CN117117177B - Battery cell - Google Patents
Battery cell Download PDFInfo
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- CN117117177B CN117117177B CN202311360689.4A CN202311360689A CN117117177B CN 117117177 B CN117117177 B CN 117117177B CN 202311360689 A CN202311360689 A CN 202311360689A CN 117117177 B CN117117177 B CN 117117177B
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- China
- Prior art keywords
- battery
- active material
- manganese
- lithium
- positive electrode
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- 239000007774 positive electrode material Substances 0.000 claims abstract description 101
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 claims abstract description 88
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 59
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 40
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 32
- 239000011574 phosphorus Substances 0.000 claims abstract description 32
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000011248 coating agent Substances 0.000 claims abstract description 18
- 238000000576 coating method Methods 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims description 42
- 239000011259 mixed solution Substances 0.000 claims description 41
- 239000011572 manganese Substances 0.000 claims description 34
- 229910052748 manganese Inorganic materials 0.000 claims description 31
- 229910001416 lithium ion Inorganic materials 0.000 claims description 21
- 238000002156 mixing Methods 0.000 claims description 20
- 239000000839 emulsion Substances 0.000 claims description 17
- 239000007795 chemical reaction product Substances 0.000 claims description 13
- 238000005245 sintering Methods 0.000 claims description 13
- 239000003792 electrolyte Substances 0.000 claims description 10
- 229910052742 iron Inorganic materials 0.000 claims description 7
- 229910003002 lithium salt Inorganic materials 0.000 claims description 7
- 159000000002 lithium salts Chemical class 0.000 claims description 7
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 6
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 6
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 6
- 229910052744 lithium Inorganic materials 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 4
- 239000007773 negative electrode material Substances 0.000 claims description 4
- 238000005056 compaction Methods 0.000 claims description 3
- 230000001804 emulsifying effect Effects 0.000 claims description 3
- 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
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- 239000003575 carbonaceous material Substances 0.000 claims description 2
- 229910021385 hard carbon Inorganic materials 0.000 claims description 2
- 229910021382 natural graphite Inorganic materials 0.000 claims description 2
- 239000002210 silicon-based material Substances 0.000 claims description 2
- 229910021384 soft carbon Inorganic materials 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 claims 1
- 239000002184 metal Substances 0.000 claims 1
- 239000004005 microsphere Substances 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 description 33
- 239000000126 substance Substances 0.000 description 27
- 238000002360 preparation method Methods 0.000 description 26
- 230000000052 comparative effect Effects 0.000 description 21
- 239000006183 anode active material Substances 0.000 description 15
- 238000010438 heat treatment Methods 0.000 description 13
- 230000001105 regulatory effect Effects 0.000 description 13
- 239000000203 mixture Substances 0.000 description 12
- 238000012360 testing method Methods 0.000 description 12
- 239000003921 oil Substances 0.000 description 11
- 238000001694 spray drying Methods 0.000 description 11
- 238000005406 washing Methods 0.000 description 11
- 238000009472 formulation Methods 0.000 description 10
- 239000007789 gas Substances 0.000 description 10
- 239000011149 active material Substances 0.000 description 6
- 238000009616 inductively coupled plasma Methods 0.000 description 6
- ILXAVRFGLBYNEJ-UHFFFAOYSA-K lithium;manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[O-]P([O-])([O-])=O ILXAVRFGLBYNEJ-UHFFFAOYSA-K 0.000 description 6
- 239000011265 semifinished product Substances 0.000 description 6
- 229910052723 transition metal Inorganic materials 0.000 description 6
- 230000005540 biological transmission Effects 0.000 description 5
- 238000001035 drying Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 239000011247 coating layer Substances 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 238000009831 deintercalation Methods 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
- 239000006256 anode slurry Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 125000004122 cyclic group Chemical group 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000006870 function Effects 0.000 description 3
- 229910001437 manganese ion Inorganic materials 0.000 description 3
- -1 manganese iron phosphate lithium manganese iron phosphate Chemical compound 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 241000234314 Zingiber Species 0.000 description 2
- 235000006886 Zingiber officinale Nutrition 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000002041 carbon nanotube Substances 0.000 description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 description 2
- 239000001768 carboxy methyl cellulose Substances 0.000 description 2
- 239000006182 cathode active material Substances 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000007865 diluting Methods 0.000 description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- 235000008397 ginger Nutrition 0.000 description 2
- AWKHTBXFNVGFRX-UHFFFAOYSA-K iron(2+);manganese(2+);phosphate Chemical compound [Mn+2].[Fe+2].[O-]P([O-])([O-])=O AWKHTBXFNVGFRX-UHFFFAOYSA-K 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000012086 standard solution Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000014509 gene expression Effects 0.000 description 1
- CPSYWNLKRDURMG-UHFFFAOYSA-L hydron;manganese(2+);phosphate Chemical compound [Mn+2].OP([O-])([O-])=O CPSYWNLKRDURMG-UHFFFAOYSA-L 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229940099596 manganese sulfate Drugs 0.000 description 1
- 235000007079 manganese sulphate Nutrition 0.000 description 1
- 239000011702 manganese sulphate Substances 0.000 description 1
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/10—Solid density
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/40—Electric properties
-
- 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
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- 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
Abstract
The invention provides a battery. The battery comprises a positive plate, wherein the positive plate comprises a positive active coating, the positive active coating contains a lithium iron manganese phosphate positive active material, the positive active material contains lithium element, manganese element, iron element and phosphorus element, and the sum n1 of the amounts of the manganese element and the iron element in the positive active material and the amount n2 of the phosphorus element in the positive active material are met, wherein n1/n2 is more than or equal to 0.94 and less than or equal to 1.0; average voltage V of battery discharged at 0.33C rate 1 Average voltage V discharged with battery at 1C rate 2 Satisfy V 1 ‑V 2 Less than or equal to 0.2V. The battery provided by the invention adopts the lithium iron manganese phosphate positive electrode active material which is more than or equal to 0.94 and less than or equal to 1/n2 and less than or equal to 1.0, and the discharge voltage equalizing V of the battery under the 0.33C multiplying power 1 Voltage equalizing V with discharge at 1C multiplying power 2 Difference V between the two 1 ‑V 2 The dynamic performance and the cycle performance of the battery can be improved by controlling the voltage below 0.2V.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a battery.
Background
The lithium ion battery has the advantages of high working voltage, long cycle service life, no memory effect, small self-discharge, environmental friendliness and the like, and is widely applied to various portable electronic products and electric automobiles. The lithium ion battery mainly comprises a positive plate, a negative plate, a diaphragm and electrolyte, wherein the positive active material is one of important components of the positive plate, and plays a vital role in electrochemical performance and safety performance of the lithium ion battery.
Currently, commonly used cathode active materials mainly include ternary materials, lithium iron phosphate materials, and lithium manganese iron phosphate materials. Compared with a ternary material, the lithium iron phosphate material has higher theoretical capacity and better cycle performance, and the lithium iron manganese phosphate material is an olivine-type phosphate positive electrode material obtained by doping manganese element on the basis of lithium iron phosphate, and has more excellent dynamic performance and cycle performance than the lithium iron phosphate material. However, after a lithium ion battery using a lithium iron manganese phosphate material as a positive electrode active material undergoes a plurality of cyclic charge and discharge processes, the transmission of lithium ions in the lithium iron manganese phosphate positive electrode active material is blocked, and the cyclic performance is significantly reduced.
Disclosure of Invention
In order to improve the situation that lithium ion transmission of a battery taking a lithium iron manganese phosphate material as a positive electrode active material is blocked in the later period of use and improve the cycle performance and the dynamic performance of the battery, the invention provides the battery.
According to a first aspect of the present invention, there is provided a battery comprising a positive electrode sheet including a positive electrode active coating layer containing a lithium manganese iron phosphate positive electrode active material containing lithium element, manganese element, iron element and phosphorus element, wherein the sum of the amounts of manganese element, iron element substances in the positive electrode active material is n1, and the amounts of phosphorus element substances in the positive electrode active material are n2, n1, n2 are satisfied, and 0.94.ltoreq.n1/n 2.ltoreq.1.0; with the average voltage of the battery discharged at 0.33C rate being V 1 With the average voltage of the battery discharged at 1C multiplying power being V 2 ，V 1 、V 2 Satisfy V 1 -V 2 ≤0.2V。
The molar ratio of manganese element, iron element and phosphorus element can influence the internal defect and lithium ion deintercalation capability of the lithium iron manganese phosphate positive electrode active material, and further influence the electrochemical performance and cycle performance of a battery taking the lithium iron manganese phosphate as the positive electrode active material, the battery provided by the invention adopts the manganese iron phosphate positive electrode active material in which the sum of the amounts n1 of the substances of the two transition metal elements of manganese element and iron element and the amount n2 of the substance of the phosphorus element satisfy that n1/n2 is less than or equal to 0.94 and less than or equal to 1.0, and the average voltage V of the battery discharged at the multiplying power of 0.33C 1 With average voltage V discharged at 1C rate 2 Difference V between the two 1 -V 2 The lithium ion transfer efficiency in the lithium manganese iron phosphate positive electrode active material can be improved by controlling the voltage below 0.2V, so that the lithium ions are smoothly released and inserted in the lithium manganese iron phosphate positive electrode active material, the dynamic performance of the lithium manganese iron phosphate positive electrode active material is improved, and on the other hand, the lithium manganese iron phosphate positive electrode active material simultaneously has the characteristics of good conductivity, good cycle performance and high gram capacity, and the battery is put under the action of the two aspectsThe average voltage change in the electrical process is more uniform and improves the dynamic and cyclic performance of the battery. If n1/n2 is more than 1.0, the molar ratio of transition metal elements (manganese element and iron element) in the lithium manganese iron phosphate positive electrode active material is too high, so that the internal defects of the lithium manganese iron phosphate positive electrode active material are fewer, and the deintercalation of lithium ions in the lithium manganese iron phosphate positive electrode active material is blocked, so that the dynamic performance and the cycle performance of the battery are reduced; if n1/n2 is less than 0.94, it indicates that the molar ratio of phosphorus element in the lithium iron manganese phosphate positive electrode active material is too high, which can cause the conductivity and gram capacity of the lithium iron manganese phosphate positive electrode active material to be obviously reduced, and further reduce the dynamic performance and cycle performance of the battery.
Detailed Description
In order to improve the situation that lithium ion transmission of a battery taking a lithium iron manganese phosphate material as a positive electrode active material is blocked in the later period of use and improve the cycle performance and the dynamic performance of the battery, the invention provides the battery.
According to a first aspect of the present invention, there is provided a battery comprising a positive electrode sheet including a positive electrode active coating layer containing a lithium manganese iron phosphate positive electrode active material containing lithium element, manganese element, iron element and phosphorus element, wherein the sum of the amounts of manganese element, iron element substances in the positive electrode active material is n1, and the amounts of phosphorus element substances in the positive electrode active material are n2, n1, n2 are satisfied, and 0.94.ltoreq.n1/n 2.ltoreq.1.0; with the average voltage of the battery discharged at 0.33C rate being V 1 With the average voltage of the battery discharged at 1C multiplying power being V 2 ，V 1 、V 2 Satisfy V 1 -V 2 ≤0.2V。
The molar ratio of manganese element, iron element and phosphorus element can influence the internal defect and the lithium ion deintercalation capability of the lithium manganese iron phosphate positive electrode active material, and further influence the electrochemical performance and the cycle performance of a battery taking the lithium manganese iron phosphate as the positive electrode active material, and the battery provided by the invention adopts the manganese iron phosphate lithium manganese iron phosphate with the sum of the amounts of manganese element and iron element and the sum of n1 of the two transition metal elements and the amount n2 of the phosphorus element to satisfy that n1/n2 is less than or equal to 0.94 and less than or equal to 1.0As a positive electrode active material in a positive electrode sheet, and discharging the battery at an average voltage V of 0.33C rate 1 With average voltage V discharged at 1C rate 2 Difference V between the two 1 -V 2 The lithium ion battery is controlled below 0.2V, on one hand, the transmission efficiency of lithium ions in the lithium iron manganese phosphate positive electrode active material can be improved, the lithium ions can be smoothly released from the lithium iron manganese phosphate positive electrode active material, the dynamic performance of the lithium iron manganese phosphate positive electrode active material is improved, on the other hand, the lithium iron manganese phosphate positive electrode active material can be ensured to have the characteristics of good conductivity, good cycle performance and high gram capacity, and the average voltage change of the battery in the discharging process is more uniform through the functions of the two aspects, and the dynamic performance and the cycle performance of the battery are improved. If n1/n2 is more than 1.0, the molar ratio of transition metal elements (manganese element and iron element) in the lithium manganese iron phosphate positive electrode active material is too high, so that the internal defects of the lithium manganese iron phosphate positive electrode active material are fewer, and the deintercalation of lithium ions in the lithium manganese iron phosphate positive electrode active material is blocked, so that the dynamic performance and the cycle performance of the battery are reduced; if n1/n2 is less than 0.94, it indicates that the molar ratio of phosphorus element in the lithium iron manganese phosphate positive electrode active material is too high, which can cause the conductivity and gram capacity of the lithium iron manganese phosphate positive electrode active material to be obviously reduced, and further reduce the dynamic performance and cycle performance of the battery.
Preferably, 0.96.ltoreq.n1/n2.ltoreq.0.99.
The manganese content in the lithium manganese phosphate positive electrode active material can be kept in a proper range by controlling the ratio n1/n2 of the sum n1 of the amounts of manganese element and iron element substances and the amount n2 of phosphorus element substances in the lithium manganese phosphate positive electrode active material of the positive electrode plate within a range of 0.96-0.99, so that on one hand, the situation that the electrochemical performance and the cycle performance of the lithium manganese phosphate positive electrode active material are poor due to the fact that the manganese content is too low is facilitated to be improved, on the other hand, the ginger Taylor effect of the lithium manganese phosphate positive electrode active material due to the fact that the manganese content is too high can be restrained to a certain extent, the crystal lattice of the lithium manganese phosphate positive electrode active material is more stable, the dissolution of manganese ions is slowed down, and the electrochemical performance of the lithium manganese phosphate positive electrode active material is further improved.
Preferably, 0.98.ltoreq.n1/n2.ltoreq.0.99.
Preferably, the positive electrode active material is prepared by the following steps:
s1, preparing a mixed solution A by using a lithium source material and a phosphorus source material;
s2, mixing and emulsifying manganese source materials and iron source materials to prepare emulsion;
s3, mixing the mixed solution A with the emulsion to obtain a mixed solution B, reacting the mixed solution B at 180-250 ℃ for 1-5 hours, and sintering the obtained reaction product at 350-950 ℃ for 3-12 hours to obtain the positive electrode active material.
Preferably, the residual manganese content of the mixed solution B is 18000-22000 ppm.
Preferably, the pH value of the mixed solution B is 6.0 to 6.25.
In the preparation process of the lithium iron manganese phosphate positive electrode active material contained in the battery, the content of residual manganese in the mixed solution B formed by the lithium salt material, the phosphorus source material, the manganese source material and the iron source material is controlled within the range of 18000-22000 ppm, the pH value of the emulsion is regulated to be 6.0-6.25, the doping amount of manganese element in the lithium iron manganese phosphate positive electrode active material is controlled within a proper range, and meanwhile, the distribution uniformity of manganese element and iron element in the lithium iron manganese phosphate positive electrode active material is improved, so that the dynamic performance, the circulation performance, the conductivity and the gram capacity of the lithium iron manganese phosphate positive electrode active material are further improved.
Preferably 0 < V 1 -V 2 ≤0.1V。
Preferably, the positive electrode active coating has a compacted density of 2.3 to 3.55g/cm 3 。
Preferably, the battery further comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode active coating, the negative electrode active coating contains a negative electrode active material, and the negative electrode active material is selected from metallic lithium, natural graphite, artificial graphite and mesophase carbonMicrospheres, hard carbon, soft carbon, silicon material, silicon oxygen material, silicon carbon material, li 4 Ti 5 O 12 At least one of them.
Preferably, the battery further comprises an electrolyte, wherein the electrolyte consists of lithium salt, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate; in the electrolyte, the concentration of lithium salt is 1-1.4M; the mass ratio of the ethylene carbonate is as follows: methyl ethyl carbonate: diethyl carbonate=1: 1:1.
the technical features of the technical solution provided in the present invention will be further clearly and completely described in connection with the detailed description below, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
A battery, the method of making comprising the steps of:
1. preparation of positive plate
The lithium iron manganese phosphate positive electrode active material, conductive carbon black (SP) and polyvinylidene fluoride (PVDF) as binders are mixed according to the mass ratio of 94:3:3, uniformly mixing and dispersing the mixture in a solvent N-methyl pyrrolidone (NMP) to prepare anode slurry; uniformly coating the anode slurry on two surfaces of a carbon-coated aluminum foil of an anode current collector to form an anode active coating, drying at 85 ℃ for 24 hours in a vacuum environment to obtain an anode sheet semi-finished product, and then carrying out cold pressing treatment on the anode sheet semi-finished product to tightly stack lithium iron manganese phosphate anode active material particles in the anode sheet semi-finished product to obtain an anode sheet, wherein the compaction density of the anode active coating in the anode sheet is 3.0g/m 3 。
The lithium iron manganese phosphate positive electrode active material adopted in the embodiment is prepared by the following steps:
s1, a lithium source material (lithium hydroxide) and a phosphorus source material (phosphoric acid) are mixed according to a molar ratio of 3:1, mixing and preparing a mixed solution A;
s2, mixing a manganese source material (manganese sulfate) and an iron source material (ferrous sulfate) according to a stoichiometric ratio, and fully emulsifying to obtain an emulsion;
s3, transferring the mixed solution A and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with pH value of 6.18 and residual manganese content of 19100ppm, heating the reaction kettle to 190 ℃, preserving heat for 5 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 8 hours at 750 ℃, and carrying out gas crushing to obtain the lithium iron manganese phosphate anode active material.
2. Preparation of negative electrode sheet
Artificial graphite serving as a cathode active material, carbon Nano Tube (CNT) serving as a conductive agent and sodium carboxymethyl cellulose (CMC) serving as a binder in mass ratio of 92:4:4, uniformly mixing and dispersing the mixture in deionized water serving as a solvent to prepare negative electrode slurry; coating the anode slurry and two surfaces of an anode current collector copper foil to form an anode active coating, drying at 100 ℃ for 12 hours in a vacuum environment to obtain an anode sheet semi-finished product, and then carrying out cold pressing treatment on the anode sheet semi-finished product to tightly stack anode active material artificial graphite particles in the anode sheet semi-finished product to obtain an anode sheet, wherein the compaction density of the anode active coating in the anode sheet is 1.62g/cm 3 。
3. Preparation of electrolyte
Ethylene Carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) are mixed according to the mass ratio of 1:1:1 to obtain an organic solvent, and then fully drying the lithium salt LiPF 6 Dissolving in the organic solvent to prepare electrolyte with lithium salt concentration of 1.2 mol/L.
4. Preparation of a separator film
Polyethylene film was selected as the separator film.
5. Preparation of a Battery
Sequentially stacking the positive plate, the isolating film and the negative plate, enabling the isolating film to be positioned between the positive plate and the negative plate to play a role of isolation, and then winding to obtain a bare cell; and placing the bare cell in a shell, drying, injecting electrolyte, standing for 12 hours, after the electrolyte completely infiltrates the positive plate, the isolating film and the negative plate, charging at 25 ℃ for 5 hours at 0.02 ℃ and then charging at 0.1 ℃ for 5 hours to form a solid electrolyte interface film (SEI film), pumping out generated gas, charging at 0.33 ℃ to an upper limit voltage (4.3V), and then charging at constant voltage to 0.05 ℃ to cut off, thus obtaining the battery.
Example 2
This example provides a battery, which is different from example 1 in the constitution in that the preparation step S3 of the lithium iron manganese phosphate positive electrode active material is different, specifically:
s3, transferring the mixed solution and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with pH value of 6.13 and residual manganese content of 18900ppm, heating the reaction kettle to 190 ℃, preserving heat for 5 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 8 hours at 750 ℃, and carrying out gas crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this example were strictly consistent with those in example 1.
Example 3
This example provides a battery, which is different from example 1 in the constitution in that the preparation step S3 of the lithium iron manganese phosphate positive electrode active material is different, specifically:
s3, transferring the mixed solution and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with pH value of 6.03 and residual manganese content of 19690ppm, heating the reaction kettle to 190 ℃, preserving heat for 5 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 8 hours at 750 ℃, and carrying out gas crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this example were strictly consistent with those in example 1.
Example 4
This example provides a battery, which is different from example 1 in the constitution in that the preparation step S3 of the lithium iron manganese phosphate positive electrode active material is different, specifically:
s3, transferring the mixed solution A and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with the pH value of 6.2 and the content of residual manganese of 19900ppm, heating the reaction kettle to 190 ℃, preserving heat for 5 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 8 hours at 750 ℃, and carrying out air crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this example were strictly consistent with those in example 1.
Example 5
This example provides a battery, which is different from example 1 in the constitution in that the preparation step S3 of the lithium iron manganese phosphate positive electrode active material is different, specifically:
s3, transferring the mixed solution A and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with the pH value of 6.11 and the residual manganese content of 19000ppm, heating the reaction kettle to 190 ℃, preserving heat for 5 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 8 hours at 750 ℃, and carrying out air crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this example were strictly consistent with those in example 1.
Example 6
This example provides a battery, which is different from example 1 in the constitution in that the preparation step S3 of the lithium iron manganese phosphate positive electrode active material is different, specifically:
s3, transferring the mixed solution A and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with pH value of 6.01 and residual manganese content of 20500ppm, heating the reaction kettle to 190 ℃, preserving heat for 5 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 8 hours at 750 ℃, and carrying out gas crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this example were strictly consistent with those in example 1.
Example 7
This example provides a battery, which is different from example 1 in the constitution in that the preparation step S3 of the lithium iron manganese phosphate positive electrode active material is different, specifically:
s3, transferring the mixed solution A and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with pH value of 6.01 and residual manganese content of 20700ppm, heating the reaction kettle to 250 ℃, preserving heat for 3 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 10 hours at 850 ℃, and carrying out gas crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this example were strictly consistent with those in example 1.
Example 8
This example provides a battery, which is different from example 1 in the constitution in that the preparation step S3 of the lithium iron manganese phosphate positive electrode active material is different, specifically:
s3, transferring the mixed solution A and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with the pH value of 6.32 and the content of residual manganese of 18900ppm, heating the reaction kettle to 185 ℃ and preserving heat for 5 hours, washing and spray-drying the obtained reaction product after the reaction is finished, sintering for 12 hours at 950 ℃, and carrying out gas crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this example were strictly consistent with those in example 1.
Comparative example 1
This comparative example provides a battery having a constitution different from that of example 1 in the preparation step S3 of the lithium iron manganese phosphate positive electrode active material, specifically:
s3, transferring the mixed solution A and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with the pH value of 6.35 and the residual manganese content of 17800ppm, heating the reaction kettle to 190 ℃, preserving heat for 5 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 14 hours at 1000 ℃, and carrying out gas crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this comparative example were strictly consistent with those in example 1.
Comparative example 2
This comparative example provides a battery having a constitution different from that of example 1 in the preparation step S3 of the lithium iron manganese phosphate positive electrode active material, specifically:
s3, transferring the mixed solution A and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with pH value of 6.27 and residual manganese content of 24000ppm, heating the reaction kettle to 190 ℃, preserving heat for 5 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 14 hours at 1000 ℃, and carrying out gas crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this comparative example were strictly consistent with those in example 1.
Comparative example 3
This comparative example provides a battery having a constitution different from that of example 1 in the preparation step S3 of the lithium iron manganese phosphate positive electrode active material, specifically:
s3, transferring the mixed solution A and the emulsion into an oil bath high-pressure reaction kettle in a pipeline transportation mode, mixing, regulating the pH value of the system to obtain a mixed solution B with the pH value of 6.18 and the residual manganese content of 19100ppm, heating the reaction kettle to 190 ℃, preserving heat for 5 hours, washing and spray drying the obtained reaction product after the reaction is finished, sintering for 14 hours at 1000 ℃, and carrying out gas crushing to obtain the lithium iron manganese phosphate anode active material.
Except for the above differences, the materials, formulation ratios and preparation operations adopted in this comparative example were strictly consistent with those in example 1.
The residual manganese content of the mixed solution B refers to the concentration of Mn element in the mixed solution B, and the regulation and control of the residual manganese content are realized by controlling the feed ratio of the lithium source material, the phosphorus source material, the manganese source material and the iron source material and regulating the pH value of the mixed solution B.
Test case
1. Reference subject
In the test example, the lithium iron manganese phosphate positive electrode active materials and batteries prepared in examples 1 to 8 and comparative examples 1 to 3 were used as reference objects to perform the related performance test.
2. Content of test
(1) Residual manganese content
The invention relates to a residual manganese content, which refers to the concentration of Mn element in a mixed solution B, and the testing method comprises the following steps: drying the mixed solution B to obtain a powder sample, weighing 0.5000g of the powder sample in a 150mL beaker, adding about 20mL of water, then adding 10mL of nitric acid, flushing with water when the volume is lower than 30mL for the first time, heating and dissolving for the second time, cooling to room temperature after heating and dissolving for about 10min, transferring the liquid in the beaker into a 100mL volumetric flask, diluting with water to a scale, mixing uniformly, and filtering to obtain a solution to be tested; before testing, preparing a standard solution, wherein the linear correlation coefficient of the concentration of the standard substance is above 0.999 and the standard solution can be used as a normal standard substance; respectively diluting standard substance solutions with the concentration of 1000 mg/L to different concentrations (generally 0,1,2,3mg/100 mL) by deionized water, and selecting element detection spectrum wavelength of 257.63nm; if the sample test concentration exceeds the range of the table, corresponding standard substances can be configured according to actual conditions; the self-help analysis function of ICP test software can read the concentration of Mn element in the sample.
(2) Amount of substance of each element
The lithium iron manganese phosphate positive electrode active materials prepared in examples 1 to 8 and comparative examples 1 to 3 contain lithium element, manganese element, iron element and phosphorus element, n1 represents the sum of the amounts of the manganese element, iron element substances in the lithium iron manganese phosphate positive electrode active material, and n2 represents the amount of the phosphorus element substance in the positive electrode active material.
The amounts of the substances of manganese element, iron element and phosphorus element were tested in the following manner: and testing the lithium manganese iron phosphate anode active material by using an inductively coupled plasma spectrometer (ICP) to obtain the mass ratio of two transition metal elements (manganese element and iron element) and phosphorus element in the lithium manganese iron phosphate anode active material, and calculating the value of n1/n2 according to the following formula, wherein n1/n 2= (manganese element ICP mass ratio/manganese element relative atomic mass+iron element ICP mass ratio/iron element relative atomic mass)/(phosphorus element ICP mass ratio/phosphorus element relative atomic mass).
For a battery taking lithium iron manganese phosphate as a positive electrode active material, the battery needs to be disassembled firstly to obtain a positive electrode plate, then the positive electrode plate is placed in dimethyl carbonate (MC) and soaked for 60 minutes at normal temperature, the positive electrode plate is taken out and dried at normal temperature under the condition that the humidity is less than or equal to 15%, then a positive electrode active material layer on the surface of a positive electrode current collector is scraped to obtain a lithium iron manganese phosphate positive electrode active material, and then the amounts of substances of manganese element, iron element and phosphorus element in the lithium iron manganese phosphate positive electrode active material are tested by adopting the mode.
(3) Average voltage of discharge
The batteries prepared in examples 1 to 8 and comparative examples 1 to 3 were discharged at a rate of 0.33C at an average voltage of V 1 The average voltage of discharge at 1C rate is V 2 。
The average discharge voltage of the batteries prepared in examples 1 to 8 and comparative examples 1 to 3 was measured as follows: the batteries prepared in examples 1 to 8 and comparative examples 1 to 3 were subjected to an empty charge treatment at 25℃to put the batteries in a 0% SOC state, then charged and discharged at a constant rate of 0.33C for 3 cycles, then charged to 4.3V at a constant rate of 0.33C, charged to a current of less than 0.05C at a constant voltage, and then discharged to a constant rate of 0.33C2.5V, obtaining the discharge energy e of the battery according to the discharge curve of the battery at 0.33C multiplying power 1 (mWh) and discharge capacity q 1 (mAh) the specific energy E of the battery at 0.33C rate was calculated by combining the mass of the active material in the battery and using the following formula 1 And specific discharge capacity Q 1 : specific discharge energy E 1 (mWh/g) =discharge energy e 1 (mWh)/active Material Mass (g), specific discharge Capacity Q 1 (mAh/g) =specific discharge capacity q 1 (mAh)/active material mass (g) and then the discharge average voltage V of the battery at 0.33C rate was calculated according to the following formula 1 : average discharge voltage V 1 (V) =specific discharge energy E 1 (mWh/g)/specific discharge Capacity Q 1 (mAh/g); then charging the battery to 4.3V at 1C rate, charging to current less than 0.05C with constant voltage, then discharging to 2.5V at 1C rate, and obtaining discharge energy e of the battery according to discharge curve of the battery at 1C rate 2 (mWh) and discharge capacity q 2 (mAh) combining the mass of the active material in the battery and calculating the specific discharge energy E of the battery at 1C rate according to the following formula 2 And specific discharge capacity Q 2 : specific discharge energy E 2 (mWh/g) =discharge energy e 2 (mWh)/active Material Mass (g), specific discharge Capacity Q 2 (mAh/g) =specific discharge capacity q 2 (mAh)/active material mass (g) and then the discharge average voltage V of the battery at 1C rate was calculated according to the following formula 2 : average discharge voltage V 2 (V) =specific discharge energy (mWh/g)/specific discharge capacity (mAh/g).
(4) Gram capacity of first-turn discharge
The batteries prepared in examples 1 to 8 and comparative examples 1 to 3 were charged and discharged at 0.33C rate for 3 cycles at 25 ℃, then charged to 4.3V at 0.33C constant rate, charged to a current of less than 0.05C at constant voltage, then discharged to 2.5V at 0.33C constant rate, and the first cycle discharge gram capacity of the battery at 0.33C rate was recorded.
(5) Cycle performance
The batteries prepared in examples 1 to 8 and comparative examples 1 to 3 were subjected to cycle performance test at 25℃according to the following procedure: the battery was fully charged to 4.25V at a current of 0.5C, and then discharged to 2.5V at a constant rate of 1C, which was taken as a charge-discharge cycle, and the number of cycles at this time was recorded when the charge-discharge cycle was performed on the battery to 80% of the initial constant volume capacity according to the above manner.
3. Experimental results
Table 1 parameters relating to lithium manganese iron phosphate positive electrode active materials
Table 2 discharge energy, discharge capacity and discharge average voltage of battery at 0.33C rate
Table 3 discharge energy, discharge capacity and discharge average voltage of battery at 1C rate
Table 4 results of related test performance of the battery
The relevant parameters of the lithium iron manganese phosphate positive electrode active materials prepared in examples 1 to 8 and comparative examples 1 to 3 are shown in table 1, the lithium iron manganese phosphate positive electrode active materials prepared in examples 1 to 8 and comparative examples 1 to 3 are applied to batteries, the specific energy of discharge, specific capacity of discharge and average voltage of discharge at 0.33C rate of the batteries are shown in table 2, the specific energy of discharge, specific capacity of discharge and average voltage of discharge at 1C rate of the batteries are shown in table 3, and the relevant test performance results of the batteries are shown in table 4.
Among all the reference cells, the cells provided in examples 1 to 8 satisfy 0.94.ltoreq.n1/n2.ltoreq.1.0 and V simultaneously 1 -V 2 The gram capacity and cycle performance test results of the two relational expressions of less than or equal to 0.2V show that the gram capacity of the first-cycle discharge of the battery of the embodiment 1-8 at 25 ℃ is as high as 130-142 mAh/g, and the cycle number of the battery at 25 ℃ when the battery is cycled to 80% of the initial constant-volume capacity is within the range of 200-360 circles; compared with examples 1 to 8, the batteries provided in comparative examples 1 and 2 are of a type that neither satisfies 0.94.ltoreq.n1/n2.ltoreq.1.0 nor satisfies V 1 -V 2 In the case of 0.2V or less, the battery provided in comparative example 3 was one satisfying 0.94.ltoreq.n1/n2.ltoreq.1.0 but not satisfying V 1 -V 2 Test results show that the initial charge-discharge gram capacity and the cycle number of the batteries provided in comparative examples 1-3 at 25 ℃ are lower than those of examples 1-8 under the condition of less than or equal to 0.2V. The reason for the above results is: examples 1 to 8 provide batteries using lithium iron manganese phosphate in which the sum of the amounts n1 of substances of two transition metal elements of manganese and iron and the amount n2 of substances of phosphorus satisfy 0.94.ltoreq.n1/n2.ltoreq.1.0 as positive electrode active materials in positive electrode sheets, and the average voltage V of the batteries discharged at a rate of 0.33C 1 With average voltage V discharged at 1C rate 2 Difference V between the two 1 -V 2 The lithium ion battery is controlled below 0.2V, on one hand, the transmission efficiency of lithium ions in the lithium iron manganese phosphate positive electrode active material can be improved, the lithium ions can be smoothly released from the lithium iron manganese phosphate positive electrode active material, the dynamic performance of the lithium iron manganese phosphate positive electrode active material is improved, on the other hand, the lithium iron manganese phosphate positive electrode active material can be ensured to have the characteristics of good conductivity, good cycle performance and high gram capacity, and the average voltage change of the battery in the discharging process is more uniform through the functions of the two aspects, and the dynamic performance and the cycle performance of the battery are improved.
Among the batteries provided in examples 1 to 8, the batteries provided in examples 1 to 5 are in a condition of satisfying 0.96.ltoreq.n1/n2.ltoreq.0.99, while the batteries provided in examples 6 to 8 are in a condition of not satisfying 0.96.ltoreq.n1/n2.ltoreq.0.99, and test results show that the initial-turn discharge gram capacity and the cycle number of the batteries provided in examples 1 to 5 at 25 ℃ are both larger than those of examples 6 to 8, mainly because the positive electrode active coating layer of the positive electrode sheet of the batteries provided in examples 1 to 5 contains manganese element, sum of the amounts of the substances of the iron element n1, and the amount of the substance of the phosphorus element n2 satisfying 0.96.ltoreq.n1/n2.ltoreq.0.99, the manganese content in the positive electrode active material of manganese phosphate can be kept within a more suitable range, on the one hand, the electrochemical performance and the poor cycle performance of the positive electrode active material of manganese phosphate lithium manganese oxide due to the excessively low content can be improved, on the other hand, the ginger Taylor effect of the lithium manganese iron phosphate positive electrode active material caused by the too high manganese content can be restrained to a certain extent, so that the crystal lattice of the lithium manganese iron phosphate positive electrode active material is more stable, the dissolution of manganese ions is slowed down, the gram capacity and the electrochemical performance of the lithium manganese iron phosphate positive electrode active material are further improved, the first-round discharge gram capacity and the cycle performance of a battery applying the lithium manganese iron phosphate positive electrode active material are improved through the actions of the two aspects, the positive electrode active coating of the positive electrode plate of the battery provided by examples 6-7 contains the manganese iron phosphate positive electrode active material, the sum n1 of the substances of the iron elements and the ratio n1/n2 of the substances of the phosphorus elements is less than 0.96, which indicates that the manganese content in the lithium manganese iron phosphate positive electrode active material is at a lower level, the initial charge capacity and cycle performance of the battery using the lithium iron manganese phosphate positive electrode active material are poor, the positive electrode active coating of the positive electrode sheet of the battery provided in the embodiment 8 contains the manganese element, the sum n1 of the substances of the iron element and the ratio n1/n2 of the substances of the phosphorus element, which are greater than 0.99, which indicates that the manganese content in the lithium iron manganese phosphate positive electrode active material is in a higher level, which leads to the lithium iron manganese phosphate positive electrode active material to be more prone to the Taylor effect, the crystal lattice of the lithium iron manganese phosphate positive electrode active material to be more prone to distortion, and the dissolution of manganese ions to be aggravated, and finally, the initial charge capacity and cycle performance of the battery using the lithium iron manganese phosphate positive electrode active material to be reduced.
In the batteries provided in examples 1 to 5, the positive electrode active coating layer of the positive electrode sheet of the battery provided in examples 2 to 3 contained the sum n1 of the amounts of the substances of manganese element and iron element and phosphorus element in the lithium iron manganese phosphate positive electrode active material, as compared with examples 1, 4 and 5The quantity n2 of the substances of (2) satisfies 0.98.ltoreq.n1/n2.ltoreq.0.99 while the average voltage V of the battery discharged at a rate of 0.33C 1 With average voltage V discharged at 1C rate 2 Satisfy 0 < V 1 -V 2 Test results show that the batteries of examples 2-3 show higher initial charge-discharge gram capacity and cycle number at 25 ℃.
The above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solution of the present invention, but these modifications or substitutions are all within the scope of the present invention.
Claims (7)
1. A battery, characterized in that: the lithium ion battery comprises a positive plate, wherein the positive plate comprises a positive active coating, the positive active coating contains a lithium iron manganese phosphate positive active material, the positive active material contains lithium element, manganese element, iron element and phosphorus element, the sum of the amounts of the manganese element and the iron element in the positive active material is n1, the amount of the phosphorus element in the positive active material is n2, the n1 and the n2 meet each other, and n1/n2 is more than or equal to 0.98 and less than or equal to 0.99;
with the average voltage of the battery discharged at 0.33C rate being V 1 With the average voltage of the battery discharged at 1C multiplying power being V 2 The V is 1 Said V 2 Meeting the requirement that V is more than or equal to 0.081 1 -V 2 ≤0.1V。
2. The battery of claim 1, wherein the positive electrode active material is prepared by:
s1, preparing a mixed solution A by using a lithium source material and a phosphorus source material;
s2, mixing and emulsifying manganese source materials and iron source materials to prepare emulsion;
s3, mixing the mixed solution A with the emulsion to obtain a mixed solution B, reacting the mixed solution B at 180-250 ℃ for 1-5 hours, and sintering the obtained reaction product at 350-950 ℃ for 3-12 hours to obtain the positive electrode active material.
3. The battery of claim 2, wherein: the residual manganese content of the mixed solution B is 18000-22000 ppm.
4. The battery of claim 2, wherein: the pH value of the mixed solution B is 6.0-6.25.
5. The battery of claim 1, wherein: the compaction density of the positive electrode active coating is 2.3-3.55 g/cm 3 。
6. The battery of claim 1, wherein: the lithium ion battery also comprises a negative plate, wherein the negative plate comprises a negative active coating, the negative active coating contains a negative active material, and the negative active material is selected from metal lithium, natural graphite, artificial graphite, mesophase carbon microspheres, hard carbon, soft carbon, silicon materials, silicon oxygen materials, silicon carbon materials and Li 4 Ti 5 O 12 At least one of them.
7. The battery of claim 1, wherein: the electrolyte consists of lithium salt, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate;
in the electrolyte, the concentration of the lithium salt is 1-1.4M; the ethylene carbonate is calculated according to the mass ratio: the methyl ethyl carbonate: diethyl carbonate=1: 1:1.
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| CN108390057A (en) * | 2018-03-07 | 2018-08-10 | 南京理工大学 | The preparation method of additive Mn lithium iron phosphate electrode material |
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