CN111490228B - Electrode for lithium battery, preparation method thereof and lithium battery containing electrode - Google Patents
Electrode for lithium battery, preparation method thereof and lithium battery containing electrode Download PDFInfo
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- CN111490228B CN111490228B CN201910086210.XA CN201910086210A CN111490228B CN 111490228 B CN111490228 B CN 111490228B CN 201910086210 A CN201910086210 A CN 201910086210A CN 111490228 B CN111490228 B CN 111490228B
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 102
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 93
- 238000002360 preparation method Methods 0.000 title abstract description 9
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical group [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 44
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 44
- 230000004048 modification Effects 0.000 claims abstract description 44
- 238000012986 modification Methods 0.000 claims abstract description 44
- 239000011248 coating agent Substances 0.000 claims abstract description 38
- 238000000576 coating method Methods 0.000 claims abstract description 38
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- 239000000463 material Substances 0.000 claims abstract description 27
- 239000007772 electrode material Substances 0.000 claims abstract description 15
- 238000000034 method Methods 0.000 claims abstract description 14
- 229920000642 polymer Polymers 0.000 claims description 47
- 239000011149 active material Substances 0.000 claims description 39
- 239000003292 glue Substances 0.000 claims description 25
- 239000002002 slurry Substances 0.000 claims description 23
- 239000002904 solvent Substances 0.000 claims description 22
- 239000011230 binding agent Substances 0.000 claims description 17
- -1 polysiloxane Polymers 0.000 claims description 15
- 239000011888 foil Substances 0.000 claims description 13
- 239000007773 negative electrode material Substances 0.000 claims description 13
- 238000001035 drying Methods 0.000 claims description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 9
- 229910052710 silicon Inorganic materials 0.000 claims description 9
- 239000010703 silicon Substances 0.000 claims description 9
- 239000006258 conductive agent Substances 0.000 claims description 8
- 239000007774 positive electrode material Substances 0.000 claims description 7
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 claims description 6
- 229920001577 copolymer Polymers 0.000 claims description 6
- 159000000002 lithium salts Chemical group 0.000 claims description 6
- 238000006116 polymerization reaction Methods 0.000 claims description 6
- 229920001296 polysiloxane Polymers 0.000 claims description 6
- BDHFUVZGWQCTTF-UHFFFAOYSA-M sulfonate Chemical compound [O-]S(=O)=O BDHFUVZGWQCTTF-UHFFFAOYSA-M 0.000 claims description 6
- 229910052717 sulfur Inorganic materials 0.000 claims description 6
- 239000011593 sulfur Substances 0.000 claims description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 5
- 239000011889 copper foil Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
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- 239000002033 PVDF binder Substances 0.000 claims description 4
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- 229920000098 polyolefin Polymers 0.000 claims description 4
- 229960002796 polystyrene sulfonate Drugs 0.000 claims description 4
- 239000011970 polystyrene sulfonate Substances 0.000 claims description 4
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 4
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 3
- 239000004642 Polyimide Substances 0.000 claims description 3
- 239000004721 Polyphenylene oxide Substances 0.000 claims description 3
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 3
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims description 3
- 229920000058 polyacrylate Polymers 0.000 claims description 3
- 229920000728 polyester Polymers 0.000 claims description 3
- 229920000570 polyether Polymers 0.000 claims description 3
- 229920001721 polyimide Polymers 0.000 claims description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 3
- RIUWBIIVUYSTCN-UHFFFAOYSA-N trilithium borate Chemical compound [Li+].[Li+].[Li+].[O-]B([O-])[O-] RIUWBIIVUYSTCN-UHFFFAOYSA-N 0.000 claims description 3
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- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 229920000144 PEDOT:PSS Polymers 0.000 description 2
- 239000004793 Polystyrene Substances 0.000 description 2
- 229920002125 Sokalan® Polymers 0.000 description 2
- 239000002041 carbon nanotube Substances 0.000 description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 description 2
- 230000008602 contraction Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 150000003949 imides Chemical class 0.000 description 2
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- 239000002245 particle Substances 0.000 description 2
- 238000005191 phase separation Methods 0.000 description 2
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- 229920002239 polyacrylonitrile Polymers 0.000 description 2
- 229920002223 polystyrene Polymers 0.000 description 2
- 238000011160 research Methods 0.000 description 2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- GKWLILHTTGWKLQ-UHFFFAOYSA-N 2,3-dihydrothieno[3,4-b][1,4]dioxine Chemical compound O1CCOC2=CSC=C21 GKWLILHTTGWKLQ-UHFFFAOYSA-N 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 239000002174 Styrene-butadiene Substances 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 239000002482 conductive additive Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002641 lithium Chemical class 0.000 description 1
- VIDXETATLKBUBY-UHFFFAOYSA-M lithium;benzenesulfonate Chemical group [Li+].[O-]S(=O)(=O)C1=CC=CC=C1 VIDXETATLKBUBY-UHFFFAOYSA-M 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
- 238000002715 modification method Methods 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- 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)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Composite Materials (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to an electrode for a lithium battery, a preparation method thereof and the lithium battery containing the electrode, belonging to the technical field of batteries. The electrode for the lithium battery comprises a current collector, an electrochemical active layer arranged on the current collector and a modification layer coated on the outer surface of the electrochemical active layer; the material of the electrochemical active layer comprises an electrode active material, and the modification layer is formed by a lithium ion exchange polymer. The electrode for the lithium battery adopts the lithium ion exchange polymer as the modification layer to coat the electrochemical active layer, and the modification layer has better shape retention to the electrode, thereby inhibiting material pulverization caused by volume change to a certain extent and inhibiting pole piece cracking; meanwhile, the lithium ion exchange capacity can also ensure the lithium ion transmission rate in the electrochemical process, and the influence of the coating on the impedance is reduced.
Description
Technical Field
The invention relates to an electrode, a preparation method thereof and a lithium battery containing the electrode, in particular to an electrode for a lithium battery, a preparation method thereof and a lithium battery containing the electrode.
Background
In recent years, lithium ion batteries have been widely used in the field of new energy automobiles. With the development of new energy automobile industry, people also put higher and higher requirements on various performances, especially energy density, of lithium ion batteries.
In order to realize the battery design and performance target that the energy density of the lithium ion battery reaches 300Wh/kg in 2020, the chemical system of the lithium ion battery with the silicon/tin-containing cathode is almost inevitably selected. The silicon/tin-based negative electrode material has high specific capacity, but in the charging and discharging processes, the stability of the electrode is poor due to huge and repeated volume expansion and contraction, a pole piece is cracked, an active substance is easy to pulverize, material particles are crushed and continuously generate an SEI film, and the cycle performance of the battery is greatly deteriorated, so that the problem which needs to be solved at present is solved urgently.
The pole piece of most of the existing lithium batteries for mass production is generally formed by coating a single active material layer on a current collector (a pure foil or a carbon-coated foil), wherein the active material layer is a mixture of an electrode active material, a binder and a conductive agent. Some advanced studies have also been directed to applying a conductive layer or polymer layer over the active material layer.
An invention of patent No. ZL 200480032587.9 (LG chemical, applicant) disclosed that an electrolyte-soluble polymer is coated on the interconnected surface of electrode active material particles, the polymer being present in a separate phase, and the main object of the invention is to improve the safety of a battery. The invention is essentially a gel-like electrolyte design, and does not have the function of electrode conformality.
Patent No. ZL201480003255.1 (yunigaku corporation) discloses an ion-permeable layer having a porosity of 30 to 90 vol% formed by applying an imide polymer on the outer surface of an electrode active material layer, wherein the application liquid contains the imide polymer and a solvent composed of an amide solvent as a good solvent and an ether solvent as a poor solvent, and phase separation is caused in the coating film to form an ion-permeable porous layer. The porous coating ensures the transmission of lithium ions to a certain extent, but has poor shape retention and pole piece surface protection effect.
The invention with the application number of 201810091731.X (applicant is Shenzhen fresh power research institute) discloses a lithium ion battery electrode modified by PEDOT: PSS (poly 3, 4-ethylenedioxythiophene: polystyrene sulfonate), and the modification method comprises the following steps: modification step 1: using PEDOT: PSS as the binder of the electrode; and/or a modification step 2: PSS is coated on the surface of the pole piece which is coated, and the invention mainly aims to improve the electronic conductivity of the electrode and improve the fixation of active substances.
When a negative electrode material containing silicon/tin or a positive electrode material containing sulfur is used in the conventional pole piece design of most of mass-produced lithium batteries, the pole piece is easy to crack due to repeated volume change because the active substance expands/contracts greatly in the charging and discharging processes, the material is pulverized and further falls off from a current collector, and meanwhile, an SEI film can be continuously thickened and consumes electrolyte, so that the capacity of the battery is attenuated and the pole piece is inactivated. Some advanced studies have been to add a conductive layer or a polymer layer on the active material layer, but most of them cannot simultaneously achieve both conformality/volume change suppression and sufficient lithium ion transport channels, or most of them have complicated production processes.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the electrode for the lithium battery, which can inhibit active material pulverization and pole piece cracking, has good lithium ion transmission rate and low battery impedance.
Meanwhile, the invention also provides a preparation method of the electrode for the lithium battery and the lithium battery containing the electrode for the lithium battery.
In order to achieve the purpose, the invention adopts the technical scheme that:
in a first aspect, the invention provides an electrode for a lithium battery, which comprises a current collector, an electrochemical active layer arranged on the current collector, and a modification layer coated on the outer surface of the electrochemical active layer; the material of the electrochemical active layer comprises an electrode active material, and the modification layer is formed by a lithium ion exchange polymer.
As a preferred embodiment of the electrode for a lithium battery of the present invention, the lithium ion exchange polymer comprises a high molecular polymer main chain and a side chain connected to the high molecular polymer main chain, wherein the polymerization degree of the high molecular polymer main chain is 200-1200, and the weight average molecular weight is 50000-500000; the side chain is at least one of phenyl, polyether, polyester, polysiloxane and polyvinyl alcohol flexible molecular chains, and the tail end of the side chain is a lithium salt group.
As a preferred embodiment of the electrode for a lithium battery of the present invention, the polymerization degree of the main chain of the high molecular polymer is 400-800, and the weight average molecular weight is 100000-300000.
In a preferred embodiment of the lithium battery electrode of the present invention, the polymer main chain is polyolefin, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, polyethylene oxide, polysiloxane, polyimide, or a copolymer thereof; the lithium salt group is lithium sulfonate, lithium carboxylate, lithium imide or lithium borate.
As a preferred embodiment of the electrode for lithium battery of the present invention, the lithium ion exchange polymer includes a lithium perfluorosulfonate-polytetrafluoroethylene copolymer (nafion-Li) or a lithium polystyrene sulfonate (PSS-Li).
In a preferred embodiment of the lithium battery electrode according to the present invention, the modified layer has a porosity of 3% to 30%.
In a preferred embodiment of the lithium battery electrode according to the present invention, the modification layer has a thickness of 50nm to 2 μm.
In a preferred embodiment of the electrode for a lithium battery according to the present invention, the material of the current collector is a battery grade copper foil, a battery grade aluminum foil, a carbon-coated foil, or a microporous foil.
As a preferred embodiment of the lithium battery electrode according to the present invention, the material of the electrochemically active layer comprises the following components in percentage by weight: 90-96% of electrode active material, 1-8% of binder and 1-8% of conductive agent.
As a preferred embodiment of the electrode for a lithium battery according to the present invention, the electrode active material is a silicon-based negative electrode material, a tin-based negative electrode material, or a sulfur-based positive electrode material.
In a second aspect, the present invention provides a method for preparing the electrode for a lithium battery, including the steps of:
(1) dissolving/dispersing the material of the electrochemical active layer in a solvent A to obtain active material slurry; meanwhile, dissolving the lithium ion exchange polymer in a solvent B to obtain a polymer glue solution;
(2) coating active material slurry and polymer glue solution on the current collector by adopting a synchronous coating mode, wherein the active material slurry is arranged below (close to the current collector), and the polymer glue solution is arranged above; or coating the active material slurry on the current collector, drying and rolling, and then soaking the current collector with the active material coating in the polymer glue solution or coating the polymer glue solution on the current collector with the active material coating;
(3) drying to obtain the electrode for the lithium battery;
wherein the solvent B is incapable of dissolving the binder in the electrochemically active layer.
In a third aspect, the present invention provides a lithium battery comprising the above-described electrode for a lithium battery.
Compared with the prior art, the invention has the beneficial effects that: the electrode for the lithium battery adopts the lithium ion exchange polymer as the modification layer to coat the electrochemical active layer, and the lithium ion exchange polymer has better mechanical properties (high tensile strength, high elastic modulus and high elongation at break) so that the modification layer has better shape retention to the electrode, thereby inhibiting material pulverization caused by volume change of a silicon/tin-containing negative electrode, a sulfur-containing positive electrode and the like in the charging and discharging processes to a certain extent and inhibiting pole piece cracking. The good coating of the modification layer can reduce the side reaction of the active substance and the electrolyte, reduce the continuous thickening of the SEI film and the consumption of the electrolyte, and further achieve the effect of improving the cycle performance of the battery. Meanwhile, the lithium ion exchange capacity can also ensure the lithium ion transmission rate in the electrochemical process, and the influence of the coating on the impedance is reduced.
The invention innovatively introduces the electrode outer surface modification coating which has both shape retention and a lithium ion transmission channel, and the coating is continuous and independent, has low porosity and high coating degree. The invention also provides a simpler preparation method/production process capable of keeping the independent phase of the complete polymer coating.
Drawings
Fig. 1 is a schematic cross-sectional view of an electrode for a lithium battery according to the present invention. In fig. 1, 1 is a current collector, 2 is an electrochemically active layer, and 3 is a modification layer.
Fig. 2 is a cycle curve diagram of an electrode for a lithium battery according to example 1 of the present invention.
Fig. 3 is an SEM image of an electrode for a lithium battery according to example 1 of the present invention after 50 cycles.
Detailed Description
To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments.
In order to solve the problems of electrode surface cracking and active material pulverization caused by repeated expansion and contraction of an electrode for a lithium battery in the charging and discharging processes and solve the problems of blocked lithium ion transmission and increased battery impedance caused by a conventional electrode surface coating, in one embodiment of the invention, the electrode for the lithium battery comprises a current collector, an electrochemical active layer arranged on the current collector and a modification layer coated on the outer surface of the electrochemical active layer; the material of the electrochemical active layer comprises an electrode active material, and the modification layer is formed by a lithium ion exchange polymer.
The modification layer is a continuous layer wrapped on the outer surface of the electrochemical active layer in an independent phase mode, and good wrapping can reduce side reactions of active substances and electrolyte, reduce continuous thickening of an SEI film and consumption of the electrolyte, and further achieve the effect of improving the cycle performance of the battery. In addition, the lithium ion exchange polymer adopted by the invention has better mechanical properties (high tensile strength, high elastic modulus and high elongation at break), so that the electrode for the lithium battery disclosed by the invention can adapt to the volume change of the electrode in the repeated charge and discharge process, the surface of a pole piece has shape retention, and the pole piece is inhibited from cracking. Meanwhile, the lithium ion exchange capacity of the modification layer can also ensure the lithium ion transmission rate in the electrochemical process, reduce the influence of the coating on the impedance and ensure that the battery has better rate capability.
As a preferred embodiment of one embodiment of the present invention, the lithium ion exchange polymer comprises a high molecular polymer main chain and a side chain connected to the high molecular polymer main chain, wherein the polymerization degree of the high molecular polymer main chain is 200-1200, and the weight average molecular weight is 50000-500000; the side chain is at least one of phenyl, polyether, polyester, polysiloxane and polyvinyl alcohol flexible molecular chains, and the tail end of the side chain is a lithium salt group. As a more preferable embodiment of one embodiment of the present invention, the polymerization degree of the polymer backbone is 400-800, and the weight average molecular weight is 100000-300000. As a preferred embodiment of one embodiment of the present invention, the high molecular polymer main chain is polyolefin, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, polyethylene oxide, polysiloxane, polyimide, or a copolymer thereof; the lithium salt group is lithium sulfonate, lithium carboxylate, lithium imide or lithium borate.
As a further preferred embodiment of one embodiment of the present invention, the lithium ion exchange polymer includes, but is not limited to, lithium perfluorosulfonate-polytetrafluoroethylene copolymer (nafion-Li) or lithium polystyrene sulfonate (PSS-Li). Both nafion-Li and PSS-Li are commercially available. Wherein, the main chain of the perfluorinated lithium sulfonate-polytetrafluoroethylene copolymer is polyperfluoroalkene, and the side chain is perfluorinated olefin ether terminated by lithium sulfonate; the main chain of the polystyrene lithium sulfonate is polyolefin, and the side chain of the polystyrene lithium sulfonate is lithium benzenesulfonate.
As a preferred embodiment of one embodiment of the present invention, the porosity of the modification layer is 3% to 30%.
In a preferred embodiment of one embodiment of the present invention, the thickness of the modification layer is 50nm to 2 μm.
As a preferred implementation of one embodiment of the present invention, the current collector is a battery grade copper foil, a battery grade aluminum foil, a carbon-coated foil, or a microporous foil. The current collector refers to a structure or a part for collecting current, and a person skilled in the art can select a suitable material to manufacture the current collector according to conventional knowledge.
As a preferred implementation of one embodiment of the present invention, the material of the electrochemically active layer comprises the following components in percentage by weight: 90-96% of electrode active material, 1-8% of binder and 1-8% of conductive agent. Among them, the binder is preferably at least one of PVDF (polyvinylidene fluoride), PAA (polyacrylic acid), PAN (polyacrylonitrile), SBR (styrene butadiene rubber), and CMC (sodium carboxymethylcellulose), and the conductive additive is preferably at least one of CNT (carbon nanotube), Super P (conductive carbon black), KB (ketjen black), graphene, and the like.
In the present invention, the electrode active material may be a positive electrode material or a negative electrode material. Preferably, the electrode active material is a silicon-based negative electrode material, a tin-based negative electrode material, or a sulfur-based positive electrode material.
An embodiment of the present invention further provides a method for preparing the electrode for a lithium battery, including the following steps:
(1) dissolving/dispersing the material of the electrochemical active layer in a solvent A to obtain active material slurry; meanwhile, dissolving the lithium ion exchange polymer in a solvent B to obtain a polymer glue solution;
(2) coating active material slurry and polymer glue solution on the current collector by adopting a synchronous coating mode, wherein the active material slurry is arranged below (close to the current collector), and the polymer glue solution is arranged above; or coating the active material slurry on the current collector, drying and rolling, and then soaking the current collector with the active material coating in the polymer glue solution or coating the polymer glue solution on the current collector with the active material coating;
(3) drying to obtain the electrode for the lithium battery;
wherein the solvent B is incapable of dissolving the binder in the electrochemically active layer.
The solvent a is a good solvent for the binder in the electrochemically active layer, and the solvent B is a good solvent for the lithium ion exchange polymer. Solvent a and solvent B may be selected by one skilled in the art based on the particular material to be dissolved and conventional knowledge in the art. Meanwhile, in order to prevent the solvent B from dissolving/damaging the active material coating and ensure that the modification layer exists in the form of an independent phase, the solvent B cannot dissolve the binder in the electrochemically active layer.
In the step (2), when a synchronous (double-gun) coating mode is adopted, the active material slurry is close to the current collector below, and the polymer glue solution is above, so that the active material slurry and the polymer glue solution can generate/keep phase separation to ensure that the modified layer is still coated on the outer surface of the electrochemical active layer as an independent phase after drying. And (3) when the active material slurry and the polymer glue solution are coated separately in the step (2), in order to keep the modification layer to form an independent phase on the outer surface of the electrochemical active layer, rolling is carried out after the active material slurry is coated, and then the polymer glue solution is further coated or impregnated.
In addition, the present invention provides a lithium battery comprising the above electrode for a lithium battery. The above-described electrode for a lithium battery may be used as a positive electrode or a negative electrode of the lithium battery depending on whether the electrode active material is a positive electrode material or a negative electrode material.
Example 1
As shown in fig. 1, an electrode for a lithium battery according to an embodiment of the present invention includes a current collector 1, an electrochemically active layer 2 disposed on the current collector 1, and a modification layer 3 coated on an outer surface of the electrochemically active layer 2; wherein, the material of the current collector 1 is a battery-grade copper foil; the material of the electrochemically active layer 2 consists of the following components in percentage by weight: 95% of silicon-based negative electrode material, 4% of binder and 1% of conductive agent; the modification layer 3 is formed of a lithium ion exchange polymer, which is nafion-Li.
In the electrode for a lithium battery of this embodiment, the porosity of the modification layer 3 is 5%, and the thickness of the modification layer 3 is 500 nm.
The preparation method of the electrode for the lithium battery in the embodiment comprises the following steps:
(1) dissolving/dispersing the material of the electrochemical active layer in deionized water to obtain active material slurry; simultaneously, dissolving a lithium ion exchange polymer in acetone to obtain a polymer glue solution;
(2) the method comprises the following steps of (1) coating active material slurry on a current collector by adopting a synchronous coating mode, wherein the active material slurry is close to a copper foil current collector below, polymer glue solution is above, and the active material slurry and the polymer glue solution are coated on the current collector;
(3) drying to obtain the electrode for the lithium battery;
wherein the acetone is incapable of dissolving the binder in the electrochemically active layer.
The lithium battery of this example contains an electrode for a lithium battery as described in this example.
The cycle curve of the lithium battery electrode of this example is shown in fig. 2, and the SEM image after 50 cycles is shown in fig. 3. Research results show that compared with a lithium battery under the same conditions and with an electrode structure only including a current collector and an electrochemical active layer (i.e., no lithium ion exchange polymer modification layer), the lithium battery of the embodiment has cycle performance improved from 450 cycles (BOL 80%) to 677 cycles (fig. 2), and has equivalent rate charge-discharge performance (the 3C discharge capacity/1C discharge capacity without the modification layer is 91%, and the 3C discharge capacity/1C discharge capacity with the modification layer is 90.5%); the electrode without the modification layer is cracked after being cycled for 20 circles through SEM observation, the electrode with the modification layer is not cracked after being cycled for 50 circles (figure 3), and the electrode piece active material is not pulverized after being cycled for 300 circles.
Example 2
An electrode for a lithium battery according to an embodiment of the present invention is the same as that of embodiment 1 in structure, and is specifically shown in fig. 1. The lithium battery electrode of the present example differs from the lithium battery electrode of example 1 only in that: in this embodiment, the material of the current collector 1 is a carbon-coated foil; the material of the electrochemically active layer 2 consists of the following components in percentage by weight: 90% of tin-based negative electrode material, 8% of binder and 2% of conductive agent; the modification layer 3 is formed of a lithium ion exchange polymer, which is nafion-Li.
In the electrode for a lithium battery of this embodiment, the porosity of the modification layer 3 is 3%, and the thickness of the modification layer 3 is 50 nm.
The method for preparing the electrode for a lithium battery of this example is the same as that of example 1.
The lithium battery of this example contains an electrode for a lithium battery as described in this example.
Example 3
The structure of the lithium battery electrode and the lithium ion exchange polymer used in the lithium battery electrode of the embodiment of the present invention are the same as those of embodiment 1, and the structure is specifically shown in fig. 1. The lithium battery electrode of the present example differs from the lithium battery electrode of example 1 only in that: in this embodiment, the material of the current collector 1 is a carbon-coated aluminum foil; the material of the electrochemically active layer 2 consists of the following components in percentage by weight: 90% of sulfur-based positive electrode material, 2% of binder and 8% of conductive agent; the modification layer 3 is formed by a lithium ion exchange polymer, and the lithium ion exchange polymer is PSS-Li.
In the electrode for a lithium battery of the present example, the porosity of the modification layer 3 is 20%, and the thickness of the modification layer 3 is 1 μm.
The preparation method of the electrode for the lithium battery in the embodiment comprises the following steps:
(1) dissolving/dispersing a material of the electrochemical active layer in NMP to obtain active material slurry; meanwhile, dissolving a lithium ion exchange polymer in an ethanol water solution to obtain a polymer glue solution;
(2) coating active material slurry on the current collector, drying and rolling, and then soaking the current collector with the active material coating in polymer glue solution or coating the polymer glue solution on the current collector with the active material coating;
(3) drying to obtain the electrode for the lithium battery;
wherein the aqueous ethanol solution is incapable of dissolving the binder in the electrochemically active layer.
The lithium battery of this example contains an electrode for a lithium battery as described in this example.
Example 4
An electrode for a lithium battery according to an embodiment of the present invention is the same as that of embodiment 1 in structure, and is specifically shown in fig. 1. The lithium battery electrode of the present example differs from the lithium battery electrode of example 1 only in that: in this embodiment, the material of the electrochemically active layer 2 is composed of the following components by weight percent: 96% of silicon-based negative electrode material, 3% of binder and 1% of conductive agent; the modification layer 3 is formed by a lithium ion exchange polymer, and the lithium ion exchange polymer is PSS-Li.
In the electrode for a lithium battery of the present embodiment, the porosity of the modification layer 3 is 30%, and the thickness of the modification layer 3 is 2 μm.
The method for preparing the electrode for a lithium battery of this example is the same as that of example 3 except that: the material of the electrochemically active layer is dissolved/dispersed in deionized water to obtain active material slurry.
The lithium battery of this example contains an electrode for a lithium battery as described in this example.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (9)
1. An electrode for a lithium battery is characterized by comprising a current collector, an electrochemical active layer arranged on the current collector and a modification layer coated on the outer surface of the electrochemical active layer; the material of the electrochemical active layer comprises an electrode active material, wherein the electrode active material is a silicon-based negative electrode material, a tin-based negative electrode material or a sulfur-based positive electrode material; the modification layer is formed by lithium ion exchange polymer, and the porosity is 3% -30%; the lithium ion exchange polymer comprises a high molecular polymer main chain and a side chain connected to the high molecular polymer main chain, wherein the polymerization degree of the high molecular polymer main chain is 200-500000, and the weight-average molecular weight is 50000-500000; the side chain is at least one of phenyl, polyether, polyester, polysiloxane and polyvinyl alcohol flexible molecular chains, and the tail end of the side chain is a lithium salt group.
2. The electrode as claimed in claim 1, wherein the degree of polymerization of the polymer backbone is 400-800, and the weight average molecular weight is 100000-300000.
3. The electrode for a lithium battery as claimed in claim 1, wherein the high molecular polymer main chain is polyolefin, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, polyethylene oxide, polysiloxane, polyimide, or a copolymer thereof; the lithium salt group is lithium sulfonate, lithium carboxylate, lithium imide or lithium borate.
4. The electrode for a lithium battery as claimed in claim 1, wherein the lithium ion exchange polymer comprises a lithium perfluorosulfonate-polytetrafluoroethylene copolymer or a lithium polystyrene sulfonate.
5. The electrode for a lithium battery as claimed in claim 1, wherein the modification layer has a thickness of 50nm to 2 μm.
6. The electrode of claim 1, wherein the current collector is a battery grade copper foil, a battery grade aluminum foil, a carbon-coated foil, or a microporous foil.
7. The electrode of claim 1, wherein the material of the electrochemically active layer comprises, in weight percent: 90-96% of electrode active material, 1-8% of binder and 1-8% of conductive agent.
8. A method for manufacturing an electrode for a lithium battery as claimed in any one of claims 1 to 7, characterized by comprising the steps of:
(1) dissolving/dispersing the material of the electrochemical active layer in a solvent A to obtain active material slurry; meanwhile, dissolving the lithium ion exchange polymer in a solvent B to obtain a polymer glue solution;
(2) coating active material slurry and polymer glue solution on the current collector by adopting a synchronous coating mode, wherein the active material slurry is arranged below the current collector, and the polymer glue solution is arranged above the current collector; or coating the active material slurry on the current collector, drying and rolling, and then soaking the current collector with the active material coating in the polymer glue solution or coating the polymer glue solution on the current collector with the active material coating;
(3) drying to obtain the electrode for the lithium battery;
wherein the solvent B is incapable of dissolving the binder in the electrochemically active layer.
9. A lithium battery comprising the electrode for a lithium battery as claimed in any one of claims 1 to 7.
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| CN112864387A (en) * | 2021-01-04 | 2021-05-28 | 昆山宝创新能源科技有限公司 | Negative electrode slurry and preparation method and application thereof |
| CN113809333B (en) * | 2021-09-17 | 2023-02-28 | 珠海冠宇电池股份有限公司 | Organic coating layer, electrode material containing coating layer and lithium ion battery |
| CN114122316B (en) * | 2021-11-22 | 2024-01-30 | 远景动力技术(江苏)有限公司 | Negative electrode and use thereof |
| CN115020672B (en) * | 2022-06-30 | 2024-03-12 | 广东邦普循环科技有限公司 | Lithium cobalt oxide positive electrode material and preparation method and application thereof |
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