CN117352731A - Natural graphite anode material and preparation method and application thereof - Google Patents

Natural graphite anode material and preparation method and application thereof Download PDF

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Publication number
CN117352731A
CN117352731A CN202311120800.2A CN202311120800A CN117352731A CN 117352731 A CN117352731 A CN 117352731A CN 202311120800 A CN202311120800 A CN 202311120800A CN 117352731 A CN117352731 A CN 117352731A
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natural graphite
anode material
lithium
intermediate product
negative electrode
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马强
宋健
杜宁
张津魁
李焱雄
岳敏
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Carbon One New Energy Hangzhou Co ltd
Zhejiang Lichen New Material Technology Co ltd
Carbon New Energy Group Co ltd
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Carbon One New Energy Hangzhou Co ltd
Zhejiang Lichen New Material Technology Co ltd
Carbon New Energy Group Co ltd
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Priority to CN202311120800.2A priority Critical patent/CN117352731A/en
Publication of CN117352731A publication Critical patent/CN117352731A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes

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  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
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  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention relates to a natural graphite anode material, a preparation method and application thereof. The natural graphite negative electrode material comprises natural graphite, and a lithium coating layer and an amorphous carbon layer which are sequentially coated on the surface of the natural graphite, wherein the lithium coating layer comprises an M element, and the M element can form a C-M-C bond with the carbon element in the natural graphite and the carbon element in the amorphous carbon layer. The natural graphite anode material has excellent structural stability and is rich in active lithium ions, and the first coulomb efficiency and the reversible discharge specific capacity of the anode material can be remarkably improved.

Description

Natural graphite anode material and preparation method and application thereof
Technical Field
The invention relates to the technical field of batteries, in particular to a natural graphite anode material and a preparation method and application thereof.
Background
The cathode material of the commercial lithium ion battery is mainly artificial graphite, but the preparation cost is high, and the price of the lithium ion battery is greatly increased. Although natural graphite has the advantages of low cost, high abundance, high capacity and the like, due to the problems of surface defects, anisotropy and the like of natural graphite, a large amount of active lithium ions are consumed to generate a solid electrolyte interface film (SEI film) in the first cycle, and the solid electrolyte interface film generated by volume expansion in the process of intercalation/deintercalation is broken, so that electrolyte is contacted with internal natural graphite, more active lithium ions are lost and side reactions are initiated, and the electrochemical performance is rapidly reduced.
Disclosure of Invention
Based on the above, it is necessary to provide a natural graphite anode material, a preparation method and application thereof; the natural graphite anode material has excellent structural stability and is rich in active lithium ions, and the first coulomb efficiency and the reversible discharge specific capacity of the anode material can be remarkably improved.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: the natural graphite anode material comprises natural graphite, and a lithium coating layer and an amorphous carbon layer which are sequentially coated on the surface of the natural graphite, wherein the lithium coating layer comprises an M element, and the M element can form a C-M-C bond with carbon elements in the natural graphite and carbon elements in the amorphous carbon layer.
In one embodiment, the M element is selected from at least one of a B element, a Ti element, or a V element.
In one embodiment, D of the natural graphite 50 The particle size is 10 μm-12 μm.
According to the natural graphite negative electrode material disclosed by the invention, the lithium coating layer and the amorphous carbon layer are sequentially coated, and firstly, the lithium coating layer and the amorphous carbon layer coated on the surface of the natural graphite can effectively solve the problem of surface defects of the natural graphite, so that the natural graphite negative electrode material has an excellent microcosmic appearance, a stable surface foundation is provided for the generation of an artificial SEI film, and the first coulombic efficiency and the reversible discharge specific capacity of the negative electrode material are improved.
Secondly, the natural graphite anode material has a unique C-M-C bond network structure, on one hand, active lithium ions in the lithium coating layer can be anchored, so that the active lithium ions are not easy to be embedded into the natural graphite anode material and stably exist in the lithium coating layer structure, and further, extra active lithium ions are provided for the formation of an SEI film during the first circulation, so that the consumption of lithium ions in electrolyte is reduced, and the first coulomb efficiency and the reversible discharge specific capacity of the anode material are improved; on the other hand, the bonding force between the amorphous carbon layer and the internal natural graphite can be improved by utilizing the C-M-C bond, so that the structural stability of the natural graphite negative electrode material is greatly improved, and further, the falling off of the surface amorphous carbon layer caused by volume expansion in the process of lithium intercalation/deintercalation can be effectively avoided.
Therefore, the natural graphite anode material has excellent structural stability and is rich in active lithium ions, and the first coulomb efficiency and the reversible discharge specific capacity of the anode material can be obviously improved.
The preparation method of the natural graphite anode material comprises the following steps:
mixing lithium salt with natural graphite and performing wet ball milling to obtain an intermediate product, wherein the intermediate product comprises the natural graphite and the lithium salt coated on the surface of the natural graphite;
and mixing the intermediate product with a polymer, coating the polymer on the surface of the intermediate product, and carbonizing to obtain the natural graphite anode material.
In one embodiment, the lithium salt is selected from at least one of lithium borate, lithium titanate, or lithium vanadate.
In one embodiment, the step of mixing the lithium salt with natural graphite and wet ball milling satisfies at least one of the following conditions:
(1) D of the natural graphite 50 The grain diameter is 10 μm-12 μm;
(2) The mass ratio of the lithium salt to the natural graphite is 0.1:1-0.7:1;
(3) The ball milling rotating speed is 300rpm-600rpm, the ball milling time is 3h-12h, and the ball-material ratio is 15:1-25:1;
(4) The solvent is at least one selected from deionized water, dilute hydrochloric acid or absolute ethanol.
In one embodiment, after the wet ball milling is finished, a drying treatment step is further performed, wherein the drying treatment temperature is 30-100 ℃, and the drying treatment time is 30-240 min.
In one embodiment, the polymer is selected from at least one of polyimide, polyacrylonitrile, polyvinylpyrrolidone, or polyetheretherketone.
In one embodiment, the step of mixing the intermediate product with a polymer and carbonizing satisfies at least one of the following conditions:
(1) The mass ratio of the intermediate product to the polymer is 1:0.5-1:1;
(2) The carbonization step is carried out in a protective atmosphere, the carbonization temperature is 300-1000 ℃ and the time is 3-10 h.
According to the preparation method, lithium salt can be coated on the surface of natural graphite through wet ball milling to form a lithium salt coating layer, the natural graphite can be shaped, defects existing on the surface of the natural graphite are reduced, then the polymer coating layer is formed on the surface of the lithium salt coating layer through polymers, in the carbonization process, the polymer coating layer is heated and decomposed into an amorphous carbon layer, the lithium salt coating layer is heated and decomposed to generate lithium oxide and/or lithium peroxide, meanwhile, an oxide containing M element is generated, the oxide containing M element can further perform alloying reaction with part of carbon in the internal natural graphite and outer polymer derived carbon to form a unique C-M-C bond network structure, and active lithium ions in the lithium oxide and/or lithium peroxide are anchored in the C-M-C bond network structure, so that the structural stability of the natural graphite negative electrode material is improved, and meanwhile, the natural graphite negative electrode material has excellent electrochemical performance.
A negative electrode tab comprising a negative electrode current collector and a negative electrode active material layer comprising a natural graphite negative electrode material as described above.
A battery comprising a negative electrode tab as described above.
An electrical device comprising a battery as described above.
Drawings
Fig. 1 is a schematic structural diagram of a natural graphite anode material according to the present invention.
Wherein, 10, natural graphite; 20. a lithium coating layer; 30. an amorphous carbon layer.
Detailed Description
The present invention will be described in more detail below in order to facilitate understanding of the present invention. It should be understood, however, that the invention may be embodied in many different forms and is not limited to the implementations or embodiments described herein. Rather, these embodiments or examples are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments or examples only and is not intended to be limiting of the invention. As used herein, the optional scope of the term "and/or" includes any one of the two or more related listed items, as well as any and all combinations of related listed items, including any two or more of the related listed items, or all combinations of related listed items.
Referring to fig. 1, the present invention provides a natural graphite anode material, which includes a natural graphite 10, and a lithium coating layer 20 and an amorphous carbon layer 30 sequentially coated on the surface of the natural graphite 10, wherein the lithium coating layer 20 includes an M element, and the M element can form a C-M-C bond with a carbon element in the natural graphite 10 and a carbon element in the amorphous carbon layer 30.
According to the natural graphite negative electrode material disclosed by the invention, the lithium coating layer 20 and the amorphous carbon layer 30 are sequentially coated, and firstly, the lithium coating layer 20 and the amorphous carbon layer 30 coated on the surface of the natural graphite 10 can effectively solve the problem of surface defects of the natural graphite 10, so that the natural graphite negative electrode material has excellent microcosmic appearance, a stable surface foundation is provided for the generation of an artificial SEI film, and the first coulombic efficiency and the reversible discharge specific capacity of the negative electrode material are improved.
Secondly, the natural graphite anode material has a unique C-M-C bond network structure, on one hand, active lithium ions in the lithium coating layer 20 can be anchored, so that the active lithium ions are not easy to be embedded into the natural graphite anode material and stably exist in the lithium coating layer 20 structure, and further, extra active lithium ions are provided for the formation of an SEI film during the first circulation, so that the consumption of lithium ions in electrolyte is reduced, and the first coulomb efficiency and the reversible discharge specific capacity of the anode material are improved.
On the other hand, the bonding force between the amorphous carbon layer 30 and the internal natural graphite 10 can be improved by using the C-M-C bond, so that the structural stability of the natural graphite negative electrode material is greatly improved, and further, the falling off of the surface amorphous carbon layer 30 caused by volume expansion in the process of lithium intercalation/deintercalation can be effectively avoided.
Preferably, the element M is at least one element selected from the group consisting of element B, element Ti and element V, which is more favorable for improving the binding force between the amorphous carbon layer 30 and the natural graphite 10, and further improving the structural stability of the natural graphite negative electrode material.
Preferably, D of the natural graphite 10 50 The particle size is 10-12 μm, which is more favorable for the surface coating of the lithium coating layer 20 and the amorphous carbon layer 30 to form the natural graphite anode material with stable structure.
Therefore, the natural graphite anode material has excellent structural stability and is rich in active lithium ions, and the first coulomb efficiency and the reversible discharge specific capacity of the anode material can be obviously improved.
The invention also provides a preparation method of the natural graphite anode material, which comprises the following steps:
s1, mixing lithium salt with natural graphite, and performing wet ball milling to obtain an intermediate product, wherein the intermediate product comprises the natural graphite and the lithium salt coated on the surface of the natural graphite;
s2, mixing the intermediate product with a polymer, coating the polymer on the surface of the intermediate product, and carbonizing to obtain the natural graphite anode material.
In the step S1, lithium salt can be coated on the surface of natural graphite through wet ball milling to form a lithium salt coating layer, and the natural graphite can be shaped, so that the defect problem existing on the surface of the natural graphite can be reduced.
In addition, the wet ball milling is adopted, so that on one hand, the preparation cost can be greatly reduced, and on the other hand, when the intermediate product is prepared by the wet ball milling, the solvent volatilizes, so that the heat released in the high-speed running process of the instrument can be reduced, the instrument is effectively protected, and the lithium salt coated on the surface of the natural graphite can be uniformly distributed.
Wherein the lithium salt is preferably at least one of lithium borate, lithium titanate or lithium vanadate.
Preferably, the mass ratio of the lithium salt to the natural graphite is 0.1:1-0.7:1, more preferably 0.3:1-0.5:1, which is favorable for fully coating the lithium salt on the surface of the natural graphite.
Specifically, the natural graphite D 50 The particle size is preferably 10 μm to 12. Mu.m.
In one embodiment, the ball milling speed is 300rpm to 600rpm, more preferably 400rpm to 500rpm; the ball milling time is 3h-12h, more preferably 5h-8h; the ball-to-material ratio is 15:1-25:1, more preferably 18:1-21:1.
Wherein the solvent used in the wet ball milling is preferably at least one of deionized water, dilute hydrochloric acid or absolute ethyl alcohol.
In one embodiment, after the wet ball milling is finished, a drying treatment step is further performed, wherein the temperature of the drying treatment is preferably 30-100 ℃, and more preferably 70-90 ℃; the drying treatment time is preferably 30min-240min, more preferably 60min-120min, and lithium salt is separated out from the solvent in the drying process, so that the lithium salt is more favorable for uniformly coating the surface of the natural graphite.
In the step S2, a polymer coating layer is formed on the surface of the lithium salt coating layer by utilizing a polymer, and in the carbonization process, the polymer coating layer is heated and decomposed into an amorphous carbon layer, the lithium salt coating layer is heated and decomposed to generate lithium oxide and/or lithium peroxide, meanwhile, an oxide containing M element is also generated, the oxide containing M element can further perform alloying reaction with partial carbon in the internal natural graphite and outer polymer derived carbon to form a unique C-M-C bond network structure, and active lithium ions in the lithium oxide and/or lithium peroxide are anchored in the C-M-C bond network structure, so that the structural stability of the natural graphite negative electrode material is improved, and meanwhile, the natural graphite negative electrode material has excellent electrochemical performance.
Wherein the polymer is preferably at least one of polyimide, polyacrylonitrile, polyvinylpyrrolidone or polyetheretherketone.
Preferably, the mass ratio of the intermediate product to the polymer is 1:0.5-1:1, more preferably 1:0.6-1:0.8, which is favorable for forming an amorphous carbon layer by amorphous carbon formed by thermal decomposition of the polymer.
In one embodiment, the carbonization step is performed under a protective atmosphere, preferably at a carbonization temperature of 300 ℃ to 1000 ℃, further preferably 400 ℃ to 600 ℃; the time is preferably 3h to 10h, more preferably 5h to 8h, which is favorable for the sufficient pyrolysis of the lithium salt and the polymer, thereby forming a lithium coating layer and an amorphous carbon layer on the surface of the natural graphite.
Specifically, the protective atmosphere is at least one selected from nitrogen, helium and argon, and more preferably nitrogen.
In one embodiment, after carbonization, crushing and sieving are also performed, and natural graphite anode materials with proper particle size are selected according to the actual product requirements.
The invention also provides a negative pole piece. The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer comprising a natural graphite negative electrode material as described above. It is understood that the negative electrode active material layer may further include a conductive agent, a binder, etc., which is not limited in the present invention.
The invention also provides a battery. The battery includes a negative electrode tab as described above. It is understood that the battery further comprises a positive electrode plate, a diaphragm and electrolyte, and the positive electrode plate, the diaphragm and the electrolyte are not limited by the invention.
The invention also provides an electric device. The power utilization device comprises a battery as described above.
Hereinafter, the natural graphite anode material, and the preparation method and application thereof will be further described by the following specific examples.
Example 1
30g of lithium titanate and 100g of natural graphite (D 50 Particle size of 10 μm), 30mL of diluted hydrochloric acid is measured as a solvent, and added into a ball mill, ball-milled for 10 hours at 400rpm, collected and dried at 50 ℃ for 120 minutes, thus obtaining an intermediate product.
100g of intermediate product is weighed and evenly mixed with 70g of polyimide powder, and is collected and carbonized for 5 hours at 600 ℃ in nitrogen atmosphere, thus obtaining the natural graphite anode material.
Example 2
50g of lithium titanate and 100g of natural graphite (D 50 Particle size of 10 μm) was put into a ball mill, and 30mL of diluted solution was measured outAdding hydrochloric acid as a solvent into a ball mill, ball milling for 10 hours at 400rpm, collecting, and drying at 50 ℃ for 120 minutes to obtain an intermediate product.
100g of intermediate product is weighed and evenly mixed with 70g of polyimide powder, and is collected and carbonized for 5 hours at 600 ℃ in nitrogen atmosphere, thus obtaining the natural graphite anode material.
Example 3
60g of lithium titanate and 100g of natural graphite (D 50 Particle size of 10 μm), 30mL of diluted hydrochloric acid is measured as a solvent, and added into a ball mill, ball-milled for 10 hours at 400rpm, collected and dried at 50 ℃ for 120 minutes, thus obtaining an intermediate product.
100g of intermediate product is weighed and evenly mixed with 70g of polyimide powder, and is collected and carbonized for 5 hours at 600 ℃ in nitrogen atmosphere, thus obtaining the natural graphite anode material.
Example 4
10g of lithium titanate and 100g of natural graphite (D 50 Particle size of 10 μm), 30mL of diluted hydrochloric acid is measured as a solvent, and added into a ball mill, ball-milled for 10 hours at 400rpm, collected and dried at 50 ℃ for 120 minutes, thus obtaining an intermediate product.
100g of intermediate product is weighed and evenly mixed with 70g of polyimide powder, and is collected and carbonized for 5 hours at 600 ℃ in nitrogen atmosphere, thus obtaining the natural graphite anode material.
Example 5
30g of lithium borate and 100g of natural graphite (D 50 Particle size of 10 μm), 30mL deionized water was measured as a solvent and added to the ball mill, ball milling was performed at 400rpm for 10 hours, and drying was performed at 70 ℃ for 120 minutes after collection, to obtain an intermediate product.
100g of intermediate product is weighed and evenly mixed with 70g of polyvinylpyrrolidone powder, and is collected and carbonized for 3 hours at 700 ℃ in nitrogen atmosphere to obtain the natural graphite anode material.
Example 6
30g of lithium vanadate and 100g of natural graphite (D 50 Particle size of 10 μm) was added to a ball mill, 30mL of diluted hydrochloric acid was measured as a solvent and added to the ball mill at 400rpmBall milling for 10h at a rotating speed, collecting, and drying for 120min at 70 ℃ to obtain an intermediate product.
100g of intermediate product is weighed and evenly mixed with 70g of polyacrylonitrile powder, and is collected and carbonized for 5 hours at 500 ℃ in nitrogen atmosphere, thus obtaining the natural graphite anode material.
Example 7
8g of lithium titanate and 100g of natural graphite (D 50 Particle size of 10 μm), 30mL of diluted hydrochloric acid is measured as a solvent, and added into a ball mill, ball-milled for 10 hours at 400rpm, collected and dried at 50 ℃ for 120 minutes, thus obtaining an intermediate product.
100g of intermediate product is weighed and evenly mixed with 70g of polyimide powder, and is collected and carbonized for 5 hours at 600 ℃ in nitrogen atmosphere, thus obtaining the natural graphite anode material.
Example 8
80g of lithium titanate and 100g of natural graphite (D 50 Particle size of 10 μm), 30mL of diluted hydrochloric acid is measured as a solvent, and added into a ball mill, ball-milled for 10 hours at 400rpm, collected and dried at 50 ℃ for 120 minutes, thus obtaining an intermediate product.
100g of intermediate product is weighed and evenly mixed with 70g of polyimide powder, and is collected and carbonized for 5 hours at 600 ℃ in nitrogen atmosphere, thus obtaining the natural graphite anode material.
Comparative example 1
30g of lithium titanate and 100g of natural graphite (D 50 Particle size of 10 μm), 30mL of diluted hydrochloric acid is measured as a solvent, and added into a ball mill, ball-milled for 10 hours at 400rpm, collected and dried at 50 ℃ for 120 minutes, thus obtaining an intermediate product.
The intermediate product was collected and subjected to heat treatment at 600 ℃ for 5 hours in a nitrogen atmosphere to obtain comparative material 1 as a negative electrode material.
Comparative example 2
60g of lithium titanate and 100g of natural graphite (D 50 Particle size of 10 μm), 30mL of diluted hydrochloric acid is measured as a solvent, and added into a ball mill, ball-milled for 10 hours at 400rpm, collected and dried at 50 ℃ for 120 minutes, thus obtaining an intermediate product.
The intermediate product was collected and subjected to heat treatment at 600 ℃ for 5 hours under a nitrogen atmosphere to obtain comparative material 2 as a negative electrode material.
Comparative example 3
100g of natural graphite (D) 50 Particle size of 10 μm), 30mL of diluted hydrochloric acid is measured as a solvent, and added into a ball mill, ball-milled for 10 hours at 400rpm, collected and dried at 50 ℃ for 120 minutes, thus obtaining an intermediate product.
The intermediate product was collected and subjected to heat treatment at 600 ℃ for 5 hours under a nitrogen atmosphere to obtain comparative material 3 as a negative electrode material.
Comparative example 4
100g of natural graphite (D) 50 Particle size of 10 μm), 30mL of diluted hydrochloric acid is measured as a solvent, and added into a ball mill, ball-milled for 10 hours at 400rpm, collected and dried at 50 ℃ for 120 minutes, thus obtaining an intermediate product.
100g of the intermediate product was weighed and uniformly mixed with 70g of polyimide powder, collected and carbonized at 600 ℃ for 5 hours in a nitrogen atmosphere to obtain a comparative material 4 as a negative electrode material.
Application examples
The negative electrode materials obtained in examples 1 to 8 and comparative examples 1 to 4 were subjected to specific surface area and tap density detection, and lithium ion batteries were each prepared as follows.
The preparation method of the button type lithium ion battery comprises the following steps:
i: according to the cathode material: SP: CMC: sbr=94.5:1.5:1.5:2.5, and the negative electrode material and SP, CMC, SBR were uniformly mixed in deionized water to prepare a slurry, and the slurry was uniformly dispersed, to obtain a stirred slurry.
II: the copper foil was pressed into a wafer having a diameter of 1.6cm, and then dried at 80℃under vacuum, and the weight was weighed and recorded as weight m 1 As a copper foil current collector.
III: uniformly coating the stirred slurry on a copper foil current collector, vacuum drying at 80 ℃ for 12 hours, rolling to prepare a negative electrode plate, drying to obtain a dried negative electrode plate, and weighing and recording the weight as weight m 2 . Wherein the weight m 2 Subtracting the weight m 1 The weight of the active substance is obtained and is expressed as weight m 3 。
IV: transferring the dried negative electrode piece into a glove box, taking a lithium piece as a counter electrode and an auxiliary electrode, and using an electrolyte 1M LiPF 6 EC: DEC (1:1, v/v), i.e. LiPF is dissolved 6 The diaphragm is Celgard2400, and the button type lithium ion battery is assembled in a glove box with oxygen and water content less than 1 ppm.
And standing the assembled button type lithium ion battery for 12 hours. And testing the electrochemical performance of the stationary button type lithium ion battery at a constant current above the Wuhan blue battery testing system.
Wherein the current is 500mA/g×weight m 3 X0.945 (first-turn current 200 mA/g. Times.weight m) 3 X 0.945) and the voltage ranges from 0.01V to 3.0V.
The test results are shown in Table 1.
TABLE 1
From examples and comparative examples 1 to 4 in Table 1, it is known that natural graphite having no surface coating by only ball milling and heat treatment has the largest specific surface area, the lowest tap density, and the worst reversible discharge specific capacity and first coulombic efficiency; the single-layer coated anode material with an amorphous carbon layer or a lithium coating layer has the advantages that the specific surface area is sequentially reduced, the tap density is sequentially increased, and the reversible discharge specific capacity and the first coulomb efficiency are also sequentially increased; the double-layer coated anode material with the amorphous carbon layer and the lithium coating layer has the advantages of low specific surface area, high tap density, excellent reversible discharge specific capacity and excellent first coulombic efficiency.
In addition, as is clear from examples 1 to 2, examples 3 to 4 and examples 7 to 8 in table 1, even if the mass ratio of lithium salt to natural graphite exceeds 0.1:1 to 0.7:1, a good coating effect can be achieved, and excellent reversible discharge specific capacity and first coulombic efficiency can be achieved; when the mass ratio of the lithium salt to the natural graphite is 0.1:1-0.7:1, the coating effect is better, and the performance is more excellent; further, when the mass ratio of the lithium salt to the natural graphite is 0.3:1-0.5:1, the coating effect is optimal, and the performance is optimal.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (12)

1. The natural graphite anode material is characterized by comprising natural graphite, and a lithium coating layer and an amorphous carbon layer which are sequentially coated on the surface of the natural graphite, wherein the lithium coating layer comprises an M element, and the M element can form a C-M-C bond with carbon elements in the natural graphite and carbon elements in the amorphous carbon layer.
2. The natural graphite anode material according to claim 1, wherein the M element is at least one selected from the group consisting of B element, ti element, and V element.
3. The natural graphite anode material of claim 1, wherein D of the natural graphite 50 The particle size is 10 μm-12 μm.
4. A method for preparing a natural graphite anode material according to any one of claims 1 to 3, comprising the steps of:
mixing lithium salt with natural graphite and performing wet ball milling to obtain an intermediate product, wherein the intermediate product comprises the natural graphite and the lithium salt coated on the surface of the natural graphite;
and mixing the intermediate product with a polymer, coating the polymer on the surface of the intermediate product, and carbonizing to obtain the natural graphite anode material.
5. The method for producing a natural graphite anode material according to claim 4, wherein the lithium salt is at least one selected from lithium borate, lithium titanate and lithium vanadate.
6. The method for preparing a natural graphite anode material according to claim 4, wherein the step of mixing a lithium salt with natural graphite and performing wet ball milling satisfies at least one of the following conditions:
(1) D of the natural graphite 50 The grain diameter is 10 μm-12 μm;
(2) The mass ratio of the lithium salt to the natural graphite is 0.1:1-0.7:1;
(3) The ball milling rotating speed is 300rpm-600rpm, the ball milling time is 3h-12h, and the ball-material ratio is 15:1-25:1;
(4) The solvent is at least one selected from deionized water, dilute hydrochloric acid or absolute ethanol.
7. The method for preparing a natural graphite anode material according to claim 4, further comprising a step of drying after the wet ball milling, wherein the drying temperature is 30-100 ℃ and the drying time is 30-240 min.
8. The method for preparing a natural graphite anode material according to claim 4, wherein the polymer is at least one selected from polyimide, polyacrylonitrile, polyvinylpyrrolidone and polyetheretherketone.
9. The method of preparing a natural graphite anode material according to claim 4, wherein the step of mixing the intermediate product with a polymer and carbonizing satisfies at least one of the following conditions:
(1) The mass ratio of the intermediate product to the polymer is 1:0.5-1:1;
(2) The carbonization step is carried out in a protective atmosphere, the carbonization temperature is 300-1000 ℃ and the time is 3-10 h.
10. A negative electrode tab comprising a negative electrode current collector and a negative electrode active material layer comprising the natural graphite negative electrode material of any one of claims 1-3.
11. A battery comprising the negative electrode tab of claim 10.
12. An electrical device comprising the battery of claim 11.
CN202311120800.2A 2023-08-31 2023-08-31 Natural graphite anode material and preparation method and application thereof Pending CN117352731A (en)

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