WO2024255517A1 - 一种获取负极活性材料的方法、负极活性材料及其应用 - Google Patents

一种获取负极活性材料的方法、负极活性材料及其应用 Download PDF

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WO2024255517A1
WO2024255517A1 PCT/CN2024/093501 CN2024093501W WO2024255517A1 WO 2024255517 A1 WO2024255517 A1 WO 2024255517A1 CN 2024093501 W CN2024093501 W CN 2024093501W WO 2024255517 A1 WO2024255517 A1 WO 2024255517A1
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Prior art keywords
negative electrode
electrode active
active material
obtaining
amorphous carbon
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English (en)
French (fr)
Inventor
简洁洁
刘静
杨红新
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Svolt Energy Technology Co Ltd
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Svolt Energy Technology Co Ltd
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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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
    • G01N5/04—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder
    • 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
    • H01M4/58—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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present disclosure relates to the field of battery technology, and in particular to a method for obtaining a negative electrode active material, a negative electrode active material and an application thereof.
  • the negative electrode active material is the key material of lithium-ion batteries, which plays a very important role in the cycle, fast charging, high and low temperature performance of lithium-ion batteries.
  • the development of safe negative electrode materials is crucial to improving the safety performance of the entire battery.
  • Graphite materials have a layered structure, which leads to slow lithium ion insertion and extraction speed.
  • the amorphous carbon coated on its surface relies on the high diffusion rate of amorphous carbon in the charging and discharging process (the diffusion rate is about 10 times that of graphite) to increase the insertion and extraction rate of lithium ions; on the other hand, it can effectively reduce DCR and improve kinetic performance.
  • excessive carbon coating leads to poor high temperature performance of the battery, which will bring risks to the safety performance of the battery.
  • the large specific surface area of graphite means smaller particles, more channels for lithium ion migration, shorter paths, and better rate performance.
  • the area of the SEI film formed is also large, the irreversible capacity is large, and the initial efficiency will be reduced.
  • more binder will be added, making processing difficult, and the slurry viscosity will be high, resulting in increased internal resistance and reduced cycle performance, leading to reduced safety performance.
  • One object of the present disclosure is to provide a method for obtaining a negative electrode active material, wherein the negative electrode active material obtained by the method can achieve a balance among cycle performance, low temperature performance and rate performance, and has excellent comprehensive performance.
  • Another object of the present disclosure is to provide a negative electrode active material that can ensure that the battery has a higher charging capacity at low temperatures, while ensuring that the battery has good safety during long-term fast charging use.
  • Another object of the present disclosure is to provide a negative electrode sheet.
  • Another object of the present disclosure is to provide a lithium ion battery.
  • Another object of the present disclosure is to provide an application of the lithium-ion battery in consumer electronics, power tools and electric vehicles.
  • a method for obtaining a negative electrode active material comprises the following steps:
  • step (b) Obtaining the coverage rate A of amorphous carbon on the graphite surface, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S of the negative electrode active material to be screened in step (a), and screening out the negative electrode active material whose relationship among A, B and S satisfies 0.005 ⁇ A*B/S ⁇ 0.075.
  • the relationship between A, B and S satisfies: 0.013 ⁇ A*B/S ⁇ 0.06.
  • the relationship between A, B and S satisfies: 0.02 ⁇ A*B/S ⁇ 0.04.
  • the range of A is 30% to 100%
  • the range of B is 0.5% to 6%
  • the range of S is 0.8 to 2 m 2 /g.
  • the method for obtaining the mass content B of the amorphous carbon in the negative electrode active material comprises:
  • thermogravimetric tests on the negative electrode active material standards respectively to obtain the thermal weight loss rates y1 of the amorphous carbon of the different negative electrode active material standards; the temperature range of the thermal weight loss rates is 200 to 620° C.;
  • thermogravimetric test includes a first heat treatment and a second heat treatment, wherein the temperature of the first heat treatment is 25-400°C, the heating rate is 5-8°C/min, the temperature of the second heat treatment is 400-800°C, the heating rate is 2-4°C/min; the oxygen flow rate of the first heat treatment and the second heat treatment is 10-100 mL/min;
  • step (d1) Drying the negative electrode active material to be tested under the same conditions as step (a1), performing a thermogravimetric test under the same conditions as step (b1) to obtain its thermal weight loss rate y2, and obtaining the mass content B of amorphous carbon in the negative electrode active material to be tested according to the relationship curve equation in step (c1).
  • the method for obtaining the specific surface area S of the negative electrode active material includes: testing with a specific surface area tester.
  • a negative electrode active material is obtained by the method for obtaining the negative electrode active material.
  • a negative electrode sheet comprises the negative electrode active material or the negative electrode active material obtained by the method for obtaining the negative electrode active material.
  • a lithium ion battery comprises the negative electrode sheet.
  • the lithium-ion battery is used in consumer electronics, power tools and electric vehicles.
  • the present invention has the following beneficial effects:
  • the present invention discloses a method for obtaining a negative electrode active material, obtaining the coverage rate A of amorphous carbon on the graphite surface, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S of the negative electrode active material, screening a negative electrode active material that satisfies 0.005 ⁇ A*B/S ⁇ 0.075, and the obtained negative electrode active material can balance the kinetic performance, cycle performance and high and low temperature performance of the negative electrode sheet.
  • the battery obtained by using the negative electrode active material disclosed in the present invention has a high charging capacity, and also has a good cycle life and safety when used for a long time with fast charging, and the effect is remarkable.
  • FIG. 1 is a fitted line graph of a standard sample of a negative electrode active material disclosed in the present invention.
  • the present disclosure relates to a method for obtaining a negative electrode active material, comprising the following steps:
  • step (b) Obtaining the coverage rate A of amorphous carbon on the graphite surface, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S of the negative electrode active material to be screened in step (a), and screening out the negative electrode active material whose relationship among A, B and S satisfies 0.005 ⁇ A*B/S ⁇ 0.075.
  • the coverage rate in the present disclosure is defined as: the percentage of the coverage area of amorphous carbon on the graphite (particle) surface to the total surface area of the graphite (particle).
  • the graphite includes artificial graphite.
  • the coated amorphous carbon in the negative electrode active material disclosed in the present invention, relies on the high diffusion rate of amorphous carbon in the charge and discharge process (the diffusion rate is about 10 times that of graphite) to increase the insertion and extraction rate of lithium ions; on the other hand, it can effectively reduce DCR and improve kinetic performance; wherein the greater the coating rate A and the mass content B of amorphous carbon in the negative electrode active material, the more effectively the DCR is reduced, the kinetic performance is improved, and the low temperature performance is good; however, if the mass content B of amorphous carbon in the negative electrode active material is too large (i.e., too much coating), the high temperature performance of the battery will be reduced, and the safety will be reduced.
  • a large specific surface area often means that its cycle storage performance is reduced. Therefore, the above-mentioned values of A, B and S play an important role in the kinetic performance, cycle performance, power and high and low temperature performance of the battery; wherein, the value of A is large, the value of B is large (more residual carbon), the high temperature performance is poor, but the low temperature storage performance is good; and the cycle performance is related to the specific surface area.
  • How to comprehensively control the cycle performance, high and low temperature storage performance and rate performance to achieve a balance is the focus and difficulty of the screening of negative electrode materials.
  • the present invention can comprehensively realize the regulation of cycle performance, low temperature performance and rate performance by controlling A*B/S within a specific range of values.
  • the cycle performance and high and low temperature performance can reach more than 88%, and the rate performance can also reach more than 89%, and the safety performance is relatively stable, thereby achieving a balance between cycle performance, high and low temperature storage performance and rate performance.
  • the present invention innovatively controls the coverage rate A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S to satisfy the relationship 0.005 ⁇ A*B/S ⁇ 0.075, and screens out the negative electrode active material.
  • the negative electrode sheet prepared using the negative electrode active material can achieve a balance between fast charging, cycling and low temperature performance.
  • A, B and S satisfy the relationship: 0.013 ⁇ A*B/S ⁇ 0.06.
  • A, B and S satisfy the relationship: 0.02 ⁇ A*B/S ⁇ 0.04.
  • the range of A is 30% to 100%, for example 30%, 40%, 45%, 50%, 55%, 60%, 70%, 80%, 90%, 95%, 100%; the range of B is 0.5% to 6%, for example 0.5%, the range of S is 0.8-2m 2 /g, for example, 0.8m 2 /g, 0.9m 2 /g, 1m 2 /g, 1.1m 2 /g, 1.2m 2 /g, 1.3m 2 / g, 1.4m 2 /g, 1.5m 2 /g, 1.6m 2 / g , 1.7m 2 / g, 1.8m 2 /g, 1.9m 2 /g or 2m 2 / g, etc.
  • the negative electrode active material of the present disclosure is obtained by purchase.
  • the coverage rate A of amorphous carbon on the graphite surface is obtained through the supplier.
  • the negative electrode active material is derived from Guangdong Kaijin New Energy Technology Co., Ltd.
  • the negative electrode active material is derived from Hunan Zhongke Xingcheng Graphite Co., Ltd.
  • the negative electrode active material is derived from Hebei Kuntian New Energy Co., Ltd.
  • the negative electrode active material is derived from Zhejiang Carbon One New Energy Co., Ltd.
  • the negative electrode active material is derived from Shanghai Shanshan Technology Co., Ltd.
  • the value of the coating amount B of the amorphous carbon is obtained by performing a TG test.
  • the method for obtaining the mass content B of the amorphous carbon in the negative electrode active material comprises:
  • thermogravimetric tests on the negative electrode active material standards respectively to obtain the thermal weight loss rates y1 of the amorphous carbon of the different negative electrode active material standards; the temperature range of the thermal weight loss rates is 200 to 620° C.;
  • thermogravimetric test includes a first heat treatment and a second heat treatment, wherein the temperature of the first heat treatment is 25-400°C, the heating rate is 5-8°C/min, the temperature of the second heat treatment is 400-800°C, the heating rate is 2-4°C/min; the oxygen flow rate of the first heat treatment and the second heat treatment is 10-100 mL/min;
  • step (d1) Drying the negative electrode active material to be tested under the same conditions as step (a1), performing a thermogravimetric test under the same conditions as step (b1) to obtain its thermal weight loss rate y2, and obtaining the mass content B of amorphous carbon in the negative electrode active material to be tested according to the relationship curve equation in step (c1).
  • the negative electrode active material standard sample is derived from Hebei Kuntian New Energy Co., Ltd., and the mass content of amorphous carbon in the standard sample is provided by the supplier.
  • the method for obtaining the specific surface area S of the negative electrode active material includes: testing with a specific surface area tester. In one embodiment, the specific surface area S of the negative electrode active material is tested by a conventional method in the prior art.
  • the method for obtaining the specific surface area S of the negative electrode active material comprises the following steps:
  • the sample weight is 1000 ⁇ 50 mg.
  • the instrument measures the sample adsorption using the direct comparison method, that is, a mixed gas of a certain ratio of carrier gas (He) and adsorbate gas (N 2 ) flows through the sample to be tested, and the adsorption amount of the sample to be tested is obtained based on the concentration change before and after adsorption;
  • the direct comparison method that is, a mixed gas of a certain ratio of carrier gas (He) and adsorbate gas (N 2 ) flows through the sample to be tested, and the adsorption amount of the sample to be tested is obtained based on the concentration change before and after adsorption;
  • the present disclosure relates to a negative electrode active material obtained by using the above method for obtaining the negative electrode active material.
  • the present disclosure also relates to a negative electrode sheet, comprising the negative electrode active material as described above or the negative electrode active material obtained by the method for preparing the negative electrode active material as described above.
  • the present disclosure also relates to a lithium-ion battery, comprising the negative electrode sheet.
  • the battery disclosed herein can achieve a balance between fast charging, cycling and low temperature performance.
  • the present disclosure also relates to the application of the lithium-ion battery in consumer electronics, power tools and electric vehicles.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the mass content B of amorphous carbon in the negative electrode active material includes:
  • thermogravimetric tests on the negative electrode active material standard samples to obtain the thermal weight loss rate y1 of the amorphous carbon of different negative electrode active material standard samples; the temperature range of the thermal weight loss rate is 200 to 620° C.;
  • thermogravimetric test includes a first heat treatment and a second heat treatment, wherein the temperature of the first heat treatment is 25-400°C (increasing from 25°C to 400°C), the heating rate is 5°C/min, and the temperature of the second heat treatment is 400-800°C (increasing from 400°C to 800°C), the heating rate is 4°C/min; the oxygen flow rate of the first heat treatment and the second heat treatment is 20mL/min;
  • step (d1) Drying the negative electrode active material to be tested under the same conditions as step (a1), and performing a thermogravimetric test under the same conditions as step (b1) to obtain its thermal weight loss rate y2. According to the relationship curve equation in step (c1), the mass content B of amorphous carbon in the negative electrode active material to be tested is obtained to be 2%.
  • the method for obtaining the specific surface area comprises the following steps:
  • the sample weight is 1000 ⁇ 50 mg.
  • the instrument measures the sample adsorption using the direct comparison method, that is, a mixed gas of a certain ratio of carrier gas (He) and adsorbate gas (N 2 ) flows through the sample to be tested, and the adsorption amount of the sample to be tested is obtained based on the concentration change before and after adsorption;
  • the direct comparison method that is, a mixed gas of a certain ratio of carrier gas (He) and adsorbate gas (N 2 ) flows through the sample to be tested, and the adsorption amount of the sample to be tested is obtained based on the concentration change before and after adsorption;
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this embodiment is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage ratio A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this comparative example is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage ratio A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this comparative example is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage ratio A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this comparative example is the same as that in Example 1.
  • the method for obtaining negative electrode active material comprises the following steps:
  • the method for obtaining the coverage ratio A, the mass content B of amorphous carbon in the negative electrode active material and the specific surface area S in this comparative example is the same as that in Example 1.
  • the negative electrode active materials in the embodiment and the comparative example are respectively prepared into soft-pack batteries, and the specific method includes:
  • the negative electrode active material, conductive agent SP, CMC and SBR were uniformly mixed to obtain negative electrode slurry, wherein the mass ratio of the negative electrode active material, conductive agent SP, CMC and SBR was 95:1.5:1.5:2.0; the negative electrode slurry was coated on a 6 ⁇ m copper foil of the negative electrode by a coater, and the negative electrode sheet was prepared by a roller press; lithium iron phosphate was used as the positive electrode, a lithium salt LiPF6 solution (concentration 1 mol/L), EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1 were used as the electrolyte, and celgard 2400 was used as the separator to prepare a 5Ah soft-pack battery.
  • LiPF6 solution concentration 1 mol/L
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • the soft-pack batteries prepared in the examples and comparative examples were tested for cycle performance, rate performance and high-temperature storage performance, and the specific test parameters were set as follows:
  • Rate performance 2C constant current ratio, constant current capacity/(constant current capacity + constant voltage capacity).
  • Low temperature storage performance The lithium-ion battery is charged to 3.65V at a rate of 0.1C, and its capacity is tested as A0. It is then placed at a temperature of -20 ⁇ 3°C for 7 days, and then its capacity A1 is tested at room temperature. It is then charged to 3.65V and its capacity A2 is tested. The capacity recovery is then calculated as A2/A0*100%, i.e., the low temperature storage performance.
  • High temperature storage performance The lithium-ion battery is charged to 3.65V at a rate of 0.1C, and its capacity is tested as A0. It is then placed at a temperature of 60 ⁇ 3°C for 7 days, and then its capacity A1 is tested at room temperature. It is then charged to 3.65V and its capacity A2 is tested. The capacity recovery is then calculated as A2/A0*100%, i.e., high temperature storage performance.
  • the negative electrode active materials in the embodiment and the comparative example are respectively prepared into button cells, and the specific method includes:
  • the negative electrode active material, conductive agent SP, CMC and SBR are uniformly mixed to obtain a negative electrode slurry, wherein the mass ratio of the negative electrode active material, conductive agent SP, CMC and SBR is 95:1.5:1.5:2.0, the negative electrode slurry is coated on the negative electrode current collector by a coating machine, and a negative electrode sheet is prepared by a roller press; a lithium salt LiPF6 solution (concentration 1mol/L), EC (ethylene carbonate) + DEC (diethyl carbonate) with a volume ratio of 1:1 as the electrolyte, lithium sheet as the positive electrode, and celgard 2400 as the separator to form a button half-cell.
  • a lithium salt LiPF6 solution concentration 1mol/L
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • DSC test After fully charged and disassembled, the electrode is cleaned with DMC and dried before DSC test. The temperature range is 20-450°C and the heating rate is 5°C/min.
  • the rate performance of Examples 1 to 12 disclosed in the present invention can be controlled to be above 85%, and the cycle performance can be made to be above 90%, and the high and low temperature performance can be made to be above 88%, which can effectively achieve the balance between the fast charge, cycle and high and low temperature performance of the negative electrode sheets prepared by the negative electrode active material group.
  • Comparative Examples 1 and 2 the low coverage, small mass content of amorphous carbon, poor kinetic performance, low temperature difference, and large specific surface area cause deviations in their cycle performance; in Comparative Examples 3 and 4, due to the large coverage, large mass content of amorphous carbon, good kinetics, good low temperature performance, but small specific surface area, poor rate performance, and poor safety performance.
  • the present disclosure provides a method for obtaining negative electrode active materials, negative electrode active materials and applications thereof.
  • the negative electrode active materials obtained by the method disclosed herein can improve the charging capacity of lithium-ion batteries, while ensuring that the lithium-ion batteries have a good cycle life and safety when used for long-term fast charging, with significant effects.

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Abstract

一种获取负极活性材料的方法、负极活性材料及其应用。所述获取负极活性材料的方法，包括以下步骤：(a)提供待筛选的负极活性材料，所述待筛选的负极活性材料为核壳结构，其中，核层为石墨，壳层为无定形碳；(b)获取步骤(a)中待筛选的负极活性材料的无定形碳在石墨表面的包覆率A、无定形碳在负极活性材料中的质量含量B和负极活性材料的比表面积S，筛选出0.005≤A*B/S≤0.075的负极活性材料。采用所述方法获取的负极活性材料可提升锂离子电池的充电能力，同时保证锂离子电池在长期快速充电使用时还具有很好的循环使用寿命和安全性。

Description

一种获取负极活性材料的方法、负极活性材料及其应用
相关申请的交叉引用
本申请要求于2023年06月14日提交中国专利局的申请号为CN202310706036.0、名称为“一种获取负极活性材料的方法、负极活性材料及其应用”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本公开涉及电池技术领域，具体而言，涉及一种获取负极活性材料的方法、负极活性材料及其应用。
背景技术
锂离子电池的安全事故常有发生，其中负极活性材料是锂离子电池的关键材料，对锂离子电池的循环、快充、高低温性能起到非常重要的作用，开发安全的负极材料对提高整个电池的安全性能至关重要。目前，随着市场对锂离子电池应用要求的提高，尤其是为了满足北方冬天的低温需求，对锂离子电池的低温性能提出更高的要求，因此，兼具优异的高安全性高低温放电性能和循环性能的锂离子电池成为首选产品。石墨材料为层状结构，导致锂离子嵌脱速度慢，在其表面包覆的无定形碳一方面依靠无定形碳充放电过程的高的扩散速率(扩散速率为石墨的10倍左右)提升锂离子的嵌脱速率；另一方面可以有效降低DCR，提高动力学性能。但是过高的碳包覆量导致电池的高温性能变差，会给电池的安全性能带来风险。石墨的比表面积大意味着颗粒较小，锂离子迁移的通道更多、路径更短、倍率性能就比较好，但由于与电解液接触面积大，形成的SEI膜的面积也大，不可逆容量大，首次效率就会降低，并且加的粘结剂会比较多，加工困难，浆料粘度偏大，造成内阻增加，循环性能降低，导致其安全性能降低。
现有技术中，绝大部分为对石墨进行碳包覆，可以提升锂离子的脱嵌速率以及有效降低DCR，提高低温性能，降低其高温性能。颗粒小，比表面积大，有利于提升其倍率性能，但是过大的比表面积意味着与电解液接触面积大，副反应多，不利于电池的循环。
因此，如何能克服上述缺陷，获取平衡快充、高安全性低温性能的负极活性材料的方法，以保证锂离子电池负极极片在低温下具有较高的充电能力，同时保证锂离子电池在长期快速充电使用时还具有很好的安全性至关重要。
申请内容
本公开的一个目的在于提供一种获取负极活性材料的方法，该方法获取的负极活性材料可达到循环性能、低温性能和倍率性能的平衡，综合性能优异。
本公开的另一个目的在于提供一种负极活性材料，可以保证电池在低温下具有较高的充电能力，同时保证电池在长期快速充电使用时还具有很好的安全性。
本公开的另一个目的在于提供一种负极片。
本公开的另一个目的在于提供一种锂离子电池。
本公开的另一个目的在于提供一种所述的锂离子电池在消费电子类、电动工具和电动汽车中的应用。
为了实现本公开的上述目的，特采用以下技术方案：
一种获取负极活性材料的方法，包括以下步骤：
(a)提供待筛选的负极活性材料，所述待筛选的负极活性材料为核壳结构，其中，核层为石墨，壳层为无定形碳；
(b)获取步骤(a)中待筛选的负极活性材料的无定形碳在石墨表面的包覆率A、无定形碳在负极活性材料中的质量含量B和负极活性材料的比表面积S，筛选出A、B和S之间关系式满足0.005≤A*B/S≤0.075的负极活性材料。
在一种实施方式中，所述A、B和S之间的关系式满足：0.013≤A*B/S≤0.06。
在一种实施方式中，所述A、B和S之间的关系式满足：0.02≤A*B/S≤0.04。
在一种实施方式中，所述A的范围为30％～100％，所述B的范围为0.5％～6％，所述S的范围为0.8～2m2/g。
在一种实施方式中，所述无定形碳在负极活性材料中的质量含量B的获取方法，包括：
(a1)将多份已知无定形碳的质量含量的负极活性材料标样进行干燥，无定形碳在负极活性材料标样中的质量含量为B1；
(b1)将负极活性材料标样分别进行热重测试，获取不同负极活性材料标样的无定形碳的热失重率y1；热失重率的温度区间范围值为200～620℃；
所述热重测试包括第一热处理和第二热处理，所述第一热处理的温度为25～400℃，升温速率5～8℃/min，所述第二热处理的温度为400～800℃，升温速率为2～4℃/min；所述第一热处理和第二热处理的氧气流量为10～100mL/min；
(c1)以无定形碳在负极活性材料中的质量含量B1为横坐标，热失重率y1为纵坐标进行线性拟合分析，得到关系方程式：y＝1.9343x+0.1317；
(d1)将待测的负极活性材料按步骤(a1)相同条件进行干燥，按步骤(b1)相同条件进行热重测试，得到其热失重率y2，根据步骤(c1)中的关系曲线方程得到待测试的负极活性材料中的无定形碳的质量含量B。
在一种实施方式中，所述负极活性材料的比表面积S的获取方法，包括：采用比表面积测试仪进行测试。
一种负极活性材料，由所述的获取负极活性材料的方法得到。
一种负极片，包括所述的负极活性材料或者所述的获取负极活性材料的方法得到的负极活性材料。
一种锂离子电池，包括所述的负极片。
所述的锂离子电池在消费电子类、电动工具和电动汽车中的应用。
与现有技术相比，本公开的有益效果为：
(1)本公开获取负极活性材料的方法，获取无定形碳在石墨表面的包覆率A、无定形碳在负极活性材料中的质量含量B和负极活性材料的比表面积S，筛选满足0.005≤A*B/S≤0.075的负极活性材料，获得的负极活性材料能够平衡负极片的动力学性能、循环性能及其高低温性能。
(2)本公开的负极活性材料得到的电池具有较高的充电能力，其在长期快速充电使用时还具有很好的循环使用寿命和安全性，效果显著。
附图说明
为了更清楚地说明本公开具体实施方式或现有技术中的技术方案，下面将对具体实施方式或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本公开的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本公开负极活性材料标样的拟合线图。
具体实施方式
根据本公开的一个方面，本公开涉及一种获取负极活性材料的方法，包括以下步骤：
(a)提供待筛选的负极活性材料，所述待筛选的负极活性材料为核壳结构，其中，核层为石墨，壳层为无定形碳；
(b)获取步骤(a)中待筛选的负极活性材料的无定形碳在石墨表面的包覆率A、无定形碳在负极活性材料中的质量含量B和负极活性材料的比表面积S，筛选出A、B和S之间关系式满足0.005≤A*B/S≤0.075的负极活性材料。
本公开中的包覆率的定义为：无定形碳在石墨(颗粒)表面的覆盖面积占石墨(颗粒)总表面积的百分比。
在一种实施方式中，所述石墨包括人造石墨。
本公开的负极活性材料中，包覆的无定形碳一方面依靠无定形碳充放电过程的高的扩散速率(扩散速率为石墨的10倍左右)提升锂离子的嵌脱速率；另一方面可以有效降低DCR，提高动力学性能；其中包覆率A、无定形碳在负极活性材料中的质量含量B越大，越有效降低DCR，提高动力学性能，低温性能好；但是无定形碳在负极活性材料中的质量含量B过大(即过多的包覆量)，会降低电池的高温性能，安全性会降低。而比表面积大往往意味着其循环存储性能下降。因此，上述A、B和S的数值对电池的动力学性能、循环性能、功率及其高低温性能起到重要作用；其中，A的数值大，B数值大(残碳量多)，高温性能差，但是低温存储性能好；而循环性能与比表面积有关系，如何综合控制循环性能、高低温存储性能和倍率性能以达到平衡是负极材料的筛选的重点和难点。本公开通过控制A*B/S在特定的范围值，可以综合实现循环性能、低温性能和倍率性能的调控，尤其是当A*B/S的值控制在0.005～0.075范围内，可以使循环性能、高低温性能达到88％以上，并且倍率性能也能达到89％以上，安全性能也相对稳定，进而达到循环性能、高低温存储性能和倍率性能的平衡。
综上，本公开首创性地通过控制包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S满足关系式0.005≤A*B/S≤0.075，筛选得到负极活性材料，采用该负极活性材料制备得到的负极极片可实现快充、循环及其低温性能之间的平衡。
在一种实施方式中，所述A、B和S之间满足关系式：0.013≤A*B/S≤0.06。
在一种实施方式中，所述A、B和S之间满足关系式：0.02≤A*B/S≤0.04。
在一种实施方式中，所述A的范围为30％～100％，例如30％、40％、45％、50％、55％、60％、70％、80％、90％、95％、100％；所述B的范围为0.5％～6％，例如0.5％、 1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％、6％等；所述S的范围为0.8～2m2/g，例如0.8m2/g、0.9m2/g、1m2/g、1.1m2/g、1.2m2/g、1.3m2/g、1.4m2/g、1.5m2/g、1.6m2/g、1.7m2/g、1.8m2/g、1.9m2/g或2m2/g等。
在一种实施方式中，本公开的负极活性材料通过购买获得。无定形碳在石墨表面的包覆率A的通过供应商方获取。在一种实施方式中，负极活性材料源自广东凯金新能源科技股份有限公司。在一种实施方式中，负极活性材料源自湖南中科星城石墨有限公司。在一种实施方式中，负极活性材料源自河北坤天新能源股份有限公司。在一种实施方式中，负极活性材料源自浙江碳一新能源有限责任公司。在一种实施方式中，负极活性材料源自上海杉杉科技有限公司。
在一种实施方式中，所述无定形碳的包覆量B的数值通过进行TG测试获得。在一种实施方式中，所述无定形碳在负极活性材料中的质量含量B的获取方法，包括：
(a1)将多份已知无定形碳的质量含量的负极活性材料标样进行干燥，干燥温度为60～80℃(例如65℃、70℃等)，无定形碳在负极活性材料标样中的质量含量为B1；
(b1)将负极活性材料标样分别进行热重测试，获取不同负极活性材料标样的无定形碳的热失重率y1；热失重率的温度区间范围值为200～620℃；
所述热重测试包括第一热处理和第二热处理，所述第一热处理的温度为25～400℃，升温速率5～8℃/min，所述第二热处理的温度为400～800℃，升温速率为2～4℃/min；所述第一热处理和第二热处理的氧气流量为10～100mL/min；
(c1)以无定形碳在负极活性材料中的质量含量B1为横坐标，热失重率y1为纵坐标进行线性拟合分析，得到关系方程式：y＝1.9343x+0.1317；
(d1)将待测的负极活性材料按步骤(a1)相同条件进行干燥，按步骤(b1)相同条件进行热重测试，得到其热失重率y2，根据步骤(c1)中的关系曲线方程得到待测试的负极活性材料中的无定形碳的质量含量B。
在一种实施方式中，负极活性材料标样源自河北坤天新能源股份有限公司，标样的无定形碳的质量含量是供应商提供。
在一种实施方式中，所述负极活性材料的比表面积S的获取方法，包括：采用比表面积测试仪进行测试。在一种实施方式中，通过现有技术常规的方法测试负极活性材料的比表面积S。
在一种实施方式中，所述负极活性材料的比表面积S的获取方法，包括以下步骤：
(1)打开保护气气阀，打开设备电源，开始测试前预热30min；
(2)仔细检查U型样品管和玻璃漏斗管口是否有裂纹、缺口，管体、内壁是否洁净；确认完好无损后方可称量空样品管质量，记录为m1(mg)；
(3)使用装样漏斗进行装样，标样称样量：1000±50mg；
(4)平稳地将样品管放在烧杯中称重，记录吹扫前样品质量和空样品管质量，该质量仅供与吹扫后总质量对比作为参考；
(5)吹扫：进行测试之前，控制进气流量在80mL/min，总出口气流量80mL/min；能够很清晰的告知操作者是否开气，可以检查样品管是否安装完好，仪器的气密性是否良好；通过脱气除去样品表面的物理吸附物质，同时要避免表面发生不可逆的变化；控制加热温度为200℃，加热时间为65min；
(6)吹扫完成后，称量样品管总质量m2(mg)，样品净重m3＝m2-m1；
(7)添加液氮：样品液氮杯加到2/3、冷阱恒温杯加到1/3；
(8)在软件界面设置储存路径、样品名称、样品净重等参数即可开始测试；仪器测量样品吸附量使用的是直接对比法，即将一定比例的载气(He)和吸附质气体(N2)的混合气体流过待测样品，根据吸附前后浓度变化，得到待测样品吸附量；
(9)实验结束后，记录实验数值并确认仪器总电源是否关闭、钢瓶总阀是否关闭，冷阱恒温杯是否取出，检查无误后整理实验台面，清洗样品管以及漏斗。
根据本公开的另一个方面，本公开涉及一种负极活性材料，采用上述获取负极活性材料的方法得到。
根据本公开的另一个方面，本公开还涉及一种负极片，包括如上所述的负极活性材料或者如上所述的负极活性材料的制备方法得到的负极活性材料。
根据本公开的另一个方面，本公开还涉及一种锂离子电池，包括所述的负极片。
本公开的电池可实现快充、循环及其低温性能之间的平衡。
根据本公开的另一个方面，本公开还涉及所述的锂离子电池在消费电子类、电动工具和电动汽车中的应用。
下面结合具体的实施例、对比例进一步解释说明。
实施例1
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为50％，获取无定形碳在负极活性材料中的质量含量B，B为2％，获取负极活性材料的比表面积S，S为1.8m2/g；A*B/S＝0.0056，即为所述负极活性材料；
无定形碳在负极活性材料中的质量含量B的获取方法包括：
(a1)将多份已知无定形碳的质量含量的负极活性材料标样进行干燥，无定形碳在负极活性材料标样中的质量含量为B1；
(b1)将负极活性材料标样进行多次热重测试，获取不同负极活性材料标样的无定形碳的热失重率y1；热失重率的温度区间范围值为200～620℃；
每次热重测试包括第一热处理和第二热处理，所述第一热处理的温度为25～400℃(从25℃升至400℃)，升温速率为5℃/min，所述第二热处理的温度为400～800℃(从400℃升至800℃)，升温速率为4℃/min；所述第一热处理和第二热处理的氧气流量为20mL/min；
(c1)以无定形碳在负极活性材料中的质量含量B1为横坐标，热失重率y1为纵坐标进行线性拟合分析，拟合线如图1所示，得到关系方程式：y＝1.9343x+0.1317；
各标样中，无定形碳在负极活性材料中的质量含量B1及热失重率y1的具体数值如表1所示。
表1各标样的B1及热失重率y1
(d1)将待测的负极活性材料按步骤(a1)相同条件进行干燥，按步骤(b1)相同条件进行热重测试，得到其热失重率y2，根据步骤(c1)中的关系曲线方程得到待测试的负极活性材料中的无定形碳的质量含量B为2％。
比表面积的获取方法包括：包括以下步骤：
(1)打开保护气气阀，打开设备电源，开始测试前预热30min；
(2)仔细检查U型样品管和玻璃漏斗管口是否有裂纹、缺口，管体、内壁是否洁净；确认完好无损后方可称量空样品管质量，记录为m1(mg)；
(3)使用装样漏斗进行装样，标样称样量：1000±50mg；
(4)平稳地将样品管放在烧杯中称重，记录吹扫前样品质量和空样品管质量，该质量仅供与吹扫后总质量对比作为参考；
(5)吹扫：进行测试之前，控制进气流量在80mL/min，总出口气流量80mL/min；检查样品管是否安装完好，仪器的气密性是否良好；通过脱气除去样品表面的物理吸附物质，同时要避免表面发生不可逆的变化；控制加热温度为200℃，加热时间为65min；
(6)吹扫完成后，称量样品管总质量m2(mg)，样品净重m3＝m2-m1；
(7)添加液氮：样品液氮杯加到2/3、冷阱恒温杯加到1/3；
(8)在软件界面设置储存路径、样品名称、样品净重等参数即可开始测试；仪器测量样品吸附量使用的是直接对比法，即将一定比例的载气(He)和吸附质气体(N2)的混合气体流过待测样品，根据吸附前后浓度变化，得到待测样品吸附量；
(9)实验结束后，记录实验数值并确认仪器总电源是否关闭、钢瓶总阀是否关闭，冷阱恒温杯是否取出，检查无误后整理实验台面，清洗样品管以及漏斗。
实施例2
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为50％，获取无定形碳在负极活性材料中的质量含量B，B为3％，获取负极活性材料的比表面积S，S为1.5m2/g；A*B/S＝0.0100；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例3
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为50％，获取无定形碳在负极活性材料中的质量含量B，B为4％，获取负极活性材料的比表面积S，S为1.5m2/g；A*B/S＝0.0133；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例4
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为70％，获取无定形碳在负极活性材料中的质量含量B，B为2％，获取负极活性材料的比表面积S，S为1.4m2/g；A*B/S＝0.0093；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例5
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为70％，获取无定形碳在负极活性材料中的质量含量B，B为3％，获取负极活性材料的比表面积S，S为1.35m2/g；A*B/S＝0.0150；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例6
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为70％，获取无定形碳在负极活性材料中的质量含量B，B为4％，获取负极活性材料的比表面积S，S为1.3m2/g；A*B/S＝0.0207；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例7
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为100％，获取无定形碳在负极活性材料中的质量含量B，B为1％，获取负极活性材料的比表面积S，S为1.6m2/g；A*B/S＝0.0063；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例8
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为100％，获取无定形碳在负极活性材料中的质量含量B，B为2％，获取负极活性材料的比表面积S，S为1.6m2/g；A*B/S＝0.0125；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例9
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为100％，获取无定形碳在负极活性材料中的质量含量B，B为3％，获取负极活性材料的比表面积S，S为1.3m2/g；A*B/S＝0.0231；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例10
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为100％，获取无定形碳在负极活性材料中的质量含量B，B为4％，获取负极活性材料的比表面积S，S为1.2m2/g；A*B/S＝0.0333；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例11
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为100％，获取无定形碳在负极活性材料中的质量含量B，B为5％，获取负极活性材料的比表面积S，S为1.0m2/g；A*B/S＝0.0500；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实施例12
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为100％，获取无定形碳在负极活性材料中的质量含量B，B为6％，获取负极活性材料的比表面积S，S为0.8m2/g；A*B/S＝0.0750；
本实施例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
对比例1
负极活性材料的获取方法，包括以下步骤：
石墨中的无定形碳在石墨表面的包覆率A为0，无定形碳在负极活性材料中的质量含量B为0，负极活性材料的比表面积S为1.8m2/g；A*B/S＝0；
本对比例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
对比例2
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为30％，获取无定形碳在负极活性材料中的质量含量B，B为1％，获取负极活性材料的比表面积S，S为1.7m2/g；A*B/S＝0.0017；
本对比例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
对比例3
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为100％，获取无定形碳在负极活性材料中的质量含量B，B为8％，获取负极活性材料的比表面积S，S为1.0m2/g；A*B/S＝0.08；
本对比例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
对比例4
负极活性材料的获取方法，包括以下步骤：
获取所述复合材料中的无定形碳在石墨表面的包覆率A，A为100％，获取无定形碳在负极活性材料中的质量含量B，B为10％，获取负极活性材料的比表面积S，S为0.8m2/g；A*B/S＝0.1000；
本对比例中的包覆率A、无定形碳在负极活性材料中的质量含量B及比表面积S的获取方法同实施例1。
实验例
一、将实施例及对比例中的负极活性材料分别制备成软包电池，具体方法包括：
将负极活性材料、导电剂SP、CMC和SBR混合均匀，得到负极浆料，其中，负极活性材料、导电剂SP、CMC和SBR的质量比为95：1.5：1.5：2.0，将负极浆料通过涂布机涂布至负极6μm铜箔上，通过辊压机制备出负极片；以磷酸铁锂为正极，以含锂盐LiPF6溶液(浓度1mol/L)、溶剂为体积比1:1的EC(碳酸乙烯酯)和DEC(碳酸二乙酯)为电解液，celgard 2400为隔膜，制备得到5Ah软包电池。
对实施例和对比例制备得到的软包电池进行循环性能、倍率性能和高温存储性能的检测，具体检测参数设置如下：
1.循环性能：1C/1C，2.5□3.65V，25±3℃。
2.倍率性能：2C恒流比，恒流容量/(恒流容量+恒压容量)。
3.低温存储性能：对锂离子电池以0.1C的倍率充电到3.65V，测试其容量为A0，之后在温度为-20±3℃放置7天，之后在常温下测试其电池的容量A1，之后再充电到3.65V，并测试其容量A2，之后计算出容量恢复＝A2/A0*100％，即低温存储性能。
4.高温存储性能：对锂离子电池以0.1C的倍率充电到3.65V，测试其容量为A0，之后在温度为60±3℃放置7天，之后在常温下测试其电池的容量A1，之后再充电到3.65V，并测试其容量A2，之后计算出容量恢复＝A2/A0*100％，即高温存储性能。
将实施例及对比例中的负极活性材料分别制备成扣电电池，具体方法包括
将负极活性材料、导电剂SP、CMC和SBR混合均匀，得到负极浆料，其中，负极活性材料、导电剂SP、CMC和SBR的质量比为95：1.5：1.5：2.0，将负极浆料通过涂布机涂布至负极集流体上，通过辊压机制备出负极片；以含锂盐LiPF6溶液(浓度 1mol/L)、溶剂为体积比1:1的EC(碳酸乙烯酯)+DEC(碳酸二乙酯)为电解液，锂片为正极，celgard 2400为隔膜组装成扣电半电池。
对实施例和对比例获取的扣电电池进行循环两次后满电留样进行DSC测试，具体检测参数设置如下表2所示：
表2检测参数设置
DSC测试：满电扣电拆解后，对极片用DMC清洗晾干后进行DSC测试，温度范围20-450℃，升温速率5℃/min。
上述软包电池和扣电电池的性能测试结果如表3所示。
表3电池性能测试结果

由表3可知，本公开实施例1～12与对比例1～4相比较，当A*B/S的值控制在0.005～0.0075范围内，不仅可以将倍率性能控制在85％以上，并且还可以使循环性能达到90％以上，高低温性能均达到88％以上，可有效实现该负极活性材料组制备得到的负极极片之间的快充、循环及其高低温性能之间的平衡。而对比例1、对比例2中包覆率低、无定形碳的质量含量小、动力学性能差，低温差，比表面积大，造成其循环性能偏差；对比例3、对比例4中由于包覆率大，无定形碳的质量含量大，动力学好，低温性能好，但是比表面积小，倍率性能差，并且其安全性能较差。
通过实施例3～6、实施例8～11与实施例1、实施例2、实施例12的对比可知，当A*B/S的值控制在0.013～0.05范围内，可以兼顾高低温性能平衡，以及综合提高倍率性能、循环性能及安全性能。
通过实施例9～10与实施例1-8、实施例11-12的对比可知，当A*B/S的值控制在0.02～0.04范围内，不仅可以将倍率性能、使循环性能、低温性能达到92％以上，高温性能也可以达到93％以上，极片满电DSC测试分解温度及能量也相对适中，同时兼顾了电池的安全性。即在具有较优异的快充性能下，有效筛选出能同时提高负极极片的循环及高低温性能的负极活性材料。
工业实用性
本公开提供了一种一种获取负极活性材料的方法、负极活性材料及其应用。本公开的方法获取的负极活性材料可提升锂离子电池的充电能力，同时保证锂离子电池在长期快速充电使用时还具有很好的循环使用寿命和安全性，效果显著。

Claims (10)

  1. 一种获取负极活性材料的方法，其特征在于，包括以下步骤：
    (a)提供待筛选的负极活性材料，所述待筛选的负极活性材料为核壳结构，其中，核层为石墨，壳层为无定形碳；
    (b)获取步骤(a)中待筛选的负极活性材料的无定形碳在石墨表面的包覆率A、无定形碳在负极活性材料中的质量含量B和负极活性材料的比表面积S，筛选出A、B和S之间关系式满足0.005≤A*B/S≤0.075的负极活性材料。
  2. 根据权利要求1所述的获取负极活性材料的方法，其特征在于，所述A、B和S之间的关系式满足：0.013≤A*B/S≤0.06。
  3. 根据权利要求2所述的获取负极活性材料的方法，其特征在于，所述A、B和S之间的关系式满足：0.02≤A*B/S≤0.04。
  4. 根据权利要求1所述的获取负极活性材料的方法，其特征在于，所述A的范围为30％～100％，所述B的范围为0.5％～6％，所述S的范围为0.8～2m2/g。
  5. 根据权利要求1所述的获取负极活性材料的方法，其特征在于，所述无定形碳在负极活性材料中的质量含量B的获取方法，包括：
    (a1)将多份已知无定形碳的质量含量的负极活性材料标样进行干燥，无定形碳在负极活性材料标样中的质量含量为B1；
    (b1)将负极活性材料标样分别进行热重测试，获取不同负极活性材料标样的无定形碳的热失重率y1；热失重率的温度区间范围值为200～620℃；
    所述热重测试包括第一热处理和第二热处理，所述第一热处理的温度为25～400℃，升温速率5～8℃/min，所述第二热处理的温度为400～800℃，升温速率为2～4℃/min；所述第一热处理和第二热处理的氧气流量为10～100mL/min；
    (c1)以无定形碳在负极活性材料中的质量含量B1为横坐标，热失重率y1为纵坐标进行线性拟合分析，得到关系方程式：y＝1.9343x+0.1317；
    (d1)将待测的负极活性材料按步骤(a1)相同条件进行干燥，按步骤(b1)相同条件进行热重测试，得到其热失重率y2，根据步骤(c1)中的关系曲线方程得到待测试的负极活性材料中的无定形碳的质量含量B。
  6. 根据权利要求1所述的获取负极活性材料的方法，其特征在于，所述负极活性材料的比表面积S的获取方法，包括：采用比表面积测试仪进行测试。
  7. 一种负极活性材料，其特征在于，由权利要求1～6中任一项所述的获取负极活性材料的方法得到。
  8. 一种负极片，其特征在于，包括权利要求7中所述的负极活性材料或者权利要求1～6中任一项所述的获取负极活性材料的方法得到的负极活性材料。
  9. 一种锂离子电池，其特征在于，包括权利要求8所述的负极片。
  10. 权利要求9所述的锂离子电池在消费电子类、电动工具和电动汽车中的应用。
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