CN114388888B - Electrolyte, positive electrode, lithium ion battery and vehicle - Google Patents

Electrolyte, positive electrode, lithium ion battery and vehicle Download PDF

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CN114388888B
CN114388888B CN202011137656.XA CN202011137656A CN114388888B CN 114388888 B CN114388888 B CN 114388888B CN 202011137656 A CN202011137656 A CN 202011137656A CN 114388888 B CN114388888 B CN 114388888B
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electrolyte
lithium
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CN114388888A (en
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王海军
郝嵘
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BYD Co Ltd
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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
    • H01M10/0567—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
    • H01M10/052—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
    • H01M10/058—Construction or manufacture
    • 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
    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
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Abstract

The application discloses an electrolyte, a positive electrode, a lithium ion battery and a vehicle. The electrolyte comprises lithium salt, an organic solvent and an additive, wherein the additive comprises a first additive, the first additive is a phosphonated cyclic ether compound, and the structural formula of the phosphonated cyclic ether compound is as follows:
Figure DDA0002737258730000011
wherein n is more than or equal to 1 and less than or equal to 3, x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1; r is R 1 、R 2 、R 3 Are independently selected from hydrogen atom, halogen atom, C 1 ～C 5 Alkyl, C 2 ～C 5 Unsaturated hydrocarbon group, C 6 ～C 10 Aryl or C of (2) 7 ～C 10 One of the alkylaryl groups of (a); c (C) 1 ～C 5 Alkyl, C 2 ～C 5 Unsaturated hydrocarbon group, C 6 ～C 10 Aryl or C of (2) 7 ～C 10 The hydrogen atoms in the alkylaryl groups of (a) may be partially or fully substituted with substituents. The electrolyte has lower oxidation potential, and a stable interface protection film is preferentially formed on the surface of the positive electrode, so that the battery capacity, the cycle life and the like of the battery under high voltage are improved.

Description

Electrolyte, positive electrode, lithium ion battery and vehicle
Technical Field
The invention relates to the field of new energy sources, in particular to electrolyte, a positive electrode, a lithium ion battery and a vehicle.
Background
Lithium ion batteries are commonly used in the field of consumer electronics due to their high specific energy, long cycle life, and no memory effect. Along with the rapid development of new energy automobile industry, the demand for high-endurance power batteries is also higher and higher, and ways for increasing the energy density of the batteries are many, one of which is to increase the working voltage (> 4.2V) of the lithium ion batteries, but the circulation and storage stability of the existing lithium ion batteries under the high-voltage condition are poor. The electrolyte of the lithium ion battery is easily oxidized at the interface of the positive electrode material under high voltage to generate side reaction, so that the battery is inflated. The existing method promotes the generation of an interface protection film at the interface of a positive electrode by adding a functional additive into the electrolyte so as to improve the performance of the lithium ion battery.
However, the existing additive still has the defects that the film formation on the positive electrode is difficult or unstable, so that the side reaction of the electrolyte at the interface of the positive electrode cannot be reduced; and the occurrence of side reaction can promote metal ions to dissolve out from the positive electrode material and migrate to the negative electrode side through electrolyte, and destroy a solid electrolyte interface protection film (SEI) on the surface of the negative electrode, thereby leading to rapid attenuation of the capacity and the cycle life of the lithium ion battery and greatly limiting the application of the high-voltage lithium ion battery.
Disclosure of Invention
In view of the above-described drawbacks or deficiencies of the prior art, it is desirable to provide an electrolyte, a positive electrode, a lithium ion battery, and a vehicle.
In a first aspect, the present invention provides an electrolyte comprising: lithium salt, organic solvent and additive;
the additive comprises: a first additive;
the first additive is a phosphonated cyclic ether compound, and the structural formula of the phosphonated cyclic ether compound is as follows:
Figure BDA0002737258720000021
wherein n is more than or equal to 1 and less than or equal to 3, x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1;
R 1 、R 2 、R 3 are independently selected from hydrogen atom, halogen atom, C 1 ～C 5 Alkyl, C 2 ～C 5 Unsaturated hydrocarbon group, C 6 ～C 10 Or C of aryl or C of (C) 7 ～C 10 One of the alkylaryl groups of (a);
C 1 ～C 5 alkyl, C 2 ～C 5 Unsaturated hydrocarbon group, C 6 ～C 10 Aryl or C of (2) 7 ～C 10 The hydrogen atoms in the alkylaryl groups of (a) may be partially or fully substituted with substituents.
Preferably, the substituent includes at least one of a halogen atom, a cyano group, a carboxyl group, and a sulfonic acid group.
Preferably, the phosphonated cyclic ether compound is selected from at least one of the following compounds:
Figure BDA0002737258720000022
Figure BDA0002737258720000031
as a preferred embodiment, the additive further comprises: and the second additive is at least one selected from ethylene carbonate, fluoroethylene carbonate, ethylene carbonate, 1, 3-propane sulfonate lactone, 1, 3-propylene sultone, ethylene sulfate, lithium difluorophosphate, lithium difluorobisoxalato phosphate and lithium tetrafluorooxalato phosphate.
Preferably, the mass fraction of the first additive is 0.1% -10% based on the total mass of the electrolyte.
Preferably, the mass fraction of the first additive is 0.5% -5% based on the total mass of the electrolyte.
Preferably, the lithium salt is at least one selected from the group consisting of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalato borate, lithium bis (trifluoromethylsulfonyl) imide and lithium difluorosulfimide salts.
Preferably, the organic solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate, gamma-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate.
In a second aspect, the invention provides a positive electrode of a lithium ion battery, which comprises a positive electrode current collector and a positive electrode active material layer positioned on the surface of the positive electrode current collector, wherein an interface protection film is arranged on the surface of the positive electrode active material layer, and the interface protection film is obtained by electrolytic solution according to the first aspect.
In a third aspect, the present invention provides a lithium ion battery comprising: the electrolyte of the first aspect and/or the positive electrode of the second aspect.
In a fourth aspect, the present invention provides a vehicle comprising: the lithium ion battery of the third aspect.
The electrolyte provided by the application comprises the first additive, wherein the first additive is a phosphonated cyclic ether compound, the oxidation potential of the phosphonated cyclic ether compound is lower, the electrolyte is used in a lithium ion battery, a stable and excellent-uniformity interface protection film can be preferentially formed on the surface of the positive electrode in the battery formation stage, the formation of the interface protection film reduces the occurrence of side reaction between the electrolyte and the positive electrode active material, maintains the stability of an electrode/electrolyte interface, effectively inhibits the oxidative decomposition of the electrolyte under high voltage, improves the problem of expanding gas of the lithium ion battery, and is also beneficial to reducing the interface impedance of the positive electrode and improving the cycle performance of the battery under high voltage.
Detailed Description
The present application is described in further detail below with reference to examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention.
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present application will be described in detail with reference to examples.
In a first aspect, embodiments of the present invention provide an electrolyte comprising: lithium salt, organic solvent and additive;
the additive comprises: a first additive;
the first additive is a phosphonated cyclic ether compound, and the structural formula of the phosphonated cyclic ether compound is as follows:
Figure BDA0002737258720000051
wherein n is more than or equal to 1 and less than or equal to 3, x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1;
R 1 、R 2 、R 3 are independently selected from hydrogen atom, halogen atom, C 1 ～C 5 Alkyl, C 2 ～C 5 Unsaturated hydrocarbon group, C 6 ～C 10 Aryl or C of (2) 7 ～C 10 One of the alkylaryl groups of (a);
C 1 ～C 5 alkyl, C 2 ～C 5 Unsaturated hydrocarbon group, C 6 ～C 10 Aryl or C of (2) 7 ～C 10 The hydrogen atoms in the alkylaryl groups of (a) may be partially or fully substituted with substituents.
The phosphonated cyclic ether compound has lower oxidation potential, and can preferentially generate a compact and stable passivation film (also called an interface protection film) on the positive electrode of the lithium ion battery in the formation process of the lithium ion battery, so that the oxidation decomposition of electrolyte on the surface of the positive electrode under high voltage can be effectively inhibited, and the problem of high-temperature flatulence of the lithium ion battery can be improved; the stable interface protection film reduces the occurrence of side reaction between the electrolyte and the positive electrode active material, maintains the stability of the electrode/electrolyte interface, is beneficial to reducing the impedance of the positive electrode interface, and prevents metal ions in the positive electrode active material from dissolving out and migrating to the negative electrode side to damage the SEI film on the negative electrode side. Therefore, the electrolyte of the invention is beneficial to improving the cycle performance of the battery under high voltage.
The electrolyte can improve the performance of a lithium ion battery, and according to the analysis of a theoretical calculation combination test result, the phosphonated cyclic ether compound is possibly due to the fact that the phosphonated cyclic ether compound has a phosphono group and a cyclic ether bond, on one hand, the cyclic ether bond is very unstable and is easy to carry out ring opening reaction, so that the electrolyte can generate a stable and uniform interface protection film on the surface of the positive electrode under a lower oxidation potential, the electrolyte is inhibited from reacting with the positive electrode active material under a high voltage, the problem of expanding gas of the lithium ion battery is solved, and meanwhile, the stability of an electrode/electrolyte interface is maintained; on the other hand, the phosphono can be complexed with lithium salt commonly used in the electrolyte, so that the phosphono exists stably, side reactions of the battery caused by decomposition of the electrolyte are reduced, the stability of the electrolyte is improved, and the phosphono is beneficial to improving the ion conductivity of the interface protective film.
Further, the hydrogen atom in the alkane group, unsaturated hydrocarbon group, aryl group or alkylaryl group may be partially or wholly substituted with one or more of halogen atom, cyano group, carboxyl group, sulfonic group. In embodiments of the present invention, hydrogen atoms in the alkyl, unsaturated alkyl, aryl or alkylaryl groups may be partially or fully substituted, increasing the reactivity of the alkyl, unsaturated alkyl, aryl or alkylaryl groups. On one hand, the first additive is beneficial to generating an interface protection film on the positive electrode of the lithium ion battery, so that oxidative decomposition of electrolyte under high voltage and damage of an SEI film on the surface of the negative electrode are reduced; on the other hand, the halogen atom, cyano, carboxyl and sulfonic acid group have high bond energy, are not easy to oxidize, have good stability on the surface of the positive electrode, and have stronger coordination capacity, and can be combined with active sites (such as high-valence metal ions, such as nickel/cobalt/manganese and the like) on the surface of the electrode to mask the active ions on the surface of the positive electrode, so that the decomposition effect of the electrode on electrolyte is reduced.
Preferably, the phosphonated cyclic ether compounds of embodiments of the present invention are selected from at least one of the following compounds:
Figure BDA0002737258720000061
as a practical way, the additive further comprises: and a second additive selected from at least one of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), ethylene carbonate (VEC), 1,3 Propane Sultone (PS), 1, 3-propenesulfonic acid lactone (1, 3-PST), vinyl Sulfate (VS), lithium Difluorophosphate (LD), lithium difluorobis-oxalato phosphate (LDP), lithium tetrafluoro-oxalato phosphate (LTP).
The second additive in the electrolyte provided by the embodiment of the invention is mainly used for improving the film formation of the negative electrode, is beneficial to forming an SEI film with low impedance and high stability of a lithium ion battery at the negative electrode, has the insolubility of an organic solvent, can stably exist in an organic electrolyte solution, and can not pass through the SEI film, so that the co-intercalation of solvent molecules can be effectively prevented, the damage to electrode materials caused by the co-intercalation of the solvent molecules is avoided, and the cycle performance and the service life of the electrode are greatly improved.
As an achievable form, the lithium salt is at least one selected from the group consisting of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalato borate, lithium bis (trifluoromethylsulfonyl) imide and lithium difluorosulfimide salts;
as a practical form, the organic solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate, γ -butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate (EP), butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.
In the electrolyte provided by the embodiment of the invention, the first additive can preferentially generate a compact and stable passivation film (also called an interface protection film) on the positive electrode of the lithium ion battery in the formation process of the lithium ion battery, so that the oxidative decomposition of the electrolyte on the surface of the positive electrode under a high-voltage condition can be effectively inhibited, and the problem of high-temperature flatulence of the lithium ion battery can be improved; the stable interface protection film reduces the occurrence of side reaction between the electrolyte and the active material, maintains the stability of the electrode/electrolyte interface, is beneficial to reducing the positive interface impedance of the material in the circulation process, and simultaneously prevents metal ions in the positive active material from migrating to the negative side and damaging the SEI film on the negative side;
the second additive is mainly used for improving film formation of the negative electrode, is favorable for forming an SEI film with low impedance and high stability of the lithium ion battery at the negative electrode, has insolubility in an organic solvent, can exist stably in an organic electrolyte solution, and can not allow solvent molecules to pass through the SEI film, so that co-intercalation of the solvent molecules can be effectively prevented, damage to electrode materials caused by co-intercalation of the solvent molecules is avoided, and therefore, the cycle performance and the service life of the electrode are greatly improved.
In conclusion, the electrolyte provided by the invention can not be subjected to oxidative decomposition under high voltage of the lithium ion battery, and can generate an interface protection film on the positive electrode and the negative electrode, so that the cycle performance of the lithium ion battery under the high voltage condition is improved.
Further, the mass fraction of the first additive is 0.1% -10% based on the total mass of the electrolyte. Preferably, the mass fraction of the first additive is 0.5% -5%. The mass fraction range of the embodiment is favorable for forming a compact and stable interface protection film on the positive electrode, so that the interface protection can better prevent the dissolution of metal ions of the positive electrode, meanwhile, the occurrence of side reaction between the electrolyte and the active material is reduced, the stability of an electrode/electrolyte interface is maintained, and the performance of the lithium ion battery is further effectively improved.
In a second aspect, an embodiment of the present invention provides a positive electrode of a lithium ion battery, where the positive electrode of the lithium ion battery includes a positive electrode current collector and a positive electrode active material layer located on a surface of the positive electrode current collector, and the surface of the positive electrode active material layer has an interface protection film, where the interface protection film is obtained by electrolytic solution according to the first aspect. This positive electrode has all the features and advantages of the above-described electrolyte, and will not be described in detail herein.
In a third aspect, embodiments of the present invention provide a lithium ion battery. The lithium ion battery comprises the electrolyte of the first aspect and/or the positive electrode of the second aspect. Accordingly, the lithium ion battery has all of the features and advantages of the above-described electrolyte and/or the above-described positive electrode, and will not be described in detail herein. In general, the lithium ion battery has the characteristics of being capable of generating a stable and uniform interface protection film at the interface of the anode and the cathode, has good cycle performance under high voltage, and has the advantages of good stability, high coulombic efficiency and the like.
Wherein, the positive electrode active material of the lithium ion battery is selected from LiFe x Mn y M z PO 4 (0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.1, x+y+z=1, wherein M is at least one of Al, mg, ga, ti, cr, cu, zn, mo), li 3 V 2 (PO 4 ) 3 、Li 3 V 3 (PO 4 ) 3 、LiNi 0.5-x Mn 1.5-y M x+y O 4 (-0.1.ltoreq.x.ltoreq.0.5, 0.ltoreq.y.ltoreq.1.5, M is at least one of Li, co, fe, al, mg, ca, ti, mo, cr, cu, zn), liVPO 4 F、Li 1+x L 1-y-z M y N z O 2 (L, M, N may be at least one of Li, co, mn, ni, fe, al, mg, ga, ti, cr, cu, zn, mo, F, I, S, B, x is 0.1-0.2, y is 0-1, z is 0-1, y+z is 0-1.0), li 2 CuO 2 、Li 5 FeO 4 One or more of (a)
In a fourth aspect, the present invention provides a vehicle comprising the lithium ion battery of the third aspect. For example, a plurality of battery packs formed of the aforementioned lithium ion batteries may be included. Thus, the vehicle has all the features and advantages of the lithium ion battery described above, and will not be described in detail herein.
The present invention will be illustrated by the following examples, which are given for illustrative purposes only and are not intended to limit the scope of the present invention in any way, and unless otherwise specified, the conditions or procedures not specifically described are conventional and the reagents and materials employed are commercially available.
The lithium ion batteries of examples 1 to 16 and comparative examples 1 to 3 were prepared as follows:
(1) Preparation of electrolyte:
mixing ethylene carbonate and methyl ethyl carbonate according to a mass ratio of 3:7 to form a mixed solvent, and adding lithium hexafluorophosphate (LiPF) into the mixed solvent 6 ) And (3) adding an additive into the solution until the molar concentration is 1.0mol/L, and stirring the solution uniformly to obtain the electrolyte. The specific types and the contents of the additives used in the electrolyte are shown in table 1, wherein the proportion of the additives is the mass percentage of the total mass of the electrolyte.
(2) Preparation of a positive plate:
mixing ternary cathode material (NCM 523), super-P, CNT and PVDF according to the mass ratio of 96.5:1.2:1:1.3, dispersing the ternary cathode material in NMP, and stirring the mixture to be stable and uniform under the action of a vacuum stirrer to obtain cathode slurry; uniformly coating the anode slurry on aluminum foil with the thickness of 20 um; and (3) airing the aluminum foil at room temperature, transferring the aluminum foil into a blast oven at 110 ℃ for drying for 2 hours, and then carrying out cold pressing and slitting procedures to obtain the positive plate.
(3) Preparing a negative plate:
mixing artificial graphite, super-P, SBR and CMC according to the mass ratio of 95.5:1.5:1:2, and dispersing the mixture in deionized water to obtain a copper foil with negative electrode slurry of 10 um; and (3) airing the copper foil at room temperature, transferring the copper foil into a blast oven at 110 ℃ for drying for 2 hours, and then carrying out cold pressing and slitting procedures to obtain the negative plate.
(4) Preparation of a lithium ion battery:
the method comprises the steps of preparing a bare cell from a positive plate, a negative plate and a separation film through a winding process, filling the cell into an aluminum plastic film packaging shell, injecting electrolyte, sequentially sealing, and performing procedures of standing, hot-cold pressing, formation, capacity division and the like to prepare the lithium ion battery.
TABLE 1 specific types and contents of additives in examples 1 to 18 and comparative example 1
Figure BDA0002737258720000101
Figure BDA0002737258720000111
The performance test procedure and test results of the lithium ion battery are described below:
(1) Normal temperature cycle test
Charging the lithium ion battery to 4.2V at 25 ℃ under a constant current of 1C, charging the lithium ion battery to a cut-off current of 0.1C under a constant voltage, standing for 30min, discharging the lithium ion battery to 2.5V under a constant current of 1C, marking as a charge-discharge cycle, and performing 800-week cycle according to the conditions; capacity retention (%) = (discharge capacity at 800 th cycle/discharge capacity at first cycle) ×100% after 800 cycles/4.2V cycle of the lithium ion battery;
charging the lithium ion battery to 4.5V at 25 ℃ under a constant current of 1C, charging the lithium ion battery to a cut-off current of 0.1C under a constant voltage, standing for 30min, discharging the lithium ion battery to 2.5V under a constant current of 1C, marking as a charge-discharge cycle, and performing 800-week cycle according to the conditions; the capacity retention (%) = (discharge capacity at 800 th cycle/discharge capacity at first cycle) ×100% after 800 cycles/4.5V cycle of the lithium ion battery.
(2) High temperature cycle performance test
Charging the lithium ion battery to 4.5V at 45 ℃ with a constant current of 1C, charging at constant voltage until the cut-off current is 0.1C, standing for 30min, discharging to 2.5V with a constant current of 1C, marking as a charge-discharge cycle, and then carrying out 500-week cycle according to the conditions; capacity retention (%) = (discharge capacity at 500 th cycle/discharge capacity at first cycle) ×100% after 500 th cycle of the lithium ion battery;
(3) High temperature storage performance test
Charging the lithium ion battery to 4.5V at 25 ℃ with a constant current and a constant voltage of 1C, stopping at 0.1C, standing for 30min, discharging the lithium ion battery to 2.5V with a constant current of 1C, measuring the battery volume V0 before storage, transferring the battery to a high-temperature test cabinet, and storing for 7 days at 60 ℃; taking out the test battery after the storage is completed, standing at room temperature for 24 hours, measuring the volume V1 of the battery after the storage, discharging to 2.5V at a constant current of 1C, recording the discharge capacity C1, standing for 60 minutes, charging to 4.5V at a constant current and constant voltage of 1C, stopping at 0.1C, standing for 30 minutes, discharging to 2.5V at a constant current of 1C, and recording the discharge capacity C2;
capacity remaining rate (%) =c1/c0×100%;
capacity recovery (%) =c2/c0×100%;
the cell volume expansion (%) = [ (V1-V0)/V0 ]. Times.100%.
The structures of the lithium ion batteries of examples 1-18 and comparative example 1 tested according to the procedure and method described above are shown in table 2:
TABLE 2 test results for examples 1-18 and comparative example 1
Figure BDA0002737258720000121
Figure BDA0002737258720000131
According to the results shown in table 2:
compared with comparative example 1, the lithium ion batteries of examples 1 to 18 are greatly improved in normal temperature cycle, high temperature cycle, and high temperature storage performance.
Examples 1-8 show that the structural formula of the phosphonated cyclic ether compound is the influence of the compound I on the performance of a lithium ion battery, and the battery test result shows that the consumption of the phosphonated cyclic ether compound has a great influence on the performance of the battery. The appropriate amount of the phosphonated cyclic ether compound can form an interface protection film on the surface of the positive electrode, so that the electrolyte is prevented from being oxidized on the surface of the positive electrode, the transition metal ions are prevented from being dissolved out, the positive electrode cannot be effectively protected by the using amount of the phosphonated cyclic ether compound, the viscosity of the electrolyte is increased due to excessive additives, the polarization of a battery is increased, and the electrolyte has negative effects on the cycle performance.
The battery test results of examples 9, 10, 14 and 15 show that the combination of the phosphonated cyclic ether additive and different negative film forming additives has a significant effect on the electrical performance of the lithium ion battery, and the proper additive combination scheme has a certain effect on further improving the electrical performance of the lithium ion battery.
The electrolytes in examples 17 and 18 contained only the first additive, and comparative example 1 contained only the second additive, as can be seen from the results shown in table 2: the lithium ion batteries of example 17 and example 18 were superior to the performance of the lithium ion battery of comparative example 3 in terms of 800-cycle capacity retention at 25 ℃, 500-cycle capacity retention at 45 ℃, capacity retention, capacity recovery, and battery volume expansion, indicating that the first additive was able to improve the performance of the lithium ion battery.
According to examples 1 to 4 and comparative example 1, the capacity retention rates at 4.2V room temperature cycle 800 weeks are relatively close, but 4.5V room temperature cycle 800 weeks capacity retention rates examples 1 to 4 are far superior to comparative example 1; in addition, the difference of capacity retention rate of the two examples 10-13 and the comparative example 1 at the normal temperature cycle of 4.2V is smaller, but the capacity retention rate of the two examples 10-13 at the normal temperature cycle of 4.5V at 800 weeks is obviously improved compared with that of the comparative example 1, which shows that the cyclic performance of the lithium ion battery at high voltage can be obviously improved by adding the phosphonylated cyclic ether compound into the electrolyte.
Battery performance can also be reflected in the addition of the phosphonated cyclic ether compound or the negative electrode film forming additive alone according to example 1, example 17, example 18, and comparative example 1; no negative electrode film forming additive is used, and negative electrode surface side reaction is continuously carried out to cause the cycle failure of the battery; the absence of the phosphonylated cyclic ether additive, the inability of the positive electrode surface to effectively form a protective layer, can result in battery cycling or storage degradation.
The foregoing description is only of the preferred embodiments of the present application and is presented as a description of the principles of the technology being utilized. It will be appreciated by persons skilled in the art that the scope of the invention referred to in this application is not limited to the specific combinations of features described above, but it is intended to cover other embodiments in which any combination of features described above or equivalents thereof is possible without departing from the spirit of the invention. Such as the above-described features and technical features having similar functions (but not limited to) disclosed in the present application are replaced with each other.

Claims (11)

1. An electrolyte, comprising: lithium salt, organic solvent and additive;
the additive comprises: a first additive;
the first additive is a phosphonated cyclic ether compound, and the structural formula of the phosphonated cyclic ether compound is as follows:
Figure FDA0002737258710000011
wherein n is more than or equal to 1 and less than or equal to 3, x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1;
R 1 、R 2 、R 3 are independently selected from hydrogen atom, halogen atom, C 1 ～C 5 Alkyl, C 2 ～C 5 Unsaturated hydrocarbon group, C 6 ～C 10 Aryl or C of (2) 7 ～C 10 One of the alkylaryl groups of (a);
the C is 1 ～C 5 Alkyl radicals of (C) 2 ～C 5 Unsaturated hydrocarbon groups of (3), saidC 6 ～C 10 Or the aryl group of C 7 ～C 10 The hydrogen atoms in the alkylaryl groups of (a) may be partially or fully substituted with substituents.
2. The electrolyte according to claim 1, wherein the substituent includes at least one of a halogen atom, a cyano group, a carboxyl group, and a sulfonic acid group.
3. The electrolyte of claim 1, the phosphonated cyclic ether compound selected from at least one of the following:
Figure FDA0002737258710000012
Figure FDA0002737258710000021
4. the electrolyte of claim 1, wherein the additive further comprises: and the second additive is selected from at least one of vinylene carbonate, fluoroethylene carbonate, ethylene carbonate, 1, 3-propane sulfonate lactone, 1, 3-propylene sultone, vinyl sulfate, lithium difluorophosphate, lithium difluorobisoxalato phosphate and lithium tetrafluorooxalato phosphate.
5. The electrolyte of claim 1 wherein the first additive is present in an amount of 0.1% to 10% by mass based on the total mass of the electrolyte.
6. The electrolyte of claim 5 wherein the first additive is present in an amount of 0.5% to 5% by mass based on the total mass of the electrolyte.
7. The electrolyte of claim 1, wherein the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalato borate, lithium bis (trifluoromethylsulfonyl) imide, and lithium difluorosulfimide salts.
8. The electrolyte of claim 1, wherein the organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate, γ -butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.
9. A positive electrode of a lithium ion battery, characterized by comprising a positive electrode current collector and a positive electrode active material layer positioned on the surface of the positive electrode current collector, wherein the surface of the positive electrode active material layer is provided with an interface protection film, and the interface protection film is obtained by electrolytic liquefaction according to any one of claims 1-8.
10. A lithium ion battery, comprising: the electrolyte of any one of claims 1-8 and/or the positive electrode of claim 9.
11. A vehicle comprising the lithium-ion battery of claim 10.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6043341A (en) * 1997-08-04 2000-03-28 Eli Lilly & Co. Cyclic peptide antifungal agents
CN102639544A (en) * 2009-10-05 2012-08-15 陶氏环球技术有限责任公司 Process for manufacturing phosphate esters from phosphoryl chloride and monoalkyl ethers of glycols or polyglycols

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6043341A (en) * 1997-08-04 2000-03-28 Eli Lilly & Co. Cyclic peptide antifungal agents
CN102639544A (en) * 2009-10-05 2012-08-15 陶氏环球技术有限责任公司 Process for manufacturing phosphate esters from phosphoryl chloride and monoalkyl ethers of glycols or polyglycols

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