CN112599852A - Electrolyte for lithium ion battery and lithium ion battery comprising same - Google Patents
Electrolyte for lithium ion battery and lithium ion battery comprising same Download PDFInfo
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- CN112599852A CN112599852A CN202011480690.7A CN202011480690A CN112599852A CN 112599852 A CN112599852 A CN 112599852A CN 202011480690 A CN202011480690 A CN 202011480690A CN 112599852 A CN112599852 A CN 112599852A
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- lithium
- ion battery
- lithium ion
- electrolyte
- carbonate
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 53
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 53
- 239000003792 electrolyte Substances 0.000 title claims abstract description 34
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 33
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 33
- -1 lithium hexafluorophosphate Chemical compound 0.000 claims abstract description 15
- 238000001556 precipitation Methods 0.000 claims abstract description 13
- FKRCODPIKNYEAC-UHFFFAOYSA-N ethyl propionate Chemical compound CCOC(=O)CC FKRCODPIKNYEAC-UHFFFAOYSA-N 0.000 claims abstract description 10
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 claims abstract description 7
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 claims abstract description 6
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims abstract description 6
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 claims abstract description 6
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 claims abstract description 6
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims abstract description 5
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims abstract description 5
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims abstract description 5
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000011888 foil Substances 0.000 claims description 18
- 239000011248 coating agent Substances 0.000 claims description 14
- 238000000576 coating method Methods 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 14
- 239000002184 metal Substances 0.000 claims description 14
- 239000006258 conductive agent Substances 0.000 claims description 12
- 239000011230 binding agent Substances 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- 238000005520 cutting process Methods 0.000 claims description 8
- 238000002360 preparation method Methods 0.000 claims description 8
- 238000005096 rolling process Methods 0.000 claims description 8
- 238000003466 welding Methods 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 5
- 239000007774 positive electrode material Substances 0.000 claims description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 4
- NIXOWILDQLNWCW-UHFFFAOYSA-M acrylate group Chemical group C(C=C)(=O)[O-] NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 4
- 239000006229 carbon black Substances 0.000 claims description 4
- 239000002041 carbon nanotube Substances 0.000 claims description 4
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 4
- 239000011889 copper foil Substances 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 239000004698 Polyethylene Substances 0.000 claims description 3
- 229920000573 polyethylene Polymers 0.000 claims description 3
- 229920006254 polymer film Polymers 0.000 claims description 3
- 150000001252 acrylic acid derivatives Chemical class 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims description 2
- 239000013543 active substance Substances 0.000 abstract description 9
- 238000007599 discharging Methods 0.000 abstract description 4
- 238000007600 charging Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000005056 compaction Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- SJHAYVFVKRXMKG-UHFFFAOYSA-N 4-methyl-1,3,2-dioxathiolane 2-oxide Chemical compound CC1COS(=O)O1 SJHAYVFVKRXMKG-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- WMNWJTDAUWBXFJ-UHFFFAOYSA-N 3,3,4-trimethylheptane-2,2-diamine Chemical compound CCCC(C)C(C)(C)C(C)(N)N WMNWJTDAUWBXFJ-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- SOXUFMZTHZXOGC-UHFFFAOYSA-N [Li].[Mn].[Co].[Ni] Chemical compound [Li].[Mn].[Co].[Ni] SOXUFMZTHZXOGC-UHFFFAOYSA-N 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000005856 abnormality Effects 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000010280 constant potential charging Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- SXLDJBWDCDALLM-UHFFFAOYSA-N hexane-1,2,6-tricarbonitrile Chemical compound N#CCCCCC(C#N)CC#N SXLDJBWDCDALLM-UHFFFAOYSA-N 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Images
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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
- 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
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
-
- 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
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
-
- 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
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0568—Liquid materials characterised by the solutes
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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
- 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
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0569—Liquid materials characterised by the solvents
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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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
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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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
- H01M2300/00—Electrolytes
- H01M2300/0088—Composites
- H01M2300/0091—Composites in the form of mixtures
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- 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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- 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
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Abstract
The invention relates to an electrolyte for a lithium ion battery and the lithium ion battery comprising the same, wherein the electrolyte for the lithium ion battery comprises the following components in percentage by weight: 10-18% of lithium hexafluorophosphate, 0.2-2.0% of lithium difluorophosphate, 0.2-1.5% of lithium difluorooxalato borate, 5-15% of ethyl propionate, 30-50% of dimethyl carbonate, 10-20% of diethyl carbonate, 15-30% of ethyl methyl carbonate, 0.5-5% of ethylene carbonate and 1.5-5% of fluoroethylene carbonate. The lithium ion battery comprises a positive plate, a negative plate, a diaphragm and the electrolyte, wherein the positive plate comprises a positive active substance, the positive active substance is at least one of lithium manganate, lithium cobaltate and lithium nickel cobalt manganate, and the granularity is 6-11 microns. The battery does not generate lithium precipitation when charged at the temperature of minus 30 ℃, has better low-temperature performance, can be suitable for the temperature of minus 40 ℃, and has a stable discharging platform.
Description
Technical Field
The invention relates to the technical field of low-temperature lithium ion batteries, in particular to an electrolyte for a lithium ion battery and the lithium ion battery comprising the same.
Background
When the lithium ion battery is charged, lithium ions are extracted from the positive electrode and are inserted into the negative electrode; but when some abnormal conditions: when abnormality occurs such as the space for lithium insertion into the negative electrode is insufficient, the resistance for lithium ion insertion into the negative electrode is too large, and lithium ions are too rapidly extracted from the positive electrode but cannot be equally inserted into the negative electrode, the lithium ions which cannot be inserted into the negative electrode can only obtain electrons on the surface of the negative electrode, so that a silvery white metallic lithium simple substance, which is also called "lithium precipitation", is formed. Many factors are involved in lithium precipitation, such as electrolyte wetting problems, lithium battery capacity grading, cell deformation, etc.
Active materials such as lithium manganate, lithium cobaltate, and lithium nickel cobalt manganate, which are typically used, are subject to lithium precipitation during charging at low temperature, for example, at-20 ℃, and the power during discharging is reduced, which results in limited application of lithium ion batteries at low temperature. For example, the invention patent CN108878976B discloses a silicon-carbon system lithium ion battery electrolyte, which comprises an organic solvent, an electrolyte lithium salt and an additive, wherein the additive is composed of a nitrile compound, propylene sulfite, a tetramethyldiamine compound and fluoroethylene carbonate; the mass percentage content of the nitrile compound in the electrolyte is 0.5-5%; the mass percentage content of the propylene sulfite in the electrolyte is 0.5-10%; the mass percentage of the tetramethyldiamine compound in the electrolyte is 1-30%; the nitrile compound is hexanetricarbonitrile; the tetramethyldiamine compound is tetramethylhexanediamine. The lithium ion battery prepared by the scheme has a general capacity retention effect at the temperature of-30 ℃, and cannot be suitable for a lower use temperature.
Disclosure of Invention
The invention aims to overcome the problem that lithium is easy to precipitate under low temperature conditions in the conventional lithium ion battery, and provides an electrolyte for the lithium ion battery and the lithium ion battery comprising the same.
At low temperature, the ion conductivity of the electrolyte decreases, the resistance of lithium ions to be extracted from the positive electrode and to be inserted into the negative electrode increases greatly, and the resistance of the inserted negative electrode increases more greatly, thereby inducing lithium precipitation. Therefore, the optimization design of the electrolyte is one of the keys for solving the problem of low-temperature lithium precipitation of the lithium ion battery.
The invention provides an electrolyte, which has high lithium ion conduction rate, and when the lithium ion is discharged at the temperature of minus 30 ℃, the lithium ion can be stably embedded into a negative electrode through the boosting action of the electrolyte, so that better capacity retention rate is ensured.
The invention also provides a battery, which comprises the electrolyte, preferably at least one of lithium manganate, lithium cobaltate and nickel cobalt lithium manganate is taken as a positive electrode active substance, the particle size is 6-11 microns, and the battery has a good matching effect with the electrolyte. The positive active material is mixed with a conductive agent and a binder and then coated on a positive metal foil, and the coating thickness is 160-220 g/m2Rolling, cutting and welding the tabs to obtain the positive plate with the compacted density of 2.8-3.5g/cm3. The migration speed of the active lithium source in the positive plate can reach a better state under a specific thickness and compaction density.
For the negative plate, as the main substances are different from the positive plate, graphite, a conductive agent and a binder are mixed and stirred according to the mass ratio and then coated on the negative metal foil, and the coating thickness is 80-120 g/m2Rolling, cutting and welding the pole ear to obtain the negative plate with the compacted density of 1.3-1.55g/cm3. Under the conditions of the thickness and the compaction density, the lithium source can be more easily inserted and can keep higher structural stability after the subsequent lithium source is removed.
The specific scheme is as follows:
the electrolyte for the lithium ion battery comprises the following components in percentage by weight: 10-18% of lithium hexafluorophosphate, 0.2-2.0% of lithium difluorophosphate, 0.2-1.5% of lithium difluorooxalato borate, 5-15% of ethyl propionate, 30-50% of dimethyl carbonate, 10-20% of diethyl carbonate, 15-30% of ethyl methyl carbonate, 0.5-5% of ethylene carbonate and 1.5-5% of fluoroethylene carbonate.
Further, the paint comprises the following components in percentage by weight: 15-17% of lithium hexafluorophosphate, 1-2.0% of lithium difluorophosphate, 1-1.5% of lithium difluorooxalato borate, 5-15% of ethyl propionate, 30-42% of dimethyl carbonate, 10-20% of diethyl carbonate, 23-30% of ethyl methyl carbonate, 1-5% of ethylene carbonate and 2-5% of fluoroethylene carbonate.
The invention also provides a lithium ion battery, which comprises a positive plate, a negative plate and a diaphragm, wherein the diaphragm is positioned between the positive plate and the negative plate, the lithium ion battery contains the electrolyte for the lithium ion battery, the positive plate comprises a positive active substance, the positive active substance is at least one of lithium manganate, lithium cobaltate and lithium nickel cobalt manganate, and the granularity is 6-11 microns.
Further, the preparation method of the positive plate comprises the following steps: and (2) mixing the positive electrode active material, the conductive agent and the binder according to a mass ratio of (93-96): (0.5-2.5): (1.5-4.5) mixing and stirring, and coating on the positive electrode metal foil, wherein the coating thickness is 160-220 g/m2Rolling, cutting and welding the tabs to obtain the positive plate with the compacted density of 2.8-3.5g/cm3。
Furthermore, the positive metal foil is an aluminum foil, and the thickness of the positive metal foil is 12-20 microns.
Further, the preparation method of the negative plate comprises the following steps: graphite, a conductive agent and a binder are mixed according to the mass ratio (93.5-95): (0.5-1.5): (2.0-4.0) mixing and stirring, and coating on a negative electrode metal foil, wherein the coating thickness is 80-120 g/m2Rolling, cutting and welding the pole ear to obtain the negative plate with the compacted density of 1.3-1.55g/cm3。
Furthermore, the negative metal foil is a copper foil, and the thickness of the negative metal foil is 8-16 microns.
Further, the conductive agent is at least one of carbon black and carbon nano tubes; the binder is acrylate or an acrylate derivative.
Further, the diaphragm is a polyethylene polymer film, and the porosity is 42-55%.
Furthermore, the lithium ion battery does not generate a lithium precipitation phenomenon after being charged and discharged for 100 times at the temperature of between 30 ℃ below zero and 25 ℃, and has a stable discharge platform at the temperature of between 40 ℃ below zero.
Has the advantages that: the invention provides an electrolyte for a lithium ion battery, which can be used at a lower temperature, and is characterized in that the electrolyte formula is optimized, lithium difluorophosphate and lithium difluorooxalato borate are matched with an electrolyte system of lithium hexafluorophosphate, so that positive active substances such as lithium manganate, lithium cobaltate, lithium nickel cobalt manganese and the like can reach a negative electrode easily through the mass transfer effect of the electrolyte in the charging process, and the normal charging and discharging at the temperature of-30 ℃ can be realized without lithium precipitation.
Furthermore, the thickness and the compaction density are ensured by optimizing the preparation process of the positive plate and the negative plate, so that lithium ions are easy to be embedded and separated, and the pole piece has a stable structure and a better capacity keeping effect.
Drawings
In order to illustrate the technical solution of the present invention more clearly, the drawings will be briefly described below, and it is apparent that the drawings in the following description relate only to some embodiments of the present invention and are not intended to limit the present invention.
FIG. 1 is a graph of a battery discharge provided by one embodiment of the present invention;
fig. 2 is a graph of a battery charge curve provided by an embodiment of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available. In the following examples, "%" means weight percent, unless otherwise specified.
Example 1
A lithium ion battery comprises a positive plate, a negative plate and a diaphragm, wherein the diaphragm is positioned between the positive plate and the negative plate, the lithium ion battery is filled with electrolyte, the composition of the electrolyte is shown in a table 1, and the lithium ion battery is prepared by weighing raw materials according to weight percentage, mixing and stirring for equalizing price.
The preparation method of the positive plate comprises the following steps: mixing a positive electrode active substance, a conductive agent and a binder according to a mass ratio of 94: 2: 4 mixing and stirring, coating on aluminum foil, wherein the coating thickness is 200g/m2Rolling, cutting and welding the tabs to obtain the positive plate with the compacted density of 3.0g/cm3. Wherein the positive active substance is lithium manganate, lithium cobaltate and lithium nickel cobalt manganate which are mixed according to the mass ratio of 1:1, and the granularity of the positive active substance is 8-9 microns; the conductive agent comprises carbon black and carbon nano tubes which are mixed according to the mass ratio of 1: 1; the adhesive is acrylate and derivatives thereof; the thickness of the aluminum foil is 15 microns.
And (3) negative plate: graphite, a conductive agent and a binder are mixed according to the mass ratio of 95: 1: 4 mixing and stirring the mixture, and coating the mixture on a copper foil, wherein the thickness of the coating is 100g/m2Rolling, cutting and welding the pole ear to obtain the negative pole piece with the compacted density of 1.40g/cm3. Wherein the conductive agent comprises carbon black and carbon nano tubes which are mixed according to the mass ratio of 1: 1; the adhesive is acrylate and derivatives thereof; the copper foil thickness was 10 microns.
The polyethylene polymer film is used as a diaphragm, and the porosity is 42-43%. And sequentially laminating and winding the positive plate, the diaphragm and the negative plate into a circle to obtain a bare cell, packaging by a steel shell, baking, injecting the prepared electrolyte, sealing, standing, forming and finishing the manufacture of the lithium ion battery.
TABLE 1 electrolyte raw material proportioning table (wt%)
Examples 2 to 5
The lithium ion battery was prepared by using the raw materials in the electrolyte in the amounts shown in Table 1, and the other preparation methods were the same as in example 1.
Comparative examples 1 to 2
Comparative batteries were prepared using the electrolyte raw materials in the amounts shown in Table 1, and the remaining preparation methods were the same as in example 1.
Performance testing
The prepared batteries were subjected to charge and discharge tests, and the batteries manufactured in example 1, comparative example 1 and comparative example 2 were selected and tested at-40 ℃, -30 ℃, -20 ℃, -10 ℃ and 20 ℃, respectively, and were charged at a constant current of 0.5C to 4.2V, then changed to constant voltage charging until the current was less than 0.02C, and then discharged at a current of 0.5C to 2.5V, and cycled for 100 times.
After the circulation is finished, the battery is fully charged, the battery is dissected, the lithium precipitation condition on the surface of the negative electrode is observed, the lithium precipitation condition of the battery is shown in table 2, and the lithium ion battery obtained in the example 1 does not generate the lithium precipitation phenomenon after being charged and discharged for 100 times at the temperature of between 30 ℃ below zero and 25 ℃.
TABLE 2 lithium precipitation during charging and discharging at different temperatures
The discharge curve and the charge curve of the battery at different temperatures are respectively shown in fig. 1 and fig. 2, and it can be seen from fig. 1 and fig. 2 that the battery prepared in example 1 has stable charge and discharge platforms at-30 ℃, -20 ℃, -10 ℃, and the battery can be continuously discharged at-40 ℃ to normally operate.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (10)
1. An electrolyte for a lithium ion battery, characterized in that: the composition comprises the following components in percentage by weight: 10-18% of lithium hexafluorophosphate, 0.2-2.0% of lithium difluorophosphate, 0.2-1.5% of lithium difluorooxalato borate, 5-15% of ethyl propionate, 30-50% of dimethyl carbonate, 10-20% of diethyl carbonate, 15-30% of ethyl methyl carbonate, 0.5-5% of ethylene carbonate and 1.5-5% of fluoroethylene carbonate.
2. The electrolyte for a lithium ion battery according to claim 2, characterized in that: the composition comprises the following components in percentage by weight: 15-17% of lithium hexafluorophosphate, 1-2.0% of lithium difluorophosphate, 1-1.5% of lithium difluorooxalato borate, 5-15% of ethyl propionate, 30-42% of dimethyl carbonate, 10-20% of diethyl carbonate, 23-30% of ethyl methyl carbonate, 1-5% of ethylene carbonate and 2-5% of fluoroethylene carbonate.
3. The utility model provides a lithium ion battery, includes positive plate, negative pole piece and diaphragm, the diaphragm is located positive plate with between the negative pole piece, its characterized in that: the lithium ion battery contains the electrolyte for the lithium ion battery of claim 1 or 2, the positive plate comprises a positive active material, and the positive active material is at least one of lithium manganate, lithium cobaltate and lithium nickel cobalt manganate, and has a particle size of 6-11 microns.
4. The lithium ion battery of claim 3, wherein: the preparation method of the positive plate comprises the following steps: and (2) mixing the positive electrode active material, the conductive agent and the binder according to a mass ratio of (93-96): (0.5-2.5): (1.5-4.5) mixing and stirring, and coating on the positive electrode metal foil, wherein the coating thickness is 160-220 g/m2Rolling, cutting and welding the tabs to obtain the positive plate with the compacted density of 2.8-3.5g/cm3。
5. The lithium ion battery of claim 4, wherein: the positive metal foil is an aluminum foil, and the thickness of the positive metal foil is 12-20 microns.
6. The lithium ion battery according to any one of claims 3 to 5, wherein: the preparation method of the negative plate comprises the following steps: graphite, a conductive agent and a binder are mixed according to the mass ratio (93.5-95): (0.5-1.5): (2.0-4.0) mixing and stirring, and coating on a negative electrode metal foil, wherein the coating thickness is 80-120 g/m2Rolling, cutting and welding the pole ear to obtain the negative plate with the compacted density of 1.3-1.55g/cm3。
7. The lithium ion battery of claim 6, wherein: the negative metal foil is a copper foil, and the thickness of the negative metal foil is 8-16 microns.
8. The lithium ion battery according to claim 4 or 5, wherein: the conductive agent is at least one of carbon black and carbon nano tubes; the binder is acrylate or an acrylate derivative.
9. The lithium ion battery according to any one of claims 3 to 5, wherein: the diaphragm is a polyethylene polymer film, and the porosity is 42-55%.
10. The lithium ion battery according to any one of claims 3 to 5, wherein: the lithium ion battery does not generate a lithium precipitation phenomenon after being charged and discharged for 100 times at a temperature of between 30 ℃ below zero and 25 ℃, and has a stable discharge platform at a temperature of between 40 ℃ below zero.
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