WO2024055204A1 - 负极极片、钠离子电池、用电装置和应用 - Google Patents

负极极片、钠离子电池、用电装置和应用 Download PDF

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WO2024055204A1
WO2024055204A1 PCT/CN2022/118758 CN2022118758W WO2024055204A1 WO 2024055204 A1 WO2024055204 A1 WO 2024055204A1 CN 2022118758 W CN2022118758 W CN 2022118758W WO 2024055204 A1 WO2024055204 A1 WO 2024055204A1
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negative electrode
sodium
active material
carbonate
electrode piece
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PCT/CN2022/118758
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English (en)
French (fr)
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李全国
刘倩
叶永煌
陈佳华
孙婧轩
肖得隽
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/118758 priority Critical patent/WO2024055204A1/zh
Priority to EP22944037.5A priority patent/EP4365994A1/en
Publication of WO2024055204A1 publication Critical patent/WO2024055204A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • 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 technical field of sodium-ion batteries, and further relates to a negative electrode plate, a sodium-ion battery, an electrical device and applications.
  • Sodium-ion batteries can utilize the deintercalation process of sodium ions between the positive electrode and the negative electrode to achieve charge and discharge. Compared with lithium in lithium-ion batteries, sodium resources are more widely distributed, more abundant, and the cost is much lower than lithium. Therefore, sodium-ion batteries are regarded as a new generation of electrochemical systems with the potential to replace lithium-ion batteries. The safety issue of sodium-ion batteries is the focus of current research. However, improving safety often leads to loss of power.
  • this application provides a negative electrode plate that can meet the comprehensive requirements of high safety and high power, and can be suitable for sodium-ion batteries. Also provided are sodium-ion batteries and electrical devices including the negative electrode sheet, and applications of the negative electrode sheet in preparing sodium-ion batteries.
  • the present application provides a negative electrode piece, the negative electrode piece includes a negative active material, and the negative active material includes hard carbon;
  • the negative electrode piece also meets the following conditions: 0.6 ⁇ g/m ⁇ ( Dv99 + Dv50 )/(2 ⁇ B) ⁇ 5 ⁇ g/m; where Dv99 represents the cumulative volume distribution of the negative active material The corresponding particle size when the percentage reaches 99%, in ⁇ m; D v 50 represents the corresponding particle size when the cumulative volume distribution percentage of the negative active material reaches 50%, in ⁇ m; B represents the ratio of the negative electrode piece Surface area, unit is m 2 /g.
  • the main factors affecting battery safety include the negative electrode, positive electrode, electrolyte, etc.
  • the inventor of this application found through extensive experimental research that the particle size of the negative active material affects the safety of the battery. In particular, it was found that the large particle size particles have a very significant impact on the safety of the battery.
  • the inventor of the present application has discovered through extensive exploration and research that the larger the particle size of the negative active material, the higher the temperature at which the thermal decomposition reaction begins, and the higher the temperature it can withstand. Moreover, the larger the particle size, the higher the temperature of the negative active material. The smaller the specific surface area, the slower the reaction rate and the safer the battery, but it will cause battery power loss.
  • the battery can have a higher initial reaction temperature while minimizing adverse effects on the reaction activity rate.
  • the negative active material includes hard carbon.
  • Hard carbon has a high pyrolysis carbonization temperature, which is conducive to better increasing the heat resistance temperature and reducing heat generation.
  • the internal layer spacing of the hard carbon structure is large, the porosity is high, and more active ions can be embedded.
  • the structure has significantly low expansion, which is beneficial to improving the charge and discharge cycle performance and battery life of the battery.
  • (D v 99 + D v 50)/2 can characterize the size of large particles.
  • This feature and the specific surface area B of the negative electrode piece are used to define the thermal stability coefficient of the negative electrode piece (D v 99 + D v 50)/(2 ⁇ B), by adjusting the thermal stability coefficient of the negative electrode piece within an appropriate range, the battery can be endowed with high safety and high power characteristics, and excellent high temperature resistance.
  • the negative active material satisfies the following conditions: 5 ⁇ m ⁇ (D v 99 + D v 50)/2 ⁇ 18 ⁇ m;
  • the negative active material satisfies the following conditions: 6 ⁇ m ⁇ (D v 99 + D v 50)/2 ⁇ 15 ⁇ m;
  • the negative active material satisfies the following conditions: 7 ⁇ m ⁇ (D v 99 + D v 50)/2 ⁇ 12 ⁇ m;
  • the negative active material satisfies the following conditions: 8 ⁇ m ⁇ (D v 99 + D v 50)/2 ⁇ 10 ⁇ m.
  • the negative electrode piece meets the following conditions: 0.7 ⁇ g/m ⁇ (D v 99+D v 50)/(2 ⁇ B) ⁇ 5 ⁇ g/m;
  • the negative electrode piece meets the following conditions: 0.8 ⁇ g/m ⁇ (D v 99 + D v 50)/(2 ⁇ B) ⁇ 4.2 ⁇ g/m.
  • thermal stability coefficient of the electrode piece By further controlling the thermal stability coefficient of the electrode piece within the above range, it is conducive to better balancing the impact of large particle size on battery safety and the impact of the specific surface area of the negative active material on battery power, thereby better balancing the high safety of the battery. sex and high power.
  • the negative electrode piece meets the following conditions: 30mAh ⁇ m -2 ⁇ C/B ⁇ 140mAh ⁇ m -2 ; where C is the gram capacity of the negative electrode piece;
  • the C/B value of the negative electrode piece can reflect the reactivity of the negative active material in the negative electrode piece to a certain extent.
  • the negative electrode piece By cooperatively controlling the gram capacity of the negative electrode piece and the specific surface area of the negative electrode piece, It is conducive to better controlling the reaction rate when the battery is thermally runaway, and is conducive to further improving battery safety.
  • Control the negative electrode piece to have an appropriate gram capacity, thereby controlling the appropriate amount of active sodium ion insertion, making the reaction rate moderate, and controlling the specific surface area of the negative electrode piece within a more appropriate range, so that the ion deintercalation path of the battery active material and the electrode Moderate optimization to ensure the best performance of battery power.
  • the gram capacity C of the negative electrode piece satisfies the following conditions of 300: 300mAh/g ⁇ C ⁇ 350mAh/g,
  • the gram capacity C of the negative electrode piece satisfies the following conditions: 310mAh/g ⁇ C ⁇ 340mAh/g.
  • the active sodium ion insertion amount is controlled appropriately, so that the reaction rate when the battery is thermally runaway is moderate and the battery safety is better.
  • the B is selected from 2.5m 2 /g ⁇ 10m 2 /g;
  • the B is selected from 3m 2 /g to 7m 2 /g.
  • the ion deintercalation path and polarization of the battery active material are moderate, which is more conducive to the performance of the battery power performance.
  • the first exothermic reaction peak position T of differential scanning calorimetry analysis of the negative electrode plate satisfies 150°C ⁇ T ⁇ 180°C; wherein, the test conditions of differential scanning calorimetry analysis Including: nitrogen atmosphere, heating rate is 10°C/min;
  • the negative active material further includes one or more of soft carbon, graphite and alloyed negative electrodes;
  • the mass proportion of hard carbon in the negative active material is ⁇ 50%
  • the mass proportion of hard carbon in the negative active material is ⁇ 90%.
  • the negative active materials including hard carbon
  • one or more other types of active materials such as soft carbon, graphite and alloyed negative electrodes can be further introduced, and the advantages of these materials can be used to give the battery better overall performance.
  • soft carbon has a low and stable charge and discharge potential platform, large charge and discharge capacity, high efficiency, and good cycle performance.
  • graphite has the advantages of good electrical conductivity, high first efficiency, and wide source.
  • alloyed negative electrodes have the advantages of good power performance and high energy density.
  • the present application provides a sodium ion battery, which includes a positive electrode sheet, a negative electrode sheet described in the first aspect of the application, an isolation film and an electrolyte.
  • the isolation film is disposed on the positive electrode sheet and the electrolyte. between the negative pole pieces.
  • the sodium-ion battery prepared by using the negative electrode sheet of the first aspect of the present application has the comprehensive advantages of high safety and high power.
  • the electrolyte includes an electrolyte sodium salt
  • the electrolyte sodium salt includes sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium trifluoromethanesulfonate, bisfluorosulfonyl
  • sodium salts of sodium imide, sodium bistrifluoromethanesulfonimide, sodium triflate and sodium difluorophosphate include sodium bistrifluoromethanesulfonimide, sodium triflate and sodium difluorophosphate;
  • the electrolyte sodium salt includes one or more sodium salts among sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate and sodium trifluoromethanesulfonate.
  • the electrolyte further includes an organic solvent, including ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate ( EMC), propylene carbonate (PC), ethers such as ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MTHF), methyl acetate, ethyl propionate, fluorinated One or more of ethylene carbonate, diethyl ether, diglyme, triglyme, tetraglyme and methyl tert-butyl ether;
  • ethylene carbonate EC
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • PC propylene carbonate
  • ethers such as ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-
  • the organic solvent includes one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethylene glycol dimethyl ether, tetrahydrofuran and 2-methyltetrahydrofuran. or more.
  • the sodium salt has a high degree of solvation in the solvent and high conductivity, which is beneficial to film formation and battery power improvement.
  • the electrolyte further includes additives, including fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propane sulfonate lactone (PS), 1,3-propenyl-sultone (PST), succinic anhydride (SA), lithium difluorobisoxalate borate (LiDFOB), lithium difluorodioxalate phosphate (LiDFOP), tris(tris) Methylsilane)phosphate (TMSP), tris(trimethylsilyl)borate (TMSB), ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate , dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate,
  • FEC fluoroethylene
  • the additives include fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, 1,3-propane sultone, 1,3-propenyl-sultone, succinic anhydride, difluoride One or more of lithium oxaloborate, lithium difluorobisoxalate phosphate, tris(trimethylsilyl)phosphate and tris(trimethylsilyl)borate.
  • SEI solid electrolyte interface
  • the negative electrode piece meets the following conditions: 0.5°C ⁇ T ⁇ M ⁇ 6°C; where T and M are respectively the differential scanning calorimetry (DSC) analysis of the negative electrode piece.
  • T and M are respectively the differential scanning calorimetry (DSC) analysis of the negative electrode piece.
  • the test conditions of differential scanning calorimetry analysis include: nitrogen atmosphere, heating rate of 10°C/min;
  • T ⁇ M can reflect the tolerance of the negative electrode piece at high temperatures to a certain extent.
  • the particle size of the negative active material affects the temperature starting point of the reaction heat. The larger the particle, the higher the temperature at which the reaction begins, and the safer the corresponding battery system. However, larger particles are detrimental to battery power. Therefore, how to balance safety and power is crucial to prepare batteries with high comprehensive performance.
  • the solid electrolyte interface (SEI) film decomposition reaction temperature (corresponding to M) can be increased. It is beneficial to increase the thickness of the SEI film, thereby further improving safety.
  • the weight loss rate M in the first stage of differential scanning calorimetry analysis of the negative electrode plate satisfies the following conditions: 0.25% ⁇ M ⁇ 3.5%; wherein, the test of differential scanning calorimetry analysis Conditions include: nitrogen atmosphere, heating rate 10°C/min;
  • the stability of the SEI interface can be improved, which is beneficial to improving battery safety and achieving better ion transmission and charging. Discharge performance.
  • the positive electrode sheet includes a positive active material
  • the positive active material includes a positive active material containing sodium ions
  • the positive active material containing sodium ions includes Prussian blue compounds, sodium transition One or more of metal oxides and polyanionic compounds.
  • Appropriate positive active materials can be flexibly selected, making sodium-ion batteries more selective and applicable to a wider range of applications.
  • the present application provides an electrical device, which includes the sodium-ion battery described in the second aspect of the present application.
  • the electrical device prepared using the sodium-ion battery provided in the second aspect of the present application not only has high safety, but also has high power, and can meet the comprehensive needs of consumers for high safety and high performance.
  • Figure 1 is the heat release curve and thermal weight loss curve of the differential scanning calorimetry (DSC) test of the negative electrode plate in an embodiment of the present application, where Mass (%) represents the weight loss rate, and DTG (%/min) represents the heat release Rate;
  • Figure 2 is a schematic diagram of a sodium-ion battery according to an embodiment of the present application.
  • Figure 3 is an exploded view of the sodium-ion battery according to an embodiment of the present application shown in Figure 2;
  • Figure 4 is a schematic diagram of an electrical device using a sodium-ion battery as a power source according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • the term "or” is inclusive unless otherwise specified.
  • the phrase "A or B” means “A, B, or both A and B.”
  • any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); Or both A and B are true (or exist).
  • the technical features described in open format include closed technical solutions composed of the listed features, and also include open technical solutions including the listed features.
  • first”, “second”, “third” and “fourth” etc. are for descriptive purposes only and shall not be understood as indicating or implying relative importance or quantity, nor shall they be understood as implicitly indicating the importance or quantity of indicated technical features.
  • first”, “second”, “third”, “fourth”, etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation of quantity.
  • room temperature generally refers to 4°C to 35°C, preferably 20°C ⁇ 5°C. In some embodiments of the present application, room temperature refers to 20°C to 30°C.
  • the weight of the relevant components mentioned in the description of the embodiments of the present application may not only refer to the content of each component, but also the proportional relationship between the weights of the components. Therefore, as long as the relevant components are measured according to the description of the embodiments of the present application
  • the proportional enlargement or reduction of the content is within the scope disclosed in the examples of this application.
  • the weight described in the description of the embodiments of this application may be units well known in the chemical industry such as ⁇ g, mg, g, kg, etc.
  • the main factors affecting battery safety include the negative electrode, positive electrode, electrolyte, etc.
  • the inventor of this application found through extensive experimental research that the particle size of the negative active material affects the safety of the battery. In particular, it was found that the large particle size particles have a very significant impact on the safety of the battery.
  • the inventor of the present application has discovered through extensive exploration and research that the larger the particle size of the negative active material, the higher the temperature at which the thermal decomposition reaction begins, and the higher the temperature it can withstand. Moreover, the larger the particle size, the higher the temperature of the negative active material. The smaller the specific surface area, the slower the reaction rate and the safer the battery, but it will cause battery power loss. Therefore, how to balance the safety requirements and power requirements of batteries is crucial to prepare batteries with excellent comprehensive performance.
  • the particle size, specific surface area and other parameters of the negative electrode materials vary greatly. This leads to the fact that when designing the particle size, specific surface area and related parameters of different types of batteries, the parameters between different types of batteries are often very different. Large, requiring special design for battery type. For example, materials or parameters that apply to lithium-ion batteries may not apply to sodium-ion batteries. For example, the negative active material of sodium-ion batteries in traditional technology usually uses hard carbon.
  • D v 50 is small, about a few microns (such as 5 to 6 ⁇ m), and the corresponding specific surface area is large; while lithium-ion batteries in traditional technology Graphite negative electrodes are more commonly used, with D v 50 usually in the tens to tens of microns, and the specific surface area is relatively small.
  • the present application provides a negative electrode piece, the negative electrode piece includes a negative active material, and the negative active material includes hard carbon;
  • the negative electrode piece also meets the following conditions: 0.6 ⁇ g/m ⁇ ( Dv99 + Dv50 )/(2 ⁇ B) ⁇ 5 ⁇ g/m; where Dv99 represents the cumulative volume distribution of the negative active material The corresponding particle size when the percentage reaches 99%, in ⁇ m; D v 50 represents the corresponding particle size when the cumulative volume distribution percentage of the negative active material reaches 50%, in ⁇ m; B represents the ratio of the negative electrode piece Surface area, unit is m 2 /g.
  • the cumulative volume distribution particle diameter D v N (where N represents any value selected from 0 to 100) can be used to characterize the particle size of the material, which refers to when the cumulative volume distribution percentage of the material reaches N% Corresponding to the particle size, the volume proportion of particle size less than or equal to D v N is N%. D v N can be obtained from the volume cumulative distribution curve of the material particle size. If not otherwise stated, the volume cumulative distribution curve is accumulated from zero on the small particle size side. Take D v 99, D v 90, D v 50, and D v 10 as examples.
  • D v 90 it means that the particle size of 90% of the material volume is less than or equal to D v 90, and the particle size of 10% of the material volume is greater than D v 90.
  • D v 10 it means that the particle size of 10% of the material volume is less than or equal to D v 10, and the particle size of 90% of the material volume is greater than D v 10.
  • D v 99, D v 90, D v 50, and D v 10 can understand the meaning of D v 99, D v 90, D v 50, and D v 10, and can use instruments and methods known in the art for measurement.
  • a laser particle size analyzer such as the Mastersizer 2000E laser particle size analyzer and LS-909 laser particle size analyzer (European and American) from Malvern Instruments Co., Ltd. in the UK. .
  • (D v 99 + D v 50)/2 can be used to characterize the size of large particles in the material, which can be recorded as the "average particle size of large particles".
  • the particle size level of large-sized particles in the material can be reflected.
  • the larger the value the larger the particle size of the large-sized particles in the material.
  • the larger the particle size of the negative active material the higher the thermal runaway onset temperature of the battery, and the better the battery safety.
  • the negative electrode sheet of the first aspect of the present application includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the specific surface area B of the negative electrode plate refers to the specific surface area of the aforementioned negative electrode film layer (that is, the contribution of the negative electrode current collector is not considered). Furthermore, the specific surface area B of the negative electrode sheet refers to the ratio of the sum of the outer surface area of the negative electrode film layer and the inner surface area of the internal pores to the weight of the negative electrode film layer, and the unit may be m 2 /g.
  • the definition of the specific surface area B of the negative electrode piece can refer to the "GB/T 19587-2004" standard.
  • the specific surface area B of the negative electrode plate can be measured using instruments and methods known in the art. For example, it can be tested using the nitrogen adsorption specific surface area analysis test method and calculated using the BET (Brunauer Emmett Teller) method, where nitrogen
  • the adsorption specific surface area analysis test can be carried out by the Tri Star II specific surface and pore analyzer of the American Micromeritics Company.
  • the test procedures can refer to GB/T19587-2004.
  • the specific surface area of the negative electrode piece can be tested in the following manner: select a sample to be tested, which can be a directly prepared negative electrode piece or a negative electrode piece disassembled from the battery (at this time, It is necessary to use absolute ethanol to clean, remove the electrolyte, and dry in a vacuum drying oven at 60°C for 1 to 2 hours); then use nitrogen or argon as the adsorption gas, and measure the relative pressure P/P 0 through the specific surface and pore analyzer. The adsorption-desorption curve of 0 to 0.99 is used to calculate the specific surface area of the negative electrode piece through the BET method, where P represents the equilibrium adsorption pressure and P 0 represents the saturated vapor pressure.
  • the test sample is a negative active material
  • the following method can be used to prepare the negative active material powder:
  • the specific surface area of the active material can be tested as follows: dry the negative active material in a vacuum drying oven at 200°C for 2 hours; then use the above method
  • the gas adsorption test method tests the specific surface area of the negative active material.
  • the larger the specific surface area of the negative electrode piece the slower the thermal runaway reaction rate of the battery and the better the safety of the battery.
  • the particle size and specific surface area of the negative electrode active material can be obtained through the following control or screening methods (but are not limited to these methods): Method 1. Preparation of different negative electrode material precursors such as wheat straw, coconut shell, asphalt, etc. Materials with the same surface area; Method 2: Obtain negative electrode materials with different particle sizes by setting different grinding times, rotation speeds and filters in the negative electrode material synthesis process.
  • (D v 99 + D v 50)/(2 ⁇ B) is defined as the thermal stability coefficient of the pole piece, denoted as S.
  • This parameter can reflect the thermal stability of the pole piece. This value When controlled within a reasonable range (0.6 ⁇ g/m ⁇ 5 ⁇ g/m), the pole piece can withstand high temperatures and the severity of thermal runaway of the pole piece is small.
  • the battery can have a higher initial reaction temperature while minimizing adverse effects on the reaction activity rate.
  • the comprehensive advantages of high safety and high power are achieved by comprehensively controlling the large particle size in the negative active material and the specific surface area of the negative electrode piece.
  • (D v 99 + D v 50)/2 is defined to characterize the large particle size, and this feature is used together with the specific surface area B of the negative electrode piece to define the thermal stability coefficient of the negative electrode piece (D v 99 +D v 50)/(2 ⁇ B), by adjusting the thermal stability coefficient of the pole piece within an appropriate range, the battery can be endowed with high safety and high power characteristics, resulting in excellent high temperature resistance.
  • the negative active material includes hard carbon.
  • Hard carbon has a higher pyrolysis carbonization temperature, which is conducive to better increasing the heat resistance temperature and reducing heat production.
  • the internal layer spacing of the hard carbon structure is large, the porosity is high, and more metal ions can be embedded.
  • the structure has significantly low expansion, which is beneficial to improving the charge and discharge cycle performance and battery life of the battery.
  • the negative active material satisfies the following condition: 5 ⁇ m ⁇ (D v 99 + D v 50)/2 ⁇ 18 ⁇ m.
  • the negative active material satisfies the following conditions: 6 ⁇ m ⁇ (D v 99 + D v 50)/2 ⁇ 15 ⁇ m.
  • the negative active material satisfies the following conditions: 7 ⁇ m ⁇ (D v 99 + D v 50)/2 ⁇ 12 ⁇ m.
  • the negative active material satisfies the following conditions: 8 ⁇ m ⁇ (D v 99 + D v 50)/2 ⁇ 10 ⁇ m.
  • (D v 99 + D v 50)/2 of the negative active material can also be selected from any one of the following sizes or any two intervals: 5 ⁇ m, 5.2 ⁇ m, 5.4 ⁇ m, 5.5 ⁇ m, 5.6 ⁇ m, 5.8 ⁇ m, 6 ⁇ m, 6.2 ⁇ m, 6.4 ⁇ m, 6.5 ⁇ m, 6.6 ⁇ m, 6.8 ⁇ m, 7 ⁇ m, 7.2 ⁇ m, 7.4 ⁇ m, 7.5 ⁇ m, 7.6 ⁇ m, 7.8 ⁇ m, 8 ⁇ m, 8.2 ⁇ m, .4 ⁇ m, 8.5 ⁇ m, 8.6 ⁇ m, .8 ⁇ m, 9 ⁇ m, 9.5 ⁇ m, 10 ⁇ m, 10.5 ⁇ m, 11 ⁇ m, 11.5 ⁇ m, 12 ⁇ m, 12.5 ⁇ m, 13 ⁇ m, 13.5 ⁇ m, 14 ⁇ m, 15 ⁇ m, 15.5 ⁇ m, 16 ⁇ m, 16.5 ⁇ m, 17 ⁇ m, 17.5 ⁇ m , 17.7 ⁇ m, etc.
  • the negative electrode piece meets the following conditions: 0.7 ⁇ g/m ⁇ (D v 99 + D v 50)/(2 ⁇ B) ⁇ 5 ⁇ g/m.
  • the negative electrode piece satisfies the following condition: 0.8 ⁇ g/m ⁇ (D v 99 + D v 50)/(2 ⁇ B) ⁇ 4.2 ⁇ g/m.
  • ( Dv 99+ Dv 50)/(2 ⁇ B) of the negative electrode piece can also be selected from any one or two of the following intervals: 0.6 ⁇ g/m, 0.7 ⁇ g/m, 0.8 ⁇ g/m, 0.9 ⁇ g/m, 1 ⁇ g/m, 1.2 ⁇ g/m, 1.4 ⁇ g/m, 1.5 ⁇ g/m, 1.6 ⁇ g/m, 1.8 ⁇ g/m, 2 ⁇ g/m, 2.2 ⁇ g/ m, 2.5 ⁇ g/m, 2.6 ⁇ g/m, 2.8 ⁇ g/m, 3 ⁇ g/m, 3.5 ⁇ g/m, 4 ⁇ g/m, 4.5 ⁇ g/m, 5 ⁇ g/m, 5.5 ⁇ g/m, 6 ⁇ g/m, etc.
  • the negative electrode piece meets the following conditions: 30mAh ⁇ m -2 ⁇ C/B ⁇ 140mAh ⁇ m -2 ; where C is the gram capacity of the negative electrode piece.
  • the C/B of the negative electrode sheet can also be selected from any one or two of the following intervals: 30mAh ⁇ m -2 , 35mAh ⁇ m -2 , 40mAh ⁇ m -2 , 45mAh ⁇ m -2 , 50mAh ⁇ m -2 , 55mAh ⁇ m - 2 , 60mAh ⁇ m -2 , 65mAh ⁇ m -2 , 70mAh ⁇ m -2 , 75mAh ⁇ m -2 , 80mAh ⁇ m -2 , 85mAh ⁇ m -2 , 90mAh ⁇ m -2 , 95mAh ⁇ m -2 , 100mAh ⁇ m -2 , 105mAh ⁇ m -2 , 110mAh ⁇ m -2 , 115mAh ⁇ m -2 , 120mAh ⁇ m -2 , 125mAh ⁇ m -2 , 130mAh ⁇ m -2 , 135mAh ⁇ m -2 , 140mAh ⁇ m -2 etc.
  • the inventor of this application found that the C/B value of the negative electrode piece can reflect the reactivity of the negative electrode piece to a certain extent.
  • the negative electrode piece By cooperatively controlling the gram capacity of the negative electrode piece and the specific surface area of the negative electrode piece, it is conducive to better Accurately controlling the reaction rate when the battery is thermally runaway is conducive to further improving battery safety.
  • Control the negative electrode piece to have an appropriate gram capacity, thereby controlling the appropriate amount of active sodium ion insertion, making the reaction rate moderate, and controlling the specific surface area of the negative electrode piece within a more appropriate range, so that the ion deintercalation path of the battery active material and the electrode Moderate optimization to ensure the best performance of battery power.
  • C/B When C/B is low (such as less than 30mAh ⁇ m -2 ), the gram capacity of the negative active material is low, the battery capacity is low, or the specific surface area of the negative electrode is too large, and the reaction rate when the battery is thermally runaway is too large. Battery safety is relatively low.
  • C/B is too large (for example, greater than 140mAh ⁇ m -2 )
  • the gram capacity of the negative active material is too high, resulting in too much active ion embedding.
  • the intensity Once out of control, the intensity will be too large, or the specific surface area of the pole piece will be very small. The material particles are larger in size, the battery active material ion deintercalation path is longer, the polarization is larger, and the battery power performance is relatively poor.
  • the gram capacity C of the negative electrode piece satisfies 300mAh/g ⁇ C ⁇ 350mAh/g.
  • the gram capacity C of the negative electrode sheet satisfies 310mAh/g ⁇ C ⁇ 340mAh/g.
  • the gram capacity C of the negative electrode sheet can also be selected from any one or two of the following intervals: 300mAh/g, 305mAh/g, 310mAh/g, 315mAh/g, 320mAh/g , 325mAh/g, 330mAh/g, 335mAh/g, 340mAh/g, 345mAh/g, 350mAh/g, etc.
  • the gram capacity of the negative electrode piece can be measured with reference to the WI-ATC-2014 gram capacity test rules.
  • Pre-test electrode piece treatment It can be a directly prepared negative electrode piece, or it can be a negative electrode piece disassembled from the battery (at this time, it needs to be cleaned with absolute ethanol to remove the electrolyte, and then placed in a vacuum drying oven for 60 °C for 2 hours). Then use a punching machine to punch multiple small discs. Weigh the weight of each disc and take the average value W1. Then clean and dry the active material on the discs. Weigh the weight of the base material of the discs and take the average value W1.
  • the average value W2 the weight of the active material (W1-W2), when the negative electrode slurry is coated on both sides, the weight of the negative active material on one side of the substrate of each small disc is (W1-W2)/2 .
  • Calculate the gram capacity based on the capacity C 0 of the small disc C 0 /(W1-W2), unit mAh/g.
  • C 0 can be tested using the following method: take a small disc prepared by a chip punching machine, wipe the active material layer on one side of the substrate with alcohol, inject electrolyte, and make a button battery. Then use 0.1C current to charge and discharge between 0V-2V. Its capacity when fully charged to 2V and fully discharged to 0V is C 0 (unit: mAh).
  • the appropriate amount of active sodium ion insertion is controlled, so that the reaction rate when the battery is thermally runaway is moderate and the battery safety is better.
  • the specific surface area B of the negative electrode piece is selected from 2.5 m 2 /g to 10 m 2 /g.
  • the specific surface area B of the negative electrode piece is selected from 3m 2 /g to 7m 2 /g.
  • the specific surface area B of the negative electrode piece can also be selected from any one or two of the following intervals: 2.5m 2 /g, 3m 2 / g, 3.5m 2 /g, 4m 2 /g, 4.5m 2 /g, 5m 2 /g, 5.5m 2 /g, 6m 2 /g, 6.5m 2 /g, 7m 2 /g, 7.5m 2 /g, 8m 2 / g, 8.5m 2 /g, 9m 2 /g, 9.5m 2 /g, 10m 2 /g, etc.
  • the ion deintercalation path and polarization of the battery active material are moderated, which is more conducive to the performance of the battery's power performance.
  • the first exothermic reaction peak position T of differential scanning calorimetry analysis of the negative electrode plate satisfies 150°C ⁇ T ⁇ 180°C; further, the test of differential scanning calorimetry analysis Conditions include: nitrogen atmosphere, heating rate of 5°C/min ⁇ 10°C/min.
  • test conditions may include: nitrogen atmosphere, temperature rise rate of 5°C/min to 10°C/min.
  • heating rates include 5°C/min, 7.5°C/min, 10°C/min, etc.
  • the T satisfies 170°C ⁇ T ⁇ 180°C.
  • the T can also be selected from any one or two of the following: 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, etc.
  • T of the first exothermic reaction peak analyzed by differential scanning calorimetry (DSC) of the negative electrode piece By controlling the position T of the first exothermic reaction peak analyzed by differential scanning calorimetry (DSC) of the negative electrode piece within a more appropriate range, it is conducive to further improving battery safety. If T is too low, it will not improve battery safety. A higher T will be technically difficult to implement.
  • the organic polymer adhesive in the traditional pole piece powder needs to be replaced with a substance that is more resistant to high temperatures. At the same time, the pyrolysis temperature of the negative active material is increased.
  • the negative active material of the negative electrode sheet provided in the first aspect of the present application at least includes hard carbon.
  • the mass proportion of hard carbon in the negative active material is ⁇ 50%.
  • the mass proportion of hard carbon in the negative active material is ⁇ 90%.
  • the mass proportion of hard carbon in the negative active material can also be selected from any one percentage or any two of the following intervals: 50%, 55%, 60%, 65%, 70%, 75 %, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 100%, etc.
  • Hard carbon has a higher pyrolysis carbonization temperature. The higher the content of hard carbon, the better it is to increase the heat resistance temperature and reduce heat production. In addition, the internal layer spacing of the hard carbon structure is large, the porosity is high, and more metal ions can be embedded. The structure has significantly low expansion, which is beneficial to improving the charge and discharge cycle performance and battery life of the battery.
  • the negative active material further includes one or more of soft carbon, graphite, and alloyed negative electrodes.
  • the negative active materials including hard carbon
  • one or more other types of active materials such as soft carbon, graphite and alloyed negative electrodes can be further introduced, and the advantages of these materials can be used to give the battery better overall performance.
  • soft carbon has a low and stable charge and discharge potential platform, large charge and discharge capacity, high efficiency, and good cycle performance.
  • graphite has the advantages of good electrical conductivity, high first efficiency, and wide source.
  • alloyed negative electrodes have the advantages of high power and high energy density.
  • the negative electrode sheet of the first aspect of the present application includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the definition of the negative active material is as described above.
  • the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy and other aluminum, aluminum alloy) on a polymer material base material (such as polypropylene (PP), polyethylene It is formed on substrates such as ethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the present application provides a sodium ion battery, which includes a positive electrode sheet, a negative electrode sheet described in the first aspect of the application, an isolation film and an electrolyte.
  • the isolation film is disposed on the positive electrode sheet and the negative electrode. between pole pieces.
  • a sodium-ion battery prepared by using the negative electrode sheet of the first aspect of the present application has the comprehensive advantages of high safety and high power.
  • a sodium-ion battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions Na +
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the sodium ion battery of the second aspect is a secondary battery.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte solution includes electrolyte sodium salt and solvent.
  • the electrolyte sodium salt may be selected from sodium hexafluorophosphate (NaPF 6 ), sodium perchlorate (NaClO 4 ), sodium tetrafluoroborate (NaBF 4 ), sodium bisfluorosulfonyl imide, bistrifluoro One or more of sodium methane sulfonyl imide, sodium triflate, sodium difluorophosphate, etc.
  • the electrolyte sodium salt includes one or more sodium salts of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, and sodium trifluoromethanesulfonate.
  • the electrolyte further includes an organic solvent.
  • the organic solvent may include ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyl Tetrahydrofuran, methyl acetate, ethyl propionate, fluoroethylene carbonate, diethyl ether, diglyme, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, methyl tert-butyl ether, etc. one or more of them.
  • the organic solvent may include ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate ( One or more of PC), ether solvents (such as ethylene glycol dimethyl ether (DME)), tetrahydrofuran (THF) and 2-methyltetrahydrofuran (2-MTHF).
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • PC propylene carbonate
  • ether solvents such as ethylene glycol dimethyl ether (DME)
  • THF tetrahydrofuran
  • 2-MTHF 2-methyltetrahydrofuran
  • the organic solvent may include ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl propionate, vinyl fluoride
  • the sodium salt has a high degree of solvation in the solvent and high conductivity, which is beneficial to film formation and battery power improvement.
  • the electrolyte further includes additives.
  • the additives include fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propane sultone (PS), 1 , 3-propenyl-sultone (PST), succinic anhydride (SA), lithium difluoroborate borate (LiDFOB), lithium difluorobisoxalate phosphate (LiDFOP), tris(trimethylsilyl)phosphate (TMSP), tris(trimethylsilane)borate (TMSB), ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, carbonic acid Methyl propyl ester, ethyl propyl carbonate, butylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate,
  • FEC fluoroethylene
  • the additives include fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propane sultone (PS), 1 , 3-propenyl-sultone (PST), succinic anhydride (SA), lithium difluoroborate borate (LiDFOB), lithium difluorobisoxalate phosphate (LiDFOP), tris(trimethylsilyl)phosphate (TMSP), tris(trimethylsilyl)borate (TMSB), etc.
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • DTD vinyl sulfate
  • PS 1,3-propane sultone
  • PST 3-propenyl-sultone
  • SA succinic anhydride
  • LiDFOB lithium difluoroborate borate
  • LiDFOP lithium difluorobisoxalate phosphate
  • TMSP tris(trimethylsilyl)phosphate
  • TMSB tris
  • the battery can quickly form a solid electrolyte interface (SEI) film, increase the thickness and stability of the SEI film, and improve battery safety.
  • SEI solid electrolyte interface
  • the current during battery formation can be reduced, for example, at a current of 0.05C or 0.1C.
  • the formation temperature can be set at 25°C, so that a thickened SEI film can be obtained.
  • the negative electrode piece meets the following conditions: 0.5°C ⁇ T ⁇ M ⁇ 6°C; where T and M are respectively the first values of differential scanning calorimetry (DSC) analysis of the negative electrode piece. The position of the exothermic reaction peak and the weight loss rate in the first stage; further, when tested in a nitrogen atmosphere, the temperature rise rate was 5°C/min to 10°C/min.
  • the negative electrode piece meets the following conditions: 0.65°C ⁇ T ⁇ M ⁇ 5.2°C.
  • the negative electrode piece meets the following conditions: 0.75°C ⁇ T ⁇ M ⁇ 4.5°C.
  • the T ⁇ M of the negative electrode plate can also be selected from any one or two of the following intervals: 0.5°C, 0.52°C, 0.54°C, 0.55°C, 0.56°C, 0.58°C, 0.60°C, 0.65°C, 0.70°C, 0.75°C, 0.80°C, 0.85°C, 0.90°C, 0.95°C, 1°C, 1.5°C, 2°C, 2.5°C, 3°C, 3.5°C, 4°C, 4.5°C, 5°C, 5.5°C , 6°C, etc.
  • the first exothermic reaction S position (T) and the first stage weight loss rate (M) of the differential scanning calorimetry (DSC) analysis of the negative electrode piece can be obtained from the DSC spectrum of the negative electrode piece.
  • M can reflect the decomposition amount of the solid electrolyte interface (SEI).
  • SEI solid electrolyte interface
  • the following test method can be used: dry the pole piece in a vacuum drying oven at 60°C for 6 hours, take a sample with a weight of W3, program the temperature to 600°C in a nitrogen atmosphere, and measure the weight loss rate and DCS exothermic peak of the sample.
  • the gas atmosphere is nitrogen, argon, or a combination thereof.
  • the heating rate may be 5°C/min to 10°C/min, non-limiting examples include 5°C/min, 10°C/min, etc.
  • test conditions may include: nitrogen atmosphere, and the heating rate is 5°C/min to 10°C/min.
  • heating rates include 5°C/min, 7.5°C/min, 10°C/min, etc.
  • T ⁇ M can reflect the tolerance of the negative electrode piece at high temperatures to a certain extent.
  • the particle size of the negative active material affects the temperature starting point of the reaction heat. The larger the particle, the higher the temperature at which the reaction begins, and the safer the corresponding battery system. However, larger particles can be detrimental to battery power. Therefore, how to balance safety and battery power is crucial to prepare batteries with high overall performance.
  • the solid electrolyte interface (SEI) film decomposition reaction temperature (corresponding to M) can be increased. It is beneficial to increase the thickness of the SEI film, thereby further improving safety.
  • the weight loss rate M in the first stage of differential scanning calorimetry analysis of the negative electrode plate satisfies the following conditions: 0.25% ⁇ M ⁇ 3.5%; further, the weight loss rate M of the differential scanning calorimetry analysis
  • the test conditions include: nitrogen atmosphere, and the temperature rising step is 5°C/min ⁇ 10°C/min (such as 10°C/min).
  • the M can also be selected from any one of the following percentages or any two intervals: 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, 3.2% , 3.3%, etc.
  • the stability of the SEI interface can be improved, which is beneficial to improving battery safety, and can also achieve better ion transmission and charge and discharge. performance.
  • M the thinner the SEI, which is less conducive to the stability of the battery interface and poor battery safety; but if it is too thick, it means that the SEI is too thick, which is not conducive to ion transmission and will worsen the charge and discharge performance.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material.
  • the positive electrode sheet includes a positive active material containing sodium ions.
  • the cathode active material containing sodium ions includes one or more of Prussian blue compounds, sodium transition oxides and polyanionic compounds. Appropriate positive active materials can be flexibly selected, making sodium-ion batteries more selective and applicable to a wider range of applications.
  • the positive active material may include, but is not limited to, one or more of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.
  • the present application is not limited to the materials listed above, and other known materials that can be used as positive electrode active materials for sodium ion batteries can also be used.
  • the transition metal in the sodium transition metal oxide may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce.
  • a non-limiting example of a sodium transition metal oxide may be Na x ZO 2 , where Z may be one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0 ⁇ x ⁇ 1 .
  • the sodium transition metal oxide can be Na 0.67 Mn 0.7 Ni q M 2 0.3-z O 2 , where M 2 can include Li, Mg, Al, Ca, Ti, Fe, Cu, Zn, and Ba One or more of them, 0 ⁇ q ⁇ 0.1.
  • the polyanionic compound may be a compound having sodium ions, transition metal ions, and tetrahedral (YO 4 ) n- anion units.
  • the transition metal here may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y may include one of P, S and Si or more;
  • n represents the valence state of (YO 4 ) n- .
  • the polyanionic compound may also be a compound having sodium ions, transition metal ions, tetrahedral (YO 4 )n- anion units and halogen anions.
  • the transition metal here may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y may include one of P, S and Si or more, n represents the valence state of (YO 4 ) n- ;
  • the halogen can include one or more of F, Cl and Br.
  • the polyanionic compound may also be a compound having sodium ions, tetrahedral (YO 4 ) n- anion units, polyhedral units (ZO y ) m+ , and optional halogen anions.
  • Y can include one or more of P, S and Si
  • n represents the valence state of (YO4)n-
  • Z represents a transition metal, which can include Mn, Fe, Ni, Co, Cr, Cu, Ti, One or more of Zn, V, Zr and Ce
  • m represents the valence state of (ZO y ) m+
  • the halogen can include one or more of F, Cl and Br.
  • the polyanionic compound may be NaFePO 4 , Na 3 V 2 (PO 4 ) 3 , NaM'PO 4 F, and Na 3 (VO y ) 2 (PO 4 ) 2 F 3- 2 y (0 ⁇ y ⁇ 1); wherein, M' in NaM'PO 4 F may include one or more of V, Fe, Mn and Ni.
  • the Prussian blue compound may be a compound having sodium ions, transition metal ions, and cyanide ions (CN — ).
  • the transition metal here may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • Non-limiting examples of Prussian blue compounds can be Na a Me b Me' c (CN) 6 , wherein Me and Me' can each independently include one of Ni, Cu, Fe, Mn, Co and Zn or Multiple, 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1.
  • the positive electrode active material layer may further include a conductive agent to improve the conductive performance of the positive electrode.
  • a conductive agent to improve the conductive performance of the positive electrode.
  • the conductive agent can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers.
  • the positive electrode film layer optionally further includes a binder.
  • a binder As a non-limiting example, the positive active material and the optional conductive agent are firmly bonded to the positive current collector. This application does not specifically limit the type of adhesive and can be selected according to actual needs.
  • the binder may be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene Ethylene fluoride terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber One or more of (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA) and carboxymethyl chitosan (CMCS).
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE vinyliden
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate or composite current collector.
  • the conductive carbon material of the conductive carbon sheet can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers; metal foil
  • the metal materials of the material, the carbon-coated metal foil material and the porous metal plate can each be independently selected from one or more of copper, aluminum, nickel and stainless steel.
  • the composite current collector may be a composite current collector formed by a combination of a metal foil material and a polymer base film.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode sheet can be prepared by using the above-mentioned components for preparing the positive electrode sheet, such as the positive active material, optional conductive agent, optional binder and any other components. Dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N-methylpyrrolidone
  • a separator membrane is further included in the sodium ion battery.
  • isolation membrane There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the isolation membrane For batteries of different systems, such as sodium-ion batteries and lithium-ion batteries, due to the different diameters of sodium ions and lithium ions, there are different requirements for the structure of the isolation membrane.
  • the diameter of sodium ions is larger, which is different from the small size of lithium ions, so it has special thickness requirements. While achieving the isolation function, it is also necessary to ensure that large-sized sodium ions can shuttle through, so as to ensure the safety of the battery. Also has good battery rate.
  • the material of the isolation membrane in the sodium ion battery of the present application can be various materials suitable for isolation membranes of electrochemical energy storage devices in the art.
  • it can include but is not limited to glass fiber, non-woven fabric, polyethylene, etc.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • At least one side surface of the isolation film includes an insulating material coating, and optionally, the insulating material coating is a ceramic coating.
  • the base material of the isolation film includes one or more of polyethylene and polypropylene.
  • the thickness of the isolation film ranges from 5 ⁇ m to 15 ⁇ m. In some embodiments, the thickness of the isolation film ranges from 7 ⁇ m to 13 ⁇ m.
  • the thickness of the isolation film can also be any one or two of the following intervals: 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, etc.
  • the TD direction shrinkage of the isolation film when heated at 90° C. for 1 hour is ⁇ 4%. In some embodiments, the TD direction shrinkage of the isolation film heated at 90° C. for 1 hour is selected from 0.5% to 3.5%.
  • the shrinkage rate in the TD direction refers to the shrinkage rate in the width direction, which corresponds to the transverse shrinkage rate.
  • the shrinkage rate of the isolation film can be tested by the following method: cut a 10cm ⁇ 10cm isolation film flatly on glass with a smooth surface, then use A4 paper to cut an area of at least 15cm ⁇ 15cm, and cover the membrane in the center , use tape to stick the four corners of the A4 paper to the glass. Then put it in the oven and heat it for 1 hour, then take it out and measure the size of the diaphragm at this time.
  • the areal density of the isolation film is selected from 2g/m 2 to 6g/m 2 . In some embodiments, the areal density of the isolation film is selected from 3g/m 2 to 5g/m 2 . In some embodiments, the area density of the isolation film can also be selected from any one or two of the following intervals: 2g/m 2 , 2.5g/m 2 , 3g/m 2 , 3.5g/m 2 , 4g /m 2 , 4.5g/m 2 , 5g/m 2 , 5.5g/m 2 , 6g/m 2 etc.
  • the surface density of the isolation film can be measured using instruments and methods known in the art.
  • a Sartorius electronic balance can be used to weigh the mass of the isolation film with a certain area, and the mass of the isolation film divided by the isolation film area, the surface density of the isolation film can be calculated.
  • the isolation film meets one or more of the following characteristics:
  • At least one side surface of the isolation film includes an insulating material coating, and optionally, the insulating material coating is a ceramic coating;
  • the base material of the isolation film includes one or more of polyethylene and polypropylene;
  • the thickness of the isolation film is 5 ⁇ m ⁇ 15 ⁇ m, optionally, the thickness of the isolation film is 7 ⁇ m ⁇ 13 ⁇ m;
  • the TD direction shrinkage of the isolation film when heated at 90°C for 1 hour is ⁇ 4%.
  • the TD direction shrinkage of the isolation film when heated at 90°C for 1 hour is selected from 0.5% to 3.5%;
  • the areal density of the isolation film is selected from 2g/m 2 to 6g/m 2 , optionally, the areal density of the isolation film is selected from 3g/m 2 to 5g/m 2 .
  • Another aspect of this application also provides the application of the negative electrode sheet described in the first aspect of this application in preparing a sodium ion battery.
  • the negative electrode sheet of the first aspect of the present application can be used to prepare a sodium-ion battery, thereby obtaining the comprehensive advantages of high safety and high energy density.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • a sodium-ion battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the sodium-ion battery may be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc.
  • the outer packaging of sodium-ion batteries can also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 2 shows a square-structured sodium ion battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the sodium ion battery 5 can be one or more, and those skilled in the art can select according to actual needs.
  • the above-mentioned positive electrode piece, isolation film, and negative electrode piece are stacked in order to obtain a battery core, so that the isolation film is placed between the positive electrode piece and the negative electrode piece to play an isolation role, and the battery core can also be obtained.
  • the battery core is obtained after winding; the battery core is placed in a packaging shell (which can be a soft bag, square aluminum shell, square steel shell, cylindrical aluminum shell, and cylindrical steel shell), and the electrolyte is injected and sealed to obtain a sodium ion battery. .
  • the present application provides an electrical device, which includes the sodium-ion battery described in the second aspect of the present application.
  • the electrical device prepared using the sodium-ion battery provided in the second aspect of the present application not only has high safety, but also has high energy density, and can meet the comprehensive needs of consumers for high safety and high performance.
  • the sodium ion battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device.
  • the electrical devices may include mobile equipment, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc. , but not limited to this.
  • a sodium-ion battery can be selected according to its usage requirements.
  • FIG. 4 shows an electrical device 6 as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • battery packs or battery modules can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a sodium-ion battery can be used as the power source.
  • room temperature refers to 20°C to 30°C, and may be 25°C.
  • the particle size control and screening method of the negative active material is as follows: using the phenolic resin generated by the reaction of resorcinol and formaldehyde as the precursor, using polyacrylonitrile (PAN) as the coating carbon source, and adjusting the material through carbon coating The specific surface area and closed pore volume were determined, and the pyrolysis temperature in a nitrogen atmosphere was set to 1300°C. After pyrolysis, the material of the target size was obtained through primary screening and fine screening.
  • PAN polyacrylonitrile
  • the negative electrode slurry prepared above is evenly coated on both sides of the negative electrode current collector copper foil through an extrusion coater or transfer coater, and dried at 85°C, and then cold pressed, trimmed, and cut. Cut into pieces and cut into strips to obtain a negative electrode piece with a size of 91mm ⁇ 5680mm.
  • Preparation of negative electrode pieces 2 to 17 adopt basically the same method as negative electrode piece 1.
  • the difference between negative electrode pieces 2 to 10, 13, and 14 and negative electrode piece 1 is that the size of the negative active material is different, and the negative electrodes with the cumulative volume distribution particle diameters D v 99, D v 50, and D v 10 shown in Table 1 are respectively used. active materials.
  • the difference between the negative electrode tabs 11 to 12, 15 to 17 and the negative electrode tab 1 lies in the type and size of the negative electrode active material. See Table 1.
  • the positive electrode slurry prepared above is evenly coated on the positive electrode current collector aluminum foil, dried at room temperature, then transferred to a 90°C oven to continue drying, and then cut into discs with a diameter of 88 mm ⁇ 5450 mm as positive electrode sheets, and cold pressed , trimming, cutting and slitting to obtain a positive electrode piece with a thickness of 150 ⁇ m.
  • a polyethylene film (PE) with a thickness of 7 ⁇ m as the base film of the separator add aluminum oxide, sodium carboxymethyl cellulose (CMC) and acrylate in a weight ratio of 93%: 3%: 4% to deionized water. Stir evenly under the action of a vacuum mixer to obtain a slurry. The solids content in this slurry was 55% by weight. The obtained slurry was evenly sprayed on both sides of the base film with a thickness of 2 ⁇ m on one side to obtain a separator.
  • PE polyethylene film
  • CMC sodium carboxymethyl cellulose
  • the positive electrode piece, isolation film and negative electrode piece in order so that the isolation film is between the positive electrode piece and the negative electrode piece to play the role of isolation.
  • the resulting laminate is then rolled into a square bare cell, the tabs are welded, the bare cell is put into a square aluminum case, and the top cover is laser welded.
  • the electrolyte prepared above was injected and sealed.
  • the finished hard-shell sodium-ion battery is obtained, with a thickness of 28mm. , width is 97.5mm, length is 148mm.
  • Sample pretreatment Take a clean beaker, add an appropriate amount of the sample to be tested, dropwise add the surfactant sodium dodecyl sulfate, add deionized water as a dispersant, and perform ultrasonic treatment (frequency 120W, duration 5 minutes) to ensure that the sample is Completely dispersed in dispersant.
  • Test Refer to GB/T 19077-2016 particle size distribution laser diffraction method, and use a laser particle size analyzer to measure each D v N.
  • the LS-909 laser particle size analyzer European and American was used for testing. Pour the sample into the injection tower and then circulate the solution to the test light path system. The scattered light emitted by the particles under the irradiation of the laser beam is accepted and its energy distribution is measured. The particle size distribution characteristics of the particles can be obtained (shading brightness: 8 % ⁇ 12%), and finally obtain each D v N value of the material.
  • the nitrogen adsorption specific surface area analysis test method is used to test, and the BET (Brunauer EmmettTeller) method is used to calculate the nitrogen adsorption specific surface area analysis test.
  • the nitrogen adsorption specific surface area analysis test can be performed by the Tri Star II specific surface and pore analyzer of the American Micromeritics company. The test steps can refer to GB /T 19587-2004.
  • the detailed steps are as follows: Select the sample to be tested, which can be the negative electrode piece directly prepared in the above steps, or the negative electrode piece disassembled from the battery (in this case, it needs to be cleaned with absolute ethanol to remove the electrolyte, and then Dry in a vacuum drying oven at 60°C for 2 hours); then use nitrogen as the adsorption gas, and measure the adsorption-desorption curve with a relative pressure P/P 0 of 0 to 0.99 through a specific surface and pore analyzer (P is the equilibrium adsorption pressure, P 0 is the saturated vapor pressure), and the specific surface area of the negative electrode piece is calculated by the BET method.
  • the following test method can be used: Dry the negative electrode piece in a vacuum drying oven at 60°C for 6 hours, take a sample with a weight of W3, and heat it to 600°C at a heating rate of 10°C/min in a nitrogen atmosphere. Measure the weight loss rate and DCS emission of the sample. Thermal peak, the first exothermic reaction peak position T and the first stage weight loss rate M are obtained.
  • Gram capacity Refer to the WI-ATC-2014 gram capacity test rules.
  • the sample to be tested can be the negative electrode directly prepared in the above steps, or the negative electrode disassembled from the battery (at this time, it is necessary to use anhydrous ethanol to clean, remove the electrolyte, and then dry it in a vacuum drying oven at 60°C for 2 hours). Then use a punching machine to punch out 15 small discs with a diameter of 16 mm, and select 12 of them at random.
  • the test method of C 0 is as follows: take the remaining 3 small discs punched out above, wipe off the active material layer on one side of the substrate with alcohol, use a Na metal sheet as the counter electrode, inject electrolyte (refer to 2.4 of the above-mentioned Example 2), and make a button battery. Then charge and discharge between 0V and 2V with a current of 0.1C. The capacity after fully charging to 2V and then fully discharging to 0V is C 0 (mAh).
  • Adopt hot box test method Refer to the lithium-ion battery heating test method in GB38031-2020.
  • SOC represents the battery state of charge, which can reflect the remaining capacity of the battery. It is numerically defined as the ratio of the remaining capacity to the battery capacity.
  • the power performance of the battery is determined by measuring the 60s pulse discharge power of the battery.
  • the battery core is placed in the Nebula battery charge and discharge test system at 25°C, charged with a constant current and constant voltage at a rate of 0.5C to the charge cut-off voltage of 3.75V, left to stand for 5 minutes, and then discharged at a specific power to ensure that At 60s, the battery voltage reaches exactly 2V and stops discharging. The power at this time is the 60s pulse discharge power.
  • the cumulative volume distribution particle size of the negative electrode piece D v N (D v 99, D v 50, D v 10), the specific surface area of the electrode piece B, the thermal stability coefficient of the electrode piece S, DSC analysis, the reaction rate factor of the electrode piece P,
  • the test and analysis results of the pole piece gram capacity C and the pole piece reaction rate factor P can be found in Table 1, Table 2 and Figure 1.
  • the DSC analysis and hot box test of the sodium ion battery prepared in each example and comparative example can withstand the temperature.
  • Figure 1 shows the heat release curve and thermal weight loss curve of the differential scanning calorimetry (DSC) test of the negative electrode piece in Example 3. It can be seen from the figure that the first exothermic reaction peak position T of the DSC spectrum is approximately 170°C, and the first stage weight loss rate M of the DSC spectrum is approximately 1.2%.
  • Negative electrode pieces 1 to 10 and negative electrode pieces 15 to 17 have a suitable (D v 99 + D v 50)/(2 ⁇ B) range, both in the range of 0.6 ⁇ g/m to 5 ⁇ g/m. Use this electrode piece
  • the prepared sodium ion batteries in Examples 1 to 16 all have high temperature resistance in the hot box test, high 60s pulse discharge power, and have the advantages of high safety and high power.
  • the corresponding (D v 99 + D v 50)/(2 ⁇ B) values of the negative electrode plates 11 to 14 of Comparative Examples 1 to 4 are outside the range of 0.6 ⁇ g/m to 5 ⁇ g/m, and the hot box test can withstand the temperature and 60s pulse discharge power are inferior to those of the previous embodiments.
  • DSC first exothermic reaction peak position T of multiple negative electrode plates is recorded as 180°C in Table 2. It is a rounded result, and there is a slight fluctuation between the actual values.

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Abstract

本申请涉及一种负极极片、钠离子电池、用电装置和应用，该负极极片包括负极活性材料，负极活性材料包括硬碳，其中，0.6μg/m≤(D v99+D v50)/(2×B)≤5μg/m；D v99、D v50分别表示负极活性材料的累计体积分布百分数达到99％、50％时对应的粒径；B表示负极极片的比表面积。

Description

负极极片、钠离子电池、用电装置和应用 技术领域
本申请涉及钠离子电池技术领域，进一步涉及一种负极极片、钠离子电池、用电装置和应用。
背景技术
这里的陈述仅提供与本申请有关的背景信息，而不必然构成现有技术。
随着新能源产业链的发展壮大，人们对新能源电池的要求也越来越高，特别是对新能源电池的安全性越来越多地被视为首要设计要点。传统的以能量续航里程为尊的思想逐渐向以高安全为达成目标转变。通常地，评价一款电池安全与否的最主要指标是电池的耐高温性能，电池耐受的温度越高则在电池发生燃烧时越不容易引发周围电池的蔓延，从而可大大提高电池组的安全性。
钠离子电池能够利用钠离子在正极与负极之间的脱嵌过程实现充放电。与锂离子电池中的锂相比，钠资源分布更为广泛、储量更丰富、成本远低于锂，因此，钠离子电池被视为具有替代锂离子电池潜力的新一代电化学体系。钠离子电池的安全性问题是当前的研究重点，然而，提升安全性的同时往往导致功率的损失。
因此，亟待开发同时满足高安全性和高功率需求的钠离子电池。
发明内容
鉴于上述问题，本申请提供了一种负极极片，其能够兼具高安全性和高功率的综合需求，可适用于钠离子电池。还提供包括该负极极片的钠离子电池以及用电装置和该负极极片在制备钠离子电池中的应用。
第一方面，本申请提供了一种负极极片，所述负极极片包括负极活性材料，所述负极活性材料包括硬碳；
所述负极极片还满足如下条件：0.6μg/m≤(D v99+D v50)/(2×B)≤5μg/m；其中，D v99表示所述负极活性材料的累计体积分布百分数达到99％时对应的粒径，单位为μm；D v50表示所述负极活性材料的累计体积分布百分数达到50％时对应的粒径，单位为μm；B表示所述负极极片的比表面积，单位为m 2/g。
通常认为影响电池安全性的主要因素包括负极、正极、电解液等。本申请的发明人经过大量实验研究发现，负极活性材料的颗粒度对电池会影响到电池的安全性，特别地发现，其中的大粒径颗粒对电池安全性的影响非常显著。本申请的发明人经过大量的探索研究发现，负极活性材料的颗粒粒径越大，其热分解开始反应的温度越高，耐受的温度越高，而且，粒径越大，负极活性材料的比表面积越小，反应速率越慢，电池越安全，但会带来电池功率损失。通过将负极活性材料的粒径和负极极片的比表面积控制在一定范围内则可以使电池既具有较高的起始反应的温度又可以尽量避免对反应活性速率造成不利影响。
在本申请中，负极活性材料包括硬碳，硬碳具有较高的热解碳化温度，有利于更好 地提高耐热温度、降低产热量。此外，硬碳的结构内部层间距较大，孔隙率高，可以嵌入较多的活性离子，结构显著膨胀低，有利于改善电池的充放电循环性能和电池寿命。在此基础上，通过综合控制负极活性材料中的大颗粒粒度和负极极片的比表面积，实现兼具高安全性和高功率的综合优点。进一步地，(D v99+D v50)/2可以表征大颗粒粒度，采用该特征与负极极片的比表面积B共同定义了负极极片的极片热稳定性系数(D v99+D v50)/(2×B)，通过调节该负极极片热稳定性系数在合适的范围内，从而能够赋予电池高安全性及高功率的特点，带来优异的耐高温性能。
在本申请的一些实施方式中，所述负极活性材料满足如下条件5μm≤(D v99+D v50)/2≤18μm；
可选地，所述负极活性材料满足如下条件：6μm≤(D v99+D v50)/2≤15μm；
可选地，所述负极活性材料满足如下条件：7μm≤(D v99+D v50)/2≤12μm；
可选地，所述负极活性材料满足如下条件：8μm≤(D v99+D v50)/2≤10μm。
通过合理控制负极活性材料中的大颗粒在较合适的范围，可以更方便结合对负极活性材料比表面积的精细控制，实现更好地实现电池高安全性兼高功率的优点。
在本申请的一些实施方式中，所述负极极片满足如下条件：0.7μg/m≤(D v99+D v50)/(2×B)≤5μg/m；
可选地，所述负极极片满足如下条件：0.8μg/m≤(D v99+D v50)/(2×B)≤4.2μg/m。
通过进一步控制极片热稳定性系数在上述的范围内，有利于更好地平衡大颗粒尺寸对电池安全性的影响以及负极活性材料比表面积对电池功率的影响，从而更好地兼顾电池高安全性和高功率。
在本申请的一些实施方式中，所述负极活性材料还满足如下条件：(x·D v10)≤D v50≤(y·D v99)；其中，x＝2.6，且y＝0.4；
可选地，x＝4，且y＝0.3。
通过合理控制负极活性材料的D v50相对于D v10、D v99的比值x、y，可以更好地确保负极活性材料中的小颗粒和大颗粒均具有合适的粒径及含量，更好地避免大颗粒带来的电池功率损失，在改善电池安全性的同时，尽可能地保持较高的功率。
在本申请的一些实施方式中，所述负极极片满足如下条件：30mAh·m -2≤C/B≤140mAh·m -2；其中，C为所述负极极片的克容量；
可选地，40mAh·m -2≤C/B≤125mAh·m -2。
本申请的发明人发现，负极极片的C/B值可以在一定程度上反映出负极极片中负极活性材料的反应活性，通过协同控制负极极片的克容量及负极极片的比表面积，有利于更好地控制电池热失控时的反应速率，有利于进一步提高电池安全性。控制负极极片具有合适的克容量，从而控制活性钠离子嵌入量适当，使反应速率适中，并且控制负极极片的比表面积在较合适的范围内，使得电池活性物质的离子脱嵌路径及极化适中，确保电池功率性能的发挥。
在本申请的一些实施方式中，所述负极极片的克容量C满足300如下条件：300mAh/g≤C≤350mAh/g，
可选地，所述负极极片的克容量C满足如下条件：310mAh/g≤C≤340mAh/g。
通过控制负极极片具有较合适的克容量，从而控制活性钠离子嵌入量适当，使电池 热失控时的反应速率适中，电池安全性更好。
在本申请的一些实施方式中，所述B选自2.5m 2/g～10m 2/g；
可选地，所述B选自3m 2/g～7m 2/g。
通过控制负极极片的比表面积在较合适的范围，使得电池活性物质的离子脱嵌路径及极化适中，更有利于电池功率性能的发挥。
在本申请的一些实施方式中，所述负极极片的差示扫描量热分析的第一放热反应峰位置T满足150℃≤T≤180℃；其中，差示扫描量热分析的测试条件包括：氮气氛围，升温速率为10℃/min；
可选地，170℃≤T≤180℃。
通过控制负极极片的差示扫描量热(DSC)分析的第一放热反应峰位置T在较合适的范围内，更有利于进一步提升电池安全性。
在本申请的一些实施方式中，所述负极活性材料还包括软碳、石墨和合金化负极中的一种或多种；
可选地，硬碳在所述负极活性材料中质量占比≥50％；
可选地，硬碳在所述负极活性材料中质量占比≥90％。
在负极活性材料包括硬碳的基础上，进一步引入软碳、石墨和合金化负极中的一种或多种其他种类的活性材料，可以利用这些材料的优点赋予电池更好的综合性能。比如，软碳具有低而平稳的充放电电位平台，充放电容量大且效率高、循环性能好。比如，石墨具有导电性好，首效高，来源广等优点。比如，合金化负极具有功率性能好，能量密度高等优点。
第二方面，本申请提供一种钠离子电池，其包括正极极片、本申请第一方面所述负极极片以、隔离膜和和电解质，所述隔离膜设置于所述正极极片和所述负极极片之间。
利用本申请第一方面的负极极片制备得到的钠离子电池兼具高安全性和高功率的综合优点。
在本申请的一些实施方式中，所述电解质包含电解质钠盐，所述电解质钠盐包括六氟磷酸钠、高氯酸钠、四氟硼酸钠、三氟甲基磺酸钠、双氟磺酰亚胺钠、双三氟甲烷磺酰亚胺钠、三氟甲磺酸钠和二氟磷酸钠中一种或多种钠盐；
可选地，所述电解质钠盐包括六氟磷酸钠、高氯酸钠、四氟硼酸钠和三氟甲基磺酸钠中一种或多种钠盐。
在本申请的一些实施方式中，所述电解质还包含有机溶剂，所述有机溶剂包括碳酸乙烯酯(EC)、碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸丙烯酯(PC)、醚类如乙二醇二甲醚(DME)、四氢呋喃(THF)、2-甲基四氢呋喃(2-MTHF)、醋酸甲酯、丙酸乙酯、氟代乙烯碳酸脂、乙醚、二甘醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚和甲基叔丁基醚中的一种或多种；
可选地，所述有机溶剂包括碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸丙烯酯、乙二醇二甲醚、四氢呋喃和2-甲基四氢呋喃中的一种或多种。钠盐在溶剂中的溶剂化度高，电导率高，有利于成膜和提高电池功率。
在本申请的一些实施方式中，所述电解质还包含添加剂，所述添加剂包括氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、硫酸乙烯酯(DTD)、1,3-丙烷磺内酯(PS)、1,3-丙烯 基-磺酸内酯(PST)、丁二酸酐(SA)、二氟草酸硼酸锂(LiDFOB)、二氟双草酸磷酸锂(LiDFOP)、三(三甲基甲硅烷)磷酸酯(TMSP)、三(三甲基甲硅烷)硼酸酯(TMSB)、碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜等中的一种或多种；
可选地，所述添加剂包括氟代碳酸乙烯酯、碳酸亚乙烯酯、硫酸乙烯酯、1,3-丙烷磺内酯、1,3-丙烯基-磺酸内酯、丁二酸酐、二氟草酸硼酸锂、二氟双草酸磷酸锂、三(三甲基甲硅烷)磷酸酯和三(三甲基甲硅烷)硼酸酯中的一种或多种。通过选择合适的添加剂，可以帮助电池快速形成固体电解质相界面(SEI)膜，增大SEI膜的厚度和稳定性，提升电池安全性。
在本申请的一些实施方式中，所述负极极片满足如下条件：0.5℃≤T×M≤6℃；其中，T和M分别为所述负极极片的差示扫描量热(DSC)分析的第一放热反应峰位置和第一阶段失重率，差示扫描量热分析的测试条件包括：氮气氛围，升温速率为10℃/min；
可选地，0.65℃≤T×M≤5.2℃；
可选地，0.75℃≤T×M≤4.5℃。
本申请的发明人推测，T×M在一定程度上可以反映负极极片在高温下的耐受程度。负极活性材料的颗粒粒度影响到反应放热的温度起点，颗粒越大，其开始反应的温度就越高，相应的电池体系越安全。然而，颗粒较大时，对电池功率不利。因此，如何平衡安全性和功率对于制备高综合性能的电池至关重要。通过将负极极片的差示扫描量热(DSC)分析的第一放热反应峰的位置(T)向高温处推移，可以将固体电解质界面(SEI)膜分解反应温度(对应M)提高，有利于增加SEI膜的厚度，从而达到进一步提高安全性的效果。
在本申请的一些实施方式中，所述负极极片的差示扫描量热分析的第一阶段失重率M满足如下条件：0.25％≤M≤3.5％；其中，差示扫描量热分析的测试条件包括：氮气氛围，升温速率为10℃/min；
可选地，0.5％≤M≤2.5％；
可选地，0.65％≤M≤2.0％。
通过控制负极极片的差示扫描量热分析的第一阶段失重率M在较合适的范围内，可以改善SEI界面稳定性，有利于提升电池安全性，还可以实现较好的离子传输及充放电性能。
在本申请的一些实施方式中，所述正极极片包括正极活性材料，所述正极活性材料包括含有钠离子的正极活性材料，所述含有钠离子的正极活性材料包括普鲁士蓝类化合物、钠过渡金属氧化物和聚阴离子类化合物中的一种或多种。
可灵活选择合适的正极活性材料，从而使钠离子电池具有更多的选择性，适用面更广。
第三方面，本申请提供一种用电装置，其包括本申请第二方面所述钠离子电池。
利用本申请第二方面提供的钠离子电池制备用得到的电装置，不仅具有高安全性， 还同时具有高功率，能够满足消费者高安全及高性能的综合需要。
本申请的一个或多个实施例的细节在下面的附图和描述中提出。本申请的其他特征、目的和优点将从说明书、附图以及权利要求书变得明显。
附图说明
为了更好地描述和说明这里公开的那些申请的实施例或示例，可以参考一幅或多幅附图。用于描述附图的附加细节或示例不应当被认为是对所公开的申请、目前描述的实施例或示例以及目前理解的这些申请的最佳模式中的任何一者的范围的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是本申请一实施例中负极极片的差示扫描量热(DSC)测试的放热曲线及热失重曲线图，其中Mass(％)表示失重率，DTG(％/min)表示放热率；
图2是本申请一实施例的钠离子电池的示意图；
图3是图2所示的本申请一实施例的钠离子电池的分解图；
图4是本申请一实施例的钠离子电池用作电源的用电装置的示意图。
附图标记说明：
5，钠离子电池；51，壳体；52，电极组件；53，盖板；6，用电装置。
具体实施方式
以下，适当地参照附图详细说明公开了本申请的负极极片、钠离子电池、用电装置和应用的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b) 和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。进一步地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
本申请中，以开放式描述的技术特征中，包括所列举特征组成的封闭式技术方案，也包括包含所列举特征的开放式技术方案。
本申请中涉及“多个”、“多种”、“几种”、“多次”等，如无特别限定，指在数量上大于2或等于2。例如，“一种或多种”表示一种或大于等于两种。
本文中所使用的“其组合”、“其任意组合”、“其任意组合方式”等中包括所列项目中任两个或任两个以上项目的所有合适的组合方式。
本文中，“合适的组合方式”、“合适的方式”、“任意合适方式”等中所述“合适”，以能够实施本申请的技术方案为准。
本文中，“优选”、“更好”、“更佳”、“为宜”仅为描述效果更好的实施方式或实施例，应当理解，并不构成对本申请保护范围的限制。如果一个技术方案中出现多处“优选”，如无特别说明，且无矛盾之处或相互制约关系，则每项“优选”各自独立。
本申请中，“进一步”、“更进一步”、“特别”等用于描述目的，表示内容上的差异，但并不应理解为对本申请保护范围的限制。
本申请中，“第一方面”、“第二方面”、“第三方面”、“第四方面”等中，术语“第一”、“第二”、“第三”、“第四”等仅用于描述目的，不能理解为指示或暗示相对重要性或数量，也不能理解为隐含指明所指示的技术特征的重要性或数量。而且“第一”、“第二”、“第三”、“第四”等仅起到非穷举式的列举描述目的，应当理解并不构成对数量的封闭式限定。
本申请中，术语“室温”一般指4℃～35℃，较佳地指20℃±5℃。在本申请的一些实施例中，室温是指20℃～30℃。
在本申请中，涉及数据范围的单位，如果仅在右端点后带有单位，则表示左端点和右端点的单位是相同的。比如，3～5h或3-5h均表示左端点“3”和右端点“5”的单位都是h(小时)。
本申请实施例说明书中所提到的相关成分的重量不仅仅可以指代各组分的含量，也可以表示各组分间重量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小均在本申请实施例说明书公开的范围之内。进一步地，本申请实施例说明书中所述的重量可以是μg、mg、g、kg等化工领域公知的单位。
通常认为影响电池安全性的主要因素包括负极、正极、电解液等。本申请的发明人经过大量实验研究发现，负极活性材料的颗粒度对电池会影响到电池的安全性，特别地发现，其中的大粒径颗粒对电池安全性的影响非常显著。本申请的发明人经过大量的探 索研究发现，负极活性材料的颗粒粒径越大，其热分解开始反应的温度越高，耐受的温度越高，而且，粒径越大，负极活性材料的比表面积越小，反应速率越慢，电池越安全，但会带来电池功率损失。因此，如何平衡电池的安全性需求和功率需求对于制备优异综合性能的电池至关重要。
对于不同类型的电池，负极材料的粒径、比表面积等参数差异较大，这就导致针对不同类型电池的粒径、比表面积及相关参数进行设计时，不同类型电池之间的参数往往差异极大，需要针对电池类型进行专门设计。例如，适用于锂离子电池的材料或参数很可能并不适用于钠离子电池。比如，传统技术中的钠离子电池的负极活性材料通常采用硬碳，D v50较小，约几个微米(比如5～6μm)，相应的比表面积较大；而锂离子电池在传统技术中更普遍地采用石墨负极，D v50通常在十几个至几十个微米，比表面积比较小。
针对上述存在的普遍技术问题，第一方面，本申请提供了一种负极极片，所述负极极片包括负极活性材料，所述负极活性材料包括硬碳；
所述负极极片还满足如下条件：0.6μg/m≤(D v99+D v50)/(2×B)≤5μg/m；其中，D v99表示所述负极活性材料的累计体积分布百分数达到99％时对应的粒径，单位为μm；D v50表示所述负极活性材料的累计体积分布百分数达到50％时对应的粒径，单位为μm；B表示所述负极极片的比表面积，单位为m 2/g。
在本申请的上下文中，可采用体积累计分布粒径D vN(其中，N表示选自0～100的任意数值)来表征材料的粒径尺寸，指材料的累计体积分布百分数达到N％时所对应的粒径，粒径小于等于D vN的体积占比为N％。D vN可以从材料粒径的体积累积分布曲线上获得，如无其他说明，体积累积分布曲线自小粒径侧从零开始累计。以D v99、D v90、D v50、D v10为例，D v99是指材料的累计体积分布百分数达到99％时所对应的粒径；D v90是指材料的累计体积分布百分数达到90％时所对应的粒径；D v50是指材料的累计体积分布百分数达到50％时所对应的粒径；D v10是指材料的累计体积分布百分数达到10％时所对应的粒径。以D v50为例，表示占材料体积50％的颗粒粒径小于等于D v50，且占材料体积50％的颗粒粒径大于D v50。以D v90为例，表示占材料体积90％的颗粒粒径小于等于D v90，且占材料体积10％的颗粒粒径大于D v90。以D v10为例，表示占材料体积10％的颗粒粒径小于等于D v10，且占材料体积90％的颗粒粒径大于D v10。本领域技术人员可以理解D v99、D v90、D v50、D v10的含义，而且可以采用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪、LS-909激光粒度仪(欧美克)。
在本申请的上下文中，(D v99+D v50)/2可用来表征材料中的大颗粒粒度，可记为“大颗粒平均粒径”。通过控制D v99和D v50的平均数值大小，能够反映出材料中大尺寸颗粒的粒径水平。该值越大，表明材料中的大尺寸颗粒的粒径越大。根据本申请发明人的研究，负极活性材料的颗粒粒径越大，电池热失控起始温度越高，电池安全性越好。
本申请第一方面的负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
在本申请的上下文中，如无特别限制，负极极片的比表面积B指前述负极膜层的比表面积(也即不考虑负极集流体的贡献)。进一步地，负极极片的比表面积B指负极膜层的外表面积及内部孔隙的内表面积之和与负极膜层的重量之比，单位可以为m 2/g。负极极片的比表面积B的定义可参考《GB/T 19587-2004》标准。
在本申请中，负极极片的比表面积B可以用本领域公知的仪器及方法进行测定，例如，可以采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer EmmettTeller)法计算得出，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri StarII型比表面与孔隙分析仪进行，测试步骤可以参照GB/T19587-2004。在一些实施例中，可以采用如下方式测试负极极片的比表面积：选取待测试样品，可以为直接制得的负极极片，也可以是将电池中拆解出的负极极片(此时，需采用无水乙醇清洗，去除电解液，在真空干燥箱60℃下干燥1～2小时)；然后采用氮气或者氩气作为吸附气体，通过比表面与孔隙分析仪测绘相对压力P/P 0为0～0.99的吸脱附曲线，通过BET方法计算出负极极片的比表面积，其中P表示平衡吸附压力，P 0表示饱和蒸汽压。当测试样品为负极活性材料时，可以采用如下的方法制得负极活性材料粉末：可以采用如下方式测试活性材料的比表面积：将负极活性材料在真空干燥箱200℃下干燥2小时；然后采用上述气体吸附测试方法测试负极活性材料的比表面积。在本申请中，负极极片的比表面积越大，则电池热失控反应速率越慢，电池安全性越好。
在一些实施方式中，负极活性材料的粒径及比表面积可通过如下控制或筛选方法(但不限于这些方法)获得：方法一、通过选择不同的负极材料前驱体麦秸椰壳和沥青等制备不同比表面积的材料；方法二、通过在负极材料合成过程设置不同的粉碎时间和转速以及过滤网得到不同的粒径负极材料。
在本申请的上下文中，将(D v99+D v50)/(2×B)定义为极片热稳定性系数，记为S，该参数可反映极片的温热稳定性，该值控制在合理范围(0.6μg/m～5μg/m)内时，极片能耐受的高温大，极片的热失控剧烈程度小。
通过将负极活性材料的粒径和负极极片的比表面积控制在一定范围内则可以使电池既具有较高的起始反应的温度又可以尽量避免对反应活性速率造成不利影响。在本申请中，通过综合控制负极活性材料中的大颗粒粒度和负极极片的比表面积，实现兼具高安全性和高功率的综合优点。进一步地，定义了(D v99+D v50)/2表征大颗粒粒度，还采用该特征与负极极片的比表面积B共同定义了负极极片的极片热稳定性系数(D v99+D v50)/(2×B)，通过调节该极片热稳定性系数在合适的范围内，从而能够赋予电池高安全性及高功率特点，带来优异的耐高温性能优异。
进一步地，负极活性材料包括硬碳。硬碳具有较高的热解碳化温度，有利于更好地提高耐热温度、降低产热量。此外，硬碳的结构内部层间距较大，孔隙率高，可以嵌入较多的金属离子，结构显著膨胀低，有利于改善电池的充放电循环性能和电池寿命。
在本申请中，负极活性材料的颗粒粒径越大，电池热失控起始温度越高，电池安全性越好；负极极片的比表面积越大，则电池热失控反应速率越慢，电池安全性越好。不过，如果(D v99+D v50)/2太大，会导致较低的电池功率及能量密度。当(D v99+D v50)/(2×B)小于0.6μg/m时，大颗粒粒径太小，不足以提升材料反应温度或者 比表面积太大容易引发热失控速率过快；当(D v99+D v50)/(2×B)大于5μg/m时，大颗粒粒径过大，使得电池正常活性位点过少，会恶化电池的充放电性能。
在一些实施方式中，所述负极活性材料满足如下条件5μm≤(D v99+D v50)/2≤18μm.
在一些实施方式中，所述负极活性材料满足如下条件：6μm≤(D v99+D v50)/2≤15μm。
在一些实施方式中，所述负极活性材料满足如下条件：7μm≤(D v99+D v50)/2≤12μm。
在一些实施方式中，所述负极活性材料满足如下条件：8μm≤(D v99+D v50)/2≤10μm。
在一些实施方式中，所述负极活性材料的(D v99+D v50)/2还可以选自下述任一种尺寸或任两种构成的区间：5μm、5.2μm、5.4μm、5.5μm、5.6μm、5.8μm、6μm、6.2μm、6.4μm、6.5μm、6.6μm、6.8μm、7μm、7.2μm、7.4μm、7.5μm、7.6μm、7.8μm、8μm、8.2μm、.4μm、8.5μm、8.6μm、.8μm、9μm、9.5μm、10μm、10.5μm、11μm、11.5μm、12μm、12.5μm、13μm、13.5μm、14μm、15μm、15.5μm、16μm、16.5μm、17μm、17.5μm、17.7μm等。
通过合理控制负极活性材料中的大颗粒在较合适的范围，可以更方便结合对负极活性材料比表面积的精细控制，实现更好地实现电池高安全性兼高功率的优点。
在一些实施方式中，所述负极极片满足如下条件：0.7μg/m≤(D v99+D v50)/(2×B)≤5μg/m。
在一些实施方式中，所述负极极片满足如下条件0.8μg/m≤(D v99+D v50)/(2×B)≤4.2μg/m。
在一些实施方式中，所述负极极片的(D v99+D v50)/(2×B)还可以选自下述任一种或任两种构成的区间：0.6μg/m、0.7μg/m、0.8μg/m、0.9μg/m、1μg/m、1.2μg/m、1.4μg/m、1.5μg/m、1.6μg/m、1.8μg/m、2μg/m、2.2μg/m、2.5μg/m、2.6μg/m、2.8μg/m、3μg/m、3.5μg/m、4μg/m、4.5μg/m、5μg/m、5.5μg/m、6μg/m等。
通过进一步控制极片热稳定性系数(D v99+D v50)/(2×B)在较合适的范围内，有利于更好地平衡大颗粒尺寸对电池安全性的影响以及负极极片的比表面积对电池功率的影响，从而更好地兼顾电池高安全性和高功率。
在本申请的一些实施方式中，所述负极活性材料还满足如下条件：(x·D v10)≤D v50≤(y·D v99)；其中，x＝2.6，且y＝0.4；
可选地，x＝3，且y＝0.3。
通过合理控制负极活性材料的D v50相对于D v10、D v99的比值x、y，可以更好地确保负极活性材料中的小颗粒和大颗粒均具有合适的粒径及含量，更好地避免大颗粒带来的能量密度损失，在改善电池安全性的同时，尽可能地保持较高的能量密度。当x较大时，小颗粒粒径偏小，比表面积偏大，可能会降低材料耐受温度；当x较小时，小颗粒粒径接近于平均粒径，可能会导致颗粒间孔隙填充不足，极片能量密度偏小。当y较大时，大颗粒偏小，可能起不到颗粒填充孔隙的作用，且极片能衡量密度偏小；当y较小时，大颗粒太大，离子穿梭路径偏长，可能造成电池功率减小。
在本申请的一些实施方式中，所述负极极片满足如下条件：30mAh·m -2≤C/B≤140mAh·m -2；其中，C为所述负极极片的克容量。
在一些实施方式中，40mAh·m -2≤C/B≤125mAh·m -2。
在一些实施方式中，负极极片的C/B还可以选自如下任一种或任两种构成的区间：30mAh·m -2、35mAh·m -2、40mAh·m -2、45mAh·m -2、50mAh·m -2、55mAh·m - 2、60mAh·m -2、65mAh·m -2、70mAh·m -2、75mAh·m -2、80mAh·m -2、85mAh·m -2、90mAh·m -2、95mAh·m -2、100mAh·m -2、105mAh·m -2、110mAh·m -2、115mAh·m - 2、120mAh·m -2、125mAh·m -2、130mAh·m -2、135mAh·m -2、140mAh·m -2等。
本申请的发明人发现，负极极片的C/B值可以在一定程度上反映出负极极片的反应活性，通过协同控制负极极片的克容量及负极极片的比表面积，有利于更好地控制电池热失控时的反应速率，有利于进一步提高电池安全性。控制负极极片具有合适的克容量，从而控制活性钠离子嵌入量适当，使反应速率适中，并且控制负极极片的比表面积在较合适的范围内，使得电池活性物质的离子脱嵌路径及极化适中，确保电池功率性能的发挥。
当C/B偏低时(如小于30mAh·m -2时)，负极活性材料克容量偏低，电池容量偏低，或者负极极片比表面积偏大，电池热失控时的反应速率偏大，电池安全性相对较低。当C/B偏大时(如大于140mAh·m -2时)，负极活性材料克容量偏高，导致活性离子嵌入量偏多，一旦失控，剧烈程度偏大，或者极片比表面积非常小，材料颗粒体积较大，电池活性物质离子脱嵌路径偏长，极化偏大，电池功率性能的发挥相对较差。
在本申请的一些实施方式中，所述负极极片的克容量C满足300mAh/g≤C≤350mAh/g。
在一些实施方式中，所述负极极片的克容量C满足310mAh/g≤C≤340mAh/g。
在一些实施方式中，所述负极极片的克容量C还可以选自如下任一种或任两种构成的区间：300mAh/g、305mAh/g、310mAh/g、315mAh/g、320mAh/g、325mAh/g、330mAh/g、335mAh/g、340mAh/g、345mAh/g、350mAh/g等。
在本申请中，负极极片的克容量可参照WI-ATC-2014克容量测试细则测得。测试前极片处理：可以是直接制得的负极极片，也可以是将电池中拆解出的负极极片(此时，需采用无水乙醇清洗，去除电解液，然后在真空干燥箱60℃下干燥2小时)。然后用冲片机冲切多个小圆片，称取每个小圆片的重量取平均值W1，然后把小圆片上的活性物质清洗干净烘干，称取小圆片基材的重量取平均值W2，活性物质的重量(W1-W2)，当双侧涂覆负极浆料时，在每个小圆片的基材单侧的负极活性材料的重量则为(W1-W2)/2。根据小圆片的容量C 0计算克容量＝C 0/(W1-W2)，单位mAh/g。在一些实施方式中，C 0可采用如下方法测试：取冲片机制备的小圆片，用酒精擦除基材一侧的活性物质层，注入电解液，制作成扣式电池。然后用0.1C电流在0V-2V间充放电。其满充2V后又满放0V的容量则为C 0(单位为mAh)。
通过控制负极极片具有合适的克容量，从而控制活性钠离子嵌入量适当，使电池热失控时的反应速率适中，电池安全性更好。
在本申请的一些实施方式中，所述负极极片的比表面积B选自2.5m 2/g～10m 2/g。
在一些实施方式中，所述负极极片的比表面积B选自3m 2/g～7m 2/g。
在一些实施方式中，所述负极极片的比表面积B还可以选自如下任一种或任两种构成的区间：2.5m 2/g、3m 2/g、3.5m 2/g、4m 2/g、4.5m 2/g、5m 2/g、5.5m 2/g、6m 2/g、6.5m 2/g、7m 2/g、7.5m 2/g、8m 2/g、8.5m 2/g、9m 2/g、9.5m 2/g、10m 2/g等。
通过控制负极极片的比表面积及负极活性材料的粒径在较合适的范围内，使得电池活性物质的离子脱嵌路径及极化适中，更有利于电池功率性能的发挥。
在本申请的一些实施方式中，所述负极极片的差示扫描量热分析的第一放热反应峰位置T满足150℃≤T≤180℃；进一步地，差示扫描量热分析的测试条件包括：氮气氛围，升温速率为5℃/min～10℃/min。
在本申请中，涉及差示扫描量热分析，如无其他说明，测试条件可以包括：氮气氛围，升温速率为5℃/min～10℃/min。升温速率的非限制性示例如5℃/min、7.5℃/min、10℃/min等。
在一些实施方式中，所述T满足170℃≤T≤180℃。
在一些实施方式中，所述T还可以选自下述任一种或任两种构成的：150℃、155℃、160℃、165℃、170℃、175℃、180℃等。
通过控制负极极片的差示扫描量热(DSC)分析的第一放热反应峰位置T在较合适的范围内，有利于进一步提升电池安全性。如果T太低，起不到改善电池安全性的作用，较高的T则在技术上存在实施困难，需要把传统极片粉料里面的有机高分子粘接剂替换成更耐高温的物质，同时提高负极活性物质的热解温度。
本申请的第一方面提供的负极极片的负极活性材料中，至少包括硬碳。
在一些实施方式中，硬碳在所述负极活性材料中质量占比≥50％。
在一些实施方式中，硬碳在所述负极活性材料中质量占比≥90％。
在一些实施方式中，硬碳在所述负极活性材料中质量占比还可以选自如下任一种百分比或任两种构成的区间50％、55％、60％、65％、70％、75％、80％、85％、90％、95％、96％、97％、98％、99％、100％等。
硬碳具有较高的热解碳化温度，硬碳的含量越高，越有利于更好地提高耐热温度、降低产热量。此外，硬碳的结构内部层间距较大，孔隙率高，可以嵌入较多的金属离子，结构显著膨胀低，有利于改善电池的充放电循环性能和电池寿命。
在本申请的一些实施方式中，所述负极活性材料还包括软碳、石墨和合金化负极中的一种或多种。
在负极活性材料包括硬碳的基础上，进一步引入软碳、石墨和合金化负极中的一种或多种其他种类的活性材料，可以利用这些材料的优点赋予电池更好的综合性能。比如，软碳具有低而平稳的充放电电位平台，充放电容量大且效率高、循环性能好。比如，石墨具有导电性好，首效高，来源广等优点。比如，合金化负极具有高功率，高能量密度等优点。
负极极片
本申请第一方面的负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。所述负极活性材料的定义如前所述。
作为非限制性示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔，铝箔，铁箔，镍箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等铝、铝合金)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
第二方面，本申请提供一种钠离子电池，其包括正极极片、本申请第一方面所述负极极片、隔离膜和电解质，所述隔离膜设置于所述正极极片和所述负极极片之间。
利用本申请第一方面的负极极片制备得到的钠离子电池兼具高安全性和高功率的综合优点。通常情况下，钠离子电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子(Na +)在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
应当理解，如无特别限定，第二方面的钠离子电池为二次电池。
电解质
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有特别的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质钠盐和溶剂。
在一些实施方式中，电解质钠盐可以选自六氟磷酸钠(NaPF 6)、高氯酸钠(NaClO 4)、四氟硼酸钠(NaBF 4)、双氟磺酰亚胺钠、双三氟甲烷磺酰亚胺钠、三氟甲磺酸钠、二氟磷酸钠等中的一种或多种。
在一些实施方式中，所述电解质钠盐包括六氟磷酸钠、高氯酸钠、四氟硼酸钠和三氟甲基磺酸钠中一种或多种钠盐。
在本申请的一些实施方式中，所述电解质还包含有机溶剂。
在本申请的一些实施方式中，所述有机溶剂可以包括碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸丙烯酯、乙二醇二甲醚、四氢呋喃、2-甲基四氢呋喃、醋 酸甲酯、丙酸乙酯、氟代乙烯碳酸脂、乙醚、二甘醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、甲基叔丁基醚等中的一种或多种。
在本申请的一些实施方式中，所述有机溶剂可以包括碳酸乙烯酯(EC)、碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸丙烯酯(PC)、醚类溶剂(如乙二醇二甲醚(DME))、四氢呋喃(THF)和2-甲基四氢呋喃(2-MTHF)中的一种或多种。
在本申请的一些实施方式中，所述有机溶剂可以包括碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸二甲酯、碳酸甲乙酯、醋酸甲酯、丙酸乙酯、氟代乙烯碳酸脂、乙醚、二甘醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、甲基叔丁基醚等中的一种或多种。
钠盐在溶剂中的溶剂化度高，电导率高，有利于成膜和提高电池功率。
在本申请的一些实施方式中，所述电解质还包含添加剂。
在本申请的一些实施方式中，所述添加剂包括氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、硫酸乙烯酯(DTD)、1,3-丙烷磺内酯(PS)、1,3-丙烯基-磺酸内酯(PST)、丁二酸酐(SA)、二氟草酸硼酸锂(LiDFOB)、二氟双草酸磷酸锂(LiDFOP)、三(三甲基甲硅烷)磷酸酯(TMSP)、三(三甲基甲硅烷)硼酸酯(TMSB)、碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的一种或多种。
在本申请的一些实施方式中，所述添加剂包括氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、硫酸乙烯酯(DTD)、1,3-丙烷磺内酯(PS)、1,3-丙烯基-磺酸内酯(PST)、丁二酸酐(SA)、二氟草酸硼酸锂(LiDFOB)、二氟双草酸磷酸锂(LiDFOP)、三(三甲基甲硅烷)磷酸酯(TMSP)、三(三甲基甲硅烷)硼酸酯(TMSB)等中的一种或多种。
通过选择合适的添加剂，可以帮助电池快速形成固体电解质相界面(SEI)膜，增大SEI膜的厚度和稳定性，提升电池安全性。
在一些实施方式中，可以减小电池化成时的电流，例如以0.05C、0.1C电流化成，进一步地，化成温度可以设定在25℃，从而可以得到加厚的SEI膜。在一些实施方式中，所述负极极片满足如下条件：0.5℃≤T×M≤6℃；其中，T和M分别为所述负极极片的差示扫描量热(DSC)分析的第一放热反应峰位置和第一阶段失重率；进一步地，氮气氛围下测试，升温速率为5℃/min～10℃/min。
在一些实施方式中，负极极片满足如下条件：0.65℃≤T×M≤5.2℃。
在一些实施方式中，负极极片满足如下条件：0.75℃≤T×M≤4.5℃。
在一些实施方式中，负极极片的T×M还可以选自如下任一种或任两种构成的区间：0.5℃、0.52℃、0.54℃、0.55℃、0.56℃、0.58℃、0.60℃、0.65℃、0.70℃、0.75℃、0.80℃、0.85℃、0.90℃、0.95℃、1℃、1.5℃、2℃、2.5℃、3℃、3.5℃、4℃、4.5℃、5℃、5.5℃、6℃等。
在本申请中，负极极片的差示扫描量热(DSC)分析的第一放热反应S位置(T)及第一段失重率(M)可以从负极极片的DSC图谱中获取。M可以反映固体电解质界面(SEI)的分解量。负极极片的DSC测试可以参照《JYT014—1996》热分析方法通则。如无其它限定，可采用如下的测试方法：将极片在60℃真空干燥箱烘干6h，取 样重量W3，在氮气氛围下程序升温至600℃，测量样品的失重率和DCS放热峰。
在一些实施方式中，气体氛围为氮气、氩气或者其组合。
在一些实施方式中，升温速率可以为5℃/min～10℃/min，非限制性示例如5℃/min、10℃/min等。
如前所述，在本申请中，涉及差示扫描量热分析，如无其他说明，测试条件可以包括：氮气氛围，升温速率为5℃/min～10℃/min。升温速率的非限制性示例如5℃/min、7.5℃/min、10℃/min等。
本申请的发明人推测，T×M在一定程度上可以反映负极极片在高温下的耐受程度。负极活性材料的颗粒粒度影响到反应放热的温度起点，颗粒越大，其开始反应的温度就越高，相应的电池体系越安全。然而，颗粒较大时，却会对电池功率不利。因此，如何平衡安全性和电池功率对于制备高综合性能的电池至关重要。通过将负极极片的差示扫描量热(DSC)分析的第一放热反应峰的位置(T)向高温处推移，可以将固体电解质界面(SEI)膜分解反应温度(对应M)提高，有利于增加SEI膜的厚度，从而达到进一步提高安全性的效果。
在本申请的一些实施方式中，所述负极极片的差示扫描量热分析的第一阶段失重率M满足如下条件：0.25％≤M≤3.5％；进一步地，差示扫描量热分析的测试条件包括：氮气氛围，升温步长为5℃/min～10℃/min(如10℃/min)。
在一些实施方式中，0.5％≤M≤2.5％。
在一些实施方式中，0.65％≤M≤2％。
在一些实施方式中，所述M还可以选自如下任一种百分比或任两种构成的区间：0.28％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％、1.0％、1.1％、1.2％、1.4％、1.5％、1.6％、1.8％、2.0％、2.1％、2.2％、2.3％、2.4％、2.5％、2.6％、2.8％、3％、3.2％、3.3％等。
通过控制负极极片的差示扫描量热分析的第一阶段失重率M在较合适的范围，可以改善SEI界面稳定性，有利于提升电池安全性，还可以实现较好的离子传输及充放电性能。M越低，表明SEI越薄，越不利于电池界面稳定，电池安全性差；但如果过多说明SEI太厚，则不利于离子传输，会恶化充放电性能。
正极极片
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料。
在一些实施方式中，所述正极极片包括含有钠离子的正极活性材料。在其中的一些实施方式中，所述含有钠离子的正极活性材料包括普鲁士蓝类化合物、钠过渡氧化物和聚阴离子类化合物中的一种或多种。可灵活选择合适的正极活性材料，从而使钠离子电池具有更多的选择性，适用面更广。
所述正极活性材料可以包括但不限于钠过渡金属氧化物、聚阴离子类化合物和普鲁士蓝类化合物中的一种或多种。但本申请并不限定于前述列举的材料，还可以使用其他可被用作钠离子电池正极活性材料的已知材料。
在一些实施方式中，钠过渡金属氧化物中的过渡金属可以是包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的一种或多种。钠过渡金属氧化物的非限制性示 例可以为Na xZO 2，其中Z可以为包括Ti、V、Mn、Co、Ni、Fe、Cr及Cu中的一种或多种，0<x≤1。
在一些实施方式中，钠过渡金属氧化物可以为Na 1-xCu hFe kMn lM 1 mO 2-y，其中M 1可以为包括Li、Be、B、Mg、Al、K、Ca、Ti、Co、Ni、Zn、Ga、Sr、Y、Nb、Mo、In、Sn及Ba中的一种或多种，0<x≤0.33，0<h≤0.24，0≤k≤0.32，0<l≤0.68，0≤m<0.1，h+k+l+m＝1，0≤y<0.2。
在一些实施方式中，钠过渡金属氧化物可以为Na 0.67Mn 0.7Ni qM 2 0.3-zO 2，其中M 2可以为包括Li、Mg、Al、Ca、Ti、Fe、Cu、Zn及Ba中的一种或多种，0<q≤0.1。
在一些实施方式中，钠过渡金属氧化物可以为Na aLi bNi cMn dFe eO 2，其中0.67<a≤1，0<b<0.2，0<c<0.3，0.67<d+e<0.8，b+c+d+e＝1。
在一些实施方式中，聚阴离子类化合物可以为具有钠离子、过渡金属离子及四面体型(YO 4) n-阴离子单元的一类化合物。此处的过渡金属可以是包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的一种或多种；Y可以是包括P、S及Si中的一种或多种；n表示(YO 4) n-的价态。
在一些实施方式中，聚阴离子类化合物还可以是具有钠离子、过渡金属离子、四面体型(YO 4 )n-阴离子单元及卤素阴离子的一类化合物。此处的过渡金属可以是包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的一种或多种；Y可以是包括P、S及Si中的一种或多种，n表示(YO 4) n-的价态；卤素可以是包括F、Cl及Br中的一种或多种。
在一些实施方式中，聚阴离子类化合物还可以是具有钠离子、四面体型(YO 4) n-阴离子单元、多面体单元(ZO y) m+及可选的卤素阴离子的一类化合物。Y可以是包括P、S及Si中的一种或多种，n表示(YO4)n-的价态；Z表示过渡金属，可以是包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的一种或多种，m表示(ZO y) m+的价态；卤素可以是包括F、Cl及Br中的一种或多种。
在一些实施方式中，聚阴离子类化合物可以是NaFePO 4、Na 3V 2(PO 4) 3、NaM’PO 4F及Na 3(VO y) 2(PO 4) 2F 3-2 y(0≤y≤1)中的一种或多种；其中，NaM’PO 4F中的M’可以为包括V、Fe、Mn及Ni中的一种或多种。
在一些实施方式中，普鲁士蓝类化合物可以是具有钠离子、过渡金属离子及氰根离子(CN —)的一类化合物。这里的过渡金属可以是包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的一种或多种。普鲁士蓝类化合物的非限制性举例可以为Na aMe bMe’ c(CN) 6，其中Me及Me’可以各自独立地为包括Ni、Cu、Fe、Mn、Co及Zn中的一种或多种，0<a≤2，0<b<1，0<c<1。
在一些实施方式中，正极活性物质层还可以包括导电剂，以改善正极的导电性能。本申请对导电剂的种类不做特别限制，可以根据实际需求进行选择。作为示例，导电剂可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或几种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为非限制性示例，以将正极活性材料和可选的导电剂牢固地粘结在正极集流体上。本申请对粘结剂的种类没有特别限定，可以根据实际需求进行选择。作为非限制性示例，粘结剂可以为聚偏氟乙烯 (PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物、含氟丙烯酸酯树脂、聚丙烯酸(PAA)、聚乙烯醇(PVA)、乙烯-醋酸乙烯酯共聚物(EVA)、丁苯橡胶(SBR)、羧甲基纤维素(CMC)、海藻酸钠(SA)、聚甲基丙烯酸(PMA)及羧甲基壳聚糖(CMCS)中的一种或多种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或多种。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可以采用导电碳片、金属箔材、涂炭金属箔材、多孔金属板或复合集流体。其中，导电碳片的导电碳材质可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或多种；金属箔材、涂炭金属箔材和多孔金属板的金属材质各自独立地可以选自铜、铝、镍及不锈钢中的一种或多种。复合集流体可以为金属箔材与高分子基膜复合形成的复合集流体。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、可选的导电剂、可选的粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
隔离膜
在一些实施方式中，钠离子电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
对于不同体系的电池，比如钠离子电池和锂离子电池，由于钠离子和锂离子的直径不同，导致对隔离膜的结构具有不同要求。钠离子的直径更大，不同于锂离子的小尺寸，因而对厚度要求较为特殊，在实现隔离功能的同时，还需要确保大粒径的钠离子可穿梭通过，以便在保证电池安全性的同时还具有良好的电池倍率。
在一些实施方式中，本申请的钠离子电池中隔离膜的材质可以是本领域各种适用于电化学储能装置隔离膜的材料，例如，可以包括但不限于玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或多种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，隔离膜的至少一侧表面包括绝缘材料涂层，可选地，所述绝缘材料涂层为陶瓷涂层。
在一些实施方式中，隔离膜的基体材料包括聚乙烯和聚丙烯中的一种或多种。
在一些实施方式中，隔离膜的厚度为5μm～15μm。在一些实施方式中，隔离膜的厚度为7μm～13μm。隔离膜的厚度举例，还可以为如下任一种或任两种构成的区间：5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm等。
在一些实施方式中，隔离膜在90℃加热1h的TD方向收缩率≤4％。在一些实施方式中，隔离膜在90℃加热1h的TD方向收缩率选自0.5％～3.5％。
在本申请中，TD方向收缩率指宽度方向收缩率，对应横向收缩率。
在本申请中，隔离膜的收缩率可以采用如下方法测试：切割10cm×10cm的隔离膜平放在表面光滑的玻璃上，然后用A4纸裁切至少15cm×15cm的面积，把隔膜居中盖住，用胶带把A4纸的四个角于玻璃粘住。然后放到烘箱内加热1h，后取出测量此时隔膜的尺寸。
收缩率越小，电池受高温烘烤时隔离膜越稳定，越不容易变形收缩，从而更有效地避免正负极隔离作用失效而短路。
在一些实施方式中，隔离膜的面密度选自2g/m 2～6g/m 2。在一些实施方式中，隔离膜的面密度选自3g/m 2～5g/m 2。在一些实施方式中，隔离膜的面密度还可以选自如下任一种或任两种构成的区间：2g/m 2、2.5g/m 2、3g/m 2、3.5g/m 2、4g/m 2、4.5g/m 2、5g/m 2、5.5g/m 2、6g/m 2等。
在本申请中，隔离膜的面密度可以采用本领域公知的仪器及方法进行测定，例如可以用赛多利斯电子天平称量具有一定面积的隔离膜的质量，以隔离膜的质量除以隔离膜的面积，即可计算得到隔离膜的面密度。
面密度越大，越不容易刺穿隔离膜，但是会增加隔离膜重量；面密度越小，隔离膜越疏松，容易被硬碳尖角刺穿短路。
在本申请的一些实施方式中，所述隔离膜满足如下特征中的一种或多种：
(tm1)：所述隔离膜的至少一侧表面包括绝缘材料涂层，可选地，所述绝缘材料涂层为陶瓷涂层；
(tm2)所述隔离膜的基体材料包括聚乙烯和聚丙烯中的一种或多种；
(tm3)所述隔离膜的厚度为5μm～15μm，可选地，所述隔离膜的厚度为7μm～13μm；
(tm4)所述隔离膜在90℃加热1h的TD方向收缩率≤4％，可选地，所述隔离膜在90℃加热1h的TD方向收缩率选自0.5％～3.5％；和
(tm5)所述隔离膜的面密度选自2g/m 2～6g/m 2，可选地，所述隔离膜的面密度选自3g/m 2～5g/m 2。
本申请的另一方面，还提供本申请第一方面所述负极极片在制备钠离子电池中的应用。
本申请第一方面的负极极片可用于制备钠离子电池，从而获得兼具高安全性和高能量密度优点的综合优点。
钠离子电池的装配
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成 电极组件。
在一些实施方式中，钠离子电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，钠离子电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。钠离子电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对钠离子电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图2是作为一个示例的方形结构的钠离子电池5。
在一些实施方式中，参照图3，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。钠离子电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据实际需求进行选择。
在一些实施方式中，将上述正极极片、隔离膜、负极极片按顺序层叠得到电芯，使隔离膜处于正极极片与负极极片之间起到隔离的作用，得到电芯，也可以是经卷绕后得到电芯；将电芯置于包装外壳(可以是软包、方形铝壳、方形钢壳、圆柱铝壳和圆柱钢壳)中，注入电解液并封口，得到钠离子电池。
第三方面，本申请提供一种用电装置，其包括本申请第二方面所述钠离子电池。
利用本申请第二方面提供的钠离子电池制备用得到的电装置，不仅具有高安全性，还同时具有高能量密度，能够满足消费者高安全及高性能的综合需要。
所述钠离子电池可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备、电动车辆、电气列车、船舶及卫星、储能系统等，但不限于此。其中，移动设备例如可以是手机、笔记本电脑等；电动车辆例如可以是纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择钠离子电池。
图4是作为一个示例的用电装置6。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对钠离子电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用钠离子电池作为电源。
以下，说明本申请的一些实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明技术或条件的详细细节的，按照上文中的描述进行，或者按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品，或者可通过市购产品按照常规方式合成。
下面的实施例中，室温是指20℃～30℃，可以为25℃。
以下各例中，如无特别说明，以下各原料的规格型号为：
以下各实施例和对比例可参考如下表1、表2和表3的参数进行制备。
1.负极极片的制备
负极极片1的制备
将负极活性材料硬碳、导电剂Super P、增稠剂羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶乳液(SBR)按照质量比97:0.7:1.8:0.5进行混合，加入至溶剂去离子水中，在真空搅拌机作用下搅拌均匀，获得负极浆料。该负极浆料中的固体含量为56重量％。
其中，负极活性材料的粒径控制及筛选方法为：用间苯二酚与甲醛反应生成的酚醛树脂为前驱体，使用聚丙烯腈(PAN)为包覆碳源，通过碳包覆来调节材料的比表面积与闭孔量，设定氮气氛围下热解温度为1300℃，热解后经过初筛和细筛得到目标尺寸的材料。
将前述制备的负极浆料通过挤压涂布机或者转移涂布机均匀涂覆在负极集流体铜箔的双侧表面上，并在85℃下烘干，然后经过冷压、切边、裁片、分条得到尺寸91mm×5680mm负极极片。
负极极片2～17的制备：采用与负极极片1基本相同的方法。负极极片2～10、13、14与负极极片1的区别在于：负极活性材料的尺寸不同，分别采用表1所示体积累计分布粒径D v99、D v50、D v10的负极活性材料。负极极片11～12、15～17与负极极片1的区别在于：负极活性材料的种类及尺寸不同。参阅表1。
2.钠离子电池的制备(实施例1～16及对比例1～4)
各实施例1～16和各对比例1～4，负极极片和电解液的获取参阅表3，其余结构件的制备及装配方法采用相同的参数。如下所示。
2.1.负极极片的选择
依照表3选择各实施例及各对比例的负极极片。
2.2.正极极片的制备
将正极活性材料Na 2MnFe(CN) 6、导电剂Super P、粘结剂聚偏氟乙烯(PVDF)按照质量比96:2.5:1.5进行混合，加入至溶剂N-甲基吡咯烷酮(NMP)中，在真空搅拌机作用下搅拌均匀，获得正极活性材料层用浆料。该浆料中的固体含量为60重量％。
将前述制备的正极浆料均匀涂覆在正极集流体铝箔上，室温晾干后转移至90℃烘箱继续干燥，然后裁切成直径为88mm×5450mm的圆片做为正极极片，进行冷压、切边、裁片和分条，得到厚度为150μm的正极极片。
2.3.隔离膜的制备
以厚度为7μm的聚乙烯膜(PE)作为隔膜的基膜，将重量比93％：3％：4％的氧化铝、羧甲基纤维素钠(CMC)和丙烯酸酯加入至去离子水中，在真空搅拌机作用下搅拌均匀，获得浆料。该浆料中的固体含量为55重量％。将得到的浆料以单面2μm的厚度均匀喷涂在基膜的两面上，获得隔膜。
2.4.电解液的制备
在含水量<10ppm的氩气气氛手套箱中，将充分干燥的钠盐(NaPF 6)溶解在有机溶剂碳酸乙烯酯(EC)中，然后加入添加剂碳酸亚乙烯酯(VC)，混合均匀，获得电解液。其中，钠盐的浓度为1mol/L。钠盐、有机溶剂和添加剂的种类及用量参阅表 3。
2.5.钠离子电池的装配
将正极极片、隔离膜和负极极片按顺序层叠放置好，使隔离膜处于正极极片和负极极片之间，起到隔离的作用。然后将得到的层叠体卷绕成方形的裸电芯，焊接极耳，将裸电芯装入方形铝壳中，激光焊接顶盖。然后在80℃下真空烘烤除水后，注入前述制备的电解液并封口。之后，经过45℃静置、化成(0.02C恒流充电到3.3V，再以0.1C恒流充电到3.6V)、整形和容量测试等工序，获得成品硬壳钠离子电池，其厚度为28mm、宽度为97.5mm、长度为148mm。
3.测试方法
3.1.负极极片
(1)负极活性材料的体积累计分布粒径D vN(D v99、D v50、D v10)的测试
样品前处理：取一洁净烧杯，加入适量待测样品，滴加表面活性剂十二烷基硫酸钠后添加去离子水作为分散剂，并进行超声处理(频率120W，时长5min)，确保样品在分散剂中完全分散。
测试：参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪测定各D vN。使用LS-909激光粒度仪(欧美克)进行测试。将样品倒入进样塔后随溶液循环到测试光路系统，对颗粒在激光束的照射下发出的散射光加以接受，并测量其能量分布，可以得出颗粒的粒度分布特征(遮亮度：8％～12％)，最终得到材料的各D vN数值。
(2)负极极片的比表面积B的测试
采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer EmmettTeller)法计算得出，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri StarII型比表面与孔隙分析仪进行，测试步骤可以参照GB/T 19587-2004。
详细步骤如下：选取待测试样品，可以为上述步骤直接制得的负极极片，也可以是将电池中拆解出的负极极片(此时，需采用无水乙醇清洗，去除电解液，然后在真空干燥箱60℃下干燥2小时)；然后采用氮气为吸附气体，通过比表面与孔隙分析仪测绘相对压力P/P 0为0～0.99的吸脱附曲线(P为平衡吸附压力，P 0为饱和蒸汽压)，通过BET方法计算出负极极片的比表面积。
(3)负极极片的极片热稳定性系数S
采用公式S＝(D v99+D v50)/2B计算得到。其中，(D v99+D v50)/2采用第(1)点方法测定，B采用第(2)点方法得到。
(4)差示扫描量热(DSC)分析
参照《JYT014—1996》热分析方法通则。可采用如下的测试方法：将负极极片在60℃真空干燥箱烘干6h，取样重量W3，在氮气氛围下以升温速率10℃/min程序升温至600℃，测量样品的失重率和DCS放热峰，得到第一放热反应峰位置T和第一阶段失重率M。
(5)负极极片的反应速率因子P
采用公式P＝C/B计算得到。其中，C根据1.6.3.部分第(2)点方法测得，B采用第(2)点方法得到。
3.2.负极极片及电芯性能
(1)负极极片的克容量
克容量：参照WI-ATC-2014克容量测试细则。选取待测试样品，可以为上述步骤直接制得的负极极片，也可以是将电池中拆解出的负极极片(此时，需采用无水乙醇清洗，去除电解液，然后在真空干燥箱60℃下干燥2小时)。然后用冲片机冲切15片直径为16mm的小圆片，其中任意选12片，称取每个小圆片的重量，取平均值记为W1；然后把小圆片上的活性物质清洗干净烘干，称取每个小圆片基材的重量，取平均值记为W2；每个小圆片上，基材单侧的负极活性材料的重量则为(W1-W2)/2。根据小圆片的容量C 0计算克容量C＝2×C 0/(W1-W2)，单位为mAh/g。
C 0的测试方法为：取上述冲切的剩余3个小圆片，用酒精擦除基材一侧的活性物质层，对电极为Na金属片，注入电解液(参考前述实施例2的2.4)，制作成扣式电池。然后用0.1C电流在0V-2V间充放电。其满充2V后又满放0V的容量则为C 0(mAh)。
(2)可耐受温度
采用热箱测试法。参照GB38031-2020中锂离子电池加热测试方法。
在1.22℃±5℃环境下，将电池以0.33C放电至0％SOC，静置1h，然后再以0.33C恒流恒压充电到100％SOC(电池规定使用电压上限)。将样品放在高温箱中，温箱以5℃/min的速率由室温升至直至电池爆炸或电压为0V停止。观察1h。
其中，SOC表示电池荷电状态，可反映电池的剩余容量，在数值上定义为剩余容量占电池容量的比值。
(4)60s脉冲放电功率的测量
通过测量电池的60s脉冲放电功率定电池的功率性能。
更详细地，在25℃下将电芯置于星云电池充放电测试系统，以0.5C的倍率恒流恒压充电至充电截止电压3.75V，静置5分钟后以特定的功率放电，确保在60s时电池的电压正好达到2V停止放电，此时的功率为60s脉冲放电功率。
4.测试结果及分析
负极极片的体积累计分布粒径D vN(D v99、D v50、D v10)、极片比表面积B、极片热稳定性系数S、DSC分析、极片反应速率因子P、极片克容量C和极片反应速率因子P的测试及分析结果可参阅表1、表2和图1。各实施例和各对比例制备的钠离子电池的DSC分析、热箱测试可耐受温度。
图1为实施例3中负极极片的差示扫描量热(DSC)测试的放热曲线及热失重曲线图。从图中可以看出，DSC图谱的第一放热反应峰位置T约为170℃，DSC图谱的第一阶段失重率M约为1.2％。
负极极片1～10及负极极片15～17具有合适的(D v99+D v50)/(2×B)范围，均在0.6μg/m～5μg/m范围内，采用该极片制备的钠离子电池实施例1～16均具有较高的热箱测试可耐受温度，具有较高的60s脉冲放电功率，兼具高安全性和高功率的优点。
对比例1～4的负极极片11～14相应的(D v99+D v50)/(2×B)值在0.6μg/m～5μg/m范围之外，热箱测试可耐受温度及60s脉冲放电功率均劣于前述各实施例。
表1.
Figure PCTCN2022118758-appb-000001
表2.
Figure PCTCN2022118758-appb-000002
其中，S＝(D v99+D v50)/(2×B)。
需要说明的是，多个负极极片的DSC第一放热反应峰位置T在表2中记为180℃，是四舍五入后的结果，实际值之间存在微小波动。
表3.
Figure PCTCN2022118758-appb-000003
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。以上所述实施例仅表达了本申请的几种实施方式，其描述较为详细，但并不能因此而理解为对专利范围的限制。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请的保护范围应以所附权利要求为准，说明书及附图可用于解释权利要求的内容。

Claims (18)

  1. 一种负极极片，其包括负极活性材料，所述负极活性材料包括硬碳；
    所述负极极片还满足如下条件：0.6μg/m≤(D v99+D v50)/(2×B)≤5μg/m，
    其中，
    D v99表示所述负极活性材料的累计体积分布百分数达到99％时对应的粒径，单位为μm；
    D v50表示所述负极活性材料的累计体积分布百分数达到50％时对应的粒径，单位为μm；
    B表示所述负极极片的比表面积，单位为m 2/g。
  2. 如权利要求1所述的负极极片，其中，所述负极活性材料满足如下条件5μm≤(D v99+D v50)/2≤18μm；
    可选地，所述负极活性材料满足如下条件：6μm≤(D v99+D v50)/2≤15μm；
    可选地，所述负极活性材料满足如下条件：7μm≤(D v99+D v50)/2≤12μm；
    可选地，所述负极活性材料满足如下条件：8μm≤(D v99+D v50)/2≤10μm。
  3. 如权利要求1或2所述的负极极片，其中，所述负极极片满足如下条件：0.7μg/m≤(D v99+D v50)/(2×B)≤4.5μg/m；
    可选地，所述负极极片满足如下条件：0.8μg/m≤(D v99+D v50)/(2×B)≤4.2μg/m。
  4. 如权利要求1～3中任一项所述的负极极片，其中，所述负极活性材料还满足如下条件：(x·D v10)≤D v50≤(y·D v99)；其中，x＝2.6，且y＝0.4；
    可选地，x＝3，且y＝0.3。
  5. 如权利要求1～4中任一项所述的负极极片，其中，所述负极极片还满足如下条件：30mAh·m -2≤C/B≤140mAh·m -2；其中，C为所述负极极片的克容量；
    可选地，40mAh·m -2≤C/B≤125mAh·m -2。
  6. 如权利要求1～5中任一项所述的负极极片，其中，所述负极极片的克容量C满足如下条件：300mAh/g≤C≤350mAh/g，
    可选地，所述负极极片的克容量C满足如下条件：310mAh/g≤C≤340mAh/g。
  7. 如权利要求1～6中任一项所述的负极极片，其中，所述B选自2.5m 2/g～10m 2/g；
    可选地，所述B选自3m 2/g～7m 2/g。
  8. 如权利要求1～7中任一项所述的负极极片，其中，所述负极极片的差示扫描量热分析的第一放热反应峰位置T满足如下条件：150℃≤T≤180℃；其中，所述差示扫描量热分析的测试条件包括：氮气氛围，升温速率为10℃/min；
    可选地，170℃≤T≤180℃。
  9. 如权利要求1～8中任一项所述的负极极片，其中，所述负极活性材料还包括软碳、石墨和合金化负极中的一种或多种；
    可选地，硬碳在所述负极活性材料中质量占比≥50％；
    可选地，硬碳在所述负极活性材料中质量占比≥90％。
  10. 一种钠离子电池，其包括正极极片、权利要求1～10任一项所述负极极片、隔 离膜和电解质，所述隔离膜设置于所述正极极片和所述负极极片之间。
  11. 如权利要求10所述的钠离子电池，其中，所述电解质包含电解质钠盐，所述电解质钠盐包括六氟磷酸钠、高氯酸钠、四氟硼酸钠、三氟甲基磺酸钠、双氟磺酰亚胺钠、双三氟甲烷磺酰亚胺钠、三氟甲磺酸钠和二氟磷酸钠中一种或多种钠盐；
    可选地，所述电解质钠盐包括六氟磷酸钠、高氯酸钠、四氟硼酸钠和三氟甲基磺酸钠中一种或多种钠盐。
  12. 如权利要求11所述的钠离子电池，其中，所述电解质还包含有机溶剂，所述有机溶剂包括碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸丙烯酯、乙二醇二甲醚、四氢呋喃、2-甲基四氢呋喃、醋酸甲酯、丙酸乙酯、氟代乙烯碳酸脂、乙醚、二甘醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚和甲基叔丁基醚中的一种或多种；
    可选地，所述有机溶剂包括碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸丙烯酯、乙二醇二甲醚、四氢呋喃和2-甲基四氢呋喃中的一种或多种。
  13. 如权利要求11或12所述的钠离子电池，其中，所述电解质还包含添加剂，所述添加剂包括氟代碳酸乙烯酯、碳酸亚乙烯酯、硫酸乙烯酯、1,3-丙烷磺内酯、1,3-丙烯基-磺酸内酯、丁二酸酐、二氟草酸硼酸锂、二氟双草酸磷酸锂、三(三甲基甲硅烷)磷酸酯、三(三甲基甲硅烷)硼酸酯、碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的一种或多种；
    可选地，所述添加剂包括氟代碳酸乙烯酯、碳酸亚乙烯酯、硫酸乙烯酯、1,3-丙烷磺内酯、1,3-丙烯基-磺酸内酯、丁二酸酐、二氟草酸硼酸锂、二氟双草酸磷酸锂、三(三甲基甲硅烷)磷酸酯和三(三甲基甲硅烷)硼酸酯中的一种或多种。
  14. 如权利要求10～13中任一项所述的钠离子电池，其中，所述负极极片满足如下条件：0.5℃≤T×M≤6℃；其中，
    T和M分别为所述负极极片的差示扫描量热分析的第一放热反应峰位置和第一阶段失重率，差示扫描量热分析的测试条件包括：氮气氛围，升温速率为10℃/min；
    可选地，0.65℃≤T×M≤5.2℃；
    可选地，0.75℃≤T×M≤4.5℃。
  15. 如权利要求10～14中任一项所述的钠离子电池，其中，所述负极极片的差示扫描量热分析的第一阶段失重率M满足如下条件：0.25％≤M≤3.5％；其中，所述差示扫描量热分析的测试条件包括：氮气氛围，升温速率为10℃/min；
    可选地，0.5％≤M≤2.5％；
    可选地，0.6％≤M≤2.1％。
  16. 如权利要求10～15中任一项所述的钠离子电池，其中，所述正极极片包括含有钠离子的正极活性材料，所述含有钠离子的正极活性材料包括普鲁士蓝类化合物、钠过渡金属氧化物和聚阴离子类化合物中的一种或多种。
  17. 一种用电装置，其中，包括权利要求10～16中任一项所述钠离子电池。
  18. 权利要求1～9中任一项所述负极极片在制备钠离子电池中的应用。
PCT/CN2022/118758 2022-09-14 2022-09-14 负极极片、钠离子电池、用电装置和应用 WO2024055204A1 (zh)

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CN109841831A (zh) * 2019-03-21 2019-06-04 宁德新能源科技有限公司 负极材料及包含该负极材料的负极及电化学装置
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