CN111628219A - Electrolyte solution, electrochemical device containing electrolyte solution, and electronic device - Google Patents

Electrolyte solution, electrochemical device containing electrolyte solution, and electronic device Download PDF

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Publication number
CN111628219A
CN111628219A CN202010504621.9A CN202010504621A CN111628219A CN 111628219 A CN111628219 A CN 111628219A CN 202010504621 A CN202010504621 A CN 202010504621A CN 111628219 A CN111628219 A CN 111628219A
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electrolyte
substituted
additive
unsubstituted
lithium
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许艳艳
徐春瑞
郑建明
韩翔龙
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—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
    • 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 present application relates to an electrolyte solution containing an additive a and a silazane, and an electrochemical device and an electronic device including the electrolyte solution. The electrochemical device of the present application, including the electrolyte, has significantly improved over-discharge storage performance and high-temperature cycle performance.

Description

Electrolyte solution, electrochemical device containing electrolyte solution, and electronic device
Technical Field
The present disclosure relates to the field of energy storage technologies, and more particularly, to an electrolyte, and an electrochemical device and an electronic device including the electrolyte.
Background
Portable electronic products such as cameras, digital video cameras, mobile phones, notebook computers, and the like are widely used in daily life of people. With the development of science and technology and market demands, higher requirements are put forward on the volume, weight, function and service life of portable electronic products. The lithium ion battery has the characteristics of high energy density, high working voltage, long service life, environmental friendliness and the like, and is widely applied to portable electronic products. The electrolyte is used as an important component of the lithium ion battery, and charges are transmitted between the anode and the cathode of the battery, so that the electrolyte plays an important role in the performance of the battery. The electrolyte is generally composed of a solvent, an additive and a lithium salt, namely commercial lithium salt LiPF6Has the advantages of good solubility, high conductivity, good film-forming property, passivation of current collector, wide electrochemical window and the like,and LiPF6Poor thermal stability, easy decomposition into LiF and PF5，PF5And reacts with trace amount of water in the electrolyte to generate HF, which causes rapid increase of acidity and chromaticity of the electrolyte, and HF corrodes the positive and negative electrodes to deteriorate the performance of the battery.
In the first charging process of the lithium ion battery, a layer of Solid Electrolyte Interface (SEI) film is formed on the surface of an electrode, and the SEI film can inhibit the contact of electrolyte and a positive electrode and a negative electrode and relieve the corrosion of HF to the electrode. Since lithium ions must pass through the SEI film regardless of charging or discharging, the properties of the SEI film determine many properties of the battery (e.g., cycle performance, high-temperature performance, rate performance). A small amount of additive is added into the electrolyte to improve an SEI film so as to improve the performance of the lithium ion battery. However, the current electrolyte additive is still not ideal in improving the high-temperature storage performance and cycle performance of the lithium ion battery, and the electrolyte still decomposes at a higher temperature to cause ballooning, which brings about a serious safety hazard, so that it is necessary to develop a new additive to further improve the high-temperature storage performance and cycle performance of the lithium ion battery.
Disclosure of Invention
The present application provides an electrolyte and an electrochemical device including the same, in an attempt to solve at least one of the problems existing in the related art to at least some extent.
The application provides an electrolyte, which can capture proton impurities in the electrolyte, can form an excellent interface protection film on a positive electrode and a negative electrode, and has excellent Li+The transportability, in turn, can improve the cycle performance and storage performance of the electrochemical device.
According to an embodiment of the present application, there is provided an electrolyte comprising an additive a and a silazane, wherein the additive a comprises at least one of a phosphate ester of formula I or a phosphite ester of formula II:
Figure BDA0002526086310000021
wherein R is1、R2、R3、R4、R5、R6Each independently selected from substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl or substituted or unsubstituted C6To C10An aryl group; wherein when substituted, the substituent is at least one of halogen or cyano.
According to embodiments herein, the silazane comprises a compound represented by formula III:
Figure BDA0002526086310000022
wherein R is7、R8、R9Each independently selected from substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl or substituted or unsubstituted C6To C10Aryl, wherein when substituted, the substituent is halogen; wherein R is10And R11Each independently selected from hydrogen, substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl, substituted or unsubstituted C6To C10Aryl or a group of formula IV; wherein when substituted, the substituent is halogen; wherein
Figure BDA0002526086310000023
Represents the connection part of the key and the key,
Figure BDA0002526086310000024
wherein R is12、R13、R14Each independently selected from substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl or substituted or unsubstituted C6To C10An aryl group; wherein when substituted, the substituent is halogen; wherein the silazane is present in an amount of 0.01 to 3 wt% based on the weight of the electrolyte.
According to an embodiment of the application, additive a comprises:
Figure BDA0002526086310000031
Figure BDA0002526086310000041
one kind of the compound is used; wherein the content of the additive A is 0.01-5 wt% based on the weight of the electrolyte.
According to embodiments herein, the silazane comprises at least one of trimethylsilyldiethylamine, heptamethyldisilazane, hexamethyldisilazane, hexaethyldisilazane, or hexapropyldisilazane.
According to an embodiment of the present application, the electrolyte includes at least one of an additive B, an additive C, an additive D, an additive E, or an additive F, wherein the additive B includes at least one of vinylene carbonate, fluoroethylene ester, vinyl ethylene carbonate, 1, 3-dioxane, 1, 4-dioxane, or dioxolane; wherein the additive C comprises at least one of 1, 3-propane sultone, 1, 4-butane sultone, vinyl sulfate, methylene methane disulfonate or propenyl-1, 3-sultone; wherein the additive D comprises at least one of succinonitrile, glutaronitrile, adiponitrile, 2-methyleneglutaronitrile, dipropylmalononitrile, 1,3, 6-hexanetricarbonitrile, 1,2, 6-hexanetricarbonitrile, 1,3, 5-pentanetrimethylonitrile, 1, 2-bis (cyanoethoxy) ethane or ethoxy (pentafluoro) cyclotriphosphazene; wherein the additive E comprises at least one of lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium bisthiooxalato borate, lithium difluorooxalato borate, lithium difluorophosphate, lithium tetrafluoroborate, or lithium 4, 5-dicyano-2-trifluoromethylimidazole; wherein the additive F comprises at least one of succinic anhydride, glutaric anhydride, citraconic anhydride, maleic anhydride, methylsuccinic anhydride, 2, 3-dimethylmaleic anhydride or trifluoromethylmaleic anhydride, and the content of any one of the additive B, the additive C, the additive D, the additive E or the additive F is 0.01-7 wt% based on the weight of the electrolyte.
According to an embodiment of the present application, an electrolyte includes a cyclic ester and a chain ester in a weight ratio of 1:9 to 7:3, wherein the cyclic ester includes at least one of ethylene carbonate, propylene carbonate, γ -butyrolactone, ethylene carbonate substituted with a fluorine-containing group, or propylene carbonate substituted with a fluorine-containing group; wherein the chain ester comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, fluoroethyl methyl carbonate or ethyl fluoropropionate.
According to an embodiment of the present application, there is provided an electrochemical device including a positive electrode, a negative electrode, a separator, and any one of the above-described electrolytic solutions.
According to an embodiment of the present application, in an electrochemical device, based on the weight of an electrolyte, H in the electrolyte2The content of O is 100ppm or less.
According to the examples of the present application, the electrolyte solution retention amount in the electrochemical device is 0.5g/Ah to 4.0 g/Ah.
According to an embodiment of the present application, a positive electrode of an electrochemical device includes a positive electrode active material layer satisfying at least one of conditions (a) and (b): (a) the positive electrode active material layer had a compacted density of 2.5g/cm in a fully discharged state3-4.5g/cm3(ii) a (b) The anode active material layer has an exothermic peak at 225-300 ℃ by adopting a differential scanning calorimeter test.
There is also provided, in accordance with an embodiment of the present application, an electronic device, including any one of the electrochemical devices described above.
Additional aspects and advantages of embodiments of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the present application.
Detailed Description
Embodiments of the present application will be described in detail below. The embodiments described herein are illustrative and are provided to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application.
As used herein, the terms "substantially", "substantially" and "about" are used to describe and illustrate minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely as well as instances where the event or circumstance occurs in close proximity. For example, when used in conjunction with numerical values, the term can refer to a range of variation that is less than or equal to ± 10% of the stated numerical value, such as less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%. For example, two numerical values are considered to be "substantially" identical if the difference between the two numerical values is less than or equal to ± 10% (e.g., less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%) of the mean of the values.
Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity, and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
In the detailed description and claims, a list of items linked by the term "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item A may comprise a single component or multiple components. Item B may comprise a single component or multiple components. Item C may comprise a single component or multiple components.
The term "alkyl" is intended to be a straight chain saturated hydrocarbon structure having from 1 to 20 carbon atoms. "alkyl" is also contemplated to be a branched or cyclic hydrocarbon structure having from 3 to 20 carbon atoms. For example, the alkyl group may be an alkyl group of 1 to 20 carbon atoms, an alkyl group of 1 to 10 carbon atoms, an alkyl group of 1 to 5 carbon atoms, an alkyl group of 5 to 20 carbon atoms, an alkyl group of 5 to 15 carbon atoms, or an alkyl group of 5 to 10 carbon atoms. When an alkyl group having a particular carbon number is specified, all geometric isomers having that carbon number are intended to be encompassed; thus, for example, "butyl" is meant to include n-butyl, sec-butyl, isobutyl, tert-butyl, and cyclobutyl; "propyl" includes n-propyl, isopropyl and cyclopropyl. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl, and the like. In addition, the alkyl group may be optionally substituted.
The term "alkenyl" refers to a monovalent unsaturated hydrocarbon group that can be straight or branched chain and has at least one and typically 1,2, or 3 carbon-carbon double bonds. Unless otherwise defined, the alkenyl group typically contains 2 to 20 carbon atoms, and may be, for example, an alkenyl group of 2 to 20 carbon atoms, an alkenyl group of 6 to 20 carbon atoms, an alkenyl group of 2 to 10 carbon atoms, or an alkenyl group of 2 to 6 carbon atoms. Representative alkenyl groups include, by way of example, ethenyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like. In addition, the alkenyl group may be optionally substituted.
The term "alkynyl" refers to a monovalent unsaturated hydrocarbon group that can be straight-chain or branched and has at least one, and typically 1,2, or 3 carbon-carbon triple bonds. Unless otherwise defined, the alkynyl group typically contains 2 to 20 carbon atoms, and may be, for example, an alkynyl group of 2 to 20 carbon atoms, an alkynyl group of 6 to 20 carbon atoms, an alkynyl group of 2 to 10 carbon atoms, or an alkynyl group of 2 to 6 carbon atoms. Representative alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like. In addition, the alkynyl group may be optionally substituted.
The term "aryl" encompasses monocyclic and polycyclic ring systems. Polycyclic rings can have two or more rings in which two carbons are common to two adjoining rings (the rings are "fused"), wherein at least one of the rings is aromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryls, heterocyclics, and/or heteroaryls. For example, the aryl group may be C6To C50Aryl radical, C6To C40Aryl radical, C6To C30Aryl radical, C6To C20Aryl or C6To C10And (4) an aryl group. Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl, and naphthalen-1-yl, naphthalen-2-yl, and the like. In addition, the aryl group may be optionally substituted.
As used herein, the term "halogen" may be F, Cl, Br or I.
When the above substituents are substituted, the substituents may be selected from the group consisting of: halogen, alkyl, cycloalkyl, alkenyl, aryl and heteroaryl.
Embodiments of the present application provide an electrolyte and an electrochemical device and an electronic device including the same. In some embodiments, the electrochemical device is a lithium ion battery.
First, electrolyte
Embodiments of the present application provide an electrolyte comprising an organic solvent, an electrolyte, and an additive comprising additive a and a silazane. In some embodiments, the electrolyte is a nonaqueous electrolyte.
Additive A
In some embodiments, additive a comprises at least one of a phosphate ester of formula I or a phosphite ester of formula II:
Figure BDA0002526086310000071
in the formulae I and II, R1、R2、R3、R4、R5、R6Each independently selected from substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl or substituted or unsubstituted C6To C10An aryl group; wherein when substituted, the substituent is at least one of halogen or cyano.
In some embodiments, additive a comprises:
Figure BDA0002526086310000072
Figure BDA0002526086310000081
Figure BDA0002526086310000082
at least one of (1).
In some embodiments, additive a is present in an amount of 0.01 wt% to 5 wt%, based on the weight of the electrolyte. The additive A in the content range can form a relatively complete interface protective film without increasing excessive interface film resistance. In some embodiments, additive a is present in an amount of about 0.01 wt%, about 0.05 wt%, about 0.1 wt%, about 0.3 wt%, about 0.5 wt%, about 1 wt%, about 1.5 wt%, about 2 wt%, about 2.5 wt%, about 3 wt%, about 3.5 wt%, about 4 wt%, about 4.5 wt%, about 5 wt%, 0.01 wt% to 1 wt%, 0.1 wt% to 0.5 wt%, 0.1 wt% to 3 wt%, 0.1 wt% to 5 wt%, 1 wt% to 3 wt%, 1 wt% to 5 wt%, or 3 wt% to 5 wt%, etc., based on the weight of the electrolyte.
Silazanes
In some embodiments, the silazane comprises a compound represented by formula III:
Figure BDA0002526086310000091
in formula III, R7、R8、R9Each independently selected from substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl or substituted or unsubstituted C6To C10Aryl, wherein when substituted, the substituent is halogen; wherein R is10And R11Each independently selected from hydrogen, substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl, substituted or unsubstituted C6To C10Aryl or a group of formula IV; wherein when substituted, the substituent is halogen; wherein
Figure BDA0002526086310000092
Represents the connection part of the key and the key,
Figure BDA0002526086310000093
in formula IV, R12、R13、R14Each independently selected from substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl or substituted or unsubstituted C6To C10An aryl group; wherein when substituted, the substituent is halogen.
In some embodiments, the silazane comprises at least one of trimethylsilyldiethylamine, heptamethyldisilazane, hexamethyldisilazane, hexaethyldisilazane, or hexapropyldisilazane.
In some embodiments, the silazane is present in an amount of 0.01 wt% to 3 wt%, based on the weight of the electrolyte. In some embodiments, the silazane is present in an amount of about 0.01 wt%, about 0.05 wt%, about 0.1 wt%, about 0.3 wt%, about 0.5 wt%, about 1 wt%, about 1.5 wt%, about 2 wt%, about 2.5 wt%, about 3 wt%, 0.01 wt% to 1 wt%, 0.1 wt% to 3 wt%, 0.5 wt% to 1 wt%, 0.5 wt% to 3 wt%, 1 wt% to 2 wt%, or 1 wt% to 3 wt%, etc., based on the weight of the electrolyte.
The additive A has higher reduction potential, so that good interface protection can be preferentially formed on the negative electrode, and the reduction decomposition of the electrolyte on the negative electrode is further inhibited; meanwhile, the silazane is added to adsorb trace water in the electrolyte, the generation of HF is inhibited, the corrosion effect of HF on the anode and the cathode is reduced, the stability of the electrolyte is enhanced, long branched chains of the silazane can be unfolded to form a net structure, and the additive A is induced to form a film on the cathode more uniformly and compactly. Therefore, the additive A and the silazane have synergistic effect, can stabilize the electrolyte, form a uniform and compact interface film with low resistance on the positive electrode and the negative electrode, and effectively improve the high-temperature cycle performance and the over-discharge storage performance of the electrochemical device.
Other additives
In some embodiments, the electrolyte can include at least one of additive B, additive C, additive D, additive E, or additive F in addition to additive a and the silazane.
In some embodiments, additive B comprises at least one of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), Vinyl Ethylene Carbonate (VEC), 1, 3-dioxane, 1, 4-dioxane, or dioxolane. In some embodiments, the additive B is present in an amount of 0.01 wt% to 7 wt%, based on the weight of the electrolyte. In some embodiments, the additive B is present in an amount of about 0.01 wt%, about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 6.5 wt%, about 7 wt%, 0.1 wt% to 5 wt%, 0.1 wt% to 6 wt%, 0.5 wt% to 6 wt%, or 1 wt% to 7 wt%, etc., based on the weight of the electrolyte.
In some embodiments, additive C comprises at least one of 1, 3-Propane Sultone (PS), 1, 4-Butane Sultone (BS), vinyl sulfate (DTD), Methylene Methanedisulfonate (MMDS), or propenyl-1, 3-sultone (PTS). In some embodiments, the additive C is present in an amount of 0.01 wt% to 7 wt%, based on the weight of the electrolyte. In some embodiments, the additive C is present in an amount of about 0.01 wt%, about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, 0.1 wt% to 2 wt%, 0.5 wt% to 5 wt%, or 1 wt% to 5 wt%, etc., based on the weight of the electrolyte.
In some embodiments, additive D comprises at least one of succinonitrile, glutaronitrile, adiponitrile, 2-methyleneglutaronitrile, dipropylacrylonitrile, 1,3, 6-hexanetricarbonitrile, 1,2, 6-hexanetricarbonitrile, 1,3, 5-pentanetrimethylonitrile, 1, 2-bis (cyanoethoxy) ethane, or ethoxy (pentafluoro) cyclotriphosphazene. In some embodiments, the additive D is present in an amount of 0.01 wt% to 7 wt%, based on the weight of the electrolyte. In some embodiments, the additive D is present in an amount of about 0.01 wt%, about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 6.5 wt%, about 7 wt%, 0.1 wt% to 5 wt%, 0.1 wt% to 2 wt%, 0.5 wt% to 5 wt%, or 1 wt% to 7 wt%, etc., based on the weight of the electrolyte.
In some embodiments, additive E comprises at least one of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (oxalato) borate, lithium difluoro (phosphorodifluoride) (LiDFP), lithium tetrafluoroborate, or lithium 4, 5-dicyano-2-trifluoromethylimidazole. In some embodiments, the additive E is present in an amount of 0.01 wt% to 5 wt%, based on the weight of the electrolyte. In some embodiments, the additive E is present in an amount of about 0.01 wt%, about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, 0.01 wt% to 1 wt%, 0.1 wt% to 2 wt%, 0.5 wt% to 2 wt%, or 0.5 wt% to 5 wt%, etc., based on the weight of the electrolyte.
In some embodiments, the additive F comprises at least one of succinic anhydride, glutaric anhydride, citraconic anhydride, maleic anhydride, methylsuccinic anhydride, 2, 3-dimethylmaleic anhydride, or trifluoromethylmaleic anhydride. In some embodiments, the additive F is present in an amount of 0.01 wt% to 7 wt%, based on the weight of the electrolyte. In some embodiments, the additive F is present in an amount of about 0.01 wt%, about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, 0.1 wt% to 2 wt%, 0.5 wt% to 5 wt%, or 1 wt% to 5 wt%, etc., based on the weight of the electrolyte.
In some embodiments, the electrolyte further comprises a non-aqueous organic solvent, wherein the non-aqueous organic solvent comprises a cyclic ester and a chain ester, and the weight ratio of the cyclic ester to the chain ester is 1:9 to 7: 3. In some embodiments, the cyclic ester comprises at least one of ethylene carbonate, propylene carbonate, γ -butyrolactone, ethylene carbonate substituted with a fluorine-containing group, or propylene carbonate substituted with a fluorine-containing group. In some embodiments, the chain ester comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, fluoroethyl carbonate, or ethyl fluoropropionate.
In some embodiments, the electrolyte comprises at least one of a lithium salt, a sodium salt, or a potassium salt.
In some embodiments, the lithium salt comprises lithium hexafluorophosphate (LiPF)6) Lithium bistrifluoromethanesulfonylimide (LiN (CF)3SO2)2) Lithium bis (fluorosulfonyl) imide (LiN (SO)2F)2) Lithium bis (oxalato) borate (LiB (C))2O4)2) Lithium difluorooxalato borate (LiBF)2(C2O4) Lithium hexafluoroarsenate (LiAsF)6) Lithium perchlorate (LiClO)4) Or lithium trifluoromethanesulfonate (LiCF)3SO3) At least one of (1). In some embodiments, the concentration of the lithium salt in the electrolyte is from 0.5mol/L to 1.5 mol/L. In some embodiments, the concentration of the lithium salt in the electrolyte is about 0.5mol/L, about 0.8mol/L, about 1.2mol/L, about 1.5mol/L, 0.5mol/L-1mol/L, 0.8mol/L-1.2mol/L, or 1mol/L-1.5mol/L, and the like.
In some embodiments, the sodium salt comprises sodium hexafluorophosphate (NaPF)6) Sodium bistrifluoromethanesulfonylimide (NaN (CF)3SO2)2) Bis (fluorosulfonyl) imide sodium (NaN (SO)2F)2) Boric acid bis (oxalato) saltSodium (NaB (C)2O4)2) Sodium difluorooxalate (NaBF)2(C2O4) Sodium hexafluoroarsenate (NaAsF)6) Sodium perchlorate (NaClO)4) Or sodium trifluoromethanesulfonate (NaCF)3SO3) At least one of (1). In some embodiments, the concentration of the sodium salt in the electrolyte is 0.5mol/L to 1.5 mol/L. In some embodiments, the concentration of the sodium salt in the electrolyte is about 0.5mol/L, about 1mol/L, about 1.2mol/L, about 1.5mol/L, 0.5mol/L-1mol/L, 0.8mol/L-1.2mol/L, or 1mol/L-1.5mol/L, and the like.
In some embodiments, the potassium salt comprises potassium hexafluorophosphate (KPF)6) Potassium bistrifluoromethanesulfonylimide (KN (CF)3SO2)2) Potassium bis (fluorosulfonyl) imide (KN (SO)2F)2) Potassium bis (oxalato) borate (KB (C)2O4)2) Potassium difluorooxalato borate (KBF)2(C2O4) Potassium hexafluoroarsenate (KAsF)6) Potassium perchlorate (KClO)4) Or potassium trifluoromethanesulfonate (KCF)3SO3) At least one of (1). In some embodiments, the concentration of the potassium salt in the electrolyte is 0.5mol/L to 1.5 mol/L. In some embodiments, the concentration of the potassium salt in the electrolyte is about 0.5mol/L, about 1mol/L, about 1.2mol/L, about 1.5mol/L, 0.5mol/L-1mol/L, 0.8mol/L-1.2mol/L, or 1mol/L-1.5mol/L, and the like.
Two, electrochemical device
Embodiments of the present application also provide an electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte of the present application. The electrochemical device of the present application may include any device in which electrochemical reactions occur, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. In some embodiments, the electrochemical device of the present application includes a positive electrode having a positive electrode active material capable of occluding and releasing metal ions; a negative electrode having a negative electrode active material capable of occluding and releasing metal ions; a separator interposed between the positive electrode and the negative electrode; and an electrolyte of the present application.
Electrolyte solution
The electrolyte used in the electrochemical device of the present application is any of the electrolytes described above in the present application. In addition, the electrolyte used in the electrochemical device of the present application may further include other electrolytes within a range not departing from the gist of the present application.
In some embodiments, in the electrochemical device, H in the electrolyte is based on the weight of the electrolyte2The weight percentage of O is less than or equal to 100 ppm. In some embodiments, H in the electrolyte is based on the weight of the electrolyte2The weight percentage of O is less than or equal to 10ppm, less than or equal to 50ppm or less than or equal to 80 ppm.
In some embodiments, the electrolyte has a retention capacity of 0.5g/Ah to 4.0g/Ah in the electrochemical device. In some embodiments, the electrolyte has a retention of about 0.5g/Ah, about 1g/Ah, about 1.5g/Ah, about 2g/Ah, about 2.5g/Ah, about 3g/Ah, about 3.5g/Ah, about 4.0g/Ah, 0.5g/Ah-1.0g/Ah, 1g/Ah-2.0g/Ah, 1g/Ah-4.0g/Ah, or 2g/Ah-4.0g/Ah, and the like.
Positive electrode
In some embodiments, the positive electrode includes a positive electrode active material layer satisfying at least one of conditions (a) and (b): (a) the positive electrode active material layer had a compacted density of 2.5g/cm in a fully discharged state3-4.5g/cm3(ii) a (b) The positive active material layer has an exothermic peak at 225 ℃ to 300 ℃ as measured by a differential scanning calorimeter.
In some embodiments, the positive electrode active material layer has a compacted density of about 2.5g/cm in a fully discharged state3About 3g/cm3About 3.5g/cm3About 4g/cm3About 4.5g/cm3、2.5g/cm3-3.5g/cm3Or 3g/cm3-4.5g/cm3And the like.
In some embodiments, the positive active material layer has an exothermic peak at 225 ℃ to 240 ℃, 225 ℃ to 280 ℃, 240 ℃ to 300 ℃, or 280 ℃ to 300 ℃ as measured using a differential scanning calorimeter.
In some embodiments, the positive electrode active material includes at least one lithiated intercalation compound that reversibly intercalates and deintercalates lithium ions. In some embodiments, the positive electrode active material includes a composite oxide. In some embodiments, the composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel.
In some embodiments, the positive active material is selected from the group consisting of lithium cobaltate, lithium Nickel Cobalt Manganese (NCM) ternary materials, lithium iron phosphate (LiFePO)4) Lithium manganate (LiMn)2O4) Or any combination thereof.
In some embodiments, the positive active material is LiNixCoyMnzO2Wherein y is more than or equal to 0 and less than or equal to 1, x is more than or equal to 0.3 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and x + y + z is less than or equal to 1.
In some embodiments, the positive active material is a mixture of lithium cobaltate and a lithium nickel manganese cobalt ternary material, wherein the ratio of lithium cobaltate to lithium nickel manganese cobalt is in the range of 1:9 to 9: 1. In some embodiments, the positive active material is a mixture of lithium cobaltate and a lithium nickel manganese cobalt ternary material, wherein the ratio of lithium cobaltate to lithium nickel manganese cobalt is in the range of 2:8 to 4: 6. The mixture of the lithium cobaltate and the lithium nickel manganese cobalt ternary material is used as the positive active material, so that the safety performance of the positive active material can be improved. Meanwhile, the quantity of transition metals is increased after the lithium cobaltate and the lithium nickel manganese cobalt ternary material are mixed, the transition metals play a certain catalytic role in film formation of the electrolyte, and the additive can play a more effective film formation effect.
In some embodiments, the positive electrode active material may have a coating layer on a surface thereof, or may be mixed with another compound having a coating layer. The coating may comprise at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element and an oxycarbonate of the coating element. The compounds used for the coating may be amorphous or crystalline.
In some embodiments, the coating elements contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, P, or otherAny combination thereof. In some embodiments, the coating in the coating layer may be AlPO4、Mg3(PO4)2、Co3(PO4)2、AlF3、MgF2、CoF3、NaF、B2O3At least one of (1). In some embodiments, the coating element is present in the coating layer in an amount of about 0.01% to about 10% based on the weight of the positive electrode active material. The coating layer may be applied by any method as long as the method does not adversely affect the properties of the positive electrode active material. For example, the method may include any coating method known to the art, such as spraying, dipping, and the like.
The positive active material layer further includes a binder, and optionally a conductive material. The binder improves the binding of the positive electrode active material particles to each other, and also improves the binding of the positive electrode active material to the current collector.
In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon, and the like.
In some embodiments, the conductive material includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from the group consisting of metal powder, metal fiber, copper, nickel, aluminum, silver. In some embodiments, the conductive polymer is a polyphenylene derivative.
In some embodiments, the current collector may be, but is not limited to, aluminum.
The positive electrode may be prepared by a preparation method well known in the art. For example, the positive electrode can be obtained by: the active material, the conductive material, and the binder are mixed in a solvent to prepare an active material composition, and the active material composition is coated on a current collector. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone, and the like.
In some embodiments, the positive electrode is made by forming a positive electrode material on a current collector using a positive electrode active material layer including a lithium transition metal-based compound powder and a binder.
In some embodiments, the positive active material layer may be generally fabricated by: the positive electrode active material and a binder (a conductive material, a thickener, and the like, which are used as needed) are dry-mixed to form a sheet, and the obtained sheet is pressure-bonded to a positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried. In some embodiments, the material of the positive electrode active material layer includes any material known in the art.
Negative electrode
The negative electrode used in the electrochemical device of the present application includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer contains a negative electrode active material, and the specific kind of the negative electrode active material is not particularly limited and can be selected as required. In some embodiments, the negative electrode is made of carbon materials, metal alloys, lithium-containing oxides, silicon-containing materials, and the like. Specifically, the negative active material may be selected from lithium metal, structured lithium metal, natural graphite, artificial graphite, mesophase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO2Spinel-structured lithiated TiO2-Li4Ti5O12And Li-Al alloy. In some embodiments, the carbon material is selected from graphite or a carbon material in which graphite is coated with amorphous carbon as compared to graphite.
Isolation film
In some embodiments, the electrochemical device of the present application is provided with a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separation film used in the electrochemical device of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance or the like formed of a material stable to the electrolyte of the present application.
For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.
At least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.
The inorganic layer comprises inorganic particles and a binder, wherein the inorganic particles are selected from one or more of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is selected from one or a combination of more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer comprises a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).
In some embodiments, the present application provides a lithium ion battery comprising the above-described positive electrode, negative electrode, separator, and electrolyte, the electrolyte being any of the electrolytes described previously herein.
In some embodiments, the present application also provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, an electrolyte, and a packaging foil; the positive electrode comprises a positive current collector and a positive film layer coated on the positive current collector; the negative electrode comprises a negative electrode current collector and a negative electrode film layer coated on the negative electrode current collector; the electrolyte is any one of the electrolytes described in the application.
Electronic device
The electrochemical device of the present application has excellent high-temperature cycle properties and overdischarge storage properties, so that the electrochemical device manufactured thereby is suitable for electronic devices in various fields.
The use of the electrochemical device of the present application is not particularly limited, and it may be used for any use known in the art. In one embodiment, the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headphones, video recorders, liquid crystal televisions, portable cleaners, portable CDs, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game machines, clocks, power tools, flashlights, cameras, household large batteries, lithium ion capacitors, and the like.
Fourth, example
The following describes performance evaluation according to examples and comparative examples of lithium ion batteries of the present application.
Preparation of lithium ion battery
(1) Preparation of the Positive electrode
Lithium nickel cobalt manganese oxide (LiNi)0.5Co0.2Mn0.3O2) Mixing the conductive carbon black and the polyvinylidene fluoride according to the weight ratio of 97:1.4:1.6, adding N-methyl pyrrolidone, and uniformly stirring under the action of a vacuum stirrer to obtain the anode slurry, wherein the solid content of the anode slurry is 72 wt%. Uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil; drying aluminum foil at 85 deg.C, cold pressing, cutting into pieces, and separatingAfter cutting, the cut sheet was dried at 85 ℃ for 4 hours under vacuum to obtain a positive electrode.
(2) Preparation of the negative electrode
Mixing artificial graphite, conductive carbon black, sodium carboxymethylcellulose and styrene butadiene rubber according to the weight ratio of 96.4:1.5:0.5:1.6, adding deionized water, and obtaining negative electrode slurry under the action of a vacuum stirrer, wherein the solid content of the negative electrode slurry is 54 wt%. Uniformly coating the negative electrode slurry on a copper foil of a negative electrode current collector; and drying the copper foil at 85 ℃, then carrying out cold pressing, cutting and slitting, and drying for 12h at 120 ℃ under a vacuum condition to obtain the cathode.
(3) Preparation of the electrolyte
Mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) in a dry argon atmosphere glove box according to the mass ratio of EC to EMC to DEC to 30:50:20, adding an additive, dissolving and fully stirring, and adding lithium salt LiPF6Mixing uniformly to obtain electrolyte, wherein, LiPF6The concentration of (2) is 1.0 mol/L. The kinds and contents of the additives of examples and comparative examples are shown in tables 1 and 2, and the additive amounts shown in tables 1 and 2 are percentage amounts by weight of the electrolyte.
(4) Preparation of the separator
A16 μm thick polyethylene separator was used.
(5) Preparation of lithium ion battery
Stacking the anode, the isolating film and the cathode in sequence to enable the isolating film to be positioned between the anode and the cathode 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.
Test method
(1) High temperature cycle performance test
And (3) placing the lithium ion battery in a constant temperature box at 45 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant. . Charging the constant-temperature lithium ion battery to a voltage of 4.2V at a constant current of 0.5C, then charging the constant-voltage lithium ion battery to a current of 0.05C at a constant voltage of 4.2V, and then discharging the constant-current lithium ion battery to a voltage of 2.8V at a constant current of 1C, wherein a charge-discharge cycle is formed, the discharge capacity is recorded as the first cycle discharge capacity, and the thickness of the lithium ion battery is recorded as the initial thickness of the lithium ion battery. And (3) repeatedly performing charge and discharge cycles for 500 circles by taking the capacity of the first discharge as 100%, stopping the test, and recording the capacity retention rate after 500 circles of cycles and the thickness of the lithium ion battery after 500 circles of cycles as indexes for evaluating the cycle performance of the lithium ion battery.
Capacity retention after cycling ═ 100% (discharge capacity at 500 cycles/discharge capacity at the first cycle).
The thickness expansion rate after cycling is (thickness of lithium ion battery after 500 cycles-initial thickness of lithium ion battery)/initial thickness of lithium ion battery x 100%.
(2) Over-discharge storage performance test
And (3) placing the lithium ion battery in a constant temperature box at 25 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant. Discharging to 3.0V at a constant current of 0.5C, standing for 30 minutes, continuously discharging to 2.8V at 0.1C, finally discharging to 1.0V at 0.01C, recording the thickness of the lithium ion battery, and recording as the initial thickness of the lithium ion battery. And (3) storing the discharged lithium ion battery in a constant temperature box at 60 ℃ for 30 days, observing the thickness change condition, and recording the thickness of the lithium ion battery after 30 days of storage. The rate of change in thickness is (thickness of lithium ion battery after 30 days of storage-initial thickness of lithium ion battery)/initial thickness of lithium ion battery x 100%.
(3) Hot box test
Charging the lithium ion battery to 4.2V at 25 ℃ under 0.5C current, charging the lithium ion battery to 0.05C at constant voltage under 4.2V, placing the fully charged lithium ion battery in a high-low temperature box, heating to 140 ℃, keeping the constant temperature for 30min at 140 ℃, monitoring the lithium ion battery, and keeping the lithium ion battery from igniting and exploding under the passing conditions.
(4) Measurement of electrolyte retention
And (3) placing the lithium ion battery in a constant temperature box at 25 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant. Charging to 4.2V at constant current and constant voltage of 0.2C, and then discharging to 2.8V at constant current of 0.2C, which is the first cycle, and recording the discharge capacity of the ion battery. Weighing a battery discharged to 2.8V, wherein the battery is m0, then disassembling the battery, quickly putting the disassembled bare cell and the outer packaging foil aluminum-plastic film into high-purity acetonitrile (the purity is more than or equal to 99.9 percent) for extraction, drying the aluminum-plastic of the extracted bare cell and the outer packaging foil in a vacuum oven, and weighing the total mass to be m1, wherein the mass of the lithium ion electrolyte is m0-m 1. The liquid retention amount was calculated as follows: the battery capacity is equal to the mass (g) of the electrolyte in the lithium ion battery/the discharge capacity (Ah) of the lithium ion battery.
Test results
Table 1 shows electrolyte parameters and performance test results of the lithium ion batteries of examples 1 to 24 and comparative example 1, in which the electrolyte retention amounts of examples 1 to 24 and comparative examples 1 to 3 were 2.3 g/Ah.
TABLE 1
Figure BDA0002526086310000181
Figure BDA0002526086310000191
As can be seen from examples 1 to 24 in comparison with comparative example 1, by adding additive a (e.g., the compound of formula I-1) and a silazane (e.g., heptamethyldisilazane), cycle gassing of a lithium ion battery can be significantly reduced and the over-discharge storage performance of the lithium ion battery can be improved. The additive A has higher reduction potential, and can form good interface protection on the negative electrode preferentially, so that the reduction decomposition of the electrolyte on the negative electrode is inhibited; meanwhile, silazane can adsorb trace water in the electrolyte, inhibit the generation of HF, reduce the corrosion effect of HF on the anode and the cathode, enhance the stability of the electrolyte, and the long branched chain of silazane can be unfolded to form a net structure, so that the additive A is induced to form a film on the cathode more uniformly and compactly. The additive A and the silazane have synergistic effect, can stabilize the electrolyte and form a uniform, compact and low-resistance interfacial film on the anode and the cathode, so that the lithium ion battery has excellent cycle performance and over-discharge storage performance.
Table 2 shows electrolyte parameters and performance test results of the lithium ion batteries of example 4 and examples 25 to 37, in which the electrolyte retention amount of example 4 and examples 25 to 37 is 2.3 g/Ah.
TABLE 2
Figure BDA0002526086310000201
As can be seen from comparison of examples 25 to 37 with example 4, the cycle performance and the overdischarge storage performance of the lithium ion battery can be further improved by further adding other additives (e.g., PS, LiDFP, FEC) on the basis that the electrolyte contains additive a and silazane. The SEI can be formed and modified on the negative electrode by other additives, so that a more excellent interface protective film is formed, and the reaction of the electrolyte on the negative electrode is relieved. Therefore, the combined use of the additives can further improve the cycle performance and the over-discharge storage performance of the lithium ion battery.
Table 3 shows the liquid retention amounts and the performance test results of the lithium ion batteries of example 32 and examples 38 to 43, in which the electrolyte compositions of example 32 and examples 38 to 43 are the same.
TABLE 3
Figure BDA0002526086310000211
It can be seen from comparing example 32 with examples 38 to 43 that the retention amount of the electrolyte has a large influence on the cycle performance and the hot box performance of the lithium ion battery, and an extremely low retention amount has a good hot box performance, but the cycle performance is poor, mainly because the extremely low electrolyte can improve the thermal stability of the battery, and effective protection of the positive and negative electrode interfaces cannot be formed due to wetting and the like; the extremely high liquid retention has poor thermal stability and cycle performance, mainly because more electrolytes are decomposed by heat to cause the thermal stability of the lithium ion battery to be poor, and more electrolytes can influence the lithium ion migration path and corrode the lithium ion battery structure.
Table 4 shows the compacted densities of the positive electrode active material layers of example 32 and examples 44 to 48 and the performance test results of the lithium ion batteries, in which the electrolyte compositions of example 32 and examples 44 to 48 are the same.
TABLE 4
Figure BDA0002526086310000212
By comparing example 32 with examples 44 to 48, the compaction density of the positive electrode active material layer had a greater effect on the cycle performance and the heat box performance of the lithium ion battery. Lower compaction densities result in lower energy densities for lithium ion batteries; higher compaction densities present a risk of particle breakage and the like, and thus deteriorate the cycle performance and hot box performance of the lithium ion battery.
Table 5 shows H in the electrolytes of examples 32 and 49 to 532O content and performance test results of the lithium ion battery in which the electrolyte compositions of example 32 and examples 49 to 53 were the same.
TABLE 5
Figure BDA0002526086310000221
As can be seen by comparing example 32 with examples 49 to 53, a suitable amount of H is present in the electrolyte2O (e.g., 100ppm or less) participates in the formation of SEI film during formation, and can improve cycle performance, while too much H2O causes a sharp increase in HF, which deteriorates cycle and hot box performance.
Reference throughout this specification to "some embodiments," "one embodiment," "another example," "an example," "a specific example," or "some examples" means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Thus, throughout the specification, descriptions appear, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "by example," which do not necessarily refer to the same embodiment or example in this application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.
Although illustrative embodiments have been illustrated and described, it will be appreciated by those skilled in the art that the above embodiments are not to be construed as limiting the application and that changes, substitutions and alterations can be made to the embodiments without departing from the spirit, principles and scope of the application.

Claims (11)

1. An electrolyte comprising an additive a and a silazane, wherein the additive a comprises at least one of a phosphate ester of formula I or a phosphite ester of formula II:
Figure FDA0002526086300000011
wherein R is1、R2、R3、R4、R5、R6Each independently selected from substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl or substituted or unsubstituted C6To C10An aryl group; wherein when substituted, the substituent is at least one of halogen or cyano.
2. The electrolyte of claim 1, wherein the silazane comprises a compound represented by formula III:
Figure FDA0002526086300000012
wherein R is7、R8、R9Each independently selected from substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl or substituted or unsubstituted C6To C10Aryl radicalsWherein when substituted, the substituent is halogen;
wherein R is10And R11Each independently selected from hydrogen, substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl, substituted or unsubstituted C6To C10Aryl or a group of formula IV; wherein when substituted, the substituent is halogen; wherein
Figure FDA0002526086300000013
Represents the connection part of the key and the key,
Figure FDA0002526086300000014
wherein R is12、R13、R14Each independently selected from substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl or substituted or unsubstituted C6To C10An aryl group; wherein when substituted, the substituent is halogen;
wherein the silazane is present in an amount of 0.01 to 3 wt% based on the weight of the electrolyte.
3. The electrolyte of claim 1, wherein the additive a comprises:
Figure FDA0002526086300000021
Figure FDA0002526086300000031
at least one of;
wherein the content of the additive A is 0.01-5 wt% based on the weight of the electrolyte.
4. The electrolyte of claim 2, wherein the silazane comprises at least one of trimethylsilyl diethylamine, heptamethyldisilazane, hexamethyldisilazane, hexaethyldisilazane, or hexapropyldisilazane.
5. The electrolyte of claim 1, wherein the electrolyte includes at least one of additive B, additive C, additive D, additive E, or additive F,
wherein the additive B comprises at least one of vinylene carbonate, fluoroethylene ester, vinyl ethylene carbonate, 1, 3-dioxane, 1, 4-dioxane or dioxolane;
wherein the additive C comprises at least one of 1, 3-propane sultone, 1, 4-butane sultone, vinyl sulfate, methylene methane disulfonate or propenyl-1, 3-sultone;
wherein the additive D comprises at least one of succinonitrile, glutaronitrile, adiponitrile, 2-methyleneglutaronitrile, dipropylmalononitrile, 1,3, 6-hexanetricarbonitrile, 1,2, 6-hexanetricarbonitrile, 1,3, 5-pentanetrimethylonitrile, 1, 2-bis (cyanoethoxy) ethane or ethoxy (pentafluoro) cyclotriphosphazene;
wherein the additive E comprises at least one of lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium bisthiooxalato borate, lithium difluorooxalato borate, lithium difluorophosphate, lithium tetrafluoroborate, or lithium 4, 5-dicyano-2-trifluoromethylimidazole;
wherein the additive F comprises at least one of succinic anhydride, glutaric anhydride, citraconic anhydride, maleic anhydride, methylsuccinic anhydride, 2, 3-dimethylmaleic anhydride or trifluoromethyl maleic anhydride,
wherein the content of any one of the additive B, the additive C, the additive D, the additive E or the additive F is 0.01 wt% -7 wt% based on the weight of the electrolyte.
6. The electrolyte of claim 1, wherein the electrolyte comprises a cyclic ester and a chain ester in a weight ratio of the cyclic ester to the chain ester of 1:9 to 7:3,
wherein the cyclic ester comprises at least one of ethylene carbonate, propylene carbonate, gamma-butyrolactone, ethylene carbonate substituted with a fluorine-containing group, or propylene carbonate substituted with a fluorine-containing group;
wherein the chain ester comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, fluoroethyl methyl carbonate or ethyl fluoropropionate.
7. An electrochemical device comprising a positive electrode, a negative electrode, a separator and the electrolyte according to any one of claims 1 to 6.
8. The electrochemical device of claim 7, wherein H in the electrolyte is based on the weight of the electrolyte2The content of O is 100ppm or less.
9. The electrochemical device according to claim 1, wherein a liquid retaining amount of the electrolyte is 0.5g/Ah to 4.0 g/Ah.
10. The electrochemical device according to claim 7, wherein the positive electrode includes a positive electrode active material layer and a positive electrode current collector, the positive electrode active material layer satisfying at least one of conditions (a) and (b):
(a) the positive electrode active material layer had a compacted density of 2.5g/cm in a fully discharged state3-4.5g/cm3；
(b) The anode active material layer has an exothermic peak at 225-300 ℃ by adopting a differential scanning calorimeter test.
11. An electronic device comprising the electrochemical device of any one of claims 7-10.
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CN114051662A (en) * 2021-03-31 2022-02-15 宁德新能源科技有限公司 Electrochemical device and electronic device comprising same
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WO2022218143A1 (en) * 2021-04-13 2022-10-20 深圳新宙邦科技股份有限公司 Iron phosphate lithium battery
WO2023051018A1 (en) * 2021-09-30 2023-04-06 株式会社村田制作所 Additive for lithium-ion battery electrolyte, electrolyte, and lithium-ion secondary battery
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CN116805730A (en) * 2022-07-19 2023-09-26 宁德时代新能源科技股份有限公司 Battery monomer, battery and power consumption device

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CN114447428A (en) * 2020-10-30 2022-05-06 张家港市国泰华荣化工新材料有限公司 Non-aqueous electrolyte and lithium battery
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CN112542613B (en) * 2020-12-01 2022-02-22 宁德新能源科技有限公司 Electrolyte solution, electrochemical device, and electronic device
CN113906606A (en) * 2020-12-23 2022-01-07 宁德新能源科技有限公司 Electrolyte solution, electrochemical device, and electronic device
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CN116805730A (en) * 2022-07-19 2023-09-26 宁德时代新能源科技股份有限公司 Battery monomer, battery and power consumption device

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