CN118073522A - Over-lithiated lithium-free positive electrode and preparation method and application thereof - Google Patents
Over-lithiated lithium-free positive electrode and preparation method and application thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 34
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 94
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 91
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 19
- 230000001502 supplementing effect Effects 0.000 claims abstract description 6
- 229910052751 metal Inorganic materials 0.000 claims description 26
- 239000002184 metal Substances 0.000 claims description 26
- 239000000843 powder Substances 0.000 claims description 25
- 239000007774 positive electrode material Substances 0.000 claims description 20
- 239000002994 raw material Substances 0.000 claims description 18
- 239000002245 particle Substances 0.000 claims description 15
- 239000011230 binding agent Substances 0.000 claims description 13
- 239000006258 conductive agent Substances 0.000 claims description 13
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 13
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 9
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 9
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 9
- -1 polytetrafluoroethylene Polymers 0.000 claims description 7
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- 230000002441 reversible effect Effects 0.000 claims description 6
- 238000005096 rolling process Methods 0.000 claims description 6
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 5
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 5
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 4
- 239000003575 carbonaceous material Substances 0.000 claims description 4
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 claims description 4
- 239000007773 negative electrode material Substances 0.000 claims description 4
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 3
- 239000006183 anode active material Substances 0.000 claims description 3
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- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims description 3
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- 238000003756 stirring Methods 0.000 claims description 3
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 2
- 206010016654 Fibrosis Diseases 0.000 claims description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims description 2
- 239000002033 PVDF binder Substances 0.000 claims description 2
- 229910000676 Si alloy Inorganic materials 0.000 claims description 2
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- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 claims description 2
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 claims description 2
- QWJYDTCSUDMGSU-UHFFFAOYSA-N [Sn].[C] Chemical compound [Sn].[C] QWJYDTCSUDMGSU-UHFFFAOYSA-N 0.000 claims description 2
- 239000004917 carbon fiber Substances 0.000 claims description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 2
- 239000002041 carbon nanotube Substances 0.000 claims description 2
- 239000006185 dispersion Substances 0.000 claims description 2
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- 229910021389 graphene Inorganic materials 0.000 claims description 2
- 229910002804 graphite Inorganic materials 0.000 claims description 2
- 239000010439 graphite Substances 0.000 claims description 2
- 229910021385 hard carbon Inorganic materials 0.000 claims description 2
- 239000003273 ketjen black Substances 0.000 claims description 2
- IDBFBDSKYCUNPW-UHFFFAOYSA-N lithium nitride Chemical compound [Li]N([Li])[Li] IDBFBDSKYCUNPW-UHFFFAOYSA-N 0.000 claims description 2
- 229910001386 lithium phosphate Inorganic materials 0.000 claims description 2
- 229910044991 metal oxide Inorganic materials 0.000 claims description 2
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- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 2
- 229910021384 soft carbon Inorganic materials 0.000 claims description 2
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- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 claims description 2
- 229910052755 nonmetal Inorganic materials 0.000 claims 2
- 150000004706 metal oxides Chemical class 0.000 claims 1
- 229910052976 metal sulfide Inorganic materials 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 6
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- 238000006138 lithiation reaction Methods 0.000 description 7
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- 239000011248 coating agent Substances 0.000 description 5
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- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- TXEYQDLBPFQVAA-UHFFFAOYSA-N tetrafluoromethane Chemical compound FC(F)(F)F TXEYQDLBPFQVAA-UHFFFAOYSA-N 0.000 description 4
- JDZCKJOXGCMJGS-UHFFFAOYSA-N [Li].[S] Chemical compound [Li].[S] JDZCKJOXGCMJGS-UHFFFAOYSA-N 0.000 description 3
- 239000011149 active material Substances 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- NFMAZVUSKIJEIH-UHFFFAOYSA-N bis(sulfanylidene)iron Chemical compound S=[Fe]=S NFMAZVUSKIJEIH-UHFFFAOYSA-N 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 210000001787 dendrite Anatomy 0.000 description 2
- 229910000339 iron disulfide Inorganic materials 0.000 description 2
- MKCDXXDWWZVCJG-UHFFFAOYSA-M lithium;4-methyl-1,3-dioxolan-2-one;perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O.CC1COC(=O)O1 MKCDXXDWWZVCJG-UHFFFAOYSA-M 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 150000003463 sulfur Chemical class 0.000 description 2
- GBVSONMCEKNESD-UHFFFAOYSA-N 1,1'-biphenyl;lithium Chemical compound [Li].C1=CC=CC=C1C1=CC=CC=C1 GBVSONMCEKNESD-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- GPVWCGHDIGTNCE-UHFFFAOYSA-N [Fe](=S)=S.[Li] Chemical compound [Fe](=S)=S.[Li] GPVWCGHDIGTNCE-UHFFFAOYSA-N 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- 238000003490 calendering Methods 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
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- 239000010949 copper Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical group FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 description 1
- 239000011245 gel electrolyte Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 1
- 239000003999 initiator Substances 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- SHXXPRJOPFJRHA-UHFFFAOYSA-K iron(iii) fluoride Chemical compound F[Fe](F)F SHXXPRJOPFJRHA-UHFFFAOYSA-K 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 239000011244 liquid electrolyte Substances 0.000 description 1
- PDZGAEAUKGKKDE-UHFFFAOYSA-N lithium;naphthalene Chemical compound [Li].C1=CC=CC2=CC=CC=C21 PDZGAEAUKGKKDE-UHFFFAOYSA-N 0.000 description 1
- 238000001755 magnetron sputter deposition Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 239000012982 microporous membrane Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 description 1
- 229910052982 molybdenum disulfide Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000000643 oven drying Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
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- 238000003825 pressing Methods 0.000 description 1
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- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Inorganic materials [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
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- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- CFJRPNFOLVDFMJ-UHFFFAOYSA-N titanium disulfide Chemical compound S=[Ti]=S CFJRPNFOLVDFMJ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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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- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides an over-lithiated lithium-free positive electrode, a preparation method and application thereof. The over-lithiated lithium-free positive electrode can be matched with a lithium-free negative electrode, solves the problems of reduced safety performance, reduced cycle performance and the like caused by the use of the existing lithium-free positive electrode matched with a lithium metal negative electrode, and simultaneously avoids the safety risk caused by severe reaction during the lithium supplementing of the negative electrode, so that a lithium ion battery with long service life, high safety and high energy density can be obtained.
Description
Technical Field
The invention belongs to the technical field of batteries, and relates to a lithium-free positive electrode for over-lithiation and a preparation method and application thereof.
Background
The lithium ion battery is the first choice of consumer electronic batteries and new energy automobile power batteries due to the advantages of high energy density, long cycle life, no memory effect and the like, but the energy density of the lithium ion battery is limited by anode and cathode materials at present, so that the space is further limited. When carbon fluoride, metal fluoride or elemental sulfur is used as a positive electrode active material, the carbon fluoride, metal fluoride or elemental sulfur has the advantage of high specific capacity, and is the positive electrode development direction of a lithium battery with high energy density in the future.
The preparation method of the lithium-iron disulfide battery is disclosed in CN 1874036A, and comprises the following steps: the negative electrode adopts lithium foil, and the positive electrode is a positive electrode plate formed by coating iron disulfide slurry on a metal strip material matrix. The separator adopts a polypropylene microporous membrane. The electrolyte adopts a solvent system such as lithium perchlorate-propylene carbonate and the like, and methyl methacrylate monomer and initiator are added. After the battery is assembled, the methyl methacrylate is polymerized by heating, and a gel electrolyte of polymethyl methacrylate and lithium perchlorate-propylene carbonate is formed in the battery.
And as CN 103035879A discloses a positive pole piece of a lithium sulfur battery and a preparation method thereof, the positive pole piece of the lithium sulfur battery is prepared by uniformly mixing and coating a surface-modified sulfur-based composite active material, a conductive agent and a binder on a current collector, and drying and pressing twice. The surface-modified sulfur-based composite active material is prepared by coating metal with excellent conductivity such as nickel, copper and the like on elemental sulfur with uniform particles by a chemical plating method, wherein the elemental sulfur particles are 10 nm-10 mu m, the thickness of the chemically plated conductive metal is 0.1-10 nm, and the content of the conductive metal is 0.8-10 wt%; the prepared positive plate and the metal lithium are assembled into a lithium-sulfur battery.
However, since the above-mentioned positive electrode such as carbon fluoride, metal fluoride or elemental sulfur does not contain lithium, it is necessary to use the positive electrode in combination with a metal lithium negative electrode, and the problems such as dendrite growth, continuous side reaction and large volume effect of the metal lithium negative electrode may result in very poor cycle life and safety of a battery using the metal lithium as the negative electrode.
Based on the above research, it is necessary to provide an over-lithiated lithium-free positive electrode, which improves the cycle and safety of the battery.
Disclosure of Invention
The invention aims to provide an over-lithiated lithium-free positive electrode, a preparation method and application thereof, and particularly relates to an over-lithiated lithium-free positive electrode matched with a lithium-free negative electrode, a preparation method and application thereof, wherein the over-lithiated lithium-free positive electrode can solve the problems of reduced safety performance, reduced cycle performance and the like caused by the use of the existing lithium-free positive electrode matched with a lithium metal negative electrode, and meanwhile, the safety risk caused by severe reaction during negative electrode lithium supplementation is avoided, so that a long-life high-energy density lithium ion battery can be obtained.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
in a first aspect, the present invention provides an over-lithiated lithium-free positive electrode, wherein the preparation raw materials of the over-lithiated lithium-free positive electrode include a lithium-free positive electrode active material, a conductive agent, metallic lithium, and a binder.
The lithium-free positive electrode is characterized in that positive electrode active materials adopt positive electrode active materials without lithium elements, and the lithium-free negative electrode is characterized in that negative electrode active materials adopt negative electrode active materials without lithium elements, and the whole electrode does not completely contain lithium elements.
In order to solve the problem that the lithium-free positive electrode prepared by the lithium-free positive electrode active material can only be used together with a lithium metal negative electrode, the invention adopts the lithium-free positive electrode active material, and metal lithium is added into the preparation raw material, so that the lithium-free positive electrode is lithiated in advance, and the lithiation of the lithium-free positive electrode is completed before the assembly of a battery cell, thereby enabling the lithium-free positive electrode to be matched with the lithium-free negative electrode; meanwhile, the lithium-free positive electrode is over-lithiated, namely the lithium-free positive electrode has metal lithium residues, and lithium supplementation is realized in the lithium-free positive electrode, so that the use of a metal lithium negative electrode is avoided, the safety risk caused by severe reaction during lithium supplementation of the negative electrode is avoided, and a long-life high-energy-density lithium ion battery can be obtained.
Preferably, the content of metallic lithium in the preparation raw material is 10-30wt%, for example, 10wt%, 15wt%, 20wt%, 25wt% or 30wt%, but is not limited to the recited values, and other non-recited values in the range of values are equally applicable.
The content of the metal lithium can influence the over-lithiation degree of the lithium-free positive electrode, thereby influencing the battery performance; if the content of the metal lithium is too small, the over-lithiation effect is affected; if the content of the metal lithium is too high, lithium is easy to be separated out in the circulation process, and if the content of the metal lithium is too low, the energy density of the battery cell is reduced.
The particle diameter D50 of the metallic lithium is preferably 10 to 50. Mu.m, and may be, for example, 10 μm, 20 μm, 30 μm, 40 μm or 50. Mu.m, but is not limited to the values recited, and other values not recited in the numerical range are equally applicable.
Preferably, the metallic lithium comprises lithium powder.
Preferably, the surface of the metal lithium is coated with a protective layer.
Preferably, the thickness of the protective layer is 5-50nm, for example, 10nm, 20nm, 30nm, 40nm or 50nm, but not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the protective layer comprises any one or a combination of at least two of lithium carbonate, lithium fluoride, lithium nitride or lithium phosphate.
The metal lithium provided by the invention comprises lithium powder with purity of more than 99.9%, for example, 99.9%, 99.95% or 99.99%, and the surface of the lithium powder is also coated with a protective layer so as to protect the lithium powder, so that the lithium powder can be normally used, and the problems of ignition and the like of the lithium powder are avoided.
The specific capacity of the metal lithium is calculated according to 3200mAh/g, and the lithium supplementing surface capacity is the positive electrode material buckling first discharge specific capacity, the active material percentage and the surface density (1.0-1.1 coefficient).
Preferably, the content of the lithium-free positive electrode active material in the preparation raw material is 60 to 90wt%, for example, 60wt%, 70wt%, 80wt% or 90wt%, but not limited to the recited values, and other non-recited values within the numerical range are equally applicable.
Preferably, the lithium-free positive electrode active material comprises any one or a combination of at least two of nonmetallic fluoride, metallic oxide, metallic sulfide, nonmetallic sulfide, elemental sulfur, vulcanized polyacrylonitrile or organic positive electrode materials, preferably any one or a combination of at least two of carbon fluoride, ferric trifluoride, titanium disulfide, molybdenum disulfide, iron disulfide, manganese dioxide, elemental sulfur or vulcanized polyacrylonitrile (the sulfur content accounts for 30-45 wt%).
Preferably, the binder is present in the preparation starting material in an amount of 0.5 to 2wt%, for example 1wt%, 1.5wt% or 2wt%, but is not limited to the values recited, other values not recited in the numerical range being equally applicable.
Preferably, the binder comprises any one or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate or polyvinylidene fluoride-hexafluoropropylene, wherein the polytetrafluoroethylene is necessary to contain the binder.
Preferably, the content of the conductive agent in the preparation raw material is 0.5 to 10wt%, for example, may be 0.5wt%, 2wt%, 4wt%, 6wt%, 8wt% or 10wt%, but is not limited to the recited values, and other non-recited values within the numerical range are equally applicable.
Preferably, the conductive agent includes any one or a combination of at least two of conductive carbon black, ketjen black, carbon nanotubes, graphene, conductive graphite, or conductive carbon fibers.
In a second aspect, the present invention provides a method for preparing the over-lithiated lithium-free positive electrode according to the first aspect, the method comprising the steps of:
mixing and rolling the lithium-free positive electrode active material, the conductive agent, the metal lithium and the binder to form a film, and then bonding and rolling the film with a current collector to obtain the over-lithiated lithium-free positive electrode.
Preferably, the mixing comprises mixing the non-lithium positive electrode active material and the conductive agent, adding lithium powder, stirring uniformly, adding the binder for dispersion, and then carrying out fibrosis;
Preferably, the fiberization gives tacky granules of diameter 0.2-3mm, which may be, for example, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm or 3mm, but is not limited to the values recited, other non-recited values within the range of values being equally applicable.
Preferably, the preparation method of the over-lithiated lithium-free positive electrode comprises the following steps:
(1) Uniformly mixing a lithium-free positive electrode active material and a conductive agent, adding lithium powder, and uniformly stirring;
(2) Adding a binder into the mixture, dispersing at a low speed, and then carrying out high-speed fiberization to form small particles with the viscosity of 0.2-3mm to be formed into a film;
(3) The small particles are sent into multi-roller integrated equipment to be formed into a film and thinned to a designed thickness, and then are attached to the two sides of an aluminum foil current collector;
(4) And rolling the dry electrode to crack the metal lithium shell and release metal lithium, and compacting the electrode to prepare the lithiated lithium-free positive electrode.
In a third aspect, the present invention provides a lithium ion battery comprising a lithium-free negative electrode and an over-lithiated lithium-free positive electrode as described in the first aspect.
Preferably, the lithium-free anode includes a lithium-free anode active material.
Preferably, the lithium-free anode active material includes any one or a combination of at least two of artificial graphite, natural graphite, silicon alloy, tin alloy, silicon carbon material, silicon oxygen material, tin carbon material, tin oxygen material, soft carbon, or hard carbon.
Preferably, the lithium-free negative electrode further comprises a lithium supplementing agent.
The lithium-free negative electrode of the present invention may be a lithium-free negative electrode that does not contain any lithium element at all, or may be a lithium-free negative electrode that contains a small amount of lithium element as a lithium-supplementing agent, and the lithium-supplementing amount may be 5 to 10wt% of the negative electrode capacity, for example, 5wt%, 8wt% or 10wt%, but is not limited to the recited values, and other non-recited values in the numerical range are equally applicable.
The lithium supplementing method of the lithium supplementing negative electrode comprises the following steps: physical methods such as lithium powder blending, thermal evaporation, magnetron sputtering, melt casting, calendaring and laminating metallic lithium and the like also comprise lithium intercalation in chemical reactions of lithiation reagents such as biphenyl lithium, naphthalene lithium and the like.
Preferably, the reversible surface capacity of the lithium-free negative electrode is 1.05 to 1.15 times that of the positive electrode, for example, 1.1 times, 1.13 times or 1.15 times, but not limited to the recited values, and other non-recited values in the numerical range are equally applicable.
The electrolyte adopted by the lithium ion battery can be a liquid electrolyte system or an all-solid-state semi-solid electrolyte system.
Compared with the prior art, the invention has the following beneficial effects:
Aiming at the problems of poor safety and short service life caused by dendrite growth, continuous side reaction, large volume effect and the like of the existing lithium-free positive electrode which is required to be matched with a metal lithium negative electrode, the lithium-free positive electrode is lithiated before the assembly of a battery core by over-lithiation, the lithium-free positive electrode is matched with the lithium-free negative electrode for use, the series problems of using the metal lithium negative electrode can be avoided, the safety risk caused by severe reaction during the lithium supplementation of the negative electrode is avoided, and the performances of safety, circulation and the like of the lithium ion battery are improved.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The embodiment provides an over-lithiated lithium-free positive electrode, wherein the preparation raw materials of the over-lithiated lithium-free positive electrode comprise 78wt% of vulcanized polyacrylonitrile (SPAN, the sulfur content of which is 40 wt%), 7wt% of SP, 1wt% of CNT, 12wt% of lithium powder and 2wt% of PTFE (polytetrafluoroethylene);
The particle size D50 of the lithium powder is 30 mu m, and the surface of the lithium powder is coated with lithium carbonate with the particle size of 25 nm;
The preparation method of the over-lithiated lithium-free positive electrode comprises the following steps:
And uniformly mixing the preparation raw materials according to the formula amount, fiberizing into sticky particles with the diameter of 2mm, forming a film in dry method integrated equipment, attaching to the two sides of a carbon-coated aluminum foil current collector, and forming a compact pole piece with the single-side surface density of 8mg/cm 2 under the pressure of a roller press 5t to obtain the over-lithiated lithium-free positive electrode.
Example 2
The embodiment provides a lithium-free positive electrode which is prepared from 65wt% of vulcanized polyacrylonitrile (SPAN, the sulfur content of which is 45 wt%), 2wt% of SP, 1wt% of CNT, 30wt% of lithium powder and 2wt% of PTFE (polytetrafluoroethylene);
The particle size D50 of the lithium powder is 50 mu m, and the surface of the lithium powder is coated with 5nm lithium carbonate;
The preparation method of the over-lithiated lithium-free positive electrode comprises the following steps:
And uniformly mixing the preparation raw materials according to the formula amount, and then, fiberizing into sticky particles with the diameter of 3mm, forming a film in dry method integrated equipment, then, attaching the sticky particles to the two sides of a carbon-coated aluminum foil current collector, and forming a compact pole piece with the single-side surface density of 8mg/cm 2 under the pressure of a roller press 5t to obtain the over-lithiated lithium-free positive electrode.
Example 3
The embodiment provides an over-lithiated lithium-free positive electrode, wherein the preparation raw materials of the over-lithiated lithium-free positive electrode comprise 88wt% of vulcanized polyacrylonitrile (SPAN, the sulfur content of which is 30 wt%), 0.5wt% of conductive agent SP, 0.5wt% of CNT, 10wt% of lithium powder and 1wt% of PTFE (polytetrafluoroethylene);
the particle size D50 of the lithium powder is 10 mu m, and the surface of the lithium powder is coated with 50nm lithium carbonate;
The preparation method of the over-lithiated lithium-free positive electrode comprises the following steps:
And uniformly mixing the preparation raw materials according to the formula amount, and then, fiberizing into sticky particles with the diameter of 0.2mm, forming a film in dry integrated equipment, then, attaching the film to the two sides of a carbon-coated aluminum foil current collector, and forming a compact pole piece with the single-side surface density of 8mg/cm 2 under the pressure of a roller press 5t to obtain the over-lithiated lithium-free positive electrode.
Example 4
This example provides an over-lithiated lithium-free positive electrode that is the same as example 1 except that the quality of the sulfidized polyacrylonitrile or the like is replaced with fluorocarbon.
Example 5
This example provides a lithium-free positive electrode that was identical to example 1 except that the lithium powder content in the raw material for preparation was 5wt% and the content adaptability of the vulcanized polyacrylonitrile was 85 wt%.
Example 6
This example provides a lithium-free positive electrode that was identical to example 1 except that the lithium powder content in the raw material for preparation was 35wt% and the content adaptability of the vulcanized polyacrylonitrile was 55 wt%.
Comparative example 1
This comparative example provides a lithium-free positive electrode that is identical to example 1 except that the lithium powder is not included in the preparation raw material, and the equivalent mass of the lithium powder is replaced with that of the vulcanized polyacrylonitrile.
Application example 1
The application example provides a lithium ion battery, which comprises a lithium-free negative electrode, electrolyte, a diaphragm and the over-lithiated lithium-free positive electrode in the embodiment example 1;
The negative electrode active material in the lithium-free negative electrode comprises artificial graphite and SiO; the separator includes a 9 μm PE-based film and a2 μm boehmite coating, and the electrolyte includes 1M LiPF 6 dissolved in EC and EMC (volume ratio of 3:7) solvent as the electrolyte;
The preparation method of the lithium ion battery comprises the following steps:
Preparation of a lithium-free negative electrode: uniformly mixing artificial graphite, siO, carbon black, CMC and SBR in a mass ratio of 86:10:1:1:2 in an aqueous solution to prepare slurry, coating the slurry on copper foil with a thickness of 6 mu m, and oven drying and rolling to obtain a surface density according to the matching of the surface density with the reversible capacity of the positive electrode, wherein the reversible capacity of the negative electrode/the reversible capacity of the positive electrode=1.1;
The matched lithium-free negative electrode, the diaphragm and the lithium-free negative electrode described in the embodiment 1 are assembled into a 5Ah battery cell, the battery cell is placed at 100 ℃ and is subjected to vacuum baking for 24 hours, and the baked battery cell is injected with the electrolyte and formed.
Application examples 2 to 6 provide a lithium ion battery, and application examples 2 to 6 are the same as application example 1 except that the over-lithiated non-lithium positive electrode described in examples 2 to 6 is used as the positive electrode, respectively.
Comparative application example 1
This comparative application example provided a lithium ion battery that was identical to application example 1 except that the over-lithiated non-lithium positive electrode described in example 1 was not matched to a non-lithium negative electrode, but that 50 μm thick metallic lithium was provided as a negative electrode on both sides of a 4.5 μm thick copper foil.
Comparative application example 2
The comparative application example provided a lithium ion battery using the non-lithium positive electrode of comparative example 1 as a positive electrode, and the rest was the same as application example 1 except that 50 μm thick metallic lithium was provided on both sides of a copper foil 4.5 μm thick as a negative electrode.
The lithium ion batteries described in the above application examples and comparative application examples were subjected to electrochemical performance tests, and room temperature cycle life: 0.5C charge and discharge cycle until the capacity retention rate reaches 80% cycle times; the test conditions for the 2C rate retention include: 0.33C is fully charged, then 2C and 0.33C are discharged, and the discharge capacity of 0.33C is divided by the discharge capacity of 2C; the volume deformation test conditions included: full electrical thickness of 0.33C divided by the original cell thickness.
The test results are shown in table 1 below:
TABLE 1
As can be seen from table 1:
As can be seen from application examples 1-6 and comparative application examples 1-2, the performances of application examples 1-6 are better than those of comparative application examples 1-2, and the over-lithiated lithium-free positive electrode obtained by the invention can be matched with a lithium-free negative electrode, so that the safety performance and the cycle performance of a battery are improved; as can be seen from application example 1 and comparative application examples 1-2, when the over-lithiated non-lithium positive electrode of the present invention is matched with a metal lithium negative electrode, or when the non-lithium positive electrode without adding lithium powder is used, the performance of the obtained battery is greatly reduced, the volume deformation amount is large, and the safety performance is low; as can be seen from application examples 1 and 4, the lithium-free positive electrode active material of the present invention is preferably a vulcanized polyacrylonitrile, so that the performance of the lithium ion battery can be further improved; as is clear from application example 1 and application examples 5 to 6, the content of the added lithium powder of the present invention affects the over-lithiation effect, thereby affecting the performance of the lithium ion battery.
In summary, the invention provides an over-lithiated lithium-free positive electrode, a preparation method and application thereof, which can solve the problems of reduced safety performance and cycle performance and the like caused by the use of the existing lithium-free positive electrode matched with a lithium metal negative electrode, and simultaneously avoid the safety risk caused by severe reaction during the lithium supplementation of the negative electrode, thereby obtaining a long-life high-energy-density lithium ion battery.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that fall within the technical scope of the present invention disclosed herein are within the scope of the present invention.
Claims (10)
1. The over-lithiated lithium-free positive electrode is characterized in that the preparation raw materials of the over-lithiated lithium-free positive electrode comprise a lithium-free positive electrode active material, a conductive agent, metallic lithium and a binder;
The over-lithiated lithium-free positive electrode is matched with a lithium-free negative electrode.
2. The over-lithiated lithium-free cathode of claim 1, wherein the content of metallic lithium in the preparation raw material is 10-30wt%;
And/or the particle diameter D50 of the metal lithium is 10-50 mu m;
And/or, the metallic lithium comprises lithium powder.
3. The over-lithiated non-lithium positive electrode of claim 1 or 2, wherein the surface of the metallic lithium is coated with a protective layer;
And/or the thickness of the protective layer is 5-50nm;
And/or the protective layer comprises any one or a combination of at least two of lithium carbonate, lithium fluoride, lithium nitride or lithium phosphate.
4. The over-lithiated non-lithium positive electrode of claim 1 or 2, wherein the content of the non-lithium positive electrode active material in the preparation raw material is 60-90wt%;
And/or the lithium-free positive electrode active material comprises any one or a combination of at least two of nonmetal fluoride, metal oxide, metal sulfide, nonmetal sulfide, elemental sulfur, vulcanized polyacrylonitrile or organic positive electrode materials.
5. The over-lithiated non-lithium positive electrode of claim 1 or 2, wherein the content of binder in the preparation raw material is 0.5-2wt%;
And/or the binder comprises any one or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate or polyvinylidene fluoride-hexafluoropropylene.
6. The over-lithiated non-lithium positive electrode of claim 1 or 2, wherein the content of conductive agent in the preparation raw material is 0.5 to 10wt%;
and/or the conductive agent comprises any one or a combination of at least two of conductive carbon black, ketjen black, carbon nanotubes, graphene, conductive graphite or conductive carbon fibers.
7. A method of preparing a dilithiated lithium-free positive electrode according to any one of claims 1 to 6, comprising the steps of:
mixing and rolling the lithium-free positive electrode active material, the conductive agent, the metal lithium and the binder to form a film, and then bonding and rolling the film with a current collector to obtain the over-lithiated lithium-free positive electrode.
8. The method of claim 7, wherein the mixing comprises mixing the non-lithium positive electrode active material and the conductive agent, adding lithium powder, stirring uniformly, and adding a binder for dispersion and fibrosis;
And/or, said fiberizing to give tacky particles having a diameter of 0.2-3 mm.
9. A lithium ion battery comprising a lithium-free negative electrode and an over-lithiated lithium-free positive electrode according to any one of claims 1-6.
10. The lithium ion battery of claim 9, wherein the lithium-free negative electrode comprises a lithium-free negative electrode active material;
and/or the lithium-free anode active material comprises any one or a combination of at least two of artificial graphite, natural graphite, silicon alloy, tin alloy, silicon carbon material, silicon oxygen material, tin carbon material, tin oxygen material, soft carbon or hard carbon;
And/or, the lithium-free negative electrode further comprises a lithium supplementing agent;
and/or the reversible surface capacity of the lithium-free negative electrode is 1.05-1.15 times of the reversible surface capacity of the positive electrode.
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| CN105609742A (en) * | 2016-03-04 | 2016-05-25 | 河北工业大学 | Positive electrode material for sulfur-based lithium ion battery and preparation method and application of positive electrode material |
| CN115579504A (en) * | 2022-09-16 | 2023-01-06 | 电子科技大学长三角研究院(湖州) | Lithium-sulfur battery based on lithium supplement technology and without lithium metal negative electrode and application thereof |
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| CN105609742A (en) * | 2016-03-04 | 2016-05-25 | 河北工业大学 | Positive electrode material for sulfur-based lithium ion battery and preparation method and application of positive electrode material |
| CN115579504A (en) * | 2022-09-16 | 2023-01-06 | 电子科技大学长三角研究院(湖州) | Lithium-sulfur battery based on lithium supplement technology and without lithium metal negative electrode and application thereof |
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