Preparation method of graphite negative electrode material for lithium ion battery, lithium ion battery, energy storage device and electrical equipment

Abstract

This application relates to the field of energy storage technology, and in particular to a method for preparing a graphite negative electrode material for lithium-ion batteries, a lithium-ion battery, an energy storage device, and electrical equipment. The method comprises the following steps: preparing a slurry mixture containing a biomass carbon source, a nitrogen-sulfur dopant, polyvinyl pyrrolidone, and a catalyst, wherein the mass ratio of the biomass carbon source, the nitrogen-sulfur dopant, the polyvinyl pyrrolidone, and the catalyst is 1:(0.5-1.5):(0.05-0.1):(0.5-2.8); pre-carbonizing the slurry mixture at a temperature of 500°C to 600°C to obtain a pre-carbonized product; and graphitizing the pre-carbonized product at a temperature of 1200°C to 1400°C to obtain a graphite negative electrode material. The graphite negative electrode material prepared by the preparation method has a high degree of graphitization, uniform and controllable sulfur and nitrogen doping, and excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a method for preparing a graphite negative electrode material for a lithium ion battery, a lithium ion battery, an energy storage device, and electrical equipment. Background Art

[0002] Graphitized carbon materials are widely used in batteries, supercapacitors, catalyst supports, and other fields due to their excellent conductivity, chemical stability, and high specific surface area. Traditional methods for preparing graphitized materials often use petroleum coke and pitch coke as raw materials, which have problems such as high cost and environmental pollution.

[0003] In recent years, biomass carbon sources have attracted attention due to their renewability and environmental friendliness, but their graphitization efficiency is low and the electrochemical performance of graphitized carbon materials needs to be further improved. Summary of the Invention

[0004] The present application proposes a method for preparing a graphite negative electrode material for a lithium-ion battery, a lithium-ion battery, an energy storage device, and an electrical equipment, aiming to solve the technical problems mentioned in the above background technology.

[0005] In a first aspect, the present invention provides a method for preparing a graphite negative electrode material for a lithium-ion battery, comprising the following steps:

[0006] Preparing a slurry mixture containing a biomass carbon source, a nitrogen-sulfur dopant, polyvinyl pyrrolidone, and a catalyst, wherein the mass ratio of the biomass carbon source, the nitrogen-sulfur dopant, the polyvinyl pyrrolidone, and the catalyst is 1:(0.5-1.5):(0.05-0.1):(0.5-2.8);

[0007] Performing a pre-carbonization treatment on the slurry mixture at a temperature of 500° C. to 600° C. to obtain a pre-carbonized product;

[0008] The pre-carbonized product is graphitized at a temperature of 1200° C. to 1400° C. to obtain a graphite negative electrode material.

[0009] In some embodiments, the nitrogen-sulfur dopant is an organic metal complex, and the central metal of the organic metal complex includes at least one of iron, cobalt, and nickel.

[0010] In some embodiments, the steps of preparing the organometallic complex include:

[0011] Under an inert environment, anhydrous ethanol is used as a solvent to prepare a mixture of nitrogen and sulfur organic matter and metal salt according to a preset molar ratio;

[0012] The mixed solution is placed at 60° C. to 80° C. and stirred for reaction for 5 h to 8 h at a stirring rate of 200 rpm / min to 400 rpm / min. The reaction mixture is purified to obtain the organometallic complex.

[0013] In some embodiments, the nitrogen-sulfur organic compound comprises one or more of thiourea, 2-mercaptoimidazole, cysteine, and ammonium thiocyanate;

[0014] The metal salt includes one or more of iron salt, cobalt salt and nickel salt.

[0015] In some embodiments, the slurry mixture further contains a boron dopant, and the boron dopant includes boric acid.

[0016] In some embodiments, the biomass carbon source comprises one or more of glucose, lignin sulfonate, malic acid, chitosan, sucrose, fructose, citric acid, oxalic acid, cellulose, lignin, and hemicellulose.

[0017] In some embodiments, the catalyst includes one or more of ferric chloride hexahydrate, cobalt chloride, nickel chloride, iron oxide, and cobalt oxide.

[0018] In some embodiments, the pre-carbonization treatment time is 4 hours to 6 hours.

[0019] In some embodiments, the graphitization treatment time is 6 hours to 8 hours.

[0020] In some embodiments, after the graphitization treatment, the preparation method further comprises: soaking the graphitization treatment product in a hydrochloric acid solution, and then filtering, filtering, washing, and drying in sequence to obtain the graphite negative electrode material.

[0021] In a second aspect, an embodiment of the present application further provides a lithium-ion battery, comprising a negative electrode sheet, the negative electrode sheet comprising a current collector and a graphite negative electrode material coated on the surface of the current collector, the graphite negative electrode material being prepared by the preparation method described in the first aspect.

[0022] In some embodiments, the graphite negative electrode material is doped with nitrogen and sulfur, the content of nitrogen in the graphite negative electrode material is 2 wt% to 8 wt%, and the content of sulfur in the graphite negative electrode material is 1 wt% to 5 wt%.

[0023] In some embodiments, the graphite negative electrode material is further doped with boron, and the content of boron in the graphite negative electrode material is 3 wt % to 5 wt %.

[0024] In some embodiments, the particle size D10 of the graphite negative electrode material is 5 μm to 8 μm.

[0025] In some embodiments, the particle size D50 of the graphite negative electrode material is 5 μm to 15 μm.

[0026] In some embodiments, the tap density of the graphite negative electrode material is 1.2 g / cm 3 ~1.3g / cm 3 .

[0027] In some embodiments, the specific surface area of the graphite negative electrode material is 1.3 m 2 / g~1.7m 2 / g.

[0028] In some embodiments, the D peak intensity of the Raman spectrum of the graphite negative electrode material is 1 D , G peak intensity is I G , 0.2≤I D / I G ≤0.5.

[0029] In a third aspect, an embodiment of the present application further provides an energy storage device, which includes a plurality of lithium-ion batteries as described in the second aspect.

[0030] In a fourth aspect, an embodiment of the present application further provides an electrical device, which includes the energy storage device as described in the third aspect.

[0031] Compared with the existing technology, this technical solution has at least the following technical effects:

[0032] In the preparation method of the present application, the preparation raw materials also include nitrogen-sulfur dopants and polyvinyl pyrrolidone, wherein the addition of nitrogen-sulfur dopants can optimize the structure of the graphite negative electrode material, enhance its graphitization degree, and introduce nitrogen and sulfur elements into the graphite negative electrode material to increase the active sites on the surface of the graphite negative electrode material. Polyvinyl pyrrolidone can improve the uniformity and controllability of sulfur and nitrogen doping in the graphite negative electrode material, and can induce the directional growth of graphite sheets and improve the graphitization degree of the biomass carbon source; specifically, in the slurry mixture preparation stage, polyvinyl pyrrolidone will combine with the biomass carbon source, nitrogen-sulfur dopants and catalyst to prevent the biomass carbon source molecules, nitrogen-sulfur dopant molecules and catalyst molecules from agglomerating / precipitating, so that the biomass carbon source, nitrogen-sulfur dopants and catalysts are evenly dispersed in the solution; in the pre-carbonization treatment stage, the nitrogen-sulfur dopants and catalysts are wrapped in polyvinyl pyrrolidone to maintain nanostructured carbon. The meter-scale structure is evenly dispersed, and the biomass carbon source will form a carbon skeleton along the extension direction of the polyvinyl pyrrolidone molecular chain, so that the carbon material produced by the pyrolysis of the biomass carbon source exists in a lamellar structure; in the graphitization treatment stage, polyvinyl pyrrolidone releases the catalyst and nitrogen-sulfur dopants, and the catalyst catalyzes the transformation of the carbon material to graphitization. In this process, the sulfur and nitrogen elements in the dopant will promote the bonding and rearrangement of carbon atoms, so that the lamellar structure continues to grow and improve, and the lamellar structure limits the growth direction of carbon atoms, so that it forms an ordered graphitized material from microscopic to macroscopic along a specific path. The graphite negative electrode material prepared by the preparation method of the present application has a high degree of graphitization, and the doping of sulfur and nitrogen elements is uniform and controllable, and its electrochemical performance is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below with reference to the accompanying drawings and examples.

[0034] Figure 1 This is a process flow chart of the method for preparing a graphite negative electrode material for lithium-ion batteries in an embodiment of the present application. DETAILED DESCRIPTION

[0035] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0036] Unless otherwise specified, the meanings of the terms in this specification are the same as those generally understood by those skilled in the art. However, if there is any conflict, the definitions in this specification shall prevail.

[0037] As used herein, "comprises," "includes," "contains," "has," "having," or other variations thereof are intended to encompass non-exclusive inclusions, and no distinction is made between these terms. The term "comprising" means that other steps and ingredients that do not affect the end result may be added. The term "comprising" also encompasses the terms "consisting of" and "consisting essentially of." The compositions and methods / processes of the present invention comprise, consist of, and consist essentially of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein.

[0038] All numerical values or expressions used in the specification and claims relating to component amounts, process conditions, etc. should be understood to be modified by "about" in all cases. All ranges relating to the same component or property include endpoints, which can be independently combined. Since these ranges are continuous, they include every numerical value between the minimum and maximum values. It should also be understood that any numerical range cited in this application is intended to include all subranges within that range.

[0039] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0040] The present application provides a method for preparing a graphite negative electrode material for lithium-ion batteries.

[0041] See also Figure 1 In the embodiment of the present application, the method for preparing the graphite negative electrode material for lithium-ion batteries comprises the following steps:

[0042] S100. Preparing a slurry mixture containing a biomass carbon source, a nitrogen-sulfur dopant, polyvinyl pyrrolidone (PVP), and a catalyst, wherein the mass ratio of the biomass carbon source, the nitrogen-sulfur dopant, the polyvinyl pyrrolidone, and the catalyst is 1:(0.5-1.5):(0.05-0.1):(0.5-2.8);

[0043] S200. The slurry mixture is pre-carbonized at a temperature of 500°C to 600°C to obtain a pre-carbonized product;

[0044] S300. The pre-carbonized product is graphitized at a temperature of 1200° C. to 1400° C. to obtain a graphite negative electrode material.

[0045] In the preparation method of the present application, the preparation raw materials also include nitrogen-sulfur dopants and polyvinyl pyrrolidone, wherein the addition of nitrogen-sulfur dopants can optimize the structure of the graphite negative electrode material, enhance its graphitization degree, and introduce nitrogen and sulfur elements into the graphite negative electrode material to increase the active sites on the surface of the graphite negative electrode material. Polyvinyl pyrrolidone can improve the uniformity and controllability of sulfur and nitrogen doping in the graphite negative electrode material, and can induce the directional growth of graphite sheets and improve the graphitization degree of the biomass carbon source; specifically, in the slurry mixture preparation stage, polyvinyl pyrrolidone will combine with the biomass carbon source, nitrogen-sulfur dopants and catalyst to prevent the biomass carbon source molecules, nitrogen-sulfur dopant molecules and catalyst molecules from agglomerating / precipitating, so that the biomass carbon source, nitrogen-sulfur dopants and catalysts are evenly dispersed in the solution; in the pre-carbonization treatment stage, the nitrogen-sulfur dopants and catalysts are wrapped in polyvinyl pyrrolidone to maintain nanostructured carbon. The meter-scale structure is evenly dispersed, and the biomass carbon source will form a carbon skeleton along the extension direction of the polyvinyl pyrrolidone molecular chain, so that the carbon material produced by the pyrolysis of the biomass carbon source exists in a lamellar structure; in the graphitization treatment stage, polyvinyl pyrrolidone releases the catalyst and nitrogen-sulfur dopants, and the catalyst catalyzes the transformation of the carbon material to graphitization. In this process, the sulfur and nitrogen elements in the dopant will promote the bonding and rearrangement of carbon atoms, so that the lamellar structure continues to grow and improve, and the lamellar structure limits the growth direction of carbon atoms, so that it forms an ordered graphitized material from microscopic to macroscopic along a specific path. The graphite negative electrode material prepared by the preparation method of the present application has a high degree of graphitization, and the doping of sulfur and nitrogen elements is uniform and controllable, and its electrochemical performance is excellent.

[0046] The preparation method of the present application is described in detail below.

[0047] S100. Prepare a slurry mixture containing a biomass carbon source, a nitrogen-sulfur dopant, polyvinyl pyrrolidone, and a catalyst, wherein the mass ratio of the biomass carbon source, the nitrogen-sulfur dopant, polyvinyl pyrrolidone, and the catalyst is 1:(0.5~1.5):(0.05~0.1):(0.5~2.8).

[0048] In the embodiments of the present application, the mass ratio of the biomass carbon source to the nitrogen-sulfur dopant is 1:(0.5-1.5), and specifically can be 1:0.5, 1:0.8, 1:1, 1:2, 1:1.5, or any ratio therebetween. The addition of nitrogen-sulfur dopants to the raw materials can increase the degree of graphitization of the pre-carbonized product, thereby further optimizing the overall structure of the resulting graphite negative electrode material and improving its electrochemical performance. Excessive nitrogen-sulfur dopants can reduce the structural stability, conductivity, and other properties of the graphite negative electrode material, thereby affecting its electrochemical performance. Excessive nitrogen-sulfur dopants can fail to effectively improve its electrochemical performance.

[0049] In the examples of the present application, the mass ratio of the biomass carbon source to polyvinyl pyrrolidone is 1:(0.05-0.1), specifically 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.10, or any value therebetween. If this ratio is too large, i.e., insufficient PVP is present, and the PVP cannot effectively disperse the biomass carbon source, nitrogen and sulfur dopants, and catalyst, resulting in particle agglomeration or precipitation. Furthermore, during the pre-carbonization stage, the PVP molecular chains cannot fully guide the directional extension of the biomass carbon source, resulting in a disordered stacking of the carbon skeleton rather than a lamellar structure. This reduces the graphitization potential and degrades the electrochemical performance of the graphite anode material. If the ratio is too small, that is, PVP is excessive, PVP will decompose violently during the pre-carbonization process, releasing a large amount of gas, which will cause the pores inside the carbon skeleton to collapse and the specific surface area to decrease; it will also hinder the effective release of the catalyst in the graphitization stage and reduce the catalytic efficiency; in addition, PVP will form an overly thick molecular chain network, which will limit the directional growth of carbon sheets, resulting in a dense structure of the graphitized material and uneven sheet thickness, affecting the electrochemical properties of the graphite negative electrode material.

[0050] In the embodiments of the present application, the mass ratio of the biomass carbon source to the catalyst is 1:(0.5-2.8), specifically 1:0.5, 1:0.8, 1:1, 1:1.3, 1:1.5, 1:1.8, 1:2, or any value therebetween. A ratio that is too large will not only fail to further improve the catalytic efficiency, but will also adversely affect the electrochemical performance of the graphite negative electrode material. A ratio that is too small will result in an inability to effectively catalyze the graphitization of the pre-carbonized product, thereby failing to effectively improve the electrochemical performance of the graphite negative electrode material.

[0051] In some preferred embodiments, the mass ratio of the biomass carbon source to the catalyst is 1:(2.4-2.8), specifically 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, or any ratio therebetween. Within this ratio range, the catalyst has a higher catalytic efficiency, the graphitization efficiency of the pre-carbonized product is higher, and this is more conducive to improving the electrochemical performance of the resulting graphite anode material.

[0052] In some embodiments, the biomass carbon source includes one or more of glucose, lignin sulfonate, malic acid, chitosan, sucrose, fructose, citric acid, oxalic acid, cellulose, lignin, and hemicellulose.

[0053] In some embodiments, the nitrogen-sulfur dopant is one or more of thiourea, 2-mercaptoimidazole, cysteine, and ammonium thiocyanate.

[0054] In other embodiments, the nitrogen-sulfur dopant is an organic metal complex, and the central metal of the organic metal complex includes at least one of iron, cobalt, and nickel. Compared with conventional nitrogen-sulfur dopants such as thiourea, 2-mercaptoimidazole, cysteine, and ammonium thiocyanate, organic metal complex nitrogen-sulfur dopants are more conducive to improving the graphitization degree of the pre-carbonized product, so that the electrochemical performance of the final graphite negative electrode material is more effectively improved. Specifically, the nitrogen-sulfur dopant uses metal ions such as iron, cobalt, and nickel as central atoms and nitrogen-sulfur organic matter as main ligands, wherein the metal ions have the function of catalyzing the graphitization of the pre-carbonized product. During the graphitization process of the pre-carbonized product, the nitrogen-sulfur organic matter can adsorb the pre-carbonized product to the vicinity of the metal ions to promote the catalysis of the metal ions, thereby improving the graphitization degree of the pre-carbonized product. In this process, the metal atoms can also stabilize the structure of the nitrogen-sulfur organic matter, so that the nitrogen and sulfur elements in the final graphite negative electrode material are more uniformly doped.

[0055] In some embodiments, the steps of preparing the organometallic complex include:

[0056] Under an inert environment, anhydrous ethanol is used as a solvent to prepare a mixture of nitrogen and sulfur organic matter and metal salt according to a preset molar ratio;

[0057] The mixed solution is stirred at 60° C. to 80° C. for 5 to 8 hours at a stirring rate of 200 rpm / min to 400 rpm / min, and the reaction mixture is purified to obtain an organometallic complex.

[0058] In the above embodiments, the amount of anhydrous ethanol used is preferably such that it can completely dissolve the nitrogen and sulfur organic matter and the metal salt and ensure that the reaction system has good fluidity.

[0059] In the above embodiment, the nitrogen-sulfur organic compound includes one or more of thiourea, 2-mercaptoimidazole, cysteine, and ammonium thiocyanate.

[0060] In the above embodiments, the metal salt includes one or more of ferric chloride hexahydrate, cobalt chloride, cobalt nitrate, ferric nitrate, nickel nitrate, nickel chloride, and the like.

[0061] In the above embodiments, the molar ratio of the nitrogen-sulfur organic compound to the metal salt is determined based on the specific types of the nitrogen-sulfur organic compound and the metal salt, and is not particularly limited in the present embodiments. For example, when the nitrogen-sulfur organic compound is 2-mercaptoimidazole and the metal salt is cobalt nitrate, the molar ratio of the nitrogen-sulfur organic compound to the metal salt is 3:1.

[0062] In the above embodiment, the steps are as follows: placing the mixed solution under the conditions of 60°C to 80°C and stirring for 5h to 8h, with a stirring rate of 200rpm / min to 400rpm / min, and purifying the reaction mixture to obtain an organometallic complex. Wherein, the conditions of 60°C to 80°C can be specifically 60°C, 65°C, 70°C, 75°C, 80°C or any temperature value therebetween; stirring for 5h to 8h, specifically 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h or any time therebetween; and stirring at a rate of 200rpm / min to 400rpm / min, specifically 200rpm / min, 250rpm / min, 300rpm / min, 350rpm / min, 400rpm / min or any value therebetween.

[0063] In some embodiments, the step of purifying the reaction mixture includes: cooling the reaction mixture and placing it in a centrifuge tube for centrifugation at a centrifugal rate of 5500 rpm / min~6500 rpm / min for 10 min~15 min; removing the supernatant in the centrifuge tube and washing the precipitate, specifically: adding an appropriate amount of anhydrous ethanol to the centrifuge tube and centrifuging again; repeating the washing step 2~3 times until no obvious impurity ions are detected in the ethanol solution after washing, and vacuum drying to obtain the organometallic complex.

[0064] In some embodiments, the catalyst includes one or more of ferric chloride hexahydrate, cobalt chloride, nickel chloride, iron oxide, and cobalt oxide.

[0065] In some embodiments, the catalyst is ferric chloride hexahydrate or ferric chloride, and the central metal ion in the organometallic complex is a cobalt ion. During the graphitization process of the biomass-carbon material, the iron ions in the catalyst and the cobalt ions in the organometallic complex can synergistically catalyze the graphitization of the pre-carbonized product.

[0066] In some embodiments, the slurry mixture further contains a boron dopant. The addition of the boron dopant to the raw materials allows the final graphite negative electrode material to be doped with boron, which can synergistically improve the electrochemical performance of the graphite negative electrode material with nitrogen and sulfur.

[0067] In the above embodiments, the boron dopant may be one or more of boric acid, boron tribromide, boron oxide, boron carbide, and the like.

[0068] In the above embodiment, the content of the boron dopant is 0.5% to 5%, and specifically can be 0.5%, 1%, 2%, 3%, 4%, 5%, or any value therebetween. Within this content range, the boron dopant can effectively cooperate with the nitrogen and sulfur dopants to improve the electrochemical performance of the graphite negative electrode material.

[0069] S200. The slurry mixture is subjected to a pre-carbonization treatment at a temperature of 500° C. to 600° C. to obtain a pre-carbonized product.

[0070] In the embodiments of the present application, the temperature of the pre-carbonization treatment is 500°C to 600°C, specifically 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C or any value therebetween. If the pre-carbonization treatment temperature is too high, the internal pores of the carbon skeleton of the pre-carbonized product will collapse, the dopant will fail, and the catalyst will be deactivated, thereby affecting the electrochemical properties of the graphite negative electrode material finally obtained. If the pre-carbonization treatment temperature is too low, the carbonization of the biomass carbon source will be incomplete, and the nitrogen and sulfur doping will be uneven, which will increase the difficulty of subsequent graphitization of the pre-carbonized product and affect the conductivity and electrochemical activity of the graphite negative electrode material finally obtained.

[0071] In some embodiments, the pre-carbonization treatment time is 4 hours to 6 hours, specifically 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours or any value therebetween.

[0072] S300. The pre-carbonized product is graphitized at a temperature of 1200° C. to 1400° C. to obtain a graphite negative electrode material.

[0073] In the embodiments of the present application, the graphitization treatment temperature is 1200°C to 1400°C, and specifically can be 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, or any value therebetween. Excessively high graphitization treatment temperatures can lead to ineffective doping of nitrogen and sulfur dopants, deactivation of the catalyst, and excessive stacking of the resulting graphite sheet structure, resulting in degraded performance of the resulting graphite negative electrode material. Excessively low graphitization treatment temperatures can lead to insufficient graphitization of the graphite negative electrode material, uneven nitrogen and sulfur doping, and poor conductivity, significantly limiting the electrochemical performance of the graphite negative electrode material.

[0074] In some embodiments, the graphitization treatment time is 6 h to 8 h, and specifically can be 6 h or any value therebetween.

[0075] In some embodiments, the heating rate from the pre-carbonization temperature to the graphitization temperature is ≤ 2° C. / min. Too fast a heating rate may increase the thermal stress inside the material, thereby causing cracks or structural damage.

[0076] In some embodiments, after graphitization, the graphitized product is cooled to room temperature at a cooling rate of ≤ 2°C / min. A cooling rate that is too fast can increase the temperature difference between the surface and interior of the material, thereby causing thermal stress concentration and potentially causing cracking or deformation of the material.

[0077] In some embodiments, after the graphitization treatment, the preparation method further includes: soaking the graphitization treatment product cooled to room temperature in a hydrochloric acid solution to remove metal impurities in the graphitization product, and then filtering, suction washing, and drying in sequence to obtain a graphite negative electrode material.

[0078] In some embodiments, the concentration of the hydrochloric acid solution is , specifically 、 、 、 、 、 or any value in between.

[0079] In some embodiments, the graphitized product is immersed in the hydrochloric acid solution for 20 hours to 24 hours, specifically 20 hours, 21 hours, 22 hours, 23 hours, 24 hours or any value therebetween.

[0080] In some embodiments, the filtration and washing are performed multiple times, for example, 2 or 3 times, and the washing solvent can be a low melting point solvent such as methanol or ethanol.

[0081] In some embodiments, the drying temperature is 50°C to 60°C, specifically 50°C, 52°C, 54°C, 56°C, 58°C, 60°C or any value therebetween.

[0082] In the embodiment of the present application, the graphite negative electrode material is doped with nitrogen and sulfur, wherein the content of nitrogen in the graphite negative electrode material is 2wt%~8wt%, and the content of sulfur in the graphite negative electrode material is 1wt%~5wt%.

[0083] In detail, the nitrogen content in the graphite negative electrode material is 2 wt % to 8 wt %, and specifically can be 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt % or any value therebetween.

[0084] The content of sulfur in the graphite negative electrode material is 1 wt% to 5 wt%, specifically 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt% or any value therebetween.

[0085] In some embodiments, the graphite negative electrode material is further doped with boron, and the content of boron in the graphite negative electrode material is 3wt%~5wt%, specifically 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% or any value therebetween.

[0086] In some embodiments, the D peak intensity of the Raman spectrum of the graphite negative electrode material is 1 D , G peak intensity is I G, 0.2≤I D / I G ≤0.5. In a specific embodiment, in the Raman spectrum of the graphite negative electrode material, the D peak and the G peak are located at and , 0.2≤I D / I G ≤0.5, which indirectly proves that the disordered soft carbon (i.e., pre-carbonization product) formed by the pre-carbonization treatment is successfully graphitized under the continuous catalytic effect of iron atoms during the graphitization process.

[0087] In some embodiments, the particle size D10 of the graphite negative electrode material is 5 μm to 8 μm, specifically 5 μm, 6 μm, 7 μm, 8 μm or any value therebetween.

[0088] In some embodiments, the particle size D50 of the graphite negative electrode material is 5 μm to 15 μm, specifically 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm or any value therebetween.

[0089] In some embodiments, the tap density of the graphite negative electrode material is 1.2 g / cm 3 ~1.3g / cm 3 , specifically 1.2 g / cm 3 , 1.22g / cm 3 , 1.24g / cm 3 , 1.26g / cm 3 , 1.28g / cm 3 , 1.3g / cm 3 or any value in between.

[0090] In some embodiments, the specific surface area of the graphite negative electrode material is 1.3 m 2 / g~1.7m 2 / g, specifically 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g or any value in between.

[0091] In a second aspect, the present application also proposes a lithium-ion battery.

[0092] In an embodiment of the present application, a lithium-ion battery includes a negative electrode sheet, the negative electrode sheet includes a current collector, and a negative electrode material coating coated on the surface of the current collector, the negative electrode material coating contains a graphite negative electrode material, and the graphite negative electrode material is prepared using the preparation method described in the first aspect. For ease of distinction, the current collector in the negative electrode sheet is recorded as the first current collector.

[0093] In the embodiment of the present application, the first current collector can be made of copper foil or other common materials, and the embodiment of the present application does not specifically limit this.

[0094] In some embodiments, the negative electrode material coating further includes a negative electrode conductor and a negative electrode binder, and the mass ratio of the negative electrode material, the negative electrode conductor and the negative electrode binder is (90~94):(2~7):(1~3).

[0095] In some embodiments, the negative electrode conductive agent is selected from at least one of Super P (SP), acetylene black, Ketjen black, conductive graphite, and carbon black.

[0096] In some embodiments, the negative electrode binder is selected from at least one of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylate binder (LA), and polyacrylic acid binder (PAA).

[0097] In the embodiments of the present application, the lithium-ion battery further includes a positive electrode sheet and a separator, with the separator positioned between the positive and negative electrodes. The positive electrode sheet, separator, and negative electrode sheet can be assembled into a stacked structure or a wound structure. The specific assembly method can be adjusted according to the specific type of lithium-ion battery.

[0098] In some embodiments, the separator is a battery separator manufactured by Celgard Corporation of the United States. Of course, other battery separators commonly used in the art may also be selected.

[0099] In the embodiment of the present application, the lithium-ion battery further includes a shell, in which the positive electrode sheet, the separator and the negative electrode sheet are arranged.

[0100] In some embodiments, the shell is filled with an electrolyte, the electrolyte includes a lithium salt and an organic solvent, and the mass ratio of the lithium salt to the organic solvent is 1:8.

[0101] In some embodiments, the lithium salt includes one or more of LiPF6, LiFSI (lithium bis(trifluoromethanesulfonyl imide), LiBF4, LiBOB (lithium dioxalatoborate), LiDFOB (lithium difluorooxalatoborate), and LiTFSI (lithium bis(trifluoromethanesulfonyl imide). Of course, those skilled in the art may also select other lithium salts commonly used in the art according to actual conditions.

[0102] In some embodiments, the organic solvent includes one or more of EC (ethylene carbonate), PC (propylene carbonate), BC (succinonitrile), DEC (diethyl carbonate), DMC (dimethyl carbonate), DME (dimethoxyethane), EMC (ethyl methyl carbonate), TEP (triethyl phosphate), and FEC (fluoroethylene carbonate). Of course, those skilled in the art can also select other electrolytes commonly used in the art according to actual conditions.

[0103] In the embodiment of the present application, illustratively, the method for preparing a lithium-ion battery includes the following steps:

[0104] Prepare positive electrode sheets and negative electrode sheets;

[0105] Assembling or winding the positive electrode sheet, the separator and the negative electrode sheet to obtain a pre-assembled component;

[0106] The preassembled component is assembled with the shell to obtain a lithium-ion battery.

[0107] In some embodiments, after assembling the pre-assembled component with the housing, the method for preparing a lithium-ion battery further comprises the step of injecting electrolyte into the housing.

[0108] In a third aspect, embodiments of the present application further provide an energy storage device comprising at least one lithium-ion battery as described in aspect 2. When the energy storage device comprises multiple lithium-ion batteries, the multiple lithium-ion batteries may be connected in at least one of parallel and series connection.

[0109] In a fourth aspect, an embodiment of the present application further provides an electrical device comprising the energy storage device described in the third aspect.

[0110] It can be understood that the electrical equipment also includes an electrical equipment body, and the energy storage device is used to supply power to the electrical equipment body.

[0111] In the embodiments of the present application, electrical equipment may include but is not limited to: containers, household energy storage systems, battery vehicles, electric vehicles, ships, spacecraft, electric toys and electric tools, etc., wherein spacecraft include airplanes, rockets, space shuttles and spacecraft, etc., electric toys include fixed or mobile electric toys, specifically electric car toys, electric ship toys and electric airplane toys, etc., electric tools include metal cutting power tools, grinding power tools, assembly power tools and railway power tools, specifically electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.

[0112] The present application is further described below through specific examples and comparative examples, but the present application is not limited to these specific examples.

[0113] Example 1

[0114] 1. Preparation of nitrogen and sulfur dopants:

[0115] In a nitrogen-protected glove box, 5.7 g of 2-mercaptoimidazole was added to a dry round-bottom flask. Then, 3.47 g of cobalt nitrate was accurately weighed and added to the round-bottom flask, according to a specific molar ratio of 3:1 between 2-mercaptoimidazole and cobalt nitrate. Subsequently, 100 ml of anhydrous ethanol was added to the round-bottom flask as a solvent. The round-bottom flask was removed from the glove box and connected to a reaction apparatus equipped with a condenser.

[0116] Stir the reaction mixture with a magnetic stirrer at 200-400 rpm / min to thoroughly mix the 2-mercaptoimidazole, cobalt nitrate, and anhydrous ethanol. Start an oil bath and slowly raise the temperature to 60-80°C. Continue the reaction for 6 hours. After the reaction is complete, turn off the oil bath and magnetic stirrer, and allow the reaction system to cool naturally to room temperature. Transfer the cooled reaction mixture to a centrifuge tube and centrifuge at 6000 rpm / min for 10-15 minutes. Then, add an appropriate amount of anhydrous ethanol to the centrifuge tube to wash the precipitate. Centrifuge again, and repeat the washing step 2-3 times until no significant impurity ions are detected in the washed ethanol solution. Vacuum dry the solution to yield 8 g of a cobalt-containing sulfur-nitrogen heterocyclic complex (i.e., a nitrogen-sulfur dopant).

[0117] 2. Preparation of graphite anode materials

[0118] (1) Weigh the raw materials: 4 g malic acid, 3 g chitosan, 3 g sodium lignin sulfonate, 8 g cobalt-containing sulfur-nitrogen heterocyclic complex, 6 g ferric chloride hexahydrate, 6 g ferric oxide, 3 g boric acid and 0.7 g polyvinyl pyrrolidone, dissolve all the raw materials in 100 mL deionized water, and stir with a magnetic stirrer for 1 h to 2 h to form a uniform solution; then, place it in a blast dryer and dry it at a drying temperature of 100 ° C to 120 ° C to obtain a viscous slurry mixture.

[0119] (2) The slurry mixture was placed in a crucible, which was fixed and placed in a tubular resistance furnace. The crucible was kept at 600 °C for 6 h at a rate of 2 °C / min in an argon atmosphere, and then the temperature was increased to 1200 °C at a rate of 2 °C / min and calcined at a constant temperature for 6 h. The mixture was then cooled to room temperature at a rate of 2 °C / min to obtain a black powder.

[0120] (3) Place the black powder material in The obtained graphite anode material was fully soaked in a hydrochloric acid solution for 24 hours, then filtered and washed, and then placed in a blast drying oven at 60°C for 2 to 3 hours until it was completely dry to obtain a graphitized negative electrode material.

[0121] Example 2

[0122] The difference from Example 1 is that:

[0123] In the preparation step (1) of the graphite negative electrode material: the contents of ferric chloride hexahydrate and ferric oxide are both increased from 6 g to 12 g.

[0124] Example 3

[0125] The difference from Example 1 is that:

[0126] In the preparation step (1) of the graphite negative electrode material: the contents of ferric chloride hexahydrate and ferric oxide were both increased from 6 g to 13 g.

[0127] Example 4

[0128] The difference from Example 1 is that:

[0129] In the preparation step (1) of the graphite negative electrode material: the contents of ferric chloride hexahydrate and ferric oxide were both increased from 6 g to 14 g.

[0130] Example 5

[0131] The difference from Example 1 is that:

[0132] No need to prepare nitrogen and sulfur dopants;

[0133] Preparation steps of graphite negative electrode material (1): 8g of cobalt-containing sulfur-nitrogen heterocyclic complex is replaced by 5.7g of 2-mercaptoimidazole and 3.47g of cobalt nitrate.

[0134] Example 6

[0135] The difference from Example 1 is that:

[0136] Preparation steps of graphite negative electrode material (1): The weighed raw materials do not contain boric acid.

[0137] Example 7

[0138] The difference from Example 1 is that:

[0139] Preparation steps of graphite negative electrode material (1): 4g malic acid is replaced by 4g glucose.

[0140] Example 8

[0141] The difference from Example 1 is that:

[0142] Preparation steps of graphite negative electrode material (1): 6g of ferric chloride hexahydrate is replaced by 6g of cobalt chloride, and 6g of iron oxide is replaced by 6g of cobalt oxide.

[0143] Example 9

[0144] 1. Preparation of Nitrogen-Sulfur Dopant (Cobalt-Containing Sulfur-Nitrogen Heterocyclic Complex) (See Example 1)

[0145] 2. Preparation of graphite negative electrode materials:

[0146] (1) Weigh the raw materials: 5 g malic acid, 5 g chitosan, 8 g thiourea, 6 g ferric chloride hexahydrate, 6 g ferric oxide, 3 g boric acid and 1 g polyvinylpyrrolidone, dissolve all the raw materials in 100 mL deionized water, and stir with a magnetic stirrer for 1 h to 2 h to form a uniform solution; then, place it in a blast dryer and dry it at a drying temperature of 100 ° C to 120 ° C to obtain a viscous slurry mixture.

[0147] (2) The slurry mixture was placed in a crucible, which was fixed and placed in a tubular resistance furnace. The crucible was kept at 550°C for 6 h at a rate of 2°C / min in an argon atmosphere, then heated to 1300°C at a rate of 2°C / min and calcined at this constant temperature for 6 h. The mixture was then cooled to room temperature at a rate of 2°C / min to obtain a black powder.

[0148] (3) Place the black powder material in The graphite anode material was fully soaked in a hydrochloric acid solution for 24 hours, then filtered and washed, and then placed in a blast drying oven at 60°C for 2 to 3 hours until it was completely dry to obtain a graphitized negative electrode material.

[0149] Comparative Example 1

[0150] The difference from Example 1 is that:

[0151] Preparation steps of graphite negative electrode material (1): the weighed raw materials do not contain polyvinyl pyrrolidone.

[0152] Comparative Example 2

[0153] The difference from Example 1 is that:

[0154] Preparation steps of graphite negative electrode material (1): the content of polyvinyl pyrrolidone is increased from 0.5g to 5g.

[0155] Comparative Example 3

[0156] The difference from Example 1 is that:

[0157] Preparation step of graphite negative electrode material (1): the contents of ferric chloride hexahydrate and ferric oxide are both reduced from 6 g to 1.5 g.

[0158] Comparative Example 4

[0159] The difference from Example 1 is that:

[0160] Preparation step of graphite negative electrode material (1): the content of ferric chloride hexahydrate and iron oxide is increased from 6g to 15g.

[0161] Comparative Example 5

[0162] The difference from Example 1 is that:

[0163] Preparation step (2) of graphite negative electrode material: placing the slurry mixture in a crucible, fixing the crucible and placing it in a tubular resistance furnace, keeping the temperature at 400°C for 6 hours at a rate of 2°C / min in an argon atmosphere, then heating to 1200°C at a rate of 2°C / min and calcining at a constant temperature for 6 hours, and then cooling to room temperature at a rate of 2°C / min to obtain black powder.

[0164] Comparative Example 6

[0165] The difference from Example 1 is that:

[0166] Preparation step (2) of graphite negative electrode material: placing the slurry mixture in a crucible, fixing the crucible and placing it in a tubular resistance furnace, keeping the temperature at 700°C for 6 hours at a rate of 2°C / min in an argon atmosphere, then heating to 1200°C at a rate of 2°C / min and calcining at a constant temperature for 6 hours, and then cooling to room temperature at a rate of 2°C / min to obtain black powder.

[0167] Comparative Example 7

[0168] The difference from Example 1 is that:

[0169] Preparation step (2) of graphite negative electrode material: placing the slurry mixture in a crucible, fixing the crucible and placing it in a tubular resistance furnace, keeping the temperature at 600°C for 6 hours at a rate of 2°C / min in an argon atmosphere, then heating to 1000°C at a rate of 2°C / min and calcining at a constant temperature for 6 hours, and then cooling to room temperature at a rate of 2°C / min to obtain black powder.

[0170] Comparative Example 8

[0171] The difference from Example 1 is that:

[0172] Preparation step (2) of graphite negative electrode material: placing the slurry mixture in a crucible, fixing the crucible and placing it in a tubular resistance furnace, keeping the temperature at 600°C for 6 hours at a rate of 2°C / min in an argon atmosphere, then heating to 1500°C at a rate of 2°C / min and calcining at a constant temperature for 6 hours, and then cooling to room temperature at a rate of 2°C / min to obtain black powder.

[0173] Performance Testing

[0174] The graphite negative electrode materials prepared in the above Examples 1-9 and Comparative Examples 1-8 were used as negative electrode materials for lithium-ion batteries and assembled into CR2032 button batteries to test their electrochemical properties.

[0175] Among them, the specific steps for CR2032 button battery include:

[0176] (1) The graphite negative electrode material and the conductive agent Super were mixed and ground until they were completely ground and uniform. The ground powder mixture was fully mixed with a polyvinylidene fluoride solution (PVDF: NMP = 1:20 (mass ratio)) under stirring conditions to prepare a slurry. The mass ratio of the graphite negative electrode material, the conductive agent Super and the polyvinylidene fluoride (PVDF) in the slurry was 91.6:6.6:1.8.

[0177] (2) The slurry was coated on copper foil and dried under vacuum at 80°C for 10 h to obtain a negative electrode sheet; the counter electrode was a lithium sheet.

[0178] (3) Use a cutting machine to cut the negative electrode sheet and lithium sheet into small discs with a diameter of 13 mm. In a glove box filled with argon (Ar), the positive electrode shell, spring, gasket, lithium sheet, separator, negative electrode sheet, and negative electrode shell are assembled into a button battery. The button battery is filled with electrolyte. The separator is Celgard 2400, a US company. The electrolyte composition is: 1wt% LiPF6 + 8wt% (EC:EMC:DMC = 3:4:3 vol%).

[0179] Electrochemical performance test:

[0180] (1) First delithiation capacity and first coulombic efficiency:

[0181] The button half-cell is discharged at 0.1C to 0.005V, discharged at a constant voltage of 0.005V to 0.02C, allowed to stand for 10 minutes, discharged at 0.05C to 0.005V, discharged at a constant voltage of 0.005V to 0.02C, allowed to stand for 10 minutes, discharged at 0.02C to 0.005V, discharged at a constant voltage of 0.005V to 0.02C, allowed to stand for 10 minutes, discharged at 0.01C to 0.005V, discharged at a constant voltage of 0.005V to 0.02C, allowed to stand for 10 minutes, then charged at 0.1C to 2V, and ended, thereby obtaining the lithium insertion capacity and lithium delithiation capacity respectively. The ratio of the first lithium delithiation capacity (charging capacity) to the first lithium insertion capacity is the first coulombic efficiency, i.e., the first efficiency.

[0182] (2) Cycle performance

[0183] The cycling and rate performance of the assembled button-type battery were tested using the LAND test system in a constant-temperature test cabinet at 25°C. The cycling performance test involved 10 activation cycles at a current density of 0.3C, followed by 10 cycles at a current density of 1C, with a voltage range of 0.01V to 3V.

[0184] Table 1. Performance test results of various embodiments and comparative examples

[0185]

[0186] analyze:

[0187] By comparing Examples 1-9 with Comparative Examples 1-8, it can be demonstrated that by controlling the mass ratio of the biomass carbon source, nitrogen-sulfur dopant, polyvinyl pyrrolidone, and catalyst in the slurry mixture to 1: (0.5-1.5): (0.05-0.1): (0.5-2.8), and by controlling the temperature of the pre-carbonization treatment to 500°C-600°C and the temperature of the graphitization treatment to 1200°C-1400°C, it is more conducive to improving the degree of graphitization of the graphite negative electrode material, and making the doping of sulfur and nitrogen elements uniform and controllable, it can effectively improve the electrochemical properties of the graphite negative electrode material, such as the first delithiation capacity, first coulombic efficiency, and cycle performance. Among them,

[0188] The test results of Examples 1-4 show that when the mass ratio of the biomass carbon source to the catalyst is 1:(2.4~2.8), the catalytic efficiency of the catalyst is higher, the graphitization efficiency of the pre-carbonized product is higher, and it is more conducive to improving the electrochemical performance of the final graphite negative electrode material.

[0189] By comparing Example 1 with Example 5 and Example 9, it can be proved that, compared with conventional nitrogen-sulfur dopants such as thiourea and 2-mercaptoimidazole, organic metal complex nitrogen-sulfur dopants are more conducive to improving the degree of graphitization of the pre-carbonized product, so that the electrochemical performance of the final graphite negative electrode material is more effectively improved.

[0190] By comparing Example 1 with Examples 6-8, it can be proved that: boron, nitrogen and sulfur elements can synergistically improve the electrochemical properties of graphite negative electrode materials; malic acid is a better carbon source due to the high reactivity of its carboxylic acid group, strong interaction with the catalyst / dopant and controllable pyrolysis behavior; the iron ions in the catalyst and the cobalt ions in the organometallic complex can synergistically catalyze the biomass carbon material to improve the electrochemical properties of the material.

[0191] By comparing Example 1 with Comparative Examples 1-2, it can be proved that polyvinyl pyrrolidone can improve the uniformity and controllability of sulfur and nitrogen doping in the graphite negative electrode material, and can induce the directional growth of graphite sheets, thereby increasing the degree of graphitization of the biomass carbon source to improve the electrochemical performance of the material. The mass ratio of the biomass carbon source to polyvinyl pyrrolidone is too large to effectively disperse the biomass carbon source, nitrogen and sulfur dopants, and catalysts to produce particle agglomeration or precipitation; in the pre-carbonization stage, the PVP molecular chain cannot fully guide the directional extension of the biomass carbon source, and the carbon skeleton is disorderedly stacked rather than a lamellar structure, which reduces the graphitization potential and leads to deterioration of the electrochemical performance.

[0192] By comparing Example 1 with Comparative Examples 3-4, it can be proved that if the mass ratio of the biomass carbon source to the catalyst is too large, not only will the catalytic efficiency not be further improved, but it will have an adverse effect on the electrochemical properties of the graphite negative electrode material. If the ratio is too small, it will lead to the inability to effectively catalyze the graphitization of the pre-carbonized product, thereby failing to effectively improve the electrochemical performance of the graphite negative electrode material.

[0193] By comparing Example 1 with Comparative Examples 5-8, it can be proved that if the pre-carbonization and graphitization temperatures are too low or too high, the electrochemical performance of the material will be limited.

[0194] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a graphite negative electrode material for a lithium ion battery, characterized in that: The steps include: Preparing a slurry mixture containing a biomass carbon source, a nitrogen-sulfur dopant, polyvinyl pyrrolidone, and a catalyst, wherein the nitrogen-sulfur dopant is an organic metal complex, the central metal of the organic metal complex includes at least one of iron, cobalt, and nickel, and the mass ratio of the biomass carbon source, the nitrogen-sulfur dopant, the polyvinyl pyrrolidone, and the catalyst is 1:(0.5-1.5):(0.05-0.1):(0.5-2.8); Performing a pre-carbonization treatment on the slurry mixture at a temperature of 500° C. to 600° C. to obtain a pre-carbonized product; The pre-carbonized product is graphitized at a temperature of 1200° C. to 1400° C. to obtain a graphite negative electrode material.

2. The preparation method according to claim 1, wherein The preparation steps of the organometallic complex include: Under an inert environment, anhydrous ethanol is used as a solvent to prepare a mixture of nitrogen and sulfur organic matter and metal salt according to a preset molar ratio; The mixed solution is placed at 60° C. to 80° C. and stirred for reaction for 5 h to 8 h at a stirring rate of 200 rpm / min to 400 rpm / min. The reaction mixture is purified to obtain the organometallic complex.

3. The preparation method according to claim 2, wherein The nitrogen and sulfur organic compounds include one or more of thiourea, 2-mercaptoimidazole, cysteine and ammonium thiocyanate; The metal salt includes one or more of iron salt, cobalt salt and nickel salt.

4. The preparation method according to claim 1, wherein The slurry mixture further contains a boron dopant, and the boron dopant includes boric acid.

5. The preparation method according to any one of claims 1 to 4, characterized in that Also includes at least one of the following features (1)-(5): (1) The biomass carbon source includes one or more of glucose, lignin sulfonate, malic acid, chitosan, sucrose, fructose, citric acid, oxalic acid, cellulose, lignin and hemicellulose; (2) The catalyst includes one or more of ferric chloride hexahydrate, cobalt chloride, nickel chloride, iron oxide and cobalt oxide; (3) The pre-carbonization treatment time is 4h~6h; (4) The graphitization treatment time is 6h~8h; (5) After the graphitization treatment, the preparation method further comprises: soaking the graphitization treatment product in a hydrochloric acid solution, and then filtering, filtering, washing, and drying in sequence to obtain the graphite negative electrode material.

6. A lithium-ion battery, characterized in that: The negative electrode comprises a negative electrode sheet, which comprises a current collector and a graphite negative electrode material coated on the surface of the current collector, wherein the graphite negative electrode material is prepared by the preparation method according to any one of claims 1 to 5.

7. The lithium-ion battery according to claim 6, wherein The graphite negative electrode material is doped with nitrogen and sulfur. The content of nitrogen in the graphite negative electrode material is 2 wt% to 8 wt%, and the content of sulfur in the graphite negative electrode material is 1 wt% to 5 wt%.

8. The lithium-ion battery according to claim 7, wherein The graphite negative electrode material is further doped with boron, and the content of boron in the graphite negative electrode material is 3 wt % to 5 wt %.

9. The lithium-ion battery according to claim 6, wherein Also includes at least one of the following features (1)-(5): (1) The particle size D10 of the graphite negative electrode material is 5 μm to 8 μm; (2) The particle size D50 of the graphite negative electrode material is 5 μm to 15 μm; (3) The tap density of the graphite negative electrode material is 1.2 g / cm 3 ~1.3g / cm 3 ; (4) The specific surface area of the graphite negative electrode material is 1.3m 2 / g~1.7m 2 / g; (5) The D peak intensity of the Raman spectrum of the graphite negative electrode material is I D , G peak intensity is I G , 0.2≤I D / I G ≤0.

5.

10. An energy storage device, characterized in that: The invention comprises a plurality of lithium-ion batteries according to any one of claims 7 to 9.

11. An electrical device, characterized in that: Comprising the energy storage device as claimed in claim 10.

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