Graphite negative electrode material and preparation method therefor, and battery

Abstract

The present invention relates to the technical field of new energy. Disclosed are a graphite negative electrode material and a preparation method therefor, and a battery. The graphite negative electrode material comprises an inner core composed of a plurality of graphite particles and a zwitterionic polymer coating layer that wraps the inner core, wherein the graphite particles are subjected to liquid phase coating with a resin material, and are granulated by means of a spray drying process and then carbonized so as to form a granulated product having a hard carbon coating layer. The granulation can improve the isotropy of the material, and a hard carbon structure is beneficial for increasing lithium-ion transport channels. After the granulated product is coated with a zwitterionic polymer, a zwitterionic structure is beneficial for improving the conductivity of lithium ions, thereby effectively promoting the transport of Li+ from an electrolyte solution to the surfaces of negative electrode material particles, and therefore the transport path of lithium ions can be effectively shortened, that is, the distance that Li+ in the electrolyte solution travels to arrive at the surface of an active material and then at a reaction center is shortened; and the graphite negative electrode material has the characteristics of a high ion transport rate and a large number of transport channels, making a lithium-ion battery electrode prepared from the graphite negative electrode material have the performance characteristics of a high capacity and a high rate.

Description

Graphite negative electrode material and preparation method thereof, and battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to application number 202311094827.9, filed with the Patent Office of China on August 29, 2023, entitled “A graphite negative electrode material, its preparation method, and battery,” the entire contents of which are incorporated by reference into this disclosure. Technical Field

[0003] The present disclosure relates to the field of new energy technology, and in particular to a graphite negative electrode material, a preparation method thereof, and a battery. Background Art

[0004] The continuous development of the new energy vehicle industry is driving advancements in the power battery industry, with increasing demands for fast-charging performance and energy density. Coating processes are an effective means of improving material rate performance. Carbonization of resin coatings forms a hard carbon layer. Hard carbon exhibits isotropic properties and a larger interlayer spacing than graphite, resulting in rapid lithium ion diffusion during charging and excellent rate performance. However, the rate performance of existing hard carbon-coated anode materials still needs to be further improved.

[0005] Summary of the Invention

[0006] The purpose of the present disclosure is to provide a graphite negative electrode material and a preparation method thereof, and a battery to solve the above problems.

[0007] To achieve the above objectives, the present disclosure adopts the following technical solutions:

[0008] The present disclosure first provides a graphite negative electrode material, including a core and a zwitterionic polymer coating layer coated on the surface of the core, wherein the core includes multiple graphite particles, the surface of the graphite particles is coated with a hard carbon coating layer, and the multiple graphite particles are adhered together by the hard carbon coating layer.

[0009] Among them, zwitterionic polymers are a type of polymer material that is electrically neutral as a whole and contains both anionic and cationic groups on the same monomer side chain. Zwitterionic polymers as coating materials are beneficial for improving ionic conductivity. The ionic structure on their chain segments can effectively promote the + transmission, thereby improving rate performance.

[0010] Graphite particles are coated with resin material in liquid phase and granulated by spray drying process and then carbonized to form granules with hard carbon coating. Granulation can improve the isotropy of the material, and the hard carbon structure is conducive to increasing the transmission channel of lithium ions. After the granules are coated with zwitterionic polymer, the zwitterionic structure on the polymer chain segment is conducive to improving the conductivity of lithium ions, effectively promoting the+ From the electrolyte to the surface of the negative electrode material particles, as shown in Figure 1, the structure of the above-mentioned negative electrode material can effectively shorten the transmission path of lithium ions, that is, shorten the Li + The distance to the surface of the active material and then to the reaction center has the characteristics of fast ion transfer rate and multiple transfer channels, which makes the lithium-ion battery electrode prepared with the graphite negative electrode material of this structure have the performance characteristics of high capacity and high rate.

[0011] Preferably, the zwitterionic polymer is polypropylsulfonate betaine. The structure diagram of polypropylsulfonate betaine is shown in Figure 2, and the infrared image is shown in Figure 3. The polypropylsulfonate betaine coating layer does not need to be carbonized and will retain its polymer segment structure. If the material is added with this coating layer, a preliminary judgment can be made through the infrared image.

[0012] Preferably, the graphite negative electrode material satisfies at least one of the following conditions:

[0013] a. The mass of the hard carbon coating layer accounts for 0.01 to 5% of the graphite negative electrode material, for example, 0.01%, 0.1%, 0.5%, 1%, 2%, 3%, 4% or 5%, or any value between 0.01 and 5%;

[0014] b. The mass of the hard carbon coating layer accounts for 0.01-2% of the graphite negative electrode material;

[0015] c. The mass of the zwitterionic polymer coating layer accounts for 0.01-10% of the graphite negative electrode material, for example, it can be 0.01%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, or any value between 0.01 and 10%;

[0016] d. The mass of the zwitterionic polymer coating layer accounts for 0.01-3% of the graphite negative electrode material;

[0017] e. The mass ratio of the hard carbon coating layer and the zwitterionic polymer coating layer is (0.01-5): (0.01-10);

[0018] f. The mass ratio of the hard carbon coating layer to the zwitterionic polymer coating layer is (1-5): (1-10).

[0019] Preferably, the graphite negative electrode material satisfies at least one of the following conditions:

[0020] g. The particle size D50 of the graphite particles is 3 to 20 μm, for example, 3 μm, 5 μm, 7 μm, 8 μm, 10 μm, 12 μm, 15 μm, 17 μm, 18 μm or 20 μm, or any value between 3 and 20 μm;

[0021] h. The particle size D50 of the graphite particles is 5 to 10 μm;

[0022] i. The particle size D50 of the graphite negative electrode material is 5 to 30 μm, for example, 5 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 15 μm, 17 μm, 18 μm, 20 μm, 22 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm or 30 μm, or any value between 5 and 30 μm;

[0023] j. The particle size D50 of the graphite negative electrode material is 8 to 18 μm.

[0024] Preferably, the graphite particles are selected from one or more combinations of natural graphite, artificial graphite, expanded graphite, graphite oxide and microcrystalline graphite.

[0025] The present disclosure also provides a method for preparing a graphite negative electrode material, as shown in FIG4 , comprising:

[0026] Mixing, granulating, and carbonizing graphite particles and a water-soluble resin material to form a uniform hard carbon coating layer on the surface of the graphite particles to obtain a first precursor;

[0027] The first precursor is mixed with a zwitterionic polymer solution and dried to form a zwitterionic polymer coating layer on the surface of a plurality of secondary particles adhered together by the first precursor, thereby obtaining the graphite negative electrode material.

[0028] Preferably, the method for preparing the graphite particles comprises:

[0029] The coke raw material is mixed with the catalyst and graphitized to obtain the graphite particles. The surface of the particles is rich in pores after the catalytic graphitization process. + Provides a transmission path to the interior of the particle and the reaction center, reducing tortuosity;

[0030] The graphite particles obtained by mixing the coke raw material with the catalyst and performing graphitization treatment meet at least one of the following conditions:

[0031] (1) The catalyst is selected from one or more combinations of ferric oxide, silicon carbide, and boron oxide;

[0032] (2) the added mass of the catalyst in the total mass of the coke raw material and the catalyst is 0.1-20%, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 6%, 8%, 10%, 12%, 15%, 16%, 18% or 20%, or any value between 0.1-20%;

[0033] (3) The added mass of the catalyst in the total mass of the coke raw material and the catalyst is 2-10%.

[0034] Preferably, the mixing, granulation, and carbonization of the graphite particles and the water-soluble resin material meet at least one of the following conditions:

[0035] A. The water-soluble resin material is selected from one or more combinations of phenolic resin, epoxy resin, furfural resin, acrylic resin, polyurethane resin, acrylic-polyurethane copolymer, furan resin, polyvinyl alcohol, chitosan, cellulose, styrene-butadiene rubber, and glucose;

[0036] B. The solid content of the solution of the water-soluble resin material is 0.1 to 90%;

[0037] C. The mass of the water-soluble resin material accounts for 0.1-20% of the graphite negative electrode material;

[0038] D. The mixing speed is 200r / min to 400r / min, and the stirring time is 40 to 80min;

[0039] E. The carbonization temperature is 400° C. to 1300° C., and the carbonization time is 2 to 15 hours.

[0040] Preferably, the mixing of the first precursor and the zwitterionic polymer solution and drying satisfies at least one of the following conditions:

[0041] F. the zwitterionic polymer solution is a polypropylsulfonate betaine solution;

[0042] G. The solid content of the zwitterionic polymer solution is 0.1 to 90%, and the amount of the zwitterionic polymer added is 0.1 to 10% of the entire negative electrode active material;

[0043] H. The mixing speed is 10 to 2000 r / min, and the mixing time is 10 min to 10 h;

[0044] I. The drying temperature is 40-150°C and the drying time is 0.5-20h.

[0045] The present disclosure also provides a battery, wherein the raw materials of the battery include the above-mentioned graphite negative electrode material.

[0046] Compared with the prior art, the advantages of the present invention include:

[0047] The graphite negative electrode material provided by the present disclosure includes a core composed of multiple graphite particles and a zwitterionic polymer coating layer covering the core. The graphite particles are coated with a resin material in liquid phase and granulated by a spray drying process and then carbonized to form a granulated product with a hard carbon coating layer. Granulation can improve the isotropy of the material. The hard carbon structure is conducive to increasing the transmission channel of lithium ions. After the granulated product is coated with the zwitterionic polymer, the zwitterionic structure on the polymer chain segment is conducive to improving the conductivity of lithium ions, effectively promoting Li + Transfer from the electrolyte to the surface of the negative electrode material particles can effectively shorten the transmission path of lithium ions, that is, shorten the Li + The distance to the surface of the active material and then to the reaction center has the characteristics of fast ion transfer rate and multiple transfer channels, which makes the lithium-ion battery electrode prepared with the graphite negative electrode material of this structure have the performance characteristics of high capacity and high rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope of the present disclosure.

[0049] Figure 1 shows Li + Model diagram of the surface and active center transfer of the graphite negative electrode material disclosed in the present invention;

[0050] FIG2 is a structural diagram of a zwitterionic polymer polypropylsulfonate betaine;

[0051] FIG3 is an infrared image of a zwitterionic polymer polypropylsulfonate betaine;

[0052] FIG4 is a schematic diagram of the preparation process of the graphite negative electrode material disclosed in the present invention;

[0053] FIG5 is a SEM morphology of graphite particles prepared by the catalytic graphitization process of Example 3;

[0054] FIG6 is a cross-sectional SEM image of the granulated product prepared by the spray drying process of Example 10;

[0055] FIG7 is a SEM morphology of the finished graphite negative electrode material of Example 10. DETAILED DESCRIPTION

[0056] As used herein:

[0057] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0058] The conjunction "consisting of" excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim, rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0059] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0060] In these examples, parts and percentages are by mass unless otherwise indicated.

[0061] "Parts by mass" refers to the basic unit of measurement used to express the mass ratio of multiple components. One part can represent any unit of mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, this means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, we could say that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number representing a multiplication factor). It's important to note that, unlike parts by mass, the sum of the mass of all components is not limited to 100 parts.

[0062] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0063] The embodiments of the present disclosure will be described in detail below with reference to specific examples. However, those skilled in the art will appreciate that the following examples are intended only to illustrate the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer were used. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0064] Example 1

[0065] 990 g of coke micron particles (D50 = 8 μm) and 10 g of boron trioxide were added to a VC machine and mixed at a stirring speed of 300 r / min for 60 min. After mixing evenly, the graphite particles of Example 1 were prepared by a graphitization process at 3000° C. in an Acheson furnace.

[0066] Example 2

[0067] 950 g of coke micron particles (D50=8 μm) and 50 g of boron trioxide were added to a VC machine and mixed at a stirring speed of 300 r / min for 60 min. After mixing evenly, the graphite particles of Example 2 were prepared by a graphitization process at 3000° C. in an Acheson furnace.

[0068] Example 3

[0069] 900 g of coke micron particles (D50 = 8 μm) and 100 g of boron trioxide were added to a VC machine and mixed at a stirring speed of 300 r / min for 60 min. After uniform mixing, the mixture was subjected to a graphitization process at 3000° C. in an Acheson furnace to obtain graphite particles of Example 3, the SEM morphology of which is shown in FIG5 .

[0070] Example 4

[0071] 850 g of coke micron particles (D50 = 8 μm) and 150 g of boron trioxide were added to a VC machine and mixed at a stirring speed of 300 r / min for 60 min. After mixing evenly, the graphite particles of Example 4 were prepared by a graphitization process at 3000° C. in an Acheson furnace.

[0072] Example 5

[0073] 800 g of coke micron particles (D50 = 8 μm) and 200 g of boron trioxide were added to a VC machine and mixed at a stirring speed of 300 r / min for 60 min. After mixing evenly, the graphite particles of Example 5 were prepared by a graphitization process at 3000° C. in an Acheson furnace.

[0074] Comparative Example 1

[0075] 1000 g of coke micron particles (D50=8 μm) were graphitized in an Acheson furnace at 3000° C. to obtain graphite particles of Comparative Example 1.

[0076] The basic indicators of the graphite particles obtained in Examples 1 to 5 and Comparative Example 1 were tested, and the buckling performance of the graphite particles after being prepared into batteries was tested. The results are shown in Table 1.

[0077] Table 1 Basic indicators of graphite particles and power-off test results

[0078] According to the results in Table 1, as the amount of catalyst added increases, the degree of graphitization increases, the capacity and rate performance improve, and the specific surface area increases, indicating that the surface pores increase, but the tap compaction decreases. Taking into account various indicators, furnace loading and cost, the graphite particles prepared in Example 3 with a catalyst addition of 10% were selected as the substrate for subsequent example experiments.

[0079] Example 6

[0080] 99.4g of the graphite particles from Example 3 were added to 100g of a dispersion of phenolic resin with a solid content of 1% and a residual carbon content of 50%, and stirred thoroughly at 300 rpm for 60 minutes. After spray drying and granulation, the mixture was carbonized in a high-pressure sand kiln at 1150°C for 10 hours in a nitrogen atmosphere. 99.9g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution with a solid content of 0.1%, stirred thoroughly, and then dried in an 80°C oven for 5 hours. This yielded the high-capacity, high-rate graphite negative electrode material from Example 6.

[0081] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 0.5% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 0.1% of the entire graphite negative electrode material.

[0082] Example 7

[0083] 98.5 g of the graphite particles of Example 3 were added to 100 g of a dispersion of phenolic resin having a solid content of 1% and a residual carbon content of 50% and were thoroughly stirred at a stirring speed of 300 r / min for 60 min. After granulation by spray drying, the mixture was carbonized in a high-pressure sand kiln at a carbonization temperature of 1150° C. for 10 hours in a nitrogen atmosphere. 99 g of the carbonized product was added to 100 g of a polypropylsulfonate betaine solution having a solid content of 1%, stirred evenly, and then dried in an 80° C. oven for 5 hours before removal to obtain the high-capacity, high-rate performance graphite negative electrode material of Example 7.

[0084] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 0.5% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 1% of the entire graphite negative electrode material.

[0085] Example 8

[0086] 96g of the graphite particles of Example 3 were added to 100g of a dispersion of phenolic resin with a solid content of 2% and a residual carbon content of 50%, and stirred thoroughly at a stirring speed of 300 r / min for 60 minutes. After granulation by spray drying, the mixture was added to a high-temperature sand kiln for carbonization at a temperature of 1150°C for 10 hours in a nitrogen atmosphere. 97g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution with a solid content of 3%, stirred thoroughly, and then dried in an 80°C oven for 5 hours. The high-capacity, high-rate performance graphite negative electrode material of Example 8 was obtained.

[0087] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 1% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 3% of the entire graphite negative electrode material.

[0088] Example 9

[0089] 95.5 g of the graphite particles of Example 3 were added to 100 g of a dispersion of phenolic resin having a solid content of 3% and a residual carbon content of 50% and were thoroughly stirred at a stirring speed of 300 r / min for 60 min. After granulation by spray drying, the mixture was carbonized in a high-pressure sand kiln at a carbonization temperature of 1150° C. for 10 hours in a nitrogen atmosphere. 97 g of the carbonized product was added to 100 g of a polypropylsulfonate betaine solution having a solid content of 3%, stirred evenly, and then dried in an 80° C. oven for 5 hours before removal to obtain the high-capacity, high-rate performance graphite negative electrode material of Example 9.

[0090] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 1.5% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 3% of the entire graphite negative electrode material.

[0091] Example 10

[0092] 95g of the graphite particles of Example 3 were added to 100g of a dispersion of phenolic resin having a solid content of 4% and a residual carbon content of 50%, and stirred thoroughly at a stirring speed of 300 r / min for 60 minutes. After granulation by spray drying, the mixture was added to a high-pressure sand kiln for carbonization at a temperature of 1150°C for 10 hours in a nitrogen atmosphere. The cross-sectional SEM image of the obtained carbonized granules is shown in Figure 6. 97g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution having a solid content of 3%, stirred uniformly, and then dried in an 80°C oven for 5 hours. The high-capacity, high-rate performance graphite negative electrode material of Example 10 was obtained, and its SEM image is shown in Figure 7.

[0093] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 2% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 3% of the entire graphite negative electrode material.

[0094] Example 11

[0095] 94 g of the graphite particles of Example 3 were added to 100 g of a dispersion of phenolic resin having a solid content of 6% and a residual carbon content of 50% and were thoroughly stirred at a stirring speed of 300 r / min for 60 min. After granulation by spray drying, the mixture was carbonized in a high-pressure sand kiln at a carbonization temperature of 1150° C. for 10 hours in a nitrogen atmosphere. 97 g of the carbonized product was added to 100 g of a polypropylsulfonate betaine solution having a solid content of 3%, stirred evenly, and then dried in an 80° C. oven for 5 hours before removal to obtain the high-capacity, high-rate performance graphite negative electrode material of Example 11.

[0096] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 3% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 3% of the entire graphite negative electrode material.

[0097] Example 12

[0098] 92g of the graphite particles of Example 3 were added to 100g of a dispersion of phenolic resin having a solid content of 6% and a residual carbon content of 50%, and stirred thoroughly at a stirring speed of 300 r / min for 60 minutes. After granulation by spray drying, the mixture was added to a high-temperature sand kiln for carbonization at a temperature of 1150°C for 10 hours in a nitrogen atmosphere. 95g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution having a solid content of 5%, stirred thoroughly, and then dried in an 80°C oven for 5 hours. The high-capacity, high-rate performance graphite negative electrode material of Example 12 was obtained.

[0099] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 3% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 5% of the entire graphite negative electrode material.

[0100] Example 13

[0101] 87g of the graphite particles of Example 3 were added to 100g of a dispersion of phenolic resin having a solid content of 10% and a residual carbon content of 50%, and stirred thoroughly at a stirring speed of 300 r / min for 60 minutes. After granulation by spray drying, the mixture was carbonized in a high-pressure sand kiln at a carbonization temperature of 1150°C for 10 hours in a nitrogen atmosphere. 92g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution having a solid content of 8%, stirred thoroughly, and then dried in an 80°C oven for 5 hours. The high-capacity, high-rate performance graphite negative electrode material of Example 13 was obtained.

[0102] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 5% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 8% of the entire graphite negative electrode material.

[0103] Example 14

[0104] 85g of the graphite particles of Example 3 were added to 100g of a dispersion of phenolic resin having a solid content of 10% and a residual carbon content of 50% and were thoroughly stirred at a stirring speed of 300 r / min for 60 minutes. After granulation by spray drying, the mixture was carbonized in a high-pressure sand kiln at a carbonization temperature of 1150°C for 10 hours in a nitrogen atmosphere. 90g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution having a solid content of 10%, stirred evenly, and then dried in an 80°C oven for 5 hours. The high-capacity, high-rate performance graphite negative electrode material of Example 14 was obtained.

[0105] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 5% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 10% of the entire graphite negative electrode material.

[0106] Example 15

[0107] 93g of the graphite particles of Example 3 were added to 100g of a dispersion of phenolic resin with an 8% solids content and a 50% residual carbon content, and stirred thoroughly at 300 rpm for 60 minutes. After granulation by spray drying, the mixture was carbonized in a high-pressure sand kiln at a temperature of 1150°C for 10 hours in a nitrogen atmosphere. 97g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution with a 3% solids content, stirred thoroughly, and then dried in an 80°C oven for 5 hours. This yielded the high-capacity, high-rate performance graphite negative electrode material of Example 15.

[0108] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 4% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 3% of the entire graphite negative electrode material.

[0109] Example 16

[0110] 95g of the graphite particles of Example 3 were added to 100g of a dispersion of phenolic resin having an 8% solid content and a 50% residual carbon content, and stirred thoroughly at 300 rpm for 60 minutes. The mixture was then spray-dried and granulated, and then carbonized in a high-pressure sand kiln at 1150°C for 10 hours in a nitrogen atmosphere. 99g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution having a 1% solid content, stirred thoroughly, and then dried in an 80°C oven for 5 hours. This yielded the high-capacity, high-rate performance graphite negative electrode material of Example 16.

[0111] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 4% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 1% of the entire graphite negative electrode material.

[0112] Example 17

[0113] 97.9 g of the graphite particles of Example 3 were added to 100 g of a dispersion of phenolic resin having a solid content of 4% and a residual carbon content of 50%, and stirred thoroughly at a stirring speed of 300 r / min for 60 min. After granulation by spray drying, the mixture was carbonized in a high-pressure sand kiln at a carbonization temperature of 1150° C. for 10 hours in a nitrogen atmosphere. 99.9 g of the carbonized product was added to 100 g of a polypropylsulfonate betaine solution having a solid content of 0.1%, stirred thoroughly, and then dried in an 80° C. oven for 5 hours. This yielded the high-capacity, high-rate performance graphite negative electrode material of Example 17.

[0114] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 2% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 0.1% of the entire graphite negative electrode material.

[0115] Example 18

[0116] 95g of microcrystalline graphite (D50 = 8μm) was added to 100g of a dispersion of phenolic resin with a solid content of 4% and a residual carbon content of 50%, and the mixture was thoroughly stirred at 300r / min for 60min. After granulation by spray drying, the mixture was carbonized in a high-pressure sand kiln at a temperature of 1150°C for 10 hours in a nitrogen atmosphere. 97g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution with a solid content of 3%, stirred thoroughly, and then dried in an 80°C oven for 5 hours. This yielded the high-capacity, high-rate performance graphite negative electrode material of Example 18.

[0117] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 2% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 3% of the entire graphite negative electrode material.

[0118] Example 19

[0119] 95g of natural graphite (D50 = 8μm) was added to 100g of a dispersion of phenolic resin with a solid content of 4% and a residual carbon content of 50%, and the mixture was thoroughly stirred at 300r / min for 60min. After granulation by spray drying, the mixture was carbonized in a high-pressure sand kiln at a temperature of 1150°C for 10 hours in a nitrogen atmosphere. 97g of the carbonized product was added to 100g of a polypropylsulfonate betaine solution with a solid content of 3%, stirred evenly, and then dried in an 80°C oven for 5 hours. The high-capacity, high-rate performance graphite negative electrode material of Example 18 was obtained.

[0120] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 2% of the entire graphite negative electrode material, and the mass of the zwitterionic polymer coating layer accounts for 3% of the entire graphite negative electrode material.

[0121] Comparative Example 2

[0122] 98 g of the graphite particles of Comparative Example 1 were added to 100 g of a dispersion of a phenolic resin having a solid content of 4% and a residual carbon of 50% and stirred thoroughly at a stirring speed of 300 r / min for 60 min. After granulation by a spray drying process, the mixture was added to a high sand kiln for carbonization at a carbonization temperature of 1150 ° C and a carbonization time of 10 hours in a nitrogen atmosphere to obtain the graphite negative electrode material of Comparative Example 2.

[0123] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 2% of the entire graphite negative electrode material.

[0124] Comparative Example 3

[0125] 97 g of the graphite particles of Comparative Example 1 were added to 100 g of a polypropylsulfonate betaine solution with a solid content of 3%, stirred evenly, and then placed in an oven at 80° C. for 5 hours for drying to obtain the graphite negative electrode material of Comparative Example 3.

[0126] The mass of the zwitterionic polymer coating layer of the prepared graphite negative electrode material product accounts for 3% of the entire graphite negative electrode material product.

[0127] Comparative Example 4

[0128] 98 g of the graphite particles of Example 3 were added to 100 g of a dispersion of a phenolic resin having a solid content of 4% and a residual carbon of 50% and stirred thoroughly at a stirring speed of 300 r / min for 60 min. After granulation by a spray drying process, the mixture was added to a high sand kiln for carbonization at a carbonization temperature of 1150 ° C and a carbonization time of 10 hours in a nitrogen atmosphere to obtain the graphite negative electrode material of Comparative Example 4.

[0129] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 2% of the entire graphite negative electrode material.

[0130] Comparative Example 5

[0131] 97 g of the graphite particles of Example 3 were added to 100 g of a polypropylsulfonate betaine solution with a solid content of 3%, stirred evenly, and then placed in an oven at 80° C. for 5 hours for drying, to obtain the graphite negative electrode material of Comparative Example 5.

[0132] The mass of the zwitterionic polymer coating layer of the prepared graphite negative electrode material product accounts for 3% of the entire graphite negative electrode material product.

[0133] Comparative Example 6

[0134] 98g of microcrystalline graphite (D50 = 8μm) was added to 100g of a dispersion of phenolic resin with a solid content of 4% and a residual carbon of 50% and stirred thoroughly at a stirring speed of 300r / min for 60min. After granulation by a spray drying process, it was added to a high sand kiln for carbonization at a carbonization temperature of 1150°C for 10 hours in a nitrogen atmosphere to obtain the graphite negative electrode material of Comparative Example 6.

[0135] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 2% of the entire graphite negative electrode material.

[0136] Comparative Example 7

[0137] 97 g of microcrystalline graphite (D50=8 μm) was added to 100 g of a polypropylsulfonate betaine solution with a solid content of 3%, stirred evenly, and then placed in an oven at 80° C. for 5 hours for drying to obtain the graphite negative electrode material of Comparative Example 7.

[0138] The mass of the zwitterionic polymer coating layer of the prepared graphite negative electrode material product accounts for 3% of the entire graphite negative electrode material product.

[0139] Comparative Example 8

[0140] 98g of natural graphite (D50 = 8μm) was added to 100g of a dispersion of phenolic resin with a solid content of 4% and a residual carbon of 50% and stirred thoroughly at a stirring speed of 300r / min for 60min. After granulation by a spray drying process, it was added to a high sand kiln for carbonization at a carbonization temperature of 1150°C for 10 hours in a nitrogen atmosphere to obtain the graphite negative electrode material of Comparative Example 8.

[0141] The mass of the hard carbon coating layer of the prepared graphite negative electrode material accounts for 2% of the entire graphite negative electrode material.

[0142] Comparative Example 9

[0143] 97 g of natural graphite (D50=8 μm) was added to 100 g of a polypropylsulfonate betaine solution with a solid content of 3%, stirred evenly, and then placed in an oven at 80° C. for 5 hours for drying to obtain the graphite negative electrode material of Comparative Example 9.

[0144] The mass of the zwitterionic polymer coating layer of the prepared graphite negative electrode material product accounts for 3% of the entire graphite negative electrode material product.

[0145] Electrode sheets were prepared using the graphite negative electrode materials prepared in Examples 6 to 19 of the present invention and Comparative Examples 2 to 9, and the following performance measurements were performed: initial discharge specific capacity, initial charge and discharge efficiency, rate performance, and impedance performance of the electrode.

[0146] The preparation method of the electrode sheet is as follows:

[0147] The above-mentioned graphite negative electrode material was prepared into a slurry in a mass ratio of: graphite negative electrode material: carbon black conductive agent SP: binder = 96.5:2:1.5, and mechanically stirred at room temperature for 30 minutes at a stirring speed of 2000 r / min. The prepared slurry was coated on the current collector, baked in a 100°C oven for 30 minutes, and then dried in a 130°C vacuum drying oven for 8 hours. The prepared pole pieces were assembled into lithium-ion button batteries for constant current charge and discharge tests. The lithium sheet was used as the counter electrode, and LiPF6 was dissolved in a mixed solvent of EC / DEC / EMC = 2:3:1 at a concentration of 1 mol / L to form a non-aqueous electrolyte, wherein EC is ethylene carbonate, EMC is methyl ethyl carbonate, and DEC is diethyl carbonate. The battery was assembled in a glove box.

[0148] where σ is the ionic conductivity, R b is the impedance, S and d are the effective area and thickness of the electrode, respectively.

[0149] The test results are shown in Table 2. Combined with the test results of Table 1 and Table 2, compared with the graphite particle negative electrode material of Example 3 and the negative electrode materials of Comparative Examples 4 to Comparative Examples 9 coated with only one hard carbon coating layer or only one zwitterionic polymer coating layer, the graphite negative electrode materials prepared after hard carbon coating granulation and zwitterionic polymer coating in Examples 6 to 19 have significantly improved rate performance, reduced impedance and improved ionic conductivity, but the introduction of the hard carbon coating layer will reduce the capacity, first effect and tap compaction, which is not conducive to improving the energy density of the electrode. Comprehensively considering the capacity, first effect, tap compaction, rate and ionic conductivity performance, the graphite negative electrode material prepared in Example 10 has better comprehensive performance.

[0150] Compared with the microcrystalline graphite material of Example 18 and the natural graphite material of Example 19, the graphite particles of the disclosed solution are prepared by catalyst catalysis, and their performance in all aspects is superior to that of microcrystalline graphite and natural graphite.

[0151] Table 2 Sample ionic conductivity and charge-discharge test results

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present disclosure.

[0153] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not other features, the combination of features from different embodiments is intended to be within the scope of this disclosure and to form different embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is intended solely to enhance understanding of the overall background of this disclosure and should not be construed as an admission or any form of implication that such information constitutes prior art already known to those skilled in the art. Industrial Applicability

[0154] The graphite negative electrode material provided by the present disclosure includes an inner core composed of multiple graphite particles and a zwitterionic polymer coating layer coating the inner core. The preparation process is simple and easy. The prepared graphite negative electrode material has the performance characteristics of high capacity and high rate, and has very good market application prospects.

Claims

1. A graphite negative electrode material, characterized in that: It comprises a core and a zwitterionic polymer coating layer coated on the surface of the core, wherein the core comprises a plurality of graphite particles, the surface of the graphite particles is coated with a hard carbon coating layer, and the plurality of graphite particles are adhered together by the hard carbon coating layer; The zwitterionic polymer is polypropanesulfonate betaine; The graphite negative electrode material meets the following conditions: a. The mass of the hard carbon coating layer accounts for 0.01 to 5% of the graphite negative electrode material; b. The mass of the zwitterionic polymer coating layer accounts for 0.01-10% of the graphite negative electrode material; c. The mass ratio of the hard carbon coating layer to the zwitterionic polymer coating layer is (0.01-5): (0.01-10).

2. The graphite negative electrode material according to claim 1, characterized in that The graphite negative electrode material meets at least one of the following conditions: d. The mass of the hard carbon coating layer accounts for 0.01-2% of the graphite negative electrode material; e. The mass of the zwitterionic polymer coating layer accounts for 0.01-3% of the graphite negative electrode material; f. The mass ratio of the hard carbon coating layer to the zwitterionic polymer coating layer is (1-5): (1-10).

3. The graphite negative electrode material according to claim 1 or 2, characterized in that: The graphite negative electrode material meets at least one of the following conditions: g. The particle size D50 of the graphite particles is 3 to 20 μm; h. The particle size D50 of the graphite negative electrode material is 5 to 30 μm.

4. The graphite negative electrode material according to claim 3, characterized in that: The graphite negative electrode material meets at least one of the following conditions: i. The particle size D50 of the graphite particles is 5 to 10 μm; j. The particle size D50 of the graphite negative electrode material is 8 to 18 μm.

5. The graphite negative electrode material according to any one of claims 1 to 4, characterized in that The graphite particles are selected from one or more combinations of natural graphite, artificial graphite, expanded graphite, oxidized graphite and microcrystalline graphite.

6. A method for preparing a graphite negative electrode material according to any one of claims 1 to 5, characterized in that: include: The graphite particles and the water-soluble resin material are mixed, granulated, and carbonized to form a uniform hard carbon coating layer on the surface of the graphite particles to obtain a first precursor; The first precursor is mixed with a zwitterionic polymer solution and dried to form a zwitterionic polymer coating layer on the surface of a plurality of secondary particles bonded together by the first precursor to obtain the graphite negative electrode material; The first precursor is mixed with the zwitterionic polymer solution and dried to meet the following conditions: The zwitterionic polymer solution is a polypropanesulfonate betaine solution; The solid content of the zwitterionic polymer solution is 0.1 to 90%, and the amount of zwitterionic polymer added is 0.1 to 10% of the entire negative electrode active material; The mixing speed is 10-2000 r / min, and the mixing time is 10 min-10 h; The drying temperature is 40-150° C., and the drying time is 0.5-20 hours.

7. The method for preparing a graphite negative electrode material according to claim 6, characterized in that: The preparation method of the graphite particles comprises: Mixing the coke raw material with the catalyst and performing graphitization treatment to obtain the graphite particles; The graphite particles obtained by mixing the coke raw material with the catalyst for graphitization satisfy at least one of the following conditions: (1) The catalyst is selected from one or more combinations of ferric oxide, silicon carbide, and boron oxide; (2) The added mass of the catalyst in the total material of the coke raw material and the catalyst is 0.1-20%.

8. The method for preparing a graphite negative electrode material according to claim 7, characterized in that: The added mass of the catalyst in the total material of the coke raw material and the catalyst is 2-10%.

9. The method for preparing a graphite negative electrode material according to any one of claims 6 to 8, characterized in that: The mixing, granulation and carbonization of the graphite particles and the water-soluble resin material satisfies at least one of the following conditions: A. The water-soluble resin material is selected from one or more combinations of phenolic resin, epoxy resin, furfural resin, acrylic resin, polyurethane resin, acrylic-polyurethane copolymer, furan resin, polyvinyl alcohol, chitosan, cellulose, styrene-butadiene rubber, and glucose; B. The solid content of the solution of the water-soluble resin material is 0.1 to 90%; C. The mass of the water-soluble resin material accounts for 0.1-20% of the graphite negative electrode material; D. The mixing speed is 200r / min to 400r / min, and the mixing time is 40 to 80min; E. The carbonization temperature is 400° C. to 1300° C., and the carbonization time is 2 to 15 hours.

10. A battery, characterized in that: The raw material of the battery includes the graphite negative electrode material according to any one of claims 1 to 5 or the graphite negative electrode material prepared by the preparation method according to any one of claims 6 to 9.

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