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] This invention relates to the technology of negative electrode materials, and more specifically to negative electrode materials and batteries. [Background technology]

[0002] Due to their superior performance, lithium-ion batteries show promising future applications in fields such as portable consumer electronics, power tools, new energy vehicles, and energy storage. Since the commercialization of lithium-ion batteries, the most mature negative electrode material used has been graphite-based negative electrode material. The main development directions for lithium-ion batteries at this stage are high capacity, high rate, and high safety; therefore, the development of high-performance graphite negative electrodes is crucial for achieving lithium-ion batteries with high rate performance and good cycle performance.

[0003] From a technical standpoint, the unique layered structure of graphite is due to Li + Since the lithium ions can only be inserted from the edge of the material, they gradually diffuse into the interior of the particles. This results in a low diffusion rate of lithium ions and poor rate performance. At the same time, high-rate lithium absorption causes lithium ions to concentrate on the graphite anode surface. When the lithium ion concentration at the interface reaches saturation, the lithium ions deposit as metal, and the diffusion channels and electrochemical reaction area cannot be fully utilized.

[0004] Therefore, at this mature stage in the development of graphite materials, improving a single parameter is insufficient to meet market demands for high-rate and good-cycle performance graphite anode materials. It is necessary to study the synergistic mechanisms of various factors and develop graphite anode materials that meet market demands. [Overview of the project] [Problems that the invention aims to solve]

[0005] In view of the above, the present invention provides a new negative electrode material and a battery that, in view of the drawbacks of the prior art, 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.

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, where 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 has an interplanar spacing of d for the (002) plane by X-ray diffraction measurement 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 of the graphite, the pores extend from the surface to the inside of the graphite, retain 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, a pore volume of V cm 3The density is Dg / cm³ / kg, and the true density is Dg / cm³. 3 Therefore, the specific surface area is Sm 2 The value is / g, and the degree of graphitization is G%, where 0.7 ≤ V × S / D ≤ 3.95 and 89 ≤ G ≤ 93. The pore volume within a certain range is Li +It is advantageous for the material surface to be inserted into the interior along the pore structure, improving the diffusion rate of lithium ions. A specific surface area within a certain range ensures a sufficient electrochemical reaction interface, promoting the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reducing concentration polarization, and is advantageous for improving the capacity and rate performance of the anode material. However, even if appropriate pore volume and specific surface area are met, there is still much room for improvement in the rate performance of the anode material. This is because, after lithium ions diffuse onto the graphite surface, if the order of carbon atoms in the graphite is relatively disordered and the degree of order is insufficient, the inhibition of lithium ions entering the interior of the graphite material, bonding with carbon atoms, and generating electrochemical reactions is relatively large. At the same time, graphite is polycrystalline, and especially in the case of artificial graphite, grain boundary defects exist between the crystal grains, the stress at the grain boundary defects is non-uniform, and since grain boundaries are a type of crystal plane defect, cracks are likely to occur, and when subjected to external force, they tend to split along the grain boundary direction, resulting in intergranular fractures, and ultimately, the crystal planes parallel to the graphite crystal layer planes split, forming the outer surface of the graphite particles.Because these outer surfaces are perpendicular to the direction of lithium ion diffusion, lithium ions must cross the carbon plane, making it difficult for them to enter the graphite. At the same time, lithium ions may accumulate on the carbon surface to form lithium clusters, thereby suppressing lithium diffusion or forming lithium deposition. Ultimately, the diffusion channels and electrochemical reaction area are not fully utilized. Therefore, the present invention provides good diffusion channels for lithium ion diffusion by controlling the degree of graphitization and true density. Combined with the design of the channel structure and pore distribution, it concentrates stress inside the graphite around the pores, disperses stress at grain boundaries, and, when the graphite is subjected to an external force, first generates cracks from the channels and ruptures, and then fractures through the crystal (transcrystalline fracture). This is advantageous for cracking to occur, and after the channel is exposed, it eventually forms the outer surface of the graphite particle. The cracks that penetrate the crystal are advantageous in increasing the number of pathway entrances parallel to the diffusion direction of lithium ions on the graphite particle surface. Furthermore, the inner surface of the channel itself has a certain number of pathway entrances that allow lithium ions to diffuse between the graphite layers, and because there are many defects, it is possible to store lithium at the ends. Therefore, cracks from the channel form the outer surface of the particle and more graphite microcrystalline surfaces parallel to the lithium ion diffusion pathways can be formed, not only creating more lithium ion diffusion pathways inside the graphite particle but also creating more pathway entrances for lithium ions to enter the particle surface. At the same time, considering that a high degree of graphitization is advantageous for the diffusion environment, it reduces the inhibitory traps on lithium ion transport caused by defects such as some crystal strain. A certain degree of graphitization is advantageous in terms of the number of grain boundaries and crystal lattice strain of the graphite polycrystalline, making the interlayer arrangement more regular and tighter, which is advantageous in improving true density and ensuring that the anode material exhibits a high specific capacity.The present invention is advantageous in that it controls the V×S / D ratio of the negative electrode material within the above range and controls the degree of graphitization of the material, thereby enabling the bonding of lithium ions with sufficient carbon atoms at low resistance. This is advantageous in that the negative electrode material has sufficient reaction space for lithium release and storage, and thus provides a negative electrode material with better rate performance and capacity. [Brief explanation of the drawing]

[0021] [Figure 1] This is a scanning electron microscope image of a graphite anode material according to Example 2 of the present invention. [Figure 2] This is another scanning electron microscope image of the graphite anode material according to Example 2 of the present invention. [Figure 3] This is a scanning electron microscope image of a graphite anode material according to Example 11 of the present invention. [Figure 4] This is another scanning electron microscope image of the graphite anode material according to Example 11 of the present invention. [Modes for carrying out the invention]

[0022] To explain the present invention and facilitate understanding of its technical aspects, the present invention will be described in further detail below. Note that the following examples are merely simplified examples of the present invention and do not indicate or limit the scope of protection of the present invention. The scope of protection of the present invention is as defined in the claims.

[0023] Since the commercialization of lithium-ion batteries, the most mature negative electrode material used has been graphite-based negative electrode material. The special layered structure of graphite is Li + Since the lithium ions can only be inserted from the edge of the material, they gradually diffuse into the interior of the particles. This results in a low diffusion rate of lithium ions and poor rate performance. At the same time, high-rate lithium absorption causes lithium ions to concentrate on the graphite anode surface. When the lithium ion concentration at the interface reaches saturation, the lithium ions deposit as metal, and the diffusion channels and electrochemical reaction area cannot be fully utilized.

[0024] Accordingly, a negative electrode material is provided, the negative electrode material comprising graphite, having pores on and / or inside the surface of the graphite, the pores extending from the surface to the interior of the graphite, and the negative electrode material having a pore volume of V cm 3 The density is Dg / cm³ / kg, and the true density is Dg / cm³. 3 Therefore, the specific surface area is Sm 2 The value is / g, and the degree of graphitization is G%, where 0.7 ≤ V × S / D ≤ 3.95 and 89 ≤ G ≤ 93. The anode material is characterized in that the pore volume is measured using an ASAP2460 instrument (Micromeristics, Inc., USA) and calculated within a pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model.

[0025] The negative electrode material according to the present invention contains graphite and has pores on and / or inside the surface of the graphite, the pores extending from the surface to the interior of the graphite, maintaining the regular graphite layered structure of the negative electrode material, and generating abundant pores on and near the surface of the graphite. The negative electrode material has a pore volume of V cm 3 The density is Dg / cm³ / kg, and the true density is Dg / cm³. 3 Therefore, the specific surface area is Sm 2 The value is / g, and the degree of graphitization is G%, where 0.7 ≤ V × S / D ≤ 3.95 and 89 ≤ G ≤ 93. The pore volume within a certain range is Li +It is advantageous for lithium ions to be inserted into the material from the surface along the pore structure, improving the diffusion rate of lithium ions. A specific surface area within a certain range ensures a sufficient electrochemical reaction interface, promoting the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reducing concentration polarization, and improving the capacity and rate performance of the anode material. However, simply satisfying appropriate pore volume and specific surface area does not leave much room for further improvement in the rate performance of the anode material. This is because, after lithium ions diffuse onto the graphite surface, if the order of carbon atoms in the graphite is relatively disordered and the degree of order is insufficient, there is a relatively large inhibition of lithium ions entering the interior of the graphite material, bonding with carbon atoms, and generating an electrochemical reaction. At the same time, since graphite is polycrystalline, and especially in the case of artificial graphite, grain boundary defects exist between crystal grains, the stress at the grain boundary defects is non-uniform, making it prone to cracking and splitting when subjected to external force. Fractures occur along the crystal, and ultimately, the crystal planes parallel to the graphite crystal layer planes split, forming the outer surface of the graphite particles. Because these outer surfaces are perpendicular to the direction of lithium ion diffusion, they must cross the carbon plane, making it difficult for lithium ions to enter the graphite interior. At the same time, they may accumulate on the carbon surface to form lithium clusters, thereby suppressing lithium diffusion or causing lithium deposition. Ultimately, the diffusion channels and electrochemical reaction area are not fully utilized. Therefore, the present invention provides good diffusion channels for lithium ion diffusion by controlling the degree of graphitization and true density. Combined with the design of the channel structure and pore distribution, it concentrates stress within the graphite around the pores, reducing stress at grain boundaries. When the graphite is subjected to an external force, it first generates cracks from the channels and ruptures, ultimately forming the outer surface of the graphite particles. This allows for the formation of more graphite microcrystalline surfaces parallel to the lithium ion diffusion channels, not only creating more lithium ion diffusion channels within the graphite particles but also creating more entrances to the particle surface for lithium ions to enter. Simultaneously, considering that a high degree of graphitization is advantageous for the diffusion environment, it reduces inhibitory traps on lithium ion transport due to crystal defects, ensuring that the anode material exhibits a high specific capacity.The present invention is advantageous in that it controls the V×S / D ratio of the negative electrode material within the above range and controls the degree of graphitization of the material, thereby enabling the bonding of lithium ions with sufficient carbon atoms at low resistance. This is advantageous in that the negative electrode material has sufficient reaction space for lithium release and storage, and thus provides 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 The value is / kg, and 1.812 ≤ V ≤ 4.987, specifically, it 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., and is not limited thereto. When pores generate electrochemical reactions inside the electrode, the pores create more lithium ion diffusion passages and electrochemical reaction interfaces in the negative electrode material, promoting the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reducing concentration polarization, and is 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 ​​Sm 2 The ratio is / g, and 0.872 ≤ S ≤ 1.773, specifically, it may be, but is not limited to, 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. As can be understood, if the specific surface area is too large, it is likely to lead to the formation of an excessive solid electrolyte film, resulting in excessive consumption of irreversible lithium salt and a decrease in the battery's initial efficiency.

[0028] In some embodiments, the negative electrode material has a true density of Dg / cm³. 3 Therefore, 2.210 ≤ D ≤ 2.265, which may be, but are not limited to, 2.2385, 2.2481, 2.2440, 2.2372, 2.2476, 2.2502, 2.2514, or 2.262.

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

[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, specifically 50 Å, 60 Å, 70 Å, 80 Å, 90 Å, 100 Å, 120 Å, 140 Å, 160 Å, or 200 Å, and are not limited thereto. By controlling the average pore diameter of the pores within the above range, Li + This is advantageous for the transport of lithium from the material surface into the graphite interior along the pore structure, and for further lithium release and storage reactions to occur. 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 into the interior.

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

[0034] In some embodiments, the negative electrode material has a particle size D 50 The particle size is 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, and is not limited thereto. Furthermore, the cumulative particle size distribution on a volume basis for particle size distribution measurement is measured using laser diffraction, and D 50 This indicates the corresponding particle size when the cumulative particle size distribution percentage reaches 50%.

[0035] In some embodiments, the negative electrode material is determined by X-ray diffraction measurement to have a (002) plane spacing of d 002 When this is done, 3.356 Å ≤ d 002 The interplanar spacing is ≤3.364 Å. 002Since the values ​​fall within the above range, it can be seen that the graphite particles have a high degree of graphitization, i.e., a high degree of graphitization, and therefore a high product volume.

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

[0037] In some embodiments, the negative electrode material further comprises amorphous carbon, which is present on the surface of the graphite and / or dispersed between graphite particles. Specifically, the graphite particles are embedded within the amorphous carbon material, with some graphite particles exposed on the surface of the amorphous carbon material.

[0038] In some embodiments, the anode material further contains amorphous carbon, with the amorphous carbon present in a mass percentage of 0.1 wt% to 3 wt% relative to the anode material. Specifically, the mass percentage of amorphous carbon in the anode material may be 0.1 wt%, 0.3 wt%, 0.5 wt%, 1 wt%, 2 wt%, 2.5 wt%, or 3 wt%, and the presence of amorphous carbon provides lithium ions with more irregular and open diffusion pathways, which is advantageous for improving material rate performance.

[0039] In some embodiments, the capacity retention rate for charging the negative electrode material 1C in 500 cycles is ≥90%, and may be, but is not limited to, 91.8%, 92.3%, 90.6%, 92.4%, 93.5%, etc.

[0040] The method for manufacturing the negative electrode material includes the following steps. In S10, softened pitch is mixed with an alkaline solution with a concentration of 0.01 mol / L to 0.05 mol / L, and sonication is performed to obtain a mixture in which the ratio of the mass content of saturated material to aromatic material in the pitch is (5 to 20):(95 to 80). In S20, the solid product after washing the mixture is dried and crushed to obtain powder D. 50 The size is 10 μm to 20 μm. In step S30, the powder is carbonized at 500°C to 1200°C under an inert atmosphere to obtain a precursor. In step S40, the precursor is graphitized at 2800°C to 3200°C to obtain the negative electrode material.

[0041] The method for manufacturing a negative electrode material according to the present invention involves mixing pitch with a low-concentration alkaline solution, and in-situ etching a pore structure within the pitch using ultrasonic means to improve the effective reaction area of ​​the material and increase the lithium ion insertion pathways. Subsequently, the in-situ etched powder is carbonized, during which impurities, volatiles, and unstable substances within the material are decomposed and released, further expanding the pore diameter and depth of the pores formed by etching. The carbonized product is further graphitized to form graphite with abundant and regular pores, enabling precise control of the pore volume of the graphite, adjusting the internal stress distribution of the graphite to some extent, and finally increasing the reactable area on the electrode of the negative electrode active material, which is advantageous for improving the high-rate charge-discharge performance of the material. The process method is simple, production costs are low, and the manufactured graphite negative electrode material has characteristics such as high specific capacity, excellent high-rate charge-discharge performance, and excellent cycle performance, and can meet the usage demands of consumers and power-side users for negative electrode energy density and rapid charging performance.

[0042] The technical aspects of the present invention will be described in detail below. In S10, softened pitch is mixed with an alkaline solution with a concentration of 0.01 mol / L to 0.05 mol / L, and sonication is performed to obtain a mixture in which the ratio of the mass content of saturated material to aromatic material 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 reformed pitch, mesophase pitch, etc.

[0044] In some embodiments, the ratio of the mass content of saturation to aroma in 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, it may be other values ​​within the above range, but is not limited thereto. By controlling the mass ratio of saturated and aromatic components in the pitch, the higher the aromatic component content, the better the pitch fluidity, the lower the softening temperature, and the higher the volatile content. The volatile components decompose and escape during the carbonization process, further expanding the pore diameter and depth of the pores formed by etching. This concentrates stress within the graphite around the pores, reducing stress at the grain boundaries. When the graphite is subjected to an external force, it first generates cracks from the channels and ruptures, ultimately forming the outer surface of the graphite particles. This allows for the formation of more graphite microcrystalline surfaces parallel to the lithium ion diffusion pathways, not only creating more lithium ion diffusion pathways within the graphite particles but also creating more pathway entrances on the particle surface for lithium ions to enter. This is advantageous in obtaining a negative electrode material with better magnification performance and lower residual carbon content.

[0045] In some embodiments, the pitch is heated to 50°C to 80°C to soften, forming a liquid pitch. The softening temperature may be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C, and may, of course, be any other value within the above range, but is not limited thereto.

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

[0047] In some embodiments, the concentration of the alkaline solution is 0.01 mol / L to 0.05 mol / L, specifically 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.045 mol / L, or 0.05 mol / L, and is not limited to other values ​​within the above range. If the concentration of the alkaline solution is too high, the number of pores formed by etching the pitch surface becomes too large, and the pore volume of the final graphite anode material becomes too large, as does the specific surface area, making it difficult to control the V×S / D ratio within the ideal range, which is detrimental to improving the high-rate charge-discharge performance and cycle performance of the anode material. By controlling the V×S / D ratio of the anode material within the above range, the anode material has sufficient chemical reaction space for lithium release and storage, which is advantageous in obtaining an anode material with better rate performance and capacity.

[0048] In some embodiments, the material ratio of pitch to alkaline solution is 50 g / 100 ml to 100 g / 100 ml, specifically 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, or 100 g / 100 ml, and of course, other values ​​within the above range are also possible and are not limited thereto. Controlling the material ratio of pitch to alkaline solution is advantageous because the alkaline solution is able to sufficiently etch the softened pitch, thereby etching and forming a number of pores adapted to the surface of the pitch, reducing stress at the grain boundaries of the graphite obtained after graphitization, which is advantageous for creating more lithium ion diffusion pathways and improving the specific capacity and rate performance of the anode material.

[0049] In some embodiments, the sonication time under heat retention is 5 to 10 hours, specifically 5, 6, 7, 8, 9, or 10 hours, but is not limited to these values, and other unlisted values ​​within that range are also applicable. During sonication, the alkaline solution constantly impacts and etches the pitch, forming a pore structure in situ within the pitch particles. This pore structure creates more lithium ion diffusion pathways and electrochemical reaction interfaces in the anode material, promoting the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reducing concentration polarization, and 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 The size is 10 μm to 20 μm.

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

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

[0053] In some embodiments, the drying temperature is 80°C to 120°C, specifically 80°C, 90°C, 100°C, 110°C, and 120°C, but is not limited to these values, and other unlisted values ​​within that range are also applicable.

[0054] In some embodiments, the median diameter D of the powder obtained by crushing is 50The median diameter of the powder is between 10 μm and 20 μm, and more specifically, it may be 12 μm, 13 μm, 14 μm, 16 μm, 18 μm, 18.5 μm, 19 μm, or 20 μm, but it is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable. Controlling the median diameter of the powder within the above range through multiple tests is advantageous in achieving a balance between processing performance, capacity, and rate performance.

[0055] In step 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 of the carbonization process is specifically 2°C / min, 3°C / min, 5°C / min, 6°C / min, 8°C / min, 9°C / min, or 10°C / min. As can be understood, when the heating rate of the carbonization process is within the above range, it is advantageous for volatile components in the raw material to escape at different rates, the pore size of the pore structure is further enlarged and / or deepened, and in combination with the heating rate of the subsequent graphitization process, an anode material satisfying 0.70 ≤ V × S / D ≤ 3.95 is obtained.

[0057] In some embodiments, the carbonization temperature may be, specifically, 500°C, 550°C, 600°C, 700°C, 750°C, 800°C, 850°C, 900°C, 1000°C, or 1200°C, but is not limited to these values, and other unlisted values ​​within that range are also applicable. As can be understood, having the carbonization temperature within the above range is advantageous for the discharge of volatile substances and other materials in the powder.

[0058] In some embodiments, the heat retention time for the carbonization treatment is 2 to 10 hours, specifically 2 hours, 3 hours, 4 hours, 4.5 hours, 5 hours, 6 hours, 8 hours, or 10 hours, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

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

[0060] In some embodiments, the heat retention temperature for the graphitization treatment may be specifically 2800°C, 2850°C, 2900°C, 2950°C, 3000°C, 3100°C, or 3200°C, but is not limited to the values ​​listed above, and other values ​​within that range that are not listed are also applicable.

[0061] In some embodiments, the holding time for the graphitization treatment is 2 to 10 hours, specifically 2 hours, 3 hours, 4 hours, 4.5 hours, 5 hours, 6 hours, 8 hours, or 10 hours, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

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

[0063] In some embodiments, the graphitization treatment is followed by at least one of crushing, sieving, and demagnetization. Preferably, the graphitization treatment is followed by crushing, demagnetization, and sieving in that order.

[0064] In some embodiments, the grinding means may be one of a mechanical grinder, an air-jet grinder, and a cryogenic grinder.

[0065] In some embodiments, the sieving method is selected from one of the following: a fixed sieve, a drum screen, a resonant sieve, a roller sieve, a vibrating sieve, and a chain grizzly sieve. The number of meshes used for sieving is 100 to 500 meshes, and specifically, the number of meshes used for 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 demagnetizer is selected from a permanent magnet drum-type magnetic separator, an electromagnetic iron remover, and a pulsating high-gradient magnetic separator, and the purpose of demagnetization is to ultimately control the magnetic material content of the negative electrode material and reduce the impact of the magnetic material 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 containing the above-mentioned negative electrode material.

[0068] As will be apparent to those skilled in the art, the battery manufacturing methods described above are merely examples. Within the scope of the present invention, other methods commonly used in the art may be employed, and other types of batteries, such as sodium-ion batteries and potassium-ion batteries, may be manufactured and measured.

[0069] The gist of the present invention will be further explained below with reference to several embodiments. However, the embodiments of the present invention are not limited to the following specific embodiments. Appropriate modifications can be made to implement the invention within the scope of protection.

[0070] Example 1 The method for manufacturing the negative electrode material in this embodiment 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 subjected to ultrasonic treatment for 10 hours while maintaining the temperature at 80°C to obtain a mixture in which the pitch mainly consists of saturated and aromatic components, and the ratio of saturated to aromatic content is 5:95. (2) The mixture is cooled to room temperature, washed repeatedly with distilled water until the filtrate is neutral, filtered, the solvent is removed by suction filtration, then placed in an oven and vacuum dried for 10 hours, crushed, and the powder (D 50 A particle size of 16.3 μm was obtained. (3) The powder was subjected to carbonization treatment at 1200°C for 10 hours to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 3000°C for 8 hours to obtain a graphite anode material.

[0071] Example 2 The method for manufacturing the negative electrode material in this embodiment 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 subjected to ultrasonic treatment for 10 hours while maintaining the temperature at 80°C to obtain a mixture in which the pitch mainly consists of saturated and aromatic components, and the ratio of saturated to aromatic content is 10:90. (2) The mixture is cooled to room temperature, washed repeatedly with distilled water until the filtrate is neutral, filtered, the solvent is removed by suction filtration, then placed in an oven and vacuum dried for 10 hours, crushed, and the powder (D 50 A particle size of 16.9 μm was obtained. (3) The powder was subjected to carbonization treatment at 1000°C for 10 hours to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 3000°C for 8 hours to obtain a graphite anode material.

[0072] Example 3 The method for manufacturing the negative electrode material in this embodiment 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 subjected to ultrasonic treatment for 10 hours while maintaining the temperature at 80°C to obtain a mixture in which the pitch mainly consists of saturated and aromatic components, and the ratio of saturated to aromatic content is 15:85. (2) The mixture is cooled to room temperature, washed repeatedly with distilled water until the filtrate is neutral, filtered, the solvent is removed by suction filtration, then placed in an oven and vacuum dried for 10 hours, crushed, and the powder (D 50 A particle size of 16.2 μm was obtained. (3) The powder was subjected to carbonization treatment at 1200°C for 10 hours to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 2900°C for 8 hours to obtain a graphite anode material.

[0073] Example 4 The method for manufacturing the negative electrode material in this embodiment includes the following steps. (1) After softening the pitch by heating it to 80°C, it is mixed with a 0.02 mol / L KOH alkaline solution and subjected to ultrasonic treatment for 10 hours while maintaining the temperature at 80°C to obtain a mixture in which the pitch mainly consists of saturated and aromatic components, and the ratio of saturated to aromatic content is 20:80. (2) The mixture is cooled to room temperature, washed repeatedly with distilled water until the filtrate is neutral, filtered, the solvent is removed by suction filtration, then placed in an oven and vacuum dried for 10 hours, crushed, and the powder (D 50 A particle size of 15.7 μm was obtained. (3) The powder was subjected to carbonization treatment at 1200°C for 10 hours to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 2800°C for 8 hours to obtain a graphite anode material.

[0074] Example 5 The method for manufacturing the negative electrode material in this embodiment includes the following steps. (1) After heating the pitch to 80°C to soften it, it is mixed with a 0.01 mol / L KOH alkaline solution and subjected to ultrasonic treatment for 10 hours while maintaining the temperature at 80°C to obtain a mixture in which the pitch mainly consists of saturated and aromatic components, and the ratio of saturated to aromatic content is 20:80. (2) The mixture is cooled to room temperature, washed repeatedly with distilled water until the filtrate is neutral, filtered, the solvent is removed by suction filtration, then placed in an oven and vacuum dried for 10 hours, crushed, and the powder (D 50 A value of 15.4 μm was obtained. (3) The powder was subjected to carbonization treatment at 500°C for 10 hours to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 2800°C for 8 hours to obtain a graphite anode material.

[0075] Example 6 The method for manufacturing the negative electrode material in this embodiment includes the following steps. (1) After softening the pitch by heating it to 80°C, it is mixed with a 0.05 mol / L KOH alkaline solution and subjected to ultrasonic treatment for 8 hours while maintaining the temperature at 70°C to obtain a mixture in which the pitch mainly consists of saturated and aromatic components, and the ratio of saturated to aromatic content is 20:80. (2) The mixture is cooled to room temperature, washed repeatedly with distilled water until the filtrate is neutral, filtered, the solvent is removed by suction filtration, then placed in an oven and vacuum dried for 10 hours, crushed, and the powder (D 50 A value of 16.1 μm was obtained. (3) The powder was subjected to carbonization treatment at 1200°C for 10 hours to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 3000°C for 8 hours to obtain a graphite anode material.

[0076] Example 7 The method for manufacturing the negative electrode material in this embodiment includes the following steps. (1) After heating the pitch to 70°C to soften it, it is mixed with a 0.04 mol / L KOH alkaline solution and subjected to ultrasonic treatment for 8 hours while maintaining the temperature at 70°C to obtain a mixture in which the pitch mainly consists of saturated and aromatic components, and the ratio of saturated to aromatic components is 20:80. (2) The mixture is cooled to room temperature, washed repeatedly with distilled water until the filtrate is neutral, filtered, the solvent is removed by suction filtration, then placed in an oven and vacuum dried for 10 hours, crushed, and the powder (D 50 A value of 16.8 μm was obtained. (3) The powder was subjected to carbonization treatment at 1000°C for 10 hours to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 3000°C for 8 hours to obtain a graphite anode material.

[0077] Example 8 The method for manufacturing the negative electrode material in this embodiment includes the following steps. (1) After heating the pitch to 70°C to soften it, it is mixed with a 0.03 mol / L KOH alkaline solution and subjected to ultrasonic treatment for 8 hours while maintaining the temperature at 70°C to obtain a mixture in which the pitch mainly consists of saturated and aromatic components, and the ratio of saturated to aromatic content is 20:80. (2) The mixture is cooled to room temperature, washed repeatedly with distilled water until the filtrate is neutral, filtered, the solvent is removed by suction filtration, then placed in an oven and vacuum dried for 10 hours, crushed, and the powder (D 50 A particle size of 16.7 μm was obtained. (3) The powder was subjected to carbonization treatment at 1000°C for 10 hours to obtain a precursor. (4) The precursor was subjected to high-temperature graphitization treatment at 2900°C for 8 hours to obtain a graphite anode material.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0092] (1) Method for measuring the particle size of the negative electrode material: The particle size distribution range of the composite anode material was measured using a Malvern laser particle size analyzer.

[0093] (2) Method for measuring the pore volume of the negative electrode material: The measurements were performed using an ASAP2460 instrument (Micromeristics, Inc., USA), and the pore volume V was calculated using the JH Desorption cumulative volume of pores model within the pore diameter range of 17 Å to 3000 Å.

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

[0095] (4) Method for measuring 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) Method for measuring the true density of the negative electrode material: The true specific gravity of the material being measured was obtained by accurately measuring its true volume using a PENTAYC 5200e true density meter (manufactured by Anton Paar Quanta). This measurement applied the Archimedes principle of gas displacement (density = mass / volume) and utilized the Borr law (PV=nRT) under constant conditions for an inert gas with small molecular diameters. The unit is g / cm³. 3 That is the case.

[0097] (6) X-ray diffraction determines the interplanar spacing d of the material (002) surface. 002 The characteristics are as follows, the unit is Å, and the microcrystalline size Lc in the c-axis direction and the ratio of peak intensities I between the (004) plane and the (110) plane are determined by X-ray diffraction. 004 / I 110 They sought it.

[0098] (7) Method for measuring battery performance: The negative electrode materials produced in Examples 1-20 and Comparative Examples 1-2—carboxymethylcellulose, conductive carbon black, and styrene-butadiene rubber—were mixed uniformly in deionized water for 8 hours by magnetic stirring in a mass ratio of 95:1.5:1.5:2. The resulting slurry was coated onto copper foil and vacuum-dried at 60°C to form the working electrode. Metallic lithium was used as the counter electrode and reference electrode, the separator was Celgard 2325, and the electrolyte was 1 mol∙L-1LiPF6-EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio 1:1:1). The assembly of the CR2016 type coin cell was completed in a glove box filled with high-purity argon gas.

[0099] The initial discharge capacity / initial discharge efficiency test is performed using a LAND battery tester. The charge / discharge conditions are as follows: leave undisturbed for 2 hours, discharge from 0.1C to 0.005V, then to 0.09C, 0.08C...0.02C to 0.001V, leave undisturbed for 15 minutes, charge from 0.1C to 1.5V, and leave undisturbed for 15 minutes.

[0100] The button-type half-cell underwent rate performance testing in an environment of 25±2℃, obtaining charge-discharge ratio capacities and Coulomb efficiencies of 0.2C, 1C, and 2C. The rate measurement charge-discharge conditions for button-type half-cells are as follows: (1) Discharge from 0.1C to 0.01V, maintain constant voltage for 5 hours, and charge from 0.1C to 1.5V; (2) Discharge from 0.2C to 0.01V, maintain constant voltage to 0.01C, and charge from 0.2C to 1.5V; (3) Discharge from 0.2C to 0.01V, maintain constant voltage to 0.01C, and charge from 2C to 1.5V; (4) Discharge from 0.2C to 0.01V, maintain constant voltage to 0.01C, and charge from 0.2C to 1.5V; (5) Discharge from 1C to 0.01V, maintain constant voltage to 0.01C, and charge from 0.2C to 1.5V; (6) Discharge from 2C to 0.01V.

[0101] Total battery measurement: The negative electrode material obtained from the production of each example was used as the negative electrode active material. The mass percentage of the negative electrode active material, conductive agent, adhesive, and dispersant was 95.2:1.5:2:1.3. It was dissolved and mixed in deionized water, the solid content was controlled to 50 wt%, and it was applied to an 8 μm thick copper foil current collector and vacuum dried to produce a negative electrode sheet. Lithium iron phosphate, polyvinylidene fluoride, and conductive carbon black were uniformly mixed with the solvent NMP (N-methylpyrrolidone) in a mass ratio of 95:2:3, and this mixture was applied to a 16 μm thick aluminum foil and vacuum dried to produce a positive electrode sheet. The applied positive and negative electrode sheets were subjected to processes such as sheet pressing, winding, drying, liquid injection, sealing, chemical conversion, and grading to produce a 554065 type soft pack lithium-ion battery.

[0102] The obtained softpack batteries were subjected to charge-discharge tests using the LAND Battery Test System (manufactured by Wuhan Jinnuo Electronics Co., Ltd.). Charge and discharge were performed under room temperature conditions and with a 1C / 1C current, and the charge-discharge voltage was limited to 3.0V to 4.35V. Initial efficiency and capacity retention rate after 500 cycles were tested (negative electrode sheet press density: 1.60 g / cm²). 3 ).

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

[0104] JPEG0007862534000001.jpg247159

[0105] JPEG0007862534000002.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 embodiments of the present invention, improving the high-rate charging performance of the material. This is advantageous because controlling the parameters of the negative electrode material to 0.7 ≤ V × S / D ≤ 3.95 and 89 ≤ G ≤ 93 is beneficial for bonding lithium ions with sufficient carbon atoms at low resistance, allowing lithium ions to rapidly diffuse into the solid-liquid interface and solid phase, suppressing the formation of lithium deposits, reducing concentration polarization, and making full use of the lithium ion diffusion channels in the negative electrode material, resulting in a negative electrode material having sufficient reaction space for lithium release and storage, which is advantageous for obtaining a negative electrode material with better rate performance and capacity.

[0107] In Comparative Example 1, the anode material produced had an excessively high concentration of the alkaline solution used, resulting in excessively large pore volume and specific surface area due to etching. The V×S / D ratio fell outside the specified range. After the pores between the anode material particles were infiltrated, a solid electrolyte film formed on the surface of the anode material particles, along with lithium storage. The lithium ions in the electrolyte, which had aggregated in large quantities on the surface of the graphite particles, underwent concentration polarization, forming lithium deposits. Furthermore, the diffusion of lithium ions was suppressed, preventing electrochemical reactions from occurring on the particle surface. This reduced the "effective electrochemical reaction space" of the anode material, resulting in poor material cycle performance.

[0108] In Comparative Example 2, if the negative electrode material is subjected to graphitization treatment without adding an alkaline solution and etching in situ during the manufacturing process, the graphite pores are not sufficiently abundant, the pore volume V is too small, the specific surface area decreases, V × S / D falls outside the above range, the lithium ion diffusion pathways are insufficient, and the rate performance of the material deteriorates.

[0109] Although the present invention is disclosed by the preferred embodiments described above, this does not limit the scope of the claims, and any person skilled in the art may make some possible changes and modifications without departing from the technical spirit of the invention. Therefore, the scope of protection of the present invention should be limited to the scope set forth in the claims.

Claims

1. A negative electrode material containing graphite, The negative electrode material has pores on and / or inside the graphite, and the pore volume is V cm. ３ The true density is Dg / cm³ / kg. ３ The specific surface area is Sm ２ When the degree of graphitization is expressed as G%, the following conditions apply: 0.7 ≤ V × S / D ≤ 3.95 and 89 ≤ G ≤ 93. The pore volume was measured using an ASAP 2460 instrument (Micromeristics, Inc., USA) and calculated within the 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 satisfying 1.812 ≤ V ≤ 5.012, 0.868 ≤ S ≤ 1.773, and 2.2370 ≤ D ≤ 2.2578.

2. The negative electrode material according to claim 1, characterized in that it satisfies at least one of the following features (1) to (3). (1) The negative electrode material has a pore volume of V cm ３ When expressed as / kg, 1.812 ≤ V ≤ 4.987; (2) The negative electrode material has a specific surface area of ​​Sm ２ When expressed as / g, 0.872 ≤ S ≤ 1.773; (3) The negative electrode material has a true density of Dg / cm³ ３ In this case, 2.238 ≤ D ≤ 2.

257.

3. The negative electrode material according to claim 1 or 2, characterized in that it satisfies 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 into the interior; (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. The negative electrode material was determined by X-ray diffraction measurement to have a (002) plane spacing of d ００２ When this is done, 3.356 Å ≤ d ００２ The negative electrode material according to claim 1 or 2, characterized in that it is ≤ 3.364 Å.

6. Particle size D ５０ The negative electrode material according to claim 1 or 2, characterized in that ５０ 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 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 anode material according to claim 7 or 8, characterized in that the amorphous carbon has a mass percentage of 0.1 wt% to 3 wt% in the anode material.

10. A battery characterized by comprising the negative electrode material described in claim 1 or 2.

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