CN115524377A - A kind of test method of expansion rate of silicon-based negative electrode material - Google Patents

Abstract

The invention belongs to the technical field of lithium ion batteries, and discloses a method for testing the expansion rate of a silicon-based negative electrode material. The button cell is assembled by pole pieces prepared from different silicon-based negative electrode materials, the required thickness of the component is measured by ten-thousandth scale after the button cell is disassembled before the button cell is assembled and in a full-electricity state (or in any step in a circulation process), the expansion rate of the silicon-based negative electrode material in the charging and discharging or circulation process can be measured by directly measuring the thickness by using the method, and the expansion rate rapid test method is provided. Meanwhile, the expansion rate of the silicon-based negative electrode material can be obtained only by assembling the material into a button battery to test the specific discharge capacity, and a foundation is laid for the research on the test method of the expansion rate of the silicon-based negative electrode material.

Description

A kind of test method of expansion rate of silicon-based negative electrode material

technical field

The invention relates to the technical field of lithium ion batteries, in particular to a method for testing the expansion rate of a silicon-based negative electrode material.

Background technique

When designing a battery, whether the negative electrode is made of graphite material or silicon-carbon composite material, the expansion rate parameter of the negative electrode is one of the key parameters in battery design. At the same time, in the development process of negative electrode materials, silicon-based negative electrode materials have entered people's field of vision due to their high capacity and low electrode potential, but their volume expansion will occur during the discharge process, and the volume expansion will cause subsequent cycle capacity decay, low Coulombic efficiency, and high rate. Therefore, the expansion problem of silicon-based negative electrode materials is a difficult problem for silicon-based materials to solve at present, so it is extremely important to analyze the expansion of silicon-based negative electrode materials. And through the test and analysis of the expansion of silicon-based negative electrode materials, one aspect can be used to evaluate the pros and cons of different silicon-based negative electrode materials. Therefore, it is of great significance to establish an analysis method for the expansion of anode materials.

The existing test method is mainly the expansion test method of the pole piece. The above-mentioned method is cumbersome and expensive. There is no rapid test method specifically for the expansion rate of silicon-based negative electrode materials, and there is no method to estimate the expansion rate of silicon based on this method. The technology based on the expansion rate of the negative electrode material. Therefore, it is urgently needed in this field to provide a test method that is specific and can quickly analyze the expansion rate of silicon-based negative electrode materials.

Contents of the invention

In view of this, the present invention provides a method for testing the expansion rate of silicon-based negative electrode materials to solve the problem that the existing analysis methods are relatively cumbersome and costly to implement, and at the same time it is a proprietary method for testing the expansion rate of silicon-based negative electrode materials There is a gap in the research.

In order to achieve the above object, the present invention adopts following technical scheme:

The invention provides a method for testing the expansion rate of a silicon-based negative electrode material, comprising the steps of:

(1) The pole piece material made of silicon-based material is cut, punched, and rolled to obtain the pole piece, and the thickness of the pole piece H1 and the thickness _of the current collector H0 are measured _; the pole piece is baked, and the amount of baking The final pole piece thickness H ₂ ;

(2) Assemble the baked pole pieces into a battery, activate the battery and test it to a fully charged state, and the discharge specific capacity at this time is Q;

(3) Disassemble the battery tested to a fully charged state to obtain the pole piece, clean the pole piece, and measure the cleaned pole piece thickness H ₃ ;

(4) Calculate the expansion rate of the silicon-based negative electrode material according to formula 1:

Expansion rate = (H ₂ -H ₁ )/(H ₁ -H ₀ )×100%+(H ₃ -H ₂ )/(H ₂ -H ₀ )×100% Formula 1;

(5) Take the discharge specific capacity Q as the abscissa and the expansion rate of the silicon-based negative electrode material as the ordinate to establish a standard curve; according to the discharge capacity and the standard curve of the battery to be tested that are assembled from the pole pieces made of the silicon-based material, the battery is obtained Expansion rate of the silicon-based negative electrode material to be tested.

Preferably, the silicon-based material is a mixed material of graphene and silicon, a mixed material of graphite and silicon oxide, a mixed material of graphite and silicon carbon, a mixed material of carbon and nano-graphite, nano-silicon, silicon alloy, carbon-coated One or more of silicon-coated and silicon oxide.

Preferably, the polar piece obtained after cutting and punching is a disc with a diameter of 11-15 mm; the rolling pressure is 1-15 MPa, and the compacted density of the pole piece after rolling is 1-1.2 g/cm ³ .

Preferably, the baking temperature is 60-120° C., and the baking time is 2-48 hours.

Preferably, when the baked pole pieces are assembled into batteries, the number of batteries assembled from pole pieces made of the same silicon-based material is ≥ 2; the discharge specific capacity Q is the average discharge specific capacity.

Preferably, the solvent used for the cleaning is dimethyl carbonate.

As preferably, the preparation method of the pole piece material made of the silicon-based material comprises the following steps:

a. Mixing silicon-based materials, conductive agents, binders, additives and solvents to obtain slurry;

b. Coating the slurry on the current collector and then drying it to obtain the electrode sheet material.

As preferably, the conductive agent is one or more of conductive carbon black, conductive graphite, Ketjen black and carbon nanotubes; the binder is a water-based binder; the additive is carbon nanotubes, chlorine Butadiene rubber or N-methylpyrrolidone; the solvent is water.

Preferably, the mass ratio of the silicon-based material, conductive agent, binder and additive is 1-3:0.05-0.4:1-15:0-10; the amount of the solvent added is the silicon-based material, conductive agent , 6-10% of the total mass of binders and additives.

Preferably, the thickness of the slurry coating is 50-200 μm; the drying is vacuum drying, the drying temperature is 80-100°C, the drying time is 8-24h, and the drying vacuum degree is -0.05--0.2 MPa.

It can be seen through the above-mentioned technical solution that, compared with the prior art, the beneficial effects of the present invention are as follows:

The test method for the expansion rate of silicon-based negative electrode materials in the present invention can accurately and quickly measure the expansion rate of silicon-based negative electrode materials, and can estimate the expansion rate of silicon-based negative electrode materials at the same time, which is the core of the test method for the expansion rate of silicon-based negative electrode materials. Research lays the groundwork.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is the flow chart of the test method of expansion rate of silicon-based negative electrode material of the present invention;

Fig. 2 is the flowchart of battery assembly described in embodiment 1 and 2 of the present invention;

Fig. 3 is the graph of the specific discharge capacity of the battery obtained in Example 1 of the present invention and the expansion rate of the silicon-based negative electrode material;

Fig. 4 is a graph showing the specific discharge capacity of the battery obtained in Example 2 of the present invention and the expansion rate of the silicon-based negative electrode material.

detailed description

The invention provides a method for testing the expansion rate of a silicon-based negative electrode material, comprising the steps of:

(1) The pole piece material made of silicon-based material is cut, punched, and rolled to obtain the pole piece, and the thickness of the pole piece H1 and the thickness _of the current collector H0 are measured _; the pole piece is baked, and the amount of baking The final pole piece thickness H ₂ ;

(2) Assemble the baked pole pieces into a battery, activate the battery and test it to a fully charged state, and the discharge specific capacity at this time is Q;

(3) Disassemble the battery tested to a fully charged state to obtain the pole piece, clean the pole piece, and measure the cleaned pole piece thickness H ₃ ;

(4) Calculate the expansion rate of the silicon-based negative electrode material according to formula 1:

Expansion rate = (H ₂ -H ₁ )/(H ₁ -H ₀ )×100%+(H ₃ -H ₂ )/(H ₂ -H ₀ )×100% Formula 1;

(5) Take the discharge specific capacity Q as the abscissa and the expansion rate of the silicon-based negative electrode material as the ordinate to establish a standard curve; according to the discharge capacity and the standard curve of the battery to be tested that are assembled from the pole pieces made of the silicon-based material, the battery is obtained Expansion rate of the silicon-based negative electrode material to be tested.

In the present invention, the calculation method of the expansion rate is: total expansion rate=electrode rebound rate (physical expansion)+full electrical expansion rate (chemical expansion). Electrode rebound rate (physical expansion) = (H ₂ -H ₁ )/(H ₁ -H ₀ )×100%, full electrical expansion rate (chemical expansion) = (H ₃ -H ₂ )/(H ₂ -H ₀ )×100%.

In the present invention, the silicon-based material is preferably a mixed material of graphene and silicon, a mixed material of graphite and silicon oxide, a mixed material of graphite and silicon carbon, a mixed material of carbon and nano-graphite, nano-silicon, and a silicon alloy , carbon-coated silicon, one or more of silicon oxide, further preferably a mixed material of graphene and silicon, a mixed material of graphite and silicon oxide, a mixed material of graphite and silicon carbon, carbon and nano-graphite One or more of mixed materials.

In the present invention, the pole piece obtained after cutting and punching is a disc, and the diameter of the disc is preferably 11-15 mm, more preferably 13-14 mm; the rolling pressure is preferably 1-15 MPa, more preferably 5-10 MPa; The compacted density of the pole piece after rolling is preferably 1-1.2 g/cm ³ , more preferably 1.12-1.18 g/cm ³ ;

The calculation formula of the compacted density of the pole piece after the rolling is shown in formula 2:

The compacted density of the pole piece after rolling = 1000×(mm ₀ )/[(H ₁ -H ₀ )×πr ² ] Formula 2

Wherein: m is the weighing quality of the negative pole piece after cutting and punching, that is, the quality of the pole piece before being assembled into a battery; _m0 is the quality of the blank copper foil of cutting and punching; r is the radius of the pole piece, the present invention The pole piece used is a disc, so the active material area of the pole piece is calculated as πr ² , H ₀ is the thickness of the current collector, and H ₁ is the thickness of the pole piece;

The thickness of the pole piece after rolling is preferably 60-90 μm, more preferably 70-80 μm, without considering the rebound.

The invention eliminates the influence of the initial thickness on the expansion of the silicon-based negative electrode material through the control of the compacted density and thickness, and improves the accuracy of the test method.

In the present invention, the baking temperature is preferably 60-120°C, more preferably 80-100°C; the baking time is preferably 2-48 hours, more preferably 24-40 hours.

In the present invention, when the pole pieces after baking are assembled into batteries, the number of batteries assembled from pole pieces made of the same silicon-based material is preferably ≥ 2, more preferably 3 to 4; the discharge specific capacity Q is preferably the average discharge specific capacity.

In the present invention, the activation stage is preferably 1 to 5 cycles, more preferably 2 to 3 cycles; the fully charged state is: discharge the battery to a fully charged state at a rate of 0.01 to 5C;

The magnification is preferably 0.02 to 2C, more preferably 0.05 to 0.5C.

In the present invention, the solvent used for cleaning is preferably dimethyl carbonate.

In the present invention, the preparation method of the pole piece material made of the silicon-based material comprises the following steps:

a. Mixing silicon-based materials, conductive agents, binders, additives and solvents to obtain slurry;

b. Coating the slurry on the current collector and then drying it to obtain the electrode sheet material.

In the present invention, the conductive agent is preferably one or more of conductive carbon black, conductive graphite, Ketjen Black and carbon nanotubes, more preferably conductive graphite and/or carbon nanotubes; the binder It is preferably a water-based binder, more preferably one or more of water-based binder LA133, water-based binder LA132 and water-based binder LA136D; the additive is preferably carbon nanotubes, neoprene or N- Methylpyrrolidone, more preferably carbon nanotubes or N-methylpyrrolidone; the solvent is preferably water.

In the present invention, the mass ratio of the silicon-based material, conductive agent, binder and additive is preferably 1-3: 0.05-0.4: 1-15: 0-10, more preferably 1.5-2.5: 0.1-0.3 : 2 to 5: 1 to 8; the added amount of the solvent is preferably 6 to 10% of the total mass of silicon-based materials, conductive agents, binders and additives, more preferably silicon-based materials, conductive agents, binders and 8-9% of the total mass of additives.

In the present invention, the thickness of the slurry coating is preferably 50-200 μm, more preferably 100-150 μm; the drying is vacuum drying, and the drying temperature is preferably 80-100°C, more preferably 90-95°C The drying time is preferably 8~24h, more preferably 10~20h; the drying vacuum is preferably -0.05~-0.2MPa, more preferably -0.08~-0.15MPa.

The present invention assembles the button battery through pole pieces prepared from different silicon-based negative electrode materials, and disassembles the button battery before assembly and in a fully charged state (or in any step in the cycle process) and uses a micrometer to measure the required components Thickness, using this method can directly measure the thickness to measure the expansion rate of the silicon-based negative electrode material during the charge and discharge of the silicon-based negative electrode or cycle, and provide a rapid method for testing the expansion rate. At the same time, the expansion rate of the silicon-based negative electrode material can be obtained by assembling the material into a button battery to test the discharge specific capacity.

The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they should not be interpreted as limiting the protection scope of the present invention.

Example 1

Step 1. Preparation of silicon-based negative electrode materials: pure silicon carbon (without mixing graphite), pure silicon carbon mixed with 10% graphite, pure silicon carbon mixed with 20% graphite, pure silicon carbon mixed with 30% graphite, silicon Pure carbon mixed with 40% graphite, pure silicon carbon mixed with 50% graphite, pure silicon carbon mixed with 60% graphite, pure silicon carbon mixed with 70% graphite, pure silicon carbon mixed with 80% graphite, silicon Pure carbon mixed with 90% graphite;

Step 2. Weigh 2.275g of silicon-based materials mixed with different proportions of graphite and silicon carbon in step 1, respectively, with 0.075g of conductive carbon black SP, 3g of water-based binder LA132 (concentration: 5%), and 0.5g of pure water. Stir and mix to obtain 10 kinds of slurries;

Step 3. Coat the obtained slurry evenly on the copper foil respectively, dry it in a blast oven at 80°C for 8 hours, roll it after drying, cut and punch it, select a pole piece with a diameter of 13mm, and measure the When the thickness of the pole piece is recorded as H ₁ and the thickness of the blank copper foil is recorded as H ₀ ; among them, H ₀ and H ₁ are average values;

Among them, the requirements for rolling: the requirements for the compaction density of the pole pieces after rolling: the compaction density of the pole pieces after rolling is required to be controlled at 1g/cm ³ ; the requirements for the thickness of the pole pieces after rolling: The thickness of the rear pole piece is required to be controlled at 60 μm (without considering the rebound);

Step 4. Put the pole piece into the oven and bake at 80°C for 8 hours. After the baking is completed, send the pole piece into the glove box to measure the thickness of the pole piece after baking, and record it as H ₂ ; where, H ₂ is the average value;

Step 5, repeat the above-mentioned steps 3 and 4 4 times to obtain 11 groups (4 parallel sample pole pieces in each group) pole pieces respectively;

Step 6. Each pole piece is assembled into a lithium battery respectively, and the assembly steps are as follows:

Step S01: Move the prepared pole piece, ceramic separator, lithium piece, negative electrode casing, positive electrode casing, spring leaf and gasket into the glove box;

Step S02: Put the negative electrode case on the bottom layer, and put the spring piece, the gasket, and the lithium piece on the top in sequence;

Step S03: Add 0.1 g of lithium hexafluorophosphate electrolyte dropwise to the lithium sheet produced in step S02, put it into the ceramic diaphragm, add 0.2 g of lithium hexafluorophosphate electrolyte dropwise again, put it into the electrode piece and cover the positive electrode case, and then complete the assembly of the battery ;

Step S04: Place the battery assembled in step S03 on the card slot of the sealing machine, and obtain the lithium battery after sealing.

Step 7. Send the lithium battery out of the glove box, activate the battery in the test cabinet and test it to a fully charged state, record the discharge specific capacity Q at this time, and remove the battery at the same time and send the battery into the glove box for disassembly;

Among them, the activation stage is the first 2 laps, and then the battery is removed at a rate of 0.1C until it is fully charged;

Step 8. Clean the silicon-based negative pole piece obtained after the battery is disassembled in the glove box with DMC, then dry the pole piece naturally and measure the thickness of the pole piece at this time as H ₃ ; where H ₃ is the average value;

Step 9. Use the data obtained in the above steps according to the expansion rate formula (H ₂ -H ₁ )/(H ₁ -H ₀ )×100%+(H ₃ -H ₂ )/(H ₂ -H ₀ )×100 % calculates the result;

The data obtained in this embodiment are shown in Table 1:

The data of 7 silicon-based materials described in table 1 embodiment 1

According to the data in Table 1, the discharge specific capacity Q is taken as the abscissa, and the corresponding expansion rate Y of the silicon-based negative electrode material is taken as the ordinate, and the curve Q and Y are approximately linearly related. As shown in Figure 3, the relationship between Q and Y is Y=0.1148Q-22.444; among them, the linear correlation coefficient R ² =0.9916, and the slope K is 0.1148, that is, Y∝0.1148Q. The expansion rate of the silicon-based negative electrode material can be quickly estimated by assembling the base negative electrode material into a button battery to test the discharge specific capacity.

Example 2

Step 1. Preparation of silicon-based negative electrode materials: silicon oxide (without mixing graphite), silicon oxide mixed with 10% graphite, silicon oxide mixed with 20% graphite, silicon oxide mixed with 30% graphite, silicon oxide mixed with 40% % graphite, silicon oxide mixed with 50% graphite, silicon oxide mixed with 60% graphite, silicon oxide mixed with 70% graphite, silicon oxide mixed with 80% graphite, silicon oxide mixed with 90% graphite;

Step 2. Weigh 1.875g of the silicon-based material mixed with different proportions of graphite and silicon carbon in step 1, respectively, and 0.125g of conductive carbon black SP, 5g of water-based binder LA132 (concentration: 5%), and conductive carbon black SFG-60.25 g, 0.5g of pure water, stirred and mixed to obtain 11 kinds of slurries;

Step 3. Coat the obtained slurry evenly on the copper foil respectively, dry it in a blast oven at 80°C for 8 hours, roll it after drying, cut and punch it, select a pole piece with a diameter of 13mm, and measure the When the thickness of the pole piece is recorded as H ₁ and the thickness of the blank copper foil is recorded as H ₀ ; among them, H ₀ and H ₁ are average values;

Among them, the requirements for rolling: the requirements for the compaction density of the pole pieces after rolling: the compaction density of the pole pieces after rolling is required to be controlled at 1g/cm ³ ; the requirements for the thickness of the pole pieces after rolling: The thickness of the rear pole piece is required to be controlled at 60 μm (without considering the rebound);

Step 4. Put the pole piece into the oven and bake at 80°C for 8 hours. After the baking is completed, send the pole piece into the glove box to measure the thickness of the pole piece after baking, and record it as H ₂ ; where, H ₂ is the average value;

Step 5, repeat the above-mentioned steps 3 and 4 4 times to obtain 11 groups (4 parallel sample pole pieces in each group) pole pieces respectively;

Step 6. Each pole piece is assembled into a lithium battery respectively, and the assembly steps are as follows:

Step S01: Move the prepared pole piece, ceramic separator, lithium piece, negative electrode casing, positive electrode casing, spring leaf and gasket into the glove box;

Step S02: Put the negative electrode case on the bottom layer, and put the spring piece, the gasket, and the lithium piece on the top in sequence;

Step S03: Add 0.1 g of lithium hexafluorophosphate electrolyte dropwise to the lithium sheet produced in step S02, put it into the ceramic diaphragm, add 0.2 g of lithium hexafluorophosphate electrolyte dropwise again, put it into the electrode piece and cover the positive electrode case, and then complete the assembly of the battery ;

Step S04: Place the battery assembled in step S03 on the card slot of the sealing machine, and obtain the lithium battery after sealing.

Step 7. Send the lithium battery out of the glove box, activate the battery in the test cabinet and test it to a fully charged state, record the discharge specific capacity Q at this time, and remove the battery at the same time and send the battery into the glove box for disassembly;

Among them, the activation stage is the first 2 laps, and then the battery is removed at a rate of 0.1C until it is fully charged;

Step 8. Clean the silicon-based negative pole piece obtained after the battery is disassembled in the glove box with DMC, then dry the pole piece naturally and measure the thickness of the pole piece at this time as H ₃ ; where H ₃ is the average value;

Step 9. Use the data obtained in the above steps according to the expansion rate formula (H ₂ -H ₁ )/(H ₁ -H ₀ )×100%+(H ₃ -H ₂ )/(H ₂ -H ₀ )×100 % calculates the result;

The data obtained in this embodiment are shown in Table 2:

The data of 7 silicon-based materials described in table 2 embodiment 2

According to the data in Table 2, the discharge specific capacity Q is taken as the abscissa, and the corresponding expansion rate Y of the silicon-based negative electrode material is taken as the ordinate, and the curve Q and Y are approximately linearly related. As shown in Figure 4, the relationship between Q and Y is Y=0.065Q-8.4085; among them, the linear correlation coefficient R ² =0.9972, and the slope K is 0.065, that is, Y∝0.065Q. The expansion rate of the silicon-based negative electrode material can be quickly estimated by assembling the base negative electrode material into a button battery to test the discharge specific capacity.

It can be seen from Examples 1 and 2 that the test method of the present invention is simple and fast, and at the same time, the expansion rate of the silicon-based negative electrode material can be quickly estimated.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. a test method of expansion rate of silicon-based negative electrode material, is characterized in that, comprises the steps: (1) The pole piece material made of silicon-based material is cut, punched, and rolled to obtain the pole piece, and the thickness of the pole piece H1 and the thickness _of the current collector H0 are measured _; the pole piece is baked, and the amount of baking The final pole piece thickness H ₂ ; (2) Assemble the baked pole pieces into a battery, activate the battery and test it to a fully charged state, and the discharge specific capacity at this time is Q; (3) Disassemble the battery tested to a fully charged state to obtain the pole piece, clean the pole piece, and measure the cleaned pole piece thickness H ₃ ; (4) Calculate the expansion rate of the silicon-based negative electrode material according to formula 1: Expansion rate = (H ₂ -H ₁ )/(H ₁ -H ₀ )×100%+(H ₃ -H ₂ )/(H ₂ -H ₀ )×100% Formula 1; (5) Take the discharge specific capacity Q as the abscissa and the expansion rate of the silicon-based negative electrode material as the ordinate to establish a standard curve; according to the discharge capacity and the standard curve of the battery to be tested that are assembled from the pole pieces made of the silicon-based material, the battery is obtained Expansion rate of the silicon-based negative electrode material to be tested. 2. according to the test method of the said silicon-based negative electrode material expansion rate of claim 1, it is characterized in that, said silicon-based material is the mixed material of graphene and silicon, the mixed material of graphite and silicon oxide, graphite and silicon carbon One or more of mixed materials, mixed materials of carbon and nano-graphite, nano-silicon, silicon alloy, carbon-coated silicon, and silicon oxide. 3. according to the test method of the expansion rate of the silicon-based negative electrode material of claim 2, it is characterized in that, the gained pole piece after cutting and punching is a disc, and the diameter of the disc is 11～15mm; the pressure of rolling is 1～15MPa , the compacted density of the pole piece after rolling is 1-1.2g/cm ³ . 4 . The method for testing the expansion rate of silicon-based negative electrode materials according to any one of claims 1 to 3 , wherein the baking temperature is 60-120° C. and the baking time is 2-48 hours. 5. The method for testing the expansion rate of silicon-based negative electrode materials according to claim 4, characterized in that, when the baked pole pieces are assembled into batteries, the number of batteries assembled from pole pieces made of the same silicon-based material is ≥2 The discharge specific capacity Q is the average discharge specific capacity. 6. The method for testing the expansion rate of the silicon-based negative electrode material according to claim 5, wherein the solvent used for cleaning is dimethyl carbonate. 7. according to the test method of silicon-based negative electrode material expansion rate described in claim 1,5 or 6, it is characterized in that, the preparation method of the pole sheet material that described silicon-based material is made comprises the steps: a. Mixing silicon-based materials, conductive agents, binders, additives and solvents to obtain slurry; b. Coating the slurry on the current collector and then drying it to obtain the electrode sheet material. 8. according to the test method of the silicon-based negative electrode material expansion rate of claim 7, it is characterized in that, described conductive agent is one or more in conductive carbon black, conductive graphite, Ketjen black and carbon nanotube; The binder is a water-based binder; the additive is carbon nanotubes, chloroprene rubber or N-methylpyrrolidone; and the solvent is water. 9. The method for testing the expansion rate of the silicon-based negative electrode material according to claim 8, wherein the mass ratio of the silicon-based material, conductive agent, binder and additive is 1 to 3:0.05 to 0.4:1 to 15: 0-10; the added amount of the solvent is 6-10% of the total mass of the silicon-based material, conductive agent, binder and additive. 10. The method for testing the expansion rate of silicon-based negative electrode materials according to claim 8 or 9, wherein the thickness of the slurry coating is 50-200 μm; the drying is vacuum drying, and the drying temperature is 80-200 μm. 100℃, the drying time is 8~24h, and the vacuum degree of drying is -0.05~-0.2MPa.

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