Electrolyte, battery and electric device

Abstract

Provided are an electrolyte, a battery and an electric device. The electrolyte comprises an organic solvent and a lithium salt. The organic solvent comprises an ionic liquid, a co-solvent and a diluent. The co-solvent comprises an ether solvent. The diluent comprises one or more of the following structural formulas: wherein in structural formula I to structural formula III, R1-R18 are each independently selected from H, F, a C6-C26 fluorine-substituted phenoxy and a C1-C20 fluorine-substituted alkyl; and R1-R8 are not H at the same time, R9-R14 are not H at the same time, and R15-R18 are not H at the same time. A stable negative electrode SEI is generated by using a cyclic fluoroether with a weak coordination capability. The use of the ionic liquid in cooperation with the other components drives a large number of anions to enter an Li+ solvation sheath layer, and the ionic liquid can also participate in the adjustment and control of a solvation structure by means of a series of weak interactions. In the case of the solvation structure being controlled by the ionic liquid, multiple instances of adjustment and control of the interface are completed. The operating temperature of a battery is widened, the cycling life thereof is long, the energy is high and the power density is high, and the high-voltage cycling stability and safety of the battery is also improved.

Description

Electrolyte, battery and electric device

[0001] The present application claims priority to the Chinese patent application No. 202411231175.3, filed on September 3, 2024, and entitled "Electrolyte, battery and electric device", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of batteries and electrochemistry, in particular to an electrolyte, a battery and an electric device. BACKGROUND

[0003] The metal lithium negative electrode of the battery has the highest specific capacity and the lowest redox potential, and is considered to be the ultimate choice of high-energy-density batteries. However, the existing electrolyte often contains carbonates, and the metal lithium will react with the electrolyte, consuming the reversible capacity of the battery, and the lithium dendrites generated in the cycle process will accelerate the consumption of lithium and electrolyte, and the current commercial electrolyte of the battery has the problem of unstable oxidative decomposition at high cut-off voltage, which eventually leads to battery failure and safety problems. Therefore, how to overcome the above technical problems and defects has become a key problem to be solved.

[0004] SUMMARY

[0005] In view of the problem of high voltage failure of the traditional carbonate electrolyte, the present application provides an electrolyte, a battery and an electric device.

[0006] The technical solution adopted by the present application to solve the above technical problems is as follows:

[0007] The first aspect of the present application provides an electrolyte, comprising an organic solvent and a lithium salt, wherein the organic solvent comprises an ionic liquid, a co-solvent and a diluent, the co-solvent comprises an ether solvent, and the diluent comprises a cyclic fluorine ether diluent.

[0008] Optionally, the cyclic fluorine ether diluent comprises one or more of the following compounds represented by the structural formulae:

[0009] In the structural formula I-III, R1-R 18 are each independently selected from H, F, a fluorine-substituted phenoxy group with C6-C26, or a fluorine-substituted alkyl group with C1-C20; and R1-R8 are not simultaneously H, R9-R14 are not simultaneously H, and R15-R18 are not simultaneously H.

[0010] Optionally, the cyclic fluoroether diluent includes one or more of 3,3,4,4-tetrafluorotetrahydrofuran, perfluorobutyltetrahydrofuran, perfluorotetrahydrofuran, difluorobutyltetrahydrofuran, 2-(trifluoromethyl)dioxolane, 2,2-bis(trifluoromethyl)-1,3-dioxolane, 4,4-bis(trifluoromethyl)-1,2-epoxy-5,5,5-trifluoropentane, hexafluoropropylene oxide.

[0011] Optionally, the ionic liquid includes a cation and an anion, the cation includes one or more of a pyrrolidine cation having a group shown in Structural Formula I' - Structural Formula V', an imidazole cation, a piperidine cation, a pyridine cation:

[0012] wherein R1'-R10' in Structural Formula I' - Structural Formula V' each independently includes one or more of a C1-C8 alkyl, a C1-C8 alkyl isomer; and / or

[0013] The anion includes one or more of a bistrifluoromethanesulfonimide anion, a bisfluoromethanesulfonimide anion, a hexafluorophosphate anion, a tetrafluoroborate anion, and a trifluoromethanesulfonate anion having a group shown in Structural Formula VI' - Structural Formula X':

[0014] Optionally, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonylimide, lithium trifluoromethylsulfonyl-n-perfluorobutylsulfonylimide, lithium fluorosulfonyl-n-perfluorobutylsulfonylimide, lithium bis(oxalato)borate, lithium difluorophosphate.

[0015] Optionally, the organic solvent accounts for 50wt% to 85wt% of the total mass of the electrolyte, based on 100% of the total mass of the electrolyte.

[0016] Optionally, the molar ratio of the diluent, the ionic liquid, the cosolvent, and the lithium salt = (0.5-8):(0.65-3):(0.6-4):(0.8-2.5).

[0017] Optionally, the cosolvent includes one or more of a linear ether compound or a cyclic ether compound.

[0018] Optionally, the cosolvent includes one or more of ethylene glycol dimethyl ether, tetrahydrofuran, ethylene glycol dibutyl ether, dioxolane, triethylene glycol dimethyl ether.

[0019] Optionally, the cosolvent accounts for 5% to 30% of the total mass of the electrolyte, based on 100% of the total mass of the electrolyte.

[0020] Optionally, the electrolyte further comprises an additive, the additive comprising one or more of fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate, vinyl sulfate, lithium nitrate, lithium borate, lithium difluoro(oxalato)borate, triphenyl phosphate, triethyl phosphate, trimethyl phosphate.

[0021] Optionally, the additive accounts for 0.05% to 5% of the total mass of the electrolyte, based on 100% of the total mass of the electrolyte.

[0022] The second aspect of the present application provides a battery comprising the electrolyte, the separator, the positive electrode sheet and the negative electrode sheet as described above.

[0023] The third aspect of the present application provides a power-using device comprising the battery as described above.

[0024] According to the electrolyte provided by the present application, the present application adopts a ring fluoroether with weak coordination ability to form a stable negative electrode SEI. Compared with linear fluoroether, the coordination ability between the ring fluoroether and lithium ions is weaker, which helps to reduce the influence on the formation process of inorganic SEI. Moreover, the solvation structure precisely controls the distance of anions around lithium ions, which is easy to form a uniform and stable SEI layer. The use of ionic liquids not only drives a large number of anions into the Li + The solvation sheath can also participate in the regulation of the solvation structure through a series of weak interactions. In the case of fluorinated anion-dominated solvation structure, the interface is multi-regulated, which not only widens the use temperature, long cycle life, high energy and high power density of the battery, but also improves the high-voltage cycle stability and safety of the battery. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0026] The test methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents and the like used are commercially available unless otherwise specified.

[0027] The first aspect of the present application provides an electrolyte comprising an organic solvent and a lithium salt, the organic solvent comprising an ionic liquid, a cosolvent and a diluent, the cosolvent comprising an ether solvent, and the diluent comprising a ring fluoroether diluent.

[0028] The application adopts a ring fluoroether with weak coordination ability to form a stable negative electrode SEI. Compared with linear fluoroether, the coordination ability between the ring fluoroether and lithium ions is weaker, which helps to reduce the influence on the formation process of inorganic SEI, and the solvation structure precisely regulates the distance of anions around lithium ions, which is easy to form a uniform and stable SEI layer. The use of ionic liquids not only drives a large number of anions into Li + The solvation sheath can also participate in the regulation of the solvation structure through a series of weak interactions. In the case of fluorinated anion-dominated solvation structure, the interface is multi-regulated, which widens the use temperature, improves the cycle life, and improves the safety of the battery with high energy / power density.

[0029] The application adopts the use of ring fluoroether and ionic liquid, solves the problem of high-pressure failure of traditional carbonate electrolyte, and by optimizing the ratio of ionic liquid with high-pressure resistance and flame retardant characteristics and ring fluoroether diluent, the solvation structure of Li + can be effectively regulated, an SEI film is generated on the negative electrode surface, a uniform and dense interface layer (CEI) is formed on the positive electrode side, the side reaction and the structural damage of the high-pressure positive electrode are inhibited, and the high-pressure cycle stability and safety of the lithium ion battery are effectively improved.

[0030] In an embodiment, the ring fluoroether diluent includes one or more of the compounds shown in the following structural formulas:

[0031] In the structural formula I-structural formula III, R1-R 18 are each independently selected from H, F, a fluorine-substituted phenoxy group with C6-C26, or a fluorine-substituted alkyl group with C1-C20; and R1-R8 are not simultaneously H, R9-R14 are not simultaneously H, and R15-R18 are not simultaneously H.

[0032] By using the above-mentioned ring fluoroether diluent and ionic liquid, the problem of high-pressure failure of traditional carbonate electrolyte is solved, and by optimizing the ratio of ionic liquid with high-pressure resistance and flame retardant characteristics and ring fluoroether diluent, the solvation structure of Li + can be effectively regulated, an SEI film is generated on the negative electrode surface, a uniform and dense interface layer (CEI) is formed on the positive electrode side, the side reaction and the structural damage of the high-pressure positive electrode are inhibited, and the high-pressure cycle stability and safety of the lithium ion battery are effectively improved.

[0033] In an embodiment, the cyclic fluoroether diluent includes one or more of 3,3,4,4-tetrafluorotetrahydrofuran (TFF), perfluorobutyltetrahydrofuran, perfluorotetrahydrofuran (OTF), di-perfluorobutyltetrahydrofuran, 2-(trifluoromethyl)dioxolane (TFDOL), 2,2-bis(trifluoromethyl)-l,3-dioxolane (BTFMD), 4,4-bis(trifluoromethyl)-l,2-epoxy-5,5,5-trifluoropentane, hexafluoropropylene oxide.

[0034] In an embodiment, the ionic liquid includes a cation and an anion, the cation includes one or more of a pyrrolidine cation having a group represented by Structural Formula I' - Structural Formula V', an imidazole cation, a piperidine cation, a pyridine cation:

[0035] wherein R1' - R10' in Structural Formula I' - Structural Formula V' each independently includes one or more of a C1 - C8 alkyl, a C1 - C8 alkyl isomer; and / or

[0036] the anion includes one or more of a bistrifluoromethanesulfonimide anion, a bisfluoromethanesulfonimide anion, a hexafluorophosphate anion, a tetrafluoroborate anion, and a triflate anion having a group represented by Structural Formula VI' - Structural Formula X':

[0037] In a preferred embodiment, the ionic liquid includes a mixture of one or more of a cation and one or more of an anion.

[0038] Specifically, the present application uses an ionic liquid having a wide liquid phase range, high heat resistance, low vapor pressure, and a wide electrochemical window, which is compounded with a cyclic fluoroether to form a local super-concentrated electrolyte system, reducing the existence of free solvent, so that the battery system has excellent cycle stability at high cut-off voltage; the electrolyte system of the present application is applied to a battery with high cut-off voltage (> 4.3V), and the introduction of the ionic liquid of the present application not only drives a large number of anions into Li + solvation sheath, but also can regulate the solvation structure through a series of weak interactions, complete the multi-regulation of the interface in the case of fluorinated anion dominant solvation structure, which can effectively adjust the solvation structure of Li + and the derived interface, not only can widen the use temperature of the battery, improve the long cycle life of the battery, improve the energy density and power density of the battery, but also can improve the safety of the battery.

[0039] The present application uses cyclic fluoroether and ionic liquid in combination, which solves the problem of high pressure failure of traditional carbonate electrolyte, and by optimizing the proportion of ionic liquid with high pressure resistance and flame retardant characteristics and cyclic fluoroether diluent, Li +The solvent structure of Li+ is optimized, SEI film is generated on the negative electrode surface, uniform and dense interface layer (CEI) is formed on the positive electrode side, side reactions and structural damage of the high-voltage positive electrode are inhibited, and the high-voltage cycle stability and safety of the lithium ion battery are effectively improved.

[0040] In an embodiment, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonylimide, lithium trifluoromethylsulfonyl-n-perfluorobutylsulfonylimide, lithium fluorosulfonyl-n-perfluorobutylsulfonylimide, lithium bis(oxalato)borate, lithium difluorophosphate.

[0041] The lithium salt is the source of Li + in the electrolyte, provides free shuttling ions for the battery and bears the role of transmitting ions inside the battery, and the lithium salt can also form a protective layer on the surface of the electrode material, which has an important influence on the capacity, cycle performance, power density, energy density and other performances of the battery.

[0042] In a preferred embodiment, the total mass of the electrolyte is 100%, and the percentage content of the organic solvent in the total mass of the electrolyte is 50wt%-85wt%.

[0043] Specifically, the percentage content of the organic solvent in the total mass of the electrolyte is any one value or a range value composed of any two point values among 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, and 85wt%; in a preferred embodiment, the percentage content of the organic solvent in the total mass of the electrolyte is 60wt%-80wt%.

[0044] When the percentage content of the organic solvent in the total mass of the electrolyte is 50wt%-85wt%, the cyclic fluorine ether and the ionic liquid are used in combination to solve the problem of high-pressure failure of the traditional carbonate electrolyte, the ratio of the ionic liquid with high-pressure resistance and flame retardance to the cyclic fluorine ether diluent is optimized to effectively adjust the solvent structure of Li+, SEI film is generated on the negative electrode surface, uniform and dense interface layer (CEI) is formed on the positive electrode side, side reactions and structural damage of the high-voltage positive electrode are inhibited, and the high-voltage cycle stability and safety of the lithium ion battery are effectively improved.

[0045] In an embodiment, the molar ratio of the diluent, the ionic liquid, the cosolvent and the lithium salt is (0.5-8):(0.65-3):(0.6-4):(0.8-2.5).

[0046] Specifically, the molar ratio of the diluent, the ionic liquid, and the lithium salt is any one of the following ratios or a range of any two of the following ratios: 0.5:0.65:0.6:0.8, 1:0.65:0.6:0.8, 2:0.65:0.6:0.8, 3:0.65:0.6:0.8, 4:0.65:0.6:0.8, 5:0.65:0.6:0.8, 6:0.65:0.6:0.8, 7:0.65:0.6:0.8, 8:0.65:0.6:0.8, 8:1:0.6:0.8, 8:1.5:0.6:0.8, 8:2:0.6:0.8, 8:2.5:0.6:0.8, 8:3:0.6:0.8, 8:3:1:0.8, 8:3:1.5:0.8, 8:3:2:0.8, 8:3:2.5:0.8, 8:3:3:0.8, 8:3:3.5:0.8, 8:3:4:0.8, 8:3:4:1, 8:3:4:1.5, 8:3:4:2, 8:3:4:2.5.

[0047] The present application effectively adjusts the solvation structure of Li + by optimizing the addition ratio of the ionic liquid, the diluent, and the lithium salt. The introduction of the ionic liquid not only drives a large number of anions into the solvation sheath of Li + , but also regulates the solvation structure by interacting with the fluorine-containing ether. In the case of fluorinated anion-dominated solvation structure, multiple regulation of the interface is completed.

[0048] In a preferred embodiment, the molar ratio of the diluent, the ionic liquid, the cosolvent, and the lithium salt is (2-4):(1-2):(2-3.5):(1-1.5).

[0049] The present application forms a local super-concentrated electrolyte system by matching a specific ratio of fluorine-containing ether diluent, reduces the existence of free solvent, and makes the battery system have excellent cycle stability at high cut-off voltage.

[0050] In an embodiment, the cosolvent includes one or more of linear ether compounds or cyclic ether compounds.

[0051] The linear ether compounds or cyclic ether compounds are designed as cosolvents for fluorine-containing ether diluents, which inherit the advantage of wide electrochemical stability window and avoid the disadvantage of high viscosity.

[0052] In an embodiment, the cosolvent includes one or more of ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), ethylene glycol dibutyl ether (EGBE), dioxolane (DOL), and triethylene glycol dimethyl ether (G3).

[0053] By using one or more of ethylene glycol dimethyl ether, tetrahydrofuran, ethylene glycol dibutyl ether, dioxolane, triglyme as a co-solvent electrolyte for fluorine ether diluents, it inherits the advantage of wide electrochemical stability window, and avoids the disadvantage of high viscosity.

[0054] In an embodiment, the percentage of the co-solvent in the total mass of the electrolyte is 5% to 30%.

[0055] Specifically, the percentage of the co-solvent in the total mass of the electrolyte is any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, or a range value consisting of any two point values; in a preferred embodiment, the percentage of the co-solvent in the total mass of the electrolyte is 10% to 20%.

[0056] In an embodiment, the electrolyte further comprises an additive, and the additive comprises one or more of fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate, vinyl sulfate, lithium nitrate, lithium borate, lithium difluoro(oxalato)borate, triphenyl phosphate (TPP), triethyl phosphate (TEP), trimethyl phosphate.

[0057] Specifically, the fluoroethylene carbonate (FEC) additive can enhance the stability of the electrode material; the 1,3-propane sultone (1,3-PS) can inhibit the occurrence of side reactions on the electrode surface and the dissolution of metal ions, improve the initial capacity of the battery, improve the high and low temperature storage performance of the battery, increase the cycle number of the battery and prolong the service life; the vinylene carbonate (VC) can form a solid electrolyte interface film (SEI film) on the negative electrode surface during the initial charge and discharge of the battery. Vinyl sulfate can inhibit the decrease of the initial capacity of the battery, increase the initial discharge capacity, reduce the expansion of the battery after high-temperature storage, and improve the charge and discharge performance and cycle number of the battery.

[0058] In an embodiment, the percentage of the additive in the total mass of the electrolyte is 0.05% to 5%.

[0059] Specifically, the percentage of the additive in the total mass of the electrolyte is any one of 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, or a range value consisting of any two point values; in a preferred embodiment, the percentage of the additive in the total mass of the electrolyte is 0.5% to 2%.

[0060] In a preferred embodiment, monomers and initiators are added in the electrolyte, and the electrolyte is cured by heating to form a gel electrolyte.

[0061] Specifically, the monomers include one or more of olefin monomers containing sulfonic acid groups, acrylamide monomers, and acrylic ester monomers; specifically, the olefin monomers containing sulfonic acid groups include one or more of 2-acrylamido-2-methylpropane sulfonic acid sodium, 2-acrylamido dodecyl sodium sulfonate, dodecyl sodium sulfonate, and 2-acrylamido octyl sodium sulfonate; specifically, the acrylamide monomers include one or more of acrylamide, methacrylamide, isopropyl acrylamide, N,N-diethyl acrylamide, isobutoxy methyl acrylamide, and diacetone acrylamide; and specifically, the acrylic ester monomers include one or more of butyl acrylate, methyl acrylate, ethyl acrylate, 2-methyl methacrylate, and isooctyl acrylate.

[0062] Specifically, the initiators include one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, 2,4,6-trimethylbenzoyl phosphinic acid ethyl ester, methyl o-benzoylbenzoate, benzophenone, 4-phenyl benzophenone, and 4-dimethylamino-benzoic acid ethyl ester; and preferably, the lithium salt is selected from one or more of lithium bistrifluoromethylsulfonimide, lithium perchlorate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium difluorophosphate, lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium difluoro oxalate borate, and lithium hexafluoroarsenate.

[0063] In an embodiment, the electrolyte accounts for 0.5% to 50% of the total mass of the gel electrolyte, the monomers account for 49.9% to 99.49% of the total mass of the gel electrolyte, and the initiators account for 0.01% to 0.1% of the total mass of the gel electrolyte.

[0064] Specifically, the electrolyte accounts for 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50% of the total mass of the gel electrolyte, or a range value consisting of any two of the above values; and in a preferred embodiment, the electrolyte accounts for 10% to 40% of the total mass of the gel electrolyte.

[0065] Specifically, the monomer accounts for 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, or 18% of the total mass of the gel electrolyte, or a range value composed of any two point values; in a preferred embodiment, the monomer accounts for 12%-16% of the total mass of the gel electrolyte.

[0066] Specifically, the electrolyte accounts for 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1% of the total mass of the gel electrolyte, or a range value composed of any two point values; in a preferred embodiment, the initiator accounts for 0.02%-0.08% of the total mass of the gel electrolyte.

[0067] Further, in an embodiment, an electrolyte is added to the solid-state electrolyte to form a semi-solid-state electrolyte.

[0068] Specifically, the solid-state electrolyte includes an inorganic solid-state electrolyte, a polymer solid-state electrolyte, and a composite solid-state electrolyte, the inorganic solid-state electrolyte includes one or more of an oxide solid-state electrolyte, a sulfide solid-state electrolyte, and a halide solid-state electrolyte; the polymer solid-state electrolyte includes a polymer matrix selected from one or more of polyethylene oxide, polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene copolymer; the composite solid-state electrolyte includes an inorganic filler and a polymer matrix, the inorganic filler is selected from at least one of an inert filler and an active filler, the inert filler is one or more of silicon dioxide, titanium dioxide, aluminum oxide, metal organic frameworks (MOFs), and zeolites; the active filler is one or more of one or more of cubic garnet lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), NASICON-type lithium aluminum titanium phosphate (LATP), perovskite lithium lanthanum titanium oxide, sulfide electrolyte, and halide electrolyte; the polymer matrix includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and its derivatives, polyacrylonitrile, polymethyl methacrylate, or polyethyl methacrylate and its derivatives.

[0069] In an embodiment, the electrolyte accounts for 0.5%-50% of the total mass of the solid-state electrolyte, based on 100% of the total mass of the solid-state electrolyte.

[0070] Specifically, the electrolyte accounts for 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50% of the total mass of the solid-state electrolyte, or a range value composed of any two point values; in a preferred embodiment, the electrolyte accounts for 10%-40% of the total mass of the solid-state electrolyte.

[0071] The second aspect of the application provides a battery comprising the electrolyte, the separator, the positive electrode sheet and the negative electrode sheet as described above.

[0072] Specifically, the separator can be selected from one or more of polypropylene (PP), polyethylene (PE), PP / PE / PP composite film, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ceramic separator, ceramic polyamide (PI), aramid (AF), non-woven fabric and the like.

[0073] In a preferred embodiment, the preparation of the battery comprises the following steps:

[0074] The positive electrode sheet, the separator and the negative electrode sheet are stacked in order, with the separator between the positive and negative electrodes to play a separating role. The electrode sheets and the separator are placed in an aluminum plastic film bag shaped by a punch shell. The electrolyte, the gel electrolyte or the solid-state electrolyte prepared above are injected into the baked and dried battery cell, respectively. After vacuum packaging, standing, formation and other processes, the battery is obtained.

[0075] In an embodiment, the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material comprises one or more of lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), lithium manganate (LMO), lithium nickelate (LNO), ternary material (NCM, NCA), lithium-rich manganese-based material (LMR), lithium nickel manganate (LNMO), lithium vanadium phosphate oxide (Li3V2(PO4)3, LiVOPO4).

[0076] Specifically, when the electrolyte system matches high-voltage positive electrodes, including ternary materials and lithium-rich manganese-based materials, the high-voltage solvent system includes an ionic liquid and a cyclic fluorine ether to form a local super-concentration system, which has good flame retardant properties. The mixed solvent system generates stable SEI and CEI through solvation structure regulation, provides a stable cycle basis for the battery system under high-voltage conditions, and improves the safety properties of the battery.

[0077] In some embodiments, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

[0078] In some embodiments, the positive electrode conductive agent comprises one or more of graphite, super-p, acetylene black, carbon black, carbon nanotube, graphene, carbon nanofiber, metal powder, metal fiber, and polyphenylene derivative.

[0079] In some embodiments, the positive electrode binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0080] In some embodiments, the mass percentage of each component in the positive electrode active material layer is 96-98 wt% of positive electrode active material, 0.5-2 wt% of conductive agent, and 1.0-2.0 wt% of binder.

[0081] The mass percentage of positive electrode active material in the positive electrode active material layer within the above range can allow the positive electrode sheet to have a higher lithium extraction and lithium intercalation capacity, and allow the battery to have a higher capacity.

[0082] The positive electrode current collector is selected from a metal material that can conduct electrons, preferably, the positive electrode current collector comprises one or more of copper, nickel, tin, copper, stainless steel, and in more preferred embodiments, the positive electrode current collector is selected from an aluminum foil.

[0083] The positive electrode sheet can be prepared according to conventional methods in the art. For example, the positive electrode active material layer is typically prepared by coating a positive electrode slurry comprising positive electrode active material, positive electrode conductive agent, positive electrode binder, and any other components on a positive electrode current collector, and drying and cold-pressing.

[0084] In an embodiment, the negative electrode sheet comprises a negative electrode active material, the negative electrode active material comprising one or more of graphite negative electrode material, silicon-oxygen negative electrode material, silicon-carbon negative electrode material, silicon negative electrode material, tin negative electrode material, tin oxide negative electrode material, tin alloy negative electrode material (Sn-Fe, Sn-Co, Sn-Cu, etc.), lithium metal negative electrode material, lithium alloy negative electrode material (Li-Ag, Li-Al, Li-Sn, Li-Mg, Li-Zn, Li-In, Li-Ga, etc.), and lithium-free negative electrode material.

[0085] The electrolyte of the present application can be used in high-voltage battery systems, matching high-voltage ternary cathodes and lithium-rich manganese cathodes, graphite anodes, silicon-carbon anodes, silicon-oxygen anodes, and lithium metal anodes, for the production of liquid and semi-solid stacked, wound, or cylindrical batteries. The electrolyte of the present application provides a stable cycling basis for battery systems under high-voltage conditions and improves the safety characteristics of the battery.

[0086] In some embodiments, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material, a conductive agent, a binder, and a thickening agent.

[0087] In some embodiments, the negative electrode conductive agent comprises one or more of graphite, superconducting carbon, acetylene black, carbon black, carbon nanotubes, graphene, carbon nanofibers, metal powder, metal fibers, and polyphenylene derivatives.

[0088] In some embodiments, the negative electrode binder comprises one or more of styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, and polymethacrylic acid.

[0089] In some embodiments, the thickening agent comprises one or more of sodium alginate, sodium carboxymethyl cellulose, and carboxymethyl chitosan.

[0090] In some embodiments, the mass percentage of each component in the negative electrode active material layer is 96-97% negative electrode active material, 0.5-1.5% conductive agent, 1-2% binder, and 0.5-1.5% thickening agent.

[0091] The mass ratio of the negative electrode active material and the mesoporous material in the negative electrode film layer is within the above range, which can enable the mesoporous material to fully contact the active material, enabling the electrolyte stored inside the mesoporous material to be directly delivered to the active material, while lithium reaches the active material interface more quickly through the mesoporous material, with improved kinetics, cycling, and other effects.

[0092] The negative electrode current collector is selected from metal materials that can conduct electrons, preferably, the negative electrode current collector comprises one or more of Al, Ni, tin, copper, and stainless steel, and in more preferred embodiments, the negative electrode current collector is selected from copper foil.

[0093] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative electrode active material layer is typically prepared by coating a negative electrode slurry comprising a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and any other components on a negative electrode current collector, and then drying and cold-pressing. The solvent can be an aqueous solvent, but is not limited thereto.

[0094] The third aspect of the present application provides a power-using device comprising the above-mentioned battery.

[0095] The third aspect of the present application provides a power consuming device comprising the battery of the second aspect of the present application. The battery is used as the power source of the device. The number of batteries in the power consuming device can be adjusted according to the application and capacity of the power consuming device.

[0096] Preferably, the power consuming device can be, but is not limited to, an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0097] The beneficial effects of the present application are further illustrated in the following examples.

[0098] In order to make the application purpose, technical solutions and beneficial technical effects of the present application clearer, the present application is further described in detail in the following examples. However, it should be understood that the examples of the present application are only for the purpose of explaining the present application, and are not intended to limit the present application, and the examples of the present application are not limited to the examples given in the specification. The specific experimental conditions or operation conditions not mentioned in the examples are made according to the conventional conditions or the conditions recommended by the material suppliers.

[0099] In addition, it should be understood that the one or more method steps mentioned in the present application do not exclude that there can be other method steps before and after the combination steps or other method steps can be inserted between the explicitly mentioned steps, unless otherwise stated; it should also be understood that the combination connection relationship between the one or more devices / apparatuses mentioned in the present application does not exclude that there can be other devices / apparatuses before and after the combination devices / apparatuses or other devices / apparatuses can be inserted between the two explicitly mentioned devices / apparatuses, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is only a convenient tool to identify each method step, and is not intended to limit the arrangement order of each method step or to limit the scope of the present application, and the change or adjustment of the relative relationship, without substantially changing the technical content, is also regarded as the scope of the present application that can be implemented.

[0100] In the following examples, the reagents, materials and instruments used are commercially available or obtained by synthesis methods known in the art, unless otherwise specified. Among them, TTE is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0101] Table 1 Design of electrolyte of Examples 1-7 and Comparative Examples 1-3;

[0102] Example 1

[0103] The present embodiment is used to illustrate the electrolyte and battery disclosed in the present application; including the following operation steps:

[0104] Preparation of electrolyte: in an argon-filled glove box (O2<1 ppm, H2O<1 ppm), ion liquid Pyr13FSI, cosolvent DME, and ring fluorine ether diluent TFF were mixed in a mass ratio of 4:4:7, and the mixed solvent was obtained after stirring uniformly. Then 25% lithium salt LiFSI was slowly added into the mixed solvent, and finally 0.05% LiNO3 was added to obtain the electrolyte.

[0105] Preparation of positive electrode sheet: the positive electrode active material lithium nickel cobalt manganese oxide (NCM), conductive agent CNT, and adhesive PVDF were mixed in a mass ratio of 97:1.5:1.5. The mixture was fully stirred in NMP solvent to form a uniform positive electrode slurry. The slurry was coated on at least one side of the positive electrode current collector aluminum foil, and after drying, rolling, die cutting and other processes, the required positive electrode sheet was obtained.

[0106] Preparation of negative electrode sheet: the negative electrode used a copper-lithium composite tape with a thickness of 20 um.

[0107] Preparation of separator: a PE porous polymer film was used as the separator substrate.

[0108] Preparation of battery:

[0109] The positive electrode sheet, the separator, and the negative electrode sheet were stacked in order, with the separator in the middle of the positive and negative electrodes to play a separating role. Then the stacked electrode sheet and the separator were placed in an aluminum-plastic film bag shaped by a punch shell. The non-aqueous electrolyte prepared above was injected into the oven-dried battery cell, and after vacuum packaging, standing, and formation, a 1 Ah capacity battery was obtained.

[0110] Examples 2-7

[0111] Examples 2-7 are used to illustrate the electrolyte and battery disclosed in the present application, including most of the operation steps in Example 1, with the difference being that:

[0112] The components and contents of the organic solvents in the electrolyte shown in Table 1 were used.

[0113] Comparative Examples 1-3

[0114] Comparative Examples 1-3 are used to illustrate the electrolyte and battery disclosed in the present application, including most of the operation steps in Example 1, with the difference being that:

[0115] The components and contents of the organic solvents in the electrolyte shown in Table 1 were used.

[0116] Performance test

[0117] The batteries prepared in the above Examples 1-7 and Comparative Examples 1-3 were subjected to the following performance tests:

[0118] (1) Oxidation potential test of electrolyte: the oxidation potential of the electrolyte separator was tested by linear sweep potential method using EC-Lab electrochemical workstation, the test voltage range was 2.5-6V, and the scan rate was 1mV·s -1 , the method uses the device structure of "stainless steel sheet | separator | lithium sheet" for testing, taking the stainless steel sheet as the working electrode and the lithium sheet as the reference electrode.

[0119] (2) Cycle performance test of the battery cell: the battery cell was subjected to 0.2C / 0.5D cycle charge-discharge test at a voltage range of 3.0V-4.3V and a temperature of 25℃, and the capacity retention rate of the battery after 100 cycles and the average charge-discharge efficiency of the battery were recorded.

[0120] The test results are shown in Table 2.

[0121] Table 2 Electrochemical performance of lithium battery

[0122] As can be seen from Table 2, compared with Examples 1-7, when the electrolyte lacks cyclofluoroether or ionic liquid, the electrochemical window is reduced, the average charge-discharge efficiency of the battery is reduced, the capacity retention rate of the battery is reduced, and the battery performance is poor. By adding a cyclofluoroether with weak coordination ability to the electrolyte, a stable negative electrode SEI is formed,

[0123] Comparative Example 3 uses linear fluoroether, and compared with Comparative Example 3, when the electrolyte uses cyclofluoroether, the coordination ability between cyclofluoroether and lithium ion is weaker, which helps to reduce the influence on the formation process of inorganic SEI, and the solvation structure precisely controls the distance of anion around lithium ion, which is easy to form a uniform and stable SEI layer. The use of ionic liquid not only drives a large number of anions into the Li+ solvation sheath, but also participates in the regulation of the solvation structure through a series of weak interactions. In the case of fluorinated anion-dominated solvation structure, the interface is multi-regulated, which not only widens the use temperature of the battery, but also improves its safety while prolonging the cycle life and increasing the energy / power density.

[0124] In summary, the cyclofluoroether and ionic liquid are used together in the present application to solve the problem of high-pressure failure of traditional carbonate electrolyte. By optimizing the ratio of ionic liquid with high-pressure resistance and flame retardant properties and cyclofluoroether diluent, the solvation structure of Li + + can be effectively adjusted, and SEI film is generated on the negative electrode surface, and a uniform and dense interface layer (CEI) is formed on the positive electrode side, which inhibits the side reaction and structural damage of the high-pressure positive electrode, effectively improving the high-pressure cycle stability and safety of lithium ion batteries.

[0125] The above only describes preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. An electrolyte, characterized by: The organic solvent includes an ionic liquid, a co-solvent including an ether solvent, and a diluent including a cyclic fluoroether diluent.

2. The electrolyte according to claim 1, characterized in that: The cyclic fluoroether diluent includes one or more of the compounds shown in the following structural formulas: wherein, in structural formula I-III, R1-R 18 are each independently selected from H, F, C6-C26 fluoro-substituted phenoxy, or C1-C20 fluoro-substituted alkyl; and R1-R8 are not simultaneously H, R9-R14 are not simultaneously H, and R15-R18 are not simultaneously H.

3. The electrolyte of claim 2, wherein: The cyclic fluoroether diluent includes one or more of 3,3,4,4-tetrafluorotetrahydrofuran, perfluorobutyltetrahydrofuran, perfluorotetrahydrofuran, difluorobutyltetrahydrofuran, 2-(trifluoromethyl)dioxolane, 2,2-bis(trifluoromethyl)-1,3-dioxolane, 4,4-bis(trifluoromethyl)-1,2-epoxy-5,5,5-trifluoropentane, hexafluoropropylene oxide.

4. The electrolyte of claim 1, wherein: The ionic liquid comprises a cation and an anion, the cation comprising one or more of a pyrrolidine cation, an imidazole cation, a piperidine cation, a pyridine cation having a group represented by Structural Formula I' - Structural Formula V': In the structural formula I' to V', R1'-R10' are each independently one or more of C1-C8 alkyl, C1-C8 alkyl isomers; and / or The anions include one or more of the following: bis-trifluoromethanesulfonylimide, bis-fluoromethanesulfonylimide, hexafluorophosphate, tetrafluoroborate, and triflate anions having the structure of Formula VI'-Formula X':

5. The electrolyte of claim 1, wherein: The lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonylimide, lithium trifluoromethylsulfonyl-n-perfluorobutylsulfonylimide, lithium fluorosulfonyl-n-perfluorobutylsulfonylimide, lithium bis(oxalato)borate, lithium difluorophosphate.

6. The electrolyte of claim 1, wherein: The percentage content of the organic solvent in the total mass of the electrolyte is 50wt% to 85wt%.

7. The electrolyte of claim 1, wherein: The molar ratio of the diluent, the ionic liquid, the co-solvent, and the lithium salt is (0.5-8):(0.65-3):(0.6-4):(0.8-2.5).

8. The electrolyte of claim 1, wherein: The co-solvent includes one or more of linear ether compounds or cyclic ether compounds.

9. The electrolyte of claim 8, wherein: The co-solvent includes one or more of ethylene glycol dimethyl ether, tetrahydrofuran, ethylene glycol dibutyl ether, dioxolane, triethylene glycol dimethyl ether.

10. The electrolyte of claim 8, wherein: The percentage content of the co-solvent in the total mass of the electrolyte is 5% to 30%.

11. The electrolyte of claim 1, wherein: The electrolyte further includes an additive including one or more of fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate, ethylene sulfate, lithium nitrate, lithium borate, lithium difluoro(oxalato)borate, triphenyl phosphate, triethyl phosphate, trimethyl phosphate.

12. The electrolyte of claim 11, wherein: The percentage content of the additive in the total mass of the electrolyte is 0.05% to 5%.

13. A battery, characterized by: The battery includes the electrolyte, the separator, the positive electrode sheet, and the negative electrode sheet according to any one of claims 1 to 12.

14. An electrical device, characterized by: The battery includes the battery according to claim 13.

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