Graphite negative electrode material precursor, graphite negative electrode material and preparation method and application thereof

Abstract

The application discloses a graphite negative electrode material precursor, a graphite negative electrode material and a preparation method and application thereof. The preparation method of the graphite negative electrode material precursor mainly comprises the following steps: performing ball milling treatment on graphite and metal oxides, and then performing heat treatment and acid washing treatment to obtain the graphite negative electrode material precursor; wherein the metal oxides account for 2-46% of the mass of the graphite, and the percentage refers to the mass percentage of the metal oxides in the graphite; in the ball milling treatment, the rotating speed of the ball milling is 400-1000 rpm. Through the method combining mechanical activation and chemical catalysis, the lithium ion transmission channel of the prepared graphite negative electrode material precursor is increased, and the further prepared graphite negative electrode material has excellent discharge capacity and fast charging performance when applied to a lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to a graphite negative material precursor, a graphite negative material and a preparation method and application thereof. BACKGROUND

[0002] Graphite has good electrical conductivity, excellent charge-discharge voltage platform, high specific capacity, and low price, and has become the mainstream negative material of commercial lithium ion batteries. Its performance has an important influence on the performance of lithium batteries. With the increasing demand for the convenience of new energy vehicles and electronic products, it has become an inevitable trend to improve the rapid charging technology of lithium ion batteries.

[0003] However, during the charging process of graphite, lithium ions preferentially insert into the graphite layer from the end face and then diffuse into the particle interior. The reaction active sites of the material are limited during the charging and discharging process, the diffusion path is lengthened, which is not conducive to the rapid insertion of lithium ions into graphite, and lithium is easily precipitated, causing safety problems. At present, improving the performance of graphite has become a key path to improve the safety and fast charging performance of lithium negative electrodes.

[0004] CN115832292A discloses a modified fast-charging graphite negative material and a modification method and application thereof. The graphite is pretreated in a CO2 atmosphere, then the graphite is compounded with fungus residue extract, bamboo source, etc., and then subjected to hydrothermal treatment and carbonization to obtain modified fast-charging graphite. The patent uses fungus residue and bamboo source as raw materials, which has the disadvantages of high ash content and unstable source, and it is difficult to effectively control the stability, which will seriously affect the performance of the negative electrode.

[0005] CN114784273A discloses a preparation method of a graphite negative material and application thereof. The graphite modification is realized by the following steps: (1) mixing, heating and rinsing the graphite and chemical etching agent in sequence to obtain porous graphite; (2) coating a polydopamine layer on the surface of the porous graphite of step (1), and drying to obtain a graphite negative material. The patent uses alkaline or strong acid to realize etching modification of the graphite negative electrode, but when applied in the production process, it has high corrosion and high requirements for equipment, and has high safety risk. In addition, the price of polydopamine is high and it is difficult to be applied to large-scale production.

[0006] CN116053442A discloses a fast-charging artificial graphite negative material, a preparation method thereof and a lithium ion battery. The patent obtains a lithium ion battery graphite negative electrode by mechanical stirring modification and coating modification. When the method is applied to resin coating, the contact between graphite and hard carbon is poor due to the difference in structure between graphite and hard carbon, which easily causes the peeling of the coating layer during the charging and discharging process of the lithium ion battery.

[0007] CN114094079A provides a preparation method of a fast-charging graphite negative electrode material and a method of a lithium ion battery. The patent adopts alkali solution etching graphite, mixing conductive agent, coating and other steps to obtain fast-charging graphite. The patent adopts alkali solution etching graphite, which has high requirements for equipment, and it is difficult to effectively form a whole stable structure between the coating agent and the graphite, which affects the performance of the lithium ion battery. SUMMARY

[0008] The technical problem to be solved by the present application is to overcome the above-mentioned defects of the prior art graphite negative electrode material, and to provide a graphite negative electrode material precursor, a graphite negative electrode material and a preparation method and application thereof. The graphite negative electrode material precursor prepared by the method of mechanical activation and chemical catalysis has increased lithium ion transmission channels. The further prepared graphite negative electrode material has excellent discharge capacity and fast-charging performance when applied to a lithium ion battery.

[0009] The present application solves the above technical problems by the following technical solutions.

[0010] The present inventors found in research that ball milling metal oxide with graphite can increase the surface defects of graphite, and the catalytic effect of metal oxide can etch and pore on the surface of graphite, effectively increasing the lithium ion diffusion channels on the surface of graphite.

[0011] The present application provides a preparation method of a graphite negative electrode material precursor, which mainly comprises the following steps: ball milling graphite and metal oxide, and then heat treatment and acid washing treatment to obtain;

[0012] Preferably, the mass percentage of the metal oxide in the graphite is 2-46%; in the ball milling process, the rotation speed of the ball milling is 400-1000 rpm.

[0013] In the present application, the graphite can be artificial graphite or natural graphite.

[0014] Preferably, in the present application, the Dmax of the graphite is ≤75 μm.

[0015] Preferably, in the present application, the D50 of the graphite is ≤50 μm, more preferably, the D50 is ≤45 μm, for example, the D50 is 10.5 μm. In the present application, Dmax is the maximum particle size of the material, and D50 is the average diameter of the material.

[0016] In the present application, other parameters of the graphite can be as follows: ash content ≤0.5%, tap density ≥0.9 g / cm 3 , specific surface area 0.8-3.2 m 2 / g, capacity ≥340 mAh / g, and first coulombic efficiency ≥90%.

[0017] In some preferred embodiments, the graphite has the following parameters: ash content 0.1%, particle size D50 of 10.5 μm, Dmax≤31.2 μm, tap density 1.01 g / cm 3 , specific surface area 1.83 m 2 / g, capacity 355 mAh / g, and first coulombic efficiency 94.5%.

[0018] In the present application, preferably, the Dmax of the metal oxide is ≤100 μm, more preferably, the particle size Dmax of the metal oxide is ≤76 μm.

[0019] In the present application, preferably, the D50 of the metal oxide is ≤75 μm, preferably 38.4 μm.

[0020] In the present application, the metal in the metal oxide can be selected from one or more of Na, Ca, Fe, V, Ni, Li, Co, Mn, K, Mg and Al, for example Ca. In the present application, the metal in the metal oxide can be a metal that is conventional in the art.

[0021] In the present application, preferably, the metal oxide accounts for 5-45% of the mass of the graphite, for example 5%, 15%, 30% or 45%, the percentage referring to the mass percentage of the metal oxide in the graphite.

[0022] In the present application, the equipment for the ball milling treatment can be conventional in the art, for example a high-energy ball mill, a planetary ball mill or a bead mill. The ball milling process can achieve uniform distribution of the metal oxide in the graphite.

[0023] In the present application, in the ball milling treatment, the rotation speed of the ball mill is preferably 300-1000 rpm, for example 400 rpm, 600 rpm, 800 rpm or 1000 rpm.

[0024] In the present application, in the ball milling treatment, the ball milling time can be 1-12 h, preferably 1-10 h, for example 1 h, 4 h, 7 h or 10 h.

[0025] In the present application, in the ball milling treatment, the ball milling medium can be zirconium oxide or a carbide material, for example tungsten carbide.

[0026] In the present application, in the ball milling treatment, the ball size ratio in the ball milling medium is (7-9):(3-1), for example 7:3.

[0027] In the present application, in the ball milling treatment, the process can further include the operation of introducing an inert atmosphere.

[0028] In the present application, the inert atmosphere can be conventional in the art, for example nitrogen or helium.

[0029] The gas flow rate of the inert atmosphere can be 0.2-2 L / h, for example 1 L / h.

[0030] In the present application, the equipment for the heat treatment can be conventional in the art, for example an atmosphere furnace. The heat treatment has certain influence on the etching and pore-forming rate of the graphite surface.

[0031] In the present application, the heat treatment can be carried out in an oxidizing atmosphere.

[0032] The oxidizing atmosphere can be air or oxygen.

[0033] The gas flow rate of the oxidizing atmosphere can be 2-30 L / h, for example 2 L / h, 9 L / h, 16 L / h, 23 L / h or 30 L / h.

[0034] In the present application, the temperature of the heat treatment can be 300-900℃, preferably 400-800℃, for example 400℃, 500℃, 600℃ or 700℃.

[0035] In the present application, the time of the heat treatment can be 1-10 h, preferably 2-8 h, for example 2 h, 4 h, 6 h or 8 h.

[0036] In the present application, preferably, after the heat treatment, the specific surface area of the product is 1.3-7.4 m 2 / g.

[0037] In the present application, preferably, after the heat treatment, the particle size D50 of the product is 20-30 μm, for example 25 μm.

[0038] In the present application, the acid washing treatment can comprise the following steps: washing the product of the heat treatment with acid, washing with water, and washing to neutral. The purpose of the acid washing is to remove metal oxides therein.

[0039] The acid used in the acid washing treatment can be dilute hydrochloric acid. The concentration of the dilute hydrochloric acid can be 0.5-3 mol / L, for example 1 mol / L.

[0040] In the acid washing treatment, mechanical stirring can be carried out simultaneously. The stirring speed can be 100-1000 rpm.

[0041] In the acid washing treatment, the temperature can be controlled at 30-80℃, for example 60℃.

[0042] The time of the acid washing treatment can be 1-24 h, for example 10 h.

[0043] In the present application, after the acid washing treatment, drying can also be carried out.

[0044] The drying temperature can be 100-120℃, for example 110℃.

[0045] The application further provides a graphite negative electrode material precursor prepared by the above preparation method.

[0046] The application further provides a preparation method of a graphite negative electrode material, which mainly comprises the following steps: coating treatment and carbonization treatment of the above graphite negative electrode material precursor.

[0047] In the application, the coating treatment can comprise the following steps: fusion treatment of the graphite negative electrode material precursor with a coating agent and a crosslinking agent, and then depolymerization treatment.

[0048] The coating agent can be a resin or a high molecular polymer.

[0049] The resin can be a thermoplastic or thermosetting resin, preferably one or more of phenolic resin, epoxy resin, vinyl resin, urea-formaldehyde resin and melamine-formaldehyde resin, for example phenolic resin.

[0050] The high molecular polymer can be one or more of polyaniline, polypyrrole and polyethylene.

[0051] The amount of the coating agent can be 1-15%, for example 1%, 5%, 10% or 15%.

[0052] The crosslinking agent can be trioxane. After adding the crosslinking agent, the fusion treatment can realize the crosslinking of graphite and resin, further improving the structural stability of hard carbon coated graphite.

[0053] The amount of the crosslinking agent can be 0.1-6%, preferably 0.5-6%, for example 0.5%, 2%, 4% or 6%.

[0054] The fusion treatment device can be conventional in the art, for example a mechanical fusion machine.

[0055] The rotation speed of the fusion treatment can be 200-1100rpm, preferably 300-900rpm, for example 300rpm, 600rpm or 900rpm.

[0056] The fusion treatment time can be 200-900s, preferably 200-800s, for example 200s, 400s, 600s or 800s.

[0057] The depolymerization treatment can be performed by a dispersing machine conventional in the art. The depolymerization treatment can control the particle size, which is beneficial to improving the compaction density and unit load of the material and increasing the energy density of the battery.

[0058] Preferably, after the heat treatment, the particle size D50 of the product is 8-17 μm, for example 9.8 μm.

[0059] In the present application, the equipment for the carbonization treatment can be conventional in the art, for example a tube furnace.

[0060] In the present application, the carbonization treatment can be carried out under an inert atmosphere.

[0061] The inert atmosphere can be conventional in the art, for example nitrogen, argon or helium.

[0062] The gas flow of the inert atmosphere can be 2-20 L / h, for example 8.3 L / h.

[0063] In the present application, the temperature of the carbonization treatment can be 800-1300℃, preferably 900-1200℃, for example 900℃, 1000℃, 1100℃ or 1200℃.

[0064] In the present application, the time of the carbonization treatment can be 1-8 h, preferably 2-6 h, for example 2 h, 4 h or 6 h.

[0065] In the present application, after the carbonization treatment, a sizing treatment can also be included. The sizing treatment can be carried out using a sizing machine conventional in the art.

[0066] The present application also provides a graphite negative electrode material prepared by the above preparation method.

[0067] In the present application, the particle size of the graphite negative electrode material can be 9.8-12.4 μm, for example 9.8 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11.0 μm, 11.1 μm, 11.2 μm, 11.3 μm, 11.4 μm, 11.5 μm, 11.6 μm, 11.7 μm, 11.9 μm, 12.2 μm or 12.4 μm.

[0068] In the present application, the tap density of the graphite negative electrode material can be 0.92-1.09 g / cm 3 , for example 0.92 g / cm 3 , 0.98 g / cm 3 , 1.01 g / cm 3 , 1.02 g / cm 3 , 1.03 g / cm 3 , 1.04 g / cm 3 , 1.05 g / cm 3 , 1.06 g / cm 31.07 g / cm 3 1.08 g / cm 3 1.09 g / cm 3 .

[0069] In the present application, the specific surface area of the graphite negative electrode material can be 2.0-3.4 m 2 / g, for example, 2.0 m 2 / g, 2.1 m 2 / g, 2.2 m 2 / g, 2.3 m 2 / g, 2.4 m 2 / g, 2.5 m 2 / g, 2.6 m 2 / g, 2.7 m 2 / g, 2.8 m 2 / g, 2.9 m 2 / g, 3.0 m 2 / g, 3.1 m 2 / g, 3.2 m 2 / g, 3.3 m 2 / g or 3.4 m 2 / g.

[0070] The present application also provides a graphite negative electrode material precursor or a graphite negative electrode material as described above for use in a lithium ion battery.

[0071] On the basis of common general knowledge in the art, the above-mentioned preferred conditions can be combined in any manner, thereby obtaining various preferred examples of the present application.

[0072] The reagents and raw materials used in the present application are commercially available.

[0073] The positive progress effect of the present application is that:

[0074] (1) The present application uses a ball milling process to increase the surface defects and active sites of the graphite material, reduce the activation energy of the graphite material, change the surface structure of the graphite, and increase the lithium ion transmission channels on the surface of the graphite; and then uses the catalytic effect of metal oxides on carbon materials and air or oxygen to realize etching and pore formation on the surface of the graphite, thereby increasing the lithium ion migration channels and improving the charging efficiency of the subsequent battery.

[0075] (2) Further, the rich pore structure of hard carbon and the characteristics of short-range carbon layer stacking are used to shorten the migration distance of lithium ion batteries and increase the transmission channels of lithium ions; in the coating process, the coating layer and the graphite matrix are combined to enhance the bonding strength between the coating layer and the graphite matrix; after carbonization, a three-dimensional network coating structure is formed to improve the stability of the overall structure of the negative electrode hard carbon coated negative electrode, and effectively improve the rate performance charging efficiency of the lithium battery negative electrode.

[0076] (3) The lithium ion transmission channel of the graphite negative electrode material precursor prepared by the method combining mechanical activation and chemical catalysis is increased, and the graphite negative electrode material prepared by further processing has excellent discharge capacity and fast charging performance when applied to a lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0077] Figure 1 SEM image of the graphite negative electrode material prepared in Example 1. DETAILED DESCRIPTION

[0078] The application will be further described in the following examples without limiting the application to the examples. The experimental methods in the following examples are not specified, and are selected according to the conventional methods and conditions or the product instructions.

[0079] In the examples and comparative examples of the application, the graphite has the following characteristics: ash content 0.1%, particle size D50 10.5 μm, Dmax≤31.2 μm, tap density 1.01 g / cm 3 , specific surface area 1.83 m 2 / g, capacity 355 mAh / g, and first coulombic efficiency 94.5%.

[0080] Example 1

[0081] S1: Ball milling treatment: a certain amount of graphite and metal oxide (calcium oxide, particle size: Dmax≤76 μm, D50 38.4 μm) were directly loaded into a high-energy ball mill, and the mass of the metal oxide accounted for 15% of the mass of the graphite. Nitrogen was introduced at a flow rate of 1 L / h, and the ball milling treatment was performed using tungsten carbide as the ball milling medium, with a ball size ratio of 7:3, a ball mill speed of 800 rpm, and a ball milling time of 7 h. The mixture of graphite and metal oxide was obtained after ball milling.

[0082] S2: Heat treatment: the mixture of graphite and metal oxide was placed in an atmosphere furnace, and heated to 600°C under an air atmosphere at an air flow rate of 9 L / h, and held for 6 h. The heat-treated product was obtained after heat treatment. The specific surface area of the product was 4.1 m 2 / g, and the particle size D50 was 25 μm.

[0083] S3: Acid washing treatment: the heat-treated product was subjected to acid washing using dilute hydrochloric acid with a concentration of 1 mol / L at 60°C for 10 h. After washing, the product was washed with water until neutral, and the metal oxide was removed. The coated precursor was obtained after drying at 110°C.

[0084] S4: Coating treatment: the coating precursor is mixed with 5% phenolic resin and 4% trioxane, and then is put into a fusion machine for fusion treatment. The fusion parameters are: rotation speed 600 rpm, time 400 s. After the fusion, a dispersing machine is used for depolymerization treatment. The particle size D50 of the product is 9.8 μm.

[0085] S5: High-temperature carbonization treatment: the product after the coating treatment is placed in a tube furnace, nitrogen gas is introduced, the nitrogen gas flow rate is 8.3 L / h, the temperature is raised to 1100℃, and the temperature is kept for 4 h. After the carbonization treatment, a shaping machine is used for shaping treatment, and the desired graphite negative electrode material is obtained after the treatment. The negative electrode material D50 is 10.5 μm.

[0086] The SEM image of the prepared graphite negative electrode material is shown in Figure 1 .

[0087] Example 2

[0088] Example 2 and Example 1 are different in that the amount of metal oxide added in the S1 step is adjusted (see Table 1). The rest of the process is the same as that of Example 1.

[0089] Table 1

[0090] Example Amount of metal oxide added (%) Example 2.1 5 Example 2.2 15 Example 2.3 30 Example 2.4 45

[0091] Example 3

[0092] Example 3 and Example 1 are different in that the rotation speed of the ball mill in the S1 step is adjusted (see Table 2). The rest of the process is the same as that of Example 1.

[0093] Table 2

[0094]

[0095]

[0096] Example 4

[0097] Example 4 and Example 1 are different in that the ball milling time in the S1 step is adjusted (see Table 3). The rest of the process is the same as that of Example 1.

[0098] Table 3

[0099] Example Ball milling time (h) Example 4.1 1 Example 4.2 4 Example 4.3 7 Example 4.4 10

[0100] Example 5

[0101] Example 5 and Example 1 are different in that the oxygen gas flow rate in the S2 step is adjusted (see Table 4). The rest of the process is the same as that of Example 1.

[0102] Table 4

[0103] Example Flow rate (L / h) Example 5.1 2 Example 5.2 9 Example 5.3 16 Example 5.4 23 Example 5.5 30

[0104] Example 6

[0105] Example 6 differs from Example 1 in the parameter step by adjusting the heat treatment temperature in the S2 step (see Table 5), and the rest of the process is the same as Example 1.

[0106] Table 5

[0107] Example Heat treatment temperature (°C) Example 6.1 400 Example 6.2 500 Example 6.3 600 Example 6.4 700

[0108] Example 7

[0109] Example 7 differs from Example 1 in the parameter step by adjusting the holding time in the S2 step (see Table 6), and the rest of the process is the same as Example 1.

[0110] Table 6

[0111] Example Soaking time (h) Example 7.1 2 Example 7.2 4 Example 7.3 6 Example 7.4 8

[0112] Example 8

[0113] Example 8 differs from Example 1 in the parameter step by adjusting the fusion rotation speed in the S4 step (see Table 7), and the rest of the process is the same as Example 1.

[0114] Table 7

[0115] Example Fusion rotation speed (rpm) Example 8.1 300 Example 8.2 600 Example 8.3 900

[0116] Example 9

[0117] Example 9 differs from Example 1 in the parameter step by adjusting the fusion time in the S4 step (see Table 8), and the rest of the process is the same as Example 1.

[0118] Table 8

[0119] Example Fusion time (s) Example 9.1 200 Example 9.2 400 Example 9.3 600 Example 9.4 800

[0120] Example 10

[0121] Example 10 differs from Example 1 in the parameter step by adjusting the addition amount of the coating agent phenolic resin in the S4 step (see Table 9), and the rest of the process is the same as Example 1.

[0122] Table 9

[0123] Example Amount of coating agent added (%) Example 10.1 1 Example 10.2 5 Example 10.3 10 Example 10.4 15

[0124] Example 11

[0125] Example 11 differs from Example 1 in the parameter step by adjusting the addition amount of the trioxane in the S4 step (see Table 10), and the rest of the process is the same as Example 1.

[0126] Table 10

[0127] Example Amount of trioxane added (%) Example 11.1 0.5 Example 11.2 2 Example 11.3 4 Example 11.4 6

[0128] Example 12

[0129] Example 12 differs from Example 1 in adjusting the carbonization temperature in S5 step (see Table 11), and the rest of the process is the same as Example 1.

[0130] Table 11

[0131] Example Carbonization temperature (°C) Example 12.1 900 Example 12.2 1000 Example 12.3 1100 Example 12.4 1200

[0132] Example 13

[0133] Example 13 differs from Example 1 in adjusting the carbonization holding time in S5 step (see Table 12), and the rest of the process is the same as Example 1.

[0134] Table 12

[0135] Example Soaking time (h) Example 13.1 2 Example 13.2 4 Example 13.3 6

[0136] Comparative Example 1

[0137] S1: Ball milling treatment: a certain amount of graphite and metal oxide (calcium oxide, particle size: Dmax≤76 μm, D50 is 38.4 μm) were taken, the mass of the metal oxide accounted for 15% of the mass of the graphite, and were directly loaded into a high-energy ball mill. Nitrogen was introduced at a flow rate of 1 L / h, and ball milling treatment was performed using tungsten carbide as the ball milling medium, with a ball size ratio of 7:3, a ball mill speed of 100 rpm, and a ball milling time of 1 h. The mixture of graphite and metal oxide was obtained after ball milling.

[0138] S2: Heat treatment: the mixture of graphite and metal oxide was placed in an atmosphere furnace, and was heated to 300°C under an air atmosphere at an air flow rate of 9 L / h, and was held for 1 h. The heat-treated product was obtained after heat treatment. The specific surface area of the product was 1.7 m 2 / g, and the particle size D50 was 32 μm.

[0139] S3: Acid washing treatment: the heat-treated product was subjected to acid washing using dilute hydrochloric acid with a concentration of 1 mol / L at 60°C, and the acid washing time was 10 h. After washing, water was used for washing until neutralization, and the metal oxide was removed. The coated precursor was obtained after drying at 110°C.

[0140] S4: Coating treatment: the coating precursor was mixed with 1% phenolic resin and 0.1% trioxane, and then was added into a fusion machine for fusion treatment. The fusion parameters were as follows: rotation speed 200 rpm, time 400 s. After the fusion, a dispersing machine was used for depolymerization treatment. The particle size D50 of the product was 10.9 μm.

[0141] S5: High-temperature carbonization treatment: the product after coating treatment was placed in a tube furnace, nitrogen was introduced, the nitrogen gas flow was 8.3 L / h, and the temperature was raised to 800°C for 4 h. After carbonization treatment, shaping treatment was performed using a shaping machine. The obtained graphite negative electrode material had a particle size D50 of 10.3 μm.

[0142] Comparative Example 2

[0143] S1: Ball milling treatment: a certain amount of graphite and metal oxide (calcium oxide, particle size: Dmax≤76 μm, D50 38.4 μm) were directly loaded into a high-energy ball mill. Nitrogen was introduced at a flow rate of 1 L / h, and the ball milling treatment was performed using tungsten carbide as the ball milling medium. The size ball ratio was 7:3, the rotation speed of the ball mill was 1100 rpm / min, and the ball milling time was 10 h. The mixture of graphite and metal oxide was obtained after ball milling.

[0144] S2: Heat treatment: the mixture of graphite and metal oxide was placed in an atmosphere furnace, and the temperature was raised to 800°C under an air atmosphere at a flow rate of 9 L / h. The heat treatment was performed for 12 h, and the heat-treated product was obtained. The specific surface area of the product was 8.3 m 2 / g, and the particle size D50 was 28 μm.

[0145] S3: Acid washing treatment: the heat-treated product was washed with 1 mol / L dilute hydrochloric acid at 60°C for 10 h. After washing, water was used for washing until the product was neutral. The metal oxide was removed, and the coating precursor was obtained after drying at 110°C.

[0146] S4: Coating treatment: the coating precursor was mixed with 1% phenolic resin and 0.1% trioxane, and then was added into a fusion machine for fusion treatment. The fusion parameters were as follows: rotation speed 200 rpm, time 400 s. After the fusion, a dispersing machine was used for depolymerization treatment. The particle size D50 of the product was 10.9 μm.

[0147] S5: high-temperature carbonization treatment: placing the product after the coating treatment in a tube furnace, passing nitrogen gas at a flow rate of 8.3 L / h, heating to 1300°C, and maintaining for 2 h. After the carbonization treatment, shaping treatment was performed using a shaper, and the desired graphite negative electrode material was obtained after the treatment. The D50 of the negative electrode material was 10.7 μm.

[0148] Comparative Example 3

[0149] The graphite was not treated.

[0150] Effect Example

[0151] The particle size was tested using a Malvern Mastersizer 3000, the BET was tested using a Micromeritics TriStar II Plus, and the tap density was tested using a Dandong Bettersize BT-310 series tap density instrument.

[0152] The electrochemical performance test process was as follows:

[0153] The prepared graphite negative electrode material, conductive carbon black, and PVDF were dissolved in a certain amount of NMP in a ratio of 90:4:2, stirred for 30 min, and then the slurry was coated on an aluminum foil and dried in a vacuum drying oven for 24 h. After drying, the aluminum foil was cut into 12 mm round pieces, and the loading amount was 26.8 μg. The positive electrode used the above-processed material, the negative electrode used lithium sheet, the separator used Celgard 2500 polypropylene film, and the electrolyte used 1 mol / L lithium hexafluorophosphate (Xingzhubang). A lithium ion battery was assembled according to the type 2032 (those skilled in the art know that, in general, when the test material is assembled into a half-cell with metal lithium, the test material is often used as the positive electrode due to the low hydrogen standard potential of metal lithium).

[0154] After the assembled battery was left to stand for 24 h, the above tests were tested using a new battery CT-4000 test, and the test conditions were as follows: before testing, a small current of 0.05 C was used for activation, and then 200 cycles were tested at 0.1 C and 8 C, respectively, to obtain the first capacity and capacity retention rate at different rates.

[0155] The test results are shown in Table 13 below:

[0156] Table 13

[0157]

[0158]

[0159]

[0160] From the above table, it can be seen that the 0.1C discharge capacity of Examples 1-13 is 352.4-358.2 mAh, the 8C discharge capacity is 308.9-324.7 mAh, and the 8C / 0.1C capacity retention rate is 87.00-90.99%.

[0161] Compared with Examples 1-13, Comparative Examples 1 and 2 can maintain comparable discharge capacity at 0.1C; but when the current is increased to 8C, the discharge capacity is only 295.6-297.2 mAh, and the 8C / 0.1C capacity retention rate is only about 84%, which is significantly lower than that of Examples 1-13. This may be due to the fact that under high-rate conditions, the ball milling speed in Comparative Example 1 is too slow, resulting in insufficient etching of the graphite surface, fewer lithium ion transport channels, and failure to meet the requirements under high-rate conditions. In Comparative Example 2, the addition of excessive metal oxides and the high ball milling speed result in excessive reaction of graphite with air / oxygen, leading to more defects. The specific capacity is related to the graphitization degree, and the etching and pore formation result in a decrease in the degree of graphitization, thus leading to a decrease in capacity and capacity retention rate under high-rate conditions.

[0162] Example 2 changes the amount of metal oxide added on the basis of Example 1. With the increase of the amount of metal oxide added, the 0.1C discharge capacity changes little; the 8C discharge capacity and the 8C / 0.1C capacity retention rate both increase first and then decrease, and when the amount of metal oxide added is 15%, the discharge capacity and the capacity retention rate both reach the highest, being 321.1 mAh and 90.78%, respectively.

[0163] Examples 3-13 change the speed of the ball mill, the ball milling time, the flow rate of the oxidizing gas, the heat treatment temperature, the holding time, the fusion speed, the fusion time, the amount of resin added as the coating agent, the amount of trioxane added, the carbonization temperature, and the carbonization holding time, respectively, on the basis of Example 1. The 0.1C discharge capacity, the 8C discharge capacity, and the 8C / 0.1C capacity retention rate all fluctuate within a normal range.

Claims

1. A method for preparing a graphite negative material precursor, characterized in that, It mainly includes the following steps: graphite and metal oxide are subjected to ball milling treatment, and then subjected to heat treatment and acid washing treatment to obtain the product; In the metal oxide, the metal is selected from Ca; the metal oxide accounts for 2-46% of the mass of the graphite, and the percentage refers to the mass percentage of the metal oxide in the graphite; in the ball milling treatment, the rotation speed of the ball milling is 400-1000 rpm; in the ball milling medium, the size ball ratio is (7-9):(3-1); the heat treatment is carried out in an oxidizing atmosphere; the oxidizing atmosphere is air or oxygen; the temperature of the heat treatment is 300-900°C.

2. The method of claim 1, wherein the graphite negative electrode material precursor is prepared by the steps of: The graphite is artificial graphite or natural graphite; ​ And / or, the Dmax of the graphite is ≤75 μm; And / or, the D50 of the graphite is ≤50 μm; and / or other parameters of the graphite are as follows: ash content ≤ 0.5%, tap density ≥ 0.9 g / cm 3 , specific surface area 0.8-3.2 m 2 / g, capacity ≥ 340 mAh / g, first coulombic efficiency ≥ 90%; And / or, the Dmax of the metal oxide is ≤100 μm; And / or, the D50 of the metal oxide is ≤75 μm; And / or, the metal oxide accounts for 5-45% of the mass of the graphite, and the percentage refers to the mass percentage of the metal oxide in the graphite.

3. The method of claim 2, wherein the graphite negative electrode material precursor is prepared by the steps of: mixing the graphite powder and the binder to form a mixture; and compressing the mixture to form the graphite negative electrode material precursor. The D50 of the graphite is ≤45 μm; And / or, the particle size Dmax of the metal oxide is ≤76 μm; And / or, the metal oxide accounts for 5%, 15%, 30% or 45% of the mass of the graphite.

4. The method of claim 1, wherein the graphite negative electrode material precursor is prepared by the steps of: mixing the graphite powder and the binder to form a mixture; and compressing the mixture to form the graphite negative electrode material precursor. In the ball milling treatment, the rotation speed of the ball milling is 300-1000 ppm; And / or, in the ball milling treatment, the ball milling time is 1-12 h; And / or, in the ball milling treatment, the ball milling medium adopts zirconium oxide or carbide material; And / or, in the ball milling treatment, the operation of introducing inert atmosphere is further included.

5. The method of claim 4, wherein the graphite negative electrode material precursor is prepared by the steps of: mixing the graphite powder and the binder to form a mixture; and compressing the mixture to form the graphite negative electrode material precursor. The rotation speed of the ball milling is 400 rpm, 600 rpm, 800 rpm or 1000 rpm; And / or, the ball milling time is 1-10 h; And / or, the gas flow of the inert atmosphere is 0.2-2 L / h.

6. The method of claim 4, wherein the graphite negative electrode material precursor is prepared by the steps of: mixing the graphite powder and the binder to form a mixture; and compressing the mixture to form the graphite negative electrode material precursor. The ball milling time is 1 h, 4 h, 7 h or 10 h.

7. The method of claim 1, wherein the graphite negative electrode material precursor is prepared by the steps of: mixing the graphite powder and the binder to form a mixture; and compressing the mixture to form the graphite negative electrode material precursor. The gas flow rate of the oxidizing atmosphere is 2-30 L / h; And / or, the temperature of the heat treatment is 400-800°C; And / or, the heat treatment time is 1-10 h; and / or, after the heat treatment, the product has a specific surface area of 1.3-7.4 m 2 / g; And / or, after the heat treatment, the particle size D50 of the product is 20-30 μm.

8. The method of claim 7, wherein the graphite negative electrode material precursor is prepared by the steps of: mixing the graphite powder and the binder to form a mixture; and compressing the mixture to form the graphite negative electrode material precursor. The gas flow rate of the oxidizing atmosphere is 2 L / h, 9 L / h, 16 L / h, 23 L / h or 30 L / h; And / or, the temperature of the heat treatment is 400°C, 500°C, 600°C or 700°C; And / or, the heat treatment time is 2-8 h; And / or, after the heat treatment, the particle size D50 of the product is 25 μm.

9. The method of claim 7, wherein the graphite negative electrode material precursor is prepared by the steps of: mixing the graphite powder and the binder to form a mixture; and compressing the mixture to form the graphite negative electrode material precursor. The heat treatment time is 2 h, 4 h, 6 h or 8 h.

10. The method of claim 1, wherein the graphite negative electrode material precursor is prepared by the steps of: The acid washing treatment includes the following steps: the product of the heat treatment is washed with acid and water until neutral; ​ And / or, after the acid washing treatment, the operation of drying is further included.

11. The method of claim 10, wherein the graphite negative electrode material precursor is prepared by the steps of: mixing the graphite powder and the binder to form a mixture; and compressing the mixture to form the graphite negative electrode material precursor. In the process of the acid washing treatment, the acid is dilute hydrochloric acid; And / or, in the process of the acid washing treatment, mechanical stirring is simultaneously carried out; And / or, in the process of the acid washing treatment, the temperature is controlled at 30-80°C; And / or, the acid washing treatment time is 1-24 h; And / or, the temperature of the drying is 100-120°C.

12. The method of claim 11, wherein the graphite negative electrode material precursor is prepared by the steps of: mixing the graphite powder and the binder to form a mixture; and compressing the mixture to form the graphite negative electrode material precursor. The concentration of the dilute hydrochloric acid is 0.5-3 mol / L; And / or, the speed of the stirring is 100-1000 rpm.

13. A graphite negative material precursor, characterized by, It is prepared by the preparation method of any one of claims 1-12.

14. A method for producing a graphite negative electrode material, characterized by, It mainly comprises the following steps: The graphite negative electrode material precursor of claim 13 is subjected to coating treatment and carbonization treatment.

15. The method of claim 14, wherein the graphite negative electrode material is prepared by the steps of: The coating treatment comprises the following steps: fusion treatment of the graphite negative electrode material precursor with a coating agent and a crosslinking agent, and then depolymerization treatment; ​ And / or, after the heat treatment, the particle size D50 of the product is 8-17 μm; And / or, the carbonization treatment is carried out in an inert atmosphere; And / or, the temperature of the carbonization treatment is 800-1300°C; And / or, the time of the carbonization treatment is 1-8 h; And / or, after the carbonization treatment, it further comprises shaping treatment.

16. The method for preparing the graphite anode material as described in claim 15, characterized in that, The coating agent is a resin or a high molecular polymer; And / or, the amount of the coating agent is 1-15%; And / or, the crosslinking agent is trioxane; And / or, the amount of the crosslinking agent is 0.1-6%; And / or, the rotation speed of the fusion treatment is 200-1100 rpm; And / or, the time of the fusion treatment is 200-900 s; And / or, the gas flow of the inert atmosphere is 2-20 L / h; And / or, the temperature of the carbonization treatment is 900-1200°C; And / or, the time of the carbonization treatment is 2-6 h.

17. The method of claim 15, wherein the graphite negative electrode material is prepared by the steps of: The amount of the coating agent is 1%, 5%, 10% or 15%; ​ And / or, the amount of the crosslinking agent is 0.5-6%; And / or, the rotation speed of the fusion treatment is 300-900 rpm; And / or, the time of the fusion treatment is 200-800 s; And / or, the temperature of the carbonization treatment is 900°C, 1000°C, 1100°C or 1200°C; And / or, the time of the carbonization treatment is 2 h, 4 h or 6 h.

18. The method of claim 15, wherein the graphite negative electrode material is prepared by the steps of: The amount of the crosslinking agent is 0.5%, 2%, 4% or 6%; ​ And / or, the rotation speed of the fusion treatment is 300 rpm, 600 rpm or 900 rpm; And / or, the time of the fusion treatment is 200 s, 400 s, 600 s or 800 s.

19. The method of claim 16, wherein the graphite negative electrode material is prepared by the steps of: The resin is a thermoplastic or a thermosetting resin; ​ And / or, the high molecular polymer is one or more of polyaniline, polypyrrole and polyethylene.

20. The method of claim 16, wherein the graphite negative electrode material is prepared by the steps of: The resin is one or more of phenolic resin, epoxy resin, vinyl resin, urea-formaldehyde resin and melamine-formaldehyde resin. ​ 21. A graphite negative electrode material, characterized by, It is prepared by the preparation method of any one of claims 14-20.

22. Use of the graphite negative electrode material precursor of claim 13 or the graphite negative electrode material of claim 21 in a lithium ion battery.

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