CN114287079A - Electrolyte solution, electrochemical device, and electronic device - Google Patents
Electrolyte solution, electrochemical device, and electronic device Download PDFInfo
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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
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- 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
- H01M10/05—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
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- H01M10/0567—Liquid materials characterised by the additives
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Abstract
The application provides an electrolyte, an electrochemical device and an electronic device. The electrolyte includes a compound represented by formula (I) in which R is11Selected from covalent bond, oxygen, sulfur, C1‑C10Alkylene group, C1‑C5Alkyleneoxy or C1‑C5Alkylenethio groups including alkylene, alkenylene, arylene; r12Selected from covalent bond, C1‑C10Alkylene or C1‑C10Alkylene sulfonyl including alkylene, alkenylene, arylene; x is selected from substituted or unsubstituted C1‑C10A heterocyclic group containing at least one of oxygen, nitrogen or sulfur atoms; when substituted, the substituent group comprises a hydrocarbon group, a cyano group and a halogen atom, and the hydrocarbon group comprises an alkyl group, an alkenyl group and an alkynyl group; the heterocycle comprises cyclic ether, morpholine, pyridine, triazole, furan, pyran, piperidine and pyrrolePyrazole, pyrazine, pyridazine, imidazole. The electrolyte can remarkably improve the high-temperature cycle performance of the electrochemical device under the high voltage of 4.4V to 4.8V, and reduce the increase of cycle impedance.
Description
Technical Field
The present application relates to the field of electrochemistry, and in particular, to an electrolyte, an electrochemical device, and an electronic device.
Background
Along with the recent reduction in weight and size of electrical products, there is an increasing demand for electrochemical devices (for example, lithium ion batteries) to be lightweight and thin. The development of lithium ion secondary batteries with high energy density is gradually advancing, the designed use upper limit voltage is also improved, the rated voltage of the lithium ion battery of the lithium cobaltate system can reach 4.45V to 4.5V at present, which means that the damage to positive and negative electrode structures is more serious in high-voltage storage and charge and discharge, and therefore higher requirements are provided for the oxidation resistance and the film forming stability of the electrolyte.
A general method of improving the oxidation resistance of an electrolyte comprises: inert solvents with high oxidation potential such as fluorinated esters and fluorinated ethers are used; the content of additives such as nitrile or propane sultone is increased. But the fluoro solvent has high viscosity and weak ion transmission capability, so that the rapid charging under high voltage is difficult to realize; and increasing the amount of the additive further deteriorates the conductivity of the electrolyte and the battery resistance.
Therefore, how to develop an electrolyte additive capable of improving the cycle performance of a battery at high voltage has become an important issue for improving the battery performance.
Disclosure of Invention
In some embodiments, the present application provides an electrolyte comprising a compound represented by formula (I),
in the formula (I), R11Selected from covalent bond, oxygen, sulfur, C1-C10Alkylene group, C1-C5Alkyleneoxy or C1-C5An alkylenethio group including an alkylene group, an alkenylene group, or an arylene group;
R12selected from covalent bond, C1-C10Alkylene or C1-C10An alkylene sulfonyl group, the alkylene group including an alkylene group, an alkenylene group, or an arylene group;
x is selected from substituted or unsubstituted C1-C10A heterocyclic group containing at least one of oxygen, nitrogen or sulfur atoms; when substituted, the substituents include hydrocarbyl, cyano, or halogen, the hydrocarbyl including alkyl, alkenyl, or alkynyl; the heterocycle comprises at least one of cyclic ether, morpholine, pyridine, triazole, furan, pyran, piperidine, pyrrole, pyrazole, pyrazine, pyridazine or imidazole.
In some embodiments, the compound represented by formula (I) includes at least one of compounds represented by formulae (I-1) to (I-7);
in some embodiments, the compound of formula (I) is present in an amount of n%, 0.02. ltoreq. n.ltoreq.7, based on the weight of the electrolyte.
In some embodiments, the electrolyte further comprises at least one of fluoroethylene carbonate, vinylene carbonate; based on the weight of the electrolyte, the content of fluoroethylene carbonate is k%, the content of vinylene carbonate is m%, wherein k is more than or equal to 0, m is more than or equal to 0, k + m is more than 0, and k, m and n meet the condition that k + m-n is more than or equal to-1 and less than or equal to 12.
In some embodiments, 0 < k + m ≦ 14.
In some embodiments, the electrolyte further comprises a carboxylic acid ester; based on the weight of the electrolyte, the content of the carboxylic ester is a%, a is more than or equal to 5 and less than or equal to 30, and a and n satisfy the relation: n/a is more than or equal to 0.0005 and less than or equal to 0.7. In some embodiments, 0.05 ≦ n/a ≦ 0.1.
In some embodiments, the carboxylic acid ester comprises at least one of ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate.
In some embodiments, the electrolyte further includes at least one of a sulfonate compound or a nitrile compound.
In some embodiments, the sulfonate compound includes at least one of 1, 3-propane sultone, 2, 4-butane sultone.
In some embodiments, the sulfonate compound is present in an amount of 0.1 to 5% by weight of the electrolyte.
In some embodiments, the nitrile compound includes at least one of the compounds represented by formula (ii) through formula (v);
wherein R is21Selected from substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C1-C12An alkyleneoxy group; r31、R32Each independently selected from the group consisting of a covalent bond, substituted or unsubstituted C1-C12An alkylene group; r41、R42、R43Each independently selected from the group consisting of a covalent bond, a substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C1-C12An alkyleneoxy group; r51Selected from substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C2-C12Alkenylene, substituted or unsubstituted C6-C12Arylene, substituted or unsubstituted C3-C12A cyclic idene group; wherein when substituted, the substituent is halogen.
In some embodiments, the nitrile compound includes at least one of the following compounds;
in some embodiments, the nitrile compound is present in an amount of 0.05-10% by weight of the electrolyte.
In some embodiments, the present application also provides an electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte as described herein.
In some embodiments, the charge cut-off voltage of the electrochemical device is 4.4 to 4.8V.
Further, the present application also provides an electronic device comprising the electrochemical device described herein.
The electrolyte provided by the application can obviously improve the high-temperature cycle performance of an electrochemical device under the high voltage of 4.4V to 4.8V, and reduce the increase of cycle impedance.
Detailed Description
It is to be understood that the disclosed embodiments are merely exemplary of the application that may be embodied in various forms and that specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present application.
In the description of the present application, unless otherwise indicated, all groups of the compounds may be substituted or unsubstituted.
In the description of this application, the term "heteroatom" means an atom other than C, H. In some embodiments, the heteroatoms include at least one of B, N, O, Si, P, S. In the description of this application, the term "heterocyclyl" refers to a cyclic group that contains at least one heteroatom. In some embodiments, heterocyclyl includes heterocyclyl containing at least one of an oxygen, nitrogen, or sulfur atom. In some embodiments, the heterocycle comprises a cyclic ether, morpholine, pyridine, triazole, furan, pyran, piperidine, pyrrole, pyrazole, pyrazine, pyridazine, imidazole.
In the description of this application, a hydrocarbylene group is a divalent group formed by a hydrocarbyl group lacking one hydrogen atom. An alkylene group is a divalent group formed by an alkyl group having one hydrogen atom removed therefrom, an alkenylene group is a divalent group formed by an alkenyl group having one hydrogen atom removed therefrom, and an arylene group is a divalent group formed by an aryl group having one hydrogen atom removed therefrom. In the description of the present application, subunit structures not explicitly described are read in accordance with the description in this paragraph.
In the description of the present application, alkyleneoxy is a divalent group formed by an ether that has two hydrogen atoms removed, which ether may contain one or more ether linkages.
In the description of the present application, the cyclic ether may contain one or more ether linkages.
In the description of the present application, terms, substitutions in structural formulae, and the like, which are not explicitly described, should be understood in accordance with conventional, customary means or manners known to those of ordinary skill in the art.
The electrolyte solution, electrochemical device and electronic device according to the present invention will be described in detail below.
[ electrolyte ]
< additive A >
In some embodiments, the electrolyte contains an additive A, wherein the additive A is at least one of the compounds represented by the formula (I);
in the formula (I), R11Selected from covalent bond, oxygen, sulfur, C1-C10Alkylene group, C1-C5Alkyleneoxy or C1-C5An alkylenethio group including an alkylene group, an alkenylene group, or an arylene group; r12Selected from covalent bond, C1-C10Alkylene or C1-C10An alkylene sulfonyl group, the alkylene group including an alkylene group, an alkenylene group, or an arylene group; x is selected from substituted or unsubstituted C1-C10A heterocyclic group containing at least one of oxygen, nitrogen or sulfur atoms; when substituted, the substituents include hydrocarbyl, cyano, or halogen, the hydrocarbyl including alkyl, alkenyl, or alkynyl; the heterocycle comprises at least one of cyclic ether, morpholine, pyridine, triazole, furan, pyran, piperidine, pyrrole, pyrazole, pyrazine, pyridazine or imidazole.
In the Electrolyte, the additive A is a heterocycle substituted furfural derivative, wherein an aldehyde group can enhance the stability of Solid Electrolyte Interface (SEI), and a dislocation substituent group containing a heteroatom and a heterocycle also has a film forming effect, particularly nitrogen-containing and sulfur-containing groups, so that the material can have the double functions of protecting a positive electrode and a negative electrode, the high-temperature cycle performance of an electrochemical device under the high voltage of 4.4V to 4.8V is remarkably improved, and the cycle impedance growth of the electrochemical device under the chemical system is reduced.
In some embodiments, the compound represented by formula (I) comprises at least one of the compounds represented by formulae (I-1) to (I-7);
in some embodiments, the compound of formula (I) is present in an amount of n%, 0.02. ltoreq. n.ltoreq.7, based on the weight of the electrolyte.
< additive B >
In some embodiments, the electrolyte may further include an additive B, where the additive B is at least one of fluoroethylene carbonate and vinylene carbonate.
In some embodiments, the fluoroethylene carbonate is present in a amount of k% and the vinylene carbonate is present in an amount of m%, wherein k is greater than or equal to 0, m is greater than or equal to 0, 0 < k + m is less than or equal to 14, and k, m, and n satisfy-1 is less than or equal to k + m-n is less than or equal to 12, based on the weight of the electrolyte.
< additive C >
In some embodiments, the electrolyte may further include at least one of a sulfonate compound or a nitrile compound.
In some embodiments, the sulfonate compound includes at least one of 1, 3-propane sultone, 2, 4-butane sultone.
In some embodiments, the sulfonate compound is present in an amount of 0.1% to 5% by weight of the electrolyte.
In some embodiments, the nitrile compound comprises at least one of the compounds represented by formula (ii) through formula (v);
wherein R is21Selected from substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C1-C12An alkyleneoxy group; r31、R32Each independently selected from the group consisting of a covalent bond, substituted or unsubstituted C1-C12An alkylene group; r41、R42、R43Each independently selected from the group consisting of a covalent bond, a substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C1-C12An alkyleneoxy group; r51Selected from substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C2-C12Alkenylene, substituted or unsubstituted C6-C12Arylene, substituted or unsubstituted C3-C12A cyclic idene group; wherein when substituted, the substituent is halogen.
In some embodiments, the nitrile compound comprises at least one of the following compounds:
in some embodiments, the nitrile compound is present in an amount of 0.05-10% by weight of the electrolyte.
In some embodiments, the nitrile compound is present in an amount of 0.1 to 10% by weight of the electrolyte.
< organic solvent >
In some embodiments, the electrolyte further comprises an organic solvent. The organic solvent is an organic solvent known in the art to be suitable for an electrochemical device, and for example, a nonaqueous organic solvent is generally used. In some embodiments, the non-aqueous organic solvent comprises at least one of a carbonate-based solvent, a carboxylate-based solvent.
In some embodiments, the carbonate-based solvent comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate.
In some embodiments, the carboxylic acid ester solvent comprises at least one of ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate.
In some embodiments, the content of the carboxylic acid ester is a% based on the weight of the electrolyte, and when the compound represented by formula (I) is contained in the electrolyte in an amount of n%, 5. ltoreq. a.ltoreq.30, and a and n satisfy the relationship: n/a is more than or equal to 0.0005 and less than or equal to 0.7, if the n/a ratio is lower, the electrolyte can not form an effective protective layer on the anode, and the solvent is easy to decompose to generate gas; if the n/a ratio is too high, the negative electrode has large film forming resistance and cannot provide a smooth lithium ion transmission channel. In some embodiments, 0.05 ≦ n/a ≦ 0.1.
In the present application, one kind of non-aqueous organic solvent may be used as the organic solvent in the electrolyte solution, or a mixture of a plurality of kinds of non-aqueous organic solvents may be used, and when a mixed solvent is used, electrochemical devices having different properties may be obtained by controlling the mixing ratio.
< electrolyte salt >
In some embodiments, the electrolyte further comprises an electrolyte salt. The electrolyte salt is well known in the art as an electrolyte salt suitable for an electrochemical device. For different electrochemical devices, suitable electrolyte salts may be selected. For example, for lithium ion batteries, lithium salts are commonly used as electrolyte salts.
In some embodiments, the lithium salt comprises at least one of an organic lithium salt or an inorganic lithium salt.
In some embodiments, the lithium salt comprises LiPF6、LiBF4、LiB(C6H5)4、LiCH3SO3、LiCF3SO3、LiN(SO2CF3)2、LiC(SO2CF3)3、LiSiF6At least one of LiBOB and LiDFOB, preferably LiPF6。
In the present application, the content of the electrolyte is not particularly limited, and may be reasonably added according to actual needs. In the present application, the preparation method of the electrolyte is not limited, and can be prepared according to a conventional preparation method of the electrolyte known to those skilled in the art.
[ electrochemical device ]
Next, the electrochemical device of the present application will be described.
The electrochemical device of the present application may be any one selected from the following devices: a lithium secondary battery or a sodium ion battery. In particular, the electrochemical device is a lithium secondary battery.
In some embodiments, the electrochemical device comprises a positive electrode tab, a negative electrode tab, a separator, and an electrolyte as described herein before.
< Positive electrode sheet >
The positive electrode tab is a positive electrode tab known in the art that can be used in an electrochemical device. In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.
In some embodiments, the positive active material includes at least one of Lithium Cobaltate (LCO), lithium nickel manganese cobalt ternary material (NCM), lithium iron phosphate, lithium iron manganese phosphate, and lithium manganate. In some embodiments, further electrochemical performance can be obtained with the electrolyte additives provided herein when the electrochemical device employs an LCO, NCM system.
The positive electrode conductive agent is used for providing conductivity for the positive electrode, and can improve the conductivity of the positive electrode. The positive electrode conductive agent is a conductive material known in the art that can be used as a positive electrode active material layer. The positive electrode conductive agent may be selected from any conductive material as long as it does not cause a chemical change. In some embodiments, the positive electrode conductive agent includes at least one of a carbon-based material (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber), a metal-based material (e.g., metal powder or metal fiber including copper, nickel, aluminum, silver, etc.), a conductive polymer (e.g., a polyphenylene derivative).
The positive electrode binder is a binder known in the art that can be used as a positive electrode active material layer. The positive electrode binder may improve binding properties between the positive electrode active material particles and the positive electrode current collector. In some embodiments, the positive electrode binder comprises at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy, nylon.
The positive current collector is a metal, in some embodiments, such as, but not limited to, aluminum foil.
In some embodiments, the structure of the positive electrode tab is a structure of a positive electrode tab that can be used in an electrochemical device, which is well known in the art.
In some embodiments, the method for preparing the positive electrode sheet is a method for preparing a positive electrode sheet that can be used for an electrochemical device, which is well known in the art. In some embodiments, in the preparation of the positive electrode slurry, a positive electrode active material, a binder, and if necessary, a conductive material and a thickener are generally added and dissolved or dispersed in a solvent to prepare a positive electrode slurry. The solvent is evaporated during the drying process. The solvent is a solvent known in the art that can be used as the positive electrode active material layer, and is, for example, but not limited to, N-methylpyrrolidone (NMP).
< negative electrode sheet >
The negative electrode tab is a negative electrode tab known in the art that may be used in an electrochemical device. In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. In some embodiments, the anode active material layer may include an anode active material, an anode conductive agent, and an anode binder.
In some embodiments, the negative active material includes at least one of lithium metal, lithium metal alloy, transition metal oxide, carbon material, and silicon-based material.
In some embodiments, the negative electrode binder may comprise various polymeric binders. In some embodiments, the negative electrode binder comprises at least one of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy, nylon.
In some embodiments, the negative electrode active material layer further includes a negative electrode conductive agent. The negative electrode conductive agent is used for providing conductivity to the negative electrode, and can improve the conductivity of the negative electrode. The negative electrode conductive agent is a conductive material known in the art that can be used as a negative electrode active material layer. The negative electrode conductive agent may be selected from any conductive material as long as it does not cause a chemical change.
In some embodiments, the structure of the negative electrode sheet is a structure of a negative electrode sheet that may be used in an electrochemical device, as is well known in the art.
In some embodiments, the method of preparing the negative electrode sheet is a method of preparing a negative electrode sheet that may be used for an electrochemical device, which is well known in the art. In some embodiments, in the preparation of the negative electrode slurry, a negative electrode active material, a binder, and if necessary, a conductive material and a thickener are generally added and then dissolved or dispersed in a solvent to prepare a negative electrode slurry. The solvent is evaporated during the drying process. The solvent is a solvent known in the art, such as, but not limited to, water, which can be used as the negative electrode active material layer. The thickener is a thickener known in the art that can be used as the anode active material layer, and is, for example, but not limited to, sodium carboxymethyl cellulose.
< isolation film >
In some embodiments, the electrochemical devices of the present application comprise a separator. The separator is a separator known in the art that can be used for an electrochemical device, such as, but not limited to, polyolefin porous films. In some embodiments, the polyolefin porous film substrate comprises a single layer or multiple layers of one or more of Polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-methyl methacrylate copolymer.
The form and thickness of the separator are not particularly limited.
The method of preparing the separator is a method of preparing a separator that can be used in an electrochemical device, which is well known in the art, for example: boehmite is mixed with polyacrylate and dissolved in deionized water to form a coating slurry, which is then uniformly coated on both surfaces of a porous substrate by a dimple coating method, and subjected to a drying process to obtain a desired separator.
In some embodiments, the charge cut-off voltage of the electrochemical devices of the present application is 4.4 to 4.8V.
[ electronic device ]
The electronic device of the present application may be any electronic device, such as, but not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a cellular phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium ion capacitor. Note that the electrochemical device of the present application is applicable to an energy storage power station, a marine vehicle, and an air vehicle, in addition to the above-listed electronic devices. The air transport carrier device comprises an air transport carrier device in the atmosphere and an air transport carrier device outside the atmosphere.
In some embodiments, an electronic device comprises an electrochemical device described herein.
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 specific embodiments of the present application, only an embodiment in which the battery is a lithium ion battery is shown, but the present application is not limited thereto. In the following examples and comparative examples, reagents, materials and the like used were commercially available or synthetically obtained, unless otherwise specified.
The lithium ion batteries of examples and comparative examples were prepared as follows.
1) Preparation of positive plate
The positive electrode active material lithium cobaltate (LiCoO)2) Mixing a conductive agent Super P and a binding agent polyvinylidene fluoride according to the weight ratio of 97.9:0.4:1.7, adding N-methylpyrrolidone (NMP), and uniformly stirring under the action of a vacuum stirrer to obtain anode slurry; uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil; and drying the aluminum foil, then carrying out cold pressing, cutting and slitting, and drying under a vacuum condition to obtain the positive plate.
2) Preparation of negative plate
Mixing the negative active material artificial graphite, the thickener sodium carboxymethyl cellulose (CMC) and the binder Styrene Butadiene Rubber (SBR) according to the weight ratio of 97:1:2, adding deionized water, and obtaining negative slurry under the action of a vacuum stirrer; uniformly coating the negative electrode slurry on a copper foil of a negative electrode current collector; and drying the copper foil, then carrying out cold pressing, cutting and slitting, and drying under a vacuum condition to obtain the negative plate.
3) Preparation of the separator
Boehmite was mixed with polyacrylate and dissolved into deionized water to form a coating slurry. And then uniformly coating the coating slurry on two surfaces of the polyethylene porous substrate by using a micro-gravure coating method, and drying to obtain the required separation film.
4) Preparation of the electrolyte
In a dry argon atmosphereIn a box, EC (ethylene carbonate), PC (propylene carbonate) and DEC (diethyl carbonate) are used as basic solvents in a weight ratio of 2:2:6, and the components are added according to the contents in tables 1 to 5, dissolved and fully stirred, and then lithium salt LiPF is added6Mixing uniformly to obtain LiPF6The content of (b) is 1 mol/L. Wherein, the contents of the components in the table are weight percentages calculated based on the weight of the electrolyte.
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; and (3) after welding a tab, placing the naked electric core into an outer packaging foil aluminum-plastic film, injecting the prepared electrolyte into the dried naked electric core, and performing vacuum packaging, standing, formation, shaping, capacity test and other processes to obtain the soft package lithium ion battery.
The performance test procedure of the lithium ion battery is explained next.
(1) High temperature cycle performance testing of lithium ion batteries
And (3) placing the lithium ion battery in a constant temperature box at 45 ℃ and standing for 30min to keep the temperature of the lithium ion battery constant. Charging the constant-temperature lithium ion battery to 4.45V at a constant current of 1C, then charging to 0.025C at a constant voltage of 4.45V, and then discharging to 3.0V at a constant current of 1C, which is a charge-discharge cycle, recording the first discharge capacity Q1. The charge and discharge cycle was repeated 400 times in the above manner, the test was stopped, and the discharge capacity Q after the cycle was recorded2. The capacity retention after high temperature cycling can be obtained by the following formula: capacity retention ratio after high temperature cycling ═ discharge capacity Q after cycling2First discharge capacity Q1×100％。
(2) Testing of cyclic impedance growth rate of lithium ion batteries
And (3) placing the lithium ion battery in a constant temperature box at 25 ℃ and standing for 1 hour. Charging the lithium ion battery to 4.45V at a constant current of 1C and charging the lithium ion battery to a current of 0.025C at a constant voltage, standing for 120min, then charging the lithium ion battery for 10 seconds at a direct current of 0.1C and charging the lithium ion battery for 360 seconds at a direct current of 1C, and then recording the direct current impedance of the lithium ion battery at a state of charge (SOC) of 80%. According to the standard in the high-temperature cycle performance test of the lithium ion battery (1), the battery is subjected to charge-discharge cycle for 400 times, and then the direct current impedance of the lithium ion battery in the 80% state of charge (SOC) is measured and recorded by the measuring method. The dc impedance of the lithium ion battery is calculated by the following formula, respectively: dc impedance (0.1C end-of-discharge voltage-1C end-of-discharge voltage)/(0.1C end-of-discharge current-1C end-of-discharge current). The cycle impedance growth rate of the lithium ion battery is calculated by the following formula: the cycle impedance increase rate is (dc impedance of lithium ion battery after cycle-dc impedance of lithium ion battery before cycle)/dc impedance of lithium ion battery before cycle × 100%.
Relevant parameters of the lithium ion batteries of examples and comparative examples and performance test results of the lithium ion batteries are shown in tables 1 to 5.
Wherein, table 1 shows the effect of the compound represented by formula (I) on the high temperature cycle performance and the cycle impedance growth rate of a lithium ion battery.
Table 2 shows the effect of the content of the compound represented by formula (I) in the electrolyte on the high-temperature cycle performance and the cycle resistance increase rate of the lithium ion battery.
Table 3 shows the effect of the content relationship of additive B and the compound represented by formula (I) on the high temperature cycle performance and the cycle resistance increase rate of the lithium ion battery.
Table 4 shows the effect of the content relationship of the carboxylate solvent and the compound represented by formula (I) on the high-temperature cycle performance and the cycle resistance increase rate of the lithium ion battery.
Table 5 shows the effect of additive C in combination with the compound represented by formula (I) on the high temperature cycle performance and the cycle impedance growth rate of a lithium ion battery.
TABLE 1
Note: "/" indicates that the component was not added.
The results of the performance tests in Table 1 show that the compound represented by the formula (I) is added to the electrolyteThe high-temperature cycle performance of the lithium ion battery can be obviously improved, and the cycle impedance increase of the lithium ion battery can be obviously reduced. Compared with the comparative examples 1-2, the compound represented by the formula (I) has more obvious high-temperature cycle improvement effect than a single furfural compound, because the LiN and Li which can enrich SEI are supported by the heterocyclic ring containing nitrogen, sulfur and oxygen atoms and connected on the furfuralxS and LixSOyAnd the compound formed by combining the heterocycle and the furfural has better high-voltage stability than the lithium alkoxide organic component formed by single furfural. As can be seen from examples 1-1 to 1-9, formula (I-4) has relatively good effects on the improvement of the high-temperature cycle capacity retention rate and the reduction of the increase in the resistance, and the following formulas (I-2) and (I-3) are probably because the branched heterocyclic groups are not too large, otherwise the steric hindrance is large, which affects the compactness of the film formation.
TABLE 2
Note: "/" indicates that the component was not added.
The performance test results of table 2 show that when the content of the compound represented by formula (I) in the electrolyte is in the range of 0.02% to 7%, it contributes to further improving the high-temperature cycle performance of the lithium ion battery and reducing the cycle resistance increase rate thereof. When the content of the compound represented by the formula (I) in the electrolyte is in the range of 0.5% to 3%, the compound has a remarkable improvement effect on the high-temperature cycle performance and the cycle impedance increase rate of the lithium ion battery. When the content of the compound shown in the formula (I) is lower than 0.02%, the improvement of the high-temperature cycle performance of the lithium battery under high voltage is not obvious; when the content of the compound represented by formula (I) is more than 7%, the compound in the electrolyte is excessive, resulting in a large interfacial film resistance, irreversible lithium precipitation, obstruction of an ion transport channel of the electrolyte, and acceleration of battery capacity fade.
TABLE 3
Note: "/" indicates that the component was not added.
The performance test results of Table 3 show that the lithium ion battery has significantly improved high temperature cycle performance and significantly reduced cycle resistance increase rate when the electrolyte contains additive B (at least one of fluoroethylene carbonate (FEC), Vinylene Carbonate (VC)) and the content of the first additive m% and the content of the compound represented by formula (I) n% satisfy-1. ltoreq. k + m-n. ltoreq.12. The appropriate amounts of FEC and VC, combined with the compound of formula (I), can further enrich the LiF content in the SEI film. Therefore, the combination use of FEC and VC with the compound of formula (I) at a proper content has a significant effect of improving the stability of the negative electrode in the high-temperature cycle of the lithium ion battery, but when the relative content of FEC and VC is high, the high-temperature cycle performance of the lithium ion battery is adversely affected, which may be because FEC and VC are easily oxidized, decomposed and gas generated at a high voltage, and the relative addition amount is too high, so that the additive composition cannot form a combined electrolyte interface having a good protection effect on the electrode plate and a good electrolyte ion channel. The combination of FEC, VC and the compound represented by formula (I) can further enhance the film-forming stability of the electrochemical device at high voltage on the negative electrode, inhibit impedance increase through synergistic effect, and improve the cycle performance of the lithium ion battery at high voltage.
TABLE 4
Note: "/" indicates that the component was not added.
The performance test results of table 4 show that when the electrolyte contains a carboxylic acid ester, it contributes to further improving the high-temperature cycle performance of the lithium ion battery and reducing the cycle resistance increase rate thereof. When the content a% of the carboxylic ester and the content n% of the compound represented by the formula (I) satisfy n/a is more than or equal to 0.05 and less than or equal to 0.1, the improvement on the high-temperature cycle performance and the increase rate of the cycle impedance of the lithium ion battery is particularly obvious. By introducing the carboxylate, the viscosity of the electrolyte can be effectively reduced, lithium ion transmission is facilitated, and film forming impedance is reduced, but excessive carboxylate is easily oxidized and decomposed under high voltage, and the lithium ion transmission in circulation is not facilitated to be maintained. By combining the compound with the compound shown in the formula (I) in a certain content proportion, the impedance growth can be further inhibited through synergistic action, and the cycle performance of the lithium ion battery under high voltage is improved.
TABLE 5
Note: "/" indicates that the component was not added.
The performance test results in table 5 show that, when the electrolyte contains the nitrile compound, the high-temperature cycle performance of the lithium ion battery is further improved and the cycle impedance growth rate is reduced, because the nitrile compound can form an organic protective layer on the surface of the positive electrode, and the organic molecules on the surface of the positive electrode can well separate the easily-oxidized components in the electrolyte from the surface of the positive electrode, so that the oxidation effect of the surface of the positive electrode on the electrolyte under high voltage is reduced, and the structural damage caused by excessive oxygen release of the transition metal oxide of the positive electrode is reduced. When the content of the nitrile is 0.5 to 5 percent, the improvement on the high-temperature cycle performance and the cycle impedance growth rate of the lithium ion battery is particularly obvious.
It is understood from examples 5 to 20, examples 5 to 24, comparative examples 2 to 4, and examples 5 to 22 that when a proper amount of a sulfonate compound is further added to the electrolyte, the high-temperature cycle performance and the resistance increase rate of the lithium ion battery are significantly improved.
From examples 5 to 20 to examples 5 to 24, it is understood from comparison with examples 2 to 4, examples 3 to 13, examples 3 to 14 and examples 5 to 18 that, in addition to the compound of formula (I) being included in the electrolyte, the stability of the positive and negative electrode electrolyte interfaces of the lithium ion battery in a high voltage system can be improved by using one or more of fluoroethylene carbonate, vinylene carbonate, carboxylic ester, nitrile compound or compound containing a sulfoxy double bond in a suitable range in combination, thereby improving the high temperature cycle performance of the lithium ion battery and suppressing the increase in impedance.
Although the present disclosure has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (12)
1. An electrolyte comprising a compound represented by the formula (I),
in the formula (I), R11Selected from covalent bond, oxygen, sulfur, C1-C10Alkylene group, C1-C5Alkyleneoxy or C1-C5An alkylenethio group including an alkylene group, an alkenylene group, or an arylene group;
R12selected from covalent bond, C1-C10Alkylene or C1-C10An alkylene sulfonyl group, the alkylene group including an alkylene group, an alkenylene group, or an arylene group;
x is selected from substituted or unsubstituted C1-C10A heterocyclic group containing at least one of oxygen, nitrogen or sulfur atoms; when substituted, the substituents include hydrocarbyl, cyano, or halogen, the hydrocarbyl including alkyl, alkenyl, or alkynyl; the heterocycle comprises at least one of cyclic ether, morpholine, pyridine, triazole, furan, pyran, piperidine, pyrrole, pyrazole, pyrazine, pyridazine or imidazole.
2. The electrolyte of claim 1, wherein the compound represented by formula (I) includes at least one of compounds represented by formulae (I-1) to (I-7);
3. the electrolyte according to claim 1, wherein the compound represented by formula (I) is contained in an amount of n%, 0.02. ltoreq. n.ltoreq.7, based on the weight of the electrolyte.
4. The electrolyte of claim 3, wherein the electrolyte further comprises at least one of fluoroethylene carbonate, vinylene carbonate;
based on the weight of the electrolyte, the content of fluoroethylene carbonate is k%, the content of vinylene carbonate is m%, wherein k is more than or equal to 0, m is more than or equal to 0, k + m is more than 0, and k, m and n meet the condition that k + m-n is more than or equal to-1 and less than or equal to 12.
5. The electrolyte of claim 3, wherein the electrolyte further comprises a carboxylic acid ester; based on the weight of the electrolyte, the content of the carboxylic ester is a%, a is more than or equal to 5 and less than or equal to 30, and a and n satisfy the relation: n/a is more than or equal to 0.0005 and less than or equal to 0.7.
6. The electrolyte of claim 5, wherein the carboxylic acid ester comprises at least one of ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.
7. The electrolyte of any of claims 1-6, wherein the electrolyte further comprises at least one of 1, 3-propane sultone, 2, 4-butane sultone, or a nitrile compound.
8. The electrolyte solution according to claim 7, wherein the nitrile compound includes at least one of compounds represented by formulae (II) to (V);
N≡C-R21-C ≡ N formula (II)
Wherein R is21Selected from substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C1-C12An alkyleneoxy group;
R31、R32each independently selected from the group consisting of a covalent bond, substituted or unsubstituted C1-C12An alkylene group;
R41、R42、R43each independently selected from the group consisting of a covalent bond, a substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C1-C12An alkyleneoxy group;
R51selected from substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C2-C12Alkenylene, substituted or unsubstituted C6-C12Arylene, substituted or unsubstituted C3-C12A cyclic idene group;
wherein when substituted, the substituent is halogen.
9. The electrolyte of claim 8, wherein the nitrile compound includes at least one of the following compounds;
10. an electrochemical device comprising a positive electrode, a negative electrode, a separator, and the electrolyte according to any one of claims 1 to 9.
11. The electrochemical device according to claim 10, wherein a charge cut-off voltage of the electrochemical device is 4.4 to 4.8V.
12. An electronic device comprising the electrochemical device according to claims 10-11.
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| CN112086682A (en) * | 2020-09-29 | 2020-12-15 | 宁德新能源科技有限公司 | Electrolyte solution, electrochemical device, and electronic device |
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| CN110783626B (en) * | 2019-10-18 | 2021-01-05 | 宁德时代新能源科技股份有限公司 | Electrolyte, lithium ion battery, battery module, battery pack and device |
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| JPH06338346A (en) * | 1993-05-28 | 1994-12-06 | Matsushita Electric Ind Co Ltd | Lithium secondary battery |
| JP2008147014A (en) * | 2006-12-11 | 2008-06-26 | Sony Corp | Nonaqueous electrolyte composition and nonaqueous electrolyte secondary battery |
| CN105580184A (en) * | 2013-09-25 | 2016-05-11 | 国立大学法人东京大学 | Non-aqueous electrolyte secondary battery |
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