Electrolyte additive, electrolyte, lithium ion battery

Abstract

The application relates to an electrolyte additive, an electrolyte and a lithium ion battery. The electrolyte additive comprises a compound with a general structure shown in formula (I): wherein, in formula (I), R is selected from substituted or unsubstituted C1-C 10 alkyl, C2-C 10 alkenyl, A ‑ is selected from one or more of PF6 ‑ , BF4 ‑ , ClO4 ‑ , FSI ‑ , TFSI ‑ , DFOB ‑ , DFOP ‑ and AsF6 ‑ . The electrolyte additive provided in the application, through the synergistic effect of N cation and N-F bond in the structure of the compound shown in formula (I), on one hand, the N cation captures H2O generated due to electrolyte decomposition, avoids further decomposition of the electrolyte salt to destroy the interface and the positive active material, and improves the cycle and storage performance of the battery at high voltage; on the other hand, the N-F bond is beneficial to generating SEI film and CEI film rich in LiF at the positive and negative electrodes, the chemical stability of the SEI film and CEI film of the inorganic component is good, and the interface stability of the positive and negative electrodes is improved, thereby improving the cycle and storage performance of the battery at high voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrolyte additive, an electrolyte and a lithium ion battery. BACKGROUND

[0002] With the wide application of lithium ion batteries in the fields of electric vehicles, electronic products and the like, users have put forward higher and higher requirements for their performance, especially the demand for higher energy density. Among them, increasing the charging voltage is one of the main methods to improve the energy density of the battery.

[0003] However, increasing the charging voltage will cause instability of the positive active material and the electrolyte, which will cause the electrolyte to decompose and produce gas, thereby affecting the service life and safety of the battery. SUMMARY

[0004] Therefore, it is necessary to provide an electrolyte additive, an electrolyte and a lithium ion battery to improve the cycle and storage performance of the battery at high voltage.

[0005] The first aspect of the present application provides an electrolyte additive, which comprises a compound having a general structure represented by formula (I):

[0006]

[0007] In formula (I), R is selected from substituted or unsubstituted C1-C5 alkyl, unsubstituted C2-C5 alkenyl, A is selected from one or more of PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. 10 unsubstituted C2-C5 alkenyl, A is selected from one or more of PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. 10 unsubstituted C2-C5 alkenyl, A is selected from one or more of PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. - PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. - PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. - PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. - PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. - PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. - PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. - PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. - PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-. - PF6-, BF4-, ClO4-, FSI-, TFSI-, DFOB-, DFOP- and AsF6-.

[0008] In some embodiments, R is selected from substituted or unsubstituted C1-C5 alkyl, unsubstituted C2-C5 alkenyl.

[0009] In some embodiments, the substituent is halogen.

[0010] In some embodiments, the compound having a general structure represented by formula (I) is any one of the compounds represented by formula (I-1) to formula (I-6):

[0011]

[0012] The second aspect of the present application provides an electrolyte, which comprises a solvent, an electrolyte salt, and the electrolyte additive provided in the first aspect.

[0013] In some embodiments, the mass percentage of the electrolyte additive in the electrolyte is 0.01% to 8%.

[0014] In some embodiments, the mass percentage of the electrolyte salt in the electrolyte is 0.5% to 20%.

[0015] In some embodiments, the electrolyte salt comprises one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisfluorosulfonylimide, lithium tetrafluoroborate, and lithium bis-trifluoromethanesulfonylimide.

[0016] In some embodiments, the electrolyte further comprises other additives, and the mass percentage of the other additives in the electrolyte is 0.1% to 10%.

[0017] In some embodiments, the other additives comprise one or more of a sulfonic acid lactone compound, a cyclic sulfate compound, a phosphoric acid ester compound, and a boronic acid ester compound.

[0018] The third aspect of the present application provides a lithium ion battery, which comprises a positive electrode, a negative electrode, a separator, and the electrolyte provided in the second aspect.

[0019] Compared with the conventional technology, the present application has at least the following beneficial effects:

[0020] The electrolyte additive provided in the present application, through the synergistic effect of N cation and N-F bond in the structure of the compound represented by formula (I), on the one hand, the N cation captures H2O generated due to electrolyte decomposition, avoids further decomposition of the electrolyte salt to destroy the interface and the positive active material, and improves the cycle and storage performance of the battery at high voltage; on the other hand, the N-F bond is conducive to the generation of SEI film and CEI film rich in LiF at the positive and negative electrodes, and the chemical stability of the SEI film and CEI film of inorganic components is good, which is conducive to improving the interface stability of the positive and negative electrodes, and improving the cycle and storage performance of the battery at high voltage.

[0021] The above is only a possible speculation of the mechanism of the present application, and does not constitute a limitation on the protection scope of the present application. DETAILED DESCRIPTION

[0022] In order to make the above objectives, features and advantages of the present application more clear and easily understood, the detailed description of the specific embodiments of the present application is made below. In the following description, a lot of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many different ways other than the one described herein, and one of ordinary skill in the art can make similar improvements without departing from the spirit of the present application, and therefore the present application is not limited to the specific embodiments disclosed below.

[0023] In the description of the present application, unless otherwise defined, the professional terms and professional words not explicitly described have the same meaning as generally understood by those skilled in the art, and are the common knowledge of those skilled in the art, and the methods not explicitly described are the conventional methods known to those skilled in the art. The term "plurality" in the present application means at least two, for example, two, three, etc., unless otherwise specifically limited.

[0024] In the present application, the technical features described in an open manner include both the closed technical solution consisting of the listed features and the open technical solution containing the listed features.

[0025] In the present application, when referring to a numerical interval, unless otherwise specified, the numerical interval is considered to be continuous and includes the minimum value and the maximum value of the range, as well as every value between the minimum value and the maximum value. Further, when the range refers to an integer, every integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0026] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0027] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0028] If not specifically stated, the "includes" and "contains" mentioned in the present application are open-ended and can also be closed. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0029] If not specifically stated, in the present 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 A and B are both true (or exist).

[0030] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0031] "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).

[0032] The term "alkenyl" refers to a group containing at least one unsaturated site, i.e., a carbon-carbon sp 2A hydrocarbon containing a positive, secondary, tertiary or cyclic carbon atom of a double bond. Phrases 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).

[0033] The term "halogen" or "halo" refers to F, Cl, Br or I.

[0034] The first aspect of the present application provides an electrolyte additive, which includes a compound having the general structural formula shown in formula (I):

[0035]

[0036] Wherein, in formula (I), R is selected from substituted or unsubstituted C1-C 10 Alkyl, unsubstituted C2-C 10 Alkenyl, A - Selected from PF6 - 、BF4 - 、ClO4 - 、FSI - TFSI - DFOB - DFOP - and AsF6 - One or more of .

[0037] The electrolyte additive provided in the present application, through the synergistic effect of the N cation and the NF bond in the structure of the compound represented by formula (I), on the one hand, the N cation captures the H2O generated by the decomposition of the electrolyte, thereby preventing further decomposition of the electrolyte salt from damaging the interface and the positive electrode active material, thereby improving the cycle and storage performance of the battery at high voltage; on the other hand, the NF bond is conducive to the formation of LiF-rich SEI film and CEI film at the positive and negative electrodes. The SEI film and CEI film of the inorganic component have good chemical stability, which is conducive to improving the interface stability of the positive and negative electrodes, and improving the cycle and storage performance of the battery at high voltage.

[0038] The above is only a possible speculation on the mechanism of this application and does not constitute a limitation on the scope of protection of this application.

[0039] In some embodiments, R is selected from substituted or unsubstituted C1-C5 alkyl, unsubstituted C2-C5 alkenyl.

[0040] In some embodiments, the substituted substituent is halogen.

[0041] In some embodiments, the compound having the general structural formula shown in formula (I) is any one of the compounds represented by formula (I-1) to formula (I-6):

[0042]

[0043] A second aspect of the present application provides an electrolyte, which includes a solvent, an electrolyte salt, and the electrolyte additive provided by the first aspect.

[0044] In some embodiments, the mass percentage of the electrolyte additive in the electrolyte is 0.01% to 8%, including but not limited to 0.01%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, and 8%. Furthermore, the mass percentage of the electrolyte additive in the electrolyte is 0.1% to 0.8%.

[0045] In some embodiments, the mass percentage of the electrolyte salt in the electrolyte is 0.5% to 20%, including but not limited to 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0046] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0047] Furthermore, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), and lithium tetrafluoroborate (LiBF4). These electrolyte salts are sensitive to trace amounts of water in the electrolyte and easily react with water, thereby generating gas or damaging the electrode. The compound having the general structural formula shown in formula (I) as an electrolyte additive can effectively absorb water, thereby improving the stability of the electrolyte and the interface stability of the electrode.

[0048] In some embodiments, the solvent comprises a non-aqueous organic solvent.

[0049] In some embodiments, the solvent includes one or more of a carbonate solvent, a carboxylate solvent, and an aromatic hydrocarbon solvent.

[0050] In some embodiments, the carbonate solvent includes halogenated carbonate and / or non-halogenated carbonate.

[0051] In some embodiments, the halogenated carbonate includes one or more of fluoroethylene carbonate, bisfluoropropylene carbonate, trifluoroethyl methyl carbonate, trifluoromethyl ethylene carbonate, 4-trifluoromethyl ethylene carbonate, chloroethylene carbonate, di(2,2,2-trifluoroethyl) carbonate, or 1,1,1,3,3,3-hexafluoroisopropyl acrylate.

[0052] In some embodiments, the non-halogenated carbonate includes one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, or ethyl methyl carbonate.

[0053] In some embodiments, the carboxylate solvent includes halogenated carboxylate and / or non-halogenated carboxylate.

[0054] In some embodiments, the halocarboxylic acid ester comprises one or more of propyl fluorobutyrate, propyl fluoroacetate, ethyl fluoroacetate, isopropyl fluoroacetate, butyl fluoropropionate, isopropyl fluoropropionate, ethyl fluorobutyrate, methyl fluoropropionate, ethyl fluoropropionate, or propyl fluoropropionate.

[0055] In some embodiments, the non-halogenated carboxylic acid ester includes one or more of ethyl acetate, methyl acetate, propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate, or propyl propionate.

[0056] In some embodiments, the aromatic hydrocarbon solvent includes halogenated aromatic hydrocarbons and / or non-halogenated aromatic hydrocarbons.

[0057] In some embodiments, the halogenated aromatic hydrocarbon includes one or more of monofluorobenzene, difluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene, or 2,4-dichlorotrifluorotoluene.

[0058] In some embodiments, the electrolyte further includes other additives, and the mass percentage of the other additives in the electrolyte is 0.1% to 10%, including but not limited to 0.1%, 0.3%, 0.5%, 1%, 2%, 4%, 6%, 8%, and 10%.

[0059] In some embodiments, the other additives include one or more of sultone compounds, cyclic sulfate compounds, phosphate compounds, and borate compounds.

[0060] In some embodiments, the sultone compound is selected from one or more of 1,3-propane sultone, 1,4-butane sultone, and propenyl-1,3-sultone.

[0061] In some embodiments, the cyclic sulfate ester compound is selected from one or more of vinyl sulfate, 4-methylvinyl sulfate, and propylene sulfate.

[0062] In some embodiments, the cyclic sulfate compound is selected from one or more compounds having the following structural formula:

[0063]

[0064]

[0065] In some embodiments, the phosphate compound is selected from at least one of a saturated phosphate compound and an unsaturated phosphate compound. The saturated phosphate compound includes tris(trimethylsilyl)phosphate; the unsaturated phosphate compound includes at least one of the compounds shown in formula (II):

[0066]

[0067] Among them, R 41 、R 42 、R 43 are independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 41 、R 42 、R 43 At least one of them is an unsaturated hydrocarbon group.

[0068] In some embodiments, the borate compound is selected from one or more of tris(trimethylsilyl)borate and tris(triethylsilyl)borate.

[0069] A third aspect of the present application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and the electrolyte provided in the second aspect.

[0070] In some embodiments, the positive electrode includes a positive electrode active material layer and a positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0071] In some embodiments, the positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium nickel manganese oxide, lithium-rich manganese-based materials, lithium vanadium phosphate, and ternary materials. Among them, the ternary material includes one or more of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

[0072] In some embodiments, the negative electrode includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes, but is not limited to, one or more of graphite, soft carbon, hard carbon, a composite material of single crystal silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate, and niobium pentoxide.

[0073] In some embodiments, a separator commonly used in lithium-ion batteries is selected, such as a porous polymer membrane prepared from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer, which can be used alone as a separator or laminated together to be used as a separator included in the lithium-ion battery of the present application. Non-woven fabrics formed of polyester fibers, aramid fibers, glass fibers, etc. can also be used; and base membranes formed by ceramic particles such as silica, alumina, and titanium dioxide attached to their surfaces can also be used.

[0074] It will be appreciated that lithium-ion batteries can be prepared and used according to conventional methods known in the art.

[0075] The present application will be further described below with reference to specific embodiments and comparative examples.

[0076] Example 1

[0077] Electrolyte additives:

[0078] The electrolyte additive includes a compound having a structure represented by the following formula (I-1).

[0079]

[0080] Electrolyte:

[0081] The electrolyte includes an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0082] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 0.5%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the balance is solvent.

[0083] Lithium-ion battery:

[0084] The lithium-ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0085] Example 2

[0086] Electrolyte additive:

[0087] The electrolyte additive comprises a compound having a structure shown in the following formula (I-2).

[0088]

[0089] Electrolyte:

[0090] The electrolyte comprises an electrolyte salt, a solvent, the above-mentioned electrolyte additive and other additives. The electrolyte salt is LiPF6; the solvent is FEC, EC and DEC combined in a ratio of FEC:EC:DEC = 2:1:7; the other additives comprise 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP).

[0091] Among them, the mass ratio of the electrolyte salt in the electrolyte is 13%; the mass ratio of the electrolyte additive in the electrolyte is 0.5%; the mass ratios of PS and TMSP in the electrolyte are 3% and 2% respectively; the balance is the solvent.

[0092] Lithium ion battery:

[0093] The lithium ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0094] Example 3

[0095] Electrolyte additive:

[0096] The electrolyte additive comprises a compound having a structure shown in the following formula (I-3).

[0097]

[0098] Electrolyte:

[0099] The electrolyte comprises an electrolyte salt, a solvent, the above-mentioned electrolyte additive and other additives. The electrolyte salt is LiPF6; the solvent is FEC, EC and DEC combined in a ratio of FEC:EC:DEC = 2:1:7; the other additives comprise 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP).

[0100] Among them, the mass ratio of the electrolyte salt in the electrolyte is 13%; the mass ratio of the electrolyte additive in the electrolyte is 0.5%; the mass ratios of PS and TMSP in the electrolyte are 3% and 2% respectively; the balance is the solvent.

[0101] Lithium ion battery:

[0102] The lithium ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, and the positive electrode active material is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, and the negative electrode active material is graphite.

[0103] Example 4

[0104] The electrolyte additive comprises a compound having the structure shown in the following formula (I-1).

[0105] The electrolyte additive comprises a compound having the structure shown in the following formula (I-1).

[0106]

[0107] The electrolyte:

[0108] The electrolyte comprises an electrolyte salt, a solvent, the above-mentioned electrolyte additive and other additives. The electrolyte salt is LiPF6; the solvent is FEC, EC and DEC combined in a ratio of FEC:EC:DEC = 2:1:7; the other additives comprise 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP).

[0109] Among them, the mass proportion of the electrolyte salt in the electrolyte is 13%; the mass proportion of the electrolyte additive in the electrolyte is 0.01%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the balance is the solvent.

[0110] The lithium ion battery:

[0111] The lithium ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, and the positive electrode active material is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, and the negative electrode active material is graphite.

[0112] Example 5

[0113] The electrolyte additive:

[0114] The electrolyte additive comprises a compound having the structure shown in the following formula (I-1).

[0115]

[0116] The electrolyte:

[0117] The electrolyte comprises an electrolyte salt, a solvent, the above-mentioned electrolyte additive and other additives. The electrolyte salt is LiPF6; the solvent is FEC, EC and DEC combined in a ratio of FEC:EC:DEC = 2:1:7; the other additives comprise 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP).

[0118] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 0.8%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the balance is solvent.

[0119] Lithium-ion battery:

[0120] The lithium-ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0121] Example 6

[0122] Electrolyte additives:

[0123] The electrolyte additive includes a compound having a structure represented by the following formula (I-1).

[0124]

[0125] Electrolyte:

[0126] The electrolyte includes an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0127] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 8%; the mass proportion of PS and TMSP in the electrolyte is 3% and 2% respectively; the balance is solvent.

[0128] Lithium-ion battery:

[0129] The lithium-ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0130] Example 7

[0131] Electrolyte additives:

[0132] The electrolyte additive includes a compound having a structure represented by the following formula (I-4).

[0133]

[0134] Electrolyte:

[0135] The electrolyte includes an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0136] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 0.5%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the balance is solvent.

[0137] Lithium-ion battery:

[0138] The lithium-ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0139] Example 8

[0140] Electrolyte additives:

[0141] The electrolyte additive includes a compound having a structure represented by the following formula (I-5).

[0142]

[0143] Electrolyte:

[0144] The electrolyte includes an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0145] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 0.5%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the balance is solvent.

[0146] Lithium-ion battery:

[0147] The lithium-ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0148] Comparative Example 1

[0149] Electrolyte:

[0150] The electrolyte includes electrolyte salt, solvent and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0151] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the rest is solvent.

[0152] Lithium-ion battery:

[0153] The lithium-ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0154] Comparative Example 2

[0155] Electrolyte additives:

[0156] The electrolyte additive includes a compound having a structure represented by the following formula (III).

[0157]

[0158] Electrolyte:

[0159] The electrolyte includes an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0160] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 0.5%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the balance is solvent.

[0161] Lithium-ion battery:

[0162] The lithium-ion battery comprises a positive electrode, a negative electrode and the above-mentioned electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0163] Performance Testing

[0164] The lithium-ion batteries of the above embodiments and comparative examples were subjected to high-voltage cycle performance tests:

[0165] The test conditions are: at 25°C, the charge and discharge potential range is 3.5V to 4.9V, and the charging current is 1C to 4.9V. The specific test process is as follows:

[0166] The lithium-ion battery was charged at a constant voltage of 4.9V to a cutoff current ≤ 0.05C, allowed to stand for 5 minutes, and then discharged at 1C to 3.5V and allowed to stand for 5 minutes. This is a charge and discharge cycle process. The discharge capacity of the first cycle was recorded. The test results are shown in Table 1.

[0167] The lithium-ion battery was charged and discharged for 100 cycles according to the above method, and the discharge capacity of the 100th cycle was measured.

[0168] The capacity retention rate (%) of the lithium-ion battery after 100 cycles is calculated as follows: (discharge capacity of the lithium-ion battery after 100 cycles / discharge capacity of the lithium-ion battery after the first cycle)×100%. The calculation results are shown in Table 1.

[0169] Table 1

[0170]

[0171]

[0172] By comparing Examples 1 to 8 with Comparative Examples 1 to 2, it can be seen that the electrolyte additive of the present application improves the capacity performance and cycle performance of the lithium-ion battery under high voltage.

[0173] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0174] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. An electrolyte additive, characterized in that Including compounds having the general structural formula shown in formula (I): Formula (I); Wherein, in formula (I), R is selected from substituted or unsubstituted C1-C 10 Alkyl, unsubstituted C2-C 10 Alkenyl, A - Selected from PF6 - 、BF4 - 、ClO4 - 、FSI - TFSI - DFOB - DFOP - and AsF6 - One or more of, wherein the substituted substituent is halogen.

2. The electrolyte additive according to claim 1, characterized in that R is selected from substituted or unsubstituted C1-C5 alkyl and unsubstituted C2-C5 alkenyl.

3. The electrolyte additive according to claim 1, wherein The compound having the general structural formula represented by formula (I) is any one of the compounds represented by formula (I-1) to formula (I-6): Formula (I-1), Formula (I-2), Formula (I-3), Formula (I-4), Formula (I-5).

4. An electrolyte, characterized in that The electrolyte composition comprises a solvent, an electrolyte salt and the electrolyte additive according to any one of claims 1 to 3.

5. The electrolyte according to claim 4, characterized in that The mass percentage of the electrolyte additive in the electrolyte is 0.01% to 8%.

6. The electrolyte according to claim 4, characterized in that The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

7. The electrolyte according to any one of claims 4 to 6, characterized in that The electrolyte further includes other additives, and the mass percentage of the other additives in the electrolyte is 0.1% to 10%.

8. The electrolyte according to claim 7, characterized in that The other additives include one or more of sultone compounds, cyclic sulfate compounds, phosphate compounds and borate compounds.

9. 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 4 to 8.

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