Electrolyte, lithium ion battery and electric device

Abstract

The invention relates to an electrolyte, a lithium ion battery and an electric device. The electrolyte comprises a lithium salt, a solvent and an additive, wherein the additive comprises a compound with a structural general formula as shown in a formula (I): # imgabs0 # in the formula (I), r1, R2 and R3 are respectively and independently selected from a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C1-C6 alkoxy group, a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C2-C6 unsaturated alkyl group, a substituted or unsubstituted C1-C6 silyl group, a substituted or unsubstituted C1-C6 ether group, a substituted or unsubstituted C2-C6 carboxylic ester group, a fluorine atom or a cyano group. According to the electrolyte provided by the invention, on one hand, sulfur atoms and nitrogen atoms in the additive can be coordinated with transition metal ions, so that the reaction activity of the transition metal ions is inhibited; on the other hand, the additive can form surface films on the anode and cathode surfaces, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, in particular to an electrolyte, a lithium ion battery and an electrical device. Background Art

[0002] As an electrochemical device, lithium-ion batteries are playing an increasingly important role in 3C digital, automotive power, energy storage systems and other fields.

[0003] However, the attenuation of battery performance and life limit are still urgent problems to be solved. Especially under high voltage and high temperature application conditions, transition metal ions in the positive electrode material are easily dissolved, resulting in the destruction and corrosion of the positive electrode structure, the oxidative decomposition and gas production of the electrolyte, and migration to the negative electrode side to destroy the SEI film, thus causing rapid attenuation of battery capacity. Summary of the invention

[0004] Based on this, it is necessary to provide an electrolyte, a lithium-ion battery and an electrical device to inhibit the dissolution of transition metal ions and the destruction of the electrode structure, reduce the decomposition and gas production of the electrolyte, improve the interface stability of the positive and negative electrodes, and increase the cycle life of the battery.

[0005] The first aspect of the present application provides an electrolyte, which includes: a lithium salt, a solvent and an additive; wherein the additive includes a compound having a structural formula as shown in formula (I):

[0006]

[0008] In formula (I), R1, R2, and R3 are each independently selected from a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C1-C6 alkoxy group, a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C2-C6 unsaturated hydrocarbon group, a substituted or unsubstituted C1-C6 silanyl group, a substituted or unsubstituted C1-C6 ether group, a substituted or unsubstituted C2-C6 carboxylate group, a fluorine atom, or a cyano group.

[0009] In some embodiments, R1 or R2 is an electron withdrawing group.

[0010] In some embodiments, R3 is an electron donating group.

[0011] In some embodiments, R1 or R2 are each independently selected from a fluorine atom, a cyano group, and a C1-C6 carboxylate group.

[0012] In some embodiments, R3 is selected from C1-C6 alkyl, C1-C6 alkoxy, C3-C6 cycloalkyl and C2-C6 unsaturated hydrocarbon.

[0013] In some embodiments, the substituted substituent is selected from a fluorine atom or a cyano group.

[0014] In some embodiments, the compound having the general structural formula as shown in formula (I) is selected from at least one of the following compounds:

[0015]

[0016]

[0017] In some embodiments, the mass percentage of the compound having the general structural formula as shown in formula (I) in the electrolyte is 0.5% to 2%.

[0018] In some embodiments, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorobis(oxalatoborate), lithium difluorobis(oxalatophosphate), lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium tetrafluorophosphate, potassium bis(fluorosulfonyl)imide, lithium 4,5-dicyano-2-trifluoromethyl-imidazole, lithium methyl sulfate, lithium ethyl sulfate, and lithium bis(nonafluorobutylsulfonyl)imide.

[0019] In some embodiments, the solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl acetate, butyl acetate, γ-butyrolactone, propyl propionate, ethyl propionate, and ethyl butyrate.

[0020] In some embodiments, the additives further include other additives, and the other additives are selected from at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, propylene sulfate, 4-methyl vinyl sulfate, vinyl carbonate, 4-ethyl vinyl sulfate, lithium difluorophosphate, 1,3-propane sultone, vinyl vinyl sulfite, tris(trimethylsilyl)borate and triallyl isocyanate.

[0021] A second aspect of the present application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and the electrolyte provided by the first aspect.

[0022] In some embodiments, the positive electrode includes a positive electrode active material, and the positive electrode active material includes at least one of a nickel cobalt lithium manganese oxide ternary material, a lithium iron manganese phosphate material, a lithium manganese oxide material, and a lithium iron manganese oxide material.

[0023] A third aspect of the present application provides an electrical device, which includes the lithium-ion battery provided in the second aspect.

[0024] Compared with the traditional technology, the present invention has the following beneficial effects:

[0025] The electrolyte provided in the present application, on the one hand, has a compound having a general structural formula as shown in formula (I) having a thiol and a pyridine structure, and the sulfur atom on the thiol and the nitrogen atom on the pyridine ring have lone pairs of electrons, which can be coordinated with transition metal ions in situ, thereby inhibiting the reactivity of transition metal ions, reducing the oxidative decomposition and gas production of the electrolyte, preventing them from migrating to the negative electrode side to damage the SEI film, and improving the cycle performance of the battery; on the other hand, the compound having a general structural formula as shown in formula (I) undergoes oxidation and reduction reactions on the electrode before the solvent, and multiple structures such as diaromatic rings and enones contained in the compound can be polymerized on the surfaces of the positive and negative electrodes, and can form surface films rich in Li2CO3 components with high chemical stability (i.e., CEI films and SEI films) on the surfaces of the positive and negative electrodes, respectively, thereby improving the interface stability of the positive and negative electrodes, and the formed surface film has high ionic conductivity, thereby improving the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is H of a compound having a structure as shown in formula (I-1) in one embodiment of the present application 1 NMR test graph. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0028] In the description of the present application, unless otherwise defined, the professional terms and professional words not clearly described are the same as the meanings commonly understood by those skilled in the art, and are common knowledge of those skilled in the art, and the methods not clearly described are conventional methods known to those skilled in the art. The meaning of the term "multiple" in the present application is at least two, such as two, three, etc., unless otherwise clearly and specifically limited. In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0029] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0031] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0032] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0033] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0034] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0035] "Hydrocarbon group" refers to a group containing only carbon and hydrogen atoms, including but not limited to alkyl, alkenyl, alkynyl, aryl, etc.

[0036] "Alkyl" refers to a saturated hydrocarbon containing primary (normal) carbon atoms, or secondary carbon atoms, or tertiary carbon atoms, or quaternary carbon atoms, or a combination thereof. Phrases containing this term, for example, "C1-C9 alkyl" refers to an alkyl group containing 1 to 9 carbon atoms, each occurrence of which can be independently C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl or C9 alkyl. Suitable examples include, but are not limited to, methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(C H3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (- CH2CH2CH(CH3)2), 2-methyl-1-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH( 2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3 and octyl (-(CH2)7CH3).

[0037] The term "cycloalkyl" refers to a non-aromatic hydrocarbon containing ring carbon atoms, which can be a monocyclic alkyl, a spirocyclic alkyl, or a bridged cycloalkyl. Phrases containing this term, for example, "C3-C9 cycloalkyl" refers to a cycloalkyl containing 3 to 9 carbon atoms, each occurrence of which can be independently C3 cycloalkyl, C4 cycloalkyl, C5 cycloalkyl, C6 cycloalkyl, C7 cycloalkyl, C8 cycloalkyl or C9 cycloalkyl. Suitable examples include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl. In addition, "cycloalkyl" may also contain one or more double bonds, and representative examples of cycloalkyl containing double bonds include cyclopentenyl, cyclohexenyl, cyclohexadienyl and cyclobutadienyl.

[0038] The term "alkoxy" refers to a group having an -O-alkyl group, i.e., an alkyl group as defined above connected to a parent core structure via an oxygen atom. Phrases containing the term, for example, "C1-C9 alkoxy" means that the alkyl portion contains 1 to 9 carbon atoms, and each occurrence can be independently C1 alkoxy, C4 alkoxy, C5 alkoxy, C6 alkoxy, C7 alkoxy, C8 alkoxy or C9 alkoxy. Suitable examples include, but are not limited to, methoxy (-O-CH3 or -OMe), ethoxy (-O-CH2CH3 or -OEt) and tert-butoxy (-OC(CH3)3 or -OtBu).

[0039] The term "unsaturated hydrocarbon group" refers to a hydrocarbon group containing at least one site of unsaturation, such as an alkenyl group, an alkynyl group, or an aryl group.

[0040] The term "alkenyl" refers to a group containing at least one unsaturated site, i.e., a carbon-carbon sp 2 A hydrocarbon containing a positive carbon atom, a secondary carbon atom, a tertiary carbon atom or a ring carbon atom of a double bond. A phrase containing this term, for example, "C2-C9 alkenyl" refers to an alkenyl group containing 2 to 9 carbon atoms, each occurrence of which can be independently C2 alkenyl, C3 alkenyl, C4 alkenyl, C5 alkenyl, C6 alkenyl, C7 alkenyl, C8 alkenyl or C9 alkenyl. Suitable examples include, but are not limited to, vinyl (-CH=CH2), allyl (-CH2CH=CH2), cyclopentenyl (-C5H7) and 5-hexenyl (-CH2CH2CH2CH2CH=CH2).

[0041] The term "alkynyl" refers to a hydrocarbon containing a positive carbon atom, a secondary carbon atom, a tertiary carbon atom or a ring carbon atom having at least one unsaturated site, i.e., a carbon-carbon sp triple bond. Phrases containing this term, for example, "C2-C9 alkenyl" refers to an alkynyl containing 2 to 9 carbon atoms, each occurrence of which can be independently C2 alkynyl, C3 alkynyl, C4 alkynyl, C5 alkynyl, C6 alkynyl, C7 alkynyl, C8 alkynyl or C9 alkynyl. Suitable examples include, but are not limited to, ethynyl (-C≡CH) and propargyl (-CH2C≡CH).

[0042] The term "aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing a hydrogen atom. It can be a monocyclic aromatic group, a condensed aromatic group, or a polycyclic aromatic group. For polycyclic rings, at least one is an aromatic ring system. For example, "C5-C 20 "Aryl" refers to an aromatic group containing 5 to 20 carbon atoms, and each occurrence can be independently C5 aromatic group, C6 aromatic group, C 10 Aryl, C 14 Aryl, C 18 Aryl or C 20 Aryl. Suitable examples include, but are not limited to, benzene, biphenyl, naphthalene, anthracene, phenanthrene, perylene, triphenylene and derivatives thereof. It is understood that multiple aromatic groups may also be interrupted by short non-aromatic units (e.g., <10% non-H atoms, such as C, N or O atoms), such as acenaphthene, fluorene, or 9,9-diarylfluorene, triarylamine, diaryl ether system should also be included in the definition of aromatic group.

[0043] The term "silyl group" refers to a -SiR'3 group, wherein R' is a linear alkyl group, a branched alkyl group or a cycloalkyl group, and each R' may be the same or different. A "C1-C6 silyl group" means that the total number of carbon atoms in R' is 1 to 6.

[0044] The term "ether group" refers to an -OR' group or a -R'-OR"- group, wherein R' and R" are straight chain alkyl, branched alkyl or cycloalkyl groups, and "C1-C6 ether group" means that the total number of carbon atoms of R' and R" is 1 to 6.

[0045] The term "carboxylate" refers to a R'C(O)O- group or a -C(O)OR' group, wherein R' is a straight chain alkyl group, a branched alkyl group or a cycloalkyl group, and a "C2-C6 carboxylate" means that the number of carbon atoms in R' is 1 to 5, and can be but is not limited to methyl carboxylate, ethyl carboxylate, n-propyl carboxylate, isopropyl carboxylate, n-butyl carboxylate, isobutyl carboxylate, sec-butyl carboxylate, tert-butyl carboxylate, n-pentyl carboxylate, isopentyl carboxylate, tert-pentyl carboxylate, and neopentyl carboxylate.

[0046] The term "fluorine atom" refers to a -F group.

[0047] The term "cyano" refers to a -CN group.

[0048] A first aspect of the present application provides an electrolyte comprising a lithium salt, a solvent and an additive.

[0049] The additive includes a compound having a general structural formula as shown in formula (I):

[0050]

[0052] In formula (I), R1, R2, and R3 are each independently selected from a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C1-C6 alkoxy group, a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C2-C6 unsaturated hydrocarbon group, a substituted or unsubstituted C1-C6 silanyl group, a substituted or unsubstituted C1-C6 ether group, a substituted or unsubstituted C2-C6 carboxylate group, a fluorine atom, or a cyano group.

[0053] The electrolyte provided in the present application, on the one hand, has a compound having a general structural formula as shown in formula (I) having a thiol and a pyridine structure, and the sulfur atom on the thiol and the nitrogen atom on the pyridine ring have lone pairs of electrons, which can be coordinated with transition metal ions in situ, thereby inhibiting the reactivity of transition metal ions, reducing the oxidative decomposition and gas production of the electrolyte, preventing them from migrating to the negative electrode side to damage the SEI film, and improving the cycle performance of the battery; on the other hand, the compound having a general structural formula as shown in formula (I) undergoes oxidation and reduction reactions on the electrode before the solvent, and multiple structures such as diaromatic rings and enones contained in the compound can be polymerized on the surfaces of the positive and negative electrodes, and can form surface films rich in Li2CO3 components with high chemical stability (i.e., CEI films and SEI films) on the surfaces of the positive and negative electrodes, respectively, thereby improving the interface stability of the positive and negative electrodes, and the formed surface film has high ionic conductivity, thereby improving the cycle performance of the battery.

[0054] It is understandable that the mercapto group is polar, and the electronegativity of the sulfur atom is lower than that of the oxygen atom. Therefore, the mercapto group has a certain positive charge, which is conducive to the coordination of the sulfur atom with the transition metal, and also improves the aromaticity of the pyridine ring and the benzene ring in the structure. The aromaticity of the aromatic ring structure is conducive to the formation of CEI film and SEI film on the surface of the positive and negative electrodes. Therefore, in the compound having the general structural formula shown in formula (I), there is a synergistic effect between the mercapto group and the double aromatic ring structure, which jointly improves the cycle stability of the battery.

[0055] In some embodiments, R1 or R2 is an electron withdrawing group.

[0056] In some embodiments, R3 is an electron donating group.

[0057] When R1 or R2 is an electron-withdrawing group, or R3 is an electron-donating group, the positive charge of the mercapto group and the aromaticity of the pyridine ring and the benzene ring are further improved, thereby further improving the coordination ability of the sulfur atom to the transition metal ions and the ability of the aromatic ring structure to form the CEI film and the SEI film. Therefore, when R1 or R2 is an electron-withdrawing group, or R3 is an electron-donating group, the cycle stability of the battery can be further improved.

[0058] In some of the embodiments, R1 or R2 are each independently selected from a fluorine atom, a cyano group, and a C1-C6 carboxylate group.

[0059] In some of these embodiments, R3 is selected from C1-C6 alkyl, C1-C6 alkoxy, C3-C6 cycloalkyl and C2-C6 unsaturated hydrocarbon.

[0060] In some of these embodiments, the substituted substituent is selected from a fluorine atom or a cyano group.

[0061] In some embodiments, the compound having the general structural formula as shown in formula (I) is selected from at least one of the following compounds:

[0062]

[0063] In some embodiments, the mass percentage of the compound having the general structural formula as shown in formula (I) in the electrolyte is 0.5% to 2%, including but not limited to 0.5%, 0.8%, 1%, 1.5%, 2%. Further, the mass percentage of the compound having the general structural formula as shown in formula (I) in the electrolyte is 0.5% to 1.5%.

[0064] In some embodiments, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorobis(oxalatoborate), lithium difluorobis(oxalatophosphate), lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium tetrafluorophosphate, potassium bis(fluorosulfonyl)imide, 4,5-dicyano-2-trifluoromethyl-imidazole lithium, lithium methyl sulfate, lithium ethyl sulfate, and lithium bis(nonafluorobutylsulfonyl)imide.

[0065] Further, the lithium salt is selected from a mixture of at least three of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorobisoxalate phosphate, lithium bisfluorosulfonyl imide, lithium difluorophosphate and lithium bis(nonafluorobutylsulfonyl)imide.

[0066] Furthermore, the lithium salt includes lithium hexafluorophosphate.

[0067] In traditional technology, when lithium hexafluorophosphate is included in the lithium salt, high temperature will promote the decomposition of LiPF6 and produce HF, leading to the decomposition of CEI / SEI and solvent, corroding the positive electrode and causing the dissolution of transition metal ions, thereby accelerating battery aging.

[0068] The electrolyte provided in the present application is particularly suitable for the electrolyte system of lithium hexafluorophosphate. The compound having the general structural formula shown in formula (I) is more easily combined with HF than the solvent, thereby reducing the generation of free acid in the electrolyte, and further reducing the oxidative decomposition and gas production of the electrolyte, and further stabilizing the interface film and inhibiting the dissolution of transition metal ions, thereby improving the cycle performance of the battery.

[0069] In some embodiments, the solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl acetate, butyl acetate, γ-butyrolactone, propyl propionate, ethyl propionate and ethyl butyrate.

[0070] In some embodiments, the additive further comprises other additives, and the other additives are selected from at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, propylene sulfate, 4-methyl vinyl sulfate, vinyl carbonate, 4-ethyl vinyl sulfate, lithium difluorophosphate, 1,3-propane sultone, vinyl vinyl sulfite, tris(trimethylsilyl)borate and triallyl isocyanate.

[0071] Further, the other additives are selected from a mixture of at least two of fluoroethylene carbonate, vinyl sulfate, vinylene carbonate, triallyl isocyanurate and 1,3-propane sultone (PS).

[0072] In some embodiments, the mass percentage of other additives in the electrolyte is 0.5% to 5%, including but not limited to 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%.

[0073] A second aspect of the present application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and the electrolyte provided by the first aspect.

[0074] In some embodiments, the positive electrode includes a positive electrode active material, and the positive electrode active material includes at least one of a nickel cobalt lithium manganese oxide ternary material, a lithium iron manganese phosphate material, a lithium manganese oxide material, and a lithium iron manganese oxide material.

[0075] It is understandable that the transition metal ions in the above-mentioned positive electrode active materials are easily dissolved during the battery cycle, so the electrolyte system of the present application is particularly suitable for lithium-ion battery systems having the above-mentioned positive electrode active materials.

[0076] In some embodiments, the negative electrode includes a negative electrode active material, and the negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon, silicon carbon, silicon oxygen, and lithium titanate.

[0077] The lithium-ion battery of the present application has no particular restrictions on the diaphragm, and any known porous structure isolation membrane with electrochemical stability and chemical stability can be selected, such as a single-layer or multi-layer film of one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).

[0078] It is understood that lithium-ion batteries can be prepared and used according to conventional methods known in the art.

[0079] A third aspect of the present application provides an electrical device, which includes the lithium-ion battery provided in the second aspect.

[0080] The electrical device of the present application is not particularly limited, and it can be any electrical device known in the prior art. For example, the electrical device can include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0081] The present application will be further described below with reference to specific embodiments and comparative examples.

[0082] The synthesis process of the compound having the general structural formula shown in formula (I) is as follows:

[0083]

[0084] The preparation method of the compound having the general structural formula shown in formula (I) comprises the following steps:

[0085] Step (1), mixing a thiophenol compound and a 3-(3-pyridine) acrylic acid compound in an acetic acid solvent, adding an I2 catalyst and stirring the reaction for 24 hours, adding a cold saturated sodium thiosulfate solution, extracting with dichloromethane, and then mixing with a saturated sodium bicarbonate solution to remove unreacted starting materials, acidifying the aqueous layer, extracting with dichloromethane again, combining the organic layers and drying them, and evaporating the solvent under reduced pressure to obtain an addition product.

[0086] Among them, the structural formula of thiophenol compounds is:

[0087]

[0088] The structural formula of 3-(3-pyridine) acrylic acid compounds is:

[0089]

[0090] The structural formula of the intermediate is:

[0091]

[0092] Step (2), cooling the addition product to 0°C and dissolving it in a CH3Cl solvent, adding concentrated sulfuric acid to carry out a cyclization reaction for 2 hours, quenching with ice water, and then extracting with dichloromethane, combining the organic layers, washing with cold water and a saturated sodium bicarbonate solution in sequence, and then washing with brine, drying, and concentrating under reduced pressure, and purifying by silica gel column chromatography using n-hexane / ethyl acetate as an eluent to obtain a compound having the general structural formula shown in formula (I);

[0093] Among them, the structural formula of the compound of the general structural formula shown in formula (I) is:

[0094]

[0095] In formulas (I) to (IV), R1, R2, and R3 are each independently selected from a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C1-C6 alkoxy group, a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C2-C6 unsaturated hydrocarbon group, a substituted or unsubstituted C1-C6 silanyl group, a substituted or unsubstituted C1-C6 ether group, a substituted or unsubstituted C2-C6 carboxylate group, a fluorine atom, or a cyano group.

[0096] Take the compound of the structure shown in formula (I-1) as an example: 15 mol of thiophenol and 10 mol of 3-(3-pyridine) acrylic acid are mixed in 20 mL of acetic acid solvent, 20 mol% I2 catalyst is added, and the reaction is stirred for 24 hours. After the reaction is completed, a cold saturated sodium thiosulfate solution is added, extracted with dichloromethane, and then mixed with a saturated sodium bicarbonate solution to remove the unreacted starting material; the water layer is acidified, extracted with dichloromethane, the organic layers are combined and dried, and the solvent is evaporated under reduced pressure to obtain an addition product; the obtained addition product is cooled to 0°C, dissolved in 20 mL of CH3Cl solvent, and concentrated sulfuric acid (10% aq) is added to carry out a cyclization reaction, quenched with ice water after 2 hours of reaction, and then extracted with dichloromethane. The organic layers are combined, washed with cold water and saturated sodium bicarbonate solution in turn, and then washed with brine, dried and concentrated under reduced pressure, and finally purified by silica gel column chromatography using n-hexane / ethyl acetate as an eluent to obtain a compound having the structure shown in formula (I-1).

[0097] Characterization: Figure 1 As shown, H 1 NMR(400HZ, CDCl3)3.21-3.41(m,2H,CH2),4.98(ddd,1H,CH),6.97(dd,1H,ArH),7.07(dd ,1H,ArH),7.21(ddd,1H,ArH),7.27-7.31(m,3H,ArH),7.42(ddd,1H,ArH),8.46(dd,1H); 13CNMR(100HZ, CDCl3)39.5,45.5,122.9,121,122.9,125,126.7,129,130.4,133.3,136.4,142.1,148.3,163.4,194.3; m / z 241.6.

[0098] The synthesis methods of the compounds of the structures shown in formula (Ⅰ-2), formula (Ⅰ-3), formula (Ⅰ-4) and formula (Ⅰ-5) used in the following Examples 2-5 are exactly the same as the synthesis method of the compound of the structure shown in the above formula (Ⅰ-1), the only difference is that thiophenol and 3-(3-pyridine)acrylic acid are adjusted accordingly.

[0099] Example 1

[0100] Electrolyte:

[0101] S1. In a glove box filled with argon (water content <10 ppm, oxygen content <1 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) were uniformly mixed in a mass ratio of 30:60:10 to obtain a solvent;

[0102] S2, adding lithium salt lithium hexafluorophosphate (LiPF6) to the solvent for dissolution, the concentration of LiPF6 is 1.15 mol / L;

[0103] S3. Continue to add a compound having a structure as shown in formula (I-1), vinylene carbonate (VC), lithium difluorophosphate (LiPO2F2) and 1,3-propane sultone (PS) as additives into the solvent, stir evenly, and obtain an electrolyte.

[0104]

[0105] Among them, the mass percentage of the compound having the structure shown in formula (I-1) in the electrolyte is 1.5%, the mass percentage of VC in the electrolyte is 1%, the mass percentage of LiPO2F2 in the electrolyte is 0.5%, and the mass percentage of PS in the electrolyte is 1%.

[0106] Lithium-ion battery:

[0107] The prepared electrolyte was injected into the fully dried 4.35V NCM622 / graphite soft-pack battery, and the battery was obtained after processes such as 45°C storage, high-temperature fixture formation and secondary sealing.

[0108] Example 2

[0109] The electrolyte and lithium-ion battery in this embodiment are substantially the same as those in Embodiment 1, except that:

[0110] In step S3, the compound having the structure represented by formula (I-1) is replaced by a compound having the structure represented by formula (I-2).

[0111]

[0112] Example 3

[0113] The electrolyte and lithium-ion battery in this embodiment are substantially the same as those in Embodiment 1, except that:

[0114] In step S3, the compound having the structure shown in formula (I-1) is replaced with a compound having the structure shown in formula (I-3).

[0115]

[0116] Example 4

[0117] The electrolyte and lithium-ion battery in this embodiment are substantially the same as those in Embodiment 1, except that:

[0118] In step S3, the compound having the structure shown in formula (I-1) is replaced with a compound having the structure shown in formula (I-4).

[0119]

[0120] Example 5

[0121] The electrolyte and lithium-ion battery in this embodiment are substantially the same as those in Embodiment 1, except that:

[0122] In step S3, the compound having the structure shown in formula (I-1) is replaced with a compound having the structure shown in formula (I-5).

[0123]

[0124] Example 6

[0125] The electrolyte and lithium-ion battery in this embodiment are substantially the same as those in Embodiment 1, except that:

[0126] In step S3, the mass percentage of the compound having the structure shown in formula (I-1) in the electrolyte is 0.5%.

[0127] Example 7

[0128] The electrolyte and lithium-ion battery in this embodiment are substantially the same as those in Embodiment 1, except that:

[0129] In step S3, the mass percentage of the compound having the structure shown in formula (I-1) in the electrolyte is 2%.

[0130] Comparative Example 1

[0131] Electrolyte:

[0132] S1. In a glove box filled with argon (water content <10 ppm, oxygen content <1 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) were uniformly mixed in a mass ratio of 30:60:10 to obtain a solvent;

[0133] S2, adding lithium salt lithium hexafluorophosphate (LiPF6) to the solvent for dissolution, the concentration of LiPF6 is 1.15 mol / L;

[0134] S3. Vinylene carbonate (VC), lithium difluorophosphate (LiPO2F2) and 1,3-propane sultone (PS) are added to the solvent as additives, and the mixture is stirred evenly to obtain an electrolyte.

[0135] Among them, the mass percentage of VC in the electrolyte is 1%, the mass percentage of LiPO2F2 in the electrolyte is 0.5%, and the mass percentage of PS in the electrolyte is 1%.

[0136] Lithium-ion battery:

[0137] The prepared electrolyte was injected into the fully dried 4.35V NCM622 / graphite soft-pack battery, and the battery was obtained after processes such as 45°C storage, high-temperature fixture formation and secondary sealing.

[0138] Comparative Example 2

[0139] The electrolyte and lithium ion battery in this comparative example are substantially the same as those in Example 1, except that:

[0140] In step S3, the mass percentage of the compound having the structure shown in formula (I-1) in the electrolyte is 0.05%.

[0141] Comparative Example 3

[0142] The electrolyte and lithium ion battery in this comparative example are substantially the same as those in Example 1, except that:

[0143] In step S3, the mass percentage of the compound having the structure shown in formula (I-1) in the electrolyte is 3%.

[0144] Comparative Example 4

[0145] The electrolyte and lithium ion battery in this comparative example are substantially the same as those in Example 1, except that:

[0146] In step S3, the compound having the structure represented by formula (I-1) is replaced by a compound having the structure represented by the following formula (V):

[0147]

[0148] Test Case

[0149] (1) Cyclic performance test

[0150] The lithium-ion batteries of the embodiment and the comparative example were placed in a 45°C thermostat for 30 minutes to allow the lithium-ion batteries to reach a constant temperature. They were charged at a constant current of 1C to a voltage of 4.3V, then charged at a constant voltage of 4.35V to a current of 0.05C, and then discharged at a constant current of 1C to a voltage of 2.8V. The first discharge capacity of the battery was recorded as C0. This is one charge and discharge cycle.

[0151] Then, 1C / 1C charging and discharging was performed at 45°C for 500 cycles, the discharge capacity was recorded as C1, and the capacity retention rate of the lithium-ion battery was calculated using the following formula: Capacity retention rate = (C1 / C0)*100%. The test results are shown in Table 1.

[0152] (2) High temperature storage performance test

[0153] At room temperature (25°C), the lithium ion batteries of the embodiment and comparative example were charged to 4.35V at 0.5C constant current and constant voltage, and then placed in a 55°C high temperature box for 90 days to test the thickness increase rate of the battery after storage. The test results are shown in Table 1.

[0154] (3)ICP test

[0155] Weigh about 0.1 g of negative electrode powder (accurate to ±0.0003 g) of each embodiment and comparative example, place it in a 100 mL beaker, add a small amount of distilled water to wet the bottom of the cup, then add 5 mL of 12 mol / L HCl to dissolve, heat on an electric heating plate for 20 min, remove and cool, and dilute for testing.

[0156] The prepared series of standard solutions were introduced into the iCAP7000 inductively coupled plasma spectrometer (ICP) to measure the intensity of each element in the standard solution at the wavelength of the element to be measured (nickel, cobalt, manganese). When the linear correlation coefficient of the working curve r≥0.9995, the measurement can be carried out. The test results are shown in Table 1.

[0157] Table 1

[0158]

[0159] As shown in Table 1, by comparing Examples 1 to 7 and Comparative Examples 1 to 4, it can be seen that the electrolyte provided in the present application, because it includes a compound having the general structural formula as shown in formula (I), inhibits the gas production of the electrolyte and the damage of the SEI film by transition metal ions on the negative electrode side, and the prepared lithium ion battery has a good capacity retention rate.

[0160] By comparing Examples 1 to 5, it can be seen that when R1 or R2 is an electron-withdrawing group, or R3 is an electron-donating group, the positive charge of the thiol group will be stronger, and the aromaticity of the pyridine ring will be stronger, which further enhances the synergistic effect between the thiol group and the pyridine ring, is beneficial to coordinate with transition metal ions and participate in the reaction at the positive and negative electrode interfaces to form CEI films and SEI films, thereby improving the high-temperature cycle performance and high-temperature storage performance of the battery.

[0161] By comparing Examples 1 to 7 with Comparative Examples 2 and 3, it can be seen that the high temperature storage and high temperature cycle performance of the battery are closely related to the added amount of the compound having the structural formula shown in formula (I). When the added amount is increased to 3%, its high temperature storage and high temperature cycle performance decreases instead. This may be related to the fact that when the added amount is too much, it fails to react completely with the positive and negative electrode interfaces in the early reaction, and in the later cycle process, on the one hand, it continues to interact with the active potential of the positive electrode interface under a high SOC state, causing the impedance to continue to increase.

[0162] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0163] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An electrolyte, characterized in that: include: Lithium salts, solvents and additives; Wherein, the additive includes a compound having a general structural formula as shown in formula (I): In formula (I), R1, R2, and R3 are each independently selected from a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C1-C6 alkoxy group, a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C2-C6 unsaturated hydrocarbon group, a substituted or unsubstituted C1-C6 silanyl group, a substituted or unsubstituted C1-C6 ether group, a substituted or unsubstituted C2-C6 carboxylate group, a fluorine atom, or a cyano group.

2. The electrolyte according to claim 1, characterized in that The R1 or the R2 is an electron withdrawing group; and / or, The R3 is an electron donating group.

3. The electrolyte according to claim 2, characterized in that The R1 or the R2 is independently selected from a fluorine atom, a cyano group and a C1-C6 carboxylate group; and / or, The R3 is selected from C1-C6 alkyl, C1-C6 alkoxy, C3-C6 cycloalkyl and C2-C6 unsaturated hydrocarbon.

4. The electrolyte according to claim 1, characterized in that The substituted substituent is selected from a fluorine atom or a cyano group.

5. The electrolyte according to claim 1, characterized in that The compound having the general structural formula as shown in formula (I) is selected from at least one of the following compounds:

6. The electrolyte according to any one of claims 1 to 5, characterized in that The mass percentage of the compound having the structural formula shown in formula (I) in the electrolyte is 0.5% to 2%.

7. The electrolyte according to any one of claims 1 to 5, characterized in that The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorobis(oxalatoborate), lithium difluorobis(oxalatophosphate), lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium tetrafluorophosphate, potassium bis(fluorosulfonyl)imide, lithium 4,5-dicyano-2-trifluoromethyl-imidazole, lithium methyl sulfate, lithium ethyl sulfate and lithium bis(nonafluorobutylsulfonyl)imide; and / or, The solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl acetate, butyl acetate, γ-butyrolactone, propyl propionate, ethyl propionate and ethyl butyrate; and / or, The additives also include other additives, and the other additives are selected from at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, propylene sulfate, 4-methyl vinyl sulfate, vinyl carbonate, 4-ethyl vinyl sulfate, lithium difluorophosphate, 1,3-propane sultone, vinyl vinyl sulfite, tris(trimethylsilyl)borate and triallyl isocyanate.

8. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the electrolyte according to any one of claims 1 to 7.

9. The lithium-ion battery according to claim 8, characterized in that: The positive electrode includes a positive electrode active material, and the positive electrode active material includes at least one of a nickel-cobalt-lithium manganese oxide ternary material, a lithium iron manganese phosphate material, a lithium manganese oxide material, and a lithium iron manganese oxide material.

10. An electrical device, characterized in that: The electrical device comprises the lithium-ion battery according to claim 8 or 9.

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