Graphite negative electrode material and preparation method thereof, and lithium ion battery
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI SHANSHAN NEW MATERIAL CO LTD
- Filing Date
- 2023-12-29
- Publication Date
- 2026-07-31
AI Technical Summary
The existing graphite anode materials have problems with insufficient high-temperature performance and long-cycle performance in lithium-ion batteries, especially when used in energy storage systems, with poor kinetic performance and reversible capacity.
By selecting petroleum coke or needle coke with a mosaic structure of 30% to 80% as raw materials, it is subjected to crushing, shaping, heat treatment and graphitization treatment, and the relationship between Raman median L and graphitization G is controlled to be 1.5<80 (L-G/17)<6, the spherical degree, convexity and aspect ratio are optimized to form a spherical single-grain graphite negative electrode material.
It improves the high-temperature performance and long-cycle performance of graphite negative electrode materials, reduces active sites, reduces side reactions, ensures sufficient kinetic performance, improves charge and discharge cycle performance and storage capacity, and extends the life of lithium batteries.
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Figure CN122497642A_ABST
Abstract
Description
Graphite negative electrode material and preparation method thereof, and lithium ion battery Technical Field
[0001] The present application relates to the field of lithium-ion batteries, and in particular to a graphite negative electrode material and a preparation method thereof, and a lithium-ion battery. Background Art
[0002] In recent years, global temperatures have continued to rise. To combat climate change, countries around the world are transitioning their energy mix toward a low-carbon future. Large-scale utilization of renewable energy, such as wind and solar power, is a key path to this transition. Due to the intermittent nature of renewable energy generation, the widespread growth of wind and solar power projects has led to a rapid increase in demand for ancillary services such as output smoothing, peak shaving, and frequency regulation. The importance and urgency of energy storage are becoming increasingly prominent.
[0003] With the rapid expansion of new energy capacity, new energy storage technologies, primarily electrochemical energy storage, have seen rapid growth in recent years, with their installed base increasing. After years of development, lithium-ion batteries have become the most comprehensive battery system in terms of overall performance and technological maturity, making them ready for large-scale deployment.
[0004] Graphite anode materials are the most widely used in lithium-ion batteries. Rapidly developing graphite anode materials suitable for energy storage systems is an urgent task.
[0005] Summary of the Invention
[0006] On the one hand, the present application provides a method for preparing a graphite negative electrode material, comprising: selecting a raw material, wherein the raw material is petroleum coke or needle coke or a mixture of petroleum coke and needle coke, and the mosaic structure accounts for 30% to 80% of the raw material; crushing and shaping the raw material to form a first powder; heat treating the first powder to form a second powder; and graphitizing the second powder to form a single-particle graphite negative electrode material, wherein the relationship between the Raman median L of the graphite negative electrode material and the graphitization degree G of the graphite negative electrode material is: 1.5<80(LG / 17)<6.
[0007] In some embodiments of the present application, the raw material has a volatile matter content of 4-13%, an ash content of ≤0.5%, and a sulfur content of ≤1.5%.
[0008] In some embodiments of the present application, the grindability index of the raw material is 60-120.
[0009] In some embodiments of the present application, the first median particle size of the first powder is D150, the first sphericity is Q150, and the first width-to-length ratio is K150, then: 3<(D150+1+15Q150) / 6<5; 0<(D150-150(K150-0.6))<8.
[0010] In some embodiments of the present application, the convexity of the first powder is T150, then: 5<(D150+25T150) / 7<8.
[0011] In some embodiments of the present application, the second median particle size of the second powder is D250, the second sphericity is Q250, and the second width-to-length ratio is K250, then: 3<(D250+1+125(Q250-0.75)) / 6<5; 0<[D250-162(K250-0.62)]<6.
[0012] In some embodiments of the present application, the second convexity of the second powder is T250, then: 4<(D250×8+85T250) / 29<7.
[0013] In some embodiments of the present application, the relationship between the Raman median L of the graphite negative electrode material and the electrode OI value I of the graphite negative electrode material must satisfy: 3<(I / 5+20L)<5; and / or the relationship between the Raman median L of the graphite negative electrode material and the reversible gram capacity R of the graphite negative electrode material must satisfy: 0<(0.15 / L-LR / 64)<3.
[0014] In some embodiments of the present application, the equipment for graphitization treatment is an Acheson crucible furnace, and the process conditions for graphitization treatment are: power supply time is 30h~50h, and power supply amount is 30000~48000Kwh.
[0015] In some embodiments of the present application, in the graphitization process, the power transmission power starts to increase from the starting power, and after increasing to the set power, the set power is maintained for a specific time until the power transmission amount is reached, wherein the starting power transmission power is 1500Kw-4000Kw, the rate of increase of the power transmission power is 300-1200kw / h, the set power is 10000Kw-15000kw, and the specific time is greater than one third of the total power transmission time.
[0016] Another aspect of the present application provides a graphite negative electrode material. The relationship between the Raman median L of a single particle of the graphite negative electrode material and the graphitization degree G of the graphite negative electrode material must satisfy: 1.5<80(LG / 17)<6.
[0017] In some embodiments of the present application, the relationship between the Raman median L of the graphite negative electrode material and the electrode OI value I of the graphite negative electrode material must satisfy: 3<(I / 5+20L)<5.
[0018] In some embodiments of the present application, the relationship between the Raman median L of the graphite negative electrode material and the reversible gram capacity R of the graphite negative electrode material must satisfy: 0<(0.15 / L-LR / 64)<3.
[0019] An embodiment of the present application further provides a lithium-ion battery, comprising a negative electrode, wherein the negative electrode is made of any one of the negative electrode materials described in the embodiment of the present application.
[0020] Compared to the prior art, the method for preparing the graphite anode material described in the embodiments of this application forms single-particle graphite anode material by subjecting the raw materials to pulverization and shaping, heat treatment, and graphitization. By screening the raw materials, the proportion of mosaic structures in the raw materials is selected to be 30% to 80%, so that the relationship between the Raman median number L and the degree of graphitization G of the graphite anode material produced is: 1.5 < 80 (LG / 17) < 6.
[0021] Furthermore, during the preparation process of the single-particle graphite negative electrode material, the relationship between the sphericity, convexity, aspect ratio and median particle size of the first powder and the second powder is matched, so that the shape of the prepared graphite negative electrode material is more spherical, the surface is smooth, complete, rounded, and has fewer sharp points. Such graphite negative electrode materials are used in lithium batteries, with fewer active sites and fewer side reactions, thereby making the high temperature, storage and long cycle performance of the lithium battery better.
[0022] Furthermore, the present application matches the relationship between the Raman median and the degree of graphitization of the single-particle graphite negative electrode material, the relationship between the Raman median and the OI value, and the relationship between the Raman median and the reversible gram capacity, thereby ensuring that the internal grain integrity of the graphite negative electrode material is high, the interlayer spacing is large, and there are few surface defects and low disorder, so that the negative electrode material has sufficient kinetic performance during the charge and discharge process and will not decay due to lithium precipitation; the charge and discharge cycle performance, storage capacity, and high temperature resistance of the battery product made of the graphite negative electrode material are better, and the overall performance is better.
[0023] The present application controls the specific surface area of the graphite negative electrode material by matching the relationship between the median particle size of the graphite negative electrode material and the specific surface area of the graphite negative electrode material, so that the battery cell made of the graphite negative electrode material has good SEI film stability during the cycle, and at the same time has high reversible specific capacity and compaction, and is applied to lithium batteries with the characteristics of long life. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The following figures describe in detail exemplary embodiments disclosed in this application. Identical reference numerals denote similar structures in several views of the drawings. Those skilled in the art will appreciate that these embodiments are non-limiting, exemplary embodiments, and that the drawings are for illustration and description purposes only and are not intended to limit the scope of this application. Other embodiments may also achieve the same inventive intent as described in this application. It should be understood that the drawings are not drawn to scale. Among them:
[0025] FIG1 is a schematic diagram of a process flow of a method for preparing a graphite negative electrode material according to an embodiment of the present application;
[0026] FIG2 is an image of the raw material of the mosaic structure under an optical microscope. DETAILED DESCRIPTION
[0027] The following description provides specific application scenarios and requirements of the present application, with the purpose of enabling those skilled in the art to make and use the content of this application. Various local modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of this application. Therefore, this application is not limited to the embodiments shown, but is intended to be of the widest scope consistent with the claims.
[0028] The present invention provides a method for preparing a graphite negative electrode material, as shown in FIG1 , comprising:
[0029] Step S1, selecting a raw material, wherein the raw material is petroleum coke or needle coke or a mixture of petroleum coke and needle coke, and the mosaic structure accounts for 30% to 80% of the raw material;
[0030] Step S2, crushing and shaping the raw materials to form a first powder;
[0031] Step S3, heat-treating the first powder to form a second powder;
[0032] Step S4: graphitizing the second powder to form a single-particle graphite negative electrode material. The relationship between the Raman median L of the graphite negative electrode material and the graphitization degree G of the graphite negative electrode material is: 1.5<80(LG / 17)<6.
[0033] Each process step is described in further detail below.
[0034] Step S1: Select a raw material. The raw material is petroleum coke, needle coke, or a mixture of petroleum coke and needle coke, and the mosaic structure accounts for 30% to 80% of the raw material. Optionally, the mosaic structure accounts for 40% to 60% of the raw material, for example, 45%, 50%, 55%, etc. Figure 2 shows an optical microscope image of the raw material with the mosaic structure. The particle size of the mosaic structure is less than 30 μm. The raw material may also include long fiber structures or flaky structures.
[0035] The graphite negative electrode material described in the embodiment of the present application is prepared using raw materials with a mosaic structure accounting for 30% to 80%, and the OI value of the graphite negative electrode material formed is low, which is beneficial to improving the kinetic properties of the graphite negative electrode material. However, if the proportion of the mosaic structure is too high, it will hinder the rearrangement of the grains during the graphitization process, and may cause the reversible gram capacity of the formed graphite negative electrode material to be low and the compaction density of the electrode prepared using the graphite negative electrode material to be low, which is not conducive to industrial application. If the proportion of the mosaic structure is too small, although it is easier to form an ordered graphite material during the graphitization process, it will cause the formed graphite negative electrode material to have poor kinetic properties and large expansion. Therefore, raw materials with a mosaic structure accounting for 30% to 80% are selected. While ensuring the kinetic properties of the formed graphite negative electrode material, the reversible gram capacity and compaction density of the graphite negative electrode material can also be guaranteed.
[0036] The raw material is raw material coke suitable for preparing single-particle long-cycle graphite negative electrode materials. Furthermore, the raw material has a volatile matter of 4-13%, an ash content of ≤0.5%, a sulfur content of ≤1.5%, and a grindability index of 60-120.
[0037] In some embodiments of the present application, in order to ensure the coating effect of the carbon coating layer in the formed negative electrode material, the raw material is further selected from petroleum coke, needle coke, or a mixture of petroleum coke and needle coke with a volatile matter of 4-13%, an ash content of ≤0.5%, and a sulfur content of ≤1.5%.
[0038] Volatile matter refers to the mass percentage of organic matter and minerals in a raw material that decomposes into gases and liquids when heated at a certain temperature, isolated from air. Ash content refers to the inorganic matter remaining after a series of physical and chemical changes at high temperatures, resulting in the volatilization of organic components. Ash is always the solid portion of a substance, not the gas or liquid portion.
[0039] In some embodiments of the present application, the grindability index of the raw material is 60-120, and the grindability index in the embodiments of the present application is 70-130, which is used to characterize the crushing and shaping performance of the raw material.
[0040] Step S2, crushing and shaping the raw materials to form a first powder; the main purpose of the crushing process is to crush the raw materials to achieve a required median particle size.
[0041] In some embodiments of the present application, the first median particle size of the first powder is D150, the first sphericity is Q150, and the first width-to-length ratio is K150, then: 3<(D150+1+15Q150) / 6<5; 0<(D150-150(K150-0.6))<8.
[0042] In some embodiments of the present application, the convexity of the first powder is T150, then: 5<(D150+25T150) / 7<8.
[0043] The first sphericity described in the present embodiment is the ratio of the circumference of the equivalent projected circle of the first powder to its actual circumference. The first sphericity data of multiple first powder samples tested are cumulatively distributed, and the particle size corresponding to the cumulative first sphericity distribution percentage reaching 50% is Q150.
[0044] In this embodiment, the first convexity is the ratio of the projected area of the first powder particles to the total area after the particles fill the recesses. It is used to indicate the degree of compactness of the first powder particles. The first convexity data from multiple first powder samples is cumulatively distributed. The particle size corresponding to the cumulative first convexity distribution percentage reaching 50% is T150.
[0045] In this embodiment of the present application, the first aspect ratio is the ratio of the FERET diameter with the shortest distance among all tangent parallel lines of the first powder to the FERET diameter with the greatest distance among all tangent parallel lines. The first aspect ratio data of multiple samples of the first powder are cumulatively distributed. The particle size corresponding to the cumulative first aspect ratio distribution percentage reaching 50% is K150.
[0046] Step S3: heat-treating the first powder to form a second powder. The purpose of heat-treating the first powder is to remove some impurities in the first powder. After the heat treatment process, the median particle size and surface structure of the second powder formed are somewhat reduced relative to the first powder. However, the embodiment of the present application controls the heat treatment process so that the relationship between the second median particle size (D250), the second sphericity (Q250), the second aspect ratio (K250), and the second convexity (T250) of the second powder still meets the process requirements.
[0047] In some embodiments of the present application, the second median particle size of the second powder is D250, the second sphericity is Q250, and the second width-to-length ratio is K250, then: 3<(D250+1+125(Q250-0.75)) / 6<5; 0 <[D250-162(K250-0.62)]<6.
[0048] In some embodiments of the present application, the second convexity of the second powder is T250, then: 4<(D250×8+85T250) / 29<7.
[0049] Among them, the methods for obtaining the second median particle size D250, the second sphericity Q250, the second width-to-length ratio K250 and the second convexity T250 are respectively the same as the methods for obtaining the first median particle size D150, the first sphericity Q150, the first width-to-length ratio K150 and the first convexity T150.
[0050] The equipment for heat treating the first powder includes a tunnel kiln, a rotary kiln, a brick kiln, a roller kiln, etc. The heat treatment temperature can be carried out at a temperature of 500-1400°C. Optionally, the heat treatment temperature can be 700-1200°C.
[0051] During the preparation process of the single-particle graphite negative electrode material, the relationship between the sphericity, convexity, aspect ratio and median particle size of the first powder and the second powder is matched, so that the shape of the prepared graphite negative electrode material is more spherical, the surface is smooth, complete, rounded and has fewer tips. Such graphite negative electrode material is used in lithium batteries, with fewer active sites and fewer side reactions, thereby making the high-temperature, storage and long-cycle performance of the lithium battery better.
[0052] Step S4: graphitizing the second powder to form a single-particle graphite negative electrode material. The relationship between the Raman median L of the graphite negative electrode material and the graphitization degree G of the graphite negative electrode material is: 1.5<80(LG / 17)<6.
[0053] The graphitization process described in the embodiments of this application involves pyrolyzing the heat-treated second powder at high temperatures to form a highly crystalline graphite structure. During the graphitization process, as the temperature rises, impurities such as hydrogen and oxygen in the raw materials are released, leaving the carbon atoms rearranged from disorder to order, reducing the molecular spacing, and gradually developing an ordered graphite lattice structure. This structural change gives the graphite material improved electrical conductivity and cyclic stability.
[0054] In the embodiment of the present application, the equipment for graphitization treatment can be an Acheson crucible furnace, an inner string furnace, a continuous graphitization furnace, or a box furnace, and the graphitization time is 15 to 60 hours.
[0055] Furthermore, the reversible gram capacity, graphitization degree and Raman median of the formed graphite negative electrode material are controlled by adjusting the power supply amount, power supply time, constant temperature power and constant temperature power time in the graphitization treatment process, the structural uniformity of the entire furnace of graphite negative electrode material is adjusted by controlling the graphitization treatment process, and the specific surface area of the formed graphite negative electrode material is controlled by controlling the discharge temperature of the product formed in the graphitization treatment process.
[0056] In the embodiment of the present application, when the materials at different positions in the whole furnace of graphite negative electrode materials are taken to test the reversible gram capacity and graphitization degree, the range of the reversible gram capacity tested by the materials at different positions in the whole furnace of graphite negative electrode materials is less than 10 mAh / g, and the range of the graphitization degree is less than 2%, then it is considered that the uniformity of the whole furnace of graphite negative electrode materials is good.
[0057] The graphitization temperature described in the embodiment of the present application is higher than 2700°C. For example, the graphitization temperature is 2800-3200°C. Optionally, the graphitization temperature is 2900-3100°C.
[0058] In some embodiments of the present application, the graphitization treatment equipment is an Acheson crucible furnace, and the graphitization treatment process conditions are: a power supply time of 30 hours to 50 hours, and a power supply of 30,000 to 48,000 Kwh. For example, the power supply time can be 35 hours, 40 hours, 45 hours, etc., and the power supply can be 35,000 Kwh, 40,000 Kwh, 45,000 Kwh, etc.
[0059] In some embodiments of the present application, in the graphitization process, the power transmission power starts to increase from the starting power, and after increasing to the set power, the set power is maintained for a specific time until the power transmission amount is reached, wherein the starting power transmission power is 1500Kw-4000Kw, the rate of increase of the power transmission power is 300-1200kw / h, the set power is 10000Kw-15000kw, and the specific time is greater than one third of the total power transmission time.
[0060] By controlling the graphitization process, the Raman median of the formed graphite negative electrode material is 0.05 to 0.15, for example, 0.06, 0.07, 0.08, 0.1, 0.12, etc. In some embodiments of the present application, the relationship between the Raman median L of the graphite negative electrode material and the electrode OI value I of the graphite negative electrode material must satisfy the following: 3 < (I / 5 + 20L) < 5. The OI value of the graphite negative electrode material represents the orientation of the graphite grains. When the graphite grain orientation and the Raman median L of the graphite negative electrode material meet the above relationship, the negative electrode graphite material prepared in the embodiments of the present application has small expansion and few surface side reactions.
[0061] In some embodiments of the present application, the relationship between the Raman median L of the graphite negative electrode material and the reversible gram capacity R of the graphite negative electrode material must satisfy: 0<(0.15 / L-LR / 64)<3.
[0062] Another aspect of the present application provides a graphite negative electrode material. The relationship between the Raman median L of a single particle of the graphite negative electrode material and the graphitization degree G of the graphite negative electrode material must satisfy: 1.5<80(LG / 17)<6.
[0063] In some embodiments of the present application, the relationship between the Raman median L of the graphite negative electrode material and the electrode OI value I of the graphite negative electrode material must satisfy: 3<(I / 5+20L)<5. In some embodiments of the present application, the relationship between the Raman median L of the graphite negative electrode material and the reversible gram capacity R of the graphite negative electrode material must satisfy: 0<(0.15 / L-LR / 64)<3.
[0064] The present application matches the relationship between the Raman median and the degree of graphitization of a single-particle graphite negative electrode material, the relationship between the Raman median and the OI value, and the relationship between the Raman median and the reversible gram capacity, thereby ensuring that the internal grain integrity of the graphite negative electrode material is high, the interlayer spacing is large, and there are few surface defects and low disorder, so that the negative electrode material has sufficient kinetic performance during the charge and discharge process and will not decay due to lithium plating; the charge and discharge cycle performance, storage capacity, and high temperature resistance of the battery product made of the graphite negative electrode material are better, and the overall performance is better.
[0065] The present application controls the specific surface area of the graphite negative electrode material by matching the relationship between the median particle size of the graphite negative electrode material and the specific surface area of the graphite negative electrode material, so that the battery cell made of the graphite negative electrode material has good SEI film stability during the cycle, and at the same time has high reversible specific capacity and compaction, and is applied to lithium batteries with the characteristics of long life.
[0066] The present application also provides a graphite negative electrode material, which is prepared using any of the above-mentioned methods for preparing graphite negative electrode materials.
[0067] The following further describes the implementation of the present application based on Reference Examples 1 to 4 and Comparative Example 1.
[0068] Examples 1 to 4:
[0069] Example 1
[0070] Petroleum coke A was selected as the raw material. The main components of petroleum coke A are carbon atoms and hydrogen atoms, with a moisture content of ≤10%, an ash content of ≤1.0%, a volatile matter content of 9-13%, and a sulfur content of ≤1.0%. The mosaic structure of petroleum coke A accounts for 47%;
[0071] Petroleum coke A is mechanically ground and shaped to form a first powder having a median particle size D150 of 13.23 μm. The first powder is heat-treated and shaped in a tunnel kiln to form a second powder at a temperature of 1100°C. The second powder is then graphitized in an Acheson crucible furnace to form a graphite anode material. The total power delivered during the graphitization process is 36,900 kWh, the total graphitization time is 38 hours, and the graphitization constant power is 12,500 kw. After reaching 12,500 kw, the constant power time is 18 hours. When the graphitized second powder is cooled and removed from the furnace, the furnace temperature is 230°C. After removal from the furnace, the graphitized second powder is sieved and demagnetized to obtain the desired graphite anode material. The median particle size D50 of the graphite negative electrode material prepared in this embodiment is 12.11 μm, the particle size distribution range is 0.88 to 35.72 μm, and the tap density is 1.30 g / cm 3 , with a specific surface area of 1.32m 2 / g.
[0072] Example 2
[0073] The difference between this embodiment and embodiment 1 is that: step (1) uses needle coke A, the main components of which are carbon atoms and hydrogen atoms, with a moisture content of ≤8%, an ash content of ≤0.5%, a volatile matter content of 5-8%, and a sulfur content of ≤0.5%; the mosaic structure accounts for 40%. The D50 median particle size of the graphite negative electrode material prepared in this embodiment is 11.88 μm, the particle size distribution range is 1.04-38.35 μm, and the tap density is 1.31 g / cm 3 , with a specific surface area of 1.20m 2 / g.
[0074] Example 3
[0075] The difference between this embodiment and embodiment 1 is that: in step (1), petroleum coke B and needle coke A are mixed in a ratio of 5:5 as raw materials and crushed. Among them, the main components of petroleum coke B are carbon atoms and hydrogen atoms, moisture ≤10%, ash ≤1.0%, volatile matter 9-13%, and S content ≤1.0%; the mosaic structure of petroleum coke B accounts for 67%; the main components of needle coke A are carbon atoms and hydrogen atoms, moisture ≤8%, ash ≤0.5%, volatile matter 5-8%, and S content ≤0.5%; the mosaic structure accounts for 40%. The D50 median particle size of the graphite negative electrode material prepared in this embodiment is 14.47μm, the particle size distribution range is 1.10-56.90μm, and the tap density is 1.34g / cm 3 , with a specific surface area of 0.97m 2 / g.
[0076] Example 4
[0077] This embodiment differs from embodiment 1 in that:
[0078] When the second powder is graphitized, the graphitization process is different from that of Example 1: the second powder is graphitized using an Acheson crucible furnace, the total power transmission is 43000KWh, the total graphitization time is 39h, the initial power transmission power is 2000Kw, the set power in the graphitization process is 14000Kw, and after reaching the set power of 14000kw, the set power is maintained for 17h. When the second powder after graphitization is cooled and taken out of the furnace, the furnace temperature is 250°C. The D50 median particle size of the graphite negative electrode material prepared in this embodiment is 10.33μm, the particle size distribution range is 0.77~28.93μm, and the tap density is 1.20g / cm 3 , with a specific surface area of 1.85m 2 / g.
[0079] Comparative Example 1
[0080] The raw material used is petroleum coke C, with a volatile matter content of 13.1% and a mosaic structure of 24%. After pulverization, heat treatment, and graphitization, the prepared graphite negative electrode material has a D50 median particle size of 16.91 μm, a particle size distribution range of 0.75 to 68.93 μm, and a tap density of 1.03 g / cm 3 , with a specific surface area of 1.56m 2 / g.
[0081] Comparative Example 2
[0082] The raw material used is petroleum coke A, which is crushed and heat-treated, and then graphitized in an Acheson crucible furnace. The graphitization process is as follows: the total power supply is 28,000 KWh, the total graphitization time is 32 hours, the set power in the graphitization process is 10,000 Kw, and after reaching the set power of 10,000 kw, the set power is maintained for 8 hours. When the second powder after graphitization is cooled and discharged from the furnace, the furnace temperature is 450 ° C. The D50 median particle size of the prepared graphite negative electrode material is 11.12 μm, the particle size distribution range is 0.88 to 35.93 μm, and the tap density is 1.22 g / cm 3 , with a specific surface area of 1.98m 2 / g.
[0083] Comparative Example 3
[0084] The raw material used is petroleum coke A. After crushing and shaping, the first median particle size D150 of the first powder is 5.34 μm. The Q150, K150 and T150 of the first powder are 0.76, 0.68 and 0.86, respectively. The first powder is then directly graphitized to form a graphite negative electrode material. The tap density of the final graphite negative electrode material is 1.02 g / cm 3 , with a specific surface area of 2.85m 2 / g.
[0085] Table 1
[0086] Table 1 shows the performance test of the graphite negative electrode materials formed in Examples 1 to 4 and Comparative Examples 1 to 3, wherein:
[0087] The median particle size D50 of the graphite negative electrode material was measured using a laser particle size distribution analyzer MS3000. Compared with Comparative Examples 1 to 3, the particle sizes of the graphite negative electrode materials in Examples 1 to 4 were moderate and the distribution was relatively uniform.
[0088] The second sphericity of the second powder after graphitization tested by the particle shape analyzer QICPIC is Q250, the second width-to-length ratio is K250 and the second convexity is T250, wherein the second sphericity Q250, the second width-to-length ratio is K250 and the second convexity T250 satisfy 3<(D250+1+125(Q250-0.75)) / 6<5; 0<(D250-150(K250-0.6))<8; 5<(D250+25T250) / 7<8.
[0089] The specific surface area of the graphite negative electrode material was tested using a specific surface area meter NOVATouch 2000. The specific surface area of the graphite negative electrode material prepared in Examples 1-4 was lower than that of the comparative example.
[0090] The tap density of the graphite negative electrode material was tested using a tap density meter TF-100B, and the tap density was higher than 1.0 g / cm 3 .
[0091] Table 2
[0092] Table 2 shows the Raman median and Raman value distribution of the graphite negative electrode materials formed in Examples 1 to 4 and Comparative Examples 1 to 3.
[0093] The confocal Raman spectrum (Renishaw) of the graphite anode material was measured using a Raman instrument (Renishaw). The G peak ("Graphite" band) was located at about 1580 cm -1The D peak (“Defect” band) is located at about 1360 cm-1, corresponding to the E2g vibration mode. -1 The Raman spectrum is calculated at 2500 points, corresponding to a disordered carbon ring structure. Each set of Raman measurements consists of 2500 points. Raman value = D peak / G peak. Because 2500 points are measured, there are 2500 sets of raw Raman data.
[0094] Arrange the Raman values from small to large, N 0.25 Sort the 625th data of Raman value from small to large, N 0.75 Sort the 1875th data from small to large Raman values, then the Raman data concentration = N 0.75 -N 0.25 The smaller the concentration value of the Raman data, the more concentrated the surface structure of the material. When the concentration value is less than 0.08, it means that the concentration of the graphite negative electrode material is better.
[0095] Arrange the Raman values from small to large, P 0.1 = the number of data with Raman value ≤ 0.1 divided by 2500; P 0.1～1.0 = The number of data with Raman values greater than 0.1 and less than 1.0 divided by 2500, P 1.0+ = The number of data with Raman values greater than or equal to 1.0 divided by 2500. Since the D peak represents a disordered structure, the larger the D peak, the higher the Raman value, which proves that the surface of the graphite negative electrode material is more disordered. 0.1 ≥80%, and P 1.0+ <1%, indicating that the surface of the graphite negative electrode material is orderly and has few defects, which is beneficial to the long cycle performance of the graphite negative electrode material.
[0096] The graphite negative electrode materials prepared in Examples 1 to 4 have a concentration of less than 0.1, a stable structure, and improved cycle performance.
[0097] Table 3
[0098] Table 3 shows the graphitization degree, electrode OI value, reversible gram capacity, first discharge efficiency, and reversible gram capacity retention rate after 1000 cycles of 0.5P constant power charge and discharge cycles and reversible gram capacity retention rate after 5000 cycles of 0.5P constant power charge and discharge cycles of the graphite negative electrode materials prepared in Examples 1 to 4 and Comparative Example 1, where:
[0099] Use Bruker equipment to test the OI value and graphitization degree of the graphite negative electrode material;
[0100] The graphite negative electrode materials prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were respectively used to prepare half-cells according to the following method:
[0101] The negative electrode materials, conductive carbon black SP, CMC, and SBR prepared in Examples 1-4 and Comparative Examples 1-3 were weighed in a mass ratio of 95:1:2:2, mixed uniformly in water to form a negative electrode slurry. The slurry was evenly coated onto copper foil using an applicator. The coated electrode was vacuum-dried in a vacuum drying oven at 110°C for 4 hours and then pressed into a sheet to form the negative electrode. The compacted density = electrode mass / (thickness of the electrode after rolling - current collector thickness). CR-2430 button cells were assembled in an argon-filled Braun glove box. The electrolyte consisted of 1M LiPF6 + EC:EMC:DMC = 1:1:1 (volume ratio). A lithium metal sheet served as the counter electrode.
[0102] The prepared half-cell was tested for discharge reversible gram capacity and first discharge efficiency on an ArbinBT2000 battery tester. The discharge reversible gram capacity and first discharge efficiency were measured according to conventional test methods in the field under the conditions of a charge and discharge voltage range of 0.005V to 1.0V and a charge and discharge rate of 0.1C. The test results show that the low-cost graphite negative electrode materials prepared in Examples 1 to 4 have a higher discharge reversible gram capacity and a higher first discharge efficiency (≥93%) after being used to prepare batteries.
[0103] The graphite materials prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were respectively used to prepare full battery tests according to the following method:
[0104] According to the mass ratio of negative electrode material: CMC: SP: SBR = 96: 1.2: 1: 1.8; weigh the negative electrode materials, conductive carbon black SP, CMC and SBR prepared in Examples 1 to 4 and Comparative Examples 1 to 3 respectively, stir them evenly in water to form a negative electrode slurry, use a coater to evenly apply it on the copper foil, place the coated electrode sheet in a vacuum drying oven at a temperature of 90°C and vacuum dry for 48 hours, and then press it into a negative electrode; where the compaction density = electrode sheet mass / (thickness of the electrode sheet after rolling - thickness of the current collector). Electrolyte: 1MLiPF6, main additives: EC, EMC, DMC, FEC. The negative electrode sheet, positive electrode sheet, etc. are stacked into a soft-pack battery cell with a reversible capacity of 1000mAh. The prepared full battery was subjected to discharge reversible gram capacity and first discharge efficiency tests. Under the conditions of charge and discharge voltage range of 0.005V to 2.5.0V and constant power 0.5P charging / 0.5P discharging, the room temperature cycle performance at 25°C was tested according to conventional testing methods in the art. The graphite negative electrode materials prepared in Examples 1 to 4 were cycled 5000 times, and the reversible gram capacity retention rate was greater than 85%.
[0105] Finally, it should be understood that the embodiments of the application disclosed herein are illustrations of the principles of the embodiments of the present application. Other modified embodiments are also within the scope of the present application. Therefore, the embodiments disclosed in the present application are merely examples and not limitations. Those skilled in the art can adopt alternative configurations based on the embodiments in the present application to implement the applications in the present application. Therefore, the embodiments of the present application are not limited to those embodiments that have been precisely described in the application.
Claims
1. A method for preparing a graphite anode material, characterized in that, Including: Selecting raw materials, where the raw materials are petroleum coke or needle coke or a mixture of petroleum coke and needle coke, and the proportion of the inlaid structure in the raw materials is 30% - 80%; Crushing and shaping the raw materials to form a first powder; Performing heat treatment on the first powder to form a second powder; Performing graphitization treatment on the second powder to form single-particle graphite anode material, and the relationship between the Raman median L of the graphite anode material and the graphitization degree G of the graphite anode material is: 1.5 < 80(L - G / 17) < 6.
2. The preparation method of the graphite anode material according to claim 1, wherein, The volatile content of the raw materials is 4 - 13%, the ash content ≤ 0.5%, and the sulfur content ≤ 1.5%.
3. The preparation method of the graphite anode material according to claim 2, characterized in that, The grindability index of the raw materials is 60 - 120.
4. The preparation method of the graphite anode material according to claim 1, wherein The first median particle size of the first powder is D150, the first sphericity is Q150, and the first aspect ratio is K150, then: 3 < (D150 + 1 + 15Q150) / 6 < 5; 0 < (D150 - 150(K150 - 0.6)) < 8.
5. The preparation method of the graphite negative electrode material according to claim 4, wherein, The convexity of the first powder is T150, then: 5 < (D150 + 25T150) / 7 < 8.
6. The preparation method of the graphite negative electrode material according to claim 1, wherein, The second median particle size of the second powder is D250, the second sphericity is Q250, and the second aspect ratio is K250, then: 3 < (D250 + 1 + 125(Q250 - 0.75)) / 6 < 5; 0 < (D250 - 150(K250 - 0.6)) < 8.
7. The preparation method of the graphite anode material according to claim 6, wherein The second convexity of the second powder is T250, then: 5 < (D250 + 25T250) / 7 < 8.
8. The preparation method of the graphite negative electrode material according to claim 1, characterized in that, The relationship between the Raman median L of the graphite anode material and the OI value I of the anode sheet of the graphite anode material satisfies: 3 < (I / 5 + 20L) < 5; and / or the relationship between the Raman median L of the graphite anode material and the reversible specific capacity R of the graphite anode material satisfies: 0 < (0.15 / L - LR / 64) < 3.
9. The preparation method of the graphite negative electrode material according to claim 1, characterized in that, The equipment for the graphitization treatment is an Acheson crucible furnace, and the process conditions for the graphitization treatment are: the power-on time is 30h - 50h, and the power-on amount is 30000 - 48000 Kwh.
10. The preparation method of the graphite negative electrode material according to claim 9, characterized in that, In the process of the graphitization treatment, the power-on power starts to increase from the starting power, and after increasing to the set power, the set power is maintained for a specific time until the power-on amount is reached. Among them, the starting power-on power is 1500 Kw - 4000 Kw, the increasing rate of the power-on power is 300 - 1200 kw / h, the set power is 10000 Kw - 15000 kw, and the specific time is greater than one-third of the total power-on time.
11. A graphite anode material, characterized in that, The relationship between the Raman median L of the single-particle graphite anode material and the graphitization degree G of the graphite anode material needs to satisfy: 1.5 < 80(L - G / 17) < 6.
12. The preparation method of the graphite anode material according to claim 11, characterized in that, The relationship between the Raman median L of the graphite anode material and the OI value I of the anode sheet of the graphite anode material satisfies: 3 < (I / 5 + 20L) < 5.
13. The preparation method of the graphite anode material according to claim 11, characterized in that, The relationship between the Raman median L of the graphite anode material and the reversible specific capacity R of the graphite anode material satisfies: 0 < (0.15 / L - LR / 64) < 3.
14. A graphite anode material, characterized in that, Prepared by using any one of the methods in claims 1 to 10.
15. A lithium-ion battery, characterized in that, Comprising a negative electrode, the negative electrode is made of the graphite anode material described in any one of claims 11 to 13.