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WO2024148829A1 - 电池及用电装置 - Google Patents

电池及用电装置 Download PDF

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Publication number
WO2024148829A1
WO2024148829A1 PCT/CN2023/115700 CN2023115700W WO2024148829A1 WO 2024148829 A1 WO2024148829 A1 WO 2024148829A1 CN 2023115700 W CN2023115700 W CN 2023115700W WO 2024148829 A1 WO2024148829 A1 WO 2024148829A1
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WIPO (PCT)
Prior art keywords
negative electrode
active material
electrode active
battery
cdl
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Application number
PCT/CN2023/115700
Other languages
English (en)
French (fr)
Inventor
刘鹏
李嫚
陈云
褚春波
Original Assignee
欣旺达动力科技股份有限公司
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Application filed by 欣旺达动力科技股份有限公司 filed Critical 欣旺达动力科技股份有限公司
Priority to EP23809074.0A priority Critical patent/EP4421895A1/en
Priority to JP2024519799A priority patent/JP2025505912A/ja
Priority to US18/523,957 priority patent/US20240234725A1/en
Publication of WO2024148829A1 publication Critical patent/WO2024148829A1/zh

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Classifications

    • 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
    • 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
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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 application relates to the field of new energy technology, and in particular to a battery and an electrical device.
  • Lithium-ion batteries have been widely used in various fields due to their advantages such as high specific energy, good power performance, low self-discharge and long cycle life.
  • the gram capacity and compaction density of the negative electrode sheet can be increased by compaction.
  • overpressure is easily generated during compaction, which will slow down the speed at which the negative electrode sheet is infiltrated by the electrolyte, and reduce the liquid absorption performance, liquid retention performance and infiltration effect of the negative electrode sheet, which is not conducive to improving the energy density and cycle performance of lithium-ion batteries.
  • the present application provides a battery and an electrical device, which improve the problem of poor electrolyte infiltration and liquid absorption of the negative electrode sheet of the battery due to overvoltage, thereby improving the problem of low energy density, rate and cycle performance of the battery caused by this.
  • a battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode membrane disposed on at least one surface of the positive electrode current collector, and the positive electrode membrane includes a positive electrode active material;
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode membrane disposed on at least one surface of the negative electrode current collector, the negative electrode membrane includes a negative electrode active material; the negative electrode active material includes porous negative electrode active material particles;
  • the non-Faraday capacitance of the negative electrode sheet is Cdl nF, and the sphericity of the negative electrode active material is S, which satisfies the following characteristics: 0.5 ⁇ Cdl ⁇ S ⁇ 5.
  • the pore size of the negative electrode active material is r nm, and Cdl and r satisfy the following characteristics: 1.2 ⁇ 0.1 ⁇ r+Cdl ⁇ 10.
  • the pore size distribution of the negative electrode active material satisfies: 2 ⁇ r ⁇ 20.
  • the pore size distribution of the negative electrode active material satisfies: the negative electrode active material has at least one peak in the region of pore size distribution of 2 nm to 6 nm.
  • the negative electrode active material contains sulfur.
  • the liquid absorption time of the negative electrode membrane is T min
  • the compaction density of the negative electrode membrane is PD g/cm 3 , which satisfies: 0.3 ⁇ T ⁇ PD ⁇ 5.8.
  • the Dv50 of the negative electrode active material is D 1 ⁇ m
  • the Dv50 of the positive electrode active material is D 2 ⁇ m
  • D 1 and D 2 satisfy at least one of the following characteristics:
  • the powder compaction density of the negative electrode active material under a pressure of 30 KN is P 1 g/cm 3
  • the powder compaction density of the positive electrode active material under a pressure of 30 KN is P 2 g/cm 3
  • the relationship between P 1 and P 2 satisfies the following characteristic: 1.5 ⁇ P 2 /P 1 ⁇ 2.5.
  • the negative electrode active material includes a carbon material, and the carbon material includes graphite.
  • an embodiment of the present application further provides an electrical device, which includes the battery in the above embodiment, and the battery serves as a power supply for the electrical device.
  • the present application adjusts the relationship between the non-Faraday capacitance (Cdl nF) of the negative electrode sheet and the sphericity (S) of the negative electrode active material contained in the negative electrode sheet, effectively reduces the specific surface area of the negative electrode active material, improves its tap density, and makes the negative electrode sheet have a higher density without overpressure.
  • the mechanical stress experienced by the negative electrode active material of the negative electrode sheet during rolling can be reduced, and the reaction area with the electrolyte can be reduced, thereby obtaining good liquid retention performance and electrolyte infiltration effect, thereby reducing gas generation and swelling, so that the battery has excellent fast charge and discharge performance, good rate performance and cycle performance.
  • the negative electrode active material particles of the present application have pores, which can further improve the liquid retention performance of the negative electrode membrane and the electrolyte infiltration effect, so that the overall performance of the battery is better.
  • FIG1 is a scan rate-current scatter plot of Example 1 of the present application.
  • the embodiment of the present application provides a battery (or lithium-ion battery), which effectively reduces the specific surface area of the negative electrode active material and increases its tap density by controlling the pore structure of the negative electrode active material particles and adjusting the non-Faraday capacitance (Cdl nF) of the negative electrode sheet and the sphericity (S) of the negative electrode active material contained in the negative electrode sheet, so as to reduce the mechanical stress experienced by the negative electrode active material of the negative electrode sheet during rolling, reduce the reaction area with the electrolyte, obtain good liquid retention performance and electrolyte infiltration effect, so that the battery has excellent fast charge and discharge performance, good rate performance and cycle performance.
  • a battery or lithium-ion battery
  • the embodiment of the present application provides a battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode membrane arranged on at least one surface of the positive electrode current collector, and the positive electrode membrane includes a positive electrode active material.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode membrane disposed on at least one surface of the negative electrode current collector.
  • the negative electrode membrane includes a negative electrode active material, the negative electrode active material includes porous negative electrode active material particles, the non-Faraday capacitance of the negative electrode sheet is Cdl nF, the sphericity of the negative electrode active material is S, and the following characteristics are satisfied: 0.5 ⁇ Cdl ⁇ S ⁇ 5.
  • the non-Faraday capacitance of the negative electrode sheet is Cdl nF
  • the sphericity of the negative electrode active material is S
  • the two satisfy 1 ⁇ Cdl ⁇ S ⁇ 4.5.
  • 1 ⁇ Cdl ⁇ S ⁇ 4.5 the specific surface area and tap density of the negative electrode active material can be further adjusted, so that the negative electrode sheet has a higher density without overvoltage, and at the same time, the reaction area between the negative electrode sheet and the electrolyte can be within a suitable range, further improving the overall performance of the battery.
  • the non-Faraday capacitance of the negative electrode sheet is Cdl nF
  • the sphericity of the negative electrode active material is S
  • 1.5 ⁇ Cdl ⁇ S ⁇ 4 the comprehensive performance of the battery can be further improved.
  • the non-Faraday capacitance of the negative electrode sheet is Cdl nF
  • the sphericity of the negative electrode active material is S, and both satisfy 2 ⁇ Cdl ⁇ S ⁇ 3.
  • the assembly process of the buckle battery includes the following steps: drying the obtained negative electrode sheet, cutting it into small discs, transferring it to a vacuum oven after weighing, drying it at 100°C for 8h, and then transferring it to a glove box filled with Ar for buckle battery assembly.
  • step of confirming the non-Faraday potential range The assembled buckle is subjected to cyclic voltammetry (CV) test to confirm the non-Faraday potential range of the buckle, wherein the voltage range is 0.005-3.0V and the scan rate is 0.1-1mV/s.
  • CV cyclic voltammetry
  • S3 non-Faraday interval cathode scanning step. Randomly select the straight section potential interval in S2 for linear scanning voltammetry (LSV) test, the scanning direction is from high potential to low potential, and the voltage-current curve is collected, where the potential range is 2.6-2.7V and the scanning speed is 0.05-5mV/s. Then select the median U of the potential interval at a specific scanning speed V1 (the specific scanning speed can be 0.1mV/s, 0.2mV/s, 0.5mV/s, 1mV/s and 2mV/s, etc.), obtain the corresponding current value, and obtain the scanning speed-current scatter plot.
  • LSV linear scanning voltammetry
  • step of calculating the non-Faradaic capacitance According to the scan rate-current scatter diagram collected in S3, a linear function is fitted, and the slope K of the linear function is the non-Faradaic capacitance Cdl value of the negative electrode sheet in the cathode scanning direction.
  • the non-Faraday capacitance (Cdl nF) of the negative electrode sheet in the embodiment of the present application is 0.5 ⁇ 8nF.
  • the non-Faraday capacitance Cdl nF of the negative electrode sheet can also be 1 ⁇ 6nF, 2 ⁇ 5nF, or 3 ⁇ 4nF.
  • the sphericity S of the negative electrode active material in the negative electrode sheet in the embodiment of the present application is measured by a dynamic image particle analyzer.
  • the method for obtaining the negative electrode active material from the negative electrode sheet can be: discharge the secondary battery at a constant current of 0.04C to the lower voltage limit, disassemble the negative electrode sheet, soak and clean the negative electrode sheet with a DMC (dimethyl carbonate) solution, then wash it with deionized water for multiple times and then pour off the upper layer of liquid, let the lower layer of solution stand and dry, and finally heat treat it at 800°C for 2h in an argon atmosphere to obtain the above test sample.
  • DMC dimethyl carbonate
  • the sphericity S of the negative electrode active material is 0.2 to 0.9.
  • S can be any one of 0.2, 0.3, 0.35, 0.4, 0.43, 0.45, 0.48, 0.5, 0.53, 0.55, 0.58, 0.6, 0.63, 0.65, 0.68, 0.7, 0.73, 0.75, 0.78, 0.8, 0.85, 0.9 or a range consisting of any two values thereof.
  • the sphericity of the negative electrode active material is within the above range, which can make the morphology of the negative electrode active material particles in a better state and improve the overall performance of the battery.
  • the sphericity S of the negative electrode active material is 0.3 to 0.85. When the sphericity When S is 0.3-0.85, the overall performance of the battery can be further improved.
  • the sphericity S of the negative electrode active material is 0.4-0.78.
  • the sphericity S of the negative electrode active material is 0.45-0.73.
  • Electrochemical reactions include Faradaic reactions in which the oxidation state of active materials changes and charges move to the interior of active materials, and non-Faradaic reactions in which ions are physically adsorbed and detached on the surface of active materials to store and release charges.
  • Faradaic reactions refer to changes in the oxidation state of active materials, where charges move through the double charge layer and through the electrode interface to the interior of active materials.
  • Non-Faradaic reactions refer to reactions in which charges are stored and released by ions being physically adsorbed and detached on the electrode surface without charge movement across the electrode interface.
  • the non-Faraday capacitance Cdl reflects the number of active sites in the negative electrode sheet.
  • the non-Faraday capacitance Cdl nF of the negative electrode sheet needs to be controlled within an appropriate range.
  • the Cdl value is within a certain range, the larger the Cdl value, the more electrochemically active points there are, the more conducive it is to the contact between the active material and the electrolyte, the faster the conduction rate of ions and electrons, the lower the charge transfer resistance, and the more effective it is to improve the rate performance.
  • the sphericity S of the negative electrode active material will affect the isotropy of the negative electrode active material particles, the direction and path of lithium ion deintercalation, and the sphericity will also affect the distribution of the negative electrode active material in the negative electrode sheet and the contact between the negative electrode active materials.
  • the negative electrode active material particles have a pore structure, which can further improve the wetting speed and liquid retention performance of the negative electrode sheet. The three work together to effectively improve the overall performance of the battery.
  • the non-Faraday capacitance Cdl nF of the negative electrode sheet and the sphericity S of the negative electrode active material are within the range of 0.5 ⁇ Cdl ⁇ S ⁇ 5, which can effectively reduce the specific surface area of the negative electrode active material and increase its tap density, so that the negative electrode sheet has a high density without overvoltage.
  • the mechanical stress of the negative electrode active material of the negative electrode sheet during rolling can be reduced, the reaction area with the electrolyte is reduced, and it has good liquid retention performance, thereby preventing gas generation and swelling, and thus making the lithium-ion battery have excellent fast charge and discharge performance and cycle performance.
  • the negative electrode active material includes graphite material, and the negative electrode active material exists in the form of negative electrode active material particles.
  • a channel can be formed between these negative electrode active material particles to allow lithium ions to quickly enter the graphite layer, shortening the solid phase diffusion path of lithium ions, thereby increasing the charge rate of the negative electrode sheet, achieving fast charging, and improving its fast charging performance.
  • the pore size of the negative electrode active material is r nm
  • the non-Faradaic capacitance of the negative electrode sheet is Cdl nF
  • the relationship between the two satisfies the following characteristics: 1.2 ⁇ 0.1 ⁇ r+Cdl ⁇ 10.
  • the pore size and non-Faradaic capacitance of the negative electrode active material will affect the fast charging capability and cycle life of the lithium-ion battery. Within a certain range, the non-Faradaic capacitance of the negative electrode active material increases, the active sites on its surface increase, the contact with the electrolyte is sufficient, the impedance of the lithium-ion battery decreases, and the capacity will increase.
  • the appropriate pore size can avoid the crushing of roller-pressed particles while shortening the lithium ion in the negative electrode active material.
  • the solid-phase diffusion path in the negative electrode can improve the kinetic performance of the lithium-ion battery.
  • the embodiment of the present application can adjust the pore size of the negative electrode active material and the non-Faraday capacitance of the negative electrode sheet so that the lithium ions can be smoothly inserted into the negative electrode active material through the pores during the subsequent electrochemical reaction, thereby improving the cycle performance of the lithium-ion battery.
  • the pore size can also buffer the volume change of the lithium-ion battery during the charging and discharging process, and improve the cycle performance of the lithium-ion battery.
  • the present application reasonably adjusts the relationship between the pore size and the non-Faraday capacitance of the negative electrode active material, and controls the relationship between the two within the range of 1.2 ⁇ 0.1 ⁇ r+Cdl ⁇ 10. It can take into account and balance the energy density, fast charging performance and long cycle life of the lithium-ion battery, and prevent the adverse effects of overvoltage on these properties of the lithium-ion battery.
  • the pore size of the negative electrode active material is r nm
  • the non-Faradaic capacitance of the negative electrode sheet is Cdl nF, satisfying 2 ⁇ 0.1 ⁇ r+Cdl ⁇ 8.
  • the pore size and non-Faradaic capacitance of the negative electrode active material are within a more suitable range, which can further affect the wetting performance of the electrolyte and the reaction with the electrolyte, so that the overall performance of the battery is better.
  • the pore size value of the negative electrode active material is r nm
  • the non-Faraday capacitance of the negative electrode sheet is Cdl nF, satisfying 3 ⁇ 0.1 ⁇ r+Cdl ⁇ 7.
  • the pore size value of the negative electrode active material is r nm
  • the non-Faraday capacitance of the negative electrode sheet is Cdl nF, satisfying 4 ⁇ 0.1 ⁇ r+Cdl ⁇ 6.
  • the pore size r of the negative electrode active material may be 2nm to 20nm.
  • r nm may be 2nm, 3nm, 3.5nm, 4nm, 4.5nm, 4.8nm, 5nm, 5.3nm, 5.5nm, 5.8nm, 6nm, 6.5nm, 6.8nm, 7nm, 7.5nm, 7.8nm, 8nm, 8.5nm, 9nm, 10nm, 11nm, 12nm, 12.5nm, 13nm, 13.5nm, 14nm, 14.5nm, 15nm, 15.5nm, 16nm, 17nm, 18nm, 19nm, 20nm, any one of them or a range consisting of any two of them.
  • the pore size of the negative electrode active material is 3 nm to 18 nm.
  • the pore size of the negative electrode active material is 3.5 nm to 12 nm.
  • the pore size of the negative electrode active material is 4 nm to 10 nm.
  • the pore size of the negative electrode active material is 5 nm to 8 nm.
  • the negative electrode active material has a suitable pore size, which can make the compression resistance of the negative electrode active material particles and the diffusion of the negative electrode active material in the electrolyte both within a relatively optimal range, can enhance the non-Faraday reaction, and improve the kinetic performance of lithium ions.
  • the pore size distribution of the negative electrode active material has at least one peak in the region of 2nm to 6nm.
  • the pore size distribution of the negative electrode active material is in a more optimal state, which can further improve the overall performance of the battery.
  • the negative electrode active material layer contains sulfur.
  • the negative electrode active material contains sulfur.
  • the negative electrode active material comprises a carbon material.
  • the negative electrode active material includes graphite.
  • the negative electrode active material includes artificial graphite.
  • the coke raw material used for the negative electrode active material contains sulfur-containing substances.
  • the sulfur content in the coke raw material used for the negative electrode active material may be 0.1 wt% to 4 wt%.
  • the sulfur content may be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.3 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt%, 2.0 wt%, 2.1 wt%, 2.5 wt%, 2.7 wt%, 3.0 wt%, 3.2 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.8 wt%, 4.0 wt%, or any one of the values or a range consisting of any two of them.
  • the sulfur content in the coke raw material used for the negative electrode active material may also be 0.2-3 wt %.
  • the sulfur content in the coke raw material used for the negative electrode active material may also be 0.5-2.5 wt %.
  • the sulfur content in the coke raw material used for the negative electrode active material may also be 1-2 wt %.
  • the content of volatile matter in the coke raw material may be 5-15wt%.
  • the content of volatile matter in the coke raw material may be 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, 10wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, 14.5wt%, 15wt%, any one of them or a range consisting of any two of them.
  • the content of volatile matter in the coke raw material may also be 6wt% to 12wt%.
  • the content of volatile matter in the coke raw material may also be 8wt% to 10wt%.
  • the coke raw material can be selected from coke, petroleum coke (such as petroleum asphalt, etc.), coal tar, asphalt coke (such as coal asphalt, etc.), etc.
  • the purpose of selecting a coke raw material with specific raw material properties is to obtain negative electrode active material particles with a suitable pore structure by controlling the raw material properties of the negative electrode active material.
  • the sulfur content in the coke raw material is measured by energy dispersive X-ray fluorescence spectrometry, and the volatile matter is measured by SH/T0026-1990 petroleum coke volatile matter determination method.
  • Sulfur is harmful to coking, gasification, combustion, storage and transportation.
  • the level of volatile matter will affect the preparation efficiency of raw materials and increase coal consumption.
  • the sulfur introduced during coking will lead to a decrease in coke production capacity, and the sulfur dioxide generated during gasification will It corrodes equipment, affects operation and product quality, and pollutes the environment.
  • the sulfur content of the coke raw material is also related to the appropriate pore size formed by the negative electrode active material during rolling.
  • the negative electrode active material forms a suitable pore size after rolling and has a suitable compaction density, it can enhance the non-Faraday reaction, thereby improving the kinetics of lithium ions and reducing overvoltage.
  • the Hardgrove grindability index HGI of the coke raw material may be 30 to 100.
  • the Hardgrove grindability index HGI of the coke raw material may be any one of 30, 32, 35, 36, 38, 40, 44, 45, 48, 50, 52, 55, 56, 58, 60, 65, 70, 75, 80, 85, 90, 93, 95, 98, 100 or a range consisting of any two of the values.
  • the Hardgrove Grindability Index (HGI) of the coke raw material may also be 40-90.
  • the Hardgrove Grindability Index (HGI) of the coke raw material may also be 50-80.
  • the Hardgrove Grindability Index refers to the ratio of the energy consumed when grinding a sample and a standard sample into a specified number of particles and crushing them to the same fineness under air-dry conditions. It is used to measure the grindability of coke raw materials, and its value reflects the difficulty of crushing different types of coke raw materials.
  • the Hardgrove Grindability Index is measured by the Hadgrove method and is an indicator to measure the hardness of coke raw materials. If the coke raw material is soft, the HGI value is relatively large, the coke raw material is easy to crush, and the compaction density of the obtained negative electrode active material is higher. However, both too large and too small Hardgrove Grindability Index HGI have a certain impact on the negative electrode active material and need to be within a certain range. After research, the applicant found that by controlling the Hardgrove Grindability Index HGI of the coke raw material within the range of 30 to 100, the compaction density and pore size distribution of the negative electrode active material can be controlled within an appropriate range.
  • the liquid absorption time of the negative electrode membrane is T min
  • the compaction density of the negative electrode membrane is PD g/cm 3
  • the relationship between the two satisfies the following characteristics: 0.3 ⁇ T ⁇ PD ⁇ 5.8.
  • the value of T ⁇ PD can be any value of 0.3, 0.4, 0.6, 0.7, 1.0, 1.2, 1.5, 1.8, 2.0, 2.3, 2.5, 2.8, 3, 3.5, 4.0, 4.4, 5.0, 5.2, 5.5, 5.6, 5.8 or a range consisting of any two numbers therein.
  • T ⁇ PD When the value of T ⁇ PD is within the above range, the degree of extrusion between the negative electrode active material particles and the porosity of the negative electrode sheet are within a suitable range, and the wettability of the electrolyte on the negative electrode membrane can be ensured, the polarization during the battery cycle is reduced, and the increase of the internal resistance of the battery is slowed down.
  • the liquid absorption time of the negative electrode membrane is T min
  • the compaction density of the negative electrode membrane is PD g/cm 3
  • the relationship between the two may also be 0.5 ⁇ T ⁇ PD ⁇ 5.5.
  • the liquid absorption time of the negative electrode membrane is T min
  • the compaction density of the negative electrode membrane is PD g/cm 3
  • the relationship between the two may also be 1 ⁇ T ⁇ PD ⁇ 5.
  • the liquid absorption time of the negative electrode membrane is T min
  • the compaction density of the negative electrode membrane is The degree is PD g/cm 3 , and the relationship between the two can be further expressed as 2 ⁇ T ⁇ PD ⁇ 4.
  • the liquid absorption time T of the negative electrode membrane may be 0.25 to 3.5 min (i.e., 0.25 ⁇ T ⁇ 3.5, and the same applies below), for example, it may be any value among 0.25, 0.3, 0.6, 0.7, 1.1, 1.5, 2, 3, 3.2, 3.5, or a range consisting of any two of them.
  • the liquid absorption time T of the negative electrode membrane may also be 0.5 to 3 minutes.
  • the liquid absorption time T of the negative electrode membrane may also be 1 to 2.5 minutes.
  • the compaction density PD of the negative electrode film may be 1.1-1.7 g/cm 3 (i.e., 1.1 ⁇ PD ⁇ 1.7).
  • the value of PD may be any value of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or a range consisting of any two of these values.
  • the absorption time of the negative electrode film can be tested by an optical contact angle meter.
  • the detection method of the absorption time is as follows: when detecting the absorption time, use a micro-injector to vertically drop a drop of electrolyte (about 10 ⁇ L) on the negative electrode film on the surface of the negative electrode sheet, and start timing with a stopwatch. After the electrolyte diffuses, the time taken for the electrolyte to completely infiltrate is recorded as the absorption time of the negative electrode film. The longer the absorption time, the worse the wetting performance of the negative electrode sheet.
  • the compaction density is closely related to the specific capacity, efficiency, internal resistance and battery cycle performance of the negative electrode sheet.
  • the Dv50 of the negative electrode active material is D 1 ⁇ m
  • the Dv50 of the positive electrode active material is D 2 ⁇ m
  • the relationship between D 1 and D 2 satisfies the following characteristics: 1 ⁇ D 1 /D 2 ⁇ 36.
  • it can be at least one of 1, 3, 4, 6, 7, 8, 9, 10, 11, 15, 21, 23, 25, 27, 30, 32, 36 or a range consisting of any two numbers therein.
  • Matching the particle size ratio of the positive electrode active material and the negative electrode active material in the range of 1 to 36 can make the positive electrode sheet and the negative electrode sheet have higher electron and lithium ion transmission performance, make the electrochemical reaction between the positive electrode sheet and the negative electrode sheet in a more matched state, and make the lithium ion battery have higher charging and discharging performance at a high rate.
  • the relationship between D 1 and D 2 may also be 2 ⁇ D 1 /D 2 ⁇ 35.
  • the relationship between D1 and D2 may also be 5 ⁇ D1 / D2 ⁇ 30 .
  • the relationship between D1 and D2 may also be 10 ⁇ D1 / D2 ⁇ 20 .
  • 6 ⁇ D 1 ⁇ 18 can be at least one of 6, 7, 8, 9, 10, 11, 12, 15, 16, 18 or a range consisting of any two of them.
  • the particle size of the negative electrode active material particles is within the above range, the density of the structure of the negative electrode film can be within a suitable range, which is conducive to the penetration of the electrolyte and makes When the interfacial resistance of the negative electrode active material particles is within an appropriate range, the kinetic performance of the lithium-ion battery is better; at the same time, the particle size of the negative electrode active material particles will affect the dispersibility of the active material particles in the slurry, which can reduce the agglomeration of the negative electrode active material particles, make the surface density distribution more uniform, and the bonding force of the electrode sheet is appropriate, so that the electronic conductivity of the negative electrode sheet is in a better state, thereby improving the kinetic performance and cycle life of the battery.
  • 0.5 ⁇ D 2 ⁇ 8 can be at least one of 0.5, 1, 1.5, 2, 2.5, 2.7, 3.0, 3.5, 3.8, 4, 4.3, 4.5, 4.8, 5, 5.5, 5.8, 6, 6.3, 6.5, 7, 8 or a range consisting of any two of them. If the particle size of the positive electrode active material particles is within the above range, the positive electrode membrane electrolyte has a strong permeability, the liquid phase diffusion capacity of lithium ions is within a suitable range, and the solid phase conduction capacity of lithium ions in the particles is strong, the comprehensive performance of the lithium ion battery can be effectively guaranteed.
  • the Dv50 of the positive electrode active material and the negative electrode active material can be measured using a laser particle size analyzer.
  • the powder compaction density of the negative electrode active material under a pressure of 30KN is P 1 g/cm 3
  • the powder compaction density of the positive electrode active material under a pressure of 30KN is P 2 g/cm 3
  • the relationship between P 1 and P 2 satisfies the following characteristics: 1.5 ⁇ P 2 /P 1 ⁇ 2.5.
  • the value of P 2 /P 1 can be any value of 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5 or a range consisting of any two numbers therein.
  • the embodiments of the present application match the ratio of the powder compaction density of the positive electrode active material and the negative electrode active material under a pressure of 30KN within the range of 1.5 to 2.5, which is beneficial to the diffusion of lithium ions inside and between active materials, improves the solid phase conduction ability of lithium ions, reduces the impedance of lithium ion batteries, and improves the fast charging ability and cycle life of lithium ion batteries.
  • the relationship between P 1 and P 2 satisfies: 1.6 ⁇ P 2 /P 1 ⁇ 2.4.
  • the relationship between P 1 and P 2 satisfies: 1.8 ⁇ P 2 /P 1 ⁇ 2.2.
  • the relationship between P 1 and P 2 satisfies: 1.9 ⁇ P 2 /P 1 ⁇ 2.1.
  • 1.5 ⁇ P 1 ⁇ 2.0 or may be a range consisting of any two of 1.6, 1.7, 1.8, and 1.9.
  • P 1 satisfies the above range, the pore structure and morphology of the negative electrode active material, such as sphericity, are in a better state, which can improve the pore structure of the negative electrode sheet and put the battery in a better state.
  • 2 ⁇ P 2 ⁇ 4 may be a range consisting of any two numbers from 2.1, 2.2, 2.5, 2.8, 3, 3.2.
  • P 2 satisfies the above range, the positive electrode sheet and the negative electrode sheet are more matched, so that the battery has better overall performance.
  • the compaction density test of negative electrode active material powder refers to GB/T 24533-2019 lithium-ion battery graphite negative electrode materials.
  • the test conditions are as follows: weigh 1g of negative electrode active material, pressurization speed: 8mm/min, pressurization and holding time: 30s, pressure after decompression: 20N, decompression speed: 30mm/min, and holding time after decompression: 10s.
  • test conditions of the positive electrode active material are as follows: 1.5 g of positive electrode active material, pressurization speed: 1 mm/min, pressurization and holding time: 60 s, pressure after decompression: 30 N, decompression speed: 4 mm/min, and holding time after decompression: 10 s.
  • the positive electrode active material includes one or more of lithium iron phosphate material, lithium iron manganese phosphate material, lithium nickel cobalt manganese material, and lithium nickel cobalt aluminum material.
  • the lithium iron phosphate material is LiFePO 4 (abbreviated as LFP).
  • the chemical formula of lithium manganese iron phosphate material is Li y Fe x Mn 1-x PO 4 ; 0.9 ⁇ y ⁇ 1.2, 0.2 ⁇ x ⁇ 0.5, for example, LiFe 0.2 Mn 0.8 PO 4 , LiFe 0.3 Mn 0.7 PO 4 , LiFe 0.4 Mn 0.6 PO 4 or LiFe 0.5 Mn 0.5 PO 4 .
  • it may be NCM523, NCM622 or NCM811.
  • the present application also provides an electrical device, which includes a battery according to any of the above embodiments, and the battery serves as a power supply for the electrical device.
  • the electrical device of the present application may include but is not limited to a backup power supply, a motor, an electric car, an electric motorcycle, a power-assisted bicycle, a bicycle, an electric tool, a large household battery, etc.
  • This embodiment provides a method for preparing a negative electrode sheet, which comprises the following steps:
  • the preparation steps of the negative electrode active material include: selecting petroleum coke with a sulfur content of 2wt%, a volatile matter of 8wt% and an HGI value of 60, and performing pretreatment processes such as crushing and premixing in a roller mill, and the particle size after crushing is 8-10 ⁇ m; the crushed product is subjected to high-temperature graphitization treatment in a protective atmosphere at a temperature of 2800-3000°C, and is kept at a maximum temperature of 3000°C for 36 hours, and the protective atmosphere is argon; then the product is polished and shaped in a continuous shaping system for 8 hours to make the surface of the product particles smooth and flat, and a negative electrode active material (particle form) with a sphericity S of 0.7 and a particle size Dv50 (D 1 ) of 12 ⁇ m is obtained.
  • the powder compaction density P 1 g/cm 3 of the negative electrode active material under a pressure of 30KN is 1.76g/cm 3 .
  • the preparation step of the negative electrode slurry includes: mixing the above-mentioned negative electrode active material (artificial graphite product), conductive agent (carbon black), binder (sodium carboxymethyl cellulose), and additive (styrene-butadiene rubber) in a mass ratio of 96.5:1.5:1.5:0.5, and then stirring with a solvent (deionized water) in a vacuum mixer in a certain proportion to form a negative electrode slurry. Extreme slurry.
  • the preparation step of the negative electrode sheet includes: uniformly coating the prepared negative electrode slurry on both sides of the negative electrode current collector (copper foil), drying by baking at 90-110°C, rolling and cutting to obtain the negative electrode sheet.
  • the compaction density of the negative electrode film formed by the negative electrode slurry on the negative electrode sheet is 1.6g/ cm3 .
  • the non-Faraday capacitance of the negative electrode sheet can be adjusted by adjusting the rolling time and the roller pressure.
  • This embodiment also provides a method for preparing a lithium ion battery containing the above-mentioned negative electrode sheet, which comprises the following steps:
  • the negative and positive electrodes are dried, they are wound together with the separator (PP film) using a winding machine to prepare a wound battery cell.
  • the positive aluminum tabs and the negative copper nickel-plated tabs are welded to the battery cell, and the welded battery cell is placed in a punched aluminum-plastic film for packaging.
  • the lithium-ion battery is then produced through liquid injection, formation, and constant capacity.
  • the method for preparing the positive electrode sheet comprises the following steps:
  • the positive electrode active material, positive electrode conductive agent, positive electrode binder and solvent are prepared into positive electrode slurry according to the proportion.
  • the prepared positive electrode slurry is evenly coated on both sides of the positive electrode current collector (aluminum foil), and then dried at 120°C, and rolled and cut into sheets to obtain positive electrode sheets.
  • the particle size Dv50 (D 2 ) of the positive electrode active material is 6.5 ⁇ m.
  • the positive electrode active material (NCM523), the positive electrode conductive agent (carbon black), and the positive electrode binder (polyvinylidene fluoride, PVDF) are mixed at a mass ratio of 96:2:2.
  • the powder compaction density P 2 g/cm 3 of the positive electrode active material under a pressure of 30 KN is 3.55 g/cm 3 .
  • the preparation method of the electrolyte includes: mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 1:1:1, and then adding 1 mol/L LiPF 6 and mixing evenly to prepare the electrolyte.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the test method is as follows:
  • Non-Faraday capacitance test which includes the following steps: step 1, assembling the negative electrode sheet and the metal lithium sheet into a button-type half-cell (i.e., button electricity); step 2, performing a CV test on the button electricity in the voltage range of 0.005-3.0V, with a scan rate of 0.1mV/s, and confirming that the non-Faraday potential interval is 2.6-2.7V; step 3, then performing an LSV test from 2.7V to 2.6V, with scan rates of 0.1mV/s, 0.2mV/s, 0.5mV/s, 1mV/s, and 2mV/s, respectively, selecting the median of the potential interval of 2.65V, and obtaining corresponding current values of 1.72E -05 , 1.62E -05 , 1.57E-05, 1.52E - 05 , and 1.37E -05 A; step 3, drawing a scan rate-current scatter plot (as shown in Figure 1), and fitting a linear function with a slope of -1.62
  • Energy density test of lithium-ion battery which includes the following steps: placing the lithium-ion battery at 25°C for 30 minutes, fully charging and discharging at 1C, and recording the actual discharge energy; weighing the lithium-ion battery with an electronic balance; and discharging at 1C.
  • the ratio of energy to weight is the actual energy density of lithium-ion batteries.
  • the actual energy density of the battery When the actual energy density is less than 80% of the target energy density, the actual energy density of the battery is considered to be very low; when the actual energy density is greater than or equal to 80% of the target energy density and less than 95%, the actual energy density of the battery is considered to be low; when the actual energy density is greater than or equal to 95% of the target energy density and less than 105%, the actual energy density of the battery is considered to be moderate; when the actual energy density is greater than or equal to 105% of the target energy density and less than 120%, the actual energy density of the battery is considered to be high; when the actual energy density is greater than or equal to 120% of the target energy density, the actual energy density of the battery is considered to be very high.
  • the cycle performance test of lithium-ion batteries includes the following steps: charging and discharging the lithium-ion battery at 25°C. Specifically, 1C constant current charging, standing for 10 minutes, 1C constant current discharging, recording the first discharge capacity, charging and discharging the battery 2000 times at 1C/1C, recording the battery discharge capacity at the 2000th time, dividing the battery discharge capacity at the 2000th time by the battery discharge capacity at the first time, and obtaining the battery capacity retention rate after 2000 charge and discharge cycles.
  • the rate performance test of lithium-ion batteries includes the following steps: the lithium-ion battery is discharged at a constant current of 1C at 25°C, left to stand for 10 minutes, and charged at a constant current of 3C, and the first discharge capacity is recorded. The charge capacity is divided by the first discharge capacity of 1C/1C charge and discharge to obtain the 3C rate performance of the battery.
  • the pore size distribution and pore size value r of the negative electrode active material are measured by mercury intrusion porosimetry.
  • the compaction density PD of the negative electrode active material is tested using a compaction density meter, and the test process refers to the national standard GB/T24533-2019.
  • the above embodiment and comparative example provide a method for preparing a battery, which adjusts the sphericity S of the negative electrode active material by adjusting the parameters of the polishing and shaping step, and the coke raw material parameters of the negative electrode active material are controlled as shown in the following table, and the non-Faraday capacitance Cdl value of the negative electrode sheet is adjusted.
  • the other steps and parameters are the same as those in Example 1.
  • the specific parameter adjustments are shown in the following table.
  • the above-mentioned embodiment and comparative example provide a method for preparing a lithium battery, which adjusts the pore size (r) of the negative electrode active material.
  • the other steps and parameters are the same as those in Example 1.
  • the control of the pore size is mainly achieved by selecting coke raw materials with different sulfur contents and volatiles.
  • the control of the non-Faraday capacitance Cdl value is adjusted in combination with the stirring process and the rolling process, as long as the Cdl value is guaranteed to be within the range shown in Table 1.
  • the above embodiment provides a method for preparing a battery, which adjusts the roller gap and pressure of the roller press in the rolling step.
  • the compaction density PD of the negative electrode membrane is adjusted by adjusting the relevant parameters such as the compaction density, pore size, and particle size of the powder.
  • the other steps and parameters are the same as those in Example 1.
  • the above embodiment provides a method for preparing a lithium battery, which adjusts the D50 (D 1 ) of the negative electrode active material by adjusting the parameters of the pulverizing step in the preparation process of the negative electrode active material (such as the current size of the main machine of the mill, etc.), and adjusts the D50 (D 2 ) of the positive electrode active material by adjusting the parameters of the pulverizing step in the preparation process of the positive electrode active material (such as the current size of the main machine of the mill, etc.).
  • Other steps and parameters are the same as those in Example 1.
  • the above embodiment provides a method for preparing a battery, which adjusts the powder compaction density P 1 of the negative electrode active material and the powder compaction density P 2 of the positive electrode active material by adjusting parameters such as D50, the type of coke raw material, and HGI. Other steps and parameters are the same as those in Embodiment 1.
  • the above embodiment provides a method for preparing a battery, which changes the type of positive electrode active material, and the other steps and parameters are the same as those in embodiment 1.
  • the above embodiment provides a method for preparing a negative electrode sheet and a lithium-ion battery, which changes the component content and properties of the coke raw material. Other steps and parameters are the same as those in Example 1.
  • Example 19 By comparing Examples 16 to 18 with Example 19, it can be seen that when the negative electrode sheet satisfies 0.5 ⁇ Cdl ⁇ S ⁇ 5, the relationship between the particle size D1 of the negative electrode active material and the particle size D2 of the positive electrode active material satisfies 1 ⁇ D1 / D2 ⁇ 36 , which can make the positive electrode sheet and the negative electrode sheet have more matched electron and lithium ion transmission performance, so that the performance of the lithium ion battery is further improved.
  • Example 23 By comparing Examples 20 to 22 with Example 23, it can be seen that, on the basis that the negative electrode sheet satisfies 0.5 ⁇ Cdl ⁇ S ⁇ 5, the relationship between the powder compaction density P1 of the negative electrode active material under a pressure of 30KN and the powder compaction density P2 of the positive electrode active material under a pressure of 30KN satisfies 1.5 ⁇ P 2 /P 1 ⁇ 2.5, which is beneficial to the diffusion of lithium ions inside and between active materials, improves the solid phase conduction ability of lithium ions, improves the matching between the positive electrode active material and the negative electrode active material, can further reduce the impedance of the lithium ion battery, and further improve the fast charging capability and cycle life of the lithium ion battery.

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Abstract

公布一种电池及用电装置。负极片的非法拉第电容为Cdl nF，负极片所含的负极活性物质的球形度为S，二者满足如下特征：0.5≤Cdl×S≤5。通过调整Cdl值与球形度S在0.5≤Cdl×S≤5的范围内，既能有效降低负极活性物质的比表面积，提高其振实密度，使得负极片在具有较高的密度的同时又不至于发生过压现象，另外也可以使负极片的负极活性物质在辊压期间经受的机械应力最小化，与电解液的反应面积最小化，且具有良好的保液性能，从而可以防止气体产生和溶胀现象发生，进而使得电池具有优异的倍率性能和循环性能。

Description

电池及用电装置
本申请要求于2023年01月09日提交中国专利局、申请号为202310027089.X、申请名称为“电池及用电装置”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
本申请涉及新能源技术领域，具体涉及一种电池及用电装置。
背景技术
锂离子电池由于具有比能量高、功率性能好、自放电低和循环寿命长等优点，因此已被广泛应用于各个领域。为了提高锂离子电池的能量密度，可以通过压实法来提高负极片的克容量和压实密度。然而在压实时容易产生过压现象，这会导致负极片被电解液浸润的速度变慢，以及负极片的吸液性能、保液性能和浸润效果降低，这些反而不利于提高锂离子电池的能量密度和循环性能。
技术问题
本申请提供一种电池及用电装置，改善了电池的负极片因为过压而导致的对电解液浸润效果和吸液效果不佳的问题，从而改善了由此导致的电池的能量密度、倍率和循环性能不高的问题。
技术解决方案
第一方面，提供了一种电池，包括正极片、负极片、隔膜和电解液。
其中，正极片包括正极集流体和设置于正极集流体的至少一个表面上的正极膜片，正极膜片包括正极活性物质；
负极片包括负极集流体以及设置于负极集流体的至少一个表面上的负极膜片，负极膜片包括负极活性物质；负极活性物质包含有孔的负极活性物质颗粒；
负极片的非法拉第电容为Cdl nF，负极活性物质的球形度为S，满足如下特征：0.5≤Cdl×S≤5。
在本申请的实施例中，0.5≤Cdl≤8，0.2≤S≤0.9。
在本申请的实施例中，负极活性物质的孔径为r nm，Cdl与r满足如下特征：1.2≤0.1×r+Cdl≤10。
在本申请的实施例中，负极活性物质孔径分布满足：2≤r≤20。
在本申请的实施例中，负极活性物质孔径分布满足：负极活性物质在孔径分布为2nm～6nm的区域至少有一个峰。
在本申请的实施例中，负极活性物质中含有硫元素。
在本申请的实施例中，负极膜片的吸液时间为T min，负极膜片的压实密度为PD g/cm3，满足：0.3≤T×PD≤5.8。
在本申请的实施例中，0.25≤T≤3.5；1.1≤PD≤1.7。
在本申请的实施例中，负极活性物质的Dv50为D1μm，正极活性物质的Dv50为D2μm，D1和D2满足如下特征中的至少一者：
(c)1≤D1/D2≤36；
(d)6≤D1≤18；
(e)0.5≤D2≤8。
在本申请的实施例中，负极活性物质在30KN压力下的粉末压实密度为P1g/cm3，正极活性物质在30KN压力下的粉末压实密度为P2g/cm3，P1和P2之间的关系满足如下特征：1.5≤P2/P1≤2.5。
可选地，1.5≤P1≤2.0，2≤P2≤4。
在本申请的实施例中，负极活性物质包含碳材料，所述碳材料包含石墨。
第二方面，本申请实施例还提供了一种用电装置，其包含上述实施例中的电池，电池作为用电装置的供电电源。
有益效果
相较于现有技术，本申请通过调整负极片的非法拉第电容(Cdl nF)与该负极片所含有的负极活性物质的球形度(S)的关系，有效降低了负极活性物质的比表面积，提高其振实密度，使得负极片在具有较高的密度的同时又不至于发生过压现象，另外也可以使负极片的负极活性物质在辊压期间经受的机械应力减小，与电解液的反应面积减小，获得了良好的保液性能和对电解液的浸润效果，从而可以减少气体产生和溶胀现象发生，使得电池具有优异的快速充放电性能、良好的倍率性能和循环性能。另外本申请的负极活性物质颗粒具有孔，能够进一步提高负极膜片的保液性能和电解液的浸润效果，使电池的综合性能更优。
可以理解的是，本申请实施例提供的用电装置具有上述电池的所有技术特征以及有益效果，在此不再赘述。
附图说明
图1是本申请实施例1的扫速-电流散点图。
本申请的实施方式
本申请提供一种电池及用电装置，为使本申请的目的、技术方案及效果更加清楚、明确，以下参照附图并举实施例对本申请进一步详细说明。应当理解，此处所描述的具体实施例仅用以解释本申请，并不用于限定本申请。
申请人在研究中发现，在制备电池的负极片的辊压过程中，如果产生过压，会影响该负极片对电解液的浸润效果，以及负极片的吸液性能，这会影响到电池的倍率性能和循环性能。
为了解决上述问题，本申请实施例提供了一种电池(或称锂离子电池)，其通过控制负极活性物质颗粒具有孔结构，同时调整负极片的非法拉第电容(Cdl nF)与该负极片所含有的负极活性物质的球形度(S)，有效降低了负极活性物质的比表面积，提高其振实密度，使得负极片在具有较高的密度的同时又不至于发生过压现象，另外也使负极片的负极活性物质在辊压期间经受的机械应力减小，与电解液的反应面积减小，获得了良好的保液性能和对电解液的浸润效果，使得电池具有优异的快速充放电性能、良好的倍率性能和循环性能。
本申请实施例提供了一种电池，其包括正极片、负极片、隔膜和电解液。隔膜设于正极片和负极片之间。
其中，正极片包括正极集流体和设置于正极集流体的至少一个表面上的正极膜片，正极膜片包括正极活性物质。
负极片包括负极集流体以及设置于负极集流体的至少一个表面上的负极膜片。负极膜片包括负极活性物质，负极活性物质包含有孔的负极活性物质颗粒，负极片的非法拉第电容为Cdl nF，负极活性物质的球形度为S，满足如下特征：0.5≤Cdl×S≤5。
在本申请的一些实施例中，负极片的非法拉第电容为Cdl nF，负极活性物质的球形度为S，二者满足1≤Cdl×S≤4.5。当1≤Cdl×S≤4.5，能够进一步调整负极活性物质的比表面积和振实密度，使得负极片在具有较高的密度的同时又不至于发生过压现象，且同时能够使负极片与电解液的反应面积在合适范围内，进一步提高电池的综合性能。
在本申请的一些实施例中，负极片的非法拉第电容为Cdl nF，负极活性物质的球形度为S，二者满足1.5≤Cdl×S≤4。当1.5≤Cdl×S≤4时，能进一步改善电池的综合性能。
在本申请的一些实施例中，负极片的非法拉第电容为Cdl nF，负极活性物质的球形度为S，二者满足2≤Cdl×S≤3。
本申请实施例中的负极片的非法拉第电容Cdl值的测试方法包括如下步骤：
S1、扣电的组装过程包括如下步骤：将得到的负极片烘干，裁成小圆片，称量后转移至真空烘箱中，在100℃下干燥8h，再转移至充满Ar的手套箱中进行扣电组装。
S2、非法拉第电位区间确认的步骤。将上述组装后的扣电进行循环伏安法(CV)测试，以确认该扣电的非法拉第电位区间。其中电压范围为0.005～3.0V，扫速为0.1～1mV/s。
S3、非法拉第区间阴极扫描的步骤。任意选取S2中的平直段电位区间进行线性扫描伏安法(LSV)测试，扫描方向从高电位到低电位，采集电压-电流曲线，其中电位范围为2.6～2.7V，扫速为0.05～5mV/s。然后在某一特定扫速V1(该特定扫速可以为0.1mV/s、0.2mV/s、0.5mV/s、1mV/s和2mV/s等)下选取电位区间中值U，获得对应的电流值，得到扫速-电流散点图。
S4、非法拉第电容计算的步骤。根据S3采集的扫速-电流散点图，拟合得到线性函数，该线性函数的斜率K即为该负极片的阴极扫描方向的非法拉第电容Cdl值。
经过上述测试，本申请实施例中的负极片的非法拉第电容(Cdl nF)为0.5～8nF。负极片的非法拉第电容Cdl nF也可以为1～6nF，还可以为2～5nF，还可以为3～4nF。电容的基本单位是法拉第，简称法(F)。1F＝1000mF，1mF＝1000μF，1μF＝1000nF。因此，1nF(纳法)＝10-9F。
本申请实施例中的负极片中负极活性物质的球形度S用动态图像颗粒分析仪测量。具体地，从负极片中获得负极活性物质的方法可以为：将二次电池以0.04C恒流放电至电压下限，拆解得到负极片，用DMC(碳酸二甲酯)溶液浸泡清洗该负极片，然后用去离子水水洗多次后倒掉上层液体，下层溶液静置烘干，最后在氩气氛围下800℃热处理2h，得到上述测试样品。
形貌上越接近于球的颗粒，其球形度越接近于1。
在本申请的一些实施例中，负极活性物质的球形度S为0.2～0.9。例如S可以为0.2、0.3、0.35、0.4、0.43、0.45、0.48、0.5、0.53、0.55、0.58、0.6、0.63、0.65、0.68、0.7、0.73、0.75、0.78、0.8、0.85、0.9中的任意一者或其中任意两个值组成的范围。负极活性物质的球形度在上述范围，能够使负极活性物质颗粒的形貌处于较优状态，能够提高电池的综合性能。在本申请的一些实施例中，负极活性物质的球形度S为0.3～0.85。当球形度 S为0.3～0.85时能进一步改善电池的综合性能。
在本申请的一些实施例中，负极活性物质的球形度S为0.4～0.78。
在本申请的一些实施例中，负极活性物质的球形度S为0.45～0.73。
锂离子电池在使用过程中会发生电化学反应。电化学反应包括活性物质的氧化态发生变化、电荷移向活性物质内部的法拉第反应和离子在活性物质表面通过物理性地吸附、脱离来存储、释放电荷的非法拉第反应。法拉第反应是指活性物质的氧化态发生变化，电荷穿过双电荷层通过电极界面移到活性物质内部。非法拉第反应是指不发生穿过电极界面的电荷移动，通过离子在电极表面被物理性地吸附脱离，将电荷存储释放的反应。
申请人发现，非法拉第电容Cdl反映了负极片中活性位点的数量，在电池使用过程中，需控制负极片的非法拉第电容Cdl nF在合适的范围内。当Cdl值在一定范围区间内，Cdl值越大，电化学活性点数量越多，越有利于活性物质与电解液的接触，加快离子和电子的传导速率，电荷传输阻力低，能够有效地提升倍率性能。同时，负极活性物质的球形度S会影响负极活性物质颗粒的各向同性，影响锂离子脱嵌方向和路径，同时球形度还影响负极活性物质在负极片中的分布，影响负极活性物质之间的接触。负极活性物质颗粒具有孔结构，可以进一步提高负极片的浸润速度和保液性能，三者共同作用，可以有效的改善电池的综合性能。因此，通过对负极活性物质及负极片的调整，使负极片的非法拉第电容Cdl nF与负极活性物质的球形度S在0.5≤Cdl×S≤5的范围内，既能有效降低负极活性物质的比表面积，提高其振实密度，使得负极片在具有较高的密度的同时又不至于发生过压现象，另外也可以使负极片的负极活性物质在辊压期间经受的机械应力减小，与电解液的反应面积减小，且具有良好的保液性能，从而可以防止气体产生和溶胀现象发生，进而使得锂离子电池具有优异的快速充放电性能和循环性能。此外，负极活性物质包括石墨材料，负极活性物质以负极活性物质颗粒的形式存在，在这些负极活性物质颗粒之间可以形成使锂离子快速进入石墨层间的通道，缩短锂离子的固相扩散路径，从而提高负极片的充电倍率，实现快速充电，提升其快充性能。
在本申请的一些实施例中，负极活性物质的孔径值为r nm，负极片的非法拉第电容为Cdl nF，二者之间的关系满足如下特征：1.2≤0.1×r+Cdl≤10。负极活性物质的孔径与非法拉第电容会影响锂离子电池的快速充电能力和循环寿命。在一定范围内，负极活性物质的非法拉第电容增大，其表面的活性位点增多，与电解液间的接触充分，锂离子电池的阻抗减小，容量会提升，而合适的孔径能够避免辊压颗粒破碎的同时缩短锂离子在负极活性物质 中的固相扩散路径，提升锂离子电池的动力学性能。本申请实施例通过调整负极活性物质的孔径以及负极片的非法拉第电容能够使得锂离子在后续电化学反应过程中可以顺利地通过孔道插入负极活性物质中，从而提高锂离子电池的循环性能。另一方面，孔径还可以缓冲锂离子电池在充放电过程中的体积变化，提高锂离子电池的循环性能，因此，本申请通过合理调节负极活性物质的孔径大小和非法拉第电容的关系，通过控制二者之间的关系在1.2≤0.1×r+Cdl≤10的范围内可以兼顾和平衡锂离子电池的能量密度、快充性能和长循环寿命，防止过压对锂离子电池的这些性能产生的不利影响。
在本申请的一些实施例中，负极活性物质的孔径值为r nm，负极片的非法拉第电容为Cdl nF，满足2≤0.1×r+Cdl≤8。当2≤0.1×r+Cdl≤8时，负极活性物质的孔径和非法拉第电容在更合适的范围内，能够进一步影响电解液的浸润性能，以及与电解液之间的反应情况，使电池的综合性能更优。
在本申请的一些实施例中，负极活性物质的孔径值为r nm，负极片的非法拉第电容为Cdl nF，满足3≤0.1×r+Cdl≤7。
在本申请的一些实施例中，负极活性物质的孔径值为r nm，负极片的非法拉第电容为Cdl nF，满足4≤0.1×r+Cdl≤6。
可选地，在本申请的一些实施例中，负极活性物质的孔径值r的大小可以为2nm～20nm。例如r nm可以为2nm、3nm、3.5nm、4nm、4.5nm、4.8nm、5nm、5.3nm、5.5nm、5.8nm、6nm、6.5nm、6.8nm、7nm、7.5nm、7.8nm、8nm、8.5nm、9nm、10nm、11nm、12nm、12.5nm、13nm、13.5nm、14nm、14.5nm、15nm、15.5nm、16nm、17nm、18nm、19nm、20nm中的任意一者或其中任意两个值组成的范围。
在本申请的一些实施例中，负极活性物质的孔径值为3nm～18nm。
在本申请的一些实施例中，负极活性物质的孔径值为3.5nm～12nm。
在本申请的一些实施例中，负极活性物质的孔径值为4nm～10nm。
在本申请的一些实施例中，负极活性物质的孔径值为5nm～8nm。
负极活性物质具有合适的孔径，能够使负极活性物质颗粒的抗压能力和负极活性物质在电解液中的扩散均处于较优范围，能够增强非法拉第反应，提升锂离子的动力学性能。
可选地，在本申请的一些实施例中，负极活性物质的孔径分布在2nm～6nm的区域至少有一个峰。当在2nm～6nm的区域有峰，负极活性物质的孔径分布处于更优状态，能够进一步提升电池的综合性能。
可选地，在本申请的一些实施例中，负极活性物质层中包含硫元素。
可选地，在本申请的一些实施例中，负极活性物质中包含硫元素。
可选地，在本申请的一些实施例中，负极活性物质包含碳材料。
可选地，在本申请的一些实施例中，负极活性物质包含石墨。
可选地，在本申请的一些实施例中，负极活性物质包含人造石墨。
可选地，在本申请的一些实施例中，负极活性物质所用的焦原料中含有含硫物质。
可选地，在本申请的一些实施例中，负极活性物质所用的焦原料中的硫含量可以为0.1wt％～4wt％。例如，硫含量可以为0.1wt％、0.2wt％、0.3wt％、0.5wt％、0.7wt％、0.8wt％、1.0wt％、1.2wt％、1.3wt％、1.5wt％、1.6wt％、1.8wt％、2.0wt％、2.1wt％、2.5wt％、2.7wt％、3.0wt％、3.2wt％、3.4wt％、3.5wt％、3.6wt％、3.8wt％、4.0wt％中的任意一者或其中任意两个值组成的范围。
可选地，在本申请的一些实施例中，负极活性物质所用的焦原料中的硫含量也可以为0.2～3wt％。
可选地，在本申请的一些实施例中，负极活性物质所用的焦原料中的硫含量还可以为0.5～2.5wt％。
可选地，在本申请的一些实施例中，负极活性物质所用的焦原料中的硫含量也可以为1～2wt％。
可选地，在本申请的一些实施例中，焦原料中挥发分的含量可以为5～15wt％。例如，焦原料中挥发分的含量可以为5wt％、5.5wt％、6wt％、6.5wt％、7wt％、7.5wt％、8wt％、8.5wt％、9wt％、9.5wt％、10wt％、10.5wt％、11wt％、11.5wt％、12wt％、12.5wt％、13wt％、13.5wt％、14wt％、14.5wt％、15wt％中的任意一者或其中任意两个值组成的范围。
可选地，在本申请的一些实施例中，焦原料中挥发分的含量也可以为6wt％～12wt％。
可选地，在本申请的一些实施例中，焦原料中挥发分的含量还可以为8wt％～10wt％。
可选地，在本申请的一些实施例中，焦原料可以选自焦炭、石油焦(如石油沥青等)、煤焦油、沥青焦(如煤沥青等)等。选择具有特定原料性质的焦原料，是为了通过控制负极活性物质的原料特性，从而得到具有适宜的孔结构的负极活性物质颗粒。
焦原料中硫含量用能量色散X射线荧光光谱法测量，挥发分用SH/T0026-1990石油焦挥发分测定法。硫对于炼焦、气化、燃烧和贮运都是有害的，挥发分高低会影响原料的制备效率，增加煤耗，炼焦时进入的硫会导致焦炭生产能力下降，气化时生成的二氧化硫会 腐蚀设备，影响操作和产品质量，污染环境。因此，选择具有合适硫含量的焦原料能够减少对环境的影响，降低杂质含量，各向同性较好，所制备而成锂离子电池的倍率性能好，保证循环过程中具有较低的阻抗和自身的稳定性。另外，焦原料的硫含量也与负极活性物质在辊压时形成合适的孔径大小有关，当负极活性材料在辊压后形成了合适的孔径，具有合适的压实密度，能够增强非法拉第反应，从而提升锂离子的动力学性能，减缓过压现象。
可选地，在本申请的一些实施例中，焦原料的哈氏可磨性指数HGI可以为30～100。例如，焦原料的哈氏可磨性指数HGI可以为30、32、35、36、38、40、44、45、48、50、52、55、56、58、60、65、70、75、80、85、90、93、95、98、100中的任意一者或其中任意两个值组成的范围。
可选地，在本申请的一些实施例中，焦原料的哈氏可磨性指数HGI也可以为40～90。
可选地，在本申请的一些实施例中，焦原料的哈氏可磨性指数HGI还可以为50～80。
哈氏可磨性指数是指在空气干燥条件下，把试样与标准样磨制成规定粒数，并破碎到相同细度时所消耗的能量比，用来衡量焦原料的可磨性，其值的大小反映了不同类型的焦原料破碎的难易程度。哈氏可磨性指数用哈德格罗夫法进行测量，是度量焦原料的软硬指标。焦原料软，则HGI值相对较大，焦原料容易破碎，所得到的负极活性物质的压实密度更高。但是哈氏可磨性指数HGI过大和过小均对负极活性物质有一定的影响，需要在一定范围内。申请人经过研究发现，控制焦原料的哈氏可磨性指数HGI在30～100的范围内，可以控制负极活性物质的压实密度和孔径分布在合适的范围内。
可选地，在本申请的一些实施例中，负极膜片的吸液时间为T min，负极膜片的压实密度为PD g/cm3，二者之间的关系满足如下特征：0.3≤T×PD≤5.8。例如T×PD的值可以为0.3、0.4、0.6、0.7、1.0、1.2、1.5、1.8、2.0、2.3、2.5、2.8、3、3.5、4.0、4.4、5.0、5.2、5.5、5.6、5.8中的任一值或其中任意两个数组成的范围。当T×PD的值在上述范围内，负极活性物质颗粒之间的挤压程度会以及负极片的孔隙率在合适的范围内，且能保证电解液在负极膜片上的浸润性，降低电池循环过程中极化，减缓电池内阻的增大。
可选地，在本申请的一些实施例中，负极膜片的吸液时间为T min，负极膜片的压实密度为PD g/cm3，二者的关系也可以为0.5≤T×PD≤5.5。
可选地，在本申请的一些实施例中，负极膜片的吸液时间为T min，负极膜片的压实密度为PD g/cm3，二者之间的关系还可以为1≤T×PD≤5。
可选地，在本申请的一些实施例中，负极膜片的吸液时间为T min，负极膜片的压实密 度为PD g/cm3，二者之间的关系可以进一步为2≤T×PD≤4。
可选地，在本申请的一些实施例中，负极膜片的吸液时间T可以为0.25～3.5min(即0.25≤T≤3.5，以下同理)。例如可以为0.25、0.3、0.6、0.7、1.1、1.5、2、3、3.2、3.5中的任一值或其中任意两个数组成的范围。
可选地，在本申请的一些实施例中，负极膜片的吸液时间T还可以为0.5～3min。
可选地，在本申请的一些实施例中，负极膜片的吸液时间T也可以为1～2.5min。
可选地，在本申请的一些实施例中，负极膜片的压实密度PD可以为1.1～1.7g/cm3(即1.1≤PD≤1.7)。例如PD的值可以为1.1、1.2、1.3、1.4、1.5、1.6、1.7中的任一值或其中任意两个数组成的范围。
负极膜片的吸液时间可通过光学接触角测量仪测试，吸液时间的检测方法如下：在检测吸液时间时，用微量进样器垂直滴一滴电解液(约10μL)在负极片表面的负极膜片上，同时用秒表开始计时，待电解液发生扩散后记录电解液完全浸润所用的时间即为负极膜片的吸液时间。吸液时间越长，负极片的浸润性能越差。而压实密度与负极片比容量、效率、内阻以及电池循环性能有密切的关系，压实密度越大，能量密度越高，但活性物质颗粒之间的挤压程度会越大，极片的孔隙率就会越小，电解液难以浸润，电池的保液能力较差，负极膜片的吸液时间增大，循环过程中极化增加，内阻增大。因此，控制负极片压实密度同时需兼顾考虑吸液时间对锂离子电池性能的影响，以便改善锂离子电池的性能。
可选地，在本申请的一些实施例中，负极活性物质的Dv50为D1μm，正极活性物质的Dv50为D2μm，D1和D2之间的关系满足如下特征：1≤D1/D2≤36。或者可以为1、3、4、6、7、8、9、10、11、15、21、23、25、27、30、32、36中的至少一者或其中任意两个数组成的范围。将正极活性物质和负极活性物质的粒径之比匹配在1～36的范围内，能够使正极片和负极片均具有较高的电子及锂离子的传输性能，使正极片和负极片之间的电化学反应处于较匹配状态，使锂离子电池在高倍率下具有较高的充电和放电性能。
可选地，在本申请的一些实施例中，D1和D2之间的关系也可以为2≤D1/D2≤35。
可选地，在本申请的一些实施例中，D1和D2之间的关系还可以为5≤D1/D2≤30。
可选地，在本申请的一些实施例中，D1和D2之间的关系还可以为10≤D1/D2≤20。
可选地，在本申请的一些实施例中，6≤D1≤18。或者可以为6、7、8、9、10、11、12、15、16、18中的至少一者或其中任意两个数组成的范围。当负极活性物质颗粒的粒径在上述范围，可以使形成负极膜片的结构致密程度在合适的范围内，有利于电解液的渗透，使 负极活性物质颗粒界面电阻在合适的范围内，锂离子电池的动力学性能较优；同时，负极活性物质颗粒的粒径会影响活性物质颗粒在浆料中的分散性，可以减少负极活性物质颗粒团聚，使面密度分布更均匀，极片的粘结力合适，使负极片的电子电导能力处于较优状态，提高电池的动力学性能和循环寿命。
可选地，在本申请的一些实施例中，0.5≤D2≤8。或者可以为0.5、1、1.5、2、2.5、2.7、3.0、3.5、3.8、4、4.3、4.5、4.8、5、5.5、5.8、6、6.3、6.5、7、8中的至少一者或其中任意两个数组成的范围。若当正极极活性物质颗粒的粒径在上述范围，正极膜片电解液的渗透能力强，锂离子的液相扩散能力在合适的范围，锂离子在颗粒内的固相传导能力强，可以有效地保障锂离子电池的综合性能。
正极活性物质和负极活性物质的Dv50可以采用激光粒度仪测试得到。
可选地，在本申请的一些实施例中，负极活性物质在30KN压力下的粉末压实密度为P1g/cm3，正极活性物质在30KN压力下的粉末压实密度为P2g/cm3，P1和P2之间的关系满足如下特征：1.5≤P2/P1≤2.5。例如P2/P1的值可以为1.5、1.6、1.7、1.8、1.9、2.0、2.1、2.2、2.3、2.4、2.5中的任一值或其中任意两个数组成的范围。本申请的实施例通过将正极活性物质和负极活性物质在30KN压力下的粉末压实密度之比匹配在1.5～2.5的范围内，有利于锂离子在活性物质内部以及活性物质之间的扩散，提高锂离子的固相传导能力，降低锂离子电池的阻抗，提升锂离子电池的快充能力和循环寿命。可选地，在本申请的一些实施例中，P1和P2之间的关系满足：1.6≤P2/P1≤2.4。
可选地，在本申请的一些实施例中，P1和P2之间的关系满足：1.8≤P2/P1≤2.2。
可选地，在本申请的一些实施例中，P1和P2之间的关系满足：1.9≤P2/P1≤2.1。
可选地，在本申请的一些实施例中，1.5≤P1≤2.0，或者可以为1.6、1.7、1.8、1.9其中任意两个数组成的范围。当P1满足上述范围，负极活性物质的孔结构及形貌，例如球形度，均处于较优状态，能够改善负极片的孔结构，使电池处于较优状态。
可选地，在本申请的一些实施例中，2≤P2≤4，或者可以为2.1、2.2、2.5、2.8、3、3.2其中任意两个数组成的范围。当P2满足上述范围，正极片与负极片的匹配度更高，使电池具有更优的综合性能。
负极活性物质粉末压实密度测试参考GB/T 24533-2019锂离子电池石墨类负极材料，测试条件为称负极活性物质1g，加压速度：8mm/min，加压保压时间：30s，撤压后压力：20N，撤压速度：30mm/min，撤压后保持时间：10s。
正极活性物质的测试条件为称正极活性物质1.5g，加压速度：1mm/min，加压保压时间：60s，撤压后压力：30N，撤压速度：4mm/min，撤压后保持时间：10s。
可选地，在本申请的一些实施例中，正极活性物质包括磷酸铁锂材料、磷酸锰铁锂材料、锂镍钴锰材料、锂镍钴铝材料中的一种或几种。
磷酸铁锂材料为LiFePO4(简称LFP)。
磷酸锰铁锂材料的化学式为LiyFexMn1-xPO4；0.9≤y≤1.2，0.2≤x≤0.5。例如，为LiFe0.2Mn0.8PO4、LiFe0.3Mn0.7PO4、LiFe0.4Mn0.6PO4或LiFe0.5Mn0.5PO4。
锂镍钴锰材料可以为LidNiaCobMncAeO2，A包含Al、Zr、Ti、B、Mg、V、Cr、Zn、Y、W、Nb或La中的至少一者，0.4＜a＜1，0＜b＜1，0＜c＜1，0.9≤d≤1.1，0≤e≤0.1，a+b+c＝1。例如，可以为NCM523、NCM622或NCM811等。
锂镍钴铝材料可以为Lid1Nia1Cob1Alc1Ae1O2，A包含Zr、Ti、B、Mg、V、Cr、Zn、Y、W、Nb或La中的至少一者，0.4＜a1＜1，0＜b1＜1，0＜c1＜1，0.9≤d1≤1.1，0≤e1≤0.1，a1+b1+c1＝1。
本申请还提供了一种用电装置，其包含上述任一实施例的电池，电池作为用电装置的供电电源。本申请的用电装置可以包括但不限于备用电源、电机、电动汽车、电动摩托车、助力自行车、自行车、电动工具、家庭用大型蓄电池等。
下面结合具体实施例进行说明。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
实施例1
本实施例提供了负极片的制备方法，其包括如下步骤：
1、负极活性物质的制备步骤，包括：选用硫含量为2wt％、挥发分为8wt％、HGI值为60的石油焦生焦在辊压磨中进行粉碎、预混等预处理过程，粉碎后的粒径为8～10μm；将粉碎后的产物在保护性气氛下进行高温石墨化处理，温度为2800～3000℃，在最高温度3000℃下保温36h，保护性气氛为氩气；然后在连续型整形系统中对产物进行打磨整形，时间为8h，使产物颗粒的表面光滑平整，得到球形度S为0.7，粒径Dv50(D1)为12μm的负极活性物质(颗粒形态)。负极活性物质在30KN压力下的粉末压实密度P1g/cm3为1.76g/cm3。
2、负极浆料的制备步骤，包括：将上述的负极活性物质(人造石墨成品)、导电剂(炭黑)、粘结剂(羧甲基纤维素钠)、添加剂(丁苯橡胶)按照质量比96.5：1.5：1.5：0.5进行混合，之后与溶剂(去离子水)按一定比例在真空搅拌机作用下搅拌，混合均匀后制成负 极浆料。
3、负极片的制备步骤，包括：将制备好的负极浆料均匀涂覆在负极集流体(铜箔)的两侧，经90～110℃烘烤干燥后进行辊压、裁片得到负极片。负极片上由负极浆料所形成的负极膜片的压实密度为1.6g/cm3。通过调整辊压时间和辊压力的大小可以调整负极片的非法拉第电容。
本实施例还提供了含有上述负极片的锂离子电池的制备方法，其包括如下步骤：
将负极片、正极片经过干燥后，与隔膜(PP膜)一起采用卷绕机制备出卷绕电芯，将正极铝极耳与负极铜镀镍极耳焊接在电芯上，并将焊接完成的电芯放入已冲坑好的铝塑膜内进行封装，然后经过注液、化成、定容制得锂离子电池。
其中，上述正极片的制备方法包括如下步骤：
将正极活性物质、正极导电剂、正极粘结剂与溶剂(N-甲基吡咯烷酮，NMP)按照比例制成正极浆料。将制得的正极浆料均匀地涂覆在正极集流体(铝箔)的两侧，然后在120℃下烘干，辊压裁片后得到正极片。
其中，正极活性物质的粒径Dv50(D2)为6.5μm。按照正极活性物质(NCM523)、正极导电剂(炭黑)、正极粘结剂(聚偏氟乙烯，PVDF)的质量比为96：2：2进行混合。正极活性物质在30KN压力下的粉末压实密度P2g/cm3为3.55g/cm3。
电解液的制备方法包括：将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照质量比1:1:1混合，然后加入1mol/L的LiPF6混合均匀，配制成电解液。
取本实施例得到的负极片，将负极片组装成的扣式半电池(即扣电)以及上述的锂离子电池进行相应的测试。测试方法如下：
1、非法拉第电容测试，其包括如下步骤：步骤1，将负极片与金属锂片组装成扣式半电池(即扣电)；步骤2，将扣电在电压范围0.005～3.0V进行CV测试，扫速为0.1mV/s，确认非法拉第电位区间为2.6～2.7V；步骤3，然后从2.7V到2.6V进行LSV测试，扫描速率分别为0.1mV/s、0.2mV/s、0.5mV/s、1mV/s、2mV/s，选取电位区间中值2.65V，获得对应的电流值1.72E-05、1.62E-05、1.57E-05、1.52E-05、1.37E-05A；步骤3，绘制扫速-电流散点图(如图1所示)，拟合得到一条线性函数，该线性函数的斜率-1.62E-06即为本实施例的负极片阴极扫描方向Cdl值1.62nF。
2、锂离子电池的能量密度测试，其包括如下步骤：将锂离子电池在25℃静置30min，以1C满充、1C满放，记录实际放电能量；用电子天平对锂离子电池进行称重；1C实际放电 能量与重量的比值即为锂离子电池的实际能量密度。其中，实际能量密度小于目标能量密度的80％时，认为电池实际能量密度非常低；实际能量密度大于或等于目标能量密度的80％且小于95％时，认为电池实际能量密度偏低；实际能量密度大于或等于目标能量密度的95％且小于105％时，认为电池实际能量密度适中；实际能量密度大于或等于目标能量密度的105％且小于120％时，认为电池实际能量密度较高；实际能量密度为大于或等于目标能量密度的120％时，认为电池实际能量密度非常高。
3、锂离子电池的循环性能测试，其包括如下步骤：将锂离子电池在25℃下进行充放电。具体地，1C恒流充电，静置10min，1C恒流放电，记录下第一次的放电容量，将电池进行1C/1C充放电循环2000次，记录第2000次的电池放电容量，将第2000次的电池放电容量除以1次的电池放电容量，得到充放电循环2000次后的电池容量保持率。
4、锂离子电池的倍率性能测试，其包括如下步骤：将锂离子电池在25℃下，1C恒流放电，静置10min，3C恒流充电，记录第一次的放电容量，将该充电容量除以1C/1C充放电的第一次放电容量，得到电池的3C倍率性能。
5、负极活性物质的孔径分布和孔径值r通过压汞法测得。
6、负极活性物质的压实密度PD采用压实密度仪进行测试，测试过程参考国标GB/T24533-2019。
其它实施例和对比例参照上述的方法进行测试。
实施例2至5、对比例1至2
上述实施例和对比例提供了一种电池的制备方法，其通过调整打磨整形步骤的参数调整了负极活性物质的球形度S，负极活性物质的焦原料参数控制如下表所示，同时调整了负极片的非法拉第电容Cdl值。其它步骤和参数与实施例1相同。具体的参数调整请见下表所示。
实施例6至10
上述实施例和对比例提供了一种锂电池的制备方法，其调整了负极活性物质的孔径大小(r)。其它步骤和参数与实施例1相同。对孔径大小的控制主要通过选择不同硫含量和挥发分的焦原料等因素来实现的。对非法拉第电容Cdl值的控制结合搅拌过程和辊压过程进行调整，只要保证Cdl值为表1所示范围即可。
实施例11至15
上述实施例提供了一种电池的制备方法，其通过调整辊压步骤中辊压机的辊缝和压力 以及配合对粉末压实密度、孔径、粒径等相关参数的调节调整了负极膜片的压实密度PD。其它步骤和参数与实施例1相同。
实施例16至19
上述实施例提供了一种锂电池的制备方法，其通过调整负极活性物质制备过程中粉碎步骤的参数(如磨粉机主机电流大小等)，调整了负极活性物质的D50(D1)，并且通过调整正极活性物质制备过程中粉碎步骤的参数(如磨粉机主机电流大小等)，调整了正极活性物质的D50(D2)。其它步骤和参数与实施例1相同。
实施例20至23
上述实施例提供了一种电池的制备方法，其通过调整D50、焦原料的种类、HGI等参数，调整了负极活性物质的粉末压实密度P1，并且调整了正极活性物质的粉末压实密度P2。其它步骤和参数与实施例1相同。
实施例24至28
上述实施例提供了一种电池的制备方法，其改变了正极活性物质的种类，其它步骤和参数与实施例1相同。
实施例29至31
上述实施例提供了一种负极片和锂离子电池的制备方法，其改变了焦原料的组分含量和性质。其它步骤和参数与实施例1相同。
各个实施例和对比例的参数和测试结果详见表1至表3所示。
表1

表2

表3

从上述各个实施例和对比例的测试结果可以看出，对比实施例和对比例可以看出当负极片的非法拉第电容(Cdl nF)和负极活性物质的球形度S之间的关系满足0.5≤Cdl×S≤5时，电池具有较高的能量密度、较好的循环性能和较高的倍率性能。
将实施例6～实施例9与实施例10对比可知，当2≤r≤20且1.2≤0.1×r+Cdl≤10时，能进一步改善电池的能量密度、循环性能和较高的倍率性能。
将实施例11～实施例13与实施例14～实施例15对比可知，当负极膜片的吸液时间(T min)和负极膜片的压实密度(PD g/cm3)之间的关系满足0.3≤T×PD≤5.8时，电池的能量密度、循环性能和倍率性能性能得到进一步改善，当0.25≤T≤3.5时，电池的性能更优。
将实施例16～实施例18与实施例19对比可知，当在负极片满足0.5≤Cdl×S≤5的基础上，负极活性物质的粒径D1和正极活性物质的粒径D2之间的关系满足1≤D1/D2≤36，能够使正极片和负极片均具有更加匹配的电子及锂离子的传输性能，使锂离子电池的性能进一步提升。
将实施例20～实施例22与实施例23对比可知，在负极片满足0.5≤Cdl×S≤5的基础上，负极活性物质在30KN压力下的粉末压实密度P1和正极活性物质在30KN压力下的粉末压实密度P2之间的关系满足1.5≤P2/P1≤2.5，有利于锂离子在活性物质内部以及活性物质之间的扩散，提高锂离子的固相传导能力，提高正极活性物质与负极活性物质之间的匹配，能够进一步降低锂离子电池的阻抗，进一步提升锂离子电池的快充能力和循环寿命。
以上对本申请实施例所提供的电池及用电装置进行了详细介绍，本申请中应用了具体个例对本申请的原理及实施方式进行了阐述，以上实施例的说明只是用于帮助理解本申请的技术方案及其核心思想；本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例的技术方案的范围。

Claims (16)

  1. 一种电池，包括正极片、负极片、隔膜和电解液，其中，所述正极片包括正极集流体和设置于所述正极集流体的至少一个表面上的正极膜片，所述正极膜片包括正极活性物质；
    所述负极片包括负极集流体以及设置于所述负极集流体的至少一个表面上的负极膜片，所述负极膜片包括负极活性物质；所述负极活性物质包含有孔的负极活性物质颗粒；
    所述负极片的非法拉第电容为Cdl nF，所述负极活性物质的球形度为S，满足如下特征：0.5≤Cdl×S≤5。
  2. 根据权利要求1所述的电池，其中，0.5≤Cdl≤8。
  3. 根据权利要求1所述的电池，其中，0.2≤S≤0.9。
  4. 根据权利要求1所述的电池，其中，所述负极活性物质的孔径为r nm，Cdl与r满足如下特征：1.2≤0.1×r+Cdl≤10。
  5. 根据权利要求4所述的电池，其中，所述负极活性物质孔径分布满足：2≤r≤20。
  6. 根据权利要求4所述的电池，其中，所述负极活性物质在孔径分布为2nm～6nm的区域至少有一个峰。
  7. 根据权利要求1所述的电池，其中，所述负极膜片的吸液时间为T min，所述负极膜片的压实密度为PD g/cm3，满足：0.3≤T×PD≤5.8。
  8. 根据权利要求7所述的电池，其中，0.25≤T≤3.5；1.1≤PD≤1.7。
  9. 根据权利要求1所述的电池，其中，所述负极活性物质的Dv50为D1μm，所述正极活性物质的Dv50为D2μm，所述D1和所述D2满足：1≤D1/D2≤36。
  10. 根据权利要求9所述的电池，其中，6≤D1≤18。
  11. 根据权利要求9所述的电池，其中，0.5≤D2≤8。
  12. 根据权利要求1所述的电池，其中，所述负极活性物质在30KN压力下的粉末压实密度为P1g/cm3，所述正极活性物质在30KN压力下的粉末压实密度为P2g/cm3，所述P1和所述P2之间的关系满足如下特征：1.5≤P2/P1≤2.5。
  13. 根据权利要求12所述的电池，其中，1.5≤P1≤2.0。
  14. 根据权利要求12所述的电池，其中，2≤P2≤4。
  15. 根据权利要求1所述的电池，其中，所述负极活性物质包含碳材料，所述碳材料 包含石墨。
  16. 一种用电装置，其中，其包含权利要求1～15中任一项所述的电池，所述电池作为所述用电装置的供电电源。
PCT/CN2023/115700 2023-01-09 2023-08-30 电池及用电装置 WO2024148829A1 (zh)

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