WO2024066624A1 - Feuille d'électrode négative et son procédé de préparation, et ensemble électrode, élément de batterie, batterie et appareil électrique - Google Patents

Feuille d'électrode négative et son procédé de préparation, et ensemble électrode, élément de batterie, batterie et appareil électrique Download PDF

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Publication number
WO2024066624A1
WO2024066624A1 PCT/CN2023/105137 CN2023105137W WO2024066624A1 WO 2024066624 A1 WO2024066624 A1 WO 2024066624A1 CN 2023105137 W CN2023105137 W CN 2023105137W WO 2024066624 A1 WO2024066624 A1 WO 2024066624A1
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WIPO (PCT)
Prior art keywords
negative electrode
active material
functional layer
electrode active
electrode sheet
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PCT/CN2023/105137
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English (en)
Chinese (zh)
Inventor
张洁
陈悦飞
杨开焕
曹俊琪
邹启凡
Original Assignee
宁德时代新能源科技股份有限公司
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Publication of WO2024066624A1 publication Critical patent/WO2024066624A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of battery technology, and in particular to a negative electrode plate and a preparation method thereof, an electrode assembly, a battery cell, a battery and an electrical device.
  • Lithium deposition inside the battery is one of the main factors affecting the electrical and safety performance of the battery. Once lithium deposition occurs in the battery, it will not only reduce the service life of the battery, but also as the amount of lithium deposition accumulates, dendrites are likely to form. Dendrites may pierce the diaphragm, thereby causing a short circuit in the battery, creating a safety hazard.
  • the present application provides a negative electrode plate and a preparation method thereof, an electrode assembly, a battery cell, a battery and an electrical device, which can reduce or avoid lithium plating and improve the safety of the battery.
  • the present application provides a negative electrode sheet, the negative electrode sheet is configured with a straight portion and a portion to be bent, the negative electrode sheet comprises: a negative electrode current collector, a negative electrode active material layer and a functional layer, the negative electrode active material layer is arranged on at least one side of the negative electrode current collector along the thickness direction, and the functional layer is convexly arranged on the surface of at least part of the negative electrode active material layer of the portion to be bent.
  • the functional layer comprises a negative electrode active material and/or a conductive agent.
  • a functional layer is arranged on the surface of the negative electrode active material layer of the part to be bent.
  • the CB value of the corresponding area of the battery can be increased, that is, the ratio of the capacity of the negative electrode active material to the capacity of the positive electrode active material in the area is increased, thereby reducing or avoiding the occurrence of lithium precipitation;
  • the functional layer includes a conductive agent, the conductive agent can provide electron and ion conductive channels to quickly dredge the accumulated lithium ions, thereby reducing or avoiding the occurrence of lithium precipitation;
  • the functional layer includes the negative electrode active material and the conductive agent, it can not only increase the CB value of the corresponding area of the battery, but also quickly dredge the accumulated lithium ions, thereby reducing or avoiding the occurrence of lithium precipitation, and improving the safety and service life of the battery.
  • the functional layer arranged on the surface of the negative electrode active material layer of the part to be bent can shorten the distance between the positive electrode sheet and the negative electrode sheet of the part to be bent, reduce the liquid phase resistance of the battery, and improve the electrochemical reaction kinetics.
  • the functional layer further includes a film-forming material. Adding the film-forming material to the functional layer 430 can improve the bonding effect between the functional layer 430 and the negative electrode active material layer 420 .
  • the functional layer includes 20 wt% to 99 wt% of negative electrode active material and 1 wt% to 80 wt% of film-forming material.
  • the functional layer includes 20 wt% to 99 wt% of a conductive agent and 1 wt% to 80 wt% of a film-forming material.
  • the functional layer includes 20wt% to 70wt% of negative electrode active material, 20wt% to 70wt% of conductive agent and 10wt% to 60wt% of film-forming material.
  • the negative electrode active material includes any one or more of a first carbon material, a lithiation-capable metal, a lithiation-capable metal alloy, and a lithiation-capable oxide.
  • the first carbon material includes hard carbon, soft carbon, activated carbon, graphite, silicon oxygen carbon, and an intermediate phase. Any one or more of carbon microspheres.
  • the conductive agent includes a second carbon material and/or a conductive organic matter.
  • the second carbon material includes any one or more of carbon fiber, conductive carbon black, carbon nanotubes and graphene.
  • the functional layer can have multiple electronic and ion conductive channels and can quickly dredge the accumulated lithium ions.
  • the porosity of the functional layer is 10% to 90%. By adjusting the porosity of the functional layer, the functional layer can be wetted with electrolyte and form a fast lithium ion channel.
  • the present application provides a method for preparing the negative electrode sheet in the above embodiment, which includes: forming a negative electrode active material layer on at least one side of the negative electrode current collector along the thickness direction, and forming a functional layer on the surface of at least part of the negative electrode active material layer to be bent.
  • the preparation method of the negative electrode plate of the present application is simple, and the functional layer is formed on the surface of the negative electrode active material layer of at least part of the portion to be bent after the negative electrode active material layer is formed.
  • an intermittent coating process is not required, and the manufacturing difficulty is low.
  • the present application provides an electrode assembly, which includes: a positive electrode sheet and a negative electrode sheet in the above embodiment, wherein the positive electrode sheet and the negative electrode sheet are wound or folded to form a bending area and a straight area, and the straight area is connected to the bending area.
  • the portion to be bent is wound or folded to form a bending portion, the bending portion is located in the bending area, and the straight portion is located in the straight area.
  • a functional layer is arranged on the surface of the negative electrode active material layer in the partial bending area, so as to increase the CB value of the corresponding area of the battery, that is, to increase the ratio of the negative electrode active material capacity to the positive electrode active material capacity in the area, and/or to provide electron and ion conductive channels to quickly guide the accumulated lithium ions, thereby reducing or avoiding the occurrence of lithium precipitation.
  • the functional layer arranged on the surface of the negative electrode active material layer in the partial bending area can shorten the distance between the positive electrode sheet and the negative electrode sheet in the partial bending area, reduce the liquid phase resistance of the battery, and improve the electrochemical reaction kinetics.
  • the positive electrode sheet and the negative electrode sheet are wound to form a winding structure, and a functional layer is provided on the surface of the negative electrode active material layer on the outer side of the negative electrode current collector of at least a part of the bend.
  • the outer side of the negative electrode current collector is smaller than the inner side of the corresponding positive electrode current collector, which results in that the negative electrode active material capacity of the outer side of the negative electrode current collector is smaller than the positive electrode active material capacity of the corresponding positive electrode current collector under normal circumstances, and lithium precipitation reaction is very easy to occur.
  • the functional layer is provided on the surface of the negative electrode active material layer on the outer side of the negative electrode current collector of at least a part of the bend, which can increase the ratio of the negative electrode active material capacity to the positive electrode active material capacity in the region, or provide an electron and ion conductive channel in the region to quickly guide the accumulated lithium ions, thereby reducing or avoiding the lithium desorption reaction of the active material layer in the partial bend area, and improving the safety and service life of the battery.
  • the positive electrode sheet and the negative electrode sheet are wound to form a winding structure
  • the negative electrode sheet has a first bend located at the innermost side of the winding structure
  • a functional layer is provided on the surface of the negative electrode active material layer on the outer side of the negative electrode current collector of the first bend.
  • the first bend located at the innermost side of the electrode assembly is the area where lithium precipitation reaction is most likely to occur, and the functional layer is provided on the surface of the negative electrode active material layer on the outer side of the negative electrode current collector of the first bend, which can increase the ratio of the negative electrode active material capacity to the positive electrode active material capacity in the area, or provide electron and ion conductive channels in the area to quickly guide the accumulated lithium ions, thereby reducing or avoiding the lithium desorption reaction of the active material layer in the partial bend area, and improving the safety and service life of the battery.
  • a functional layer is provided on the surface of the negative electrode active material layer on the inner side of the negative electrode current collector of the first bend.
  • the functional layer is provided on the surface of the negative electrode active material layer on the inner side of the negative electrode current collector of the first bend, which can reduce the curvature of the negative electrode sheet in this area and improve the powder shedding of the negative electrode sheet in this area.
  • the negative electrode sheet has a second bend, a third bend, a fourth bend and a fifth bend that are adjacent to the first bend in sequence, and the second bend, the third bend, the fourth bend and the fifth bend are all provided with a functional layer on the surface of the negative electrode active material layer on the outer side of each negative electrode current collector.
  • the first bend, the second bend, the third bend, the fourth bend and the fifth bend located at the innermost side of the electrode assembly are the areas where lithium precipitation reaction is most likely to occur, and the surface of the negative electrode active material layer on the outer side of the negative electrode current collector of the first bend, the second bend, the third bend, the fourth bend and the fifth bend is provided with a functional layer, which can increase the ratio of the negative electrode active material capacity to the positive electrode active material capacity in the multiple regions, or provide electronic and ion conductive channels in the multiple regions to quickly guide the accumulated lithium ions, thereby reducing or avoiding the lithium desorption reaction of the active material layer in some bend areas, and improving the safety and service life of the battery.
  • the second bend, the third bend, the fourth bend, and the fifth bend are all provided with a functional layer on the surface of the negative electrode active material layer on the inner side of each negative electrode current collector.
  • the functional layer is provided on the surface of the negative electrode active material layer on the inner side of the negative electrode current collector of the second bend, the third bend, the fourth bend, and the fifth bend, so that the curvature of the negative electrode sheets in the multiple regions can be reduced and the powder loss of the negative electrode sheets in the multiple regions can be improved.
  • the positive electrode sheet and the negative electrode sheet are wound to form a winding structure having multiple bends, and the functional layers corresponding to the multiple bends are thinned in sequence along the winding direction.
  • the possibility of the multiple bends of the electrode assembly being prone to lithium deposition is reduced in sequence, or the severity of the lithium deposition reaction is reduced in sequence, and the functional layers corresponding to the multiple bends are thinned in sequence along the winding direction, so that they can correspond to the possibility of lithium deposition or the severity of the lithium deposition reaction, which is beneficial to improving the overall energy density of the battery.
  • the thickness difference of the functional layers corresponding to two adjacent bends is 1 ⁇ m to 70 ⁇ m. Adjusting the thickness of the functional layers corresponding to the multiple bends is beneficial to both improving lithium deposition and ensuring the overall energy density of the battery.
  • the positive electrode sheet and the negative electrode sheet are folded to form a laminate structure
  • the negative electrode sheet has a sixth bend covered by the positive electrode sheet
  • the surface of the negative electrode active material layer on the outer side of the negative electrode current collector of the sixth bend is provided with a functional layer.
  • the sixth bend located in the laminate structure is an area where lithium precipitation reaction is prone to occur, and the surface of the negative electrode active material layer on the inner side of the negative electrode current collector of the sixth bend is provided with a functional layer, which can increase the ratio of the negative electrode active material capacity to the positive electrode active material capacity in the area, or provide electron and ion conductive channels in the area to quickly guide the accumulated lithium ions, thereby reducing or avoiding the lithium desorption reaction of the active material layer in the partial bend area, improving the safety and service life of the battery, and ensuring the energy density of the battery.
  • a functional layer is provided on the surface of the negative electrode active material layer on the inner side of the negative electrode current collector of the sixth bend.
  • the functional layer is provided on the surface of the negative electrode active material layer on the inner side of the negative electrode current collector of the sixth bend, which can reduce the curvature of the negative electrode sheet in this area and improve the powder shedding of the negative electrode sheet in this area.
  • the present application provides a battery cell comprising the electrode assembly in the above embodiment.
  • the present application provides a battery, which includes the battery cell in the above embodiment.
  • the present application provides an electrical device, which includes the battery in the above embodiment, and the battery is used to provide electrical energy.
  • FIG1 is a schematic structural diagram of a vehicle according to some embodiments of the present application.
  • FIG2 is a schematic diagram of an exploded structure of a battery according to some embodiments of the present application.
  • FIG3 is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application.
  • FIG4 is a top view of a negative electrode sheet according to some embodiments of the present application.
  • FIG5 is a cross-sectional view of a first negative electrode sheet according to some embodiments of the present application.
  • FIG6 is a cross-sectional view of a second negative electrode sheet according to some embodiments of the present application.
  • FIG7 is a cross-sectional view of a third negative electrode sheet according to some embodiments of the present application.
  • FIG8 is a schematic structural diagram of a first electrode assembly in some embodiments of the present application.
  • FIG9 is a schematic structural diagram of a second electrode assembly according to some embodiments of the present application.
  • FIG10 is a schematic diagram of a first partial structure of a first electrode assembly according to some embodiments.
  • FIG11 is a schematic diagram of a second partial structure of the first electrode assembly in some embodiments of the present application.
  • FIG12 is a schematic diagram of a third partial structure of the first electrode assembly according to some embodiments of the present application.
  • FIG. 13 is a schematic structural diagram of a third electrode assembly according to some embodiments of the present application.
  • the term "and/or" is only a description of the association relationship of associated objects, indicating that three relationships may exist.
  • a and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone.
  • the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.
  • multiple refers to more than two (including two).
  • multiple groups refers to more than two groups (including two groups), and “multiple pieces” refers to more than two pieces (including two pieces).
  • Power batteries are not only used in hydraulic, It is widely used in energy storage power supply systems such as thermal, wind and solar power stations, and electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding.
  • the inventor of the present application has noticed that during the cycle of lithium-ion batteries, lithium ions will be embedded and de-embedded between the cathode and anode of the battery.
  • lithium ions migrate from the cathode to the anode, due to the limitations of the battery structure, in the area where the cathode wraps the anode at the bend of the inner circle, the capacity ratio of the cathode and anode of the battery is insufficient, and too many lithium ions in the cathode are embedded in the anode, while the anode does not have enough capacity to meet the embedding of lithium ions, resulting in the precipitation of excess lithium ions in the area where the cathode wraps the anode in the inner circle.
  • Lithium precipitation at the anode will seriously reduce the cycle performance of the battery.
  • the precipitated lithium metal is very active and will react with the electrolyte, causing the battery's self-heating starting temperature to decrease and the self-heating rate to increase, seriously endangering the safety of the battery.
  • the de-embedded lithium ions will also form lithium crystals on the surface of the anode, and the lithium crystals can pierce the isolation membrane, causing short-circuit thermal runaway of adjacent cathodes and anodes.
  • the applicant's research found that lithium deposition often occurs in the bending area of the electrode assembly.
  • the negative electrode active material in the bending area of the negative electrode sheet is easy to fall off, which causes the lithium insertion sites of the negative electrode active material layer of the negative electrode sheet to be further less than the number of lithium ions that can be provided by the positive electrode active material layer of the adjacent positive electrode sheet.
  • lithium deposition is easy to occur.
  • the inventor has designed a negative electrode plate after in-depth research.
  • the CB value of the corresponding area of the battery can be increased, that is, the ratio of the capacity of the negative electrode active material to the capacity of the positive electrode active material in the area is increased, thereby reducing or avoiding the occurrence of lithium deposition;
  • the functional layer includes a conductive agent, the conductive agent can provide electron and ion conductive channels to quickly dredge the accumulated lithium ions, thereby reducing or avoiding the occurrence of lithium deposition;
  • the functional layer includes a negative electrode active material and a conductive agent, it can increase the CB value of the corresponding area of the battery, and can also quickly dredge the accumulated lithium ions, thereby reducing or avoiding the occurrence of lithium deposition, and improving the safety and service
  • the functional layer set on the surface of the negative electrode active material layer of the part to be bent can shorten the distance between the positive electrode plate and the negative electrode plate of the part to be bent, reduce the liquid phase resistance of the battery, and improve the electrochemical reaction kinetics.
  • the battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.
  • the battery generally includes a battery box for encapsulating one or more battery cells, and the battery box can prevent liquid or other foreign matter from affecting the charging or discharging of the battery cells.
  • the battery cell may include a lithium-ion battery cell.
  • the battery cell may be cylindrical, flat, rectangular or other shapes, and the present application embodiment does not limit this.
  • Battery cells are generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells and soft-pack battery cells.
  • the battery cell includes an electrode assembly and an electrolyte.
  • the electrode assembly is composed of a positive electrode sheet, a negative electrode sheet and a separator.
  • the battery cell mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work.
  • the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer.
  • the positive electrode active material layer is coated on the surface of the positive electrode collector.
  • the positive electrode collector not coated with the positive electrode active material layer protrudes from the positive electrode collector coated with the positive electrode active material layer.
  • the positive electrode collector not coated with the positive electrode active material layer serves as the positive electrode tab.
  • the material of the positive electrode collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide.
  • the negative electrode sheet includes a negative electrode collector and a negative electrode active material layer.
  • the negative electrode active material layer is coated on the surface of the negative electrode collector.
  • the negative electrode collector not coated with the negative electrode active material layer protrudes from the negative electrode collector coated with the negative electrode active material layer.
  • the negative electrode collector not coated with the negative electrode active material layer serves as the negative electrode tab.
  • the material of the negative electrode current collector may be copper, and the negative electrode active material may be carbon or silicon, etc.
  • the number of positive electrode tabs is multiple and stacked together, and the number of negative electrode tabs is multiple and stacked together.
  • the material of the isolation film may be polypropylene (PP) or polyethylene (PE), etc.
  • the electrode assembly may be a winding structure or a laminated structure, and the embodiments of the present application are not limited thereto.
  • the battery cell also includes a current collecting component, which is used to electrically connect the tabs and electrode terminals of the battery cell to transmit electrical energy from the electrode assembly to the electrode terminals and then to the outside of the battery cell through the electrode terminals; multiple battery cells are electrically connected through a current collecting component to achieve series, parallel or mixed connection of multiple battery cells.
  • a current collecting component which is used to electrically connect the tabs and electrode terminals of the battery cell to transmit electrical energy from the electrode assembly to the electrode terminals and then to the outside of the battery cell through the electrode terminals; multiple battery cells are electrically connected through a current collecting component to achieve series, parallel or mixed connection of multiple battery cells.
  • the battery also includes a sampling terminal and a battery management system.
  • the sampling terminal is connected to the busbar to collect information about the battery cells, such as voltage or temperature, etc.
  • the sampling terminal transmits the collected information about the battery cells to the battery management system.
  • the battery management system detects that the information about the battery cells exceeds the normal range, it will limit the output power of the battery to achieve safety protection.
  • the electrical devices used by the batteries described in the embodiments of the present application 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, such as 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, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.
  • the battery cells and batteries described in the embodiments of the present application are not limited to the electrical devices described above, but can also be applied to all electrical devices using battery cells and batteries. However, for the sake of simplicity, the following embodiments are described using electric vehicles as examples.
  • FIG. 1 is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of the present application.
  • the vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle.
  • the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc.
  • a battery 100 is arranged inside the vehicle 1000, and the battery 100 can be arranged at the bottom, head or tail of the vehicle 1000.
  • the battery 100 can be used to power the vehicle 1000.
  • the battery 100 can be used as an operating power source for the vehicle 1000.
  • the vehicle 1000 may also include a controller 200 and a motor 300.
  • the controller 200 is used to control the battery 100 to power the motor 300, for example, for the starting, navigation and driving power requirements of the vehicle 1000.
  • the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.
  • FIG. 2 is an exploded view of a battery 100 provided in some embodiments of the present application.
  • the battery 100 may include a box body 10 and a battery cell 20, and the battery cell 20 is contained in the box body 10.
  • the box body 10 is used to contain the battery cell 20, and the box body 10 may be a variety of structures.
  • the box body 10 may 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 cell 20.
  • the second part 12 may 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 may 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 may be a variety of shapes, such as a cylinder, a cuboid, etc.
  • the battery 100 there can be one or more battery cells 20. If there are more than one battery cell 20, the multiple battery cells 20 can be connected in series, in parallel, or in a mixed connection.
  • a mixed connection means that the multiple battery cells 20 are both connected in series and in parallel.
  • the multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10.
  • multiple battery cells 20 can be connected in series, in parallel, or in a mixed connection to form a battery module, and the multiple battery modules are then connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10.
  • the battery 100 may also include other structures.
  • the multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of the multiple battery cells 20.
  • Each battery cell 20 may be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto.
  • the battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.
  • FIG. 3 is an exploded view of the battery cell 20 shown in FIG. 2.
  • the battery cell 20 refers to the smallest unit constituting the battery 100.
  • the battery cell 20 may include a housing 21 and an electrode assembly 22, and the electrode assembly 22 is accommodated in the housing 21.
  • the housing 21 may also be used to accommodate an electrolyte, such as an electrolyte.
  • the housing 21 may be in a variety of structural forms.
  • the housing 21 may include a shell 211 and a cover 212 .
  • the shell 211 is a component used to match 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 shell 211 and the cover 212 can be independent components, and an opening can be set on the shell, and the internal environment of the battery cell 20 is formed by covering the opening with the cover 212 at the opening.
  • the cover 212 and the shell 211 can also be integrated. Specifically, the cover 212 and the shell 211 can form a common connection surface before other components are put into the shell, and when the interior of the shell 211 needs to be encapsulated, the cover 212 covers the shell 211.
  • the shell 211 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 211 can be determined according to the specific shape and size of the electrode assembly 22.
  • the material of the shell 211 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.
  • the cover 212 is a part that covers the opening of the housing 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 match the shell 211.
  • the cover 212 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the cover 212 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved.
  • the material of the cover 212 can also be other, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose special restrictions on this.
  • an insulating member can also be provided on the inner side of the cover 212, and the insulating member can be used to isolate the electrical connection components in the shell 211 from the cover 212 to reduce the risk of short circuit.
  • the insulating member can be plastic, rubber, etc.
  • Electrodes 23 may be provided on the cover 212.
  • the electrode terminals 23 are mounted on the cover 212.
  • the electrode terminals 23 are electrically connected to the electrode assembly 22 to output the electrical energy generated by the battery cell 20.
  • the electrode terminals 23 and the electrode assembly 22 may be electrically connected via an adapter (not shown).
  • the battery cell 20 may further include a pressure relief structure 24, which is used to release the pressure inside the battery cell 20 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value.
  • the pressure relief structure 24 may be a component such as an explosion-proof valve, an explosion-proof disk, an air valve, a pressure relief valve, or a safety valve.
  • the electrode assembly 22 When assembling the battery cell 20 , the electrode assembly 22 may be placed in the housing 211 first, and the housing 211 may be filled with electrolyte, and then the cover 212 may be closed on the opening of the housing 211 .
  • Figure 4 is a top view of the negative electrode sheet 400 of some embodiments of the present application
  • Figure 5 is a cross-sectional view of the first negative electrode sheet 400 of some embodiments of the present application
  • Figure 6 is a cross-sectional view of the second negative electrode sheet 400 of some embodiments of the present application
  • Figure 7 is a cross-sectional view of the third negative electrode sheet 400 of some embodiments of the present application.
  • the present application provides a negative electrode sheet 400, which is provided with a straight portion 401 and a portion to be bent 402, and includes: a negative electrode current collector 410, a negative electrode active material layer 420 and a functional layer 430, wherein the negative electrode active material layer 420 is disposed on at least one side of the negative electrode current collector 410 in the thickness direction, and the functional layer 430 is convexly disposed on the surface of the negative electrode active material layer 420 of at least a portion of the portion to be bent 402.
  • the functional layer 430 includes a negative electrode active material and/or a conductive agent.
  • the straight portion 401 is a portion of the negative electrode plate 400 that is formed into a straight region 501 after being wound or bent.
  • the portion to be bent 402 is a portion of the negative electrode sheet 400 that forms a bending area 502 after being wound or bent.
  • the functional layer 430 is a layered structure disposed on the surface of the negative electrode active material layer 420 at least partially on the portion to be bent 402 and can provide lithium ion active sites or electron and ion channels.
  • the negative electrode active material is a component that can serve as a lithium ion active site.
  • Conductive agents are components that can provide pathways for electrons and ions.
  • the functional layer 430 may include a negative electrode active material but not a conductive agent; or may include a conductive agent but not a negative electrode active material; or may include both a negative electrode active material and a conductive agent.
  • a functional layer 430 is provided on the surface of the negative electrode active material layer 420 of the part to be bent 402.
  • the CB value of the corresponding area of the battery can be increased, that is, the ratio of the negative electrode active material capacity to the positive electrode active material capacity in the area is increased, thereby reducing or avoiding the occurrence of lithium precipitation;
  • the conductive agent can provide electron and ion conductive channels to quickly dredge the accumulated lithium ions, thereby reducing or avoiding the occurrence of lithium precipitation;
  • the functional layer 430 includes a negative electrode active material and a conductive agent, it can increase the CB value of the corresponding area of the battery, and can also quickly dredge the accumulated lithium ions, thereby reducing or avoiding the occurrence of lithium precipitation, and improving the safety and service life of the battery.
  • the functional layer 430 provided on the surface of the negative electrode active material layer 420 of the part to be bent 402 can shorten the distance between the positive electrode sheet 600 and the negative electrode sheet 400 of the part to be bent 402, reduce the liquid phase resistance of the battery, and improve the electrochemical reaction kinetics.
  • the negative electrode active material layer 420 is disposed on only one side of the negative electrode current collector 410 along the thickness direction, and the functional layer 430 is disposed on the surface of a layer of the negative electrode active material layer 420 .
  • the negative electrode active material layer 420 is disposed on both sides of the negative electrode current collector 410 along the thickness direction, and the functional layer 430 is disposed on the surface of one layer of the negative electrode active material layer 420 .
  • the negative electrode active material layer 420 is disposed on both sides of the negative electrode current collector 410 along the thickness direction, and the functional layer 430 is disposed on the surfaces of the two negative electrode active material layers 420 .
  • the functional layer 430 also includes a film-forming material.
  • Adding a film-forming material to the functional layer can improve the bonding effect between the functional layer and the negative electrode active material layer.
  • the functional layer 430 includes 20 wt % to 99 wt % of negative electrode active material and 1 wt % to 80 wt % of film-forming material.
  • the film-forming material is a component of the solution or slurry that is conducive to the formation of a thin film structure after the solvent is removed.
  • the film-forming material includes any one or more of polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polypropylene (PP), polyethylene (PE), polyacrylonitrile (PAN), polyacrylic acid (PAA) and polyvinyl alcohol (PVA).
  • PVDF polyvinylidene difluoride
  • PTFE polytetrafluoroethylene
  • CMC carboxymethyl cellulose
  • SBR styrene butadiene rubber
  • PP polypropylene
  • PE polyethylene
  • PAN polyacrylonitrile
  • PAA polyacrylic acid
  • PVA polyvinyl alcohol
  • the functional layer 430 may include 20wt% negative electrode active material and 80wt% film-forming material, or may include 30wt% negative electrode active material and 70wt% film-forming material, or may include 40wt% negative electrode active material and 60wt% film-forming material, or may include 50wt% negative electrode active material and 50wt% film-forming material, or may include 60wt% negative electrode active material and 40wt% film-forming material, or may include 70wt% negative electrode active material and 30wt% film-forming material, or may include 80wt% negative electrode active material and 20wt% film-forming material, or may include 90wt% negative electrode active material and 10wt% film-forming material, or may include 99wt% negative electrode active material and 1wt% film-forming material.
  • the CB value of the corresponding area of the battery and the bonding effect of the functional layer 430 can be regulated.
  • the functional layer 430 includes 20 wt % to 99 wt % of a conductive agent and 1 wt % to 80 wt % of a film-forming material.
  • the functional layer 430 may include 20wt% conductive agent and 80wt% film-forming material, or may include 30wt% conductive agent and 70wt% film-forming material, or may include 40wt% conductive agent and 60wt% film-forming material, or may include 50wt% conductive agent and 50wt% film-forming material, or may include 60wt% conductive agent and 40wt% film-forming material, or may include 70wt% conductive agent and 30wt% film-forming material, or may include 80wt% conductive agent and 20wt% film-forming material, or may include 90wt% conductive agent and 10wt% film-forming material, or may include 99wt% conductive agent and 1wt% film-forming material.
  • the number of electronic and ion conductive channels and the bonding effect of the functional layer 430 can be controlled.
  • the functional layer 430 includes 20 wt % to 70 wt % of negative electrode active material, 20 wt % to 70 wt % of conductive agent and 10 wt % to 60 wt % of film-forming material.
  • the functional layer 430 may include 20wt% negative electrode active material, 20wt% conductive agent and 60wt% film-forming material, or may include 30wt% negative electrode active material, 30wt% conductive agent and 40wt% film-forming material, or may include 40wt% negative electrode active material, 40wt% conductive agent and 20wt% film-forming material, or may include 70wt% negative electrode active material, 20wt% conductive agent and 10wt% film-forming material, or may include 20wt% negative electrode active material, 70wt% conductive agent and 10wt% film-forming material, or may include 50wt% negative electrode active material, 30wt% conductive agent and 20wt% film-forming material, or may include 30wt% negative electrode active material, 50wt% conductive agent and 20wt% film-forming material.
  • the proportions of the negative electrode active material, the conductive agent and the film-forming material in the functional layer 430 can be controlled.
  • the negative electrode active material includes any one or more of a first carbon material, a lithiation-capable metal, a lithiation-capable metal alloy, and a lithiation-capable oxide.
  • the first carbon material includes any one or more of hard carbon, soft carbon, activated carbon, graphite, silicon oxycarbon and mesophase carbon microbeads.
  • the lithiation-capable metal includes any one or more of Al, Mg and Zn.
  • the lithiation-capable metal alloys include LiAl alloys and/or MgAl alloys.
  • the lithiable oxide includes ZnO and/or MnO.
  • the functional layer 430 can have more lithium ion active sites and the CB value of the corresponding area of the battery can be improved.
  • the conductive agent includes a second carbon material and/or a conductive organic matter.
  • the second carbon material includes any one or more of carbon fiber, conductive carbon black, carbon nanotube and graphene.
  • the carbon nanotubes include single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
  • the graphene includes any one or more of single-layer graphene, few-layer graphene, few-layer graphene, multi-layer graphene and three-dimensional graphene.
  • the conductive organic material includes polypyrrole and/or polythiophene.
  • the functional layer 430 can have multiple electronic and ion conductive channels and can quickly conduct the accumulated lithium ions.
  • the porosity of the functional layer 430 is 10% to 90%.
  • the porosity of the functional layer 430 may be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%.
  • the functional layer 430 can be infiltrated with electrolyte and form a fast lithium ion channel.
  • the present application also provides a method for preparing the negative electrode plate 400 in the above embodiment, which includes: forming a negative electrode active material layer 420 on at least one side of the negative electrode current collector 410 along the thickness direction, and forming a functional layer 430 on the surface of the negative electrode active material layer 420 of at least part of the portion to be bent 402.
  • the preparation method of the negative electrode plate 400 of the present application is simple, and the functional layer 430 is formed on the surface of the negative electrode active material layer 420 of at least a portion of the bending portion 402 after the negative electrode active material layer 420 is formed.
  • an intermittent coating process is not required, and the manufacturing difficulty is low.
  • Figure 8 is a structural schematic diagram of the first electrode assembly 22 of some embodiments of the present application
  • Figure 9 is a structural schematic diagram of the second electrode assembly 22 of some embodiments of the present application
  • Figure 10 is a structural schematic diagram of the third electrode assembly 22 of some embodiments of the present application
  • Figure 11 is a first partial structural schematic diagram of the first electrode assembly 22 of some embodiments of the present application
  • Figure 12 is a second partial structural schematic diagram of the first electrode assembly 22 of some embodiments of the present application.
  • the present application also provides an electrode assembly 22, which includes: a positive electrode sheet 600 and a negative electrode sheet 400 in the above embodiment, wherein the positive electrode sheet 600 and the negative electrode sheet 400 are wound or folded to form a bending area 502 and a straight area 501, and the straight area 501 is connected to the bending area 502.
  • the portion to be bent 402 is wound or folded to form a bending portion, the bending portion is located in the bending area 502, and the straight portion 401 is located in the straight area 501.
  • the positive electrode sheet 600, the negative electrode sheet 400 and the separator 700 are wound to form the electrode assembly 22 of the wound structure, the middle of the electrode assembly 22 is a straight area 501, and the two ends of the straight area 501 are respectively bending areas 502. And the closer the positive electrode sheet 600 and the negative electrode sheet 400 located in the bending area 502 are to the center of the wound structure, the greater the curvature of the positive electrode sheet 600 and the negative electrode sheet 400 after winding.
  • the positive electrode sheet 600, the negative electrode sheet 400 and the separator 700 are folded to form an electrode assembly 22 of a laminated structure.
  • the middle of the electrode assembly 22 is a straight area 501, and the two ends of the straight area 501 are respectively a plurality of bending areas 502.
  • Each bending area 502 includes an inner electrode sheet and an outer electrode sheet.
  • Each inner positive electrode sheet 600 and the negative electrode sheet 400 have the same curvature after folding, and each outer positive electrode sheet 600 and the negative electrode sheet 400 have the same curvature after folding in the bending area 502.
  • the bent portion includes a negative electrode current collector 410 , a negative electrode active material layer 420 located only on the outer side of the negative electrode current collector 410 , and a functional layer 430 located on the surface of the negative electrode active material layer 420 .
  • the bent portion includes a negative electrode current collector 410, a negative electrode active electrode located on the outer side and the inner side of the negative electrode current collector 410, and a negative electrode active electrode located on the outer side and the inner side of the negative electrode current collector 410.
  • the negative electrode active material layer 420 and the functional layer 430 are located on the surface of the negative electrode active material layer 420 on the outer side of the negative electrode current collector 410.
  • the functional layer 430 is provided on the surface of the negative electrode active material layer 420 of the partial bending area 502, so that the CB value of the corresponding area of the battery can be increased, that is, the ratio of the negative electrode active material capacity to the positive electrode active material capacity in the area is increased, and/or an electron and ion conductive channel is provided to quickly guide the accumulated lithium ions, thereby reducing or avoiding the occurrence of lithium precipitation.
  • the functional layer 430 provided on the surface of the negative electrode active material layer 420 of the partial bending area 502 can shorten the distance between the positive electrode plate 600 and the negative electrode plate 400 of the partial bending area 502, reduce the liquid phase resistance of the battery, and improve the electrochemical reaction kinetics.
  • the positive electrode sheet 600 and the negative electrode sheet 400 are wound to form a wound structure, and a functional layer 430 is provided on the surface of the negative active material layer 420 on the outer side of the negative electrode current collector 410 of at least part of the bent portion.
  • the outer side surface of the negative electrode current collector 410 is a convex surface of the negative electrode current collector 410 after being bent.
  • the outer side surface of the negative electrode collector 410 is smaller than the inner side surface of the corresponding positive electrode collector, which results in that under normal circumstances, the negative electrode active material capacity of the outer side surface of the negative electrode collector 410 is smaller than the positive electrode active material capacity of the corresponding positive electrode collector, and lithium precipitation reaction is very likely to occur.
  • a functional layer 430 is provided on the surface of the negative electrode active material layer 420 on the outer side surface of at least part of the bent portion of the negative electrode collector 410, which can increase the ratio of the negative electrode active material capacity to the positive electrode active material capacity in the area, or provide electron and ion conductive channels in the area to quickly guide the accumulated lithium ions, thereby reducing or avoiding the lithium desorption reaction of the active material layer in the partial bending area 502, thereby improving the safety and service life of the battery.
  • the positive electrode sheet 600 and the negative electrode sheet 400 are wound to form a winding structure, and the negative electrode sheet 400 has a first bending portion 403 located at the innermost side of the winding structure, and a functional layer 430 is provided on the surface of the negative active material layer 420 on the outer side of the negative electrode current collector 410 of the first bending portion 403.
  • the first bending portion 403 is a structure of the negative electrode plate 400 with the largest bending curvature.
  • the first bent portion 403 located at the innermost side of the electrode assembly 22 is the area most prone to lithium deposition reaction, and a functional layer 430 is provided on the surface of the negative electrode active material layer 420 on the outer side of the negative electrode current collector 410 of the first bent portion 403, which can increase the ratio of the negative electrode active material capacity to the positive electrode active material capacity in this area, or provide electron and ion conductive channels in this area to quickly guide the accumulated lithium ions, thereby reducing or avoiding the lithium desorption reaction of the active material layer in the partial bending area 502, thereby improving the safety and service life of the battery.
  • FIG. 12 a third partial structural diagram of the first electrode assembly 22 of some embodiments of the present application.
  • a functional layer 430 is disposed on the surface of the negative active material layer 420 on the inner side of the negative current collector 410 of the first bent portion 403 .
  • the inner side surface of the negative electrode current collector 410 is a concave surface of the negative electrode current collector 410 after being bent.
  • a functional layer 430 is provided on the surface of the negative active material layer 420 on the inner side of the negative current collector 410 of the first bent portion 403 , which can reduce the curvature of the negative electrode sheet 400 in this area and improve the powder shedding of the negative electrode sheet 400 in this area.
  • FIG. 13 is a schematic structural diagram of a third electrode assembly 22 of some embodiments of the present application.
  • the negative electrode sheet 400 has a second bending portion 404, a third bending portion 405, a fourth bending portion 406 and a fifth bending portion 407 which are adjacent to the first bending portion 403 in sequence, and the second bending portion 404, the third bending portion 405, the fourth bending portion 406 and the fifth bending portion 407 are all provided with a functional layer 430 on the surface of the negative active material layer 420 on the outer side of the respective negative current collectors 410.
  • the second bending portion 404 is a structure with the second largest curvature of the negative electrode plate 400 , and a straight portion 401 is disposed between the second bending portion 404 and the first bending portion 403 .
  • the third bending portion 405 is a structure having the third largest curvature of the negative electrode plate 400 , and a straight portion 401 is disposed between the third bending portion 405 and the second bending portion 404 .
  • the fourth bending portion 406 is a structure with the fourth largest curvature of the negative electrode plate 400 , and a straight portion 401 is disposed between the fourth bending portion 406 and the third bending portion 405 .
  • the fifth bending portion 407 is a structure with the fifth largest curvature of the negative electrode plate 400 , and a straight portion 401 is disposed between the fifth bending portion 407 and the fourth bending portion 406 .
  • the first bend 403, the second bend 404, the third bend 405, the fourth bend 406 and the fifth bend 407 located at the innermost side of the electrode assembly 22 are the areas most prone to lithium deposition reactions, and a functional layer 430 is provided on the surface of the negative electrode active material layer 420 on the outer side of the negative electrode current collector 410 of the first bend 403, the second bend 404, the third bend 405, the fourth bend 406 and the fifth bend 407, which can increase the ratio of the negative electrode active material capacity to the positive electrode active material capacity in these multiple areas, or provide electron and ion conductive channels in these multiple areas to quickly guide the accumulated lithium ions, thereby reducing or avoiding the delithiation reaction of the active material layer in the partial bend area 502, thereby improving the safety and service life of the battery.
  • the second bend 404 , the third bend 405 , the fourth bend 406 and the fifth bend 407 are all provided with a functional layer 430 on the surface of the negative electrode active material layer 420 on the inner side of each negative electrode current collector 410 .
  • a functional layer 430 is provided on the surface of the negative active material layer 420 on the inner side of the negative electrode current collector 410 of the second bend 404, the third bend 405, the fourth bend 406 and the fifth bend 407, which can reduce the curvature of the negative electrode sheets 400 in these multiple regions and improve the powder shedding of the negative electrode sheets 400 in these multiple regions.
  • the positive electrode sheet 600 and the negative electrode sheet 400 are wound to form a winding structure having a plurality of bends, and along the winding direction, the functional layers 430 corresponding to the plurality of bends are sequentially thinned.
  • the functional layers 430 corresponding to the multiple bent portions are thinned successively along the winding direction, so that they can correspond to the possibility of lithium deposition reaction or the severity of lithium deposition reaction, which is beneficial to improving the overall energy density of the battery.
  • a thickness difference of the functional layer 430 corresponding to two adjacent bending portions is 1 ⁇ m to 70 ⁇ m.
  • the thickness difference between the functional layer 430 corresponding to two adjacent bending portions may be 1 ⁇ m, 5 ⁇ m, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, 60 ⁇ m or 70 ⁇ m.
  • Adjusting the thickness of the functional layer 430 corresponding to the multiple bending portions is beneficial to both improving lithium deposition and ensuring the overall energy density of the battery.
  • the thickness of the functional layer 430 is 0.1 ⁇ m to 200 ⁇ m.
  • the thickness of the functional layer 430 may be 0.1 ⁇ m, 5 ⁇ m, 10 ⁇ m, 20 ⁇ m, 50 ⁇ m, 80 ⁇ m, 100 ⁇ m, 120 ⁇ m, 150 ⁇ m, 180 ⁇ m, or 200 ⁇ m.
  • the positive electrode sheet 600 and the negative electrode sheet 400 are folded to form a stacked structure, the negative electrode sheet 400 has a sixth bent portion 408 covered by the positive electrode sheet 600, and a functional layer 430 is provided on the surface of the negative active material layer 420 on the outer side of the negative electrode current collector 410 of the sixth bent portion 408.
  • the sixth bending portion 408 can be a bending portion at any position.
  • the sixth bend 408 located in the stacked structure is an area where lithium deposition reaction is prone to occur, and a functional layer 430 is provided on the surface of the negative electrode active material layer 420 on the inner side of the negative electrode current collector 410 of the sixth bend 408, which can increase the ratio of the negative electrode active material capacity to the positive electrode active material capacity in this area, or provide electron and ion conductive channels in this area to quickly guide the accumulated lithium ions, thereby reducing or avoiding the lithium desorption reaction of the active material layer in the partial bend area 502, improving the safety and service life of the battery, while ensuring the energy density of the battery.
  • a functional layer 430 is provided on the surface of the negative electrode active material layer 420 on the inner side of the negative electrode current collector 410 of the sixth bent portion 408 .
  • a functional layer 430 is provided on the surface of the negative active material layer 420 on the inner side of the negative current collector 410 of the sixth bent portion 408 , which can reduce the curvature of the negative electrode sheet 400 in this area and improve the powder shedding of the negative electrode sheet 400 in this area.
  • the electrode assembly of the present application is further described in detail below in conjunction with the embodiments.
  • the structures and parameters of the electrode assemblies of embodiments 1 to 38 and comparative examples 1 to 3 are shown in Tables 1 to 3.
  • Batteries were made using the electrode assemblies of Examples 1 to 38 of the present application and Comparative Examples 1 to 3, and the capacity retention rate and the distance (gap) between the positive electrode sheet and the negative electrode sheet at the bending portion of the batteries were measured. The test results are shown in Tables 4 to 6.
  • the preparation method of the battery is as follows:
  • the positive electrode sheet, the negative electrode sheet and the isolation film are wound to form a battery, and the designs of the electrolyte and the aluminum-plastic film are consistent.
  • the prepared battery was subjected to capacity cycle test according to the following steps: 1 0.33C full charge to the charge limit voltage, and test its initial capacity Cap0 according to the 1.0C discharge limit voltage; 2 At 25°C ⁇ 5°C, the battery was fully charged to the charge limit voltage at 1.5C, the cut-off current was 0.05C, and left for 5min ⁇ 10min; 3 At 25°C ⁇ 5°C, the battery was discharged to the discharge cut-off voltage at 1.0C, and left for 5min ⁇ 10min; 4 Repeat steps 2-3 for 50 times. Compare the capacity retention rate after the cycle and the full charge disassembly interface.
  • test method for the gap between the positive and negative electrodes of the battery is as follows:
  • a functional layer is provided on the surface of the negative electrode active material layer on the outer side of the negative electrode current collector at the first bend, or the first, second, third, fourth, fifth bend, or sixth bend, and the functional layer includes a negative electrode active material material, which can reduce or avoid the occurrence of lithium precipitation, so that the capacity retention rate of the battery after 50 cycles reaches more than 93%, the highest is 97%, and the Gap value is less than 50 ⁇ m.
  • Comparative Example 1 has no functional layer, and the capacity retention rate of the battery after 50 cycles is less than 90%, and the Gap value is less than 200 ⁇ m.
  • a functional layer is provided on the surface of the negative electrode active material layer on the outer side of the negative electrode current collector at the first bend, or the first, second, third, fourth, fifth bend, or sixth bend, and the functional layer includes a conductive agent, which can reduce or avoid the occurrence of lithium precipitation, so that the capacity retention rate of the battery after 50 cycles reaches more than 91%, the highest is 95%, and the Gap value is less than 50 ⁇ m.
  • Comparative Example 2 has no functional layer, and the capacity retention rate of the battery after 50 cycles is less than 90%, and the Gap value is less than 200 ⁇ m.
  • a functional layer is provided on the surface of the negative electrode active material layer on the outer side of the negative electrode current collector at the first bend, or the first, second, third, fourth, fifth bend, or sixth bend, and the functional layer includes a negative electrode active material and a conductive agent, which can reduce or avoid the occurrence of lithium precipitation, so that the capacity retention rate of the battery after 50 cycles reaches more than 91%, the highest is 95%, and the Gap value is less than 50 ⁇ m.
  • Comparative Example 3 has no functional layer, and the capacity retention rate of the battery after 50 cycles is less than 90%, and the Gap value is less than 200 ⁇ m.

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Abstract

La présente demande se rapporte au domaine technique des batteries. L'invention concerne une feuille d'électrode négative et son procédé de préparation, et un ensemble électrode, un élément de batterie, une batterie et un appareil électrique. La feuille d'électrode négative comprend un collecteur de courant d'électrode négative, une couche de substance active d'électrode négative et une couche fonctionnelle, la couche de substance active d'électrode négative étant disposée sur au moins une face du collecteur de courant d'électrode négative dans la direction de l'épaisseur, et la couche fonctionnelle dépassant de la surface de la couche de substance active d'électrode négative d'au moins une partie d'une section à plier, et la couche fonctionnelle comprenant une substance active d'électrode négative et/ou un agent conducteur. La couche fonctionnelle est disposée sur la surface de la couche de substance active d'électrode négative d'une partie de la section à plier, et la couche fonctionnelle peut augmenter une valeur CB d'une zone correspondante d'une batterie, c'est-à-dire que le rapport entre la capacité d'une substance active d'électrode négative dans la zone et la capacité d'une substance active d'électrode positive dans la zone est augmenté ; et/ou un canal conducteur électronique et ionique est mis en place, de telle sorte que les ions lithium accumulés sont rapidement évacués, réduisant ou évitant ainsi l'apparition d'une précipitation de lithium. La couche fonctionnelle peut réduire la distance entre une feuille d'électrode positive et une feuille d'électrode négative, réduire la résistance en phase liquide d'une batterie et améliorer la cinétique des réactions électrochimiques.
PCT/CN2023/105137 2022-09-26 2023-06-30 Feuille d'électrode négative et son procédé de préparation, et ensemble électrode, élément de batterie, batterie et appareil électrique WO2024066624A1 (fr)

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