A negative electrode material, a preparation method thereof, a lithium ion battery and an electrical device

Abstract

This invention provides a negative electrode material and its preparation method, a lithium-ion battery, and electrical equipment, wherein the negative electrode material satisfies the following condition: (1), where T is the tap density of the negative electrode material, in g / cm³. 3 S is the specific surface area of ​​the negative electrode material, in m². 2 / g, where P is the compaction density of the negative electrode material at 5t, in g / cm³. 3 (1) G is the degree of graphitization of the negative electrode material; (2) T is 0.8 g / cm³. 3 -1.0 g / cm 3 (3) S is 2.5 m 2 / g -5.5 m 2 / g; (4) P is 1.7 g / cm 3 -1.9 g / cm 3 (5) G is 0.95-0.98. The anode material of this application can simultaneously have high energy density and high rate performance, solving the problem that existing anode materials cannot take into account both energy density and rate performance.

Description

Technical Field

[0001] This application belongs to the field of lithium-ion battery anode material technology, and in particular relates to an anode material and its preparation method, lithium-ion batteries and related electrical equipment. Background Technology

[0002] Natural graphite, as a negative electrode material for lithium-ion batteries, has achieved widespread commercial application due to its excellent charge-discharge platform stability and mature processing technology. Natural graphite is classified into two types based on its crystal morphology: flake graphite and microcrystalline graphite, which exhibit significant differences in their electrochemical behavior.

[0003] While flake graphite possesses advantages such as complete crystallization and high capacity, its preferential orientation along the a-axis means that lithium ions can only be embedded at the edges, resulting in a longer diffusion path and poorer rate performance. Microcrystalline graphite, composed of randomly stacked graphite crystals smaller than 1 μm, naturally possesses an isotropic framework, which can significantly shorten the lithium-ion diffusion path. + Its diffusion distance and rate performance are superior to those of flake graphite.

[0004] Therefore, microcrystalline graphite is considered an ideal matrix material for developing high-rate anode products. However, in practical applications, due to the inherent structure of microcrystalline graphite, it is difficult to achieve both rate performance and energy density. Currently, there is no microcrystalline graphite-based anode material on the market that can simultaneously achieve high energy density and excellent rate performance. Summary of the Invention

[0005] This invention provides an anode material and its preparation method, a lithium-ion battery, and electrical equipment, aiming to solve the technical problem that existing anode materials cannot simultaneously achieve high energy density and excellent rate performance.

[0006] In a first aspect, embodiments of the present invention provide a negative electrode material, the negative electrode material satisfying the following conditions:

[0007] (1) Where T is the tap density of the negative electrode material, in g / cm³. 3 S is the specific surface area of ​​the negative electrode material, in m². 2 / g, where P is the compacted density of the negative electrode material at 5t, in g / cm³. 3 G represents the degree of graphitization of the negative electrode material;

[0008] (2) The T is 0.8 g / cm³. 3 -1.0 g / cm 3 ;

[0009] (3) The value of S is 2.5 m. 2 / g -5.5 m 2 / g;

[0010] (4) The P value is 1.7 g / cm³. 3 -1.9 g / cm 3 ;

[0011] (5) The value of G is 0.95-0.98.

[0012] Secondly, embodiments of the present invention also provide a method for preparing the negative electrode material as described above, comprising:

[0013] Microcrystalline graphite concentrate is crushed and shaped to obtain spheroidized microcrystalline graphite;

[0014] The spheroidized microcrystalline graphite was mixed with an acidic solution and purified to obtain purified microcrystalline graphite.

[0015] The purified microcrystalline graphite is mixed with a coating agent and subjected to carbonization treatment to obtain a negative electrode material, wherein the coating agent includes asphalt.

[0016] Thirdly, embodiments of the present invention also provide a lithium-ion battery, the lithium-ion battery comprising the negative electrode material described above or a negative electrode material prepared by the method described above.

[0017] Fourthly, embodiments of the present invention also provide an electrical device, the electrical device including the lithium-ion battery described above.

[0018] The beneficial effects of the embodiments of the present invention are as follows:

[0019] The tap density, specific surface area, compaction density, and degree of graphitization of the negative electrode material of this invention are within a specific content range, and the tap density, specific surface area, compaction density, and degree of graphitization of the negative electrode material satisfy a specific content relationship. When this negative electrode material is used as a battery electrode, the particle size distribution of the negative electrode material is uniform and the defect concentration is moderate, which can take into account both surface characteristics and structural integrity. It can simultaneously have high energy density and high rate performance, effectively solving the problem that existing negative electrode materials cannot achieve both high energy density and excellent rate performance.

[0020] The method for preparing the anode material of this invention adjusts the surface morphology and defects of the material by controlling the crushing, shaping, and coating modification processes, thereby optimizing parameters such as tap density and specific surface area of ​​the graphite anode material. This improves the processing performance and electrochemical performance of the anode material, resulting in anode materials with both high energy density and excellent rate performance. Furthermore, the method of this invention has advantages such as simple process and low production cost, which is conducive to large-scale application.

[0021] Because the lithium-ion battery of the present invention uses the above-mentioned negative electrode material, the lithium-ion battery has both high energy density and high rate performance.

[0022] The electrical device of the present invention has excellent electrochemical performance due to the use of the aforementioned lithium-ion battery. Attached Figure Description

[0023] To more clearly illustrate the solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a SEM image of the negative electrode material prepared in Example 1 of this application;

[0025] Figure 2 This is a graph showing the initial charge-discharge capacity of the negative electrode material prepared in Example 4 of this application;

[0026] Figure 3 This is a charge-discharge rate curve of the negative electrode material prepared in Example 4 of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention. In the present invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0028] To address the technical problem that existing anode materials cannot simultaneously achieve high energy density and excellent rate performance, this application provides an anode material that satisfies the following conditions:

[0029] (1) Where T is the tap density of the negative electrode material, in g / cm³. 3 S is the specific surface area of ​​the negative electrode material, in m². 2 / g, where P is the compacted density of the negative electrode material at 5t, in g / cm³. 3 G is the degree of graphitization of the negative electrode material; when Within the aforementioned range, the anode material simultaneously exhibits high energy density and high rate performance. If If the ratio is too small, the surface disorder of the negative electrode material is low, the compaction density is high, and the tap density is low, resulting in insufficient rate performance and a bias towards high energy density materials; if If the ratio is too large, the surface disorder of the negative electrode material is high, the compaction density is low, the tap density is high, the energy density is insufficient, and it tends to be a high-rate material.

[0030] For example, It can be any value between 80, 100, 120, 150, 170, 200, 220, 250 or 80-250.

[0031] (2) The T is 0.8 g / cm³. 3 -1.0 g / cm 3 When the tap density of the negative electrode material is within the above range, it can result in a lower internal resistance and allow for sufficient electrolyte wetting, which is beneficial for the rapid insertion and extraction of lithium ions and improves rate performance and energy density. If the tap density of the negative electrode material is too low, there will be insufficient contact between particles, leading to an increase in the internal resistance of the electrode. On the other hand, an excessively high tap density will make electrolyte wetting difficult, increase the resistance to lithium ion migration, and affect rate performance. Moreover, an excessively high tap density requires sophisticated equipment and complex processes, which will lead to increased production costs and reduced yield.

[0032] For example, T is 0.8 g / cm³. 3 0.9 g / cm 3 1.0 g / cm 3 Or 0.8 g / cm 3 -1.0 g / cm 3 Any value between.

[0033] (3) The value of S is 2.5 m. 2 / g -5.5 m 2 / g; When the specific surface area of ​​the negative electrode material is within the above range, it can provide a sufficient and efficient electrochemical reaction interface, which is beneficial to improving the rate performance of the battery and can also avoid the occurrence of side reactions, which is beneficial to improving the cycle performance of the battery. If the specific surface area of ​​the negative electrode material is too low, it will lead to a reduction in lithium-ion migration channels and damage the rate performance of the battery. If the specific surface area of ​​the negative electrode material is too high, it will lead to an increase in surface side reactions, consume more electrolyte, and deteriorate the cycle performance of the battery.

[0034] For example, S is 2.5 g / cm³. 3 3 g / cm 3 3.5 g / cm 3 4 g / cm3 4.5 g / cm 3 5 g / cm 3 5.5 g / cm 3 Or 2.5 m 2 / g -5.5 m 2 Any value between / g.

[0035] (4) The P value is 1.7 g / cm³. 3 -1.9 g / cm 3 When the compaction density of the negative electrode material is within the above-mentioned range, the electrode exhibits excellent processing performance. Simultaneously, the suitable pore structure formed within the negative electrode material ensures sufficient electrolyte wetting and rapid lithium ion migration; while the dense packing of active materials is beneficial for improving the battery's energy density. If the compaction density of the negative electrode material is too low, it will affect the electrode's processing performance; if the compaction density of the negative electrode material is too high, it will lead to poor electrolyte wetting and increased polarization.

[0036] For example, P is 1.7 g / cm³. 3 1.8 g / cm 3 1.9 g / cm 3 Or 1.7 g / cm 3 -1.9 g / cm 3 Any value between.

[0037] (5) The value of G is 0.95-0.98. When the graphitization degree of the negative electrode material is within the above range, it has high structural stability, high energy density and excellent rate performance. If the graphitization degree of the negative electrode material is too low, the interlayer structure is incomplete, the structural stability during charge and discharge is poor, which will lead to poor cycle performance of the battery; if the graphitization degree of the negative electrode material is too high, it will lead to a long diffusion path of lithium ions and high resistance, which will limit the rate performance.

[0038] For example, G can be any value between 0.95, 0.96, 0.97, 0.98, or 0.95-0.98.

[0039] This application achieves a balance between the first coulombic efficiency and rate performance of the anode material by controlling its specific surface area and graphitization degree, and by synergistically optimizing the tap density and compaction density of the material, thereby obtaining an anode material with both high energy density and excellent rate performance.

[0040] The inventors believe that pores within graphite particles, defects on the particle surface, and other structures that disrupt the six-membered ring arrangement of graphite can all be considered defects existing within the graphite particles, representing an ideal graphite structure. Properly controlling these defects not only does not degrade the performance of graphite materials but can also improve their electrical properties to some extent. To obtain the optimal graphite defect structure, it is necessary to precisely adjust the overall structural distribution of graphite particles. Through extensive exploratory experiments, the inventors discovered that when the tap density T, specific surface area S, compaction density P, and degree of graphitization G of the negative electrode material satisfy a specific content relationship, and... When the temperature is controlled within the range of 80 to 250, the anode material can fully utilize its structural advantages, achieving both high energy density and excellent rate performance.

[0041] In one embodiment, the D50 of the negative electrode material is 14μm-18μm;

[0042] For example, the D50 of the negative electrode material can be any value between 14μm, 15μm, 16μm, 17μm, 18μm, or 14μm-18μm.

[0043] In one embodiment, the D90 of the negative electrode material is 26μm-38μm.

[0044] For example, the D90 of the negative electrode material can be any value between 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm or 26μm-38μm.

[0045] In one embodiment, the D10 of the negative electrode material is 7μm-10μm.

[0046] For example, the D10 of the negative electrode material can be any value between 7μm, 8μm, 9μm, 10μm, or 7μm-10μm.

[0047] In one embodiment, the (D90-D10) / D50 ratio of the negative electrode material is 1.0-2.0.

[0048] For example, the (D90-D10) / D50 of the negative electrode material is 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or any value between 1.0 and 2.0.

[0049] In one embodiment, the negative electrode material includes a core and a coating layer located on the outer surface of the core, the core comprising microcrystalline graphite and the coating layer comprising amorphous carbon.

[0050] In one embodiment, the specific capacity of the negative electrode material is 356-365 mAh / g.

[0051] In one embodiment, the first-efficiency of the negative electrode material is 90-92.5%.

[0052] This application also provides a method for preparing the aforementioned negative electrode material, comprising:

[0053] Microcrystalline graphite concentrate is crushed and shaped to obtain spheroidized microcrystalline graphite;

[0054] The spheroidized microcrystalline graphite was mixed with an acidic solution and purified to obtain purified microcrystalline graphite.

[0055] The purified microcrystalline graphite is mixed with a coating agent and subjected to carbonization treatment to obtain a negative electrode material, wherein the coating agent includes asphalt.

[0056] In some embodiments, the method for preparing the microcrystalline graphite concentrate includes: crushing and flotation of raw graphite ore to obtain microcrystalline graphite concentrate.

[0057] In one embodiment, the fixed carbon content of the microcrystalline graphite concentrate is 88%-90%; for example, the fixed carbon content of the microcrystalline graphite concentrate is any value between 88%, 89%, 90%, or 88%-90%.

[0058] The (D90-D10) / D50 of the spheroidized microcrystalline graphite is 1.0-2.0. If the particle size distribution of the spheroidized microcrystalline graphite is too small, the preparation cost will increase, and the pore distribution between particles will be uniform, making densification difficult. If the particle size distribution of the spheroidized microcrystalline graphite is too large, it will lead to local differences in the material's performance, affecting the stability and consistency of the performance.

[0059] For example, the (D90-D10) / D50 of spheroidized microcrystalline graphite is 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or any value between 1.0 and 2.0;

[0060] The D50 of the spheroidized microcrystalline graphite is 14μm-16μm. If the particle size of the spheroidized microcrystalline graphite is too small, the preparation cost will increase, and the final anode material particles will be prone to pulverization during cycling, shortening the cycle life. If the particle size of the spheroidized microcrystalline graphite is too large, the particle size of the final anode material will be too large, which will increase the difficulty of battery processing and lengthen the lithium-ion insertion / extraction path, reducing the rate performance of the battery.

[0061] For example, the D50 of spheroidized microcrystalline graphite is 14μm, 15μm, 16μm, or any value between 14μm and 16μm.

[0062] The sphericity of the spheroidized microcrystalline graphite is 0.80-0.85.

[0063] For example, the sphericity of spheroidized microcrystalline graphite is 0.80, 0.81, 0.82, 0.83, 0.84, 0.85 or any value between 0.80 and 0.85.

[0064] In one embodiment, the mass ratio of the spheroidized microcrystalline graphite to the acidic solution is 1:1-3. For example, the mass ratio of the spheroidized microcrystalline graphite to the acidic solution is any value between 1:1, 1:2, 1:3 or 1:1-3.

[0065] The acidic solution includes hydrofluoric acid, hydrochloric acid, and nitric acid, wherein the concentration of hydrofluoric acid in the acidic solution is 30wt%-45wt%, the concentration of hydrochloric acid in the acidic solution is 30wt%-38wt%, and the concentration of nitric acid in the acidic solution is 40wt%-68wt%.

[0066] For example, the concentration of hydrofluoric acid in the acidic solution is any value within the range of 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, or 30wt%-45wt%; the concentration of hydrochloric acid in the acidic solution is any value within the range of 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, or 30wt%-38wt%; and the concentration of nitric acid in the acidic solution is any value within the range of 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 68wt%, or 40wt%-68wt%.

[0067] The purification temperature is 60℃~85℃. If the purification temperature is too low, the reaction rate will be slow, the impurities will be difficult to decompose fully, and the purification effect will be poor. If the purification temperature is too high, the energy consumption and cost will increase, and the difficulty of exhaust gas treatment and environmental risks will also increase.

[0068] The purification time is 8-15 hours;

[0069] For example, the purification time can be any value between 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, or 8-15h.

[0070] The asphalt includes at least one of oil-based asphalt and coal-based asphalt;

[0071] The softening point of the asphalt is 180-250℃. If the softening point of the asphalt is too low, it will cause more pores in the coating layer and more graphite particles to agglomerate, which will not effectively suppress the volume expansion and side reactions of graphite. If the softening point of the asphalt is too high, energy consumption will increase and the coating layer thickness will be uneven, which will easily lead to peeling problems.

[0072] For example, the softening point of asphalt is 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃ or any value between 180℃ and 250℃.

[0073] In one embodiment, the mass ratio of the purified microcrystalline graphite to the coating agent is (88-96):(4-12). If the coating amount is too low, a continuous and dense coating layer cannot be formed on the surface of the graphite particles, affecting the first efficiency and cycle life. If the coating amount is too high, the amorphous carbon layer is too thick, increasing the resistance to lithium ion transport and reducing the rate performance.

[0074] For example, the mass ratio of purified microcrystalline graphite to coating agent is any value between 88:12, 89:11, 90:10, 91:9, 92:8, 93:7, 94:6, 95:5, 96:4 or (88-96):(4-12).

[0075] The carbonization temperature is 1150℃-2400℃. If the carbonization temperature is too low, the asphalt will not be carbonized sufficiently and a dense protective structure cannot be formed. If the carbonization temperature is too high, the amorphous carbon will transform into graphitized carbon, losing the buffering effect of amorphous carbon, affecting the cycle performance, and increasing energy consumption.

[0076] For example, the carbonization temperature can be any value between 1150℃, 1200℃, 1300℃, 1400℃, 1500℃, 1600℃, 1700℃, 1800℃, 1900℃, 2000℃, 2100℃, 2200℃, 2300℃, 2400℃, or 1150℃-2400℃.

[0077] The carbonization process takes 3-13 hours. If the carbonization time is too short, the asphalt will not be fully carbonized and a dense protective structure cannot be formed. If the carbonization time is too long, energy consumption and cost will increase, the crystal structure of the graphite matrix will be altered, and the electrochemical performance will deteriorate.

[0078] For example, the carbonization time can be any value between 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, or 3-13h.

[0079] This application also provides a lithium-ion battery, which includes the negative electrode material described above or a negative electrode material prepared by the method described above.

[0080] This application also provides an electrical device, which includes the lithium-ion battery described above.

[0081] The present application will be further described below through specific embodiments. Unless otherwise specified, the experimental materials used in the embodiments can be purchased from conventional biochemical reagent companies.

[0082] I. Preparation of Anode Materials

[0083] Example 1

[0084] Example 1 provides a negative electrode material, the preparation method of which includes:

[0085] (1) The graphite ore is crushed and floated to obtain microcrystalline graphite concentrate, which has a fixed carbon content of 90%.

[0086] (2) The microcrystalline graphite concentrate is crushed and shaped to obtain spheroidized microcrystalline graphite. The (D90-D10) / D50 of the spheroidized microcrystalline graphite is 1.42, and the D50 of the spheroidized microcrystalline graphite is 15 micrometers.

[0087] (3) The spheroidized microcrystalline graphite obtained in step (2) is mixed with an acidic solution for purification. The mass ratio of spheroidized microcrystalline graphite to acidic solution is 1:3. The acidic solution includes hydrofluoric acid, hydrochloric acid and nitric acid. The concentration of hydrofluoric acid in the acidic solution is 40wt%, the concentration of hydrochloric acid is 35wt%, and the concentration of nitric acid is 50wt%. The purification temperature is 70℃ and the purification time is 10h. After washing and drying, purified microcrystalline graphite with a carbon content >99.9% is obtained.

[0088] (4) The purified microcrystalline graphite obtained in step (3) is mixed with oil-based asphalt with a softening point of 180°C at a mass ratio of 96:4. Then carbonization is carried out at a temperature of 1150°C for 13 hours. The carbonization is carried out under a nitrogen atmosphere. After sieving and demagnetizing, microcrystalline graphite anode material is obtained.

[0089] SEM image of the negative electrode material prepared in Example 1 is shown below. Figure 1 As shown.

[0090] Example 2

[0091] The difference between Example 2 and Example 1 is that the mass ratio of purified microcrystalline graphite to oil-based asphalt in step (4) is 92:8. The rest is the same as in Example 1.

[0092] Example 3

[0093] The difference between Example 3 and Example 1 is that the mass ratio of purified microcrystalline graphite to oil-based asphalt in step (4) is 90:10. The rest is the same as in Example 1.

[0094] Example 4

[0095] The difference between Example 4 and Example 1 is that the softening point of the oil-based asphalt used in step (4) is 250°C. The rest is the same as in Example 1.

[0096] Example 5

[0097] The difference between Example 5 and Example 1 is that the mass ratio of purified microcrystalline graphite to oil-based asphalt in step (4) is 94:6. The rest is the same as in Example 1.

[0098] Example 6

[0099] The difference between Example 6 and Example 3 is that the (D90-D10) / D50 of the spheroidized microcrystalline graphite in step (2) is 1.78. The rest is the same as in Example 3.

[0100] Example 7

[0101] The difference between Example 7 and Example 1 is that the mass ratio of purified microcrystalline graphite to oil-based asphalt in step (4) is 88:12. The rest is the same as in Example 1.

[0102] Example 8

[0103] The difference between Example 8 and Example 5 is that the (D90-D10) / D50 of the spheroidized microcrystalline graphite in step (2) is 1.32. The rest is the same as in Example 5.

[0104] Example 9

[0105] The difference between Example 9 and Example 1 is that the (D90-D10) / D50 ratio of the spheroidized microcrystalline graphite in step (2) is 1.57, and the softening point of the oil-based asphalt used in step (4) is 150℃. The rest is the same as in Example 1.

[0106] Example 10

[0107] The difference between Example 10 and Example 3 is that the softening point of the oil-based asphalt used in step (4) is 250°C. The rest is the same as in Example 3.

[0108] Example 11

[0109] The difference between Example 11 and Example 3 is that the carbonization temperature in step (4) is 2400℃. The rest is the same as in Example 3.

[0110] Example 12

[0111] The difference between Example 12 and Example 2 is that the (D90-D10) / D50 ratio of the spheroidized microcrystalline graphite in step (2) is 1.6. The rest is the same as in Example 2.

[0112] Example 13

[0113] The difference between Example 13 and Example 1 is that the mass ratio of purified microcrystalline graphite to oil-based asphalt in step (4) is 88:12, and the softening point of the oil-based asphalt is 250℃. The rest is the same as in Example 1.

[0114] Example 14

[0115] The difference between Example 14 and Example 2 is that the softening point of the oil-based asphalt used in step (4) is 250°C. The rest is the same as in Example 2.

[0116] Example 15

[0117] The difference between Example 15 and Example 2 is that the carbonization temperature in step (4) is 2400℃. The rest is the same as in Example 2.

[0118] Example 16

[0119] The difference between Example 16 and Example 3 is that the D50 of the spheroidized microcrystalline graphite in step (2) is 11 micrometers. The rest is the same as in Example 3.

[0120] Example 17

[0121] The difference between Example 17 and Example 3 is that the D50 of the spheroidized microcrystalline graphite in step (2) is 19 micrometers. The rest is the same as in Example 3.

[0122] Example 18

[0123] The difference between Example 18 and Example 9 is that the (D90-D10) / D50 of the spheroidized microcrystalline graphite in step (2) is 0.99. The rest is the same as in Example 9.

[0124] Example 19

[0125] The difference between Example 19 and Example 1 is that the (D90-D10) / D50 ratio of the spheroidized microcrystalline graphite in step (2) is 2.03. The rest is the same as in Example 1.

[0126] Comparative Example 1

[0127] The difference between Comparative Example 1 and Example 1 is that: in step (3), no acidic solution is added during purification, and a high-temperature purification method is used, in which spheroidized microcrystalline graphite is purified at 2800°C under a chlorine atmosphere; in step (4), the mass ratio of purified microcrystalline graphite to oil-based asphalt is 98:2. The rest is the same as in Example 1.

[0128] Comparative Example 2

[0129] The difference between Comparative Example 2 and Example 1 is that: in step (3), no acidic solution is added during purification, and a high-temperature purification method is used, in which spheroidized microcrystalline graphite is purified at 2800°C under a chlorine atmosphere; in step (4), the mass ratio of purified microcrystalline graphite to oil-based asphalt is 88:12. The rest is the same as in Example 1.

[0130] Comparative Example 3

[0131] The difference between Comparative Example 3 and Example 1 is that: in step (3), no acidic solution is added during purification, and a high-temperature purification method is used, in which spheroidized microcrystalline graphite is purified at 2800°C under a chlorine atmosphere; in step (4), the mass ratio of purified microcrystalline graphite to oil-based asphalt is 99:1. The rest is the same as in Example 1.

[0132] Comparative Example 4

[0133] The difference between Comparative Example 4 and Example 1 is that: in step (3), no acidic solution is added during purification, and a high-temperature purification method is used, in which spheroidized microcrystalline graphite is purified at 2800°C under a chlorine atmosphere; in step (4), the mass ratio of purified microcrystalline graphite to oil-based asphalt is 86:14, and the softening point of the oil-based asphalt used is 250°C. The rest is the same as in Example 1.

[0134] Comparative Example 5

[0135] The difference between Comparative Example 5 and Example 1 is that: in step (3), no acidic solution is added during purification, and a high-temperature purification method is used, in which spheroidized microcrystalline graphite is purified at 2800°C under a chlorine atmosphere; in step (4), the mass ratio of purified microcrystalline graphite to oil-based asphalt is 97:3, and the softening point of the oil-based asphalt used is 150°C. The rest is the same as in Example 1.

[0136] Comparative Example 6

[0137] The difference between Comparative Example 6 and Example 1 is that the mass ratio of purified microcrystalline graphite to oil-based pitch in step (4) is 99:1, and the carbonization temperature is 2400℃. The rest is the same as Example 1.

[0138] Comparative Example 7

[0139] The difference between Comparative Example 7 and Example 1 is that the mass ratio of purified microcrystalline graphite to oil-based pitch in step (4) is 99:1. The rest is the same as in Example 1.

[0140] Comparative Example 8

[0141] The difference between Comparative Example 8 and Example 1 is that the mass ratio of purified microcrystalline graphite to oil-based pitch in step (4) is 97:3, and the carbonization temperature is 2400℃. The rest is the same as Example 1.

[0142] II. Testing the physical properties of the negative electrode material

[0143] The physical properties of the negative electrode materials in the examples and comparative examples were tested under the same conditions. The specific test methods are as follows.

[0144] The tap density T was tested using a Dual Autotap tap density analyzer from Anton Paar Shanghai Trading Co., Ltd., in accordance with Appendix M of GB / T 24533-2019.

[0145] The specific surface area S was tested using a precision high-performance (dynamic) specific surface area tester in accordance with GB / T 19587-2017 7.2.

[0146] The compaction density P was tested using a Shenzhen Sansi Zongheng UTM7305 automatic powder compaction density meter (pressure set to 5T) in accordance with Appendix L of GB / T 24533-2019 Analysis Methods for Graphite Anode Materials of Lithium-ion Batteries.

[0147] The degree of graphitization G was measured using a Panaco Xpert X-ray diffractometer. First, the corrected diffraction angle 2θ of the (002) plane was obtained using the internal standard method, and the d002 of the sample was calculated according to the Bragg equation. Then, the degree of graphitization was calculated by substituting the values ​​into the formula. .

[0148] Particle size was measured using a Malvern 3000 laser particle size analyzer in accordance with Appendix A of GB / T 24533-2019.

[0149] The formula for calculating Span is Span = (D90 - D10) / D50.

[0150] The physical performance data of the negative electrode materials in the examples and comparative examples are shown in Table 1.

[0151] Table 1. Comparison of physical properties of the negative electrode materials in the examples and comparative examples.

[0152]

[0153] III. Testing the Electrochemical Performance of Anode Materials

[0154] The negative electrode materials of the examples and comparative examples were assembled into batteries under the same conditions, and their electrochemical performance was tested under the same test conditions.

[0155] Battery preparation and testing methods:

[0156] The negative electrode materials prepared in Examples 1-19 and Comparative Examples 1-8 were used in an N-type ... The mixture was magnetically stirred in a methylpyrrolidone solution (NMP, AR) for 8 hours to ensure homogeneity. The resulting slurry was coated onto copper foil and vacuum dried at 60°C to serve as the working electrode. Lithium metal was used as both the counter and reference electrodes, Celgard 2325 was used as the separator, and a 1 mol·L⁻¹ electrolyte was employed. 1 LiPF6 The CR2016 button cell was assembled in a glove box filled with high-purity argon using EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) in a volume ratio of 1:1:1. Four cells were prepared for each sample.

[0157] The initial discharge capacity / initial discharge efficiency test was conducted on a LAND battery tester under the following charging and discharging conditions: rest for 2 hours; discharge: 0.1C to 0.005V, 0.09C, 0.08C…0.02C to 0.001V; rest for 15 minutes; charge: 0.1C to 1.5V; rest for 15 minutes.

[0158] The coin charge rate test conditions are as follows: ① 0.1C discharge to 0.01V, constant voltage for 5 hours; ② 0.1C charge to 1.5V; ③ 0.2C discharge to 0.01V, constant voltage for 0.01C; ④ 0.2C charge to 1.5V; ⑤ 1C discharge to 0.01V, constant voltage for 0.01C; ⑥ 2C discharge to 0.01V.

[0159] The electrochemical performance test results of the examples and comparative examples are shown in Table 2.

[0160] Table 2. Comparison of electrochemical energy between the examples and comparative examples.

[0161]

[0162] From Table 2 and Figure 2 , Figure 3As can be seen from the comparison between Example 1 and Comparative Example 1, Comparative Example 1 has a lower first-efficiency and a lower rate of return. This is because the coating amount of Comparative Example 1 is less than that of Example 1, the graphite surface has more defects, the amount of side reactions increases, and the crystal structure changes after high-temperature purification, which leads to changes in the lithium ion transport path and a deterioration in rate performance.

[0163] By comparing Example 7 and Comparative Example 2, it can be found that the difference in magnification of Comparative Example 2 is due to the fact that, under the same asphalt coating amount, high-temperature purification rearranges the crystal structure and removes impurities more thoroughly, but reduces the isotropy of the crystal, resulting in a decrease in magnification performance.

[0164] By comparing Example 2 and Comparative Example 3, it can be found that Comparative Example 3 has a low first-efficiency and poor rate performance. The reason is that the coating amount of Comparative Example 3 is less than that of Example 2, the graphite surface has more defects, the amount of side reactions increases, and the crystal structure is changed after high-temperature purification, which leads to changes in the lithium ion transport path and thus a deterioration in rate performance.

[0165] By comparing Example 1 and Comparative Example 4, it can be found that Example 1 has high capacity, high initial efficiency, and good rate capability, while Comparative Example 4 has low capacity, low initial efficiency, and poor rate capability. The reason is that the coating amount of Comparative Example 4 is more than that of Example 1, the asphalt softening point is higher, the graphite surface has more defects, the amount of side reactions is increased, and the crystal structure is changed after high temperature purification, which leads to changes in the lithium ion transport path and a deterioration in rate capability.

[0166] By comparing Example 1 and Comparative Example 5, it can be found that the capacity first-efficiency ratio of Example 1 is higher than that of Comparative Example 5. The reason is that the coating amount of Comparative Example 5 is slightly lower than that of Example 1, the softening point is lower, and the crystal structure is changed after high-temperature purification. The problem of low first-efficiency caused by low coating amount is made up by high-temperature purification, so the capacity first-efficiency ratio is only slightly lower than that of Example 1, and the ratio is worse than that of Example 1.

[0167] By comparing Example 1 and Comparative Example 6, it can be found that the first-efficiency capacity of Example 1 is higher than that of Comparative Example 6. The reason is that the coating amount of Comparative Example 6 is much lower than that of Example 1. The insufficient coating amount results in the graphite surface not being completely coated, forming an uneven SEI film. In addition, the carbonization temperature is too high, resulting in changes in the amorphous carbon structure on the surface, thus deteriorating the first-efficiency capacity and rate performance.

[0168] By comparing Example 1 and Comparative Example 7, it can be found that the first-efficiency ratio of Example 1 is higher than that of Comparative Example 7. The reason is that the coating amount of Comparative Example 7 is lower than that of Example 1. The insufficient coating amount results in the graphite surface not being completely coated, forming an uneven SEI film, which leads to a much lower first-efficiency ratio than that of Example 1.

[0169] By comparing Example 1 and Comparative Example 8, it can be found that the first-efficiency ratio of Example 1 is higher than that of Comparative Example 8. The reason is that the coating amount of Comparative Example 8 is lower than that of Example 1. The insufficient coating amount results in the graphite surface not being completely coated, forming an uneven SEI film. In addition, the carbonization temperature is too high, resulting in changes in the amorphous carbon structure on the surface, thus causing the first-efficiency ratio of the capacity to be much lower than that of Example 1.

[0170] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A negative electrode material, characterized in that, The negative electrode material includes a core and a coating layer located on the outer surface of the core. The core includes microcrystalline graphite, and the coating layer includes amorphous carbon. The negative electrode material satisfies the following conditions: (1) 80≤1000 T / (S) P G)≤200, where T is the tap density of the negative electrode material, in g / cm³. 3 S is the specific surface area of ​​the negative electrode material, in m². 2 / g, where P is the compacted density of the negative electrode material at 5t, in g / cm³. 3 G represents the degree of graphitization of the negative electrode material; (2) The T is 0.8 g / cm³. 3 -1.0 g / cm 3 ; (3) The S is 3 m 2 / g -5.5 m 2 / g; (4) The P value is 1.7 g / cm³. 3 -1.9 g / cm 3 ; (5) The value of G is 0.95-0.

98.

2. The negative electrode material according to claim 1, characterized in that, The D50 of the negative electrode material is 14μm-18μm; And / or, the D90 of the negative electrode material is 26μm-38μm; And / or, the D10 of the negative electrode material is 7μm-10μm.

3. The negative electrode material according to claim 2, characterized in that, The ratio of (D90-D10) / D50 of the negative electrode material is 1.0-2.

0.

4. A method for preparing a negative electrode material as described in any one of claims 1-3, characterized in that, include: Microcrystalline graphite concentrate is crushed and shaped to obtain spheroidized microcrystalline graphite; The spheroidized microcrystalline graphite was mixed with an acidic solution and purified to obtain purified microcrystalline graphite. The purified microcrystalline graphite is mixed with a coating agent and subjected to carbonization treatment to obtain a negative electrode material, wherein the coating agent includes asphalt.

5. The method for preparing the negative electrode material according to claim 4, characterized in that, The fixed carbon content of the microcrystalline graphite concentrate is 88%-90%; And / or, the (D90-D10) / D50 of the spheroidized microcrystalline graphite is 1.0-2.0; And / or, the D50 of the spheroidized microcrystalline graphite is 14 μm - 16 μm; And / or, the sphericity of the spheroidized microcrystalline graphite is 0.80-0.

85.

6. The method for preparing the negative electrode material according to claim 4, characterized in that, The mass ratio of the spheroidized microcrystalline graphite to the acidic solution is 1:1-3; And / or, the acidic solution includes hydrofluoric acid, hydrochloric acid, and nitric acid, wherein the concentration of hydrofluoric acid in the acidic solution is 30wt%-45wt%, the concentration of hydrochloric acid in the acidic solution is 30wt%-38wt%, and the concentration of nitric acid in the acidic solution is 40wt%-68wt%. And / or, the purification temperature is 60℃-85℃; And / or, the purification time is 8-15 hours; And / or, the asphalt includes at least one of oil-based asphalt and coal-based asphalt; And / or, the softening point of the asphalt is 180-250℃.

7. The method for preparing the negative electrode material according to any one of claims 4-6, characterized in that, The mass ratio of the purified microcrystalline graphite to the coating agent is (88-96):(4-12). And / or, the carbonization treatment temperature is 1150-2400℃; And / or, the carbonization treatment time is 3-13 hours.

8. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode material according to any one of claims 1-3 or the negative electrode material prepared by the preparation method of the negative electrode material according to any one of claims 4-7.

9. An electrical-related device, characterized in that, The electrical equipment includes the lithium-ion battery as described in claim 8.

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