Secondary battery and device

Abstract

The invention relates to a secondary battery and an apparatus. The secondary battery comprises a positive pole piece, a negative pole piece and an electrolyte, the positive pole piece comprises a positive active material, and the positive active material comprises a lithium-nickel transition metal oxide; the electrolyte comprises fluorine-containing lithium sulfimide and an alkoxy boric acid additive shown as a formula 1; relative to every 100g of nickel element in the positive electrode active material, the content of the alkoxy boric acid additive is X g; relative to every 100g of nickel element in the positive electrode active material, the content of the fluorine-containing lithium sulfimide is Y g; wherein 0.1 < = X < = 6, 4 < = Y < = 12, and 6 < = 2X + Y < = 18. Therefore, the capacity retention ratio, the storage discharge rate, the impedance (DCR) growth rate and the rapid charge and discharge performance of the battery are effectively improved.

Description

Technical Field

[0001] The present application relates to the field of energy storage, and in particular to a secondary battery and a device. Background Art

[0002] With the development of science and technology, people's demand for electronic devices has increased significantly. Among them, the high energy density of secondary batteries in electronic devices has always been one of the goals pursued by people. Improving the working voltage of the existing system and developing a high specific capacity battery system are the key ways to solve the problem of battery energy density. At present, the most commonly used lithium-ion battery electrolyte is lithium hexafluorophosphate (LiPF 6 ) dissolved in carbonate solvents, however, this type of electrolyte has a relatively low oxidation window and is prone to oxidation side reactions in high voltage systems, resulting in rapid capacity decay and shortened battery life. 6 Its thermal stability and oxidation stability are also poor, which directly affects its use under high voltage.

[0003] Therefore, current secondary batteries and devices still need to be improved. Summary of the invention

[0004] The inventors have found that the thermal stability and oxidative stability of fluorinated lithium sulfonyl imide (e.g., lithium bis(fluorinated) sulfonyl imide LiFSI) are better than those of LiPF. 6 Well, it can be used as the main lithium salt to replace LiPF 6However, during the charging process, the fluorinated sulfonyl imide lithium reacts with the aluminum current collector on the positive electrode side to produce an aluminum-containing complex, which is continuously dissolved in the electrolyte, leading to a continuous reaction between the fluorinated sulfonyl imide lithium and the aluminum current collector. On the one hand, the fluorinated sulfonyl imide lithium is consumed as a lithium salt in the electrolyte. On the other hand, the aluminum current collector is continuously consumed, interrupting the transmission path of lithium ions and even causing safety hazards such as short circuits. The above problems seriously restrict the application of fluorinated sulfonyl imide lithium. In view of the above-mentioned problems existing in the prior art, the present application provides a secondary battery and a device. By introducing an appropriate amount of fluorinated sulfonyl imide lithium and an alkoxy boric acid additive based on the nickel content in the lithium nickel transition metal oxide of the positive electrode plate, the two can form a synergistic effect. On the one hand, the use of fluorinated sulfonyl imide lithium as the main lithium salt can make lithium ions quickly transported in the electrolyte, thereby improving the charging and discharging speed of the battery; and, the fluorinated sulfonyl imide lithium itself has good thermal stability and oxidation resistance, which can reduce the side reactions of the electrolyte, reduce the impedance (DCR) growth rate of the battery, and significantly improve the cycle performance and storage performance of the high-voltage battery; on the other hand, by adding alkoxy boric acid additives, the continuous corrosion of the fluorinated sulfonyl imide lithium to the positive electrode collector can be prevented, which can not only realize the application of fluorinated sulfonyl imide lithium as the main lithium salt in the high-voltage battery system, maintain its advantages of fast charging and discharging, cycling and storage performance, but also improve the safety performance of the high-voltage battery.

[0005] One aspect of the present application provides a secondary battery, the secondary battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte; the positive electrode sheet comprises a positive electrode active material, the positive electrode active material comprises a lithium nickel transition metal oxide; the electrolyte comprises a fluorinated lithium sulfonyl imide and an alkoxyboric acid additive as shown in Formula 1;

[0006]

[0007] In Formula 1, R 1 , R 2 , R 3 and R 4 are independently selected from substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted C1-C8 alkoxy, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkenyloxy, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C2-C6 alkynyloxy, substituted or unsubstituted C3-C6 cycloalkyl, substituted or unsubstituted C3-C6 epoxyalkyl, substituted or unsubstituted C6-C12 aryl or substituted or unsubstituted C6-C12 heteroaryl; the substituted substituents are independently selected from fluorine;

[0008] The content of the alkoxyboric acid additive is X g for every 100 g of nickel in the positive electrode active material; the content of the fluorinated sulfonyl imide lithium is Y g for every 100 g of nickel in the positive electrode active material; wherein 0.1≤X≤6, 4≤Y≤12, and 6≤2X+Y≤18.

[0009] Another aspect of the present application provides a device, which includes the secondary battery described above.

[0010] The beneficial effects of this application are:

[0011] The secondary battery of the present application introduces a suitable amount of fluorinated sulfonyl imide lithium and alkoxy boric acid additives based on the nickel content in the lithium nickel transition metal oxide of the positive electrode plate, and the two can form a synergistic effect. On the one hand, the fluorinated sulfonyl imide lithium is used as the main lithium salt, and its lithium ion migration number is relatively high, which can make lithium ions quickly transported in the electrolyte and improve the charge and discharge speed of the battery; and the fluorinated sulfonyl imide lithium itself has good thermal stability and oxidation resistance stability, which can reduce the side reactions of the electrolyte, reduce the impedance (DCR) growth rate of the battery, and significantly improve the cycle performance and storage performance of the high-voltage battery; on the other hand, the fluorinated sulfonyl imide lithium Lithium imide will react with the aluminum current collector on the positive electrode side to produce an aluminum-containing complex. This aluminum-containing complex will be continuously dissolved by the electrolyte, resulting in a continuous reaction between lithium fluorinated sulfonyl imide and aluminum, which not only continuously consumes lithium fluorinated sulfonyl imide and aluminum current collector, but also may interrupt the transmission path of lithium ions and even cause safety hazards such as short circuits. By adding alkoxyboric acid additives, the continuous corrosion of lithium fluorinated sulfonyl imide on the positive electrode current collector can be prevented, which can not only realize the application of lithium fluorinated sulfonyl imide as the main lithium salt in the high-voltage battery system, maintain its advantages in fast charge and discharge, cycle and storage performance, but also improve the safety performance of high-voltage batteries. Therefore, based on the above improvements, the capacity retention rate, storage discharge rate, impedance (DCR) growth rate and fast charge and discharge performance of the battery are effectively improved. DETAILED DESCRIPTION

[0012] For simplicity, this application only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, and any upper limit can be combined with any other upper limit to form an undefined range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an undefined range.

[0013] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0014] A list of items connected by the terms "at least one of," "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 only A; 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 only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0015] The term "C1-C8 alkyl" includes, but is not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, n-octyl, and the like.

[0016] The term "C1-C8 alkoxy" includes, but is not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy, n-hexoxy, n-heptyloxy, n-octyloxy, and the like.

[0017] The term "C2-C6 alkenyl" includes, but is not limited to, ethenyl, propenyl, butenyl, pentenyl or hexenyl and the like.

[0018] The term "C2-C6 alkenyloxy" includes, but is not limited to, vinyloxy, propenyloxy, butenyloxy, pentenyloxy or hexenyloxy and the like.

[0019] The term "C2-C6 alkynyl" includes, but is not limited to, ethynyl, propynyl, butynyl, pentynyl or hexynyl and the like.

[0020] The term "C2-C6 alkynyloxy" includes, but is not limited to, ethynyloxy, propynyloxy, butynyloxy, pentynyloxy or hexynyloxy and the like.

[0021] The term "C6-C12 aryl" includes, but is not limited to, phenyl or naphthyl, and the like.

[0022] The term "C6-C12 heteroaryl" includes, but is not limited to, phenyl or naphthyl containing heteroatoms such as nitrogen, oxygen, sulfur, and the like.

[0023] The present application is further described below in conjunction with specific implementations. It should be understood that these specific implementations are only used to illustrate the present application and are not used to limit the scope of the present application.

[0024] Primary and secondary batteries

[0025] One aspect of the present application provides a secondary battery, the secondary battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte; the positive electrode sheet comprises a positive electrode active material, the positive electrode active material comprises a lithium nickel transition metal oxide; the electrolyte comprises a fluorinated lithium sulfonyl imide and an alkoxyboric acid additive as shown in Formula 1;

[0026]

[0027] In Formula 1, R 1 , R 2 , R 3 and R 4 are independently selected from substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted C1-C8 alkoxy, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkenyloxy, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C2-C6 alkynyloxy, substituted or unsubstituted C3-C6 cycloalkyl, substituted or unsubstituted C3-C6 epoxyalkyl, substituted or unsubstituted C6-C12 aryl or substituted or unsubstituted C6-C12 heteroaryl; the substituted substituents are independently selected from fluorine;

[0028] The content of the alkoxyboric acid additive is X g for every 100 g of nickel in the positive electrode active material; the content of the fluorinated sulfonyl imide lithium is Y g for every 100 g of nickel in the positive electrode active material; wherein 0.1≤X≤6, 4≤Y≤12, and 6≤2X+Y≤18.

[0029] The secondary battery of the present application introduces a suitable amount of fluorinated sulfonyl imide lithium and alkoxy boric acid additives based on the nickel content in the lithium nickel transition metal oxide of the positive electrode plate, and the two can form a synergistic effect. On the one hand, the fluorinated sulfonyl imide lithium is used as the main lithium salt, and its lithium ion migration number is relatively high, which can make lithium ions quickly transported in the electrolyte and improve the charge and discharge speed of the battery; and the fluorinated sulfonyl imide lithium itself has good thermal stability and oxidation resistance stability, which can reduce the side reactions of the electrolyte, reduce the impedance (DCR) growth rate of the battery, and significantly improve the cycle performance and storage performance of the high-voltage battery; on the other hand, the fluorinated sulfonyl imide lithium Lithium imide will react with the aluminum current collector on the positive electrode side to produce an aluminum-containing complex. This aluminum-containing complex will be continuously dissolved by the electrolyte, resulting in a continuous reaction between lithium fluorinated sulfonyl imide and aluminum, which not only continuously consumes lithium fluorinated sulfonyl imide and aluminum current collector, but also may interrupt the transmission path of lithium ions and even cause safety hazards such as short circuits. By adding alkoxyboric acid additives, the continuous corrosion of lithium fluorinated sulfonyl imide on the positive electrode current collector can be prevented, which can not only realize the application of lithium fluorinated sulfonyl imide as the main lithium salt in the high-voltage battery system, maintain its advantages in fast charge and discharge, cycle and storage performance, but also improve the safety performance of high-voltage batteries. Therefore, based on the above improvements, the capacity retention rate, storage discharge rate, impedance (DCR) growth rate and fast charge and discharge performance of the battery are effectively improved.

[0030] In some embodiments, the fluorine-containing lithium sulfonyl imide includes at least one of lithium bisfluorosulfonyl imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, lithium (fluorosulfonyl)(perfluorobutylsulfonyl)imide, lithium (trifluoromethylsulfonyl)(perfluorobutylsulfonyl)imide (LiFNFSI), and lithium bis(pentafluoroethylsulfonyl)imide (LiBETI).

[0031] In some embodiments, in Formula 1, R 1 , R 2 , R 3 and R 4 Each is independently selected from C1-C6 alkyl, fluorine-substituted C1-C6 alkyl, C2-C4 alkenyl, fluorine-substituted C2-C4 alkenyl, C2-C4 alkynyl, fluorine-substituted C2-C4 alkynyl, phenyl or fluorine-substituted phenyl.

[0032] In some embodiments, R 1 , R 2 , R 3 and R 4 Contains at least one fluorine.

[0033] In some embodiments, the fluorine-containing lithium sulfonyl imide includes lithium bis(fluorosulfonyl) imide (LiFSI).

[0034] In some embodiments, the alkoxyboric acid additive includes at least one of the following compounds:

[0035]

[0036] In some embodiments, 0.1≤X≤6. In some embodiments, X is 0.1, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or any value therebetween. In some embodiments, 0.5≤X≤5. In some embodiments, 1≤X≤4. The alkoxyboric acid additive in the electrolyte can prevent the continuous corrosion of lithium salts such as fluorinated sulfonyl imide lithium to the positive electrode current collector, which can not only realize the application of fluorinated sulfonyl imide lithium as the main lithium salt in high-voltage battery systems (e.g., 4.4V and above), maintain its advantages of fast charge and discharge, cycle and storage performance, but also improve the safety performance of high-voltage batteries. If the content of alkoxyboric acid additive in the electrolyte is too high, the viscosity of the electrolyte will be higher, the advantage of fast charging and discharging brought by fluorinated sulfonyl imide lithium will be lost, and the cost will be increased; if the content of alkoxyboric acid additive in the electrolyte is too low, it will not be enough to block the continuous corrosion of fluorinated sulfonyl imide lithium on the positive electrode collector, the battery's cycle and storage performance will not be guaranteed, and the safety performance will be reduced.

[0037] In some embodiments, 4≤Y≤12. In some embodiments, Y is 4, 5, 6, 7, 8, 9, 10, 11, 12 or any value therebetween. In some embodiments, 4≤Y≤10. In some embodiments, 4≤Y≤6. The fluorinated lithium sulfonyl imide in the electrolyte helps to increase the lithium ion transmission rate and improve the cycle and storage performance of the battery; if the content of the fluorinated lithium sulfonyl imide in the electrolyte is too high, the cost will increase, the viscosity of the electrolyte will increase, the polarization will intensify, and the lithium ion transmission rate will decrease; if the content of the fluorinated lithium sulfonyl imide in the electrolyte is too low, the lithium ion concentration of the electrolyte will be insufficient, and the rate performance of the battery will be suppressed.

[0038] In some embodiments, 2X+Y is 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or any value therebetween. In some embodiments, 6≤2X+Y≤16. In some embodiments, 7≤2X+Y≤13. If the value of 2X+Y is too high, the fluorinated sulfonyl imide lithium is too high or the alkoxy boric acid additive is too high, which will cause the viscosity of the electrolyte to be larger, the lithium ion transmission resistance to increase, the charge and discharge speed of the battery to decrease, and the capacity loss caused by polarization during the cycle will increase; if the value of 2X+Y is too low, the fluorinated sulfonyl imide lithium is too low or the alkoxy boric acid additive is too low, which will cause insufficient lithium ion concentration in the electrolyte and reduce the rate performance of the battery.

[0039] In some embodiments, the electrolyte further includes a first additive, and the first additive includes at least one of a cyclic carbonate containing a carbon-carbon double bond, a phosphate ester containing a silyl group, a nitrile compound, and a pyridinium propane sulfonate. In some embodiments, the first additive includes at least one of vinylene carbonate (VC), ethylene vinylene carbonate, tris(trimethylsilyl) phosphate (TMSP), succinonitrile, adiponitrile, glutaronitrile, and hexane trinitrile. In some embodiments, the additive further includes at least one of methylene methyl disulfonate (MMDS), ethylene ethyl disulfonate, 1,3-propane sultone (1,3-PS), 1-propene-1,3-sultone (PST), 1,4-butane sultone (1,4-BS), divinyl sulfate (DTD), ethylene methyl sulfate (PCS), ethylene ethyl sulfate (PES), ethylene propyl sulfate (PEGLST), propylene sulfate (TS), ethylene sulfite (DTO), dimethyl sulfite (DMS), and diethyl sulfite (DES).

[0040] In some embodiments, based on the mass of the electrolyte, the mass percentage content of the first additive is 0.05% to 10%. In some embodiments, the mass percentage content of the first additive is 0.05%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, or any value therebetween. In some embodiments, the mass percentage content of the additive is 0.1% to 5%.

[0041] In some embodiments, the electrolyte further includes a first lithium salt, and the first lithium salt includes at least one of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium trifluoromethanesulfonate (LiTf), lithium trifluoromethanesulfonate, lithium bis(fluoromalonate) borate (LiBFMB), lithium bis(oxalate) borate (LiBOB), lithium difluoro(oxalate) borate (LiDFOB), lithium difluorodioxalate phosphate, and lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDI).

[0042] In some embodiments, based on the mass of the electrolyte, the mass percentage content of the first lithium salt is 4% to 25%. In some embodiments, the mass percentage content of the first lithium salt is 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or any value therebetween. In some embodiments, the mass percentage content of the lithium salt is 6% to 18%.

[0043] In some embodiments, the electrolyte further includes an organic solvent, and the organic solvent includes at least one of a linear carbonate, a cyclic carbonate, and a carboxylic acid ester.

[0044] In some embodiments, linear carbonate is selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate and fluorinated linear carbonate. In some embodiments, fluorinated linear carbonate includes fluoroethylene carbonate. In some embodiments, cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate and butylene carbonate. In some embodiments, carboxylate is selected from at least one of methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, gamma-butyrolactone and fluorinated carboxylate.

[0045] In some embodiments, the mass percentage of the organic solvent is 40% to 80% based on the mass of the electrolyte. In some embodiments, the mass percentage of the solvent is 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or any value therebetween. In some embodiments, the mass percentage of the solvent is 50% to 70%.

[0046] In some embodiments, the electrolyte has a relative ratio of Li / Li + The oxidation potential Z satisfies: Z ≥ 5.5 V. Therefore, by adding fluorinated sulfonyl imide lithium and alkoxyboric acid additives, the oxidation potential of the electrolyte is increased, the stability of the electrolyte is improved, and the problem of nickel dissolution in the positive electrode active material under high-voltage battery systems (for example, 4.4V and above) can be alleviated (nickel is more easily dissolved in high-voltage systems), thereby reducing the dissolution of nickel elements, making it more suitable for high-voltage systems, and improving the cycle performance, storage performance and safety performance of the battery.

[0047] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on the surface of the positive electrode current collector, the positive electrode active material of the positive electrode active material layer includes lithium nickel transition metal oxide, and the lithium nickel transition metal oxide includes LiNi m A 1-m O 2 , A includes at least one of cobalt, manganese, iron, chromium, titanium, zinc, vanadium, aluminum, zirconium, cerium, magnesium, calcium, molybdenum, strontium, tungsten, yttrium, lanthanum, silver and niobium, and 0.1≤m≤1.

[0048] In some embodiments, m is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or any value therebetween.

[0049] In some embodiments, the positive electrode active material includes at least one of lithium nickel oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese cobalt magnesium oxide, and lithium nickel manganese oxide. In some embodiments, the positive electrode active material includes at least one of NCA, NCM111, NCM523, NCM622, NCM811, Ni90, Ni92, and Ni95.

[0050] In some embodiments, the positive electrode active material layer further includes a binder, and optionally a conductive material. The binder improves the bonding of the positive electrode active material particles to each other and also improves the bonding of the positive electrode active material to the current collector.

[0051] In some embodiments, the binder 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 fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon, etc.

[0052] 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 metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0053] In some embodiments, the positive electrode current collector includes aluminum. For example, aluminum foil can be used.

[0054] In some embodiments, the negative electrode plate includes a negative current collector and a negative active material layer located on the surface of the negative current collector, and the negative active material of the negative active material layer includes a silicon-based material, or a mixture of a silicon-based material and at least one material selected from a carbon-based material, a tin-based material, a phosphorus-based material, and metallic lithium. In some embodiments, the silicon-based material includes at least one of silicon, a silicon alloy, a silicon oxide compound, and a silicon-carbon compound, the carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon nanotubes, and graphene, the tin-based material includes at least one of tin, tin oxide, and a tin alloy, and the phosphorus-based material includes phosphorus and / or a phosphorus-carbon composite.

[0055] In some embodiments, the mass percentage of the silicon-based material is 0.1% to 30% based on the mass of the negative electrode active material. In some embodiments, the mass percentage of the silicon-based material is 0.1%, 1%, 2%, 3%, 5%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 25%, 27%, 28%, 29%, 30% or any value therebetween. In some embodiments, the mass percentage of the silicon-based material is 1% to 28%. In some embodiments, the mass percentage of the silicon-based material is 5% to 15%.

[0056] In some embodiments, the negative electrode active material layer further includes a binder and a conductive agent. In some embodiments, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon, etc.

[0057] In some embodiments, the conductive agent 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 metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0058] In some embodiments, the negative electrode plate further includes a negative electrode current collector, and the negative electrode current collector includes: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof.

[0059] In some embodiments, a separator is provided between the positive electrode plate and the negative electrode plate to prevent short circuit. The material and shape of the separator that can be used in the embodiments of the present application are not particularly limited, and it can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or an inorganic substance formed of a material that is stable to the electrolyte of the present application.

[0060] For example, the isolation 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 having a porous structure, and the material of the substrate layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0061] A surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic layer.

[0062] The inorganic layer includes inorganic particles and a binder, wherein the inorganic particles include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, 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 includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

[0063] The polymer layer contains polymers, and the polymer material includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride and poly(vinylidene fluoride-hexafluoropropylene).

[0064] In some embodiments, the preparation method of the secondary battery includes providing an electrode assembly, injecting, packaging and forming. In some embodiments, the temperature of the formation is 40°C to 50°C, for example, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C or 49°C.

[0065] In some embodiments, the formation comprises: charging to 4.25V at 0.05C current and standing for 60min at a temperature of 40°C to 50°C, such as 45°C, and a pressure of 150kgf to 250kgf, such as 210kgf, followed by charging to 4.25V at 0.1C, and then discharging to 3.0V at 0.2C.

[0066] In some embodiments, the secondary battery is a lithium secondary battery or a sodium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0067] In some embodiments, the secondary battery may include an outer package, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0068] In some embodiments, the shape of the secondary battery is not particularly limited, and it may be cylindrical, square, or any other shape.

[0069] In some embodiments, the present application also provides a battery module. The battery module includes the above-mentioned secondary battery. The battery module of the present application uses the above-mentioned secondary battery, and therefore has at least the same advantages as the secondary battery. The number of secondary batteries contained in the battery module of the present application can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0070] In some embodiments, the present application further provides a battery pack, which includes the above-mentioned battery module. The number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0071] 3. Device

[0072] The present application also provides a device, which includes at least one of the above-mentioned secondary battery, battery module and battery pack. Therefore, the device can have all the features and advantages of the above-mentioned secondary battery, battery module or battery pack, which will not be repeated here.

[0073] In some embodiments, the device includes, but is not limited to: electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, etc. In order to meet the device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module may be used.

[0074] In other embodiments, the device may be a mobile phone, a tablet computer, a laptop computer, etc. The device is usually required to be light and thin, and a secondary battery may be used as a power source.

[0075] The technical solution of the present application will be further illustrated below with reference to specific embodiments and comparative examples.

[0076] Examples and Comparative Examples

[0077] Example 1

[0078] The preparation steps of the positive electrode plate are as follows: the positive electrode active material LiNi 0.9 Co 0.05 Mn 0.05 O 2 (Ni900), CNT (conductive carbon nanotube) / Super-P (conductive carbon black), binder polyvinylidene fluoride PVDF, by weight ratio LiNi 0.9 Co 0.05 Mn 0.05 O 2 :CNT / Super-P:PVDF=95:(2.0 / 1.0):2 In N-methylpyrrolidone NMP, after being fully homogenized, it is coated on a 12μm thick aluminum current collector, and then the positive electrode sheet is obtained through drying, rolling, hot pressing and other steps.

[0079] The preparation steps of the negative electrode sheet are as follows: add the negative electrode active material silicon oxide (SiOx, 0.5≤x≤1.5)-graphite composite (Si / C=14:86), conductive agent acetylene black, binder styrene butadiene rubber SBR, thickener sodium carboxymethyl cellulose CMCNa, and polyacrylic acid PAA in a weight ratio of 95:2:1.5:1:0.5 to deionized water, and after sufficient homogenization, apply it on a 8μm thick copper current collector, and then dry, roll, hot press and other steps to obtain the negative electrode sheet. Among them, the specific surface area of ​​the negative electrode active material (silicon oxide-graphite composite) is 1.4m 2 / g.

[0080] Preparation of electrolyte: In a glove box filled with argon (H 2 O<0.1ppm,O 2 <0.1ppm), EC / DMC / EMC / VC / FEC (ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate / vinylene carbonate / fluoroethylene carbonate)=15 / 65 / 10 / 0.5 / 9.5 are mixed to form a mixed solution, and then an alkoxyboric acid additive (the alkoxyboric acid additive is compound I-3, and for every 100g of nickel element in the positive electrode active material, the content of the corresponding compound I-3 in the electrolyte is 1.28g) and a fluorinated sulfonyl imide lithium additive (the fluorinated sulfonyl imide lithium additive is LiFSI, and for every 100g of nickel element in the positive electrode active material, the content of the corresponding LiFSI in the electrolyte is 5.16g) are added, and the electrolyte is obtained after uniform stirring.

[0081] Isolation film: PP / PE / PP (polypropylene / polyethylene / polypropylene) three-layer composite isolation film is used.

[0082] Preparation of lithium-ion secondary batteries: The prepared positive electrode sheet, separator (PP / PE / PP three-layer composite film), and negative electrode sheet are overlapped in sequence, with the separator being located between the positive electrode sheet and the negative electrode sheet, and are wound to obtain a bare cell, which is placed in a punched aluminum-plastic film soft package shell, and after being fully dried, the prepared electrolyte is injected. The battery is left at 45°C for 48h, formed in a high-temperature fixture (formation conditions are: temperature 45°C, pressure 210kgf, 0.05C current charged to 4.25V and allowed to stand for 60min, then 0.1C charged to 4.25V, then 0.2C discharged to 3.0V, and so on, repeated three times) and secondary sealed, and then conventional capacity division is performed.

[0083] Examples 2 to 12 and Comparative Examples 1 to 7

[0084] Examples 2 to 12 and Comparative Examples 1 to 7 are achieved by adjusting the type and content of the additive in the electrolyte, the type and content of the first lithium salt, etc. on the basis of Example 1. The specific adjustment measures and detailed data are shown in Table 1. Among them, the first lithium salt LiPF 6 , the addition amount is shown in Table 1.

[0085] Test Method

[0086] 1. Cycle performance test

[0087] At 25°C, the prepared lithium-ion secondary battery was charged to 4.3V at a constant current rate of 1C, and then charged at a constant voltage until the current was less than 0.05C. After standing for 5 minutes, it was discharged to 2.5V at a rate of 1C, and the initial discharge capacity was recorded. The lithium-ion secondary battery was charged and discharged 300 times by the above method, and the discharge capacity was recorded each time. The capacity retention rate of the lithium-ion secondary battery after 300 cycles at 25°C = the discharge capacity of the 300th time / initial discharge capacity × 100%.

[0088] 2. 60℃ storage test:

[0089] The battery was charged at 0.5C to 4.3V and then transferred to a 60°C thermostat for storage for 30 days.

[0090] 3. Impedance (DCR) growth rate test

[0091] Discharge the fresh lithium-ion battery at 1C constant current to 2.5V at 25±2℃, then charge it to 4.3V at 0.5C constant current, charge it to 0.05C at 4.3V, then discharge it to 50% SOC at 1C constant current, let it stand for 60min, and record the voltage U after the standing period. 1 , and then discharge at 2C constant current for 10s, and record the voltage U after the discharge. 2 , 2C current is recorded as I, and left to stand for 60 minutes. According to the formula DCR = (U 1 -U 2 ) / I, calculate the discharge DCR of the battery at 50% SOC 0 .

[0092] After the battery was stored at 60℃ for 30 days, it was taken out and placed for 6 hours to return to room temperature. Then the DCR test method was used again. The impedance of the battery after 60℃ storage for 30 days was DCR. 1 .

[0093] Then the DCR growth rate is (DCR 1 -DCR 0 ) / DCR 0 .

[0094] 4. Storage self-discharge rate test

[0095] The fresh battery before storage is discharged at 1C constant current to 2.5V at 25±2℃, then charged to 4.3V at 0.5C constant current, charged to 0.05C at 4.3V, and then discharged to 2.5V at 1C constant current to obtain the capacity CAP0. The battery after storage for 30 days is charged and discharged in the same way to obtain the capacity CAP1, and the storage self-discharge rate is (CAP0-CAP1) / CAP0.

[0096] 5. Charging performance test

[0097] The finished lithium-ion batteries of the above embodiments and comparative examples were placed in a room temperature environment of 25°C, discharged at 1C to 2.5V, left to stand for 5 minutes, charged at 1C to 4.3V, charged at a constant voltage to 0.05C, left to stand for 5 minutes, and the 1C constant current and constant voltage charging time was recorded.

[0098] Test Results

[0099] Table 1

[0100]

[0101]

[0102] It can be seen from Examples 1 to 12 and Comparative Examples 1 to 7 that when an appropriate amount of fluorinated lithium sulfonyl imide and alkoxyboric acid additives are introduced based on the nickel content in the lithium nickel transition metal oxide of the positive electrode plate, and the preset relationship is satisfied, the battery's cycle capacity retention rate and storage performance are improved, the DCR growth rate during the storage process is reduced, and the rapid charge and discharge performance is improved.

[0103] Comparison of Example 1 shows that when the alkoxyboric acid additive is not added, the capacity retention rate and storage performance of the battery are poor. Comparison of Examples 2 to 3 shows that when the alkoxyboric acid additive and the fluorinated sulfonyl imide lithium are not added, or the fluorinated sulfonyl imide lithium is not added, the capacity retention rate, storage performance, and rapid charge and discharge performance of the battery are poor, and the DCR growth rate is large. Comparison of Example 4 shows that when the content of the fluorinated sulfonyl imide lithium is too large, the preset relationship is not satisfied, resulting in an increase in the viscosity of the electrolyte, an increase in polarization, and a decrease in the lithium ion transmission rate. The 1C charging time is significantly increased, and the rapid charge and discharge performance of the battery is poor. Comparison Example 5 shows that when the content of the alkoxyboric acid additive is too large, the preset relationship is not satisfied, resulting in an increase in the viscosity of the electrolyte, a significant increase in the 1C charging time, and poor rapid charge and discharge performance of the battery. From Comparative Examples 6 to 7, it can be seen that when the content of fluorinated sulfonyl imide lithium is too small, or the content of alkoxyboric acid additive is too small, the preset relationship is not satisfied, resulting in poor capacity retention, storage performance, and fast charge and discharge performance of the battery, and a large DCR growth rate.

[0104] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those skilled in the art will recognize that some modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims.

Claims

1. A secondary battery, It is characterized in that Including positive electrode sheet, negative electrode sheet and electrolyte; The positive electrode plate includes a positive electrode active material, and the positive electrode active material includes lithium nickel transition metal oxide; The electrolyte includes fluorinated lithium sulfonyl imide and an alkoxyboric acid additive as shown in Formula 1; In Formula 1, R 1 , R 2 , R 3 and R 4 are independently selected from substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted C1-C8 alkoxy, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkenyloxy, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C2-C6 alkynyloxy, substituted or unsubstituted C3-C6 cycloalkyl, substituted or unsubstituted C3-C6 epoxyalkyl, substituted or unsubstituted C6-C12 aryl or substituted or unsubstituted C6-C12 heteroaryl; the substituted substituents are independently selected from fluorine; The content of the alkoxyboric acid additive is X g for every 100 g of nickel in the positive electrode active material; the content of the fluorinated sulfonyl imide lithium is Y g for every 100 g of nickel in the positive electrode active material; wherein 0.1≤X≤6, 4≤Y≤12, and 6≤2X+Y≤18.

2. The secondary battery according to claim 1, It is characterized in that The fluorine-containing lithium sulfonyl imide comprises at least one of lithium bisfluorosulfonyl imide, lithium bis(trifluoromethylsulfonyl)imide, lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, lithium (fluorosulfonyl)(perfluorobutylsulfonyl)imide, lithium (trifluoromethylsulfonyl)(perfluorobutylsulfonyl)imide and lithium bis(pentafluoroethylsulfonyl)imide; and / or In formula 1, R 1 , R 2 , R 3 and R 4 Each is independently selected from C1-C6 alkyl, fluorine-substituted C1-C6 alkyl, C2-C4 alkenyl, fluorine-substituted C2-C4 alkenyl, C2-C4 alkynyl, fluorine-substituted C2-C4 alkynyl, phenyl or fluorine-substituted phenyl.

3. The secondary battery according to claim 1 or 2, It is characterized in that The fluorine-containing lithium sulfonyl imide comprises lithium bis(fluorosulfonyl)imide; and / or The alkoxyboric acid additive comprises at least one of the following compounds:

4. The secondary battery according to claim 1, It is characterized in that 0.5≤X≤5; and / or, 4≤Y≤10; and / or, 6≤2X+Y≤16.

5. The secondary battery according to claim 4, It is characterized in that 1≤X≤4; and / or, 4≤Y≤6; and / or, 7≤2X+Y≤13.

6. The secondary battery according to claim 1, It is characterized in that The electrolyte further includes a first additive, the first additive including at least one of a cyclic carbonate containing a carbon-carbon double bond, a silyl-containing phosphate, a nitrile compound, and a pyridinium propanesulfonate; based on the mass of the electrolyte, the mass percentage of the first additive is 0.05% to 10%; and / or The electrolyte further includes a first lithium salt, the first lithium salt including at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, trifluorosulfonyl lithium, lithium trifluoromethanesulfonate, lithium bis(fluoromalonate)borate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium difluorobisoxalatophosphate and lithium 4,5-dicyano-2-(trifluoromethyl)imidazole; based on the mass of the electrolyte, the mass percentage of the lithium salt is 4% to 25%; and / or The electrolyte also includes an organic solvent, which includes at least one of chain carbonate, cyclic carbonate and carboxylate; based on the mass of the electrolyte, the mass percentage of the organic solvent is 40% to 80%.

7. The secondary battery according to claim 1, It is characterized in that The lithium nickel transition metal oxide includes LiNi m A 1-m O 2 , A includes at least one of cobalt, manganese, iron, chromium, titanium, zinc, vanadium, aluminum, zirconium, cerium, magnesium, calcium, molybdenum, strontium, tungsten, yttrium, lanthanum, silver and niobium, 0.1≤m≤1; the positive electrode plate includes a positive electrode collector, and the positive electrode collector includes aluminum.

8. The secondary battery according to claim 1, It is characterized in that The negative electrode plate includes a negative electrode active material, which includes the silicon-based material, or a mixture of the silicon-based material and at least one material selected from a carbon-based material, a tin-based material, a phosphorus-based material and metallic lithium; wherein the silicon-based material includes at least one of silicon, a silicon alloy, a silicon oxide compound and a silicon-carbon compound, the carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon nanotubes and graphene, the tin-based material includes at least one of tin, tin oxide and a tin alloy, and the phosphorus-based material includes phosphorus and / or a phosphorus-carbon composite; based on the mass of the negative electrode active material, the mass percentage of the silicon-based material is 0.1% to 30%.

9. The secondary battery according to claim 1, It is characterized in that The electrolyte is relative to Li / Li + The oxidation potential Z satisfies: Z≥5.5V. 10 . A device comprising the secondary battery according to claim 1 .

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