Negative electrode material and battery

Abstract

The invention provides a negative electrode material and a battery, the negative electrode material comprises an inner core and a coating layer located on at least part of the surface of the inner core, the inner core comprises graphite, the coating layer comprises a polymer, and the negative electrode material comprises at least one of an element N, an element S and an element P; the repose angle of the negative electrode material is theta degrees, the tap density of the negative electrode material is rho g / cm < 3 >, the compaction density of the negative electrode material under the pressure of 5T is T1 g / cm < 3 >, and the negative electrode material meets the formula: M = theta / rho * T1, and M is more than or equal to 105 and less than or equal to 160. According to the negative electrode material provided by the invention, the negative electrode material has high capacity, high compaction density and low expansion performance, and the fast charging performance of the negative electrode material is improved.

Description

Anode materials and batteries Technical Field

[0001] This application relates to the field of negative electrode material technology, specifically to negative electrode materials and batteries. Background Technology

[0002] Graphite is one of the main raw materials for lithium-ion batteries, possessing advantages such as high capacity, high compaction, environmental friendliness, and low price, and is widely used in 3C, power tools, and other fields. However, due to graphite's poor compatibility with electrolytes, it is prone to solvated lithium-ion co-intercalation during charging and discharging, and it is difficult to form a uniform SEI film on its surface, significantly affecting the battery's capacity, lifespan, and fast-charging performance. To improve the overall performance of the material, the anode material usually needs to be coated with a layer of amorphous carbon.

[0003] Currently, a layer of pitch carbon is typically coated onto the surface of graphite to mitigate the expansion, peeling, and structural damage of the graphite layer caused by lithium-ion insertion and extraction during charging and discharging, as well as to increase the compatibility between the electrolyte and graphite and improve fast-charging performance. Generally, graphite and pitch are mixed and then carbonized at high temperatures (typically ≥900℃). While this improves the cycle expansion and charging performance of the prepared negative electrode material, the capacity, initial efficiency, and compaction density of the negative electrode material decrease after carbon coating, and the carbon coating process is energy-intensive.

[0004] It is evident that current anode materials still struggle to simultaneously achieve capacity, fast-charging performance, and high real density. Summary of the Invention

[0005] In view of this, this application provides a negative electrode material and a battery. The negative electrode material has the advantages of high capacity, high compaction density and low expansion performance, which improves the fast charging performance of the negative electrode material.

[0006] In a first aspect, this application provides a negative electrode material, the negative electrode material comprising a core and a coating layer located on at least a portion of the surface of the core, the core comprising graphite, the coating layer comprising a polymer, and the negative electrode material comprising at least one of N, S and P elements;

[0007] The angle of repose of the negative electrode material is θ°, and the tap density of the negative electrode material is ρg / cm³. 3 The compaction density of the negative electrode material under 5T pressure is T1 g / cm³. 3 The negative electrode material satisfies: M=θ / ρ×T1, 105≤M≤160.

[0008] In some implementations, 1.9 ≤ T1 ≤ 2.2.

[0009] In some implementations, 50 ≤ θ ≤ 60.

[0010] In some implementations, 0.70 ≤ ρ ≤ 0.90.

[0011] In some embodiments, the negative electrode material is placed in an oxygen-containing atmosphere and heated to 600°C at a heating rate of 5°C / min for 30 min. The resulting heat-treated product has a compaction density of T2 g / cm³ under a pressure of 5T. 3 , 1.0≤T1 / T2≤1.1.

[0012] In some embodiments, the negative electrode material is treated at a temperature of 400°C to 600°C for 2 hours, and the weight loss rate of the negative electrode material is 0.1% to 0.5%.

[0013] In some embodiments, the graphite includes at least one of artificial graphite and natural graphite.

[0014] In some embodiments, the polymer includes at least one of polyaniline, polydopamine, polyetheramine, polyacrylamide, polyacrylic acid, polyformamide, polythiophene, polyphenylene sulfide, polythiourea, vulcanized polyethylene, vulcanized polypropylene, vulcanized rubber, polysulfone, ammonium polyphosphate, and phosphonyl polymer.

[0015] In some embodiments, the nitrogen element in the negative electrode material has a mass content of 0.01% to 0.1%.

[0016] In some embodiments, the S element in the negative electrode material has a mass content of 0.01% to 0.1%.

[0017] In some embodiments, the P element in the negative electrode material has a mass content of 0.01% to 0.1%.

[0018] In some embodiments, the polymer is aged at 150°C to 450°C for 1 to 10 hours.

[0019] In some embodiments, the mass percentage of the coating layer in the negative electrode material is 0.1% to 0.5%.

[0020] In some embodiments, the median particle size of the negative electrode material is 5 μm to 19 μm.

[0021] In some embodiments, the specific surface area of ​​the negative electrode material is 0.1 m². 2 / g~2m 2 / g.

[0022] In some embodiments, the tap density of the negative electrode material is 0.7 g / cm³. 3 ~1.2g / cm 3 .

[0023] The technical solution of this application has at least the following beneficial effects:

[0024] The negative electrode material provided in this application includes a core and a coating layer. The core includes graphite, and the coating layer includes a polymer. The negative electrode material includes at least one of N, S, and P elements. These elements have strong binding forces with lithium ions, which can promote the desolvation of lithium ions in the electrolyte, reduce the interfacial impedance of the solid-liquid interface of the negative electrode material, facilitate lithium ion transport, and improve the specific capacity of the negative electrode material. At the same time, the angle of repose, tap density, and compaction density of the negative electrode material are synergistically controlled to meet the above-mentioned ranges. Under the action of the polymer, the interaction force between particles is enhanced, and slippage is not easy to occur. Thus, the angle of repose of the negative electrode material is higher in the static state, the particles of the negative electrode material are more tightly stacked, and the compaction density of the negative electrode material is increased. Therefore, the negative electrode material can have high capacity, high compaction density, and low expansion performance, thereby improving the fast charging performance of the negative electrode material. Attached Figure Description

[0025] Figure 1 is a schematic diagram of the discharge state of the battery provided in an embodiment of this application. Detailed Implementation

[0026] To better illustrate this application and facilitate understanding of its technical solutions, the following detailed description is provided. However, the following embodiments are merely simplified examples and do not represent or limit the scope of protection of this application. The scope of protection of this application is determined by the claims.

[0027] In a first aspect, this application provides a negative electrode material, as shown in FIG1, the negative electrode material comprising a core and a coating layer located on at least a portion of the surface of the core, the core comprising graphite, the coating layer comprising a polymer, and the negative electrode material comprising at least one of N, S and P elements;

[0028] The angle of repose of the negative electrode material is θ°, and the tap density of the negative electrode material is ρg / cm³. 3 The compaction density of the negative electrode material under 5T pressure is T1 g / cm³. 3 The negative electrode material satisfies: M=θ / ρ×T1, 105≤M≤160.

[0029] The negative electrode material provided in this application includes a core and a coating layer. The core includes graphite, and the coating layer includes a polymer. The negative electrode material includes at least one of N, S, and P elements. These elements have strong binding forces with lithium ions, which can promote the desolvation of lithium ions in the electrolyte, reduce the interfacial impedance of the solid-liquid interface of the negative electrode material, facilitate lithium ion transport, and improve the specific capacity of the negative electrode material. At the same time, the angle of repose, tap density, and compaction density of the negative electrode material are synergistically controlled to meet the above-mentioned ranges. Under the action of the polymer, the interaction force between particles is enhanced, and slippage is not easy to occur. Thus, the angle of repose of the negative electrode material is higher in the static state, the particles of the negative electrode material are more tightly stacked, and the compaction density of the negative electrode material is increased. Therefore, the negative electrode material can have high capacity, high compaction density, and low expansion performance, thereby improving the fast charging performance of the negative electrode material.

[0030] In some implementations, the M value of the negative electrode material can specifically be 105, 110, 120, 130, 140, 150, 160, etc., or other values ​​within the above range, which are not limited here. When the M value is too large, the tap density of the negative electrode material decreases, the angle of repose is too large, and the friction between the negative electrode material particles is too large, which is not conducive to the electrolyte fully wetting the negative electrode material. The lithium-ion transport resistance of the negative electrode material increases, the tap density of the negative electrode material decreases, and the fast charging performance also decreases. When the M value is too small, the compaction density of the negative electrode material decreases, the angle of repose is too small, the side reactions between the negative electrode material and the electrolyte are aggravated, resulting in a significant decrease in the capacity retention rate of the negative electrode material.

[0031] In some embodiments, the angle of repose of the negative electrode material is θ°, where 50 ≤ θ ≤ 60°. Specifically, it can be 50, 52, 53, 54, 55, 56, 57, 58, 59, or 60°, or other values ​​within the above range, which are not limited here. When the angle of repose of the negative electrode material is too large, the friction between the particles is too high, which is not conducive to the electrolyte fully wetting the negative electrode material. This increases the lithium-ion transport resistance of the negative electrode material, reduces the tap density, and decreases the fast-charging performance. When the angle of repose of the negative electrode material is too small, although the tap density slightly increases, the compaction density decreases, and the energy density also decreases. This application controls the angle of repose of the negative electrode material within the above range, which can promote the electrolyte to fully wet the negative electrode material, improve the specific capacity and fast-charging performance, and also improve the compaction density.

[0032] In some embodiments, the tap density of the negative electrode material is ρg / cm³. 3 0.70≤ρ≤0.90, specifically 0.7g / cm³ 3 0.72g / cm 3 0.74g / cm 3 0.75g / cm3 0.77g / cm 3 0.78g / cm 3 0.8g / cm 3 0.82g / cm 3 0.84 g / cm 3 0.85g / cm 3 0.87g / cm 3 0.88g / cm 3 or 0.9g / cm 3 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0033] In some embodiments, the compaction density of the negative electrode material under a pressure of 5T is T1 g / cm³. 3 1.9≤T1≤2.2; specifically, it could be 1.9 g / cm³. 3 1.95g / cm 3 1.98g / cm 3 2.0g / cm 3 2.05g / cm 3 2.1g / cm 3 2.12 g / cm 3 2.15g / cm 3 2.18 g / cm 3 2.19 g / cm 3 Or 2.2g / cm 3 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0034] In some embodiments, the negative electrode material is placed in an oxygen-containing atmosphere and heated to 600°C at a heating rate of 5°C / min for 30 min. The resulting heat-treated product has a compaction density of T2 g / cm³ under a pressure of 5T. 3 The T1 / T2 ratio should be 1.0 ≤ T1 / T2 ≤ 1.1. The specific T1 / T2 ratio can be 1.0, 1.05, 1.06, 1.07, 1.08, 1.09, or 1.1, or other values ​​within the above range. When the compaction density T1 / T2 of the negative electrode material is too high, the porosity of the electrode sheet will be too low when the negative electrode material is made into a battery. This is not conducive to electrolyte entry and lithium-ion transport, leading to problems such as insufficient battery kinetics. Controlling the T1 / T2 ratio within the above range, the compaction density of the polymer-coated negative electrode material is higher than that of the graphite core, which is beneficial to improving the volumetric energy density of the negative electrode material, ensuring that the electrolyte can fully wet the electrode sheet, and improving the lithium-ion transport efficiency of the negative electrode material.

[0035] In some embodiments, the negative electrode material is treated at a temperature of 400°C to 600°C for 2 hours, and the weight loss rate of the negative electrode material is 0.1% to 0.5%, specifically 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0036] In some embodiments, the graphite includes at least one of artificial graphite and natural graphite.

[0037] Natural graphite is typically formed from sedimentary rocks rich in organic matter or carbon through regional metamorphism. Based on its crystal morphology, natural graphite is industrially classified into three categories: dense crystalline graphite, flake graphite, and cryptocrystalline graphite.

[0038] Artificial graphite can be, for example, graphite material formed by graphitizing coke raw materials.

[0039] In some embodiments, natural flake graphite is spheroidized to obtain spherical graphite.

[0040] In some embodiments, the median particle size of graphite is 5 μm to 18 μm, more specifically, it can be 5 μm, 5.5 μm, 6 μm, 6.5 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 15 μm, 16 μm, 17 μm, or 18 μm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Multiple experiments have shown that controlling the median particle size of graphite within the above range is beneficial for achieving a balance between processing performance, volume, and rate performance.

[0041] In some embodiments, the polymer includes at least one of polyaniline, polydopamine, polyetheramine, polyacrylamide, polyacrylic acid, polyformamide, polythiophene, polyphenylene sulfide, polythiourea, vulcanized polyethylene, vulcanized polypropylene, vulcanized rubber, polysulfone, ammonium polyphosphate, and phosphonyl polymer.

[0042] In some embodiments, the polymer is aged at 150°C to 450°C for 1 to 10 hours. The surface of the aged polymer has abundant functional groups, which can promote the desolvation of lithium ions in the electrolyte, reduce the interfacial impedance of the solid-liquid interface of the negative electrode material, facilitate lithium ion transport, and improve the specific capacity of the negative electrode material.

[0043] In some embodiments, the nitrogen element in the negative electrode material has a mass content of 0.01% to 0.1%; specifically, it can be 0.01%, 0.02%, 0.05%, 0.06%, 0.08%, 0.09%, or 0.1%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Appropriate doping with nitrogen can improve the electronic conductivity of aged polymers and their interaction with lithium ions, promoting electron transport and lithium ion transport.

[0044] In some embodiments, the S element in the negative electrode material has a mass content of 0.01% to 0.1%; specifically, it can be 0.01%, 0.05%, 0.08% or 0.1%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] In some embodiments, the mass content of the P element in the negative electrode material is 0.01% to 0.1%. Specifically, it can be 0.01%, 0.02%, 0.05%, 0.06%, 0.08%, 0.09%, or 0.1%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] In some embodiments, the mass percentage of the coating layer in the negative electrode material is 0.1% to 0.5%. Specifically, it can be 0.1%, 0.15%, 0.18%, 0.2%, 0.3%, 0.4%, or 0.5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] In some embodiments, the specific surface area of ​​the negative electrode material is 0.1 m². 2 / g~2m 2 / g; specifically, it can be 0.1m 2 / g, 0.2m 2 / g, 0.3m 2 / g, 0.5m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.5m 2 / g, 1.8m 2 / g or 2.0m 2 / g, etc., can also be other numbers within the above range, and are not limited here. The inventors have found through multiple experiments that controlling the specific surface area of ​​the negative electrode material within the above range is beneficial to improving the first-efficiency and cycle performance of lithium batteries made from this negative electrode material.

[0048] In some embodiments, the thickness of the coating layer is 5nm to 100nm, specifically 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 40nm, 50nm, 60nm, 80nm, or 100nm, etc., and is not limited thereto. Controlling the thickness of the coating layer within the above range is beneficial to reducing the occurrence of side reactions between the negative electrode material and the electrolyte, and to improving the cycle capacity retention rate of the negative electrode material.

[0049] In some embodiments, the median particle size of the negative electrode material is 5μm to 19μm. Specifically, it can be 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 10μm, 12μm, 15μm, 18μm or 19μm, etc., and is not limited here.

[0050] Secondly, this application provides a method for preparing a negative electrode material, comprising the following steps:

[0051] S10, Prepare a coating solution, the coating solution comprising an organic solvent, a polymer and a conductive agent, wherein the polymer in the coating solution has a mass percentage content of 0.001% to 0.1%, and the polymer contains at least one of N, S and P elements;

[0052] S20, graphite is added to the coating solution and mixed, and the organic solvent is removed to obtain the precursor;

[0053] S30, the precursor is subjected to aging treatment at 150℃~450℃ for 1~10 hours to obtain the negative electrode material.

[0054] The method for preparing the negative electrode material provided in this application involves adding graphite to a polymer-containing coating solution, mixing thoroughly to allow a large amount of polymer to adhere to the graphite surface, then removing the solvent to obtain a precursor, and subjecting the precursor to aging treatment at a suitable temperature. After aging treatment, the polymer adheres and binds to the surface of the negative electrode material. The polymer has abundant functional groups, including at least one of N, S, and P elements. These elements have strong binding forces with lithium ions, which can promote the desolvation of lithium ions in the electrolyte, reduce the interfacial impedance of the solid-liquid interface of the negative electrode material, facilitate lithium ion transport, and improve the specific capacity of the negative electrode material. At the same time, it helps to control the angle of repose, tap density, and compaction density of the negative electrode material to meet the above-mentioned ranges. The surface of the negative electrode material has abundant functional groups, enhancing the interparticle interaction forces and making it less prone to slippage. Furthermore, the negative electrode material has a high angle of repose and a low tap density in the static state, enabling the negative electrode material to have high capacity, high tap density, and low expansion performance, thereby improving the fast-charging performance of the negative electrode material.

[0055] The preparation method provided in this scheme is described in detail below:

[0056] Step S10: Prepare a coating solution, the coating solution comprising a solvent, a polymer and a conductive agent, wherein the polymer in the coating solution has a mass percentage content of 0.001% to 0.1%, and the polymer contains at least one of N, S and P elements.

[0057] In some embodiments, the solvent includes at least one selected from water, ethanol, N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, and dichloromethane.

[0058] In some embodiments, the polymer includes at least one of polyaniline, polydopamine, polyetheramine, polyacrylamide, polyacrylic acid, polyformamide, polythiophene, polyphenylene sulfide, polythiourea, vulcanized polyethylene, vulcanized polypropylene, vulcanized rubber, polysulfone, ammonium polyphosphate, and phosphonyl polymer.

[0059] In some embodiments, the polymer content in the coating liquid is 0.001% to 0.1% by mass, specifically 0.001%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, or 0.1%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0060] In some embodiments, the mixing and dispersion methods include at least one of mechanical stirring and ultrasonic dispersion. When mechanical stirring is used for mixing, a propeller agitator, turbine agitator, or flatbed agitator can be used, as long as the components in the modifier are fully and uniformly mixed.

[0061] Stirring can be carried out at room temperature or under preheating. Preferably, the stirring temperature can be controlled between 20°C and 80°C. Understandably, proper preheating is beneficial for the organic solvent to fully dissolve and dilute the solid asphalt, so that the saturated components, aromatic components, resins and asphaltenes in the solid asphalt are fully dispersed, which is conducive to the mixing of the components to form a homogeneous liquid.

[0062] S20, graphite is added to the coating solution and mixed, and the organic solvent is removed to obtain the precursor.

[0063] In some embodiments, the median particle size of graphite is 5 μm to 18 μm, more specifically, it can be 5 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 14 μm, 15 μm, 16 μm, or 18 μm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Multiple experiments have shown that controlling the median particle size of graphite within the above range is beneficial for balancing processing performance, capacity, and rate performance. Preferably, the median particle size of graphite is 6 μm to 15 μm.

[0064] In some implementations, the graphite may be natural graphite and / or synthetic graphite.

[0065] In some embodiments, the carbon content in the graphite is ≥95% by mass, specifically 95%, 96%, 97%, 97.5%, 98.3%, 98.8%, or 99%, etc., but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] In some embodiments, the mass ratio of graphite to polymer is 100:(0.1 to 1), specifically 100:0.1, 100:0.2, 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.7, 100:0.8, or 100:1, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Insufficient polymer addition leads to poor coating uniformity and limited performance improvement, while excessive coating reduces the capacity and initial efficiency of the composite material.

[0067] Using liquid phase coating technology can achieve uniform coating with low coating amount, which can improve the uniformity of coating compared with solid phase mixed coating.

[0068] In some embodiments, graphite is added to the coating liquid and thoroughly mixed and dispersed to form a mixture, wherein the mixing method includes at least one of mechanical stirring and ultrasonic dispersion.

[0069] When mechanical stirring is used for mixing, propeller mixers, turbine mixers, or flatbed mixers can be used, as long as the components in the mixture are thoroughly and evenly mixed. Stirring can be carried out at room temperature.

[0070] In some embodiments, the stirring rate is 10 r / min to 1000 r / min, specifically 10 r / min, 50 r / min, 70 r / min, 100 r / min, 120 r / min, 150 r / min, 200 r / min, 300 r / min, 350 r / min, 400 r / min, 500 r / min, or 1000 r / min, etc., and is not limited here. Stirring makes the mixing of the conductive agent, graphite, and modifier more uniform, but too slow a stirring speed will result in poor uniformity of the mixture, leading to poor dispersion of the conductive agent in the final negative electrode material; however, too fast a stirring speed will place higher demands on the equipment and increase costs.

[0071] In some embodiments, the drying temperature is higher than the boiling point of the organic solvent, with a difference of 5°C to 10°C. The drying method may include, for example, oven drying, agitated evaporation, or spray drying. The drying process in this embodiment can remove the organic solvent from the mixture as much as possible.

[0072] In some embodiments, the drying process involves stirring and evaporating, and the stirring and evaporating apparatus is equipped with a condensation recovery device. Through the condensation recovery device, the solvent can be recycled, significantly reducing solvent usage and lowering production costs.

[0073] In some embodiments, the drying process is carried out under stirring conditions.

[0074] S30, the precursor is subjected to aging treatment at 150℃~450℃ for 1~10 hours to obtain the negative electrode material.

[0075] In some embodiments, the aging treatment is carried out in a rotary kiln with a rotation speed of 2 rpm to 20 rpm, specifically 2 rpm, 4 rpm, 5 rpm, 8 rpm, 10 rpm, 12 rpm, 15 rpm or 20 rpm, etc., which are not limited here.

[0076] In some embodiments, the aging treatment temperature is 150°C to 450°C. Specifically, it can be 150°C, 180°C, 200°C, 220°C, 250°C, 300°C, 350°C, 400°C, or 450°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0077] In some embodiments, the holding time for the aging treatment is 1 hour to 10 hours. Specifically, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or 10 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Preferably, the holding time for the aging treatment is 1 hour to 3 hours.

[0078] Optionally, the heating rate of the aging treatment is 0.5℃ / min to 5℃ / min, specifically 0.5℃ / min, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0079] This application controls the temperature, time, and heating rate of the aging process, which enables the polymer to retain a large number of functional groups after aging. The presence of these abundant functional groups can enhance the interaction force between the negative electrode material particles, reduce the slippage between particles, and increase the compaction density of the negative electrode material.

[0080] In some embodiments, the aging process is carried out under a protective atmosphere, which includes at least one of nitrogen, helium, neon, argon, krypton, and xenon.

[0081] In some embodiments, the gas flow rate of the protective atmosphere is 120 ml / min to 1200 ml / min, specifically 120 ml / min, 150 ml / min, 180 ml / min, 300 ml / min, 600 ml / min, 800 ml / min or 1200 ml / s, etc., and is not limited here.

[0082] In some embodiments, after aging treatment, at least one of crushing, screening and demagnetization is performed; preferably, after carbonization treatment, crushing, demagnetization and screening are performed in sequence.

[0083] In some implementations, the crushing method is any one of a mechanical pulverizer, an air jet mill, and a cryogenic pulverizer.

[0084] In some implementations, the screening method is any one of a fixed screen, drum screen, resonant screen, roller screen, vibrating screen, and chain screen, and the screening mesh is 200 to 500 mesh. Specifically, the screening mesh can be 200 mesh, 300 mesh, 400 mesh, 500 mesh, etc. Controlling the particle size of the negative electrode material within the above range is beneficial to improving the processing performance of the negative electrode material.

[0085] In some implementations, the demagnetizing equipment is any one of a permanent magnet drum magnetic separator, an electromagnetic iron remover, and a pulsed high-gradient magnetic separator. Demagnetization is to ultimately control the magnetic material content of the negative electrode material, reduce the discharge effect of magnetic materials on the lithium-ion battery, and improve the safety of the battery during use.

[0086] Thirdly, this application provides a battery comprising the negative electrode material described in the first aspect or the negative electrode material prepared by the method described in the second aspect.

[0087] The battery provided in this application can be a secondary battery (such as a lithium-ion battery, sodium-ion battery, etc.), including a casing, electrode assembly, and electrolyte. Both the electrode assembly and electrolyte are located inside the casing. The casing can be a packaging bag sealed with an encapsulation film (such as an aluminum-plastic film), such as a soft-pack battery for the secondary battery. In other embodiments, the secondary battery can also be a steel-cased battery, an aluminum-cased battery, etc. Figure 1 is a schematic diagram of the discharge state of the battery provided in an embodiment of this application. As shown in Figure 1, the battery includes a casing and an electrode assembly. The electrode assembly includes a positive electrode 1, a negative electrode 2, and a separator 3, with the separator 3 disposed between the positive electrode 1 and the negative electrode 2. The electrode assembly can be a stacked structure, formed by alternately stacking the positive electrode 1, the separator 3, and the negative electrode 2. In other embodiments, the electrode assembly can also be a wound structure, formed by sequentially stacking and winding the positive electrode, the separator, and the negative electrode.

[0088] In some embodiments, the positive electrode 1 includes a positive current collector 101 and a positive active layer 102 disposed on at least one surface of the positive current collector 101.

[0089] In some embodiments, the positive current collector 101 may be made of aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, current collectors formed by combining the aforementioned conductive foil (aluminum foil or nickel foil, etc.) with a polymer substrate. The positive active layer 102 comprises a positive active material, which includes compounds that reversibly insert and deintercalate metal ions.

[0090] In some embodiments, the positive electrode active material may include lithium transition metal composite oxides, sodium transition metal composite oxides, etc. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel.

[0091] In some embodiments, the positive electrode active material may include, but is not limited to, lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary materials (NCM), lithium manganese oxide (LiMn2O4), and lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5 At least one of lithium iron phosphate (LiFePO4) or lithium iron phosphate (LiFePO4).

[0092] In some embodiments, the negative electrode 2 includes a negative electrode current collector 201 and a negative electrode active material layer 202 disposed on at least one surface of the negative electrode current collector.

[0093] In some embodiments, the negative electrode current collector 201 can be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or carbon-based current collector, or any composite current collector disclosed in the prior art, such as, but not limited to, current collectors formed by combining the aforementioned conductive foil and polymer substrate. The negative electrode active material layer 202 includes a negative electrode material, which is the negative electrode material described in the first aspect or the negative electrode material prepared by the aforementioned preparation method. The battery provided in this application embodiment has the advantages of high capacity, high initial efficiency, long cycle life, excellent rate performance, and low expansion. The battery can be a lithium-ion battery, a sodium-ion battery, a solid electrolyte battery, etc., and is not limited thereto.

[0094] The embodiments of the present invention will be further described below with reference to several examples. However, the embodiments of the present invention are not limited to the specific embodiments described below. Appropriate modifications can be made within the scope of the original claims.

[0095] Example 1

[0096] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0097] (1) Take 0.2 parts of polyacrylamide and ultrasonically disperse it in 200 parts of water, and ultrasonically disperse it for 2 hours to obtain the coating solution;

[0098] (2) Add 40 parts of graphite (D50 = 13.1 μm) to the above coating solution and stir for 4 hours to obtain a mixture. The mixture is dried by spray drying at a temperature of 180°C to obtain the precursor.

[0099] (3) The precursor is placed in a rotary kiln for aging treatment. Nitrogen gas is introduced at a rate of 300 mL / min. The aging process is as follows: the temperature is increased to 350℃ at a rate of 2℃ / min, and the aging holding time is 3h. After natural cooling, the negative electrode material is obtained.

[0100] Example 2

[0101] The difference from Example 1 is:

[0102] In step (2), add 20 parts of graphite (D50 = 13.1 μm).

[0103] Example 3

[0104] The difference from Example 1 is:

[0105] In step (2), add 50 parts of graphite (D50 = 13.1 μm).

[0106] Example 4

[0107] The difference from Example 1 is:

[0108] In step (2), add 80 parts of graphite (D50 = 13.1 μm).

[0109] Example 5

[0110] The difference from Example 1 is:

[0111] Add 0.2 parts of polyphosphoric acid in step (1).

[0112] Example 6

[0113] The difference from Example 1 is:

[0114] Add 0.2 parts of polythiophene in step (1).

[0115] Example 7

[0116] The difference from Example 1 is:

[0117] Add 0.2 parts of ammonium polyphosphate in step (1).

[0118] Example 8

[0119] The difference from Example 1 is:

[0120] Add 0.2 parts of polythiourea in step (1).

[0121] Example 9

[0122] The difference from Example 1 is:

[0123] The aging temperature in step (3) is 450℃.

[0124] Example 10

[0125] The difference from Example 1 is:

[0126] The aging temperature in step (3) is 250℃.

[0127] Example 11

[0128] The difference from Example 1 is:

[0129] The aging time in step (3) is 10 hours.

[0130] Example 12

[0131] The difference from Example 1 is:

[0132] The aging time in step (3) is 1 hour.

[0133] Example 13

[0134] Unlike Example 4:

[0135] (3) The precursor is placed in a rotary kiln for aging treatment. Nitrogen gas is introduced at a rate of 300 mL / min. The aging process is as follows: the temperature is increased to 300℃ at a rate of 3℃ / min, and the temperature is maintained for 3 hours. After natural cooling, the negative electrode material is obtained.

[0136] Comparative Example 1

[0137] The preparation method of the graphite anode material in this embodiment includes the following steps:

[0138] (1) Take 2 parts of solid asphalt and 100 parts of graphite and mix them evenly to obtain asphalt-coated graphite precursor A;

[0139] (2) Precursor A is placed in a kiln for carbonization under nitrogen atmosphere. The temperature is raised to 950℃ at a rate of 5℃ / min and held for 3 hours. The resulting sample is the negative electrode material.

[0140] Comparative Example 2

[0141] The difference from Example 1 is:

[0142] Step (3) was not performed.

[0143] The preparation process parameters of the negative electrode material obtained in this embodiment are detailed in Table 1, and the performance parameters of the negative electrode material are shown in Table 2.

[0144] Table 1. Preparation process parameters of negative electrode materials

[0145]

[0146]

[0147] Test methods

[0148] (1) Test method for median particle size of negative electrode material:

[0149] The cumulative particle size distribution range of the negative electrode material was tested using a Malvern laser particle size analyzer.

[0150] (2) Test method for tap density of negative electrode material:

[0151] Place the negative electrode material in the sample chamber of the tap density meter, vibrate it 1000 times, and record the sample volume at this time. The tap density can then be calculated according to the mass-volume ratio.

[0152] (3) Test method for specific surface area of ​​negative electrode material:

[0153] After measuring the amount of gas adsorbed on the solid surface at different relative pressures under constant temperature and low temperature, the amount of monolayer adsorption of the sample is obtained based on the Brownnor-Etter-Taylor adsorption theory and its formula (BET formula), thereby calculating the specific surface area of ​​the material.

[0154] (4) Test method for compaction density of negative electrode material:

[0155] The compaction density T1 was tested according to the test method of GB / T 24533-2009 for graphite anode materials of lithium-ion batteries, with a test pressure of 5 tons.

[0156] The negative electrode material was placed in an oxygen-containing atmosphere and heated to 600℃ at a heating rate of 5℃ / min for 30 min. The compaction density of the heat-treated product under 5T pressure was T2. The units of T1 and T2 are both g / cm³. 3 .

[0157] (5) Thickness test of the coating layer of the negative electrode material:

[0158] The surface morphology and thickness of the negative electrode material were characterized using a high-resolution transmission electron microscope (HRTEM, model: FEITitan 80-300 300KV).

[0159] (6) Test of the angle of repose of the negative electrode material:

[0160] The negative electrode material is slowly added from above the funnel, and then the angle of repose (angle of repose tester, model SPT-105) is measured as the angle of repose of the negative electrode material that leaks from the bottom of the funnel and forms a cone-shaped accumulation on the horizontal plane.

[0161] (7) Determination of M element in negative electrode material:

[0162] Elemental analysis was performed using an X-ray photoelectron spectrometer (XPS, ThermoESCALAB 250XI).

[0163] (8) Rate performance test of lithium-ion button cell half-cell:

[0164] The negative electrode materials prepared in each embodiment and comparative example were used as active materials. They were mixed in a mass ratio of active material: conductive carbon black: CMC: SBR = 95.3:1.5:1.4:1.8, and the mixture was coated onto copper foil using deionized water as a solvent. The coating surface density was 6.5 ± 0.1 mg / cm³. 2 After vacuum drying at 90℃, electrode sheets are obtained. The electrode sheets are then rolled to a compaction density of 1.50±0.02 g / cm³. 3Electrodes, lithium plates, electrolyte (1 mol / L LiPF6, EC:EMC:DMC = 1:1:1) and Celgard 2400 separator were assembled into a 2016 type coin cell.

[0165] Coin cell half-cells were subjected to rate performance testing at 25±2℃ to obtain charge / discharge specific capacities and coulombic efficiencies at 0.1C, 0.2C, 1C, and 2C. Rate test conditions: ① 0.1C discharge to 0.01V, constant voltage to 0.01C, 0.1C charge to 1.5V; ② 0.2C discharge to 0.01V, constant voltage to 0.01C, 0.2C charge to 1.5V; ③ 1C discharge to 0.01V, constant voltage to 0.01C, 0.2C charge to 1.5V; ④ 2C discharge to 0.01V, constant voltage to 0.01C, 0.2C charge to 1.5V. The 1C / 0.2C discharge capacity retention rate can be calculated by dividing the 1C discharge specific capacity by the 0.2C discharge specific capacity. The 2C / 0.2C discharge capacity retention rate can be calculated by dividing the 2C discharge specific capacity by the 0.2C discharge specific capacity.

[0166] The results of the above performance tests are as follows:

[0167] Table 2. Performance Comparison Results of Anode Materials

[0168]

[0169]

[0170] Table 3. Battery Performance Parameters

[0171]

[0172] According to the test data of Examples 1 to 12, this application controls the angle of repose, tap density, and compaction density of the negative electrode material to satisfy 105≤M≤160. The surface of the negative electrode material has abundant functional groups, the interaction force between particles is enhanced, and slippage is not easy to occur. Furthermore, the negative electrode material has a high angle of repose and a low tap density in the static state, which enables the negative electrode material to have high capacity, high tap density, and low expansion performance, thereby improving the fast charging performance of the negative electrode material.

[0173] According to the test data from Examples 1 to 4, as the amount of polymer added decreases, the thickness of the coating layer on the graphite surface also gradually decreases. An appropriate ratio of polymer to graphite can improve the fast-charging performance of the negative electrode material. Preferably, the mass ratio of graphite to polymer is 20-40:0.2.

[0174] According to the test data of Examples 5 to 8, different types of polymers have little impact on the performance of the negative electrode material. As long as the M value of the negative electrode material is between 105 and 160, the negative electrode material can have high capacity, high compaction density, low expansion performance, and excellent fast charging performance.

[0175] According to Examples 9-10 and Examples 11-12, if the aging temperature is too low or the aging time is too short, the degree of aging of the polymer coating layer on the graphite surface decreases and the thickness increases, resulting in a slight increase in the angle of repose of the negative electrode material, an increase in the lithium-ion transport resistance of the negative electrode material, a decrease in the tap density of the negative electrode material, and a decrease in fast charging performance.

[0176] Based on the test data from Example 1 and Comparative Example 1, it can be seen that in Example 1, the graphite was not coated with a polymer-containing coating solution; instead, it was directly mixed with asphalt for coating and carbonization. This resulted in a small angle of repose and a significant decrease in compaction density, leading to a low M value for the negative electrode material. Consequently, the side reactions between the negative electrode material and the electrolyte were exacerbated, resulting in a significant decrease in capacity retention compared to Example 1. Although the data advantage of Comparative Example 1 compared to other examples is relatively weak—this is because different polymer addition amounts and aging processes affect the performance of the final product—as long as M is controlled within a suitable range, it is beneficial for the negative electrode material to achieve a balance between angle of repose, tap density, and compaction density. Although this represents only a small improvement, achieving even a small improvement in graphite-based negative electrode materials is extremely difficult.

[0177] According to the test data of Example 1 and Comparative Example 2, the coating layer on the graphite surface was not aged, the tap density of the negative electrode material decreased, the angle of repose was too large, the friction between the particles of the negative electrode material was too large, resulting in an excessively large M value of the negative electrode material, an increase in the lithium-ion transmission resistance of the negative electrode material, a decrease in the tap density of the negative electrode material, and a significant decrease in fast charging performance compared to Example 1.

[0178] Although this application discloses preferred embodiments as described above, it is not intended to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

Claims

1. A negative electrode material, characterized in that, The negative electrode material includes a core and a coating layer located on at least a portion of the surface of the core. The core includes graphite, and the coating layer includes a polymer. The negative electrode material includes at least one of nitrogen (N), sulfur (S), and phosphorus (P). The angle of repose of the negative electrode material is θ°, and the tap density of the negative electrode material is ρg / cm³. 3 The compaction density of the negative electrode material under 5T pressure is T1 g / cm³. 3 The negative electrode material satisfies: M=θ / ρ×T1, 105≤M≤160.

2. The negative electrode material according to claim 1, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) 1.9≤T1≤2.2; (2) 50≤θ≤60; (3) 0.70≤ρ≤0.

90.

3. The negative electrode material according to claim 1, characterized in that, The negative electrode material was placed in an oxygen-containing atmosphere and heated to 600℃ at a heating rate of 5℃ / min for 30 min. The compaction density of the heat-treated product under 5T pressure was T2 g / cm³. 3 , 1.0≤T1 / T2≤1.

1.

4. The negative electrode material according to claim 1, characterized in that, The negative electrode material was treated at a temperature of 400℃ to 600℃ for 2 hours, and the weight loss rate of the negative electrode material was 0.1% to 0.5%.

5. The negative electrode material according to claim 1, characterized in that, The graphite includes at least one of artificial graphite and natural graphite.

6. The negative electrode material according to claim 1, characterized in that, The polymer includes at least one of polyaniline, polydopamine, polyetheramine, polyacrylamide, polyacrylic acid, polyformamide, polythiophene, polyphenylene sulfide, polythiourea, vulcanized polyethylene, vulcanized polypropylene, vulcanized rubber, polysulfone, ammonium polyphosphate, and phosphonyl polymer.

7. The negative electrode material according to claim 1, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) the mass content of the N element in the negative electrode material is 0.01% to 0.1%; (2) the mass content of the S element in the negative electrode material is 0.01% to 0.1%; (3) the mass content of the P element in the negative electrode material is 0.01% to 0.1%.

8. The negative electrode material according to any one of claims 1 to 7, characterized in that, The polymer is aged at 150℃ to 450℃ for 1 to 10 hours.

9. The negative electrode material according to any one of claims 1 to 7, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) the mass percentage of the coating layer in the negative electrode material is 0.1% to 0.5%; (2) the median particle size of the negative electrode material is 5 μm to 19 μm; (3) the specific surface area of ​​the negative electrode material is 0.1 m². 2 / g~2m 2 / g.

10. A battery comprising a negative electrode material according to any one of claims 1 to 9.

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