Fast-charging negative electrode material, preparation method and application

Abstract

The invention discloses a fast-charging negative electrode material, a preparation method and application. The fast-charging negative electrode material comprises a negative electrode active core material, a first amorphous carbon layer and a second amorphous carbon layer, wherein the surface of the negative electrode active core material is coated with the first amorphous carbon layer; the surface of the first amorphous carbon layer is coated with the second amorphous carbon layer; a carbon layer material forming the first amorphous carbon layer satisfies 6 < = P1 < = 20, a carbon layer material forming the second amorphous carbon layer satisfies 5 < = P2 < = 10, and # imgabs1. According to the present invention, the surface of the negative electrode active core material is coated with amorphous carbon so as to improve the rapid charging performance of the negative electrode material; furthermore, the microcrystal size Lc and the interlayer spacing d002 of the first amorphous carbon layer and the second amorphous carbon layer are reasonably controlled, so that the fast-charging negative electrode material which has excellent fast-charging performance and also can take the first-effect performance, the high-temperature performance and the like into account is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of anode materials, and more particularly to fast-charging anode materials, preparation methods and applications. Background Art

[0002] With the rapid development of electric vehicles, people have higher and higher requirements for the driving range and fast charging of electric vehicles. A key material that determines the fast-charging performance is the anode material of the battery cell. Since the lithium intercalation potential of the graphite anode is relatively low during charging, about 0.1V (vs. Li / Li + ), once the charging current is too high and lithium ions accumulate on the surface of the graphite, the lithium ions will directly obtain electrons on the surface of the anode and undergo a reduction reaction to generate lithium metal, which will lead to serious safety problems.

[0003] Based on this, it is particularly necessary to develop a fast-charging anode material. Summary of the Invention

[0004] The purpose of the present invention is to provide a fast-charging anode material, a preparation method and an application, so as to overcome the problem of poor fast-charging performance of existing graphite materials.

[0005] The present invention is implemented as follows:

[0006] In a first aspect, the present invention provides a fast-charging anode material, comprising: a negative electrode active core material, a first amorphous carbon layer coated on the surface of the negative electrode active core material, and a second amorphous carbon layer coated on the surface of the first amorphous carbon layer;

[0007] The carbon layer material constituting the first amorphous carbon layer satisfies 6 ≤ P1 ≤ 20, where L1c and d1 002 are respectively the microcrystalline size in the c-axis direction and the layer spacing of the 002 crystal plane of the carbon layer material corresponding to the first amorphous carbon layer obtained by XRD, and the units are both nm;

[0008] The carbon layer material constituting the second amorphous carbon layer satisfies 5 ≤ P2 ≤ 10, where L2c and d2 002 are respectively the microcrystalline size in the c-axis direction and the layer spacing of the 002 crystal plane of the carbon layer material corresponding to the second amorphous carbon layer obtained by XRD, and the units are both nm.

[0009] In an alternative embodiment, P1 > P2;

[0010] and / or, the first amorphous carbon layer satisfies 8 ≤ P1 ≤ 15;

[0011] and / or, the second amorphous carbon layer satisfies 6.4 ≤ P2 ≤ 7.5.

[0012] In an alternative embodiment, the first amorphous carbon layer satisfies 1.09 ≤ L1c ≤ 1.19;

[0013] and / or, the second amorphous carbon layer satisfies 2.40 ≤ L2c ≤ 3.90;

[0014] and / or, the first amorphous carbon layer satisfies 0.36 ≤ d1 002 ≤ 0.38;

[0015] and / or, the second amorphous carbon layer satisfies 0.34 ≤ d2 002 ≤ 0.35.

[0016] In an alternative embodiment, in the fast-charging negative electrode material, the total mass fraction of the first amorphous carbon layer and the second amorphous carbon layer in the fast-charging negative electrode material is 0.4% - 5%, preferably 0.5% - 2%;

[0017] and / or, the volume distribution particle size Dv50 of the fast-charging negative electrode material is 5um - 20um, preferably 6um - 15um;

[0018] and / or, the volume distribution particle size Dv90 of the fast-charging negative electrode material is 10um - 40um, preferably 14um - 30um;

[0019] and / or, the volume distribution particle size Dv01 of the fast-charging negative electrode material is 0.5um - 10um, preferably 3um - 8um;

[0020] and / or, the tap density of the fast-charging negative electrode material is 0.9g / cm 3 - 1.5g / cm 3 , preferably 0.9g / cm 3 - 1.2g / cm 3 ;

[0021] and / or, the negative electrode active core material is selected from one or more composites of natural graphite, artificial graphite, silicon-based materials, hard carbon materials, and lithium metal materials.

[0022] In an alternative embodiment, at least a part between the negative electrode active core material of the fast-charging negative electrode material and the first amorphous carbon layer is further coated with at least one of a modified layer, a passivation layer, or a conduction layer.

[0023] and / or, at least a part between the first amorphous carbon layer and the second amorphous carbon layer of the fast-charging negative electrode material is coated with at least one of a modified layer, a passivation layer, or a conduction layer;

[0024] and / or, at least a part of the outside of the second amorphous carbon layer of the fast-charging negative electrode material is coated with at least one of a modified layer, a passivation layer, or a conduction layer;

[0025] In a second aspect, the present invention provides a method for preparing the fast-charging negative electrode material according to any one of the foregoing embodiments, including:

[0026] Performing a first carbonization treatment on a first mixture of a negative electrode active core material, a first amorphous carbon layer raw material, and a first solvent to obtain a primary carbonized material;

[0027] Performing a second carbonization treatment on a second mixture containing the primary carbonized material, a second amorphous carbon layer raw material, and a second solvent to obtain the fast-charging negative electrode material.

[0028] In an optional embodiment, the Dv50 of the negative electrode active core material is 5 μm - 20 μm, preferably 8 μm - 13 μm;

[0029] and / or, the specific surface area of the negative electrode active core material is 1 m 2 / g - 3 m 2 / g, preferably 1 m 2 / g - 2 m 2 / g;

[0030] and / or, the tap density of the negative electrode active core material is 0.9 g / cm 3 - 1.2 g / cm 3 , preferably 1 g / cm 3 - 1.1 g / cm 3 ;

[0031] In an optional embodiment, both the first carbonization treatment and / or the second carbonization treatment are carried out in a protective gas atmosphere and in a one-stage heating or multi-stage heating manner;

[0032] and / or, the mass ratio of the first amorphous carbon layer raw material, the second amorphous carbon layer raw material to the negative electrode active core material is (0.2 - 2):(0.2 - 2):100;

[0033] and / or, before the first carbonization treatment, the first mixture is granulated and dried first, and the granulation and drying step adopts one or more of spray drying, vacuum drying, or hot air drying methods. Optionally, the granulation and drying step adopts spray drying.

[0034] and / or, further, the granulation and drying temperature is 100 - 400 °C, preferably 200 - 300 °C.

[0035] And / or, the first amorphous carbon layer raw material and / or the second amorphous carbon layer raw material are independently selected from one or more of organic polymers, resinous materials, saccharides, and pitch materials; the molecular weight of the organic polymer is 400 - 100,000; the curing temperature of the resinous material is 20 - 200 °C; the softening point of the pitch material is above 26.7 °C;

[0036] Preferably, the first amorphous carbon layer raw material and the second amorphous carbon layer raw material are each independently selected from at least one of polyacrylic acid, polyacrylate salts, polyacrylonitrile, polyacrylonitrile salts, carboxymethyl cellulose, carboxymethyl cellulose salts, polyvinylpyrrolidone, polystyrene, polyvinylidene chloride, polyurethane, polyethylene glycol, polyvinyl alcohol, polyetheramine, poly(meth)acrylic acid, polymethyl methacrylate, polyfurfuryl alcohol, polydopamine, polylactic acid, phenolic resin, epoxy resin, natural resin, chitosan, sucrose, glucose, fructose, lactose, xylose, cellulose, maltose, glucose-6-phosphate, N-acetylglucosamine, peptidoglycan, coal tar pitch, petroleum pitch, and modified pitch.

[0037] And / or, the first solvent and the second solvent are each independently selected from deionized water, methanol, ethanol, propanol, butanol, isopropanol, and isobutanol.

[0038] In an alternative embodiment, the first carbonization treatment and / or the second carbonization treatment are each independently selected from one of single-stage heating, two-stage heating, three-stage heating, and four-stage heating;

[0039] Preferably, the first carbonization treatment uses single-stage heating, and the second carbonization treatment uses multi-stage heating.

[0040] In an alternative embodiment, when the first carbonization treatment and / or the second carbonization treatment select single-stage heating, the carbonization temperature is 1000 °C - 1500 °C, and the heat preservation time is 7 h - 9 h;

[0041] When the first carbonization treatment and / or the second carbonization treatment select multi-stage heating, each stage of heating includes a heating stage and a heat preservation stage. The temperature of the heat preservation stage corresponding to the last stage of heating is 1000 °C - 1500 °C, the difference in the heating range of each stage is less than 100 °C, and the cumulative heat preservation time is 5 h - 10 h.

[0042] In a third aspect, the present invention provides a secondary battery, including the fast-charging negative electrode material according to any one of the foregoing embodiments.

[0043] The present invention has the following beneficial effects:

[0044] This application improves the fast charging performance of the negative electrode material by coating amorphous carbon on the surface of the negative electrode active core material; further, in order to comprehensively consider the first efficiency and high-temperature performance of the negative electrode material, this application sets two amorphous carbon coating layers and reasonably controls the crystallite size Lc and the layer spacing d in the two amorphous carbon coating layers. 002 Meeting the limited range simultaneously is beneficial to improving the ion conduction rate of the negative electrode material; and by controlling the crystallite size Lc and the layer spacing d of the second amorphous carbon layer 002 , it is beneficial to reduce the active sites of the reaction, lower the surface activity, and improve the first efficiency and high-temperature performance. Therefore, the fast-charging negative electrode material of this application has excellent fast-charging performance while being able to balance performance such as the first efficiency and high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0046] Figure 1 It is a schematic structural diagram of the fast-charging negative electrode material in this application;

[0047] Figure 2 It is a TEM image of the fast-charging negative electrode material prepared in Example 1;

[0048] Figure 3 It is the charge-discharge curve of the full battery corresponding to the fast-charging negative electrode material prepared in Example 1. SPECIFIC EMBODIMENTS

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0050] Coating an amorphous carbon structure (including hard carbon and soft carbon) on the surface of the negative electrode material can, on the one hand, provide more lithium-ion channels by the amorphous carbon, and on the other hand, reduce the desolvation barrier of lithium ions, overall reducing the concentration polarization and the possibility of lithium deposition. At the same time, the amorphous carbon on the surface can also prevent the direct contact between the negative electrode active material and the electrolyte, ensuring that the structure of the material is not easily damaged. Therefore, the performance of the negative electrode material can be improved by coating amorphous carbon on the surface of the active material. However, when the coating amount is small, the improvement of the fast charging performance cannot meet the requirements; while when the coating amount is large, although the fast charging performance will be significantly improved, due to more active sites in the amorphous carbon itself, more active lithium ions will be consumed during the first charging process, resulting in a decrease in the first efficiency, and the side reactions will be more intense under high temperature conditions, leading to the deterioration of the high temperature performance of the negative electrode material such as high temperature storage and high temperature cycling performance.

[0051] An embodiment of the present invention provides a fast charging negative electrode material, as shown in Figure 1 which includes: a negative electrode active core material, a first amorphous carbon layer coated on the surface of the negative electrode active core material, and a second amorphous carbon layer coated on the surface of the first amorphous carbon layer;

[0052] The carbon layer material constituting the first amorphous carbon layer satisfies 6≤P1≤20, where L1c and d1 002 are respectively the microcrystalline size in the c-axis direction and the layer spacing of the 002 crystal plane of the carbon layer material corresponding to the first amorphous carbon layer obtained by XRD, and the units are both nm;

[0053] The carbon layer material constituting the second amorphous carbon layer satisfies 5≤P2≤10, where L2c and d2 002 are respectively the microcrystalline size in the c-axis direction and the layer spacing of the 002 crystal plane of the carbon layer material corresponding to the second amorphous carbon layer obtained by XRD, and the units are both nm.

[0054] This application improves the fast charging performance of the negative electrode material by coating amorphous carbon on the surface of the negative electrode active core material; further, in order to comprehensively consider the first efficiency and high temperature performance of the negative electrode material, this application sets two amorphous carbon coating layers, reasonably controlling the microcrystalline size Lc and layer spacing d in the two amorphous carbon coating layers 002 to simultaneously meet the limited range, which is beneficial to improving the ion conduction rate of the negative electrode material; and by controlling the microcrystalline size Lc and layer spacing d of the second amorphous carbon layer 002 , it is beneficial to reduce the active sites of the reaction, lower the surface activity, and improve the first efficiency and high temperature performance. Therefore, the fast charging negative electrode material of this application has excellent fast charging performance while also being able to take into account performance such as the first efficiency and high temperature.

[0055] In an alternative embodiment, P1 > P2; this is beneficial for the fast-charging anode material to balance fast-charging performance, initial efficiency, and high-temperature performance.

[0056] In an alternative embodiment, the first amorphous carbon layer satisfies 8 ≤ P1 ≤ 15. For example, P1 can be 8, 9, 10, 11, 12, 13, 14, 15, etc. When P1 is within this range, it is beneficial for improving the fast-charging performance of the anode material.

[0057] In an alternative embodiment, the second amorphous carbon layer satisfies 6.4 ≤ P2 ≤ 7.5. For example, P2 can be 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, etc. When P2 is within this range, it is beneficial for improving the initial efficiency and high-temperature performance of the anode material.

[0058] In an alternative embodiment, the first amorphous carbon layer satisfies 1.09 ≤ L1c ≤ 1.19, such as 1.09, 1.11, 1.13, 1.15, 1.17, 1.18, 1.19, etc.;

[0059] And / or, the second amorphous carbon layer satisfies 2.40 ≤ L2c ≤ 3.90, such as 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 3.9, etc.;

[0060] And / or, the first amorphous carbon layer satisfies 0.36 ≤ d1 002 ≤ 0.38, such as 0.360, 0.365, 0.370, 0.375, 0.380, etc.;

[0061] And / or, the second amorphous carbon layer satisfies 0.34 ≤ d2 002 ≤ 0.35, such as 0.340, 0.342, 0.344, 0.346, 0.348, 0.350, etc.

[0062] The range limitations of L1c, L2c, d1 002 and d2 002 are beneficial for further balancing fast-charging performance, initial efficiency, and high-temperature performance.

[0063] In an alternative embodiment, in the fast-charging anode material, the total mass fraction of the first amorphous carbon layer and the second amorphous carbon layer in the fast-charging anode material is 0.4% - 5%, such as 0.4%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5%. Preferably, it is 0.5% - 2%; if the total content of the amorphous carbon layer is too low, the improvement effect on the fast-charging performance of the anode material is poor; if the total content of the amorphous carbon layer is too high, it will lead to a decrease in the initial efficiency and high-temperature performance of the anode material.

[0064] In an alternative embodiment, the volume-based particle size Dv50 of the fast-charging negative electrode material is 5 μm - 20 μm, such as 5 μm, 8 μm, 11 μm, 14 μm, 17 μm, 20 μm, preferably 6 μm - 15 μm;

[0065] and / or, the volume-based particle size Dv90 of the fast-charging negative electrode material is 10 μm - 40 μm, such as 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, preferably 14 μm - 30 μm;

[0066] and / or, the volume-based particle size Dv01 of the fast-charging negative electrode material is 0.5 μm - 10 μm, such as 0.5 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, preferably 3 μm - 8 μm;

[0067] When the volume-based particle sizes DV01, DV50, and DV90 of the fast-charging negative electrode material are within the above ranges, it is beneficial to improve the ionic conductivity and electronic conductivity. There is less fine powder in the fast-charging negative electrode material, and when applied to secondary batteries, it is beneficial to improve the fast-charging performance and high-temperature performance.

[0068] In an alternative embodiment, the tap density of the fast-charging negative electrode material is 0.9 g / cm 3 - 1.5 g / cm 3 , such as 0.9 g / cm 3 , 1.0 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , preferably 0.9 g / cm 3 - 1.5 g / cm 3 ; When the tap density is within the above range, it is beneficial to improve the energy density and fast-charging performance of the negative electrode material.

[0069] In an alternative embodiment, the negative electrode active core material is selected from one or more composite materials of natural graphite, artificial graphite, silicon-based materials, hard carbon materials, and lithium metal materials, and the composite materials therein include, for example, silicon-carbon composite materials, etc.

[0070] In an alternative embodiment, at least part of the negative electrode active core material of the fast-charging negative electrode material is further coated with at least one of a modified layer, a passivation layer, or a conduction layer between the negative electrode active core material and the first amorphous carbon layer;

[0071] And / or, at least part of the first amorphous carbon layer and the second amorphous carbon layer of the fast-charging negative electrode material is coated with at least one of a modification layer, a passivation layer, or a conduction layer;

[0072] And / or, at least part of the outside of the second amorphous carbon layer of the fast-charging negative electrode material is coated with at least one of a modification layer, a passivation layer, or a conduction layer.

[0073] The modification layer, the passivation layer, or the conduction layer can be adjusted according to the material performance requirements. Specifically, the modification layer can include lithium disilicate, silicon dioxide, aluminum oxide, polymers, polymer lithium salts, phosphates, inorganic lithium salts, etc.; the passivation layer can include carbon elements, oxygen elements, and various metal elements to isolate the silicon material from direct contact with the electrolyte, reduce side reactions, and thus help improve the specific capacity and first efficiency; for the conduction layer, the conduction layer can include at least one of a conductive layer and an ion-conducting layer, and the material of the conductive layer can include at least one of conductive polymers, carbon materials, metal elements, and alloys; the material of the ion-conducting layer can include at least one of LISICON-type solid electrolytes, NASICION-type solid electrolytes, garnet-type solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, LiPO4, Li3PO4, LiAlO2, and LiAlF4.

[0074] The embodiment of the present invention also provides a preparation method of the fast-charging negative electrode material according to any one of the foregoing embodiments, including:

[0075] Performing a first carbonization treatment on a first mixture of a negative electrode active core material, a first amorphous carbon layer raw material, and a first solvent to obtain a primary carbonized material;

[0076] Performing a second carbonization treatment on a second mixture containing the primary carbonized material, a second amorphous carbon layer raw material, and a second solvent to obtain the fast-charging negative electrode material.

[0077] The preparation method of the fast-charging negative electrode material in the present application is simple, without complex operations and precise control, and has good industrial application prospects.

[0078] In an optional embodiment, the Dv50 of the negative electrode active core material is 5 μm - 20 μm, preferably 6 μm - 15 μm;

[0079] And / or, the specific surface area of the negative electrode active core material is 1 m 2 / g - 3 m 2 / g, preferably 1 m 2 / g - 2 m 2 / g;

[0080] And / or, the tap density of the negative electrode active core material is 0.9 g / cm 3-1.5 g / cm 3 , preferably 1 g / cm 3 -1.2 g / cm 3 .

[0081] By selecting the core material of the negative electrode active material with appropriate particle size, specific surface area and tapped density, it is beneficial to control parameters such as the particle size, specific surface area and tapped density of the fast charging negative electrode material product, and thus beneficial to balance the fast charging performance, initial efficiency and high temperature performance.

[0082] In an alternative embodiment, both the first carbonization treatment and / or the second carbonization treatment are carried out in a protective gas atmosphere and in a one-stage heating or multi-stage heating manner. Compared with one-stage heating for carbonization, multi-stage heating is beneficial to improve the degree of disorder of the layer structure of the fast charging negative electrode material, and thus can adjust the P1 and P2 values of the first amorphous carbon layer and the second amorphous carbon layer.

[0083] In an alternative embodiment, the mass ratio of the first amorphous carbon layer raw material, the second amorphous carbon layer raw material to the negative electrode active core material is (0.2-2):(0.2-2):100, for example, it can be 0.2:2:100, 0.5:1.5:100, 1:1:100, 1.5:0.5:100, 2:0.1:100, etc. When the proportion of the first amorphous carbon layer raw material increases, the proportion of the first amorphous carbon layer in the obtained fast charging negative electrode material increases, which is beneficial to the improvement of the fast charging performance; when the proportion of the second amorphous carbon layer raw material increases, the proportion of the second amorphous carbon layer in the obtained fast charging negative electrode material increases, which is beneficial to the improvement of the initial efficiency and high temperature performance. In order to balance the initial efficiency, high temperature performance and fast charging performance, the proportions of the first amorphous carbon layer raw material, the second amorphous carbon layer raw material and the negative electrode active core material need to be within a reasonable range.

[0084] In an alternative embodiment, before the first carbonization treatment, the first mixture is granulated and dried first, and the granulation and drying step adopts one or more of spray drying, vacuum drying or hot air drying methods; preferably, the granulation and drying temperature is 100-400 °C, more preferably 200-300 °C;

[0085] In an alternative embodiment, the granulation and drying step is carried out by spray drying;

[0086] In an alternative embodiment, the first amorphous carbon layer raw material and / or the second amorphous carbon layer raw material are independently selected from one or more of organic polymers, resinous materials, sugars, pitchy materials; the molecular weight of the organic polymer is 400-100000; the curing temperature of the resinous material is 20-200 °C; the softening point of the pitchy material is above 26.7 °C;

[0087] Preferably, the first amorphous carbon layer raw material and the second amorphous carbon layer raw material are each independently selected from at least one of polyacrylic acid, polyacrylates, polyacrylonitrile, polyacrylonitrile salts, carboxymethyl cellulose, carboxymethyl cellulose salts, polyvinylpyrrolidone, polystyrene, polyvinylidene chloride, polyurethane, polyethylene glycol, polyvinyl alcohol, polyetheramine, poly(meth)acrylic acid, polymethyl methacrylate, polyfurfuryl alcohol, polydopamine, polylactic acid, phenolic resin, epoxy resin, natural resin, chitosan, sucrose, glucose, fructose, lactose, xylose, cellulose, maltose, glucose-6-phosphate, N-acetylglucosamine, peptidoglycan, coal tar pitch, petroleum pitch, and modified pitch;

[0088] More preferably, the first amorphous carbon layer raw material is selected from one or more of polyacrylic acid, polyacrylates, polyacrylonitrile, polyacrylonitrile salts, carboxymethyl cellulose, carboxymethyl cellulose salts, polyvinylpyrrolidone, polystyrene, polyvinylidene chloride, polyurethane, polyethylene glycol, polyvinyl alcohol, polyetheramine, poly(meth)acrylic acid, polymethyl methacrylate, polyfurfuryl alcohol, polydopamine, polylactic acid, phenolic resin, epoxy resin, natural resin, chitosan, sucrose, glucose, fructose, lactose, xylose, cellulose, maltose, glucose-6-phosphate, N-acetylglucosamine, peptidoglycan, and / or the second amorphous carbon layer raw material is selected from one or more of coal tar pitch, petroleum pitch, and modified pitch.

[0089] In an alternative embodiment, the first amorphous carbon layer raw material and / or the second amorphous carbon layer raw material are selected from polyacrylic acid with a molecular weight of 10,000 - 100,000, polyacrylonitrile with a molecular weight of 10,000 - 20,000, polyvinylpyrrolidone with a molecular weight of 8,000 - 60,000, polyvinylidene fluoride with a molecular weight of 50,000 - 100,000, polyurethane with a molecular weight of 10,000 - 100,000, polyetheramine with a molecular weight of 400 - 2,000, polyethylene glycol with a molecular weight of 300 - 20,000, polyvinyl alcohol with a molecular weight of 9,000 - 30,000, poly(meth)acrylic acid with a molecular weight of 2,000 - 10,000, polymethyl methacrylate with a molecular weight of 100,000 - 200,000, and polylactic acid with a molecular weight of 30,000 - 60,000.

[0090] And / or, the first solvent and the second solvent are each independently selected from deionized water, methanol, ethanol, propanol, butanol, isopropanol, and isobutanol.

[0091] In an alternative embodiment, the first carbonization treatment and / or the second carbonization treatment are each independently selected from one of one-stage heating, two-stage heating, three-stage heating, and four-stage heating;

[0092] Preferably, the first carbonization treatment uses one-stage heating, and the second carbonization treatment uses multi-stage heating.

[0093] In an alternative embodiment, when the first carbonization treatment and / or the second carbonization treatment selects one-stage heating, the carbonization temperature is 1000°C - 1500°C, such as 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, the heat preservation time is 7h - 9h, such as 7h, 7.5h, 8h, 8.5h, 9h, and the heating rate can be 5°C / min - 15°C / min, such as 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min.

[0094] When the first carbonization treatment and / or the second carbonization treatment selects multi-stage heating, each stage of heating includes a heating section and a heat preservation section. The temperature of the heat preservation section corresponding to the last stage of heating is 1000°C - 1500°C, such as 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C. The difference between the heating ranges of each stage is less than 100°C. The cumulative time of the heat preservation section is 5h - 10h, and the heating rate can be 5°C / min - 15°C / min, such as 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min.

[0095] In the embodiments of the present application, the difference between the heating ranges of each stage is less than 100°C. It can be understood that if two-stage heating is used to reach 1000°C, the first stage is heated to about 500°C, and the second stage is heated to about 1000°C; if three-stage heating is used to reach 1200°C, the first stage is heated to about 400°C, the second stage is heated to about 800°C, and the third stage is heated to about 1200°C.

[0096] In the present application, the carbonization treatment is carried out in stages. During the carbonization process, the organic components in the carbon source are pyrolyzed and carbonized into carbon. As the released carbon atoms or small molecular carbon chains are deposited on the particle surface and gradually form a carbon layer, the segmented carbonization treatment can accurately control the degree of disorder and graphitization of the carbon layer compared with the carbon layer formed by one-time carbonization, resulting in a large difference in the microcrystal size in the c-axis direction and the layer spacing of the 002 crystal plane of the carbon layer material.

[0097] More preferably, in the present application, the first carbonization uses one-stage heating, and the second carbonization uses multi-stage heating, which can accurately control the degree of disorder and graphitization of the first amorphous carbon layer and the second amorphous carbon layer.

[0098] An embodiment of the present invention also provides a secondary battery, including the fast-charging negative electrode material described in any one of the foregoing embodiments.

[0099] The features and performance of the present invention will be further described in detail below with reference to the embodiments.

[0100] Example 1

[0101] This example provides a preparation method for a fast-charging negative electrode material, which specifically includes the following steps:

[0102] Step 1: Mix artificial graphite (volume distribution particle size Dv50 is 13um, specific surface area is 1.7m 2 / g, tapped density is 1.1g / cm 3 , and specific capacity is 353mAh / g) and polyacrylonitrile (molecular weight 20,000) in a mass ratio of 100:2, add ethanol for stirring (solid content is 10%), stir for 2 hours to mix evenly, and then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250°C to obtain a primary coated product. Place the obtained primary coated product in a carbonization furnace for primary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, heat up to 1200°C at a rate of 10°C / min, and keep the temperature for 6h. After the temperature of the carbonization furnace drops to room temperature, disperse and screen the material to obtain a primary carbonized product.

[0103] Step 2: Homogenize and mix the obtained primary carbonized product and pitch (softening point 55°C) in a mass ratio of 102:2, place the mixed product in a carbonization furnace for secondary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, first heat up to 200°C at a rate of 10°C / min, keep the temperature for 2h, then heat up to 800°C at a rate of 5°C / min, keep the temperature for 2h, and then heat up to 1200°C at a rate of 3°C / min, keep the temperature for 4h. After the temperature of the carbonization furnace drops to room temperature, disperse, screen, and demagnetize the material to obtain a secondary carbonized product. The TEM image is as Figure 2 shown.

[0104] Testing

[0105] (1) Determination of Lc and d 002 Measurements: Test the primary carbonized product Gr@CJA1 and the secondary carbonized product Gr@CJA1@CLA2 by XRD (angle range: 2θ = 10 - 80°) to obtain the XRD curve. Use origin for Gaussian fitting to obtain 2θ and the full width at half maximum of the 002 peak, and then calculate the interlayer spacing d002 through the Bragg formula and Lc through the Scherrer formula.

[0106] (2) Preparation and testing of coin cells

[0107] The fast-charging anode material prepared above was mixed with a binder (SBR), a dispersant (CMC), and a conductive agent (SP) in a mass ratio of 95.7:1.8:1.5:1 and uniformly stirred and dispersed in an appropriate amount of deionized water. Subsequently, it was coated on the surface of the copper foil anode current collector and dried in an 80°C oven to obtain the anode electrode sheet. Then, the anode electrode sheet was die-cut into anode electrode sheets with a diameter of 14 mm and assembled with a lithium metal sheet, an electrolyte (concentration: 1 mol / L, solvent: EC:EMC:DEC = 1:1:1, solute: LiPF6), and a separator (polyethylene) into a CR2016 button-type half-cell battery model.

[0108] Button cell test: The assembled button cell was placed in a 25°C constant temperature oven for charge-discharge testing. First, it was activated at 0.05C for two weeks (voltage range: 0.005 - 1.5V) to obtain the capacity and initial efficiency. The last step was to charge at a constant current of 0.05C to 1.5V, and then discharge at a constant current of 1C for 60 minutes. Record the capacity Q0 at 0V and the discharge capacity Q. T , and calculate the SOC (%) at 0V at 1C = Q0 / Q T *100. If the SOC at 0V is higher, it indicates that the polarization of the fast-charging anode material is smaller and the fast-charging performance is better.

[0109] (3) Preparation and testing of full cell

[0110] The fast-charging anode material prepared above was mixed with a binder (SBR), a dispersant (CMC), and a conductive agent (SP) in a mass ratio of 95:2:2:1 and uniformly stirred and dispersed in an appropriate amount of deionized water. Subsequently, it was coated on the surface of the copper foil anode current collector and dried and rolled to obtain the anode electrode sheet.

[0111] LFP (lithium iron phosphate) was mixed with a conductive agent (SP) and a binder (PVDF) in a mass ratio of 97:1:2 and stirred and dispersed in an appropriate amount of NMP. Subsequently, it was coated on the surface of the aluminum foil cathode current collector and dried and rolled to obtain the cathode electrode sheet.

[0112] A polypropylene film with a thickness of 10 μm was used as the separator, and the electrode assembly was laminated in the order of anode, separator, and cathode and placed in the outer package. After drying, processes such as liquid injection, first sealing, vacuum pumping, formation and grading, and second sealing were carried out to obtain the full cell.

[0113] Full cell test: Place the assembled fresh battery in a constant temperature oven at 25°C, perform constant current charging at 0.1C current until 3.65V, then constant voltage until 0.05C, and then select 0.1C constant current discharge until 2.5V. This is one cycle. Then perform 2 more cycles according to this test procedure. Take the discharge capacity of the last cycle as the reference Q1. Then charge the battery at a constant current of 0.1C until 3.65V, and place the battery in a fully charged state with constant voltage to 0.05C in a high temperature oven at 55°C and keep it for 7 days without opening the box. After 7 days, take out the battery, let it stand at room temperature of 25°C for 4h, and after it returns to 25°C, perform a discharge test. Discharge at a constant current of 0.1C, and the cut-off voltage is 2.5V. Record the discharge capacity at this time as the discharge capacity Q2 after storage at 55°C for 7 days. The charge-discharge curve is as Figure 3 shown. The calculation formula for the storage capacity retention rate A% after storage at 55°C for 7 days is as follows: A% = Q1 / Q2 * 100. The higher the storage capacity retention rate A% after storage at 55°C for 7 days, the less side reactions occur on the surface of the fast-charging anode material and the better the high-temperature performance.

[0114] Comparative Example 1

[0115] This comparative example provides a preparation method for a fast-charging anode material, which specifically includes the following steps:

[0116] Step 1: Mix artificial graphite (volume distribution particle size Dv50 is 13um, specific surface area is 1.72m 2 / g, tap density is 1.12g / cm 3 , and the specific capacity is 353mAh / g) and tar (softening point below 26.7°C) in a mass ratio of 100:2, add methanol for stirring (solid content is 10%), stir for 2 hours to mix evenly, and then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250°C to obtain a primary coated product. Place the obtained primary coated product in a carbonization furnace for primary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, heat up to 1200°C at a rate of 10°C / min and hold for 6h. After the temperature of the carbonization furnace drops to room temperature, disperse and sieve the material to obtain a primary carbonized product.

[0117] Step 2: Homogenize and mix the obtained primary carbonized product and pitch (softening point 55°C) in a mass ratio of 102:2. Place the mixed product in a carbonization furnace for secondary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, heat up to 1200°C at a rate of 10°C / min and hold for 8h. After the temperature of the carbonization furnace drops to room temperature, disperse, sieve, and demagnetize the material to obtain a secondary carbonized product.

[0118] The test method, preparation and testing of the coin cell, and preparation and testing of the full cell are all the same as those in Example 1.

[0119] Comparative Example 2

[0120] This comparative example provides a method for preparing a fast-charging anode material, which specifically includes the following steps:

[0121] Step 1: Mix artificial graphite (with a volume distribution particle size Dv50 of 13 μm, a specific surface area of 1.72 m 2 / g, a tapped density of 1.12 g / cm 3 , and a specific capacity of 353 mAh / g) and polyvinyl alcohol (with a molecular weight of 10,000) in a mass ratio of 100:4, add ethanol and stir (the solid content is 10%), stir for 2 hours to mix evenly, then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250 °C to obtain a coated product. Place the obtained coated product in a carbonization furnace for primary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, heat up to 1300 °C at a rate of 10 °C / min and hold for 8 h. After the temperature of the carbonization furnace drops to room temperature, disperse and screen the material to obtain a carbonized product.

[0122] The test method, coin cell preparation and testing, full cell preparation and testing are all the same as those in Example 1.

[0123] Comparative Example 3

[0124] This comparative example provides a method for preparing a fast-charging anode material, which specifically includes the following steps:

[0125] Step 1: Mix artificial graphite (with a volume distribution particle size Dv50 of 13 μm, a specific surface area of 1.72 m 2 / g, a tapped density of 1.11 g / cm 3 , and a specific capacity of 353 mAh / g) and coal tar pitch (softening point 45 °C) in a mass ratio of 100:4, add ethanol and stir (the solid content is 20%), stir for 2 hours to mix evenly, then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250 °C to obtain a coated product. Place the obtained coated product in a carbonization furnace for primary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, first heat up to 1000 °C at a rate of 8 °C / min and hold for 7 h. After the temperature of the carbonization furnace drops to room temperature, disperse and screen the material to obtain a carbonized product.

[0126] The test method, coin cell preparation and testing, full cell preparation and testing are all the same as those in Example 1.

[0127] Comparative Example 4

[0128] This comparative example provides a method for preparing a fast-charging anode material, which specifically includes the following steps:

[0129] Step 1: Mix artificial graphite (volume distribution particle size Dv50 is 13um, specific surface area is 1.72m 2 / g, tapped density is 1.11g / cm 3 , and the gram capacity is 353mAh / g) and polyacrylonitrile (molecular weight 20000) in a mass ratio of 100:2, add water and stir (solid content is 20%), stir for 2 hours to mix evenly, and then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250°C to obtain a primary coated product. Place the obtained primary coated product in a carbonization furnace for primary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, first heat up to 1200°C at a rate of 10°C / min and hold for 6h. After the temperature of the carbonization furnace drops to room temperature, disperse and screen the material to obtain a primary carbonized product.

[0130] Step 2: Homogenize and mix the obtained primary carbonized product and polyetheramine (molecular weight 100000) in a mass ratio of 102:2, place the mixed product in a carbonization furnace for secondary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, first heat up to 1200°C at a rate of 10°C / min and hold for 8h. After the temperature of the carbonization furnace drops to room temperature, disperse, screen, and demagnetize the material to obtain a secondary carbonized product.

[0131] The test method, preparation and test of coin cells, and preparation and test of full cells are all the same as those in Example 1.

[0132] Example 2

[0133] This example provides a preparation method for a fast-charging negative electrode material, which specifically includes the following steps:

[0134] Step 1: Mix artificial graphite (volume distribution particle size Dv50 is 13um, specific surface area is 1.7m 2 / g, tapped density is 1.1g / cm 3 , and the gram capacity is 353mAh / g) and polyacrylic acid (molecular weight 20000) in a mass ratio of 100:2, add ethanol and stir (solid content is 10%), stir for 2 hours to mix evenly, and then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250°C to obtain a primary coated product. Place the obtained primary coated product in a carbonization furnace for primary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, first heat up to 200°C at a rate of 10°C / min and hold for 2h, then heat up to 800°C at a rate of 5°C / min and hold for 2h, and then heat up to 1200°C at a rate of 3°C / min and hold for 4h. After the temperature of the carbonization furnace drops to room temperature, disperse and screen the material to obtain a primary carbonized product.

[0135] Step 2: Homogenously mix the obtained primary carbonized product and asphalt (softening point 55°C) in a mass ratio of 102:2, and place the mixture in a carbonization furnace for secondary carbonization. Specifically, in a nitrogen atmosphere, first heat it to 200°C at a rate of 10°C / min and hold for 2 h, then heat it to 800°C at a rate of 5°C / min and hold for 2 h, and then heat it to 1200°C at a rate of 3°C / min and hold for 4 h. After the temperature of the carbonization furnace drops to room temperature, disperse the material, sieve it, and perform magnetic removal treatment to obtain the secondary carbonized product.

[0136] The testing method, preparation and testing of coin cells, and preparation and testing of full cells are all the same as those in Example 1.

[0137] Example 3

[0138] This example provides a preparation method for a fast-charging anode material, which specifically includes the following steps:

[0139] Step 1: Mix spherical natural graphite (volume distribution particle size Dv50 is 12 μm, specific surface area is 1.8 m 2 / g, tap density is 1.2 g / cm 3 , and the specific capacity is 370 mAh / g) and polyurethane (molecular weight 30000) in a mass ratio of 100:2, add water and stir (solid content is 10%), stir for 2 hours to mix evenly, and then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250°C to obtain a primary coated product. Place the obtained primary coated product in a carbonization furnace for primary carbonization. Specifically, in a nitrogen atmosphere, first heat it to 1200°C at a rate of 10°C / min and hold for 6 h. After the temperature of the carbonization furnace drops to room temperature, disperse the material and sieve it to obtain the primary carbonized product.

[0140] Step 2: Homogenously mix the obtained primary carbonized product and polyvinylpyrrolidone (molecular weight 10000) in a mass ratio of 102:2, and place the mixture in a carbonization furnace for secondary carbonization. Specifically, in a nitrogen atmosphere, first heat it to 200°C at a rate of 10°C / min and hold for 2 h, then heat it to 800°C at a rate of 5°C / min and hold for 2 h, and then heat it to 1200°C at a rate of 3°C / min and hold for 4 h. After the temperature of the carbonization furnace drops to room temperature, disperse the material, sieve it, and perform magnetic removal treatment to obtain the secondary carbonized product.

[0141] The testing method, preparation and testing of coin cells, and preparation and testing of full cells are all the same as those in Example 1.

[0142] Example 4

[0143] This example provides a preparation method for a fast-charging anode material, which specifically includes the following steps:

[0144] Step 1: Mix artificial graphite (volume distribution particle size Dv50 is 13um, specific surface area is 1.7m 2 / g, tapped density is 1.1g / cm 3 , and the gram capacity is 353mAh / g) and polyacrylic acid (molecular weight 50000) in a mass ratio of 100:2, add water and stir (solid content is 10%), stir for 2 hours to mix evenly, and then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250°C to obtain a primary coated product. Place the obtained primary coated product in a carbonization furnace for primary carbonization treatment. The carbonization treatment is specifically as follows: Under a nitrogen atmosphere, heat up to 1200°C at a rate of 10°C / min and hold for 8h. After the temperature of the carbonization furnace drops to room temperature, break up and screen the material to obtain a primary carbonized product.

[0145] Step 2: Homogenize and mix the obtained primary carbonized product and glucose in a mass ratio of 102:2, and place the mixed product in a carbonization furnace for secondary carbonization treatment. The carbonization treatment is specifically as follows: Under a nitrogen atmosphere, first heat up to 200°C at a rate of 10°C / min and hold for 2h, then heat up to 800°C at a rate of 5°C / min and hold for 2h, and then heat up to 1200°C at a rate of 3°C / min and hold for 4h. After the temperature of the carbonization furnace drops to room temperature, break up, screen, and demagnetize the material to obtain a secondary carbonized product.

[0146] The test method, preparation and test of coin cells, and preparation and test of full cells are all the same as those in Example 1.

[0147] Example 5

[0148] This example provides a preparation method for a fast-charging anode material, which specifically includes the following steps:

[0149] Step 1: Mix artificial graphite (volume distribution particle size Dv50 is 13um, specific surface area is 1.7m 2 / g, tapped density is 1.1g / cm 3 , and the gram capacity is 353mAh / g) and phenolic resin (curing point 155°C) in a mass ratio of 100:2, add ethanol and stir (solid content is 10%), stir for 2 hours to mix evenly, and then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250°C to obtain a primary coated product. Place the obtained primary coated product in a carbonization furnace for primary carbonization treatment. The carbonization treatment is specifically as follows: Under a nitrogen atmosphere, heat up to 1100°C at a rate of 10°C / min and hold for 6h. After the temperature of the carbonization furnace drops to room temperature, break up and screen the material to obtain a primary carbonized product.

[0150] Step 2: Homogenize and mix the obtained primary coated product with petroleum asphalt (softening point 50°C) at a mass ratio of 102:2, and place the mixture in a carbonization furnace for secondary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, first heat it to 200°C at a rate of 10°C / min and hold for 2 h, then heat it to 800°C at a rate of 5°C / min and hold for 2 h, and then heat it to 1200°C at a rate of 3°C / min and hold for 4 h. After the temperature of the carbonization furnace drops to room temperature, disperse the material, sieve it, and remove magnetic substances to obtain the secondary carbonized product.

[0151] The test method, the preparation and testing of the coin cell, and the preparation and testing of the full cell are all the same as those in Example 1.

[0152] Example 6

[0153] This example provides a preparation method for a fast-charging anode material, which specifically includes the following steps:

[0154] Step 1: Mix hard carbon (volume distribution particle size Dv50 is 6 um, specific surface area is 2.5 m 2 / g, tapped density is 1.1 g / cm 3 , and the specific capacity is 323 mAh / g) and polyacrylic acid (molecular weight 50000) at a mass ratio of 100:2, add ethanol and stir (solid content is 10%), stir for 2 hours to mix evenly, and then perform spray treatment through a spray dryer. The inlet temperature of the spray dryer is controlled at 250°C to obtain the primary coated product. Place the obtained primary coated product in a carbonization furnace for primary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, first heat it to 200°C at a rate of 10°C / min and hold for 2 h, then heat it to 800°C at a rate of 5°C / min and hold for 2 h, and then heat it to 1200°C at a rate of 3°C / min and hold for 4 h. After the temperature of the carbonization furnace drops to room temperature, disperse the material and sieve it to obtain the primary carbonized product.

[0155] Step 3: Homogenize and mix the obtained primary carbonized product with coal tar pitch (softening point 45°C) at a mass ratio of 102:2, and place the mixture in a carbonization furnace for secondary carbonization treatment. The carbonization treatment is specifically as follows: under a nitrogen atmosphere, first heat it to 200°C at a rate of 10°C / min and hold for 2 h, then heat it to 800°C at a rate of 5°C / min and hold for 2 h, and then heat it to 1200°C at a rate of 3°C / min and hold for 4 h. After the temperature of the carbonization furnace drops to room temperature, disperse the material, sieve it, and remove magnetic substances to obtain the secondary carbonized product.

[0156] The test method, the preparation and testing of the coin cell, and the preparation and testing of the full cell are all the same as those in Example 1.

[0157] The parameters and performance of the fast - charging materials prepared in the above - mentioned examples and comparative examples were tested, and the test results are shown in Table 1.

[0158] Table 1

[0159]

[0160]

[0161] The particle size, specific surface area, tapped density, capacity and other parameters of the fast - charging anode materials prepared in each example and comparative example are all within the range described in the specification of this application.

[0162] Generally speaking, the first amorphous carbon layer is mainly to increase the ionic conductivity. Therefore, when L c is too large and d 002 is too small, the resistance to the diffusion of lithium ions inside is greater, which is not conducive to the improvement of fast - charging performance. The structure of the second amorphous carbon layer has a greater impact on the initial efficiency and high - temperature performance. Therefore, when Lc is too small and d 002 is too large, it indicates that the carbon microcrystals in the surface carbon layer structure are smaller, and more active sites are exposed, which will cause an increase in side reactions, resulting in the deterioration of the initial efficiency and high - temperature performance.

[0163] For the fast - charging anode material prepared in Example 1, the Lc and d 002 of the first amorphous carbon layer meet 8 ≤ P1 ≤ 15, and the second amorphous carbon layer also meets 6.4 ≤ P2 ≤ 7.5. Its overall initial efficiency, high - temperature performance and fast - charging performance are good. For the fast - charging anode material prepared in Comparative Example 1, the Ps of the first amorphous carbon layer and the second amorphous carbon layer are not within the limited range. The L c of the first amorphous carbon layer is larger and d 002 is smaller, so the resistance to the diffusion of lithium ions inside is greater. And for the second amorphous carbon layer, Lc is smaller and d002 is larger, so there are more surface active sites and more side reactions. Therefore, although the fast - charging performance of the fast - charging anode material prepared in Comparative Example 1 has been improved to some extent, its initial efficiency and high - temperature performance are significantly poor.

[0164] For the fast - charging anode materials prepared in Comparative Examples 1 and 4, there is a situation where the Lc and d 002 of one of the first amorphous carbon layer and the second amorphous carbon layer do not satisfy the limited relational formula. Therefore, when the fast - charging performance is good, the initial efficiency and high - temperature performance are poor, and when the initial efficiency and high - temperature performance are good, the fast - charging performance is discounted. In Comparative Examples 2 - 3, only one layer of carbon layer is coated. Although the fast - charging performance is improved compared with Example 1, the initial efficiency and high - temperature performance are relatively poor.

[0165] In Examples 2 - 6, the Lc and d 002 of the first amorphous carbon layer and the second amorphous carbon layer both satisfy the limited relational formula, so they can better balance fast - charging, high - temperature, initial - efficiency and other performances.

[0166] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fast-charging negative electrode material, characterized in that, Comprising: a negative electrode active core material, a first amorphous carbon layer coated on the surface of the negative electrode active core material, and a second amorphous carbon layer coated on the surface of the first amorphous carbon layer; The carbon layer material forming the first amorphous carbon layer satisfies 6 ≤ P1 ≤ 20, where L1c and d1 002 are respectively the crystallite size in the c-axis direction and the layer spacing of the 002 crystal plane of the carbon layer material corresponding to the first amorphous carbon layer obtained by XRD, and the units are both nm; The carbon layer material forming the second amorphous carbon layer satisfies 5 ≤ P2 ≤ 10, where L2c and d2 002 are respectively the crystallite size in the c-axis direction and the layer spacing of the 002 crystal plane of the carbon layer material corresponding to the second amorphous carbon layer obtained by XRD, and the units are both nm.

2. The fast-charging negative electrode material according to claim 1, wherein wherein P1 > P2; and / or, the first amorphous carbon layer satisfies 8 ≤ P1 ≤ 15; and / or, the second amorphous carbon layer satisfies 6.4 ≤ P2 ≤ 7.

5.

3. The fast-charging negative electrode material according to claim 1, characterized in that, The first amorphous carbon layer satisfies 1.09 ≤ L1c ≤ 1.19; and / or, the second amorphous carbon layer satisfies 2.40 ≤ L2c ≤ 3.90; and / or, the first amorphous carbon layer satisfies 0.36 ≤ d1 002 ≤ 0.38; And / or, the second amorphous carbon layer satisfies 0.34 ≤ d2 002 ≤ 0.

35.

4. The fast-charging negative electrode material according to claim 1, characterized in that In the fast charging negative electrode material, the total mass fraction of the first amorphous carbon layer and the second amorphous carbon layer in the fast charging negative electrode material is 0.4% - 5%, preferably 0.5% - 2%; and / or, the volume distribution particle size Dv50 of the fast charging negative electrode material is 5 μm - 20 μm, preferably 6 μm - 15 μm; and / or, the volume distribution particle size Dv90 of the fast charging negative electrode material is 10 μm - 40 μm, preferably 14 μm - 30 μm; and / or, the volume distribution particle size Dv01 of the fast charging negative electrode material is 0.5 μm - 10 μm, preferably 3 μm - 8 μm; And / or, the tap density of the fast charging negative electrode material is 0.9 g / cm 3 -1.5 g / cm 3 , preferably 0.9 g / cm 3 -1.2 g / cm 3 ; and / or, the negative electrode active core material is selected from one or more of natural graphite, artificial graphite, silicon-based materials, hard carbon materials, and lithium metal materials.

5. The fast-charging negative electrode material according to claim 1, wherein Between the negative electrode active core material and the first amorphous carbon layer of the fast charging negative electrode material, at least part is further coated with at least one of a modified layer, a passivation layer or a conduction layer; and / or, between the first amorphous carbon layer and the second amorphous carbon layer of the fast charging negative electrode material, at least part is coated with at least one of a modified layer, a passivation layer or a conduction layer; and / or, at least part of the outside of the second amorphous carbon layer of the fast charging negative electrode material is coated with at least one of a modified layer, a passivation layer or a conduction layer.

6. A method for preparing the fast-charging anode material according to any one of claims 1-5, characterized in that, Comprising: Performing a first carbonization treatment on a first mixture of a negative electrode active core material, a first amorphous carbon layer raw material and a first solvent to obtain a primary carbonized material; Performing a second carbonization treatment on a second mixture containing the primary carbonized material, a second amorphous carbon layer raw material and a second solvent to obtain the fast charging negative electrode material.

7. The preparation method of the fast-charging negative electrode material according to claim 6, wherein, The Dv50 of the negative electrode active core material is 5 μm - 20 μm, preferably 6 μm - 15 μm; And / or, the specific surface area of the negative electrode active core material is 1 m 2 / g - 3 m 2 / g, preferably 1 m 2 / g - 2 m 2 / g; And / or, the tapped density of the negative electrode active core material is 0.9 g / cm 3 - 1.5 g / cm 3 , preferably 1 g / cm 3 - 1.2 g / cm 3 .

8. The preparation method of the fast-charging negative electrode material according to claim 6, characterized in that, Both the first carbonization treatment and / or the second carbonization treatment are carried out in a protective gas atmosphere and in a one-stage heating or multi-stage heating manner; and / or, the mass ratio of the first amorphous carbon layer raw material, the second amorphous carbon layer raw material to the negative electrode active core material is (0.2 - 2):(0.2 - 2):100; and / or, before the first carbonization treatment, granulating and drying the first mixture first, and the granulating and drying step adopts one or more of spray drying, vacuum drying or hot air drying methods; preferably, the granulating and drying temperature is 100 - 400 °C, more preferably 200 - 300 °C; and / or, the first amorphous carbon layer raw material and / or the second amorphous carbon layer raw material are independently selected from one or more of organic polymers, resinous materials, sugars, asphaltous materials; the molecular weight of the organic polymer is 400 - 100000; the curing temperature of the resinous material is 20 - 200 °C; the softening point of the asphaltous material is above 26.7 °C; Preferably, the first amorphous carbon layer raw material and the second amorphous carbon layer raw material are each independently selected from at least one of polyacrylic acid, polyacrylate salts, polyacrylonitrile, polyacrylonitrile salts, carboxymethyl cellulose, carboxymethyl cellulose salts, polyvinylpyrrolidone, polystyrene, polyvinylidene chloride, polyurethane, polyethylene glycol, polyvinyl alcohol, polyetheramine, poly(meth)acrylic acid, polymethyl methacrylate, polyfurfuryl alcohol, polydopamine, polylactic acid, phenolic resin, epoxy resin, natural resin, chitosan, sucrose, glucose, fructose, lactose, xylose, cellulose, maltose, glucose-6-phosphate, N-acetylglucosamine, peptidoglycan, coal tar pitch, petroleum pitch, modified pitch; and / or, the first solvent and the second solvent are each independently selected from deionized water, methanol, ethanol, propanol, butanol, isopropanol and isobutanol.

9. The preparation method of the fast-charging anode material according to claim 8, wherein, The first carbonization treatment and / or the second carbonization treatment are each independently selected from one of single-stage heating-up, two-stage heating-up, three-stage heating-up and four-stage heating-up; Preferably, the first carbonization treatment adopts single-stage heating-up, and the second carbonization treatment adopts multi-stage heating-up.

10. The preparation method of the fast-charging anode material according to claim 9, characterized in that, When the first carbonization treatment and / or the second carbonization treatment select single-stage heating-up, the carbonization temperature is 1000°C - 1500°C, and the heat preservation time is 7h - 9h; When the first carbonization treatment and / or the second carbonization treatment select multi-stage heating-up, each stage of heating-up includes a heating-up stage and a heat preservation stage. The temperature of the heat preservation stage corresponding to the last stage of heating-up is 1000°C - 1500°C, the difference in the heating-up amplitude of each stage is less than 100°C, and the cumulative time of the heat preservation stage is 5h - 10h.

11. A secondary battery, characterized in that, Comprising the fast-charging negative electrode material according to any one of claims 1 - 5.

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