CN113745638A - High-safety and high-power ternary positive plate for lithium battery and preparation method and application thereof - Google Patents
High-safety and high-power ternary positive plate for lithium battery and preparation method and application thereof Download PDFInfo
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 36
- 238000002360 preparation method Methods 0.000 title abstract description 14
- 239000002245 particle Substances 0.000 claims abstract description 109
- 239000007784 solid electrolyte Substances 0.000 claims abstract description 102
- 239000007774 positive electrode material Substances 0.000 claims abstract description 45
- 239000006258 conductive agent Substances 0.000 claims abstract description 32
- 239000000463 material Substances 0.000 claims abstract description 32
- 239000011230 binding agent Substances 0.000 claims abstract description 25
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 31
- 150000001875 compounds Chemical class 0.000 claims description 19
- 239000003792 electrolyte Substances 0.000 claims description 19
- 238000002156 mixing Methods 0.000 claims description 17
- 239000002033 PVDF binder Substances 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 12
- 239000006245 Carbon black Super-P Substances 0.000 claims description 11
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 9
- 239000006182 cathode active material Substances 0.000 claims description 9
- 230000008569 process Effects 0.000 claims description 9
- 239000002002 slurry Substances 0.000 claims description 9
- 239000006183 anode active material Substances 0.000 claims description 8
- 239000013078 crystal Substances 0.000 claims description 7
- 239000002041 carbon nanotube Substances 0.000 claims description 6
- 238000000576 coating method Methods 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 6
- 239000000126 substance Substances 0.000 claims description 6
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- 239000006229 carbon black Substances 0.000 claims description 5
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 5
- 239000011248 coating agent Substances 0.000 claims description 5
- 239000003292 glue Substances 0.000 claims description 5
- 125000005842 heteroatom Chemical group 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 5
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 4
- 239000011244 liquid electrolyte Substances 0.000 claims description 4
- 239000011572 manganese Substances 0.000 claims description 4
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 4
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 4
- 238000005096 rolling process Methods 0.000 claims description 4
- 229910005313 Li14ZnGe4O16 Inorganic materials 0.000 claims description 3
- 229910013418 LiNixCoyM1-x-yO2 Inorganic materials 0.000 claims description 3
- 229910010252 TiO3 Inorganic materials 0.000 claims description 3
- 239000002134 carbon nanofiber Substances 0.000 claims description 3
- 239000002227 LISICON Substances 0.000 claims description 2
- 229910000572 Lithium Nickel Cobalt Manganese Oxide (NCM) Inorganic materials 0.000 claims description 2
- 239000002228 NASICON Substances 0.000 claims description 2
- PFYQFCKUASLJLL-UHFFFAOYSA-N [Co].[Ni].[Li] Chemical compound [Co].[Ni].[Li] PFYQFCKUASLJLL-UHFFFAOYSA-N 0.000 claims description 2
- 239000006230 acetylene black Substances 0.000 claims description 2
- 150000001768 cations Chemical class 0.000 claims description 2
- 239000002223 garnet Substances 0.000 claims description 2
- 229910021389 graphene Inorganic materials 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- -1 polytetrafluoroethylene Polymers 0.000 claims description 2
- LLYXJBROWQDVMI-UHFFFAOYSA-N 2-chloro-4-nitrotoluene Chemical compound CC1=CC=C([N+]([O-])=O)C=C1Cl LLYXJBROWQDVMI-UHFFFAOYSA-N 0.000 claims 1
- FBDMTTNVIIVBKI-UHFFFAOYSA-N [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] Chemical compound [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] FBDMTTNVIIVBKI-UHFFFAOYSA-N 0.000 claims 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 23
- 229910052759 nickel Inorganic materials 0.000 description 20
- 230000000694 effects Effects 0.000 description 16
- 238000012360 testing method Methods 0.000 description 16
- 239000010406 cathode material Substances 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 14
- 210000004027 cell Anatomy 0.000 description 12
- 239000000243 solution Substances 0.000 description 9
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- 238000006243 chemical reaction Methods 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- 230000006872 improvement Effects 0.000 description 6
- 238000004080 punching Methods 0.000 description 6
- 230000035939 shock Effects 0.000 description 6
- 229910019142 PO4 Inorganic materials 0.000 description 5
- 230000020169 heat generation Effects 0.000 description 5
- 239000002243 precursor Substances 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 4
- 239000011247 coating layer Substances 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- 230000002427 irreversible effect Effects 0.000 description 4
- 239000011268 mixed slurry Substances 0.000 description 4
- 238000013021 overheating Methods 0.000 description 4
- 230000002441 reversible effect Effects 0.000 description 4
- 238000011076 safety test Methods 0.000 description 4
- 238000005245 sintering Methods 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-L Phosphate ion(2-) Chemical compound OP([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-L 0.000 description 3
- 239000006256 anode slurry Substances 0.000 description 3
- 238000004880 explosion Methods 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229910000664 lithium aluminum titanium phosphates (LATP) Inorganic materials 0.000 description 3
- 229910003002 lithium salt Inorganic materials 0.000 description 3
- 159000000002 lithium salts Chemical class 0.000 description 3
- 230000007704 transition Effects 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- 238000001467 acupuncture Methods 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 239000007767 bonding agent Substances 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
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- 238000001035 drying Methods 0.000 description 2
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- 239000002994 raw material Substances 0.000 description 2
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- 239000010959 steel Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000005279 LLTO - Lithium Lanthanum Titanium Oxide Substances 0.000 description 1
- 229910021102 Li0.5La0.5TiO3 Inorganic materials 0.000 description 1
- 229910009150 Li1.3Al0.3Ge1.7(PO4)3 Inorganic materials 0.000 description 1
- 229910009178 Li1.3Al0.3Ti1.7(PO4)3 Inorganic materials 0.000 description 1
- 229910009274 Li1.4Al0.4Ti1.6 (PO4)3 Inorganic materials 0.000 description 1
- 229910009511 Li1.5Al0.5Ge1.5(PO4)3 Inorganic materials 0.000 description 1
- 229910009515 Li1.5Al0.5Ti1.5(PO4)3 Inorganic materials 0.000 description 1
- 229910002984 Li7La3Zr2O12 Inorganic materials 0.000 description 1
- 229910002995 LiNi0.8Co0.15Al0.05O2 Inorganic materials 0.000 description 1
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
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- 230000014759 maintenance of location Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 239000005518 polymer electrolyte Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/364—Composites as mixtures
-
- 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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
- H01M10/0562—Solid materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention discloses a high-safety and high-power ternary positive plate for a lithium battery, and a preparation method and application thereof. The positive plate comprises a current collector and a positive material layer positioned on the surface of the current collector, and the positive electrodeThe material layer comprises ternary positive electrode active material particles, a conductive agent, a binder and oxide solid electrolyte particles capable of conducting lithium ions; the surface capacity of the positive plate<4mAh/cm2The particle diameter D50 of the oxide solid electrolyte particles is 0.1 to 3 μm. The invention adds oxide solid electrolyte with specific grain diameter into the positive plate, and matches with conductive agent and binder to adjust the surface capacity of the positive plate<4mAh/cm2The positive plate can ensure high safety on the premise of ensuring high capacity and good cycle performance.
Description
Technical Field
The invention relates to the technical field of new energy, relates to a positive plate, a preparation method and application thereof, and particularly relates to a high-safety and high-power ternary positive plate for a lithium battery, a preparation method thereof, a method for improving the safety of the lithium battery, a corresponding positive plate and the lithium battery.
Background
With the popularization and application of electric automobiles, the ternary cathode material in the lithium ion battery is considered to be one of the most potential cathode materials of the next generation due to the advantages of high theoretical capacity, low raw material price, environmental friendliness and the like. However, the ternary cathode material has the problems of poor thermal stability, poor rate capability and the like. These factors have limited their widespread use in electric vehicles.
The heat generation of the lithium ion battery comprises reversible reaction entropy heat, irreversible resistance heat, mixed heat and phase change heat, wherein the heat generation rates of the reversible reaction entropy heat, the irreversible resistance heat, the mixed heat and the phase change heat are small and can be ignored generally. Wherein irreversible resistance heat always manifests as heat release; the reversible reaction entropy heat appears as an endotherm as a whole during charging of the battery; during discharge of the battery, heat is generally released, and therefore the heat generation of the battery during discharge tends to be greater than the heat generation during charge. The problem of heat generation of ternary materials and the problem of poor thermal stability thereof directly limit further applications thereof.
At present, the problem of poor thermal stability of a ternary material can be improved to a certain extent by performing surface coating on the ternary material, for example, CN107482204A discloses a metal solid solution modified high-nickel ternary positive electrode material and a preparation method thereof, wherein the material is of a core-shell structure and sequentially comprises a high-nickel ternary positive electrode material substrate, a transition layer and a coating layer from inside to outside, the coating layer comprises a metal lithium salt and a solid solution positive electrode active substance generated by the reaction of one or more heterogeneous metal precursors and the high-nickel ternary positive electrode material precursors, and the transition layer is a heterogeneous metal element doped high-nickel ternary positive electrode material. The preparation method comprises the following steps: (1) uniformly mixing a high-nickel ternary positive electrode material precursor, a heterogeneous metal precursor and lithium salt to form a mixture; (2) and calcining the mixture at high temperature to obtain the metal solid solution modified high-nickel ternary cathode material. The process flow is simple, the production process is environment-friendly, and the metal solid solution modified high-nickel ternary cathode material has better thermal stability, charge-discharge specific capacity and excellent cycle performance, and can meet the consumption field with requirements on high capacity and high safety.
CN110844945A discloses a high-nickel ternary cathode material, a preparation method and application thereof. The method for preparing the high-nickel ternary cathode material comprises the following steps of: (1) mixing a high-nickel ternary positive electrode material precursor, a metal oxide and a lithium salt to obtain a mixed material; (2) sequentially carrying out first sintering treatment and second sintering treatment on the mixed material to obtain a first product; (3) mixing the first product with a hydrogen phosphate solution to enable the hydrogen phosphate to wrap the surface of the first product to obtain mixed slurry; (4) adding alkali liquor into the mixed slurry to enable the hydrogen phosphate to have a precipitation reaction and form a coating layer on the surface of the first product, so as to obtain a second product containing the coating layer; (5) and carrying out third sintering treatment on the second product to obtain the high-nickel ternary cathode material. The method can realize that the surface of the high-nickel ternary material is uniformly coated with the phosphate layer, thereby inhibiting the generation of NiO cubic phase on the surface layer of the high-nickel ternary cathode material and the collapse of the material structure, and improving the cycle performance and the thermal stability of the battery.
However, the above surface coating method has high requirements for controlling the ternary material result and process, and the thickness and composition of the transition layer of the positive electrode material prepared by the first method are difficult to control, and the stability is low; the second method has high requirements on the sintering condition and temperature of the ternary material, and has the disadvantages of high energy consumption, complex process and high cost, and the two methods are not favorable for mass production application.
Therefore, a modification means for maintaining good electrical properties while ensuring higher safety performance of the battery is still required.
Disclosure of Invention
In view of the above problems in the prior art, an object of the present invention is to provide a positive plate, a method for preparing the same, and a use thereof, and in particular, to provide a high-safety and high-power ternary positive plate for a lithium battery, a method for preparing the same, a method for improving the safety of a lithium battery, a corresponding positive plate, and a lithium battery.
In the positive plate with high safety and high power, the high power is as follows: the discharge capacity ratio of 5C/1C and 1C/1C of rate discharge of the lithium battery prepared by the positive plate at 25 ℃ reaches 90 percent; high safety: can pass the acupuncture and 180 ℃ thermal shock test, and the acupuncture and the thermal shock test do not catch fire, explode or smoke.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a ternary positive plate for a lithium battery with high safety and high power, which comprises a current collector and a positive material layer positioned on the surface of the current collector, wherein the positive material layer comprises ternary positive active material particles, a conductive agent, a binder and oxide solid electrolyte particles capable of conducting lithium ions;
the surface capacity of the positive plate<4mAh/cm2The particle diameter D50 of the oxide solid electrolyte particles is 0.1 to 3 μm.
In the present invention, the surface capacity of the positive electrode sheet<4mAh/cm2E.g. 3.6mAh/cm2、3.5Ah/cm2、3mAh/cm2、2.5mAh/cm2、2mAh/cm2Or 1mAh/cm2And the like.
In the positive plate, the ternary positive active material particles are used as main active components, and the surface volume of the positive plate isMeasurement of<4mAh/cm2Under the condition, the obtained pole piece faces safety challenge in high-power discharge, and particularly, under the condition of high-rate discharge, due to the fact that current is increased and chemical reaction speed is accelerated, heat release power of reversible reaction entropy heat and irreversible resistance heat is obviously increased, and the temperature of the battery is rapidly increased. For the high specific energy battery with the mass specific energy of more than 260Wh/kg, the potential safety hazard brought by discharging under a larger multiplying power is more obvious.
The invention adds oxide solid electrolyte with the grain diameter D50 of 0.1-3 mu m into the positive plate, and the oxide solid electrolyte is matched with a conductive agent and a bonding agent, so as to ensure the surface capacity of the positive plate<4mAh/cm2On the basis of not influencing high power, the thermal stability of the positive plate is improved, and the safety of the battery is guaranteed. The technical principle is as follows: firstly, the oxide solid electrolyte particles have certain ion transmission capability, and can effectively block the contact between the ternary positive electrode active material particles and the particles, so that the thermal stability is improved on the premise of ensuring the ion transmission; secondly, the oxide solid electrolyte has a heat absorption function and can absorb a part of heat to relieve the overheating of the anode; and the oxide solid electrolyte has high chemical stability, can not change the current mainstream preparation process of the positive plate, the diaphragm and the battery, has the advantages of high stability and low cost, and is suitable for large-scale application.
In the present invention, the particle diameter D50 of the oxide solid electrolyte particles is 0.1 to 3 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 2.5 μm, or 3 μm. The particle size of the oxide solid electrolyte is too small, the interface resistance is increased, and the ion transmission is blocked; the particle size is too large, the effect of blocking the ternary positive active material particles is not obvious, and the safety is not obviously improved.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
Preferably, the particle diameter D50 of the oxide solid electrolyte particles is 0.5 to 2 μm.
Preferably, the content of the ternary cathode active material particles is 80 to 98%, for example, 80%, 83%, 85%, 90%, 92%, 93%, 96%, or the like, based on 100% by mass of the total of the ternary cathode active material particles, the conductive agent, the binder, and the oxide solid electrolyte particles.
Preferably, the content of the oxide solid electrolyte is 0.5 to 20%, for example, 0.5%, 0.6%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 7.5%, 8%, 8.5%, 9%, 10%, 12%, 13%, 14%, 15%, 17%, 18%, or 20%, etc., preferably 1 to 10%, and more preferably 3 to 5%, based on 100% by mass of the total of the ternary cathode active material particles, the conductive agent, the binder, and the oxide solid electrolyte particles.
Preferably, the content of the conductive agent is 0.1 to 8%, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, or the like, based on 100% by mass of the total of the ternary positive electrode active material particles, the conductive agent, the binder, and the oxide solid electrolyte particles.
Preferably, the content of the binder is 0.1 to 10%, for example, 0.1%, 0.8%, 1.2%, 3%, 5%, 6%, 7%, 8%, 10%, or the like, based on 100% by mass of the total of the ternary positive electrode active material particles, the conductive agent, the binder, and the oxide solid electrolyte particles.
Preferably, the oxide solid electrolyte particles include any one of or a combination of at least two of the following compounds: li of NASICON structure1+x1Alx1Ge2-x1(PO4)3(LAGP) or isomorphous heteroatom-doped compound thereof, Li1+ x2Alx2Ti2-x2(PO4)3(LATP) or isomorphous heteroatom-doped compound thereof, Li of perovskite structurex3La2/3-x3TiO3(LLTO) or isomorphous heteroatom-doped compound thereof, Li3/8Sr7/16Ta3/4Hf1/4O3(LSTH) or isomorphous heteroatom-doped compound thereof, Li2x4-y1Sr1-x4Tay1Zr1-y1O3(LSTZ) or isomorphous heteroatom doping chemical combination thereofLi of substance, anti-perovskite structure3-2x5Mx5HalO、Li3OCl or isoatomic doped compound of same crystal form thereof, Li of LISICON structure4-x6Si1-x6Px6O4Or isoatomic doped compound of the same crystal type, Li14ZnGe4O16(LZGO) or isomorphous heteroatom-doped compound thereof, Li in garnet structure7-x7La3Zr2-x7O12(LLZO) or an isomorphous heteroatom-doped compound thereof, wherein 0<x1≤0.75，0<x2≤0.5，0.06≤x3≤0.14，0.25≤y1≤1，x4＝0.75y1，0≤x5≤0.01，0.5≤x6≤0.6；0≤x7<1; wherein M includes but is not limited to Mg2+、Ca2+、Sr2+Or Ba2+Any one or a combination of at least two, other art-recognized higher cations are also suitable for use herein, and Hal is the element Cl or I.
Preferably, the oxide solid electrolyte particles include Li1+x2Alx2Ti2-x2(PO4)3And/or Li7- x7La3Zr2-x7O12Preferably Li1+x2Alx2Ti2-x2(PO4)3。
The ternary positive electrode active material particles include lithium nickel cobalt manganese oxide (NCM) and/or lithium Nickel Cobalt Aluminate (NCA).
Preferably, the chemical composition of the ternary positive electrode active material particles is LiNixCoyM1-x-yO2M is at least one of Mn or Al, x is more than or equal to 0.6, such as 0.6, 0.65, 0.7, 0.75 or 0.8, and the like, the ternary positive active material of the preferred technical scheme is a high-nickel ternary positive material, the specific energy is high, and the thermal stability is poor.
Preferably, the conductive agent includes any one of Super-P, KS-6, carbon black, carbon nanofibers, CNTs, acetylene black, or graphene, or a combination of at least two thereof. Typical but non-limiting examples of such combinations are: a combination of Super-P and KS-6, a combination of Super-P and carbon black, a combination of Super-P and carbon nanofibers, a combination of carbon black and CNT, a combination of KS-6, carbon black and CNT, and the like, preferably a combination of carbon nanotubes and Super-P.
Preferably, the binder comprises any one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), or Polytetrafluoroethylene (PTFE), or a combination of at least two thereof. Illustrative examples of typical ranges for such combinations are: a combination of PVDF and PEO, a combination of PVDF and PTFE, a combination of PVDF and PVDF-HFP, and the like, preferably polyvinylidene fluoride.
Preferably, the ratio of the particle diameter D50 of the ternary cathode active material particles to the particle diameter D50 of the oxide solid electrolyte particles is 3 or more. If the particle sizes of the three positive electrode active material particles are close to each other, the solid electrolyte content limits the particle sizes, and the content of the solid electrolyte is insufficient to block the contact between the three positive electrode active material particles, so that the safety performance of the material is poor.
In a second aspect, the present invention provides a method for producing a positive electrode sheet according to the first aspect, the method comprising the steps of:
s1: premixing anode active material particles and oxide solid electrolyte particles to obtain a premixed material, wherein the anode active material particles comprise ternary anode active material particles;
s2: adding glue solution of a binder into the premixed material, and mixing to obtain primary slurry;
s3: adding a conductive agent into the primary slurry, and mixing to obtain secondary slurry;
s4: coating the secondary slurry on a current collector to control the sheet surface capacity of the electrode<4mAh/cm2And baking and rolling to obtain the positive plate.
In the method of the present invention, step S2 and step S3 may be added at once or in steps, independently of each other.
Preferably, the premixing is vacuum premixing or is conducted at dew point ≦ -30 deg.C (e.g., -30 deg.C, -35 deg.C, -40 deg.C, -45 deg.C, or-50 deg.C, etc.). In the preferred technical scheme, firstlyThe positive active material particles and the oxide solid electrolyte particles are premixed in vacuum or at the dew point of less than or equal to minus 30 ℃, so that the positive active material particles and the oxide solid electrolyte particles are uniformly dispersed, and the stability of the ternary positive active material and the oxide solid electrolyte is ensured. For example, Li at dew point ≧ 0 deg.C7-x7La3Zr2-x7O12(0≤x7<1) Side reaction with water is easy to occur, which results in the structural damage and the performance deterioration of the product.
Preferably, the premixing and mixing process is carried out in a ball mill or blender.
Preferably, the premixing and mixing are carried out by using a rotation revolution stirrer, the revolution speed is not less than 20rpm, such as 20rpm, 30rpm, 40rpm, 50rpm, 60rpm, 70rpm, 80rpm, 85rpm or 100rpm, and the like, independently preferably 30-90 rpm; the rotation speed is 200rpm or more, for example, 200rpm, 300rpm, 400rpm, 600rpm, 800rpm, 1000rpm, 1200rpm, 1300rpm, 1500rpm, 1750rpm, 2000rpm, 2200rpm, 2500rpm, 3000rpm, etc., and independently preferably 500rpm or 2000 rpm.
Preferably, the time of the premixing is 1 to 10h, such as 1h, 1.5h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, etc., preferably 2 to 4 h.
Preferably, the dew point is ≦ 45 deg.C, more preferably ≦ 60 deg.C.
In order to ensure good dispersibility and structural stability of the oxide solid electrolyte, to achieve effective blocking of contact between particles of the ternary positive active material and to improve thermal stability of the positive electrode sheet, the revolution speed, rotation speed and dew point conditions described above are preferably followed.
As a further preferred technical solution of the method of the present invention, the method comprises the steps of:
s1: carrying out vacuum premixing on ternary positive electrode active material particles and oxide solid electrolyte particles in an autorotation revolution stirrer, wherein the revolution speed is 30-90rpm, the autorotation speed is 500-2000rpm, and the premixing time is 2-4h, so as to obtain a uniformly mixed premixed material;
s2: gradually adding the uniformly mixed glue solution into the uniformly mixed premixed material in the S1, wherein the revolution speed is 30-90rpm, and the rotation speed is 500-2000rpm, so as to obtain uniformly mixed slurry;
s3: gradually adding a conductive agent into the uniformly mixed slurry of S2, wherein the revolution speed is 30-90rpm, and the rotation speed is 500-2000rpm, and finally obtaining the uniformly mixed ternary anode slurry;
s4: coating the slurry described in S3 on a current collector, and controlling the surface capacity of the electrode to be less than 4mAh/cm2And drying, rolling and die cutting are carried out to obtain the ternary positive electrode plate with high safety and high power.
In a third aspect, the present invention provides a method for improving the safety of a lithium battery, the method comprising adding oxide solid electrolyte particles having a particle diameter D50 of 0.1 to 3 μm to and dispersing them between positive electrode active material particles during the production of a positive electrode sheet having a surface capacity<4mAh/cm2。
The invention also provides the positive plate obtained by the method in the third aspect.
In a fourth aspect, the present invention provides a lithium battery comprising the positive electrode sheet of the first aspect.
Preferably, the lithium battery includes a liquid lithium battery or a semi-solid lithium battery.
Preferably, the liquid lithium battery includes the positive electrode tab according to the first aspect, the negative electrode tab, and a liquid electrolyte (also referred to as an electrolyte).
Preferably, the semi-solid lithium battery includes the positive electrode sheet according to the first aspect, the negative electrode sheet, and an electrolyte layer containing a liquid electrolyte.
Compared with the prior art, the invention has the following beneficial effects:
the invention adds oxide solid electrolyte with the grain diameter D50 of 0.1-3 mu m into the positive plate, and the oxide solid electrolyte is matched with a conductive agent and a bonding agent, so as to ensure the surface capacity of the positive plate<4mAh/cm2On the basis of not influencing high power, the thermal stability of the positive plate is improved, and the safety of the battery is guaranteed. The technical principle is as follows: firstly, the oxide solid electrolyte particles have certain ion transmission capability and can effectively block the ternary positive electrode active materialThe contact between the material particles improves the thermal stability on the premise of ensuring the ion transmission; secondly, the oxide solid electrolyte has certain heat capacity, can absorb part of heat generated by the anode and relieve the overheating of the anode; and the oxide solid electrolyte has high chemical stability, can not change the current mainstream preparation process of the positive plate, the diaphragm and the battery, has the advantages of high stability and low cost, and is suitable for large-scale application.
The lithium battery assembled on the basis of the positive plate has the characteristics of high power, high safety and long cycle, and the battery can smoothly pass a needling test. The preferable scheme of the positive plate can realize high specific energy (generally, the energy of the battery is more than or equal to 260Wh/Kg) of the battery while having the effects.
Drawings
FIG. 1 is a schematic structural diagram of a ternary positive electrode sheet according to an embodiment of the present invention, in which a 1-oxide solid electrolyte, a 2-ternary positive electrode active material, a 3-conductive agent, and a 4-aluminum foil;
FIG. 2 is a photograph of the battery after the needle test of example 1;
fig. 3 is a photograph of the battery after the needle punching test of comparative example 1.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
Preparation of ternary electrode slice of oxide-doped solid electrolyte
Weighing the ternary positive electrode active material, the oxide solid electrolyte, the conductive agent and the binder according to the data proportion listed in C1-C23 and C26-C32 in the table 1, firstly, carrying out vacuum premixing on the ternary positive electrode active material and the oxide solid electrolyte in advance to obtain a uniformly dispersed premixed material; gradually adding NMP (N-methyl pyrrolidone) glue solution of PVDF (polyvinylidene fluoride) into the uniformly dispersed premixed material; after uniformly mixing, gradually adding conductive agents Super-P and CNT, and uniformly mixing to obtain a ternary anode slurry with certain fluidity; then, the positive electrode plate was coated on an aluminum foil, air-dried, and rolled, and the obtained positive electrode plates were named C1 and C2 … C32, respectively.
The conductive agent is carbon nano tubes and conductive carbon black (CNT + Super-P, the mass ratio of the carbon nano tubes to the conductive carbon black is 1:2), and the binder is polyvinylidene fluoride (PVDF).
The internal structure schematic diagram of the positive electrode material layer in the high-safety, high-magnification and long-cycle ternary electrode plate is shown in the attached figure 1.
Preparation of ternary electrode slice of two-element and non-mixed oxide solid electrolyte
Weighing the ternary positive electrode active material, the conductive agent and the binder according to the data proportion listed in C24 and C25 in the table 1, and gradually adding NMP glue solution of PVDF into the ternary positive electrode active material; after uniformly mixing, gradually adding conductive agents Super-P and CNT, and uniformly mixing to obtain a ternary anode slurry with certain fluidity; then, the positive electrode plate was coated on an aluminum foil, air-dried, and rolled, and the obtained positive electrode plates were named C24 and C25, respectively.
Here, the kinds of the conductive agent and the binder were the same as those of example 1, except that the preliminary vacuum premixing step was not performed, and the other operations were the same as those of example 1.
TABLE 1 ternary electrode slice parameters
Note: alpha is the ratio of the ternary cathode material D50 to the oxide solid electrolyte D50.
The proportion is the mass ratio of the ternary positive electrode active material, the oxide solid electrolyte, the conductive agent and the binder.
The oxide solid electrolyte is Li1.4Al0.4Ti1.6(PO4)3(abbreviated as LATP-1), Li1.3Al0.3Ti1.7(PO4)3(abbreviated as LATP-2), Li1.5Al0.5Ti1.5(PO4)3(abbreviated as LATP-3), Li6.4La3Zr1.6Ta0.6O12(abbreviated as LLZO-1), Li7La3Zr2O12(abbreviated as LLZO-2), Li0.5La0.5TiO3(abbreviated as LLTO-1), Li0.34La0.56TiO3(abbreviated as LLTO-2), Li3OCl (abbreviated LOC), Li1.5Al0.5Ge1.5(PO4)3(abbreviated as LAGP-1) and Li1.3Al0.3Ge1.7(PO4)3(abbreviated as LAGP-2) and Li3/8Sr7/16Ta3/4Zr1/4O3(abbreviated as LSTZ), Li14ZnGe4O16(abbreviated as LZGO).
The ternary positive electrode material is LiNi0.8Co0.1Mn0.1O2(abbreviated as Ni80) and LiNi0.83Co0.12Mn0.05O2(abbreviated as Ni83) and LiNi0.88Co0.09Mn0.03O2(abbreviated as Ni88) and LiNi0.8Co0.15Al0.05O2(abbreviated NCA).
Preparation of negative pole piece
Adding a main negative material active substance, a conductive agent and a binder into deionized water according to a mass ratio of 96:2:2, and uniformly mixing and stirring to obtain negative electrode slurry with certain fluidity; and then coating the copper foil with the conductive agent, drying by blowing and rolling to obtain a negative plate, wherein the conductive agent is a mixture of carbon nano tube CNT and conductive carbon black Super-P according to a mass ratio of 1:2, and the binder is a mixture of CMC and SBR according to a mass ratio of 1: 1.
Fourthly, preparation of battery cell
Adopting ceramic diaphragm, negative pole piece and the positive plate of each embodiment and comparative example, the lamination equipment prepares 15Ah soft-packaged electrical core, and the pole piece size: positive electrode 107mm 83mm, negative electrode 109mm 85 mm.
TABLE 2 high safety, high power ternary electrode sheet parameters
Wherein, the liquid lithium battery adopts a double-sided ceramic diaphragm, the electrolyte adopts a commercial conventional electrolyte, and the electrolyte composition of the comparative examples 1-4 and the examples 1-25 is 1mol/L LiPF6EC/DEC (3:7, V/V) +2 wt% VC +1 wt% LiDFOB; examples 26-27 electrolyte compositions were 1.2mol/L LiPF6-EC/EMC (3:7, V/V) +2 wt% FEC +1 wt% LiDFOB; examples 28-29 electrolyte compositions were 1.2mol/L LiPF6-EC/DEC (3:7, V/V) +2 wt% FEC +1 wt% LiDFOB +1 wt% 1,3-PS semi solid lithium battery using PVDF-HFP based gel polymer electrolyte membrane and 1mol/L LiPF6-EC/DEC (volume ratio) 3:7+2 wt% VC +1 wt% LiDFOB.
The SiOC material is S450-2A SiOC negative electrode material of New energy materials of fibrate Rafimi, Inc.
Fifth, testing the battery performance
The lithium batteries prepared in the examples and the comparative examples are subjected to a rate test of 2.5-4.2V, wherein the charging rate is 1C, and the discharging rate is 1C, 3C and 5C; the lithium batteries prepared in the respective examples and comparative examples were tested for the (1C/5C)/(1C/1C) discharge capacity retention rate, and the energy density was calculated based on the quality and first-cycle discharge energy of the batteries, wherein the test voltage range: 2.75-4.2V, constant current charge and discharge multiplying power: 1C/1C.
TABLE 3 lithium cell Electrical Performance
According to the invention, the oxide solid electrolyte is mixed in the high-nickel ternary positive plate, so that the safety of the battery is improved. Comparative examples 1-2 and examples 1-29 (except for examples 6, 13, 14, 17) show that batteries prepared using the present invention have less effect on the performance of the batteries. The oxide solid electrolyte particles have certain ion conductivity, so that the introduction of the oxide solid electrolyte does not obviously hinder the ion transport capacity in the anode within the content range of the solid electrolyte, and in addition, the heat absorption effect of the oxide solid electrolyte reduces the average temperature of the anode active material in the charge-discharge process and reduces the side reaction of the ternary anode active material at high temperature. However, too small a particle size of the oxide solid electrolyte to be blended or too much a blending amount increases the internal resistance of the battery, and decreases the energy density and rate capability of the battery.
Sixthly, testing the needling safety of the battery core
The lithium batteries prepared in the embodiments and the comparative examples are subjected to a needling safety test according to the safety requirements and the test method of the power storage battery for the lithium ion battery GB/T31485-.
And (3) needle punching test: the battery is charged according to a constant current and a constant voltage of 1C, and the cut-off current is 0.05C; a high-temperature resistant steel needle with the diameter of 6mm penetrates the accumulator plate from the direction vertical to the accumulator plate at the speed of 40mm/s, the penetrating position is close to the geometric center of the punctured surface, and the steel needle stays in the accumulator; and observing for 1h, monitoring the change of the surface temperature of the battery cell in the process, and recording whether the battery cell is on fire or not.
TABLE 4 lithium cell needling safety test results
According to the invention, the oxide solid electrolyte is mixed in the high-nickel ternary positive plate, so that the safety of the battery is improved. As can be seen from comparison of comparative examples 1-2 with examples 1-29 (except examples 6, 13, 14 and 17), the safety of the battery can be obviously improved by adding the oxide solid electrolyte into the positive electrode, and the battery prepared by the invention does not ignite or explode when being needled; the surface temperature of the battery core is 40.9-57.2 ℃ during needling, so that the safety of the battery is improved; the anode plate of the comparative example 1-2 is not added with oxide solid electrolyte, and the battery prepared by the anode plate can be ignited and exploded during needling, thermal runaway is generated, and the surface temperature of the battery core can reach 785.8 ℃ at most. The oxide solid electrolyte is added into the ternary positive electrode active material, so that the contact between ternary active particles is effectively blocked, and the thermal stability of the material is improved; secondly, the oxide solid electrolyte has certain heat capacity, can absorb part of heat generated by the anode and relieve the overheating of the anode.
As can be seen from comparative examples 3 to 4 and examples 1 to 5, in comparative examples 3 to 4, although the oxide solid electrolyte was added, the oxide solid electrolyte having a too small particle size increased interfacial resistance, blocked ion transmission, increased interfacial resistance, and decreased energy density of the battery; the particle size of the oxide solid electrolyte is too large, so that the contact effect between isolated positive electrode particles is not obvious, the safety is not obviously improved, and the needle punching cannot be performed.
Examples 6 to 13 show that, although the oxide solid electrolyte is added to the positive electrode sheet of example 6, the amount of the oxide solid electrolyte blended is too small, the heat absorption and heat insulation effects of the solid electrolyte are not obvious, and the improvement on safety is not obvious; example 13 the positive electrode sheet to which the oxide solid electrolyte was added but the amount of the oxide solid electrolyte blended was too large, and although the battery safety was improved by the needling, the energy density of the battery was lowered.
Example 14 although the oxide solid electrolyte was added with the particle diameter D50 in the preferred range of 0.1 to 3 μm and the addition amount in the preferred range of 0.1 to 20%, the ratio of the ternary cathode material D50 to the oxide solid electrolyte D50 was less than 3, i.e., the particle diameters were relatively close, resulting in that the amount of the oxide solid electrolyte in the particle diameter and content range was insufficient to block the contact between particles of the ternary cathode active material, resulting in poor safety performance, and thus failing to pass the needle punching.
In example 17, although the oxide solid electrolyte was added, the particle size D50 was in the preferable range of 0.1 to 3 μm, the addition amount was in the preferable range of 0.1 to 20%, and the ratio of the ternary cathode material D50 to the oxide solid electrolyte D50 was greater than 3, the premixing rotational speed was too small, the dispersion effect was poor, and particles were easily agglomerated, resulting in poor safety, and thus it was impossible to pass needle punching.
Examples 3, 28, 19, 23-29 show that doping with different oxide solid electrolytes provides some improvement in cell safety, with the best improvement in LATP safety; examples 3, 25-26 and examples 21, 27 and examples 18, 28 and examples 19, 29 show that the electrolyte composition has little effect on battery safety for each electrolyte.
Examples 26 to 29 show that a good technical effect can be achieved by using other electrolytes, that is, the present invention is not related to the electrolytes, the positive electrode sheet provided by the present invention can achieve the effect of improving the safety by matching with the conventional commercial electrolytes, and the corresponding battery cell can smoothly pass the needle punching and hot box test.
Seven, test of electrical core thermal shock safety
The battery is charged according to a constant current and a constant voltage of 1C, and the cut-off current is 0.05C; heating at 180 ℃ for 2 h: heating to 180 ℃ at a heating rate of 5 ℃/mm, keeping the temperature for 2h, and observing for 1 h; "no fire and no explosion" are recorded as pass, otherwise fail, and the change in the cell surface temperature during the process is monitored.
TABLE 5 cell thermal shock safety results
According to the invention, the oxide solid electrolyte is mixed in the high-nickel ternary positive plate, so that the safety of the battery is improved. As can be seen from comparison between examples 1-2 and examples 1-29 (except examples 6, 13, 14 and 17), the safety of the battery can be obviously improved by adding the oxide solid electrolyte into the positive electrode, and the battery prepared by the method has no ignition or explosion during thermal shock test, so that the safety of the battery is improved; the positive plates of comparative examples 1-2 were not added with oxide solid electrolyte, and the batteries prepared by using the electrolyte were ignited and exploded during thermal shock test, resulting in thermal runaway. The oxide solid electrolyte is added into the ternary positive electrode active material, so that the contact between ternary active particles is effectively blocked, and the thermal stability of the material is improved; secondly, the oxide solid electrolyte has certain heat capacity, can absorb part of heat generated by the anode and relieve the overheating of the anode.
As can be seen from comparative examples 3 to 4 and examples 1 to 5, in comparative examples 3 to 4, although the oxide solid electrolyte was added, the oxide solid electrolyte having a too small particle size increased interfacial resistance, blocked ion transmission, increased interfacial resistance, and decreased energy density of the battery; the oxide solid electrolyte has too large particle size, and the contact effect between isolated positive electrode particles is not obvious, so that the safety is not obviously improved.
Examples 6 to 13 show that, although the oxide solid electrolyte is added to the positive electrode sheet of example 6, the amount of the oxide solid electrolyte blended is too small, the heat absorption and heat insulation effects of the solid electrolyte are not obvious, and the improvement on safety is not obvious; example 13 the positive electrode sheet to which the oxide solid electrolyte was added but the amount of the oxide solid electrolyte blended was too large, and although the battery safety was improved by the needling, the energy density of the battery was lowered.
Example 14 although the oxide solid electrolyte was added with the particle diameter D50 in the preferred range of 0.1 to 3 μm and the addition amount in the preferred range of 0.1 to 20%, the ratio of the ternary cathode material D50 to the oxide solid electrolyte D50 was less than 3, i.e., the particle diameters were relatively close, resulting in an insufficient amount of the oxide solid electrolyte to block the contact between particles of the ternary cathode active material in the particle diameter and content range, resulting in poor safety performance.
In example 17, although the oxide solid electrolyte was added, the particle size D50 was in the preferable range of 0.1 to 3 μm, the addition amount was in the preferable range of 0.1 to 20%, and the ratio of the ternary cathode material D50 to the oxide solid electrolyte D50 was greater than 3, the premixing rotational speed was too small, the dispersion effect was poor, and particles were easily agglomerated, resulting in poor safety.
Examples 3, 28, 19, 23-29 show that doping with different oxide solid electrolytes provides some improvement in cell safety, with the best improvement in LATP safety; examples 3, 25-26 and examples 21, 27 and examples 18, 28 and examples 19, 29 show that the electrolyte composition has little effect on battery safety for each electrolyte.
Examples 26-29 show that other electrolytes can be used to achieve a good technical result, i.e., the present invention is independent of the electrolyte, and any conventional or commercial electrolyte can achieve the effect of improving safety by using the technique of the present invention.
Eighthly, 50% deformation extrusion safety test of battery core
The battery is charged according to a constant current and a constant voltage of 1C, and the cut-off current is 0.05C; standing at 25 deg.C for 1h, pressing with an extrusion plate (semi-cylinder with radius of 75 mm) perpendicular to the direction of lithium battery at speed of 2 mm/s; firstly, extruding the battery to achieve 15% deformation, keeping the deformation for more than or equal to 5min, extruding the battery again to achieve 50% deformation, keeping the deformation for 10min, and observing for 1h after the test is finished; "no fire and no explosion" are recorded as pass, otherwise fail, and the change in the cell surface temperature during the process is monitored.
Table 6 test results of 50% deformation extrusion safety of electrical core
The 50% deformation extrusion safety test of the battery cells of examples 1-2 and examples 1-29 (except examples 6, 13, 14 and 17) further illustrates that the addition of the oxide solid electrolyte to the positive electrode can obviously improve the safety of the battery.
In the embodiment provided by the invention, the used ternary cathode material LiNixCoyM1-x-yO2The nickel content x of the positive electrode sheet is 0.80, 0.83 or 0.88, the more the nickel content of the high-nickel ternary positive electrode material is, the poorer the thermal stability is, and as can be seen from examples 17 and 18, the positive electrode sheet provided by the invention uses the Ni88 positive electrode material with poorer stability, the corresponding battery core can still successfully pass the needling, 180 ℃ hot box and 50% deformation extrusion tests, and for the positive electrode active material with lower Ni content (x is 0.6-0.8), the positive electrode sheet provided by the invention can also ensure good safety.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The ternary positive plate for the lithium battery with high safety and high power is characterized by comprising a current collector and a positive material layer positioned on the surface of the current collector, wherein the positive material layer comprises ternary positive active material particles, a conductive agent, a binder and oxide solid electrolyte particles capable of conducting lithium ions;
the surface capacity of the positive plate<4mAh/cm2The particle diameter D50 of the oxide solid electrolyte particles is 0.1 to 3 μm.
2. The positive electrode sheet according to claim 1, wherein the oxide solid electrolyte particles have a particle diameter D50 of 0.5 to 2 μm;
preferably, the content of the ternary cathode active material particles is 80-98% by mass of the total mass of the ternary cathode active material particles, the conductive agent, the binder and the oxide solid electrolyte particles being 100%;
preferably, the content of the oxide solid electrolyte is 0.5 to 20%, preferably 1 to 10%, and more preferably 3 to 5%, based on 100% by mass of the total of the ternary positive electrode active material particles, the conductive agent, the binder, and the oxide solid electrolyte particles;
preferably, the content of the conductive agent is 0.1 to 8% based on 100% by mass of the total of the ternary positive electrode active material particles, the conductive agent, the binder and the oxide solid electrolyte particles;
preferably, the content of the binder is 0.1 to 10% by mass of the total mass of the ternary cathode active material particles, the conductive agent, the binder and the oxide solid electrolyte particles being 100%.
3. The positive electrode sheet according to claim 1 or 2, wherein the oxide solid electrolyte particles include any one of or a combination of at least two of the following compounds: li of NASICON structure1+x1Alx1Ge2-x1(PO4)3Or isoatomic doped compound of the same crystal type, Li1+x2Alx2Ti2-x2(PO4)3Or isomorphous heteroatom doped compound thereof, and Li with perovskite structure3x3La2/3-x3TiO3Or isoatomic doped compound of the same crystal type, Li3/8Sr7/16Ta3/4Hf1/4O3Or isoatomic doped compound of the same crystal type, Li2x4-y1Sr1-x4Tay1Zr1-y1O3Or isomorphous heteroatom doped compound thereof, and Li with anti-perovskite structure3- 2x5Mx5HalO、Li3OCl or isoatomic doped compound of same crystal form thereof, Li of LISICON structure4-x6Si1-x6Px6O4Or isoatomic doped compound of the same crystal type, Li14ZnGe4O16Or isomorphous heteroatom doped compound thereof, and Li of garnet structure7- x7La3Zr2-x7O12Or isomorphic heteroatom doped compound thereof, wherein, 0<x1≤0.75，0<x2≤0.5，0.06≤x3≤0.14，0.25≤y1≤1，x4＝0.75y1，0≤x5≤0.01，0.5≤x6≤0.6；0≤x7<1; wherein M comprises Mg2+、Ca2 +、Sr2+Or Ba2+Any one or the combination of at least two of high valence cations, Hal is element Cl or I;
preferably, the oxide solid electrolyte particles include Li1+x2Alx2Ti2-x2(PO4)3And/or Li7-x7La3Zr2-x7O12Preferably Li1+x2Alx2Ti2-x2(PO4)3。
4. The positive electrode sheet according to any one of claims 1 to 3, wherein the ternary positive electrode active material particles comprise lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate;
preferably, the chemical composition of the ternary positive electrode active material particles is LiNixCoyM1-x-yO2M is at least one of Mn or Al, and x is more than or equal to 0.6;
preferably, the conductive agent comprises any one or a combination of at least two of Super-P, KS-6, carbon black, carbon nanofiber, CNT, acetylene black or graphene, preferably a combination of carbon nanotube and Super-P;
preferably, the binder comprises any one or a combination of at least two of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide or polytetrafluoroethylene, preferably polyvinylidene fluoride.
5. The positive electrode sheet according to any one of claims 1 to 4, wherein the ratio of the particle diameter D50 of the ternary positive electrode active material particles to the particle diameter D50 of the oxide solid electrolyte particles is 3 or more.
6. The method for producing a positive electrode sheet according to any one of claims 1 to 5, comprising the steps of:
s1: premixing anode active material particles and oxide solid electrolyte particles to obtain a premixed material, wherein the anode active material particles comprise ternary anode active material particles;
s2: adding glue solution of a binder into the premixed material, and mixing to obtain primary slurry;
s3: adding a conductive agent into the primary slurry, and mixing to obtain secondary slurry;
s4: coating the secondary slurry on a current collector to control the sheet surface capacity of the electrode<4mAh/cm2And baking and rolling to obtain the positive plate.
7. The method of claim 6, wherein the premixing is vacuum premixing or is conducted at a dew point ≦ -30 ℃;
preferably, the premixing and mixing process is carried out in a ball mill or blender;
preferably, the premixing and the mixing are carried out by using a rotation revolution stirrer, the revolution speed is more than or equal to 20rpm and independently preferably 30-90rpm, the rotation speed is more than or equal to 200rpm and independently preferably 500-2000 rpm;
preferably, the time of the premixing is 1 to 10 hours, preferably 2 to 4 hours;
preferably, the dew point is ≦ 45 deg.C, more preferably ≦ 60 deg.C.
8. A method for improving the safety of a positive electrode sheet for a lithium battery, comprising adding oxide solid electrolyte particles having a particle diameter D50 of 0.1 to 3 μm to the positive electrode sheet during the production of the positive electrode sheet, and dispersing the oxide solid electrolyte particles between particles of a positive electrode active material, the positive electrode sheet having a surface capacity<4mAh/cm2。
9. A lithium battery comprising the positive electrode sheet as claimed in any one of claims 1 to 5.
10. The lithium battery of claim 9, wherein the lithium battery comprises a liquid lithium battery or a semi-solid lithium battery;
preferably, the liquid lithium battery includes the positive electrode tab according to any one of claims 1 to 5, the negative electrode tab, and a liquid electrolyte;
preferably, the semi-solid lithium battery includes the positive electrode tab according to any one of claims 1 to 5, the negative electrode tab, and an electrolyte layer containing a liquid electrolyte.
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