WO2024087055A1 - 正极极片、电极组件、电池单体、电池及用电设备 - Google Patents

正极极片、电极组件、电池单体、电池及用电设备 Download PDF

Info

Publication number
WO2024087055A1
WO2024087055A1 PCT/CN2022/127692 CN2022127692W WO2024087055A1 WO 2024087055 A1 WO2024087055 A1 WO 2024087055A1 CN 2022127692 W CN2022127692 W CN 2022127692W WO 2024087055 A1 WO2024087055 A1 WO 2024087055A1
Authority
WO
WIPO (PCT)
Prior art keywords
positive electrode
functional layer
active material
material layer
battery
Prior art date
Application number
PCT/CN2022/127692
Other languages
English (en)
French (fr)
Inventor
许宝云
付成华
欧阳少聪
林运美
Original Assignee
宁德时代新能源科技股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to PCT/CN2022/127692 priority Critical patent/WO2024087055A1/zh
Publication of WO2024087055A1 publication Critical patent/WO2024087055A1/zh

Links

Images

Classifications

    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/139—Processes of manufacture

Definitions

  • the present application relates to the field of battery technology, and in particular to a positive electrode sheet, an electrode assembly, a battery cell, a battery and an electrical device.
  • the present application provides a positive electrode plate, an electrode assembly, a battery cell, a battery and an electrical device, which can improve the problem of long charging time of the battery cell at low temperature.
  • an embodiment of the present application provides a positive electrode plate, comprising a positive electrode current collector, a positive electrode active material layer located on the surface of the positive electrode current collector, and a functional layer connected to the positive electrode active material layer; under the condition of a temperature ⁇ 0°C, the resistivity of the functional layer is greater than the resistivity of the positive electrode active material layer.
  • a functional layer with a relatively large resistivity at low temperature is provided in the positive electrode plate.
  • the charging voltage deviates more from the equilibrium potential, which can accelerate polarization heat generation, thereby causing the battery cell to heat up more quickly, which is beneficial to quickly increase the charging rate window of the battery cell and effectively shorten the low-temperature charging time while keeping the surface of the negative electrode plate free of lithium deposition.
  • R1 and R2 satisfy the relationship of 1.2 ⁇ (R2+R1)/R1 ⁇ 2, that is, 0.2 ⁇ R2/R1 ⁇ 1, indicating that the resistance of the positive electrode active material layer at low temperature and the resistance of the functional layer at low temperature have a suitable relative size relationship, so that the functional layer has a more suitable polarization ability at low temperature, and while the functional layer effectively improves the polarization to shorten the low-temperature charging time, it avoids excessive polarization of the functional layer to affect the capacity and energy density of the battery cell.
  • the volume of the positive electrode active material layer is V1
  • the volume of the functional layer is V2, and 0.05 ⁇ V2/V1 ⁇ 0.2.
  • V1 and V2 satisfy the relationship of 0.05 ⁇ V2/V1 ⁇ 0.2, indicating that the volume of the positive electrode active material layer and the volume of the functional layer have a suitable relative size relationship, so that the functional layer can generate suitable heat by increasing polarization at low temperatures, and while the functional layer effectively shortens the low-temperature charging time, it avoids excessive heat generated by the functional layer to cause energy loss of the battery cell.
  • the resistivity of the functional layer is less than the resistivity of the positive electrode active material layer.
  • the resistivity of the functional layer at room temperature is less than the resistance of the positive electrode active material layer at room temperature, that is, the polarization heat generation capacity of the functional layer is smaller than that of the positive electrode active material layer at room temperature, which is beneficial to reduce the energy loss caused by the functional layer to the battery cell at room temperature.
  • the resistance of the positive electrode active material layer is R3, the resistance of the functional layer is R4, and R4 ⁇ 0.2 ⁇ R3.
  • the resistance of the functional layer at room temperature is significantly lower than the resistance of the positive electrode active material layer at room temperature, which is conducive to better reducing the energy loss caused by the functional layer to the battery cell at room temperature.
  • the functional layer is a negative temperature coefficient coating.
  • the functional layer is configured in the form of a negative temperature coefficient coating, so that the functional layer can better take into account the characteristics of high resistance at low temperatures and low resistance at room temperature; at the same time, the coating is easy to prepare and is conducive to stable connection to the positive electrode active material layer.
  • the functional layer includes at least one of P(VDF-HFP), PAN and PEO.
  • the functional layer has a specific composition that can easily form a negative temperature coefficient coating.
  • the functional layer satisfies at least one of the following conditions (a1) and (a2); (a1) the porosity of the functional layer is 70% to 85%; (a2) more than 70% of the pores in the functional layer have a pore size distribution of 0.1 ⁇ m to 1 ⁇ m.
  • the functional layer has a specific porosity, which can provide a suitable number of channels for metal ions; the pore sizes of most of the pores in the functional layer are distributed in a specific range, which can provide channels of suitable sizes for metal ions.
  • the positive electrode current collector, the positive electrode active material layer and the functional layer are sequentially arranged along the thickness direction of the positive electrode sheet.
  • the functional layer is connected to the side of the positive electrode active material layer away from the positive electrode current collector, so that the positive electrode active material layer is directly connected to the positive electrode current collector to maintain a good conductive connection; at the same time, the functional layer is connected to the positive electrode active material layer, and compared with connecting the functional layer to the positive electrode current collector, the functional layer also has better connection stability and can effectively avoid falling off.
  • an embodiment of the present application provides an electrode assembly, including a negative electrode plate, a separator, and a positive electrode plate as described in the above embodiment.
  • an embodiment of the present application provides a battery cell, comprising a housing and an electrode assembly as described in the above embodiment; the electrode assembly is accommodated in the housing.
  • an embodiment of the present application provides a battery, comprising a battery cell as described in the above embodiment.
  • an embodiment of the present application provides an electrical device, including a battery cell as in the above embodiment or a battery as in the above embodiment.
  • FIG. 1 is a schematic diagram of the structure of a vehicle provided in some embodiments of the present application.
  • FIG2 is an exploded view of a battery provided in some embodiments of the present application.
  • FIG3 is an exploded view of a battery cell provided in some embodiments of the present application.
  • FIG4 is a schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application.
  • FIG5 is a cross-sectional view of a first positive electrode sheet provided in some embodiments of the present application.
  • FIG6 is a cross-sectional view of a second positive electrode sheet provided in some embodiments of the present application.
  • FIG7 is a cross-sectional view of a third positive electrode sheet provided in some embodiments of the present application.
  • FIG8 is a cross-sectional view of a fourth positive electrode sheet provided in some embodiments of the present application.
  • FIG9 is a cross-sectional view of a fifth positive electrode plate provided in some embodiments of the present application.
  • 100-battery module 200-controller; 300-motor;
  • orientations or positional relationships indicated by the technical terms “inside” and “outside” are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.
  • Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding.
  • Power batteries store and release energy through the migration of metal ions between the positive and negative electrodes.
  • the migration of metal ions between the positive and negative electrodes is greatly affected by temperature.
  • the kinetic conditions of the positive and negative electrodes deteriorate, coupled with factors such as increased electrolyte viscosity and decreased conductivity, which leads to a sharp deterioration in battery performance at low temperatures, resulting in problems such as long charging time.
  • the applicant has discovered through in-depth research that by adding a functional layer 2213 with high impedance at low temperatures in the positive electrode plate 221, the charging voltage deviates more from the equilibrium potential during rapid hot charging, which can accelerate polarization heat generation, thereby allowing the battery cell 20 to heat up more quickly, which is beneficial to quickly increase the charging rate window of the battery cell 20, and can effectively shorten the low-temperature charging time while keeping the surface of the negative electrode plate 222 free of lithium deposition.
  • the applicant designed a positive electrode plate 221, adding a functional layer 2213 with high impedance at low temperatures, so that during rapid hot charging, the low-temperature charging time can be effectively shortened while keeping the surface of the negative electrode plate 222 free from lithium deposition.
  • electrical equipment can be in various forms, for example, mobile phones, portable devices, laptops, battery vehicles, electric cars, ships, spacecraft, electric toys and electric tools, etc.
  • spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.
  • Electric toys include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys and electric airplane toys, etc.
  • Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, for example, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.
  • FIG. 1 is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of the present application.
  • the vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc.
  • a battery is provided inside the vehicle 1000, and the battery may be provided at the bottom, head or tail of the vehicle 1000.
  • the battery may be used to power the vehicle 1000, for example, the battery may be used as an operating power source for the vehicle 1000.
  • the vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.
  • the battery can not only serve as the operating power source of the vehicle 1000, but also serve as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.
  • a battery refers to a single physical module including multiple battery cells 20 to provide higher voltage and capacity, which can be in the form of a battery pack, a battery module 100, etc.
  • the battery may include a box 10 for encapsulating multiple battery cells 20, and the box 10 may prevent liquid or other foreign matter from affecting the charging or discharging of the battery cells 20.
  • FIG. 2 is an exploded view of a battery provided in some embodiments of the present application.
  • the battery includes a box body 10 and a plurality of battery cells 20, and the plurality of battery cells 20 are contained in the box body 10.
  • the box body 10 is used to contain the battery cells 20, and the box body 10 can be a variety of structures.
  • the box body 10 can include a first part 11 and a second part 12, and the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a containing space 13 for containing the battery cells 20.
  • the second part 12 can be a hollow structure with one end open, and the first part 11 is a plate-like structure, and the first part 11 covers the open side of the second part 12 to form a box body 10 with a containing space 13; the first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12 to form a box body 10 with a containing space 13.
  • the first part 11 and the second part 12 can be a variety of shapes, such as a cylinder, a cuboid, etc.
  • multiple battery cells 20 can be connected in series, in parallel, or in a hybrid connection.
  • a hybrid connection means that multiple battery cells 20 are connected in series and in parallel. Multiple battery cells 20 can be directly connected in series, in parallel, or in a hybrid connection, and then the whole formed by multiple battery cells 20 is accommodated in the box 10. Alternatively, multiple battery cells 20 can be connected in series, in parallel, or in a hybrid connection to form a module, and multiple modules can be connected in series, in parallel, or in a hybrid connection to form a whole, and then accommodated in the box 10.
  • the battery can also include other structures. For example, multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or hybrid connection of multiple battery cells 20.
  • the battery cell 20 refers to the smallest unit constituting the battery pack.
  • the battery cell 20 may be a secondary battery or a primary battery; it may also be a lithium-sulfur battery, a sodium-ion battery or a magnesium-ion battery, but is not limited thereto.
  • the battery cell 20 may include a housing 21 , an electrode assembly 22 , and an electrolyte, and both the electrode assembly 22 and the electrolyte are accommodated in the housing 21 .
  • the housing 21 may include a shell 211 and a cover 212.
  • the shell 211 is a component used to cooperate with the cover 212 to form an internal sealed space 213 of the battery cell 20, wherein the formed sealed space 213 can be used to accommodate the electrode assembly 22, electrolyte and other components.
  • the cover 212 refers to a component that covers the opening of the shell 211 to isolate the internal environment of the battery cell 20 from the external environment.
  • the shape of the cover 212 can be adapted to the shape of the shell 211 to cooperate with the shell 211, and the cover 212 may also be provided with functional components such as electrode terminals 23 and pressure relief structures 24.
  • a sealing ring may be configured between the opening of the shell 211 and the cover 212 to achieve sealing between the shell 211 and the cover 212.
  • the shell 211 and the cover 212 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shapes of the shell 211 and the cover 212 can be determined according to the specific shape and size of the electrode assembly 22.
  • the shell 211 and the cover 212 can be made of various materials, such as but not limited to metals such as copper, iron, aluminum, stainless steel, and aluminum alloy.
  • the sealing ring can be made of various materials, such as but not limited to PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate) and other materials that are resistant to electrolyte corrosion, high toughness and fatigue resistance.
  • a coating can be formed on the outer surface of the shell 211, and the material of the coating can be various, such as but not limited to corrosion-resistant materials such as Ni and Cr.
  • the electrode assembly 22 may be composed of a positive electrode sheet 221 , a negative electrode sheet 222 and a separator 223 .
  • the battery cell 20 mainly relies on the movement of metal ions between the positive electrode sheet 221 and the negative electrode sheet 222 to work.
  • the positive electrode sheet 221 includes a positive current collector 2211 and a positive active material layer 2212 .
  • the material of the positive current collector 2211 may be aluminum
  • the positive active material material in the positive active material layer 2212 may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganate, lithium-rich manganese-based materials, lithium sulfur materials, etc.
  • the negative electrode sheet 222 includes a negative current collector and a negative active material layer.
  • the material of the negative current collector may be copper, and the negative active material material in the negative active material layer may be carbon, silicon, etc.
  • the electrode assembly 22 may be a winding structure or a laminated structure, and the embodiments of the present application are not limited thereto.
  • an embodiment of the present application provides a positive electrode plate 221, comprising a positive electrode collector 2211, a positive electrode active material layer 2212 located on the surface of the positive electrode collector 2211, and a functional layer 2213 connected to the positive electrode active material layer 2212; under the condition of a temperature ⁇ 0°C, the resistivity of the functional layer 2213 is greater than the resistivity of the positive electrode active material layer 2212.
  • a positive electrode active material layer 2212 and a functional layer 2213 may be disposed on one side surface of the positive electrode collector 2211, as shown in FIG5; or a positive electrode active material layer 2212 and a functional layer 2213 may be disposed on both sides of the positive electrode collector 2211, as shown in FIG6.
  • the positive electrode active material layers 2212 on both sides of the positive electrode collector 2211 are symmetrically disposed along the positive electrode collector 2211, and the functional layers 2213 on both sides of the positive electrode collector 2211 are symmetrically disposed along the positive electrode collector 2211.
  • the functional layer 2213 can be connected to the surface of the positive electrode active material layer 2212 away from the positive electrode current collector 2211, as shown in FIG5 ; it can also be connected between the positive electrode active material layer 2212 and the positive electrode current collector 2211, as shown in FIG7 ; it can also be sandwiched between two layers of positive electrode active material layers 2212, as shown in FIG8 ; it can also be embedded inside the positive electrode active material layer 2212, as shown in FIG9 .
  • the positive electrode active material layer 2212 can be configured according to conventional active material layer requirements, including material type, material particle size, resistance, thickness, etc.
  • the functional layer 2213 may or may not include positive electrode active materials. Compared with the positive electrode active material layer 2212, the functional layer 2213 has a relatively large resistivity under the condition of a temperature ⁇ 0°C, and the resistivity can be regulated in any manner, such as but not limited to regulating the material type, material particle size, material thickness, etc. of the functional layer 2213.
  • resistivity is a physical quantity used to represent the resistance characteristics of various materials.
  • the resistance of a material made of a certain material with a length of 1m and a cross-sectional area of 1m2 is numerically equal to the resistivity of the material.
  • the resistivity test method can adopt the test method known in the art.
  • a functional layer 2213 with a relatively large resistivity at low temperatures is provided in the positive electrode plate 221.
  • the charging voltage deviates more from the equilibrium potential, which can accelerate polarization heat generation, thereby allowing the battery cell 20 to heat up more quickly, which is beneficial to quickly increase the charging rate window of the battery cell 20, and can effectively shorten the low-temperature charging time while keeping the surface of the negative electrode plate 222 free from lithium deposition.
  • the resistance of the positive electrode active material layer 2212 is R1
  • the resistance of the functional layer 2213 is R2
  • the ratio of (R2+R1)/R2 is, for example but not limited to, any one of 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 and 1.9, or a range of values between any two of them.
  • the test method of the resistors R1 and R2 can adopt the test method known in the art.
  • a film resistor meter connected with red and black test wires of an internal resistance meter is used for testing, wherein the test temperature is a preset temperature of ⁇ 0°C, for example, -10°C.
  • R1 is a result of testing under the condition of -20°C to 0°C, for example, a result of testing under the condition of -10°C (or other temperatures ⁇ 0°C), and the range is 0.1 m ⁇ to 3 m ⁇ .
  • R2 is the result of testing under the condition of -20°C to 0°C, for example, the result of testing under the condition of -10°C (or other temperatures ⁇ 0°C), and the range is 0.02m ⁇ to 3m ⁇ .
  • R1 and R2 satisfy the relationship 1.2 ⁇ (R2+R1)/R1 ⁇ 2, that is, 0.2 ⁇ R2/R1 ⁇ 1, which means that the resistance of the positive electrode active material layer 2212 at low temperature and the resistance of the functional layer 2213 at low temperature have a suitable relative size relationship, so that the functional layer 2213 has a more suitable polarization ability at low temperature. While the functional layer 2213 effectively improves the polarization to shorten the low-temperature charging time, it avoids excessive polarization of the functional layer 2213 affecting the capacity and energy density of the battery cell 20.
  • the volume of the positive electrode active material layer 2212 is V1
  • the volume of the functional layer 2213 is V2
  • the ratio of V2/V1 is, for example but not limited to, any one of 0.05, 0.1, 0.15 and 0.2, or a range of values between any two of them.
  • the positive electrode active material layer 2212 and the functional layer 2213 are stacked and distributed along the thickness direction A of the positive electrode sheet.
  • the thickness of the positive electrode active material layer 2212 is H1
  • the thickness of the functional layer 2213 is H2. Based on the relationship of 0.05 ⁇ V2/V1 ⁇ 0.2, the sizes of H1 and H2 satisfy 0.05 ⁇ H2/H1 ⁇ 0.2.
  • V1 and V2 satisfy the relationship of 0.05 ⁇ V2/V1 ⁇ 0.2, which means that the volume of the positive electrode active material layer 2212 and the volume of the functional layer 2213 have a suitable relative size relationship, so that the functional layer 2213 can generate suitable heat by increasing polarization at low temperatures. While the functional layer 2213 effectively shortens the low-temperature charging time, it avoids excessive heat generated by the functional layer 2213 and causing energy loss of the battery cell 20.
  • the resistivity of the functional layer 2213 is less than the resistivity of the positive electrode active material layer 2212 .
  • the ratio of the resistivity of the functional layer 2213 to the resistivity of the positive electrode active material layer 2212 satisfies ⁇ 1, ⁇ 0.9, ⁇ 0.8, ⁇ 0.7, ⁇ 0.6, ⁇ 0.5, ⁇ 0.4, ⁇ 0.3, ⁇ 0.2 or ⁇ 0.1.
  • the resistivity of the functional layer 2213 at room temperature is less than the resistivity of the positive electrode active material layer 2212 at room temperature, that is, the polarization heat generation capacity of the functional layer 2213 at room temperature is smaller than that of the positive electrode active material layer 2212, which is beneficial to reduce the energy loss caused by the functional layer 2213 to the battery cell 20 at room temperature.
  • the resistance of the positive electrode active material layer 2212 is R3
  • the resistance of the functional layer 2213 is R4, and R4 ⁇ 0.2 ⁇ R3.
  • the value of R4/R3 is any one of 0.05, 0.1, 0.15 and 0.2, or a range of values between any two of them.
  • the resistance of the functional layer 2213 at room temperature is significantly lower than that of the positive electrode active material layer 2212 at room temperature, which is beneficial to better reduce the energy loss of the functional layer 2213 to the battery cell 20 at room temperature.
  • the functional layer 2213 is a negative temperature coefficient coating.
  • Negative temperature coefficient coating is a coating containing negative temperature coefficient material, which has negative temperature coefficient phenomenon.
  • negative temperature coefficient material refers to a material whose resistance decreases exponentially with the increase of temperature
  • negative temperature coefficient phenomenon refers to the phenomenon that the resistance decreases exponentially with the increase of temperature.
  • the type of negative temperature coefficient material in the negative temperature coefficient coating is not limited, and materials known in the art can be used.
  • it can be a semiconductor ceramic material sintered by two or more metal oxides such as manganese, copper, silicon, cobalt, iron, nickel, zinc, etc., or it can be a gel material including at least one of P (VDF-HFP), PAN, PEO, etc.
  • the functional layer 2213 is configured in the form of a negative temperature coefficient coating, so that the functional layer 2213 can better balance the characteristics of high resistance at low temperatures and low resistance at room temperature; at the same time, the coating form is easy to prepare and is conducive to stable connection to the positive electrode active material layer 2212.
  • the functional layer 2213 includes at least one of P(VDF-HFP), PAN, and PEO.
  • P(VDF-HFP) stands for polyvinylidene fluoride-co-hexafluoropropylene
  • PAN stands for polyacrylonitrile
  • PEO stands for polyethylene oxide, also known as polyethylene oxide.
  • the above-mentioned functional layer 2213 is formed by the following method: at least one of P(VDF-HFP), PAN and PEO is mixed and stirred with solvents such as N-methylpyrrolidone (NMP), dimethyl carbonate (DMC), acetone, etc. to form a gel, which is applied in the form of a coating, and then the solvent is removed by heating or the like to form a functional layer 2213 with holes.
  • solvents such as N-methylpyrrolidone (NMP), dimethyl carbonate (DMC), acetone, etc.
  • the functional layer 2213 has a specific composition, which can easily form a negative temperature coefficient coating.
  • the functional layer 2213 satisfies at least one of the following conditions (a1) and (a2); (a1) the porosity of the functional layer 2213 is 70% to 85%; (a2) more than 70% of the pores in the functional layer 2213 have a pore size distribution of 0.1 ⁇ m to 1 ⁇ m.
  • the porosity of the functional layer 2213 can be tested by a method known in the art, for example, a mercury intrusion method.
  • the porosity of the functional layer 2213 is, for example but not limited to, any one of 70%, 75%, 80% and 85%, or a range of values between any two of them.
  • the pore size distribution range of more than 70% of the pores in the functional layer 2213 can be tested by a method known in the art, for example, a mercury intrusion method.
  • the pore size distribution range of more than 70% of the pores in the functional layer 2213 is, for example but not limited to, any point value among 0.1 ⁇ m, 0.2 ⁇ m, 0.3 ⁇ m, 0.4 ⁇ m, 0.5 ⁇ m, 0.6 ⁇ m, 0.7 ⁇ m, 0.8 ⁇ m, 0.9 ⁇ m and 1 ⁇ m, or a range value between any two of them.
  • the functional layer 2213 has a specific porosity, which can provide a suitable number of channels for metal ions; the pore sizes of most of the pores in the functional layer 2213 are distributed in a specific range, which can provide channels of suitable sizes for metal ions.
  • metal ions can smoothly pass through the functional layer 2213 during the charge and discharge process.
  • the positive electrode current collector 2211 , the positive electrode active material layer 2212 and the functional layer 2213 are sequentially arranged along the thickness direction A of the positive electrode sheet.
  • the functional layer 2213 is connected to the side of the positive electrode active material layer 2212 away from the positive electrode current collector 2211, so that the positive electrode active material layer 2212 is directly connected to the positive electrode current collector 2211 to maintain a good conductive connection; at the same time, the functional layer 2213 is connected to the positive electrode active material layer 2212, and compared with connecting the functional layer 2213 to the positive electrode current collector 2211, the functional layer 2213 also has better connection stability and can effectively avoid falling off.
  • an embodiment of the present application provides an electrode assembly 22 , including a negative electrode plate 222 , a separator 223 , and a positive electrode plate 221 as in the above embodiment.
  • an embodiment of the present application provides a battery cell 20 , including a housing 21 and an electrode assembly 22 as described in the above embodiment; the electrode assembly 22 is accommodated in the housing 21 .
  • an embodiment of the present application provides a battery, comprising a battery cell 20 as described in the above embodiment.
  • an embodiment of the present application provides an electrical device, including a battery cell 20 as in the above embodiment or a battery as in the above embodiment.
  • the positive electrode sheet 221 includes a positive electrode current collector 2211, a positive electrode active material layer 2212 and a functional layer 2213 arranged in sequence.
  • the following conditions are met: (1) 1.2 ⁇ (R2+R1)/R2 ⁇ 2; (2) R4 ⁇ 0.2 ⁇ R3; (3) 0.05 ⁇ V2/V1 ⁇ 0.2, 0.05 ⁇ H2/H1 ⁇ 0.2; (4) the functional layer 2213 includes at least one of P(VDF-HFP), PAN and PEO; (5) the porosity of the functional layer 2213 is 70% to 85%; (6) more than 70% of the pores in the functional layer 2213 have a pore size distribution of 0.1 ⁇ m to 1 ⁇ m.
  • Graphite, conductive carbon SP, binder SBR, and dispersant CMC are mixed in a mass ratio of 97%, 0.5%, 1.5%, and 1%, respectively, dispersed in a deionized water solution, and stirred into a slurry with a solid content of about 50%, which is then coated on the surface of the negative electrode current collector to form a negative electrode active material layer.
  • the negative electrode sheet is prepared by cold pressing and cutting for use.
  • LFP material, conductive carbon SP, and binder PVDF are mixed in a mass ratio of 96.5%, 2%, and 1.5%, dispersed in an NMP solution, and stirred into a slurry with a solid content of about 70%, which is then coated on the surface of the positive electrode current collector to form a positive electrode active material layer.
  • P(VDF-HFP) and dimethyl carbonate (DMC) solvent are mixed and stirred to form a gel, which is then coated on the positive electrode active material layer.
  • the solvent is removed by heating or the like to form a functional layer with holes.
  • the positive electrode sheets are prepared by cold pressing and cutting for use.
  • Assembling battery cells The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, and then wound, injected, formed, and divided into different capacities to prepare a battery cell.
  • Resistance test Cut the electrode into 4cm*25cm samples, then connect the red and black test wires of the internal resistance meter and the test wires of the film resistance meter. Then use dust-free paper soaked in anhydrous ethanol to clean the upper and lower probes; connect the red and black wires to the sample to be tested; and test the resistance value of the film layer to be tested by adjusting the height and compaction of the probes.
  • test temperature of R1 and R2 is -10°C
  • test temperature of R3 and R4 is 25°C.
  • Test of pore size distribution range of more than 70% pores The mercury intrusion method is used, and the volume pore distribution result of 70% is taken as the pore size distribution range.
  • Charging time test without lithium deposition Charging is performed at a temperature of -10°C. The charging strategy is adjusted during the charging process to ensure that no lithium deposition occurs on the negative electrode. The time taken to charge from 10% SoC to 80% SoC is recorded, i.e., the fast charging time.
  • Lithium deposition test under fast charging strategy The fast charging strategy shown in Table 1 below is used for charging. After charging is completed, the battery cells are disassembled to confirm the lithium deposition status of the negative electrode plate.
  • classification standards for lithium precipitation are as follows:
  • lithium deposition occurs at the edge of the electrode, and the area of lithium deposition accounts for ⁇ 1/8 of the electrode area;
  • Moderate lithium deposition 1 lithium deposition occurs in the middle position, 1/8 ⁇ lithium deposition area accounts for ⁇ 1/4 of the electrode area;
  • Moderate lithium deposition 2 lithium deposition occurs in the middle position, 1/4 ⁇ lithium deposition area accounts for ⁇ 1/2 of the electrode area;
  • Moderate lithium deposition 3 lithium deposition occurs in the middle position, 1/2 ⁇ lithium deposition area accounts for ⁇ 3/4 of the electrode area;
  • Severe lithium deposition Lithium deposition occurs on the entire surface of the electrode, and the area of lithium deposition is less than 3/4 of the electrode area.
  • the relevant conditions of the different positive electrode sheets used in each experimental group are shown in Table 2.
  • the battery cells in each experimental group are charged under low temperature conditions.
  • the fast charging time without lithium precipitation and the lithium precipitation under the fast charging strategy are shown in Table 3.
  • the positive electrode active material layer and the functional layer have the same area and different thicknesses.
  • R1, R2, R3, R4 and the ratio of V2/V1 the relative size relationship of the resistivity of the positive electrode active material layer and the functional layer under different temperature conditions can be determined. Specifically, in each embodiment, under the condition of temperature ⁇ 0°C, the resistivity of the functional layer is greater than the resistivity of the positive electrode active material layer.
  • the positive electrode plate provided in the embodiment of the present application is provided with a functional layer having a relatively high resistance at low temperature compared with comparative example 1.
  • the charging time of the battery cell at low temperature is shortened; when fast charging is performed at low temperature with the same charging strategy, the lithium plating situation is improved.
  • Examples 7 to 10 mainly adjust the value of V2/V1. Among them, the value of V2/V1 in Example 7 is smaller, the value of V2/V1 in Example 7 is closer to 10, and the improvement effect of low-temperature fast charging and lithium precipitation in Examples 1 to 3 is better.
  • Examples 11 to 14 mainly adjust the porosity of the functional layer. Among them, the porosity in Examples 11 and 12 is relatively low, and the improvement effect of low-temperature rapid charging and lithium precipitation in Examples 1 to 3 is better.
  • Examples 15 to 18 mainly adjust the pore size of most pores in the functional layer. Among them, the pore size of most pores in the functional layer in Example 15 is smaller, and the pore size of most pores in the functional layer in Example 18 is larger. The improvement effect of low-temperature rapid charging and lithium precipitation in Examples 1 to 3 is better.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

本申请公开了一种正极极片、电极组件、电池单体、电池及用电设备，正极极片包括正极集流体、位于正极集流体表面的正极活性物质层和连接于正极活性物质层的功能层；在温度≤0℃的条件下，功能层的电阻率大于正极活性物质层的电阻率。正极极片中，设有低温下电阻率相对较大的功能层，在低温下充电时，充电电压偏离平衡电位更大，能够加快极化产热，从而使电池单体更快速升温，有利于快速提高电池单体的充电倍率窗口，能有效缩短低温充电时间。

Description

正极极片、电极组件、电池单体、电池及用电设备 技术领域
本申请涉及电池技术领域，具体而言，涉及一种正极极片、电极组件、电池单体、电池及用电设备。
背景技术
现有的电池单体低温性能不佳，充电时间通常较长。
发明内容
鉴于上述问题，本申请提供一种正极极片、电极组件、电池单体、电池及用电设备，能改善电池单体在低温下充电时间较长的问题。
本申请的实施例是这样实现的：
第一方面，本申请实施例提供一种正极极片，包括正极集流体、位于正极集流体表面的正极活性物质层和连接于正极活性物质层的功能层；在温度≤0℃的条件下，功能层的电阻率大于正极活性物质层的电阻率。
本申请实施例的技术方案中，正极极片中设有低温下电阻率相对较大的功能层，和未设置功能层相比，在低温下充电时，充电电压偏离平衡电位更大，能够加快极化产热，从而使电池单体更快速升温，有利于快速提高电池单体的充电倍率窗口，在保持负极极片表面不出现析锂现象的情况下，能有效缩短低温充电时间。
在一些实施例中，1.2≤(R2+R1)/R2≤2。该实施例中，R1和R2满足1.2≤(R2+R1)/R1≤2的关系式，即0.2≤R2/R1≤1，表示正极活性物质层在低温下的电阻和功能层在低温下的电阻具有合适的相对大小关系，使得功能层在低温下具有更合适的极化能力，在功能层有效提高极化以缩短低温充电时间的同时，避免功能层极化过高影响电池单体的容量与能量密度。
在一些实施例中，正极活性物质层的体积为V1，功能层的体积为V2，0.05≤V2/V1≤0.2。该实施例中，V1和V2满足0.05≤V2/V1≤0.2的关系式，表示正极活性物质层的体积和功能层的体积具有合适的相对大小关系，使得功能层在低温下通过提高极化能够产生合适的热量，在功能层有效缩短低温充电时间的同时，避免功能层产生的热量过多而导致电池单体的能量损失。
在一些实施例中，在温度为25℃的条件下，功能层的电阻率小于正极活性物质层的电阻率。该实施例中，表示功能层在常温下的电阻率小于正极活性物质层在常温下的电阻，即功能层相较于正极活性物质层在常温下的极化产热能力更小，有利于降低功能层在常温下对电池单体造成的能量损失。
在一些实施例中，在温度为25℃的条件下，正极活性物质层的电阻为R3，功能层的电阻为R4，R4≤0.2×R3。该实施例中，表示功能层在常温下的电阻明显小于正极活性物质层在常温下的电阻，有利于更好地降低功能层在常温下对电池单体造成的能量损失。
在一些实施例中，功能层为负温度系数涂层。该实施例中，以负温度系数涂层的形式配置功能层，使得功能层能够较好地兼顾低温下具有高电阻且常温下具有低电阻的特性；同时，涂层的形式制备方便，且有利于稳定地连接在正极活性物质层。
在一些实施例中，功能层包括P(VDF-HFP)、PAN和PEO中的至少一种。该实施例中，功能层含有特定的组成，能够方便地形成负温度系数涂层。
在一些实施例中，功能层满足以下条件(a1)和(a2)中的至少一项；(a1)功能层的孔隙率为70％～85％；(a2)功能层中70％以上的孔的孔径分布在0.1μm～1μm。该实施例中，功能层中具有特定的孔隙率，能够为金属离子提供合适数量的通道；功能层中大部分的孔的孔径分布在特定的范围，能够为金属离子提供合适大小的通道。通过上述的特定标准，使得在充放电过程中，金 属离子能够顺畅地通过功能层。
在一些实施例中，正极集流体、正极活性物质层和功能层沿正极极片的厚度方向依次设置。该实施例中，功能层连接在正极活性物质层远离正极集流体的一侧，使得正极活性物质层与正极集流体直接连接以保持较好的导电连接；同时，功能层连接在正极活性物质层上，和将功能层连接在正极集流体上相比，功能层还具有较好的连接稳定性，能有效避免脱落。
第二方面，本申请实施例提供一种电极组件，包括负极极片、隔离膜以及如上述实施例的正极极片。
第三方面，本申请实施例提供一种电池单体，包括外壳以及如上述实施例的电极组件；电极组件容纳于外壳内。
第四方面，本申请实施例提供一种电池，包括如上述实施例的电池单体。
第五方面，本申请实施例提供一种用电设备，包括如上述实施例的电池单体或者如上述实施例的电池。
上述说明仅是本申请技术方案的概述，为了能够更清楚了解本申请的技术手段，而可依照说明书的内容予以实施，并且为了让本申请的上述和其它目的、特征和优点能够更明显易懂，以下特举本申请的具体实施方式。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对实施例中所需要使用的附图作简单地介绍，应当理解，以下附图仅示出了本申请的某些实施例，因此不应被看作是对范围的限定，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他相关的附图。
图1为本申请一些实施例提供的车辆的结构示意图
图2为本申请一些实施例提供的电池的爆炸图；
图3为本申请一些实施例提供的电池单体的爆炸图；
图4为本申请一些实施例提供的电极组件的结构示意图；
图5为本申请一些实施例提供的第一种正极极片的剖视图；
图6为本申请一些实施例提供的第二种正极极片的剖视图；
图7为本申请一些实施例提供的第三种正极极片的剖视图；
图8为本申请一些实施例提供的第四种正极极片的剖视图；
图9为本申请一些实施例提供的第五种正极极片的剖视图。
图标：
1000-车辆；
100-电池模组；200-控制器；300-马达；
10-箱体；11-第一部分；12-第二部分；13-容纳空间；
20-电池单体；21-外壳；22-电极组件；23-电极端子；24-泄压结构；
211-壳体；212-盖体；213-密封空间；
221-正极极片；222-负极极片；223-隔离膜；
2211-正极集流体；2212-正极活性物质层；2213-功能层；
A-正极极片的厚度方向。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将对本申请实施例中的技术方案进行清楚、完整地描述。实施例中未注明具体条件者，按照常规条件或制造商建议的条件进行。所用试剂或仪器未注明生产厂商者，均为可以通过市售购买获得的常规产品。
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”、“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。
在本申请实施例的描述中，技术术语“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请实施例和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请实施例的限制。
在本申请实施例的描述中，除非另有明确的规定和限定，技术术语“安装”“相连”“连接”“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或成一体；可以是直接相连，也可以通过中间媒介间接相连。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请实施例中的具体含义。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请的实施例中，相同的附图标记表示相同的部件，并且为了简洁，在不同实施例中，省略对相同部件的详细说明。应理解，附图示出的本申请实施例中的各种部件的高度、长宽等尺寸，以及集成装置的整体高度、长宽等尺寸仅为示例性说明，而不应对本申请构成任何限定。
目前，从市场形势的发展来看，动力电池的应用越加广泛。动力电池不仅被应用于水力、火力、风力和太阳能电站等储能电源系统，而且还被广泛应用于电动自行车、电动摩托车、电动汽车等电动交通工具，以及军事装备和航空航天等多个领域。随着动力电池应用领域的不断扩大，其市场的需求量也在不断地扩增。
动力电池通过金属离子在正负极之间的迁移实现能量存储和释放，然而金属离子在正负极之间迁移受到温度影响很大；特别是在低温下，正负极的动力学条件变差，加上电解液粘度上升、电导率下降等因素，从而导致电池在低温下性能极剧恶化，出现如充电时间长等问题。
为了降低低温对电池性能的影响，在目前提出的一些技术方案中，通常在低温环境下采用短时大倍率脉冲充放电策略进行速热充电，即在充电过程中让电极组件22的充电曲线尽可能多地偏离平衡电位，用以增大极化产热提高温升，从而改善电池低温充电能力。
然而，申请人注意到，以锂离子电池为例，目前采用短时大倍率脉冲充放电策略进行速热充电时，对温升的提高有限，使得充电速度提升有限，在保持负极极片222表面不出现析锂现象的情况下，充电时间仍然偏长；若以更快的速度进行充电，则负极极片222的表面容易出现严重的析锂现象。
基于此，申请人经过深入研究发现，通过在正极极片221中增设低温下具有高阻抗的功能层2213，在进行速热充电时，充电电压偏离平衡电位更大，能够加快极化产热，从而使电池单体 20更快速升温，有利于快速提高电池单体20的充电倍率窗口，在保持负极极片222表面不出现析锂现象的情况下，能有效缩短低温充电时间。
基于以上研究，申请人设计了一种正极极片221，增设了低温下具有高阻抗的功能层2213，使得在进行速热充电时，在保持负极极片222表面不出现析锂现象的情况下，能有效缩短低温充电时间。
本申请中，用电设备可以为多种形式，例如，手机、便携式设备、笔记本电脑、电瓶车、电动汽车、轮船、航天器、电动玩具和电动工具等等，例如，航天器包括飞机、火箭、航天飞机和宇宙飞船等等，电动玩具包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等，电动工具包括金属切削电动工具、研磨电动工具、装配电动工具和铁道用电动工具，例如，电钻、电动砂轮机、电动扳手、电动螺丝刀、电锤、冲击电钻、混凝土振动器和电刨。
以下实施例为了方便说明，以本申请实施例的一种用电设备为车辆1000为例进行说明。
参见图1，图1为本申请一些实施例提供的车辆1000的结构示意图。车辆1000可以为燃油汽车、燃气汽车或新能源汽车，新能源汽车可以是纯电动汽车、混合动力汽车或增程式汽车等。车辆1000的内部设置有电池，电池可以设置在车辆1000的底部或头部或尾部。电池可以用于车辆1000的供电，例如，电池可以作为车辆1000的操作电源。车辆1000还可以包括控制器200和马达300，控制器200用来控制电池为马达300供电，例如，用于车辆1000的启动、导航和行驶时的工作用电需求。
在本申请一些实施例中，电池不仅仅可以作为车辆1000的操作电源，还可以作为车辆1000的驱动电源，代替或部分地代替燃油或天然气为车辆1000提供驱动动力。
本申请中，电池是指包括多个电池单体20以提供更高的电压和容量的单一的物理模块，其可以是电池包、电池模组100等形式。电池可以包括用于封装多个电池单体20的箱体10，箱体10可以避免液体或其他异物影响电池单体20的充电或放电。
参见图2，图2为本申请一些实施例提供的电池的爆炸图。电池包括箱体10和多个电池单体20，多个电池单体20容纳于箱体10内。其中，箱体10用于容纳电池单体20，箱体10可以是多种结构。在一些实施例中，箱体10可以包括第一部分11和第二部分12，第一部分11与第二部分12相互盖合，第一部分11和第二部分12共同限定出用于容纳电池单体20的容纳空间13。第二部分12可以是一端开口的空心结构，第一部分11为板状结构，第一部分11盖合于第二部分12的开口侧，以形成具有容纳空间13的箱体10；第一部分11和第二部分12也可以是均为一侧开口的空心结构，第一部分11的开口侧盖合于第二部分12的开口侧，以形成具有容纳空间13的箱体10。当然，第一部分11和第二部分12可以是多种形状，比如，圆柱体、长方体等。
在电池中，多个电池单体20之间可串联或并联或混联，混联是指多个电池单体20中既有串联又有并联。多个电池单体20之间可直接串联或并联或混联在一起，再将多个电池单体20构成的整体容纳于箱体10内。也可以是多个电池单体20先串联或并联或混联组成模块，多个模块再串联或并联或混联形成一个整体，并容纳于箱体10。电池还可以包括其他结构，例如，多个电池单体20之间可通过汇流部件实现电连接，以实现多个电池单体20的并联或串联或混联。
电池单体20是指组成电池包的最小单元。电池单体20可以为二次电池或一次电池；还可以是锂硫电池、钠离子电池或镁离子电池，但不局限于此。
参见图3，电池单体20可以包括外壳21、电极组件22和电解液，电极组件22和电解液均容纳于外壳21内。
外壳21可以包括壳体211和盖体212。壳体211是用于配合盖体212以形成电池单体20的内部密封空间213的组件，其中，形成的密封空间213可以用于容纳电极组件22、电解液以及其他部件。盖体212是指盖合于壳体211的开口处以将电池单体20的内部环境隔绝于外部环境的部件，盖体212的形状可以与壳体211的形状相适应以配合壳体211，盖体212上还可以设置有电极端子23、泄压结构24等功能性部件。壳体211的开口处和盖体212之间可以配置密封圈，用于实 现壳体211和盖体212之间的密封。
壳体211和盖体212可以是多种形状和多种尺寸的，例如长方体形、圆柱体形、六棱柱形等。具体地，壳体211和盖体212的形状可以根据电极组件22的具体形状和尺寸大小来确定。壳体211和盖体212的材质可以是多种，例如但不限于为铜、铁、铝、不锈钢、铝合金等金属。密封圈的材质可以是多种，例如但不限于为PP(聚丙烯)、PC(聚碳酸酯)、PET(聚对苯二甲酸乙二酯)等耐电解液腐蚀、高韧性且耐疲劳的材料。壳体211的外表面可以形成镀层，镀层的材质可以是多种，例如但不限于为Ni、Cr等耐腐蚀材料。
参见图4，电极组件22可以由正极极片221、负极极片222和隔离膜223组成。电池单体20主要依靠金属离子在正极极片221和负极极片222之间移动来工作。正极极片221包括正极集流体2211和正极活性物质层2212，以锂离子电池单体20为例，正极集流体2211的材料可以为铝，正极活性物质层2212中的正极活性物质材料可以为钴酸锂、磷酸铁锂、三元锂、锰酸锂、富锂锰基材料、锂硫材料等。负极极片222包括负极集流体和负极活性物质层，负极集流体的材料可以为铜，负极活性物质层中的负极活性物质材料可以为碳、硅等。此外，电极组件22可以是卷绕式结构，也可以是叠片式结构，本申请实施例并不限于此。
接下来结合附图对本申请实施例提出的正极极片221进行详细阐述。
参见图5～图9，第一方面，本申请实施例提供一种正极极片221，包括正极集流体2211、位于正极集流体2211表面的正极活性物质层2212和连接于正极活性物质层2212的功能层2213；在温度≤0℃的条件下，功能层2213的电阻率大于正极活性物质层2212的电阻率。
在正极极片221中，可以在正极集流体2211的一侧表面设置正极活性物质层2212和功能层2213，如图5所示；也可以在正极集流体2211的两侧表面分别设置正极活性物质层2212和功能层2213，如图6所示。示例性的，在如图6所示的正极极片221中，正极集流体2211两侧的正极活性物质层2212沿正极集流体2211对称设置，且正极集流体2211两侧的功能层2213沿正极集流体2211对称设置。
功能层2213连接在正极活性物质层2212的方式不限，作为一些示例，可以连接在正极活性物质层2212远离正极集流体2211的一侧表面，如图5所示；也可以连接在正极活性物质层2212和正极集流体2211之间，如图7所示；也可以夹设在两层正极活性物质层2212之间，如图8所示；还可以嵌设在正极活性物质层2212内部，如图9所示。
正极活性物质层2212可以按照常规的活性物质层要求进行配置，其要求包括材料种类、材料粒径、电阻、厚度等。
在功能层2213中，可以包括正极活性物质，也可以不包括正极活性物质。功能层2213和正极活性物质层2212相比，在温度≤0℃的条件下电阻率相对较大，其电阻率调控方式不限，例如但不限于调控功能层2213的材料种类、材料粒径、材料厚度等。
本申请中，电阻率是用来表示各种物质电阻特性的物理量，某种材料制成的长为1m，横截面积为1m 2的材料的电阻，在数值上等于这种材料的电阻率。电阻率的测试方法可以采用本领域公知的测试方法。
本申请实施例的技术方案中，正极极片221中设有低温下电阻率相对较大的功能层2213，和未设置功能层2213相比，在低温下充电时，充电电压偏离平衡电位更大，能够加快极化产热，从而使电池单体20更快速升温，有利于快速提高电池单体20的充电倍率窗口，在保持负极极片222表面不出现析锂现象的情况下，能有效缩短低温充电时间。
在一些实施例中，在温度≤0℃的条件下，正极活性物质层2212的电阻为R1，功能层2213的电阻为R2，1.2≤(R2+R1)/R2≤2。
作为示例，(R2+R1)/R2的比值例如但不限于为1.2、1.3、1.4、1.5、1.6、1.7、1.8和1.9中的任意一者点值或者任意两者之间的范围值。
本申请中，电阻R1和R2的测试方法可以采用本领域公知的测试方法。作为示例，采用 连接有内阻仪红黑测试线的膜片电阻仪测试，其中，测试温度为≤0℃的预设温度，例如为-10℃。
作为示例，R1为在-20℃～0℃条件下测试的结果，例如为在-10℃(也可以是其他≤0℃的温度)条件下测试的结果，范围为0.1mΩ～3mΩ。
作为示例，R2为在-20℃～0℃条件下测试的结果，例如为在-10℃(也可以是其他≤0℃的温度)条件下测试的结果，范围为0.02mΩ～3mΩ。
该实施例中，R1和R2满足1.2≤(R2+R1)/R1≤2的关系式，即0.2≤R2/R1≤1，表示正极活性物质层2212在低温下的电阻和功能层2213在低温下的电阻具有合适的相对大小关系，使得功能层2213在低温下具有更合适的极化能力，在功能层2213有效提高极化以缩短低温充电时间的同时，避免功能层2213极化过高影响电池单体20的容量与能量密度。
在一些实施例中，正极活性物质层2212的体积为V1，功能层2213的体积为V2，0.05≤V2/V1≤0.2。
作为示例，V2/V1的比值例如但不限于为0.05、0.1、0.15和0.2中的任意一者点值或者任意两者之间的范围值。
本申请中，在如图5、图7、图8等所示意的实施例中，正极活性物质层2212和功能层2213沿正极极片的厚度方向A层叠分布。在上述实施方式中，沿正极极片的厚度方向A，正极活性物质层2212的厚度H1，功能层2213的厚度为H2，基于0.05≤V2/V1≤0.2的关系式，H1和H2的大小满足0.05≤H2/H1≤0.2。
该实施例中，V1和V2满足0.05≤V2/V1≤0.2的关系式，表示正极活性物质层2212的体积和功能层2213的体积具有合适的相对大小关系，使得功能层2213在低温下通过提高极化能够产生合适的热量，在功能层2213有效缩短低温充电时间的同时，避免功能层2213产生的热量过多而导致电池单体20的能量损失。
在一些实施例中，在温度为25℃的条件下，功能层2213的电阻率小于正极活性物质层2212的电阻率。
作为示例，在温度为25℃的条件下，功能层2213的电阻率和正极活性物质层2212的电阻率的比值满足＜1、≤0.9、≤0.8、≤0.7、≤0.6、≤0.5、≤0.4、≤0.3、≤0.2或者≤0.1。
该实施例中，表示功能层2213在常温下的电阻率小于正极活性物质层2212在常温下的电阻率，即功能层2213相较于正极活性物质层2212在常温下的极化产热能力更小，有利于降低功能层2213在常温下对电池单体20造成的能量损失。
在一些实施例中，在温度为25℃的条件下，正极活性物质层2212的电阻为R3，功能层2213的电阻为R4，R4≤0.2×R3。
作为示例，R4/R3的值为0.05、0.1、0.15和0.2中的任意一者点值或者任意两者之间的范围值。
该实施例中，表示功能层2213在常温下的电阻明显小于正极活性物质层2212在常温下的电阻，有利于更好地降低功能层2213在常温下对电池单体20造成的能量损失。
在一些实施例中，功能层2213为负温度系数涂层。
负温度系数涂层为含有负温度系数材料的涂层，具有负温度系数现象。其中，负温度系数材料是指随温度上升电阻呈指数关系减小的材料，负温度系数现象是指随温度上升电阻呈指数关系减小的现象。
本申请中，负温度系数涂层中的负温度系数材料的种类不限，可以采用本领域公知的材料。作为示例，可以为锰、铜、硅、钴、铁、镍、锌等两种或两种以上的金属氧化物烧结而成的半导体陶瓷材料，也可以是包括P(VDF-HFP)、PAN、PEO等中至少一种的凝胶材料。
该实施例中，以负温度系数涂层的形式配置功能层2213，使得功能层2213能够较好地兼顾低温下具有高电阻且常温下具有低电阻的特性；同时，涂层的形式制备方便，且有利于稳定地连 接在正极活性物质层2212。
在一些实施例中，功能层2213包括P(VDF-HFP)、PAN和PEO中的至少一种。
P(VDF-HFP)即聚偏氟乙烯-共六氟丙烯；PAN即聚丙烯腈；PEO即聚氧化乙烯，又称聚环氧乙烷。
作为示例，上述的功能层2213通过以下方式形成：将P(VDF-HFP)、PAN和PEO中的至少一种与N-甲基吡咯烷酮(NMP)、碳酸二甲酯(DMC)、丙酮等溶剂混合搅拌形成凝胶，涂覆成涂层的形式，然后通过加热等方式去除溶剂，形成具有孔洞的功能层2213。
该实施例中，功能层2213含有特定的组成，能够方便地形成负温度系数涂层。
在一些实施例中，功能层2213满足以下条件(a1)和(a2)中的至少一项；(a1)功能层2213的孔隙率为70％～85％；(a2)功能层2213中70％以上的孔的孔径分布在0.1μm～1μm。
功能层2213的孔隙率的测试方法可以采用本领域公知的测试方法。作为示例，采用压汞法。
作为示例，功能层2213的孔隙率例如但不限于70％、75％、80％和85％中的任意一者点值或者任意两者之间的范围值。
功能层2213中70％以上的孔的孔径分布范围的测试方法可以采用本领域公知的测试方法。作为示例，采用压汞法。
作为示例，功能层2213中70％以上的孔的孔径分布范围例如但不限于为0.1μm、0.2μm、0.3μm、0.4μm、0.5μm、0.6μm、0.7μm、0.8μm、0.9μm和1μm中的任意一者点值或者任意两者之间的范围值。
该实施例中，功能层2213中具有特定的孔隙率，能够为金属离子提供合适数量的通道；功能层2213中大部分的孔的孔径分布在特定的范围，能够为金属离子提供合适大小的通道。通过上述的特定标准，使得在充放电过程中，金属离子能够顺畅地通过功能层2213。
参见图5和图6，在一些实施例中，正极集流体2211、正极活性物质层2212和功能层2213沿正极极片的厚度方向A依次设置。
该实施例中，功能层2213连接在正极活性物质层2212远离正极集流体2211的一侧，使得正极活性物质层2212与正极集流体2211直接连接以保持较好的导电连接；同时，功能层2213连接在正极活性物质层2212上，和将功能层2213连接在正极集流体2211上相比，功能层2213还具有较好的连接稳定性，能有效避免脱落。
第二方面，本申请实施例提供一种电极组件22，包括负极极片222、隔离膜223以及如上述实施例的正极极片221。
第三方面，本申请实施例提供一种电池单体20，包括外壳21以及如上述实施例的电极组件22；电极组件22容纳于外壳21内。
第四方面，本申请实施例提供一种电池，包括如上述实施例的电池单体20。
第五方面，本申请实施例提供一种用电设备，包括如上述实施例的电池单体20或者如上述实施例的电池。
根据本申请的一些实施例，正极极片221包括依次设置的正极集流体2211、正极活性物质层2212和功能层2213。其中，满足以下条件：(1)1.2≤(R2+R1)/R2＜2；(2)R4≤0.2×R3；(3)0.05≤V2/V1≤0.2，0.05≤H2/H1≤0.2；(4)功能层2213包括P(VDF-HFP)、PAN和PEO中的至少一种；(5)功能层2213的孔隙率为70％～85％；(6)功能层2213中70％以上的孔的孔径分布在0.1μm～1μm。
下面列举了一些具体实施例以更好地对本申请进行说明。
一、制备电池单体
(1)制备负极极片：
将石墨、导电碳SP、粘结剂SBR、分散剂CMC依次按照97％、0.5％、1.5％、1％的质量占比配料，分散在去离子水溶液中，并搅拌成固含量50％左右的浆料，之后涂布在负极集流体表面形成负极活性物质层。
经冷压、分切制备出负极极片备用。
(2)制备如图5所示的正极极片：
将LFP材料、导电碳SP、粘结剂PVDF按照96.5％、2％、1.5％的质量占比配料，分散在NMP溶液中，并搅拌成固含量70％左右的浆料，之后涂布在正极集流体表面，形成正极活性物质层。
将P(VDF-HFP)与碳酸二甲酯(DMC)溶剂混合搅拌形成凝胶，涂覆在正极活性物质层，通过加热等方式去除溶剂形成具有孔洞的功能层。
经冷压、分切制备出正极极片备用。
(3)组装电池单体：将正极极片、隔离膜、负极极片依次层叠，然后进行卷绕、注液、化成、分容等工艺，制备出电池单体。
二、测试方法
(1)电阻测试：将极片裁切成4cm*25cm样品，之后将内阻仪红黑测试线和膜片电阻仪测试线连接。然后使用无尘纸浸润无水乙醇清洁上下探针；将红黑线与待测样品相连接；通过调节探针的高度以及压密，测试待测膜层电阻值大小。
其中，R1和R2的测试温度为-10℃，R3和R4的测试温度为25℃。
(2)功能层的孔隙率测试：压汞法。
(3)70％以上的孔的孔径分布范围测试：采用压汞法，以70％的体积孔隙分布结果作为孔径分布范围。
(4)不析锂情况下的充电时间测试：在-10℃的温度条件下进行充电，充电过程中调整充电策略，保证负极极片不出现析锂现象，记录从10％SoC开始充电至80％SoC所使用的时间，即快充时间。
(5)快充策略下的析锂情况测试：采用如以下表1所示的速充策略进行充电，充电完成后拆解电池单体确认负极极片的析锂情况。
表1
序号 步骤 温度
1 调节至10％SoC 25℃
2 2C倍率恒流(CC)1S -10℃
3 Rest 3S -10℃
4 重复步骤2～3至30％SoC -10℃
5 采用1C倍率充电至80％SoC -10℃
6 拆解 确认负极极片的析锂情况
其中，析锂情况的等级划分标准如下：
无析锂：界面金黄；
轻微析锂：极片边缘出现析锂，析锂面积占极片面积≤1/8；
中度析锂1：中间位置出现析锂，1/8＜析锂面积占极片面积≤1/4；
中度析锂2：中间位置出现析锂，1/4＜析锂面积占极片面积≤1/2；
中度析锂3：中间位置出现析锂，1/2＜析锂面积占极片面积≤3/4；
严重析锂：极片大面全部出现析锂，3/4＜析锂面积占极片面积。
三、实验条件及测试结果
各实验组中所使用的不同正极极片的相关条件如表2所示，各实验组中电池单体在低温条件下充电，不析锂情况下的快充时间和快充策略下的析锂情况如表3所示。
表2
Figure PCTCN2022127692-appb-000001
Figure PCTCN2022127692-appb-000002
表2中，关于几组的几类比值结果，均为各实施例以统一的小数保留位数点四舍五入得到的结果。
其中，正极活性物质层和功能层的面积相同、厚度不同。根据R1、R2、R3、R4以及V2/V1的比值，可以判断不同温度条件下正极活性物质层和功能层的电阻率的相对大小关系。具体的，在各实施例中，在温度≤0℃的条件下，功能层的电阻率均大于正极活性物质层的电阻率。
表3
Figure PCTCN2022127692-appb-000003
根据表2和表3可知：
本申请实施例提供的正极极片，和对比例1相比，增设了低温下具有相对较高阻值的功能层，在负极极片不出现析锂现象的情况下，电池单体在低温下的充电时间缩短；在以相同的充电策略在低温下进行快充时，析锂情况得到改善。
和实施例1～3相比，实施例4中(R1+R2)/R1的值偏大，实施例5中(R1+R2)/R1的值偏小，实施例1～3中低温速充和析锂现象的改善效果更好。
和实施例1～3相比，实施例7～10主要对V2/V1的值进行了调整。其中，实施例7中V2/V1的值偏小，实施例7中V2/V1的值偏10，实施例1～3中低温速充和析锂现象的改善效果更好。
和实施例1～3相比，实施例11～14主要对功能层的孔隙率进行了调整。其中，实施例11和实施例12中孔隙率相对较低，实施例1～3中低温速充和析锂现象的改善效果更好。
和实施例1～3相比，实施例15～18主要对功能层中大部分孔的孔径进行了调整。其中，实施例15中功能层中大部分孔的孔径偏小，实施例18中功能层中大部分孔的孔径偏大，实施例1～3中低温速充和析锂现象的改善效果更好。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围，其均应涵盖在本申请的权利要求和说明书的范围当中。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (13)

  1. 一种正极极片，其中，包括正极集流体、位于所述正极集流体表面的正极活性物质层和连接于所述正极活性物质层的功能层；在温度≤0℃的条件下，所述功能层的电阻率大于所述正极活性物质层的电阻率。
  2. 根据权利要求1所述的正极极片，其中，在温度≤0℃的条件下，所述正极活性物质层的电阻为R1，所述功能层的电阻为R2，1.2≤(R2+R1)/R1≤2。
  3. 根据权利要求1或2所述的正极极片，其中，所述正极活性物质层的体积为V1，所述功能层的体积为V2，0.05≤V2/V1≤0.2。
  4. 根据权利要求1～3中任一项所述的正极极片，其中，在温度为25℃的条件下，所述功能层的电阻率小于所述正极活性物质层的电阻率。
  5. 根据权利要求4所述的正极极片，其中，在温度为25℃的条件下，所述正极活性物质层的电阻为R3，所述功能层的电阻为R4，R4≤0.2×R3。
  6. 根据权利要求1～5中任一项所述的正极极片，其中，所述功能层为负温度系数涂层。
  7. 根据权利要求4～6中任一项所述的正极极片，其中，所述功能层包括P(VDF-HFP)、PAN和PEO中的至少一种。
  8. 根据权利要求4～7中任一项所述的正极极片，其中，所述功能层满足以下条件(a1)和(a2)中的至少一项；
    (a1)所述功能层的孔隙率为70％～85％；
    (a2)所述功能层中70％以上的孔的孔径分布在0.1μm～1μm。
  9. 根据权利要求1～8中任一项所述的正极极片，其中，所述正极集流体、所述正极活性物质层和所述功能层沿所述正极极片的厚度方向依次设置。
  10. 一种电极组件，其中，包括负极极片、隔离膜以及如权利要求1～9中任一项所述的正极极片。
  11. 一种电池单体，其中，包括外壳以及如权利要求10所述的电极组件；
    所述电极组件容纳于所述外壳内。
  12. 一种电池，其中，包括如权利要求11所述的电池单体。
  13. 一种用电设备，其中，包括如权利要求11所述的电池单体或者如权利要求12所述的电池。
PCT/CN2022/127692 2022-10-26 2022-10-26 正极极片、电极组件、电池单体、电池及用电设备 WO2024087055A1 (zh)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/CN2022/127692 WO2024087055A1 (zh) 2022-10-26 2022-10-26 正极极片、电极组件、电池单体、电池及用电设备

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2022/127692 WO2024087055A1 (zh) 2022-10-26 2022-10-26 正极极片、电极组件、电池单体、电池及用电设备

Publications (1)

Publication Number Publication Date
WO2024087055A1 true WO2024087055A1 (zh) 2024-05-02

Family

ID=90829789

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2022/127692 WO2024087055A1 (zh) 2022-10-26 2022-10-26 正极极片、电极组件、电池单体、电池及用电设备

Country Status (1)

Country Link
WO (1) WO2024087055A1 (zh)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20080010169A (ko) * 2006-07-26 2008-01-30 주식회사 엘지화학 새로운 유/무기 복합 전해질 및 이를 이용하여 열적안전성이 향상된 전기 화학 소자
CN101609897A (zh) * 2008-06-16 2009-12-23 现代自动车株式会社 燃料电池双极板及其制造方法
CN106784617A (zh) * 2016-12-15 2017-05-31 宁德时代新能源科技股份有限公司 一种锂离子电池正极极片，其制备方法及使用该极片的电池
CN113497268A (zh) * 2020-03-18 2021-10-12 荣盛盟固利新能源科技有限公司 一种软包电芯结构、软包电池及电化学装置
CN114464927A (zh) * 2021-12-31 2022-05-10 北京卫蓝新能源科技有限公司 一种基于ntc材料的自适应电加热电芯、电池系统及ntc材料

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20080010169A (ko) * 2006-07-26 2008-01-30 주식회사 엘지화학 새로운 유/무기 복합 전해질 및 이를 이용하여 열적안전성이 향상된 전기 화학 소자
CN101609897A (zh) * 2008-06-16 2009-12-23 现代自动车株式会社 燃料电池双极板及其制造方法
CN106784617A (zh) * 2016-12-15 2017-05-31 宁德时代新能源科技股份有限公司 一种锂离子电池正极极片，其制备方法及使用该极片的电池
CN113497268A (zh) * 2020-03-18 2021-10-12 荣盛盟固利新能源科技有限公司 一种软包电芯结构、软包电池及电化学装置
CN114464927A (zh) * 2021-12-31 2022-05-10 北京卫蓝新能源科技有限公司 一种基于ntc材料的自适应电加热电芯、电池系统及ntc材料

Similar Documents

Publication Publication Date Title
JP7222147B2 (ja) 二次電池及びそれを備える装置
JP4630855B2 (ja) 組電池およびその製造方法
WO2022077371A1 (zh) 二次电池、其制备方法、及其相关的电池模块、电池包和装置
KR20120137289A (ko) 전극조립체 및 이를 포함하는 리튬 이차전지
CN115832209A (zh) 阴极极片、锂离子电池及用电装置
EP4131473A1 (en) Positive electrode, and lithium secondary battery comprising same
CN113270571B (zh) 锂离子二次电池的制造方法和负极材料
JP2023538082A (ja) 負極およびこれを含む二次電池
JP2000090932A (ja) リチウム二次電池
WO2024077635A1 (zh) 电池单体、电池及用电装置
WO2024087055A1 (zh) 正极极片、电极组件、电池单体、电池及用电设备
WO2023134340A1 (zh) 负极活性材料、负极极片、二次电池、电池模块、电池包及其用电装置
CN115995547A (zh) 一种正极活性材料、正极片及制备方法、电池单体、电池和用电设备
WO2023155208A1 (zh) 电池、用电设备、制备电池的方法和设备
WO2023137673A1 (zh) 电极组件、电化学装置及用电设备
WO2023060517A1 (zh) 一种极片、电极组件、电池单体、电池以及用电设备
WO2024077628A1 (zh) 极片、电极组件、电池单体、电池及用电设备
JP7365566B2 (ja) 非水電解液二次電池
CN115832183A (zh) 正极极片及其制备方法、二次电池、电池模块、电池包及用电装置
CN115832277A (zh) 正极浆料、正极极片、电芯、电池单体、电池及用电装置
WO2024082139A1 (zh) 电池及用电设备
CN113097440A (zh) 电化学装置及用电设备
WO2024031351A1 (zh) 正极活性材料、正极极片、电极组件、电池单体、电池以及用电设备
WO2024103350A1 (zh) 正极极片、电极组件、电池单体、电池及用电设备
WO2023216076A1 (zh) 极片、电池单体、电池以及用电装置