CN113782828A - High-temperature-resistant and high-voltage-resistant lithium ion battery electrolyte and preparation method and application thereof - Google Patents
High-temperature-resistant and high-voltage-resistant lithium ion battery electrolyte and preparation method and application thereof Download PDFInfo
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 90
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 28
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 27
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 28
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 27
- 150000003839 salts Chemical class 0.000 claims abstract description 25
- 239000003960 organic solvent Substances 0.000 claims abstract description 19
- 238000004770 highest occupied molecular orbital Methods 0.000 claims abstract description 9
- 238000000034 method Methods 0.000 claims abstract description 7
- 230000008569 process Effects 0.000 claims abstract description 7
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 claims description 25
- -1 lithium hexafluorophosphate Chemical compound 0.000 claims description 22
- 229910052744 lithium Inorganic materials 0.000 claims description 15
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 13
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 12
- 239000002904 solvent Substances 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 9
- 150000005676 cyclic carbonates Chemical class 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 9
- 239000002808 molecular sieve Substances 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 7
- 239000003795 chemical substances by application Substances 0.000 claims description 6
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical group [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 6
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical group O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 2
- WXNUAYPPBQAQLR-UHFFFAOYSA-N B([O-])(F)F.[Li+] Chemical compound B([O-])(F)F.[Li+] WXNUAYPPBQAQLR-UHFFFAOYSA-N 0.000 claims 2
- 235000002639 sodium chloride Nutrition 0.000 abstract description 23
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 abstract description 17
- 230000014759 maintenance of location Effects 0.000 abstract description 11
- 229910052759 nickel Inorganic materials 0.000 abstract description 11
- 230000001351 cycling effect Effects 0.000 abstract description 9
- 239000007774 positive electrode material Substances 0.000 abstract description 7
- 229910052796 boron Inorganic materials 0.000 abstract description 5
- 229910052731 fluorine Inorganic materials 0.000 abstract description 5
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 abstract description 4
- 239000011780 sodium chloride Substances 0.000 abstract description 4
- 230000002427 irreversible effect Effects 0.000 abstract description 3
- 229910052698 phosphorus Inorganic materials 0.000 abstract description 3
- 230000007704 transition Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 19
- 239000000654 additive Substances 0.000 description 8
- 230000000996 additive effect Effects 0.000 description 8
- 238000002156 mixing Methods 0.000 description 8
- 238000012360 testing method Methods 0.000 description 5
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical group CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
- 239000003990 capacitor Substances 0.000 description 4
- VYFYYTLLBUKUHU-UHFFFAOYSA-N dopamine Chemical compound NCCC1=CC=C(O)C(O)=C1 VYFYYTLLBUKUHU-UHFFFAOYSA-N 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- NDZWKTKXYOWZML-UHFFFAOYSA-N trilithium;difluoro oxalate;borate Chemical compound [Li+].[Li+].[Li+].[O-]B([O-])[O-].FOC(=O)C(=O)OF NDZWKTKXYOWZML-UHFFFAOYSA-N 0.000 description 4
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- 239000002033 PVDF binder Substances 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 238000000840 electrochemical analysis Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 description 2
- 229910013872 LiPF Inorganic materials 0.000 description 2
- 101150058243 Lipf gene Proteins 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 229960003638 dopamine Drugs 0.000 description 2
- 239000008151 electrolyte solution Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- XSUMSESCSPMNPN-UHFFFAOYSA-N propane-1-sulfonate;pyridin-1-ium Chemical compound C1=CC=NC=C1.CCCS(O)(=O)=O XSUMSESCSPMNPN-UHFFFAOYSA-N 0.000 description 2
- 239000011833 salt mixture Substances 0.000 description 2
- 125000001424 substituent group Chemical group 0.000 description 2
- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical compound O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 description 1
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 229910004761 HSV 900 Inorganic materials 0.000 description 1
- 229910013706 LiNixMnyCozO2 (NMC) Inorganic materials 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000006056 electrooxidation reaction Methods 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- OUZJBBOOILNOCJ-UHFFFAOYSA-M lithium;difluoro phosphate Chemical compound [Li+].FOP(=O)([O-])OF OUZJBBOOILNOCJ-UHFFFAOYSA-M 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical group C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000012982 microporous membrane Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 150000002989 phenols Chemical class 0.000 description 1
- 125000004437 phosphorous atom Chemical group 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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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
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Secondary Cells (AREA)
Abstract
The invention belongs to the field of lithium ion batteries, and particularly relates to a high-temperature-resistant and high-voltage-resistant lithium ion battery electrolyte and a preparation method and application thereof. The electrolyte comprises electrolyte salt and an organic solvent, wherein the electrolyte salt is mixed lithium salt, the HOMO energy level of the mixed lithium salt is higher than that of the organic solvent, and the mixed lithium salt can be decomposed on the surface of a positive electrode in the charging process to form an inorganic component interface film. According to the electrolyte disclosed by the invention, a high-voltage-resistant interface film containing F, B and P can be formed on the positive electrode by using the mixed lithium salt, the irreversible transition of a high-nickel ternary positive electrode active material from a layered state to an inert rock salt phase under high voltage can be inhibited, so that the cycling stability of the lithium ion battery under the high cut-off voltage of 4.7V at normal temperature is improved, the capacity retention ratio is still 92% after the lithium ion battery is cycled for 180 times under the high cut-off voltage of 4.7V, and the cycling stability of the lithium ion battery under the high temperature of 45 ℃ and the high cut-off voltage of 4.5V can be improved.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a high-temperature-resistant and high-voltage-resistant lithium ion battery electrolyte and a preparation method and application thereof.
Background
Among the numerous positive electrode materials, the ternary material LiNixMnyCozO2(NMC) has excellent theoretical specific capacity (270mAh/g), and the high-nickel ternary positive electrode NMC811(x is approximately equal to 0.8) has excellent reversible capacity,excellent rate capability and satisfactory conductivity (about 2.8X 10)-5S/cm) and lithium ion mobility (about 10)-8-10-9cm2/s) to become one of the preferred positive electrode materials for commercial electric vehicles at present. However, increased nickel content, increased charge cut-off voltage, and increased temperature all make the high nickel ternary positive-electrolyte interface more susceptible to electrochemical oxidation, release of oxygen inside the cell causing capacity fade, and inter-particle cracking. Meanwhile, the Li/Ni cation mixed-discharging condition is particularly serious at the interface of the high-nickel anode material, which is also a great source of capacity attenuation of the battery. Therefore, it is an important step to design a high nickel positive electrolyte interface that can be stabilized at high temperature and high pressure.
CN 110994030 a discloses an electrolyte for lithium ion battery, which comprises organic solvent, lithium salt and additive, wherein the additive comprises fluoroethylene carbonate and one or more than two selected from pyridinium propanesulfonate, dopamine, lithium difluoro-oxalato-borate and lithium difluoro-phosphate. The synergistic effect of pyridinium propanesulfonate, dopamine, lithium difluoro-oxalato-borate and lithium difluoro-phosphate is utilized to replace the traditional propane sultone, the high-temperature storage and high-temperature cycle performance of the battery are improved, the low-temperature discharge capacity is greatly improved, and no harmful substance is generated; and simultaneously, the wettability of the electrolyte to an electrode material and a diaphragm is improved under a low-temperature condition by adopting ethyl acetate. However, the technical scheme mainly solves the problems of silicon-carbon cathode interface and high temperature at lower voltage, and does not relate to the interface of a cathode high-nickel ternary material at high voltage, the problem that the high-temperature performance attenuation of the battery is more serious at high voltage and the like.
CN111934009A discloses a high-voltage-resistant fast-charging lithium ion battery electrolyte and a preparation method and application thereof, wherein the electrolyte comprises electrolyte salt, an organic solvent, a first additive and a second additive, the first additive is functional lithium salt, the functional lithium salt contains fluorine and/or boron, the second additive is a phenol derivative at least containing one substituent, the substituent is positioned at the ortho position or the para position of phenolic hydroxyl, and the HOMO energy level of the second additive is higher than that of the electrolyte salt and the organic solvent. According to the technical scheme, the polymer capable of conducting lithium ions is prepared by oxidative polymerization of the organic monomer, and the polymer and the first additive act synergistically, so that the cycle performance and the rate performance of the lithium ion battery at the cut-off voltage of 4.5V are improved, but the cycle stability of the lithium ion battery at high temperature still has an improvement space.
In summary, the prior art still lacks a high-temperature and high-voltage resistant lithium ion battery electrolyte capable of solving the problem of the interface phase of the high-nickel ternary cathode material anode electrolyte.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the electrolyte with the mixed lithium salt as the electrolyte salt, the mixed lithium salt can be preferentially decomposed in a small amount to form an anode-electrolyte interface film, the problem of serious electrolyte decomposition under the high cut-off voltage of 4.7V can be solved, and the problem of more serious side reaction at the interface of the anode electrolyte under the high cut-off voltage of 4.5V and the high temperature of 45 ℃ can be solved, so that the cycle performance of the lithium ion battery under the high voltage/high temperature condition is improved. The detailed technical scheme of the invention is as follows.
In order to achieve the above object, according to one aspect of the present invention, there is provided an electrolyte for a lithium ion battery, comprising an electrolyte salt and an organic solvent, wherein the electrolyte salt is a mixed lithium salt, and the HOMO energy level of the mixed lithium salt is higher than that of the organic solvent, and the mixed lithium salt can be decomposed on the surface of a positive electrode during charging to form an inorganic component interface film.
Preferably, the lithium salt mixture includes lithium difluorooxalato borate (LiDFOB), lithium difluorophosphate (LiPO)2F2) And lithium hexafluorophosphate (LiPF)6)。
Preferably, the lithium difluorooxalato borate and lithium difluorophosphate (LiPO) are used2F2) And lithium hexafluorophosphate in a mass ratio of (5-10): (1-5):(1-5).
Preferably, the lithium difluorooxalato borate and lithium difluorophosphate (LiPO) are used2F2) And lithium hexafluorophosphate in a mass ratio of (4-6): (2-3) and more preferably 5: 2:3.
Preferably, the total concentration of the mixed lithium salt is 0.7-2 mol/L.
Preferably, the organic solvent comprises one or a mixture of two of a linear carbonate solvent and a cyclic carbonate solvent; the linear carbonate is one or more of diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate, and the cyclic carbonate is ethylene carbonate.
Preferably, the volume ratio of the linear carbonate to the cyclic carbonate is (4-7) to (6-3).
According to another aspect of the invention, the preparation method of the lithium ion battery electrolyte is provided, electrolyte salt is added into an anhydrous organic solvent and is uniformly stirred to obtain the electrolyte, and the adding sequence of the electrolyte salt is that lithium difluoro oxalate borate is added firstly, lithium difluoro phosphate is added after the mixture is stirred to be clear and transparent, and finally lithium hexafluorophosphate is added and is stirred to be clear and transparent.
Preferably, the anhydrous organic solvent is prepared by adding an organic solvent into a water removing agent and standing for 2-4 days, wherein the water removing agent is a molecular sieve with the model of
And
any one of the above types.
According to another aspect of the invention, the electrolyte is applied to a lithium ion battery, preferably a high-nickel ternary cathode material lithium ion battery.
The lithium salt mixture has high HOMO energy level and is decomposed preferentially at the interface of the positive electrode and the electrolyte in the first charging process by using an organic solvent to form an interface film with more inorganic components.
The HOMO is the highest occupied orbital of the molecule, and the higher the HOMO energy level, the more volatile the material is to remove electrons. For the electrolyte, the HOMO energy level can be used for judging the decomposition sequence of each component in the charging process, and the component with the higher HOMO energy level means that the component is easier to oxidize to form a positive electrolyte interface film, so that other components are prevented from directly contacting with the electrolyte in the subsequent charging and discharging processes, and the interface side reaction is inhibited.
The electrolyte salt is a mixed lithium salt, and comprises lithium difluoro oxalate borate (LiDFOB) and lithium difluoro phosphate (LiPO)2F2) Lithium hexafluorophosphate (LiPF)6). The mixed lithium salt forms an inorganic component interface phase, inhibits the decomposition of the solvent and the lithium salt in the subsequent circulation process, and enlarges the electrochemical window of the electrolyte. The interface film formed by the mixed lithium salt can prevent side reaction at the interface of the anode and the electrolyte under the conditions of high temperature and high pressure, and stabilize the interface of the anode and the electrolyte, thereby improving the cycling stability of the battery under the conditions of high temperature and high pressure.
First, a stable inorganic component interface phase containing F, B, P elements can be formed on the positive electrode, and the cycle performance of the battery under a high-voltage system (4.7V) can be remarkably improved.
Secondly, the interface phase has higher stability under the simultaneous action of high pressure and high temperature, and can improve the cycling stability of the lithium ion battery under the environment of high pressure of 4.5V and high temperature of 45 ℃.
Thirdly, the irreversible change of the high-nickel ternary positive electrode active material from a layered state to an inert rock salt phase under a high voltage/high temperature environment can be inhibited, and Ni in the positive electrode material is protected by an interface film4+Can not be in direct contact with the electrolyte, and avoids Ni4+Reacting with electrolyte to convert into rock salt phase NiO.
The NCM811/Li battery assembled by the electrolyte can still have a capacity retention rate of 92% after being cycled for 180 times under a high cut-off voltage of 4.7V, can realize a capacity retention rate of 81% after being cycled for 130 times under a high temperature environment of 45 ℃ under a high cut-off voltage of 4.5V, and has a wide market application prospect.
The structural formula of the mixed lithium salt is shown as follows:
as shown above, lithium difluorooxalato borate (I-1), lithium difluorophosphate (I-2) and lithium hexafluorophosphate (I-3) are excellent in film-forming stability, and F, B, P atoms are allowed to react with Li+And the components and properties of the interfacial film are optimized.
The invention has the following beneficial effects:
(1) according to the electrolyte disclosed by the invention, a high-voltage-resistant interface film containing F, B, P can be formed on the positive electrode by using the mixed lithium salt, and the irreversible transition of a high-nickel ternary positive electrode active material from a layered state to an inert rock salt phase under high voltage can be inhibited, so that the cycling stability of the lithium ion battery under the high cut-off voltage of 4.7V at normal temperature is improved, and the capacity retention rate is still 92% after 180 cycles under the high cut-off voltage of 4.7V.
(2) The electrolyte disclosed by the invention has higher stability under the simultaneous action of high voltage and high temperature, can improve the cycling stability of the lithium ion battery under the environment of high voltage of 4.5V and high temperature of 45 ℃, and can realize that the capacity retention rate reaches 81% after 130 times of cycling under the environment of high cut-off voltage of 4.5V and high temperature of 45 ℃.
(3) The preparation method of the electrolyte provided by the invention is simple in process, strong in operability and convenient for practical popularization and large-scale application.
Drawings
FIG. 1 is a graph comparing the cycle performance at 2.7-4.7V of the high temperature, high pressure electrolyte prepared in example 7 of the present invention and a base electrolyte battery.
Fig. 2 is a graph comparing the cycle performance of the high-temperature, high-pressure electrolyte prepared in example 7 of the present invention and the basic electrolyte battery at a high temperature of 45 c at 2.7-4.5V.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Examples
Preparation examples
Preparing the organic solvent. Mixing linear carbonate solvent and cyclic carbonate solvent in a volume ratio of 1:1 in an inert gas-protected glove box, adding the mixture after mixing
And standing the molecular sieve water removing agent for 2 days, then adding lithium hexafluorophosphate, uniformly stirring, controlling the final concentration of the lithium hexafluorophosphate to be 1.0mol/L, marking the lithium hexafluorophosphate as basic electrolyte, wherein the water content in the glove box is less than 0.1ppm, and the oxygen content is less than 0.1 ppm.
The molecular sieve water remover is Alfa L05335-250 g.
Examples of the invention
The mixed lithium salt of the embodiment of the invention is shown in formula I-1, formula I-2 and formula I-3, and the specific structural formula is shown in the specification.
Example 1
Mixing linear carbonate solvent and cyclic carbonate solvent in a volume ratio of 1:1 in an inert gas-protected glove box, adding the mixture after mixing
And (2) standing for 2 days, adding lithium difluoro (oxalate) borate, controlling the concentration of the lithium difluoro (oxalate) borate to be 0.5mol/L, stirring until the solution is clear and transparent, adding lithium difluoro (phosphate) I-2 with the concentration of 0.1mol/L, finally adding 0.1mol/L lithium hexafluorophosphate (I-3), stirring until the solution is clear and transparent, and uniformly mixing to obtain a finished product. The water content in the glove box is less than 0.1ppm, and the oxygen content is less than 0.1 ppm.
The molecular sieve water remover is Alfa L05335-250 g.
Inventive examples 2 to 15 and comparative example were prepared in a manner different from that of example 1 in the kind and concentration of the electrolyte salt used, and for the sake of simplicity of description, the details are shown in table 1.
TABLE 1 complete parameter table of the example
| Examples | Concentration of electrolyte salt (I-1) | Concentration of electrolyte salt (I-2) | Electrolyte salt (I-3) concentration |
| Example 1 | 0.5M | 0.1M | 0.1M |
| Example 2 | 0.5M | 0.2M | 0.1M |
| Example 3 | 0.5M | 0.3M | 0.1M |
| Example 4 | 0.5M | 0.4M | 0.1M |
| Example 5 | 0.5M | 0.5M | 0.1M |
| Example 6 | 0.5M | 0.2M | 0.2M |
| Example 7 | 0.5M | 0.2M | 0.3M |
| Example 8 | 0.5M | 0.2M | 0.4M |
| Example 9 | 0.5M | 0.2M | 0.5M |
| Example 10 | 0.6M | 0.2M | 0.2M |
| Example 11 | 0.6M | 0.2M | 0.3M |
| Example 12 | 0.8M | 0.2M | 0.2M |
| Example 13 | 0.8M | 0.2M | 0.3M |
| Example 14 | 1.0M | 0.2M | 0.2M |
| Example 15 | 1.0M | 0.2M | 0.3M |
Comparative examples
Comparative example 1
Mixing linear carbonate solvent and cyclic carbonate solvent in a volume ratio of 1:1 in an inert gas-protected glove box, adding the mixture after mixing
And (3) standing the molecular sieve water removing agent for 2 days, then adding lithium difluoro (oxalato) borate (I-1), controlling the concentration of the lithium difluoro (oxalato) borate to be 0.8mol/L, and stirring until the solution is clear and transparent to obtain a finished product.
Comparative examples 2 to 10 were prepared in such a manner that the kind and content of the electrolyte salt used were different from those of comparative example 1, and details are shown in table 2 for the sake of simplicity of description.
TABLE 2 complete parameter table for comparative examples
| Examples | Concentration of electrolyte salt (I-1) | Concentration of electrolyte salt (I-2) | Electrolyte salt (I-3) concentration |
| Comparative example 1 | 0.8M | -- | -- |
| Comparative example 2 | 1.0M | -- | -- |
| Comparative example 3 | 0.6M | 0.2M | -- |
| Comparative example 4 | 0.6M | 0.3M | -- |
| Comparative example 5 | 0.6M | 0.4M | -- |
| Comparative example 6 | 0.6M | 0.5M | -- |
| Comparative example 7 | 0.6M | -- | 0.2M |
| Comparative example 8 | 0.6M | -- | 0.3M |
| Comparative example 9 | 0.6M | -- | 0.4M |
| Comparative example 10 | 0.6M | -- | 0.5M |
| Basic electrolyte | -- | -- | 1.0M |
Test examples
The base electrolyte, the electrolytes of the inventive example and the comparative example were fabricated into batteries, and electrochemical tests were performed, the test methods being as follows.
First, a positive electrode sheet is prepared. The positive electrode active material is LiNi0.8Co0.1Mn0.1O2(NCM811), the conductive agent is conductive carbon black (Super P, Timcal Ltd.), the binder is polyvinylidene fluoride (PVDF, HSV 900, Arkema), the dispersant is N-methyl-2-pyrrolidone (NMP), and the conductive agent is LiNi0.8Co0.1Mn0.1O2: super P: mixing and grinding PVDF (polyvinylidene fluoride) in a mass ratio of 7:2:1, coating the mixture on an aluminum foil, drying, rolling, punching to prepare an electrode plate, and controlling an active substance NCM811 on the surface of the electrode to be 2-4mg/cm2. And then, manufacturing a button cell in a glove box filled with argon, wherein the negative electrode is a lithium sheet, and the polypropylene microporous membrane is a diaphragm, and changing the electrolyte to obtain different cells for testing.
Electrochemical performance testing the novalr electrochemical tester was used. And (3) activating the half cell for 5 times by 0.2C circulation, and then circulating by adopting a current density of 1C, wherein the charging and discharging voltage range is 2.7-4.5/4.7V. The temperature is set to 25 ℃ at normal temperature and 45 ℃ at high temperature. The test data are detailed in tables 3 and 4, and fig. 1 and 2.
TABLE 3 electrochemical test data sheet of the examples
TABLE 4 electrochemical test data sheet of comparative example
Fig. 1 is a graph comparing the cycle performance of the high-temperature, high-pressure electrolyte prepared in example 7 of the present invention with that of a basic electrolyte battery at 2.7 to 4.7V, in which the basic electrolyte is labeled Baseline and the high-temperature/high-pressure electrolyte is labeled MLS.
Fig. 2 is a graph comparing the cycle performance of the high-temperature, high-pressure electrolyte prepared in example 7 of the present invention and the basic electrolyte battery at a high temperature of 45 c at 2.7-4.5V.
As can be seen from FIG. 1, in 180 cycles of high cut-off voltage of 4.7V, 1C rate, 25 ℃ and high pressure resistant electrolyte, the cycling stability of the battery assembled by the electrolyte is obviously better than that of the basic electrolyte; as can be seen from FIG. 2, in the high cut-off voltage of 4.5V, the multiplying power of 1C, the temperature of 45 ℃ and 130 cycles, the cycling stability of the battery assembled by the high-voltage resistant electrolyte is obviously better than that of the basic electrolyte; tables 3 and 4 show the comparison of the cycle performance of the battery under the action of the high-temperature and high-pressure resistant electrolyte and the basic electrolyte prepared by the invention, and the cycle performance is optimal when the lithium difluorooxalato borate, the lithium difluorophosphate and the lithium hexafluorophosphate are mixed and matched.
The comparison of examples 1 to 15 shows that, among them, example 7 is the most effective. The capacity retention rate of the high-voltage capacitor is still 92% after the high-voltage capacitor is cycled for 180 times under the high cut-off voltage of 4.7V, the capacity retention rate of the high-voltage capacitor is up to 81% after the high-voltage capacitor is cycled for 130 times under the ultrahigh cut-off voltage of 4.5V and the high temperature of 45 ℃, and the capacity retention rate is far higher than that of other comparative test examples.
In summary, it was found by comparison that an electrolyte solution using a mixed lithium salt (lithium difluorooxalato borate, lithium difluorophosphate, lithium hexafluorophosphate) as an electrolyte salt can improve the capacity retention of a battery at a high voltage of 4.7V and a battery at a high voltage of 4.5V and a high temperature of 45 ℃ in comparison with a base electrolyte solution, wherein the lithium difluorooxalato borate and the lithium difluorophosphate (LiPO)2F2) And lithium hexafluorophosphate in a mass ratio of (4-6): (2-3) the effect was good, and the battery having a lithium difluorooxalato borate content of 0.5M, a lithium difluorophosphate content of 0.2M and a lithium hexafluorophosphate content of 0.3M exhibited the best cycle stability. The capacity retention rate of the assembled NCM811/Li battery is still 92% after the assembled NCM811/Li battery is cycled for 180 times under the high cut-off voltage of 4.7V, and the capacity retention rate can reach 81% after the assembled NCM811/Li battery is cycled for 130 times under the high temperature environment of 4.5V and 45 ℃, and specific experimental data can be seen in tables 3 and 4 and attached figures 1 and 2.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. The electrolyte of the lithium ion battery comprises electrolyte salt and an organic solvent, and is characterized in that the electrolyte salt is mixed lithium salt, the HOMO energy level of the mixed lithium salt is higher than that of the organic solvent, and the mixed lithium salt can be decomposed on the surface of a battery anode in the charging process to form an inorganic component interface film.
2. The electrolyte of claim 1, wherein the mixed lithium salt comprises lithium difluorooxalato borate, lithium difluorophosphate, and lithium hexafluorophosphate.
3. The electrolyte according to claim 2, wherein the ratio of the amounts of the lithium difluoroborate, the lithium difluorophosphate and the lithium hexafluorophosphate is (5-10): (1-5):(1-5).
4. The electrolyte according to claim 3, wherein the ratio of the amounts of the lithium difluoroborate, the lithium difluorophosphate and the lithium hexafluorophosphate is (4-6): (2-3) and more preferably 5: 2:3.
5. The electrolyte of claim 3 or 4, wherein the total concentration of the mixed lithium salts is 0.7-2 mol/L.
6. The electrolyte of claim 1, wherein: the organic solvent comprises one or a mixture of two of linear carbonate solvent and cyclic carbonate solvent; the linear carbonate is one or more of diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate, and the cyclic carbonate is ethylene carbonate.
7. The electrolyte of claim 6, wherein the volume ratio of the linear carbonate to the cyclic carbonate is (4-7): (6-3).
8. The preparation method of the lithium ion battery electrolyte is characterized in that the electrolyte of any one of claims 1 to 7 can be obtained by adding electrolyte salt into an anhydrous organic solvent and uniformly stirring, wherein the electrolyte salt is added in the sequence of adding lithium difluorooxalato borate, stirring until the mixture is clear and transparent, then adding lithium difluorophosphate, finally adding lithium hexafluorophosphate and stirring until the mixture is clear and transparent.
9. The preparation method of claim 8, wherein the anhydrous organic solvent is prepared by adding a water removing agent into the organic solvent and standing for 2-4 days, wherein the water removing agent is a molecular sieve with the type of molecular sieve
And
any one of the above types.
10. Use of the electrolyte according to any of claims 1-7 in a lithium ion battery.
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| JPWO2017057588A1 (en) * | 2015-12-22 | 2018-08-23 | 宇部興産株式会社 | Non-aqueous electrolyte for lithium secondary battery or lithium ion capacitor and lithium secondary battery or lithium ion capacitor using the same |
| CN109921092A (en) * | 2019-03-06 | 2019-06-21 | 杉杉新材料（衢州）有限公司 | A kind of silicon-based anode non-aqueous electrolyte for lithium ion cell and the silicon-based anode lithium ion battery containing the electrolyte |
| CN110190332A (en) * | 2019-06-20 | 2019-08-30 | 东莞东阳光科研发有限公司 | Nickelic tertiary cathode material system battery electrolytic solution and lithium ion battery |
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| JPWO2017057588A1 (en) * | 2015-12-22 | 2018-08-23 | 宇部興産株式会社 | Non-aqueous electrolyte for lithium secondary battery or lithium ion capacitor and lithium secondary battery or lithium ion capacitor using the same |
| CN109921092A (en) * | 2019-03-06 | 2019-06-21 | 杉杉新材料（衢州）有限公司 | A kind of silicon-based anode non-aqueous electrolyte for lithium ion cell and the silicon-based anode lithium ion battery containing the electrolyte |
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