Negative electrode material, battery

Abstract

The present invention provides a negative electrode material and a battery. 【Solution means】 The negative electrode material contains graphite and has pores on the surface and / or inside of the graphite. The negative electrode material has a pore volume of V cm 3 / kg, a true density of D g / cm 3 , a specific surface area of S m 2 / g, and a graphitization degree of G%. Here, 0.7 ≦ V × S / D ≦ 3.95 and 89 ≦ G ≦ 93. The negative electrode material and the battery according to the present invention can improve the rate performance and cycle performance of the graphite negative electrode material at a high rate current.

Description

Technical Field

[0001] The present invention relates to the technical field of negative electrode materials, and specifically relates to negative electrode materials and batteries.

Background Art

[0002] Due to its excellent performance, lithium-ion batteries also show good application prospects in fields such as portable consumer electronic devices, power tools, new energy vehicles, and energy storage. Since the commercialization of lithium-ion batteries, the most mature negative electrode material used is the graphite-based negative electrode material. Since the main current development direction of lithium-ion batteries is high capacity, high rate, and high safety, the development of high-performance graphite negative electrodes is extremely important for obtaining lithium-ion batteries with high rate performance and good cycle performance.

[0003] Technically speaking, the special layered structure of graphite determines that Li + can only be inserted from the end face of the material and gradually diffuses into the particle interior. The diffusion rate of lithium ions is low, and the rate performance is poor. At the same time, by storing lithium at a high rate, lithium ions tend to concentrate on the surface of the graphite negative electrode. When the lithium ion concentration at the interface reaches saturation, lithium ions deposit as a metal, and the diffusion path and the electrochemical reaction area cannot be fully utilized.

[0004] Therefore, at the current stage where the development of graphite materials has matured, improving a single parameter cannot meet the market requirements for obtaining graphite negative electrode materials with high rate performance and good cycle performance. It is necessary to study the synergistic mechanism of various factors and develop graphite negative electrode materials that meet the market requirements.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the above, the present invention provides a new negative electrode material and a battery that achieve accurate control of the internal and / or surface pore volume, specific surface area, and true density, and maintain them within a reasonable range in combination, thereby improving the capacity and rate performance of the negative electrode material, in response to the drawbacks of the prior art.

Means for Solving the Problems

[0006] In a first aspect, a negative electrode material is provided. The negative electrode material contains graphite, has pores on the surface and / or inside of the graphite, and when the negative electrode material has a pore volume of V cm 3 / kg, a true density of D g / cm 3 , a specific surface area of S m 2 / g, and a graphitization degree of G%, 0.7 ≦ V × S / D ≦ 3.95 and 89 ≦ G ≦ 93, wherein the pore volume is measured using an ASAP 2460 apparatus (manufactured by Micromeritics, USA) and calculated within a pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model. The negative electrode material is characterized by this.

[0007] In some embodiments, when the negative electrode material has a pore volume of V cm 3 / kg, 1.812 ≦ V ≦ 4.987.

[0008] In some embodiments, when the negative electrode material has a specific surface area of S m 2 / g, 0.872 ≦ S ≦ 1.773.

[0009] In some embodiments, when the negative electrode material has a true density of D g / cm 3 , 2.238 ≦ D ≦ 2.257.

[0010] In some embodiments, the pores include at least one of micropores and mesopores.

[0011] In some embodiments, the pores extend from the surface to the inside of the graphite.

[0012] In some embodiments, the graphite is artificial graphite.

[0013] In some embodiments, the pores have an average pore diameter of 50 Å to 200 Å.

[0014] In some embodiments, when the negative electrode material is subjected to X-ray diffraction measurement and the interplanar spacing of the (002) plane is d 002 it satisfies 3.356 Å ≤ d 002 ≤ 3.364 Å.

[0015] In some embodiments, the negative electrode material has a particle size D 50 of 10 μm to 20 μm.

[0016] In some embodiments, the negative electrode material further contains amorphous carbon, and the amorphous carbon is present on the surface of the graphite and / or dispersed between the graphite particles.

[0017] In some embodiments, the negative electrode material further includes an amorphous carbon coating layer located on the surface of the graphite, and the thickness of the amorphous carbon coating layer is 10 nm to 500 nm.

[0018] In some embodiments, the mass ratio of the amorphous carbon in the negative electrode material is 0.1 wt% to 3 wt%.

[0019] In a second aspect, the present invention provides a battery including the negative electrode material described in the first aspect.

Advantages of the Invention

[0020] The technical solution of the present invention has at least the following beneficial effects. The negative electrode material according to the present invention includes graphite, has pores on the surface and / or inside the graphite, the pores extend from the surface to the inside of the graphite, maintain the regular graphite layer structure of the negative electrode material, and generate abundant pores on the surface and near the surface of the graphite. The negative electrode material has pores, and the pore volume is V cm 3 / kg, with a true density of D g / cm 3 and a specific surface area of S m 2 / g, a graphitization degree of G%, where 0.7 ≤ V×S / D ≤ 3.95 and 89 ≤ G ≤ 93. The pore volume within a certain range is Li +is advantageous for being inserted into the interior along the pore structure from the material surface, improving the diffusion rate of lithium ions, and the specific surface area within a certain range guarantees a sufficient electrochemical reaction interface, promotes the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reduces concentration polarization, and is advantageous for improving the capacity and rate performance of the anode material. However, just meeting an appropriate pore volume and specific surface area still leaves a large room for further improvement in the rate performance of the anode material. This is because after lithium ions diffuse to the graphite surface, if the order of carbon atoms in the graphite is relatively disrupted and the degree of regularity is insufficient, the inhibition for lithium ions to enter the interior of the graphite material and combine with carbon atoms to generate an electrochemical reaction is relatively large. At the same time, graphite is polycrystalline, especially for artificial graphite, there are grain boundary defects between crystal grains, the stress of the grain boundary defects is non-uniform, the grain boundary is a type of crystal plane defect, cracks are likely to occur, and when subjected to an external force, it is easy to split along the grain boundary direction, resulting in an intergranular fracture along the crystal, and finally, the crystal plane in the direction parallel to the graphite crystal layer plane is split to form the outer surface of the graphite particles.Since these outer surfaces are perpendicular to the diffusion direction of lithium ions, the carbon plane must be crossed, making it difficult for lithium ions to enter the interior of the graphite, and at the same time, there is a possibility that lithium ions accumulate on the carbon surface to form lithium clusters, thereby suppressing the diffusion of lithium or forming lithium deposition. Finally, the diffusion path and the electrochemical reaction area are not fully utilized. Therefore, the present invention provides a good diffusion path for the diffusion of lithium ions by controlling the graphitization degree and the true density, and in combination with the design of the channel structure and the pore distribution, concentrates the stress inside the graphite around the pores and disperses the stress at the grain boundaries. When the graphite is subjected to an external force, it is first advantageous to generate cracks from the channels and rupture, causing transcrystalline cracking that penetrates the crystal. After the channels are exposed, finally, the outer surface of the graphite particles is formed. The transcrystalline cracking that penetrates the crystal is advantageous for increasing the passage entrances parallel to the diffusion direction of lithium ions on the surface of the graphite particles. Also, the inner surface of the channel itself has a certain number of passage entrances that can diffuse lithium ions into the graphite interlayer, and since there are many defects, it is possible to store lithium at the ends. Therefore, more graphite microcrystal surfaces parallel to the lithium ion diffusion path can be formed by cracking from the channels to form the outer surface of the particles, not only forming more lithium ion diffusion paths inside the graphite particles, but also forming more passage entrances for lithium ions to enter the particle surface. At the same time, considering that a high graphitization degree is advantageous for the diffusion environment, the inhibition traps for lithium ion transport due to defects such as some crystal strains are reduced. A certain degree of high graphitization degree affects the number of graphite polycrystalline grain boundaries and the crystal lattice strain, increases the regularity and tightness of the interlayer arrangement, is advantageous for improving the true density, and ensures that the negative electrode material exhibits a high specific capacity.The present invention is advantageous in that by controlling V×S / D of the negative electrode material within the above range and controlling the graphitization degree of the material, lithium ions and sufficient carbon atoms can be bonded with low resistance, whereby the negative electrode material has a sufficient reaction space for lithium release and absorption, and it is advantageous to obtain a negative electrode material with better rate performance and capacity.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0022] In order to explain the present invention and make it easier to understand the technical solution of the present invention, the present invention will be described in more detail below. It should be noted that the following examples are only simplified examples of the present invention and do not indicate or limit the protection scope of the present invention. The protection scope of the present invention shall be in accordance with the scope of the claims.

[0023] Since the commercialization of lithium-ion batteries, the most mature negative electrode material used is the graphite-based negative electrode material. The special layered structure of graphite determines that Li + can only be inserted from the end face of the material and gradually diffuses into the particle interior. The diffusion rate of lithium ions is low, and the rate performance is poor. At the same time, by absorbing lithium at a high rate, lithium ions tend to concentrate on the surface of the graphite negative electrode. When the lithium ion concentration at the interface reaches saturation, lithium ions deposit as a metal, and the diffusion path and the electrochemical reaction area cannot be fully utilized.

[0024] Therefore, a negative electrode material is provided. The negative electrode material contains graphite and has pores on the surface and / or inside of the graphite. The pores extend from the surface to the inside of the graphite. The negative electrode material has a pore volume of V cm 3 / kg, a true density of D g / cm 3 , a specific surface area of S m 2 / g, and a graphitization degree of G%. Here, 0.7 ≤ V × S / D ≤ 3.95 and 89 ≤ G ≤ 93. The pore volume is measured using an ASAP 2460 apparatus (manufactured by Micromeritics, USA) and calculated within a pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model. The negative electrode material is characterized by this.

[0025] The negative electrode material according to the present invention contains graphite and has pores on the surface and / or inside of the graphite. The pores extend from the surface to the inside of the graphite, maintaining the regular graphite layer structure of the negative electrode material and generating abundant pores on the surface and near the surface of the graphite. The negative electrode material has a pore volume of V cm 3 / kg, a true density of D g / cm 3 , a specific surface area of S m 2 / g, and a graphitization degree of G%. Here, 0.7 ≤ V × S / D ≤ 3.95 and 89 ≤ G ≤ 93. The pore volume within a certain range allows Li +is advantageous for being inserted into the interior along the pore structure from the material surface, improving the diffusion rate of lithium ions. The specific surface area within a certain range guarantees a sufficient electrochemical reaction interface, promotes the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reduces concentration polarization, and is advantageous for improving the capacity and rate performance of the anode material. However, merely satisfying an appropriate pore volume and specific surface area still leaves a large room for further improvement in the rate performance of the anode material. This is because after lithium ions diffuse to the graphite surface, if the order of carbon atoms in the graphite is relatively disrupted and the degree of regularity is insufficient, the inhibition for lithium ions to enter the interior of the graphite material and combine with carbon atoms to generate an electrochemical reaction is relatively large. At the same time, graphite is polycrystalline, especially for artificial graphite, there are grain boundary defects between crystal grains, the stress of the grain boundary defects is non-uniform, cracks are likely to occur, it is easy to split when subjected to an external force, fracture along the crystal occurs, and finally, the crystal plane in the direction parallel to the graphite crystal layer plane is split to form the outer surface of the graphite particles. Since these outer surfaces are perpendicular to the diffusion direction of lithium ions, it is necessary to cross the carbon plane, making it difficult to enter the interior of the graphite, and at the same time, there is a possibility of gathering on the carbon surface to form lithium clusters, thereby suppressing the diffusion of lithium or forming lithium deposition. Finally, the diffusion passage and the electrochemical reaction area are not fully utilized. Therefore, the present invention provides a good diffusion passage for the diffusion of lithium ions by controlling the graphitization degree and true density, and in combination with the design of the channel structure and pore distribution, concentrates more stress inside the graphite around the pores, reduces the stress at the grain boundaries, so that when the graphite is subjected to an external force, cracks are first generated from the channels and rupture occurs, and finally, the outer surface of the graphite particles is formed. Thereby, more graphite microcrystalline surfaces parallel to the lithium ion diffusion passage can be formed, not only more lithium ion diffusion passages can be formed inside the graphite particles, but also more passage entrances for lithium ions to enter the particle surface can be formed. At the same time, considering that a high graphitization degree is advantageous for the diffusion environment, the inhibition traps for lithium ion transport due to crystal defects are reduced to ensure that the anode material exhibits a high specific capacity.The present invention is advantageous in that by controlling V×S / D of the negative electrode material within the above range and controlling the graphitization degree of the material, lithium ions and sufficient carbon atoms can be bonded with low resistance. As a result, the negative electrode material has a sufficient reaction space for lithium release and absorption, which is advantageous for obtaining a negative electrode material with better rate performance and capacity.

[0026] In some embodiments, the negative electrode material has a pore volume of V cm 3 / kg, where 1.812≦V≦4.987. Specifically, V may be 1.812, 2.016, 2.582, 2.897, 3.348, 3.476, 3.755, 3.896, 4.013, 4.167, 4.275, 4.512, or 4.987, etc., without limitation here. When pores generate an electrochemical reaction inside the electrode, the pores create more lithium ion diffusion paths and electrochemical reaction interfaces with the negative electrode material, promote the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reduce concentration polarization, and are advantageous for improving the rate performance of the negative electrode material.

[0027] In some embodiments, the negative electrode material has a specific surface area of S m 2 / g, where 0.872≦S≦1.773. Specifically, S may be 1.773, 1.643, 1.593, 1.532, 1.498, 1.446, 1.386, 1.315, 1.267, 1.157, 1.044, 0.912, or 0.872, etc., without being limited here. As can be understood, if the specific surface area is too large, it is likely to cause the formation of an excessive solid electrolyte film, consume irreversible lithium salts excessively, and reduce the initial efficiency of the battery.

[0028] In some embodiments, the negative electrode material has a true density of D g / cm 3 , where 2.210≦D≦2.265. Specifically, D may be 2.2385, 2.2481, 2.2440, 2.2372, 2.2476, 2.2502, 2.2514, or 2.262, etc., without being limited here.

[0029] In some embodiments, the negative electrode material has a graphitization degree of G%, where 89 ≦ G ≦ 93, and specifically, it may be 89, 90, 90.5, 91, 91.5, 92, 92.5, or 93, etc., and is not limited herein.

[0030] In some embodiments, the pores include at least one of micropores and mesopores.

[0031] In some embodiments, the pores have an average pore diameter of 50 Å to 200 Å, and specifically, it may be 50 Å, 60 Å, 70 Å, 80 Å, 90 Å, 100 Å, 120 Å, 140 Å, 160 Å, or 200 Å, etc., and is not limited herein. By controlling the average pore diameter of the pores within the above range, Li + is transported from the material surface into the graphite along the pore structure, which is further advantageous for the occurrence of the lithium release and absorption reaction. Preferably, the pores have an average pore diameter of 80 Å to 140 Å.

[0032] In some embodiments, the pores extend from the surface of the graphite to the inside.

[0033] In some embodiments, the graphite is artificial graphite.

[0034] In some embodiments, the negative electrode material has a particle size D 50 of 10 μm to 20 μm. Specifically, it may be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 18 μm, 19 μm, or 20 μm, etc., and is not limited herein. Note that the volume-based cumulative particle size distribution of the particle size distribution is measured using the laser diffraction method, and D 50 represents the corresponding particle size when the percentage of the cumulative particle size distribution reaches 50%.

[0035] In some embodiments, when the negative electrode material has an interplanar spacing of the (002) plane of d 002 by X-ray diffraction measurement, 3.356 Å ≦ d 002 ≦ 3.364 Å. The interplanar spacing d 002Since it is within the above range, it can be seen that the graphite crystallinity of the graphite particles is high, that is, the graphitization degree is high, and the capacity of the product is high.

[0036] In some embodiments, the negative electrode material further includes an amorphous carbon coating layer located on the surface of the graphite, and the thickness of the amorphous carbon coating layer is 10 nm to 500 nm. Specifically, it may be 10 nm, 15 nm, 20 nm, 30 nm, 50 nm, 80 nm, 100 nm, 150 nm, 180 nm, 200 nm, 400 nm, 500 nm, etc., and is not limited herein. Preferably, the thickness of the amorphous carbon coating layer is 10 nm to 100 nm.

[0037] In some embodiments, the negative electrode material further includes amorphous carbon, and the amorphous carbon is present on the surface of the graphite and / or dispersed between the graphite particles. Specifically, the graphite particles may have an amorphous carbon material as a substrate and be embedded in the amorphous carbon material, and a part of the graphite particles may be exposed on the surface of the amorphous carbon material.

[0038] In some embodiments, the negative electrode material further includes amorphous carbon, and for the negative electrode material, the mass ratio of the amorphous carbon is 0.1 wt% to 3 wt%. Specifically, the mass ratio of the amorphous carbon in the negative electrode material may be 0.1 wt%, 0.3 wt%, 0.5 wt%, 1 wt%, 2 wt%, 2.5 wt%, or 3 wt%, etc., and is not limited. The presence of the amorphous carbon provides more irregular and more open diffusion paths for lithium ions, which is beneficial to the improvement of the material rate performance.

[0039] In some embodiments, the capacity retention rate of charging the negative electrode material at 1C for 500 cycles is ≧90%, and specifically, it may be 91.8%, 92.3%, 90.6%, 92.4%, 93.5%, etc., and is not limited herein.

[0040] The manufacturing method of the negative electrode material includes the following steps. In S10, softened pitch is mixed with an alkaline solution having a concentration of 0.01 mol / L to 0.05 mol / L, and ultrasonic treatment is performed to obtain a mixture. Here, the ratio of the mass contents of the saturated component and the aromatic component in the pitch is (5 to 20):(95 to 80). In S20, after washing the mixture, drying and crushing treatments are performed on the solid product to obtain powder D 50 is 10 μm to 20 μm. In S30, the powder is carbonized at 500°C to 1200°C in an inert atmosphere to obtain a precursor. In S40, the precursor is graphitized at 2800°C to 3200°C to obtain a negative electrode material.

[0041] The method for manufacturing a negative electrode material according to the present invention mixes pitch with a low-concentration alkaline solution, and in-situ etches a pore structure inside the pitch by ultrasonic means to form an effective reaction area of the material, increase the lithium ion insertion path, and then carbonize the powder in-situ etched. During the carbonization process, impurities, volatile substances and unstable substances inside the material are decomposed and escaped, and the pore diameter and pore depth of the pores formed by etching are further enlarged. The carbonization product is further graphitized to form graphite having abundant and regular pores, realizing accurate control of the pore volume of the graphite, adjusting the internal stress distribution of the graphite to a certain extent, and finally increasing the reactive area of the negative electrode active material in the electrode, which is beneficial to improving the high-rate charge and discharge performance of the material. The process method is simple, the production cost is low, and the manufactured graphite negative electrode material has characteristics such as high specific capacity, excellent high-rate charge and discharge performance, and excellent cycle performance, and can meet the usage requirements of consumers and power-side users for the negative electrode energy density and rapid charging performance.

[0042] Hereinafter, the technical solution of the present invention will be described in detail. In S10, softened pitch is mixed with an alkaline solution having a concentration of 0.01 mol / L to 0.05 mol / L, and ultrasonic treatment is performed to obtain a mixture. Here, the ratio of the mass contents of the saturated component and the aromatic component in the pitch is (5 to 20):(95 to 80).

[0043] In some embodiments, the pitch includes coal pitch and / or petroleum pitch, and the petroleum pitch may be modified pitch, mesophase pitch, etc.

[0044] In some embodiments, the mass content ratio of the saturated component to the aromatic component in the pitch is (5 - 20):(95 - 80). Specifically, it may be 5:95, 8:92, 10:90, 13:87, 15:85, 18:82, 20:80, etc., and of course, other values within the above range may also be possible and are not limited herein. By controlling the mass ratio of the saturated component to the aromatic component in the pitch, the higher the content of the aromatic component, the better the fluidity of the pitch, the lower the softening temperature, the higher the volatile content, and the volatile component decomposes and escapes during the carbonization process. The pores formed by etching further expand the pore diameter and pore depth, and most of the stress inside the graphite is concentrated around the pores, reducing the stress at the grain boundaries. When the graphite is subjected to an external force, cracks are first generated from the channels and rupture occurs, and finally, the outer surface of the graphite particles is formed. As a result, more graphite microcrystal surfaces parallel to the lithium ion diffusion path can be formed, not only more lithium ion diffusion paths can be formed inside the graphite particles, but also more passage entrances for lithium ions to enter the particle surface can be formed, which is advantageous for obtaining a negative electrode material with better rate performance and lower residual carbon content.

[0045] In some embodiments, the pitch is heated to 50°C - 80°C to soften and form a softened liquid pitch. Specifically, the softening temperature may be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc., and of course, other values within the above range may also be possible and are not limited herein.

[0046] In some embodiments, the alkaline solution includes at least one of a NaOH solution and a KOH solution.

[0047] In some embodiments, the concentration of the alkaline solution is 0.01 mol / L to 0.05 mol / L. Specifically, it may be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.045 mol / L, 0.05 mol / L, etc. Of course, other values within the above range may also be used and are not limited here. If the concentration of the alkaline solution is too high, the number of pores formed by etching the pitch surface will be too large, and furthermore, the pore volume of the final graphite negative electrode material will be too large, the specific surface area will also increase, and it will be difficult to control the ratio of V×S / D within an ideal range, which is disadvantageous for improving the high-rate charge-discharge performance and cycle performance of the negative electrode material. By controlling the ratio of V×S / D of the negative electrode material within the above range, the negative electrode material has a sufficient chemical reaction space for lithium release and absorption, which is advantageous for obtaining a negative electrode material with better rate performance and capacity.

[0048] In some embodiments, the material ratio of pitch to the alkaline solution is 50 g / 100 ml to 100 g / 100 ml. Specifically, it may be 50 g / 100 ml, 60 g / 100 ml, 70 g / 100 ml, 75 g / 100 ml, 80 g / 100 ml, 85 g / 100 ml, 90 g / 100 ml, 100 g / 100 ml, etc. Of course, other values within the above range may also be used and are not limited here. Controlling the material ratio of pitch to the alkaline solution is advantageous for sufficiently etching the softened pitch with the alkaline solution. Thereby, an appropriate number of pores are etched and formed on the surface of the pitch, reducing the stress at the grain boundaries of the graphite obtained after graphitization, which is advantageous for creating more lithium ion diffusion paths and improving the specific capacity and rate performance of the negative electrode material.

[0049] In some embodiments, the time of ultrasonic treatment in the heat preservation state is 5h to 10h. Specifically, it may be 5h, 6h, 7h, 8h, 9h or 10h, etc., but it is not limited to the listed numerical values, and other unlisted numerical values within this numerical range are equally applicable. During ultrasonic treatment, the alkaline solution constantly collides to etch the pitch, so that a pore structure is etched and formed in-situ inside the pitch fine particles. The pore structure creates more lithium ion diffusion channels and electrochemical reaction interfaces for the anode material, promotes the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reduces concentration polarization, and is beneficial to improving the rate performance of the anode material.

[0050] In S20, the solid product after washing the mixture is dried and crushed to obtain powder D 50 is 10μm to 20μm.

[0051] In some embodiments, the mixture is cooled to room temperature and repeatedly washed with distilled water until the filtrate becomes neutral, then filtered to perform solid-liquid separation to obtain a solid product.

[0052] In some embodiments, the method of solid-liquid separation includes at least one of centrifugal separation and filtration, and the filtration may be at least one of normal pressure filtration, vacuum suction filtration, and reduced pressure filtration.

[0053] In some embodiments, the drying temperature is 80°C to 120°C. Specifically, it may be 80°C, 90°C, 100°C, 110°C and 120°C, etc., but it is not limited to the listed numerical values, and other unlisted numerical values within this numerical range are equally applicable.

[0054] In some embodiments, the median diameter D of the powder obtained by crushing 50is from 10 μm to 20 μm, more specifically, it may be 12 μm, 13 μm, 14 μm, 16 μm, 18 μm, 18.5 μm, 19 μm or 20 μm, etc., but is not limited to the listed values, and other unlisted values within the said numerical range are equally applicable. Through multiple tests, controlling the median diameter of the powder within the above range is beneficial for achieving both processing performance, capacity and rate performance.

[0055] In S30, the powder is carbonized at 500°C to 1200°C under an inert atmosphere to obtain a precursor.

[0056] In some embodiments, the heating rate during the carbonization process is specifically, for example, 2°C / min, 3°C / min, 5°C / min, 6°C / min, 8°C / min, 9°C / min or 10°C / min, etc. As can be understood, when the heating rate of the carbonization treatment is within the above range, it is beneficial for the volatile components in the raw material to escape at different rates, the pore diameter of the pore structure further expands and / or deepens, and in combination with the heating rate of the subsequent graphitization process, a negative electrode material satisfying 0.70 ≦ V × S / D ≦ 3.95 is obtained.

[0057] In some embodiments, the temperature of the carbonization treatment may specifically be 500°C, 550°C, 600°C, 700°C, 750°C, 800°C, 850°C, 900°C, 1000°C or 1200°C, etc., but is not limited to the listed values, and other unlisted values within the said numerical range are equally applicable. As can be understood, when the carbonization treatment temperature is within the above range, it is beneficial for the discharge of substances such as volatile components in the powder.

[0058] In some embodiments, the heat preservation time of the carbonization treatment is 2 h to 10 h, specifically, it may be 2 h, 3 h, 4 h, 4.5 h, 5 h, 6 h, 8 h or 10 h, etc., but is not limited to the listed values, and other unlisted values within the said numerical range are equally applicable.

[0059] In S40, the precursor is graphitized at 2800°C to 3200°C to obtain a negative electrode material.

[0060] In some embodiments, the heat preservation temperature of the graphitization treatment may specifically be 2800°C, 2850°C, 2900°C, 2950°C, 3000°C, 3100°C, 3200°C, etc., but is not limited to the listed values, and other unlisted values within the said numerical range are equally applicable.

[0061] In some embodiments, the heat preservation time of the graphitization treatment is 2h to 10h, and specifically may be 2h, 3h, 4h, 4.5h, 5h, 6h, 8h, 10h, etc., but is not limited to the listed values, and other unlisted values within the said numerical range are equally applicable.

[0062] In some embodiments, the heating rate of the graphitization treatment may be 2°C / min to 10°C / min, and specifically may be 2°C / min, 3°C / min, 4°C / min, 6°C / min, 8°C / min, 10°C / min, etc., but is not limited to the listed values, and other unlisted values within the said numerical range are equally applicable. A specific heating rate is advantageous for the formation of internal and / or surface pores of the material graphite and the control of the specific surface area.

[0063] In some embodiments, after the graphitization treatment, it includes at least one of grinding, sieving, and demagnetization. Preferably, after the graphitization treatment, grinding, demagnetization, and sieving are performed in sequence.

[0064] In some embodiments, the grinding means may be any one of a mechanical grinder, a pneumatic grinder, and a cryogenic grinder.

[0065] In some embodiments, the sieving method is any one selected from a fixed sieve, a drum screen, a resonance sieve, a roller sieve, a vibrating sieve, and a chain grizzly, and the mesh number of the sieving is 100 to 500 meshes. Specifically, the mesh number of the sieving may be 100 meshes, 200 meshes, 250 meshes, 325 meshes, 400 meshes, 500 meshes, etc. Controlling the particle size of the negative electrode material within the above range is advantageous for improving the processing characteristics of the negative electrode material.

[0066] In some embodiments, the demagnetization device is any one selected from a permanent magnet drum type magnetic separator, an electromagnetic iron remover, and a pulsating high-gradient magnetic separator. Demagnetization is ultimately to control the magnetic substance content of the negative electrode material and reduce the influence of the magnetic substance on the discharge effect of the lithium-ion battery and the safety of the battery during use.

[0067] The present invention further provides a battery including the above negative electrode material.

[0068] As is obvious to those skilled in the art, the battery manufacturing method described above is only an example. Other methods commonly used in the art may be adopted without departing from the content of the present invention, and other types of batteries, such as sodium-ion batteries, potassium-ion batteries, etc., may also be manufactured and measured.

[0069] Hereinafter, the gist of the present invention will be further described with multiple examples. However, the examples of the present invention are not limited to the following specific examples. Appropriate changes can be made and implemented within the protection scope.

[0070] Example 1 The manufacturing method of the negative electrode material in this example includes the following steps. (1) After heating the pitch to 80 °C to soften it, it is mixed with a 0.05 mol / L KOH alkaline solution, and ultrasonic treatment is performed for 10 h while maintaining the temperature at 80 °C to obtain a mixture. Here, the pitch mainly consists of a saturated component and an aromatic component, and the ratio of the content of the saturated component to the aromatic component is 5:95. (2) The mixture is cooled to room temperature, repeatedly washed with distilled water until the filtrate becomes neutral and then filtered. After removing the solvent by suction filtration, it is placed in an oven and vacuum dried for 10 h, followed by crushing treatment to obtain a powder (D 50 with a particle size of 16.3 μm). (3) The powder is carbonized at 1200 °C for 10 h to obtain a precursor. (4) The precursor is subjected to high-temperature graphitization treatment at 3000 °C for 8 h to obtain a graphite negative electrode material.

[0071] Example 2 The manufacturing method of the negative electrode material of this example includes the following steps. (1) After heating the pitch to 80 °C to soften it, it is mixed with a 0.04 mol / L KOH alkaline solution, and ultrasonic treatment is carried out for 10 h while maintaining the temperature at 80 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 10:90. (2) The mixture is cooled to room temperature, repeatedly washed with distilled water until the filtrate becomes neutral and then filtered. After removing the solvent by suction filtration, it is placed in an oven and dried under vacuum for 10 h, and then subjected to a crushing treatment to obtain a powder (D 50 is 16.9 μm). (3) The powder is carbonized under the condition of 1000 °C for 10 h to obtain a precursor. (4) The precursor is subjected to high-temperature graphitization treatment at 3000 °C for 8 h to obtain a graphite negative electrode material.

[0072] Example 3 The manufacturing method of the negative electrode material of this example includes the following steps. (1) After heating the pitch to 80 °C to soften it, it is mixed with a 0.03 mol / L KOH alkaline solution, and ultrasonic treatment is carried out for 10 h while maintaining the temperature at 80 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 15:85. (2) The mixture is cooled to room temperature, repeatedly washed with distilled water until the filtrate becomes neutral and then filtered. After removing the solvent by suction filtration, it is placed in an oven and dried under vacuum for 10 h, and then subjected to a crushing treatment to obtain a powder (D 50 is 16.2 μm). (3) The powder is carbonized under the condition of 1200 °C for 10 h to obtain a precursor. (4) The precursor is subjected to high-temperature graphitization treatment at 2900 °C for 8 h to obtain a graphite negative electrode material.

[0073] Example 4 The manufacturing method of the negative electrode material of this example includes the following steps. (1) Heat the pitch to 80 °C to soften it, then mix it with a 0.02 mol / L KOH alkaline solution, and perform ultrasonic treatment for 10 h while maintaining the temperature at 80 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 20:80. (2) Cool the mixture to room temperature, repeatedly wash it with distilled water until the filtrate becomes neutral, filter it, remove the solvent by suction filtration, then place it in an oven and dry it under vacuum for 10 h, and perform a crushing treatment to obtain a powder (D 50 with a D of 15.7 μm). (3) Carbonize the powder under the condition of 1200 °C for 10 h to obtain a precursor. (4) Perform high-temperature graphitization treatment on the precursor at 2800 °C for 8 h to obtain a graphite negative electrode material.

[0074] Example 5 The method for manufacturing the negative electrode material of this example includes the following steps. (1) Heat the pitch to 80 °C to soften it, then mix it with a 0.01 mol / L KOH alkaline solution, and perform ultrasonic treatment for 10 h while maintaining the temperature at 80 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 20:80. (2) Cool the mixture to room temperature, repeatedly wash it with distilled water until the filtrate becomes neutral, filter it, remove the solvent by suction filtration, then place it in an oven and dry it under vacuum for 10 h, and perform a crushing treatment to obtain a powder (D 50 with a D of 15.4 μm). (3) Carbonize the powder under the condition of 500 °C for 10 h to obtain a precursor. (4) Perform high-temperature graphitization treatment on the precursor at 2800 °C for 8 h to obtain a graphite negative electrode material.

[0075] Example 6 The method for manufacturing the negative electrode material of this example includes the following steps. (1) Heat the pitch to 80 °C to soften it, then mix it with a 0.05 mol / L KOH alkaline solution, and perform ultrasonic treatment for 8 h while maintaining the temperature at 70 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 20:80. (2) Cool down the mixture to room temperature, repeatedly wash it with distilled water until the filtrate becomes neutral, filter it, remove the solvent by suction filtration, then place it in an oven and dry it under vacuum for 10 h, perform crushing treatment, and obtain powder (D 50 with a size of 16.1 μm). (3) Carbonize the powder at 1200 °C for 10 h to obtain a precursor. (4) Graphitize the precursor at 3000 °C for 8 h to obtain a graphite negative electrode material.

[0076] Example 7 The manufacturing method of the negative electrode material in this example includes the following steps. (1) Heat the pitch to 70 °C to soften it, then mix it with a 0.04 mol / L KOH alkaline solution, perform ultrasonic treatment for 8 h while maintaining the temperature at 70 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 20:80. (2) Cool down the mixture to room temperature, repeatedly wash it with distilled water until the filtrate becomes neutral, filter it, remove the solvent by suction filtration, then place it in an oven and dry it under vacuum for 10 h, perform crushing treatment, and obtain powder (D 50 with a size of 16.8 μm). (3) Carbonize the powder at 1000 °C for 10 h to obtain a precursor. (4) Graphitize the precursor at 3000 °C for 8 h to obtain a graphite negative electrode material.

[0077] Example 8 The manufacturing method of the negative electrode material in this example includes the following steps. (1) Heat the pitch to 70 °C to soften it, then mix it with a 0.03 mol / L KOH alkaline solution, perform ultrasonic treatment for 8 h while maintaining the temperature at 70 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 20:80. (2) Cool down the mixture to room temperature, repeatedly wash it with distilled water until the filtrate becomes neutral, filter it, remove the solvent by suction filtration, then place it in an oven and dry it under vacuum for 10 h, perform crushing treatment, and obtain powder (D 50 with a size of 16.7 μm). (3) The powder was carbonized at 1000 °C for 10 h to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 2900 °C for 8 h to obtain a graphite negative electrode material.

[0078] Example 9 The method for manufacturing the negative electrode material of this example includes the following steps. (1) After heating the pitch to 70 °C to soften it, it was mixed with a 0.02 mol / L KOH alkaline solution, and ultrasonic treatment was carried out for 8 h while maintaining the temperature at 70 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 20:80. (2) The mixture was cooled to room temperature, repeatedly washed with distilled water until the filtrate became neutral and then filtered. After removing the solvent by suction filtration, it was placed in an oven and vacuum dried for 10 h, followed by crushing treatment to obtain a powder (D 50 is 16.8 μm). (3) The powder was carbonized at 800 °C for 10 h to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 2800 °C for 8 h to obtain a graphite negative electrode material.

[0079] Example 10 The method for manufacturing the negative electrode material of this example includes the following steps. (1) After heating the pitch to 70 °C to soften it, it was mixed with a 0.01 mol / L KOH alkaline solution, and ultrasonic treatment was carried out for 8 h while maintaining the temperature at 70 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 20:80. (2) The mixture was cooled to room temperature, repeatedly washed with distilled water until the filtrate became neutral and then filtered. After removing the solvent by suction filtration, it was placed in an oven and vacuum dried for 10 h, followed by crushing treatment to obtain a powder (D 50 is 15.6 μm). (3) The powder was carbonized at 500 °C for 10 h to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 2800 °C for 8 h to obtain a graphite negative electrode material.

[0080] Example 11 The difference from Example 1 is that after heating and softening the pitch at 60°C in step (1), it was mixed with a 0.05 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 6 h while maintaining the temperature at 60°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0081] Example 12 The difference from Example 2 is that after heating and softening the pitch at 60°C in step (1), it was mixed with a 0.04 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 6 h while maintaining the temperature at 60°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0082] Example 13 The difference from Example 3 is that after heating and softening the pitch at 60°C in step (1), it was mixed with a 0.03 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 6 h while maintaining the temperature at 60°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0083] Example 14 The difference from Example 4 is that after heating and softening the pitch at 60°C in step (1), it was mixed with a 0.02 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 6 h while maintaining the temperature at 60°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0084] Example 15 The difference from Example 5 is that after heating and softening the pitch at 60°C in step (1), it was mixed with a 0.01 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 6 h while maintaining the temperature at 60°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0085] Example 16 The difference from Example 1 is that after heating and softening the pitch at 50°C in step (1), it was mixed with a 0.05 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 5 h while maintaining the temperature at 50°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0086] Example 17 The difference from Example 2 is that after heating and softening the pitch at 50°C in step (1), it was mixed with a 0.04 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 5 h while maintaining the temperature at 50°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0087] Example 18 The difference from Example 3 is that after heating and softening the pitch at 50°C in step (1), it was mixed with a 0.03 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 5 h while maintaining the temperature at 50°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0088] Example 19 The difference from Example 4 is that after heating and softening the pitch at 50°C in step (1), it was mixed with a 0.02 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 5 h while maintaining the temperature at 50°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0089] Example 20 The difference from Example 5 is that after heating and softening the pitch at 50°C in step (1), it was mixed with a 0.01 mol / L NaOH alkaline solution, and ultrasonic treatment was carried out for 5 h while maintaining the temperature at 50°C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is only 20:80.

[0090] Comparative Example 1 The manufacturing method of the negative electrode material of the comparative example includes the following steps. (1) After heating the pitch to 80 °C to soften it, it was mixed with a 0.2 mol / L KOH alkaline solution, and ultrasonic treatment was carried out for 10 h while maintaining the temperature at 80 °C to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 5:95. (2) The mixture was cooled to room temperature, repeatedly washed with distilled water until the filtrate became neutral and then filtered. After removing the solvent by suction filtration, it was placed in an oven and vacuum dried for 10 h, and then crushed to obtain a powder (D 50 is 16.6 μm). (3) The powder was carbonized at 1200 °C for 10 h to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 3000 °C for 8 h to obtain a graphite negative electrode material.

[0091] Comparative Example 2 The manufacturing method of the negative electrode material of this comparative example includes the following steps. (1) After heating the pitch to 70 °C to soften it, deionized water was added while maintaining the temperature at 70 °C, and ultrasonic treatment was carried out for 8 h to obtain a mixture. Here, the pitch mainly consists of saturated components and aromatic components, and the ratio of the content of saturated components to aromatic components is 20:80. (2) The mixture was cooled to room temperature, repeatedly washed with distilled water until the filtrate became neutral and then filtered. After removing the solvent by suction filtration, it was placed in an oven and vacuum dried for 10 h, and then shaped to obtain a powder (D 50 is 16.8 μm). (3) The powder was carbonized at 1200 °C for 10 h to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 3000 °C for 8 h to obtain a graphite negative electrode material. Measurement Method

[0092] (1) Measurement method for the particle size of the negative electrode material: The particle size distribution range of the composite negative electrode material was measured by a Malvern laser particle size analyzer.

[0093] (2) Measurement method of the pore volume of the negative electrode material: It is measured using an ASAP2460 device (manufactured by Micromeritics, USA). The pore volume V is calculated within the pore size range of 17 Å to 3000 Å using the JH Desorption cumulative volume of pores model.

[0094] (3) Measurement method of the specific surface area of the negative electrode material: It is measured using a JW-DX dynamic specific surface area rapid measuring instrument (manufactured by Beijing Jingwei Gaobo Science and Technology Co., Ltd.). The unit is m 2 / g.

[0095] (4) Measurement method of the surface morphology of the negative electrode material: The surface morphology of the negative electrode material particles was observed using an S4800 scanning electron microscope (manufactured by Hitachi).

[0096] (5) Measurement method of the true density of the negative electrode material: It is measured using a PENTAYC 5200e true density meter (manufactured by Anton Paar Quanta). By applying the Archimedes principle of gas replacement (density = mass / volume) and using Boyle's law (PV = nRT) under certain conditions of an inert gas with a small molecular diameter, the true volume of the material to be measured is accurately measured to obtain its true specific gravity. The unit is g / cm 3 .

[0097] (6) The interplanar spacing d of the (002) plane of the material is characterized by X-ray diffraction 002 , and the unit is Å. The crystallite size Lc in the c-axis direction and the ratio I of the peak intensities of the (004) plane and the (110) plane are obtained by X-ray diffraction 004 / I 110 .

[0098] (7) Measurement method of battery performance: The negative electrode materials produced in Examples 1 to 20 and Comparative Examples 1 and 2, carboxymethyl cellulose, conductive carbon black, and styrene-butadiene rubber were magnetically stirred in deionized water at a mass ratio of 95:1.5:1.5:2 for 8 h to be uniformly mixed. The slurry obtained by mixing was coated on a copper foil and vacuum dried at 60 °C to obtain a working electrode. Lithium metal was used as the counter electrode and the reference electrode, the separator was Celgard 2325, and the electrolyte was 1 mol∙L-1 LiPF6-EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio 1:1:1). The assembly of CR2016 coin cells was completed in a glove box filled with high-purity argon gas.

[0099] The initial discharge capacity / initial discharge efficiency test was performed using a LAND battery tester. The charge-discharge conditions were to stand for 2 h, discharge from 0.1C to 0.005V, from 0.09C, 0.08C…0.02C to 0.001V, stand for 15 min, charge from 0.1C to 1.5V, and stand for 15 min.

[0100] The button-type half-cell was subjected to a rate performance test at 25 ± 2 °C to obtain the charge-discharge specific capacity and Coulomb efficiency at 0.2C, 1C, and 2C. The charge-discharge conditions for the rate measurement of the button-type half-cell were: (1) discharge from 0.1C to 0.01V, constant voltage for 5 h, charge from 0.1C to 1.5V; (2) discharge from 0.2C to 0.01V, constant voltage to 0.01C, charge from 0.2C to 1.5V; (3) discharge from 0.2C to 0.01V, constant voltage to 0.01C, charge from 2C to 1.5V; (4) discharge from 0.2C to 0.01V, constant voltage to 0.01C, charge from 0.2C to 1.5V; (5) discharge from 1C to 0.01V, constant voltage to 0.01C, charge from 0.2C to 1.5V; (6) discharge from 2C to 0.01V.

[0101] Full battery measurement: The negative electrode material obtained by manufacturing in each example was used as the negative electrode active material, and the mass percentages of the negative electrode active material, conductive agent, adhesive, and dispersant were 95.2:1.5:2:1.3. They were dissolved in deionized water and mixed, and the solid content was controlled to 50 wt%. It was applied to a copper foil current collector with a thickness of 8 μm and vacuum dried to obtain a negative electrode sheet. Lithium iron phosphate, polyvinylidene fluoride, and conductive agent carbon black were uniformly mixed with a mass ratio of 95:2:3 in a solvent NMP (N-methylpyrrolidone), then applied to an aluminum foil with a thickness of 16 μm and vacuum dried to manufacture a positive electrode sheet. The coated positive and negative electrode sheets were processed through steps such as sheet pressing, winding, drying, electrolyte injection, sealing, formation, and grading to manufacture a 554065-type soft pack lithium-ion battery.

[0102] The obtained soft pack battery was subjected to charge and discharge tests using a LAND battery test system (manufactured by Wuhan Jinnuo Electronics Co., Ltd.). Charging and discharging were carried out at a current of 1C / 1C under normal temperature conditions, and the charging and discharging voltage was limited to 3.0V to 4.35V. The initial efficiency and the capacity retention rate test for 500 cycles were conducted (the press density of the negative electrode sheet was 1.60 g / cm 3 ).

[0103] The results of the performance tests of the negative electrode materials obtained in the above examples are shown in Table 1 below, and the results of the performance tests of the batteries manufactured with the negative electrode materials are shown in Table 2 below.

[0104] JPEG2025524253000002.jpg247159

[0105] JPEG2025524253000003.jpg243152

[0106] As can be seen from the test data of Examples 1 to 20, pores are formed inside and / or on the surface of the graphite produced in the examples of the present invention, improving the high-rate charging performance of the material. This is advantageous for binding lithium ions and sufficient carbon atoms with low resistance by controlling the parameters of the negative electrode material to 0.7 ≦ V×S / D ≦ 3.95 and controlling G to 89 ≦ G ≦ 93. Lithium ions diffuse rapidly into the solid-liquid interface and within the solid phase, suppressing the formation of lithium deposits, reducing concentration polarization, and fully utilizing the lithium ion diffusion pathway of the negative electrode material, so that the negative electrode material has a sufficient reaction space for the release and absorption of lithium, which is advantageous for obtaining a negative electrode material with better rate performance and capacity.

[0107] For the negative electrode material produced in Comparative Example 1, the concentration of the alkaline solution used is too high, the pore volume generated by etching is too large, the specific surface area is too large, V×S / D is out of the above range, and after the pores between the negative electrode material particles are infiltrated, a solid electrolyte film is formed on the surface of the negative electrode material particles and a lithium storage is formed on the surface. The lithium ions in the electrolyte solution that have aggregated a lot on the surface of the graphite particles cause concentration polarization, form lithium deposits, and further suppress the diffusion of lithium ions, so that an electrochemical reaction cannot occur on the particle surface, the "effective electrochemical reaction space" of the negative electrode material decreases, and the cycle performance of the material is poor.

[0108] For the negative electrode material produced in Comparative Example 2, if the graphite treatment is carried out directly without adding an alkaline solution and performing in-situ etching treatment during the manufacturing process, the graphite pores are not sufficiently abundant, the pore volume V is too small, the specific surface area also decreases, V×S / D is out of the above range, the lithium ion diffusion pathway is not sufficient, and the rate performance of the material deteriorates.

[0109] Although the present invention is disclosed by the above preferred embodiments, it does not limit the scope of the claims. Any person skilled in the art can make some possible changes and modifications without departing from the technical idea of the present invention. Therefore, the protection scope of the present invention should conform to the scope defined in the claims.

Claims

1. A negative electrode material containing graphite, The graphite has pores on its surface and / or inside, and the negative electrode material has a pore volume of V cm ３ / kg, a true density of D g / cm ３ , a specific surface area of S m ２ / g, and a graphitization degree of G%. When 0.7 ≤ V × S / D ≤ 3.95 and 89 ≤ G ≤ 93, the pore volume is measured using an ASAP 2460 apparatus (manufactured by Micromeritics, USA) and calculated within a pore diameter range of 17 Å to 3000 Å using a BJH Desorption cumulative volume of pores model. The negative electrode material is characterized by this.

2. The negative electrode material according to Claim 1, characterized by satisfying at least one of the following features (1) to (3). (1) When the pore volume of the negative electrode material is V cm ３ / kg, 1.812 ≤ V ≤ 4.987; (2) When the specific surface area of the negative electrode material is Sm ２ / g, 0.872 ≦ S ≦ 1.773; (3) When the true density of the negative electrode material is D g / cm ３ it satisfies 2.238 ≤ D ≤ 2.

257.

3. The negative electrode material according to Claim 1 or 2, characterized by satisfying at least one of the following features (1) to (3). (1) The pores include at least one of micropores and mesopores; (2) The pores extend from the surface of the graphite to the inside; (3) The graphite is artificial graphite.

4. The negative electrode material according to Claim 3, characterized in that the pores have an average pore diameter of 50 Å to 200 Å.

5. When the negative electrode material has an interplanar spacing of d for the (002) plane as measured by X-ray diffraction, ００２ it satisfies 3.356 Å ≤ d ００２ ≤ 3.364 Å, and the negative electrode material according to claim 1 or 2 is characterized by this.

6. Particle size D ５０ The negative electrode material according to claim 1 or 2, characterized in that the particle size D is 10 μm to 20 μm.

7. The negative electrode material according to Claim 1, further comprising amorphous carbon, wherein the amorphous carbon is present on the surface of the graphite and / or dispersed between the graphite particles.

8. The negative electrode material according to Claim 1, further comprising an amorphous carbon coating layer located on the surface of the graphite, wherein the thickness of the amorphous carbon coating layer is 10 nm to 500 nm.

9. The negative electrode material according to Claim 7 or 8, characterized in that the mass ratio of the amorphous carbon in the negative electrode material is 0.1 wt% to 3 wt%.

10. A battery comprising the negative electrode material according to any one of Claims 1 to 9.

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