CN109994777B - Electrolyte solution and secondary battery - Google Patents
Electrolyte solution and secondary battery Download PDFInfo
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- CN109994777B CN109994777B CN201711475132.XA CN201711475132A CN109994777B CN 109994777 B CN109994777 B CN 109994777B CN 201711475132 A CN201711475132 A CN 201711475132A CN 109994777 B CN109994777 B CN 109994777B
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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
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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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- 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
- 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
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention provides an electrolyte and a secondary battery. The additives comprise a first additive with an oxidation potential of 4.5V-5.0V and a second additive. The invention can effectively improve the safety problem caused by the overcharge of the secondary battery, and simultaneously can reduce the direct current discharge resistance of the secondary battery and improve the power performance of the secondary battery.
Description
Technical Field
The invention relates to the field of batteries, in particular to an electrolyte and a secondary battery.
Background
In recent years, with the gradual depletion of fossil energy and the more serious global environmental pollution, new energy vehicles using rechargeable batteries as power systems are rapidly developed, and among them, power batteries are distinguished. The development of the new energy automobile industry has higher and higher requirements on energy density, power performance and safety of power batteries, which is a great challenge for traditional secondary batteries.
In order to increase the energy density of the secondary battery, the gram capacity of the positive electrode material is preferably increased, and the ternary positive electrode material is preferably used. However, ternary materials generate a significant amount of heat when overcharged. If the heat can not be dissipated in time, the internal temperature of the battery continuously rises, thermal runaway is easily caused, even safety accidents such as fire or explosion are caused, and great potential safety hazards are brought to new energy automobiles.
How to increase the energy density of the secondary battery while maintaining high safety of the secondary battery has been a common effort in the industry.
Disclosure of Invention
In view of the problems of the background art, an object of the present invention is to provide an electrolyte and a secondary battery, which can effectively improve the safety problem caused by overcharge of the secondary battery, and can reduce the dc discharge resistance of the secondary battery to improve the power performance of the secondary battery.
In order to achieve the above object, in one aspect of the present invention, there is provided an electrolyte solution including an electrolyte salt, an organic solvent, and an additive. The additives comprise a first additive with an oxidation potential of 4.5V-5.0V and a second additive. The first additive is selected from one or more compounds shown in formula 1, wherein in formula 1, substituent R is1、R2Each independently selected from alkyl of C1-C10, alkoxy of C1-C10, alkenyl of C2-C5, alkenyloxy of C2-C5,One of alkynyl of C2-C5, alkynyloxy of C2-C5, aryl of C6-C10 and aryloxy of C6-C10, and substituent R3One selected from C1-C10 alkyl, C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and a substituent R1、R2、R3The H in the above can be partially or completely substituted by one or more of F, Cl and Br. The second additive is one or more selected from compounds shown in formula 2, wherein in the formula 2, a substituent R4、R5、R6Each independently selected from one of C1-C12 alkyl, C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and a substituent R4、R5、R6The H can be partially or completely substituted by one or more of F, Cl and Br, and a substituent R4、R5、R6Two of them may also form a ring.
In another aspect of the present invention, there is provided a secondary battery including a positive electrode tab, a negative electrode tab, a separator, and the electrolyte according to one aspect of the present invention.
Compared with the prior art, the invention at least comprises the following beneficial effects:
the first additive and the second additive with the oxidation potential of 4.5V-5.0V are added into the electrolyte, so that the safety problem caused by overcharge of the secondary battery can be effectively improved, the direct-current discharge resistance of the secondary battery can be reduced, and the power performance of the secondary battery can be improved.
The electrolyte is particularly suitable for secondary batteries using a high nickel content positive electrode active material, can combine high energy density, high safety and excellent electrochemical performance of the secondary battery, and can be normally used in a low-temperature environment.
Detailed Description
The electrolyte and the secondary battery according to the present invention will be described in detail below.
First, the electrolytic solution according to the first aspect of the invention is explained.
The electrolyte according to the first aspect of the present invention includes an electrolyte salt, an organic solvent, and additives including a first additive having an oxidation potential of 4.5V to 5.0V and a second additive.
In the electrolyte of the first aspect of the present invention, the first additive is one or more selected from compounds represented by formula 1, wherein in formula 1, the substituent R is1、R2Each independently selected from one of C1-C10 alkyl, C1-C10 alkoxy, C2-C5 alkenyl, C2-C5 alkenyloxy, C2-C5 alkynyl, C2-C5 alkynyloxy, C6-C10 aryl and C6-C10 aryloxy, and a substituent R3One selected from C1-C10 alkyl, C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and a substituent R1、R2、R3H of the above (namely alkyl, alkoxy, alkenyl, alkenyloxy, alkynyl, alkynyloxy, aryl and aryloxy) can be partially or completely substituted by one or more of F, Cl and Br. In formula 1, the number of halogen atoms (F, Cl, Br) and their substitution positions are not particularly limited and can be selected according to actual needs.
In the electrolyte of the first aspect of the invention, the first additive with the oxidation potential of 4.5V-5.0V is an organic phosphite compound, and the oxidation potential of the organic phosphite compound is lower than that of an organic solvent, so that the compound can preferentially act on the surface of a positive electrode after being applied to a secondary battery, and is combined with oxygen on the surface of a positive electrode active material to form a protective layer on the surface of the positive electrode active material to inhibit the activity of the oxygen, and the compound can also absorb O released by the positive electrode active material2-、O2 2-And active oxygen is added to the positive electrode active material, thereby avoiding the release of active oxygen of the positive electrode active material and the irreversible oxidation of the active oxygen to the electrolyte, and further effectively improving the safety problem caused by the overcharge of the secondary battery. If the oxidation potential of the first additive is too high,the organic solvent cannot preferentially act on the surface of the positive electrode, and cannot serve the purpose of suppressing the action of oxygen on the surface of the positive electrode active material with the electrolyte, so that the oxidation potential of the first additive cannot be greater than 5.0V. If the oxidation potential of the first additive is too low, the film formation on the surface of the positive electrode is early and thick, resulting in an increase in the battery resistance, and the first additive is rapidly consumed, so that the oxygen release of the positive electrode active material does not function to absorb O released from the positive electrode active material2-、O2 2-Etc. are effective in improving the safety problem caused by overcharge of the secondary battery, and thus the oxidation potential of the first additive cannot be less than 4.5V.
In the electrolyte of the first aspect of the present invention, the first additive may be selected from trimethyl phosphite, triethyl phosphite, triisopropyl phosphite, tri-n-propyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triphenyl phosphite, trivinyl phosphite, triallyl phosphite, tridecyl phosphite, one or more of tris (trifluoromethyl) phosphite, tris (2,2,3, 3-tetrafluoropropyl) phosphite, tris (3,3, 3-trifluoropropyl) phosphite, tris (2, 2-difluorovinyl) phosphite, tris (1,1,1,3,3, 3-hexafluoro-2-propyl) phosphite, tris (2,2, 2-trifluoroethyl) phosphite, methyldiethoxyphosphine, dimethyl phenylphosphate, ethyldiethoxyphosphine and diisopropylphenylphosphate.
Preferably, in formula 1, the substituent R1、R2Each independently selected from one of C1-C10 alkyl, C1-C10 alkoxy, C2-C5 alkenyl, C2-C5 alkenyloxy, C2-C5 alkynyl, C2-C5 alkynyloxy, C6-C10 aryl and C6-C10 aryloxy and substituent R1、R2At least one of the substituents is selected from one of C1-C10 alkyl, C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and the substituent R1、R2The H in the above can be partially or completely substituted by one or more of F, Cl and Br. Specifically, the first additive can be one or more selected from methyl diethoxy phosphine, ethyl diethoxy phosphine, dimethyl phenyl phosphate and diisopropyl phenyl phosphateAnd (4) seed preparation.
Preferably, in formula 1, the substituent R1、R2Each independently selected from one of C2-C5 alkenyl, C2-C5 alkenyloxy, C2-C5 alkynyl, C2-C5 alkynyloxy, C6-C10 aryl and C6-C10 aryloxy, and a substituent R3One of C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and substituent R1、R2、R3H of the above (namely alkenyl, alkenyloxy, alkynyl, alkynyloxy, aryl and aryloxy) can be partially or completely substituted by one or more of F, Cl and Br. Specifically, the first additive can be one or more selected from triphenyl phosphite, triethylene phosphite and triallyl phosphite.
Preferably, in formula 1, R1、R2Each independently selected from one of C1-C10 fluorine-containing alkyl, C1-C10 fluorine-containing alkoxy, C2-C5 fluorine-containing alkenyl, C2-C5 fluorine-containing alkenyloxy, C2-C5 fluorine-containing alkynyl and C2-C5 fluorine-containing alkynyloxy, R is R3One selected from C1-C10 fluorine-containing alkyl, C2-C5 fluorine-containing alkenyl and C2-C5 fluorine-containing alkynyl. Fluorine atom can improve the oxidation resistance of the organic phosphite ester compound, so that the organic phosphite ester compound is not easily oxidized in the normal working process of the secondary battery, and the cycle life of the secondary battery is not influenced. Specifically, the first additive may be selected from one or more of the following compounds:
in the electrolyte solution of the first aspect of the present invention, a content of the first additive is less than or equal to 15% of a total weight of the electrolyte solution, preferably, a content of the first additive is 0.1% to 15% of the total weight of the electrolyte solution, further preferably, a content of the first additive is 0.2% to 15% of the total weight of the electrolyte solution, and further preferably, a content of the first additive is 0.3% to 10% of the total weight of the electrolyte solution.
In the electrolyte solution of the first aspect of the present invention, the second additive is one or more selected from compounds represented by formula 2, wherein in formula 2, the substituent R is4、R5、R6Each independently selected from one of C1-C12 alkyl, C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and a substituent R4、R5、R6H of the above (alkyl, alkenyl, alkynyl and aryl) can be partially or completely substituted by one or more of F, Cl and Br, and a substituent R4、R5、R6Two of which may or may not be looped. In formula 2, the number of halogen atoms (F, Cl, Br) and substitution positions thereof are not particularly limited and may be selected according to actual needs.
In the electrolyte of the first aspect of the present invention, the second additive is a borate compound, which can improve the interface of the secondary battery, reduce the direct current discharge resistance, and improve the power performance of the secondary battery.
In the electrolyte of the first aspect of the present invention, preferably, the second additive may be one or more selected from the group consisting of trimethyl borate, triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-n-butyl borate, triisobutyl borate, pinacol boronate isopropoxide, pinacol methoxyborate, triphenylboronate, tribenzylboronate, pinacol cyclohexaneboorate, tris (2,2, 2-trifluoroethyl) borate, tris (hexafluoroisopropyl) borate, triallyl borate, tri-n-decyl borate, trilauryl borate, and trioctyl borate.
In the electrolyte of the first aspect of the present invention, a content of the second additive is less than or equal to 10% of a total weight of the electrolyte, preferably, a content of the second additive is 0.01% to 10% of the total weight of the electrolyte, more preferably, a content of the second additive is 0.1% to 5% of the total weight of the electrolyte, and even more preferably, a content of the second additive is 0.1% to 3% of the total weight of the electrolyte.
In the electrolyte solution of the first aspect of the present invention, the type of the organic solvent is not particularly limited, and may be selected according to actual needs. Preferably, a non-aqueous organic solvent is used. The non-aqueous organic solvent may include any kind of carbonate, carboxylate. The carbonate may include cyclic carbonates as well as chain carbonates. The non-aqueous organic solvent may further include a halogenated compound of a carbonate. Specifically, the organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, pentylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, 1, 4-butyrolactone, tetrahydrofuran, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate and ethyl butyrate.
In the electrolyte solution of the first aspect of the present invention, the kind of the electrolyte salt is not particularly limited, and may be selected according to actual needs. For example, the electrolyte salt may be selected from lithium salts, sodium salts, zinc salts, and the like. Specifically, taking lithium salt as an example, the lithium salt is selected from LiPF6、LiBF4、LiN(SO2F)2(abbreviated LiFSI) and LiClO4、LiAsF6、LiB(C2O4)2(abbreviated as LiBOB) and LiBF2(C2O4) (abbreviated as LiDFOB), LiN (SO)2RF)2、LiN(SO2F)(SO2RF) One or more of them. Preferably, the lithium salt is selected from LiPF6、LiN(SO2F)2、LiN(CF3SO2)2、LiB(C2O4)2、LiBF2(C2O4) One or more of them. Further preferably, the lithium salt is selected from LiPF6、LiN(SO2F)2、LiBF2(C2O4) One or more of them. Wherein R isFIs represented as CnF2n+1N is an integer of 1 to 10, preferably an integer of 1 to 3, and more preferably RFMay be-CF3、-C2F5or-CF2CF2CF3。
In the electrolyte solution of the first aspect of the present invention, the content of the electrolyte salt is not particularly limited and may be selected according to actual needs. Specifically, the content of the electrolyte salt is 6.25% to 25% of the total weight of the electrolyte, and preferably, the content of the electrolyte salt is 6.25% to 18.8% of the total weight of the electrolyte.
In the electrolyte solution according to the first aspect of the present invention, a third additive may be included in addition to the first additive and the second additive. Preferably, the third additive is selected from one or two of vinylene carbonate and fluoroethylene carbonate.
Next, a secondary battery according to a second aspect of the invention is explained.
The secondary battery according to the second aspect of the invention includes a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte according to the first aspect of the invention. The secondary battery according to the second aspect of the present invention may be a lithium battery, a sodium battery, a zinc battery, and any other secondary battery using the electrolyte according to the first aspect of the present invention. Wherein, the lithium battery can be a lithium ion battery or a metal lithium battery.
In the secondary battery of the second aspect of the invention, the positive electrode sheet includes a current collector and a positive electrode sheet that is disposed on a surface of the current collector and contains a positive electrode active material. Taking a lithium ion battery as an example, the positive active material is LiaNixAyB(1-x-y)O2A, B are respectively and independently selected from one of Co, Al and Mn, A and B are different, a is more than or equal to 0.9 and less than or equal to 1.1, x is more than or equal to 0.5 and less than or equal to 1.1<1、0<y<1 and x + y<1. Preferably, the positive electrode active material is selected from LiNi0.8Co0.1Mn0.1O2、LiNi0.6Co0.2Mn0.2O2、LiNi0.8Co0.15Al0.05O2、LiNi0.5Co0.2Mn0.3O2One or more of them.
In the secondary battery of the second aspect of the invention, the negative electrode sheet includes a current collector and a negative electrode sheet that is disposed on a surface of the current collector and contains a negative electrode active material. Taking a lithium ion battery as an example, the negative active material may be selected from metallic lithium. The anode active material may also be selected relative to Li/Li+A material capable of intercalating lithium when the electrode potential of the equilibrium potential is < 2V. Specifically, the negative active material is selected from natural graphite, artificial graphite, mesophase micro carbon spheres (abbreviated as MCMB), hard carbon, soft carbon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO2Spinel-structured lithiated TiO2-Li4Ti5O12And one or more of Li-Al alloy.
In the secondary battery of the second aspect of the invention, the kind of the separator is not particularly limited and may be selected according to actual needs. Specifically, the separator may be selected from the group consisting of a polyethylene film, a polypropylene film, a polyvinylidene fluoride film, and a multi-layer composite film thereof.
The present application is further illustrated below with reference to examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application. In the following examples and comparative examples, reagents, materials and instruments used therefor were commercially available unless otherwise specified. In the specific embodiment, only an example in which the secondary battery is a lithium ion battery is shown, but the present application is not limited thereto.
The lithium ion batteries of examples 1 to 20 and comparative examples 1 to 4 were prepared as follows:
(1) preparation of positive plate
LiNi serving as a positive electrode active material0.8Co0.1Mn0.1O2Mixing polyvinylidene fluoride serving as a binder and acetylene black serving as a conductive agent according to a weight ratio of 98:1:1, adding N-methyl pyrrolidone, and stirring to be stable and uniform under the action of a vacuum stirrer to obtain anode slurry; uniformly coating the positive electrode slurry on an aluminum foil with the thickness of 12 mu m; drying the aluminum foil at room temperature, transferring the aluminum foil to a blast oven at 120 ℃ for dryingDrying for 1h, and then performing cold pressing and slitting to obtain the positive plate.
(2) Preparation of negative plate
Mixing the negative active material artificial graphite, the conductive agent acetylene black, the thickening agent sodium carboxymethyl cellulose and the binder styrene-butadiene rubber emulsion according to the weight ratio of 97:1:1:1, adding deionized water, and stirring to be stable and uniform under the action of a vacuum stirrer to obtain negative slurry; uniformly coating the negative electrode slurry on a copper foil with the thickness of 8 mu m; and (3) airing the copper foil at room temperature, transferring the copper foil into a blast oven at 120 ℃ for drying for 1h, and then carrying out cold pressing and slitting to obtain the negative plate.
(3) Preparation of the electrolyte
The organic solvent is a mixed solution containing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC), wherein the weight ratio of EC, EMC and DEC is 1:1: 1. The lithium salt being LiPF6，LiPF6The content of (b) was 12.5% by weight of the total electrolyte. The kinds of additives and their contents are shown in table 1, wherein the contents of the additives are ratios to the total weight of the electrolyte.
(4) Preparation of the separator
A16 μm thick polypropylene film (model A273, supplied by Celgard) was used.
(5) Preparation of lithium ion battery
Stacking the positive plate, the isolating film and the negative plate in sequence to enable the isolating film to be positioned between the positive plate and the negative plate to play an isolating role, and then winding to obtain a bare cell; placing the bare cell in a packaging shell, injecting the prepared electrolyte into the dried bare cell, and performing vacuum packaging, standing, formation, shaping and other processes to obtain the lithium ion battery.
TABLE 1 additives and their contents for examples 1-20 and comparative examples 1-4
The performance test procedure and test results of the lithium ion battery are explained next.
(1) Low temperature DC discharge resistance testing of lithium ion batteries
Charging the lithium ion battery to a voltage of 4.2V at a constant current of 1C (nominal capacity) at 25 ℃, further charging to a current of less than or equal to 0.05C at a constant voltage of 4.2V, standing for 5min, discharging to a voltage of 2.8V at a constant current of 1C, recording the actual discharge capacity of the lithium ion battery, regulating the lithium ion battery to 50% SOC (state of charge) by taking the discharge capacity as a reference (100% SOC), and testing the voltage of the lithium ion battery after regulation is finished and is marked as U0。
The lithium ion battery is charged at a current (I) of 4C at 25 DEG C1) Discharging for 30s continuously, testing the voltage of the lithium ion battery after the discharging is finished, and recording the voltage as U1. Dc discharge resistance DCIR ═ U (U)0-U1)/I1。
The lithium ion battery is placed at-25 ℃ for more than 4h to ensure that the internal temperature of the lithium ion battery reaches-25 ℃, and then the current (I) of 0.3 ℃ is applied2) Discharging for 10s continuously, testing the voltage of the lithium ion battery after the discharging is finished, and recording the voltage as U2. Dc discharge resistance DCIR ═ U (U)0-U2)/I2。
(2) Overcharge performance test of lithium ion battery
And (2) charging the lithium ion battery to 4.2V at a constant current of 1C at 45 ℃, continuing to charge for 1h at the constant current of 1C, detecting the change of the surface temperature and the voltage of the lithium ion battery in the overcharging process, and passing the lithium ion battery when the battery is not ignited and not exploded after the charging is finished.
And (2) charging the lithium ion battery to 4.2V at a constant current of 1C at 45 ℃, continuing to charge at the constant current of 1C until the voltage reaches 6.3V, detecting the surface temperature and voltage changes of the lithium ion battery in the overcharging process, and passing the lithium ion battery when the battery is not ignited and not exploded after the charging is finished.
TABLE 2 test results of examples 1 to 20 and comparative examples 1 to 4
According to the results shown in table 2: compared with comparative examples 1 to 3, the lithium ion batteries of examples 1 to 20 were significantly reduced in dc discharge resistance at 25 ℃ and-25 ℃ and also greatly increased in the pass rate of the lithium ion batteries during overcharge.
In comparative example 2, in which tris (2,2, 2-trifluoroethyl) borate was added alone, the direct current discharge resistance of the lithium ion battery at 25 ℃ and-25 ℃ was reduced, but the passing rate in overcharge of the lithium ion battery was not significantly improved.
In comparative example 3, only tris (2,2, 2-trifluoroethyl) phosphite, which is capable of binding with oxygen on the surface of the positive active material and also absorbing active oxygen released from the positive active material, was added, thereby preventing the release of active oxygen from the positive active material and the irreversible oxidation of the active oxygen to the electrolyte, and thus effectively improving the safety problem caused by overcharge of the lithium ion battery. But the direct current discharge resistance of the lithium ion battery at 25 ℃ and-25 ℃ is not obviously reduced.
When the boric acid tris (2,2, 2-trifluoroethyl) ester and the tris (2,2, 2-trifluoroethyl) phosphite ester are added into the electrolyte at the same time, due to the cooperation effect of the boric acid tris (2,2, 2-trifluoroethyl) ester and the tris (2,2, 2-trifluoroethyl) phosphite ester, the interface of the lithium ion battery can be improved, the direct-current discharge resistance is reduced, and the power performance of the lithium ion battery is improved, while the tris (2,2, 2-trifluoroethyl) phosphite ester is an anion acceptor and can be matched with O on the surface of a positive active material2-、O2 2-Plasma binding to avoid highly active O2-、O2 2-The oxidation of the plasma to the electrolyte further reduces the direct current discharge resistance of the lithium ion battery, especially the direct current discharge resistance at low temperature. Meanwhile, the existence of the tris (2,2, 2-trifluoroethyl) phosphite ester can also reduce the release of active oxygen of the positive active material in the overcharge process, reduce the irreversible oxidation of the active oxygen to the electrolyte,the passing rate of the lithium ion battery in the overcharging process is improved.
Meanwhile, it is noted that, as can be seen from comparison between example 12 and comparative examples 2 to 3, when tris (2,2, 2-trifluoroethyl) borate and tris (2,2, 2-trifluoroethyl) phosphite are added to the electrolyte at the same time, the direct current discharge resistance of the lithium ion battery at 25 ℃ and-25 ℃ is lower than that of comparative example 2, the passing rate of the lithium ion battery in overcharge is higher than that of comparative example 3, and the performances of the lithium ion battery are further improved, indicating that tris (2,2, 2-trifluoroethyl) borate and tris (2,2, 2-trifluoroethyl) phosphite do not act in the electrolyte in isolation, but act in a synergistic manner.
In comparative example 4, in which triethyl borate and tris (2,2, 2-trifluoroethyl) phosphate were simultaneously added, since phosphorus in tris (2,2, 2-trifluoroethyl) phosphate was already in the highest valence state and could not be combined with oxygen on the surface of the positive electrode active material or active oxygen released from the positive electrode active material, the passing rate of the lithium ion battery during overcharge could not be effectively improved.
Those skilled in the art to which the present application pertains can also make appropriate changes and modifications to the above-described embodiments, based on the disclosure of the above description. Therefore, the present application is not limited to the specific embodiments disclosed and described above, and some modifications and variations of the present application should fall within the scope of the claims of the present application.
Claims (17)
1. An electrolyte comprises electrolyte salt, organic solvent and additive, and is characterized in that,
the additive comprises:
a first additive having an oxidation potential of 4.5V to 5.0V; and
a second additive;
wherein the content of the first and second substances,
the first additive is selected from one or more compounds shown in formula 1, wherein in formula 1, substituent R is1、R2Each independently selected from C1-C10 alkyl, C1-C10 alkoxy, C2-C5 alkenyl, C2-C5 alkenyloxy, C2-C5 alkynyl, C2-C5 alkynyloxyOne of aryl of C6-C10 and aryloxy of C6-C10, and a substituent R3One selected from C1-C10 alkyl, C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and a substituent R1、R2、R3The H in the above can be partially or completely substituted by one or more of F, Cl and Br;
the second additive is one or more selected from compounds shown in formula 2, wherein in the formula 2, a substituent R4、R5、R6Each independently selected from one of C1-C12 alkyl, C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and a substituent R4、R5、R6The H can be partially or completely substituted by one or more of F, Cl and Br, and a substituent R4、R5、R6Two of them can also form a ring;
2. the electrolyte of claim 1, wherein in formula 1, the substituent R is1、R2Each independently selected from one of C1-C10 alkyl, C1-C10 alkoxy, C2-C5 alkenyl, C2-C5 alkenyloxy, C2-C5 alkynyl, C2-C5 alkynyloxy, C6-C10 aryl and C6-C10 aryloxy and substituent R1、R2At least one of the substituents is selected from one of C1-C10 alkyl, C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and the substituent R1、R2The H in the above can be partially or completely substituted by one or more of F, Cl and Br.
3. The electrolyte according to claim 2, wherein the first additive is one or more selected from the group consisting of methyldiethoxyphosphine, ethyldiethoxyphosphine, dimethyl phenylphosphate, and diisopropylphenylphosphate.
4. The electrolyte of claim 1, wherein in formula 1, the substituent R is1、R2Each independently selected from one of C2-C5 alkenyl, C2-C5 alkenyloxy, C2-C5 alkynyl, C2-C5 alkynyloxy, C6-C10 aryl and C6-C10 aryloxy, and a substituent R3One of C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, and substituent R1、R2、R3The H in the above can be partially or completely substituted by one or more of F, Cl and Br.
5. The electrolyte as claimed in claim 4, wherein the first additive is one or more selected from triphenyl phosphite, trivinyl phosphite and triallyl phosphite.
6. The electrolyte of claim 1, wherein R is1、R2Each independently selected from one of C1-C10 fluorine-containing alkyl, C1-C10 fluorine-containing alkoxy, C2-C5 fluorine-containing alkenyl, C2-C5 fluorine-containing alkenyloxy, C2-C5 fluorine-containing alkynyl and C2-C5 fluorine-containing alkynyloxy, R is R3One selected from C1-C10 fluorine-containing alkyl, C2-C5 fluorine-containing alkenyl and C2-C5 fluorine-containing alkynyl.
7. The electrolyte of claim 6, wherein the first additive is selected from one or more of the following compounds:
8. the electrolyte as claimed in claim 1, wherein the second additive is selected from one or more of trimethyl borate, triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-n-butyl borate, triisobutyl borate, pinacol boronate isopropoxide, pinacol ester methoxyborate, triphenyl borate, tribenzyl borate, pinacol ester cyclohexaneboorate, tris (2,2, 2-trifluoroethyl) borate, tris (hexafluoroisopropyl) borate, triallyl borate, tri-n-decyl borate, trilauryl borate, trioctyl borate.
9. The electrolyte of claim 1,
the content of the first additive is less than or equal to 15% of the total weight of the electrolyte;
the content of the second additive is less than or equal to 10% of the total weight of the electrolyte.
10. The electrolyte of claim 1, wherein the first additive is present in an amount of 0.1% to 15% by weight of the total electrolyte.
11. The electrolyte of claim 1, wherein the first additive is present in an amount of 0.2% to 15% by weight of the total electrolyte.
12. The electrolyte of claim 1, wherein the first additive is present in an amount of 0.3% to 10% by weight of the total electrolyte.
13. The electrolyte of claim 1, wherein the second additive is present in an amount of 0.01% to 10% by weight of the total electrolyte.
14. The electrolyte of claim 1, wherein the second additive is present in an amount of 0.1% to 5% by weight of the total electrolyte.
15. The electrolyte of claim 1, wherein the second additive is present in an amount of 0.1% to 3% by weight of the total electrolyte.
16. A secondary battery comprising:
the positive plate comprises a current collector and a positive plate which is arranged on the surface of the current collector and contains a positive active material;
the negative plate comprises a current collector and a negative membrane which is arranged on the surface of the current collector and contains a negative active material;
an isolation film; and
an electrolyte;
it is characterized in that the preparation method is characterized in that,
the electrolyte is according to any one of claims 1-15.
17. The secondary battery according to claim 16, wherein the positive electrode active material is LiaNixAyB(1-x-y)O2A, B are respectively and independently selected from one of Co, Al and Mn, A and B are different, a is more than or equal to 0.9 and less than or equal to 1.1, x is more than or equal to 0.5 and less than or equal to 1.1<1、0<y<1 and x + y<1。
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| CN112164825A (en) * | 2019-12-26 | 2021-01-01 | 华南师范大学 | High-voltage phosphate electrolyte additive and lithium ion battery electrolyte containing same |
| WO2023000255A1 (en) * | 2021-07-22 | 2023-01-26 | 宁德时代新能源科技股份有限公司 | Electrolyte, lithium-ion battery, and power device |
| CN113594547B (en) * | 2021-08-20 | 2023-07-07 | 蜂巢能源科技有限公司 | Electrolyte and lithium ion battery |
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