WO2024092501A1 - 正极极片、制法、二次电池和用电装置 - Google Patents

正极极片、制法、二次电池和用电装置 Download PDF

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WO2024092501A1
WO2024092501A1 PCT/CN2022/128964 CN2022128964W WO2024092501A1 WO 2024092501 A1 WO2024092501 A1 WO 2024092501A1 CN 2022128964 W CN2022128964 W CN 2022128964W WO 2024092501 A1 WO2024092501 A1 WO 2024092501A1
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positive electrode
silicon
containing compound
compound additive
active material
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PCT/CN2022/128964
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English (en)
French (fr)
Inventor
谢庭祯
许宝云
欧阳少聪
付成华
林运美
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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/CN2022/128964 priority Critical patent/WO2024092501A1/zh
Publication of WO2024092501A1 publication Critical patent/WO2024092501A1/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
    • 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

Definitions

  • the present application relates to the technical field of lithium batteries, and in particular to a positive electrode sheet, a manufacturing method, a secondary battery and an electrical device.
  • lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • lithium-ion batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • lithium hexafluorophosphate is usually used as lithium salt in lithium-ion battery electrolytes.
  • the lithium hexafluorophosphate used will inevitably carry acidic substances such as hydrofluoric acid into the final product during its preparation process, and lithium hexafluorophosphate can produce acidic substances such as hydrofluoric acid when it comes into contact with water.
  • the hydrofluoric acid content in a lithium-ion battery exceeds a certain concentration, it will consume limited lithium ions, increase the irreversible capacity of the battery, and increase the pressure inside the battery.
  • the positive and negative electrode structures of the lithium-ion battery may be destroyed, and its charging and discharging, cycle efficiency and other performances may decrease, and even safety accidents may occur. Therefore, there is still room for improvement in the acid resistance of the positive and negative electrodes.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode plate, wherein the positive electrode film layer contains a silicon-containing compound additive of a specific particle size, which significantly reduces the direct current internal resistance (DCR) of the battery and improves the cycle performance of the battery; and the additive has a simple synthesis path, low cost, stable structure, and can be widely used in industrial production.
  • DCR direct current internal resistance
  • the present application provides a positive electrode plate, a manufacturing method, a secondary battery and an electrical device.
  • the first aspect of the present application provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode film layer contains a positive electrode active material and a silicon-containing compound additive of formula mM x Q ⁇ nSi y Q z , wherein
  • M is one or more of alkali metals, alkaline earth metals, Al, Fe, and Zn;
  • Q is one or more of O, F, Cl, Br, I, and At;
  • n are positive integers
  • the silicon compound additive comprises small particles having an average volume particle size D v50 of 0.01-1 ⁇ m.
  • the positive electrode plate of the present application can consume hydrogen fluoride present in the electrode liquid by including a silicon-containing compound additive with a specific average volume particle size in its positive electrode film layer, while reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the content of small particles with an average volume particle size Dv50 of 0.01 ⁇ m-1 ⁇ m is 50%-100%, based on the total weight of the silicon-containing compound additive.
  • the small particles react with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the silicon-containing compound additive comprises 0-40% of medium particles with a size of 1 ⁇ m ⁇ D v50 ⁇ 2 ⁇ m and 0-10% of large particles with a size of 2 ⁇ m ⁇ D v50 ⁇ 10 ⁇ m, each based on the total weight of the silicon-containing compound additive.
  • the silicon-containing compound additive reacts with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the silicon-containing compound additive has a D v99 of less than 20 ⁇ m, thereby reacting with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current resistance
  • the silicon-containing compound additive comprises at least one of potassium silicate, sodium silicate, lithium silicate, aluminum silicate, lithium fluorosilicate, potassium fluorosilicate or sodium fluorosilicate, thereby reacting with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the content of the silicon-containing compound additive is 0.01%-2%, based on the weight of the positive electrode film layer, thereby reacting with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the weight ratio of the silicon-containing compound additive to the positive electrode active material is 0.0125%-2.5%, thereby reacting with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • a second aspect of the present application provides a method for preparing a positive electrode sheet, comprising:
  • the silicon-containing compound additive is of the formula mM x Q ⁇ nSi y Q z , wherein
  • M is one or more of alkali metals, alkaline earth metals, Al, Fe, and Zn;
  • Q is one or more of O, F, Cl, Br, I, and At;
  • n are positive integers
  • the silicon compound additive comprises small particles having an average volume particle size D v50 of 0.01-1 ⁇ m.
  • the obtained positive electrode plate contains a silicon-containing compound additive with a specific particle size, which can effectively consume the hydrogen fluoride present in the electrode liquid, while reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the silicon-containing compound additive in step (1), can be prepared by air flow crushing, ball milling, or reprecipitation.
  • the silicon-containing compound additive has a simple synthesis route, low cost, and stable structure, and can be better applied to the battery of the present application.
  • the silicon-containing compound additive in step (2), can be deposited on the surface of the positive electrode active material by a deposition method, the deposition method comprising dissolving the silicon-containing compound additive in solvent A to prepare solution A; dispersing the positive electrode active material in solvent B to prepare solution B; and then mixing solution A with solution B, so that the silicon-containing compound additive is deposited on the surface of the positive electrode active material. Therefore, the silicon-containing compound additive has a simple synthesis path, low cost, stable structure, and can be better applied to the battery of the present application.
  • the concentration of the silicon-containing compound additive in solution A is 1 wt%-10 wt%; the concentration of the positive electrode active material in solution B is 5 wt%-20 wt%. Therefore, the silicon-containing compound additive has a simple synthesis route, low cost, and stable structure, and can be better applied to the battery of the present application.
  • the silicon-containing compound additive in solvent B at room temperature and pressure is less than 1 g/100 g. Therefore, the silicon-containing compound additive has a simple synthesis route, low cost, stable structure, and can be better applied to the battery of the present application.
  • a third aspect of the present application provides a secondary battery, characterized in that:
  • the fourth aspect of the present application provides an electrical device, characterized in that it includes the secondary battery described in the third aspect of the present application.
  • the positive electrode plate of the present application can consume hydrogen fluoride in the electrode liquid more quickly by including a silicon-containing compound additive with a smaller average volume particle size in its positive electrode film layer, while reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • FIG1 is a SEM image of a silicon-containing compound additive prepared by a deposition method attached to the surface of a positive electrode active material in one embodiment of the present application; wherein the gray dots in the black box represent the silicon-containing compound additive.
  • FIG. 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 3 is an exploded view of a secondary battery according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • Secondary battery 51. Casing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is an integer ⁇ 2
  • the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • 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.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, 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).
  • lithium hexafluorophosphate is usually used as lithium salt in lithium ion battery electrolyte.
  • the lithium hexafluorophosphate used will inevitably carry acidic substances such as hydrofluoric acid into the final product during its preparation process, and lithium hexafluorophosphate can produce acidic substances such as hydrofluoric acid when it comes into contact with water.
  • the hydrofluoric acid content in the lithium ion battery exceeds a certain concentration, it will consume limited lithium ions, increase the irreversible capacity of the battery, and increase the pressure inside the battery.
  • the positive and negative electrode structures of the lithium ion battery may be destroyed, and its charging and discharging, cycle efficiency and other performances may decrease, and even safety accidents may occur. Therefore, there is still room for improvement in the acid resistance of the positive and negative electrodes.
  • the inventors have found through a lot of research that the positive electrode sheet of the first aspect of the present application contains a silicon-containing compound additive with a smaller average volume particle size in its positive electrode film layer, which significantly reduces the direct current internal resistance (DCR) of the battery and improves the cycle performance of the battery; and the additive has a simple synthesis path, low cost, stable structure, and can be widely used in industrial production.
  • DCR direct current internal resistance
  • the first aspect of the present application provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material and a formula
  • M is one or more of alkali metals, alkaline earth metals, Al, Fe, and Zn;
  • Q is one or more of O, F, Cl, Br, I, and At;
  • n are positive integers
  • the silicon compound additive comprises small particles having an average volume particle size D v50 of 0.01-1 ⁇ m, optionally 0.01-0.8 ⁇ m, and further optionally 0.05-0.15 ⁇ m.
  • the positive electrode plate of the present application includes a silicon-containing compound additive with a specific average volume particle size in its positive electrode film layer, so that the silicon-containing compound additive is evenly dispersed, and the contact surface with the hydrogen fluoride present in the electrode liquid is large, which is more conducive to chemical reaction.
  • the generated by-products with more stable structures are deposited on the surface of the positive electrode active material, which can reduce the direct current internal resistance (DCR) of the battery and improve the cycle performance of the battery.
  • DCR direct current internal resistance
  • the content of small particles with an average volume particle size D v50 of 0.01 ⁇ m-1 ⁇ m, optionally 0.01-0.8 ⁇ m, and further optionally 0.05-0.15 ⁇ m is 50%-100%, optionally 80%-100%, based on the total weight of the silicon-containing compound additive.
  • the small particles react with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the silicon-containing compound additive consists of small particles with an average volume particle size D v50 of 0.01 ⁇ m-1 ⁇ m, optionally consisting of small particles with an average volume particle size D v50 of 0.01-0.8 ⁇ m, and further optionally consisting of small particles with an average volume particle size D v50 of 0.05-0.15 ⁇ m.
  • the silicon-containing compound additive may further include 0-40% of medium particles with a size of 1 ⁇ m ⁇ D v50 ⁇ 2 ⁇ m and 0-10% of large particles with a size of 2 ⁇ m ⁇ D v50 ⁇ 10 ⁇ m, each based on the total weight of the silicon-containing compound additive. This adjusts the pore structure of the coating to avoid agglomeration of too many small-particle silicon-containing compound additives, resulting in poor electrolyte wetting and deterioration of lithium ion transport performance.
  • the ratio of the medium particles to the small particles is 1:2:8, and can be 1:3-5, based on the weight of the two particles.
  • the content ratio of the large particles to the small particles is 1:5-13, optionally 1:8-10, based on the weight of the two particles.
  • the silicon-containing compound additive when the silicon-containing compound additive contains both large particles and small particles, the content ratio of large particles, medium particles and small particles is 1:(1.1-4):(4.5-11), and can be optionally 1:(1.5-2.5):(6-8), based on the weight of the particles of both.
  • the silicon-containing compound additive has a D v99 of less than 20 ⁇ m, and optionally less than 10 ⁇ m, thereby reacting with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current resistance
  • D v50 is the particle size corresponding to when the volume cumulative distribution percentage of the sample starting from the small particle size reaches 50%, also known as the average volume particle size
  • D v90 is the particle size corresponding to when the volume cumulative distribution percentage of the sample starting from the small particle size reaches 90%
  • D v99 is the particle size corresponding to when the volume cumulative distribution percentage of the sample starting from the small particle size reaches 99%.
  • the particle size of the above-mentioned materials is well known in the art, and is determined by using a laser particle size analyzer to measure the volume particle size and its distribution of the material, for example, the Mastersizer 3000 laser particle size analyzer produced by Malvern Instruments Ltd., UK.
  • the silicon-containing compound additive may include a silicate or a fluorosilicate, for example, at least one of potassium silicate, sodium silicate, lithium silicate, aluminum silicate, lithium fluorosilicate, potassium fluorosilicate or sodium fluorosilicate, and potassium silicate or lithium silicate may be selected.
  • the silicon-containing compound additive reacts with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the content of the silicon-containing compound additive is 0.2%-2%, and optionally 0.5%-1%, based on the weight of the positive electrode film layer, thereby reacting with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the weight ratio of the silicon-containing compound additive to the positive electrode active material is 0.0125%-2.5%, and optionally 0.5%-1.1%, thereby reacting with hydrogen fluoride in the electrolyte more quickly, thereby reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the silicon-containing compound additive is attached to the surface of the positive electrode active material particles and exists as a coating on the surface of the positive electrode active material particles.
  • the silicon-containing compound additive particles are added to the positive electrode film layer by the following methods: (1) the silicon-containing compound additive is physically mixed with the active material in advance, and then prepared into a positive electrode slurry; (2) the silicon-containing compound additive dispersion is directly added to the positive electrode slurry; (3) the silicon-containing compound additive is directly precipitated and deposited on the surface of the positive electrode material, and then a positive electrode slurry is prepared (preferably, it is subsequently sintered for a more reliable bond and more uniform particles); and (4) the silicon-containing compound additive is uniformly coated on the surface of the positive electrode active material layer away from the positive electrode current collector to form a silicon-containing compound coating.
  • the positive electrode film layer includes a positive electrode active material layer and a silicon-containing compound coating arranged on the surface of the positive electrode active material layer on the side contacting the isolation membrane, the silicon-containing compound coating has a thickness of 1-10um, the thickness of the positive electrode active material layer is 50-150um, and the ratio of the thickness of the silicon-containing compound coating to the thickness of the positive electrode active material layer is 0.67%-20%.
  • the average volume particle size Dv50 of the positive electrode active material is 20-100 nm.
  • the ratio of the Dv50 of the silicon-containing compound to the average volume particle size of the positive electrode active material is 1:20-100, and can be 1:30-50.
  • the thickness of the positive electrode sheet is 100-250 um, and the porosity is 20%-35%.
  • the thickness of the positive electrode sheet is the sum of the thickness of the positive electrode current collector and the thickness of the positive electrode film layer (also called the positive electrode active material layer).
  • the second aspect of the present application provides a method for preparing a positive electrode sheet, comprising:
  • the silicon-containing compound additive is of the formula mM x Q ⁇ nSi y Q z , wherein
  • M is one or more of alkali metals, alkaline earth metals, Al, Fe, and Zn;
  • Q is one or more of O, F, Cl, Br, I, and At;
  • n are positive integers
  • the silicon compound additive comprises small particles having an average volume particle size D v50 of 0.01-1 ⁇ m.
  • the obtained positive electrode plate contains a silicon-containing compound additive with a specific particle size, which can effectively consume the hydrogen fluoride present in the electrode liquid, while reducing the direct current internal resistance (DCR) of the battery and improving the cycle performance of the battery.
  • DCR direct current internal resistance
  • the silicon-containing compound additive provided may be a commercially available silicon-containing compound, or may be prepared by methods known to those skilled in the art.
  • the silicon-containing compound additive in step (1), can be prepared by air flow crushing method and re-precipitation method. Therefore, the silicon-containing compound additive has a simple synthesis route, low cost, stable structure, and can be better applied to the battery of the present application.
  • the silicon-containing compound additive of the particle size described in the present application can be prepared by a gas flow crushing method.
  • the gas flow crushing method comprises crushing the commercially available silicon-containing compound through a gas flow mill at a gas pressure of 0.7-1 MPa and a gas flow rate of 3-20 m3/min, and adjusting the average volume particle size of the particles to a desired level after grading and screening.
  • a silicon-containing compound additive of the particle size described in the present application can be prepared by a reprecipitation method.
  • the reprecipitation method comprises dissolving a commercially available silicon-containing compound additive in a solvent 1 at room temperature, stirring evenly, and preparing a solution 1 having a silicon-containing compound concentration of 1wt%-10wt%; then adding the solution 1 to a solvent 2 in which the silicon-containing compound is slightly soluble or insoluble while stirring at a speed of 400-800rpm to prepare a solution 2, wherein the concentration of the solution 2 is 5wt%-20wt%, and the silicon-containing compound additive is reprecipitated during the stirring process, and the average volume particle size of the particles can be adjusted to a desired level.
  • the solvent 1 is generally any substance capable of dissolving the silicon-containing compound at room temperature, for example, including but not limited to deionized water.
  • the solvent 2 may be a substance known to those skilled in the art that is slightly soluble or incompatible with the silicon-containing compound, for example, including but not limited to anhydrous ethanol, N-methylpyrrolidone (NMP), acetone, carbon tetrachloride and other organic solvents.
  • step (2) comprises mixing the silicon-containing compound additive with a positive electrode active material, a solvent, and an optional binder or other additives to prepare a positive electrode slurry.
  • a silicon-containing compound additive having a particle size as described in the present application may be deposited on the surface of the positive electrode active material by a deposition method.
  • the deposition method includes dissolving the silicon-containing compound additive in solvent A to prepare solution A; dispersing the positive electrode active material in solvent B to prepare solution B; and then mixing solution A with solution B, so that the silicon-containing compound additive is deposited on the surface of the positive electrode active material. Therefore, the silicon-containing compound additive has a simple synthesis path, low cost, stable structure, and can be better applied to the battery of the present application.
  • the concentration of the silicon-containing compound additive in solution A is 1 wt%-10 wt%; the concentration of the positive electrode active material in solution B is 5 wt%-20 wt%. Therefore, the silicon-containing compound additive has a simple synthesis route, low cost, and stable structure, and can be better applied to the battery of the present application.
  • the solvent A is generally any substance that can dissolve the silicon-containing compound at room temperature, including but not limited to deionized water.
  • the solubility of the silicon-containing compound additive in the solvent B at room temperature and pressure is less than 1 g/100 g. Therefore, the silicon-containing compound additive has a simple synthesis route, low cost, and stable structure, and can be better applied to the battery of the present application.
  • the solvent B may be a substance known to those skilled in the art that is slightly soluble or insoluble in the silicon-containing compound and poorly soluble or even insoluble in the positive electrode active material, such as but not limited to anhydrous ethanol, NMP, acetone, carbon tetrachloride and other organic solvents.
  • the term "slightly soluble" means that the solubility of a solute in 100 grams of a solvent is 0.01 grams to 1 gram at room temperature and pressure.
  • the term “poorly soluble” means that the solubility of the solute in 100 grams of solvent is less than 0.01 grams at room temperature and pressure.
  • the deposition method includes dissolving the silicon-containing compound additive in solvent A to prepare solution A with a silicon-containing compound additive concentration of 1wt%-10wt%; and dispersing the positive electrode active material in solvent B to prepare solution B; then adding solution A to solution B, stirring and mixing, so that the silicon-containing compound additive is deposited on the surface of the positive electrode active material, filtering, and then preferably sintering at 300-500°C in air or an inert atmosphere to obtain a product in which the silicon-containing compound additive is attached to the surface of the positive electrode active material at the desired average volume particle size level.
  • the deposition method is similar to the reprecipitation method, except that the precipitated silicon-containing compound additive is directly deposited on the surface of the positive electrode active material particles, and the silicon-containing compound additive is in the form of spherical small particles, which are evenly distributed on the surface of the positive electrode active material particles.
  • the solvent in step (2) may typically be N-methylpyrrolidone (NMP).
  • the positive electrode slurry has a solid content of 40-80 wt % and a viscosity of 5000-25000 mPa ⁇ s at room temperature.
  • step (3) the positive electrode slurry is coated on a positive electrode current collector, dried to form a positive electrode film layer, and then cold-pressed by a cold rolling mill to obtain the positive electrode sheet.
  • the unit surface density of the positive electrode film layer is 40-350 g/m2, and the compaction density of the positive electrode sheet is 2.0-3.6 g/cm3, and can be optionally 3.3-3.5 g/cm3.
  • Compacted density unit surface density/(thickness of the electrode after extrusion - thickness of the current collector).
  • the mass M of the positive electrode active material per unit area of the positive electrode film layer can be obtained by weighing using a standard balance.
  • the thickness T of the positive electrode film layer can be measured by using a micrometer, for example, a Mitutoyo 293-100 with an accuracy of 0.1 ⁇ m. It should be noted that the thickness of the positive electrode film layer described in the present invention refers to the thickness of the positive electrode film layer in the positive electrode sheet used for assembling the battery after cold pressing and compaction.
  • a third aspect of the present application provides a secondary battery, characterized in that:
  • the secondary battery is a lithium ion secondary battery or a sodium ion secondary battery.
  • the initial direct current internal resistance (DCR) of the secondary battery at 25° C. is 1-1.7 ⁇ , optionally 1.05-1.35 ⁇ ; after 1000 cycles at 25° C., the DCR is 2.4-3.8 ⁇ , optionally 2.6-3.0 ⁇ .
  • the fourth aspect of the present application provides an electrical device, characterized in that it includes the secondary battery described in the third aspect of the present application.
  • the components, material types or contents of the batteries mentioned are applicable to both lithium-ion secondary batteries and sodium-ion secondary batteries.
  • a secondary battery is provided.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the positive electrode sheet is the positive electrode sheet of the first aspect of the present application.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material on a polymer material substrate.
  • the metal material includes but is not limited to aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • Polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • the positive electrode active material may include a positive electrode active material for a battery known in the art.
  • the positive electrode active material of the lithium ion secondary battery may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to , lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide (such as LiNiO2 ), lithium manganese oxide (such as LiMnO2 , LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333 ), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ) , LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211 ) , LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622 ), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode active material of the sodium ion secondary battery may include at least one of the following materials: at least one of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.
  • the transition metal in the sodium transition metal oxide, may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the sodium transition metal oxide is, for example, Na x MO 2 , wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 ⁇ x ⁇ 1.
  • the polyanionic compound can be a class of compounds having sodium ions, transition metal ions and tetrahedral (YO 4 ) n- anion units.
  • the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y can be at least one of P, S and Si;
  • 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 may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y may be at least one of P, S and Si, and n represents the valence state of (YO 4 ) n- ;
  • the halogen may be at least one 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 may be at least one of P, S and Si, and n represents the valence state of (YO 4 ) n- ;
  • Z represents a transition metal, and may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents the valence state of (ZO y ) m+ ;
  • the halogen may be at least one of F, Cl and Br.
  • the polyanionic compound is, for example, at least one of NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 ( P2O7 ) , NaM'PO4F ( M ' is one or more of V, Fe, Mn and Ni) and Na3 ( VOy ) 2 ( PO4 ) 2F3-2y ( 0 ⁇ y ⁇ 1 ).
  • the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN - ).
  • the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the Prussian blue compound is, for example, Na a Me b Me' c (CN) 6 , wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1.
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80-100 weight %, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • the weight ratio of the binder in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer may further include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its 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.
  • a metal foil a copper foil may 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 substrate.
  • the composite current collector may be formed by forming a metal material on a polymer material substrate.
  • the metal material includes but is not limited to copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • the polymer material substrate includes but is not limited to polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other substrates.
  • the negative electrode active material may be a negative electrode active material for a battery known in the art.
  • the negative electrode active material of the lithium ion secondary battery may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode active material of the sodium ion secondary battery is generally a hard carbon material, a two-dimensional metal carbide or a nitride.
  • the negative electrode active material of the sodium ion secondary battery is generally a hard carbon material.
  • the weight ratio of the negative electrode active material in the negative electrode film layer is 70-100 weight %, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include 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 weight ratio of the conductive agent in the negative electrode film layer is 0-20 weight %, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer may further include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc.
  • a thickener such as sodium carboxymethyl cellulose (CMC-Na)
  • the weight ratio of the other additives in the negative electrode film layer is 0-15% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa ⁇ s; the obtained negative electrode slurry is coated on the negative electrode collector, and after a drying process, cold pressing such as a roller is performed to obtain the negative electrode sheet.
  • a solvent such as deionized water
  • the negative electrode powder coating unit area density is 50-150g/ m2 , and the negative electrode sheet compaction density is 1.2-2.0g/ m3 ; the thickness of the negative electrode sheet is 50-200um, wherein the thickness of the negative electrode collector such as aluminum foil is 5-10um.
  • the mass M of the negative electrode active material per unit area of the negative electrode film layer can be obtained by weighing using a standard balance.
  • the thickness T of the negative electrode film layer or the electrode piece can be measured by using a micrometer, for example, a micrometer of model Mitutoyo293-100 with an accuracy of 0.1 ⁇ m. It should be noted that the thickness of the negative electrode film layer described in the present invention refers to the thickness of the negative electrode film layer in the negative electrode electrode piece used to assemble the battery after cold pressing. In this application, the "thickness" mentioned can be measured in the same way as above.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt of the lithium ion secondary battery can be selected from one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • the electrolyte salt of the sodium ion secondary battery can be selected from one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.
  • the concentration of the electrolyte salt is usually 0.5-5 mol/L.
  • the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (FEC),
  • the electrolyte may further include other additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the isolation film has a thickness of 5-20 ⁇ m, and optionally 5-15 ⁇ m.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package that can be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG2 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack may include a battery box and a plurality of battery modules disposed in the battery box.
  • the battery box includes an upper box body and a lower box body, and the upper box body can be covered on the lower box body to form a closed space for accommodating the battery modules.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • FIG4 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.
  • step (2) dispersing the product prepared in step (2) above (a positive electrode active material having potassium silicate particles with an average volume particle size of 200 nm deposited on the surface), conductive carbon black SP and binder PVDF in a weight ratio of 98:1:1 into a solvent NMP and mixing them uniformly to obtain a positive electrode slurry;
  • the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained, and the coating amount per unit area is 0.27 g/1540.25 mm 2 .
  • the thickness of the positive electrode sheet is 150 um.
  • step (2i) the concentration of the silicon-containing compound in solution A was 1 wt %, and the total concentration of the solution after mixing was still 10 wt %.
  • Potassium silicate particles with an average volume particle size of 100 nm deposited on the surface of the positive electrode active material were obtained.
  • step (2i) the concentration of the silicon-containing compound in solution A was 10 wt %, to obtain potassium silicate particles with an average volume particle size of 500 nm deposited on the surface of the positive electrode active material.
  • step (2i) the concentration of the silicon-containing compound in solution A was 0.5 wt %, to obtain potassium silicate particles with an average volume particle size of 50 nm deposited on the surface of the positive electrode active material.
  • step (2i) The steps of Preparation Example 1 were repeated, except that in step (2i), the concentration of the silicon-containing compound in solution A was 5%, and the amount of solvent B was 800 g; potassium silicate particles with an average volume particle size of 1 um deposited on the surface of the positive electrode active material were obtained.
  • step (2i) The steps of Preparation Example 1 were repeated, except that in step (2i), the concentration of the silicon-containing compound in solution A was 15%, and the amount of solvent B was 600 g; potassium silicate particles with an average volume particle size of 2 ⁇ m deposited on the surface of the positive electrode active material were obtained.
  • Step (1) The steps of Preparation Example 1 were repeated, except that commercially available potassium fluorosilicate (purchased from MacLean Reagent Network, CAS No. 16871-90-2, Product No. P816423, D v50 average particle size 150 um) was provided in step (1).
  • commercially available potassium fluorosilicate purchased from MacLean Reagent Network, CAS No. 16871-90-2, Product No. P816423, D v50 average particle size 150 um
  • Example 1 The steps of Example 1 were repeated, except that in step (1), commercially available sodium silicate (McLean Reagent Network, CAS No. 1344-09-8, Product No. S871944, Dv50 average particle size 150 ⁇ m) was provided.
  • commercially available sodium silicate McLean Reagent Network, CAS No. 1344-09-8, Product No. S871944, Dv50 average particle size 150 ⁇ m
  • Example 1 The steps of Example 1 were repeated, except that in step (1), commercially available aluminum silicate (McLean Reagent Network, CAS No. 1302-93-8, Product No. A823215, Dv50 average particle size 6.5 ⁇ m) was provided.
  • commercially available aluminum silicate McLean Reagent Network, CAS No. 1302-93-8, Product No. A823215, Dv50 average particle size 6.5 ⁇ m
  • step (2i) the positive electrode active material was Na 2 FePO 4 .
  • Potassium silicate powder (composition as shown in Table 1) was dispersed in NMP solution and then ultrasonically uniformly prepared into a potassium silicate dispersion with a concentration of 10%. According to the order of adding positive electrode active material, potassium silicate dispersion, conductive carbon black SP and binder PVDF, they were dispersed into the solvent NMP in a weight ratio of 97:1:1:1 and mixed evenly to obtain positive electrode slurry.
  • potassium silicate powders with Dv50 of 200 nm, 1 ⁇ m and 5 ⁇ m were dispersed in a solvent NMP in a weight ratio of 7:2:1, and 2% of a binder PVDF was added, and the mixture was stirred to obtain a potassium silicate slurry;
  • the thickness of the positive electrode active material layer is 150 um, and the thickness of the potassium silicate layer is 10 um.
  • the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained, and the coating amount per unit area is 0.27g/ 1540.25mm2 .
  • the thickness of the positive electrode film layer is 150um.
  • Potassium silicate powder (composition as shown in Table 1) with a particle size of ⁇ 1um was dispersed in NMP solution and then ultrasonically uniformly prepared into a potassium silicate dispersion with a concentration of 10%. According to the order of adding positive electrode active material, potassium silicate dispersion, conductive carbon black SP and binder PVDF, they were dispersed into the solvent NMP in a weight ratio of 97:1:1:1 and mixed evenly to obtain positive electrode slurry.
  • the positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained, and the coating amount per unit area was 0.27 g/1540.25 mm 2 .
  • the potassium silicate powder (composition as shown in Table 1) with small particles accounting for only 20% was dispersed in the NMP solution and then ultrasonically uniformly prepared into a potassium silicate dispersion with a concentration of 10%. According to the order of adding the positive electrode active material, potassium silicate dispersion, conductive carbon black SP and binder PVDF, they were dispersed into the solvent NMP at a weight ratio of 97:1:1:1 and mixed evenly to obtain a positive electrode slurry.
  • the positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained, and the coating amount per unit area was 0.27 g/1540.25 mm 2 .
  • step (1) 10 g of commercially available potassium silicate was added to 190 g of deionized water at room temperature, dissolved and stirred evenly at a speed of 400 rpm; 1800 g of anhydrous ethanol was taken and stirred at a speed of 800 rpm, and the potassium silicate solution was dripped into it while stirring, and the potassium silicate gradually precipitated; after continuous stirring for 0.5 h, the solution was filtered and dried to obtain potassium silicate; (ii) step (2i) was not performed; (iii) in step (2ii), the potassium silicate prepared above and the positive electrode active material LiMn 0.5 Ni 0.3 Co 0.2 O 2 material, conductive carbon black SP and binder PVDF were dispersed in a solvent NMP in a weight ratio of 1:97:1:1 and mixed evenly to obtain a positive electrode slurry.
  • step (1) 2 kg of commercially available potassium silicate was added to a jet mill at room temperature and crushed for 2 h at an air pressure of 1 MPa and an air flow of 10 m 3 /min to obtain potassium silicate particles.
  • the positive electrode sheet prepared in Example 1 was used.
  • the negative electrode active material graphite, the thickener sodium carboxymethyl cellulose, the binder styrene butadiene rubber, and the conductive agent acetylene black were mixed in a mass ratio of 97:1:1:1, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on a copper foil; the copper foil was dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then supercooled pressed and cut to obtain a negative electrode sheet, and the coating amount per unit area was 0.17g/ 1540.25mm2 .
  • a 12 ⁇ m thick polypropylene isolation film (provided by Celgard) was selected.
  • the organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the volume ratio of EC, EMC and DEC is 20:20:60.
  • argon atmosphere glove box with a water content of ⁇ 10ppm fully dried lithium salt LiPF6 is dissolved in the organic solvent and mixed evenly to obtain an electrolyte.
  • the concentration of the lithium salt is 1 mol/L.
  • the positive electrode sheet, the isolation film, and the negative electrode sheet are stacked in order, so that the isolation film is placed between the positive and negative electrode sheets to play an isolating role. Then, they are wound into a square bare battery cell, loaded with an aluminum-plastic film, and then baked at 80°C to remove water. After that, 150g of the corresponding non-aqueous electrolyte is injected and sealed. After standing, hot and cold pressing, formation, clamping, capacity division and other processes, a finished battery with a capacity of 50Ah is obtained.
  • the secondary batteries of Examples 2-12 and Comparative Examples 1-3 were prepared in a similar manner to the secondary battery of Example 1, but the positive electrode sheets of the corresponding preparation examples were used.
  • the resistance value is measured based on the battery cell of Example 1.
  • the resistance values of batteries in different modes are different.
  • the test temperature is 25, and the battery is charged to 4.35V at a constant current of 1Cn, charged to 0.05Cn at a constant voltage, and discharged to 2.5V at 0.33Cn after standing for 30 minutes.
  • the capacity obtained in this step is taken as the initial capacity, and a cycle test is performed with 1Cn charge/0.33Cn discharge.
  • the capacity of each step is compared with the initial capacity as the capacity retention rate.
  • the number of cycles until the capacity retention rate reaches 85% after 25 cycles is recorded as the cycle life performance of the lithium-ion battery.
  • the DC internal resistance at the corresponding cycle temperature is tested for every 1000 cycles.
  • the batteries of the embodiments and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 2 below.
  • the battery of the present invention has good technical effects. For example, after 1000 cycles at 25°C, the DCR of the battery can reach 2.67 ⁇ , and the number of cycles of the battery when the capacity retention rate drops to 80% can even reach more than 2000 cycles. Compared with Comparative Example 1 in which no silicon-containing compound additive is added, the cycle life is increased by more than 30%.

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Abstract

正极极片及其制备方法、二次电池和用电装置，正极极片包括正极集流体以及设置在正极集流体的至少一侧的正极膜层，正极膜层包含正极活性材料和式mM xQ·nSi yQ z所示的含硅化合物的添加剂，式中 M为碱金属、碱土金属、Al、Fe、Zn 元素中的一种或者多种；Q为O、F、Cl、Br、I、At元素中的一种或多种；x值取决于 M； y、z值取决于Q；m、n 为正整数；含硅化合物的添加剂包含平均体积粒径 D v50为0.01-1um的小颗粒。正极极片的正极膜层中包含的特定粒径的含硅化合物的添加剂可以显著降低相应的二次电池的直流内阻，改善电池的循环性能。

Description

正极极片、制法、二次电池和用电装置 技术领域
本申请涉及锂电池技术领域，尤其涉及一种正极极片、制法、二次电池和用电装置。
背景技术
近年来，随着锂离子电池的应用范围越来越广泛，锂离子电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于锂离子电池取得了极大的发展，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。
但是锂离子电池电解液通常使用六氟磷酸锂作为锂盐，所使用的六氟磷酸锂在其制备过程中不可避免的会夹带氢氟酸等酸性物质进入最终成品，并且六氟磷酸锂遇水可产生氢氟酸等酸性物质。当锂离子电池中氢氟酸含量超过一定浓度时，会消耗有限的锂离子，使电池的不可逆容量增大，同时会导致电池内压力增大。随着氢氟酸含量增加，锂离子电池的正负极结构可能会被破坏，其充放电、循环效率等性能下降，甚至发生安全事故。因此，目前对正负极在耐酸性物质方面仍有待改进。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种正极极片，其正极膜层中包含特定粒径的含硅化合物添加剂，显著降低了电池的直流内阻(DCR)，改善电池的循环性能；并且该添加剂合成路径简单，成本低廉，结构稳定，能够在工业生产中广泛应用。
为了达到上述目的，本申请提供一种正极极片、制法、二次电池和用电装置。
本申请的第一方面提供了一种正极极片，其包括正极集流体以及设置在所述正极集流体的至少一侧的正极膜层，所述正极膜层包含正极活性材料和式mM xQ·nSi yQ z含硅化合物添加剂，其中
M为碱金属、碱土金属、Al、Fe、Zn元素中的一种或者多种；
Q为O、F、Cl、Br、I、At元素中的一种或多种；
x值取决于M；
y、z值取决于Q；以及
m、n为正整数；
所述含硅化合物添加剂包含平均体积粒径D v50为0.01-1μm的小颗粒。
本申请的正极极片通过在其正极膜层中包含特定平均体积粒径的含硅化合物添加剂，可以消耗电极液中存在的氟化氢，同时降低电池的直流内阻(DCR)，改善电池的循环性能。
在任意的实施方式中，平均体积粒径Dv50为0.01μm-1μm的小颗粒的含量为50％-100％，基于含硅化合物添加剂的总重量计。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在任意的实施方式中，所述含硅化合物添加剂包含含量为0-40％的1μm<D v50≤2μm的中颗粒和含量为0-10％的2μm＜D v50≤10μm的大颗粒，各自基于含硅化合物添加剂的总重量计。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在任意的实施方式中，所述含硅化合物添加剂的D v99为小于20μm。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在任意的实施方式中，所述含硅化合物添加剂包含硅酸钾、硅酸钠、硅酸锂、硅酸铝、氟硅酸锂、氟硅酸钾或氟硅酸钠中的至少一种。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在任意的实施方式中，所述含硅化合物添加剂的含量为0.01％-2％，基于所述正极膜层的重量计。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在任意的实施方式中，所述含硅化合物添加剂与所述正极活性材料的重量比为0.0125％-2.5％。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
本申请的第二方面提供一种制备正极极片的方法，其包括，
(1)提供含硅化合物添加剂；
(2)将所述含硅化合物添加剂与正极活性材料、溶剂混合，制备正极浆料；
(3)将所述正极浆料涂覆在正极集流体上，形成正极膜层，得到所述正极极片；
所述含硅化合物添加剂为式mM xQ·nSi yQ z，其中
M为碱金属、碱土金属、Al、Fe、Zn元素中的一种或者多种；
Q为O、F、Cl、Br、I、At元素中的一种或多种；
x值取决于M；
y、z值取决于Q；和
m、n为正整数；
所述含硅化合物添加剂包含平均体积粒径D v50为0.01-1μm的小颗粒。
由此，本申请的方法添加含硅化合物添加剂的方式简单，成本低廉，便于大规模生产应用，所得的正极极片包含特定粒径的含硅化合物添加剂，能有效地消耗电极液中存在的氟化氢，同时降低电池的直流内阻(DCR)，改善电池的循环性能。
在任意的实施方式中，在步骤(1)中，可通过气流破碎法、球磨法、重析出法制备含硅化合物添加剂。由此，所述含硅化合物添加剂合成路径简单，成本低廉，结构稳定，能更好地应用到本申请的电池中。
在任意的实施方式中，在步骤(2)中，可利用沉积法将所述含硅化合物添加剂沉积在正极活性材料表面，所述沉积法包括将所述含硅化合物添加剂溶解在溶剂A配成溶液A；并将正极活性材料分散在溶剂B配置成溶液B；然后将溶液A与溶液B混合，使得含硅化合物添加剂沉积在正极活性材料表面。由此，所述含硅化合物添加剂合成路径简单，成本低廉，结构稳定，能更好地应用到本申请的电池中。
在任意的实施方式中，在溶液A中所述含硅化合物添加剂的浓度为1重量％-10重量％；在溶液B中所述正极活性材料的浓度为5重量％-20重量％。由此，所述含硅化合物添加剂合成路径简单，成本低廉，结构稳定，能更好地应用到本申请的电池中。
在任意的实施方式中，其特征在于，含硅化合物添加剂在室温和常压下在溶剂B中的溶解度小于1g/100g。由此，所述含硅化合物添加剂合成路径简单，成本低廉，结构稳定，能更好地应用到本申请的电池中。
本申请的第三方面提供一种二次电池，其特征在于，
包括本申请的第一方面所述的正极极片或根据本申请的第二方面所述的方法制备的正极极片。
本申请的第四方面提供一种用电装置，其特征在于，包括本申请的第三方面所述 的二次电池。
本申请的正极极片通过在其正极膜层中包含具有较小的平均体积粒径的含硅化合物添加剂，可更快地消耗电极液中存在的氟化氢，同时降低电池的直流内阻(DCR)，改善电池的循环性能。
附图说明
图1是本申请一实施方式中通过沉积法制备的含硅化合物添加剂附着在正极活性材料表面的SEM图像；其中黑色方框内的灰点代表含硅化合物添加剂。
图2是本申请一实施方式的二次电池的示意图。
图3所示的本申请一实施方式的二次电池的分解图。
图4是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
5、二次电池；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具体公开了本申请的正极极片、制备方法、二次电池和用电装置的实施方式。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，本申请的所有技术特征以及可选技术特征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”。更具体地，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)。
目前，锂离子电池电解液通常使用六氟磷酸锂作为锂盐，所使用的六氟磷酸锂在其制备过程中不可避免的会夹带氢氟酸等酸性物质进入最终成品，并且六氟磷酸锂遇水可产生氢氟酸等酸性物质。当锂离子电池中氢氟酸含量超过一定浓度时，会消耗有限的锂离子，使电池的不可逆容量增大，同时会导致电池内压力增大。随着氢氟酸含量增加，锂离子电池的正负极结构可能会被破坏，其充放电、循环效率等性能下降，甚至发生安全事故。因此，目前对正负极在耐酸性物质方面仍有待改进。发明人通过大量的研究发现，本申请第一方面的正极极片在其正极膜层中包含具有较小平均体积粒径的含硅化合物添加剂，显著降低了电池的直流内阻(DCR)，改善电池的循环性能；并且该添加剂合成路径简单，成本低廉，结构稳定，能够在工业生产中广泛应用。
正极极片
在一些实施方式中，本申请的第一方面提供了一种正极极片，其包括正极集流体 以及设置在所述正极集流体的至少一侧的正极膜层，所述正极膜层包含正极活性材料和式
mM xQ·nSi yQ z含硅化合物添加剂，其中
M为碱金属、碱土金属、Al、Fe、Zn元素中的一种或者多种；
Q为O、F、Cl、Br、I、At元素中的一种或多种；
x值取决于M；
y、z值取决于Q；和
m、n为正整数；
所述含硅化合物添加剂包含平均体积粒径D v50为0.01-1μm、可选为0.01-0.8μm、进一步可选为0.05-0.15μm的小颗粒。
本申请的正极极片通过在其正极膜层中包含特定平均体积粒径的含硅化合物添加剂，使得含硅化合物添加剂分散均匀，与电极液中存在的氟化氢接触面大，更有利于进行化学反应，同时生成的结构更稳定的副产物沉积在正极活性材料表面，能够降低电池的直流内阻(DCR)，改善电池的循环性能。
在一些实施方式中，平均体积粒径D v50为0.01μm-1μm、可选为0.01-0.8μm、进一步可选为0.05-0.15μm的小颗粒的含量为50％-100％，可选地80％-100％，基于含硅化合物添加剂的总重量计。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在一个优选的实施方式中，所述含硅化合物添加剂由平均体积粒径D v50为0.01μm-1μm的小颗粒组成，可选地由平均体积粒径D v50为0.01-0.8μm的小颗粒组成，进一步可选地由平均体积粒径D v50为0.05-0.15μm的小颗粒组成。
在一些实施方式中，所述含硅化合物添加剂还可包含含量为0-40％的1μm<D v50≤2μm的中颗粒和含量为0-10％的2μm＜Dv50≤10μm的大颗粒，各自基于含硅化合物添加剂的总重量计。由此调整涂层孔隙结构，避免过多小粒径含硅化合物添加剂团聚造成电解液浸润不良以及锂离子传输性能恶化。
在一些实施方式中，在所述含硅化合物添加剂包含中颗粒的情况下，中颗粒与小颗粒的含量比例为1:2:8，可选为1：3-5，基于两者颗粒的重量计。
在一些实施方式中，在所述含硅化合物添加剂包含大颗粒的情况下，大颗粒与小颗粒的含量比例为1:5-13，可选为1:8-10，基于两者颗粒的重量计。
在一些实施方式中，在所述含硅化合物添加剂同时包含大颗粒和小颗粒的情况下，大颗粒、中颗粒与小颗粒的含量比例为1:(1.1-4):(4.5-11)，可选为1:(1.5-2.5):(6-8)，基于两者颗粒的重量计。
在一些实施方式中，所述含硅化合物添加剂的D v99为小于20μm，可选为小于10μm。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在本申请中，D v50为从小粒径开始样品的体积累计分布百分数达到50％时对应的粒径，也称为平均体积粒径；D v90为从小粒径开始样品的体积累计分布百分数达到90％时对应的粒径；D v99为从小粒径开始样品的体积累计分布百分数达到99％时对应的粒径。
上述材料的粒径尺寸为本领域公知的含义，其是以采用激光粒度分析仪测定材料的体积粒径及其分布，例如采用英国马尔文仪器有限公司的Mastersizer 3000型激光粒度分析仪。
在一些实施方式中，所述含硅化合物添加剂可包括硅酸盐或氟硅酸盐，例如可包含硅酸钾、硅酸钠、硅酸锂、硅酸铝、氟硅酸锂、氟硅酸钾或氟硅酸钠中的至少一种，可选为硅酸钾或硅酸锂。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在一些实施方式中，所述含硅化合物添加剂的含量为0.2％-2％，可选为0.5％-1％，基于所述正极膜层的重量计。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在一些实施方式中，所述含硅化合物添加剂与所述正极活性材料的重量比为0.0125％-2.5％，可选为0.5％-1.1％。由此，更快地与电解液中的氟化氢反应，从而降低电池的直流内阻(DCR)，改善电池的循环性能。
在一些可选的实施方式中，所述含硅化合物添加剂附着在所述正极活性材料颗粒表面，作为所述正极活性材料颗粒表面的涂层存在。
在一些实施方式中，所述含硅化合物添加剂颗通过以下方式添加在正极膜层中：(1)将所述含硅化合物添加剂事先与活性材料物物理混合，然后制备成正极浆料；(2)将所述含硅化合物添加剂分散液直接加入正极浆料；(3)将所述含硅化合物添加剂直接析出沉积在正极材料表面，然后制备正极浆料(优选，后续要烧结，结合更牢靠、 颗粒更均匀)；及(4)将所述含硅化合物添加剂均匀涂覆在正极活性材料层远离正极集流体一侧的表面上形成含硅化合物涂层，在这种情况下，所述正极膜层包含正极活性材料层和设置在所述正极活性材料层接触隔离膜一侧的表面上的含硅化合物涂层，所述含硅化合物涂层厚度为1-10um，所述正极活性材料层的厚度为50-150um，所述含硅化合物涂层厚度与所述正极活性材料层的厚度的比值为0.67％-20％。
在一些实施方式中，所述正极活性材料的平均体积粒径Dv50为20-100nm。所述含硅化合物的Dv50与正极活性材料的平均体积粒径的比值为1：20-100，可选为1:30-50。
在一些实施方式中，正极极片的厚度为100-250um，孔隙率为20％-35％。所述正极极片的厚度为正极集流体的厚度与正极膜层(也称为正极活性材料层)的厚度之和。
在一些实施方式中，本申请的第二方面提供一种制备正极极片的方法，其包括，
(1)提供含硅化合物添加剂；
(2)将所述含硅化合物添加剂与正极活性材料、溶剂混合，制备正极浆料；
(3)将所述正极浆料涂覆在正极集流体上，形成正极膜层，得到所述正极极片；
所述含硅化合物添加剂为式mM xQ·nSi yQ z，其中
M为碱金属、碱土金属、Al、Fe、Zn元素中的一种或者多种；
Q为O、F、Cl、Br、I、At元素中的一种或多种；
x值取决于M；
y、z值取决于Q；
m、n为正整数；
所述含硅化合物添加剂包含平均体积粒径D v50为0.01-1μm的小颗粒。
由此，本申请的方法添加含硅化合物添加剂的方式简单，成本低廉，便于大规模生产应用，所得的正极极片包含特定粒径的含硅化合物添加剂，能有效地消耗电极液中存在的氟化氢，同时降低电池的直流内阻(DCR)，改善电池的循环性能。
在一些实施方式中，在步骤(1)中，提供含硅化合物添加剂可采用市售的含硅化合物，或者通过本领域技术人员已知的方法制备。
在一些实施方式中，在步骤(1)中，可通过气流破碎法、重析出法制备含硅化合物添加剂。由此，所述含硅化合物添加剂合成路径简单，成本低廉，结构稳定，能更好地应用到本申请的电池中。
大部分的市售的含硅化合物的平均体积粒径D v50通常为50-100μm，这对于本申请 来说，颗粒粒径过大。
在一些实施方式中，可采用气流破碎法制备本申请所述粒径的含硅化合物添加剂。所述气流破碎法包括将市售的含硅化合物通过气流粉碎机在0.7-1MPa的气压下在3-20m3/min的气体流量下进行破碎，分级筛选后将颗粒的平均体积粒径调控至所需的水平。
在一些实施方式中，可采用重析出法制备本申请所述粒径的含硅化合物添加剂。所述重析出法包括在室温下将市售的含硅化合物添加剂用溶剂1溶解，搅拌均匀，配置成含硅化合物浓度为1wt％-10wt％的溶液1；随后在400-800rpm转速的搅拌的同时将溶液1加入所述含硅化合物微溶或难溶的溶剂2中，配置成溶液2，溶液2浓度为5wt％-20wt％，搅拌过程中含硅化合物添加剂重新析出，可将颗粒的平均体积粒径调控至所需的水平。
在一些实施方式中，溶剂1通常为能够在室温下溶解所述含硅化合物的任何物质，例如包括但不限于去离子水。所述溶剂2可为本领域技术人员已知的与所述含硅化合物微溶或不相溶的物质，例如包括但不限于无水乙醇、N-甲基吡咯烷酮(NMP)、丙酮、四氯化碳等有机溶剂。
在一些实施方式中，步骤(2)包括将所述含硅化合物添加剂与正极活性材料、溶剂和任选的粘结剂或其他添加剂混合，制备正极浆料。
在一些实施方式中，在步骤(2)中，可采用沉积法将本申请所述粒径的含硅化合物添加剂沉积在正极活性材料表面。
在一些实施方式中，在步骤(2)中，所述沉积法包括将所述含硅化合物添加剂溶解在溶剂A配成溶液A；并将正极活性材料分散在溶剂B配置成溶液B；然后将溶液A与溶液B混合，使得含硅化合物添加剂沉积在正极活性材料表面。由此，所述含硅化合物添加剂合成路径简单，成本低廉，结构稳定，能更好地应用到本申请的电池中。
在一些实施方式中，在溶液A中所述含硅化合物添加剂的浓度为1重量％-10重量％；在溶液B中所述正极活性材料的浓度为5重量％-20重量％。由此，所述含硅化合物添加剂合成路径简单，成本低廉，结构稳定，能更好地应用到本申请的电池中。
在一些实施方式中，溶剂A通常为能够在室温下溶解所述含硅化合物的任何物质，例如包括但不限于去离子水。
在一些实施方式中，含硅化合物添加剂在室温和常压下在溶剂B中的溶解度小于 1g/100g。由此，所述含硅化合物添加剂合成路径简单，成本低廉，结构稳定，能更好地应用到本申请的电池中。
在一些实施方式中，所述溶剂B可为本领域技术人员已知的与所述含硅化合物微溶或不溶并且与正极活性材料难溶甚至不溶的物质，例如包括但不限于无水乙醇、NMP、丙酮、四氯化碳等有机溶剂。
在本申请中，术语“微溶”是指在室温和常压下，溶质在每100克溶剂中的溶解度为0.01克至1克。
在本申请中，术语“难溶”是指在室温和常压下，溶质在每100克溶剂中的溶解度小于0.01克。
在一些可选的实施方式中，所述沉积法包括将所述含硅化合物添加剂溶解在溶剂A配成含硅化合物添加剂浓度为1wt％-10wt％的溶液A；并将正极活性材料分散在溶剂B配置成溶液B；然后将溶液A加入至溶液B中，搅拌混合，使得含硅化合物添加剂沉积在正极活性材料表面，过滤，然后优选空气或惰性气氛中在300-500℃下烧结，得到所需平均体积粒径水平的所述含硅化合物添加剂附着在正极活性材料表面的产品。所述沉积法类似于重析出法，不同之处在于析出的含硅化合物添加剂直接沉积在正极活性材料颗粒的表面，所述含硅化合物添加剂呈球状的小颗粒，在正极活性材料颗粒表面分布均匀。
在一些实施方式中，在步骤(2)中所述溶剂通常可为N-甲基吡咯烷酮(NMP)。
在一些实施方式中，在步骤(2)中所述正极浆料固含量为40-80wt％，室温下的粘度为5000-25000mPa·s。
在一些实施方式中，在步骤(3)中，将所述正极浆料通过涂覆在正极集流体上，干燥，形成正极膜层，然后经过冷轧机冷压得到所述正极极片。
在一些实施方式中，正极膜层单位面密度为40-350g/m2，正极极片压实密度为2.0-3.6g/cm3，可选为3.3-3.5g/cm3。
所述压实密度的计算公式为
压实密度＝单位面密度/(挤压后极片厚度-集流体厚度)。
单位面积正极膜层中正极活性物质的质量M的可使用标准天平称量得到。
所述正极膜层的厚度T可采用万分尺测量得到，例如可使用型号为Mitutoyo293-100、精度为0.1μm的万分尺测量得到。需要说明的是，本发明所述的正极膜层厚度是 指经冷压压实后并用于组装电池的正极极片中的正极膜层的厚度。
本申请的第三方面提供一种二次电池，其特征在于，
包括本申请的第一方面所述的正极极片或根据本申请的第二方面所述的方法制备的正极极片。
所述二次电池为锂离子二次电池钠离子二次电池。
在一些实施方式中，所述二次电池在25℃下的初始直流内阻(DCR)为1-1.7Ω，可选为1.05-1.35Ω；25℃下循环1000圈后DCR为2.4-3.8Ω，可选为2.6-3.0Ω。
本申请的第四方面提供一种用电装置，其特征在于，包括本申请的第三方面所述的二次电池。
以下适当参照附图对本申请的二次电池和用电装置进行说明。
除非特别说明，否则提及的电池的组件、材料种类或含量同时适用于锂离子二次电池和钠离子二次电池。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、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。
正极极片
正极极片为本申请第一方面的正极极片。
所述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，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形成在高分子材料基材上而形成。其中，金属材料包括但不限于铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等。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)
在一些实施方式中，正极活性材料可包含本领域公知的用于电池的正极活性材料。
作为示例，锂离子二次电池的正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
作为示例，钠离子二次电池的正极活性材料可包括以下材料中的至少一种：钠过渡金属氧化物、聚阴离子型化合物和普鲁士蓝类化合物中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作钠离子电池正极活性材料的传统公知的材料。
作为本申请可选的技术方案，钠过渡金属氧化物中，过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。钠过渡金属氧化物例如为Na xMO 2，其中M为Ti、V、Mn、Co、Ni、Fe、Cr及Cu中的一种或几种，0＜x≤1。
作为本申请可选的技术方案，聚阴离子型化合物可以是具有钠离子、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。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可以是P、S及Si中的至少一种；n表示(YO 4) n-的价态。
聚阴离子型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。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可以是P、S及Si中的至少一种，n表示(YO 4) n-的价态；卤素可以是F、Cl及Br中的至少一种。
聚阴离子型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P、S及Si中的至少一种，n表示(YO 4) n-的价态；Z表示过渡金属，可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种，m表示(ZO y) m+的价态；卤素可以是F、Cl及Br中的至少一种。
聚阴离子型化合物例如是NaFePO 4、Na 3V 2(PO4) 3(磷酸钒钠，简称NVP)、Na 4Fe 3(PO 4) 2(P 2O 7)、NaM’PO4F(M’为V、Fe、Mn及Ni中的一种或几种)及Na 3(VO y) 2(PO 4) 2F 3-2y(0≤y≤1)中的至少一种。
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。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。普鲁士蓝类化合物例如为Na aMe bMe’ c(CN) 6，其中Me及Me’各自独立地为Ni、Cu、Fe、Mn、Co及Zn中的至少一种，0＜a≤2，0＜b＜1，0＜c＜1。
所述正极活性材料在正极膜层中的重量比为80-100重量％，基于正极膜层的总重量计。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(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-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。所述粘结剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。
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至少一种。所述导电剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。
负极极片
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。
作为示例，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。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形成在高分子材料基材上而形成。其中，金属材料包括但不限于铜、铜合金、镍、镍合金、钛、钛合金、银及 银合金等，高分子材料基材包括但不限于聚丙烯(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)等基材。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。
作为示例，锂离子二次电池的负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
作为示例，钠离子二次电池的负极活性材料通常为硬碳材料，二维金属碳化物或氮化物。优选钠离子二次电池的负极活性材料通常为硬碳材料。
所述负极活性材料在负极膜层中的重量比为70-100重量％，基于负极膜层的总重量计。
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。所述粘结剂在负极膜层中的重量比为0-30重量％，基于负极膜层的总重量计。
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。所述导电剂在负极膜层中的重量比为0-20重量％，基于负极膜层的总重量计。
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。所述其他助剂在负极膜层中的重量比为0-15重量％，基于负极膜层的总重量计。
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，其中所述负极浆料固含量为30-70wt％，室温下的粘度调整到2000-10000mPa·s；将所得到的负极浆料涂覆在负极集流体上，经过干燥工序，冷压例如对辊，得到负极极片。负极粉末涂布单位面密度为50-150g/m 2，负极极片压实 密度1.2-2.0g/m 3；负极极片的厚度为50-200um，其中负极集流体例如铝箔的厚度为5-10um。
单位面积负极膜层中负极活性物质的质量M的可使用标准天平称量得到。
所述负极膜层或极片的厚度T可采用万分尺测量得到，例如可使用型号为Mitutoyo293-100、精度为0.1μm的万分尺测量得到。需要说明的是，本发明所述的负极膜层厚度是指经冷压压实后并用于组装电池的负极极片中的负极膜层的厚度。在本申请中，所提及“厚度”可采用上述同样的方式测量。
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具体的限制，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盐和溶剂。
在一些实施方式中，锂离子二次电池的电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
钠离子二次电池的电解质盐可选自六氟磷酸钠、双氟磺酰亚胺钠、双三氟甲烷磺酰亚胺钠、三氟甲磺酸钠、四氟硼酸钠、二氟磷酸钠、高氯酸钠、氯化钠中的一种或几种。
所述电解质盐的浓度通常为0.5-5mol/L。
在一些实施方式中，溶剂可选自氟代碳酸乙烯酯(FEC)、碳酸亚乙酯(EC)、碳酸亚丙基酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，所述电解液还可选地包括其他添加剂。例如其他添加剂可以 包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
隔离膜
在一些实施方式中，二次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。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。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，所述隔离膜的厚度为5-20μm，可选为5-15μm。
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，二次电池可包括外包装。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，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次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。
本申请对二次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二次电池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。二次电池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具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
在电池模块中，多个二次电池5可以是沿电池模块的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5 进行固定。
可选地，电池模块还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
在电池包中可以包括电池箱和设置于电池箱中的多个电池模块。电池箱包括上箱体和下箱体，上箱体能够盖设于下箱体，并形成用于容纳电池模块的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包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(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、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)、电气列车、船舶及卫星、储能系统等，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二次电池、电池模块或电池包。
图4是作为一个示例的用电装置。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二次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，可以采用二次电池作为电源。
实施例
为了使本申请所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图对本申请进行进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其他实施例都属于本申请保护的范围。
实施例中未注明具体技术或条件的，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。
一、正极极片的制备
制备实施例1
(1)提供500g的市售的硅酸钾(麦克林试剂网购买，CAS号1312-76-1，货号P850160，D v50平均粒径70um)；
(2i)将上述10g的市售的硅酸钾加入到190g的去离子水中，搅拌溶解，配成硅酸钾浓度为5wt％的溶液A；并将2kg的平均体积粒径为5um的正极活性材料LiMn 0.5Ni 0.3Co 0.2O 2物质分散在1800g的溶剂NMP中，配置成溶液B；然后在800rpm转速的搅拌的同时，将溶液A加入至溶液B中，搅拌混合，在溶液A加入的同时硅酸钾添加剂重新沉积出来，使得硅酸钾添加剂沉积在正极活性材料表面；用抽滤设备抽真空，在常温下抽滤干燥后，然后在氮气中在500℃温度下烧结4h，得到沉积在所述正极活性材料表面的平均体积粒径为200nm的硅酸钾颗粒。
(2ii)将上述步骤(2)制备的产物(表面沉积有平均体积粒径为200nm的硅酸钾颗粒的正极活性材料)、导电炭黑SP及粘结剂PVDF按照重量比98:1:1分散至溶剂NMP中进行混合均匀，得到正极浆料；
(3)将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压后，得到正极极片，其单位面积的涂覆量为0.27g/1540.25mm 2。其中正极极片的厚度为150um。
产品相关参数汇总于表1中。
制备实施例2
重复制备实施例1的步骤，其不同之处在于在步骤(2i)中溶液A中含硅化合物的浓度为1wt％，混合后溶液总浓度依旧为10wt％。得到沉积在所述正极活性材料表面的平均体积粒径为100nm的硅酸钾颗粒。
制备实施例3
重复制备实施例1的步骤，其不同之处在于在步骤(2i)中溶液A中含硅化合物的浓度为10wt％，，得到沉积在所述正极活性材料表面的平均体积粒径为500nm的硅酸钾颗粒。
制备实施例4
重复制备实施例1的步骤，其不同之处在于在步骤(2i)中溶液A中含硅化合物的 浓度为0.5wt％，，得到沉积在所述正极活性材料表面的平均体积粒径为50nm的硅酸钾颗粒。
制备实施例5
重复制备实施例1的步骤，其不同之处在于在步骤(2i)中溶液A中含硅化合物的浓度为5％，溶剂B的用量为800g；得到沉积在所述正极活性材料表面的平均体积粒径为1um的硅酸钾颗粒。
制备实施例6
重复制备实施例1的步骤，其不同之处在于在步骤(2i)中溶液A中含硅化合物的浓度为15％，溶剂B的用量为600g；得到沉积在所述正极活性材料表面的平均体积粒径为2um的硅酸钾颗粒。
制备实施例7
重复制备实施例1的步骤，其不同之处在于在步骤(1)中提供市售的氟硅酸钾(麦克林试剂网购买，CAS号16871-90-2，货号P816423，D v50平均粒径150um)。
制备实施例8
重复制备实施例1的步骤，其不同之处在于在步骤(1)中提供市售的硅酸钠(麦克林试剂网，CAS号1344-09-8，货号S871944，Dv50平均粒径150um)
制备实施例9
重复制备实施例1的步骤，其不同之处在于在步骤(1)中提供市售的硅酸铝(麦克林试剂网，CAS号1302-93-8，货号A823215，Dv50平均粒径6.5um)
制备实施例10
重复制备实施例1的步骤，其不同之处在于在步骤(2i)中正极活性材料为Na 2FePO 4。
制备实施例11
将硅酸钾粉末(组成如表1所示)分散在NMP溶液中后超声均匀配置成浓度为10％的硅酸钾分散液。按照正极活性材料、硅酸钾分散液、导电炭黑SP及粘结剂PVDF的添加顺序，按照重量比97:1:1:1分散至溶剂NMP中进行混合均匀，得到正极浆料。
制备实施例12
(1)将正极活性材料LiMn 0.5Ni 0.3Co 0.2O 2、导电炭黑SP及粘结剂PVDF按照重量比98:1:1分散至溶剂NMP中进行混合均匀，得到正极浆料；
(2)将Dv50为200nm、1um及5um的硅酸钾粉末按照重量7：2：1的配比，分散至溶剂NMP中，同时加入2％粘结剂PVDF，搅拌均匀后得到硅酸钾浆料；
(3)将正极浆料均匀涂布于正极集流体铝箔上，烘干后再将硅酸钾浆料均匀涂覆再正极活性材料层表面，冷压后，得到正极极片，其单位面积的涂覆量为0.27g/1540.25mm 2。
正极活性材料层的厚度为150um，硅酸钾层的厚度为10um。
对比例1
(1)将正极活性材料LiMn 0.5Ni 0.3Co 0.2O 2、导电炭黑SP及粘结剂PVDF按照重量比98:1:1分散至溶剂NMP中进行混合均匀，得到正极浆料；
(2)将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压后，得到正极极片，其单位面积的涂覆量为0.27g/1540.25mm 2。其中正极膜层厚度为150um。
对比例2
将粒径均≥1um的硅酸钾粉末(组成如表1所示)分散在NMP溶液中后超声均匀配置成浓度为10％的硅酸钾分散液。按照正极活性材料、硅酸钾分散液、导电炭黑SP及粘结剂PVDF的添加顺序，按照重量比97:1:1:1分散至溶剂NMP中进行混合均匀，得到正极浆料。
将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压后，得到正极极片，其单位面积的涂覆量为0.27g/1540.25mm 2。
对比例3
将小颗粒仅占20％的硅酸钾粉末(组成如表1所示)分散在NMP溶液中后超声均匀配置成浓度为10％的硅酸钾分散液。按照正极活性材料、硅酸钾分散液、导电炭黑SP及粘结剂PVDF的添加顺序，按照重量比97:1:1:1分散至溶剂NMP中进行混合均匀，得到正极浆料。
将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压后，得到正极极片，其单位面积的涂覆量为0.27g/1540.25mm 2。
对比例4
重复制备实施例1的步骤，其不同之处在于(i)在步骤(1)中，在室温下将10g市售的硅酸钾加入190g去离子水中，溶解搅拌均匀，转速400rpm；取1800g无水乙醇进行搅拌，转速800rpm，边搅拌边向其中滴入硅酸钾溶液，硅酸钾逐渐析出；连续搅 拌0.5h后，将溶液进行抽滤干燥，得到硅酸钾；(ii)不进行步骤(2i)；(iii)在步骤(2ii)中将上述制得的硅酸钾和正极活性材料LiMn 0.5Ni 0.3Co 0.2O 2物质、导电炭黑SP及粘结剂PVDF按照重量比1:97:1:1分散至溶剂NMP中进行混合均匀，得到正极浆料。
对比例5
重复对比例4的步骤，其不同之处在于在步骤(1)中，在室温下将2kg市售的硅酸钾加入气流粉碎机中在1MPa的气压下，在10m 3/min的气流下破碎2h，得到硅酸钾颗粒。
各实施例和对比例的不同的产品参数详见表1。
表1各制备实施例和对比例的正极极片中含硅化合物的相关参数
Figure PCTCN2022128964-appb-000001
Figure PCTCN2022128964-appb-000002
二、应用实施例
实施例1
1)正极极片的制备
使用制备实施例1的正极极片。
2)负极极片的制备
将负极活性材料石墨、增稠剂羧甲基纤维素钠、粘接剂丁苯橡胶、导电剂乙炔黑，按照质量比97:1:1:1进行混合，加入去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在铜箔上；将铜箔在室温晾干后转移至120℃烘箱干燥1h，然后过冷压、分切得到负极片，其单位面积的涂覆量为0.17g/1540.25mm 2。
3)隔离膜
选用12μm厚的聚丙烯隔离膜(Celgard公司提供)。
4)电解液的制备
有机溶剂为含有碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)的混液，其中，EC、EMC和DEC的体积比为20:20:60。在含水量<10ppm的氩气气氛手套箱中，将充分干燥的锂盐LiPF6溶解于有机溶剂中，混合均匀，获得电解液。其中，锂盐的浓度为1mol/L。
5)电池的制备
将正极片、隔离膜、负极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，再卷绕成方形的裸电芯后，装入铝塑膜，然后在80℃下烘烤除水后，注入150g相应的非水电解液、封口，经静置、热冷压、化成、夹具、分容等工序后，得到容量为50Ah的成品电池。
实施例2-12的二次电池和对比例1-3的二次电池与实施例1的二次电池制备方法相似，但是使用对应的制备实施例的正极极片。
三、电池性能测试
1.直流内阻测试
调整电池容量至50％SOC：在25℃环境中，以固定倍率1/3C对锂离子电池进行充放电(1C＝电池额定容量)，充放电电压区间为2.5-4.35V，重复此步骤三次，所取第三次放电容量记为电池标称容量Cn，以1/3Cn开始充电至标称容量一半，调整电池SOC状态为50％SOC；
在25℃环境中，将如上电池，采用4Cn放电30s，记录放电前后电压值，分别为V0和V1，(V0-V1)/4Cn记为25℃对应电池初始内阻值DCR。
注：阻值基于实施例1的电芯进行测量，不同模式的电芯阻值不同。
2.循环寿命及循环DCR测试：
测试温度为25，以1Cn恒流充电到4.35V，恒压充电到0.05Cn，静置30分钟后以0.33Cn放电到2.5V。以此步得到的容量为初始容量，进行1Cn充电/0.33Cn放电进行循环测试，以每一步的容量与初始容量做比值记为容量保持率。以25循环截至到容量保持率为85％的圈数记为锂离子电池的循环寿命性能。循环过程中，每循环1000圈测试对应循环温度下直流内阻。
四、各实施例、对比例测试结果
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表2。
表2各实施例和对比例的电池性能
编号 25℃下初始DCR/Ω 25℃循环1000圈后DCR/Ω 循环圈数
1 1.32 2.9337 1935
2 1.2 2.667 2010
3 1.44 3.2004 1875
4 1.08 2.4003 2100
5 1.488 3.30708 1800
6 1.632 3.62712 1725
7 1.392 3.09372 1830
8 1.536 3.41376 1770
9 1.728 3.84048 1680
10 1.43 2.9337 2000
11 1.392 3.09372 1890
12 1.248 2.77368 1950
对比例1 2.4 5.67 1500
对比例2 2.208 4.90728 1620
对比例3 2.04 4.5339 1650
对比例4 2.2272 4.949952 1620
对比例5 2.244 4.98729 1575
由表1和表2可知，在含硅化合物添加剂包含小颗粒并且小颗粒的平均体积粒径D V50更小的情况下，本发明的电池具有良好的技术效果，例如，25℃循环1000圈后电池的DCR可达到2.67Ω，容量保持率降至80％时的电池的循环圈数甚至可达到2000圈以上，与不添加含硅化合物添加剂的对比例1相比，循环寿命提高30％以上。
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。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。

Claims (14)

  1. 一种正极极片，其包括正极集流体以及设置在所述正极集流体的至少一侧的正极膜层，所述正极膜层包含正极活性材料和式mM xQ·nSi yQ z含硅化合物添加剂，其中
    M为碱金属、碱土金属、Al、Fe、Zn元素中的一种或者多种；
    Q为O、F、Cl、Br、I、At元素中的一种或多种；
    x值取决于M；
    y、z值取决于Q；和
    m、n为正整数；
    含硅化合物所述含硅化合物添加剂包含平均体积粒径D v50为0.01-1μm的小颗粒。
  2. 根据权利要求1所述的正极极片，其特征在于，平均体积粒径Dv50为0.01μm-1μm的小颗粒的含量为50％-100％，基于含硅化合物添加剂的总重量计。
  3. 根据权利要求1或2所述的正极极片，其特征在于，所述含硅化合物添加剂包含含量为0-40％的1μm<D v50≤2μm的中颗粒和含量为0-10％的2μm＜D v50≤10μm的大颗粒，各自基于含硅化合物添加剂的总重量计。
  4. 根据权利要求1-3中任一项所述的正极极片，其特征在于，所述含硅化合物添加剂的D v99为小于20μm。
  5. 根据权利要求1-4中任一项所述的正极极片，其特征在于，所述含硅化合物添加剂包含硅酸钾、硅酸钠、硅酸锂、硅酸铝、氟硅酸锂、氟硅酸钾或氟硅酸钠中的至少一种。
  6. 根据权利要求1-5中任一项所述的正极极片，其特征在于，所述含硅化合物添加剂的含量为0.2％-2％，基于所述正极膜层的重量计。
  7. 根据权利要求1-6中任一项所述的正极极片，其特征在于，所述含硅化合物添加剂与所述正极活性材料的重量比为0.25-2.5:1。
  8. 一种制备正极极片的方法，其包括，
    (1)提供含硅化合物添加剂；
    (2)将所述含硅化合物添加剂与正极活性材料、溶剂混合，制备正极浆料；
    (3)将所述正极浆料涂覆在正极集流体上，形成正极膜层，得到所述正极极片；所述含硅化合物添加剂为式mM xQ·nSi yQ z，其中
    M为碱金属、碱土金属、Al、Fe、Zn元素中的一种或者多种；
    Q为O、F、Cl、Br、I、At元素中的一种或多种；
    x值取决于M；
    y、z值取决于Q；和
    m、n为正整数；
    所述含硅化合物添加剂包含平均体积粒径D v50为0.01-1μm的小颗粒。
  9. 根据权利要求8所述的方法，其特征在于，在步骤(1)中，可通过气流破碎法或重析出法制备含硅化合物添加剂。
  10. 根据权利要求8或9所述的方法，其特征在于，在步骤(2)中，可利用沉积法将所述含硅化合物添加剂沉积在正极活性材料表面；其中所述沉积法包括将所述含硅化合物添加剂溶解在溶剂A配成溶液A；并将正极活性材料分散在溶剂B配置成溶液B；然后将溶液A与溶液B混合，使得含硅化合物添加剂沉积在正极活性材料表面。
  11. 根据权利要求10所述的方法，其特征在于，在溶液A中所述含硅化合物添加剂的浓度为1重量％-10重量％；在溶液B中所述正极活性材料的浓度为5重量％-20重量％。
  12. 根据权利要求10或11所述的方法，其特征在于，含硅化合物添加剂在室温和常压下在溶剂B中的溶解度小于1g/100g。
  13. 一种二次电池，其特征在于，
    包括权利要求1-7中任一项所述的正极极片或根据权利要求8-12中任一项所述的方法制备的正极极片。
  14. 一种用电装置，其特征在于，包括权利要求13所述的二次电池。
PCT/CN2022/128964 2022-11-01 2022-11-01 正极极片、制法、二次电池和用电装置 WO2024092501A1 (zh)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013073832A (ja) * 2011-09-28 2013-04-22 Cosmo Oil Co Ltd リチウムイオン二次電池用正極活物質
JP2017228435A (ja) * 2016-06-22 2017-12-28 日立化成株式会社 リチウムイオン二次電池
JP2018110065A (ja) * 2016-12-28 2018-07-12 株式会社半導体エネルギー研究所 活物質粒子、および活物質粒子を有する正極、および正極を有する蓄電装置およびその作製方法
CN108780889A (zh) * 2016-03-30 2018-11-09 松下知识产权经营株式会社 非水电解质二次电池用正极活性物质和非水电解质二次电池
CN111162247A (zh) * 2018-11-07 2020-05-15 宁德时代新能源科技股份有限公司 正极极片及锂离子二次电池

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013073832A (ja) * 2011-09-28 2013-04-22 Cosmo Oil Co Ltd リチウムイオン二次電池用正極活物質
CN108780889A (zh) * 2016-03-30 2018-11-09 松下知识产权经营株式会社 非水电解质二次电池用正极活性物质和非水电解质二次电池
JP2017228435A (ja) * 2016-06-22 2017-12-28 日立化成株式会社 リチウムイオン二次電池
JP2018110065A (ja) * 2016-12-28 2018-07-12 株式会社半導体エネルギー研究所 活物質粒子、および活物質粒子を有する正極、および正極を有する蓄電装置およびその作製方法
CN111162247A (zh) * 2018-11-07 2020-05-15 宁德时代新能源科技股份有限公司 正极极片及锂离子二次电池

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