CN114024030A - Non-aqueous electrolyte and battery containing same - Google Patents
Non-aqueous electrolyte and battery containing same Download PDFInfo
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- CN114024030A CN114024030A CN202111228166.5A CN202111228166A CN114024030A CN 114024030 A CN114024030 A CN 114024030A CN 202111228166 A CN202111228166 A CN 202111228166A CN 114024030 A CN114024030 A CN 114024030A
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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
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0088—Composites
- H01M2300/0091—Composites in the form of mixtures
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a non-aqueous electrolyte and a battery containing the same. The non-aqueous electrolyte can form a uniform and compact protective film on the surfaces of a positive electrode and a negative electrode through the synergistic action of the isothiazole additive and the non-isothiazole additive, so that the oxidation of the electrolyte on the surface of the positive electrode under high voltage can be inhibited, the further contact between the electrolyte and the surface of a negative electrode material is avoided, the occurrence of side reactions is reduced, and the polarization of the battery is reduced due to the small film-forming impedance, so that the normal-temperature cycle and high-temperature storage performance of the battery are improved, and the battery can keep good rate performance and low-temperature discharge performance.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a non-aqueous electrolyte, a preparation method thereof and a battery containing the non-aqueous electrolyte.
Background
There are two main ways to improve the energy density of lithium ion batteries: 1) improving the specific capacity of the anode and cathode materials, such as developing high nickel anode materials and silicon-based cathode materials; 2) the charge cut-off voltage is increased. The ternary layered oxide has excellent comprehensive performance of high energy density, good cycle performance, moderate price and the like, and is a positive electrode material with the most application prospect in the current lithium ion battery. However, with the rapid development of pure electric vehicles and hybrid electric vehicles, people have raised higher requirements on energy density, cycle life and safety performance of lithium ion batteries. And with the increase of the charge cut-off voltage of the ternary material, the reactivity between the anode material and the electrolyte is increased, so that the electrolyte is decomposed and oxidized on the surface of the anode to generate a ballooning effect, and the normal-temperature cycle performance, the high-temperature cycle characteristic, the safety and the high-temperature storage performance of the battery are reduced. However, the above problem also causes a decrease in the interfacial properties between the positive electrode and the electrolyte. Therefore, it is very necessary to develop a functional electrolyte additive to improve the contact interface between the active positive electrode and the electrolyte.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a nonaqueous electrolyte, a preparation method thereof and a battery containing the nonaqueous electrolyte. The non-aqueous electrolyte disclosed by the invention not only avoids the problem of increase of negative electrode impedance caused by addition of a positive electrode film-forming additive by optimizing the composition and/or the dosage of the additive, but also can keep good rate performance and low-temperature performance of the battery.
In order to achieve the purpose, the invention is realized by the following technical scheme:
the invention provides a non-aqueous electrolyte which comprises an isothiazole additive and a non-isothiazole additive.
The non-aqueous electrolyte provided by the invention is suitable for a high-voltage battery, and the high voltage is more than 4.4V.
According to the present invention, the isothiazole additive is at least one selected from the group consisting of compounds having a structure represented by formula 1 or formula 2 below:
in the formula 1, R1 is C1-4An alkyl group;
in the formula 2, R1 is C1-4An alkyl group; r2 is selected from H, halogen, C unsubstituted or optionally substituted by one or more halogen1-4Alkyl, C unsubstituted or optionally substituted by one or more halogen1-4An alkoxy group.
According to the invention, in formula 1, R1 is at least one of methyl, ethyl, propyl (such as n-propyl or isopropyl), butyl (such as n-butyl, isobutyl, sec-butyl or tert-butyl).
According to the invention, in the formula 2, R1 is at least one of methyl, ethyl, propyl (such as n-propyl or isopropyl), butyl (such as n-butyl, isobutyl, sec-butyl or tert-butyl).
According to the invention, in the formula 2, R2 is at least one of hydrogen, fluorine, methyl, trifluoromethyl, isopropyl, tert-butyl and methoxy.
Illustratively, the isothiazole additive is selected from at least one of the following compounds a-1 to a-9:
according to the present invention, the non-isothiazole additive includes at least one of an ester additive, a nitrile additive and a phosphorous additive.
Preferably, the ester additive includes at least one of fluoroethylene carbonate, ethylene carbonate, vinyl ethylene carbonate, ethylene sulfate, 1, 3-propane sultone, and 1, 4-butane sultone.
Preferably, the nitrile additive comprises adiponitrile and/or succinonitrile.
Preferably, the phosphorus-containing additive comprises at least one of lithium difluorophosphate, lithium difluorooxalate phosphate, lithium tetrafluorooxalate phosphate, triallyl phosphate, tripropargyl phosphate, and tris (trimethylsilyl) phosphate.
The ester additive, the nitrile additive and the phosphorus-containing additive can be well matched with isothiazole additives, so that the performance of the battery is synergistically improved.
According to the present invention, the electrolyte further comprises a non-aqueous solvent. Preferably, the nonaqueous solvent includes at least one of a cyclic carbonate and a chain carbonate, and preferably both of the cyclic carbonate and the chain carbonate.
For example, the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, and γ -butyrolactone.
For example, the chain carbonate includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl methyl carbonate, and propyl ethyl carbonate.
According to the present invention, the electrolyte further includes a lithium salt.
Preferably, the lithium salt includes LiPF6、LiBF4、LiClO4、LiAsF6、LiSO2CF3、LiN(CF3SO2)2LiBOB, LiDFOB and LiN (C)2F5SO2)2At least one of (1).
According to the present invention, when the nonaqueous solvent includes both of a cyclic carbonate and a chain carbonate, the mass ratio of the cyclic carbonate to the chain carbonate is 1 (2-3), for example, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, or any one of two or more combinations of the above.
The cyclic carbonate and the chain carbonate with the mass ratio are adopted, so that the viscosity of the electrolyte is too low due to too low content of the cyclic carbonate, the conductivity is too low, the polarization of the battery is increased, and the cycle and rate performance is poor; when the content of the cyclic carbonate is too high, the viscosity of the electrolyte is increased, the polarization of the battery is also large, and the electrochemical performance of the battery is further reduced. Therefore, in order to ensure reasonable viscosity and conductivity of the electrolyte and ensure better electrochemical performance, the invention preferably selects the mass ratio of the cyclic carbonate to the chain carbonate as 1 (2-3).
Preferably, the molar concentration of the lithium salt in the mixed solvent formed by the cyclic carbonate and the chain carbonate is 1.0-1.5mol/L, such as 1.0mol/L, 1.1mol/L, 1.2mol/L, 1.3mol/L, 1.4mol/L, 1.5mol/L or any point in between any two combinations of the above points.
Preferably, the mass of the isothiazole additive is 0.1-1.0% of the total mass of the lithium salt, the cyclic carbonate and the chain carbonate, such as 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0% or any point between any two combinations of the above.
In the invention, if the dosage of the isothiazole additive (such as sulfonic anhydride additive) is too much, the film forming resistance of the positive electrode is too large, the first effect and the capacity of the battery are low, and the rate capability is reduced; however, if the amount of the isothiazole additive (e.g., sulfonic anhydride additive) is too small, a good protective film cannot be formed on the positive electrode, that is, an effective SEI film cannot be formed on the surface of the ternary positive electrode, thereby deteriorating high voltage performance.
Preferably, the mass of the non-isothiazole additive is 1.0-5.0% of the total mass of the lithium salt, cyclic carbonate and chain carbonate, for example, 1.0%, 2.0%, 3.0%, 4.0%, 5.0% or any point between any two combinations of the above.
In the present invention, if the non-isothiazole additive is used in an excessive amount, it may cause the battery impedance to be too large; if the amount of the non-isothiazole additive is too small, it may result in failure to form a uniform and stable SEI film on the negative electrode.
The invention also provides a preparation method of the non-aqueous electrolyte, which comprises the following steps:
and mixing an isothiazole additive, a non-isothiazole additive, cyclic carbonate, chain carbonate and lithium salt to obtain the non-aqueous electrolyte.
According to the present invention, the isothiazole additive, the non-isothiazole additive, the cyclic carbonate, the chain carbonate and the lithium salt have the definitions and the amount ratios as described above.
The preparation method provided by the invention is simple to operate, short in flow and suitable for industrial large-scale production.
According to the invention, the mixing comprises stirring or ultrasonic mixing.
Preferably, the temperature of the mixing is 10-50 ℃, such as 10 ℃, 20 ℃, 30 ℃, 40 ℃ or 50 ℃ and the like.
The invention also provides application of the electrolyte in a battery.
The invention also provides a battery, which comprises the nonaqueous electrolyte.
According to the present invention, the battery may be a high voltage battery.
According to the present invention, the battery further includes a positive electrode sheet, a negative electrode sheet, and a separator.
Preferably, the membrane is a microporous membrane.
According to the present invention, the positive electrode active material used in the positive electrode sheet is selected from at least one of ternary layered materials. Preferably selected from layered lithium transition metal composite oxides. For example, the layered lithium transition metal composite oxide has a chemical formula of { Li [ NixCoyMz]O2(0 < x, y, z < 1, M ═ Mn, abbreviated NCM; M ═ Al, abbreviated NCA).
According to the present invention, the negative active material used in the negative electrode sheet is selected from at least one of a carbon-based material, a silicon-based material, a tin-based material, or their corresponding alloy materials. According to the invention, the positive electrode sheet and the negative electrode sheet optionally contain a conductive agent and/or a binder.
Preferably, the mass ratio of the positive electrode active material/the negative electrode active material to the conductive agent and the adhesive is (60-99.8): (0.1-20): (0.1-20), exemplary are 60:20:20, 70:20:10, 80:10:10, 90:5:5, 92:3:5, 94:2:4, 95:3:2, 99:0.5:0.5, 99:0.1:0.9, 99:0.9:0.1, 99.8:0.1: 0.1.
For example, the binder may be one, two or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), and Styrene Butadiene Rubber (SBR); preferably polyvinylidene fluoride.
For example, the conductive agent may be at least one of acetylene black, conductive carbon black (Super-P), and conductive graphite (KS-6).
The invention also provides a preparation method of the battery, which comprises the steps of stacking the positive plate, the diaphragm and the negative plate in sequence, ensuring that the isolation diaphragm is positioned between the positive plate and the negative plate to play an isolation role, and then winding to obtain a naked battery cell without liquid injection; placing the bare cell in an outer packaging foil, injecting the electrolyte into the dried bare cell, and carrying out vacuum packaging, standing, formation, shaping, sorting and other processes to obtain the required battery.
Compared with the prior art, the invention has the following beneficial effects:
(1) in the non-aqueous electrolyte provided by the invention, the strong electron-withdrawing substituent ester group in the structure of the isothiazole additive reduces the electron cloud density of an isothiazole ring, so that molecules are easier to be oxidized on the surface of a positive electrode to form a compact and stable CEI (CeI) film, and in addition, the lone pair on the oxygen atom on the ester group presents weaker Lewis base property in the electrolyte and can be combined with other components (such as PF (positive electrode) in the electrolyte5) A complex (e.g., a hexa-ligand complex) is formed to reduce the acidity and reactivity of the electrolyte, thereby suppressing the rise of free acid in the electrolyte. The isothiazole additive and the non-isothiazole additive are matched with each other, and can be used for uniformly and compactly forming a film on the surfaces of the anode and the cathode in a synergistic manner so as to inhibit the oxidation of the electrolyte of the anode under high voltage and avoid the further contact of the electrolyte and the surface of a cathode material, thereby reducing the occurrence of side reactions. And because the film-forming impedance is smaller, the polarization of the battery is reduced, so that the normal-temperature cycle and high-temperature storage performance of the battery are improved, and the battery can keep good rate performance and low-temperature discharge performance.
(2) In the non-aqueous electrolyte, the performance of the battery is synergistically improved through the combined action of the components, and specifically:
the cyclic carbonate can dissolve lithium salt, isothiazole additives and non-isothiazole additives, so that the electrolyte has high conductivity; the chain carbonate can dissolve lithium salt, isothiazole additives and non-isothiazole additives and regulate and control the viscosity of the electrolyteWithin a reasonable range; lithium salt conducts between positive and negative electrodes to provide Li for battery system+(ii) a The isothiazole additive and the non-isothiazole additive can form a film on the surface of the positive electrode or the negative electrode to protect the positive electrode or the negative electrode.
Definition and description of terms
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value, unless otherwise indicated herein. For example, a numerical range of "1 to 6" is equivalent to reciting each integer value in the numerical range of "1 to 6," i.e., 1,2, 3, 4, 5, 6. It is understood that, of the one, more, used herein in describing substituents, "plurality" refers to an integer ≧ 2, such as 2,3, 4, 5, 6, 7, 8, 9, or 10.
The term "halogen" denotes fluorine, chlorine, bromine and iodine.
The term "C1-4Alkyl "denotes a straight or branched chain saturated hydrocarbon group having 1,2, 3 or 4 carbon atoms. The alkyl group is, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a 2-methylbutyl group, a 1-ethylpropyl group, a 1, 2-dimethylpropyl group, a neopentyl group, a 1, 1-dimethylpropyl group, a 4-methylpentyl group, a 3-methylpentyl group, a 2-ethylbutyl group, a 1-ethylbutyl group, a 3, 3-dimethylbutyl group, a 2, 2-dimethylbutyl group, a 1, 1-dimethylbutyl group, a 2, 3-dimethylbutyl group, a 1, 3-dimethylbutyl group or a 1, 2-dimethylbutyl group, or the like, or isomers thereof.
Unless otherwise indicated, the definitions of terms herein apply equally to groups comprising the term, e.g. C1-4The definition of alkyl also applies to C1-4An alkoxy group.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. The technical solution of the present invention should be covered by the protection scope of the present invention, in which modifications or equivalent substitutions are made without departing from the spirit scope of the technical solution of the present invention.
Example 1
This example provides a nonaqueous electrolytic solution composed of a cyclic carbonate, a chain carbonate, a lithium salt, and an additive.
The additive consists of an isothiazole additive and a non-isothiazole additive, wherein the isothiazole additive is a compound A-1, and the non-isothiazole additive is 1, 4-butanesultone. The cyclic carbonate is ethylene carbonate, the chain carbonate is dimethyl carbonate, and the lithium salt is LiPF6。
The mass ratio of the cyclic carbonate to the chain carbonate is 1: 2.5; the molar concentration of the lithium salt in a mixed solvent formed by cyclic carbonate and chain carbonate is 1.3 mol/L; the mass of the isothiazole additive is 0.5% of the total mass of the lithium salt, the cyclic carbonate and the chain carbonate; the mass of the non-isothiazole additive is 3.0% of the total mass of the lithium salt, the cyclic carbonate and the chain carbonate.
The preparation method of the non-aqueous electrolyte comprises the following steps: and stirring and mixing the cyclic carbonate, the chain carbonate, the lithium salt and the additive at a formula ratio at 25 ℃ to obtain the non-aqueous electrolyte, wherein the additive comprises an isothiazole additive and a non-isothiazole additive.
Example 2
This example provides a nonaqueous electrolytic solution composed of a cyclic carbonate, a chain carbonate, a lithium salt, and an additive.
The additive comprises an isothiazole additive and a non-isothiazole additive, wherein the isothiazole additive is a compound A-3, and the non-isothiazole additive is 1, 3-propane sultone and 1, 4-butane sultone (the mass ratio of the 1, 3-propane sultone to the 1, 4-butane sultone is 1: 2). The cyclic carbonate is gamma-butyrolactone, the chain carbonate is methyl ethyl carbonate, and the lithium salt is LiPF6。
The mass ratio of the cyclic carbonate to the chain carbonate is 1: 2; the molar concentration of the lithium salt in a mixed solvent formed by cyclic carbonate and chain carbonate is 1.0 mol/L; the mass of the isothiazole additive is 0.1% of the total mass of the lithium salt, the cyclic carbonate and the chain carbonate; the mass of the non-isothiazole additive is 1.0% of the total mass of the lithium salt, the cyclic carbonate and the chain carbonate.
The nonaqueous electrolytic solution was prepared in the same manner as in example 1.
Example 3
This example provides a nonaqueous electrolytic solution composed of a cyclic carbonate, a chain carbonate, a lithium salt, and an additive.
The additive consists of an isothiazole additive and a non-sulfonic anhydride additive, wherein the sulfonic anhydride additive is a compound A-5, and the non-isothiazole additive is adiponitrile and lithium difluorophosphate (the mass ratio of the adiponitrile to the lithium difluorophosphate is 1: 1). The cyclic carbonate is propylene carbonate, the chain carbonate is diethyl carbonate, and the lithium salt is LiPF6。
The mass ratio of the cyclic carbonate to the chain carbonate is 1: 3; the molar concentration of the lithium salt in a mixed solvent formed by cyclic carbonate and chain carbonate is 1.5 mol/L; the mass of the isothiazole additive is 1.0% of the total mass of the lithium salt, the cyclic carbonate and the chain carbonate; the mass of the non-isothiazole additive is 5.0% of the total mass of the lithium salt, the cyclic carbonate and the chain carbonate.
The nonaqueous electrolytic solution was prepared in the same manner as in example 1.
Example 4
The nonaqueous electrolytic solution provided in this example was the same as the nonaqueous electrolytic solution of example 1 in the kinds and contents of the components except that the mass of the isothiazole additive was 0.05% of the total mass of the cyclic carbonate and the chain carbonate.
The nonaqueous electrolytic solution was prepared in the same manner as in example 1.
Example 5
The nonaqueous electrolytic solution provided in this example was the same as the nonaqueous electrolytic solution of example 1 in the kinds and contents of the components except that the mass of the isothiazole additive was 2.5% of the total mass of the cyclic carbonate and the chain carbonate.
The nonaqueous electrolytic solution was prepared in the same manner as in example 1.
Example 6
The nonaqueous electrolytic solution provided in this example was the same as the nonaqueous electrolytic solution of example 1 in the kinds and contents of the components except that the mass of the non-isothiazole additive was 0.5% of the total mass of the cyclic carbonate and the chain carbonate.
The nonaqueous electrolytic solution was prepared in the same manner as in example 1.
Example 7
The nonaqueous electrolytic solution provided in this example was the same as the nonaqueous electrolytic solution of example 1 except that the amount of the non-isothiazole additive was 8% by mass based on the total amount of the cyclic carbonate and the chain carbonate.
The nonaqueous electrolytic solution was prepared in the same manner as in example 1.
Comparative example 1
The comparative example was the same as the nonaqueous electrolytic solution of example 1 except that the additive consisted of only isothiazole additives and contained no non-isothiazole additives.
The nonaqueous electrolytic solution was prepared in the same manner as in example 1.
Comparative example 2
The comparative example was the same as the nonaqueous electrolytic solution of example 1 in the kinds and contents of the components except that the additive consisted of only the non-isothiazole additive and did not contain the isothiazole additive.
The nonaqueous electrolytic solution was prepared in the same manner as in example 1.
Comparative example 3
This comparative example consisted of an additive other than the additive consisting of only the additive not containing the ester group isothiazoles
And a non-isothiazole additive were combined, and the kinds and contents of the other components were the same as those of the non-aqueous electrolyte of example 1.
The nonaqueous electrolytic solution was prepared in the same manner as in example 1.
Test method
The nonaqueous electrolyte solutions provided in examples 1 to 7 or comparative examples 1 to 3 were used as the electrolyte solution of the test cell, and the PP separator was used as the separator of the test cell. The current collector of the positive plate of the test battery is an aluminum foil, and the positive coating is composed of NCM523, acetylene black and PVDF in a mass ratio of 95:3: 2; the current collector of the negative plate of the test battery is copper foil, and the negative coating is composed of artificial graphite, acetylene black and SBR in a mass ratio of 94:3: 3.
And assembling the positive pole piece, the negative pole piece, the PP diaphragm and the electrolyte prepared in the examples 1-7 or the comparative examples 1-3 into a flexible package battery, and performing electrochemical test by adopting a blue charging and discharging test cabinet.
(1) And (3) testing the quick charge cycle performance of the battery:
charging the battery at a constant current of 1C (nominal capacity) to a voltage of 4.4V at a temperature of 25 ℃/45 ℃, then charging the battery at a constant voltage of 4.4V to a current of 0.05C, standing for 10min, and discharging the battery at a constant current of 1C to a cut-off voltage of 2.8V, wherein the above is a charge-discharge cycle. The battery is subjected to 500 charge-discharge cycles at 25 ℃ according to the conditions; 500 charge-discharge cycles at 45 ℃.
The capacity retention (%) after N cycles of the battery was (discharge capacity at N-th cycle/first discharge capacity) × 100%, and N was the number of cycles of the battery.
(2) Battery-10 ℃ rate discharge performance test
Discharging the battery at a constant current of 0.5 ℃ to a cut-off voltage of 2.8V at 25 ℃, standing for 10min, charging the battery at a constant current of 1C and a constant voltage to a cut-off current of 4.4V of 0.05C, moving the battery core into a high-low temperature box at-10 ℃, standing for 120min, discharging at a constant current of 4C/7C to a cut-off voltage of 2.8V, and recording the inflection point voltage.
(3) High temperature storage experiment at 60 deg.C
The cells were charged at 25 ℃ at 1C constant current to a voltage of 4.4V and then at 4.4V constant voltage to a current of 0.05C, the volume of the test cell being V0(ii) a The cells were then placed in a 60 ℃ incubator, stored for 30 days, 60 days, respectively, and the volume of the test cell was taken out and recorded as Vn.
Volume expansion ratio (%) after storage of the battery at 60 ℃ for n days (Vn-V)0)/V0The results of the 100% test are shown in the following table
TABLE 1 comparison of cell test results for examples 1-7 and comparative examples 1-3
It can be known from the test results of the above examples and comparative examples that the isothiazole additive and the non-isothiazole additive are matched with each other in the non-aqueous electrolyte provided in examples 1 to 3, and can cooperate with each other to form a film uniformly and densely on the surfaces of the positive electrode and the negative electrode, thereby inhibiting the oxidation of the electrolyte of the positive electrode at high voltage, and avoiding the further contact between the electrolyte and the surface of the negative electrode material, further reducing the occurrence of side reactions, and reducing the polarization of the battery due to the small film formation resistance, thereby improving the normal-temperature cycle and high-temperature storage performance of the battery, and simultaneously maintaining the good rate performance and low-temperature discharge performance of the battery.
Example 4 the results show that: when the amount of the isothiazole additive is less than 0.1%, the battery cycle performance and high-temperature storage are deteriorated; while example 5 results show that: when the isothiazole additive is used in an amount of more than 1.0%, the cycle, rate and low temperature properties of the battery are degraded.
Example 6 the results show that: when the non-isothiazole additive is used in an amount of less than 1.0%, the cycle performance of the battery may be deteriorated; while the results of example 7 show that: when the non-isothiazole additive is used in an amount of more than 5.0%, the impedance of the battery is increased and the gas production during high-temperature storage is increased.
Comparative example 1 the results show that: when the non-isothiazole additive is not added to the electrolyte, the battery cycle is deteriorated.
Comparative example 2 the results show that: when no isothiazole additive is added to the electrolyte, the cycle performance and storage performance of the battery are significantly reduced.
Comparative example 3 the results show that: when the ester group-containing isothiazole additive is not added into the electrolyte, the electrochemical performance of the battery is affected, and the performance of the electrolyte can be remarkably improved by adding the ester group-containing isothiazole additive into the electrolyte.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The non-aqueous electrolyte is characterized by comprising an isothiazole additive and a non-isothiazole additive.
2. The nonaqueous electrolytic solution of claim 1, wherein the isothiazole additive is at least one selected from compounds having a structure represented by formula 1 or formula 2 below:
in the formula 1, R1 is C1-4An alkyl group;
in the formula 2, R1 is C1-4An alkyl group; r2 is selected from H, halogen, C unsubstituted or optionally substituted by one or more halogen1-4Alkyl, C unsubstituted or optionally substituted by one or more halogen1-4An alkoxy group.
3. The electrolyte according to claim 1 or 2, wherein the isothiazole additive a is selected from at least one of the following compounds a-1 to a-9:
4. the nonaqueous electrolytic solution of any one of claims 1 to 3, wherein the non-isothiazole additive comprises at least one of an ester additive, a nitrile additive, or a phosphorus-containing additive;
and/or the ester additive comprises at least one of fluoroethylene carbonate, ethylene carbonate, vinyl ethylene carbonate, ethylene sulfate, 1, 3-propane sultone or 1, 4-butane sultone;
and/or, the nitrile additive comprises adiponitrile and/or succinonitrile;
and/or the phosphorus-containing additive comprises at least one of lithium difluorophosphate, lithium difluorooxalate phosphate, lithium tetrafluorooxalate phosphate, triallyl phosphate, tripropargyl phosphate, and tris (trimethylsilyl) phosphate.
5. The nonaqueous electrolytic solution of any one of claims 1 to 4, wherein the electrolytic solution further comprises a nonaqueous solvent;
and/or the nonaqueous solvent comprises at least one of cyclic carbonate and chain carbonate;
and/or the cyclic carbonate comprises at least one of ethylene carbonate, propylene carbonate and gamma-butyrolactone;
and/or the chain carbonate comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl methyl carbonate and propyl ethyl carbonate.
6. The nonaqueous electrolytic solution of any one of claims 1 to 5, wherein the electrolytic solution further comprises a lithium salt;
and/or, the lithium salt comprises LiPF6、LiBF4、LiClO4、LiAsF6、LiSO2CF3、LiN(CF3SO2)2LiBOB, LiDFOB and LiN (C)2F5SO2)2At least one of (1).
7. The nonaqueous electrolytic solution of claim 5, wherein when the nonaqueous solvent includes both of a cyclic carbonate and a chain carbonate, the mass ratio of the cyclic carbonate to the chain carbonate is 1 (2-3);
and/or the molar concentration of the lithium salt in a mixed solvent formed by the cyclic carbonate and the chain carbonate is 1.0-1.5 mol/L.
8. The nonaqueous electrolytic solution of any one of claims 1 to 7, wherein the mass of the isothiazole additive is 0.1 to 1.0% of the total mass of the lithium salt, the cyclic carbonate and the chain carbonate;
and/or the mass of the non-isothiazole additive accounts for 1.0-5.0% of the total mass of the lithium salt, the cyclic carbonate and the chain carbonate.
9. A battery comprising the electrolyte of any one of claims 1-8.
10. The battery of claim 9, further comprising a positive plate, a negative plate, and a separator;
and/or the positive active material adopted in the positive plate is selected from at least one of ternary layered materials;
and/or the negative active material adopted in the negative plate is selected from at least one of carbon-based materials, silicon-based materials, tin-based materials or alloy materials corresponding to the carbon-based materials, the silicon-based materials and the tin-based materials.
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