CN114447418B - Electrochemical device and electronic device - Google Patents
Electrochemical device and electronic device Download PDFInfo
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- CN114447418B CN114447418B CN202210099517.5A CN202210099517A CN114447418B CN 114447418 B CN114447418 B CN 114447418B CN 202210099517 A CN202210099517 A CN 202210099517A CN 114447418 B CN114447418 B CN 114447418B
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- 239000011149 active material Substances 0.000 claims abstract description 73
- 239000011148 porous material Substances 0.000 claims description 61
- 239000002245 particle Substances 0.000 claims description 49
- 239000000463 material Substances 0.000 claims description 33
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 2
- 229910002804 graphite Inorganic materials 0.000 claims description 2
- 239000010439 graphite Substances 0.000 claims description 2
- 239000002210 silicon-based material Substances 0.000 claims description 2
- 239000003792 electrolyte Substances 0.000 abstract description 55
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 9
- 229910052744 lithium Inorganic materials 0.000 abstract description 9
- 238000001556 precipitation Methods 0.000 abstract description 8
- 230000000694 effects Effects 0.000 description 16
- 239000011295 pitch Substances 0.000 description 16
- 238000000034 method Methods 0.000 description 15
- 230000008595 infiltration Effects 0.000 description 11
- 238000001764 infiltration Methods 0.000 description 11
- 239000011236 particulate material Substances 0.000 description 11
- 230000008569 process Effects 0.000 description 9
- 239000008187 granular material Substances 0.000 description 6
- 238000004891 communication Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 230000035699 permeability Effects 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 239000012466 permeate Substances 0.000 description 4
- 230000010287 polarization Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 239000006258 conductive agent Substances 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000009736 wetting Methods 0.000 description 3
- 241001391944 Commicarpus scandens Species 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 230000001788 irregular Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 239000011163 secondary particle Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
-
- 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
-
- 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)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The embodiment of the invention relates to the technical field of batteries, in particular to a battery packAn electrochemical device and an electronic device are provided, the electrochemical device includes a first pole piece, the first pole piece includes a first current collector, a first layer body and a second layer body. The first current collector includes a first wall. The first layer body is arranged on one side of the first wall surface of the first current collector, and the first layer body comprises a first active material. The second layer body is arranged on the wall surface of the first layer body, which is away from the first current collector, and comprises a second active material. Wherein the second layer body is provided with a plurality of first holes, and the hole depth h of each first hole along the thickness direction of the second layer body 1 Average thickness H with the second layer body 1 Satisfies H of 0 μm or less 1 ‑h 1 Less than or equal to 2 mu m. In the scheme, the concentration difference of the electrolyte infiltrated by the first layer body and the second layer body of the first pole piece is reduced, the generation of the lithium precipitation phenomenon is reduced, the dynamic performance of the first pole piece is improved, and the battery capacity attenuation of the electrochemical device is relieved.
Description
Technical Field
The embodiment of the invention relates to the technical field of batteries, in particular to an electrochemical device and an electronic device.
Background
A battery is a device that converts external energy into electric energy and stores the electric energy therein to power external electric devices (e.g., portable electronic devices, etc.) at a desired time. At present, the battery is widely applied to electric equipment such as unmanned aerial vehicles, mobile phones, flat plates, notebook computers and the like. The existing battery is easy to generate the phenomenon of lithium precipitation after multiple charge and discharge, and the battery capacity of the battery is attenuated after the lithium precipitation.
Disclosure of Invention
The technical problem to be solved by the embodiments of the present invention is to provide an electrochemical device and an electronic device, which can alleviate battery capacity degradation while not excessively reducing energy density.
In order to solve the technical problems, the invention adopts a technical scheme that: an electrochemical device is provided, which includes a first pole piece including a first current collector, a first layer body, and a second layer body. The first current collector includes a first wall. The first layer body is arranged on one side of the first wall surface of the first current collector and comprises a first active material, the first layer body is provided with a plurality of second holes, and the hole depth H2 of each second hole along the thickness direction of the first layer body and the average thickness H2 of the first layer body are more than or equal to 0 mu m and less than or equal to H2-H2 and less than or equal to 80 mu m. The second layer body is arranged on the wall surface of the first layer body, which is far away from the first current collector, and comprises a second active material, the second active material and the first active material are different in material, density and structural form, and the structural form comprises Particle size and particle shape. Wherein, the second layer body is provided with a plurality of first holes, the number of the first holes is larger than that of the second holes, and the hole depth h of each first hole along the thickness direction of the second layer body 1 Average thickness H with the second layer body 1 Satisfies H of 0 μm or less 1 -h 1 Less than or equal to 2 mu m. In the scheme, one side of the first pole piece is provided with the first layer body and the second layer body, and two active material layers are arranged on the first layer body and the second layer body, so that the electrochemical device has higher energy density. Meanwhile, a plurality of first holes are formed in the second layer body, the hole depth of each first hole is basically the same as the thickness of the second layer body (the error is 2 mu m), so that electrolyte can permeate the first layer body to infiltrate the second layer body, the concentration difference of the electrolyte infiltrated by the first layer body and the second layer body of the first pole piece is reduced, the generation of a lithium precipitation phenomenon is reduced, the dynamic performance of the first pole piece is improved, and the battery capacity attenuation of the electrochemical device is relieved.
In some embodiments, the average hole spacing L of the first holes 1 Average hole spacing L from each second hole 2 Satisfy 0 μm < L 2 -L 1 Less than or equal to 500 mu m. By optimizing the relation between the average hole spacing of the first holes and the average hole spacing of the second holes, the electrolyte infiltration effect of the first layer body and the second layer body in the first pole piece can be improved, and the influence on the energy density of the electrochemical device can be reduced.
In some embodiments, the average pore diameter R of each first pore 1 Average pore diameter R of each second pore 2 Satisfy R of 0 μm < 1 -R 2 Less than or equal to 100 mu m. By optimizing the relationship between the average pore diameters of the first pores and the second pores, the electrolyte infiltration effect of the first layer body and the second layer body in the first pole piece can be improved, and the influence on the energy density of the electrochemical device can be reduced.
In some embodiments, the average pore diameter R of each first pore 1 Average pore diameter R of each second pore 2 Satisfy R of 1 to less than or equal to 1 /R 2 And is less than or equal to 5. Satisfying this relationship, a better electrolyte wetting effect can be obtained, and the influence on the energy density of the electrochemical device can be reduced.
In some embodiments, the second layer has an open porosity Q 1 Meet Q of 10 percent or less 1 Less than or equal to 50 percent. The aperture ratio Q of the first layer body 2 Q is more than or equal to 0.1 percent 2 Less than or equal to 20 percent. By setting the aperture ratio of the first layer and/or the second layer in a proper range, the electrolyte infiltration effect is improved, and the influence on the energy density of the electrochemical device is reduced.
In some embodiments, the average thickness H of the second layer 1 Satisfies H of 80 mu m or less 1 The aperture ratio Q of the second layer body 1 Meet Q of 30 percent or less 1 Less than or equal to 50 percent. Average thickness H of first layer body 2 Satisfies H of 50 mu m or less 2 The aperture ratio Q of the first layer body 2 Meet Q of 10 percent or less 2 Less than or equal to 20 percent. And the electrolyte infiltration effect is further improved by optimizing the relation between the opening ratio of the first layer and the thickness of the first layer and/or the relation between the opening ratio of the second layer and the thickness of the second layer.
In some embodiments, at least a portion of the second apertures are in one-to-one communication with the first apertures. By the arrangement, the time for the electrolyte to infiltrate the first-layer pole piece can be reduced, and the electrolyte infiltration effect is improved.
In some embodiments, the plane perpendicular to the thickness direction of the first layer body is a first plane, the projection of the first hole on the first plane is a first projection, the projection of the second hole on the first plane is a second projection, and the second projection is located in the corresponding first projection in the first hole and the second hole which are communicated with each other. The electrolyte infiltration effect is improved, and meanwhile, the influence on the energy density of the electrochemical device is reduced.
In some embodiments, the average thickness H of the first layer 1 Average thickness H with the second layer body 2 The method meets the following conditions: h is less than or equal to 100 mu m 1 +H 2 ＜200μm、1.05≤H 1 /H 2 Less than or equal to 1.5; or the average thickness of the first layer body and the average thickness H of the second layer body 2 The method meets the following conditions: h is more than or equal to 200 mu m 1 +H 2 ≤500μm、3≤H 1 /H 2 And is less than or equal to 5. Through setting up the second layer thickness and being less than first layer thickness and satisfying the scope of requirement, can reduce the difficulty that electrolyte infiltrated first layer from first pole piece surface, set up first hole at the second layer simultaneously, can promote the effect that electrolyte infiltrated in coordination.
In some embodiments, the first electrode sheet is a positive electrode sheet, and the first active material and the second active material each include nickel cobalt lithium manganate, wherein the nickel cobalt lithium manganate in the first active material is a polycrystalline material, and the nickel cobalt lithium manganate in the second active material is a monocrystalline material. The single crystal material is not easy to break in the circulation process, the second active material is set to be single crystal material, the first layer can be protected in the circulation process, and the integral gas production condition of the electrochemical device can be improved. Meanwhile, the monocrystal material has large polarization and poor dynamic performance, and the second layer body is perforated or provided with larger pore parameters, so that the dynamic performance of the monocrystal material can be further improved. The polycrystalline material has small polarization and good multiplying power performance, and the first layer body can meet the dynamic requirements without perforating or setting smaller pore parameters. Therefore, the advantages of the two can be combined, the gas production in the large-rate long-circulation process is reduced, and the effect of the large-rate long-circulation is improved.
In some embodiments, the first electrode sheet is a negative electrode sheet, the first active material comprises a silicon-containing material, and the second active material is graphite. The second active material is made of artificial graphite with small expansion, and can be used as buffer to inhibit the expansion of the first active material. If the first layer is also provided with openings, electrolyte can be stored and expansion of the first layer can be relieved.
In some embodiments, the first layer and the second layer satisfy at least one of the following conditions c) -d): a) The materials of the first active material and the second active material are all particle materials, and the average particle diameter D of the particles of the first active material 1 Average particle diameter D of particles with the second active material 2 Satisfy 2 is less than or equal to D 2 /D 1 Less than or equal to 20; b) The first active material and the second active material are all particles, and the average particle diameter D of the particles of the first active material 1 Satisfies D of 0.2 mu m 1 Average particle diameter D of particles of the second active material of 6 μm or less 2 Satisfy D of 5 μm 2 Less than or equal to 30 mu m. The first active material is provided with smaller particles, so that the electrolyte infiltration effect can be further improved, the lithium ion diffusion resistance is reduced, and the dynamics is improved.
In some implementationsIn an embodiment, the first pole piece is a positive pole piece. Area density M of first layer 1 Meets 10 mg/cm 2 ≤M 1 ≤30 mg/cm 2 Bulk density ρ of the first layer 1 Meets 3.4 mg/cm 3 ≤ρ 1 ≤4.5 mg/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the Area density M of the second layer 2 Meets 6 mg/cm 2 ≤M 2 ≤15 mg/cm 2 Bulk density ρ of the second layer 2 Meets 2.0 mg/cm 3 ≤ρ 2 ≤3.5 mg/cm 3 。
In some embodiments, the first pole piece is a negative pole piece. Area density M of first layer 3 Meets 8 mg/cm 2 ≤M 3 ≤20 mg/cm 2 Bulk density ρ of the first layer 3 Meets 1.5 mg/cm 3 ≤ρ 3 ≤2.0 mg/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the Area density M of the second layer 4 Meets 3 mg/cm 2 ≤M 4 ≤10 mg/cm 2 Bulk density ρ of the second layer 4 Meets 1.2 mg/cm 3 ≤ρ 4 ≤1.6 mg/cm 3 . By the arrangement, the electrolyte infiltration effect can be improved, and the influence on the energy density of the electrochemical device is reduced.
In some embodiments, the first layer has an areal density M 5 Area density M with the second layer body 6 Satisfies M of 1.1 ∈ 5 /M 6 And is less than or equal to 5. Or, the volume density ρ of the first layer body 5 Bulk density ρ with the second layer body 6 Satisfy ρ of 1.02 5 /ρ 6 Less than or equal to 1.3. By the arrangement, the electrolyte infiltration effect can be improved, and the influence on the energy density of the electrochemical device is reduced.
In some embodiments, the first pole piece further comprises a third layer, one side surface of the third layer is attached to the first wall surface, and the other side surface of the third layer is attached to the wall surface, facing away from the second layer, of the first layer. The third layer includes a conductive agent and a binder. By the arrangement, the binding force and conductivity between the first pole piece and the first current collector can be improved, the risk of falling off of the first pole piece is reduced, and the rate capability is improved.
In some embodiments, the first poleThe sheet further includes a fourth layer body and a fifth layer body. The fourth layer body is arranged on one side of the first current collector, which is away from the first wall surface, and comprises a third active material. The fifth layer body is arranged on the wall surface of the fourth layer body, which is away from the first current collector, and comprises a fourth active material. Wherein the fifth layer body is provided with a plurality of third holes, each third hole extends to the wall surface of the fifth layer body, which is away from the first layer body, and each third hole has a hole depth h along the thickness direction of the fifth layer body 3 Average thickness H with fifth layer body 3 Satisfies H of 0 μm or less 3 -H 3 Less than or equal to 2 mu m; the fourth layer body is provided with a plurality of fourth holes, and the depth h of each fourth hole along the thickness direction of the fourth layer body 4 The average thickness of the second layer and the fourth layer is more than or equal to 0 mu m and less than or equal to H 4 -h 4 ≤80μm。
In some embodiments, the electrochemical device further comprises a second electrode sheet, the second electrode sheet also having a polarity phase with the first electrode sheet, the second electrode sheet comprising a second current collector, a sixth layer, and a seventh layer. The second current collector includes a second wall. The sixth layer body is arranged on one side of the second wall surface of the second current collector, and the sixth layer body comprises a fifth active material. The seventh layer body is arranged on the wall surface of the sixth layer body, which is away from the second current collector, and the seventh layer body comprises a sixth active material. Wherein the seventh layer body is provided with a plurality of fifth holes, each fifth hole extends to the wall surface of the seventh layer body deviating from the sixth layer body, and each fifth hole has a hole depth h along the thickness direction of the seventh layer body 5 Average thickness H with seventh layer 5 Satisfies H of 0 μm or less 5 -H 5 ≤2μm。
The second aspect of the present invention also provides an electronic device comprising the electrochemical device of any one of the above.
According to the electrochemical device provided by the invention, the first layer body and the second layer body are arranged on one side of the first pole piece, so that the electrochemical device has higher energy density. Simultaneously, set up a plurality of first holes on the second layer body, and the hole depth of each first hole is the same basically with the thickness of second layer body for electrolyte can permeate first layer body and infiltrate the second layer body, makes the electrolyte concentration difference that first layer body and the second layer body of first pole piece infiltrate reduce, has reduced the production of lithium phenomenon of separating out, has promoted the dynamic performance of first pole piece, has alleviated electrochemical device's battery capacity decay.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic illustration of a first pole piece of a first embodiment of the present invention in full section;
FIG. 2 is a schematic illustration in full section of a first pole piece provided by a second embodiment of the present invention;
FIG. 3 is an enlarged partial schematic view at A in FIG. 2;
FIG. 4 is a schematic illustration in full section of a first pole piece provided by a third embodiment of the present invention;
FIG. 5 is a schematic illustration of a first pole piece according to a fourth embodiment of the present invention
FIG. 6 is an enlarged partial schematic view at B in FIG. 5;
fig. 7 is a schematic perspective view of a first pole piece according to a fifth embodiment of the present invention;
FIG. 8 is a schematic illustration in full section of a first pole piece provided by a sixth embodiment of the present invention;
FIG. 9 is a schematic representation of a first pole piece of a sixth embodiment of the present invention in full section exploded;
FIG. 10 is a schematic illustration in full section of a second pole piece provided in accordance with a first embodiment of the present invention;
Fig. 11 is a schematic side view of a rolled electrode assembly according to a seventh embodiment of the present invention, as viewed in the direction of the axis of the roll;
fig. 12 is a schematic front view of an electrochemical device according to an eighth embodiment of the present invention; wherein an internal electrode assembly is shown;
fig. 13 is an exploded view of an electrochemical device according to a ninth embodiment of the present invention;
fig. 14 is a schematic perspective view of an electronic device according to a first embodiment of the present invention.
Detailed Description
In order that the invention may be readily understood, a more particular description thereof will be rendered by reference to specific embodiments that are illustrated in the appended drawings. It will be understood that when an element is referred to as being "fixed" to another element, it can be directly on the other element or one or more intervening elements may be present therebetween. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or one or more intervening elements may be present therebetween. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.
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 invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used in this specification includes any and all combinations of one or more of the associated listed items.
The existing battery has the problem of serious battery capacity decay after multiple charge and discharge. The applicant found that when the active material layer of the electrode sheet in the battery is thicker, the active material in the inner layer is insufficiently impregnated, resulting in a phenomenon of easily generating lithium precipitation, thereby attenuating the capacity of the battery.
In view of this, referring to fig. 1 to 13, the present embodiment provides an electrochemical device 50, and the electrochemical device 50 may be a battery having an advantage of a low battery capacity degradation rate while having a high energy density. Specifically, the electrochemical device 50 includes an electrode assembly 40 and a case 51 accommodating the electrode assembly 40, the case 51 defining a receiving chamber 52, the electrode assembly 40 being disposed in the receiving chamber 52. The electrode assembly 40 includes a first electrode sheet 10 and a second electrode sheet 20. The electrode assembly 40 further includes a first tab 41 and a second tab 42 for conducting out electric energy within the electrochemical device 50. The first tab 41 is connected to the first pole piece 10, and the second tab 42 is connected to the second pole piece 20. The first tab 41 and the second tab 42 pass through the outer casing 51. The electrode assembly 40 may be a wound electrode assembly 40 or a stacked electrode assembly 40, i.e., the first electrode sheet 10 and the second electrode sheet 20 may be stacked in a single direction, or the first electrode sheet 10 and the second electrode sheet 20 may be stacked and wound around an axis. The electrode assembly 40 may include only the first electrode sheet 10 or the second electrode sheet 20, and the electrode assembly 40 may include other electrode sheets. For convenience of description, in the following embodiments, the electrode assembly 40 includes only the first electrode sheet 10 and the second electrode sheet 20, and the electrode assembly 40 is illustrated as a winding structure.
The polarity of the first pole piece 10 is different from that of the second pole piece 20. The first electrode sheet 10 may be a positive electrode sheet or a negative electrode sheet. When the first pole piece 10 is a positive pole piece, the second pole piece 20 is a negative pole piece. When the first pole piece 10 is a negative pole piece, the second pole piece 20 is a positive pole piece. For convenience of description, the following embodiments will be exemplified by taking the first electrode sheet 10 as a positive electrode sheet and the second electrode sheet 20 as a negative electrode sheet.
The first pole piece 10 includes a first current collector 100, a first layer 200, a second layer 300, and a first tab 41 connected to the first current collector 100. The first current collector 100 includes a first wall surface 110. The first layer 200 is disposed on one side of the first wall 110 of the first current collector 100, and the first layer 200 includes a first active material. The first layer 200 may be directly disposed on the first wall 110 or indirectly disposed on the first wall 110. When the first layer 200 is indirectly disposed on the first wall 110, the first wall 110 of the first layer 200 may further be provided with a third layer 400, where the third layer 400 includes a conductive agent and an adhesive, and the third layer 400 is disposed between the first layer 200 and the first wall 110 and used for adhering the first layer 200 to the first wall 110.
The second layer 300 is disposed on a wall surface of the first layer 200 facing away from the first current collector 100, and the second layer 300 includes a second active material. The thickness of the first layer 200 may be the same as or different from the thickness of the second layer 300. In some embodiments, the first active material of the first layer 200 is different from the second active material of the second layer 300, which may specifically be different in material, density, or structural form (e.g., different particle sizes, different particle shapes), etc. In this embodiment, the first active material and the second active material are different in material, density and structural form.
In this embodiment, two active layers are disposed on the first wall 110 side of the first current collector 100, so that the energy density of the battery is relatively high. In some embodiments, the second layer 300 is provided with a number (one or more) of first holes 310, as viewed in the thickness direction X of the second layer 300. The first holes 310 have a hole depth h along the thickness direction X of the second layer 300 1 Average thickness H with second layer 300 1 Satisfies H of 0 μm or less 1 -h 1 Less than or equal to 2 mu m. Illustratively H 1 -h 1 Specifically, it may be 0 μm, 1 μm or 2. Mu.m. That is, the hole depth of each first hole 310 is substantially the same as the thickness of the second layer 300, so that the electrolyte can infiltrate the second layer 300 through the first layer 200, thereby reducing the concentration difference of the electrolyte infiltrated by the first layer 200 and the second layer 300 of the first pole piece 10, reducing the amount of lithium precipitation, improving the dynamic performance of the first pole piece 10, and relieving the battery capacity attenuation of the electrochemical device 50. Specifically, each first hole 310 may extend to a surface wall of the second layer 300 facing away from the first layer 200, and for convenience of description, the following will exemplify that each first hole 310 extends to a surface wall of the second layer 300 facing away from the first layer 200.
It should be noted that "h" above 1 "not specifically defined, it means the hole depth of each first hole 310 in the thickness direction X of the second layer 300. In other words, the first holes 310 at different positions have H 1 The values are different and the hole depths H of all the first holes 310 1 All satisfy H which is more than or equal to 0 mu m 1 -h 1 Less than or equal to 2 mu m. In some embodiments, the thickness direction of the first layer 200 and the thickness direction of the second layer 300 may or may not overlap, and for convenience of description, the thickness direction of the first layer 200 and the thickness direction of the second layer 300 are illustrated in the following embodiments. The thickness direction X of the first layer 200 in common with the second layer 300 is shown in fig. 1-2.
In this embodiment, referring to fig. 3, when the hole formed from the surface wall of the second layer 300 facing away from the first layer 200 penetrates the second layer 300 and is formed on the first layer 200, the hole 311 is considered to have two parts, one part is located in the second layer 300 and the other part is located in the first layer 200. The portion of the hole 311 located in the second layer 300 is defined as the first hole 310, and the hole depth h1 of the first hole 310 is equal to the average thickness of the second layer 300.
In order to further reduce the concentration difference of the infiltrated electrolyte between the first layer body 200 and the second layer body 300. Referring to fig. 2-7, in one embodiment, the first layer 200 is provided with a plurality of second holes 210, each second hole 210 may extend to a wall of the second layer 200 facing the second layer 300, and for convenience of description, each second hole 210 extends to a wall of the second layer 200 facing the second layer 300. The second holes 210 have a hole depth h along the thickness direction X of the first layer 200 2 Average thickness H with first layer 200 2 Satisfy 0 μm < H 2 -H 2 And is less than or equal to 80 mu m. Illustratively H 2 -h 2 May be 20 μm, 40 μm, 60 μm or 80 μm. When the second holes 210 are formed in the first layer 200, the electrolyte that reaches the position of the first layer 200 through the second layer 300 can infiltrate all the positions of the first layer 200 through the second holes 210 again, so that the concentration of the electrolyte infiltrated by all the positions of the first layer 200 and the second layer 300 is more balanced, the dynamic performance of the battery is improved, and the battery capacity attenuation rate of the battery is relieved.
It should be noted that "h" above 2 "not specifically defined, it means the hole depth of each of the second holes 210 in the thickness direction X of the first layer 200. In other words, the second holes 210 are at different positions, h 2 The values are different and the hole depths h of all the second holes 210 2 All satisfy 0 μm < H 2 -H 2 And is less than or equal to 80 mu m. In some embodiments, referring to fig. 5-6, when the first hole 310 at a location has a hole depth greater than the thickness of the second layer 300, the first layer 200 is provided with the second hole 210 at a location opposite the location, the first hole 310 has a hole diameter greater than the second hole 210, and the first hole 310 is adjacent to the second holeWhen the end of the first layer 200 completely covers the end of the second hole 210 near the second layer 300, the hole depth of the second hole 210 is calculated from the wall surface of the first layer 200 facing the second layer 300, but not from the bottom wall of the first layer 200 where the first hole 310 is located. Referring to fig. 3, when the hole formed from the surface wall of the second layer 300 facing away from the first layer 200 penetrates the second layer 300 and is formed on the first layer 200, the portion 312 of the hole 311 located on the first layer 200 is not the second hole 210.
To enable the first layer 200 to be more fully wetted by the electrolyte, in one embodiment, the number of first holes 310 is greater than the number of second holes 210. When the number of the first holes 310 on the second layer 300 is relatively larger, the electrolyte is easier to infiltrate the first layer 200 through the second layer 300, so that the concentration of the electrolyte infiltrated by the first layer 200 and the second layer 300 is more uniform. The dynamic performance of the battery is improved, and the battery capacity decay rate of the battery is relieved. When the number of the second holes 210 on the first layer 200 is relatively smaller, the number of the holes on the whole first pole piece 10 can be reduced, and the battery can have higher energy density.
In one embodiment, the average hole spacing L of each first hole 310 1 Average hole spacing L from each second hole 210 2 Satisfy 0 μm < L 2 -L 1 Less than or equal to 500 mu m. Illustratively, L 2 -L 1 May be 50 μm, 100 μm, 150 μm, 200 μm, 300 μm, 400 μm, or 500 μm. In other words, the average hole spacing of the first holes 310 is smaller than the average hole spacing of the second holes 210. When the average hole pitch of each first hole 310 is relatively smaller, the electrolyte is more likely to infiltrate the first layer 200 through the second layer 300, so that the concentration of the electrolyte infiltrated by each of the first layer 200 and the second layer 300 is more uniform. The dynamic performance of the battery is improved, and the battery capacity decay rate of the battery is relieved. When the average pore spacing of the respective second pores 210 is relatively large, the first active material on the first layer body 200 is relatively more, ensuring that the battery can have a high energy density.
For ease of understanding, the average hole spacing L of the first holes 310 is herein 1 And an average hole spacing L of the second holes 210 2 The following definitions are made. The "hole pitch" in the "average hole pitch" refers to the closest distance between two holes, i.e., the distance between the end edge of one hole closest to the other hole and the end edge of the other hole closest to the one hole, which is the hole pitch between the two holes. Illustratively, when the two holes are cylindrical holes each having a diameter of one millimeter, the axes of the two cylindrical holes are parallel and five millimeters apart, then the hole spacing of the two holes is three millimeters. Further, when there are one hundred first holes 310, each first hole 310 and all other first holes 310 have a corresponding hole pitch, that is, each first hole 310 has ninety-nine hole pitches, and the minimum value of the ninety-nine hole pitches is taken as the hole pitch value of the first hole 310. Thus, one hundred first holes 310 have one hundred hole pitch values, which are accumulated and one hundred values are the average hole pitch L 1 . Similarly, when there are one hundred second holes 210, each second hole 210 and all other second holes 210 have a corresponding hole pitch, that is, each second hole 210 has ninety-nine hole pitches, and the minimum value of the ninety-nine hole pitches is taken as the hole pitch value of the second hole 210. Thus, one hundred second holes 210 have one hundred hole pitch values, which are accumulated and one hundred values are the average hole pitch L 2 。
In one embodiment, the average pore diameter R of each first pore 310 1 Average pore diameter R of each second pore 210 2 Satisfy R of 0 μm < 1 -R 2 Less than or equal to 100 mu m. Illustratively, R is 1 -R 2 May be 0 μm, 20 μm, 40 μm, 60 μm, 80 μm, or 100 μm. I.e., the average pore diameter R of each first pore 310 1 Greater than the average pore diameter R of each second pore 210 2 . When the average pore diameter R of each first pore 310 is equal to 1 When the electrolyte is relatively larger, the electrolyte is easier to infiltrate the first layer body 200 through the second layer body 300, so that the concentration of the electrolyte infiltrated by the first layer body 200 and the second layer body 300 is more balanced. The dynamic performance of the battery is improved, and the battery capacity decay rate of the battery is relieved. When the average of the second holes 210 isPore diameter R 2 Relatively less, relatively more of the first active material on the first layer 200 ensures that the battery can have a higher energy density.
Due to the limitation of the processing process, even if the first hole 310 is designed as a regular hole, such as a rectangular hole or a round hole, the hole section of the first hole 310 actually processed may be an irregular section, and there may be a slight difference in the sectional area of the first hole 310 along the thickness direction X of the first pole piece 10. For ease of understanding, the average pore diameter R of the first pores 310 is herein 1 Average pore diameter R of second pores 210 2 The following definitions are made: accordingly, in the present application, the aperture size of the first hole 310 is defined by the aperture size of the surface of the second layer 300 facing away from the first layer 200. Each first hole 310 has an area S1 at the aperture of the surface of the second layer 300 facing away from the first layer 200, and each first hole 310 has an aperture of. In other words, even though the orifice shape of each first orifice 310 is irregular, each has a circle equal to the area of the orifice, and the diameter of the circle is equivalent to the aperture of the first orifice 310. The average pore size of each first pore 310 can be obtained from the equivalent pore sizes of all the first pores 310. Likewise, the area of the aperture of each second hole 210 at the surface of the first layer body 200 facing the second layer body 300 is S2, and the aperture of each second hole 210 is +.>. The average pore size of each second pore 210 can be obtained from the equivalent pore sizes of all the second pores 210.
In the actual testing process, the surface of the second layer 300 facing away from the first layer 200 may be photographed along the thickness direction X of the first pole piece 10, and the aperture area of each first hole 310 (i.e., the area of the aperture of the first hole 310 when viewed along the thickness direction X of the first pole piece 10) is determined by the photographed image. The second layer 300 may be scraped off, the scraped thickness may be greater than the thickness of the second layer 300 by 2 μm to 10 μm, the first layer 200 is exposed, the scraped surface of the first layer 200 is photographed in the thickness direction X of the first pole piece 10, and the aperture area of each second hole 210 is determined by the photographed image. The above photographing device may be determined according to actual needs, in some embodiments, in the determining process of the aperture of the second hole 210, the second layer 300 may not be scraped, the image photographing device with perspective function may be used to obtain the images of the first hole 310 and the second hole 210 observed along the thickness direction X of the first pole piece 10, and the aperture area of each second hole 210 may be obtained after excluding the image of the first hole 310.
In one embodiment, the average pore diameter R of each first pore 310 1 Average pore diameter R of each second pore 210 2 Satisfy R of 1 to less than or equal to 1 /R 2 And is less than or equal to 5. Illustratively, R is 1 /R 2 May be 1, 2, 3, 4 or 5. In other words, the average pore diameter R of each first pore 310 1 Greater than the average pore diameter R of each second pore 210 2 And the average pore diameter R of each first pore 310 1 May be the average pore diameter R of each second pore 210 2 From one to five times more than before. In this embodiment, the first holes 310 and the second holes 210 may satisfy R.ltoreq.1 1 /R 2 At the same time of less than or equal to 5, also satisfies R less than 0 mu m 1 -R 2 ≤100μm。
In one embodiment, each first hole 310 has an open area ratio Q relative to the second layer 300 1 Meet Q of 10 percent or less 1 Less than or equal to 50 percent. The aperture ratio Q of each second hole 210 relative to the first layer 200 2 Q is more than or equal to 0.1 percent 2 Less than or equal to 20 percent. In the above scheme, the applicant considers that when Q 1 When the amount is less than 10%, the electrolyte permeability is difficult to satisfy the requirement, and when Q 1 When the energy density of the battery is more than 50%, the energy density of the battery is reduced, so Q is selected to be less than or equal to 10 percent 1 Less than or equal to 50 percent, so that the electrolyte can be ensured to have better permeability and higher energy density. Similarly, when Q 2 When the content is less than 0.1%, the electrolyte permeability is difficult to satisfy the requirement, and when Q 2 When the energy density of the battery is more than 20%, the energy density of the battery is reduced, so Q is selected to be less than or equal to 0.1 percent 2 Less than or equal to 20 percent, so that not only can the electrolyte be soaked more uniformly in the first layer body 200, but also the battery can be ensured to have higher energy densityDegree.
Further, the first holes 310 and the second holes 210 may be formed in such a manner that 10% Q.ltoreq.Q is satisfied 1 ≤50％、0.1％≤Q 2 Not less than 20%, and also satisfies 0 not more than L 2 -L 1 ≤500μm、0≤R 1 -R 2 Less than or equal to 100 mu m and 1 less than or equal to R 1 /R 2 At least one of less than or equal to 5.
For easy understanding, the aperture ratio Q of each first hole 310 to the second layer 300 is herein described 1 And an opening ratio Q of each second hole 210 with respect to the first layer 200 2 The definition is as follows: the aperture ratio Q of each first hole 310 relative to the second layer 300 1 The first holes 310 are a ratio of the size of the space of the second layer 300 to the volume of the entire second layer 300 (including the space occupied by the first holes 310). Since there may be a case where the hole depth of the first hole 310 is greater than the thickness of the second layer 300, when the hole depth of the first hole 310 is greater than the thickness of the second layer 300, only a portion of the first hole 310 occupying the space of the second layer 300 is calculated. In other words, in the alternative,wherein->For the average aperture area of each first aperture 310, +.>Is the average pore depth (when h 1 Greater than H 1 When h 1 The value of (1) takes H 1 ），X 1 F for the number of first holes 310 1 For the area of the surface of the second layer 300 facing away from the first layer 200, H 1 Is the average thickness of the second layer 300. For Q 2 It should be noted that the volume of the first hole 310 on the first layer 200 is not calculated, and when the first hole 310 and the second hole 210 have overlapping portions, only the volume of the second hole 210 is calculated. Likewise, a +>Wherein->For the average aperture area of the second apertures 210, +.>For the average hole depth of each second hole 210, X 2 For the number of second holes 210, F 2 H is the area of the surface of the first layer 200 near the second layer 300 1 Is the average thickness of the first layer 200.
The applicant considered that, in order to maintain a preferable electrolyte wetting effect, the opening ratio Q of each first hole 310 with respect to the second layer 300 1 Should be related to the average thickness of the second layer 300. Thus, in one embodiment, the average thickness H of the second layer 300 1 Satisfies H of 80 mu m or less 1 The aperture ratio Q of each first hole 310 relative to the second layer 300 1 Meet Q of 30 percent or less 1 Less than or equal to 50 percent. In other words, when the average thickness H of the second layer 300 is 1 When the particle size is larger than 80 mu m, Q is 30 percent or less 1 50% or less, illustratively, Q 1 May be 30%, 35%, 40%, 45% or 50%. That is, when the thickness of the second layer 300 is large and larger than 80 μm, the opening ratio Q of each first hole 310 relative to the second layer 300 1 Not less than 30%, which makes it easier for the electrolyte to infiltrate the first layer 200 through the second layer 300.
Similarly, in order to maintain a preferable electrolyte wetting effect, the opening ratio Q of each second hole 210 with respect to the first layer 200 2 Should be related to the thickness of the first layer 200, in one embodiment, the average thickness H of the first layer 200 2 Satisfies H of 50 mu m or less 2 The opening ratio Q of each second hole 210 with respect to the first layer 200 2 Meet Q of 10 percent or less 2 Less than or equal to 20 percent. In other words, when the average thickness of the first layer body 200 is greater than 50. Mu.m, 10% Q 2 Less than or equal to 20 percent, illustratively, Q 2 May be 10%, 12%, 16%, 18% or 20%. That is, when the thickness of the first layer 200 is large and larger than 50 μm, the opening ratio Q of each second hole 210 with respect to the first layer 200 2 Not less than 10%, which can make the electrolyte more likely to infiltrate everywhere the first layer 200.
When the first layer 200 is provided with a plurality of second holes 210 and the second layer 300 is provided with a plurality of first holes 310, in one embodiment, all the first holes 310 may not be communicated with all the second holes 210; in another embodiment, a portion of the first holes 310 may be in communication with a portion of the second holes 210, and a portion of the first holes 310 may not be in communication with a portion of the second holes 210; in yet another embodiment, all of the second holes 210 are in communication with the first holes 310. To facilitate the electrolyte to infiltrate the first layer 200 through the second layer 300 and to facilitate the processing of the first holes 310 and the second holes 210, referring to fig. 2 to 7, in this embodiment, at least part of the second holes 210 are in one-to-one correspondence with the first holes 310. In the above-mentioned scheme, the electrolyte may sequentially pass through the first holes 310 and the second holes 210, which are partially communicated, to infiltrate the first layer 200, so that the infiltration effect is better.
When at least a part of the second holes 210 are in one-to-one correspondence with the first holes 310, the first holes 310 may cover the second holes 210 as viewed in the thickness direction X of the first pole piece 10 (when the aperture of the first holes 310 is not smaller than the aperture of the second holes 210); the first hole 310 and the second hole 210 may have overlapping portions; the second hole 210 may also cover the first hole 310 (in this case, the second hole 210 has a smaller pore diameter than the first hole 310). In a specific embodiment, a plane perpendicular to the thickness direction X of the first layer 200 is a first plane, a projection of the first hole 310 on the first plane is a first projection, a projection of the second hole 210 on the first plane is a second projection, and the second projection is located in the corresponding first projection among the first hole 310 and the second hole 210 that are in communication with each other. In other words, in this embodiment, the aperture of the first hole 310 is larger than that of the second hole 210, and the first hole 310 completely covers the second hole 210 as viewed in the thickness direction X of the first pole piece 10. In the above-described aspect, the passage port area of the interface between the first holes 310 and the second holes 210 can be maximized, so that the electrolyte can more easily reach into the second holes 210 to infiltrate the first layer body 200.
In one embodiment, the average thickness H of the first layer 200 1 Average thickness H with second layer 300 2 The method meets the following conditions: h is less than or equal to 100 mu m 1 +H 2 ＜200μm、1.05≤H 1 /H 2 Less than or equal to 1.5. Illustratively H 1 +H 2 May be 100 μm, 120 μm, 140 μm, 160 μm, 180 μm or 200 μm. H 1 /H 2 May be 1.05, 1.1, 1.2, 1.3, 1.4 or 1.5. In other words, when the total thickness of the first layer body 200 and the second layer body 300 is between 100 μm and 200 μm, the average thickness of the first layer body 200 is greater than the average thickness of the second layer body 300, and 1.05.ltoreq.H 1 /H 2 ≤1.5。
In another embodiment, the average thickness H of the first layer 200 1 Average thickness H with second layer 300 2 The method meets the following conditions: h is more than or equal to 200 mu m 1 +H 2 ≤500μm、3≤H 1 /H 2 And is less than or equal to 5. Illustratively H 1 +H 2 May be 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm or 500 μm. H 1 /H 2 May be 3, 3.5, 4, 4.5, or 5. In other words, when the total thickness of the first layer 200 and the second layer 300 is greater than 200 μm and less than 500 μm, the average thickness of the first layer 200 is greater than the average thickness of the second layer 300, and 3.ltoreq.H 1 /H 2 ≤5。
In the above-described scheme, the relative thickness ratio of the first layer 200 and the second layer 300 is related to the total thickness of both the first layer 200 and the second layer 300. When the thickness of the first layer 200 and the second layer 300 is relatively small, the ratio of the relative thicknesses of the first layer 200 and the second layer 300 is small. When the thickness of the first layer 200 and the second layer 300 is relatively large, the ratio of the relative thicknesses of the first layer 200 and the second layer 300 is large.
In one embodiment, the first electrode sheet 10 is a positive electrode sheet, and the first layer 200 and the second layer 300 are both made of a lithium nickel cobalt manganate material, wherein the first active material is a polycrystalline material, and the second active material is a monocrystalline material. In some embodiments, the first pole piece 10 is a negative pole piece, the first active material is a silicon material, and the second active material is a graphite material. Single crystals refer to materials formed from individual dispersed particles, with polycrystal being secondary particles of primary particle agglomeration. The monocrystal is not easy to break in the circulation process, and the outermost layer (namely the second layer 300) of the pole piece is set to be a monocrystal coating, so that the internal coating can be protected in the circulation process, and the overall gas production condition of the battery cell can be improved. The monocrystal has large polarization and poor dynamic performance, and the opening ratio of the outer layer is designed to be large, so that the dynamic performance of the outer monocrystal is further improved. The polycrystalline material has small polarization and good multiplying power performance, and the small aperture ratio of the inner layer (namely the first layer body 200) can meet the dynamic requirement. Therefore, the advantages of the outer monocrystal and the inner polycrystal can be combined, gas production in the large-rate long-cycle process is reduced, and the effect of large-rate long-cycle is achieved.
In one embodiment, the first layer 200 and the second layer 300 satisfy at least one of the following conditions a) -b):
a) The materials of the first layer 200 and the second layer 300 are all granular materials, i.e. the first active material and the second active material are all granular materials, and the average particle diameter D of the granular materials of the first layer 200 1 Average particle diameter D of particulate material of second layer 300 2 Satisfy 2 is less than or equal to D 2 /D 1 And is less than or equal to 20. Illustratively D 2 /D 1 May be 2, 5, 8, 11, 14, 17 or 20. The particle size of the particulate material of the first layer 200 may be equivalent to the diameter of a sphere equal to the volume of the particulate material. Likewise, the particle size of the particulate material of the second layer 300 may be equivalent to the diameter of a sphere equal to the volume of the particulate material. In this embodiment, the particle size of the particle material of the first layer 200 is smaller than that of the particle material of the second layer 300. In this way, the first layer 200 is relatively dense, so that the total amount of active materials can be increased, and the energy density of the battery can be increased; the second layer 300 has relatively large pores, and can have better permeability, so that electrolyte can permeate through to infiltrate the first layer 200. The average particle size of the particulate material in this example is Dv50, i.e. it is 50% of the corresponding particle size in the volume distribution. The volume of the particles can be measured by a laser particle size analyzer.
b) The materials of the first layer 200 and the second layer 300 are all granular materials, i.e. the first active material and the second active material are all granular materials, and the average particle diameter D of the granular materials of the first layer 200 1 Satisfies D of 0.2 mu m 1 Less than or equal to 6 mu m, secondAverage particle diameter D of particulate material of layer 300 2 Satisfy D of 5 μm 2 Less than or equal to 30 mu m. Illustratively D 1 May be 0.2 μm, 0.5 μm, 1 μm, 2 μm, 4 μm or 6 μm. D (D) 2 May be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm. The particle size of the particulate material of the first layer 200 may be equivalent to the diameter of a sphere equal to the volume of the particulate material. Likewise, the particle size of the particulate material of the second layer 300 may be equivalent to the diameter of a sphere equal to the volume of the particulate material. In this embodiment, the particle size of the particle material of the first layer 200 is smaller than that of the particle material of the second layer 300. In this way, the first layer 200 is relatively dense, so that the total amount of active materials can be increased, and the energy density of the battery can be increased; the second layer 300 has relatively large pores, and can have better permeability, so that electrolyte can permeate through to infiltrate the first layer 200. In addition, as a whole, the outer layer is made of large-particle materials, the inner layer is made of small-particle materials, so that the infiltration of electrolyte is further ensured, the diffusion resistance of the battery cell is reduced, and the dynamics is improved.
In one embodiment, when the first electrode sheet 10 is a positive electrode sheet, the area density M of the first layer 200 1 Meets 10 mg/cm 2 ≤M 1 ≤30 mg/cm 2 Bulk density ρ of the first layer 200 1 Meets 3.4 mg/cm 3 ≤ρ 1 ≤4.5 mg/cm 3 . Area density M of the second layer 300 2 Meets 8 mg/cm 2 ≤M 2 ≤15 mg/cm 2 Bulk density ρ of the second layer 300 2 Meets 2.0 mg/cm 3 ≤ρ 2 ≤3.5 mg/cm 3 . Illustratively M 1 Can be 10 mg/cm 2 、15 mg/cm 2 、20 mg/cm 2 、25 mg/cm 2 Or 30 mg/cm 2 。M 2 Can be 8 mg/cm 2 、10 mg/cm 2 、12 mg/cm 2 、14 mg/cm 2 Or 15 mg/cm 2 。ρ 1 Can be 3.4. 3.4 mg/cm 3 、3.7 mg/cm 3 、4.0 mg/cm 3 、4.3 mg/cm 3 Or 4.5 mg/cm 3 。ρ 2 Can be 2.0 mg/cm 3 、2.5 mg/cm 3 、3.0 mg/cm 3 Or 3.5 mg/cm 3 。
The term "area density" as used herein refers to the mass of all the substances distributed in the thickness direction X per unit area. The area density of the first layer body means, for example, the mass of all substances in a unit area of the first layer body, in other words, the unit area is divided on the surface wall of the first layer body facing the second layer body, and all substances distributed in the thickness direction X of the unit area are intercepted, and the value of the intercepted mass of the substances is the area density value of the first layer body. "bulk density" is the mass of a substance per unit volume. In another embodiment, when the first electrode sheet 10 is a negative electrode sheet, the area density M of the first layer 200 3 Meets 6 mg/cm 2 ≤M 3 ≤20 mg/cm 2 Bulk density ρ of the first layer 200 3 Meets 1.5 mg/cm 3 ≤ρ 3 ≤2.0 mg/cm 3 . Area density M of the second layer 300 4 Meets 3 mg/cm 2 ≤M 4 ≤10 mg/cm 2 Bulk density ρ of the second layer 300 4 Meets 1.2 mg/cm 3 ≤ρ 4 ≤1.6 mg/cm 3 . Illustratively M 3 Can be 6 mg/cm 2 、8 mg/cm 2 、10 mg/cm 2 、12 mg/cm 2 、14 mg/cm 2 、16 mg/cm 2 、18 mg/cm 2 Or 20 mg/cm 2 。M 4 Can be 3 mg/cm 2 、4 mg/cm 2 、5 mg/cm 2 、6 mg/cm 2 、7 mg/cm 2 、8 mg/cm 2 、9 mg/cm 2 Or 10 mg/cm 2 。ρ 3 Can be 1.5 mg/cm 3 、1.6 mg/cm 3 、1.7 mg/cm 3 、1.8 mg/cm 3 、1.9 mg/cm 3 Or 2.0. 2.0 mg/cm 3 。ρ 4 Can be 1.2 mg/cm 3 、1.3 mg/cm 3 、1.4 mg/cm 3 、1.6 mg/cm 3 Or 1.6 mg/cm 3 。
In some embodiments, regardless of whether the first pole piece 10 is a positive pole piece or a negative pole piece, the area density M of the first layer 200 5 Area density M with second layer 300 6 The ratio can be between 1.1 and 5. I.e. 1.1.ltoreq.M 5 /M 6 And is less than or equal to 5. Illustratively M 5 /M 6 May be 1.1, 2, 3, 4 or 5. The applicant has found that when the area density of the first layer body 200 is greater than that of the second layer body 300 and the ratio is between 1.1 and 5, the electrolyte is more likely to infiltrate from the second layer body 300 to the first layer body 200, so that the electrolyte concentration is more uniform throughout the first pole piece 10 in the thickness direction X of the first pole piece 10.
Likewise, the first layer 200 has a bulk density ρ 5 Bulk density ρ with second layer 300 6 The ratio can be between 1.02 and 1.3, i.e. 1.02. Ltoreq.ρ 5 /ρ 6 Less than or equal to 1.3. Illustratively ρ 5 /ρ 6 May be 1.02, 1.07, 1.12, 1.17, 1.22, 1.27 or 1.3. The applicant has found that when the bulk density of the first layer body 200 is greater than the bulk density of the second layer body 300 by a ratio of between 1.02 and 1.3, the electrolyte is more likely to infiltrate from the second layer body 300 to the first layer body 200, so that the concentration of the electrolyte is more uniform throughout the first pole piece 10 along the thickness direction X of the first pole piece 10.
In the embodiment of fig. 1-7, the first pole piece 10 has active material on only one side, and in other embodiments, active material may be disposed on both sides of the first pole piece 10. Referring to fig. 8-9, in this embodiment, the first pole piece 10 further includes a fourth layer 500 and a fifth layer 600. The fourth layer 500 is disposed on a side of the first current collector 100 facing away from the first wall 110 (i.e., referring to fig. 9, the fourth layer 500 is disposed on the third wall 120 of the first current collector 100), and the fourth layer 500 includes a third active material. The fifth layer body 600 is provided on a wall surface of the fourth layer body 500 facing away from the first current collector 100, and the fifth layer body 600 includes a fourth active material. Wherein, the surface wall of the fifth layer body 600 facing away from the fourth layer body 500 is provided with a plurality of third holes 510, and the hole depth h of each third hole 510 along the thickness direction X of the fifth layer body 600 3 Average thickness H with fifth layer 600 3 Satisfies H of 0 μm or less 3 -H 3 Less than or equal to 2 mu m. Illustratively H 3 -h 3 Can be-2 μm, -1 μm, 0 μm, 1 μm or 2 μm. The wall surface of the fourth layer 500 facing the fifth layer 600 is provided with a plurality of fourth holes 610, and each fourth hole 610 has a hole depth h along the thickness direction X of the fourth layer 500 4 And a fourth layer bodyAverage thickness H of 500 4 Satisfies H of 0 μm or less 4 -h 4 And is less than or equal to 80 mu m. Illustratively H 4 -h 4 May be 0 μm, 20 μm, 40 μm, 60 μm or 80 μm. Likewise, the third hole 510 may make the electrolyte more easily penetrate the fifth layer 600 to infiltrate the fourth layer 500, and the fourth hole 610 makes the electrolyte infiltrated into the fourth layer 500 more uniformly, so that the concentration difference of the electrolyte infiltrated into the first layer 200 and the second layer 300 of the first electrode sheet 10 is reduced, the generation of the lithium precipitation phenomenon is reduced, the dynamic performance of the first electrode sheet 10 is improved, and the battery capacity attenuation of the electrochemical device 50 is alleviated.
In some embodiments, referring to fig. 10, the electrochemical device 50 further includes a second electrode sheet 20, the second electrode sheet 20 and the first electrode sheet 10 also have a polarity phase, and the second electrode sheet 20 includes a second current collector 21, a sixth layer 22, and a seventh layer 23. The second current collector 21 includes a second wall surface. The sixth layer 22 is disposed on one side of the second wall surface of the second current collector 21, and the sixth layer 22 includes a fifth active material. The seventh layer 23 is disposed on a wall surface of the sixth layer 22 facing away from the second current collector 21, and the seventh layer 23 includes a sixth active material. Wherein the surface wall of the seventh layer 23 facing away from the sixth layer 22 is provided with a plurality of fifth holes 231, and the hole depth h of each fifth hole 231 along the thickness direction X of the seventh layer 23 5 Average thickness H with seventh layer 23 5 Satisfies H of 0 μm or less 5 -H 5 Less than or equal to 2 mu m. Illustratively H 5 -h 5 Can be-2 μm, -1 μm, 0 μm, 1 μm or 2 μm. Likewise, the arrangement of the fifth hole 231 can make the electrolyte more easily pass through the seventh layer 23 to infiltrate the sixth layer 22, so that the concentration difference of the electrolyte infiltrated by the first layer 200 and the second layer 300 of the first electrode sheet 10 is reduced, the generation of the lithium precipitation phenomenon is reduced, the dynamic performance of the first electrode sheet 10 is improved, and the battery capacity attenuation of the electrochemical device 50 is relieved.
Referring to fig. 10, the second electrode sheet 20 may further include an eighth layer 24, the eighth layer 24 including a conductive agent and an adhesive, and the eighth layer 24 being used to adhere the sixth layer 22 to the second current collector 21 and to provide the sixth layer 22 to the second current collector 21.
Referring to fig. 14, the second aspect of the present invention also provides an electronic device 1 including the electrochemical device 50 in any of the above embodiments.
It should be noted that the description of the present invention and the accompanying drawings illustrate preferred embodiments of the present invention, but the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, which are not to be construed as additional limitations of the invention, but are provided for a more thorough understanding of the present invention. The above-described features are further combined with each other to form various embodiments not listed above, and are considered to be the scope of the present invention described in the specification; further, modifications and variations of the present invention may be apparent to those skilled in the art in light of the foregoing teachings, and all such modifications and variations are intended to be included within the scope of this invention as defined in the appended claims.
Claims (16)
1. An electrochemical device comprising a first pole piece, the first pole piece comprising:
a first current collector including a first wall surface;
the first layer body is arranged on one side of the first wall surface of the first current collector and comprises a first active material, the first layer body is provided with a plurality of second holes, and the hole depth H2 of each second hole along the thickness direction of the first layer body and the average thickness H2 of the first layer body meet that H2-H2 is more than or equal to 0 mu m and less than or equal to 80 mu m;
the second layer body is arranged on the wall surface of the first layer body, which is away from the first current collector, and comprises a second active material, wherein the second active material is different from the first active material in material, density and structural form, and the structural form comprises particle size and particle shape;
wherein, the second layer body is provided with a plurality of first holes, the number of the first holes is larger than that of the second holes, and the hole depth h of each first hole along the thickness direction of the second layer body is observed along the thickness direction of the second layer body 1 And the first is connected withAverage thickness H of two layers 1 Satisfies H of 0 μm or less 1 -h 1 ≤2μm。
2. The electrochemical device according to claim 1, wherein,
Average hole spacing L of each first hole 1 Average hole spacing L from each of the second holes 2 Satisfy 0 μm < L 2 -L 1 ≤500μm。
3. The electrochemical device according to claim 1, wherein,
average pore diameter R of each of the first pores 1 Average pore diameter R of each of the second pores 2 Satisfy R of 0 μm < 1 -R 2 ≤100μm。
4. The electrochemical device according to claim 1, wherein,
average pore diameter R of each of the first pores 1 Average pore diameter R of each of the second pores 2 Satisfy R of 1 to less than or equal to 1 /R 2 ≤5。
5. The electrochemical device according to claim 1, wherein,
the aperture ratio Q of the second layer body 1 Meet Q of 10 percent or less 1 ≤50％；
The aperture ratio Q of the first layer body 2 Q is more than or equal to 0.1 percent 2 ≤20％。
6. The electrochemical device according to claim 1, wherein,
average thickness H of the second layer body 1 Satisfies H of 80 mu m or less 1 The aperture ratio Q of the second layer body 1 Meet Q of 30 percent or less 1 ≤50％；
Average thickness H of the first layer body 2 Satisfies H of 50 mu m or less 2 The aperture ratio Q of the first layer body 2 Meet Q of 10 percent or less 2 ≤20％。
7. The electrochemical device according to claim 1, wherein,
at least part of the second holes are communicated with the first holes in a one-to-one correspondence.
8. The electrochemical device according to claim 7, wherein,
The plane perpendicular to the thickness direction of the first layer body is a first plane, the projection of the first hole on the first plane is a first projection, the projection of the second hole on the first plane is a second projection, and the second projection is positioned in the corresponding first projection in the first hole and the second hole which are communicated with each other.
9. The electrochemical device according to claim 1, wherein,
100μm≤H 1 +H 2 ＜200μm，1.05≤H 1 /H 2 less than or equal to 1.5; or (b)
200μm≤H 1 +H 2 ≤500μm，3≤H 1 /H 2 ≤5。
10. The electrochemical device according to claim 1, wherein,
the first pole piece is a positive pole piece, the first active material and the second active material both comprise nickel cobalt lithium manganate, wherein the nickel cobalt lithium manganate in the first active material is a polycrystalline material, and the nickel cobalt lithium manganate in the second active material is a monocrystalline material.
11. The electrochemical device according to claim 1, wherein,
the first pole piece is a negative pole piece, the first active material contains silicon material, and the second active material is graphite.
12. The electrochemical device of claim 1, wherein the first layer and the second layer satisfy at least one of the following conditions a) -b):
a) The materials of the first active material and the second active material are all particle materials, and the average particle diameter D of the particles of the first active material 1 Average particle diameter D of particles with the second active material 2 Satisfy 2 is less than or equal to D 2 /D 1 ≤20；
b) The materials of the first active material and the second active material are all particle materials, and the average particle diameter D of the particles of the first active material 1 Satisfies D of 0.2 mu m 1 And less than or equal to 6 mu m, wherein the average particle diameter D of the particles of the second active material 2 Satisfy D of 5 μm 2 ≤30μm。
13. The electrochemical device according to claim 1, wherein,
the first pole piece is a positive pole piece;
area density M of the first layer body 1 Meets 10 mg/cm 2 ≤M 1 ≤30 mg/cm 2 The volume density ρ of the first layer body 1 Meets 3.4 mg/cm 3 ≤ρ 1 ≤4.5 mg/cm 3 ；
Area density M of the second layer body 2 Meets 6 mg/cm 2 ≤M 2 ≤15 mg/cm 2 The volume density ρ of the second layer body 2 Meets 2.0 mg/cm 3 ≤ρ 2 ≤3.5 mg/cm 3 。
14. The electrochemical device according to claim 1, wherein,
the first pole piece is a negative pole piece;
area density M of the first layer body 3 Meets 8 mg/cm 2 ≤M 3 ≤20 mg/cm 2 The volume density ρ of the first layer body 3 Meets 1.5 mg/cm 3 ≤ρ 3 ≤2.0 mg/cm 3 ；
Area density M of the second layer body 4 Meets 3 mg/cm 2 ≤M 4 ≤10 mg/cm 2 The volume density ρ of the second layer body 4 Meets 1.2 mg/cm 3 ≤ρ 4 ≤1.6 mg/cm 3 。
15. The electrochemical device according to claim 1, wherein,
area density M of the first layer body 5 Area density M with the second layer body 6 Satisfies M of 1.1 ∈ 5 /M 6 Less than or equal to 5; or (b)
The volume density ρ of the first layer body 5 Bulk density ρ with the second layer body 6 Satisfy ρ of 1.02 5 /ρ 6 ≤1.3。
16. An electronic device comprising the electrochemical device of any one of claims 1-15.
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