CN114497445A - Pole piece, electrochemical device and electric equipment - Google Patents

Pole piece, electrochemical device and electric equipment Download PDF

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Publication number
CN114497445A
CN114497445A CN202210172535.1A CN202210172535A CN114497445A CN 114497445 A CN114497445 A CN 114497445A CN 202210172535 A CN202210172535 A CN 202210172535A CN 114497445 A CN114497445 A CN 114497445A
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China
Prior art keywords
active material
pole piece
groove
lithium
width direction
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CN202210172535.1A
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CN114497445B (en
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江静
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Dongguan Poweramp Technology Ltd
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Dongguan Poweramp 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/025—Electrodes composed of, or comprising, active material with shapes other than plane or cylindrical
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • 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

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

Abstract

The application relates to a pole piece, an electrochemical device and electric equipment, which comprise a current collector and an active substance layer, wherein the active substance layer is arranged on at least one surface of the current collector, and at least one groove is formed in the active substance layer along the length direction of the pole piece; the groove can be used as a soaking channel of electrolyte to the active substance layer to increase the contact area of the active substance layer and the electrolyte, so that the electrolyte can fully soak the active substance layer in a short time, thereby reducing the risk of electrolyte breaking and improving the cycle life of the electrochemical device.

Description

Pole piece, electrochemical device and electric equipment
Technical Field
The application relates to the technical field of batteries, in particular to a pole piece, an electrochemical device and electric equipment.
Background
Lithium ion batteries are widely used in products such as mobile phones, flat panels, notebook computers, and electric vehicles due to their characteristics of high energy density, long cycle performance, and low pollution.
The lithium ion battery generally comprises electrolyte and a pole piece with an active substance layer, and the electrolyte is difficult to fully soak the active substance layer in a short time in the charging and discharging processes of the lithium ion battery, so that the cycle life of the lithium ion battery is influenced.
Disclosure of Invention
In view of the above problems, the present application provides a pole piece, an electrochemical device, and an electrical apparatus, which can alleviate the problem that the cycle life of a lithium ion battery is affected due to the difficulty of fully soaking an active material layer in an electrolyte in a short time.
The technical scheme of the application is realized as follows:
in a first aspect, an embodiment of the present application provides a pole piece, including a current collector and an active material layer, the active material layer is disposed on at least one surface of the current collector, along a length direction of the pole piece, the active material layer is provided with at least one groove.
In the technical scheme of this application, the area of contact of active material layer and electrolyte can be increased to the slot to electrolyte is in the short time fully soaks the active material layer, thereby reduces the risk that the bridge cut-off takes place for electrolyte, with the cycle life who improves electrochemical device. On the other hand, the grooves can store electrolyte and provide electrolyte replenishment during recycling.
According to some embodiments of the application, the trench penetrates the active material layer.
When the groove penetrates through the active material layer, the groove can store electrolyte, so that the effect of improving pole piece infiltration is achieved; further, the pole piece can improve the infiltration of the pole piece in the middle of the innermost layer of the electrode assembly.
According to some embodiments of the application, the trench satisfies at least one of the following conditions: a) the depth of the groove with the diameter of 5 mu m or more is less than or equal to the thickness of the pole piece; b) 0< width of the slot <0.05 x pole piece in the width direction of the pole piece.
According to some embodiments of the present application, the depth of the trench is 5 μm to 400 μm, and the width of the trench is 0.05mm to 5 mm.
The depth of the groove can be set to be more than or equal to 5 mu m and less than or equal to the thickness of the active material layer, namely, the maximum depth of the groove can be equal to the thickness of the active material layer, so as to prevent the current collector from being broken due to the fact that holes are directly formed in the current collector; in addition, the depth of the groove can be set to be smaller than the thickness of the active material layer, so that potential safety hazards caused by direct exposure of the substrate can be prevented; specifically, in one embodiment, taking a pole piece with a thickness of 500 μm as an example, the depth of the groove can be set to be 5 μm-400 μm. The width of the groove along the width direction of the pole piece can also influence the charge-discharge cycle of the electrochemical device; therefore, a reasonable width of the groove needs to be selected, in this embodiment, the width of the groove can be selected to be greater than 0 μm and less than 0.05 times the width of the pole piece in the width direction of the pole piece, and specifically, the width of the groove can be set to be 0.05mm-5 mm.
According to some embodiments of the application, at least one of the grooves separates the active material layer into at least two active material blocks along a width direction of the pole piece, and the at least two active material blocks are arranged in sequence along the width direction of the pole piece.
Set up two active material blocks on a surface of mass flow body to adopt side by side coating, side by side coating only need set up two or more discharge gates side by side, and each discharge gate is independent each other, and each discharge gate can carry out the coating to the mass flow body simultaneously, compares in bilayer structure coating or mixed material coating, and side by side coating does not influence production efficiency, also need not increase extra process and the processing degree of difficulty.
According to some embodiments of the present application, two active material blocks on both sides of any one of the grooves satisfy at least one of the following conditions in a width direction of the pole piece: a) the active material types of the two active material blocks on the two sides of the groove are different; b) the active material proportions of the two active material blocks on the two sides of the groove are different; c) the two active material blocks on the two sides of the groove have different compaction densities; d) and the coating quality of the two active material blocks at the two sides of the groove is different.
Different types of active substances can cause different chemical properties of the active substance blocks, and different active substance types and active substance proportions can be selected according to different requirements so as to realize different functions of each active substance block; the proportion of the active material affects the energy density of the electrochemical device, and the proportion of the active material in each active material block can be selected according to the specific energy density requirement; the compacted density of the active material blocks directly influences the energy density of the electrochemical device, the greater the compacted density, the greater the energy density, and the appropriate compacted density of each active material block can be selected according to the specific use scenario.
According to some embodiments of the present application, the groove divides the active material layer into a first active material block and a second active material block in a width direction of the pole piece. The active material of the first active material block comprises at least one of lithium cobaltate, lithium-rich manganese base, lithium iron manganese phosphate, nickel cobalt manganese, lithium manganate and polyanion compound. The active material of the second active material block includes at least one of lithium cobaltate, a lithium-rich manganese group, lithium iron phosphate, lithium iron manganese phosphate, lithium manganate, and a polyanion compound.
According to some embodiments of the present application, still include utmost point ear, utmost point ear be close to set up in one side on the width direction of pole piece is followed the width direction of pole piece, two arbitrary in the active material block, be close to the bonding strength of the active material block of utmost point ear is greater than keeps away from the bonding strength of the active material block of utmost point ear.
The bonding strength of the active material block close to the pole lug is set to be larger than that of the active material block far away from the pole lug, so that the pole piece is prevented from being bent and powdering during winding.
According to some embodiments of the present application, the pole piece further includes a tab, the tab is disposed on one side of the pole piece in the width direction, the tab is close to the first active material block, and the pressure proof performance of the active material of the first active material block is greater than the pressure proof performance of the active material of the second active material block. The upper limit of the compaction density of the pole piece is related to the type of the active substance. Under the condition that other factors influencing the compaction density are constant, the active substance of the pole piece with higher upper limit of the compaction density has better compaction resistance.
Active materials of the active material blocks at two ends are designed to have higher compaction-resistant density than other active material blocks on the pole piece, so that the problem that the lithium is separated out on the edge of the pole piece under excessive pressure and the current collector is broken under excessive pressure can be effectively solved. Further, in some embodiments, the ends of the active material block located at both ends may be designed to have a superior pressure proof performance than other portions of the active material block.
According to some embodiments of the present application, in a second aspect, there is also provided an electrochemical device comprising a pole piece as described in any of the above embodiments.
According to some embodiments of the present application, the pole piece includes positive pole piece and negative pole piece, the groove depth of positive pole piece is greater than the groove depth of negative pole piece, follows the width direction of pole piece, the width of the groove of positive pole piece is greater than the width of the groove of negative pole piece.
The groove depth of the positive pole piece is set to be larger than that of the negative pole piece, and the width of the groove of the positive pole piece is set to be larger than that of the groove of the negative pole piece, so that the active substance of the negative pole piece is more than that of the positive pole piece, and the lithium separation phenomenon is prevented.
According to some embodiments of the present application, in a third aspect, embodiments of the present application further provide an electric device, characterized by comprising the electrochemical device according to any of the embodiments described above.
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 additional 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. Moreover, like reference numerals are used to refer to like elements throughout. In the drawings:
FIG. 1 is a schematic structural view of a pole piece according to some embodiments of the present disclosure;
FIG. 2 is a schematic structural view of a pole piece according to some embodiments of the present disclosure;
fig. 3 is a schematic view of the application of an active material layer on a current collector according to some embodiments of the present application;
FIG. 4 is a schematic coating of a pole piece according to some embodiments of the present application;
FIG. 5 is a schematic structural view of a pole piece according to some embodiments of the present disclosure;
FIG. 6a is an enlarged view A of a portion of FIG. 1;
FIG. 6b is a schematic structural view of a trench according to some embodiments of the present application;
FIG. 6c is a schematic structural view of a trench according to some embodiments of the present application;
FIG. 7 is a schematic winding of a pole piece according to some embodiments of the present application;
FIG. 8 is a schematic structural view of a pole piece according to some embodiments of the present application;
FIG. 9 is a schematic structural view of a pole piece according to some embodiments of the present application;
FIG. 10 is a schematic view of a pole piece structure according to some embodiments of the present disclosure
FIG. 11 is a schematic structural view of an electrochemical device according to some embodiments of the present application
The reference numbers in the detailed description are as follows:
100. pole piece
10. A current collector;
20. an active material layer; 21. a first active material block; 22. a second active material block; 23. a third active material block; 24. a fourth active material block;
30. a trench;
40. a tab;
50. an insulating member;
200. an electrochemical 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.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "including" and "having," and any variations thereof, in the description and claims of this application and the description of the above figures are intended to cover non-exclusive inclusions.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. In the description of the embodiments of the present application, the term "plurality" refers to two or more (including two), and similarly, "plural sets" refers to two or more (including two), and "plural pieces" refers to two or more (including two).
In the description of the embodiments of the present application, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", and the like indicate the orientations and positional relationships based on the orientations and positional relationships shown in the drawings, and are only for convenience of describing the embodiments of the present application and simplifying the description, but do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the embodiments of the present application.
In the description of the embodiments of the present application, unless otherwise explicitly stated or limited, the terms "mounted," "connected," "fixed," and the like are used in a broad sense, and for example, may be 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 addition, the technical features mentioned in the different embodiments of the present application described below may be combined with each other as long as they do not conflict with each other.
A secondary battery is also called a rechargeable battery or a secondary battery, and refers to a battery that can be continuously used by activating an active material by charging after the battery is discharged. By utilizing the reversibility of chemical reactions, a new battery can be constructed, namely after one chemical reaction is converted into electric energy, the chemical system can be repaired by using the electric energy, and then the electric energy is converted into the electric energy by utilizing the chemical reaction, so the battery is called a secondary battery (a rechargeable battery). The main rechargeable batteries in the market include lithium ion batteries, polymer lithium ion batteries and the like.
In a secondary battery, an active substance is coated on a current collector in a slurry form, higher requirements are provided for the battery in the current market, such as low cost, high energy density and high safety, in order to meet the market demands, the coating weight and the compaction density of the active substance are higher and higher, so that the resistance of the electrolyte for infiltrating the active substance layer is increased, when the time for infiltrating the electrolyte from two ends of the active substance layer to the middle part is short, the electrolyte can be poorly infiltrated in the middle part of the active substance layer, and an electrolyte bridge cut-off easily occurs in the cycle process of the battery, so that black spots appear on the surface of a pole piece, and even the problem of attenuation and water jump caused by the circulation of the battery occurs.
In order to alleviate the problem that the cycle life of the lithium ion battery is affected due to the fact that the active material layer is difficult to fully soak the electrolyte, an embodiment of the present application provides a pole piece, and referring to fig. 1, the pole piece 100 includes a current collector 10 and an active material layer 20.
Referring to fig. 1 and 2, the electrode sheet 100 is an important component of an electrode assembly, and the electrode sheet 100 is generally formed by lamination or winding. For ease of lamination or winding, pole piece 100 may be provided in the form of a long sheet, and pole piece 100 has a length direction, a width direction, and a thickness direction, and when pole piece 100 is wound, it is usually wound along the length direction of pole piece 100. As can be seen from fig. 1 and 2, the longitudinal direction of the pole piece 100 is the X direction in fig. 2, the width direction is the Y direction in fig. 1 and 2, and the thickness direction is the Z direction in fig. 1.
Referring to fig. 1, a current collector 10 is a current collector 10 in which a pole piece 100 is a conductive substrate, the pole piece 100 generally includes a positive pole piece and a negative pole piece (both the positive pole piece and the negative pole piece are labeled in the figure), and different materials can be selected as the current collector 10 of the pole piece 100 according to the different kinds of the pole pieces 100, for example, an aluminum foil can be used as the current collector 10 for the positive pole piece, and a copper foil can be used as the current collector 10 for the negative pole piece.
Active material layer 20, referring to fig. 1, active material layer 20 may be disposed on at least one surface of current collector 10. Since the current collector 10 is a conductive substrate of the pole piece 100, and the outline thereof is usually a long sheet, in general, referring to fig. 1 and 3, the active material layer 20 is coated on the upper surface or the lower surface of the pole piece 100, or the active material layer 20 is coated on both the upper surface and the lower surface of the pole piece 100.
The active material layer 20 generally includes active materials, conductive agents, dispersants, additives, binders, and the like, and according to different categories of the electrode sheet 100, the active material layer 20 can select different active materials, and for a positive electrode sheet, the active material layer 20 can adopt some common positive active materials, such as: lithium cobaltate, rich lithium manganese base, lithium iron phosphate manganese, nickel cobalt manganese ternary, lithium manganate, polyanion compound, Prussian blue and the like, wherein the active material layer 20 of the positive pole piece can select one or more of the positive active materials, and the proportion of the positive active material in the active material layer 20 can be set to be 60-99.5%; for the negative electrode tab, the active material layer 20 may be selected from common negative active materials, such as: the active material layer 20 of the negative electrode plate can be one or more of the negative electrode active materials, and the proportion of the negative electrode active material in the active material layer 20 can be set to be 60-99.5%; either the positive or negative pole piece may have grooves 30 disposed thereon. Different active material blocks may employ different active materials. For example, the active material of some active material blocks includes at least one of lithium cobaltate, lithium rich manganese base, lithium iron manganese phosphate, nickel cobalt manganese ternary, lithium manganate, polyanionic compounds; the active material of the other active material blocks comprises at least one of lithium cobaltate, lithium-rich manganese base, lithium iron phosphate, lithium iron manganese phosphate, lithium manganate and polyanion compound.
Referring to fig. 1 and fig. 4, at least one groove 30 is disposed on the active material layer 20 of the pole piece 100, and the groove 30 is disposed along the length direction of the pole piece 100. As shown in fig. 1, taking a groove 30 as an example, the groove 30 is disposed in the middle of the pole piece 100 along the width direction of the pole piece 100, the groove 30 can divide the active material layer 20 into two active material blocks, which may be the same or different, and see fig. 1 for the case that the two active material blocks are the same, and see fig. 2 for the case that the two active material blocks are the same.
The inner cavity of the electrochemical device is generally provided with the pole piece 100 and the electrolyte, when the pole piece 100 is disposed in the inner cavity of the electrochemical device, the groove 30 on the pole piece 100 is used for storing the electrolyte, and the groove 30 can be used as a wetting channel of the electrolyte to the active material layer 20. Referring to fig. 5, the trenches 30 can increase the contact area between the active material layer 20 and the electrolyte, so that the electrolyte can sufficiently infiltrate the active material layer 20 in a short time, thereby reducing the risk of electrolyte bridge breakage and improving the cycle life of the electrochemical device. Alternatively, the channels 30 may store electrolyte and provide electrolyte replenishment during recycling.
Referring to fig. 2 and 5, the groove 30 is a straight continuous groove 30, and the groove 30 may penetrate the active material layer 20 or may not penetrate the active material layer 20 in the longitudinal direction of the pole piece 100. It is understood that trench 30, which may or may not extend through active material layer 20, may store electrolyte. When the groove 30 penetrates through the active material layer 20, the groove 30 can store electrolyte, thereby improving the wetting of the pole piece 100. Further, the function of improving the infiltration of the pole piece 100 at the middle position of the innermost layer of the electrode assembly can be achieved; it can be understood that, for a single trench 30, the trench 30 may be continuous or discontinuous, and may also be used as a wetting channel for the electrolyte to the active material layer 20, and when the trench 30 is a continuous trench 30, a larger contact area between the active material layer 20 and the electrolyte may be ensured; but in general, a partial area of the groove 30 may be closed off discontinuously due to production fluctuations, and the discontinuous portion should be less than 5% of the total length of the groove 30.
Referring to fig. 6a, fig. 6b and fig. 6c, the cross-sectional shape of the groove 30 can be selected from a triangle, a trapezoid, a rectangle, etc., wherein the cross-section is a section of the groove 30 perpendicular to the length direction of the pole piece 100, and the shape of the groove 30 can be selected according to the circumstances, and is not limited to the above shape in the present embodiment. In order to facilitate the rapid entry of the electrolyte into the trench 30, the opening of the trench 30 may be made as large as possible, and referring to fig. 6a, the cross-sectional area of the trench 30 is gradually reduced along the direction from the active material layer 20 to the current collector 10 in fig. 6a, so that the cross-sectional area of the trench 30 at the opening is maximized to facilitate the entry of the electrolyte into the trench 30 from the opening. The opening of the groove 30 can be smoothly connected with the active material layer 20, and the connection part has no rough appearance, so that the powder falling condition of the active material layer 20 at the opening of the groove 30 can be reduced.
Referring to fig. 7, an electrode assembly of an electrochemical device is generally formed by laminating and winding a positive electrode tab, a separator and a negative electrode tab, wherein the winding direction is generally the length direction of the positive electrode tab or the negative electrode tab, and therefore, in a general case, the gap between the positive electrode tab and the separator and the gap between the negative electrode tab and the separator are small, which makes it difficult for the electrolyte to enter the groove 30; in order to facilitate the entry of the electrolyte into the groove 30, in the present embodiment, a structure in which the groove 30 penetrates the active material layer 20 along the length direction of the pole piece 100 is preferably adopted. It can be understood that, when the positive electrode sheet, the separator or the negative electrode sheet is wound along the length direction, since the groove 30 penetrates through the active material layer 20, the groove 30 can store the electrolyte, thereby improving the wetting of the electrode sheet 100. Further, it may serve to improve the wetting of the pole piece 100 at the middle position of the innermost layer of the electrode assembly.
Referring to fig. 5, the pole piece 100 further includes a tab 40, the tab 40 is disposed on one side of the pole piece 100 in the width direction, and an insulating member 50 is further disposed on the pole piece 100 on the same side as the tab 40 for insulating the tab 40. The tab 40 is close to the first active material block 21, and the second active material block 22 is far from the tab, and the pressure proof performance of the active material of the first active material block 21 is higher than that of the active material of the second active material block 22. The upper limit of the compaction density of the pole piece 100 is related to the type of the active material, and the active material with the higher upper limit of the compaction density has higher compaction resistance under the condition that other factors influencing the compaction density are constant. In the case of the pole piece 100, the tab 40 may be connected to both sides in the width direction, and the active material pressure-proof performance of the active material blocks at both ends of the pole piece 100 is greater than that of the active material block in the middle in the width direction of the pole piece 100. It should be noted that the first active material block 21 and the second active material block 22 are the same as the active material blocks described above, and the following description is also applicable. In some embodiments, as shown in fig. 4, the active material layer 20 may be further divided into a first active material block 21, a second active material block 22, a third active material block 23 and a fourth active material block 24, and the four active material blocks may be all the same, two by two the same or different.
Referring to fig. 8, when the depth of the groove 30 is equal to the thickness of the pole piece 100, the groove 30 penetrates through the active material layer 20 and the current collector 10 in the thickness direction of the pole piece 100, so that the electrolyte can enter the groove 30 from the side of the current collector 10 away from the active material layer 20, and this structure can further improve the infiltration speed of the electrolyte on the active material layer 20.
However, the groove 30 penetrates through the current collector 10, the capacity loss of the inner cavity of the electrochemical device is large, and a through hole needs to be formed in the current collector 10, so that the tensile strength and the shear strength of the current collector 10 are reduced, the current collector 10 is prone to fracture when being wound, a potential safety hazard exists when a substrate is exposed, and the problem that the active material layer 20 around the groove 30 collapses and powder falls off is prone to be caused; the trench 30 is too shallow to effectively store electrolyte to improve charge-discharge cycle. In order to ensure that the trench 30 can effectively store the electrolyte and prevent the current collector 10 from breaking, in the present embodiment, the depth of the trench 30 may be greater than or equal to 5 μm and less than or equal to the thickness of the active material layer 20 along the thickness direction of the pole piece 100, that is, the maximum depth of the trench 30 may be equal to the thickness of the active material layer 20, so as to prevent the current collector 10 from breaking due to the hole being directly formed on the current collector 10. In addition, the depth of the trench 30 may be set to be smaller than the thickness of the active material layer 20 to prevent the substrate from being directly exposed to cause a safety hazard. Specifically, in one embodiment, taking pole piece 100 as an example with a thickness of 500 μm, the depth of trench 30 may be set to 5 μm-400 μm.
Based on the same inventive concept, the width of the groove 30 along the width direction of the pole piece 100 also has an effect on the charge-discharge cycle of the electrochemical device. The width of the groove 30 is too large, so that the capacity loss of the inner cavity of the electrochemical device is large, and the energy density of the electrochemical device is not improved; the width of the trench 30 is too small to effectively store the electrolyte to improve the charge and discharge cycle, and when the active material layers on both sides of the trench 30 are different, the active material layers 20 on both sides are likely to be entangled with each other when the active material layers are applied. Therefore, a reasonable width of the groove 30 needs to be selected, in this embodiment, the width of the groove 30 can be selected to be greater than 0 μm and less than 0.05 times the width of the pole piece 100 along the width direction of the pole piece 100, and specifically, the width of the groove 30 can be set to be 0.05mm-5 mm.
For the coating of the active material layer 20, the conventional coating method is to show different functions by matching different anode and cathode materials, for example, different slurry coatings are applied to the upper layer and the lower layer of the current collector 10 to make the upper layer and the lower layer have different functions, for example, the upper layer is changed by the slurry to improve the voltage platform, and the lower layer is changed by the slurry to improve the high temperature resistance, but the coating method is only applied to the upper layer and the lower layer of the current collector 10, and the production process and the production time are increased; there is another solution to mix and coat different functional materials, but the coating method may cause new problems, for example, the processing windows of the materials are different, so that the materials are difficult to be compatible, which increases the processing difficulty.
Therefore, in the present embodiment, referring to fig. 4, the current embodiment employs side-by-side coating on the surface of the current collector 10. The method of coating side by side can coat different active material layers on one surface of the current collector 10, during coating, two or more independent discharge ports can be adopted, each discharge port is arranged side by side along the width direction of the current collector 10, and the surface of the current collector 10 is coated along the length direction of the current collector 10, and a gap is preset between each discharge port, so that when coating, a gap exists between the active material layers 20 coated by two adjacent discharge ports, and the gap is the groove 30 in the above embodiment.
In one embodiment, referring to fig. 2 and 8, along the width direction of the pole piece 100, at least one groove 30 divides the active material layer 20 into at least two active material blocks, and the at least two active material blocks are sequentially arranged along the width direction of the pole piece 100. It is understood that the active material blocks in this embodiment are the active material layers 20 coated on the current collector 10 by the discharge ports in the side-by-side coating. And, side by side coating only need set up two or more discharge gates side by side, and each discharge gate can coat current collector 10 simultaneously, compares in bilayer structure coating or mixed material coating, and side by side coating does not influence production efficiency, does not need to increase extra process and the processing degree of difficulty either.
According to some embodiments of the present application, the two active material areas on both sides of any one groove 30 in the width direction of the pole piece 100 satisfy at least one of the following conditions: a. the two active material blocks on both sides of the trench 30 have different active material types; b. the active material proportions of the two active material blocks at the two sides of the groove 30 are different; c. the two active material areas on both sides of the groove 30 have different compaction densities; d) and the coating quality of the two active material blocks at the two sides of the groove is different.
It is understood that, in the present embodiment, the two active material blocks on two sides of the trench 30 are different, and include at least one of the above conditions a, b, and c, the different types of the active materials may cause different chemical properties of the active material blocks, the active material blocks further include a conductive agent, a dispersant, a binder, an additive, and the like, and the ratio of the active materials refers to the mass ratio of the active materials in the active material blocks, the ratio of each active material, or the type of non-active material auxiliary material. Different active material types and active material proportions can be selected according to different requirements, for example, in order to improve the bonding strength of the active material blocks on the current collector 10, the proportion of the binder in the active material blocks can be improved, namely, the proportion of the active material is reduced; in order to increase the energy density of the electrochemical device, the ratio of the active material can be increased. The compacted density of the active material block directly affects the energy density of the electrochemical device, and the greater the compacted density, the greater the energy density; however, the large compaction density can cause difficulty in infiltrating the whole active material block with the electrolyte in a short time, and the appropriate compaction density needs to be selected according to a specific use scene.
According to some embodiments of the present application, referring to fig. 10, the tab 40 is disposed on one side of the pole piece 100 in the width direction, and in any two active material blocks along the width direction of the pole piece 100, the bonding strength of the active material block close to the tab 40 is greater than that of the active material block far from the tab 40.
The electrode assembly needs to be formed by laminating and winding a positive electrode plate, an isolating film and a negative electrode plate, when the electrode plate 100 is welded with the electrode tab 40, part of the electrode tab 40 needs to be welded on the current collector 10, so that the thickness of the side close to the electrode tab 40 of the electrode plate 100 is increased, when the electrode plate 100 is wound, the side close to the electrode tab 40 of the electrode plate 100 is easy to bend and fall powder, therefore, an active substance block with high bonding strength needs to be adopted on the side close to the electrode tab 40, the bonding strength of the active substance block is related to the proportion of a bonding agent in the active substance block, and the bonding strength is higher when the proportion of the bonding agent is higher; on the side of the pole piece 100 far from the tab 40, it is not affected by the welding tab 40, so the active material block on the side of the far tab 40 usually does not need high bonding strength, i.e. on the side of the far tab 40, the ratio of the active material in the active material block is higher than that on the side of the near tab 40, in order to improve the energy density of the electrochemical device. It will be understood that the near tab 40 side is the portion of the pole piece 100 near the tab 40, and the far tab 40 side is the portion of the pole piece 100 away from the tab 40.
Referring to fig. 9, when active material layer 20 is coated on current collector 10, along the width direction of pole piece 100, both ends of active material layer 20 are generally referred to as thinning regions of pole piece 100, and the compressive strength of the active material in the thinning regions can be selected to be greater than that of the active material in the middle of the pole piece.
In order to obtain the optimal data of the depth and the width of the groove 30, some embodiments of the present application provide grooves 30 with different widths and depths on the pole piece 100, and use the pole piece 100 as a positive pole piece and a negative pole piece to manufacture an electrochemical device, and perform a capacity test and a cycle test on the electrochemical device, where the capacity test is as follows: constant current charging at 25 deg.C at 0.5 deg.C, constant voltage charging at CV0.05C to upper limit cut-off voltage, standing for 30min, discharging at 0.2 deg.C to lower limit cut-off voltage, repeating for three times, and taking and placing the maximum value of capacitance as the capacity of electrochemical device.
The cycle test was: charging at a constant current of 0.5C at a normal temperature of 25 ℃, charging at CV0.05C with a stabilized voltage to reach an upper limit cut-off voltage, standing for 30min, discharging at 1C to reach a lower limit cut-off voltage, and calculating a discharge capacity retention ratio (the discharge capacity ratio of the 500 th cycle to the discharge capacity of the initial first cycle);
the test results refer to table 1, where the interface refers to the surface morphology of the negative electrode sheet in the full charge state of the electrochemical device, and the substrate is the current collector 10.
TABLE 1
Figure BDA0003518930560000131
As can be seen from table 1 above, the absence of grooves 30 or the discontinuity of grooves 30 results in black spots at the interface, and the influence of grooves 30 on the capacitance is small, so that continuous grooves are preferred in the present application.
As for the depth and width of the trench 30, as can be seen from example 3 and comparative example 5 in table 1, when the width of the trench 30 is constant, the larger the depth of the trench 30 is, the smaller the capacitance is; as can be seen from example 4 and comparative example 6 in table 1, when the depth of the trench 30 is constant, the larger the width of the trench 30 is, the smaller the capacitance is; when the groove 30 penetrates through the whole pole piece 100, that is, the depth of the groove 30 is equal to the thickness of the pole piece 100, although no black spot appears on the interface, the current collector 10 is prone to powder falling and the base material is prone to fracture in production.
As can be seen from the above table, when the depth of the trench 30 is 50 μm to 400 μm and the width of the trench 30 is 2 μm to 5 μm, no black spots appear at the interface and the substrate is not broken; therefore, the depth of the trench 30 in the present application is preferably selected to be 50 μm to 400 μm, and the width is preferably selected to be 2 μm to 5 μm. In addition, when the depth of the trench 30 is 5 μm and the depth of the trench 30 is 0.05 μm, the interface is slightly blackened and the substrate is not broken, so that the depth of the trench 30 may be selected from 5 μm to 400 μm and the depth may be selected from 0.05 μm to 5 μm in the present application.
According to some embodiments of the present application, in a second aspect, the present application further provides an electrochemical device 200, please refer to fig. 11, in which the electrochemical device 200 includes the pole piece 100 according to any of the above embodiments.
According to some embodiments of the present application, the pole piece 100 of the electrochemical device 200 comprises a positive pole piece and a negative pole piece, the groove 30 of the positive pole piece has a depth greater than the groove 30 of the negative pole piece, and the width of the groove 30 of the positive pole piece is greater than the width of the groove 30 of the negative pole piece along the width direction of the pole piece 100.
The active material of the positive pole piece is less than that of the negative pole piece, and if the active material of the positive pole piece is more than that of the negative pole piece, lithium ions which are excessive from the positive pole piece cannot be inlaid, so that lithium precipitation is caused, and safety risk exists. Therefore, in the present embodiment, the depth of the groove 30 of the positive electrode plate is set to be greater than the depth of the groove 30 of the negative electrode plate, and the width of the groove 30 of the positive electrode plate is set to be greater than the width of the groove 30 of the negative electrode plate, so that the active material of the negative electrode plate is greater than the active material of the positive electrode plate, thereby preventing the lithium precipitation phenomenon.
It can be understood that, the larger the depth of the groove 30 is, the smaller the occupation ratio of the active material layer 20 in the pole piece 100 is, and likewise, the larger the width of the groove 30 is, the smaller the occupation ratio of the active material layer 20 in the pole piece 100 is, when the lengths of the grooves 30 of the positive pole piece and the negative pole piece are the same, the depth of the groove 30 of the positive pole piece is greater than the depth of the groove 30 of the negative pole piece and the width of the groove 30 of the positive pole piece is greater than the width of the groove 30 of the negative pole piece, which indicates that the occupation ratio of the active material layer 20 of the negative pole piece is greater than that of the active material layer 20 of the positive pole piece; when the active material ratio of the active material layers 20 of the two electrode sheets 100 is the same, the active material of the negative electrode sheet is more than that of the positive electrode sheet.
According to some embodiments of the present application, in a third aspect, the present application further provides an electric device, including the electrochemical device 200 according to any of the above embodiments, where the electric device includes a mobile phone, a tablet, a notebook, an electric vehicle, and other products.
It should be noted that the description of the present application and the accompanying drawings set forth preferred embodiments of the present application, however, the present application may be embodied in many different forms and is not limited to the embodiments described in the present application, which are not intended as additional limitations to the present application, but are provided for the purpose of providing a more thorough understanding of the present disclosure. Moreover, the above-mentioned technical features are combined with each other to form various embodiments which are not listed above, and all the embodiments are regarded as the scope described in the present specification; further, modifications and variations may occur to those skilled in the art in light of the foregoing description, and it is intended to cover all such modifications and variations as fall within the scope of the appended claims.

Claims (10)

1. The utility model provides a pole piece, includes the mass flow body and active substance layer, the active substance layer set up in at least one surface of the mass flow body, its characterized in that, follow the length direction of pole piece, the active substance layer is provided with at least one slot.
2. The pole piece of claim 1 wherein the groove extends through the active material layer.
3. The pole piece of claim 1, wherein the groove satisfies at least one of the following conditions:
a) the depth of the groove with the diameter of 5 mu m or more is less than or equal to the thickness of the pole piece;
b) 0< width of groove <0.05 x width of pole piece along width direction of said pole piece.
4. The pole piece of any one of claims 1 to 3, wherein at least one of the grooves divides the active material layer into at least two active material blocks in the width direction of the pole piece, the at least two active material blocks being arranged in sequence in the width direction of the pole piece.
5. The pole piece of claim 4, wherein along the width direction of the pole piece, the two active material areas on both sides of any one of the grooves satisfy at least one of the following conditions:
a) the active material types of the two active material blocks on the two sides of the groove are different;
b) the active material proportions of the two active material blocks on the two sides of the groove are different;
c) the two active material blocks on the two sides of the groove have different compaction densities;
d) and the coating quality of the two active material blocks at the two sides of the groove is different.
6. The pole piece of claim 4, wherein the groove separates the active material layer into a first active material block and a second active material block along a width direction of the pole piece;
the active material of the first active material block comprises at least one of lithium cobaltate, lithium-rich manganese base, lithium iron manganese phosphate, nickel cobalt manganese, lithium manganate and polyanion compound;
the active material of the second active material block includes at least one of lithium cobaltate, a lithium-rich manganese group, lithium iron phosphate, lithium iron manganese phosphate, lithium manganate, and a polyanion compound.
7. The pole piece of claim 6, further comprising a tab disposed on one side of the pole piece in the width direction, wherein the tab is close to the first active material block, the second active material block is far from the tab, and the active material of the first active material block has a greater pressure solid resistance than the active material of the second active material block.
8. An electrochemical device comprising a pole piece according to any one of claims 1 to 7.
9. The electrochemical device of claim 8, wherein the pole pieces comprise a positive pole piece and a negative pole piece, wherein the groove depth of the positive pole piece is greater than the groove depth of the negative pole piece, and the width of the groove of the positive pole piece is greater than the width of the groove of the negative pole piece along the width direction of the pole pieces.
10. An electric device comprising the electrochemical device according to claim 8 or 9.
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