A negative electrode material, a surface modification method thereof and application thereof

Abstract

The application provides a negative electrode material and a surface modification method and application thereof, wherein the content of hydrogen element is not higher than 0.2%, the content of nitrogen element is not higher than 0.05%, the content of sulfur element is not higher than 0.02%, and the content of oxygen element is not higher than 0.03%. By regulating the content of hydrogen element, nitrogen element, sulfur element and oxygen element in the negative electrode material, the first efficiency, energy density and cycle performance of the battery can be optimized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of battery materials, and particularly relates to a negative electrode material and a surface modification method and application thereof. BACKGROUND

[0002] With the research and development of lithium ion batteries, due to its advantages, it has had a profound impact on many industries, such as new energy vehicle industry, energy storage system, portable electronic devices, aerospace field, unmanned and equipment, electric tools and household electrical appliances, wearable devices and the like. Therefore, the research of lithium ion batteries can not only promote the progress of related technologies, but also has important strategic significance for energy consumption mode and environmental protection.

[0003] The negative electrode material will directly affect the performance of the lithium ion battery, which is mainly because in the lithium ion battery, the negative electrode material is the embedding and de-embedding place of lithium ions, which is responsible for storing and releasing energy, and at the same time ensures the electronic flow and structural stability of the battery in the charging and discharging process. The performance of the negative electrode material will directly affect the energy density, cycle life, safety and cost-effectiveness of the battery.

[0004] And graphite, silicon-carbon is the most main negative electrode material of lithium ion battery. In the prior art, graphite is mainly divided into natural graphite and artificial graphite, but there are a large number of groups on the surface of these two materials. These groups will be reduced by active lithium in the first charge and discharge of the lithium ion battery, thereby reducing the content of active lithium and reducing the energy density of the battery. The graphite material needs to be treated at high temperature, so the generation of surface groups is unavoidable. In addition, graphite has a special layered structure, and if the method of eliminating surface groups is too harsh and destroys the layered structure, the graphite will lose the lithium storage function. As for silicon-carbon, the first cycle coulombic efficiency of silicon-carbon material is low, generally between 80-88%, and a large amount of active lithium is consumed in the first charge and discharge. In addition, the silicon-carbon material expands greatly in volume in the first charge and discharge, which makes the pole piece easy to fall off or crack. SUMMARY

[0005] In order to remove the surface groups of the negative electrode material while maintaining the normal performance of the negative electrode material, the present application provides a negative electrode material and a surface modification method and application thereof.

[0006] In a first aspect of the present application, a negative electrode material is provided, in which the content of hydrogen element is not higher than 0.2%, the content of nitrogen element is not higher than 0.05%, the content of sulfur element is not higher than 0.02%, and the content of oxygen element is not higher than 0.03%. By adjusting the content of hydrogen element, nitrogen element, sulfur element and oxygen element in the negative electrode material, the first efficiency, energy density and cycle performance of the battery can be optimized.

[0007] According to a second aspect of the present application, a surface modification method of a negative electrode material is provided, comprising the following steps: S1. mixing a negative electrode material precursor with a first reaction solution in an inert gas atmosphere to obtain a first reactant; wherein the first reaction solution comprises an aromatic hydrocarbon lithium compound; S2. cleaning the first reactant with a second reaction solution, and after drying treatment, obtaining a negative electrode material; wherein in S1, the amount of substance of the aromatic hydrocarbon lithium compound used is M mol, and the amount of the negative electrode material precursor used is W g, the specific capacity of the negative electrode material precursor is C mAh / g, and the amounts of the aromatic hydrocarbon lithium compound and the negative electrode material precursor satisfy the following relationship: M = W x C x γ; wherein,

[0008] By adjusting the mass ratio of the negative electrode material precursor to the amount of substance of the aromatic hydrocarbon lithium compound, the present application can control the reducing capacity of the aromatic hydrocarbon lithium compound, and then use the aromatic hydrocarbon lithium compound to eliminate only the surface groups of the negative electrode material precursor without damaging the structure of the negative electrode material precursor, and a small amount of lithium ions enter the interior of the negative electrode material precursor. In addition, after the reduction reaction of the negative electrode material precursor in step S1, the aromatic hydrocarbon lithium compound remains on the surface of the negative electrode material precursor, and when the second reaction solution is added for cleaning, it will react with the residual aromatic hydrocarbon lithium compound to generate free lithium ions. The free lithium ions formed will undergo complexation reaction with solvent molecules, change the electronic cloud structure of the solvent molecules, and make them be reduced and decomposed on the surface of the negative electrode material precursor, forming substances similar to SEI film on the surface of the negative electrode material precursor, so as to further improve the initial coulombic efficiency of the negative electrode material.

[0009] Preferably, the negative electrode material precursor is graphite, and the specific capacity C of the graphite satisfies: 340 mAh / g ≤ C < 355 mAh / g. (C) Preferably, the negative electrode material precursor is graphite, and the specific capacity C of the graphite satisfies: 340 mAh / g ≤ C < 355 mAh / g. (C) Preferably, the negative electrode material precursor is graphite, and the specific capacity C of the graphite satisfies: 340 mAh / g ≤ C < 355 mAh / g.

[0010] Preferably, in S1, the volume of the first reaction solution is V (C) L, and satisfies the following relationship: V (c) = 2 x W x λ; wherein,

[0011] Preferably, the negative electrode material precursor is a silicon-carbon material, and the specific capacity C of the silicon-carbon material satisfies: 400 mAh / g ≤ C < 450 mAh / g. (Si) Preferably, the negative electrode material precursor is a silicon-carbon material, and the specific capacity C of the silicon-carbon material satisfies: 400 mAh / g ≤ C < 450 mAh / g. (Si)≤2000 mAh / g. For example, the specific capacity of the silicon-carbon material is 400 mAh / g, 450 mAh / g, 650 mAh / g, 1000 mAh / g, 1500 mAh / g, 1800 mAh / g, or 2000 mAh / g, etc. For the silicon-carbon negative electrode material, the aromatic hydrocarbon lithium compound will react with silicon and carbon, but even so, the amount of the aromatic hydrocarbon lithium compound required for removing the silicon-carbon material cannot be estimated by the silicon content or the carbon content in the silicon-carbon material. The inventors have found through experiments that the required amount of the silicon-carbon material and the aromatic hydrocarbon lithium compound can be quickly calculated by using the specific capacity of the silicon-carbon material (which can be obtained when the silicon-carbon material is purchased). After surface treatment of the silicon-carbon material, the surface defects and active groups of the silicon-carbon material can be removed, the loss of active lithium can be reduced, and the first coulombic efficiency of the silicon-carbon material can be significantly improved. Moreover, through the surface modification method provided in the present application, a small amount of active lithium will enter the material, causing the silicon-carbon material to swell in advance, and producing a film on the surface of the silicon-carbon material in subsequent washing, thereby playing a certain role in inhibiting the swelling of the silicon-carbon material, and reducing the impact on the pole piece.

[0012] Preferably, in S1, the volume of the first reaction solution is V (Si) L, satisfying the following relationship: V (Si) = W x l; wherein, Similarly, the inventors have found through experiments that the required volume of the first reaction solution can be quickly calculated by the above formula.

[0013] Preferably, the first reaction solution is prepared by mixing an aromatic hydrocarbon, a lithium source, and a solvent, and the aromatic hydrocarbon includes at least one of biphenyl and derivatives thereof, naphthalene and derivatives thereof, pyrene and derivatives thereof, and diphenylmethane.

[0014] Preferably, the aromatic hydrocarbon includes at least one of naphthalene, biphenyl, 2-methylbiphenyl, 3,3'-dimethylbiphenyl, 4,4'-dimethylbiphenyl, and 3,3',4,4'-tetramethylbiphenyl.

[0015] Preferably, the solvent includes at least one of tetrahydrofuran, 2-methyltetrahydrofuran, pentafluorofuran, hexahydrofuran, tetrahydropyran, 3-methyltetrahydropyran, and 2,3-dichlorotetrahydropyran.

[0016] Preferably, the second reaction solution includes at least one of 2-methyltetrahydrofuran, tetrahydropyran, pentafluorofuran, and hexahydrofuran.

[0017] Preferably, the second reaction solution includes 2-methyltetrahydrofuran and tetrahydropyran, and the volume ratio of 2-methyltetrahydrofuran to tetrahydropyran is 1-2:1-2.

[0018] Preferably, the mass ratio of the negative electrode material precursor to the substance amount of the aromatic hydrocarbon lithium compound is 1 g: 0.00010-0.00750 mol.

[0019] Preferably, the mass ratio of the graphite to the substance amount of the aromatic hydrocarbon lithium compound is 1 g: 0.001270-0.001325 mol.

[0020] Preferably, the mass ratio of the silicon-carbon material to the substance amount of the aromatic hydrocarbon lithium compound is 1 g: 0.001493-0.007465 mol.

[0021] Preferably, in S1, the negative electrode material precursor is mixed with the first reaction solution under an inert gas atmosphere, the reaction temperature is 25-35℃, and the reaction time is 0.5-2 hours.

[0022] Preferably, in S2, the mass ratio of the first reaction substance to the volume of the second reaction solution is 500 g: 1.5-2 L.

[0023] Preferably, in S2, the step of cleaning treatment is that after the first reaction substance is mixed with the second reaction solution, the mixture is stirred at 30-50℃ under the condition of a rotation speed of 500-200 rpm for 0.5-2 hours.

[0024] Preferably, in S2, the cleaning treatment is performed not less than twice.

[0025] In a third aspect, the present application provides a battery, which comprises the negative electrode material. DETAILED DESCRIPTION

[0026] In order to make the person skilled in the art better understand the technical solutions in the present application, the technical solutions in the present application will be described clearly and completely in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0027] Embodiment 1

[0028] In this embodiment, the negative electrode material is prepared by the following method:

[0029] S1. 30.85 g of biphenyl, 1.39 g of lithium metal, 1 L of 2-methyltetrahydrofuran were mixed to obtain a first reaction solution; then 500 g of graphite (C = 345 mAh / g) was mixed with 42 L of the first reaction solution (the concentration unit of the first reaction solution refers to the content of the lithium aromatic compound, the mass of the graphite and the amount of substance of the lithium aromatic compound, the mass of the graphite and the amount of substance of the lithium aromatic compound satisfy the following relationship: M = W x C x γ; wherein, ) were mixed, and then reacted at a temperature of 25-35°C at a rotation speed of 100-200 rpm, and after filtration and separation, a first reaction product was obtained;

[0030] S2. The second reaction solution was prepared according to the volume ratio of 2-methyltetrahydrofuran: tetrahydropyran = 2:1; then the first reaction product obtained by the reaction was stirred with 2 L of the second reaction solution at a rotation speed of 50-200 rpm at 40°C for 1 hour, and after filtering the liquid, the above washing step was repeated once; after filtration, the solid was vacuum dried to obtain the negative electrode material.

[0031] The negative electrode, battery of the present embodiment were prepared by the following method:

[0032] Negative electrode: the negative electrode material prepared above, conductive carbon (SP), and binder (SBR) were added to deionized water in a ratio of 93:2:5 to prepare a slurry, the slurry was coated on a copper foil, and after drying, a negative electrode was obtained.

[0033] Battery: lithium iron phosphate positive electrode material, conductive carbon (SP), and binder (PVDF) were added to NMP in a ratio of 92:3:5 to prepare a slurry, the slurry was coated on an aluminum foil, and after drying, a positive electrode was obtained; then the positive electrode / negative electrode was assembled into a soft pack battery.

[0034] Example 2

[0035] The negative electrode material, negative electrode and battery of the present embodiment were prepared according to the formula and method provided in Example 1, and the difference between the present embodiment and Example 1 is that, in the preparation of the negative electrode material, 500 g of graphite with a capacity of C = 355 mAh / g was used as the negative electrode material precursor, and the mass of the graphite and the amount of substance of the lithium aromatic compound satisfy the following relationship: M = W x C x γ; wherein, In addition to the above difference, the operation steps for preparing the negative electrode material of the present embodiment are strictly consistent with those of Example 1.

[0036] Example 3

[0037] The negative electrode material, the negative electrode and the battery are prepared according to the formula and the method provided in Embodiment 1, and the difference from Embodiment 1 is that, in the preparation of the negative electrode material, 500 g of graphite with a capacity C = 340 mAh / g is used as the negative electrode material precursor, and the mass of the graphite and the amount of substance of the aromatic lithium compound satisfy the following relationship: M = W x C x γ; wherein, In addition to the above difference, the operation steps for preparing the negative electrode material in this embodiment are strictly consistent with those in Embodiment 1.

[0038] Embodiment 4

[0039] The negative electrode material, the negative electrode and the battery are prepared according to the formula and the method provided in Embodiment 1, and the difference from Embodiment 1 is that, in the preparation of the negative electrode material, 500 g of silicon-carbon material with a capacity C = 450 mAh / g is used as the negative electrode material precursor, and specifically, the step S1 is: mixing 500 g of silicon-carbon material with a capacity C = 450 mAh / g and 21 L of 0.0125 mol / L first reaction solution (the mass of the silicon-carbon material and the amount of substance of the aromatic lithium compound satisfy the following relationship: M = W x C x γ; wherein, In addition to the above difference, the operation steps for preparing the negative electrode material in this embodiment are strictly consistent with those in Embodiment 1.

[0040] The negative electrode: the negative electrode material prepared above, conductive carbon (SP), and binder (SBR) are added into deionized water in a ratio of 90:5:5 to form a slurry, the slurry is coated on a copper foil, and the negative electrode is obtained after drying.

[0041] The battery: NCM ternary positive electrode material, conductive carbon (SP), and binder (PVDF) are added into NMP in a ratio of 92:3:5 to form a slurry, the slurry is coated on an aluminum foil, and the positive electrode is obtained after drying; then the positive electrode / negative electrode is assembled into a soft package battery.

[0042] Embodiment 5

[0043] The negative electrode material, the negative electrode and the battery are prepared according to the formula and the method provided in Embodiment 4, and the difference from Embodiment 4 is that, in the preparation of the negative electrode material, 500 g of silicon-carbon material with a capacity C = 1800 mAh / g is used as the negative electrode material precursor, and specifically, the step S1 is: mixing 1800 mAh / g of silicon-carbon material and 21 L of 0.05 mol / L first reaction solution (the mass of the silicon-carbon material and the amount of substance of the aromatic lithium compound satisfy the following relationship: M = W x C x γ; wherein, In addition to the above difference, the operation steps for preparing the negative electrode material, the negative electrode and the battery in this embodiment are strictly consistent with those in Embodiment 4.

[0044] Example 6

[0045] The negative electrode material, negative electrode and battery of the present embodiment are prepared according to the formula and method provided in Example 5, except that in the preparation of the negative electrode material, 500 g of silicon-carbon material with a capacity of C = 1800 mAh / g is used as the precursor of the negative electrode material. Specifically, in step S1, 1800 mAh / g silicon-carbon material is mixed with 25 L of 0.042 mol / L first reaction solution (the volume of the lithium compound of aromatic hydrocarbon does not satisfy the following relationship: V (Si) = W x λ; where, The operation steps for preparing the negative electrode material, negative electrode and battery of the present embodiment are strictly consistent with those of Example 5, except for the above-mentioned difference.

[0046] Example 7

[0047] The negative electrode material, negative electrode and battery of the present embodiment are prepared according to the formula and method provided in Example 5, except that in the preparation of the negative electrode material, in step S2, the second reaction solution is configured with a volume ratio of 2-methyltetrahydrofuran: tetrahydropyran = 1:2. The operation steps for preparing the negative electrode material, negative electrode and battery of the present embodiment are strictly consistent with those of Example 5, except for the above-mentioned difference.

[0048] Example 8

[0049] The negative electrode material, negative electrode and battery of the present embodiment are prepared according to the formula and method provided in Example 5, except that in the preparation of the negative electrode material, in step S2, the second reaction solution is configured with a volume ratio of 2-methyltetrahydrofuran: tetrahydropyran = 4:1. The operation steps for preparing the negative electrode material, negative electrode and battery of the present embodiment are strictly consistent with those of Example 5, except for the above-mentioned difference.

[0050] Example 9

[0051] The negative electrode material, negative electrode and battery of the present embodiment are prepared according to the formula and method provided in Example 5, except that in the preparation of the negative electrode material, in step S2, the second reaction solution is configured with only 2-methyltetrahydrofuran. The operation steps for preparing the negative electrode material, negative electrode and battery of the present embodiment are strictly consistent with those of Example 5, except for the above-mentioned difference.

[0052] Example 10

[0053] The negative electrode material, the negative electrode and the battery of the present example are prepared according to the formula and method provided in Example 5. The difference between the present example and Example 5 is that, in the preparation of the negative electrode material, the second reaction solution is configured only with tetrahydropyran in step S2. Except for the above difference, the operation steps for preparing the negative electrode material, the negative electrode and the battery of the present example are strictly consistent with those of Example 5.

[0054] Example 11

[0055] The negative electrode material, the negative electrode and the battery of the present example are prepared according to the formula and method provided in Example 5. The difference between the present example and Example 5 is that, in the preparation of the negative electrode material, the step S2 is not performed. Except for the above difference, the operation steps for preparing the negative electrode material, the negative electrode and the battery of the present example are strictly consistent with those of Example 5.

[0056] Comparative Example 1

[0057] The negative electrode material, the negative electrode and the battery of the present example are prepared according to the formula and method provided in Example 5. The difference between the present example and Example 5 is that, in the preparation of the negative electrode material, a silicon-carbon material with a capacity of 500 g and C = 1800 mAh / g is used as the negative electrode material precursor. Specifically, the step S1 is: mixing the silicon-carbon material with a capacity of 1800 mAh / g and 21 L of the first reaction solution with a concentration of 0.07 mol / L (the mass of the silicon-carbon material and the amount of substance of the aromatic lithium compound do not satisfy the following relationship: M = W x C x γ). Except for the above difference, the operation steps for preparing the negative electrode material, the negative electrode and the battery of the present example are strictly consistent with those of Example 5.

[0058] Comparative Example 2

[0059] The negative electrode and the battery of the present comparative example are prepared according to the formula and method provided in Example 1. The difference between the present comparative example and Example 1 is that, in the present comparative example, the graphite is not treated in any way. Except for the above difference, the operation steps for preparing the negative electrode and the battery of the present comparative example are strictly consistent with those of Example 1.

[0060] Comparative Example 3

[0061] The negative electrode and the battery of the present comparative example are prepared according to the formula and method provided in Example 5. The difference between the present comparative example and Example 5 is that, in the present comparative example, the silicon-carbon material (C = 1800 mAh / g) is not treated in any way. Except for the above difference, the operation steps for preparing the negative electrode and the battery of the present comparative example are strictly consistent with those of Example 5.

[0062] Test Example

[0063] 1. Test object

[0064] Examples 1-10 use the negative electrode materials prepared in Comparative Examples 1-4 and the batteries using the same.

[0065] 2. Test method

[0066] (1) First cycle coulombic efficiency (initial efficiency): The first charge capacity and the first discharge capacity of the battery are measured using a 0.2C current density, and the calculation formula of the first cycle coulombic efficiency is: (first charge capacity / first discharge capacity)*100%.

[0067] (2) Energy density: For a ternary material battery, the calculation formula of the energy density is: first discharge capacity*3.6V / battery weight; for a lithium iron phosphate battery, the calculation formula of the energy density is: first discharge capacity*3.2V / battery weight.

[0068] (3) Cycle performance: At room temperature, the battery is subjected to cyclic charging and discharging using a 1C current density, and the capacity retention rate of the battery after 1000 cycles is compared.

[0069] (4) Negative electrode material surface element content test: 5-30mg of the powder test object is taken, ensuring that the sample has no magnetism, no corrosiveness, no volatile elements, and the length, width and height do not exceed 5*5*3mm; then it is directly stuck on the sample table with double-sided tape (ordinary / conductive glue); the test object is transmitted into the XPS test chamber, positioned, parameters are set, the full spectrum and target element narrow spectrum of the sample are tested, and the negative electrode material surface element content is tested. When the H content is ≤0.2%, the N content is ≤0.05%, the S content is ≤0.02%, and the O content is ≤0.03%, it is represented by "O"; when any of the above element content conditions is not met, it is represented by "X".

[0070] 3. Test results and analysis

[0071] The test results of the present test example are shown in Table 1. In Examples 1-4, different negative electrode precursor materials are used to prepare negative electrode materials, and in combination with Comparative Examples 1-3, it can be seen that the surface modification method provided by the present application can achieve the purpose of removing the surface groups of the negative electrode material without damaging the structure of the negative electrode material, and further enhance the electrochemical performance of the negative electrode material, thereby enhancing the first cycle coulombic efficiency, energy density and cycle performance of the battery using the same. Comparative Example 1 provides the conventional role of the present aromatic lithium compound, i.e. modifying the negative electrode material as a pre-lithiation or lithium supplementing agent, so that lithium ions can enter the interior of the negative electrode material, and the negative electrode material reaches a lithium-rich state. However, the present application reduces the reducing power of the reagent, so that it only plays a role in eliminating the surface groups of the graphite material, and only a small amount of lithium ions enter the graphite interior. Therefore, another inventive concept for surface modification of the negative electrode material is provided.

[0072] As can be seen from Examples 1-3, when graphite is used as the negative electrode material, when the aromatic lithium compound of the first reaction solution satisfies M=WxCy; (wherein, ), and the specific capacity of the graphite satisfies 340 mAh / g ≤ C (C) ≤ 355 mAh / g has a better modification effect.

[0073] It can be illustrated by Examples 4-6 that when the silicon-carbon material is used as the negative electrode material, when the arene lithium compound of the first reaction solution satisfies M = W x C x γ; (wherein, ), and the specific capacity of the silicon-carbon material satisfies 400 mAh / g ≤ C (Si) ≤ 2000 mAh / g has a better modification effect. In addition, when the volume of the first reaction solution satisfies V (Si) = W x λ has a better modification effect.

[0074] It can be known from the test data of Example 5, Examples 7-10 and Comparative Example 4 that different second reaction solutions also affect the electrochemical performance of the negative electrode material. This is likely because after the reduction reaction in the S1 step, there are residual arene lithium on the surface of the negative electrode material precursor. When the second reaction solution is added for cleaning, free lithium ions are generated due to the reaction between the second reaction solution and the residual arene lithium; and the free lithium ions further produce complexation reactions with unreacted solvent molecules, thereby changing the electronic cloud structure of the solvent molecules and forming substances similar to SEI films on the surface of the negative electrode material precursor. In addition, it can be known through tests that the second reaction solution of 2-methyltetrahydrofuran has a better effect, but its price is higher, which is easy to cause cost increase. By matching tetrahydropyran and making the volume ratio of 2-methyltetrahydrofuran to tetrahydropyran be 1-2:1-2, a better effect is obtained.

[0075] Table 1. Test results of the test example

[0076] Group Initial efficiency / % Energy density / (Wh / kg) Cycle performance / % Element content Example 1 92.5 183 97.5 O Example 2 92.5 185 97.3 O Example 3 92.4 180 97.6 O Example 4 91.0 300 93.8 O Example 5 90.5 320 92.5 O Example 6 88.1 298 89.1 X Example 7 91.8 318 91.7 O Example 8 91.3 332 93.1 O Example 9 92.0 335 93.1 O Example 10 91.6 319 91.3 X Example 11 91.2 306 90.0 O Comparative Example 1 89.4 310 89.7 X Comparative Example 2 92.0 170 97.0 X Comparative Example 3 85.0 298 88.6 X

[0077] The above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for surface modification of a negative electrode material, characterized by, The method comprises the following steps: S1. mixing a negative electrode material precursor with a first reaction solution under an inert gas atmosphere to obtain a first reactant; wherein the first reaction solution comprises a lithium compound of an aromatic hydrocarbon; and the negative electrode material precursor is graphite or silicon-carbon material; The first reaction solution is prepared by mixing an aromatic hydrocarbon, a lithium source and a solvent, wherein the aromatic hydrocarbon comprises at least one of biphenyl, a biphenyl derivative, naphthalene, a naphthalene derivative, pyrene, a pyrene derivative, and diphenylmethane; S2. cleaning the first reactant with a second reaction solution, and drying to obtain a negative electrode material; In the S1, the amount of substance of the arene lithium compound is M mol, the amount of the negative electrode material precursor is W g, the specific capacity of the negative electrode material precursor is C mAh / g, and the amounts of the arene lithium compound and the negative electrode material precursor satisfy the following relationship: ; wherein, .

2. The surface modification method of claim 1, wherein The negative material precursor is graphite, the specific capacity C of the graphite satisfies: 340 mAh / g ≤ C ≤ 355 mAh / g. (C) The specific capacity C of the graphite satisfies: 340 mAh / g ≤ C ≤ 355 mAh / g. (C) The specific capacity C of the graphite satisfies: 340 mAh / g ≤ C ≤ 355 mAh / g.

3. The surface modification method of claim 1, wherein the surface modification method is performed in a vacuum chamber. The negative electrode material precursor is a silicon-carbon material, and the specific capacity C of the silicon-carbon material satisfies: 400 mAh / g ≤ C ≤ 2000 mAh / g. (Si) 400 mAh / g ≤ C ≤ 2000 mAh / g. (Si) 400 mAh / g ≤ C ≤ 2000 mAh / g.

4. The surface modification method of claim 1, wherein The second reaction solution comprises at least one of 2-methyltetrahydrofuran, tetrahydropyran, pentahydrofuran, and hexahydrofuran.

5. The surface modification method of claim 4, wherein the surface modification method is performed in a vacuum. The second reaction solution comprises 2-methyltetrahydrofuran and tetrahydropyran; and the volume ratio of 2-methyltetrahydrofuran to tetrahydropyran is 1-2:1-2.

6. A negative electrode material, characterized by, The negative electrode material is prepared by the surface modification method according to any one of claims 1-5.

7. A battery, characterized by The battery comprises the negative electrode material prepared by the surface modification method according to any one of claims 1-5.

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