CN109994778B - Electrolyte solution and secondary battery - Google Patents
Electrolyte solution and secondary battery Download PDFInfo
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- CN109994778B CN109994778B CN201711478144.8A CN201711478144A CN109994778B CN 109994778 B CN109994778 B CN 109994778B CN 201711478144 A CN201711478144 A CN 201711478144A CN 109994778 B CN109994778 B CN 109994778B
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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
- H01M10/052—Li-accumulators
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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
- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
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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
Abstract
The invention provides an electrolyte and a secondary battery, wherein the electrolyte comprises electrolyte salt, an organic solvent and an additive, and the additive comprises a first additive and a second additive with oxidation potential of 4.5-5.0V. The invention can effectively improve the safety problem caused by the overcharge of the secondary battery, simultaneously reduce the volume expansion rate of the secondary battery during high-temperature storage, and improve the electrochemical performance of the secondary battery in a high-temperature environment.
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 increasing exhaustion of fossil energy and the increasing global environmental pollution, new energy vehicles using rechargeable batteries as power systems are rapidly developing. In order to meet the requirements of the development of the new energy automobile industry on the power battery, the power battery must have higher power performance, longer cycle life, longer storage life and higher energy density, which is a great challenge for the traditional secondary battery.
In order to increase the energy density of the secondary battery, the operating voltage of the secondary battery is generally increased or the gram capacity of the positive electrode material is increased. Both of these measures pose greater challenges to the safety and high-temperature storage performance of the secondary battery.
Therefore, 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 in 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 simultaneously reduce the volume expansion rate of the secondary battery when stored at high temperature, thereby improving the electrochemical performance of the secondary battery in a high-temperature environment.
In order to achieve the above object, in one aspect of the present invention, there is provided an electrolyte comprising 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. The first additive is selected from compounds represented by formula 1One or more of the compounds, in formula 1, 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 a substituent R3One selected from C1-C10 alkyl, C2-C5 alkenyl, C2-C5 alkynyl and C6-C10 aryl, wherein the substituent R1、R2、R3The H in the above can be partially or completely substituted by one or more of F, Cl, Br, cyano, carboxyl, sulfonic group and silicon group. The second additive is selected from one or more of mononitrile and dinitrile.
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 volume expansion rate of the secondary battery during high-temperature storage is reduced, and the electrochemical performance of the secondary battery in a high-temperature environment is improved.
The electrolyte of the present invention is particularly suitable for use in a secondary battery using a high nickel content positive electrode active material, which can achieve a balance between high energy density, high safety, and excellent electrochemical performance of the secondary battery, and can also achieve a balance between use in a high 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, wherein the 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, Br, cyano, carboxyl, sulfonic group and silicon group. 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 act preferentially on the surface of the positive electrode, and the inhibition of the positive electrode active material cannot be achievedThe oxygen on the surface of the charge reacts 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 the group consisting of trimethyl phosphite, triethyl phosphite, triisopropyl phosphite, tri-N-propyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triphenyl phosphite, triethylene phosphite, tripropylene phosphite, tridecyl phosphite, 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, diphenyl-N, N' -diisopropylphosphoramidite, and the like, One or more of ethyl diethoxy phosphine, diisopropyl phenyl phosphate and tris (trimethylsilyl) phosphite.
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 phosphate。
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 of the first aspect of the present invention, the second additive is one or more selected from mononitriles and dinitriles. The second additive is a nitrile substance, and a-CN group with strong electronegativity in the structure of the second additive can be complexed with transition metal elements on the surface of the positive active material, such as Co, Mn, Ni and the like, so that the dissolution of the transition metal elements on the surface of the positive electrode can be reduced, the surface of the positive electrode can be passivated after complexing, the side reaction of the positive electrode and electrolyte can be reduced, and the volume expansion rate of the secondary battery during high-temperature storage can be reduced.
Wherein:
the mononitrile is one or more compounds shown in formula 2, and in the formula 2, a substituent R4Is selected from one of C1-C10 alkyl, C1-C10 alkoxyalkyl, C2-C6 alkenyl, C2-C6 alkynyl, C6-C10 aryl and C5-C10 heteroaryl, wherein, the substituent R is4The H of the (alkyl, alkoxyalkyl, alkenyl, alkynyl, aryl and heteroaryl) can be partially or completely substituted by one or more of F, Cl, Br, cyano, carboxyl, sulfonic group and silicon base.
R4-CN formula 2
Dinitrile is selected from one or more compounds shown in formula 3, n is an integer from 1 to 8, and a substituent R5、R6Each independently selected from H, C1-C10 alkyl, C1-C10 alkoxy, C2-C6 alkenyl, C2-C6 alkynyl and C6-C10 aryl, wherein, the substituent R is5、R6H of the (alkyl, alkoxy, alkenyl, alkynyl and aryl) can be partially or completely substituted by one or more of F, Cl, Br, cyano, carboxyl, sulfonic group and silicon group.
In the electrolyte of the first aspect of the present invention, preferably, the second additive may be selected from the group consisting of carbonitrile, acetonitrile, propionitrile, butyronitrile, n-valeronitrile, isovaleronitrile, n-hexanonitrile, cyclohexylnitrile, acrylonitrile, benzonitrile, phenylacetonitrile, nitrilothiophene, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, 2-methylsuccinonitrile, tetramethylsuccinonitrile, 2-methylglutaronitrile, fumarodinitrile, 2-methyleneglutaronitrile, 3, 5-dioxa-pimelonitrile, ethylene glycol di (2-cyanoethyl) ether, diethylene glycol di (2-cyanoethyl) ether, triethylene glycol di (2-cyanoethyl) ether, tetraethylene glycol di (2-cyanoethyl) ether, 1, 2-bis (2-cyanoethoxy) ethane, 1, 3-bis (2-cyanoethoxy) propane, and mixtures thereof, 1, 4-di (2-cyanoethoxy) butane, 1, 5-di (2-cyanoethoxy) pentane, 1, 6-dicyanohexane and 1, 2-dibromo-2, 4-dicyanobutane.
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 0.05% to 10% of the total weight of the electrolyte, more preferably, a content of the second additive is 0.1% to 8% of the total weight of the electrolyte, and even more preferably, a content of the second additive is 0.5% 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% to 25% of the total weight of the electrolyte solution, preferably, the content of the electrolyte salt is 6% to 20% of the total weight of the electrolyte solution, and more preferably, the content of the electrolyte salt is 10% to 15% of the total weight of the electrolyte solution.
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 22 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; and (3) airing the aluminum foil at room temperature, transferring the aluminum foil to a blast oven at 120 ℃ for drying for 1h, and then carrying out 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 1-22 and comparative examples 1-4
The performance test procedure and test results of the lithium ion battery are explained next.
(1) High-temperature gas production performance test of lithium ion battery
At room temperature, the lithium ion battery is charged with a constant current of 1C (nominal capacity) to a voltage of 4.2V, further charged with a constant voltage of 4.2V to a current of 0.05C, and after full charge, the volume of the lithium ion battery is tested by a drainage method.
And storing the lithium ion battery in an environment of 80 ℃, taking out the lithium ion battery after 24 hours, standing for 60min in a room temperature environment, cooling to room temperature, testing the volume by using a drainage method within 1 hour, and recording. And then performing storage test according to the steps until the storage is full of 10 days.
The lithium ion battery has a volume expansion ratio (%) after storage at 80 ℃ for 10 days (volume measured after storage for 10 days/volume measured before storage) -1.
(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 22 and comparative examples 1 to 4
According to the results shown in table 2: the lithium ion batteries of examples 1 to 22 were significantly reduced in the volume expansion rate after storage at 80 c for 10 days, while the lithium ion batteries were greatly increased in the pass rate during overcharge, as compared to comparative examples 1 to 3.
In comparative example 2, the volume expansion rate of the lithium ion battery after storage at 80 ℃ for 10 days was improved to some extent by adding only adiponitrile, but the passage 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. However, the volume expansion rate of the lithium ion battery after storage at 80 ℃ for 10 days cannot be effectively improved.
When adiponitrile and tris (2,2, 2-trifluoroethyl) phosphite are added into the electrolyte at the same time, the adiponitrile can be complexed with transition metal on the surface of the anode active material due to the cooperation effect of the adiponitrile and the tris (2,2, 2-trifluoroethyl) phosphite, so that the dissolution of the transition metal is reduced, the surface of the anode can be passivated after complexation, and the occurrence of side reaction of the anode and the electrolyte is reduced, thereby reducing the possibility of side reactionThe volume expansion rate of the lithium ion battery during high-temperature storage, and the tris (2,2, 2-trifluoroethyl) phosphite ester is an anion acceptor and can be matched with O on the surface of the positive active material2-、O2 2-Plasma binding to avoid highly active O2-、O2 2-And the plasma oxidizes the electrolyte, so that the storage performance of the lithium ion battery at high temperature is further improved. Meanwhile, the tri (2,2, 2-trifluoroethyl) phosphite ester can also reduce the release of active oxygen of the positive electrode active material in the overcharge process, reduce the irreversible oxidation of the active oxygen on the electrolyte and improve the passing rate of the lithium ion battery in the overcharge process.
Meanwhile, it is noted that, as can be seen from comparison between example 13 and comparative examples 2 to 3, when adiponitrile and tris (2,2, 2-trifluoroethyl) phosphite are added to the electrolyte at the same time, the volume expansion rate of the lithium ion battery after storage for 10 days at 80 ℃ 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 all performances of the lithium ion battery are further improved, indicating that adiponitrile and tris (2,2, 2-trifluoroethyl) phosphite do not act in the electrolyte in isolation, but act synergistically.
In comparative example 4, in which succinonitrile 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 (12)
1. 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;
the 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
adiponitrile;
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 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, wherein the substituent R1、R2、R3The H can be partially or completely substituted by one or more of F, Cl, Br, cyano, carboxyl, sulfonic group and silicon group;
the content of the first additive accounts for 5-15% of the total weight of the electrolyte;
the content of adiponitrile is less than or equal to 10% of the total weight of the electrolyte.
2. The secondary battery according to claim 1, wherein the first additive is selected from the group consisting of trimethyl phosphite, triethyl phosphite, triisopropyl phosphite, tri-N-propyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triphenyl phosphite, trivinyl phosphite, tripropylene phosphite, tridecyl phosphite, 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, diphenyl-N, one or more of N' -diisopropyl phosphoramidite, ethyl diethoxy phosphine, diisopropyl phenyl phosphate and tris (trimethylsilyl) phosphite.
3. The secondary battery according to 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.
4. The secondary battery according to claim 3, wherein the first additive is selected from one or more of the following compounds:
5. the secondary battery according to claim 1,
the additive also comprises at least one of additive A and additive B; wherein the content of the first and second substances,
the additive A is selected from one or more compounds shown in a formula 2, and in the formula 2, a substituent R4Is selected from one of C1-C10 alkyl, C1-C10 alkoxy, C2-C6 alkenyl, C2-C6 alkynyl, C6-C10 aryl and C5-C10 heteroaryl, wherein, the substituent R is4The H in the above may be partially or totally substituted by F, Cl, Br, cyano, carboxyl, sulfonic group, or silylOne or more of them;
R4-CN formula 2;
the additive B is selected from one or more compounds shown in a formula 3, in the formula 3, n is an integer from 1 to 8, and a substituent R5、R6Each independently selected from H, C1-C10 alkyl, C1-C10 alkoxy, C2-C6 alkenyl, C2-C6 alkynyl and C6-C10 aryl, wherein, the substituent R is5、R6The H can be partially or completely substituted by one or more of F, Cl, Br, cyano, carboxyl, sulfonic group and silicon group; the additive B is not adiponitrile;
6. the secondary battery according to claim 5, wherein the additive A is selected from one or more of formonitrile, acetonitrile, propionitrile, butyronitrile, n-valeronitrile, isovaleronitrile, n-capronitrile, cyclohexylnitrile, acrylonitrile, benzonitrile, phenylacetonitrile and nitrilotriphene.
7. The secondary battery according to claim 5, wherein the additive B is selected from malononitrile, succinonitrile, glutaronitrile, pimelonitrile, suberonitrile, 2-methylsuccinonitrile, tetramethylsuccinonitrile, 2-methylglutaronitrile, fumarodinitrile, 2-methyleneglutaronitrile, 3, 5-dioxa-pimelonitrile, ethylene glycol di (2-cyanoethyl) ether, diethylene glycol di (2-cyanoethyl) ether, triethylene glycol di (2-cyanoethyl) ether, tetraethylene glycol di (2-cyanoethyl) ether, 1, 2-bis (2-cyanoethoxy) ethane, 1, 3-bis (2-cyanoethoxy) propane, 1, 4-bis (2-cyanoethoxy) butane, 1, 5-bis (2-cyanoethoxy) pentane, 1, 6-dicyano hexane and 1, 2-dibromo-2, 4-dicyano butane.
8. The secondary battery according to claim 1, wherein the content of adiponitrile is 0.05 to 10% by weight based on the total weight of the electrolyte.
9. The secondary battery according to claim 1, wherein the content of adiponitrile is 0.1 to 8% by weight based on the total weight of the electrolyte.
10. The secondary battery according to claim 1, wherein the content of adiponitrile is 0.5 to 3% by weight based on the total weight of the electrolyte.
11. The secondary battery of claim 1 wherein the additive further comprises one or both of vinylene carbonate and fluoroethylene carbonate.
12. The secondary battery according to claim 1, 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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| CN110875497B (en) * | 2018-08-29 | 2021-04-27 | 中南大学 | Ternary lithium ion battery and preparation method thereof |
| 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 |
| CN113130993A (en) * | 2019-12-30 | 2021-07-16 | 深圳市研一新材料有限责任公司 | Electrolyte and electrochemical device thereof |
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