%. For example, it may be about 80% or 81%.

Wherein the FEC here is: the silicon-carbon negative electrode material is used as a test electrode, a lithium sheet is used as a counter electrode, and the first effect of the silicon-carbon negative electrode material is achieved when the button cell is assembled; further specifically, FCE _2.0V For a test voltage upper limit of 2.0V, the silicon carbonFirst effect of negative electrode material, FCE _0.8V And when the upper limit of the test voltage is 0.8V, the first effect of the silicon-carbon anode material is achieved.

According to some embodiments of the invention, the gram specific capacity of the silicon-carbon negative electrode material is 1600-2600 mAh/g. For example, about 1650mAh/g, 2000mAh/g, 2100mAh/g, 2150mAh/g, 2180mAh/g, 2200mAh/g or 2500mAh/g may be mentioned.

According to some embodiments of the invention, the silicon-carbon anode material is used as an anode piece of the anode active material, and the thickness increase proportion is less than or equal to 140% when lithium is fully intercalated. Therefore, when the graphite anode is mixed with a graphite anode to serve as an anode active material, the gram specific capacity of the anode can be obviously improved on the basis of no obvious volume expansion. The thickening ratio is as low as 83%, and may be, for example, about 85%, 90%, 95%, 100% or 110%.

According to an embodiment of the second aspect of the present invention, there is provided a preparation method of the silicon carbon anode material, the preparation method including the steps of:

s1, cracking a carbon raw material to obtain the porous carbon skeleton;

s2, depositing the silicon-based component in the porous carbon skeleton to obtain the core;

s3, wrapping the substance obtained in the step S2 to form the shell.

The preparation method adopts all the technical schemes of the silicon-carbon anode material of the embodiment, so that the preparation method has at least all the beneficial effects brought by the technical schemes of the embodiment.

Furthermore, graphite is also used as a base material in the traditional technology, and the preparation method provided by the invention adopts the cracking carbon as a porous carbon skeleton, so that the preparation method has the following advantages:

(1) The graphite layer cleavage is obvious, interlayer slippage exists, the expansion inhibition effect on isotropy is poor, that is, the internal stress has obvious anisotropy.

(2) The cracking carbon has good controllability, can be synthesized from different organic raw materials, and has single graphite matrix and poor performance controllability.

(3) The pores of graphite are difficult to ream and modify, so in particles of micrometer scale, connectivity between the pores may be poor, i.e., the pores in porous graphite are difficult to uniformly distribute, and thus even if a silicon-based component is deposited therein, uniform dispersion distribution of the silicon-based component cannot be achieved.

The invention adopts the cracking carbon, and has the advantages of good isotropy, controllable performance, easy modification of pore structure and better distribution uniformity and dispersivity of silicon-based components.

The invention adopts a deposition method to produce the silicon-based component, is a bottom-up micro-nano particle construction method, has smaller particle size and is limited by the pore diameter of the porous carbon skeleton compared with the traditional top-down construction method such as grinding and the like, and can realize the maximum dispersion distribution of the silicon-based component in the porous carbon skeleton. Therefore, the stress impact of the volume change of the silicon-based component on the battery in the charging and discharging processes is further relieved.

According to some embodiments of the invention, the carbon feedstock comprises at least one of a bio-based carbon feedstock and other organics.

According to some embodiments of the invention, the bio-based carbon feedstock comprises at least one of corn stover, wheat straw, rice straw, peanut straw, soybean straw, sorghum straw, cotton straw, reed straw, common sweetgum fruit, common flowery herb, sesame straw, wood flour, peanut shells, husks, rice husks, walnut shells, rubber shells, bagasse, red-surgical-residue, soybean residue, pine needles, pine cones, apple branches, pear branches, peach branches, eucalyptus branches, pig manure, cow manure, sheep manure, chicken manure, kitchen waste, apples, and bananas.

According to some embodiments of the invention, the other organic matter includes at least one of benzene ring, c=c, nitrogen atom, sulfur atom, heterocycle, and bridged ring.

According to some embodiments of the invention, the temperature of the cleavage is 350-1200 ℃.

According to some embodiments of the invention, the temperature of the cleavage is 500-700 ℃. For example, it may be about 650 ℃.

According to some embodiments of the invention, the duration of the cleavage is between 0.5 and 24 hours.

According to some embodiments of the invention, the duration of the cleavage is 1 to 3 hours. For example, it may be about 2 hours.

Under the conditions of the temperature and the duration, the obtained cracking product can be directly used as a porous carbon skeleton or is convenient to carry out subsequent Kong Xiushi.

When the mass percentage of carbon and silicon in the silicon-carbon anode material is calculated, all carbon in the porous carbon skeleton generated by default pyrolysis is carbon.

According to some embodiments of the invention, in step S1, pore modification of the cleavage product after the cleavage is further included. Therefore, the deposition of the silicon-based component in the step S2 can be further facilitated, and the silicon-based component with target particle size and content can be obtained.

According to some embodiments of the invention, the Kong Xiushi includes at least one of reaming, plugging and chemical modification.

According to some embodiments of the invention, the method of pore modification comprises at least one of a physical method and a chemical method.

According to some embodiments of the invention, in Kong Xiushi, the chemical method comprises reaming the lysate with a base or salt. Thus, a large number of mesopores and micropores can be generated in the cleavage product.

The base includes at least one of potassium hydroxide and sodium hydroxide;

when the Kong Xiushi is carried out with a base, the method comprises immersing the cleaved product in an alkaline solution until the mesoporous structure of the product meets the requirements. The concentration of the lye is 1 to 4mol/L, and may be, for example, about 2mol/L or 3mol/L. The mass ratio of the alkali in the alkali liquor to the cracked product is 1:8-12. And may specifically be about 1:10. At this time, the temperature of the pore modification is 50 to 200 ℃. For example, it may be about 100℃or 175 ℃.

The salt includes at least one of potassium carbonate and zinc chloride.

According to some embodiments of the invention, in Kong Xiushi, the physical method comprises heat treating the pyrolysis product with carbon dioxide or water vapor. The resulting pyrolysis product may be reamed.

According to some embodiments of the invention, in Kong Xiushi, CVD deposition may also be performed in the holes using a carbon element-containing organic gas. I.e. filling holes, blocking holes, etc., and further finely modifying the pore volume distribution.

According to some embodiments of the invention, in step S2, the deposition method comprises a chemical vapor deposition method.

Specifically, the chemical vapor deposition method comprises diffusing a gaseous silicon source into pores of the porous carbon skeleton and then pyrolyzing, or comprises diffusing pyrolysis products of the gaseous silicon source into the pores of the porous carbon skeleton; or both mechanisms may occur simultaneously.

According to some embodiments of the invention, the silicon source is in a gas phase at 500 ℃.

According to some embodiments of the invention, the silicon source comprises at least one of silane and substituted silane.

According to some embodiments of the invention, the silane comprises SiH ₄ 、Si ₂ H ₆ 、Si ₂ H ₄ 、Si ₃ H ₈ 、Si ₃ H ₆ 、Si ₃ H ₄ 、Si ₄ H ₁₀ 、Si ₄ H ₈ 、Si ₄ H ₆ 、Si ₅ H ₁₂ 、Si ₅ H ₁₀ 、Si ₅ H ₈ 、Si ₅ H ₆ 、Si ₆ H ₁₄ 、Si ₆ H ₁₂ 、Si ₆ H ₁₀ 、Si ₆ H ₈ 、Si ₆ H ₆ 、Si ₇ H ₁₆ 、Si ₇ H ₁₄ 、Si ₇ H ₁₂ 、Si ₇ H ₁₀ 、Si ₇ H ₈ 、Si ₇ H ₆ 、Si ₈ H ₁₈ 、Si ₈ H ₁₆ 、Si ₈ H ₁₄ 、Si ₈ H ₁₂ 、Si ₈ H ₁₀ 、Si ₈ H ₈ 、Si ₉ H ₂₀ 、Si ₉ H ₁₈ 、Si ₉ H ₁₆ 、Si ₉ H ₁₄ 、Si ₉ H ₁₂ 、Si ₉ H ₁₀ 、Si ₉ H ₈ 、Si ₁₀ H ₂₂ 、Si ₁₀ H ₂₀ 、Si ₁₀ H ₁₈ 、Si ₁₀ H ₁₆ 、Si ₁₀ H ₁₄ And Si (Si) ₁₀ H ₁₀ At least one of them.

According to some embodiments of the invention, the substituted silane is obtained by substituting H of the silane with at least one of B, N, F, P, S and Cl.

Compared with the traditional silicon-oxygen material, the pre-lithiated silicon-oxygen material and the silicon-carbon material prepared by grinding, the silicon raw material adopted by the silicon-carbon anode material provided by the invention is a relatively upstream product in a silicon industry chain, and has obvious cost advantage in a calculation mode of unit capacity. Specifically, referring to the recent selling price of the silicon carbon of about 160w/ton, the silicon carbon negative electrode material provided by the invention can realize the advantage of 50% reduction of the cost of the silicon carbon negative electrode material on the premise of ensuring production profits.

According to some embodiments of the invention, the chemical vapor deposition of the silicon-based component is performed at a temperature of 250 ℃ to 1100 ℃.

According to some embodiments of the invention, the chemical vapor deposition of the silicon-based component is performed at a temperature of 450-800 ℃. For example, it may be about 600 ℃.

And the time when the chemical vapor deposition is finished is the time when the deposition of the designed dosage of the silicon-based component is finished. Typically between 3 and 12 hours. For example, it may be about 4 hours.

Under the condition of vapor deposition, uniform and diffuse deposition of the silicon-based component can be obtained, and parameters such as true density of the obtained silicon-based component can also fall within a designed value range.

When the mass percentage of carbon and silicon in the silicon-carbon anode material is calculated, the silicon-based component obtained by adopting the silane deposition is pure silicon by default.

According to some embodiments of the invention, in step S3, when the material of the shell includes carbon, the wrapping is performed by performing chemical vapor deposition with a gaseous precursor; wherein the gaseous precursor comprises acetylene. The temperature of the chemical vapor deposition is 350-750 ℃. For example, it may be about 500 ℃, 550 ℃ or 600 ℃. The deposition time is determined according to the feeding amount of the gaseous precursor until the gaseous precursor is completely reacted. For example, the time may be specifically 0.5 to 6 hours. And more specifically may be about 2 hours or 3 hours. The flow rate of the gaseous precursor is 1.5 to 7.5L/min, and may be about 4L/min, for example.

Under the above deposition conditions, the carbon coating layer formed is more uniform, and the quality of the obtained carbon coating layer is also substantially consistent with the design value.

According to some embodiments of the invention, in step S3, when the shell material comprises carbon, the encapsulation is performed by mixing a liquid precursor and the core and then pyrolysis; wherein the liquid precursor comprises pitch.

According to some embodiments of the invention, in step S3, when the material of the shell includes the metal oxide, the encapsulation includes at least one of spray drying, ALD, wet encapsulation, and ball milling. Wherein the wet coating comprises in situ deposition, i.e. placing the core in a dispersion comprising the shell precursor, such that the shell is deposited onto the surface of the core.

According to some embodiments of the invention, in step S3, when the material of the shell includes the organic polymer, the encapsulation, the method includes liquid-phase in-situ polymerization and drying performed sequentially.

According to an embodiment of the third aspect of the present invention, there is provided a lithium ion battery, wherein the preparation raw material of the lithium ion battery includes the silicon carbon material.

The lithium ion battery adopts all the technical schemes of the silicon-carbon anode material of the embodiment, so that the lithium ion battery has at least all the beneficial effects brought by the technical schemes of the embodiment.

Further, the lithium ion battery has the following beneficial effects:

(1) Because the silicon-carbon negative electrode material can remarkably improve gram specific capacity on the basis of no obvious volume expansion, when the silicon-carbon negative electrode material is used for preparing a lithium ion battery (taking a 4690 cylindrical cell which is the main stream of the current power battery as an example), compared with a traditional pure graphite system, the silicon-carbon negative electrode material can realize the improvement of GED (mass specific energy) of about 20 percent.

(2) Due to the constraint of structural design and parameters of the silicon-carbon anode material, the volume change of the silicon-carbon anode material in the charge and discharge process is obviously inhibited, and the silicon-carbon anode material has high structural compatibility in a lithium ion battery, so that the silicon-carbon anode material can be used in a large scale in the lithium ion battery, for example, the silicon-carbon anode material provided by the invention is used as an anode active material. Therefore, the lithium ion battery provided by the invention can greatly improve ED (energy density) due to the introduction of the silicon-carbon anode material.

In general, the lithium ion battery provided by the invention can obviously improve the energy density on the basis of maintaining the cycle performance and the multiplying power performance.

According to some embodiments of the invention, when the lithium ion battery is a button cell battery, the number of cycles required is greater than or equal to 665 weeks when the capacity decays to 80%. Up to 1105 weeks. Specifically, the time period may be 700 weeks, 800 weeks, 900 weeks or 1000 weeks.

According to some embodiments of the invention, when the lithium ion battery is a full battery and the test temperature is about 25 ℃, the number of turns required for capacity fade to 80% is greater than or equal to 620 turns. Up to 1320 turns. For example, it may be about 800, 900, 1100, 1200 or 1300 turns.

According to some embodiments of the invention, when the lithium ion battery is a full battery and the test temperature is about 45 ℃, the number of turns required for capacity fade to 80% is greater than or equal to 390 turns. Up to 1100 turns. Specifically, the number of turns may be about 650, 700, 800, 900 or 1000.

According to an embodiment of the fourth aspect of the present invention, there is provided the use of said lithium ion battery in the field of energy storage batteries, 3C batteries and power batteries.

The application adopts all the technical schemes of the lithium ion battery of the embodiment, so that the lithium ion battery has at least all the beneficial effects brought by the technical schemes of the embodiment.

The term "about" as used herein, unless otherwise specified, means that the tolerance is within + -2%, for example, about 100 is actually 100 + -2%. Times.100.

Unless otherwise specified, the term "between … …" in the present invention includes the present number, for example "between 2 and 3" includes the end values of 2 and 3.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram showing the main flow of the preparation method in example 1 of the present invention.

Detailed Description

The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.

In the description of the present invention, the descriptions of the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Example 1

The silicon-carbon negative electrode material is prepared by the embodiment, and comprises the following specific steps:

D1. pyrolyzing carbon source wood powder in the precursor at 650 ℃ in an air-isolated (nitrogen protection) way for 120min to obtain pyrolysis carbon; after the pore volume is tested, the pore volume is found to be not in accordance with the requirements of Table 1;

D2. kong Xiushi the cracked carbon obtained in the step D1 is subjected to alkali liquor;

wherein, the solute in the alkali liquor is sodium hydroxide, and the concentration is 2mol/L; the mass ratio of the alkali in the alkali liquor to the cracked carbon obtained in the step D1 is 1:10.

In this step, the pore volume test was performed at 100℃every 10min until the design in Table 1 (error within 2%) was satisfied, and Kong Xiushi was stopped. Obtaining the porous carbon skeleton.

D3. Placing the porous carbon skeleton obtained in the step D2 into a chemical vapor deposition chamber to obtain SiH ₄ As a silicon source, silicon deposition was performed at 600℃for 4 hours to obtain a core (the addition amount was calculated in terms of deposition amount). The amount of silicon deposited is shown in table 1. The flow of this step and the schematic diagram of the lithium removal and intercalation mechanism of the obtained core are shown in FIG. 1.

D4. And D3, continuously placing the core obtained in the step D3 in a chemical vapor deposition chamber, introducing a gas phase hydrocarbon gas source (acetylene is adopted in the embodiment), and performing CVD coating (carbon deposition), wherein the introduced gas flow of hydrocarbon is 4L/min, the temperature is 550 ℃, and the deposition time is 2 hours, so as to obtain the coated carbon quality in the table 1, namely the silicon-carbon anode material with the carbon shell coating.

In order to verify the influence of the design parameters of the silicon-carbon anode material on the final physical and chemical properties and the electrochemical properties, the invention also designs examples 2-9 and comparative examples 1-3.

To verify the effect of each parameter on the properties of the resulting silicon carbon negative electrode material, examples 2 to 9 and comparative examples 1 to 3 were designed according to the present invention.

The specific differences from example 1 are:

example 2

In step D2, the duration of silicon deposition is increased by 2h in example 2.

Example 3

In step D2, the duration of silicon deposition was increased by 3.5h in example 1.

Example 4

In step D4, the gas flow rate of acetylene was 50% in examples 1 to 3.

Example 5

In step D4, the gas flow rate of acetylene was 2.5 times that in examples 1 to 3.

Example 6

In step D2, the temperature of the pore modification was 50 ℃.

Example 7

In step D2, the temperature of the pore modification was 175 ℃.

Example 8

In the step D2, the concentration of the alkali liquor used by Kong Xiushi is 4mol/L, and the total modification time is the same.

Example 9

In the step D2, the concentration of the alkali liquor used by Kong Xiushi is 1mol/L, and the total modification time is the same.

Comparative example 1

Step D4 is not included.

Comparative example 2

Step D2 is not included.

Comparative example 3

In step D2, the duration of silicon deposition is reduced by 1h in example 1.

Test example 1

The physicochemical parameters of the silicon-carbon anode materials obtained in examples 1 to 9 and comparative examples 1 to 3 were first tested, and the specific method was as follows:

ρ _C and ρ _RD The test method of (2) is helium specific gravity method; the PV test method is a gas adsorption and desorption method, and the gas adopted is N ₂ And CO ₂ Then integrating the adsorption and desorption curves by using an NLDFT method to obtain a test value; ρ _Si Test method and ρ of (2) _C The test method is equivalent to the test method, and is specifically obtained by carrying out differential method calculation on the core after silicon loading and the porous carbon matrix. W (W) _Si And the mass ratio of the coated carbon is calculated by adopting a differential method, the differential before and after the step D3 is used for obtaining the mass of the deposited silicon-based component, and the differential before and after the step D4 is used for obtaining the mass of the deposited shell. The test results are shown in Table 1.

Table 1 physicochemical parameters of silicon carbon anode materials in examples 1 to 9 and comparative examples 1 to 3

Sequence number	W _Si ％	Coated carbon mass ratio	ρ _RD g/cc	PV cc/g	ρ _C g/cc	ρ _Si g/cc
							Example 1	32％	2.1％	1.67	0.71	1.8	1.57
Example 2	46％	2.2％	1.95	0.7	1.8	2.07
							Example 3	57％	1.9％	2.09	0.72	1.8	2.31
Example 4	47％	0.7％	1.96	0.73	1.8	2.08
							Example 5	43％	5.3％	1.93	0.71	1.8	2.03
Example 6	46％	2.2％	2.03	0.47	1.8	2.30
							Example 7	46％	1.9％	1.72	0.92	1.8	1.67
Example 8	46％	2.1％	1.93	0.69	1.6	2.23
							Example 9	46％	2.1％	1.96	0.72	2.1	1.87
Comparative example 1	48％	0％	1.96	0.71	1.8	2.09
							Comparative example 2	46％	1.9％	1.87	0.32	1.8	1.99
Comparative example 3	46％	2.1％	1.88	0.7	2.3	1.62

The present test example also tested the particle diameters of silicon-based components in the silicon-carbon anode materials obtained in examples 1 to 9 and comparative examples 1 to 3. The specific test method is to adopt FIB-TEM to carry out optical observation, but the particle size of the silicon-based component is generally less than 10nm, and the optical observation under the scale can only obtain the difference of brightness and contrast, so that the silicon, namely the particle size of the component, can only be obtained within the range of 2-10 nm, but cannot obtain a definite numerical value. But within this scale, it has been possible to alleviate as much as possible the volume change of the silicon-based component during delithiation. The application performance of the silicon-carbon anode material obtained by the invention in a lithium ion battery is improved.

The silicon carbon negative electrode materials obtained in examples 1 to 9 and comparative examples 1 to 3 were also tested for tap density. The electrochemical performance of the obtained silicon-carbon anode material in the button cell is tested, and the specific method is as follows:

testing electrode formula: si84% + CNTs slurry +10% PAA-Li (lithiated PAA binder) +5% sp; in the CNTs slurry, the solids are CNTs and CMC mixed according to the mass ratio of 4:6, wherein the mass of the solids accounts for 1% of the mass of all solids in the test electrode formula.

The counter electrode is a lithium metal sheet.

A battery case: 2032, and a spring piece, foam nickel or a gasket are arranged between the test electrode or the negative electrode and the battery case to avoid breaking, so that the test result can be accurately reflected.

Electrolyte solution: A1M solution of lithium hexafluorophosphate in carbonate contains 15% FEC+VC1-2%.

Test electrode coat weight: about 4mg/cm ² ；

Test voltage range: 2V-0.005V, or 0.8V-0.005V.

The testing process comprises the following steps:

standing for 8-12 h;0.05C lithium is intercalated to 5mV and kept stand for 5min;50uA intercalates lithium to 5mV and stands for 5min;10uA intercalates lithium to 5mV and stands for 5min; delithiation to 2V at 0.05C and standing for 5min.

And testing to obtain the gram specific capacity, the first effect and the thickness increase percentage of the obtained silicon-carbon anode material when the lithium intercalation thickness is full.

At the same time, the cycle number (compared with the first week of 0.33C rate) at which the gram specific capacity decays to 90% was tested at 0.33C charge-discharge rate (1C current of 1700 mAh/g).

The test results are shown in Table 2.

Table 2 physicochemical properties and electrochemical properties of the silicon carbon anodes obtained in examples 1 to 9 and comparative examples 1 to 3

Sequence number

CAP mAh/g

ρ _TD g/cc

FCE _2.0V ％

FCE _0.8V ％

Thickness increase

Cycle number

Example 1

1637.8

0.82

84.10％

76.30％

83％

1105

Example 2

2164.7

0.93

90.70％

80.70％

95％

997

Example 3

2579.3

1.13

93.30％

82.70％

118％

729

Example 4

2194.6

0.94

89.20％

80.10％

103％

844

Example 5

2080.2

0.92

90.90％

81.40％

92％

1097

Example 6

2077.4

1.1

91.40％

82.30％

137％

669

Example 7

2114.7

0.84

87.30％

78.20％

89％

1084

Example 8

2182.7

0.92

88.30％

78.50％

92％

1042

Example 9

2144.8

0.97

91.30％

81.90％

99％

962

Comparative example 1

2209.6

0.94

98.10％

79.40％

121％

819

Comparative example 2

2099.1

1.3

91.70％

83.10％

142％

582

Comparative example 3

2140.8

0.89

81.70％

72.60％

98％

975

Table 2 test results illustrate:

examples 1-3 used the same carbon matrix (PV-0.7 g/cc) and deposited silicon at different levels, with increasing amounts of silicon deposited, the denser the material, the fewer internal voids remaining, the better the electron and ion conductivity, and the denser the material, with a consequent increase in true and tap densities and a higher onset of performance in button cells. Meanwhile, as the deposition amount of the silicon-based component is increased, and the lithium intercalation expansion of the silicon-based component is larger, the increase percentage of the full intercalation thickness in the button cell pole piece is inevitably large, so that the attenuation is accelerated. ρ of example 1 _TD Outside its preferred range, it is seen that the apparent material first efficiency is lower because the pores inside the carbon matrix are underutilized, which would result in a portion of the "dead lithium" present in the lithium-intercalated silicon-carbon negative electrode material during delithiation.

Examples 4, 5 and comparative example 1, with example 2 as a comparison, show the difference in performance of the carbon-coated silicon-carbon negative electrode material of the present invention itself and in a button cell. The increase of the carbon coating amount has a slight reduction effect on the true density and tap density of the silicon-carbon anode material, and the reduction effect on the capacity of the silicon-carbon anode material is more obvious because the capacity of the silicon-based component is far greater than that of the deposited carbon. Meanwhile, because of the agglomeration of small particles and the reduction of the specific surface area of the particles caused by the increase of the carbon coating, the first effect of the silicon-carbon anode material is improved to a certain extent. While less carbon coating, especially no carbon coating in comparative example 1, will have an important impact on the cycling performance of the silicon carbon negative electrode material designed according to the present invention in a button cell: without or with less carbon coating, more SEI components will be formed due to the sensitivity of the silicon-based component to the electrolyte, thereby increasing the resistance of the silicon-carbon negative electrode material during cycling, resulting in rapid decay of cycling.

The silicon-based component in the silicon-carbon anode material designed by the invention should exist in the pore volume of the porous carbon skeleton in a great part. While examples 6, 7 and comparative example 2 were compared with example 2, although the lithium intercalation capacities were similar, i.e., the total lithium intercalation capacities provided by the silicon-based component and the porous carbon skeleton were similar, the carbon matrix PV used was 0.47g/cc, 0.92g/cc, 0.11g/cc, respectively, and at the same amount of silicon-based component deposition, example 6 and comparative example 2 were even lower to 0.11g/cc due to insufficient pore volume (the carbon matrix PV used in example 6 was less than the lower limit of the preferred range, and the comparative example was even more lower than the lower limit of the defined range), resulting in deposition of a certain amount of silicon on the outer layer of the particles, forming a pure silicon coating, and comparative example 2 was even more preferred. Whereas the silicon deposition in example 7 does not fully utilize the pores within the carbon matrix. Comparative example 2> example 6> example 2> example 7 were made in terms of true density and tap density. Because of the existence of the pure silicon coating layer, the first effect of the silicon-carbon anode material in the button cell in the comparative example 1 is improved, meanwhile, because the expansion of the silicon-based component is fully restrained by the porous carbon matrix, the lithium intercalation expansion of the obtained silicon-carbon anode material is increased, and further, because the expansion is overlarge, ion and electron bridge breakage in the pole piece is caused, and the cycle attenuation of the battery is accelerated.

Examples 8, 9 and comparative example 3 were compared with example 2 using carbon substrates having different strengths in the order of strength of example 9> example 2> example 8> comparative example 3. Because the porous carbon skeleton has opposite relation between isotropic strength uniformity and graphitization degree, and the high graphitization degree usually corresponds to the porous carbon skeleton with higher true density, and the porous carbon skeleton with high graphitization degree is beneficial to the first effect of the silicon-carbon negative electrode material designed by the invention, the relation between the true density and tap density of the four is as follows: comparative example 3> example 9> example 2> example 8; the first effect relation of the button cell is as follows: comparative example 3> example 9> example 2> example 8. However, it should be noted that the high true density of the porous carbon skeleton as in comparative example 3 is not different from that of graphite because of the relationship between true density of the porous carbon skeleton and graphitization degree and strength, because too high true density would result in a decrease in the uniformity of strength of the porous carbon skeleton in isotropy due to higher graphitization degree: in particular, example 8 is below the preferable range, so that it has a better expansion suppressing effect; comparative example 3 exceeded the upper limit of the defined range, but rather reduced the uniformity of the expansion suppressing effect in all directions inside the resultant silicon carbon negative electrode material due to the increase in graphitization degree, so the expansion and cycle relationship in the button cell was: example 8> example 2> example 9> comparative example 3.

Test example 2

This test example uses the silicon carbon negative electrode materials and commercial graphite materials (purchased from Jiangxi-purple-cell technology Co., ltd., raw materials were artificial and touched by raw materials) obtained in the examples and comparative examples as negative electrode active materials (wherein the silicon carbon negative electrode materials were represented by the following table 3) and 9-series ternary materials (purchased from Jiangmen-Kogyo Co., ltd., the molar content of nickel was about 90%) as positive electrode materials, and a soft pack battery having an NP ratio of 1.08 was designed. And the obtained soft-packed battery is subjected to electrochemical test under the conditions of 0.5C charge multiplying power and 1C discharge multiplying power within the voltage range of 2.5-4.2V, and the initial effect, gram specific capacity, the thickness increase percentage of the negative plate when lithium is fully embedded and the number of turns when the capacity is attenuated to 80% at 25 ℃ and 45 ℃ of the soft-packed battery are specifically tested. Some of the design parameters and the results are shown in Table 3.

Table 3 performance of the silicon carbon negative electrode materials obtained in examples 1 to 9 and comparative examples 1 to 3 in soft pack batteries

Table 3 results illustrate:

the silicon carbon negative electrode materials obtained in example 2 were used for the tests with the serial numbers of 1 to 3, and negative electrode sheets were prepared according to the same negative electrode formulation (96.6%). And when the first effect of the negative electrode obtained by accounting the NP ratio is the same as that of the positive electrode, the silicon-carbon doping amount provided by the invention is 10.3%, so that when the gram capacity of the negative electrode is designed at 420mAh/g, the first effect of the full cell is determined by the first effect of the negative electrode by taking the positive electrode material as a reference, and when the using amount of the silicon-carbon negative electrode material is further improved, and the gram capacity of the negative electrode is designed at 500mAh/g and 630 mAh/g. Meanwhile, as the usage amount of the silicon-carbon anode material is increased, the expansion ratio of anode lithium intercalation is increased; meanwhile, the bridge is broken by electrons and ions in the circulating process of the negative electrode plate in the full cell more easily, so that the circulating life is reduced.

In the soft pack batteries of numbers 4 to 5 and 10, the silicon carbon negative electrode materials used were obtained in examples 4, 5 and comparative example 1 in this order, and the negative electrode active formulation was designed using the same negative electrode gram capacity as that of the soft pack battery of number 2. The results were similar to the trend of the results for the button cell in table 2, and even in the case of no adequate carbon coating, even in comparative example 1, the silicon-carbon negative electrode material in the full cell was insufficiently protected, a large amount of SEI was accumulated, and limited active lithium ions in the positive electrode material were continuously consumed in the cycle, resulting in cycle degradation.

In the soft pack batteries of nos. 6 to 7 and 11, the silicon carbon negative electrode materials used were sequentially from examples 6, 7 and comparative example 2, and the design of the negative electrode gram capacity of the soft pack battery and the formulation of the negative electrode active material were the same as those of the soft pack battery of No. 2. The trend of the test results of the soft pack full cell is similar to the test results of the button cell in table 2: in the matched porous carbon skeleton Kong Rongxia, the volume expansion of the silicon-carbon anode material is reasonably controlled, and the volume inside the material can be fully utilized to relieve the impact of the lithium intercalation expansion on the cell structure and the cycle performance; in the abundant porous carbon skeleton Kong Rongxia, the cycle performance of the full cell is obviously improved, but the initial effect is insufficient, so that the usage amount of the silicon-carbon anode material is increased; in the case of the shortage, even as in the case of the very few porous carbon frameworks Kong Rongxia of comparative example 2, there was a significant silicon layer in the silicon-carbon negative electrode material, and it was not sufficiently protected by the carbon coating layer during the cycling, thereby causing a similar cycle acceleration decay phenomenon as the button cell.

In the soft pack batteries of serial nos. 8 to 9 and 12, the silicon carbon negative electrode materials used were sequentially from examples 8, 9 and comparative example 3, and the negative electrode gram capacity design and the negative electrode active material formulation of the soft pack battery were the same as those of the soft pack battery of serial No. 2. The trend of the test result of the full electricity is similar to that of the test result of the button cell: the greater the strength of the porous carbon skeleton, the more the lithium intercalation expansion of the silicon-based component in the silicon-carbon negative electrode material can be restrained. However, also because the strength of the porous carbon skeleton and the graphitization degree are opposite, the increase of the strength of the porous carbon skeleton can reduce the first effect of the silicon-carbon negative electrode material, as shown in the silicon-carbon negative electrode material obtained in comparative example 3, although the porous carbon skeleton can obviously inhibit the lithium intercalation expansion of the silicon-carbon negative electrode material and ensure the cycle performance, the low first effect of the porous carbon skeleton can obviously increase the use amount of the silicon-carbon negative electrode material under the same design of gram capacity of the negative electrode, and the increase of the BoM cost of cell production is brought.

In conclusion, the silicon-carbon anode material provided by the invention can improve the comprehensive performances such as cycle performance, safety performance (volume change), first effect and the like under the condition of extremely small volume expansion through structural design and parameter constraint. Is expected to be widely applied in the fields of energy storage batteries, 3C batteries and power batteries.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention. Furthermore, embodiments of the invention and features of the embodiments may be combined with each other without conflict.

Claims

1. The silicon-carbon negative electrode material is characterized by comprising a core and a shell wrapping the surface of the core; the true density of the silicon-carbon anode material is ρ _RD ；

And satisfies formula (I):

formula (I);

wherein: ρ is 1.5g/cc _RD ≤2.4g/cc；0.55cc/g≤PV≤0.95cc/g；1g/cc≤ρ _Si ≤2.35g/cc；1.5g/cc≤ρ _C ≤2.2g/cc；

The silicon-based component accounts for W, the mass percent of the silicon-carbon anode material _Si The value range of the (C) is 30-55%.

2. The silicon-carbon negative electrode material according to claim 1, wherein in formula (I), ρ _RD 1.75 to 2.25g/cc.

3. The silicon-carbon negative electrode material according to claim 1, wherein in formula (I), ρ _Si 1.25 to 1.75g/cc.

4. The silicon-carbon negative electrode material according to claim 1, wherein the silicon-based component accounts for W in mass percent of the silicon-carbon negative electrode material _Si The lithium intercalation capacity of the silicon-carbon anode material is CAP; and satisfies formula (II);

180≤CAP-3769×W _Si less than or equal to 680, formula (II);

wherein, W is more than or equal to 30 percent _Si ≤55%。

5. The silicon-carbon negative electrode material according to any one of claim 1 to 4, wherein,particle diameter D of the silicon-based component _Si Is defined in the following range: d is less than or equal to 2nm _Si ≤10nm。

6. The silicon-carbon anode material according to any one of claims 1 to 4, wherein the silicon-carbon anode material has a tap density ρ of _TD The range of (2) is: rho of 0.8g/cc _TD ≤1.2g/cc。

7. The silicon-carbon negative electrode material according to any one of claims 1 to 4, wherein the sum of mass percentages of silicon element and carbon element in the silicon-carbon negative electrode material is >98%.

8. The silicon-carbon negative electrode material according to any one of claims 1 to 4, wherein the material of the shell comprises at least one of carbon, metal oxide, and organic polymer.

9. A method for preparing a silicon-carbon negative electrode material according to any one of claims 1 to 8, comprising the steps of:

s1, cracking a carbon raw material to obtain a porous carbon skeleton;

s2, depositing the silicon-based component in the porous carbon skeleton to obtain a core;

s3, wrapping the substance obtained in the step S2 to form a shell.

10. The method of claim 9, further comprising pore modification of the cleavage product after the cleavage in step S1.

11. The method of claim 9, wherein in step S2, the deposition method comprises chemical vapor deposition.

12. A lithium ion battery, wherein the preparation raw material of the lithium ion battery comprises the silicon-carbon negative electrode material according to any one of claims 1 to 8 or the silicon-carbon negative electrode material prepared by the preparation method according to any one of claims 9 to 11.

13. Use of a lithium ion battery according to claim 12 in the field of energy storage batteries, 3C batteries and in the field of power batteries.