Negative electrode material, secondary battery, and electric device

Abstract

The application provides a negative electrode material, a secondary battery and an electric device. The application prepares a secondary battery with high capacity and high compaction by matching the relationship between the G-peak half-peak width of the negative electrode material and the powder compaction density of the negative electrode material powder under 3T and 5T pressure. The negative electrode material comprises a carbonaceous material and satisfies the following relationship: 12.0≤2×(Y-Q)+1.5×Gh≤60.5; Gh cm ‑1 represents the half-peak width of the G-peak of the negative electrode material at a position with a Raman spectrum displacement of 1580±10 cm ‑1 ; Y g / cm 3 represents the powder compaction density of the negative electrode material under 5T pressure; Q g / cm 3 represents the powder compaction density of the negative electrode material under 3T pressure. The specific capacity of the negative electrode material is all above 354 mAh / g, and the cycle number of the obtained battery under 45℃, 1C / 1C cycle and the capacity retention rate of 80% is all above 1200 cycles.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a negative electrode material, a secondary battery, and an electrical device. Background Technology

[0002] Lithium-ion rechargeable batteries have been widely used in many industries due to their advantages such as high energy / power density, long cycle life, and pollution-free operation. Graphite remains the mainstream anode material for lithium-ion rechargeable batteries. Graphite is typically prepared using sulfur-containing coke as a raw material, which can be classified into low-sulfur coke, medium-sulfur coke, and high-sulfur coke based on its sulfur content, with high-sulfur coke accounting for the majority (approximately 40%). Using high-sulfur coke ensures a stable supply of raw materials, and its capacity is higher than that of low-sulfur coke. However, the high sulfur content results in higher internal porosity and lower material compaction density. Therefore, achieving both high capacity and high compaction density in rechargeable batteries prepared using high-sulfur coke remains a key technological challenge. Summary of the Invention

[0003] The purpose of this application is to provide a negative electrode material, a secondary battery, and an electrical device to improve the battery's capacity, energy density, and cycle performance.

[0004] To achieve the above objectives, a first aspect of this application provides a negative electrode material, the negative electrode material comprising a carbonaceous material, the negative electrode material satisfying the following relationship:

[0005] 12.0≤2×(YQ)+1.5×Gh≤60.5

[0006] In the formula, Gh cm -1 This indicates that the shift of the negative electrode material in the Raman spectrum is 1580 ± 10 cm. -1 The half-width of the G peak at its location;

[0007] Y g / cm 3 This indicates the compaction density of the negative electrode material under 5T pressure;

[0008] Q g / cm 3 This indicates the compaction density of the negative electrode material under a pressure of 3T.

[0009] As an embodiment of this application, the negative electrode material satisfies the following relationship: 20.0≤2×(YQ)+1.5×Gh≤50.0.

[0010] As an embodiment of this application, the full width at half maximum (FWHM) Gh of the negative electrode material in the Raman spectrum satisfies: 8 cm⁻¹ -1 ≤Gh≤40cm -1 .

[0011] As an embodiment of this application, the powder compaction density Y of the negative electrode material under 5T pressure satisfies: 1.800 g / cm³. 3 ≤Y≤1.900g / cm 3 .

[0012] As an embodiment of this application, the powder compaction density Q of the negative electrode material under 3T pressure satisfies: 1.600 g / cm³. 3 ≤Q≤1.700g / cm 3 .

[0013] As an embodiment of this application, the specific surface area BET of the negative electrode material satisfies: 0.5m² 2 / g≤BET≤2.7m 2 / g.

[0014] As an embodiment of this application, the degree of graphitization of the negative electrode material is G, which satisfies: 92% ≤ G ≤ 95%.

[0015] As an embodiment of this application, the particle size corresponding to the cumulative volume of the negative electrode material reaching 90% is D. V 90, satisfying: 20μm≤D V 90≤50μm.

[0016] As an embodiment of this application, the particle size corresponding to the cumulative volume of the negative electrode material reaching 50% is D. V 50, satisfying: 10μm≤D V 50≤20μm.

[0017] As an embodiment of this application, the particle size corresponding to the cumulative volume of the negative electrode material reaching 10% is D. V 10, satisfying: 5μm≤D V 10≤12μm.

[0018] As an embodiment of this application, the negative electrode material satisfies: 1.5 ≤ (D V 90-D V 10) / D V 50≤2.0.

[0019] As an embodiment of this application, the specific capacity of the negative electrode material is ≥354mAh / g.

[0020] As an embodiment of this application, the sulfur content of the negative electrode material is ≤0.01wt%.

[0021] A second aspect of this application provides a secondary battery, the secondary battery comprising a positive electrode, an electrolyte, a separator, and a negative electrode; the negative electrode comprises a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer comprising the negative electrode material described in the first aspect of this application.

[0022] A third aspect of this application provides an electrical device comprising the secondary battery described in the second aspect of this application.

[0023] Compared with the prior art, the beneficial effects of this application are:

[0024] This application aims to prepare a secondary battery with both high capacity and high compaction by matching the relationship between the half-peak width of the G peak of the negative electrode material and the compaction density of the negative electrode material powder under 3T and 5T pressures. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0027] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0028] Unless otherwise specified, all reagents or instruments used in this application are commercially available products.

[0029] A first aspect of this application provides a negative electrode material, said negative electrode material comprising a carbonaceous material, said negative electrode material satisfying the following relationship:

[0030] 12.0≤2×(YQ)+1.5×Gh≤60.5

[0031] In the formula, Gh cm-1 This indicates that the shift of the negative electrode material in the Raman spectrum is 1580 ± 10 cm. -1 The half-width of the G peak at its location;

[0032] Y g / cm 3 This indicates the compaction density of the negative electrode material under 5T pressure;

[0033] Q g / cm 3 This indicates the compaction density of the negative electrode material under a pressure of 3T.

[0034] This application aims to prepare a secondary battery with both high capacity and high compaction by matching the relationship between the half-peak width of the G peak of the negative electrode material and the compaction density of the negative electrode material powder under 3T and 5T pressures.

[0035] Gh represents the Raman spectrum of the negative electrode material at 1580 cm⁻¹. -1 The full width at half maximum (FWHM) of the G peak nearby. The G peak is an important characteristic peak in the Raman spectrum of carbon materials, generally appearing at approximately 1580 cm⁻¹. -1 Nearby, it reflects the sp of carbon atoms 2 The vibrational modes in the hybrid state, and their specific location and shape (including the full width at half maximum) can provide information about the material's structure and quality; the full width at half maximum (FWHM) of the G peak is often used in Raman spectroscopy to characterize properties such as the density of internal defects in a material. The density of the carbonaceous material in the negative electrode is related to the defect concentration and disorder of the carbonaceous material. The higher the disorder, the higher the lattice defect concentration in the negative electrode material. The magnitude of the defect concentration of the carbonaceous material affects the rate of lithium ion migration in the solid phase, thus affecting the kinetic performance of the secondary battery, especially the first efficiency and cycle life. The powder compaction density of the negative electrode material has a certain impact on the porosity of the negative electrode sheet and the battery performance. Generally, the higher the powder compaction density, the denser the negative electrode active material layer and the smaller the porosity. The particles of the negative electrode active material will be more closely packed, resulting in higher energy density. However, it is not conducive to the wetting of the electrolyte, and the diffusion rate of the liquid phase is affected, which further affects the cycle performance of the battery. This application found through a large number of experimental studies that by controlling the half-peak width of the G peak of the negative electrode material and the powder compaction density of the negative electrode material powder under 3T and 5T pressures, so that the three satisfy a specific relationship, a secondary battery with high capacity, high compaction, high energy density and excellent cycle performance can be prepared.

[0036] When the negative electrode material satisfies 12.0 ≤ 2 × (YQ) + 1.5 × Gh ≤ 60.5, the kinetic performance of the secondary battery is better. For example, the value of the relationship can be any one of 12.400, 15.390, 22.870, 27.366, 30.360, 37.870, 42.366, 45.352, 48.364, 52.846, 54.344, 58.880, 60.378, or a range between any two values. In some embodiments, the negative electrode material satisfies the following relationship: 20.0 ≤ 2 × (YQ) + 1.5 × Gh ≤ 50.0.

[0037] In some embodiments, the full width at half maximum (FWHM) Gh of the negative electrode material in the Raman spectrum satisfies: 8 cm⁻¹ -1 ≤Gh≤40cm -1 For example, the value of the full width at half maximum (FWHM) Gh can be 8 cm. -1 10cm -1 15cm -1 18cm -1 20cm -1 25cm -1 28cm -1 30cm -1 35cm -1 37cm -1 40cm -1 The range of values ​​between any one or any two values ​​in the range.

[0038] In some embodiments, the powder compaction density Y of the negative electrode material under a pressure of 5T satisfies: 1.800 g / cm³. 3 ≤Y≤1.900g / cm 3 For example, the value of Y can be 1.808 g / cm³. 3 1.81 g / cm 3 1.817 g / cm 3 1.834 g / cm 3 1.840 g / cm 3 1.853 g / cm 3 1.860 g / cm 3 1.870 g / cm 3 1.875g / cm 3 1.890 g / cm 3 1.900g / cm 3 The range of values ​​between any one or any two values ​​in the range.

[0039] In some embodiments, the powder compaction density Q of the negative electrode material under 3T pressure satisfies: 1.600 g / cm³.3 ≤Q≤1.700g / cm 3 For example, the value of Q can be 1.619 g / cm³. 3 1.624 g / cm 3 1.645 g / cm 3 1.652 g / cm 3 1.670 g / cm 3 1.675g / cm 3 1.682 g / cm 3 1.687 g / cm 3 1.695g / cm 3 1.700g / cm 3 The value is any one of the values ​​or any range between any two values. Appropriate powder compaction density can reduce the internal resistance of the electrode and decrease polarization loss, which is beneficial for extending the cycle life of the prepared secondary battery.

[0040] In some embodiments, the specific surface area BET of the negative electrode material satisfies: 0.5 m² / g. 2 / g≤BET≤2.7m 2 / g. The specific surface area of ​​the negative electrode material mainly affects the formation of the SEI film, and thus the kinetic performance of the secondary battery. Within a suitable range, the specific surface area of ​​the negative electrode material can reduce capacity loss caused by the reaction between the negative electrode material and the electrolyte in the secondary battery, and also reduce the possibility of lithium plating during high-rate current cycling, thereby further improving the kinetic performance of the prepared secondary battery. For example, the specific surface area BET of the negative electrode material can be 0.98m². 2 / g, 1.15m 2 / g, 1.25m 2 / g, 1.30m 2 / g, 1.40m 2 / g, 1.54m 2 / g, 1.68m 2 / g, 1.95m 2 / g, 2.31m 2 Any value in / g or a range between any two values.

[0041] In some embodiments, the graphitization degree of the negative electrode material is G, satisfying: 92% ≤ G ≤ 95%. As the name suggests, the graphitization degree refers to the degree to which the crystal structure of the negative electrode material closely resembles the complete layered structure of ideal graphite. A higher graphitization degree indicates a higher degree of ordering at the microscopic level, fewer defects such as stacking faults and dislocations in the crystal, resulting in a higher specific capacity and a higher energy density for the secondary battery. However, as the graphitization degree of the negative electrode material increases, the solid-state conduction of active ions is affected, making it more difficult for active ions to enter and exit, leading to poorer kinetic performance of the secondary battery, especially unfavorable for high-rate charge and discharge. Therefore, within the aforementioned suitable range, the graphitization degree of the negative electrode material can ensure that the secondary battery possesses both high energy density and high-rate cycle performance. For example, the value of G can be any one of 92.0%, 92.5%, 93.0%, 93.5%, 93.8%, 94.5%, or 95.0%, or a range between any two values.

[0042] Furthermore, a suitable particle size and distribution of the negative electrode material helps increase the compaction density of the negative electrode sheet, thereby improving the volumetric energy density of the secondary battery. A suitable particle size of the negative electrode material also facilitates the insertion and extraction of active ions, saving conduction time and resulting in better charge-discharge performance.

[0043] In some embodiments, the particle size corresponding to the cumulative volume of the negative electrode material reaching 90% is D. V 90, satisfying: 20μm≤D V 90 ≤ 50 μm. For example, the D... V The value of 90 can be any one of the following values ​​or a range between any two values: 27.8μm, 28.5μm, 29μm, 29.5μm, 30.2μm, 31.5μm, 32μm, 32.5μm, 32.8μm, 33.8μm, 44.0μm, 45.0μm, and 48.0μm.

[0044] In some embodiments, the particle size corresponding to the cumulative volume of the negative electrode material reaching 50% is D. V 50, satisfying: 10μm≤D V 50 ≤ 20 μm. For example, the D... V The value of 50 can be any one of the following values ​​or a range between any two values: 12.5μm, 12.9μm, 13.2μm, 13.6μm, 14.0μm, 14.2μm, 15.0μm, 16.5μm, 17.0μm, and 18.0μm.

[0045] In some embodiments, the particle size corresponding to the cumulative volume of the negative electrode material reaching 10% is D. V 10, satisfying: 5μm≤DV 10 ≤ 12 μm. For example, the D... V The value of 10 can be any one of the following values: 6.2μm, 6.6μm, 6.8μm, 7.2μm, 7.6μm, 7.9μm, 8.2μm, 10.0μm, 10.4μm, 11.5μm, or a range between any two values.

[0046] In some embodiments, the particle density (also known as K90) of the negative electrode material satisfies: 1.5 ≤ K90 = (D V 90-D V 10) / D V 50 ≤ 2.0. Particle size distribution reflects the particle size distribution of powder materials. When the particle size distribution of the negative electrode material satisfies the above relationship, smaller particles in the system can fill the gaps between larger particles, which helps to increase the compaction density of the negative electrode sheet, thereby improving the volumetric energy density of the prepared secondary battery. A reasonable particle size distribution can not only improve the compaction density of the secondary battery but also improve its cycle performance. For example, the value of K90 can be any one of 1.51, 1.53, 1.58, 1.64, 1.76, 1.86, 1.90, 1.96, 2.03, 2.04, 2.06 or a range between any two values.

[0047] Improving the specific capacity of anode materials is a key contributing factor to increasing the energy density of lithium-ion secondary batteries. The anode materials prepared in this application all have a specific capacity of over 354 mAh / g, which can meet the requirements for secondary battery use.

[0048] The sulfur content of the negative electrode material prepared in this application is less than 0.01 wt%.

[0049] It should be noted that the anode material described in this application is prepared by high-sulfur coke as raw material through a front-end high-temperature rearrangement reaction. Using high-sulfur coke as raw material can not only alleviate the shortage of low-sulfur coke resources, but also reduce costs at the raw material end. Furthermore, it can control the G peak half-peak width of the anode material and the powder compaction density of the anode material powder under 3T and 5T pressure to satisfy a specific relationship, so as to prepare a secondary battery with high capacity, high energy density and cycle performance.

[0050] In some embodiments, the sulfur content in the high-sulfur coke is in the range of 3% to 7%.

[0051] In some embodiments, the specific process of the front-end high-temperature rearrangement reaction is as follows:

[0052] Petroleum coke raw material with a sulfur content of 3% to 7% is selected and calcined at a low temperature of 600℃ to 900℃ for 4 to 6 hours. Then, it is crushed and dried to obtain coarse powder. The coarse powder is placed in a high-temperature furnace and heated to 2700 to 3000℃ at a heating rate of 5 to 15℃ / min under an argon inert atmosphere for high-temperature graphitization treatment for 20 to 24 hours to obtain single-particle graphitized products. The obtained single-particle graphitized products are then screened and demagnetized to obtain the finished product.

[0053] A second aspect of this application provides a secondary battery, the secondary battery comprising a positive electrode, an electrolyte, a separator, and a negative electrode; the negative electrode comprises a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer comprising the negative electrode material described in the first aspect of this application.

[0054] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer containing a negative active material.

[0055] The types of negative electrode current collectors and positive electrode current collectors are not specifically limited and can be selected according to actual needs.

[0056] In some embodiments, the negative electrode current collector is preferably made of copper foil or carbon-coated copper foil; the positive electrode current collector may include, but is not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, etc.; carbon materials such as carbon cloth, carbon paper, etc.; and composite materials formed by polymer and metal layer. In some embodiments, the positive electrode current collector is preferably made of aluminum foil.

[0057] In this application, the type of positive electrode active material is not limited and can be selected according to actual needs. For example, the positive electrode active material can be lithium iron phosphate, lithium manganese iron phosphate, or ternary positive electrode material. The positive electrode active material may also contain doping elements and / or coating elements. There are no special requirements for doping elements and / or coating elements, as long as they can make the positive electrode active material more stable.

[0058] In addition, the negative electrode active material layer and the positive electrode active material layer also contain at least one of a conductive agent, a binder, and a thickener.

[0059] Commonly used battery conductive agents, binders, and thickeners in this field can all be used in this application.

[0060] In some embodiments, the conductive agent includes, but is not limited to, at least one of graphite, carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene.

[0061] In some embodiments, the adhesive includes, but is not limited to, at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, and vinylidene fluoride-hexafluoropropylene copolymer.

[0062] In some embodiments, the thickener includes, but is not limited to, at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0063] In some embodiments, there is no limitation on the type of solvent used to form the positive electrode slurry and / or negative electrode slurry, as long as it is a solvent capable of dissolving or dispersing the positive electrode active material, the negative electrode active material, the conductive agent, the binder, or the dispersant.

[0064] In the secondary battery described in this application, the type of separator is not particularly limited and can be selected according to actual needs. The separator can be a polypropylene membrane, a polyethylene membrane, a polyvinylidene fluoride membrane, a spandex membrane, an aramid membrane, or a multilayer composite membrane modified with a coating.

[0065] In the secondary battery described in this application, the type of electrolyte is not particularly limited and can be selected according to actual needs.

[0066] In some embodiments, the preparation of a secondary battery includes: stacking a positive electrode, a separator, and a negative electrode in sequence, with the separator positioned between the positive and negative electrodes to provide isolation; then winding the cells into a square bare cell; inserting the cell into a battery casing; baking the cell at 65–95°C to remove water; injecting electrolyte; sealing the cell; and then performing processes such as settling, hot and cold pressing, formation, clamping, and capacity testing to obtain the secondary battery.

[0067] A third aspect of this application provides an electrical device, which includes the secondary battery described in the second aspect of this application. The electrical device can be an application device such as a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, and power tool. Vehicles can be new energy vehicles, including pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles; spacecraft include airplanes, rockets, space shuttles, and spacecraft; electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. This application does not impose special limitations on the above-described device.

[0068] The following are specific embodiments of this application, and the technical solutions of this application are further described in conjunction with the embodiments. However, this application is not limited to these embodiments. Unless otherwise specified, the reagents, methods, and equipment used in this application are all conventional reagents, methods, and equipment in this technical field.

[0069] Example 1

[0070] A negative electrode material is provided, and the preparation method of the negative electrode material specifically includes the following steps:

[0071] Petroleum coke with a sulfur content of 3% was selected as raw material and subjected to shallow calcination at 600℃. It was then crushed and dried to obtain coarse powder. The coarse powder was placed in a high-temperature furnace and heated to 3000℃ at a heating rate of 10℃ / min under an inert argon atmosphere for 24 hours to obtain single-particle graphitized products. The obtained single-particle graphitized products were then screened and demagnetized to obtain the finished product.

[0072] Examples 2-17, Comparative Examples 1-3

[0073] A series of anode materials are provided and prepared according to the method of Example 1. By changing the parameters such as sulfur content, heating rate, graphitization temperature and processing time in the petroleum coke raw material in Example 1, anode materials with different physical properties are obtained. The parameters of the obtained anode materials are detailed in Table 1.

[0074] Regarding the physical properties of the aforementioned negative electrode material:

[0075] 1) In this application, the particle size of the negative electrode material (including D) V 90. D V 50. D V 10 (unit: μm) was obtained by particle size analysis using a particle size analyzer. Detailed results are shown in Table 1.

[0076] 2) In this application, the specific conditions for Raman spectroscopy testing of the negative electrode material are: exposure time 0.5s, cumulative number of points 2500, objective lens magnification 100x, and the test results are detailed in Table 1;

[0077] 3) Powder compaction density of the negative electrode material (unit: g / cm³) 3 The compaction density was tested using a compaction density meter. The compaction density of the powder at 3T was denoted as Q. The test parameters were: pressurization rate 8mm / min, pressurization to 30kN and holding for 30s, depressurization rate 30mm / min, depressurization to 20N and holding for 10s; the compaction density of the powder at 5T was denoted as Y. The test parameters were: pressurization rate 8mm / min, pressurization to 50kN and holding for 30s, depressurization rate 30mm / min, depressurization to 20N and holding for 10s.

[0078] 4) The specific surface area (BET) of the negative electrode material was obtained by measuring the specific surface area. The specific test results are shown in Table 1, with the unit being m². 2 / g;

[0079] 5) Sulfur content (mass content): The sulfur content of the material was tested using ICP-OES equipment. The specific test conditions were as follows:

[0080] Sample weight: 0.4g; Digestion method: microwave digestion; Acid and volume used for digestion: 12mL aqua regia; Volume adjusted: 100mL;

[0081] 6) Graphitization degree G (in %): The graphitization degree of the material was tested using a Panaco Empyrean instrument. Test conditions: copper target, voltage and current 45kV, 40mA, test angle 24°~30°, test step 0.01°. ， Silicon-to-carbon ratio 1.5:3.5;

[0082] The test results are detailed in Table 1.

[0083] Table 1

[0084]

[0085] Table 1 (continued)

[0086]

[0087] The negative electrode materials prepared in the above examples and comparative examples were used to prepare secondary batteries, and then the electrochemical performance of the secondary batteries was tested.

[0088] The preparation of secondary batteries includes the following steps:

[0089] Preparation of positive electrode sheet

[0090] The positive electrode active material NCM622, conductive agent SP (conductive carbon black), additive CNT (carbon nanotubes), and binder PVDF were mixed at a mass ratio of 96.3:1.9:0.5:1.3. NMP solvent was added, and the mixture was stirred evenly under vacuum to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a positive electrode current collector aluminum foil to form a positive electrode active material layer. The coating was subsequently dried at 100±10℃, and the resulting sheets were rolled and cut to obtain the positive electrode sheet. The thickness of the positive electrode active material layer was 96 μm, and the compaction density was 3.4 g / cm³. 3 ;

[0091] Negative electrode preparation

[0092] The negative electrode material, conductive carbon black, binder styrene-butadiene rubber, and additive sodium carboxymethyl cellulose prepared in the above examples and comparative examples were mixed at a mass ratio of 96.5:0.7:1.8:1.0. Deionized water was added as a solvent, and the mixture was stirred evenly under vacuum to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto the negative electrode current collector copper foil through transfer coating to form a negative electrode active material layer. It was then dried at a temperature of 80±10℃, and the negative electrode sheet was obtained by rolling and cutting. The thickness of the negative electrode active material layer was 121μm. The compaction density of the negative electrode sheet was recorded. The specific test results are shown in Table 3.

[0093] Electrolyte preparation

[0094] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain a mixed organic solvent. LiPF6 was then dissolved in the mixed organic solvent and mixed evenly to obtain an electrolyte with a lithium ion concentration of 1 mol / L.

[0095] Assembly of secondary batteries

[0096] The prepared positive electrode, separator (polypropylene separator, Celgard 2300, purchased from Celgard in the United States), and negative electrode are stacked in sequence, with the separator in the middle of the positive and negative electrodes. Then, they are wound to obtain a bare cell, which is then packed into a soft-pack casing. After top and side sealing, electrolyte injection, formation, and sorting, a lithium-ion secondary battery is obtained.

[0097] The specific performance tests for the secondary batteries are as follows:

[0098] 1) Lithium plating on the negative electrode: The lithium-ion secondary battery was left to stand at 25℃ for 30 minutes, then charged at a constant current of 2.2C to 4.4V, left to stand for 30 minutes, discharged at a constant current of 1C to 2.8V, left to stand for 10 minutes, and after 10 charge-discharge cycles, the lithium-ion battery was charged again at a constant current of 2.2C to 4.4V, left to stand for 10 minutes, and then the charging was stopped. The battery was then disassembled and the interface condition of the negative electrode was observed. Specifically, the disassembled negative electrode interface was placed under an electron microscope, and the degree of lithium plating was classified into the following levels according to the proportion of lithium plating area (denoted by S) (see Table 2):

[0099] Table 2

[0100] Percentage of Lithium Plating Area at Interface Corresponding level Lithium plating degree S≤2％ 0 Non-lithium plating 2％<S≤20％ I Slight lithium plating 20％<S≤40％ II Moderate lithium plating 40％<S≤60％ III Severe lithium plating

[0101] 2) Specific capacity test: Assemble the coin cell in the following order: "coin cell positive electrode cap - gasket - membrane - electrolyte - separator - electrolyte - lithium sheet - filler - coin cell negative electrode cap". Place it in a glove box under argon atmosphere. Before testing, let the assembled coin cell stand for 3-4 hours to allow the electrolyte to fully wet the electrode sheets, thus obtaining a coin cell half-cell. The negative electrode sheet of the coin cell half-cell is prepared as follows: Mix the negative electrode material according to the ratio of SP:CMC:LA133 = 94.5:1.5:1.5:2.5, stir for 30 minutes, and then evenly coat the slurry onto the negative electrode copper foil with a scraper. Then, vacuum dry the negative electrode sheet at 105℃ for more than 2 hours to prepare the negative electrode sheet of the coin cell half-cell. The specific capacity of the negative electrode material was tested using a coin cell. The specific test steps were as follows: discharge to 5mV at 0.05C, let stand for 5 minutes, discharge to 5mV at 0.05mA, let stand for 5 minutes, discharge to 5mV at 0.01mA, and then charge to 2V at 0.1C. The charging capacity at this time is the specific capacity of the negative electrode material, and the unit is mAh / g.

[0102] 3) Cyclic performance: The secondary battery was placed in a charge-discharge test cabinet and subjected to constant temperature cycling test at 45℃ (0~97% SOC). It was charged to 4.35V at 1C constant current and constant voltage, and the cutoff current was 0.05C. After standing for 30 minutes, it was discharged to 2.8V at 1C constant current and then stood for 10 minutes. This was considered one charge-discharge cycle. Cyclic charge-discharge was performed. When the cycle capacity retention rate was ≤80%, the test was stopped, and the discharge capacity of the first cycle and the number of cycles when the test was stopped were recorded.

[0103] 4) Rate performance: The secondary battery was placed in a charge-discharge test chamber at a constant temperature of 25°C, charged at 1C constant current and constant voltage to 4.2V, cut off current at 0.05C, and allowed to stand for 30 minutes. Then it was discharged at 0.33C constant current to 2.8V. After each constant current and constant voltage charge to 4.2V, it was allowed to stand for 30 minutes. The batteries were then discharged at 0.33C, 0.5C, 1C, 2C, 3C, and 4C, and the capacity at different rates was recorded as C1, C2, C3, C4, C5, and C6, respectively. The capacity retention rate after different rate cycles was calculated as (C6 / initial discharge capacity) * 100%.

[0104] The test results are shown in Table 3:

[0105] Table 3

[0106]

[0107] The results above show that:

[0108] By matching the relationship between the half-peak width of the G peak of the anode material and the compaction density of the anode material powder under 3T and 5T pressures, a secondary battery with both high energy density and good cycle performance was prepared.

[0109] The specific capacity of the negative electrode materials prepared in this application is above 354 mAh / g, and the number of cycles when the capacity retention rate of the resulting batteries reaches 80% under 45℃ and 1C / 1C charge-discharge conditions is above 1200; the capacity retention rate at 4C rate is above 85%.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A negative electrode material, characterized by, The negative electrode material includes a carbonaceous material, and satisfies the following relationship: 12.0 ≤ 2 × (Y - Q) + 1.5 × Gh ≤ 60.5 In the formula, Ghcm -1 represents that the negative electrode material has a G peak at a position of 1580±10 cm -1 in the Raman spectrum, and the half-peak width of the G peak at the position satisfies: 8 cm -1 ≤ Gh ≤ 40 cm -1 ; Y g / cm 3 represents the powder compaction density of the negative electrode material under 5T pressure, and satisfies: 1.800 g / cm 3 ≤ Y ≤ 1.900 g / cm 3 ; Qg / cm 3 represents the powder compaction density of the negative electrode material under 3T pressure, and satisfies: 1.600 g / cm 3 ≤ Q ≤ 1.700 g / cm 3 .

2. The negative electrode material of claim 1, wherein, The negative electrode material satisfies the following relationship: 20.0 ≤ 2 × (Y - Q) + 1.5 × Gh ≤ 50.

0.

3. The negative electrode material of claim 1, wherein, The negative electrode material satisfies at least one of the following characteristics: (1) the specific surface area BET of the negative electrode material satisfies: 0.5 m 2 / g≤BET≤2.7 m 2 / g; (2) The graphitization degree G of the negative electrode material satisfies: 92% ≤ G ≤ 95%.

4. The negative electrode material of claim 1, wherein, The negative electrode material satisfies at least one of the following characteristics: (1) the volume of the negative electrode material accumulatively reaches 90% when the corresponding particle size is D V 90, satisfies: 20 μm≤D V 90≤50 μm; (2) the volume of the negative electrode material accumulatively reaches 50% at a particle size of D V 50, satisfies: 10 μm ≤ D V 50 ≤ 20 μm; (3) the volume of the negative electrode material accumulatively reaches 10% when the corresponding particle size is D V 10, satisfies: 5 μm ≤ D V 10 ≤ 12 μm; (4) the negative electrode material satisfies: 1.5≤(D V 90-D V 10) / D V 50≤2.

0.

5. The negative electrode material of claim 1, wherein the carbon-based material is a carbon-based material having a specific surface area of 1000 m2 / g or more. The negative electrode material satisfies at least one of the following characteristics: (a) The specific capacity of the negative electrode material is ≥ 354 mAh / g; (b) The sulfur content of the negative electrode material is ≤ 0.01 wt%.

6. A secondary battery comprising a positive electrode sheet, an electrolytic solution, a separator, and a negative electrode sheet, characterized by The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer contains the negative electrode material according to any one of claims 1 to 5.

7. An electric device, characterized by The electric device includes the secondary battery according to claim 6.

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