Pre-lithiated lithium ion battery negative plate, preparation method thereof and lithium ion battery

Abstract

The invention relates to a pre-lithiated lithium ion battery negative plate, a preparation method thereof and a lithium ion battery. The method comprises the following steps that S1, metal lithium and a matrix material are mixed and subjected to ball milling treatment, a pre-lithiated precursor is obtained, and the matrix material is selected from one or two of silicon and silicon monoxide; s2, mixing the pre-lithiated precursor with an electrolyte, and performing stabilization treatment to obtain a stabilized pre-lithiated solution; wherein the electrolyte comprises a carbonic ester compound, a fluorine-containing compound and an optional fluoro-ester compound; and S3, coating the stabilized pre-lithium solution on the negative pole piece. The pole piece pre-lithiation realizes uniform pre-lithiation of the surface of the pole piece, and the electrolyte used by the pre-lithiation solution and the electrolyte assembled by the subsequent battery belong to the same system, so that the pre-lithiation solution has good compatibility with the existing battery system.

Description

Technical Field

[0001] The present disclosure relates to the technical field of lithium-ion batteries, and in particular to a pre-lithiated lithium-ion battery negative electrode sheet, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries, with their energy density, high safety, and long cycle life, are a research hotspot in the energy storage field today. Improving battery energy density primarily relies on the development of key electrode materials, such as the continuous improvement of the capacity of positive and negative electrode materials. Existing lithium-ion battery anode materials are approaching their capacity limits. To meet the energy demands of the next generation and increase battery energy density, the development of new lithium-ion battery anode materials is crucial.

[0003] Silicon materials have attracted much attention due to their high theoretical capacity, abundant reserves, and low discharge voltage. However, silicon materials have large irreversible capacity loss in the first cycle and low first coulombic efficiency, resulting in a large amount of lithium ion consumption and loss in the first cycle, reducing the battery's energy density and cycle life, and seriously restricting the application of silicon-based materials in high-energy-density lithium-ion batteries.

[0004] Pre-lithiation technology provides an effective solution to solve the irreversible capacity loss and improve the coulombic efficiency. At present, pre-lithiation technology can be divided into powder pre-lithiation and pole piece pre-lithiation. The stable lithium metal powder SLMP (Stabilized Lithiμm Metal Powder) is evenly sprayed on the electrode surface and the pole piece can be pre-lithiated after rolling. However, due to the lighter specific gravity of lithium powder, how to ensure the uniform distribution of lithium powder on the pole piece after spraying is still a major difficulty in its practical application. At the same time, the high chemical activity of lithium powder will also cause greater safety hazards. Therefore, it is an urgent problem for those skilled in the art to study a pre-lithiation method that is simple to operate, has a short pre-lithiation time, low equipment requirements, high economic value, can be promoted on a large scale, and is compatible with existing battery systems. Summary of the Invention

[0005] The purpose of the present disclosure is to provide a pre-lithiation lithium-ion battery negative electrode sheet, a preparation method thereof, and a lithium-ion battery. The pre-lithiation of the electrode sheet realizes uniform pre-lithiation of the electrode sheet surface, and the electrolyte used in the pre-lithiation solution belongs to the same system as the electrolyte used in subsequent battery assembly, and has good compatibility with the existing battery system.

[0006] In order to achieve the above-mentioned object, the present disclosure provides a first aspect of a method for preparing a negative electrode sheet of a pre-lithiated lithium-ion battery, comprising the following steps:

[0007] S1, mixing metallic lithium with a matrix material and performing ball milling to obtain a pre-lithiation precursor, wherein the matrix material is selected from one or both of silicon and silicon monoxide;

[0008] S2. Mixing the pre-lithiation precursor with an electrolyte and performing a stabilization treatment to obtain a stabilized pre-lithiation solution; wherein the electrolyte comprises a carbonate compound, a fluorine-containing compound, and optionally a fluorinated ester compound;

[0009] S3, coating the stabilized pre-lithium solution on the negative electrode;

[0010] Steps S1 to S2 are respectively carried out under inert conditions.

[0011] Optionally, in step S1, the weight ratio of the metallic lithium to the matrix material is 1:0.01-1, preferably 1:0.1-0.5;

[0012] Optionally, the metallic lithium is selected from one or more of lithium ingots, lithium wires, lithium powders or lithium sheets;

[0013] Preferably, in the matrix, silicon is in the form of powder, the average particle size of the silicon powder is 0.5 to 10 μm, and the BET specific surface area is 0.1 to 50 μm. 2 / g; the silicon oxide is a powder, the average particle size of the silicon oxide powder is 1 to 20 μm; the BET specific surface area is 0.5 to 100 m 2 / g.

[0014] Optionally, in step S1, the conditions for the ball milling treatment include: a rotation speed of 300 to 2000 r / min, preferably 500 to 1000 r / min; a time of 6 to 72 hours, preferably 12 to 24 hours; and a ball-to-material ratio of 1 to 20:1, preferably 10 to 20:1.

[0015] Optionally, in step S2, the carbonate compound is selected from one or more of ethylene carbonate, propylene carbonate, diethyl carbonate and dimethyl carbonate;

[0016] The fluorine-containing compound is selected from one or more of lithium hexafluorophosphate, phosphorus pentafluoride and hydrofluoric acid;

[0017] The fluoroester compound is selected from one or more of fluoroethylene carbonate and fluoropropylene carbonate;

[0018] Preferably, the weight ratio of carbonate compound: fluorine-containing compound: fluorinated ester compound in the electrolyte is 1-20:1:0.1-10; preferably 1-10:1:0.1-1;

[0019] Optionally, in step S2, based on the total weight of the pre-lithiation precursor and the electrolyte, the content of the pre-lithiation precursor is 10 to 60 weight %, preferably 10 to 30 weight %.

[0020] Optionally, in step S2, the conditions for the stabilization treatment include: a ball milling speed of 200 to 1000 r / min, preferably 200 to 500 r / min; a time of 6 to 72 hours, preferably 10 to 20 hours; a ball to material ratio of 1 to 20:1, preferably 10 to 20:1;

[0021] Preferably, the particle size of the lithium particles in the stabilized pre-lithium solution is 0.05 to 5 μm, preferably 0.1 to 2 μm.

[0022] Optionally, in step S3, the coating thickness of the stabilized pre-lithium solution is 5 to 200 μm, preferably 10 to 50 μm;

[0023] Optionally, the method further comprises: drying the negative electrode plate coated with the stabilized pre-lithium solution; preferably, the drying conditions include: a drying temperature of 80 to 120° C. and a drying time of 6 to 48 hours.

[0024] Optionally, the negative electrode plate is prepared by the following method:

[0025] Mixing a negative electrode material, a conductive agent, and a binder to obtain a negative electrode slurry; coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode sheet;

[0026] Preferably, based on the total weight of the negative electrode material, the conductive agent and the binder, the content of the negative electrode material is 75-95% by weight, the content of the conductive agent is 3-20% by weight, and the content of the binder is 2-15% by weight; preferably, the content of the negative electrode material is 80-90% by weight, the content of the conductive agent is 5-10% by weight, and the content of the binder is 5-10% by weight;

[0027] Optionally, the negative electrode material is selected from one or more of silicon monoxide negative electrode material, graphite negative electrode material, silicon-carbon negative electrode material and silicon negative electrode material;

[0028] Optionally, the conductive agent is selected from one or more of acetylene black, conductive carbon black and carbon fiber tubes;

[0029] Optionally, the binder is selected from one or more of sodium carboxymethyl cellulose, polystyrene butadiene copolymer and polyvinylidene fluoride.

[0030] A second aspect of the present disclosure provides a pre-lithiated lithium-ion battery negative electrode sheet prepared according to the method described in the first aspect.

[0031] A third aspect of the present disclosure provides a pre-lithiated lithium-ion battery negative electrode sheet, which comprises a copper foil layer, a negative electrode material layer and a pre-lithiated layer stacked in sequence; the pre-lithiated layer comprises lithium-containing particles of a core-shell structure; the lithium-containing particles comprise a core, a buffer layer coated on the outer surface of the core, and a passivation layer coated on the outer surface of the buffer layer; the passivation layer is formed as an outer shell of the core-shell structure; the core comprises a lithium active component and a matrix material, and the matrix material is selected from one or both of silicon and silicon oxide; the buffer layer comprises a silicon-lithium alloy or a lithium silicate; the passivation layer comprises lithium fluoride and lithium carbonate; the negative electrode material layer comprises a negative electrode material, and the negative electrode material is selected from one or more of silicon oxide negative electrode material, graphite negative electrode material, silicon-carbon negative electrode material and silicon negative electrode material.

[0032] Optionally, the thickness ratio of the negative electrode material layer to the pre-lithiation layer is 1:0.01 to 2, preferably 1:0.1 to 1.7;

[0033] Preferably, the thickness of the passivation layer of the lithium-containing particles is 1 to 500 nm.

[0034] Optionally, based on the total weight of the lithium-containing particles, the content of the core is 50 to 95% by weight, preferably 80 to 95% by weight;

[0035] Optionally, the particle size of the lithium-containing particles ranges from 0.1 to 10 μm.

[0036] A fourth aspect of the present disclosure provides a lithium-ion battery, comprising the pre-lithiation lithium-ion battery negative electrode sheet described in the second aspect of the present disclosure.

[0037] Through the above technical solution, the present disclosure provides a pre-lithiated lithium-ion battery negative electrode sheet and a preparation method thereof, and a lithium-ion battery, which have at least the following beneficial effects:

[0038] (1) The present invention uses metal lithium and silicon and / or silicon oxide for ball milling treatment, and obtains a stabilized pre-lithiation solution through an electrolyte. The core of the stabilized lithium particles is a lithium active layer, the lithium silicon alloy / lithium silicate layer is a buffer layer, and the outer shell is a lithium fluoride / lithium carbonate passivation layer. The internal activity is high and the external stability is stable. The stable metal lithium powder prepared by the present invention has a small particle size. During the pre-lithiation treatment of the battery pole piece, a uniformly distributed and dense pre-lithiation layer can be formed on the surface of the pole piece, which can improve the kinetics of lithium metal ion extraction during pre-lithiation, and the pre-lithiation effect is good.

[0039] (2) The electrolyte used in the preparation of the pre-lithium solution disclosed herein belongs to the same system as the electrolyte used in subsequent battery assembly, is compatible with modern battery systems, and completely avoids the possibility of contact with impurities such as water and oxygen.

[0040] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0042] Figure 1 This is a scanning electron microscope photograph of a cross section of a negative electrode sheet of a pre-lithiation battery prepared according to the method of Example 1;

[0043] Figure 2 Element distribution diagram of the cross section of the negative electrode sheet of the pre-lithiation battery prepared according to the method of Example 1;

[0044] Figure 3 This is a scanning electron microscope photograph of the surface of the negative electrode sheet of a pre-lithiation battery prepared according to the method of Example 1;

[0045] Figure 4 Elemental spectrum of the surface of the negative electrode sheet of the pre-lithiation battery prepared according to the method of Example 1;

[0046] Figure 5 is a scanning electron microscope photograph of lithium particles in the pre-lithium solution prepared according to the method of Example 1;

[0047] Figure 6 is a transmission electron microscope photograph of lithium particles in the pre-lithium solution prepared according to the method of Example 1;

[0048] Figure 7 This is the first charge and discharge curve of a battery assembled using a pre-lithiation battery negative electrode sheet as the negative electrode prepared according to the method of Example 1 at a current density of 0.2C. DETAILED DESCRIPTION

[0049] The following describes the specific embodiments of the present disclosure in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0050] A first aspect of the present disclosure provides a method for preparing a pre-lithiated lithium-ion battery negative electrode sheet, comprising the following steps:

[0051] S1, mixing metallic lithium with a matrix material and performing ball milling to obtain a pre-lithiation precursor, wherein the matrix material is selected from one or both of silicon and silicon monoxide;

[0052] S2. Mixing the pre-lithiation precursor with an electrolyte and performing a stabilization treatment to obtain a stabilized pre-lithiation solution; wherein the electrolyte comprises a carbonate compound, a fluorine-containing compound, and optionally a fluorinated ester compound;

[0053] S3, coating the stabilized pre-lithium solution on the negative electrode;

[0054] Steps S1 to S2 are respectively carried out under inert conditions.

[0055] The present disclosure provides a method for preparing a negative electrode plate of a pre-lithiated lithium-ion battery. The present disclosure adopts ball milling treatment of metallic lithium with silicon and / or silicon dioxide, and obtains a stabilized pre-lithiated solution through an electrolyte. The inner core of the stabilized lithium particles is a lithium active layer, the lithium silicon alloy / lithium silicate layer is a buffer layer, and the outer shell is a lithium fluoride / lithium carbonate passivation layer. The inner activity is high and the outer stability is stable. The stable metallic lithium powder prepared by the present disclosure has a small particle size. During the pre-lithiated treatment of the battery electrode plate, a uniformly distributed and dense pre-lithiated layer can be formed on the surface of the electrode plate, which can improve the kinetics of lithium metal deintercalation and ion extraction during pre-lithiation, and the pre-lithiation effect is better. The electrolyte used in the preparation of the pre-lithiated solution of the present disclosure belongs to the same system as the electrolyte for subsequent battery assembly, is compatible with modern battery systems, and completely avoids the possibility of contact with impurities such as water and oxygen.

[0056] In one embodiment, the inert atmosphere comprises one or more of nitrogen, helium, neon, argon, krypton, and xenon; the inert atmosphere has a water content of less than 0.1% by weight and an oxygen content of less than 0.1% by weight. In this embodiment, the preferred inert gas environment further prevents lithium from reacting with oxygen and water in the environment, thereby making the material structure more stable.

[0057] In the present disclosure, the ball milling process and the stabilization process are both performed using a conventional ball mill device.

[0058] In one embodiment, in step S1, the weight ratio of the metallic lithium to the matrix material is 1:0.01 to 1, preferably 1:0.1 to 0.5. According to the preferred weight ratio in this embodiment, a pre-lithiated negative electrode sheet with better performance can be prepared.

[0059] In a specific embodiment, based on the total weight of the metallic lithium and the matrix material, the content of the metallic lithium is 5 to 50 weight%, and the content of the matrix material is 50 to 95 weight%; preferably, the content of the metallic lithium is 5 to 20 weight%, and the content of the matrix material is 80 to 95 weight%.

[0060] In one embodiment, the metallic lithium is selected from one or more of lithium ingots, lithium wires, lithium powders, or lithium sheets;

[0061] In the matrix, silicon is in powder form, the average particle size of the silicon powder is 0.5 to 10 μm, and the BET specific surface area is 0.1 to 50 m 2 / g; the silicon oxide is a powder, the average particle size of the silicon oxide powder is 1 to 20 μm; the BET specific surface area is 0.5 to 100 m 2 / g.

[0062] The raw materials used in the present disclosure can be purchased through common channels or prepared by known preparation methods.

[0063] In one embodiment, in step S1, the conditions of the ball milling treatment include: a rotation speed of 300 to 2000 r / min, a time of 6 to 72 hours, and a ball-to-material ratio of (1 to 50):1.

[0064] In a preferred embodiment, in step S1, the ball milling conditions include: a rotation speed of 500 to 1000 r / min, a time of 12 to 24 hours, and a ball-to-material ratio of (10 to 20): 1. Ball milling according to this embodiment helps to more evenly disperse the metallic lithium and the matrix material, thereby improving the performance of the lithium-containing material.

[0065] In one embodiment, in step S2, the carbonate compound is selected from one or more of ethylene carbonate, propylene carbonate, diethyl carbonate and dimethyl carbonate; preferably one or two of ethylene carbonate and propylene carbonate;

[0066] The fluorine-containing compound is selected from one or more of lithium hexafluorophosphate, phosphorus pentafluoride and hydrofluoric acid; preferably one or two of lithium hexafluorophosphate and phosphorus pentafluoride;

[0067] The fluorinated ester compound is selected from one or more of fluorinated ethylene carbonate and fluorinated propylene carbonate.

[0068] In a preferred embodiment, the weight ratio of the carbonate compound: the fluorine-containing compound: the fluorinated ester compound in the electrolyte is 1-20:1:0.1-10; preferably 1-10:1:0.1-1.

[0069] In one embodiment, in step S2, the content of the pre-lithiation precursor is 10 to 60% by weight, preferably 10 to 30% by weight, based on the total weight of the pre-lithiation precursor and the electrolyte. Stabilization treatment according to the preferred weight ratio in this embodiment can achieve a better passivation layer effect.

[0070] In a specific embodiment, in step S2, the conditions of the stabilization treatment include: a ball milling speed of 200 to 1000 r / min; a time of 6 to 72 hours; and a ball-to-material ratio of (1 to 50):1.

[0071] In a preferred embodiment, in step S2, the stabilization treatment conditions include: a ball milling speed of 200 to 500 r / min; a time of 10 to 20 hours; and a ball-to-material ratio of (10 to 20): 1. The passivation layer coating effect is better according to this embodiment, and the thickness of the passivation layer can be within an appropriate range.

[0072] In a preferred embodiment, the particle size of the lithium particles in the stabilized pre-lithium solution is 0.05 μm to 5 μm, preferably 0.1 μm to 2 μm.

[0073] In one embodiment, the negative electrode plate is prepared by the following method:

[0074] The negative electrode material, conductive agent and binder are mixed to obtain a negative electrode slurry; the negative electrode slurry is coated on copper foil and dried to obtain the negative electrode sheet. The negative electrode slurry is coated on the copper foil to form a negative electrode material layer on the copper foil.

[0075] In a specific embodiment, based on the total weight of the negative electrode material, the conductive agent and the binder, the content of the negative electrode material is 75-95 weight%, the content of the conductive agent is 3-20 weight%, and the content of the binder is 2-15 weight%; preferably, the content of the negative electrode material is 80-90 weight%, the content of the conductive agent is 5-10 weight%, and the content of the binder is 5-10 weight%.

[0076] In a specific embodiment, the negative electrode material is selected from one or more of silicon monoxide negative electrode materials, graphite negative electrode materials, silicon-carbon negative electrode materials and silicon negative electrode materials;

[0077] Optionally, the conductive agent is selected from one or more of acetylene black, conductive carbon black (such as Super P) and carbon fiber tubes;

[0078] Optionally, the binder is selected from one or more of sodium carboxymethyl cellulose, polystyrene butadiene copolymer (SBR), and polyvinylidene fluoride (PVDF).

[0079] The negative electrode material, conductive agent and binder used in the present disclosure can be obtained through common commercial channels or prepared by known methods.

[0080] In the present disclosure, the coating process of the negative electrode slurry is a conventional operation in the art.

[0081] A second aspect of the present disclosure provides a pre-lithiated lithium-ion battery negative electrode sheet prepared according to the method described in the second aspect of the present disclosure.

[0082] A third aspect of the present disclosure provides a pre-lithiated lithium-ion battery negative electrode sheet, which comprises a copper foil layer, a negative electrode material layer and a pre-lithiated layer stacked in sequence; the pre-lithiated layer comprises lithium-containing particles of a core-shell structure; the lithium-containing particles comprise a core, a buffer layer coated on the outer surface of the core, and a passivation layer coated on the outer surface of the buffer layer; the passivation layer is formed as an outer shell of the core-shell structure; the core comprises a lithium active component and a matrix material, and the matrix material is selected from one or both of silicon and silicon oxide; the buffer layer comprises a silicon-lithium alloy or a lithium silicate; the passivation layer comprises lithium fluoride and lithium carbonate; the negative electrode material layer comprises a negative electrode material, and the negative electrode material is selected from one or more of silicon oxide negative electrode material, graphite negative electrode material, silicon-carbon negative electrode material and silicon negative electrode material.

[0083] The present disclosure provides a pre-lithiated lithium-ion battery negative electrode sheet, which achieves uniform pre-lithiation on the electrode sheet surface. When the pre-lithiated negative electrode sheet is used in a lithium-ion battery, it significantly improves the initial coulombic efficiency and cycle stability of the lithium-ion battery. The pre-lithiated layer on the surface of the negative electrode sheet comprises lithium-containing particles with a core-shell structure, including a core, a buffer layer, and an outer shell; the core is a lithium-active core, the buffer layer is a lithium-silicon alloy or a lithium-silicate layer, and the outer shell is a passivation layer comprising lithium fluoride and lithium carbonate, wherein the buffer layer is a lithium-silicon alloy / lithium-silicate layer, which is a rigid layer and can prevent the formation of lithium dendrites during pre-lithiation of metallic lithium powder; the lithium fluoride / lithium carbonate passivation layer is a component of the battery SEI film and has good compatibility with the battery system, does not affect the electrochemical performance of the battery system, and the passivation layer prevents direct contact between the internal active lithium and the outside world, which can improve the stability of the material. In addition, the lithium-containing particles in the pre-lithiation layer have a smaller particle size, which can form a uniformly distributed and dense pre-lithiation layer on the surface of the negative electrode material layer, thereby improving the kinetics of lithium metal ion extraction during pre-lithiation and achieving a better pre-lithiation effect.

[0084] In one embodiment, the thickness ratio of the negative electrode material layer and the pre-lithiation layer is 1:0.01~2, preferably 1:0.1~1.7; preferably, the thickness of the passivation layer of the lithium-containing particles is 1~500nm. When the thickness ratio of the negative electrode material layer and the pre-lithiation layer in the negative electrode plate is within the preferred range in this embodiment, the negative electrode plate has better performance.

[0085] In a preferred embodiment, the surface porosity of the pre-lithiation layer is 30-60%, preferably 40-50%.

[0086] In one embodiment, based on the total weight of the lithium-containing particles, the content of the core is 50-95 weight %; the content of the buffer layer is 1-40 weight %; and the content of the passivation layer is 1-10 weight %.

[0087] In a preferred embodiment, based on the total weight of the lithium-containing particles, the core comprises 80-95% by weight, the buffer layer comprises 5-10% by weight, and the passivation layer comprises 1-5% by weight. The lithium-containing material provided by this embodiment can have higher stability, and the negative electrode sheet can achieve a higher initial coulombic efficiency in battery applications.

[0088] In the present disclosure, the contents of the core, buffer layer and passivation layer of the lithium-containing particles are calculated by ratio.

[0089] In one embodiment, the particle size of the lithium-containing particles ranges from 0.1 to 10 μm; the thickness of the passivation layer of the lithium-containing particles ranges from 1 to 500 nm. When the thickness of the passivation layer is within the range of this embodiment, the activity of the internal lithium can be maximized while ensuring the stability of the lithium-containing particles. The thickness of the passivation layer of the lithium-containing particles disclosed herein can be measured using electron microscopy images.

[0090] A fourth aspect of the present disclosure provides a lithium-containing battery, which comprises the pre-lithiated lithium-ion battery negative electrode sheet described in the second and third aspects of the present disclosure.

[0091] The materials such as the diaphragm used in the lithium-containing battery are all conventionally selected reagents in the art.

[0092] The present disclosure is further described in detail below through examples. The raw materials used in the examples can be obtained through commercial channels.

[0093] In the following examples, the specific testing methods are as follows:

[0094] The SEM test method is scanning electron microscopy, and the instrument model is S4800 from Hitachi, Japan;

[0095] The electrochemical cycling performance was tested using the Blue Electric test system, with the instrument model being CT3001A.

[0096] In the following examples and comparative examples, commercially available silicon oxide powder was used, with an average particle size of 2 to 10 μm. The chemical formula of the silicon oxide powder is SiO x , where 0.5≤x<2.

[0097] The chemical reagents used in the following examples and comparative examples are all common commercially available products.

[0098] In the following embodiments, when the carbonate compound in the electrolyte composition comprises a plurality of specific carbonate reagents, the content of each specific carbonate reagent in the electrolyte is the same. For example, the electrolyte comprises 6 wt % of carbonate compounds, and the carbonate compound comprises three carbonates (e.g., ethylene carbonate, propylene carbonate, and diethyl carbonate), then the content of each carbonate in the electrolyte is 2 wt %. When the electrolyte comprises a plurality of fluorine-containing compounds and a plurality of fluoroester compounds, the content is similar to that of the carbonate compound.

[0099] Example 1

[0100] A negative electrode material (silicon dioxide), a conductive agent (acetylene black), and a binder (sodium carboxymethyl cellulose) are mixed to obtain a negative electrode slurry; the negative electrode slurry is coated on a copper foil and dried to obtain a negative electrode sheet; wherein the weight ratio of the negative electrode material, the conductive agent, and the binder is 80:10:10 (i.e., based on the total weight of the negative electrode material, the conductive agent, and the binder, the content of the negative electrode material is 80% by weight, the content of the conductive agent is 10% by weight, and the content of the binder is 10% by weight); and the negative electrode slurry coating thickness is 30 μm;

[0101] Under an argon environment, 2 g of metallic lithium ingot and 0.2 g of silicon oxide were weighed and placed in a zirconia ball mill (the weight ratio of metallic lithium to matrix material was 1:0.1). After sealing, the jar was transferred to a planetary ball mill for ball milling. The ball-to-material ratio was 20:1, the diameters of the zirconium balls were 5.5 mm, 3.0 mm, and 2.0 mm, and the ratio was 2:5:3. The ball milling speed was 500 rpm and the ball milling time was 12 hours to obtain a pre-lithiation precursor. Then, 20 mL of electrolyte was added and ball milling was continued. The electrolyte included ethylene carbonate, propylene carbonate, lithium hexafluorophosphate, VC (vinylene carbonate), and FEC (fluoroethylene carbonate). The weight ratio of carbonate compounds: fluorine-containing compounds: fluoroester compounds in the electrolyte was 5:1:0.5. Based on the total weight of the pre-lithiation precursor and the electrolyte, the content of the pre-lithiation precursor was 10% by weight. The ball milling speed was 350 rpm and the ball milling time was 10 hours to obtain a stabilized pre-lithiation solution (the lithium particle size in the stabilized pre-lithiation solution was 0.2 to 2 μm). The pre-lithiation solution was coated on the prepared silicon oxide negative electrode sheet with a coating thickness of 50 μm and dried (drying temperature was 100°C and drying time was 12 hours) to obtain a pre-lithiation negative electrode sheet.

[0102] Assemble the above negative electrode sheets into a battery as follows:

[0103] A CR2025 button cell was assembled using the pre-lithiated negative electrode sheet prepared in the example as the electrode sheet and a lithium sheet as the counter electrode. The electrolyte was a mixture of 1M LiPF6, the solvent of which was a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate) (EC:DMC volume ratio of 1:1). The separator was a Celgard 2300 polypropylene microporous membrane. The sealed battery was left to rest for 24 hours, and its electrochemical performance was tested. The battery was subjected to charge and discharge tests and cycle performance tests using a Land battery performance test system.

[0104] Figure 1 This is a scanning electron microscope photograph of the cross section of the negative electrode sheet of a pre-lithiation battery prepared according to the method of Example 1. Figure 2 The element distribution diagram of the cross section of the negative electrode sheet of the pre-lithiation battery prepared according to Example 1; Figures 1-2 It can be seen that the pre-lithiation battery negative electrode sheet prepared by the method provided in the present invention has a clear three-layer structure, namely a copper foil layer, a silicon oxide layer and a lithium layer. The lithium layer and the silicon oxide layer are densely combined and have good compatibility. According to the electron microscope photos, it can be measured that the thickness ratio of the negative electrode material layer and the pre-lithiation layer is 3:5.

[0105] Figure 3 This is a scanning electron microscope photograph of the surface of the negative electrode sheet of a pre-lithiation battery prepared according to the method of Example 1. Figure 5 The scanning electron microscope photograph of the lithium-containing particles prepared according to the method of this embodiment (measured before the pre-lithium solution is applied). Figure 3 and Figure 5 It can be seen that the lithium-containing particles prepared in the present disclosure have a relatively small particle size, ranging from about 0.2 to 2 μm (e.g. Figure 5 As shown), during the pre-lithiation treatment of the battery electrode, a uniformly distributed and dense pre-lithiation layer can be formed on the surface of the electrode, which can have a positive impact on improving the kinetics of lithium metal ion extraction and deintercalation during pre-lithiation and improving the pre-lithiation effect.

[0106] Figure 4 This is the elemental spectrum of the surface of the pre-lithiation battery negative electrode prepared according to the method of Example 1; as can be seen from the figure, after the metal lithium powder is passivated, characteristic peaks of lithium fluoride and lithium carbonate, the main components of the SEI film, appear on the surface, indicating that an artificial SEI passivation layer is formed on the surface of the metal lithium powder.

[0107] Figure 6 TEM image of the stable metallic lithium powder prepared according to the method of Example 1. Figure 6 It can be clearly seen that the stable metallic lithium powder prepared in this embodiment includes a passivation layer, a buffer layer and a core structure. The buffer layer and the artificial SEI passivation layer structure improve the stability of the metallic lithium powder, making it possible to perform coating pre-lithiation in an air environment, which is compatible with modern battery systems.

[0108] Comparative Example 1

[0109] This comparative example refers to the preparation method of Example 1, and the difference from Example 1 is that no silicon oxide is added, and the pre-lithium solution obtained in this comparative example is a non-uniform slurry, in which the lithium particles are large and small discs, which cannot be evenly coated on the prepared silicon oxide negative electrode plate.

[0110] Comparative Example 2

[0111] This comparative example refers to the preparation method of Example 1, and the difference from Example 1 is:

[0112] The electrolyte contains only pure ethylene carbonate and no other reagents; the rest of the process is the same as in Example 1.

[0113] Comparative Example 3

[0114] This comparative example refers to the preparation method of Example 1, and the difference from Example 1 is:

[0115] The electrolyte contains only lithium hexafluorophosphate (using cyclohexane as solvent) and no other reagents; the rest of the process is the same as in Example 1.

[0116] Example 2

[0117] A negative electrode material (silicon oxide), a conductive agent (conductive carbon black), and a binder (sodium carboxymethyl cellulose) are mixed to obtain a negative electrode slurry; the negative electrode slurry is coated on a copper foil and dried to obtain a negative electrode sheet; wherein the weight ratio of the negative electrode material, the conductive agent, and the binder is 80:10:10 (i.e., based on the total weight of the negative electrode material, the conductive agent, and the binder, the content of the negative electrode material is 80% by weight, the content of the conductive agent is 10% by weight, and the content of the binder is 10% by weight); and the negative electrode slurry coating thickness is 50 μm;

[0118] Under an argon environment, 2 g of metallic lithium ingot and 0.5 g of silicon oxide were weighed and placed in a zirconia ball mill (the weight ratio of metallic lithium to matrix material was 1:0.25). After sealing, they were transferred to a planetary ball mill for ball milling. The ball-to-material ratio of the ball milling was 20:1, the diameters of the zirconium balls were 5.5 mm, 3.0 mm, and 2.0 mm, and the ratio was 2:5:3. The ball milling speed was 400 rpm and the ball milling time was 48 hours to obtain a pre-lithiation precursor. Then, 50 mL of electrolyte was added and ball milling was continued. The electrolyte included ethylene carbonate, propylene carbonate, lithium hexafluorophosphate, VC, and FEC. The weight ratio of carbonate compounds: fluorine-containing compounds: fluoroester compounds in the electrolyte was 1:1:1. Based on the total weight of the pre-lithiation precursor and the electrolyte, the content of the pre-lithiation precursor was 20% by weight. The ball milling speed was 350 rpm and the ball milling time was 12 hours to obtain a stabilized pre-lithiation solution (the particle size of lithium particles in the stabilized pre-lithiation solution was 0.05 to 1 μm). The pre-lithiation solution was coated on the prepared silicon oxide negative electrode sheet with a coating thickness of 30 μm. After drying (drying temperature was 100°C and drying time was 12 hours), a pre-lithiation negative electrode sheet was obtained.

[0119] The negative electrode sheets were assembled into a battery according to the method in Example 1.

[0120] Example 3

[0121] A negative electrode material (silicon dioxide), a conductive agent (carbon nanotubes), and a binder (sodium carboxymethyl cellulose) are mixed to obtain a negative electrode slurry; the negative electrode slurry is coated on a copper foil and dried to obtain a negative electrode sheet; wherein the weight ratio of the negative electrode material, the conductive agent, and the binder is 90:7:3 (i.e., based on the total weight of the negative electrode material, the conductive agent, and the binder, the content of the negative electrode material is 90 weight%, the content of the conductive agent is 7 weight%, and the content of the binder is 3 weight%), and the negative electrode slurry coating thickness is 80 μm;

[0122] Under an argon environment, 2 g of metallic lithium ingot and 1 g of silicon oxide were weighed and placed in a zirconia ball mill (the weight ratio of metallic lithium to matrix material was 1:0.5). After sealing, the jar was transferred to a planetary ball mill for ball milling. The ball-to-material ratio was 20:1, the diameters of the zirconium balls were 5.5 mm, 3.0 mm, and 2.0 mm, and the ratio was 2:5:3. The ball milling speed was 500 rpm and the ball milling time was 12 hours to obtain a pre-lithiation precursor. Then, 6 mL of electrolyte was added and ball milling was continued. The electrolyte included ethylene carbonate, propylene carbonate, lithium hexafluorophosphate, VC, and FEC. The weight ratio of carbonate compounds: fluorine-containing compounds: fluoroester compounds in the electrolyte was 8:1:0.5. Based on the total weight of the pre-lithiation precursor and the electrolyte, the content of the pre-lithiation precursor was 30% by weight. The ball milling speed was 350 rpm and the ball milling time was 10 hours to obtain a stabilized pre-lithiation solution (the particle size of lithium particles in the stabilized pre-lithiation solution was 0.05 to 1 μm). The pre-lithiation solution was coated on the prepared silicon oxide negative electrode sheet with a coating thickness of 30 μm. After drying (drying temperature was 100°C and drying time was 24 hours), a pre-lithiation negative electrode sheet was obtained.

[0123] The negative electrode sheets were assembled into a battery according to the method in Example 1.

[0124] Example 4

[0125] A negative electrode material (silicon dioxide), a conductive agent (acetylene black), and a binder (sodium carboxymethyl cellulose) are mixed to obtain a negative electrode slurry; the negative electrode slurry is coated on a copper foil and dried to obtain a negative electrode sheet; wherein the weight ratio of the negative electrode material, the conductive agent, and the binder is 80:10:10 (i.e., based on the total weight of the negative electrode material, the conductive agent, and the binder, the content of the negative electrode material is 80% by weight, the content of the conductive agent is 10% by weight, and the content of the binder is 10% by weight); and the negative electrode slurry coating thickness is 100 μm;

[0126] Under an argon environment, 2 g of metallic lithium ingot and 0.2 g of silicon oxide were weighed and placed in a zirconia ball mill (the weight ratio of metallic lithium to matrix material was 1:0.1). After sealing, the jar was transferred to a planetary ball mill for ball milling. The ball-to-material ratio was 20:1, the diameters of the zirconium balls were 5.5 mm, 3.0 mm, and 2.0 mm, and the ratio was 2:5:3. The ball milling speed was 500 rpm and the ball milling time was 12 hours to obtain a pre-lithiation precursor. Then, 22 mL of electrolyte was added and ball milling was continued. The electrolyte included ethylene carbonate, propylene carbonate, lithium hexafluorophosphate, VC, and FEC. The weight ratio of carbonate compounds: fluorine-containing compounds: fluoroester compounds in the electrolyte was 8:1:1. Based on the total weight of the pre-lithiation precursor and the electrolyte, the content of the pre-lithiation precursor was 15% by weight. The ball milling speed was 350 rpm and the ball milling time was 10 hours to obtain a stabilized pre-lithiation solution (the particle size of lithium particles in the stabilized pre-lithiation solution was 0.1 to 2 μm). The pre-lithiation solution was coated on the prepared silicon negative electrode sheet with a coating thickness of 60 μm. After drying (drying temperature was 100°C and drying time was 12 hours), a pre-lithiation negative electrode sheet was obtained.

[0127] The negative electrode sheets were assembled into a battery according to the method in Example 1.

[0128] Example 5

[0129] This example follows the preparation method of Example 1, with the difference being that silicon dioxide is replaced with micronized silicon. The remaining steps are the same as in Example 1, resulting in a pre-lithiated negative electrode sheet. The negative electrode sheet is assembled into a battery according to the method of Example 1.

[0130] Example 6

[0131] This example refers to the preparation method in Example 1, and the difference from Example 1 is that the raw material ratio is changed, specifically including:

[0132] A negative electrode material (silicon dioxide), a conductive agent (acetylene black) and a binder (sodium carboxymethyl cellulose) are mixed to obtain a negative electrode slurry; the negative electrode slurry is coated on a copper foil and dried to obtain a negative electrode sheet; wherein the weight ratio of the negative electrode material, the conductive agent and the binder is 75:20:5 (i.e., based on the total weight of the negative electrode material, the conductive agent and the binder, the content of the negative electrode material is 75% by weight, the content of the conductive agent is 20% by weight, and the content of the binder is 5% by weight; the negative electrode slurry coating thickness is 30 μm);

[0133] Under an argon atmosphere, 2g of lithium metal and 2g of silicon oxide were weighed and placed in a zirconia ball mill (the weight ratio of lithium metal to matrix material was 1:1). After sealing, the mixture was transferred to a planetary ball mill for ball milling to obtain a pre-lithiation precursor. 20mL of electrolyte was then added and ball milling continued. The electrolyte consisted of ethylene carbonate, propylene carbonate, lithium hexafluorophosphate, VC, and FEC (fluoroethylene carbonate). The weight ratio of carbonate compound: fluorine-containing compound: fluoroester compound in the electrolyte was 20:1:10. The content of the pre-lithiation precursor was 50% by weight, based on the total weight of the pre-lithiation precursor and electrolyte, to obtain a stable pre-lithiation solution (lithium particles in the stabilized pre-lithiation solution had a particle size of 0.2 to 2 μm). The pre-lithiation solution was applied to the prepared silicon oxide negative electrode sheet to a coating thickness of 50 μm and dried to obtain a pre-lithiation negative electrode sheet. The negative electrode sheets were assembled into a battery according to the method in Example 1.

[0134] Example 7

[0135] This example refers to the preparation method in Example 1, and the difference from Example 1 is that the raw material ratio is changed, specifically including:

[0136] A negative electrode material (silicon dioxide), a conductive agent (acetylene black) and a binder (sodium carboxymethyl cellulose) are mixed to obtain a negative electrode slurry; the negative electrode slurry is coated on a copper foil and dried to obtain a negative electrode sheet; wherein the weight ratio of the negative electrode material, the conductive agent and the binder is 70:20:10 (i.e., based on the total weight of the negative electrode material, the conductive agent and the binder, the content of the negative electrode material is 70% by weight, the content of the conductive agent is 20% by weight, and the content of the binder is 10% by weight; the negative electrode slurry coating thickness is 30 μm);

[0137] Under argon, 2g of lithium metal and 4g of silicon dioxide were weighed and placed in a zirconia ball mill (the weight ratio of lithium metal to matrix material was 1:2). After sealing, the mixture was transferred to a planetary ball mill for ball milling to obtain a pre-lithiation precursor. 20mL of electrolyte was then added and ball milling continued. The electrolyte consisted of ethylene carbonate, propylene carbonate, lithium hexafluorophosphate, VC, and FEC (fluoroethylene carbonate). The weight ratio of carbonate compounds to fluorinated compounds to fluoroester compounds in the electrolyte was 20:1:0.05. The content of the pre-lithiation precursor was 5% by weight, based on the total weight of the pre-lithiation precursor and electrolyte, to obtain a stable pre-lithiation solution (lithium particles in the stabilized pre-lithiation solution had a particle size of 0.2-2 μm). The pre-lithiation solution was applied to the prepared silicon dioxide negative electrode sheet to a thickness of 50 μm and dried to obtain the pre-lithiation negative electrode sheet. The negative electrode sheets were assembled into a battery according to the method in Example 1.

[0138] Example 8

[0139] This example refers to the preparation method in Example 1, and the difference from Example 1 is that the process conditions are changed, specifically including:

[0140] The negative electrode material (silicon dioxide), the conductive agent (acetylene black) and the binder (sodium carboxymethyl cellulose) are mixed to obtain a negative electrode slurry, and the negative electrode slurry is coated with a thickness of 150 μm;

[0141] Under an argon atmosphere, 2g of lithium metal ingot and 0.2g of silicon dioxide were weighed and placed in a zirconia ball mill. The jar was sealed and transferred to a planetary ball mill for ball milling at a ball-to-material ratio of 1:1, a milling speed of 2000 rpm, and a milling time of 72 hours to obtain a pre-lithiation precursor. 20mL of electrolyte was then added and ball milling continued at a milling speed of 1000 rpm for 72 hours to obtain a stabilized pre-lithiation solution (the lithium particles in the stabilized pre-lithiation solution had a particle size of 0.05 to 0.1 μm). The pre-lithiation solution was applied to the prepared silicon dioxide negative electrode sheet to a coating thickness of 200 μm and dried (drying temperature of 150°C for 10 hours) to obtain a pre-lithiation negative electrode sheet. The negative electrode sheet was assembled into a battery according to the method in Example 1.

[0142] Example 9

[0143] This example refers to the preparation method in Example 1, and the difference from Example 1 is that the process conditions are changed, specifically including:

[0144] The negative electrode material (silicon dioxide), the conductive agent (acetylene black) and the binder (sodium carboxymethyl cellulose) are mixed to obtain a negative electrode slurry, and the negative electrode slurry is coated with a thickness of 200 μm;

[0145] Under an argon atmosphere, 2g of metallic lithium ingot and 0.2g of silicon dioxide were weighed and placed in a zirconia ball mill. The jar was sealed and transferred to a planetary ball mill for ball milling. The ball-to-material ratio was 10:1, the ball milling speed was 250 rpm, and the ball milling time was 5 hours to obtain a pre-lithiation precursor. 30mL of electrolyte was then added and the ball milling was continued at a speed of 150 rpm for 5 hours to obtain a stabilized pre-lithiation solution (the lithium particles in the stabilized pre-lithiation solution had a particle size of 0.5 to 5 μm). The pre-lithiation solution was applied to the prepared silicon dioxide negative electrode sheet to a coating thickness of 5 μm. After drying (drying temperature was 150°C and drying time was 5 hours), a pre-lithiation negative electrode sheet was obtained. The negative electrode sheet was assembled into a battery according to the method in Example 1.

[0146] The test data of the component content and structural parameters of the lithium-containing particles in the stabilized pre-lithiation solution prepared in the above examples and comparative examples are listed in Table 1 below. The test results of the battery assembled with the pre-lithiation negative electrode sheets prepared in the above examples and comparative examples are listed in Table 2 below.

[0147] Table 1

[0148]

[0149]

[0150] In Table 1, the core content, the total content of the buffer layer and the passivation layer are calculated by the raw material ratio.

[0151] Table 2

[0152]

[0153] Figure 7 The first charge and discharge curve (solid line curve) of the battery assembled with the pre-lithiation battery negative electrode sheet as the negative electrode prepared according to the method in the disclosed embodiment 1 at a current density of 0.2C; Figure 7 It can be seen that after pre-lithiation, the first charge specific capacity is 1004.4mAh / g, the first discharge specific capacity is 1174.77mAh / g, and the first coulombic efficiency is 85.5%. The electrochemical capacity-voltage test results (dashed curve) of the lithium-ion battery assembled with non-pre-lithiated silicon dioxide material as the negative electrode material are as follows: the current density is 0.2C, the first charge specific capacity is 1241.94mAh / g, the first discharge specific capacity is 2308.58mAh / g, and the first coulombic efficiency is 53.8%. This shows that the pre-lithiation method for lithium-ion battery negative electrode sheets provided by the present invention can significantly reduce irreversible lithium loss and greatly improve the first coulombic efficiency of the electrode, which is of great significance to promoting the application of silicon dioxide-based composite materials in the field of power batteries.

[0154] From the data in Table 2 above, we can see that:

[0155] Comparing Example 1 with Comparative Examples 1 to 3, in Comparative Example 1, no silicon oxide was added, and the pre-lithium solution obtained was a non-uniform slurry, in which the lithium particles were large and small discs, and could not be evenly coated on the prepared silicon oxide negative electrode sheet. In addition, the first coulombic efficiency and 100 cycle capacity retention rate of the battery assembled with the negative electrode sheet obtained in Example 1 were higher than those of the negative electrode sheets of Comparative Examples 1 to 3.

[0156] Comparing Example 6 with Example 7, the negative electrode sheet in Example 6 was prepared according to the raw material addition ratio provided in the present disclosure, and the raw material addition ratio in Example 7 was not within the scope provided in the present disclosure. The first coulombic efficiency and 100 cycle capacity retention rate of the negative electrode sheet prepared in Example 6 were higher; comparing Example 1 with Example 6, the negative electrode sheet in Example 1 was prepared according to the optimized raw material addition ratio provided in the present disclosure. The first coulombic efficiency and cycle capacity retention rate of the negative electrode sheet obtained in Example 1 were higher than those of the negative electrode sheet in Example 6.

[0157] Comparing Example 8 with Example 9, Example 8 was prepared according to the process conditions of the negative electrode sheet provided in the present disclosure. Compared with the sheet obtained in Example 9, the negative electrode sheet obtained in Example 8 had higher first coulombic efficiency and cycle capacity retention rate; comparing Example 1 with Example 8, the negative electrode sheet was prepared according to the preferred conditions in Example 1. The first coulombic efficiency and cycle capacity retention rate of the negative electrode sheet obtained in Example 1 were higher than those of the negative electrode sheet in Example 8.

[0158] The preferred embodiments of the present disclosure are described in detail above. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0159] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0160] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for preparing a pre-lithiated lithium-ion battery negative electrode sheet, characterized in that: The following steps are involved: S1, mixing metallic lithium with a matrix material and performing ball milling to obtain a pre-lithiation precursor, wherein the matrix material is selected from one or both of silicon and silicon monoxide; S2, mixing the pre-lithiation precursor with an electrolyte and performing a stabilization treatment to obtain a stabilized pre-lithiation solution; wherein the electrolyte comprises a carbonate compound, a fluorine-containing compound, and optionally a fluorinated ester compound; S3, coating the stabilized pre-lithium solution on the negative electrode; Steps S1 to S2 are respectively carried out under inert conditions.

2. The method according to claim 1, characterized in that In step S1, the weight ratio of the metallic lithium to the matrix material is 1:0.01-1, preferably 1:0.1-0.5; Optionally, the metallic lithium is selected from one or more of lithium ingots, lithium wires, lithium powders and lithium sheets; Preferably, in the matrix, silicon is in the form of powder, the average particle size of the silicon powder is 0.5 to 10 μm, and the BET specific surface area is 0.1 to 50 μm. 2 / g; the silicon oxide is a powder, the average particle size of the silicon oxide powder is 1 to 20 μm; the BET specific surface area is 0.5 to 100 m 2 / g.

3. The method according to claim 1, characterized in that In step S1, the conditions of the ball milling treatment include: a rotation speed of 300 to 2000 r / min, preferably 500 to 1000 r / min; a time of 6 to 72 hours, preferably 12 to 24 hours; and a ball-to-material ratio of 1 to 20:1, preferably 10 to 20:

1.

4. The method according to claim 1, wherein In step S2, the carbonate compound is selected from one or more of ethylene carbonate, propylene carbonate, diethyl carbonate and dimethyl carbonate; The fluorine-containing compound is selected from one or more of lithium hexafluorophosphate, phosphorus pentafluoride and hydrofluoric acid; The fluoroester compound is selected from one or more of fluoroethylene carbonate and fluoropropylene carbonate; Preferably, the weight ratio of carbonate compound: fluorine-containing compound: fluorinated ester compound in the electrolyte is 1-20:1:0.1-10; preferably 1-10:1:0.1-1; Optionally, in step S2, based on the total weight of the pre-lithiation precursor and the electrolyte, the content of the pre-lithiation precursor is 10 to 60 weight %, preferably 10 to 30 weight %.

5. The method according to claim 1, wherein In step S2, the conditions of the stabilization treatment include: a ball milling speed of 200 to 1000 r / min, preferably 200 to 500 r / min; a time of 6 to 72 hours, preferably 10 to 20 hours; a ball to material ratio of 1 to 20:1, preferably 10 to 20:1; Preferably, the particle size of the lithium particles in the stabilized pre-lithium solution is 0.05 to 5 μm, preferably 0.1 to 2 μm.

6. The method according to claim 1, characterized in that In step S3, the coating thickness of the stabilized pre-lithium solution is 5 to 200 μm, preferably 10 to 50 μm; Optionally, the method further comprises: drying the negative electrode plate coated with the stabilized pre-lithium solution; preferably, the drying conditions include: a drying temperature of 80 to 120° C. and a drying time of 6 to 48 hours.

7. The method according to claim 1, characterized in that The negative electrode plate is prepared by the following method: Mixing a negative electrode material, a conductive agent, and a binder to obtain a negative electrode slurry; coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode sheet; Preferably, based on the total weight of the negative electrode material, the conductive agent and the binder, the content of the negative electrode material is 75-95% by weight, the content of the conductive agent is 3-20% by weight, and the content of the binder is 2-15% by weight; preferably, the content of the negative electrode material is 80-90% by weight, the content of the conductive agent is 5-10% by weight, and the content of the binder is 5-10% by weight; Optionally, the negative electrode material is selected from one or more of silicon monoxide negative electrode material, graphite negative electrode material, silicon-carbon negative electrode material and silicon negative electrode material; Optionally, the conductive agent is selected from one or more of acetylene black, conductive carbon black and carbon fiber tubes; Optionally, the binder is selected from one or more of sodium carboxymethyl cellulose, polystyrene butadiene copolymer and polyvinylidene fluoride.

8. A pre-lithiated lithium-ion battery negative electrode sheet prepared according to the method of any one of claims 1 to 7.

9. A pre-lithiated lithium-ion battery negative electrode sheet, characterized in that: The pre-lithiation lithium-ion battery negative electrode sheet comprises a copper foil layer, a negative electrode material layer and a pre-lithiation layer which are stacked in sequence; the pre-lithiation layer comprises lithium-containing particles of a core-shell structure; the lithium-containing particles comprise a core, a buffer layer coated on the outer surface of the core, and a passivation layer coated on the outer surface of the buffer layer; the passivation layer forms an outer shell of the core-shell structure; the core comprises a lithium active component and a matrix material, the matrix material being selected from one or both of silicon and silicon monoxide; the buffer layer comprises a silicon-lithium alloy or a lithium silicate; the passivation layer comprises lithium fluoride and lithium carbonate; the negative electrode material layer comprises a negative electrode material, the negative electrode material being selected from one or more of silicon monoxide negative electrode material, graphite negative electrode material, silicon-carbon negative electrode material and silicon negative electrode material.

10. The pre-lithiation lithium-ion battery negative electrode sheet according to claim 9, characterized in that: The thickness ratio of the negative electrode material layer to the pre-lithiation layer is 1:0.01-2, preferably 1:0.1-1.7; Preferably, the thickness of the passivation layer of the lithium-containing particles is 1 to 500 nm.

11. The pre-lithiation lithium-ion battery negative electrode sheet according to claim 9, characterized in that: Based on the total weight of the lithium-containing particles, the content of the core is 50 to 95 weight %, preferably 80 to 95 weight %; Optionally, the particle size of the lithium-containing particles ranges from 0.1 to 10 μm.

12. A lithium ion battery, characterized in that: The invention comprises the pre-lithiation lithium-ion battery negative electrode sheet according to any one of claims 9 to 11.

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