CN113555527A - Negative plate and lithium ion battery - Google Patents
Negative plate and lithium ion battery Download PDFInfo
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- CN113555527A CN113555527A CN202110823602.7A CN202110823602A CN113555527A CN 113555527 A CN113555527 A CN 113555527A CN 202110823602 A CN202110823602 A CN 202110823602A CN 113555527 A CN113555527 A CN 113555527A
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- coating
- current collector
- negative electrode
- mass
- coating layer
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 17
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 17
- 238000000576 coating method Methods 0.000 claims abstract description 95
- 239000011248 coating agent Substances 0.000 claims abstract description 93
- 239000013076 target substance Substances 0.000 claims abstract description 31
- 239000011247 coating layer Substances 0.000 claims description 52
- 229910001338 liquidmetal Inorganic materials 0.000 claims description 25
- 239000011230 binding agent Substances 0.000 claims description 22
- 239000006258 conductive agent Substances 0.000 claims description 22
- 239000002270 dispersing agent Substances 0.000 claims description 21
- 229910045601 alloy Inorganic materials 0.000 claims description 14
- 239000000956 alloy Substances 0.000 claims description 14
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 10
- 239000010439 graphite Substances 0.000 claims description 10
- 229910002804 graphite Inorganic materials 0.000 claims description 10
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims description 9
- 229910052733 gallium Inorganic materials 0.000 claims description 9
- 150000001875 compounds Chemical class 0.000 claims description 7
- 229920000642 polymer Polymers 0.000 claims description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 5
- 239000011889 copper foil Substances 0.000 claims description 5
- 229910000846 In alloy Inorganic materials 0.000 claims description 4
- 239000004698 Polyethylene Substances 0.000 claims description 4
- 229910001128 Sn alloy Inorganic materials 0.000 claims description 4
- -1 polyethylene Polymers 0.000 claims description 4
- 229920000573 polyethylene Polymers 0.000 claims description 4
- 239000004760 aramid Substances 0.000 claims description 3
- 229920003235 aromatic polyamide Polymers 0.000 claims description 3
- 229910052738 indium Inorganic materials 0.000 claims description 3
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 3
- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims description 3
- 229920001610 polycaprolactone Polymers 0.000 claims description 3
- 239000004632 polycaprolactone Substances 0.000 claims description 3
- 239000004926 polymethyl methacrylate Substances 0.000 claims description 3
- 229920002635 polyurethane Polymers 0.000 claims description 3
- 239000004814 polyurethane Substances 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 12
- 239000007773 negative electrode material Substances 0.000 description 8
- 239000002210 silicon-based material Substances 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 239000002775 capsule Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 239000006229 carbon black Substances 0.000 description 4
- 239000001768 carboxy methyl cellulose Substances 0.000 description 4
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 4
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- RHZWSUVWRRXEJF-UHFFFAOYSA-N indium tin Chemical compound [In].[Sn] RHZWSUVWRRXEJF-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000013543 active substance Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000007769 metal material Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000006183 anode active material Substances 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229920000592 inorganic polymer Polymers 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 229920000620 organic polymer Polymers 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
- PAPBSGBWRJIAAV-UHFFFAOYSA-N ε-Caprolactone Chemical compound O=C1CCCCCO1 PAPBSGBWRJIAAV-UHFFFAOYSA-N 0.000 description 1
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- 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)
- Secondary Cells (AREA)
Abstract
The application provides a negative plate and a lithium ion battery, wherein the negative plate comprises a current collector, a first coating, a second coating and a tab; a tab is arranged on at least one surface of the current collector, a first coating is coated on at least one surface of the current collector, the tab and the first coating which are arranged on the same surface are positioned in different areas of the surface, and a second coating is coated on one side, far away from the current collector, of the first coating; wherein the first coating comprises a target substance. In the embodiment of the application, the target substance of the first coating can improve the contact area between the first coating and the second coating, so that after a local fault phenomenon occurs between the current collector and the coating, the contact area of the first coating and the second coating is increased by utilizing the flowability of the target substance at normal temperature, and further the conductivity of the negative plate in the circulating charge and discharge process is enhanced, so that the local fault phenomenon caused by the current collector and the coating of the negative plate is avoided, and the cycle performance of the battery is reduced.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a negative plate and a lithium ion battery.
Background
At present, in order to further improve the energy density of the lithium ion battery, more and more manufacturers begin to develop the lithium ion battery with the silicon-based negative electrode material, and compared with the traditional graphite negative electrode material, the theoretical capacity of the silicon-based negative electrode material is higher.
However, the silicon-based negative electrode material may generate a great volume expansion in the charge and discharge cycles of the lithium ion battery, which may cause a local fault phenomenon of a current collector and a coating in a negative electrode plate, thereby reducing the cycle performance of the battery. Among them, the decrease in the cycle performance of the battery is represented by the decrease in the battery capacity and the expansion in the battery volume after the battery is charged and discharged for a plurality of cycles.
Disclosure of Invention
The embodiment of the invention mainly aims to provide a negative plate and a lithium ion battery, and aims to solve the technical problem that the cycle performance of the battery is reduced due to the fact that a current collector and a coating have local faults caused by expansion of a silicon-based negative material in the charging and discharging processes.
In order to achieve the above object, an embodiment of the present invention provides a negative electrode sheet, which includes a current collector, a first coating, a second coating, and a tab;
the tab is arranged on at least one surface of the current collector, the first coating is coated on at least one surface of the current collector, the tab and the first coating which are arranged on the same surface are positioned in different areas of the surface, and the second coating is coated on one side, far away from the current collector, of the first coating;
wherein the first coating comprises a target substance comprising a shell and a liquid metal or alloy contained in the shell.
Optionally, the target substance is spherical and the target substance has a diameter of less than 2 microns.
Optionally, the target substance is used to increase the contact area of the first coating layer with the second coating layer;
wherein a portion of the liquid metal flows out of the case after the negative electrode sheet is rolled.
Optionally, the liquid metal comprises at least one of a gallium indium alloy and a gallium indium tin alloy.
Optionally, the housing comprises a polymer compound, the polymer compound comprises at least one of polyurethane, polymethylmethacrylate, polyethylene, polycaprolactone, and aromatic polyamide, and the thickness of the housing is greater than or equal to 5 nanometers and less than or equal to 100 nanometers.
Optionally, the thickness of the first coating layer is greater than or equal to 0.5 microns and less than or equal to 2 microns, and the thickness of the second coating layer is greater than the thickness of the first coating layer.
Optionally, the first coating further comprises a conductive agent, a binder and a dispersing agent, wherein the target substance is 30-70% by mass, the conductive agent is 5-20% by mass, the binder is 5-30% by mass, and the dispersing agent is 5-30% by mass.
Optionally, the second coating comprises graphite, a silicon material, a conductive agent, a binder and a dispersing agent, wherein the mass fraction of the silicon material is 3% to 20%, the mass fraction of the graphite is 70% to 94%, the mass fraction of the conductive agent is 0% to 5%, the mass fraction of the binder is 0.5% to 5%, and the mass fraction of the dispersing agent is 0.5% to 5%.
Optionally, the current collector is a copper foil.
The embodiment of the invention also provides a lithium ion battery, which comprises the negative plate.
The application provides a negative plate and a lithium ion battery, wherein the negative plate comprises a current collector, a first coating, a second coating and a tab; a tab is arranged on at least one surface of the current collector, a first coating is coated on at least one surface of the current collector, the tab and the first coating which are arranged on the same surface are positioned in different areas of the surface, and a second coating is coated on one side, far away from the current collector, of the first coating; wherein the first coating comprises a target substance comprising a shell and a liquid metal or alloy contained in the shell. In the embodiment of the application, the target substance in the first coating can improve the contact area between the first coating and the second coating, so that after a local fault phenomenon occurs between the current collector and the coating, the contact area between the first coating and the second coating is increased by utilizing the fluidity of the target substance at normal temperature, and further the conductivity of the negative plate in the circulating charge and discharge process is enhanced, so that the problem that the battery cycle performance is reduced due to the fact that the current collector and the coating of the negative plate have local faults is avoided.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is one of the structural schematic diagrams of a negative electrode sheet provided by the present invention;
fig. 2 is a second schematic structural diagram of a negative electrode sheet according to the present invention;
fig. 3 is a schematic structural diagram of a rolled negative electrode sheet provided by the present invention.
Description of reference numerals:
10. a current collector; 20. a first coating layer; 30. a second coating layer; 40. a tab; 21. a target substance.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a negative electrode sheet according to the present invention. The negative plate provided by the embodiment of the invention comprises a current collector 10, a first coating 20, a second coating 30 and a tab 40; at least one surface of the current collector 10 is provided with the tab 40, at least one surface coating of the current collector 10 the first coating 20 is arranged on the same surface of the tab 40 and the first coating 20 are located in different areas of the surface, and the second coating 30 is coated on one side of the current collector 10 far away from the first coating 20.
The negative electrode tab provided by the present embodiment includes a current collector 10, a first coating layer 20, a second coating layer 30, and a tab 40. As shown in fig. 1, a surface of the current collector 10 is provided with a tab 40, and the surface is coated with a first coating layer 20, and a side of the first coating layer 20 away from the tab 40 is coated with a second coating layer 30.
In an alternative embodiment, a tab 40 is provided on one surface of the current collector 10, a first coating 20 is provided on the other surface of the current collector 10, and a second coating 30 is coated on a side of the first coating 20 away from the tab 40.
In another alternative embodiment, tabs 40 are provided on both surfaces of the current collector 10, the first coating layer 20 is provided on one surface of the current collector 10, and the second coating layer 30 is coated on the side of the first coating layer 20 away from the tabs 40.
Optionally, referring to fig. 2, fig. 2 is a second schematic structural diagram of a negative electrode sheet provided in the present invention. As shown in fig. 2, one surface of the current collector 10 is provided with a tab 40, and both surfaces of the current collector 10 are coated with a first coating layer 20 and a second coating layer 30 on a side of the first coating layer 20 away from the tab 40. That is, the negative electrode tab shown in fig. 2 includes 2 first coating layers 20 and 2 second coating layers 30.
In an alternative embodiment, tabs 40 are provided on both surfaces of current collector 10, and both representations of current collector 10 are coated with first coating 20 and second coating 30 on the side of first coating 20 away from tabs 40.
It should be understood that, in the above possible embodiments, when the tab 40 and the first coating layer 20 are simultaneously provided on one surface of the current collector 10, the tab 40 and the first coating layer 20 provided on the same surface are located on different regions of the surface.
Optionally, the current collector 10 is a copper foil.
Optionally, the first coating 20 further includes a conductive agent, a binder, and a dispersant, the target substance is 30% to 70% by mass, the conductive agent is 5% to 20% by mass, the binder is 5% to 30% by mass, and the dispersant is 5% to 30% by mass.
Optionally, the second coating 30 includes graphite, a silicon material, a conductive agent, a binder, and a dispersant, the silicon material is 3% to 20% by mass, the graphite is 70% to 94% by mass, the conductive agent is 0% to 5% by mass, the binder is 0.5% to 5% by mass, and the dispersant is 0.5% to 5% by mass.
In this embodiment, the current collector 10 is made of copper foil, and it is understood that the current collector 10 may also be made of aluminum foil or other metal materials or non-metal materials that can be used as the current collector 10, which is not limited herein.
The first coating layer 20 is made of a conductive agent, a binder, and a dispersant. The conductive agent can be conductive carbon black, the binder can be styrene butadiene rubber, and the dispersant can be carboxymethyl cellulose. It is understood that in some embodiments, the conductive agent, binder, and dispersant may be other materials, and are not particularly limited herein.
The second coating layer 30 includes a negative electrode active material, a conductive agent, a binder, and a dispersant. The negative electrode active material includes graphite and a silicon material, and the silicon material may be silicon dioxide. It is to be understood that in some embodiments, other silicon-based compounds may be used as the silicon material, and the negative active material may be an active material other than graphite.
Optionally, the thickness of the first coating layer 20 is greater than or equal to 0.5 microns and less than or equal to 2 microns, and the thickness of the second coating layer 30 is greater than the thickness of the first coating layer 20.
In the present embodiment, the thickness of the first coating layer 20 may be set to be greater than or equal to 0.5 micrometers and less than or equal to 2 micrometers, and it is understood that the thickness of the second coating layer 30 including the anode active material should be greater than the thickness of the first coating layer 20. Here, the thickness range of the second coating layer 30 is not particularly limited.
In this embodiment, the first coating 20 further includes a target substance 21, and the target substance 21 includes a shell and a liquid metal or alloy contained in the shell.
In this embodiment, the target substance 21 may be a liquid metal capsule including a hermetically sealed housing and a liquid metal or alloy contained in the housing.
The application provides a negative plate, which comprises a current collector 10, a first coating 20, a second coating 30 and a tab 40; a tab 40 is arranged on at least one surface of the current collector 10, a first coating 20 is coated on at least one surface of the current collector 10, the tab 40 and the first coating 20 which are arranged on the same surface are located in different areas of the surface, and a second coating 30 is coated on one side of the first coating 20 away from the current collector 10; wherein the first coating 20 comprises a target substance 21, the target substance 21 comprising a shell and a liquid metal or alloy contained in said shell. In the embodiment of the application, the target substance 21 of the first coating 20 can improve the contact area between the first coating 20 and the second coating 30, so that after a local fault phenomenon occurs between the current collector 10 and the coating, the contact area between the first coating 20 and the second coating 30 is increased by utilizing the fluidity of the target substance 21 at normal temperature, and further the conductivity of the negative plate in the cyclic charge and discharge process is enhanced, so that the problem that the cycle performance of the battery is reduced due to the local fault phenomenon occurring on the current collector 10 and the coating of the negative plate is avoided.
Optionally, the target substance 21 is used to increase the contact area of the first coating layer 20 and the second coating layer 30;
wherein the liquid metal flows out of the case after the negative electrode sheet is rolled.
Optionally, the target substance 21 is spherical, and the diameter of the target substance 21 is less than 2 microns.
In this embodiment, an optional implementation is that the liquid metal capsule, i.e. the target substance 21, is spherical, in which case the liquid metal capsule may be set to have a diameter of less than 2 microns. It is understood that in other alternative embodiments, the liquid metal capsule may be oval, rectangular, or other shapes, and is not specifically limited herein.
Optionally, the liquid metal or alloy comprises at least one of gallium, indium, a gallium indium alloy, and a gallium indium tin alloy.
Optionally, the housing comprises a polymer compound, the polymer compound comprises at least one of polyurethane, polymethylmethacrylate, polyethylene, polycaprolactone, and aromatic polyamide, and the thickness of the housing is greater than or equal to 5 nanometers and less than or equal to 100 nanometers.
As described above, the target substance 21 may be a liquid metal capsule including a shell and a liquid metal or alloy contained in the shell. Among them, the outer shell is made of an inorganic or organic polymer compound, and preferably polyethylene and caprolactone polymer. The liquid metal or alloy includes at least one of gallium, indium, gallium indium alloy, and gallium indium tin alloy.
It should be understood that in the rolling process of the negative electrode sheet, the liquid metal capsules are broken, and the liquid metal or alloy flows out from the casing, as shown in fig. 3, and fig. 3 is a schematic structural diagram of the rolled negative electrode sheet provided by the present invention. Wherein the liquid metal or alloy is distributed at the bottom of the first coating layer 20 and the second coating layer 30 in a liquid state,
after the liquid metal or the liquid alloy flows out, the contact area between the first coating 20 and the second coating 30 is increased by utilizing the liquidity of the liquid metal or the liquid alloy, so that the contact degree between the first coating 20 and the second coating 30 is enhanced, the conductive network between the current collector 10 and the coatings is improved, the conductive performance of the negative plate is improved, and the cycle performance of the negative plate is further improved.
To further explain, example 1 and comparative example 1 were set up according to the structure of the above negative electrode sheet as follows.
Example 1:
lithium cobaltate is used as an anode active substance, carbon black is used as a conductive agent, polyvinylidene fluoride is used as a binder, the three are added into a stirring tank according to the mass ratio of 97.2:1.5:1.3, a methyl pyrrolidone solvent is added into the stirring tank for stirring, and the mixture is sieved by a 200-mesh sieve to prepare anode slurry. And drying the positive electrode current collector which is an aluminum foil at the temperature of 120 ℃ to obtain the positive plate.
Adding the target substance 21, the conductive agent, the binder and the dispersant into a stirring tank according to the mass ratio of 4:2:2:2, and adding deionized water into the stirring tank for stirring to prepare the coating of the first coating 20. Wherein the target substance 21 is a liquid metal capsule, the conductive agent is carbon black, the binder is polyvinylidene fluoride, and the dispersant is carboxymethyl cellulose. Adding the negative electrode active material, the conductive agent, the binder and the dispersant into a stirring tank according to the mass ratio of 96.9:0.5:1.3:1.3, adding deionized water, fully stirring, and sieving with a 200-mesh sieve to prepare the coating of the second coating 30.
Wherein, the negative active substance is graphite and silicon dioxide with the mass ratio of 19:1, the conductive agent is carbon black, the binder is polyvinylidene fluoride, and the dispersant is carboxymethyl cellulose; the second coating 30 has a solids content of 40 to 45 wt.%. And (3) coating first coatings 20 on two surfaces of the negative current collector by using a coating device, coating a second coating 30 on one side of the first coating 20, which is far away from the negative current collector, and drying at the temperature of 120 ℃ to prepare the negative plate, wherein the negative current collector is a copper foil.
As described above, the first coating layer 20 is coated on both surfaces of the negative electrode current collector in example 1, and here, the surface where the first coating layer 20 having a long length is located may be referred to as an a-surface of the current collector 10, and the other surface may be referred to as a C-surface of the current collector 10. If the 2 first coating layers 20 have the same length, one surface of the current collector 10 may be referred to as an a-surface and the other surface may be referred to as a C-surface. And the tab 40 of the negative electrode sheet is disposed on the a-side of the current collector 10 in example 1.
The length of the first coating layer 20 corresponding to the first coating layer 20 of the A-surface coating is set to be greater than or equal to 942 millimeters and less than or equal to 946 millimeters, the length of the second coating layer 30 corresponding to the first coating layer 20 of the C-surface coating is set to be greater than or equal to 828 millimeters and less than or equal to 832 millimeters, and the search between the length of the first coating layer 20 and the length of the second coating layer 30 is greater than or equal to 112 millimeters and less than or equal to 116 millimeters. The distance between the tab 40 and the first coating layer 20 provided on the a-face is greater than or equal to 34.5 mm and less than or equal to 35.5 mm. The width of current collector 10 is greater than or equal to 77.4 mm and less than or equal to 77.6 mm.
And (3) after the positive and negative pole pieces are subjected to a rolling process and a slitting process, winding the positive and negative pole pieces by using a diaphragm, and performing an encapsulating process, a baking and liquid injection process, a formation process, a secondary encapsulating process and a sorting process on the positive and negative pole pieces and the diaphragm to obtain the lithium ion battery.
Comparative example 1:
comparative example 1 differs from example 1 only in that the coating material of the first coat 20 in comparative example 1 is made of a conductive agent, a binder and a dispersant in a ratio of 6:2: 2. Wherein the conductive agent is carbon black, the binder is polyvinylidene fluoride, and the dispersant is carboxymethyl cellulose.
The batteries of example 1 and comparative example 1 were subjected to a normal temperature cyclic charge and discharge test, in which a lithium ion battery was charged to a full upper limit voltage at a rate of 2C in an environment of 25 degrees, charged at a constant voltage using the upper limit voltage until a cutoff current was 0.05C, and then discharged to a battery voltage of 3V at a rate of 0.7C, using the above process as one cycle. The test results are shown in table one.
Table one:
in example 1, after the battery is cyclically charged and discharged for 100 times at normal temperature, the capacity retention rate of the battery is 97.1%, and the ratio of the volume of the battery after the cycle to the volume of the battery before the cycle is 4.8%; after the battery is circularly charged and discharged for 500 times at normal temperature, the capacity retention rate of the battery is 85%, and the ratio of the volume of the battery after the circulation to the volume of the battery before the circulation is 10.2%.
Comparative example 1 after 100 times of charge and discharge cycles at normal temperature, the capacity retention ratio of the battery was 95.2%, and the ratio of the battery volume after cycles to the battery volume before cycles was 5.2%; after the battery is circularly charged and discharged for 500 times at normal temperature, the capacity retention rate of the battery is 81.2%, and the ratio of the volume of the battery after the circulation to the volume of the battery before the circulation is 11.8%.
The test result shows that the battery in the embodiment 1 can still maintain higher battery capacity after being cycled for multiple times, and the battery has lower volume expansion rate, so that the cycling performance of the battery can be effectively improved.
The embodiment of the present invention further provides a lithium ion battery, where the lithium ion battery includes the above negative electrode sheet, and the structure of the negative electrode sheet may refer to the above embodiment, and details are not repeated here. Since the negative electrode sheet in the above embodiment is adopted in this embodiment, the lithium ion battery provided by the embodiment of the present invention has the same beneficial effects as the negative electrode sheet in the above embodiment.
The above description is only an alternative embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. The negative plate is characterized by comprising a current collector, a first coating, a second coating and a tab;
the tab is arranged on at least one surface of the current collector, the first coating is coated on at least one surface of the current collector, the tab and the first coating which are arranged on the same surface are positioned in different areas of the surface, and the second coating is coated on one side, far away from the current collector, of the first coating;
wherein the first coating comprises a target substance comprising a shell and a liquid metal or alloy contained in the shell.
2. A negative electrode sheet according to claim 1, wherein the target substance has a spherical shape and a diameter of less than 2 μm.
3. The negative electrode sheet according to claim 1, wherein the target substance is used to increase a contact area of the first coating layer with the second coating layer; wherein a portion of the liquid metal flows out of the case after the negative electrode sheet is rolled.
4. The negative plate of claim 1, wherein said liquid metal or alloy comprises at least one of gallium, indium, gallium-indium alloy, and gallium-indium-tin alloy.
5. The negative electrode sheet according to claim 1, wherein the outer cover comprises a polymer compound, the polymer compound comprises at least one of polyurethane, polymethylmethacrylate, polyethylene, polycaprolactone, and aromatic polyamide, and the outer cover has a thickness greater than or equal to 5 nm and less than or equal to 100 nm.
6. The negative electrode sheet according to claim 1, wherein the thickness of the first coating layer is greater than or equal to 0.5 micrometers and less than or equal to 2 micrometers, and the thickness of the second coating layer is greater than the thickness of the first coating layer.
7. The negative electrode sheet according to claim 1, wherein the first coating layer further comprises a conductive agent, a binder, and a dispersant, the target substance is 30 to 70% by mass, the conductive agent is 5 to 20% by mass, the binder is 5 to 30% by mass, and the dispersant is 5 to 30% by mass.
8. The negative electrode sheet according to claim 1, wherein the second coating layer comprises 3 to 20 mass% of graphite, 70 to 94 mass% of graphite, 0 to 5 mass% of a conductive agent, 0.5 to 5 mass% of a binder, and 0.5 to 5 mass% of a dispersant.
9. The negative electrode sheet according to claim 1, wherein the current collector is a copper foil.
10. A lithium ion battery, characterized in that the lithium ion battery comprises the negative electrode sheet according to any one of claims 1 to 9.
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