CN117977022A - Negative electrode sheet, preparation method thereof and battery - Google Patents
Negative electrode sheet, preparation method thereof and battery Download PDFInfo
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- CN117977022A CN117977022A CN202311808982.2A CN202311808982A CN117977022A CN 117977022 A CN117977022 A CN 117977022A CN 202311808982 A CN202311808982 A CN 202311808982A CN 117977022 A CN117977022 A CN 117977022A
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- 238000002360 preparation method Methods 0.000 title abstract description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 68
- 238000002161 passivation Methods 0.000 claims abstract description 58
- 239000011149 active material Substances 0.000 claims abstract description 57
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 56
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 39
- 239000010703 silicon Substances 0.000 claims abstract description 39
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 39
- 239000002131 composite material Substances 0.000 claims abstract description 19
- 229910018516 Al—O Inorganic materials 0.000 claims abstract description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 28
- 239000011248 coating agent Substances 0.000 claims description 19
- 238000000576 coating method Methods 0.000 claims description 19
- 239000002210 silicon-based material Substances 0.000 claims description 15
- 229910052799 carbon Inorganic materials 0.000 claims description 11
- 239000003575 carbonaceous material Substances 0.000 claims description 11
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 10
- 229910052744 lithium Inorganic materials 0.000 claims description 10
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims description 9
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 9
- 229910052731 fluorine Inorganic materials 0.000 claims description 9
- 239000011737 fluorine Substances 0.000 claims description 9
- 239000002002 slurry Substances 0.000 claims description 9
- KLZUFWVZNOTSEM-UHFFFAOYSA-K Aluminum fluoride Inorganic materials F[Al](F)F KLZUFWVZNOTSEM-UHFFFAOYSA-K 0.000 claims description 8
- 229910002804 graphite Inorganic materials 0.000 claims description 8
- 239000010439 graphite Substances 0.000 claims description 8
- 239000011230 binding agent Substances 0.000 claims description 7
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 6
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims description 6
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 6
- 229910052802 copper Inorganic materials 0.000 claims description 6
- 239000010949 copper Substances 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 6
- IRPGOXJVTQTAAN-UHFFFAOYSA-N 2,2,3,3,3-pentafluoropropanal Chemical compound FC(F)(F)C(F)(F)C=O IRPGOXJVTQTAAN-UHFFFAOYSA-N 0.000 claims description 5
- -1 aluminum fluoride compound Chemical class 0.000 claims description 5
- 150000001875 compounds Chemical class 0.000 claims description 5
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 5
- 239000002904 solvent Substances 0.000 claims description 5
- 229910018085 Al-F Inorganic materials 0.000 claims description 4
- 229910018179 Al—F Inorganic materials 0.000 claims description 4
- 239000011889 copper foil Substances 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 4
- 238000005507 spraying Methods 0.000 claims description 4
- 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 3
- FHVDTGUDJYJELY-UHFFFAOYSA-N 6-{[2-carboxy-4,5-dihydroxy-6-(phosphanyloxy)oxan-3-yl]oxy}-4,5-dihydroxy-3-phosphanyloxane-2-carboxylic acid Chemical compound O1C(C(O)=O)C(P)C(O)C(O)C1OC1C(C(O)=O)OC(OP)C(O)C1O FHVDTGUDJYJELY-UHFFFAOYSA-N 0.000 claims description 3
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 3
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 3
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 claims description 3
- 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 claims description 3
- 239000006230 acetylene black Substances 0.000 claims description 3
- 229940072056 alginate Drugs 0.000 claims description 3
- 235000010443 alginic acid Nutrition 0.000 claims description 3
- 229920000615 alginic acid Polymers 0.000 claims description 3
- SMZOGRDCAXLAAR-UHFFFAOYSA-N aluminium isopropoxide Chemical compound [Al+3].CC(C)[O-].CC(C)[O-].CC(C)[O-] SMZOGRDCAXLAAR-UHFFFAOYSA-N 0.000 claims description 3
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 3
- 239000002134 carbon nanofiber Substances 0.000 claims description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 3
- 239000002041 carbon nanotube Substances 0.000 claims description 3
- 239000000839 emulsion Substances 0.000 claims description 3
- 239000004744 fabric Substances 0.000 claims description 3
- 239000006260 foam Substances 0.000 claims description 3
- 229910021389 graphene Inorganic materials 0.000 claims description 3
- 229910021385 hard carbon Inorganic materials 0.000 claims description 3
- 239000003273 ketjen black Substances 0.000 claims description 3
- 239000004005 microsphere Substances 0.000 claims description 3
- 239000005543 nano-size silicon particle Substances 0.000 claims description 3
- 239000002121 nanofiber Substances 0.000 claims description 3
- 239000002070 nanowire Substances 0.000 claims description 3
- 229910021382 natural graphite Inorganic materials 0.000 claims description 3
- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 claims description 3
- 229920000058 polyacrylate Polymers 0.000 claims description 3
- 239000011591 potassium Substances 0.000 claims description 3
- 229910052700 potassium Inorganic materials 0.000 claims description 3
- 235000007686 potassium Nutrition 0.000 claims description 3
- 239000000737 potassium alginate Substances 0.000 claims description 3
- 235000010408 potassium alginate Nutrition 0.000 claims description 3
- MZYRDLHIWXQJCQ-YZOKENDUSA-L potassium alginate Chemical compound [K+].[K+].O1[C@@H](C([O-])=O)[C@@H](OC)[C@H](O)[C@H](O)[C@@H]1O[C@@H]1[C@@H](C([O-])=O)O[C@@H](O)[C@@H](O)[C@H]1O MZYRDLHIWXQJCQ-YZOKENDUSA-L 0.000 claims description 3
- 229920005614 potassium polyacrylate Polymers 0.000 claims description 3
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 3
- 239000000661 sodium alginate Substances 0.000 claims description 3
- 235000010413 sodium alginate Nutrition 0.000 claims description 3
- 229940005550 sodium alginate Drugs 0.000 claims description 3
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 claims description 3
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 claims description 3
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 claims description 3
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 3
- 229920001909 styrene-acrylic polymer Polymers 0.000 claims description 3
- 239000010410 layer Substances 0.000 description 96
- 238000012360 testing method Methods 0.000 description 28
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 15
- 229910001416 lithium ion Inorganic materials 0.000 description 15
- 239000003792 electrolyte Substances 0.000 description 13
- 238000000034 method Methods 0.000 description 13
- 239000007773 negative electrode material Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 6
- 239000010405 anode material Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 125000004122 cyclic group Chemical group 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000007774 positive electrode material Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000009472 formulation Methods 0.000 description 2
- 239000007770 graphite material Substances 0.000 description 2
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000011356 non-aqueous organic solvent Substances 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000011856 silicon-based particle Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 125000005234 alkyl aluminium group Chemical group 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
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- 238000003466 welding Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Landscapes
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a negative electrode plate, a preparation method thereof and a battery, wherein the negative electrode plate comprises a current collector and an active material composite layer, the active material composite layer comprises an aluminum-containing passivation layer and a silicon-containing active material layer, the active material layer is arranged on at least one surface of the current collector, al-F bonds and Al-O bonds exist in the aluminum-containing passivation layer, and the aluminum-containing passivation layer is arranged on one surface of the active material layer, which is away from the current collector.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a negative plate, a preparation method thereof and a battery.
Background
Silicon, which is a new generation of negative electrode material in lithium ion batteries, has an ultra-high theoretical specific capacity of 4200mAh/g, is currently considered as the most likely material to replace the traditional graphite negative electrode. However, silicon is accompanied by a volume expansion of 300 to 400% during lithium ion intercalation, and a huge volume expansion causes a loss of energy density of various lithium ion batteries, damages the formed SEI film, and deteriorates cycle performance. In order to solve the problem of expansion of silicon in the circulation process, a method of carbon coating and polymer coating silicon materials is adopted, but the expansion of silicon is still not restrained in the later period of circulation by the carbon coating, so that the coating layer is broken, the electrical contact of the silicon materials is invalid, the SEI film is destroyed, the circulation retention rate is rapidly deteriorated, and the side reaction in the later period is increased.
Disclosure of Invention
Aiming at the problem that the existing battery cannot solve the expansion problem of silicon of a negative electrode in the circulation process, the invention provides a negative electrode sheet, a preparation method thereof and the battery.
The technical scheme adopted by the invention for solving the technical problems is as follows:
In one aspect, the invention provides a negative electrode sheet, which comprises a current collector and an active material composite layer, wherein the active material composite layer comprises an aluminum-containing passivation layer and a silicon-containing active material layer, the active material layer is arranged on at least one surface of the current collector, al-F bonds and Al-O bonds exist in the aluminum-containing passivation layer, and the aluminum-containing passivation layer is arranged on one surface of the active material layer, which is away from the current collector.
Optionally, the mass ratio of aluminum element in the aluminum-containing passivation layer in the active material composite layer is w, and w is more than or equal to 0.05% and less than or equal to 10%; the thickness of the aluminum-containing passivation layer is d, d is more than or equal to 0.01 mu m and less than or equal to 5 mu m, the mass ratio of silicon element in the silicon-containing active material layer in the active material composite layer is n, n is more than or equal to 0.5% and less than or equal to 30%, and
Optionally, the mass ratio of the aluminum element in the aluminum-containing passivation layer is 0.1% -70%, and the mass ratio of the fluorine element in the aluminum-containing passivation layer is 5% -60%.
Alternatively, the Al-F bond is derived from an aluminum fluoride compound comprising aluminum fluoride, and the Al-O bond is derived from one or more of aluminum isopropoxide, aluminum oxide, aluminum alkyl, and aluminum borohydride.
Optionally, the negative electrode sheet further includes a conductive layer disposed between the current collector and the active material layer; the conductive layer comprises one or more of a carbon material coating, a nano silver coating and an organic coating.
Optionally, the active material layer includes graphite, a silicon-based material, a conductive carbon material, and a binder; the graphite comprises one or more of natural graphite, artificial graphite, mesophase carbon microspheres and hard carbon;
The silicon-based material comprises one or more of silicon oxide particles, nano silicon particles, silicon carbon particles, silicon nanowires and silicon nanofibers;
the conductive carbon material comprises one or more of Super P, ketjen black, acetylene black, carbon nanotubes, carbon nanofibers and graphene;
The binder comprises one or more of lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, styrene-acrylic emulsion, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, lithium alginate, sodium alginate and potassium alginate.
Alternatively, the Dv50 of the silicon-based material is 4 μm to 20 μm, and the specific surface area of the silicon-based material is 0.5m 2/g-10m2/g.
Optionally, the current collector comprises one or more of copper foil, copper foam, copper mesh, carbon cloth and carbon mesh.
In another aspect, the present invention provides a method for preparing the negative electrode sheet according to any one of the above, comprising the following steps:
Coating the slurry of the active material layer on the surface of the current collector;
and uniformly mixing a compound containing fluorine element and aluminum element in a solvent, extruding and spraying the mixture to the surface of the active material layer to form the aluminum-containing passivation layer, and drying to obtain the negative plate.
In another aspect, the present invention provides a battery comprising a positive electrode sheet, a separator, and a negative electrode sheet as described above.
According to the invention, the aluminum-containing passivation layer is coated on the surface of the silicon-containing active material layer, so that the silicon negative electrode material is protected, meanwhile, the surface protection of the graphite material is considered, the area of the negative electrode active material directly contacting electrolyte and electrolyte decomposition substances is reduced, al-F bonds and Al-O bonds in the aluminum-containing passivation layer are beneficial to lithium ion and electron conduction, the tensile strength of an SEI film is enhanced, the mechanical property of the SEI film on the surface of the negative electrode active material is improved, the volume expansion of the negative electrode active material in the circulation process is reduced, and the circulation and energy density are improved.
Drawings
Fig. 1 is an SEM image of a negative electrode sheet provided in example 15 of the present invention;
Fig. 2 is an SEM image of a negative electrode sheet provided in comparative example 1 of the present invention.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects solved by the invention more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
An embodiment of the invention provides a negative electrode plate, which comprises a current collector and an active material composite layer, wherein the active material composite layer comprises an aluminum-containing passivation layer and a silicon-containing active material layer, the active material layer is arranged on at least one surface of the current collector, al-F bonds and Al-O bonds exist in the aluminum-containing passivation layer, and the aluminum-containing passivation layer is arranged on one surface of the active material layer, which is away from the current collector.
According to the invention, the aluminum-containing passivation layer is coated on the surface of the silicon-containing active material layer, so that the silicon negative electrode material is protected, meanwhile, the surface protection of the graphite material is considered, the area of the negative electrode active material directly contacting electrolyte and electrolyte decomposition substances is reduced, al-F bonds and Al-O bonds in the aluminum-containing passivation layer are beneficial to lithium ion and electron conduction, the tensile strength of an SEI film is enhanced, the mechanical property of the SEI film on the surface of the negative electrode active material is improved, the volume expansion of the negative electrode active material in the circulation process is reduced, and the circulation and energy density are improved.
In some embodiments, the mass ratio of aluminum element in the aluminum-containing passivation layer in the active material composite layer is w, and w is more than or equal to 0.05% and less than or equal to 10%; the thickness of the aluminum-containing passivation layer is d, d is more than or equal to 0.01 mu m and less than or equal to 5 mu m, the mass ratio of silicon element in the silicon-containing active material layer in the active material composite layer is n, n is more than or equal to 0.5% and less than or equal to 30%, andWhen d is more than or equal to 0.01 mu m and less than or equal to 5 mu m, the aluminum-containing passivation layer can well protect the silicon anode material, prevent silicon particles from being continuously etched by electrolyte or hydrogen fluoride decomposed by the electrolyte, improve circulation, and prevent the conduction of unfavorable electrons when the thickness of the aluminum-containing passivation layer exceeds 5 mu m, and when the thickness of the aluminum-containing passivation layer is less than 0.01 mu m, the silicon anode material cannot be well protected. When the content of aluminum element, the thickness of the passivation layer containing aluminum and the content of silicon element meet/>During the process, the aluminum-containing passivation layer forms an SEI film with higher mechanical property on the surface of the silicon anode material, so that the circulation is obviously improved, and meanwhile, the expansion in the circulation process is reduced.
Specifically, the mass ratio of the aluminum element in the aluminum-containing passivation layer in the active material composite layer may be 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%. The thickness of the aluminum-containing passivation layer may be 0.01 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm. The mass ratio of silicon element in the active material composite layer containing silicon may be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 15%, 20%, 25%, 30%.
In a preferred embodiment, the mass ratio of the aluminum element in the aluminum-containing passivation layer in the active material composite layer is w, and w is more than or equal to 0.1% and less than or equal to 6%; the thickness of the aluminum-containing passivation layer is d which is more than or equal to 1 mu m and less than or equal to 3 mu m, the mass ratio of silicon element in the silicon-containing active material layer in the active material composite layer is n which is more than or equal to 2% and less than or equal to 10%, and
In some embodiments, the aluminum element accounts for 0.1% -70% of the aluminum-containing passivation layer by mass, and the fluorine element accounts for 5% -60% of the aluminum-containing passivation layer by mass.
In some embodiments, the Al-F bond is derived from an aluminum fluoride compound comprising aluminum fluoride, and the Al-O bond is derived from one or more of aluminum isopropoxide, aluminum oxide, aluminum alkyl, and aluminum borohydride. Specifically, alkyl aluminum and aluminum borohydride hydrolyze to form Al-O bonds after dissolution in water.
In some embodiments, the negative electrode sheet further includes a conductive layer disposed between the current collector and the active material layer. The conductive layer comprises one or more of a carbon material coating, a nano silver coating and an organic coating.
In some embodiments, the active material layer includes graphite, a silicon-based material, a conductive carbon material, and a binder; the graphite comprises one or more of natural graphite, artificial graphite, mesophase carbon microspheres and hard carbon.
The silicon-based material comprises one or more of silicon oxide particles, nano silicon particles, silicon carbon particles, silicon nanowires and silicon nanofibers.
The conductive carbon material comprises one or more of Super P, ketjen black, acetylene black, carbon nanotubes, carbon nanofibers and graphene.
The binder comprises one or more of lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, styrene-acrylic emulsion, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, lithium alginate, sodium alginate and potassium alginate.
In some embodiments, the Dv50 of the silicon-based material is 4 μm to 20 μm and the specific surface area of the silicon-based material is 0.5m 2/g-10m2/g.
In some embodiments, the current collector comprises one or more of copper foil, copper foam, copper mesh, carbon cloth, and carbon mesh.
In another aspect, an embodiment of the present invention provides a method for preparing a negative electrode sheet according to any one of the above embodiments, including the following steps:
and coating the slurry of the active material layer on the surface of the current collector.
And uniformly mixing a compound containing fluorine element and aluminum element in a solvent, extruding and spraying the mixture to the surface of the active material layer to form the aluminum-containing passivation layer, and drying to obtain the negative plate.
Further, when the negative electrode sheet is provided with a conductive layer, the conductive layer is coated on the surface of the current collector before the slurry of the active material layer is coated on the surface of the current collector, and dried.
In another aspect, an embodiment of the present invention provides a battery including a positive electrode sheet, a separator, and a negative electrode sheet as described above.
The invention is further illustrated by the following examples.
Examples
The embodiment is used for explaining the negative plate and the battery disclosed by the invention, and comprises the following operation steps:
Preparation of negative electrode sheet
And (3) coating the carbon material coating on the surface of the current collector, and drying.
Coating the slurry of the active material layer on the surface of the conductive layer, wherein the slurry of the active material layer is graphite, a silicon-based material, a conductive carbon material and a binder according to the mass ratio of 92:5:0.5:2.5 mixing with water to a slurry with a solids content of 50%.
And uniformly mixing a compound containing fluorine element and aluminum element in a solvent, extruding and spraying the mixture to the surface of the active material layer to form the aluminum-containing passivation layer, and drying to obtain the negative plate.
Manufacturing a positive plate:
The positive electrode active material lithium cobaltate, conductive carbon black and polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 95:
2.5:2.5, then adding N-methyl pyrrolidone (NMP) as a solvent, preparing slurry with the solid content of 75 percent, and uniformly stirring. Uniformly coating the slurry on one surface of an aluminum foil with the thickness of 12 mu m, drying at 90 ℃, cold pressing to obtain a positive plate with the positive active material layer thickness of 110 mu m, and repeating the steps on the other surface of the positive plate to obtain the positive plate with the positive active material layer coated on both sides. And cutting the positive plate into a specification of 76mm multiplied by 851mm, and welding the tab for later use.
Preparation of electrolyte:
In the environment with the water content less than 10ppm, the nonaqueous organic solvents of Propylene Carbonate (PC), ethylene Carbonate (EC) and diethyl carbonate (DEC) are mixed according to the mass ratio of 1:1:1, adding lithium hexafluorophosphate (LiPF 6) into a nonaqueous organic solvent for dissolving and uniformly mixing, and adding fluoroethylene carbonate (FEC) to obtain the electrolyte. Wherein, the molar concentration of LiPF 6 in the electrolyte is 1.15mol/L, and the mass concentration of FEC in the electrolyte is 12.5%.
Manufacturing a lithium ion battery:
And sequentially stacking the prepared positive plate, the isolating film and the negative plate, so that the isolating film is positioned between the positive plate and the negative plate to play a role in isolation, and winding to obtain the electrode assembly. A Polyethylene (PE) porous polymeric film having a thickness of 15 μm was used as a separator. And (3) filling the electrode assembly into an aluminum plastic film packaging bag, dehydrating at 80 ℃, injecting the prepared electrolyte, and carrying out the procedures of vacuum packaging, standing, formation, shaping and the like to obtain the lithium ion battery.
Examples 1 to 23
The examples are used for illustrating the negative electrode sheet and the battery disclosed by the invention, and comprise most of the operation steps in the examples, wherein the difference is that: the formulation in table 1 was used.
Comparative examples 1 to 3
Comparative example for comparative illustration of the negative electrode sheet and battery of the present disclosure, most of the operation steps in example 1 were included, except that: the formulation in table 1 was used.
TABLE 1
Performance testing
And (3) testing the cycle performance:
The test temperature was 25℃or 45℃and was charged to 4.4V at a constant current of 0.7℃and 0.025℃at a constant voltage, and after standing for 5 minutes, was discharged to 3.0V at 0.5 ℃. And taking the capacity obtained in the step as initial capacity, performing a cyclic test by adopting 0.7C charge/0.5C discharge, and obtaining a capacity attenuation curve by taking the ratio of the capacity of each step to the initial capacity. The cycle count at 25℃up to 90% of the capacity retention rate was recorded as the room temperature cycle performance of the battery, the cycle count at 45℃up to 80% of the capacity retention rate was recorded as the high temperature cycle performance of the battery, and the cycle performance of the materials was compared by comparing the cycle counts in the two cases.
And (3) testing the full charge expansion rate of the lithium ion battery:
And testing the thickness of the lithium ion battery in a half-charge mode, namely the thickness in a 50% state of charge (SOC) mode by using a spiral micrometer, and circulating to 400 circles, wherein the lithium ion battery is fully charged, namely in a 100% SOC state, testing the thickness of the lithium ion battery at the moment by using the spiral micrometer, and comparing the thickness of the lithium ion battery in the initial half-charge mode with the thickness of the lithium ion battery to obtain the expansion rate of the fully charged lithium ion battery at the moment.
And (3) testing the aluminum content of the passivation layer:
The powder was fixed on a sample stage by SEM-EDS testing, and the cross section of the powder was ion polished with argon to obtain a sample for subsequent testing. The test sample is placed in a test vacuum bin, and the mass fraction content of fluorine element is tested by using an EDS test function of a field emission scanning electron microscope (JSM 6360LV type of JEOL company) at any selected position.
Silicon content test of active material layer:
The powder was fixed on a sample stage by SEM-EDS testing, and the cross section of the powder was ion polished with argon to obtain a sample for subsequent testing. The test sample is placed in a test vacuum bin, and the mass fraction content of the silicon element is tested by using an EDS test function of a field emission scanning electron microscope (JSM 6360LV type of JEOL company) at any selected position.
Passivation layer thickness test:
1. the thickness of the passivation layer is controlled in the pole piece manufacturing process: the thickness L1 of the pole piece when the passivation layer is not coated is tested by a ten-thousandth ruler, and the thickness L2 of the pole piece coated with the passivation layer is tested, wherein the thickness L2-L1 is the thickness of the passivation layer.
2. Testing the thickness of the passivation layer after the pole piece is manufactured: firstly preparing a pole piece of the pole piece, shooting by an SEM-EDS mode, shooting the position of the copper foil, watching the content distribution of aluminum element to determine the thickness, and taking an interface layer with the fluorine element content of more than 0.05% as a passivation layer, wherein the thickness of the passivation layer is obtained by SEM equipment. The test results are shown in Table 2.
TABLE 2
As can be seen from fig. 1 and 2, the passivation layer is not covered in the active material layer in fig. 2, and the passivation layer is uniformly covered on the active material layer in embodiment 1. As can be seen from the test results of examples 1 to 12, as the content of aluminum fluoride or aluminum oxide increases, the tensile strength of the SEI film formed on the surface of the material increases, the cycle is significantly improved, and the expansion during the cycle is reduced; however, when the content of aluminum fluoride or aluminum oxide is increased to some extent, the conductivity of the pole piece is lowered, which results in deterioration of circulation and expansion.
From the test results of examples 10 and examples 13 to 17, it is understood that increasing the thickness of the passivation layer containing aluminum can well protect the silicon anode material, prevent silicon particles from being continuously etched by electrolyte or hydrogen fluoride decomposed by the electrolyte, and improve the cycle. The thickness of the passivation layer is too thin to improve electrochemical performance, and the energy density of the battery core is deteriorated and the electron conduction is deteriorated.
From the test results of examples 10 and examples 18 to 20, it is clear that the aluminum passivation layer still can play a role in protecting the active material by changing the content of silicon in the active material composite layer.
From the test results of examples 21 to 23, it was found that the cyclic performance of the cell could be improved and the expansion during the cyclic process could be reduced by changing the compounds forming the Al-F bond and the Al-O bond.
From the test results of example 10 and comparative examples 1 to 3, it is understood that al—f bonds and al—o bonds exist in the aluminum-containing passivation layer at the same time, which is more favorable for lithium ion and electron conduction, so that the formed SEI film obtains optimal mechanical properties.
As is clear from the test results of all examples and comparative examples, when the aluminum element content, the aluminum-containing passivation layer thickness and the silicon element content satisfyDuring the process, the aluminum-containing passivation layer forms an SEI film with higher mechanical property on the surface of the silicon anode material, so that the circulation is obviously improved, and meanwhile, the expansion in the circulation process is reduced.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (10)
1. The negative electrode plate is characterized by comprising a current collector and an active material composite layer, wherein the active material composite layer comprises an aluminum-containing passivation layer and a silicon-containing active material layer, the active material layer is arranged on at least one surface of the current collector, al-F bonds and Al-O bonds exist in the aluminum-containing passivation layer, and the aluminum-containing passivation layer is arranged on one surface, facing away from the current collector, of the active material layer.
2. The negative plate according to claim 1, wherein the mass ratio of aluminum element in the aluminum-containing passivation layer in the active material composite layer is w, and w is more than or equal to 0.05% and less than or equal to 10%; the thickness of the aluminum-containing passivation layer is d, d is more than or equal to 0.01 mu m and less than or equal to 5 mu m, the mass ratio of silicon element in the silicon-containing active material layer in the active material composite layer is n, n is more than or equal to 0.5% and less than or equal to 30%, and
3. The negative electrode sheet according to claim 2, wherein the mass ratio of the aluminum element in the aluminum-containing passivation layer is 0.1 to 70%, and the mass ratio of the fluorine element in the aluminum-containing passivation layer is 5 to 60%.
4. The negative electrode sheet of claim 1, wherein the Al-F bond is derived from an aluminum fluoride compound comprising aluminum fluoride, and the Al-O bond is derived from one or more of aluminum isopropoxide, aluminum oxide, aluminum alkyl, and aluminum borohydride.
5. The negative electrode sheet according to claim 1, further comprising a conductive layer provided between the current collector and the active material layer; the conductive layer comprises one or more of a carbon material coating, a nano silver coating and an organic coating.
6. The negative electrode sheet according to claim 1, wherein the active material layer includes graphite, a silicon-based material, a conductive carbon material, and a binder; the graphite comprises one or more of natural graphite, artificial graphite, mesophase carbon microspheres and hard carbon;
The silicon-based material comprises one or more of silicon oxide particles, nano silicon particles, silicon carbon particles, silicon nanowires and silicon nanofibers;
the conductive carbon material comprises one or more of Super P, ketjen black, acetylene black, carbon nanotubes, carbon nanofibers and graphene;
The binder comprises one or more of lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, styrene-acrylic emulsion, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, lithium alginate, sodium alginate and potassium alginate.
7. The negative electrode sheet according to claim 6, wherein Dv50 of the silicon-based material is 4 μm to 20 μm and the specific surface area of the silicon-based material is 0.5m 2/g-10m2/g.
8. The negative electrode sheet of claim 1, wherein the current collector comprises one or more of copper foil, copper foam, copper mesh, carbon cloth, and carbon mesh.
9. A method for producing the negative electrode sheet according to any one of claims 1 to 8, comprising the steps of:
Coating the slurry of the active material layer on the surface of the current collector;
and uniformly mixing a compound containing fluorine element and aluminum element in a solvent, extruding and spraying the mixture to the surface of the active material layer to form the aluminum-containing passivation layer, and drying to obtain the negative plate.
10. A battery comprising a positive electrode sheet, a separator, and the negative electrode sheet of any one of claims 1 to 9.
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