CN114975862A - Secondary battery, electronic device, and method for manufacturing secondary battery - Google Patents

Secondary battery, electronic device, and method for manufacturing secondary battery Download PDF

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Publication number
CN114975862A
CN114975862A CN202210895107.1A CN202210895107A CN114975862A CN 114975862 A CN114975862 A CN 114975862A CN 202210895107 A CN202210895107 A CN 202210895107A CN 114975862 A CN114975862 A CN 114975862A
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cathode
active material
cathode active
secondary battery
lithium
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CN114975862B (en
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刘奥
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The application provides a secondary battery, an electronic device and a preparation method of the secondary battery, wherein an electrode assembly of the secondary battery comprises a cathode pole piece, a cathode active material layer in the cathode pole piece comprises a cathode active material and a lithium supplement material, the cathode active material layer comprises a first surface far away from a cathode current collector, and a concave part penetrating through the first surface is arranged on the cathode active material layer. Lithium elements in the lithium supplement material can form active lithium during formation of a cathode plate, so that the irreversible capacity of the first charge and discharge is supplemented, and the discharge performance of the battery is improved; the concave part can be used as a diffusion channel of substances generated by the decomposition of the lithium supplement material, the accumulation of the decomposed substances in the cathode active material layer is reduced, the insufficient adhesive force of the cathode pole piece caused by the accumulation of the decomposed substances is relieved, the processing performance of the cathode pole piece is improved, the concave part can also be used as a diffusion channel of lithium ions, the diffusion efficiency of the lithium ions generated by the decomposition of the lithium supplement material is accelerated, the decomposition rate of the lithium supplement material is improved, and the decomposition of the lithium supplement material is more sufficient.

Description

Secondary battery, electronic device, and method for manufacturing secondary battery
Technical Field
The present disclosure relates to the field of energy storage technologies, and in particular, to a secondary battery, an electronic device, and a method for manufacturing the secondary battery.
Background
A secondary battery is a battery that can be continuously used by activating an active material by charging after the battery is discharged. Secondary batteries are widely used in various electronic devices.
In the development of battery technology, secondary batteries such as lithium ion batteries have been widely used because of their advantages of high output power, long cycle life, and low environmental pollution. How to improve the processability of the battery and obtain better performance is always the research direction of workers in the technical field of energy storage.
Disclosure of Invention
Provided are a secondary battery, an electronic device, and a method for manufacturing the secondary battery, which can improve the discharge performance and improve the processability.
In order to achieve the purpose, the following technical scheme is adopted in the application:
in a first aspect, the present application provides a secondary battery comprising an electrode assembly including a cathode sheet including a cathode current collector and a cathode active material layer disposed on the cathode current collector; the cathode active material layer comprises a cathode active material and a cathode binder, and is subjected to lithium supplement treatment; the cathode active material layer has a first surface remote from the cathode current collector, and the cathode active material layer is provided with a recess penetrating the first surface.
In the above scheme, the lithium supplement material is added into the cathode active material layer when the lithium supplement treatment is performed on the cathode active material layer, and lithium elements in the lithium supplement material can form active lithium when a cathode pole piece is formed, so that the irreversible capacity of the first charge and discharge is supplemented, the first coulomb efficiency and the battery capacity retention rate of the battery are favorably improved, and the discharge performance of the battery is improved. The concave part can be used as a diffusion channel for substances generated by the decomposition of the lithium supplement material, so that the decomposed substances can be smoothly discharged along the concave part, the accumulation of the decomposed substances in the cathode active material layer is reduced, the problem of insufficient adhesive force of the cathode pole piece caused by the accumulation of the decomposed substances is solved, the processing performance of the cathode pole piece is improved, and the processing performance of the secondary battery is improved; the concave part can also be used as a diffusion channel of lithium ions, so that the diffusion efficiency of the lithium ions generated by the decomposition of the lithium supplement material is accelerated, the decomposition rate of the lithium supplement material is improved, and the decomposition of the lithium supplement material is more sufficient.
In some embodiments, the recess comprises a hole and/or a slot. The concave part comprises the hole, so that the concave part is accurately positioned in the machining process, and the accurate control of the concave part is favorably realized; the concave part comprises the groove, so that the continuous processing of the concave part can be realized, and the processing efficiency of the concave part is improved.
In some embodiments, the radius of the recesses is R μm, 10 ≦ R ≦ 50. The concave part with the size range can not only enable substances generated by decomposition of the lithium supplement material to be smoothly discharged, but also reduce the influence of the concave part on the cathode active material layer so as to maintain the original appearance of the cathode active material layer and reduce the adverse effect on the electrochemical performance of the cathode active material layer.
In some embodiments, the depth of the recesses is H μm, 5 ≦ H ≦ 30. The concave part within the depth range can extend into the cathode active material layer, so that lithium ions generated by decomposition of the lithium supplement material in the cathode active material layer can be diffused, substances generated by decomposition of the lithium supplement material in the cathode active material layer can be discharged, the possibility of accumulation of the decomposed substances in the cathode active material layer is reduced, the bonding force of the cathode active material layer on a cathode current collector can be improved, and the processing performance of a cathode pole piece can be improved.
In some embodiments, the cathode active material layer is provided with a plurality of recesses, and a distance between adjacent two recesses is L μm, L.ltoreq.50 L.ltoreq.300. The plurality of concave parts have enough capacity of discharging decomposed substances, substances generated by decomposition of the lithium supplement material in the cathode active material layer can be smoothly discharged, and the possibility of gas accumulation in the cathode active material layer is reduced; and also can promote the diffusion of lithium ions generated by the decomposition of the lithium supplement material inside the cathode active material layer; meanwhile, the distance range enables the distance between the concave parts not to be too small, and the processing difficulty of the cathode pole piece is reduced.
In some embodiments, the cathode active material layer is provided with a plurality of recesses having a radius of R μm, a depth of H μm, and a distance between two adjacent recesses of L μm, defining A = L/(R × H), 0.2 ≦ A ≦ 5, and a parameter A of the recesses being 0.2 or more and 5 or less, so that the recesses not only facilitate processing but also can be made to have a sufficient ability to discharge decomposed substances.
In some embodiments, the height at which the edge portion of the recess projects from the first surface is h μm, 3. ltoreq. h.ltoreq.10. The edge part of the concave part protrudes out of the cathode active material layer, so that the diffusion area of the diffusion channel is increased, the diffusion effect of the concave part on lithium ions is favorably improved, the contact area of the cathode active material layer and the electrolyte can be increased, the reaction sites of the cathode active material layer and the electrolyte are favorably increased, and the discharge rate performance of the secondary battery is favorably improved.
In some embodiments, the cross-sectional shape of the concave portion is a V shape, which can reduce the processing difficulty of the concave portion, and is beneficial to improving the processing efficiency of the concave portion, and is also beneficial to spreading decomposed substances at the bottom of the concave portion outwards along the concave portion, and discharging the decomposed substances from the concave portion smoothly from the opening of the concave portion, and is beneficial to reducing the possibility of accumulation of the decomposed substances in the concave portion.
In some embodiments, the recesses are formed by a laser processing process that can remove material on the cathode active material layer to form the recesses, so that the recesses have a better effect on diffusion of ions and diffusion of the electrolyte.
In some embodiments, the cathode active material layer is disposed on a surface of the cathode current collector, facilitating direct contact of the cathode active material with the cathode current collector, facilitating electron conduction, and improving electrical performance.
In some embodiments, the bonding strength between the cathode active material layer and the cathode current collector is F N/m, and F is greater than or equal to 15 and less than or equal to 30, so that the cathode active material layer can be more firmly connected to the surface of the cathode current collector, the possibility that the cathode active material layer falls off from the cathode current collector in the process of processing the cathode plate can be reduced, the cathode active material layer can be more firmly connected to the cathode current collector, and the processing performance of the cathode plate is improved.
In some embodiments, the cathode active material layer further comprises a lithium-supplementing material comprising LiN 3 、Li 2 O 2 、Li 2 O、Li 2 C 3 O 3 、Li 2 C 4 O 4 、Li 2 C 2 O 4 、Li 2 C 3 O 5 、Li 2 C 5 O 5 、Li 2 C 6 O 6 、Li 2 C 4 O 6 、Li x S y Wherein x is more than or equal to 1 and less than or equal to 10, and y is more than or equal to 1 and less than or equal to 10, and the lithium supplement material can release enough lithium ions when the secondary battery is subjected to formation charging, so that the lithium supplement material is beneficial to supplementing the lithium ions consumed by the secondary battery during the first charging and discharging, and has a better lithium supplement effect.
In some embodiments, the cathode active material includes at least one of lithium cobaltate, lithium nickelate, lithium manganate, lithium cobalt phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese phosphate, and lithium nickel cobalt aluminate, and such cathode active material can provide sufficient lithium ions, not only has excellent electrochemical performance, but also is beneficial to improving the stability of the performance of the secondary battery.
In some embodiments, the electrode assembly further comprises an anode plate and a diaphragm, wherein the cathode plate, the diaphragm and the anode plate are stacked, the first surface is connected with the diaphragm, and the diaphragm can separate the anode plate from the cathode plate, prevent the cathode plate and the anode plate from contacting and short-circuiting, and also facilitate the transmission of electrolyte absorbed in the diaphragm into the cathode plate through the concave portion and improve the transmission speed and efficiency of ions between the cathode and the anode through the concave portion.
In a second aspect, the present application provides an electronic device, characterized by including the secondary battery provided in any one of the above technical aspects.
In a third aspect, the present application provides a method of manufacturing a secondary battery, the method comprising: preparing a lithium supplement material, a cathode active material and a cathode binder into cathode slurry according to a preset proportion; arranging the cathode slurry on a cathode current collector to form a cathode active material layer and obtain a cathode plate; forming a recess on a cathode active material layer, the cathode active material layer having a first surface remote from the cathode current collector, the recess penetrating the first surface; assembling the cathode pole pieces into an electrode assembly; assembling the electrode assembly to obtain a secondary battery; and (4) performing formation on the secondary battery. Can be obtained by the above-mentioned method for producing a secondary batteryThe cathode pole piece contains a lithium supplement material and is provided with a secondary battery with a concave part, and the secondary battery has better discharge performance and processing performance. In some embodiments, the lithium-doped material in the above preparation method comprises LiN 3 、Li 2 O 2 、Li 2 O、Li 2 C 3 O 3 、Li 2 C 4 O 4 、Li 2 C 2 O 4 、Li 2 C 3 O 5 、Li 2 C 5 O 5 、Li 2 C 6 O 6 、Li 2 C 4 O 6 、Li x S y Wherein x is more than or equal to 1 and less than or equal to 10, and y is more than or equal to 1 and less than or equal to 10.
In some embodiments, the recess is formed on the cathode pole piece by a laser machining process.
The foregoing description is only an overview of the technical solutions of the present application, and the present application can be implemented according to the content of the description in order to make the technical means of the present application more clearly understood, and the following detailed description of the present application is given in order to make the above and other objects, features, and advantages of the present application more clearly understandable.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a schematic view of an electrode assembly according to some embodiments of the present application;
FIG. 2 is a schematic structural view of a cathode plate according to some embodiments of the present disclosure;
fig. 3 is a schematic structural view of a cathode active material layer provided in some embodiments of the present application;
fig. 4 is a schematic top view of a cathode active material layer with a hole as a recess according to some embodiments of the present disclosure;
fig. 5 is a schematic view of the internal structure of a cathode active material layer when recesses are holes according to some embodiments of the present disclosure;
fig. 6 is a schematic top view of a cathode active material layer with recesses as grooves according to some embodiments of the present disclosure;
fig. 7 is a schematic view of the internal structure of a cathode active material layer when recesses are grooves according to some embodiments of the present disclosure;
FIG. 8 is a schematic illustration of a recess edge portion according to some embodiments of the present disclosure;
fig. 9 is a schematic structural diagram of an electronic device according to some embodiments of the present disclosure.
In the figure: 1. a cathode current collector; 2. a cathode active material layer; 21. a first surface; 22. a second surface; 23. a recess; 3. supplementing a lithium material; 4. a cathode active material; 5. an anode plate; 6. a cathode plate; 7. an anode current collector; 8. an anode active material layer; 9. a diaphragm; 10. an electrode assembly; 101. an anode tab; 102. a cathode tab; 2000. a secondary battery; 3000. an electronic device.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are merely used to more clearly illustrate the technical solutions of the present application, and therefore are only examples, and the protection scope of the present application is not limited thereby.
It is to be noted that technical terms or scientific terms used in the embodiments of the present application should be taken as a general meaning understood by those skilled in the art to which the embodiments of the present application belong, unless otherwise specified.
In the description of the embodiments of the present application, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations and positional relationships that are based on the orientations and positional relationships shown in the drawings, and are used only for convenience in describing the embodiments of the present application and for simplicity in description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the embodiments of the present application.
Furthermore, the technical terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of the embodiments of the present application, "a plurality" means two or more unless specifically defined otherwise.
In the description of the embodiments of the present application, unless otherwise explicitly specified or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly, e.g., as meaning fixedly connected, detachably connected, or integrated; mechanical connection or electrical connection is also possible; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the embodiments of the present application can be understood by those of ordinary skill in the art according to specific situations.
In the description of the embodiments of the present application, unless otherwise explicitly specified or limited, a first feature "on" or "under" a second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
At present, the application of the battery is more and more extensive from the development of market situation. The battery is not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles and the like, and a plurality of fields such as communication equipment, military equipment, aerospace and the like. As the field of application of batteries is continuously expanded, the market demand thereof is also continuously expanded.
The technical solutions of the secondary battery and the electronic device provided in the present application will be further described below with reference to specific embodiments.
Some embodiments of the present application provide a secondary battery, as shown in fig. 1, including an electrode assembly 10, the electrode assembly 10 including a cathode tab 6, as shown in fig. 1 and 2, the cathode tab 6 including a cathode current collector 1 and a cathode active material layer 2 disposed on the cathode current collector 1; the cathode active material layer 2 comprises a cathode active material 4 and a cathode binder, and the cathode active material layer 2 is subjected to lithium supplement treatment; the cathode active material layer 2 includes a first surface 21 distant from the cathode current collector 1, and the cathode active material layer 2 is provided with a recess 23 penetrating the first surface 21.
The secondary battery can be used as a power supply independently and outputs electric energy to the outside for use, or a plurality of secondary batteries can be connected in series or in parallel or in series-parallel to form a battery pack, the battery pack is used as the power supply to output electric energy to the outside, and the series-parallel connection refers to the series connection and the parallel connection of the plurality of secondary batteries. The secondary battery may be a lithium ion battery. The secondary battery may be in the shape of a cylinder, a flat body, a rectangular parallelepiped, or other shapes, etc. The following further describes the secondary battery as a lithium ion battery.
In the first circulation of the lithium ion battery, an SEI film (a solid electrolyte interface film) formed on the surface of a graphite cathode has 5% -15% of first irreversible capacity loss, and the loss of a high-capacity silicon-based material is 15% -35%, while the pre-lithiation technology can eliminate the capacity loss. The electrode material is compensated with lithium by a pre-lithiation technology, so that active lithium released in the charging process compensates the first irreversible lithium loss, and is used for forming an SEI (solid electrolyte interphase) film on the surface of a negative electrode, so that the reversible cycle capacity and the cycle life of the lithium battery are improved.
The electrode assembly 10 is an important component of a secondary battery, wherein the cathode plate 6 includes a cathode current collector 1 and a cathode active material layer 2 disposed on the cathode current collector 1, the cathode active material layer 2 may be directly formed on the surface of the cathode current collector 1, or other functional layers may be disposed between the cathode active material layer 2 and the cathode current collector 1 to achieve a predetermined function.
The cathode active material layer 2 may be formed by applying a corresponding material on the cathode current collector 1 through a coating process, the cathode current collector 1, to which the cathode active material layer 2 is not applied, protruding from the cathode current collector 1, to which the cathode active material layer 2 is applied, and the cathode current collector 1, to which the cathode active material layer 2 is not applied, serving as a cathode tab 102. In some embodiments, the cathode tab 102 may also be formed by attaching a member as the cathode tab 102 to the cathode current collector 1 by welding or the like. In some embodiments of the present application, the material of the cathode current collector 1 may be metallic aluminum, which is processed into an aluminum foil to form the cathode current collector 1.
In some embodiments of the present application, the cathode active material layer 2 further includes a lithium supplement material 3. The lithium supplement material 3 comprises a compound containing lithium elements, the compound is decomposed during formation charging of the secondary battery, a decomposed substance can be released, lithium ions in the decomposed substance can supplement irreversible capacity of first charging and discharging, the first coulombic efficiency and the battery capacity retention rate of the battery can be improved, and meanwhile, the porosity of the cathode pole piece 6 can be increased after the lithium supplement material 3 is decomposed, and the discharge rate performance of the secondary battery can be improved.
In some embodiments of the present application, the lithium supplement material 3 comprises LiN 3 、Li 2 O 2 、Li 2 O、Li 2 C 3 O 3 、Li 2 C 4 O 4 、Li 2 C 2 O 4 、Li 2 C 3 O 5 、Li 2 C 5 O 5 、Li 2 C 6 O 6 、Li 2 C 4 O 6 、Li x S y Wherein x is more than or equal to 1 and less than or equal to 10, and y is more than or equal to 1 and less than or equal to 10.
The lithium supplement material 3 can release enough lithium ions when the secondary battery is charged, is beneficial to supplement the lithium ions consumed by the first charge and discharge of the secondary battery, and has better lithium supplement effect. The lithium-supplementing material 3 may be one of the above-mentioned materials, or may be the above-mentioned materialThe mixture of two or more of the materials can be selected by those skilled in the art according to the actual situation. LiN is a polar or polar group 3 、Li 2 O 2 、Li 2 O、Li 2 C 3 O 3 、Li 2 C 4 O 4 、Li 2 C 2 O 4 、Li 2 C 3 O 5 、Li 2 C 5 O 5 、Li 2 C 6 O 6 、Li 2 C 4 O 6 、Li x S y Decomposed substances generated during formation and charging of the secondary battery comprise gases such as hydrogen, carbon dioxide, alkane and the like, and the porosity of the cathode plate 6 can be increased during generation of the gases, so that the discharge rate performance of the secondary battery can be improved; meanwhile, the concave part 23 is arranged on the cathode active material layer 2, and the concave part 23 can be used as a diffusion channel of gas generated by decomposing the lithium supplement material, so that decomposed substances can be smoothly discharged along the concave part 23, accumulation of the gas in the cathode active material layer 2 is reduced, the problem of insufficient adhesive force of the cathode pole piece 6 caused by accumulation of the gas is solved, the processability of the cathode pole piece 6 is improved, and the processability of the secondary battery is improved. Preferably, the lithium supplement material 3 includes Li 2 C 4 O 4 ，Li 2 C 4 O 4 The lithium ion battery has better oxidation stability and moisture stability, is beneficial to the manufacture of the secondary battery, can decompose and release lithium ions and gas when the secondary battery is formed and charged, not only supplements the consumed lithium ions, but also can release the gas to increase the porosity of the cathode plate 6; in addition, the generated gas may be used as an inert gas to suppress decomposition of the electrolyte to protect the battery, and to optimize the negative electrode SEI film and improve cycle performance.
The cathode active material 4 may include at least one of lithium cobaltate, lithium nickelate, lithium manganate, lithium cobalt phosphate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate, and those skilled in the art may select the cathode active material 4 according to actual conditions as long as the electrochemical performance of the cathode plate 6 is not affected. Preferably, the cathode active material 4 may be lithium cobaltate, which is not only superior in electrochemical properties but also advantageous in improving the stability of the performance of the secondary battery.
The charge cut-off potential of the cathode active material 4 is larger than the decomposition potential at which the lithium supplement material 3 is decomposed into lithium ions and gas, which enables the lithium supplement material 3 to be decomposed into lithium ions and gas before the charge cut-off at the time of formation charge of the secondary battery to complete the lithium supplement process of the cathode electrode sheet 6.
The first surface 21 is the surface of the cathode active material layer 2 itself structure, this surface is far away from the cathode current collector 1 and is set up, the concave part 23 arranged on the cathode active material layer 2 runs through the first surface 21, make the concave part 23 far away from the cathode current collector 1, the concave part 23 can be used as the discharge passage of the gas generated by the decomposition of the lithium supplement material 3, make the gas smoothly discharge from the surface far away from the cathode current collector 1 along the concave part 23, the accumulation of the gas in the cathode active material layer 2 is reduced, thereby being beneficial to relieving the problem of insufficient adhesive force of the cathode pole piece 6 caused by the generation of the gas, the processability of the cathode pole piece 6 can be improved, and the processability of the secondary battery is improved. In addition, the concave portion 23 can also serve as a diffusion channel for lithium ions, thereby increasing the diffusion efficiency of lithium ions generated by the decomposition of the lithium supplement material 3, contributing to an increase in the decomposition rate of the lithium supplement material 3, and making the decomposition of the lithium supplement material 3 more sufficient.
Meanwhile, the concave part 23 on the cathode active material layer 2 can reduce the tortuosity of the cathode pole piece 6, reduce the path through which ions are transferred, and is beneficial to improving the discharge rate performance of the secondary battery, thereby improving the discharge performance of the secondary battery.
The concave portion 23 refers to a concave structure provided on the cathode active material layer 2, which is formed by the cathode active material layer 2 being concave from the side close to the first surface 21 to the side far from the first surface 21, and needs to be distinguished from the uneven portion on the first surface 21 which may exist after the processes of coating, rolling, and the like in the prior art. The depressions may be formed by removing material by laser drilling, machining, or the like, or may be formed by pressing the first surface 21 by machining or the like to partially recess the first surface 21 into the cathode active material layer 2.
The concave portion 23 is formed on the first surface 21 of the cathode active material layer 2 by removing material, and the cathode active material layer 2 is processed outside the first surface 21 by removing material so that the concave portion 23 is a depression inside the cathode active material layer 2.
In some embodiments of the present application, the cathode active material layer 2 further includes a cathode binder. The cathode binder is a material mixed in the material forming the cathode active material layer 2 to perform a binding action, and not only allows the cathode active material layer 2 to be bound to the cathode current collector 1, but also allows the cathode active materials 4 in the cathode active material layer 2 to be bound to each other to form a single body, thereby maintaining the cathode active material layer 2 in a predetermined shape and structure.
In some embodiments of the present application, the cathode active material layer 2 further includes a conductive agent. The conductive agent can improve the charge-discharge performance of the cathode plate 6, can play a role in collecting micro-current between the cathode active materials 4 and the cathode current collector 1, can reduce the contact resistance of the cathode plate 6 to accelerate the movement rate of electrons, and can effectively improve the migration rate of lithium ions in the material of the cathode plate 6, thereby improving the charge-discharge efficiency of the cathode plate 6.
In some embodiments, the cathode active material 4 includes lithium cobaltate, and the mass fraction of the lithium cobaltate in the cathode active material layer 2 is 95.5%. The cathode binder includes polyvinylidene fluoride, and the mass fraction of the polyvinylidene fluoride in the cathode active material layer 2 is 1.7%. The conductive agent includes conductive carbon black, and the mass fraction of the conductive carbon black in the cathode active material layer 2 is 1.6%. Preferably, super p conductive carbon black can be adopted as the conductive carbon black, and the conductive carbon black has good conductivity, moderate specific surface area, excellent processing performance and no influence on an electrochemical mechanism. The mass fraction of the lithium supplement material 3 in the cathode active material layer 2 was 1.2%.
In some embodiments of the present application, the cathode active material layer 2 is provided on the surface of the cathode current collector 1. The cathode active material layer 2 is directly arranged on the surface of the cathode current collector 1, and no other functional layer is arranged between the cathode active material layer 2 and the cathode current collector 1, so that the adhesive force between the cathode active material layer 2 and the surface of the cathode current collector 1 can be improved, the firmness of connection between the cathode active material layer 2 and the cathode current collector 1 can be improved, and the processability of the cathode pole piece 6 can be improved.
In some embodiments of the present application, the adhesive strength of the cathode active material layer 2 to the surface of the cathode current collector 1 is F N/m, 15. ltoreq. F.ltoreq.30. The bonding strength of the cathode active material layer 2 and the surface of the cathode current collector 1 is in the range of 15N/m to 30N/m, so that the cathode active material layer 2 can be firmly connected to the surface of the cathode current collector 1, the possibility that the cathode active material layer 2 falls off from the cathode current collector 1 in the processing process of the cathode pole piece 6 can be reduced, the cathode active material layer 2 can be firmly connected to the cathode current collector 1, and the processing performance of the cathode pole piece 6 is improved. The adhesive strength of the cathode active material layer 2 to the surface of the cathode current collector 1 may be 20N/m, 25N/m, or 25N/m.
In some embodiments of the present application, as shown in fig. 3, the cathode active material layer 2 is provided with a second surface 22, the second surface 22 is a structural surface of the cathode active material layer 2 itself, and is arranged in parallel with and spaced apart from the first surface 21, the second surface 22 is arranged close to the cathode current collector 1 relative to the first surface 21, the cathode current collector 1 is arranged on the second surface 22 of the cathode active material layer 2, the cathode active material layer 2 including the cathode active material 4 is formed between the first surface 21 and the second surface 22, and the concave portion 23 on the first surface 21 enables the gas in the cathode active material layer 2 to be smoothly discharged from the side far from the cathode current collector 1.
In some embodiments of the present application, the recess 23 is formed by a laser machining process. Since the laser has energy, the laser beam interacts with the material and can remove the material to form the concave portion 23 on the first surface 21 of the cathode active material layer 2, and the laser processing technology can remove the material on the cathode active material layer 2 to form the concave portion 23, so that the concave portion 23 has good effects on diffusion of ions and diffusion of electrolyte, and the adhesive strength and compaction density of the material around the concave portion 23 are not affected while the adhesive at the processing part is removed.
In some embodiments of the present application, the recess 23 comprises a hole and/or a slot. As shown in fig. 4 and 5, the holes are in a hole-like structure disposed on the cathode active material layer 2, and the cross-sectional shape thereof may be circular, triangular, square or polygonal, or may be other irregular closed curves, and those skilled in the art may set the cross-sectional shape of the holes according to actual circumstances. Since the holes facilitate positioning during machining, the recesses 23 include holes, which allows the recesses 23 to be positioned accurately during machining, facilitating accurate control of the recesses. It is understood that the diameters of the plurality of holes may be the same or different; the arrangement positions of the holes can be arranged in a matrix mode, a circumferential array mode and other preset rules, and also can be arranged out of order, and the arrangement mode of the holes can be set according to actual conditions by technicians in the field.
As shown in fig. 6 and 7, the grooves are groove-like structures provided on the cathode active material layer 2, having a length along the arrangement direction of the cathode active material layer 2, and the sectional shape of the grooves may be V-shaped or U-shaped, and those skilled in the art can set the sectional shape of the grooves according to actual circumstances. Because the groove can realize continuous processing, the processing efficiency is higher, and the concave part 23 comprises the groove, the continuous processing of the concave part 23 can be realized, and the processing efficiency of the concave part 23 is favorably improved. It is to be understood that the continuous extending direction of the grooves may be arranged along the length direction of the cathode active material layer 2, or may be arranged along the width direction of the cathode active material layer 2, the length direction of the cathode active material layer 2 being the X direction as shown in fig. 6, and the width direction of the cathode active material layer 2 being the Y direction as shown in fig. 6. It will be understood that the direction of continuous extension of the grooves can be set by a person skilled in the art as a function of the actual situation.
In some embodiments of the present application, the cross-sectional shape of the recess 23 in the thickness direction of the cathode active material layer 2 is V-shaped. The thickness direction of the cathode active material layer 2 refers to the Z direction shown in fig. 3. As shown in fig. 3, the cross-sectional shape of the concave portion 23 is V-shaped, which means that the concave portion 23 is tapered, and the area of the opening of the concave portion 23 on the first surface 21 is larger than the area of the bottom of the concave portion 23, and the concave portion 23 with such a shape is not only convenient for processing, and can reduce the processing difficulty, but also is beneficial for improving the processing efficiency of the concave portion 23, and is beneficial for the gas at the bottom of the concave portion 23 to expand outwards along the concave portion 23, and can be smoothly discharged from the concave portion 23 from the opening of the concave portion 23, and is beneficial for reducing the possibility of accumulation of the gas in the concave portion 23. In addition, the V-shaped concave portion 23 can increase the contact area between the electrolyte and the diffusion channel, and increase the diffusion efficiency of lithium ions.
In some embodiments of the present application, the radius of the recesses 23 is R μm, 10 ≦ R ≦ 50. The radius of the concave portion 23 refers to a radius of a circle equivalent to the area of the concave portion 23, that is, the area of a figure formed at the first surface 21 of the concave portion 23 is taken as the area of an equivalent circle, and the radius of the equivalent circle calculated by the area of the equivalent circle is the radius of the concave portion 23. When the concave portion 23 is a hole, the area of the pattern formed at the first surface 21 by the hole is measured, and the radius of the equivalent circle calculated using the measured area is the radius of the concave portion 23. When the concave portion 23 is a groove, the area of the pattern formed at the first surface 21 by the groove is measured, and the radius of the equivalent circle calculated using the measured area is the radius of the concave portion 23.
The area of the formed pattern of the recess 23 at the first surface 21 may be obtained by acquiring an image of the first surface 21 of the cathode pole piece 6 with a Charge Coupled Device (CCD) camera, by measuring the area of the image of the recess 23 in the image.
The radius of the concave portion 23 is not less than 10 μm and not more than 50 μm, and the concave portion 23 having the size range not only enables the gas generated by the decomposition of the lithium supplement material 3 to be smoothly discharged, but also reduces the influence of the concave portion 23 on the first surface 21, so as to maintain the original shape of the first surface 21 and reduce the adverse effect on the electrochemical performance of the cathode active material layer 2.
In some embodiments of the present application, the depth of the recesses 23 is H μm, 5 ≦ H ≦ 30. As shown in fig. 3, the depth of the concave portion 23 refers to the distance from the cathode active material layer 2 to the bottom of the concave portion 23.
The depth of the concave portion 23 can be obtained by irradiating the first surface 21 of the cathode active material layer 2 in the cathode sheet 6 with a CCD camera, or can be obtained by taking a photograph of a sliced sample in the thickness direction of the cathode sheet 6 with a scanning electron microscope and measuring it in an image obtained by the scanning electron microscope. The person skilled in the art can select the method of measuring the depth of the recess 23 according to the actual situation.
The depth of the concave part 23 is more than or equal to 5 μm and less than or equal to 30 μm, and the concave part 23 within the depth range can extend into the cathode active material layer 2, so that lithium ions generated by decomposition of the lithium supplement material 3 in the cathode active material layer 2 can be favorably diffused, gas generated by decomposition of the lithium supplement material 3 in the cathode active material layer 2 can be exhausted, the possibility of gas accumulation in the cathode active material layer 2 is reduced, the adhesive force of the cathode active material layer 2 on the cathode current collector 1 can be favorably improved, and the processing performance of the cathode pole piece 6 can be improved.
Alternatively, the depth of the concave portion 23 may be set to 15 μm or 25 μm, and the concave portion 23 may discharge the gas generated by decomposition of the lithium supplement material 3 in the cathode active material layer 2 in a certain depth, preventing the gas from accumulating inside the cathode active material layer 2.
In some embodiments of the present application, the cathode active material layer 2 is provided with a plurality of recesses 23, and the distance between two adjacent recesses 23 is L μm, 50. ltoreq. L.ltoreq.300.
The plurality of recesses 23 means that the number of the recesses 23 provided on the cathode active material layer 2 is three or more, and the plurality of recesses 23 make the cathode active material layer 2 have a porous structure, which is beneficial to improving the porosity of the cathode plate 6 and the discharge rate performance of the secondary battery.
The distance between two adjacent concave portions 23 can refer to the shortest distance between the edges of two adjacent concave portions 23, and by setting the distance between two adjacent concave portions 23, the plurality of concave portions 23 can be distributed on the first surface 21 of the cathode active material layer 2 with certain uniformity, so that the gas decomposed by the lithium supplement material 3 in the cathode active material layer 2 can be uniformly discharged outwards along the concave portions 23, and the possibility of gas accumulation at local positions is reduced.
The distance between two adjacent concave portions 23 is greater than or equal to 50 μm and less than or equal to 300 μm, and the distance range enables the plurality of concave portions 23 to have sufficient gas discharge capacity, so that gas generated by decomposition of the lithium supplement material 3 in the cathode active material layer 2 can be smoothly discharged, and the possibility of gas accumulation in the cathode active material layer 2 is reduced; and also promotes diffusion of lithium ions generated by decomposition of the lithium supplement material 3 inside the cathode active material layer 2; meanwhile, the distance range also prevents the distance between the concave parts 23 from being too small, which is beneficial to reducing the processing difficulty of the cathode pole piece 6. Alternatively, the distance between two adjacent recesses 23 is set to 150 μm or 250 μm, which not only allows the recesses 23 to have sufficient gas discharge capacity, but also facilitates the processing of the recesses 23 on the cathode active material layer 2, which helps to reduce the difficulty in processing the cathode sheet 6.
In some embodiments of the present application, the cathode active material layer 2 is provided with a plurality of recesses 23, the radius of the recesses 23 is R μm, the depth of the recesses 23 is H μm, and the distance between two adjacent recesses 23 is L μm, defining A = L/(R × H), 0.2 ≦ A ≦ 5.
Defining a as one parameter of the concave portion 23, a = L/(R × H), using a as one parameter of the concave portion 23 is to facilitate setting of the relationship between the radius, depth, and pitch of the concave portion 23, and the parameter a of the concave portion 23 is 0.2 or more and 5 or less, which is advantageous for improving the exhaust capacity of the concave portion 23. Preferably, the parameter a of the recess 23 is 2, where L =200, R =5, and H =20, and the recess 23 of this parameter not only facilitates the machining but also enables the recess 23 to have a sufficient capability of discharging gas.
In some embodiments of the present application, the height at which the edge portions of the recesses 23 protrude from the first surface 21 is h μm, 3. ltoreq. h.ltoreq.10.
The edge portion of the concave portion 23 refers to an opening of the concave portion 23 on the cathode active material layer 2, as shown in fig. 8, when the concave portion 23 is processed on the cathode active material layer 2, a certain influence is exerted on the first surface 21, so that the material at the opening of the concave portion 23 is accumulated and protrudes out of the first surface 21, and the edge portion of the concave portion 23 protrudes out of the first surface 21, thereby not only increasing the diffusion area of the diffusion channel and being beneficial to improving the diffusion effect of the concave portion 23 on lithium ions, but also increasing the contact area of the cathode active material layer 2 and the electrolyte, being beneficial to increasing the reaction sites of the cathode active material layer 2 and the electrolyte, and being beneficial to improving the discharge rate performance of the secondary battery. The edge portion of the concave portion 23 may be formed when the concave portion 23 is processed by a laser processing process, and since the laser has a certain energy, when the cathode active material layer 2 is melted, the material at the opening of the concave portion 23 is accumulated, so that the edge portion of the concave portion 23 protrudes from the first surface 21, and a person skilled in the art can adjust the height of the edge portion of the concave portion 23 protruding from the first surface 21 by adjusting the power and the irradiation time of the laser.
The height of the edge part of the concave part 23 protruding from the first surface 21 is not less than 3 μm and not more than 10 μm, so that the edge part can play a role in increasing the contact area, and the influence of the concave part 23 on the roughness of the first surface 21 of the cathode active material layer 2 and the influence on the cathode and anode interface can be reduced.
In some embodiments of the present application, the electrode assembly 10 in the secondary battery further includes an anode sheet 5 and a separator 9, the cathode sheet 6, the separator 9 and the anode sheet 5 are stacked, and the first surface 21 is in contact with the separator 9.
The anode tab 5 includes an anode current collector 7 and an anode active material layer 8, the anode active material layer 8 is applied to a surface of the anode current collector 7, the anode active material layer 8 may be formed by applying a corresponding material to the surface of the anode current collector 7 through a coating process, the anode current collector 7 not coated with the anode active material layer 8 protrudes from the anode current collector 7 coated with the anode active material layer 8, and the anode current collector 7 not coated with the anode active material layer 8 serves as an anode tab 101. In some embodiments of the present application, the material of the anode current collector 7 may be metallic copper, which is processed into a copper foil to form the anode current collector 7.
The anode active material layer 8 includes an anode active material including graphite having a mass fraction of 98% in the anode active material layer 8, an anode binder including a silicone resin having a mass fraction of 1% in the anode active material layer 8, and a thickener including sodium carboxymethylcellulose having a mass fraction of 1% in the anode active material layer 8.
The diaphragm 9 can separate the anode pole piece 5 from the cathode pole piece 6, and prevent the contact short circuit of the cathode pole piece 6 and the anode pole piece 5. In some embodiments of the present application, the separator 9 is a high adhesion composite film, which can separate the anode plate 5 from the cathode plate 6, and has good adhesion, so that the first surface 21 of the cathode active material layer 2 is firmly connected with the separator 9.
The advantageous effects of the secondary battery provided in the embodiments of the present application will be further described below through comparative experiments.
A secondary battery composed of a cathode electrode sheet formed of a cathode active material layer provided with no recess in the related art was set as an experimental object in a comparative example of a comparative experiment; a secondary battery composed of a cathode electrode sheet formed of a cathode active material layer provided with a concave portion was set as an experimental object in the examples of the comparative experiment.
The manufacturing method of the cathode pole piece in the secondary battery comprises the following steps: mixing a cathode active material, a conductive agent, conductive carbon black and a binder, namely polyvinylidene fluoride according to a certain mass ratio, adding N-methyl pyrrolidone (NMP), and uniformly stirring under the action of a vacuum stirrer to obtain cathode slurry, wherein the solid content of the cathode slurry is 70 wt%. And (3) uniformly coating the cathode slurry on one surface of a cathode current collector aluminum foil with the thickness of 12 mu m, and drying the aluminum foil at 120 ℃ for 1h to obtain the cathode pole piece with the single surface coated with the cathode active material layer. And repeating the steps on the other surface of the aluminum foil to obtain the cathode plate with the cathode active material layer coated on the two surfaces. Then, after cold pressing, cutting into pieces and slitting, drying for 1h under the vacuum condition of 120 ℃ to obtain the cathode plate with the specification of 74 mm multiplied by 867 mm. And a cathode tab is welded on the cathode pole piece, and the cathode tab is made of aluminum foil.
The manufacturing method of the anode plate in the secondary battery comprises the following steps: mixing anode active material graphite, binder styrene butadiene rubber and thickener carboxymethylcellulose sodium according to the mass ratio of 97.4:1.4:1.2, adding deionized water, and uniformly stirring under the action of a vacuum stirrer to obtain anode slurry, wherein the solid content of the anode slurry is 75 wt%. And uniformly coating the anode slurry on one surface of an anode current collector copper foil with the thickness of 12 mu m, and drying the copper foil at 120 ℃ to obtain the anode with the coating thickness of 130 mu m and the single-side coated with the anode active material layer. Repeating the steps on the other surface of the aluminum foil to obtain the anode plate with the anode active material layer coated on the two surfaces. Then, after cold pressing, cutting into pieces and slitting, drying for 1h under the vacuum condition of 120 ℃ to obtain the anode piece with the specification of 78 mm multiplied by 875 mm. And (3) welding and connecting an anode tab on the anode pole piece, wherein the anode tab is made of copper foil plated with nickel.
The diaphragm of the secondary battery is a porous polyethylene film with the thickness of 7 mu m.
And (3) sequentially stacking the cathode pole piece, the diaphragm and the anode pole piece obtained by the preparation, enabling the diaphragm to be positioned between the cathode pole piece and the anode pole piece to play a role in isolation, and winding to obtain the electrode assembly. The electrode assembly is assembled with the case to obtain a packaged secondary battery. Dehydrating at 80 deg.C, injecting into prepared electrolyte, packaging, standing, and forming to obtain secondary battery. The electrolyte can be prepared from ethylene carbonate, propylene carbonate and diethyl carbonate according to the mass ratio of 1:1, wherein the concentration of lithium hexafluorophosphate is 1.15 mol/L.
The differences between the cathode plates in the respective comparative examples and examples are as follows:
comparative example 1
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 ，Li 2 C 4 O 4 The mass fraction of (a) was 1.2%, and the secondary battery produced using the cathode 6 was used as an experimental object without providing the concave portion 23 in the cathode 6.
Example 1
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 ，Li 2 C 4 O 4 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 2
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =1 of the concave portion 23, where L =200, R =10, and H = 20.
Example 3
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, wherein the parameter a = L/(R × H) =0.33 of the concave portion 23, where L =200, R =30, and H = 20.
Example 4
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, wherein the parameter a = L/(R × H) =0.2 of the concave portion 23, where L =200, R =50, and H = 20.
Example 5
In the cathode active material slurry, the mass fraction of the cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and the lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode plate 6 is arranged by a laser drilling processRecess 23, the parameter a = L/(R × H) =0.18 of recess 23, where L =200, R =55, H = 20.
Example 6
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, wherein the parameter a = L/(R × H) =13.33 of the concave portion 23, where L =200, R =5, and H = 3.
Example 7
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =4 of the concave portion 23, where L =200, R =5, and H = 10.
Example 8
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =1.33 of the concave portion 23, where L =200, R =5, and H = 30.
Example 9
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =1.14 of the concave portion 23, where L =200, R =5, and H = 35.
Example 10
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, wherein the parameter a = L/(R × H) =0.5 of the concave portion 23, where L =50, R =5, and H = 20.
Example 11
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =1 of the concave portion 23, where L =100, R =5, and H = 20.
Example 12
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, the cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =1.5 of the concave portion 23, where L =150, R =5, and H = 20.
Example 13
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =3 of the concave portion 23, where L =300, R =5, and H = 20.
Example 14
The mass fraction of the cathode active material 4 in the cathode active material slurry was 95.5%, and the cathode active material 4 was lithium cobaltateThe mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and the lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, and the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =5 of the concave portion 23, where L =500, R =5, and H = 20.
Example 15
In the cathode active material slurry, the mass fraction of the cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and the lithium supplement material 3 is Li 2 C 4 O 4 The mass fraction of Li2C4O4 is 1.2%, the cathode sheet 6 is provided with the concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =6 of the concave portion 23, where L =600, R =5, and H = 20.
Example 16
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium nickelate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 ，Li 2 C 4 O 4 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 17
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium manganate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 4 O 4 ，Li 2 C 4 O 4 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 18
The mass fraction of the cathode active material 4 in the cathode active material slurry is 95.5%, the mass fraction of the cathode active material 4 is lithium cobalt phosphate, the mass fraction of polyvinylidene fluoride is 1.7%, and the mass fraction of super p conductive carbon blackThe mass fraction is 1.6 percent, and the lithium supplement material 3 is Li 2 C 4 O 4 ，Li 2 C 4 O 4 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 19
In the cathode active material slurry, the mass fraction of the cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is 1:1 mixed lithium cobaltate and lithium nickelate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and the lithium supplement material 3 is Li 2 C 4 O 4 ，Li 2 C 4 O 4 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 20
The mass fraction of the cathode active material 4 in the cathode active material slurry is 95.5%, the mass fraction of the cathode active material 4 is 1:1 mixed lithium cobaltate and lithium manganate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and the mass fraction of the lithium supplement material 3 is Li 2 C 4 O 4 ，Li 2 C 4 O 4 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 21
The mass fraction of the cathode active material 4 in the cathode active material slurry is 95.5%, the mass fraction of the cathode active material 4 is 1:1 mixed lithium cobalt oxide and lithium cobalt phosphate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and the mass fraction of the lithium supplement material 3 is Li 2 C 4 O 4 ，Li 2 C 4 O 4 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 22
The mass fraction of the cathode active material 4 in the cathode active material slurry was 95.5%, and the cathode active material 4 wasLithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and the lithium supplement material 3 is Li 2 C 3 O 3 ，Li 2 C 3 O 3 Is 1.2%, the cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the concave portion 3, where L =200, R =5, and H = 20.
Example 23
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 5 O 5 ，Li 2 C 5 O 5 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 24
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and a lithium supplement material 3 is Li 2 C 6 O 6 ，Li 2 C 6 O 6 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 25
In the cathode active material slurry, the mass fraction of the cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, and the lithium supplement material 3 is LiN 3 ，LiN 3 Is 1.2%, the cathode sheet 6 is provided with a recess 23 by a laser drilling process, and the parameter a = L/(R × H) =2 of the recess 23, where L =200, R =5, and H = 20.
Example 26
The mass fraction of the cathode active material 4 in the cathode active material slurry was 95.5%, the cathode active material 4 was lithium cobaltate, the mass fraction of polyvinylidene fluoride was 1.7%, suThe mass fraction of per p conductive carbon black is 1.6%, the mass fraction of the lithium supplement material 3 is 1.2%, and the mass fraction of the lithium supplement material 3 is 1:1 mixed Li 2 C 3 O 3 And Li 2 C 4 O 4 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =2 of the concave portion 23, where L =200, R =5, and H = 20.
Example 27
In the cathode active material slurry, the mass fraction of the cathode active material 4 was 95.5%, the mass fraction of the cathode active material 4 was lithium cobaltate, the mass fraction of polyvinylidene fluoride was 1.7%, the mass fraction of super p conductive carbon black was 1.6%, the mass fraction of the lithium supplement material 3 was 1.2%, and the mass fraction of the lithium supplement material 3 was 1:1 mixed Li 2 C 3 O 3 And Li 2 C 5 O 5 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =2 of the concave portion 23, where L =200, R =5, and H = 20.
Example 28
In the cathode active material slurry, the mass fraction of the cathode active material 4 was 95.5%, the mass fraction of the cathode active material 4 was lithium cobaltate, the mass fraction of polyvinylidene fluoride was 1.7%, the mass fraction of super p conductive carbon black was 1.6%, the mass fraction of the lithium supplement material 3 was 1.2%, and the mass fraction of the lithium supplement material 3 was 1:1 mixed Li 2 C 3 O 3 And Li 2 C 6 O 6 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =2 of the concave portion 23, where L =200, R =5, and H = 20.
Example 29
In the cathode active material slurry, the mass fraction of the cathode active material 4 was 95.5%, the mass fraction of the cathode active material 4 was lithium cobaltate, the mass fraction of polyvinylidene fluoride was 1.7%, the mass fraction of super p conductive carbon black was 1.6%, the mass fraction of the lithium supplement material 3 was 1.2%, and the mass fraction of the lithium supplement material 3 was 1:1 mixed Li 2 C 3 O 3 And LiN 3 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =2 of the concave portion 23, where L =200, R =5, and H = 20.
Example 30
Mass fraction of cathode active material 4 in cathode active material slurry95.5 percent, the cathode active material 4 is 1:1 mixed lithium cobaltate and lithium nickelate, the mass fraction of polyvinylidene fluoride is 1.7 percent, the mass fraction of super p conductive carbon black is 1.6 percent, the mass fraction of the lithium supplement material 3 is 1.2 percent, and the mass fraction of the lithium supplement material 3 is 1:1 mixed Li 2 C 3 O 3 And Li 2 C 5 O 5 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =2 of the concave portion 23, where L =200, R =5, and H = 20.
Example 31
The mass fraction of the cathode active material 4 in the cathode active material slurry was 95.5%, the mass fraction of the cathode active material 4 was 1:1 mixed lithium cobalt oxide and lithium cobalt phosphate, the mass fraction of polyvinylidene fluoride was 1.7%, the mass fraction of super p conductive carbon black was 1.6%, the mass fraction of the lithium supplement material 3 was 1.2%, and the mass fraction of the lithium supplement material 3 was 1:1 mixed Li 2 C 3 O 3 And Li 2 C 6 O 6 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =2 of the concave portion 23, where L =200, R =5, and H = 20.
Example 32
In the cathode active material slurry, the mass fraction of the cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, the mass fraction of the lithium supplement material 3 is 1.2%, and the mass fraction of the lithium supplement material 3 is Li 2 C 4 O 4 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =1 of the concave portion 23, where L =50, R =10, and H = 5.
Example 33
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, the mass fraction of a lithium supplement material 3 is 1.2%, and the mass fraction of the lithium supplement material 3 is Li 2 C 4 O 4 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =0.2 of the concave portion 23, where L =300, R =50, and H = 30.
Example 34
Cathode electrodeThe mass fraction of the cathode active material 4 in the active material slurry is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, the mass fraction of the lithium supplement material 3 is 1.2%, and the mass fraction of the lithium supplement material 3 is Li 2 C 4 O 4 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =0.03, where L =50, R =50, and H =30, of the concave portion 23.
Example 35
In the cathode active material slurry, the mass fraction of a cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, the mass fraction of a lithium supplement material 3 is 1.2%, and the mass fraction of the lithium supplement material 3 is Li 2 C 4 O 4 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =6 of the concave portion 23, where L =300, R =10, and H = 5.
Example 36
In the cathode active material slurry, the mass fraction of the cathode active material 4 is 95.5%, the mass fraction of the cathode active material 4 is lithium cobaltate, the mass fraction of polyvinylidene fluoride is 1.7%, the mass fraction of super p conductive carbon black is 1.6%, the mass fraction of the lithium supplement material 3 is 1.2%, and the mass fraction of the lithium supplement material 3 is Li 2 C 4 O 4 The cathode sheet 6 is provided with a concave portion 23 by a laser drilling process, and a parameter a = L/(R × H) =5 of the concave portion 23, where L =300, R =10, and H = 6.
The cathode sheet 6 in the secondary batteries of the above comparative examples and examples was subjected to an adhesion test. The adhesion test method of the cathode plate 6 is as follows:
discharging the formed full-charge secondary battery to 3V with the discharge rate of 1C, disassembling the secondary battery, cutting a cathode plate 6 into a rectangular sample with the length of 100mm and the width of 10 mm, adhering the side face, away from the cathode current collector 1, of the electrode plate sample on a stainless steel plate at one end of the electrode plate sample by using a double-faced adhesive tape, fixing the stainless steel plate, connecting the cathode current collector 1 at the other end of the electrode plate sample with a tensile force measuring device, testing the stripping force of a cathode active material layer 2 and the cathode current collector 1 in the cathode plate 6 by adopting a 180-degree stripping strength test method, wherein the stripping speed in the testing process is 300 mm/min, the stripping length in the testing process is 40 mm, and the adhesive force of the cathode plate 6 can be obtained through the test.
In some embodiments of the present application, the decomposition rate of the lithium supplement material 3 in the cathode electrode sheet 6 in the secondary battery in the above comparative examples and embodiments can be tested, and the actual capacity of the secondary battery is divided by the design capacity as the decomposition rate of the lithium supplement material 3, and the higher the decomposition rate of the lithium supplement material 3 represents the more sufficient the decomposition of the lithium supplement material 3.
The design capacity of the secondary battery can be calculated according to the gram charge capacity of the cathode material after complete lithium removal, and the theoretical exertion capacity of the lithium supplement material 3.
The method for testing the actual capacity of the secondary battery is as follows: under the environment of 25 ℃, the secondary battery is subjected to constant current charging at the charging rate of 0.2C until the voltage of the secondary battery reaches 4.45V; charging the secondary battery at a constant voltage with a charging voltage of 4.45V until the charging rate reaches 0.025C; performing constant current discharge on the secondary battery at a discharge rate of 0.2C until the voltage of the secondary battery reaches 3.0V; the above-described procedure was repeated 3 times, and the average capacity of the secondary battery was taken as the actual capacity of the secondary battery.
In some embodiments of the present application, qualitative tests can also be performed on the existence of residues of the lithium supplement material 3 in the cathode electrode sheet 6 in the secondary battery in the above comparative examples and embodiments.
The test method comprises the following steps: taking the formed secondary battery, and carrying out constant current discharge on the secondary battery at a discharge rate of 0.2C until the voltage of the secondary battery reaches 3.0V; disassembling the secondary battery and scraping off all the materials on the cathode active material layer 2; drying the scraped material for 24 hours at the temperature of 80 ℃; the scraped-off material was subjected to analysis for the presence or absence of residue in the cathode active material layer 2 by X-ray diffraction analysis or raman spectroscopy.
The secondary batteries manufactured by the cathode pole piece 6 in the comparative examples and the embodiments are tested for the discharge capacity retention rate, and the discharge capacity retention rate testing method under the discharge rate of 1C under the environment of 25 ℃ is as follows:
performing constant-current charging on the secondary battery at a charging rate of 0.2C until the voltage of the secondary battery reaches 4.45V; charging the secondary battery at a constant voltage with a charging voltage of 4.45V until the charging rate reaches 0.025C; performing constant-current discharge on the secondary battery at a discharge rate of 0.2C until the voltage of the secondary battery reaches 3.0V; repeating the above-mentioned procedure 3 times, and taking the average discharge capacity of the secondary battery as the actual discharge capacity (discharge capacity at 0.2C discharge rate) of the secondary battery;
performing constant-current charging on the secondary battery at a charging rate of 0.2C until the voltage of the secondary battery reaches 4.45V; charging the secondary battery at a constant voltage with a charging voltage of 4.45V until the charging rate reaches 0.025C; performing constant current discharge on the secondary battery at a discharge rate of 1C until the voltage of the secondary battery reaches 3.0V; repeating the above process for 3 times, and taking the average discharge capacity as the actual discharge capacity of the secondary battery at the discharge rate of 1C;
the discharge capacity retention rate of the secondary battery at the 1C discharge rate can be obtained by dividing the actual discharge capacity of the secondary battery at the 1C discharge rate by the actual discharge capacity of the secondary battery.
The method for testing the discharge capacity retention rate at the 2C discharge rate in the environment of 25 ℃ is as follows:
performing constant-current charging on the secondary battery at a charging rate of 0.2C until the voltage of the secondary battery reaches 4.45V; charging the secondary battery at a constant voltage with a charging voltage of 4.45V until the charging rate reaches 0.025C; performing constant current discharge on the secondary battery at a discharge rate of 0.2C until the voltage of the secondary battery reaches 3.0V; repeating the above-mentioned procedure 3 times, and taking the average discharge capacity of the secondary battery as the actual discharge capacity (discharge capacity at 0.2C discharge rate) of the secondary battery;
performing constant-current charging on the secondary battery at a charging rate of 0.2C until the voltage of the secondary battery reaches 4.45V; charging the secondary battery at a constant voltage with a charging voltage of 4.45V until the charging rate reaches 0.025C; performing constant-current discharge on the secondary battery at a discharge rate of 2C until the voltage of the secondary battery reaches 3.0V; repeating the above process for 3 times, and taking the average discharge capacity as the actual discharge capacity of the secondary battery at the 2C discharge rate;
and dividing the actual discharge capacity of the secondary battery at the 2C discharge rate by the actual discharge capacity of the secondary battery to obtain the discharge capacity retention rate of the secondary battery at the 2C discharge rate.
And (3) carrying out porosity test on the cathode plate 6 in the comparative examples and the embodiments, wherein a mercury porosimeter is required to be used in the porosity test process, and the porosity test method of the cathode plate 6 comprises the following steps:
taking the cathode pole piece 6 provided with the cathode active material layer 2 as a test sample;
selecting a suitable dilatometer based on the prediction of density and porosity of the test sample;
placing the test sample in an oven to be baked for 2 hours to remove moisture in the test sample;
weighing the test specimen without water;
loading the test sample into an dilatometer, sealing and weighing, wherein the weights of the test sample and the dilatometer are obtained;
loading the dilatometer into a low pressure station, and performing low pressure analysis according to a preset low pressure analysis program so that the pressure is in the range of 0.5psi to 50 psi;
after the low-pressure analysis is finished, taking out the dilatometer and weighing, wherein the weight of the dilatometer, the test sample and the mercury is the weight of the mercury;
the expansion meter is arranged in a high-pressure station, the high-pressure cabin head is screwed in after the expansion meter is fixed, and the high-pressure cabin head is screwed in the bottom and drives away bubbles of the expansion meter;
performing high-pressure analysis according to a preset high-pressure analysis program to enable the pressure to be in the range of 100psi to 60000 psi;
and (5) after the high-pressure analysis is finished, cleaning the dilatometer and testing the structure.
The method for testing the bonding strength of the cathode plate 6 comprises the following steps:
testing with a high-speed rail tensile machine, fixing the cathode (30 mm wide multiplied by length (100mm to 160mm)), fixing a double-sided gummed paper (model: 3M9448A, 20mm wide multiplied by length (90mm to 150mm)) on a steel plate, fixing a paper tape with the same width as the cathode and one side of the cathode with gummed paper, adjusting a limiting block of the tensile machine to a proper position, turning and sliding the paper tape upwards for 40 mm at a sliding speed of 50 mm/min, and testing the bonding strength between the cathode active material layer 2 and the cathode current collector 1 under 180 degrees (namely, stretching in the opposite direction).
The pore volume of the test sample can be obtained by dividing the measured weight of the mercury by the density of the mercury through the test process, and the porosity of the test sample can be obtained through calculation. This procedure is a commonly used technical means and method by a person skilled in the art and will not be described in detail here.
Table 1 is an example of various parameters of the secondary battery and the cathode sheet 6 in comparative examples and examples obtained by testing in comparative experiments of the present application.
As can be seen from table 1, the provision of the concave portion 23 significantly increases the adhesion of the cathode sheet, because the concave portion 23 can serve as a diffusion channel for the gas generated by the decomposition of the lithium supplement material 3, so that the gas in the decomposed substance can be smoothly discharged along the concave portion 23, the accumulation of the gas in the decomposed substance in the cathode active material layer 2 is reduced, the problem of insufficient adhesion of the cathode sheet 6 due to the accumulation of the gas in the decomposed substance is alleviated, and the processability of the cathode sheet 6 is improved, thereby improving the processability of the secondary battery; in addition, the concave part 23 can reduce the concentration difference of lithium ions on the surface layer and the inner layer of the pole piece active material layer, and can balance the internal and external reaction rates of the pole piece active material layer, so that the lithium supplement material 3 is decomposed more fully in the cathode pole piece 6, the overall porosity of the cathode pole piece 6 is improved after the lithium supplement material 3 is decomposed fully, and the discharge rate performance of the secondary battery is improved.
Compared with the other examples, in the embodiments 6, 15 and 32 to 36, when A is more than or equal to 0.2 and less than or equal to 5, the bonding strength of the cathode plate 6 is more than 20N/m, the decomposition rate of the lithium supplement material 3 is more than 90%, the discharge capacity retention rate under the 1C discharge rate is more than 90%, and the discharge capacity retention rate under the 2C discharge rate is more than 85%; when A exceeds the range of 0.2 to 5, the bonding strength of the cathode pole piece 6 is less than 20N/m, the decomposition rate of the lithium supplement material 3 is less than or equal to 90 percent, the discharge capacity retention rate under the 1C discharge rate is less than or equal to 90 percent, and the discharge capacity retention rate under the 2C discharge rate is less than 85 percent. It can be shown that A is more than or equal to 0.2 and less than or equal to 5, which can improve the adhesive force of the cathode plate 6 in the secondary battery, accelerate the decomposition of the lithium supplement material 3 in the cathode plate 6, and effectively improve the discharge rate performance of the secondary battery.
The embodiment of the present application further provides a method for manufacturing a secondary battery, which includes the following steps:
preparing a lithium supplement material 3, a cathode active material 4 and a cathode binder into cathode slurry according to a preset proportion; disposing the cathode slurry on a cathode current collector 1 to form a cathode active material layer 2, and obtaining a cathode sheet 6; forming a concave portion 23 on the cathode active material layer 2, the cathode active material layer 2 having a first surface 21 distant from the cathode current collector 1, the concave portion 23 penetrating the first surface 21; assembling the cathode plate 6, the separator 9 and the anode plate 5 into an electrode assembly 10; assembling the electrode assembly 10 to obtain a secondary battery; and (4) performing formation on the secondary battery.
TABLE 1
Figure 613350DEST_PATH_IMAGE001
By the preparation method of the secondary battery, the cathode pole piece in the secondary battery provided by the technical scheme can be obtained, the cathode pole piece not only contains the lithium supplement material 3, but also has a concave part, so that the secondary battery has better discharge performance and processing performance, and the improvement of user experience is facilitated.
As shown in fig. 9, the present embodiment also provides an electronic device 3000 using a secondary battery 2000 as a power source, and the electronic device 3000 may be a mobile phone, a portable device, a notebook computer, an electric toy, an electric tool, or the like. Power tools include metal cutting power tools, cleaning tools, and the like, such as electric drills, electric wrenches, vacuum cleaners, sweeping robots, and the like. The electronic device 3000 according to the embodiment of the present application is not particularly limited.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; these modifications and substitutions do not depart from the spirit of the embodiments of the present application, and they should be construed as being included in the scope of the claims and description of the present application. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. The present application is not intended to be limited to the particular embodiments disclosed herein, but rather to cover all embodiments falling within the scope of the appended claims.

Claims (18)

1. A secondary battery comprising an electrode assembly including a cathode plate including a cathode current collector and a cathode active material layer disposed on the cathode current collector;
the cathode active material layer comprises a cathode active material and a cathode binder, and is subjected to lithium supplement treatment;
the cathode active material layer has a first surface far from the cathode current collector, and the cathode active material layer is provided with a concave portion penetrating through the first surface.
2. The secondary battery according to claim 1, wherein the recess includes a hole and/or a groove.
3. The secondary battery according to claim 1, wherein the radius of the concave portion is R μm, and R is 10. ltoreq. R.ltoreq.50.
4. The secondary battery according to claim 1, wherein the depth of the concave portion is H μm, 5. ltoreq. H.ltoreq.30.
5. The secondary battery according to claim 1, wherein the cathode active material layer is provided with a plurality of the recesses, and a distance between adjacent two of the recesses is L μm, L.ltoreq.50.ltoreq.L.ltoreq.300.
6. The secondary battery according to claim 1, wherein the cathode active material layer is provided with a plurality of the recesses having a radius of R μm, a depth of H μm, and a distance between adjacent two of the recesses of L μm, defining a = L/(R × H), 0.2 ≦ a ≦ 5.
7. The secondary battery according to claim 1, wherein a height of the edge portion of the concave portion protruding from the first surface is h μm, 3. ltoreq. h.ltoreq.10.
8. The secondary battery according to claim 1, wherein a sectional shape of the concave portion is a V-shape.
9. The secondary battery according to claim 1, wherein the recess is formed by a laser processing process.
10. The secondary battery according to claim 1, wherein the cathode active material layer is provided on a surface of the cathode current collector.
11. The secondary battery according to claim 10, wherein the adhesive strength of the cathode active material layer to the cathode current collector is F N/m, 15 ≦ F ≦ 30.
12. The secondary battery of claim 1, wherein the cathode active material layer further comprises a lithium-supplementing material comprising LiN 3 、Li 2 O 2 、Li 2 O、Li 2 C 3 O 3 、Li 2 C 4 O 4 、Li 2 C 2 O 4 、Li 2 C 3 O 5 、Li 2 C 5 O 5 、Li 2 C 6 O 6 、Li 2 C 4 O 6 、Li x S y Wherein x is more than or equal to 1 and less than or equal to 10, and y is more than or equal to 1 and less than or equal to 10.
13. The secondary battery of claim 1, wherein the cathode active material comprises at least one of lithium cobaltate, lithium nickelate, lithium manganate, lithium cobalt phosphate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate.
14. The secondary battery according to claim 1, wherein the electrode assembly further comprises an anode sheet and a separator, the cathode sheet, the separator and the anode sheet are stacked, and the first surface is in contact with the separator.
15. An electronic device characterized by comprising the secondary battery according to any one of claims 1 to 14.
16. A method of manufacturing a secondary battery, comprising:
preparing a lithium supplement material, a cathode active material and a cathode binder into cathode slurry according to a preset proportion;
arranging the cathode slurry on a cathode current collector to form a cathode active material layer and obtain a cathode plate;
forming a recess on the cathode active material layer, the cathode active material layer having a first surface remote from the cathode current collector, the recess penetrating the first surface;
assembling the cathode sheets into an electrode assembly;
assembling the electrode assembly to obtain the secondary battery according to any one of claims 1 to 14;
and performing formation on the secondary battery.
17. The method of claim 16, wherein the lithium-supplementing material comprises LiN 3 、Li 2 O 2 、Li 2 O、Li 2 C 3 O 3 、Li 2 C 4 O 4 、Li 2 C 2 O 4 、Li 2 C 3 O 5 、Li 2 C 5 O 5 、Li 2 C 6 O 6 、Li 2 C 4 O 6 、Li x S y Wherein x is more than or equal to 1 and less than or equal to 10, and y is more than or equal to 1 and less than or equal to 10.
18. The method of manufacturing a secondary battery according to claim 16, wherein the concave portion is formed on the cathode active material layer by a laser processing process.
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