Electrolyte, battery and electric device

Abstract

The invention provides an electrolyte, a battery and an electric device, the electrolyte comprises an additive, a diluent, a solvent and a lithium salt, the additive comprises an ionic liquid and a siloxane compound; the ionic liquid and the siloxane compound are introduced into the electrolyte to serve as additives, the siloxane compound has high thermal stability due to Si-O bonds in the structure of the siloxane compound, the stability of the electrolyte can be kept under the high-temperature condition, the risk of thermal runaway is reduced, the incombustible ionic liquid is matched, the safety of the battery is improved, and the service life of the battery is prolonged. The risks of fire and explosion are reduced; the high-temperature stability of a local super-concentrated electrolyte system can be effectively improved, and the overall performance and safety of the battery are improved.

Description

Technical Field

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

[0002] Currently, battery electrolytes are prone to failure at high temperatures, which hinders the further development of batteries into high-temperature resistant batteries. Summary of the invention

[0003] In view of the problem that the existing electrolyte is easily ineffective due to high temperature, the present invention provides an electrolyte, a battery and an electrical device.

[0004] The technical solution adopted by the present invention to solve the above technical problems is as follows: A first aspect of the present invention provides an electrolyte comprising an additive, a diluent, a solvent and a lithium salt, wherein the additive comprises an ionic liquid and a siloxane compound.

[0005] Optionally, the siloxane compound includes one or more compounds having structural formula I to structural formula III: , , ; Wherein, R1~R18 in structural formula I to structural formula III are independently selected from one or more of hydrogen group, phenyl group, C1~C4 alkyl group, oxygen-containing alkyl group or oxygen-containing alkylene group.

[0006] Optionally, the silane compound includes one or more of dimethyldimethoxysilane, propoxytrimethylsilane, allyloxytrimethylsilane, hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, cyclosiloxane, bisphenyldimethylcyclosiloxane, heptamethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, tetraethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, and 2,4,6,8-tetramethylcyclotetrasiloxane.

[0007] Optionally, taking the total mass of the additive as 100%, the content of the siloxane compound in the total mass of the additive is 1 wt% to 40 wt%.

[0008] Optionally, the ionic liquid includes cations, and the cations include one or more of pyrrolidine cations, imidazolium cations, piperidine cations, and pyridine cations having groups represented by structural formula I' to structural formula V': , , , , ; Wherein, R1'-R10' in the structural formula I' to the structural formula V' are independently selected from one or more of C1-C8 alkyl and C1-C8 alkyl isomers; and / or Optionally, the ionic liquid includes anions, and the anions include one or more of bisfluorosulfonyl imide anions, bistrifluoromethanesulfonyl imide anions, trifluoromethanesulfonate anions, dinitrile amide anions, tetrafluoroborate anions, hexafluorophosphate anions, perchlorate anions, dioxalatoborate anions, and difluorooxalatoborate anions.

[0009] Optionally, based on the total mass of the additive being 100%, the percentage of the ionic liquid in the total mass of the additive is 55 wt% to 95 wt%.

[0010] Optionally, the solvent includes an ether solvent, and the ether solvent includes one or more of linear ethers or cyclic ethers.

[0011] Optionally, the ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, ethylene glycol dibutyl ether, triethylene glycol dimethyl ether, tetrahydrofuran, and dioxolane.

[0012] Optionally, the diluent includes one or more fluorine-containing ether compounds having structural formula I'' to structural formula II'': , ; Among them, R1''~R4'' in structural formula I''-structural formula II'' are independently one or more of C1-C5 fluoroalkyl, C1-C5 fluoroalkoxy, and C1-C5 fluoroalkene.

[0013] Optionally, the diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, perfluorononenyl trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0014] Optionally, the DN value of the diluent is ≤10 kcal / mol.

[0015] Optionally, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethylsulfonyl-perfluorobutylsulfonyl imide, lithium fluorosulfonyl-perfluorobutylsulfonyl imide, lithium bis(oxalatoborate), and lithium difluorophosphate.

[0016] Optionally, taking the total mass of the electrolyte as 100%, the additive accounts for 0.1 wt%~15 wt% of the total mass of the electrolyte; the solvent accounts for 5 wt%~65 wt% of the total mass of the electrolyte; the diluent accounts for 1 wt%~85 wt% of the total mass of the electrolyte; and the lithium salt accounts for 5 wt%~50 wt% of the total mass of the electrolyte.

[0017] A second aspect of the present invention provides a battery, comprising the above-mentioned electrolyte, separator, positive electrode sheet and negative electrode sheet.

[0018] A third aspect of the present invention provides an electrical device, comprising the battery described above.

[0019] According to the electrolyte provided by the present invention, by introducing ionic liquids and siloxane compounds as additives into the electrolyte, the siloxane compounds have high thermal stability due to the Si—O bonds in their structure, which helps to maintain the stability of the electrolyte under high temperature conditions and reduce the risk of thermal runaway. The combination with non-flammable ionic liquids helps to improve the safety of the battery and reduce the risk of fire and explosion; the high-temperature stability of the local super-concentrated electrolyte system can be effectively improved; the ionic liquid can enhance the thermal stability and electrochemical properties of the electrolyte, the siloxane compounds have excellent wettability and easy-to-form stable solid electrolyte interface (SEI) on the lithium metal negative electrode, which helps to inhibit the growth of lithium dendrites. By introducing ionic liquids and siloxane compounds as additives into the electrolyte system, an interface film containing silicon and oxygen elements can be formed on the surface of the positive electrode, and a dense SEI layer containing a Si—O—Si cross-polymer network is formed on the surface of the negative electrode, which inhibits the decomposition of the electrolyte and helps to improve the cycle life of the battery system; the thermal stability of the electrolyte is effectively improved, the risk of thermal runaway is reduced, and uniform and dense lithium deposition is promoted, dendrite growth is inhibited, and the overall performance and safety of the battery are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 It is the GC-MS test result of an embodiment of the present invention and a comparative example. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0024] In the present application, a plurality of refers to two or more.

[0025] In one embodiment, the first aspect of the present invention provides an electrolyte comprising an additive, a diluent, a solvent and a lithium salt, wherein the additive comprises an ionic liquid and a siloxane compound.

[0026] The present application introduces ionic liquids and siloxane compounds as additives into the electrolyte. The siloxane compounds have high thermal stability due to the Si—O bonds in their structure, which helps to maintain the stability of the electrolyte under high temperature conditions and reduce the risk of thermal runaway. The combination of non-flammable ionic liquids helps to improve the safety of the battery and reduce the risk of fire and explosion; it can effectively improve the high-temperature stability of the local ultra-concentrated electrolyte system; Ionic liquids can enhance the thermal stability and electrochemical properties of electrolytes. Siloxane compounds have excellent wettability to lithium metal negative electrodes and are easy to form a stable solid electrolyte interface (SEI), which helps to inhibit the growth of lithium dendrites. By introducing ionic liquids and siloxane compounds as additives in the electrolyte system, an interface film containing silicon and oxygen elements can be formed on the positive electrode surface, and a dense SEI layer composed of a Si-O-Si cross-polymer network is formed on the negative electrode surface, which inhibits the decomposition of the electrolyte and helps to increase the cycle life of the battery system; it effectively improves the thermal stability of the electrolyte, reduces the risk of thermal runaway, and promotes uniform and dense lithium deposition, inhibits dendrite growth, and improves the overall performance and safety of the battery.

[0027] In one embodiment, the siloxane compound includes one or more compounds having structural formula I to structural formula III: , , ; Wherein, R1~R18 in structural formula I to structural formula III are independently selected from one or more of hydrogen group, phenyl group, C1~C4 alkyl group, oxygen-containing alkyl group or oxygen-containing alkylene group.

[0028] The use of the above-mentioned siloxane compounds helps to maintain the stability of the electrolyte under high temperature conditions and reduce the risk of thermal runaway. The combination with non-flammable ionic liquids helps to improve the safety of the battery and reduce the risk of battery fire and explosion. At the same time, it promotes uniform and dense lithium deposition, inhibits dendrite growth, and improves the overall performance and safety of the battery.

[0029] In one embodiment, the siloxane compound includes one or more of dimethyldimethoxysilane, propoxytrimethylsilane, allyloxytrimethylsilane, hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, cyclosiloxane, bisphenyldimethylcyclosiloxane, heptamethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, tetraethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, and 2,4,6,8-tetramethylcyclotetrasiloxane.

[0030] Siloxane compounds have high thermal stability due to the Si-O bonds in their structure, which helps to maintain the stability of the electrolyte under high temperature conditions and reduce the risk of thermal runaway. When combined with non-flammable ionic liquids, it helps to improve battery safety and reduce the risk of battery fire and explosion. At the same time, it promotes uniform and dense lithium deposition, inhibits dendrite growth, and improves the overall performance and safety of the battery.

[0031] In one embodiment, the content of the siloxane compound in the total weight of the additive is 1 wt%-40 wt%.

[0032] Specifically, the percentage of the siloxane compound in the total mass of the additive is any point value of 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt% or 40wt% or a range value consisting of any two point values; in a preferred embodiment, the percentage of the siloxane compound in the total mass of the additive is 10wt%~40wt%; When the percentage of siloxane compounds in the total mass of additives is 1 wt%~40 wt%, the combination of siloxane compounds and ionic liquids solves the problem of high-temperature failure of lithium-containing electrolytes. By optimizing the ratio of ionic liquids with high voltage resistance and flame retardant properties to siloxane compounds with high thermal stability, the solvation structure of Li+ can be effectively adjusted, and a dense SEI layer composed of a Si-O-Si cross-polymer network can be formed on the surface of the negative electrode, which inhibits the decomposition of the electrolyte and helps to increase the cycle life of the battery system; effectively improve the thermal stability of the electrolyte, reduce the risk of thermal runaway, and at the same time promote uniform and dense lithium deposition, inhibit dendrite growth, and improve the overall performance and safety of the battery.

[0033] In one embodiment, the ionic liquid includes cations, and the cations include one or more of pyrrolidine cations, imidazolium cations, piperidine cations, and pyridinium cations having groups represented by structural formula I' to structural formula V': , , , , ; Wherein, R1'-R10' in the structural formula I' to the structural formula V' are independently selected from one or more of C1-C8 alkyl and C1-C8 alkyl isomers.

[0034] In one embodiment, the ionic liquid includes anions, and the anions include one or more of bisfluorosulfonyl imide anion, bistrifluoromethanesulfonyl imide anion, trifluoromethanesulfonate anion, dinitrile amide anion, tetrafluoroborate anion, hexafluorophosphate anion, perchlorate anion, dioxalatoborate anion, and difluorooxalatoborate anion.

[0035] The present application adopts the combination of siloxane compounds and ionic liquids to solve the problem of high-temperature failure of lithium-containing electrolytes. By optimizing the ratio of ionic liquids with high voltage resistance and flame retardant properties to siloxane compounds with high thermal stability, the solvation structure of Li+ can be effectively adjusted, and a dense SEI layer composed of a Si-O-Si cross-polymer network is formed on the surface of the negative electrode, which inhibits the decomposition of the electrolyte and helps to increase the cycle life of the battery system; effectively improves the thermal stability of the electrolyte, reduces the risk of thermal runaway, and at the same time promotes uniform and dense lithium deposition, inhibits dendrite growth, and improves the overall performance and safety of the battery.

[0036] In one embodiment, based on the total mass of the additive being 100%, the content of the ionic liquid in the total mass of the additive is 55 wt%-95 wt%.

[0037] Specifically, the percentage of the ionic liquid in the total mass of the additive is any point value of 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt% or 95wt% or a range value consisting of any two point values; in a preferred embodiment, the percentage of the ionic liquid in the total mass of the additive is 60 wt%~90 wt%; When the percentage of ionic liquid in the total mass of additives is 55 wt%~95 wt%, the combination of ionic liquid and siloxane compounds solves the problem of high-temperature failure of lithium-containing electrolytes. By optimizing the ratio of ionic liquids with high voltage resistance and flame retardant properties to siloxane compounds with high thermal stability, the solvation structure of Li+ can be effectively adjusted, and a dense SEI layer composed of a Si-O-Si cross-polymer network can be formed on the surface of the negative electrode, which inhibits the decomposition of the electrolyte and helps to increase the cycle life of the battery system; effectively improve the thermal stability of the electrolyte, reduce the risk of thermal runaway, and at the same time promote uniform and dense lithium deposition, inhibit dendrite growth, and improve the overall performance and safety of the battery.

[0038] In some embodiments, monomers and initiators are added to the electrolyte, which is then heated and cured to form a gel electrolyte.

[0039] Specifically, the monomer includes one or more of sulfonic acid group-containing vinyl monomers, acrylamide monomers, and acrylate monomers; specifically, the sulfonic acid group-containing vinyl monomers include one or more of 2-acrylamide-2-methylpropane sodium sulfonate, 2-acrylamide sodium dodecyl sulfonate, sodium dodecyl sulfonate, and 2-acrylamide sodium octane sulfonate; specifically, the acrylamide monomers include one or more of acrylamide, methacrylamide, isopropyl acrylamide, N,N-diethylacrylamide, isobutoxymethyl acrylamide, and diacetone acrylamide; specifically, the acrylate monomers include one or more of butyl acrylate, methyl acrylate, ethyl acrylate, 2-methyl methacrylate, and isooctyl acrylate.

[0040] Specifically, the initiator includes one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6 (trimethylbenzoyl) diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphosphonate, methyl o-benzoylbenzoate, benzophenone, 4-phenylbenzophenone, and ethyl 4-dimethylaminobenzoate; preferably, the lithium salt is selected from one or more of lithium bis(trifluoromethylsulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, lithium dioxalatoborate, lithium difluorophosphate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium difluorooxalatoborate, and lithium hexafluoroarsenate.

[0041] In one embodiment, taking the total mass of the gel electrolyte as 100%, the percentage of the electrolyte in the total mass of the gel electrolyte is 0.5%-50%; the percentage of the monomer in the total mass of the gel electrolyte is 49.9%-99.49%; and the percentage of the initiator in the total mass of the gel electrolyte is 0.01%-0.1%.

[0042] Specifically, the percentage of the electrolyte to the total mass of the gel electrolyte is 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%, or a range of any two of the values; in a preferred embodiment, the percentage of the electrolyte to the total mass of the gel electrolyte is 10%-40%.

[0043] Specifically, the percentage of the monomer in the total mass of the gel electrolyte is any point value of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17% or 18%, or a range value consisting of any two point values; in a preferred embodiment, the percentage of the monomer in the total mass of the gel electrolyte is 12%-16%.

[0044] Specifically, the percentage of the electrolyte in the total mass of the gel electrolyte is any point value among 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%, or a range value consisting of any two point values; in a preferred embodiment, the percentage of the initiator in the total mass of the gel electrolyte is 0.02%-0.08%.

[0045] Furthermore, in one embodiment, an electrolyte is added to the solid electrolyte to form a semi-solid electrolyte.

[0046] Specifically, the solid electrolyte includes an inorganic solid electrolyte, a polymer solid electrolyte and a composite solid electrolyte, the inorganic solid electrolyte includes one or more of an oxide solid electrolyte, a sulfide solid electrolyte and a halide solid electrolyte; the polymer solid electrolyte includes a polymer matrix, the polymer matrix is ​​selected from one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer; the composite solid 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 framework (MOFs) and zeolite; the active filler is 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 type 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.

[0047] In one embodiment, taking the total mass of the solid electrolyte as 100%, the percentage of the electrolyte in the total mass of the solid electrolyte is 0.5%-50%.

[0048] Specifically, the percentage of the electrolyte to the total mass of the solid electrolyte is 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%, or a range of any two points; in a preferred embodiment, the percentage of the electrolyte to the total mass of the solid electrolyte is 10%-40%.

[0049] In one embodiment, the solvent includes an ether solvent, and the ether solvent includes one or more of linear ethers or cyclic ethers.

[0050] In one embodiment, the ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, ethylene glycol dibutyl ether, triethylene glycol dimethyl ether, tetrahydrofuran, and dioxolane.

[0051] In one embodiment, the diluent includes one or more fluorine-containing ether compounds having structural formula I'' to structural formula II'': , ; Among them, R1''~R4'' in structural formula I''-structural formula II'' are independently one or more of C1-C5 fluoroalkyl, C1-C5 fluoroalkoxy, and C1-C5 fluoroalkene.

[0052] The role of ether solvents is to dissolve lithium salts and improve the stability of the negative electrode. In this technology, by introducing ionic liquids and siloxane dual additives, the high-temperature stability of the local ultra-concentrated electrolyte system is effectively improved. Ionic liquids can enhance the thermal stability and electrochemical properties of the electrolyte. Siloxane compounds have excellent wettability and easy-to-form stable solid electrolyte interface (SEI) for lithium metal negative electrodes, which helps to inhibit the growth of lithium dendrites. By introducing ionic liquids and siloxane dual additives into the ether local ultra-concentrated electrolyte system, an interface film containing silicon, oxygen, and fluorine elements can be formed on the positive electrode surface. At the same time, a dense SEI layer composed of a Si-O-Si cross-polymerization network is formed on the negative electrode surface, which effectively improves the thermal stability of the electrolyte, reduces the risk of thermal runaway, and promotes uniform and dense lithium deposition, inhibits dendrite growth, and improves the overall performance and safety of the battery.

[0053] In one embodiment, the diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, perfluorononenyl trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0054] The role of the diluent is to regulate the electrolyte solvation structure, improve the oxidation stability of the electrolyte system, improve the ion transport performance of the electrolyte system, promote the formation of LiF-rich SEI, and improve the stability of the negative electrode.

[0055] In one embodiment, the diluent has a DN (donor number) value of ≤ 10 kcal / mol.

[0056] Specifically, the DN value of the diluent is any point value among 0kcal / mol, 1kcal / mol, 2kcal / mol, 3kcal / mol, 4kcal / mol, 5kcal / mol, 6kcal / mol, 7kcal / mol, 8kcal / mol, 9kcal / mol or 10kcal / mol, or a range value consisting of any two point values; in a preferred embodiment, the DN value of the diluent is 1kcal / mol-8 kcal / mol.

[0057] When the DN value of the diluent is ≤10 kcal / mol, it can significantly improve the solvation environment of lithium ions in the electrolyte and the electrode interface behavior, thereby improving the charge and discharge performance and cycle stability of the battery. In one embodiment, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethylsulfonyl-perfluorobutylsulfonyl imide, lithium fluorosulfonyl-perfluorobutylsulfonyl imide, lithium bis(oxalatoborate), and lithium difluorophosphate.

[0058] Lithium salt is Li in the electrolyte + Lithium salts are the source of ions, providing the battery with free-moving ions and playing the role of transporting ions inside the battery. In addition, lithium salts can also form a protective layer on the surface of electrode materials, which has an important influence on the battery's capacity, cycle performance, power density, energy density and other properties.

[0059] In one embodiment, taking the total mass of the electrolyte as 100%, the percentage of the additive in the total mass of the electrolyte is 0.1 wt%~15 wt%; the percentage of the solvent in the total mass of the electrolyte is 5 wt%~65 wt%; the percentage of the diluent in the total mass of the electrolyte is 1 wt%~85 wt%; and the percentage of the lithium salt in the total mass of the electrolyte is 5 wt%~50 wt%.

[0060] Specifically, the percentage of the additive in the total mass of the electrolyte is 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt% or any two points in the range; in a preferred embodiment, the percentage of the additive in the total mass of the electrolyte is 5wt% to 10wt%; Specifically, the percentage of the solvent in the total mass of the electrolyte is 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt% or 65wt% or a range of any two values; in a preferred embodiment, the percentage of the solvent in the total mass of the electrolyte is 10wt% to 35wt%; Specifically, the percentage of the diluent in the total mass of the electrolyte is 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt% or 85wt%, or a range of any two values; in a preferred embodiment, the percentage of the diluent in the total mass of the electrolyte is 15wt% to 70wt%; Specifically, the percentage of lithium salt in the total mass of the electrolyte is 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt% or 50wt% or a range of any two values; in a preferred embodiment, the percentage of lithium salt in the total mass of the electrolyte is 10wt% to 40wt%; The present invention optimizes the addition ratio of ionic liquid, diluent and lithium salt to effectively adjust Li + The solvation structure of the ionic liquid not only drives a large number of anions into the Li + The solvation sheath can also regulate the solvation structure by interacting with cyclopentadiene, and when the fluorinated anion dominates the solvation structure, multiple controls of the interface can be achieved.

[0061] A second aspect of the present invention provides a battery, comprising the above-mentioned electrolyte, a separator, a positive electrode sheet and a negative electrode sheet.

[0062] Specifically, the diaphragm can be selected from one or more materials such as polypropylene (PP), polyethylene (PE), PP / PE / PP composite film, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ceramic diaphragm, ceramic polyamide (PI), aramid (AF), non-woven fabric, etc.

[0063] In a preferred embodiment, the production of the battery includes the following steps: The positive electrode sheet, the separator and the negative electrode sheet are stacked in order, so that the separator is located between the positive and negative electrodes to play an isolating role. The electrode sheet and the separator are placed in an aluminum-plastic film bag formed by punching and shelling by stacking. The electrolyte, gel electrolyte or solid electrolyte prepared as above are respectively injected into the baked and dried battery cells. After vacuum packaging, standing, formation and other processes, a battery is obtained.

[0064] In one embodiment, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes one or more of lithium iron phosphate (LFP), lithium iron manganese phosphate (LMFP), lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel oxide (LNO), ternary materials (NCM, NCA), lithium manganese-rich base (LMR), lithium nickel manganese oxide (LNMO), and lithium vanadium phosphate (Li3V2(PO4)3, LiVOPO4).

[0065] Specifically, when the electrolyte system is matched with a high-voltage positive electrode, including ternary materials and lithium-rich manganese-based materials, the high-voltage solvent system includes ionic liquids and cyclofluoroethers to form a local super-concentrated system with good flame retardant properties. The mixed solvent system generates stable SEI and CEI through solvation structure regulation, providing a stable circulation basis for the battery system under high voltage conditions and improving the safety characteristics of the battery.

[0066] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one side or both sides of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder.

[0067] In some embodiments, the positive electrode conductive agent includes one or more of graphite, superconducting carbon, acetylene black, carbon black, carbon nanotubes, graphene, carbon nanofibers, metal powder, metal fibers, and polyphenylene derivatives.

[0068] In some embodiments, the positive electrode binder includes 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.

[0069] 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.

[0070] When the mass ratio of the positive electrode active material in the positive electrode active material layer is within the above range, the positive electrode plate can have a higher lithium removal and lithium insertion capacity, and the battery can have a higher capacity.

[0071] The positive electrode current collector is selected from a metal material that can conduct electrons. Preferably, the positive electrode current collector includes one or more of copper, nickel, tin, copper, and stainless steel. In a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

[0072] The positive electrode sheet can be prepared according to conventional methods in the art. For example, the positive electrode active material layer is usually prepared by coating a positive electrode slurry made of a positive electrode active material, a positive electrode conductive agent, a positive electrode binder and any other components on a positive electrode current collector, followed by drying and cold pressing. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0073] In one embodiment, the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes one or more of a graphite negative electrode material, a silicon-oxygen negative electrode material, a silicon-carbon negative electrode material, a silicon negative electrode material, a tin negative electrode material, a tin oxide negative electrode material, a tin alloy negative electrode material (Sn-Fe, Sn-Co, Sn-Cu, etc.), a lithium metal negative electrode material, a lithium alloy negative electrode material (Li-Ag, Li-Al, Li-Sn, Li-Mg, Li-Zn, Li-In, Li-Ga, etc.), and a lithium-free negative electrode material.

[0074] The electrolyte of the present invention can be used in a high-voltage battery system, matched with a high-voltage ternary positive electrode and a lithium-manganese-rich positive electrode, a graphite negative electrode, a silicon-carbon negative electrode, a silicon-oxygen negative electrode, and a lithium metal negative electrode, and is used to make liquid, semi-solid laminated, wound or cylindrical batteries. The electrolyte of the present invention provides a stable circulation basis for the battery system under high voltage conditions, thereby improving the safety characteristics of the battery.

[0075] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a conductive agent, a binder, and a thickener.

[0076] In some embodiments, the negative electrode conductive agent includes one or more of graphite, superconducting carbon, acetylene black, carbon black, carbon nanotubes, graphene, carbon nanofibers, metal powders, metal fibers, and polyphenylene derivatives.

[0077] In some embodiments, the negative electrode binder includes one or more of styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, and polymethacrylic acid.

[0078] In some embodiments, the thickener includes one or more of sodium alginate, sodium carboxymethyl cellulose, and carboxymethyl chitosan.

[0079] In some embodiments, the mass percentage of each component in the negative electrode active material layer is: 96%-97% of negative electrode active material, 0.5%-1.5% of conductive agent, 1%-2% of binder and 0.5%-1.5% of thickener.

[0080] 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 allows the mesoporous material to be in full contact with the active material, and enables the electrolyte stored in the mesopores to be directly transported to the active material. At the same time, lithium reaches the active material interface faster through the mesopores, and the improvement effects on kinetics, circulation, etc. are better.

[0081] The negative electrode current collector is selected from a metal material that can conduct electrons. Preferably, the negative electrode current collector includes one or more of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0082] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative electrode active material layer is usually prepared by coating a negative electrode slurry made of a negative electrode active material, a negative electrode conductive agent, a negative electrode binder and any other components on a negative electrode current collector, followed by drying and cold pressing. The solvent can be an aqueous solvent, but is not limited thereto.

[0083] A third aspect of the present invention provides an electrical device, comprising the battery described above.

[0084] The third aspect of the present invention provides an electric device, which includes the battery described in the second aspect of the present invention. The battery is used as a power source for the device. The number of batteries in the electric device can be adjusted according to the application and capacity of the electric device.

[0085] Preferably, the electrical device may 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.

[0086] The beneficial effects of the present invention are further illustrated below in conjunction with embodiments.

[0087] In order to make the invention purpose, technical scheme and beneficial technical effect of the present invention clearer, the present invention is further described in detail below in conjunction with examples. However, it should be understood that the examples of the present invention are only for explaining the present invention, not for limiting the present invention, and the examples of the present invention are not limited to the examples given in the specification. The specific experimental conditions or operating conditions not specified in the examples are made under conventional conditions, or are made under the conditions recommended by the material supplier.

[0088] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these explicitly mentioned two devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0089] In the following examples, the reagents, materials and instruments used, unless otherwise specified, can be purchased commercially or obtained by synthetic methods known in the art.

[0090] Table 1 Design of electrolytes of Examples 1-7 and Comparative Examples 1-3; Example 1 This embodiment is used to illustrate the electrolyte and battery disclosed in the present invention; it includes the following operating steps: Preparation of electrolyte: In a glove box filled with argon (O2 <1ppm, H2O <1ppm), lithium salt LiFSI, ether solvent DME, and ionic liquid Pyr13FSI are mixed in a mass ratio of 5:4:0.9, and then TTE is added and stirred evenly to obtain a mixed solvent. Finally, 0.5% DMMS is slowly added to the mixed solvent to obtain the electrolyte.

[0091] Preparation of positive electrode sheet: Mix the positive electrode active material lithium nickel cobalt manganese oxide (NCM), the conductive agent CNT, and the adhesive PVDF in a mass ratio of 97:1.5:1.5. Stir and mix thoroughly in NMP solvent to form a uniform positive electrode slurry. Apply this slurry on at least one side of the positive electrode current collector aluminum foil, and obtain a positive electrode sheet that meets the requirements after drying, rolling, die-cutting and other processes.

[0092] Production of negative electrode sheet: The negative electrode uses a copper-lithium composite strip with a metal lithium thickness of 20um. Preparation of diaphragm: PE porous polymer film is used as the diaphragm substrate; Battery production: The positive electrode sheet, the separator and the negative electrode sheet are stacked in order, and the separator is placed between the positive and negative electrodes to play an isolating role. Then the stacked electrode sheets and the separator are placed in the aluminum-plastic film bag formed by punching and forming. The non-aqueous electrolyte prepared above is respectively injected into the baked and dried battery cells. After vacuum packaging, standing, formation and other processes, a battery with a capacity of 1Ah is obtained.

[0093] Embodiment 2-7 Examples 2-7 are used to illustrate the electrolyte and battery disclosed in the present invention, and include most of the operating steps in Example 1, except that: The components and contents of the organic solvent in the electrolyte shown in Table 1 were used.

[0094] Comparative Examples 1-3 Comparative Examples 1-3 are used to illustrate the electrolyte and battery disclosed in the present invention, and include most of the operating steps in Example 1, except that: The components and contents of the organic solvent in the electrolyte shown in Table 1 were used. Performance Testing The following performance tests were performed on the batteries prepared in Examples 1 to 7 and Comparative Examples 1 to 3: 1. Electrolyte oxidation potential test: The linear scanning potential method was used and the EC-Lab electrochemical workstation was used to test the oxidation potential of the electrolyte membrane. The test voltage range was 2.5~6V and the scanning rate was 1 mV·s-1. This method used the device structure of "stainless steel sheet|diaphragm|lithium sheet" for testing, with the stainless steel sheet as the working electrode and the lithium sheet as the reference electrode.

[0095] 2. Electrolyte thermal stability test: The electrolyte system was tested using a differential scanning calorimeter (DSC). The thermal stability of the electrolyte was analyzed by observing the endothermic and exothermic reactions of the electrolyte under high temperature conditions. The test was carried out in a nitrogen atmosphere with a temperature range of 30°C to 300°C, a heating rate of 5°C / min, and a cooling rate of 10°C / min.

[0096] 3. Electrolyte GC-MS test: The electrolyte components were analyzed by gas chromatography-mass spectrometry (GC-MS). The electrolyte sample was diluted with ethyl acetate and directly tested on the machine. The column flow rate was 1 ml / min, the split ratio was 20:1, and the injection port temperature was 260°C, maintained at 40°C for 1 min, then increased to 180°C at a rate of 15°C / min and maintained for 5 min, and then increased to 280°C at a rate of 5°C / min and maintained for 5 min. 4. Battery cycle performance test: In the voltage range of 3.0V~4.3V, temperature of 25℃, 0.1C / 0.3D cycle charge and discharge test, record the capacity retention rate of the battery after 100 cycles, as well as the average efficiency of battery charge and discharge.

[0097] The test results are shown in Table 2.

[0098] Table 2 Electrochemical performance of lithium batteries From Table 2 and Figure 1 It can be seen that compared with Examples 1-7, when there is a lack of siloxane or ionic liquid in the electrolyte, the electrochemical window will be reduced, the thermal decomposition temperature will be reduced, the average charge and discharge efficiency of the battery will be reduced, the battery capacity retention rate will be reduced, and the battery performance will be poor.

[0099] In summary, the present invention can effectively improve the thermal stability of the electrolyte system by introducing ionic liquid and siloxane dual additives into the electrolyte system, wherein Si in the siloxane additive is easy to react chemically with F, and O to H + Has strong affinity through Si and F, O and H + Paired chemical reactions are used to remove HF from the electrolyte and protect the transition metal elements in the positive electrode, which can effectively improve the stability of the high-nickel positive electrode surface. Ionic liquids with high-temperature stability are further introduced to form a dense SEI layer on the negative electrode surface, which effectively improves the formation of an interface film containing silicon, oxygen, and fluorine elements, improves the thermal stability of the electrolyte system, reduces the risk of thermal runaway, and promotes uniform and dense lithium deposition, inhibits dendrite growth, and improves the cycle stability and safety of the battery system.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An electrolyte, characterized in that: The invention comprises additives, solvents and lithium salts, wherein the additives comprise ionic liquids and siloxane compounds.

2. The electrolyte according to claim 1, characterized in that: The siloxane compound includes one or more compounds having structural formula I to structural formula III: 、 、 ； Wherein, R1~R18 in structural formula I to structural formula III are independently selected from one or more of hydrogen group, phenyl group, C1~C4 alkyl group, oxygen-containing alkyl group or oxygen-containing alkylene group.

3. The electrolyte according to claim 1, characterized in that: The siloxane compound includes one or more of dimethyldimethoxysilane, propoxytrimethylsilane, allyloxytrimethylsilane, hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, cyclosiloxane, bisphenyldimethylcyclosiloxane, heptamethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, tetraethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, and 2,4,6,8-tetramethylcyclotetrasiloxane.

4. The electrolyte according to any one of claims 1 to 3, characterized in that: Taking the total mass of the additive as 100%, the percentage of the siloxane compound in the total mass of the additive is 1 wt% to 40 wt%.

5. The electrolyte according to claim 1, characterized in that: The ionic liquid includes cations, and the cations include one or more of pyrrolidine cations, imidazolium cations, piperidine cations, and pyridinium cations having groups shown in structural formula I' to structural formula V': , , , , ; wherein, in the structural formula I' to structural formula V', R1'-R10' are each independently selected from one or more of C1-C8 alkyl groups and C1-C8 alkyl isomers.

6. The electrolyte according to claim 1, characterized in that: The ionic liquid includes anions, and the anions include one or more of bisfluorosulfonyl imide anions, bistrifluoromethanesulfonyl imide anions, trifluoromethanesulfonate anions, dinitrile amide anions, tetrafluoroborate anions, hexafluorophosphate anions, perchlorate anions, dioxalate borate anions, and difluorooxalate borate anions.

7. The electrolyte according to any one of claims 1 or 6, characterized in that: Taking the total mass of the additive as 100%, the percentage of the ionic liquid in the total mass of the additive is 55 wt% to 95 wt%.

8. The electrolyte according to claim 1, characterized in that: The solvent includes an ether solvent, and the ether solvent includes one or more of linear ethers or cyclic ethers.

9. The electrolyte according to claim 8, characterized in that: The ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, ethylene glycol dibutyl ether, triethylene glycol dimethyl ether, tetrahydrofuran, and dioxolane.

10. The electrolyte according to claim 1, characterized in that: The diluent includes one or more fluorine-containing ether compounds having structural formula I'' to structural formula II'': 、 ； Among them, R1''~R4'' in structural formula I''-structural formula II'' are independently one or more of C1-C5 fluoroalkyl, C1-C5 fluoroalkoxy, and C1-C5 fluoroalkene.

11. The electrolyte according to claim 10, characterized in that: The diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, perfluorononenyl trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

12. The electrolyte according to claim 10, characterized in that: The DN value of the diluent is ≤10 kcal / mol.

13. The electrolyte according to claim 1, characterized in that: The lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethylsulfonyl-perfluorobutylsulfonylimide, lithium fluorosulfonyl-perfluorobutylsulfonylimide, lithium bis(oxalatoborate), and lithium difluorophosphate.

14. The electrolyte according to claim 1, characterized in that: Taking the total mass of the electrolyte as 100%, the percentage of the additive in the total mass of the electrolyte is 0.1 wt%~15 wt%; the percentage of the solvent in the total mass of the electrolyte is 5 wt%~65 wt%; the percentage of the diluent in the total mass of the electrolyte is 1 wt%~85wt%; and the percentage of the lithium salt in the total mass of the electrolyte is 5 wt%~50 wt%.

15. A battery, characterized in that: The invention comprises an electrolyte, a separator, a positive electrode sheet and a negative electrode sheet as described in any one of claims 1 to 14.

16. An electrical device, characterized in that: Comprising a battery according to claim 15.

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