Anode material, anode slurry and lithium ion battery

Abstract

The present application relates to a negative electrode material and a manufacturing method thereof for a lithium ion battery. The negative electrode material includes a silicon-based active material and a coating layer located on at least a portion of the silicon-based active material. The silicon-based active material includes silicon and lithium silicate. The negative electrode material of the present application controls the type and crystallinity of the lithium silicate in the material, thereby improving the storage stability of the negative electrode slurry, extending the cycle life of the negative electrode material, increasing the adhesion ability between the negative electrode material and the current collector, and improving the high-temperature storage performance of the cell, thereby improving the cycle performance of the lithium ion battery.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority from a Chinese patent application entitled "Negative electrode material and manufacturing method thereof for lithium-ion batteries," filed with the State Intellectual Property Office of the People's Republic of China on September 22, 2023, bearing application number 202311231152.8, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the field of anode material technology, and more particularly to anode materials, anode slurries, and lithium ion batteries. [Background technology]

[0003] Lithium-ion batteries have advantages such as high operating voltage, long cycle life, no memory effect, low self-discharge, and environmental friendliness, leading to their widespread use in portable electronic products and electric vehicles. Currently, commercial lithium-ion batteries primarily use graphite-based anode materials, but the theoretical specific capacity of graphite is a maximum of 372 mAh / g, which does not meet the high energy density requirements of future lithium-ion batteries. While conventional silicon has a high theoretical capacity of 4200 mAh / g, its expansion rate reaches 300%, which impacts cycle performance and limits its market penetration and application.

[0004] The corresponding silicon-oxygen materials have better cycle performance but lower initial efficiency. During the first charge, 20-50% of the lithium must be consumed to form an SEI film, which significantly reduces the initial coulombic efficiency. As the initial efficiency of positive electrode materials becomes increasingly higher, improving the initial efficiency of silicon-oxygen materials is particularly important.

[0005] Currently, an effective way to improve the initial efficiency of silicon-oxygen materials is to pre-dope them with lithium, thereby pre-reacting the phase that irreversibly consumes lithium in the silicon-oxygen materials. The traditional industrial method is to directly coat the surface of the electrode sheet with a lithium layer, which achieves the effect of reducing the electrode lithium consumption. However, this method has high requirements for the operating environment and poses significant security risks, making it difficult to achieve industrial widespread use.

[0006] In the current state of technological development, silicon-oxygen materials generally have poor processing performance when pre-lithiated to improve initial efficiency. This is mainly due to the short stable storage time of the slurry produced from the pre-lithiated silicon-oxygen negative electrode material, which is prone to settling, stratification, and gas generation during storage, resulting in non-uniform distribution of the active material in the applied electrode sheet, large differences in the thickness and surface density of the electrode sheet, and an uneven appearance of the electrode sheet, making it impossible to assemble the whole battery. The degree of pre-lithiation is difficult to control, which leads to instability in the type and content of lithium silicate in the silicon-oxygen material, making the prepared slurry unstable and likely to cause non-uniformity in the applied electrode sheet, which further reduces the peel strength of the electrode sheet and makes the active material prone to peeling from the current collector. Furthermore, the introduction of the lithium source and the formation of lithium silicate in the pre-lithiated silicon-oxygen material destroys the original stable structure of the silicon-oxygen material, shortening the cycle life of the negative electrode material. Summary of the Invention

[0007] In a first aspect, the present application provides a negative electrode material, a negative electrode slurry, and a lithium-ion battery, the negative electrode material comprising a silicon-based active material and a coating layer located on at least a portion of the silicon-based active material, the silicon-based active material comprising silicon and lithium silicate; In the X-ray diffraction spectrum of the negative electrode material measured by an XRD ray diffraction method, the peak intensity of the strongest diffraction peak in the 2θ range of 18° to 20° is A1, the peak intensity of the strongest diffraction peak in the 2θ range of 26° to 27.9° is A2, and the peak intensity of the strongest diffraction peak in the 2θ range of 32° to 34° is A3, where A1+A2+A3=A; In the negative electrode material, the peak intensity of the strongest diffraction peak within a 2θ range of 16° to 17° is B1, the peak intensity of the strongest diffraction peak within a 2θ range of 22° to 25.9° is B2, and the peak intensity of the strongest diffraction peak within a 2θ range of 36° to 38° is B3, where B1+B2+B3=B; In the negative electrode material, the peak intensity of the strongest diffraction peak within a 2θ range of 28° to 30° is C1, the peak intensity of the strongest diffraction peak within a 2θ range of 46° to 48° is C2, and the peak intensity of the strongest diffraction peak within a 2θ range of 56° to 58° is C3, where C1+C2+C3=C; Furthermore, the relationship between the three, A, B, and C, satisfies 0<(A+B) / C≦10, 0<(A+C) / B≦5.

[0008] In some embodiments, the negative electrode material is tested using a powder resistivity testing device to obtain a powder conductivity σ1 at a powder density ρ1 of the negative electrode material, and a powder conductivity σ2 at a powder density ρ2 of the negative electrode material, where the relationship (σ2-σ1) / (ρ2-ρ1)≦0.8 is satisfied.

[0009] In some embodiments, the relationship among A, B, and C further satisfies 1≦(B+C) / A≦30.

[0010] In some embodiments, the silicon-based active material further comprises a silicon oxygen complex.

[0011] In some embodiments, the molar ratio of oxygen atoms to silicon atoms in the negative electrode material is 0.5 to 2.

[0012] In some embodiments, the silicon comprises nanosilicon crystal particles, and the average particle size of the nanosilicon crystal particles is between 0 nm and 20 nm, but not including 0 nm.

[0013] In some embodiments, the coating layer comprises a carbon material, and the carbon material comprises at least one of amorphous carbon, graphene, graphite, carbon nanotubes, and carbon fibers.

[0014] In some embodiments, the lithium silicate comprises at least one of Li2SiO3, Li2Si2O5, and Li4SiO4.

[0015] In some embodiments, the coating layer includes a carbon material, and the mass content of the carbon material in the negative electrode material is 10% or less.

[0016] In some embodiments, the mass content of silicon in the negative electrode material is 20% to 70%.

[0017] In some embodiments, the mass content of lithium silicate in the negative electrode material is 30% to 75%.

[0018] In some embodiments, the specific surface area of ​​the negative electrode material is 10 m 2 / g or less.

[0019] In some embodiments, the negative electrode material has a pH value of 7.2 to 11.0.

[0020] In some embodiments, an active material, carboxymethyl cellulose, conductive carbon black, and styrene butadiene rubber are mixed in a mass ratio of 95.3:1.3:1.5:1.9 to form an anode slurry having a solids content of 50%, wherein the active material comprises the anode material and graphite in a mass ratio of 9:1. The rheological properties of the anode slurry are tested using a Haake rotational rheometer to obtain a rheological curve of the anode slurry, and the rheological curve shows a shear rate of 0 S.-1 , 150S -1 , 300S -1 , the corresponding shear stresses in the rheological curve are τ0, τ1, and τ2, and the relationship between the shear stresses satisfies 2τ1>(τ2-τ0).

[0021] In a second aspect, the present application provides an anode slurry comprising the anode material according to the first aspect.

[0022] In a third aspect, the present application provides a method for producing a negative electrode material, comprising: Silicon oxide SiO x is put into an acid solution to perform a first surface modification treatment, <x<2であるステップと、 Silicon oxide SiO after the first surface modification treatment x and a reductive lithium-containing compound, and a prelithiation treatment and a carbon coating treatment are performed at 300°C to 800°C to obtain a precursor, <x<2であるステップと、 and performing a second surface modification treatment on the precursor to obtain a negative electrode material, the negative electrode material comprising a silicon-based active material and a coating layer located on at least a portion of the silicon-based active material, the silicon-based active material comprising silicon and lithium silicate.

[0023] In some embodiments, the acid solution comprises at least one of hydrofluoric acid, nitric acid, fluorosulfonic acid, magic acid, hydrochloric acid, hydrobromic acid, and hydroiodic acid.

[0024] In some embodiments, the concentration of the acid solution is ≦2 mol / L.

[0025] In some embodiments, the temperature of the first surface modification treatment is 30°C to 100°C.

[0026] In some embodiments, the duration of the first surface modification treatment is 2 hours to 8 hours.

[0027] In some embodiments, the manufacturing method further comprises the step of: x The method further includes the step of subjecting the solid-liquid separation, washing, and drying treatment to the solid-liquid separation.

[0028] In some embodiments, the manufacturing method further comprises the step of: x The method further includes a step of subjecting the solid-liquid separation, washing and drying treatment to the solid-liquid separation, and the drying temperature is 50°C to 180°C.

[0029] In some embodiments, the silicon oxide is silicon monoxide.

[0030] In some embodiments, the reducible lithium-containing compound comprises at least one of lithium hydride, alkyl lithium, metallic lithium, lithium aluminum hydride, lithium amide, lithium borohydride, and lithium silicon alloy.

[0031] In some embodiments, the mass ratio of the silicon oxide to the reductive lithium-containing compound after the first surface modification treatment is 1:(0.03 to 0.2).

[0032] In some embodiments, the prelithiation is carried out in a protective atmosphere.

[0033] In some embodiments, the protective atmosphere comprises at least one of nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and xenon gas.

[0034] In some embodiments, the pre-lithiation time is 3 hours to 9 hours.

[0035] In some embodiments, the coating treatment comprises a carbon coating treatment, and the carbon coating treatment process comprises at least one of a liquid phase coating method, a vapor phase coating method, and a solid phase coating method.

[0036] In some embodiments, the coating process comprises a carbon coating process, and the coating material of the carbon coating process comprises at least one of amorphous carbon, graphene, graphite, carbon nanotubes, and carbon fibers.

[0037] In some embodiments, the lithium silicate comprises at least one of Li2SiO3, Li2Si2O5, and Li4SiO4.

[0038] In some embodiments, the method further comprises the step of: x and a mixture containing a reductive lithium-containing compound, before prelithiation at 300°C to 800°C, silicon oxide SiO after the first surface modification treatment x and a step of mixing and processing the mixture containing the reducible lithium-containing compound.

[0039] In some embodiments, the temperature of the mixing treatment is 60°C to 320°C.

[0040] In some embodiments, the mixing time is 0.5 hours to 10 hours.

[0041] In some embodiments, the equipment necessary for the mixing process includes at least one of equipment having a dispersing function and equipment having a shearing force function.

[0042] In some embodiments, the second surface treatment comprises at least one of a purification treatment, a coating treatment, a heat treatment, an oxidation treatment, and an etching treatment.

[0043] In some embodiments, the temperature of the second surface treatment is 50°C to 900°C.

[0044] In some embodiments, the second surface treatment is performed for a period of 0.5 hours to 10 hours.

[0045] In some embodiments, the second surface treatment comprises subjecting the precursor to a purification treatment in an aluminum hydroxide solution.

[0046] In a fourth aspect, the present application provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode material according to the first aspect or the negative electrode material produced by the method according to the third aspect. [Effects of the Invention]

[0047] Compared with the prior art, the technical solution of the present application has at least the following beneficial effects:

[0048] The present application provides a negative electrode material comprising a silicon-based active material, the silicon-based active material comprising silicon and lithium silicate, and when measured by XRD ray diffraction, the X-ray diffraction spectrum of the negative electrode material is such that A represents the sum of peak intensities at different peak positions of Li2SiO3 in a crystalline state, B represents the sum of peak intensities at different peak positions of Li2SiO5 in a crystalline state, and C represents the sum of peak intensities at different peak positions of silicon, and the relationships among A, B, and C satisfy 0<(A+B) / C≦10, 0<(A+C) / B≦5. 3. The three components, Li2Si2O5 and silicon, influence each other in a balanced manner, the surface lithiation degree of the anode material is appropriate, and the processing performance of the anode material is stable. The anode material and the adhesive solution have good interfacial contact. When the anode material is prepared into anode slurry, the anode material can be uniformly dispersed and suspended in the adhesive solution, and the prepared anode slurry can be stably stored. Furthermore, the battery containing the above anode material further reduces the destructive effect of lithium silicate on the adhesive during charge and discharge, improves the structural stability of the electrode sheet, and extends the cycle life of the anode material.

[0049] The negative electrode material provided herein adjusts the type and crystallinity of lithium silicate, i.e., satisfies the relationship between the three elements A, B, and C, thereby reducing the destructive effect of basic substances on the adhesive, improving the structural stability of the electrode sheet, and improving the cycle performance and extending the cycle life of batteries manufactured using the negative electrode material.

[0050] The method for producing the negative electrode material provided in the present application is to use silicon oxide SiO x The first surface modification treatment is carried out by placing the silicon dioxide (SiO) in an acid solution. x The surface is oxidized and etched to form silicon oxide SiO x The surface of silicon oxide SiO x This can increase the reaction points in the pre-lithiation process, make the pre-lithiation reaction more uniform, obtain more lithium silicate growth points, and promote the uniform distribution of lithium silicate inside the negative electrode material particles. This is also beneficial for adjusting the crystalline phase type and content of lithium silicate on the surface of the material. In addition, the silicon oxide SiO x By performing a pre-lithiation treatment using the above, catalytic growth of lithium silicate on silicon crystal grains can be significantly reduced, and the silicon oxide SiO x Since the silicon oxide SiO2 has growth sites uniformly distributed on the surface of the silicon dioxide after the first surface modification treatment, xand a reducible lithium-containing compound, the pre-lithiation treatment can improve the lithium utilization rate and the uniformity of the distribution of the pre-lithiation product, so that the pre-lithiation product is uniformly distributed in the anode material, which is beneficial to buffering the volume change of the silicon-based active material during charge and discharge processes, maintaining the stability of the overall structure of the anode material, extending the cycle life, reducing the regeneration of the SEI film on the surface of the anode material, and improving the initial efficiency of the material. By performing a second surface modification treatment on the precursor, the surface morphology of the anode material can be continuously adjusted, and the crystalline phase type and content of the lithium silicate on the surface of the material can be adjusted, stabilizing the solid-liquid contact interface between the anode material and the electrolyte, reducing the risk of the anode material being eroded by the electrolyte, and improving the high-temperature storage performance of batteries manufactured using the anode material. Meanwhile, the adhesion strength of the adhesive to the anode material can be improved, the peel strength of the electrode sheet can be strengthened, the repulsion of the electrode sheet can be reduced, and the conductive network of the electrode sheet can be stabilized, thereby improving the cycle life of batteries manufactured using the anode material. [Brief explanation of the drawings]

[0051] The present application will be further described below with reference to the figures and examples. [Figure 1] 1 is a process flow chart of a method for manufacturing a negative electrode material provided herein. [Figure 2] FIG. 2 is a graph showing the relationship between powder density and powder conductivity of the negative electrode material produced in Example 1 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0052] In order to better understand the technical solution of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0053] Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments, and all other embodiments obtained by those skilled in the art based on the embodiments of the present application without any creative effort fall within the scope of protection of the present application.

[0054] The terminology used in the examples herein is for the purpose of describing particular examples only and is not intended to be limiting of the present application. As used in the examples herein and the appended claims, the singular forms "a," "the," and "the" are intended to include the plural forms unless the context clearly dictates otherwise.

[0055] It should be understood that the term "and / or" used herein is merely a relational relationship describing related objects, and indicates that three types of relationships can exist, for example, A and / or B can indicate three cases: A exists alone, A and B exist simultaneously, and B exists alone. Also, in this specification, the character " / " generally indicates that the related objects before and after are in an "or" relationship.

[0056] In a first aspect, the present application provides a negative electrode material, the negative electrode material comprising a silicon-based active material and a coating layer located on at least a portion of the silicon-based active material, the silicon-based active material comprising silicon and lithium silicate; In the X-ray diffraction spectrum of the negative electrode material measured by XRD ray diffraction method, the peak intensity of the strongest diffraction peak in the 2θ range of 18° to 20° is A1, the peak intensity of the strongest diffraction peak in the 2θ range of 26° to 27.9° is A2, and the peak intensity of the strongest diffraction peak in the 2θ range of 32° to 34° is A3, where A1+A2+A3=A; The negative electrode material has a peak intensity of B1 of the strongest diffraction peak in the 2θ range of 16° to 17°, a peak intensity of B2 of the strongest diffraction peak in the 2θ range of 22° to 25.9°, and a peak intensity of B3 of the strongest diffraction peak in the 2θ range of 36° to 38°, where B1+B2+B3=B; The negative electrode material has a peak intensity of the strongest diffraction peak in the 2θ range of 28° to 30° that is C1, a peak intensity of the strongest diffraction peak in the 2θ range of 46° to 48° that is C2, and a peak intensity of the strongest diffraction peak in the 2θ range of 56° to 58° that is C3, where C1+C2+C3=C; Furthermore, the relationship between the three, A, B, and C, satisfies 0<(A+B) / C≦10, 0<(A+C) / B≦5.

[0057] The negative electrode material provided in the present application comprises a silicon-based active material, the silicon-based active material comprising silicon and lithium silicate, and is measured by XRD ray diffraction method. In the X-ray diffraction spectrum of the negative electrode material, A represents the sum of peak intensities at different peak positions of Li2SiO3 in a crystalline state, B represents the sum of peak intensities at different peak positions of Li2SiO3 in a crystalline state, and C represents the sum of peak intensities at different peak positions of silicon, and the relationship between A, B, and C satisfies 0<(A+B) / C≦10, 0<(A+C) / B≦5. When the relationship between A, B, and C satisfies 0<(A+C) / B≦5, the negative electrode material is The three components, SiO and silicon, influence each other in a balanced manner, ensuring an appropriate degree of lithiation on the surface of the anode material and stabilizing the processing performance of the anode material. The anode material and adhesive solution have good interfacial contact. When the anode material is prepared into an anode slurry, the anode material can be uniformly dispersed and suspended in the adhesive solution, allowing the prepared anode slurry to be stably stored. Furthermore, during the charge and discharge process of a battery containing the above anode material, the destructive effect of lithium silicate in the anode material on the adhesive is further reduced, improving the structural stability of the electrode sheet and extending the cycle life of the material.

[0058] The negative electrode material provided herein adjusts the type and crystallinity of lithium silicate, i.e., satisfies the relationship between the three elements A, B, and C, thereby reducing the destructive effect of basic substances on the adhesive, improving the structural stability of the electrode sheet, and improving the cycle performance and extending the cycle life of batteries manufactured using the negative electrode material.

[0059] Specifically, the value of (A+B) / C may be, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, and 10, and may of course be other values ​​within the above ranges, and is not limited thereto. The value of (A+C) / B may be, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5, and is not limited thereto.

[0060] In some embodiments, the relationship among the three elements A, B, and C further satisfies 1≦(B+C) / A≦30. Specifically, the value of (B+C) / A may be, for example, 1, 3, 5, 8, 10, 12, 15, 17, 20, 21, 23, 25, 28, and 30, and may of course be other values ​​within the above ranges, and is not limited thereto.

[0061] As can be seen, when the anode material contains three components, Li2SiO3 represented by A, Li2SiO2O5 represented by B, and silicon represented by C, and satisfies 1≦(B+C) / A≦30, the storage performance of the anode slurry produced by the anode material is improved, and the sedimentation, stratification, and gas generation phenomena during the storage of the anode slurry are reduced, so that the distribution of the active material in the applied electrode sheet is uniform, the difference in thickness and surface density of the electrode sheet is small, and the appearance of the electrode sheet is flat, making it suitable for assembling a whole battery.

[0062] In some embodiments, a powder resistivity tester is used to test the negative electrode material to obtain a powder conductivity σ1 at a powder density ρ1 of the negative electrode material, and a powder conductivity σ2 at a powder density ρ2 of the negative electrode material, where the relationship (σ2-σ1) / (ρ2-ρ1)≦0.8 is satisfied. Specifically, the value of (σ2-σ1) / (ρ2-ρ1) may be 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc., and may of course be other values ​​within the above range, and is not limited thereto. The powder density ρ1 and powder conductivity σ1, and the powder density ρ2 and powder conductivity σ2 are measured at different pressures, respectively.

[0063] As can be understood, the powder conductivity is related to the appearance and internal structure of the negative electrode material and can reflect the electron conductivity ability of the negative electrode material.

[0064] After the preliminary lithiation treatment, the silicon-based active material may reduce the electron conductivity ability of the entire negative electrode material due to the increase of lithium silicate. The powder conductivity of the negative electrode material changes with the change of the powder density. The present application can further balance the relationship between the powder conductivity and the powder density by controlling the balance relationship among the three components of Li2SiO3, Li2Si2O5 and silicon, ensure the electrical contact between the negative electrode material particles, improve the stability of the conductive network between the negative electrode material particles, increase the electrical contact probability between the particles during the cycling process, and extend the cycle life of the material.

[0065] In some embodiments, the molar ratio of oxygen atoms to silicon atoms in the negative electrode material is 0.5 to 2, specifically, it may be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 and 2, etc. Of course, other values within the above range may also be possible and are not limited here.

[0066] In some embodiments, the silicon-based active substance further includes a silicon oxygen complex. The silicon oxygen complex includes oxygen atoms and silicon atoms, and the molar ratio of oxygen atoms to silicon atoms is 0 to 2. The silicon oxygen complex is represented by the general formula SiO x (0 < x ≦ 2). This may be a material formed by dispersing silicon particles in SiO2, or a material having a tetrahedral structural unit in which silicon atoms are located at the center of the tetrahedral structural unit and silicon atoms and oxygen atoms are located at the four vertices of the tetrahedral structural unit.

[0067] In some embodiments, the silicon comprises nanocrystalline silicon particles, and the nanocrystalline silicon particles have an average particle size of 0 nm to 20 nm, but not including 0 nm. Specifically, the average particle size of the nanocrystalline silicon particles may be 1 nm, 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 20 nm, etc., and of course, may be other values ​​within the above range, and is not limited thereto. As can be understood, for the same silicon content, due to the expansion isotropy of silicon, the expansion stress of small crystalline silicon particles is more uniform compared to silicon crystalline particles with large crystal sizes, and the expansion effect of the silicon crystalline particles is smaller, resulting in a longer cycle life, which is advantageous for improving the cycle performance and rate performance of the negative electrode material.

[0068] In some embodiments, the coating layer comprises a carbon material, the carbon material comprising at least one of amorphous carbon, graphene, graphite, carbon nanotubes, and carbon fibers.

[0069] In some embodiments, the lithium silicate comprises at least one of Li2SiO3, Li2Si2O5, and Li4SiO4.

[0070] In some embodiments, the coating layer includes a carbon material, and the mass content of the carbon material in the negative electrode material is 10% or less, specifically, 0.1%, 1%, 2%, 3%, 5%, 7%, 8%, 9%, and 10%, and may naturally be other values ​​within the above range, and is not limited thereto.

[0071] In some embodiments, the specific surface area of ​​the negative electrode material is 10 m 2 / g or less, specifically 1m 2 / g, 2m 2 / g, 3m 2 / g, 4m 2 / g, 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g and 10m 2 / g, etc., and of course may be other values ​​within the above range, and is not limited thereto.

[0072] In some embodiments, the mass content of silicon in the negative electrode material is 20% to 70%, and specifically may be 20%, 24%, 28%, 30%, 35%, 40%, 48%, 52%, 56%, 60%, 63%, 65%, 67%, 70%, etc., and of course may be other values ​​within the above range, and is not limited thereto.

[0073] In some embodiments, the mass content of silicate in the negative electrode material is 30% to 75%, and specifically may be 30%, 32%, 35%, 38%, 40%, 45%, 50%, 56%, 60%, 64%, 67%, 70%, 72%, 73%, 75%, etc., and of course may be other values ​​within the above range, and is not limited thereto.

[0074] In some embodiments, the pH value of the negative electrode material is 7.2 to 11.0, and may be, for example, 7.2, 7.6, 7.8, 8, 8.3, 8.5, 8.7, 9.6, 9.9, 10, 10.25, 10.36, 10.47, 10.58, 10.87, 10.98, or 11, and may be other values ​​within the above range, and is not limited thereto.

[0075] In some embodiments, an active material, carboxymethyl cellulose, conductive carbon black, and styrene butadiene rubber are mixed in a mass ratio of 95.3:1.3:1.5:1.9 to form an anode slurry with a solids content of 50%, wherein the active material comprises an anode material and graphite in a mass ratio of 9:1. The rheological properties of the anode slurry are tested using a German Hack rotational rheometer to obtain a rheological curve of the anode slurry, and the rheological curve shows a shear rate of 0 S. -1 , 150S -1 , 300S -1 , the corresponding shear stresses in the rheological curve are τ0, τ1, and τ2, and the relationship between the shear stresses satisfies 2τ1>(τ2-τ0).

[0076] As can be seen, the relationship between shear stresses in the rheological curve of the negative electrode slurry is related to the leveling performance, sagging performance, and sedimentation performance of the negative electrode material, and limiting this relationship can improve the storage stability of the negative electrode material in the negative electrode slurry.

[0077] By limiting the shear rate and shear stress, the fluidity and stability of the negative electrode material slurry can be improved, the uniformity and conformity of the electrode sheet can be increased, the adhesive strength between the active material and the current collector can be increased, and the active material can be prevented from falling off the current collector. When the rheological curve satisfies the above formula, the negative electrode material has excellent anti-settling and anti-sagging properties and good storage stability.

[0078] This also helps to ensure that the active material in the electrode sheet adheres uniformly to the current collector, improving the peel strength of the electrode sheet.If 2τ1≦(τ2−τ0), the negative electrode material in the negative electrode slurry is prone to settling, tailing, and layer separation, which is unfavorable for applying the electrode sheet and reduces the battery conformity.

[0079] In a second aspect, the present application provides an anode slurry comprising the anode material of the first aspect. In some embodiments, the anode slurry is formed by mixing an active material, carboxymethyl cellulose, conductive carbon black, and styrene butadiene rubber in a mass ratio of 95.3:1.3:1.5:1.9, where the active material comprises anode material and graphite in a mass ratio of 9:1. The rheological properties of the anode slurry are tested using a Deutsche Hack rotational rheometer to obtain a rheological curve for the anode slurry, and the rheological curve shows a shear rate of 0 S. -1 , 150S -1 , 300S -1 , the corresponding shear stresses in the rheological curve are τ0, τ1, and τ2, and the relationship between the shear stresses satisfies 2τ1>(τ2-τ0).

[0080] In a third aspect, the present application provides a method for producing a negative electrode material, as shown in FIG. Silicon oxide SiO x is put into an acid solution to perform a first surface modification treatment, <x<2であるステップS100と、 Silicon oxide SiO after the first surface modification treatment x and a step of subjecting a mixture containing a reductive lithium-containing compound to a prelithiation treatment and a coating treatment at 300°C to 800°C to obtain a precursor, <x<2であるステップS200と、 and step S300 of subjecting the precursor to a second surface modification treatment to obtain a negative electrode material, the negative electrode material including a silicon-based active material and a coating layer located on at least a portion of the silicon-based active material, the silicon-based active material including silicon and lithium silicate.

[0081] The method for producing the negative electrode material provided in the present application is to use silicon oxide SiO x The first surface modification treatment is carried out by placing the silicon dioxide (SiO) in an acid solution. x The surface is oxidized and etched to form silicon oxide SiO x By forming weak defect sites on the surface of silicon oxide SiO after the first surface modification treatment, x This can increase the reaction points in the pre-lithiation process, make the pre-lithiation reaction more uniform, obtain more growth points for lithium silicate, and promote the uniform distribution of lithium silicate inside the particles, which is beneficial for adjusting the crystalline phase type and content of lithium silicate on the surface of the material.

[0082] In addition, silicon oxide SiO after surface modification treatment x The pre-lithiation treatment using Li2SiO3, Li2Si2O5 and silicon can significantly reduce the catalytic growth of silicon grains, thereby adjusting the type, content and grain growth of the three components of the anode material, Li2SiO3, Li2Si2O5 and silicon, and the silicon oxide SiO xSince the silicon oxide SiO2 has growth sites uniformly distributed on the surface of the silicon dioxide after the first surface modification treatment, x and a reducible lithium-containing compound, the pre-lithiation treatment can improve the lithium utilization rate and the uniformity of the distribution of the pre-lithiation product, so that the pre-lithiation product is uniformly distributed in the anode material, which is beneficial for buffering the volume change of the silicon-based active material during the charge and discharge process, maintaining the stability of the overall structure of the anode material, extending the cycle life, reducing the regeneration of the SEI film on the surface of the anode material, and improving the initial efficiency of the anode material. By performing a second surface modification treatment on the precursor, the surface shape of the anode material can be continuously adjusted, and the crystalline phase type and content of the lithium silicate on the surface of the material can be adjusted, stabilizing the solid-liquid contact interface between the anode material and the electrolyte, reducing the risk of the anode material being eroded by the electrolyte, and improving the high-temperature storage performance of the battery. Meanwhile, the adhesion strength of the adhesive to the anode material can be improved, the peel strength of the electrode sheet can be strengthened, the repulsion of the electrode sheet can be reduced, and the conductive network of the electrode sheet can be stabilized, thereby improving the cycle life of batteries manufactured using the anode material.

[0083] The manufacturing method provided by this solution will be introduced in detail below.

[0084] In step S100, silicon oxide SiO x The first surface modification treatment was carried out by placing the <x<2である。

[0085] In some embodiments, the silicon oxide is SiO x where 0 <x<2であり、SiO x Specifically, SiO 0.5 , SiO 0.7 , SiO, SiO 1.2 , SiO 1.4 , SiO 1.6 , SiO 1.8 and SiO 1.9 The present invention is not limited to the above. xThe composition of is complex, and it is understood to be formed by uniformly dispersing at least one of amorphous silicon and crystalline silicon in SiO2. At high temperatures, its thermodynamic properties are very unstable, and it is prone to undergo a reduction reaction with a lithium source to produce lithium silicate.

[0086] In some embodiments, the acid solution comprises at least one of hydrofluoric acid, nitric acid, fluorosulfonic acid, magic acid, hydrochloric acid, hydrobromic acid, and hydroiodic acid. As will be appreciated, the acid solution can also be used to remove silicon oxide (SiO ). x By performing surface modification treatment on silicon oxide SiO x Surface oxidation and etching treatment of silicon oxide SiO x This can form weak defects on the surface of the silicon dioxide particles, increasing the reaction sites for the prelithiation process, making the prelithiation reaction more uniform, and providing more growth points for lithium silicate, which is beneficial for the uniform distribution of lithium silicate within the particles. When the amount of prelithiation is constant, it is beneficial for adjusting the crystalline phase type and content of lithium silicate. Furthermore, by using surface-modified silicon oxide for the prelithiation process, the catalytic growth of lithium silicate on silicon crystal grains can be significantly reduced.

[0087] In some embodiments, the concentration of the acid solution is ≦2 mol / L. Specifically, the concentration of the acid solution may be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, etc., and of course, may be other values ​​within the above range, and is not limited thereto.

[0088] In some embodiments, the temperature of the first surface modification treatment is 30°C to 100°C, and specifically may be 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc., and of course may be other values ​​within the above range and is not limited thereto.

[0089] In some embodiments, the duration of the first surface modification treatment is 2 hours to 8 hours, and may be specifically 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc., and may of course be other values ​​within the above range, and is not limited thereto.

[0090] In some embodiments, the method for producing silicon oxide (SiO ) after the first surface modification treatment. x The method further includes the step of subjecting the solid-liquid separation, washing, and drying treatment to the solid-liquid separation.

[0091] In some embodiments, the manufacturing method includes the step of: x The method further includes a step of subjecting the resulting mixture to solid-liquid separation, washing, and drying, and the drying temperature is 50° C. to 180° C. Specifically, the drying temperature may be 50° C., 60° C., 70° C., 80° C., 90° C., 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., or the like, and may of course be any other value within the above range, and is not limited thereto.

[0092] In step S200, silicon oxide SiO after the first surface modification treatment x and a mixture containing a reductive lithium-containing compound is subjected to a prelithiation treatment and a coating treatment at 300 to 800°C to obtain a precursor, <x<2である。

[0093] In the above method, the temperature of the pre-lithiation treatment may be specifically 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 710°C, 800°C, etc., and of course, may be other values ​​within the above range, and is not limited thereto.

[0094] As can be seen, if the temperature of the pre-lithiation treatment is too low, the reductive lithium-containing compound cannot completely react with the silicon oxide, causing the remaining silicon oxide to increase the oxygen content in the negative electrode material, which is disadvantageous to improving the initial efficiency of the negative electrode material; if the temperature of the pre-lithiation treatment is too high, the reaction between the reductive lithium-containing compound and the silicon oxide will be too severe, resulting in the rapid and large production of lithium silicate, which will catalyze the growth of silicon crystal particles in the material and deteriorate the cycle performance of the negative electrode material; and if the lithium silicate is produced too quickly and in a large amount, it will reduce the stability of the negative electrode slurry, making it impossible to stably store the negative electrode slurry.

[0095] Controlling the pre-lithiation temperature within this range is beneficial to the reaction between the lithium source and silicon oxide, to balance the crystalline phase type and content of the lithium silicate, and to obtain silicon crystal particles of appropriate size, thereby further improving the slurry storage stability of the material.

[0096] In some embodiments, the silicon oxide is silicon monoxide.It can be understood that when silicon oxide is silicon monoxide, the problem of unstable processing performance after doping silicon monoxide with lithium to improve the initial effect can be effectively solved.

[0097] In some embodiments, the reducible lithium-containing compound comprises at least one of lithium hydride, alkyl lithium, metallic lithium, lithium aluminum hydride, lithium amide, lithium borohydride, and lithium silicon alloy.

[0098] As can be seen, by selecting a reductive lithium-containing compound as the lithium source for the pre-lithiation treatment and having growth sites uniformly distributed on the surface of the silicon oxide after the first surface modification, performing the pre-lithiation treatment on a mixture containing the silicon oxide after the first surface modification treatment and the reductive lithium-containing compound can improve the lithium utilization rate and the uniformity of the distribution of the pre-lithiation product on the surface of the silicon oxide. This improves the lithium utilization rate, which is beneficial for reducing costs and improving the pre-lithiation effect (primary efficiency). The pre-lithiation product is uniformly distributed in the negative electrode material, which is beneficial for buffering the volume change during the charge and discharge process of a battery manufactured using the negative electrode material and improving the cycle performance.

[0099] In some embodiments, the mass ratio of silicon oxide to reductive lithium-containing compound after the first surface modification treatment is 1:(0.03 to 0.2), and specifically may be 1:0.03, 1:0.05, 1:0.08, 1:0.1, 1:0.15, 1:0.2, etc., and may of course be other values ​​within the above range and is not limited thereto.

[0100] In some embodiments, the pre-lithiation treatment is carried out in a protective atmosphere. As can be seen, the pre-lithiation treatment in a protective atmosphere can reduce the risk of introducing oxygen element, ensure the initial efficiency of the pre-lithiated material is improved, and is also advantageous for adjusting the composition of the lithium silicate, which further improves the storage stability of the slurry.

[0101] In some embodiments, the protective atmosphere comprises at least one of nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and xenon gas.

[0102] In some embodiments, the pre-lithiation time is 3 hours to 9 hours, and may be, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, etc., and may be other values ​​within the above range, and is not limited thereto. As can be understood, if the pre-lithiation time is within the above range, sufficient roasting can be achieved, and Li2SiO3 can be sufficiently converted to Li2SiO5.

[0103] In some embodiments, the lithium silicate comprises at least one of Li2SiO3, Li2Si2O5, Li4SiO4.

[0104] In some embodiments, the method further comprises the step of mixing the mixture containing the silicon oxide and the reductive lithium-containing compound after the first surface-modification treatment before subjecting the mixture containing the silicon oxide and the reductive lithium-containing compound after the first surface-modification treatment to a pre-lithiation treatment at 300°C to 800°C.

[0105] In some embodiments, the temperature of the mixing treatment is 60°C to 320°C, and specifically may be 60°C, 70°C, 80°C, 90°C, 100°C, 150°C, 200°C, 250°C, 300°C, 310°C, 320°C, etc., and of course may be other values ​​within the above range, and is not limited thereto.

[0106] In some embodiments, the time for the mixing treatment is 0.5 hours to 10 hours, and specifically may be 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc., and of course may be other values ​​within the above range and is not limited thereto.

[0107] In some embodiments, the equipment required for the mixing process includes at least one of equipment having a dispersing function and equipment having a shearing force. As will be understood, prior to the pre-lithiation process, the mixture containing the silicon oxide and the reducible lithium-containing compound after the first surface modification process may be mixed using an equipment having a high-speed dispersing function and a shearing force, which can effectively reduce the severity of the initial reaction of the pre-lithiation process and contribute to adjusting the lithium silicate component to meet the requirements of the present application, thereby improving the storage stability of the slurry and the adhesive ability of the active material on the electrode sheet.

[0108] In some embodiments, the method further comprises coating the silicon oxide after the first surface modification treatment before pre-lithiation of the mixture containing the silicon oxide after the first surface modification treatment and the reducible lithium-containing compound.

[0109] As will be understood, the coating treatment may be carried out before the mixture containing the silicon oxide and the reducible lithium-containing compound after the first surface modification treatment is subjected to a pre-lithiation treatment, or may be carried out after the mixture containing the silicon oxide and the reducible lithium-containing compound after the first surface modification treatment is subjected to a pre-lithiation treatment, and is not limited thereto.

[0110] In addition, when the coating treatment is carried out before the pre-lithiation treatment of the mixture containing the silicon oxide and the reductive lithium-containing compound after the first surface modification treatment, the coating treatment needs to be carried out before the mixing treatment of the mixture containing the silicon oxide and the reductive lithium-containing compound after the first surface modification treatment.

[0111] In some embodiments, the coating treatment comprises a carbon coating treatment, and the carbon coating treatment process comprises at least one of a liquid phase coating method, a vapor phase coating method, and a solid phase coating method.

[0112] In some embodiments, the coating process includes a carbon coating process, and the coating material of the carbon coating process includes at least one of amorphous carbon, graphene, graphite, carbon nanotubes, and carbon fibers. Preferably, the coating material of the carbon coating is amorphous carbon. As will be understood, amorphous carbon is produced by high-temperature decomposition and has a certain degree of graphitization. By using amorphous carbon to coat the surface of silicon oxide, the conductivity of the negative electrode material can be improved. Meanwhile, the amorphous carbon produced by high-temperature decomposition develops a pore structure, and coating it on the surface of silicon oxide can suppress the volume expansion of the negative electrode material, which is advantageous for improving the cycle performance of the negative electrode material.

[0113] In step S300, the precursor is subjected to a second surface modification treatment to obtain a negative electrode material, wherein the negative electrode material includes a silicon-based active material and a coating layer located on at least a portion of the silicon-based active material, and the silicon-based active material includes silicon and lithium silicate.

[0114] In some embodiments, the second surface modification treatment includes at least one of a purification treatment, a coating treatment, a heat treatment, an oxidation treatment, and an etching treatment.

[0115] In some embodiments, the coating process may be, but is not limited to, a secondary carbon coating process, a polymer coating process, or an inorganic coating process.

[0116] In a specific embodiment, the heat treatment is combined with other processes, such as, but not limited to, a polymer coating process, an etching process, etc.

[0117] In some embodiments, the temperature of the second surface modification treatment is 50°C to 900°C, and specifically may be 50°C, 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, etc., and of course may be other values ​​within the above range and is not limited thereto.

[0118] In some embodiments, the duration of the second surface modification treatment is 0.5 hours to 10 hours, and specifically may be 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc., and may of course be other values ​​within the above range and is not limited thereto.

[0119] In some embodiments, the second surface modification treatment includes purifying the precursor in an aluminum hydroxide solution. As will be appreciated, since the coatings on the aluminum foil and the separator are the same in the cell system, purifying the precursor in an aluminum hydroxide solution can improve the compatibility of the constructed cell system.

[0120] In the above manufacturing method, if the surface modification treatment is carried out excessively, there will be too many reaction points for pre-lithiation on the surface of the silicon oxide, which will react violently with the lithium source on the surface layer of the negative electrode material, resulting in the production of a lot of Li2SiO3 and even Li4SiO4. If the Li2SiO5 content is particularly low and the surface modification treatment is too weak, there will be insufficient reaction points for pre-lithiation on the surface of the silicon oxide, and the content of lithium silicate produced will be low, making it impossible to achieve the effect of pre-lithiation.

[0121] In addition, the reaction temperature and reaction time during the pre-lithiation process also affect the product composition of the negative electrode material after pre-lithiation. If the reaction temperature is too high and the reaction time is too long, the Li2SiO3 content will be high, and if the reaction temperature is too low and the reaction time is too short, the Li2Si2O5 content will be high. Overall, it is necessary to control the appropriate active points, temperature, and time. Only by combining these three factors can a negative electrode material that meets the requirements be produced.

[0122] In a fourth aspect, the present application provides a lithium ion battery, the lithium ion battery comprising the negative electrode material of the first aspect or the negative electrode material produced by the production method of the third aspect.

[0123] The above are merely preferred embodiments of the present application, and do not limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included within the scope of protection of the present application.

[0124] Example Example 1 (1) Silicon monoxide (SiO) was placed in a 1 mol / L mixed acid solution of nitric acid and hydrochloric acid, stirred and dispersed at 50°C for 4 hours, and then filtered with suction and washed with pure water. The resulting product was dried at 80°C to obtain surface-modified silicon monoxide (SiO).

[0125] (2) A mixture containing 1000 g of surface-modified silicon monoxide (SiO) and 200 g of lithium hydride was placed in a high-speed disperser, argon gas was introduced, the mixture was heated to 80°C, and dispersed and mixed at 2000 rpm for 1 hour. The mixture was then cooled to room temperature and placed in a crucible. The crucible was then placed in a box furnace and pre-lithiated at 500°C for 4 hours. The temperature was then lowered to 25°C to obtain a silicon-based active material. Subsequently, 2% wt of amorphous carbon was coated on the surface of the silicon-based active material using a liquid-phase coating method to obtain a precursor.

[0126] (3) The precursor was placed in Al(OH)3, purified at 40°C for 2 hours, and then filtered and washed to remove the alkaline solution remaining on the surface of the precursor. Subsequently, the surface of the precursor was coated with 2% wt amorphous carbon using a liquid-phase coating method to obtain the negative electrode material.

[0127] The negative electrode material prepared in this example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate, and the silicon comprises nanocrystalline silicon particles. The negative electrode material was measured using XRD. Calculations based on the XRD spectrum of the negative electrode material showed that the relationships between A, B, and C in the negative electrode material were (A + B) / C = 4.6, (A + C) / B = 2.1, and (B + C) / A = 12.3. Figure 2 shows the relationship between powder density and powder conductivity of the negative electrode material prepared in this example. As can be seen from Figure 2, the relationship between ρ1, ρ2, σ1, and σ2 was (σ2 - σ1) / (ρ2 - ρ1) = 0.32. The shear force relationship in the rheological curve was 2τ1 > (τ2 - τ0).

[0128] When the negative electrode material prepared in this example is made into a negative electrode slurry, it can be stably stored for 72 hours or more.

[0129] Example 2 The negative electrode material was produced in a manner basically similar to that of Example 1, with the following differences.

[0130] (2) Using the liquid-phase coating method, 1000 g of surface-modified silicon monoxide (SiO) was coated with 2% wt amorphous carbon. 200 g of lithium hydride was then weighed out and placed in a high-speed disperser. Argon gas was introduced, the mixture was heated to 80°C, and dispersed and mixed at 2000 rpm for 1 hour. The mixture was then cooled to room temperature and placed in a crucible. The crucible was then placed in a box furnace and subjected to a pre-lithiation treatment at 500°C for 4 hours. The temperature was then lowered to 25°C, yielding a precursor.

[0131] All other operations are the same as in Example 1.

[0132] The negative electrode material prepared in this example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate, and the silicon comprises nanocrystalline silicon particles. The negative electrode material was measured using XRD ray diffraction and calculated based on the X-ray diffraction spectrum of the negative electrode material. The relationships among the three elements A, B, and C in the negative electrode material were (A + B) / C = 5.1, (A + C) / B = 2.0, and (B + C) / A = 10.3. The relationships among ρ1, ρ2, σ1, and σ2 were (σ2 - σ1) / (ρ2 - ρ1) = 0.33. The relationship between the shear forces in the rheological curves was 2τ1 > (τ2 - τ0).

[0133] When the negative electrode material prepared in this example is made into a negative electrode slurry, it can be stably stored for 72 hours or more.

[0134] Example 3 The negative electrode material was produced in a manner basically similar to that of Example 1, with the following differences.

[0135] (2) A mixture containing 1000 g of surface-modified silicon monoxide (SiO) and 150 g of metallic lithium was placed in a high-speed disperser, argon gas was introduced, the mixture was heated to 80°C, and dispersed and mixed at 2000 rpm for 1 hour. The mixture was then cooled to room temperature and placed in a crucible. The crucible was then placed in a box furnace and pre-lithiated at 500°C for 4 hours. The temperature was then lowered to 25°C to obtain a silicon-based active material. Subsequently, 2% wt of amorphous carbon was coated on the surface of the silicon-based active material using a liquid-phase coating method to obtain a precursor.

[0136] All other operations are the same as in Example 1.

[0137] The negative electrode material prepared in this example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate, and the silicon comprises nanocrystalline silicon particles. The negative electrode material was measured using XRD ray diffraction and calculated based on the X-ray diffraction spectrum of the negative electrode material. The relationships among the three elements A, B, and C in the negative electrode material were (A + B) / C = 4.1, (A + C) / B = 2.2, and (B + C) / A = 8.8. The relationships among ρ1, ρ2, σ1, and σ2 were (σ2 - σ1) / (ρ2 - ρ1) = 0.46. The relationship between the shear forces in the rheological curves was 2τ1 > (τ2 - τ0).

[0138] When the negative electrode material prepared in this example is made into a negative electrode slurry, it can be stably stored for 72 hours or more.

[0139] Example 4 (1) Silicon oxide (SiO 1.5 ) was added to a mixed acid solution of nitric acid and hydrochloric acid with a concentration of 1 mol / L, stirred and dispersed at 50 °C for 4 h, then suction filtered and washed with pure water, and the resulting product was dried at 80 °C to obtain silicon oxide (SiO 1.5 ) was obtained.

[0140] (2) 1000 g of silicon oxide (SiO ) after surface modification treatment 1.5 A mixture containing 100g of alkyllithium was placed in a high-speed disperser, argon gas was introduced, the temperature was raised to 80°C, and the mixture was dispersed and mixed for 1 hour at 2000 rpm. The mixture was then cooled to room temperature and placed in a crucible. The crucible was then placed in a box furnace and pre-lithiation was carried out at 500°C for 4 hours, and the temperature was lowered to 25°C to obtain a silicon-based active material. Subsequently, 2% wt of amorphous carbon was coated on the surface of the silicon-based active material using a liquid-phase coating method to obtain a precursor.

[0141] (3) The precursor was placed in Al(OH)3, purified at 40°C for 2 hours, and then filtered and washed to remove the alkaline solution remaining on the surface of the precursor. Subsequently, the surface of the precursor was coated with 2% wt amorphous carbon using a liquid-phase coating method to obtain the negative electrode material.

[0142] The negative electrode material prepared in this example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate, and the silicon comprises nanocrystalline silicon particles. The negative electrode material was measured using XRD ray diffraction and calculated based on the X-ray diffraction spectrum of the negative electrode material. The relationships among the three elements A, B, and C in the negative electrode material were (A + B) / C = 2.5, (A + C) / B = 1.8, and (B + C) / A = 1.2. The relationships among ρ1, ρ2, σ1, and σ2 were (σ2 - σ1) / (ρ2 - ρ1) = 0.52. The relationship between the shear forces in the rheological curves was 2τ1 > (τ2 - τ0).

[0143] When the negative electrode material prepared in this example is made into a negative electrode slurry, it can be stably stored for 72 hours or more.

[0144] Example 5 The negative electrode material was produced in a manner basically similar to that of Example 1, with the following differences.

[0145] (1) Silicon monoxide (SiO) was placed in a 2 mol / L mixed acid solution of nitric acid and hydrochloric acid, stirred and dispersed at 50°C for 4 hours, and then filtered with suction and washed with pure water. The resulting product was dried at 80°C to obtain surface-modified silicon monoxide (SiO).

[0146] All other operations are the same as in Example 1.

[0147] The negative electrode material prepared in this example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate, and the silicon comprises nanocrystalline silicon particles. The negative electrode material is measured using XRD ray diffraction. Calculations based on the X-ray diffraction spectrum of the negative electrode material show that the relationships among the three elements A, B, and C in the negative electrode material are (A + B) / C = 2.8, (A + C) / B = 1.5, and (B + C) / A = 1.9. The relationships among ρ1, ρ2, σ1, and σ2 are (σ2 - σ1) / (ρ2 - ρ1) = 0.61. The relationship between the shear forces in the rheological curves is 2τ1 > (τ2 - τ0).

[0148] When the negative electrode material prepared in this example is made into a negative electrode slurry, it can be stably stored for 72 hours or more.

[0149] Example 6 The negative electrode material was produced in a manner basically similar to that of Example 1, with the following differences.

[0150] (2) A mixture containing 1000 g of surface-modified silicon monoxide (SiO) and 200 g of lithium hydride was placed in a high-speed disperser, argon gas was introduced, the mixture was heated to 80 ° C, and dispersed and mixed at 2000 rpm for 1 hour. The mixture was then cooled to room temperature and placed in a crucible. The crucible was placed in a box furnace and pre-lithiated at 300 ° C for 5 hours. The temperature was then lowered to 25 ° C to obtain a silicon-based active material. Subsequently, 2% wt of amorphous carbon was coated on the surface of the silicon-based active material using a liquid-phase coating method to obtain a precursor. All other procedures were the same as in Example 1.

[0151] The negative electrode material prepared in this example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate, and the silicon comprises nanocrystalline silicon particles. The negative electrode material was measured using XRD ray diffraction and calculated based on the X-ray diffraction spectrum of the negative electrode material. The relationships among the three elements A, B, and C in the negative electrode material were (A + B) / C = 10, (A + C) / B = 1.0, and (B + C) / A = 30. The relationships among ρ1, ρ2, σ1, and σ2 were (σ2 - σ1) / (ρ2 - ρ1) = 0.46. The relationship between the shear forces in the rheological curves was 2τ1 > (τ2 - τ0).

[0152] When the negative electrode material prepared in this example is made into a negative electrode slurry, it can be stably stored for 72 hours or more.

[0153] Example 7 The negative electrode material was produced in a manner basically similar to that of Example 1, with the following differences.

[0154] (2) A mixture containing 1000 g of surface-modified silicon monoxide (SiO) and 200 g of lithium hydride was placed in a high-speed disperser, argon gas was introduced, the mixture was heated to 80°C, and dispersed and mixed at 2000 rpm for 1 hour. The mixture was then cooled to room temperature and placed in a crucible. The crucible was then placed in a box furnace and pre-lithiated at 800°C for 4 hours. The temperature was then lowered to 25°C to obtain a silicon-based active material. Subsequently, 2% wt of amorphous carbon was coated on the surface of the silicon-based active material using a liquid-phase coating method to obtain a precursor.

[0155] All other operations are the same as in Example 1.

[0156] The negative electrode material prepared in this example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate, and the silicon comprises nanocrystalline silicon particles. The negative electrode material is measured using XRD ray diffraction and calculated based on the X-ray diffraction spectrum of the negative electrode material. The relationships among the three elements A, B, and C in the negative electrode material are (A + B) / C = 1.3, (A + C) / B = 5, and (B + C) / A = 29.3. The relationships among ρ1, ρ2, σ1, and σ2 are (σ2 - σ1) / (ρ2 - ρ1) = 0.5. The relationship between the shear forces in the rheological curves is 2τ1 > (τ2 - τ0).

[0157] When the negative electrode material prepared in this example is made into a negative electrode slurry, it can be stably stored for 72 hours or more.

[0158] (Comparative Example 1) The differences from the first embodiment are as follows.

[0159] In this comparative example, the crucible was placed in a box furnace and pre-lithiation treatment was carried out at 200°C for 5 hours in step (2), but the other operating conditions and raw materials were all the same as those in Example 1.

[0160] The negative electrode material prepared in this comparative example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate. The negative electrode material is measured by XRD ray diffraction and calculated from the X-ray diffraction spectrum of the negative electrode material. The relationships among the three elements A, B, and C in the negative electrode material are (A+B) / C=8, (A+C) / B=13, and (B+C) / A=40. The relationships among ρ1, ρ2, σ1, and σ2 are (σ2-σ1) / (ρ2-ρ1)=0.9. The relationship between the shear forces in the rheological curves is 2τ1>(τ2-τ0).

[0161] If the negative electrode material produced in this comparative example is made into a negative electrode slurry, it cannot be stored stably.

[0162] (Comparative Example 2) The differences from the first embodiment are as follows.

[0163] In this comparative example, the crucible was placed in a box furnace and pre-lithiation treatment was carried out at 900°C for 2 hours in step (2), but the other operating conditions and raw materials were all the same as those in Example 1.

[0164] The negative electrode material prepared in this comparative example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate. The negative electrode material is measured by XRD ray diffraction and calculated from the X-ray diffraction spectrum of the negative electrode material. The relationships among the three elements A, B, and C in the negative electrode material are (A+B) / C=1.8, (A+C) / B=18, and (B+C) / A=30. The relationships among ρ1, ρ2, σ1, and σ2 are (σ2-σ1) / (ρ2-ρ1)=0.96. The relationship between the shear forces in the rheological curves is 2τ1<(τ2-τ0).

[0165] If the negative electrode material produced in this comparative example is made into a negative electrode slurry, it cannot be stored stably.

[0166] (Comparative Example 3) The differences from the first embodiment are as follows.

[0167] In this comparative example, the step (1) in Example 1 was not carried out, and the other operating conditions and raw materials were all the same as those in Example 1.

[0168] The negative electrode material prepared in this comparative example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate. The negative electrode material is measured by XRD ray diffraction and calculated from the X-ray diffraction spectrum of the negative electrode material. The relationships among the three elements A, B, and C in the negative electrode material are (A+B) / C=2.1, (A+C) / B=6.2, and (B+C) / A=6.9. The relationships among ρ1, ρ2, σ1, and σ2 are (σ2-σ1) / (ρ2-ρ1)=0.72. The relationship between the shear forces in the rheological curves is 2τ1<(τ2-τ0).

[0169] If the negative electrode material produced in this comparative example is made into a negative electrode slurry, it cannot be stored stably.

[0170] Comparative Example 4 The differences from the first embodiment are as follows.

[0171] In this comparative example, the step (3) in Example 1 was not carried out, and the other operating conditions and raw materials were all the same as those in Example 1.

[0172] The negative electrode material prepared in this comparative example comprises a silicon-based active material and a carbon material located on at least a portion of the surface of the silicon-based active material. The silicon-based active material comprises silicon and lithium silicate. The negative electrode material is measured by XRD ray diffraction and calculated from the X-ray diffraction spectrum of the negative electrode material. The relationships among the three elements A, B, and C in the negative electrode material are (A+B) / C=1.8, (A+C) / B=7.0, and (B+C) / A=19. The relationships among ρ1, ρ2, σ1, and σ2 are (σ2-σ1) / (ρ2-ρ1)=0.96. The relationship between the shear forces in the rheological curves is 2τ1<(τ2-τ0).

[0173] If the negative electrode material produced in this comparative example is made into a negative electrode slurry, it cannot be stored stably.

[0174] The measurement test method is as follows.

[0175] (1) XRD measurement test method for negative electrode materials The XRD spectrum of the material was measured using a Bruker AXS D8-Focus instrument from Germany. The instrument's measurement test parameters were CuKα radiation, divergence slit 1.0°, anti-scatter slit 2.0°, receiving slit 9.6°, voltage range 40 kV, current 40 mA, scan range 10-90°, scan step 0.01313, continuous scan mode, scan time per step 10.2 s, and calculated wavelength 1.5406 Å. The A / B / C values ​​and the average grain size of the silicon crystal grains were calculated.

[0176] (2) Test methods for measuring powder conductivity and powder density of negative electrode materials The measurement test equipment is manufactured by Mitsubishi Chemical Corporation of Japan. The measurement test parameters include the initial resistance order of -3, the voltage limit value of 10V, the sample mass of 20KN, and the sample thickness of 3-5mm. The set pressures are 4, 8, 12, 16, and 20KN, respectively, the electrode radius is 0.7mm, and the sample radius is 10mm. The corresponding powder density and powder conductivity are measured at different pressures.

[0177] (3) Test method for measuring the rheology curve of the negative electrode slurry The active material, carboxymethyl cellulose, conductive carbon black, and styrene butadiene rubber are mixed in a mass ratio of 95.3:1.3:1.5:1.9 to form a negative electrode slurry with a solid content of 50%, where the active material includes a negative electrode material and graphite in a mass ratio of 9:1. A German Hack rotational rheometer is used to measure the rheological properties of the negative electrode slurry, and a rheological curve of the negative electrode slurry is obtained.

[0178] (4) Regarding the 50-cycle performance measurement test for button batteries, Based on the equipment and methods used in BTR's BTRTC / ZY / 01-020 "Button Cell Battery Manufacturing Manual," a 5% solids adhesive solution was prepared using PAA as the adhesive. The negative electrode active material and conductive agent were then added in a mass ratio of 75:15:10 (negative electrode active material:conductive agent (SP):adhesive (PAA)). This was uniformly dispersed using a high-speed disperser to form a negative electrode slurry. The slurry was then uniformly coated onto 10-micron-thick copper foil, which was then dried, roll-pressed, punched, and re-dried to obtain the negative electrode. A lithium sheet was used for the positive electrode, and the button battery was assembled in the following order: case, gasket, nickel sheet, lithium sheet, separator, negative electrode, and case. The counter electrode was a lithium metal sheet, the separator was a PP-PE-PP composite membrane with a diameter of 19.2 mm, the electrolyte composition was EC / EMC / DMC=1 / 1 / 1, and the concentration of lithium salt (LiPF6) was 1.05 mol / L. Using a button battery charge / discharge device, the first cycle was discharged at 0.1 C to 0.01 V, then discharged at 0.01 C incrementally to 0.01 V, then discharged at 0.01 C to 0.005 V, and charged at 0.1 C to 1.5 V. The second cycle was discharged at 0.2 C to 0.01 V, then discharged at 0.02 C incrementally to 0.01 V, then discharged at 0.02 C to 0.005 V, and charged at 0.2 C to 1.5 V. The third cycle was discharged at 0.5 C to 0.01 V, then discharged at 0.005 V. Discharge at 5C incrementally to 0.01V, discharge at 0.05C to 0.005V, charge at 0.5C to 1.5V, from the 4th to the 50th cycles, discharge at 1C to 0.01V, discharge at 0.1C incrementally to 0.01V, discharge at 0.1C to 0.005V, charge at 1C to 1.5V, and in the 51st cycle, discharge at 0.1C to 0.01V, discharge at 0.01C incrementally to 0.01V, discharge at 0.01C to 0.005V.

[0179] (5) Evaluation method for storage stability of negative electrode slurry An active material, carboxymethyl cellulose, conductive carbon black, and styrene-butadiene rubber are mixed in a mass ratio of 95.3:1.3:1.5:1.9 to form a negative electrode slurry with a solids content of 50%, where the active material comprises a negative electrode material and graphite in a mass ratio of 9:1. The negative electrode slurry is then allowed to stand at 25°C, and changes in the viscosity, fluidity, solids content, fineness, coating condition, etc. of the slurry are observed during the standing process. If the viscosity increases or decreases, it indicates that particle aggregation or dispersion may have occurred in the slurry, which is detrimental to the stability of the slurry. If significant stratification or fluid thickening occurs, the dispersibility of the slurry will decrease, the fluidity will deteriorate, and the stability will decrease. If the solid content changes significantly, particle aggregation or precipitation will occur in the slurry, affecting its stability. If large particle aggregation occurs or the fineness of the particles changes significantly, the stability of the slurry will decrease. The slurry is applied to a substrate and the uniformity and adhesion of the coating film are observed. If the coating film is uneven, peeling, cracks, or the like, it indicates poor stability of the slurry.

[0180] (6) Regarding the test method for measuring specific capacitance, Using a button battery charging / discharging device, charge the battery at a constant current of 0.1C up to 10mV, then at a constant current of 0.02C up to 5mV, and finally discharge at a constant current of 0.1C down to 1.5V.

[0181] The results of the above measurement tests are shown in detail in Table 1.

[0182] [Table 1]

[0183] As can be seen from the above examples and comparative examples, in Examples 1 to 7, by controlling the balance between the three components of the negative electrode material, Li2SiO3, Li2Si2O5, and silicon, the uniformity of lithiation of the negative electrode material can be improved, the processing performance of the negative electrode material can be improved, and the storage stability of the negative electrode slurry produced from the negative electrode material can be improved. Furthermore, by controlling the balance between the three components of the negative electrode material, Li2SiO3, Li2Si2O5, and silicon, the content of Li2Si2O5 in the negative electrode material can be increased, which reduces the destructive effect of lithium silicate on the adhesive, improves the stability of the electrode sheet, improves the cycle performance of the negative electrode material, and extends the cycle life.

[0184] Compared with Example 1, the temperature of the pre-lithiation treatment of the negative electrode material in Comparative Example 1 is too low, and the lithium source cannot completely react with silicon monoxide during the pre-lithiation process, resulting in a high oxygen content in the prepared negative electrode material and a low initial efficiency of the negative electrode material.

[0185] Compared with Example 1, the temperature of the pre-lithiation treatment of the anode material in Comparative Example 2 is too high. During the pre-lithiation process, the reaction between the lithium source and silicon monoxide is intense, producing lithium silicate at a rapid rate and in large amounts. This catalyzes the growth of silicon crystal particles in the anode material, causing deterioration of the cycle performance of the material. It also reduces the storage stability of the anode slurry produced from the anode material, making the slurry unable to be stably stored for long periods of time.

[0186] Compared with Example 1, the anode material of Comparative Example 3 did not perform surface modification on the silicon monoxide, which reduced the reaction sites in the pre-lithiation process, resulting in a non-uniform pre-lithiation reaction, a reduced number of growth sites for lithium silicate, and a non-uniform distribution of lithium silicate inside the anode material particles. This was unfavorable for adjusting the crystalline phase type and content of lithium silicate, and resulted in an imbalance in the relative relationships between the three components of the anode material, namely Li2SiO3, Li2SiO5, and silicon. This reduced the storage performance of the anode slurry produced from the anode material, making the anode slurry unable to be stably stored for long periods of time. The slurry was prone to settling, layer separation, and gas generation during storage, resulting in a non-uniform distribution of the active material in the applied electrode sheet, and the lithium silicate in the anode material had a significant destructive effect on the adhesive, reducing the structural stability of the electrode sheet and reducing the cycle performance of the anode material.

[0187] Compared with Example 1, the negative electrode material of Comparative Example 4 did not undergo a second surface treatment of the precursor, resulting in poor interface stability of the negative electrode material, reduced performance stability of the formed SEI film, and increased risk of erosion of the negative electrode material in the electrolyte. At the same time, the adhesive strength to the negative electrode material was weakened, causing a decrease in the peel strength of the electrode sheet, making the electrode sheet more susceptible to repulsion, reducing the stability of the conductive network of the electrode sheet, and reducing the cycle performance of the negative electrode material.

Claims

1. a negative electrode material comprising a silicon-based active material and a coating layer located on at least a portion of the silicon-based active material, the silicon-based active material comprising silicon and lithium silicate; In the X-ray diffraction spectrum of the negative electrode material measured by an XRD ray diffraction method, the negative electrode material has a peak intensity A1 of the strongest diffraction peak in the 2θ range of 18° to 20°, a peak intensity A2 of the strongest diffraction peak in the 2θ range of 26° to 27.9°, and a peak intensity A3 of the strongest diffraction peak at a 2θ range of 32° to 34°, where A1+A2+A3=A; In the negative electrode material, the peak intensity of the strongest diffraction peak within a 2θ range of 16° to 17° is B1, the peak intensity of the strongest diffraction peak within a 2θ range of 22° to 25.9° is B2, and the peak intensity of the strongest diffraction peak within a 2θ range of 36° to 38° is B3, and B1+B2+B3=B; In the negative electrode material, the peak intensity of the strongest diffraction peak within a 2θ range of 28° to 30° is C1, the peak intensity of the strongest diffraction peak within a 2θ range of 46° to 48° is C2, and the peak intensity of the strongest diffraction peak within a 2θ range of 56° to 58° is C3, where C1+C2+C3=C; The relationships among the three elements A, B, and C simultaneously satisfy the following conditions: 0<(A+B) / C≦10, 0<(A+C) / B≦5.

2. The negative electrode material according to claim 1, characterized in that the negative electrode material is tested using a powder resistivity testing device to obtain a powder conductivity σ1 at a powder density ρ1 of the negative electrode material, and a powder conductivity σ2 at a powder density ρ2 of the negative electrode material, wherein the relationship (σ2-σ1) / (ρ2-ρ1)≦0.8 is satisfied.

3. 2. The negative electrode material according to claim 1, wherein the relationship among the three elements A, B, and C further satisfies 1≦(B+C) / A≦30.

4. 10. The negative electrode material of claim 1, wherein the silicon-based active material further comprises a silicon-oxygen complex.

5. 2. The negative electrode material according to claim 1, wherein the molar ratio of oxygen atoms to silicon atoms in the negative electrode material is 0.5 to 2.

6. 2. The negative electrode material according to claim 1, wherein the silicon in the negative electrode material comprises nanosilicon crystalline particles, and the average particle size of the nanosilicon crystalline particles is 0 nm to 20 nm but does not include 0 nm.

7. The lithium silicate is Li 2 SiO 3 , Li 2 Si 2 O 5 and Li 4 SiO 4 The negative electrode material according to claim 1, comprising at least one of:

8. 2. The negative electrode material according to claim 1, wherein the coating layer contains a carbon material, and the mass content of the carbon material in the negative electrode material is 10% or less.

9. 2. The negative electrode material according to claim 1, wherein the mass content of silicon in the negative electrode material is 20% to 70%.

10. 2. The negative electrode material according to claim 1, wherein the mass content of the lithium silicate in the negative electrode material is 30% to 75%.

11. The specific surface area of ​​the negative electrode material is 10 m 2 2. The negative electrode material according to claim 1, wherein the Cr content is 0.15 / g or less.

12. 2. The negative electrode material according to claim 1, wherein the pH value of the negative electrode material is 7.2 to 11.

0.

13. An active material, carboxymethyl cellulose, conductive carbon black, and styrene butadiene rubber were mixed in a mass ratio of 95.3:1.3:1.5:1.9 to form a negative electrode slurry having a solids content of 50%, wherein the active material included the negative electrode material and graphite in a mass ratio of 9:

1. The rheological properties of the negative electrode slurry were tested using a German Hack rotational rheometer to obtain a rheological curve of the negative electrode slurry, and the rheological curve showed that the shear rate was 0 S. -1 , 150S -1 , 300S -1 13. The negative electrode material according to claim 1, wherein, when the shear stresses in the rheological curve are τ0, τ1, and τ2, the relationship between the shear stresses satisfies 2τ1>(τ2-τ0).

14. An anode slurry comprising the anode material according to any one of claims 1 to 13.

15. A lithium ion battery comprising the negative electrode material according to any one of claims 1 to 13.

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