CN117253986A - Lithium supplementing negative electrode sheet, preparation method thereof and lithium ion battery - Google Patents
Lithium supplementing negative electrode sheet, preparation method thereof and lithium ion battery Download PDFInfo
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- CN117253986A CN117253986A CN202311423220.0A CN202311423220A CN117253986A CN 117253986 A CN117253986 A CN 117253986A CN 202311423220 A CN202311423220 A CN 202311423220A CN 117253986 A CN117253986 A CN 117253986A
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 138
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 136
- 230000001502 supplementing effect Effects 0.000 title claims abstract description 112
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 24
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 24
- 238000002360 preparation method Methods 0.000 title abstract description 11
- 239000007773 negative electrode material Substances 0.000 claims abstract description 36
- 229920000642 polymer Polymers 0.000 claims abstract description 35
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 29
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 28
- 239000010703 silicon Substances 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 26
- 239000006183 anode active material Substances 0.000 claims abstract description 22
- 239000006258 conductive agent Substances 0.000 claims abstract description 19
- 239000010405 anode material Substances 0.000 claims abstract description 16
- 239000000499 gel Substances 0.000 claims description 35
- 239000000017 hydrogel Substances 0.000 claims description 19
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 15
- 239000002002 slurry Substances 0.000 claims description 15
- 238000000576 coating method Methods 0.000 claims description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 11
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 11
- 229910052799 carbon Inorganic materials 0.000 claims description 10
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- XMWRBQBLMFGWIX-UHFFFAOYSA-N C60 fullerene Chemical compound C12=C3C(C4=C56)=C7C8=C5C5=C9C%10=C6C6=C4C1=C1C4=C6C6=C%10C%10=C9C9=C%11C5=C8C5=C8C7=C3C3=C7C2=C1C1=C2C4=C6C4=C%10C6=C9C9=C%11C5=C5C8=C3C3=C7C1=C1C2=C4C6=C2C9=C5C3=C12 XMWRBQBLMFGWIX-UHFFFAOYSA-N 0.000 claims description 3
- 229920001661 Chitosan Polymers 0.000 claims description 3
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 3
- 239000006229 carbon black Substances 0.000 claims description 3
- 229920002678 cellulose Polymers 0.000 claims description 3
- 239000001913 cellulose Substances 0.000 claims description 3
- QNIHZKIMYOTOTA-UHFFFAOYSA-N fluoroform;lithium Chemical compound [Li].FC(F)F.FC(F)F QNIHZKIMYOTOTA-UHFFFAOYSA-N 0.000 claims description 3
- 229910003472 fullerene Inorganic materials 0.000 claims description 3
- 229910021389 graphene Inorganic materials 0.000 claims description 3
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- 239000010439 graphite Substances 0.000 claims description 3
- 239000003273 ketjen black Substances 0.000 claims description 3
- 229920005610 lignin Polymers 0.000 claims description 3
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 claims description 3
- 239000002086 nanomaterial Substances 0.000 claims description 3
- 229920002401 polyacrylamide Polymers 0.000 claims description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 3
- 150000003949 imides Chemical class 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 19
- 239000003792 electrolyte Substances 0.000 abstract description 14
- 239000007788 liquid Substances 0.000 abstract description 5
- 230000014759 maintenance of location Effects 0.000 abstract description 5
- 239000007784 solid electrolyte Substances 0.000 abstract description 5
- 230000008595 infiltration Effects 0.000 abstract description 3
- 238000001764 infiltration Methods 0.000 abstract description 3
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 6
- 239000011888 foil Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 239000002775 capsule Substances 0.000 description 4
- 239000011889 copper foil Substances 0.000 description 4
- 238000009831 deintercalation Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000009776 industrial production Methods 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 239000013589 supplement Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 230000002687 intercalation Effects 0.000 description 3
- 238000009830 intercalation Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000013268 sustained release Methods 0.000 description 3
- 239000012730 sustained-release form Substances 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
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- -1 lithium bis-fluorosulfonyl imide Chemical class 0.000 description 2
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- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- ZJPPTKRSFKBZMD-UHFFFAOYSA-N [Li].FS(=N)F Chemical compound [Li].FS(=N)F ZJPPTKRSFKBZMD-UHFFFAOYSA-N 0.000 description 1
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
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- 239000004917 carbon fiber Substances 0.000 description 1
- 239000006182 cathode active material Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
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- 230000001351 cycling effect Effects 0.000 description 1
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- 239000000203 mixture Substances 0.000 description 1
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- 229910052759 nickel Inorganic materials 0.000 description 1
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- 238000012827 research and development Methods 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000005096 rolling process Methods 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
- H01M4/134—Electrodes based on metals, Si or alloys
-
- 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
- H01M4/139—Processes of manufacture
- H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
-
- 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
-
- 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)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a lithium supplementing negative electrode sheet, a preparation method thereof and a lithium ion battery. The lithium supplementing negative electrode sheet comprises a negative electrode active material layer, a lithium supplementing layer and a current collector, wherein the current collector is provided with a first outer surface and a second outer surface which are oppositely arranged, and the lithium supplementing layer is arranged on the first outer surface and/or the second outer surface; the negative electrode active material layer is arranged on the outer surface of the lithium supplementing layer far away from the current collector; the lithium supplementing layer comprises polymer gel, and a lithium supplementing agent and a conductive agent which are dispersed in the polymer gel; the anode active material layer includes a silicon-based anode material. The lithium supplementing layer is of a gel structure, and is activated by electrolyte, so that the polymer gel can absorb the electrolyte, the liquid retention coefficient of the battery cell is improved, and the problem that a solid electrolyte layer (SEI) with uniform thickness cannot be generated on the surface of a negative electrode in the circulation process due to poor infiltration of the electrolyte into the battery cell is solved, so that the performances of the battery, such as the circulation performance, the doubling performance, the temperature resistance and the like, are improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium supplementing negative electrode sheet, a preparation method thereof and a lithium ion battery.
Background
In recent years, with the advent of the two-carbon age, the need for clean new energy has grown. Lithium ion batteries are widely used in both energy storage markets and power automobile markets, and the increase of the cycle life and energy density of the lithium batteries is an important concern in the current battery production. Silicon has a gram capacity of more than 3000mAh/g, and can improve the mass energy density and the volume energy density when used for a lithium battery. However, in the process of lithium intercalation and deintercalation, the volume expansion of the silicon particles is more than 300%, so that the cathode material and the current collector are easily stripped, and the silicon particles are pulverized and further react with electrolyte to generate a thicker solid electrolyte layer (SEI), so that lithium ions are continuously consumed in the cycle process of the lithium battery containing the silicon cathode, and the cycle performance of the lithium battery is reduced.
Intrinsic expansion of the silicon negative electrode is not resolvable and lithium ion consumption is a necessary consequence. In recent years, a part of research institutions report methods for improving the cycling stability of a silicon anode material, including methods of pre-lithium of a silicon oxygen material, pre-lithium of pole piece calendaring, pre-lithium of electrochemistry, improvement of anode slurry formulation, addition of a binder and the like. In the chemical pre-lithium technology, research and development personnel are more prone to make lithium slowly supplement, so that the lithium supplementing persistence is improved, and the service life of the battery is prolonged. In the aspect of slow release lithium supplement: patent CN112366351a discloses a lithium-supplementing slow-release capsule, an electrolyte thereof and a lithium ion battery, and by adding the lithium-supplementing slow-release capsule into the electrolyte, the lithium ions are slowly released by the lithium-supplementing slow-release capsule in the circulation process, thereby achieving the effect of lithium supplementation. However, when the sustained-release lithium-supplementing capsule is prepared, the pH parameter needs to be regulated and controlled for many times, the raw materials are more, the preparation process is complex and tedious, the cost is higher, and the industrial production is difficult to realize.
Therefore, the invention needs to provide a simpler and more convenient lithium-supplementing negative electrode sheet with lower cost and a preparation method thereof, so that the lithium-supplementing negative electrode sheet has better slow-release lithium-supplementing effect in the battery cycle process and better cycle performance of the lithium battery.
Disclosure of Invention
The invention mainly aims to provide a lithium-supplementing negative electrode sheet, a preparation method thereof and a lithium ion battery, so as to solve the problems that the preparation process of a slow-release lithium-supplementing material in the prior art is complex and tedious, the cost is high, and industrial production is difficult to realize.
In order to achieve the above object, according to one aspect of the present invention, there is provided a lithium-compensating negative electrode sheet including a negative electrode active material layer, a lithium-compensating layer, and a current collector having first and second outer surfaces disposed opposite to each other, the lithium-compensating layer being disposed on the first and/or second outer surfaces; the negative electrode active material layer is arranged on the outer surface of the lithium supplementing layer far away from the current collector; the lithium supplementing layer comprises polymer gel, and a lithium supplementing agent and a conductive agent which are dispersed in the polymer gel; the anode active material layer includes a silicon-based anode material.
Further, the thickness of the anode active material layer is 50 to 200 μm.
Further, the thickness of the current collector is 4.5 to 20 μm.
Further, the thickness of the lithium supplementing layer is 5 to 100. Mu.m, more preferably 10 to 50. Mu.m.
Further, the weight percentage of the lithium-supplementing agent in the lithium-supplementing layer is 3 to 30%, and more preferably 10 to 20%.
Further, the weight percentage of the conductive agent in the lithium supplementing layer is 3-10%.
Further, the weight percentage of the polymer gel in the lithium supplementing layer is 60 to 94%, and more preferably 60 to 80%.
Further, the silicon-based anode material is selected from one or more of silicon, silicon oxide, carbon composite silicon oxide or carbon composite silicon oxide.
Further, in the anode active material layer, the weight percentage of the silicon-based anode material in the anode active material layer is 87 to 97%.
Further, the lithium supplementing agent is selected from one or more of lithium difluorosulfimide, lithium difluorophosphate, lithium dioxaborate or lithium bistrifluoromethane yellow imide.
Further, the polymer gel is selected from one or more of chitosan hydrogel, cellulose hydrogel, lignin hydrogel, polyacrylic acid hydrogel, polyacrylamide hydrogel or polyvinyl alcohol hydrogel.
Further, the conductive agent is selected from one or more of carbon black, graphene, conductive graphite, fullerene, ketjen black or carbon nanomaterial.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for manufacturing a lithium-compensating negative electrode sheet, providing a current collector having a first outer surface and a second outer surface disposed opposite to each other; coating a first slurry comprising a lithium supplementing agent, a polymer gel and a conductive agent on the first outer surface and/or the second outer surface of the current collector, and forming a lithium supplementing layer after a first curing treatment; and coating a second slurry containing a silicon-based negative electrode material on the outer surface of the lithium supplementing layer far away from the current collector, and forming a negative electrode active material layer after second curing treatment to obtain the lithium supplementing negative electrode plate.
Further, the solid content of the first slurry is 30-60%.
Further, the temperature of the first curing treatment is-20-0 ℃ and the time is 10-30 min.
Further, the temperature of the second curing treatment is 60-80 ℃ and the time is 5-10 min.
According to another aspect of the invention, a lithium ion battery is provided, which comprises a positive plate, a negative plate and a diaphragm, wherein the negative plate is the lithium supplementing negative plate.
Compared with the traditional battery cell structure, the lithium-supplementing negative electrode plate has better conductivity and higher liquid retention coefficient. The polymer gel with the conductive agent dispersed in the lithium supplementing layer can enhance the adhesion between the anode active material layer and the current collector, avoid the risk of stripping the anode active material and the current collector conductive network, increase the conductive network of the anode active material and the current collector, and further improve the conductivity of the anode. Meanwhile, the lithium supplementing layer is of a gel structure, and is activated by electrolyte, so that the polymer gel can absorb the electrolyte, the liquid retention coefficient of the battery cell is improved, and the problem that a solid electrolyte layer (SEI) with uniform thickness cannot be generated on the surface of a negative electrode in the circulation process due to poor infiltration of the electrolyte into the battery cell is solved, so that the performances of the battery, such as the circulation performance, the doubling performance, the temperature resistance and the like, are improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
fig. 1 is a schematic structural view showing a lithium-supplementing negative electrode sheet according to an embodiment of the present invention;
fig. 2 shows a schematic diagram of a process of slowly releasing lithium-supplementing lithium of a lithium-supplementing negative electrode tablet in an embodiment of the invention.
Wherein the above figures include the following reference numerals: a negative electrode active material layer; 2, a lithium supplementing layer; and 3, a current collector.
Detailed Description
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present invention will be described in detail with reference to examples.
As described in the background section of the application, the preparation process of the slow-release lithium-supplementing material in the prior art is complex and tedious, has higher cost and is difficult to realize the problem of industrial production. In order to solve this problem, the present application provides a lithium-supplementing negative electrode sheet including a negative electrode active material layer, a lithium-supplementing layer, and a current collector having a first outer surface and a second outer surface disposed opposite to each other, the lithium-supplementing layer being disposed on the first outer surface and/or the second outer surface of the current collector; the negative electrode active material layer is arranged on the outer surface of the lithium supplementing layer far away from the current collector; the lithium supplementing layer comprises polymer gel, and a lithium supplementing agent and a conductive agent which are dispersed in the polymer gel; the anode active material layer includes a silicon-based anode material.
The lithium supplementing negative electrode sheet comprises a negative electrode active material layer, a lithium supplementing layer and a current collector, wherein the lithium supplementing layer comprises polymer gel, and a lithium supplementing agent and a conductive agent which are dispersed in the polymer gel, and the negative electrode active material layer comprises a silicon-based negative electrode material. In the battery core circulation process comprising the lithium-supplementing negative electrode sheet, the lithium-supplementing negative electrode sheet can produce a slow-release lithium-supplementing effect. The process for producing the slow-release lithium supplement by the lithium supplement negative electrode tablet comprises the following steps: the silicon-based anode material in the anode active material layer is subjected to reversible alloying/dealloying process in the anode deintercalation lithium, and is different from intercalation reaction in the layered anode material, the alloying/dealloying process of the silicon-based anode material in the anode deintercalation lithium can cause crystal reconstruction and phase change of the material, so that the silicon-based anode material is subjected to larger volume expansion, the anode active material layer extrudes the lithium supplementing layer, and the lithium supplementing layer is subjected to permeation process due to electrolyte activation in the cell cycle process, so that the lithium supplementing agent distributed in the polymer gel in the lithium supplementing layer is slowly released for supplementing lithium. The lithium supplementing negative electrode plate disclosed by the invention extrudes the polymer gel dispersed lithium supplementing agent in the lithium supplementing layer along with the volume expansion of the silicon-based negative electrode material in the use process of the battery so as to slowly release the lithium supplementing, the lithium ion balance in the system is not influenced while the lithium supplementing is carried out, and the problem that the transmission of lithium ions is influenced by excessively thick SEI (solid electrolyte interface) film caused by adding a large amount of lithium supplementing agent is avoided, so that the performance of the battery is further deteriorated. The lithium-supplementing negative plate has the advantages of simple raw materials, low cost and simple subsequent processing process, and can be slightly modified on the existing production line to realize industrial production.
Compared with the traditional battery cell structure, the lithium-supplementing negative electrode plate also has better electric conductivity and higher liquid retention coefficient. The polymer gel with the conductive agent dispersed in the lithium supplementing layer can enhance the adhesion between the anode active material layer and the current collector, avoid the risk of stripping the anode active material and the current collector conductive network, increase the conductive network of the anode active material and the current collector, and further improve the conductivity of the anode. Meanwhile, the lithium supplementing layer is of a gel structure, and is activated by electrolyte, so that the polymer gel can absorb the electrolyte, the liquid retention coefficient of the battery cell is improved, and the problem that a solid electrolyte layer (SEI) with uniform thickness cannot be generated on the surface of a negative electrode in the circulation process due to poor infiltration of the electrolyte into the battery cell is solved, so that the performances of the battery, such as the circulation performance, the doubling performance, the temperature resistance and the like, are improved.
In a preferred embodiment, as shown in fig. 1, the lithium-compensating negative electrode sheet includes a negative electrode active material layer 1, a lithium-compensating layer 2, and a current collector 3, the current collector 3 having oppositely disposed first and second outer surfaces, the lithium-compensating layer 2 being disposed on the first outer surface of the current collector 1, the negative electrode active material layer 1 being disposed on the outer surface of the lithium-compensating layer 2 remote from the current collector 3. The slow-release lithium supplementing process of the battery core containing the lithium supplementing negative electrode sheet in the battery core circulation process is shown in fig. 2, the negative electrode active material layer 1 expands in volume, and the negative electrode active material layer 1 extrudes the lithium supplementing layer 2 in the expansion process, so that the lithium supplementing agent in the polymer gel in the lithium supplementing layer 2 is slowly released for supplementing lithium.
In a preferred embodiment, the thickness of the anode active material layer is 50 to 200 μm (for example, may be 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm). The present invention limits the thickness of the anode active material layer to the above range based on the following consideration: when the thickness of the anode active material layer is too high, the rate capability of the battery core is poor; when the thickness of the anode active material layer is too low, the rolling during the coating process is difficult to be adapted when the anode material is prepared later.
In order to obtain a lithium-compensating negative electrode sheet having more excellent performance, the thickness of the current collector is 4.5 to 20 μm (for example, 4.5 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm may be used). When the thickness of the current collector is controlled within the range, the lithium-supplementing negative electrode sheet has better mechanical property and better specific capacity, and can better bear the lithium-supplementing layer and the negative electrode active material layer.
In a preferred embodiment, the thickness of the lithium-compensating layer is 5 to 100 μm (for example, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm may be used), and more preferably 10 to 50 μm. The invention limits the thickness of the lithium supplementing layer in the range, and can simultaneously have better energy density of the battery core and better lithium supplementing effect. When the thickness of the lithium supplementing layer is too high, the energy density of the battery cell is reduced; when the thickness of the lithium supplementing layer is too low, the lithium supplementing amount is insufficient.
In a preferred embodiment, the weight percentage of the lithium-supplementing agent in the lithium-supplementing layer is 3 to 30% (for example, 3%, 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%) in the lithium-supplementing layer. The lithium supplementing agent has better lithium supplementing effect when the weight percentage of the lithium supplementing agent accounting for the lithium supplementing layer is limited in the range, and the lithium precipitating risk can be caused when the content of the lithium supplementing agent is too high, and the energy density of the battery cell can be reduced. More preferably 10 to 20%.
In a preferred embodiment, the weight percentage of the conductive agent in the lithium supplementing layer is 3 to 10% (for example, 3%, 5%, 6%, 7%, 8%, 9%, 10%). The invention limits the weight percentage of the conductive agent in the lithium supplementing layer to the above range, and can increase the conductive network between the negative electrode active material of the lithium supplementing negative electrode plate and the current collector. When the content of the conductive agent is too high, the release of the lithium supplementing agent distributed on the polymer gel in the lithium supplementing layer can be influenced, so that the lithium supplementing effect of the battery is poor.
In a preferred embodiment, the weight percentage of the polymer gel in the lithium supplementing layer is 60 to 94% (for example, 60%, 65%, 70%, 75%, 77%, 80%, 82%, 85%, 87%, 90%, 92%, 94%). The invention limits the weight percentage of the polymer gel in the lithium supplementing layer to the above range, can effectively bond the current collector and the active material layer, and can lead the release of the lithium supplementing agent to be too slow when the content of the polymer gel is too high, and the active material of the battery core is pulverized; too low may cause it to peel off the current collector layer. More preferably, the weight percentage of the polymer gel in the lithium supplementing layer is 60-80%.
In order to further improve the slow-release lithium supplementing effect of the lithium supplementing negative electrode sheet, the silicon-based negative electrode material is selected from one or more of silicon, silicon oxide, carbon composite silicon oxide or carbon composite silicon oxide. The silicon-based negative electrode material has a good volume expansion coefficient in the negative electrode lithium intercalation and deintercalation process, and the volume expansion change rate is low, so that the lithium supplementing layer can be fully extruded for a long time to release lithium ions from the polymer gel for supplementing lithium, the sustained-release lithium supplementing effect of the lithium supplementing negative electrode plate is higher in durability, and the lithium supplementing effect is better.
In order to further improve the sustained-release lithium supplementing effect of the lithium supplementing negative electrode sheet, the silicon-based negative electrode material in the negative electrode active material layer accounts for 87-97% by weight (for example, 87%, 88%, 90%, 92%, 94%, 95%, 96%, 97%) of the negative electrode active material layer. The silicon-based anode material is limited in the range, so that the anode active material layer can further release the lithium supplementing agent in the polymer gel, and the lithium supplementing effect is better.
In a preferred embodiment, the lithium-supplementing agent is selected from one or more of lithium bis-fluorosulfonyl imide, lithium difluorophosphate, lithium bisoxalato borate, or lithium bis-trifluoromethane xanthimide. Compared with other lithium supplementing agents, the lithium supplementing agent has the advantages of better thermal stability, hydrolytic stability, difficult expansion and the like.
In a preferred embodiment, the polymeric gel is selected from one or more of chitosan hydrogels (e.g., available from aletin), cellulose hydrogels (e.g., available from stroway-allen-su), lignin hydrogels (e.g., available from stroway-allen-su), polyacrylic acid hydrogels (e.g., available from aletin), polyacrylamide hydrogels (e.g., available from the glabrous chemical industry), or polyvinyl alcohol hydrogels (e.g., available from the key-kava technology). Compared with other polymer hydrogels, the polymer gel has the advantages of enriching nano channels and effectively releasing the lithium supplementing agent.
In order to further increase the conductive network between the negative electrode active material of the lithium supplementing negative electrode sheet and the current collector, the conductive agent is one or more selected from carbon black, graphene, conductive graphite, fullerene, ketjen black or carbon nanomaterial.
The material of the current collector of the present invention may be a current collector material commonly used in the art, and is not particularly limited, and may be one or more selected from a metal foil, a metal plastic composite foil, a porous metal foil, or a carbon fiber foil, for example.
In another aspect of the present invention, there is also provided a method for preparing a lithium-supplementing negative electrode sheet, comprising the steps of: providing a current collector having a first outer surface and a second outer surface; coating a first slurry comprising a lithium supplementing agent, a polymer gel and a conductive agent on the first outer surface and/or the second outer surface of the current collector to form a lithium supplementing layer; and coating a second slurry containing a silicon-based negative electrode material on the outer surface of the lithium supplementing layer far away from the current collector to obtain the lithium supplementing negative electrode sheet.
Based on the reasons, the lithium-supplementing negative electrode tablet prepared by the method has a better slow-release lithium-supplementing effect, and better electric conductivity and liquid-retaining coefficient. The lithium-supplementing negative plate has the advantages of simple raw materials, low cost and simple preparation process, and can be industrially produced by slightly modifying the existing production line.
In order to obtain a lithium supplementing layer with more uniform coating and better performance, the solid content of the first slurry is preferably 30-60%; preferably, the temperature of the first curing treatment is-20 to 0 ℃ and the time is 10 to 30 minutes. The first curing treatment of the present invention is performed in a vacuum oven.
In order to obtain a cathode active material layer with more uniform coating and better performance, the solid content of the second slurry is 10-30%; preferably, the temperature of the second curing treatment is 60 to 80 ℃ and the time is 5 to 10 minutes. Preferably, the running speed of the second curing treatment in the coating process is 5-10 m/min.
The invention also provides a lithium ion battery, which comprises a positive plate, a negative plate and a diaphragm, wherein the negative plate is the lithium supplementing negative plate. Based on the reasons, the lithium ion battery has the advantages of excellent cycle performance, rate performance, temperature resistance, conductivity and the like.
The lithium-supplementing negative electrode sheet is applicable to any type of cell structure, for example, any one of soft package, square shell or cylindrical form.
The present application is described in further detail below in conjunction with specific embodiments, which should not be construed as limiting the scope of the claims.
Examples
The lithium-supplementing negative electrode sheet of each example was prepared according to the following method: providing a metal copper foil with the thickness of 6 mu m, uniformly mixing conductive carbon black (Super-p), polymer gel and lithium supplementing agent (lithium bis-fluorosulfonyl imide) to obtain first slurry (the solid content is 35%), coating the first slurry on two sides of the metal copper foil, and curing for 30min at the temperature of-20 ℃ to form a lithium supplementing layer;
uniformly mixing silicon oxide, conductive carbon black (Super-p), polyacrylic acid and styrene-butadiene rubber to obtain second slurry (the solid content is 42%), coating the second slurry on the surface of the lithium supplementing layer, and curing for 10min at 80 ℃ to form a negative electrode active material layer (the thickness is 100 mu m) to obtain the lithium supplementing negative electrode plate. Wherein the silicon-based anode material accounts for 90 weight percent of the anode material layer.
Specific parameters of the lithium-supplementing negative electrode sheet of each example are shown in table 1, and the content of the lithium-supplementing agent, the content of the conductive agent and the content of the polymer gel in table 1 refer to the content in the lithium-supplementing layer.
Comparative example 1
The negative electrode sheet of comparative example 1 does not include a lithium supplementing layer, and the negative electrode sheet is composed of a negative electrode active material layer and a current collector.
The preparation method of the negative electrode active material layer is the same as that of the embodiment, silicon oxide, conductive carbon black, polyacrylic acid and styrene-butadiene rubber are uniformly mixed and then coated on two sides of a metal copper foil with the thickness of 6 mu m, and the metal copper foil is cured for 10 minutes at 80 ℃ to form the negative electrode active material layer, so that a negative electrode plate is obtained.
TABLE 1
Performance testing
Preparing a lithium ion battery: the lithium-supplementing negative electrode sheet of each example and the negative electrode sheet of the comparative example in the present invention were assembled with a positive electrode sheet (positive electrode active material is a 5-series nickel ternary positive electrode material, positive electrode current collector is a 12 μm metal aluminum foil), a separator (common PE separator), and an electrolyte (EC: DMC: dc=1:1:1) to prepare a lithium ion battery.
And (3) testing the internal resistance of the battery: the stability time of the assembled lithium ion battery was 10s when the assembled lithium ion battery was discharged to 50% soc at 2C at room temperature (25 ℃), and the DCR was tested, and the test results are shown in table 2.
Normal temperature (25 ℃) cycle performance test: the assembled lithium ion battery is tested at the temperature of 25 ℃ by constant current charge and discharge at the temperature of 0.5 ℃, and the test results are shown in table 2.
High temperature (45 ℃) cycle performance test: the assembled lithium ion battery is tested at a constant current of 0.5C at 45 ℃, and the test results are shown in Table 2.
TABLE 2
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The lithium supplementing negative electrode sheet is characterized by comprising a negative electrode active material layer (1), a lithium supplementing layer (2) and a current collector (3), wherein the current collector (3) is provided with a first outer surface and a second outer surface which are oppositely arranged, and the lithium supplementing layer (2) is arranged on the first outer surface and/or the second outer surface; the negative electrode active material layer (1) is arranged on the outer surface of the lithium supplementing layer (2) far away from the current collector (3);
the lithium supplementing layer (2) comprises polymer gel, and a lithium supplementing agent and a conductive agent which are dispersed in the polymer gel; the anode active material layer (1) includes a silicon-based anode material.
2. The lithium-compensating negative electrode sheet according to claim 1, characterized in that the thickness of the negative electrode active material layer (1) is 50 to 200 μm;
preferably, the thickness of the current collector (3) is 4.5-20 μm;
the thickness of the lithium supplementing layer (2) is preferably 5 to 100. Mu.m, more preferably 10 to 50. Mu.m.
3. The lithium-compensating negative electrode sheet according to claim 1 or 2, characterized in that in the lithium-compensating layer (2), the weight percentage of the lithium-compensating agent in the lithium-compensating layer (2) is 3-30%, further preferably 10-20%;
preferably, the weight percentage of the conductive agent in the lithium supplementing layer (2) is 3-10%;
preferably, the weight percentage of the polymer gel in the lithium supplementing layer (2) is 60-94%, more preferably 60-80%.
4. The lithium-compensating negative electrode sheet according to any of claims 1 to 3, wherein the silicon-based negative electrode material is selected from one or more of silicon, silicon oxide, carbon composite silicon oxide, or carbon composite silicon oxide;
preferably, in the anode active material layer (1), the weight percentage of the silicon-based anode material in the anode active material layer (1) is 87 to 97%.
5. The lithium-compensating negative electrode sheet according to any of claims 1 to 4, wherein the lithium-compensating agent is selected from one or more of lithium difluorosulfonimide, lithium difluorophosphate, lithium dioxaborate or lithium bistrifluoromethane yellow imide.
6. The lithium-compensating negative electrode sheet of any of claims 1-5, wherein the polymeric gel is selected from one or more of chitosan hydrogel, cellulose hydrogel, lignin hydrogel, polyacrylic acid hydrogel, polyacrylamide hydrogel, or polyvinyl alcohol hydrogel.
7. The lithium-compensating negative electrode sheet of any of claims 1-6, wherein the conductive agent is selected from one or more of carbon black, graphene, conductive graphite, fullerene, ketjen black, or carbon nanomaterial.
8. A method for producing the lithium-compensating negative electrode sheet according to any one of claims 1 to 7, comprising the steps of:
providing a current collector having oppositely disposed first and second outer surfaces;
coating a first slurry comprising a lithium supplementing agent, a polymer gel and a conductive agent on the first outer surface and/or the second outer surface of the current collector, and forming a lithium supplementing layer after a first curing treatment;
and coating second slurry containing a silicon-based negative electrode material on the outer surface of the lithium supplementing layer far away from the current collector, and forming a negative electrode active material layer after second curing treatment to obtain the lithium supplementing negative electrode plate.
9. The method for preparing a lithium-compensating negative electrode sheet according to claim 8, wherein the solid content of the first slurry is 30 to 60%;
preferably, the solid content of the second slurry is 10-45%;
preferably, the temperature of the first curing treatment is-20-0 ℃ and the time is 10-30 min;
preferably, the temperature of the second curing treatment is 60-80 ℃ for 5-10 min.
10. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet and a separator, wherein the negative electrode sheet is the lithium-compensating negative electrode sheet of any one of claims 1 to 7.
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