CN112909262A - Silicon cathode and preparation method and application thereof - Google Patents
Silicon cathode and preparation method and application thereof Download PDFInfo
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- CN112909262A CN112909262A CN201911130639.0A CN201911130639A CN112909262A CN 112909262 A CN112909262 A CN 112909262A CN 201911130639 A CN201911130639 A CN 201911130639A CN 112909262 A CN112909262 A CN 112909262A
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 130
- 239000010703 silicon Substances 0.000 title claims abstract description 130
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 130
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000000463 material Substances 0.000 claims abstract description 51
- 239000011230 binding agent Substances 0.000 claims abstract description 43
- 239000007773 negative electrode material Substances 0.000 claims abstract description 32
- 239000006258 conductive agent Substances 0.000 claims abstract description 26
- 230000009477 glass transition Effects 0.000 claims abstract description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 56
- 229910001416 lithium ion Inorganic materials 0.000 claims description 56
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 16
- 229910052744 lithium Inorganic materials 0.000 claims description 16
- 239000011248 coating agent Substances 0.000 claims description 13
- 238000000576 coating method Methods 0.000 claims description 13
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 11
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 10
- 239000002174 Styrene-butadiene Substances 0.000 claims description 10
- 239000011889 copper foil Substances 0.000 claims description 10
- 239000003792 electrolyte Substances 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 9
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 claims description 8
- 229920002125 Sokalan® Polymers 0.000 claims description 8
- 239000002270 dispersing agent Substances 0.000 claims description 8
- 239000004816 latex Substances 0.000 claims description 8
- 229920000126 latex Polymers 0.000 claims description 8
- 229940070721 polyacrylate Drugs 0.000 claims description 8
- 239000004584 polyacrylic acid Substances 0.000 claims description 8
- 238000005303 weighing Methods 0.000 claims description 8
- 229920002907 Guar gum Polymers 0.000 claims description 7
- MTAZNLWOLGHBHU-UHFFFAOYSA-N butadiene-styrene rubber Chemical compound C=CC=C.C=CC1=CC=CC=C1 MTAZNLWOLGHBHU-UHFFFAOYSA-N 0.000 claims description 7
- 239000000665 guar gum Substances 0.000 claims description 7
- 235000010417 guar gum Nutrition 0.000 claims description 7
- 229960002154 guar gum Drugs 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 229920000058 polyacrylate Polymers 0.000 claims description 7
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 claims description 6
- 239000000661 sodium alginate Substances 0.000 claims description 6
- 235000010413 sodium alginate Nutrition 0.000 claims description 6
- 229940005550 sodium alginate Drugs 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 5
- 238000001125 extrusion Methods 0.000 claims description 5
- 238000005096 rolling process Methods 0.000 claims description 5
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 claims description 5
- 239000011115 styrene butadiene Substances 0.000 claims description 5
- 229920001661 Chitosan Polymers 0.000 claims description 4
- 229940045110 chitosan Drugs 0.000 claims description 4
- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 claims description 4
- 229910000572 Lithium Nickel Cobalt Manganese Oxide (NCM) Inorganic materials 0.000 claims 1
- FBDMTTNVIIVBKI-UHFFFAOYSA-N [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] Chemical group [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] FBDMTTNVIIVBKI-UHFFFAOYSA-N 0.000 claims 1
- 238000012545 processing Methods 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 93
- 239000001768 carboxy methyl cellulose Substances 0.000 description 24
- 238000000034 method Methods 0.000 description 15
- 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 13
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 12
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 12
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 12
- 229940105329 carboxymethylcellulose Drugs 0.000 description 12
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 12
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 12
- 230000008569 process Effects 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 230000007547 defect Effects 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 238000004804 winding Methods 0.000 description 4
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical group [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 description 3
- 239000007772 electrode material Substances 0.000 description 3
- 238000011031 large-scale manufacturing process Methods 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 238000007600 charging Methods 0.000 description 2
- 238000010280 constant potential charging Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
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- 238000011160 research Methods 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229920003123 carboxymethyl cellulose sodium Polymers 0.000 description 1
- 229940063834 carboxymethylcellulose sodium Drugs 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 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
- 239000005543 nano-size silicon particle Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/64—Carriers or collectors
- H01M4/66—Selection of materials
- H01M4/665—Composites
- H01M4/667—Composites in the form of layers, e.g. coatings
-
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- 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)
- Composite Materials (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The invention relates to a silicon cathode and a preparation method and application thereof, belonging to the technical field of battery materials. The silicon negative electrode comprises a current collector, a first electrochemical active layer and a second electrochemical active layer, wherein the first electrochemical active layer is coated on the outer surface of the current collector, and the second electrochemical active layer is coated on the outer surface of the first electrochemical active layer; the material of the first electrochemical active layer comprises a silicon-based negative electrode material, a conductive agent and a binder A with the glass transition temperature of less than 25 ℃; the material of the second electrochemical active layer comprises a silicon-based negative electrode material, a conductive agent and a binder B with the glass transition temperature of more than 25 ℃. The silicon negative electrode has a double-layer electrochemical active layer structure, can ensure the bonding and interface performance of an electrode and a current collector, and simultaneously inhibits the expansion of the silicon negative electrode through the high-modulus rigid binder, so the silicon negative electrode has good processing performance and better cycle performance.
Description
Technical Field
The invention relates to a silicon cathode and a preparation method and application thereof, belonging to the technical field of battery materials.
Background
In recent years, lithium ion batteries are widely used, and the main application directions include the consumer electronics field and the power battery field, while users have higher and higher requirements on the performance of the lithium ion batteries. The energy density of the lithium ion battery is required to be higher no matter the requirement of consumer electronics on the endurance time or the requirement of the endurance mileage in the application of the power battery.
In order to increase the energy density of the lithium ion battery, increasing the gram capacity of the positive and negative electrode materials is the most effective method. The theoretical capacity upper limit of the traditional graphite cathode material is 372mAh/g, and the capacity of the graphite cathode material applied in large scale at present is mostly distributed before 350mAh/g to 365mAh/g, which is close to the theoretical upper limit, so that the lifting space is limited. The theoretical capacity upper limit of the silicon negative electrode material can reach 4200mAh/g, and the silicon negative electrode material is greatly improved relative to graphite, and has the potential of greatly improving the energy density of the lithium ion battery. Most of the silicon negative electrode plates for the existing lithium ion batteries mostly adopt a single-layer structure, and the binder mainly comprises Styrene Butadiene Rubber (SBR), modified SBR, acrylate emulsion, acrylic acid, modified acrylic acid and the like. The preparation method comprises the steps of fully and uniformly mixing the dispersing agent and the active substance, coating the mixture on a current collector, drying, rolling and slitting to obtain the required silicon negative pole piece. However, the silicon negative electrode material is accompanied by a drastic volume change during charge and discharge, and the solid electrolyte interface film (SEI) on the surface thereof is significantly damaged, and the cycle performance is significantly deteriorated compared to that of a graphite negative electrode.
Many documents/patents report that some high-modulus binders have an inhibiting effect on expansion of a silicon negative electrode material in a charging and discharging process and can improve the cycle performance of the silicon negative electrode material, however, the binders such as polyacrylic acid, lithium/sodium polyacrylate, polyacrylic acid modified polymers (such as LA133 series), sodium alginate, chitosan, sodium carboxymethyl cellulose and the like have generally strong rigidity, are easy to cause problems of dry cracking, demolding, hard brittleness and the like in actual industrial production, and cause great troubles to a production process, particularly a winding process.
Therefore, the binders which have obvious improvement effect on the cycle performance of the silicon cathode and are reported in the current research have the characteristics of hardness and brittleness, have small challenges in the large-scale production process, particularly the winding process, and have the defects of low binding power and easiness in demoulding; the SBR binder with good flexibility and strong caking property can not well inhibit the expansion of the silicon cathode, and the cycle performance is influenced.
As the lithium ion battery industry continues to develop, more and more new devices/new technologies are being applied to the industry. The Chinese patent with the publication number of CN106469825A discloses a high-power large-capacity lithium ion battery and a preparation method thereof, the lithium ion battery is characterized in that an electrode material layer is arranged between two current collectors to form an electrode plate by changing the structure of the electrode plate and the placement positions of the current collectors in the existing lithium ion battery, and positive and negative current collectors are respectively arranged at two sides of a diaphragm instead of the inner part of the electrode material layer, so that a battery electrode layer is close to a reaction region of a porous current collector and always has a low internal resistance region, therefore, the battery can meet the requirement of instantaneous high-power work, meanwhile, the thickness of the electrode layer can be greatly increased, the requirement of large capacity of the battery is met, and the contradiction that the instantaneous power of the battery is; meanwhile, a porous current collector is arranged between the electrode layer and the diaphragm, so that the direct contact between the electrode material layer and the diaphragm is avoided, the risk that the positive and negative electrode active particles and the nano conductive layer enter the diaphragm to generate internal short circuit is reduced, and the safety of the battery is improved.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a silicon cathode with better cycle performance, and a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the technical scheme that:
in a first aspect, the present invention provides a silicon negative electrode comprising a current collector, a first electrochemically active layer coated on an outer surface of the current collector, and a second electrochemically active layer coated on an outer surface of the first electrochemically active layer; the material of the first electrochemical active layer comprises a silicon-based negative electrode material, a conductive agent and a binder A with the glass transition temperature of less than 25 ℃; the material of the second electrochemical active layer comprises a silicon-based negative electrode material, a conductive agent and a binder B with the glass transition temperature of more than 25 ℃.
As a preferred embodiment of the silicon negative electrode of the present invention, the binder a is styrene-butadiene latex, modified styrene-butadiene latex, acrylate; the binder B is polyacrylic acid, lithium polyacrylate, sodium polyacrylate, modified polyacrylic acid, sodium alginate, polyacrylate, chitosan or guar gum.
As a preferred embodiment of the silicon negative electrode of the present invention, the material of the first electrochemically active layer comprises the following components in parts by weight: 90-99 parts of silicon-based negative electrode material, 0.1-5 parts of conductive agent, 0.1-5 parts of binder A and 0.1-5 parts of dispersant; the material of the second electrochemical active layer comprises the following components in parts by weight: 90-99 parts of silicon-based negative electrode material, 0.1-5 parts of conductive agent, 0.1-5 parts of binder B and 0.1-5 parts of dispersant.
In a preferred embodiment of the silicon negative electrode according to the present invention, the first electrochemically active layer has a thickness of 1 to 50 μm, and the second electrochemically active layer has a thickness of 20 to 200 μm.
As a preferred embodiment of the silicon negative electrode of the present invention, the current collector is a battery grade copper foil.
In a preferred embodiment of the silicon negative electrode of the present invention, the silicon negative electrode is a sheet.
In a second aspect, the present invention provides a method for preparing the silicon negative electrode, which comprises the following steps:
(1) weighing the components in the first electrochemical active layer in proportion, and uniformly mixing to obtain a material of the first electrochemical active layer; meanwhile, weighing all components in the second electrochemical active layer in proportion, and uniformly mixing to obtain a material of the second electrochemical active layer;
(2) placing the material of the first electrochemical active layer in a lower die head, placing the material of the second electrochemical active layer in an upper die head, and coating the material on a current collector simultaneously by adopting a slit extrusion type double-layer coating mode;
(3) and (3) drying and rolling the current collector coated in the step (2) to obtain the silicon negative electrode.
In a third aspect, the invention provides an application of the silicon negative electrode in preparation of a lithium ion battery cell, a lithium ion battery pack or a lithium ion battery.
In a fourth aspect, the invention provides a lithium ion battery cell or a lithium ion battery pack comprising the silicon negative electrode described above.
As a preferred embodiment of the lithium ion battery cell of the present invention, the lithium ion battery cell is a soft-package lithium ion battery cell or a hard-package lithium ion battery cell.
In a fifth aspect, the present invention provides the use of the above lithium ion battery pack in an automobile, a motorcycle or a bicycle.
In a sixth aspect, the invention provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode is the silicon negative electrode.
In a preferred embodiment of the lithium ion battery of the present invention, the positive electrode of the lithium ion battery is nickel cobalt lithium manganate.
In a preferred embodiment of the lithium ion battery of the present invention, the lithium ion battery is subjected to 1C/1C cycle at a temperature of 25 ℃ and a voltage of 2.5 to 4.2V, and the battery capacity is reduced to 70% after 700 cycles.
Compared with the prior art, the invention has the beneficial effects that: the silicon negative electrode has a double-layer electrochemical active layer structure, the first electrochemical active layer (bottom layer) close to the current collector adopts a binder with good flexibility and strong cohesiveness, and the second electrochemical active layer (top layer) far away from the current collector adopts a binder with strong rigidity and an inhibiting effect on the expansion of the silicon negative electrode. The bottom layer of the adhesive ensures the adhesion and interface performance of the electrode and the current collector, and the top layer of the high-modulus rigid adhesive inhibits the expansion of the silicon negative electrode. Therefore, the silicon cathode has good processing performance and better cycle performance.
Drawings
FIG. 1 is a schematic structural view of a silicon anode of the present invention; wherein 1 is a current collector, 2 is a first electrochemically active layer, and 3 is a second electrochemically active layer.
Fig. 2 is a graph showing the results of cycle performance of silicon anodes of the experimental group and the reference group in effect example 1 of the present invention.
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 the prior art, a common silicon cathode mostly adopts a single-layer structure, however, the binder which has an obvious improvement effect on the cycle performance of the silicon cathode and is reported in the research at present mostly has the characteristic of hardness and brittleness, has little challenge in the large-scale production process, particularly in the winding process, and also has the defects of weak binding power and easy demoulding; the SBR binder with good flexibility and strong caking property can not well inhibit the expansion of the silicon cathode, and the cycle performance is influenced. In order to overcome the defect, the invention provides a silicon negative electrode, which comprises a current collector, a first electrochemical active layer coated on the outer surface of the current collector and a second electrochemical active layer coated on the outer surface of the first electrochemical active layer; the material of the first electrochemical active layer comprises a silicon-based negative electrode material, a conductive agent and a binder A with the glass transition temperature of less than 25 ℃; the material of the second electrochemical active layer comprises a silicon-based negative electrode material, a conductive agent and a binder B with the glass transition temperature of more than 25 ℃.
The invention develops the effects of different binders by the design of different formulas of the double-layer structure. Select high flexible high viscosity binder A for use with the mass flow body contact, guaranteed the interface combination with the mass flow body, prevent the drawing of patterns risk among the cycle process, and fully consider the matching of binder and silicon negative pole material at the top layer, through the effect of hydrogen bond isodynamic, cooperate the high modulus of binder B, restrain the inflation of silicon negative pole, promote the cycle performance.
The invention applies the high modulus hard binder to the silicon negative electrode material, and avoids the defect of hard and brittle pole pieces caused by the binder through the design of a double-layer structure, so that the hard binder can be used for large-scale production, particularly the winding process.
As a preferred embodiment of the silicon negative electrode of the present invention, the binder a is styrene-butadiene latex (SBR), modified SBR latex, acrylate; the binder B is polyacrylic acid, lithium polyacrylate, sodium polyacrylate, modified polyacrylic acid, sodium alginate, polyacrylate and chitosan guar gum. Preferably, the binder B is sodium alginate, lithium polyacrylate or guar gum. The binder A is a high-binder and high-flexibility binder, and the binder B is a high-modulus hard binder and is well combined with silicon-based materials.
As a preferred embodiment of the silicon negative electrode of the present invention, the material of the first electrochemically active layer comprises the following components in parts by weight: 90-99 parts of silicon-based negative electrode material, 0.1-5 parts of conductive agent, 0.1-5 parts of binder A and 0.1-5 parts of dispersant; the material of the second electrochemical active layer comprises the following components in parts by weight: 90-99 parts of silicon-based negative electrode material, 0.1-5 parts of conductive agent, 0.1-5 parts of binder B and 0.1-5 parts of dispersant. The silicon-based anode material and the conductive agent can be selected conventionally according to actual needs, for example, nano silicon can be used as the silicon-based anode material. The dispersant can be sodium carboxymethylcellulose (CMC).
In a preferred embodiment of the silicon negative electrode according to the present invention, the first electrochemically active layer has a thickness of 1 to 50 μm, and the second electrochemically active layer has a thickness of 20 to 200 μm.
As a preferred embodiment of the silicon negative electrode of the present invention, the current collector is a battery grade copper 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.
In a preferred embodiment of the silicon negative electrode of the present invention, the silicon negative electrode is a sheet.
In addition, the invention also provides a preparation method of the silicon cathode, which comprises the following steps:
(1) weighing the components in the first electrochemical active layer in proportion, and uniformly mixing to obtain a material of the first electrochemical active layer; meanwhile, weighing all components in the second electrochemical active layer in proportion, and uniformly mixing to obtain a material of the second electrochemical active layer;
(2) placing the material of the first electrochemical active layer in a lower die head, placing the material of the second electrochemical active layer in an upper die head, and coating the material on a current collector simultaneously by adopting a slit extrusion type double-layer coating mode; the material extruded by the lower die head is firstly contacted with the copper foil and is positioned at the bottom layer; the extruded material is contacted with the copper foil and positioned on the top layer;
(3) and (3) drying and rolling the current collector coated in the step (2) to obtain the silicon negative electrode.
The slit extrusion type double-layer coating mode is adopted, and double-layer coating of slurry with different formulas can be met.
In addition, the invention also provides application of the silicon negative electrode in preparation of a lithium ion battery cell, a lithium ion battery pack or a lithium ion battery.
In addition, the invention also provides a lithium ion battery cell or a lithium ion battery pack containing the silicon cathode.
As a preferred embodiment of the lithium ion battery cell of the present invention, the lithium ion battery cell is a soft-package lithium ion battery cell or a hard-package lithium ion battery cell.
In addition, the invention also provides the application of the lithium ion battery pack in automobiles, motorcycles or bicycles.
In addition, the invention also provides a lithium ion battery which comprises a positive electrode, a negative electrode, a separator and electrolyte, wherein the separator and the electrolyte are arranged between the positive electrode and the negative electrode, and the negative electrode is the silicon negative electrode.
Preferably, the positive electrode of the lithium ion battery is nickel cobalt lithium manganate. The lithium ion battery has good cycle performance, 1C/1C cycle is carried out under the conditions that the temperature is 25 ℃ and the voltage is 2.5-4.2V, and the battery capacity is attenuated to 70% after 700 cycles.
Example 1
As shown in fig. 1, a silicon negative electrode according to an embodiment of the present invention includes a current collector 1, a first electrochemically active layer 2 coated on an outer surface of the current collector 1, and a second electrochemically active layer 3 coated on an outer surface of the first electrochemically active layer 2; the material of the first electrochemically active layer 2 consists of the following components in parts by weight: 95 parts of silicon-based negative electrode material, 1 part of conductive agent, 2.5 parts of styrene-butadiene latex and 1.5 parts of sodium carboxymethyl cellulose (CMC); the material of the second electrochemically active layer 3 consists of the following components in parts by weight: 95 parts of silicon-based negative electrode material, 1 part of conductive agent, 4 parts of sodium alginate and 0.5 part of sodium carboxymethyl cellulose (CMC);
wherein the thickness of the first electrochemically active layer 2 is 5 μm and the thickness of the second electrochemically active layer 3 is 50 μm; the current collector 1 is a battery grade copper foil; the silicon negative electrode is sheet-shaped.
The preparation method of the silicon negative electrode in the embodiment comprises the following steps:
(1) weighing the components in the first electrochemical active layer in proportion, and uniformly mixing to obtain a material of the first electrochemical active layer; meanwhile, weighing all components in the second electrochemical active layer in proportion, and uniformly mixing to obtain a material of the second electrochemical active layer;
(2) placing the material of the first electrochemical active layer in a lower die head, placing the material of the second electrochemical active layer in an upper die head, and coating the material on a current collector simultaneously by adopting a slit extrusion type double-layer coating mode;
(3) and (3) drying and rolling the current collector coated in the step (2), and cutting to obtain the silicon negative electrode.
A lithium battery of this embodiment includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, where the negative electrode is the silicon negative electrode of this embodiment. Further, the lithium battery is a lithium ion battery.
Example 2
The silicon cathode of the embodiment of the invention has the same structure as the silicon cathode of the embodiment 1; the silicon negative electrode of this example is different from the silicon negative electrode of example 1 in that: in this embodiment, the material of the first electrochemically active layer 2 is composed of the following components in parts by weight: 96 parts of silicon-based negative electrode material, 1 part of conductive agent, 2 parts of acrylate and 1 part of sodium carboxymethyl cellulose (CMC); the material of the second electrochemically active layer 3 consists of the following components in parts by weight: 96 parts of silicon-based negative electrode material, 1 part of conductive agent, 3 parts of lithium polyacrylate and 4 parts of sodium carboxymethyl cellulose (CMC); the thickness of the first electrochemically active layer 2 was 10 μm and the thickness of the second electrochemically active layer 3 was 40 μm; the current collector 1 is a battery-grade copper foil; the silicon negative electrode is sheet-shaped.
The method for manufacturing the silicon negative electrode of this example is the same as that of example 1.
A lithium battery of this embodiment includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, where the negative electrode is the silicon negative electrode of this embodiment. Further, the lithium battery is a lithium ion battery.
Example 3
The silicon cathode of the embodiment of the invention has the same structure as the silicon cathode of the embodiment 1; the silicon negative electrode of this example is different from the silicon negative electrode of example 1 in that: in this embodiment, the material of the first electrochemically active layer 2 is composed of the following components in parts by weight: 94 parts of silicon-based negative electrode material, 2 parts of conductive agent, 3 parts of acrylate and 1 part of sodium carboxymethyl cellulose (CMC); the material of the second electrochemically active layer 3 consists of the following components in parts by weight: 94 parts of silicon-based negative electrode material, 2 parts of conductive agent, 4 parts of guar gum and 2 parts of sodium carboxymethyl cellulose (CMC); the thickness of the first electrochemically active layer 2 was 10 μm and the thickness of the second electrochemically active layer 3 was 60 μm; the current collector 1 is a battery-grade copper foil; the silicon negative electrode is sheet-shaped.
The method for manufacturing the silicon negative electrode of this example is the same as that of example 1.
A lithium battery of this embodiment includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, where the negative electrode is the silicon negative electrode of this embodiment. Further, the lithium battery is a lithium ion battery.
Example 4
The silicon cathode of the embodiment of the invention has the same structure as the silicon cathode of the embodiment 1; the silicon negative electrode of this example is different from the silicon negative electrode of example 1 in that: in this embodiment, the material of the first electrochemically active layer 2 is composed of the following components in parts by weight: 99 parts of silicon-based negative electrode material, 0.1 part of conductive agent, 5 parts of acrylate and 5 parts of sodium carboxymethyl cellulose (CMC); the material of the second electrochemically active layer 3 consists of the following components in parts by weight: 99 parts of silicon-based negative electrode material, 0.1 part of conductive agent, 5 parts of guar gum and 5 parts of sodium carboxymethyl cellulose (CMC); the thickness of the first electrochemically active layer 2 is 1 μm and the thickness of the second electrochemically active layer 3 is 20 μm; the current collector 1 is a battery-grade copper foil; the silicon negative electrode is sheet-shaped.
The method for manufacturing the silicon negative electrode of this example is the same as that of example 1.
A lithium battery of this embodiment includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, where the negative electrode is the silicon negative electrode of this embodiment. Further, the lithium battery is a lithium ion battery.
Example 5
The silicon cathode of the embodiment of the invention has the same structure as the silicon cathode of the embodiment 1; the silicon negative electrode of this example is different from the silicon negative electrode of example 1 in that: in this embodiment, the material of the first electrochemically active layer 2 is composed of the following components in parts by weight: 90 parts of silicon-based negative electrode material, 5 parts of conductive agent, 0.1 part of acrylate and 0.1 part of sodium carboxymethyl cellulose (CMC); the material of the second electrochemically active layer 3 consists of the following components in parts by weight: 90 parts of silicon-based negative electrode material, 5 parts of conductive agent, 0.1 part of guar gum and 0.1 part of sodium carboxymethyl cellulose (CMC); the thickness of the first electrochemically active layer 2 was 50 μm and the thickness of the second electrochemically active layer 3 was 200 μm; the current collector 1 is a battery-grade copper foil; the silicon negative electrode is sheet-shaped.
The method for manufacturing the silicon negative electrode of this example is the same as that of example 1.
A lithium battery of this embodiment includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, where the negative electrode is the silicon negative electrode of this embodiment. Further, the lithium battery is a lithium ion battery.
Effect example 1
The experimental group (double-layer coating design) and the reference group silicon negative electrode (cycle performance of conventional coating design, experimental group is the silicon negative electrode described in example 1. the reference group silicon negative electrode only differs from the experimental group in that the reference group only comprises one electrochemical active layer, the reference group silicon negative electrode has a structure comprising a current collector and an electrochemical active layer coated on the outer surface of the current collector, wherein the electrochemical active layer comprises, by weight, 95 parts of silicon-based negative electrode material, 1 part of conductive agent, 2.5 parts of styrene-butadiene latex and 1.5 parts of carboxymethylcellulose sodium (CMC), and the thickness of the electrochemical active layer in the reference group is 55 μm and is consistent with the total thickness of the first electrochemical active layer and the second electrochemical active layer in the experimental group.
And in the reference group, the experimental group and the reference group silicon negative pole piece are matched with a high-nickel positive pole piece (the material of the positive pole piece is nickel-cobalt lithium manganate, wherein the mass of nickel is 80% of the total amount of nickel, cobalt and manganese), an 2614895 standard type square aluminum shell battery cell is assembled, 1C/1C circulation is carried out at room temperature, the circulation voltage range is 2.5V-4.2V, the charging mode is constant current to 4.2V, then constant voltage charging is carried out, the constant voltage charging cutoff current is 0.05C, and 1C discharging is carried out after standing for 30 min. The cyclic effect pair is shown in figure 2. As can be seen from fig. 2, the cycle performance of the silicon cathode prepared by the method is obviously improved, and the cycle performance is improved from 400 weeks to 70% to 700 weeks to 70%; and the pole piece has good processing performance.
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 (13)
1. The silicon negative electrode is characterized by comprising a current collector, a first electrochemical active layer coated on the outer surface of the current collector, and a second electrochemical active layer coated on the outer surface of the first electrochemical active layer; the material of the first electrochemical active layer comprises a silicon-based negative electrode material, a conductive agent and a binder A with the glass transition temperature of less than 25 ℃; the material of the second electrochemical active layer comprises a silicon-based negative electrode material, a conductive agent and a binder B with the glass transition temperature of more than 25 ℃.
2. The silicon negative electrode of claim 1, wherein the binder a is a styrene-butadiene latex, a modified styrene-butadiene latex, an acrylate; the binder B is polyacrylic acid, lithium polyacrylate, sodium polyacrylate, modified polyacrylic acid, sodium alginate, polyacrylate, chitosan or guar gum.
3. The silicon negative electrode of claim 1, wherein the first electrochemically active layer is made of a material comprising, in parts by weight: 90-99 parts of silicon-based negative electrode material, 0.1-5 parts of conductive agent, 0.1-5 parts of binder A and 0.1-5 parts of dispersant; the material of the second electrochemical active layer comprises the following components in parts by weight: 90-99 parts of silicon-based negative electrode material, 0.1-5 parts of conductive agent, 0.1-5 parts of binder B and 0.1-5 parts of dispersant.
4. The silicon negative electrode of claim 1, wherein the first electrochemically active layer has a thickness of 1 to 50 μ ι η and the second electrochemically active layer has a thickness of 20 to 200 μ ι η.
5. The silicon negative electrode of claim 1, wherein the current collector is a battery grade copper foil.
6. The method for producing a silicon negative electrode as claimed in any one of claims 1 to 5, comprising the steps of:
(1) weighing the components in the first electrochemical active layer in proportion, and uniformly mixing to obtain a material of the first electrochemical active layer; meanwhile, weighing all components in the second electrochemical active layer in proportion, and uniformly mixing to obtain a material of the second electrochemical active layer;
(2) placing the material of the first electrochemical active layer in a lower die head, placing the material of the second electrochemical active layer in an upper die head, and coating the material on a current collector simultaneously by adopting a slit extrusion type double-layer coating mode;
(3) and (3) drying and rolling the current collector coated in the step (2) to obtain the silicon negative electrode.
7. Use of the silicon negative electrode of any one of claims 1 to 5 in the preparation of a lithium ion battery cell, a lithium ion battery pack or a lithium ion battery.
8. A lithium ion battery cell or a lithium ion battery pack comprising a silicon negative electrode according to any one of claims 1 to 5.
9. The lithium ion battery cell of claim 8, wherein the lithium ion battery cell is a soft-pack cell or a hard-pack cell.
10. Use of a lithium ion battery pack according to claim 8 in applications in automobiles, motorcycles or bicycles.
11. A lithium ion battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode is the silicon negative electrode according to any one of claims 1 to 5.
12. The lithium ion battery of claim 11, wherein the positive electrode of the lithium ion battery is lithium nickel cobalt manganese oxide.
13. The lithium ion battery of claim 12, wherein the lithium ion battery is cycled at a temperature of 25 ℃ and a voltage of 2.5-4.2V for 1C/1C cycles, and the battery capacity decays to 70% after 700 cycles.
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