Lithium ion battery negative electrode structure for inhibiting lithium precipitation and preparation method of lithium ion battery negative electrode structure

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery negative electrode structure for inhibiting lithium precipitation and a preparation method of the lithium ion battery negative electrode structure. Comprising a graphite layer and a lithium storage functional layer which are stacked, the lithium storage functional layer comprises at least two silicon negative electrode materials with different particle sizes, and the thickness of the graphite layer is larger than that of the lithium storage functional layer. When the lithium ion battery is used for charging and discharging circulation, the lithiation degree of the lithium storage layer is controlled to achieve the effects of reducing the lithium precipitation tendency and controlling the volume expansion at the same time, so that the cycle life of the battery is prolonged, and the charging safety of the battery is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery negative electrode structure for inhibiting lithium precipitation and a preparation method thereof. BACKGROUND

[0002] As a core energy device, lithium ion batteries are widely used in the fields of portable electronic devices, electric vehicles and energy storage systems. Their performance and service life depend largely on the structural stability and reaction uniformity of the negative electrode material. Graphite has been the mainstream negative electrode material for lithium ion batteries for a long time due to its good reversible lithium intercalation performance, high first coulomb efficiency and low cost.

[0003] However, with the increasing demand for battery energy density, the negative electrode material faces greater challenges in fast charging performance and high rate performance. In practical applications, especially in the case of thick electrode design, the reaction of the graphite negative electrode along the thickness direction is obviously uneven. The area close to the electrolyte side (i.e. the surface layer of the electrode) often preferentially undergoes lithium intercalation reaction due to the short lithium ion transport path and small polarization degree. This leads to a high degree of lithiation of the surface layer graphite particles in a short time, even exceeding the theoretical capacity limit, and further triggering the precipitation of lithium metal.

[0004] The problem of lithium precipitation not only reduces the reversible capacity and cycle life of the battery, but also may promote the formation of lithium dendrites, causing serious safety hazards. Although the existing technology can alleviate the problem of lithium precipitation to some extent by optimizing the thickness of the electrode, improving the electrolyte formula or adjusting the charging strategy, it is difficult to fundamentally solve the problem of excessive lithium intercalation in the surface layer caused by uneven reaction along the thickness direction.

[0005] Therefore, there is an urgent need for a new negative electrode structure design method that can not only fully utilize the high energy density advantage of graphite material, but also effectively alleviate the problem of lithium precipitation caused by uneven lithiation along the thickness direction, thereby improving the service life and safety of lithium ion batteries. SUMMARY

[0006] The purpose of the present application is to provide a lithium ion battery negative electrode structure for inhibiting lithium precipitation and a preparation method thereof, which introduces a low-thickness lithium storage functional layer on the surface of a high-thickness graphite negative electrode to solve the problem of lithium precipitation caused by lithium ion concentration gradient.

[0007] To achieve the above-mentioned purpose, the first aspect of the present application provides a lithium ion battery negative electrode structure, which comprises a graphite layer and a lithium storage functional layer arranged in layers, the lithium storage functional layer comprises a silicon negative electrode material, and the thickness of the graphite layer is greater than the thickness of the lithium storage functional layer.

[0008] Further, the thickness of the graphite layer is ≥40 μm, and the thickness of the lithium storage functional layer is ≤10 μm.

[0009] Further, the thickness of the graphite layer is 40-200 μm, and the thickness of the lithium storage functional layer is 0.5-8 μm, preferably 3-5 μm.

[0010] Further, the lithium storage functional layer comprises at least two kinds of silicon negative electrode materials with different particle sizes, and the silicon negative electrode materials preferably comprise silicon negative electrode materials with a particle size of ≤100 nm and silicon negative electrode materials with a particle size of 0.5-5 μm.

[0011] Further, the mass ratio of the silicon negative electrode materials with a particle size of ≤100 nm and the silicon negative electrode materials with a particle size of 0.5-5 μm is 1:(0.5-4), preferably 1:(1-3).

[0012] Further, the silicon negative electrode materials comprise one or more of nano-silicon, silicon-carbon composite material, silicon oxide, and silicon-coated metal oxide; and the lithium storage functional layer preferably further comprises a conductive agent and a binder.

[0013] The second aspect of the present application provides a preparation method of the lithium ion battery negative electrode structure according to any one of the above aspects, comprising the following steps:

[0014] S1, preparing graphite slurry and lithium storage material slurry;

[0015] S2, coating the graphite slurry on the surface of the current collector, and roll-pressing after drying to form a graphite layer;

[0016] S3, coating the lithium storage material slurry on the surface of the graphite layer, and roll-pressing after drying to form a lithium storage functional layer.

[0017] Further, the graphite slurry comprises graphite powder, a conductive agent, and a binder, and the solvent is N-methyl pyrrolidone or water;

[0018] The lithium storage material slurry comprises silicon negative electrode materials, a conductive agent, and a binder, and the solvent is water or an organic solvent.

[0019] The third aspect of the present application provides a lithium ion battery comprising the lithium ion battery negative electrode structure according to any one of the above aspects.

[0020] The fourth aspect of the present application provides a method for inhibiting lithium precipitation of the lithium ion battery according to the above aspects, comprising: when the lithium ion battery is used for charging and discharging cycles, controlling the maximum capacity of each charging and discharging to be 0.2-0.5 times the sum of the capacity of the lithium storage functional layer and the capacity of the graphite layer, so as to inhibit lithium precipitation on the surface of the graphite layer by using the lithium storage functional layer, and reduce the expansion of the lithium storage functional layer.

[0021] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages:

[0022] 1. The lithium ion battery negative electrode structure for inhibiting lithium precipitation provided by the present application, by introducing a lithium storage functional layer with a larger specific capacity than graphite on the surface of the graphite electrode sheet, the lithium ion distribution in the thickness direction of the graphite negative electrode can be effectively adjusted, the precipitation of surface metal lithium is inhibited, and the cycle life and charging safety of the battery are improved.

[0023] 2. The present application reduces the life reduction problem caused by expansion through different particle size silicon negative electrode materials, and balances the lithium precipitation and cycle life by adjusting the proportion of the two particle sizes, so as to obtain a lithium ion battery negative electrode structure with excellent comprehensive performance, improve the cycle stability and safety performance, and especially perform superiorly under the conditions of fast charging and thick electrode sheet.

[0024] 3. The present application adjusts the thickness of the graphite layer and the lithium storage functional layer, and only a thinner lithium storage functional layer is needed on the surface of the graphite layer with larger thickness to inhibit the lithium precipitation phenomenon, and the expansion rate of the lithium storage functional layer with smaller thickness is significantly reduced, so it will not cause a significant reduction in cycle life.

[0025] 4. The structure design of the present application is simple and easy to implement on existing production lines; it is suitable for various negative electrode material systems and has good universality; the thinner lithium storage functional layer will not significantly increase the thickness of the electrode sheet and the cost of electrode preparation, and maintain a high energy density. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic cross-sectional view of the lithium storage layer graphite negative electrode structure of the present application.

[0027] Figure 2 is an SEM cross-sectional view of the lithium storage layer graphite negative electrode manufactured by the present application.

[0028] Figure 3 is a typical thickness-direction lithium ion distribution schematic diagram of the graphite negative electrode at 60% SOC under 1C rate discharge.

[0029] Figure 4 is a process flow chart for manufacturing the lithium storage layer electrode.

[0030] Figure 5 is a cycle performance curve comparison result graph of the lithium storage layer electrode, LSL represents the lithium storage functional layer.

[0031] Figure 6 is a surface SEM comparison graph of the electrode with and without lithium storage layer at 60% SOC under 3C rate. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0033] The first aspect of the present application provides a lithium ion battery negative electrode structure, comprising a graphite layer and a lithium storage functional layer arranged in a stack, the lithium storage functional layer comprising at least two silicon negative electrode materials with different particle sizes, and the thickness of the graphite layer being greater than the thickness of the lithium storage functional layer.

[0034] The lithium storage functional layer of the present application is composed of lithium ion intercalation materials with higher capacity than graphite, which is used to absorb lithium ions that preferentially intercalate into the surface layer of graphite during rapid charging, so as to inhibit the generation of lithium dendrites on the surface layer of graphite.

[0035] In particular, the other side of the graphite layer is also attached with a current collector, such as a copper foil, which plays a supporting and conductive role. Its surface is often treated to enhance the bonding force with the active layer.

[0036] The graphite layer is composed of natural graphite or artificial graphite particles, with conductive agents and binders (such as PVDF, SBR / CMC, etc.), which is formed on the surface of the copper foil through the first coating process. This layer serves as the main lithium ion intercalation / deintercalation carrier, and its thickness is usually greater than 40 μm, and the purpose of the present application is to solve the problem of lithium precipitation on the surface of the graphite negative electrode with large thickness.

[0037] The graphite layer is subjected to roller pressing treatment to achieve a compacted density of 1.4-1.6 g / cm 3 , which helps to improve the overall load of the electrode.

[0038] The thickness of the graphite layer is ≥40 μm, and the thickness of the lithium storage functional layer is ≤10 μm.

[0039] The thickness of the graphite layer is 40-200 μm, and the thickness of the lithium storage functional layer is 0.5-8 μm, preferably 1-3 μm (when the thickness of the graphite layer is <80 um) or 3-5 μm (when the thickness of the graphite layer is >80 um). Within this thickness range, the buffer effect can be significantly played, and the problem of structural instability caused by excessive deformation of the material due to expansion can be avoided, thereby affecting the cycle life.

[0040] Further, the silicon negative electrode material includes silicon negative electrode material with particle size ≤100 nm and silicon negative electrode material with particle size between 0.5-5 μm. By multiple particle size distribution, the lithium ion reaction rate is controlled, the priority absorption of lithium ion and the synergistic control of the reduction of expansion rate are realized, and then the adverse effects caused by the expansion of the silicon negative electrode material are effectively prevented. Preferably, the silicon negative electrode material includes silicon negative electrode material with particle size of 20-100 nm and silicon negative electrode material with particle size between 2-5 μm. Or includes silicon negative electrode material with particle size of 20-100 nm and silicon negative electrode material with particle size between 0.5-1 μm.

[0041] Further, the mass ratio of the silicon negative electrode material with particle size ≤100 nm and the silicon negative electrode material with particle size between 0.5-5 μm is 1:(0.5-4), preferably 1:(1-3).

[0042] The present application proposes to control the particle size distribution of the silicon negative electrode material in the lithium storage material, realize the control of the lithium ion intercalation reaction rate thereof, and specifically:

[0043] Small particle size (such as nanometer <100 nm) active material has higher specific surface area and faster reaction kinetics, which improves the initial lithium absorption capacity; the active material with large particle size (such as 0.5-5 μm) has slower reaction rate, which can reduce the initial lithium absorption speed, thereby avoiding the interface expansion and structure damage caused by too fast reaction under certain conditions. The particle size of the lithium storage layer material is determined according to the actual working condition (rate, capacity).

[0044] After the particle size is controlled, the lithium intercalation speed gradient is formed, the graphite main layer is better protected, and the lithium dendrite formation is delayed.

[0045] When the thickness of the graphite layer increases, the thickness of the lithium storage functional layer is increased, and the proportion of small particle nano-silicon is correspondingly increased, so that more excellent lithium storage effect is realized. The lithium storage layer after the particle size of the silicon particles is controlled can realize the following synergistic effects:

[0046] Under the condition of fast charging, the fine particle silicon on the surface of the lithium storage layer preferentially intercalates lithium, effectively intercepts part of the high flux lithium ions; due to the reduced reaction rate, the medium particle size silicon gradually participates in the lithium intercalation in the subsequent stage, effectively reducing the peak value of the volume expansion; further reducing the local lithium ion concentration on the surface of the graphite electrode, relieving the super-lithiation of the graphite surface layer, and significantly inhibiting the lithium precipitation.

[0047] Further, the silicon negative electrode material includes one or more of nano-silicon, silicon-carbon composite material (Si / C, Si@C, SiO x -C), silicon oxide (SiO x ), and silicon-coated metal oxide; and the lithium storage functional layer preferably further includes a conductive agent and a binder.

[0048] The binder in the lithium storage functional layer can be the same as or different from that in the graphite layer, and preferably a flexible binder system such as SBR / CMC or LA133 is used to buffer the expansion of the silicon-based material and enhance the cycle stability.

[0049] Referring to Figure 1 and 4 , the second aspect of the present application provides a preparation method of the lithium ion battery negative electrode structure according to any one of the preceding aspects, comprising the following steps:

[0050] S1, preparing a graphite slurry and a lithium storage material slurry;

[0051] S2, coating (such as doctor blade coating or slot die coating) the graphite slurry on the surface of the current collector, and roll pressing after drying to form a graphite layer;

[0052] S3, coating the lithium storage material slurry on the surface of the graphite layer, and roll pressing after drying to form a lithium storage functional layer.

[0053] The dried double-layer negative electrode sheet can be directly used for cell assembly, or can be further roll pressed or cut.

[0054] Further, the graphite slurry comprises graphite powder, a conductive agent and a binder, and the solvent is N-methyl pyrrolidone or water; the mass ratio of the graphite powder and the conductive agent is (85-95):(5-10).

[0055] The lithium storage material slurry comprises 60-70wt% of the silicon negative electrode material, 15-20wt% of the conductive agent and 15-20wt% of the binder, and the solvent is water or an organic solvent.

[0056] The lithium storage functional layer and the graphite main layer are in physical interface contact and have good interface bonding strength.

[0057] The third aspect of the present application provides a lithium ion battery comprising the lithium ion battery negative electrode structure according to any one of the preceding aspects. The present application is suitable for various types of graphite negative electrodes, and is particularly suitable for thick electrodes with high loading density. When the thickness of the graphite increases, the thickness of the lithium storage layer can be increased accordingly.

[0058] The fourth aspect of the present application provides a method for inhibiting lithium precipitation of the lithium ion battery described above, comprising: when the lithium ion battery is used for charging and discharging cycles, controlling the maximum capacity of each charging and discharging to be 0.2-0.5 times the sum of the capacity of the lithium storage functional layer and the capacity of the graphite layer, so as to inhibit the lithium precipitation on the surface of the graphite layer by using the lithium storage functional layer, and at the same time reduce the expansion of the lithium storage functional layer. At the same time, since the specific capacity of the lithium storage functional layer is higher than that of the graphite, the overall charging and discharging capacity is also higher than that of the graphite alone.

[0059] The application can significantly reduce lithium precipitation and improve the cycle life of the battery under 2C and above rate charging and discharging conditions.

[0060] Specifically, the preparation method of the lithium ion battery negative electrode structure comprises the following steps:

[0061] (1) Preparation of the graphite main layer

[0062] Slurry preparation

[0063] The natural or artificial graphite powder is mixed with the conductive agent (such as super carbon black) at a certain proportion (for example: graphite: conductive agent = 90:5, mass ratio). The binder (such as polyvinylidene fluoride PVDF or SBR / CMC system) is added, and an appropriate amount of N-methyl pyrrolidone (NMP) or water is added as a solvent, and the mixture is stirred and mixed uniformly to prepare a graphite slurry.

[0064] Coating and drying

[0065] The graphite slurry is coated on the surface of the pretreated copper foil (or other current collector) by using a doctor blade coating, a slot die coating or other conventional coating equipment. The coating parameters are adjusted according to the required electrode thickness (for example, 40-200 microns of dry film thickness). After coating, heat drying is carried out at room temperature or 50-60°C, and the drying time is usually about 60 minutes to ensure that the solvent is fully volatilized.

[0066] Compaction treatment

[0067] The dried graphite electrode sheet is subjected to roller pressing treatment, and the pressure is adjusted to increase the negative electrode density while ensuring the close contact between the particles. The roller pressing pressure is usually in the range of 0.5-1 MPa, which is optimized according to specific requirements.

[0068] (2) Preparation of the lithium storage functional layer

[0069] Slurry preparation

[0070] The lithium storage material is selected from silicon powder or silicon-based composite material. To reduce the silicon expansion effect and improve the cycle stability, pre-coated silicon particles or silicon-carbon composite material can be used. The mixing ratio can be set as follows: active material (silicon or composite material) accounts for 60-70% of the total solids, conductive agent (such as carbon black or conductive carbon fiber) accounts for 15-20%, and binder (such as SBR / CMC or LA133 flexible system) accounts for 15-20%. The solvent can be water or environmentally friendly organic solvent, and the slurry is stirred until it is uniformly dispersed.

[0071] Coating and drying

[0072] The above lithium storage slurry is uniformly coated on the surface of the pre-prepared, dried and compacted graphite electrode sheet. To ensure the uniformity and thickness control of the lithium storage layer, a precisely controlled coating machine can be used during the coating process. The target thickness is controlled at 0.5-8 microns, preferably 3-5 microns. After coating, a second drying is performed at 50-80°C for 6-8 hours to ensure complete evaporation of the solvent in the slurry.

[0073] Rolling solidification (optional step)

[0074] A slight re-rolling process is performed on the two-layer structure, which helps to further improve the interface contact between the lithium storage layer and the graphite layer, and improve the overall mechanical strength and electrical conductivity. The pressure is usually low to avoid damaging the lithium storage material.

[0075] (3) Electrode post-processing and assembly

[0076] According to actual needs, the double-layer electrode sheet is cut, the edges are trimmed and preheating treatment is performed to ensure that the electrode sheet size is consistent and the surface is flat.

[0077] Example 1

[0078] A method for preparing a lithium ion battery negative electrode structure, comprising the following steps:

[0079] (1) Preparation of graphite main layer

[0080] The graphite powder and super carbon black conductive agent are mixed in a mass ratio of 90:5, a binder polyvinylidene fluoride (PVDF) is added, and an appropriate amount of N-methyl pyrrolidone (NMP) is added as a solvent, and the mixture is stirred uniformly to prepare a graphite slurry.

[0081] The graphite slurry is coated on the surface of the pre-processed copper foil, and after coating, heat drying is performed at 70°C, and the drying time is usually about 6 hours to ensure sufficient evaporation of the solvent.

[0082] The dried graphite electrode sheet is subjected to rolling treatment, the pressure is adjusted to increase the negative electrode density, and at the same time ensure the close contact between the particles, and the rolling pressure is in the range of 0.5-1 MPa.

[0083] (2) Preparation process of lithium storage layer composed of multiple particle sizes of silicon particles

[0084] In the preparation of the lithium storage slurry, the following components are selected:

[0085] Silicon active material: nano-silicon with particle size D50≈80nm (denoted as Si1) and silicon microparticles with particle size D50≈3μm (denoted as Si2) are mixed in a mass ratio of 1:1, and the total addition amount is 60wt%;

[0086] Conductive agent: conductive carbon black (20wt%);

[0087] Binder: SBR / CMC (20 wt%);

[0088] Solvent: deionized water.

[0089] After sufficient stirring and ultrasonic dispersion, the mixture was coated on the surface of the graphite main layer, and then dried and slightly rolled. As shown in the table, the thickness of the graphite layer in the composite negative electrode prepared in this example was about 54.5 μm, and the thickness of the lithium storage functional layer was about 4.69 μm. Figure 2

[0090] The obtained electrode can be cycled for 96 times under fast charging (2C) conditions, and the cycle life of the battery is improved by about 100% compared with the pure graphite electrode, and the lithium precipitation phenomenon is obviously alleviated.

[0091] The treated negative electrode sheet, separator, electrolyte, lithium metal or pre-lithiated positive electrode material were assembled into a prototype battery (half battery) for electrochemical performance test and verification. During the cycle performance test, the maximum discharge capacity of each cycle was controlled to be 0.4 times the capacity of the lithium storage functional layer and the capacity of the graphite layer.

[0092] Example 2

[0093] The difference between Example 1 and Example 2 is that in step 2, the nano-silicon with a particle size D50 of about 80 nm (denoted as Si1) and the silicon microparticles with a particle size D50 of about 3 μm (denoted as Si2) are mixed in a mass ratio of 1:3. The other steps are the same as those in Example 1 and will not be repeated here.

[0094] Example 3

[0095] The difference between Example 1 and Example 3 is that in step 2, only nano-silicon with a particle size D50 of about 80 nm is included. The other steps are the same as those in Example 1 and will not be repeated here.

[0096] As can be seen from Figure 3 , after adding the lithium storage functional layer, the embedding speed and amount of lithium in the lithium storage functional layer are more, which can reduce the concentration on the surface of the graphite layer and inhibit lithium precipitation. As can be seen from Figure 6 , after adding the lithium storage functional layer, there is basically no lithium precipitation at 60% SOC under 3C rate, while lithium dendrites appear on the surface of the graphite layer without the lithium storage functional layer.

[0097] Comparative Example 1

[0098] The difference between Example 1 and Comparative Example 1 is that the negative electrode only contains the graphite layer prepared in step 1. The other steps are the same as those in Example 1 and will not be repeated here.

[0099] Table 1 Performance test results of examples and comparative examples

[0100]

[0101] ​The cycle life in Table 1 refers to the capacity dropping to 80% of the theoretical initial capacity.

[0102] As can be seen from Table 1, the rate performance and cycle life of the pure graphite electrode are low, and lithium is extracted at 1.5C rate. The example 3 with pure nano-silicon added can not extract lithium at 1.5C and 3C rates, and the cycle life is improved compared with the pure graphite electrode. When two kinds of silicon particles are used, the cycle life is further improved, and when Si1:Si2=1:3, the cycle life is the highest. This is because the specific surface area of large particles is relatively small, so the reaction speed is slower, and the expansion is lower. At the same time, the large particles can form a basic skeleton, and the small particles are small, so the expansion will collide between the pores formed by the large particles, and will not damage the overall structure. Therefore, when the mass ratio of large particles is appropriately increased, the cycle life is further improved. However, if the mass ratio of large particles continues to increase, although the silicon expansion is reduced, the cycle life is prolonged, but the lithium extraction phenomenon at high rate will gradually increase. Therefore, by reasonably controlling the content of two kinds of silicon particles, the lithium extraction and cycle life can be comprehensively controlled, and a lithium ion battery with excellent comprehensive performance can be obtained.

[0103] Those skilled in the art will readily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A lithium-ion battery negative electrode structure, characterized in that, It includes a graphite layer and a lithium storage functional layer stacked together, wherein the lithium storage functional layer includes a silicon anode material, and the thickness of the graphite layer is greater than the thickness of the lithium storage functional layer.

2. The lithium-ion battery negative electrode structure according to claim 1, characterized in that, The lithium storage functional layer includes at least two silicon anode materials with different particle sizes. The silicon anode materials preferably include silicon anode materials with a particle size ≤100nm and silicon anode materials with a particle size between 0.5-5μm.

3. The lithium-ion battery negative electrode structure according to claim 2, characterized in that, The mass ratio of the silicon anode material with a particle size ≤100nm to the silicon anode material with a particle size between 0.5-5μm is 1:(0.5-4), preferably 1:(1-3).

4. The lithium-ion battery negative electrode structure according to claim 1, characterized in that, The thickness of the graphite layer is ≥40μm, and the thickness of the lithium storage functional layer is ≤10μm.

5. The lithium-ion battery negative electrode structure according to claim 4, characterized in that, The thickness of the graphite layer is 40-200 μm, and the thickness of the lithium storage functional layer is 0.5-8 μm, preferably 3-5 μm.

6. The lithium-ion battery negative electrode structure according to claim 1, characterized in that, The silicon anode material includes one or more of nano-silicon, silicon-carbon composite material, silicon oxide, and silicon-coated metal oxide; the lithium storage functional layer preferably also includes a conductive agent and a binder.

7. A method for preparing a lithium-ion battery negative electrode structure according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Prepare graphite slurry and lithium storage material slurry; S2. Apply graphite slurry to the surface of the current collector, dry it, and then roll it to form a graphite layer. S3. Apply lithium storage material slurry to the surface of the graphite layer, dry it, and then roll it to form a lithium storage functional layer.

8. The method for preparing the lithium-ion battery negative electrode structure according to claim 7, characterized in that, The graphite slurry comprises graphite powder, a conductive agent, and a binder, and the solvent is N-methylpyrrolidone or water; The lithium storage material slurry includes silicon anode material, conductive agent and binder, and the solvent is water or organic solvent.

9. A lithium-ion battery, characterized in that, Includes the lithium-ion battery negative electrode structure according to any one of claims 1-6.

10. A method for suppressing lithium plating in a lithium-ion battery as described in claim 9, characterized in that, include: When the lithium-ion battery is used for charge-discharge cycles, the maximum capacity of each charge-discharge cycle is controlled to be 0.2 to 0.5 times the capacity of the lithium storage functional layer and the sum of the capacity of the graphite layer, so as to utilize the lithium storage functional layer to suppress lithium plating on the surface of the graphite layer and reduce the expansion of the lithium storage functional layer.

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