Electrolyte, battery, and power utilization device

Abstract

The application discloses an electrolyte, a battery and a power utilization device. The electrolyte comprises a first additive, a lithium salt and a solvent, and the first additive comprises at least one of thioimidazolidinone compounds containing carbon-carbon double bonds. The electrolyte of the application contains the first additive, the first additive has the multifunctional effects of forming films on the positive and negative electrodes and complexing transition metal ions, so that the interface films formed on the positive and negative electrodes have excellent ion conductivity and film stability, the DCR increase in the charging and discharging process can be effectively inhibited, the dissolution and deposition of transition metal ions in the positive electrode material under high temperature / high pressure can be effectively inhibited, and therefore the high-temperature cycle performance and storage performance of the battery are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of batteries, and particularly relates to an electrolyte, a battery and a power utilization device. BACKGROUND

[0002] Lithium ion secondary batteries are widely used in power systems and energy storage systems due to their high energy density, long cycle life, no memory effect and other characteristics. With the continuous development of society and the increasing demand of consumers, the demand for high energy density of lithium batteries is also increasing. In order to further improve the energy density of lithium batteries, it is necessary to innovate the lithium battery chemical system, especially the positive electrode material. The current mainstream scheme is to improve the specific capacity of the positive electrode material and to increase the use voltage range of the battery. For example, based on the current mainstream systems of lithium iron phosphate (LFP) and nickel cobalt manganese ternary (NCM) lithium batteries, the upgraded positive electrode materials of lithium manganese iron phosphate (LMFP) and NCM system with higher nickel content are developed, which can significantly improve the energy density of the battery when used with higher voltage. However, LMFP or high nickel NCM has a serious problem of transition metal ion (Ni, Co, Mn, Fe, etc.) dissolution when used at high voltage. The transition metal ions are dissolved from the positive electrode (exacerbated at high temperature / high voltage), resulting in loss of positive active material, blocked ion intercalation and deintercalation, transmission through the electrolyte, penetration through the separator, deposition at the negative electrode, destruction of the SEI film, induction of electrolyte decomposition, continuous thickening of the SEI film, continuous consumption of active lithium and impedance increase, and ultimately leading to rapid capacity loss and impedance growth. The above problems limit the practical application of the above-mentioned upgraded positive electrode materials. SUMMARY

[0003] The present application aims to at least partially solve one of the technical problems in the related art. To this end, one object of the present application is to provide an electrolyte, a battery and a power utilization device. The electrolyte of the present application comprises a first additive, which has the multifunctional effects of positive and negative electrode film formation and complexation of transition metal ions, so that the interface film formed by the positive and negative electrodes has excellent ion conductivity and film stability, and can effectively inhibit the DCR increase during charging and discharging, and can effectively inhibit the dissolution and deposition of transition metal ions in the positive electrode material at high temperature / high pressure, thereby improving the high temperature cycle performance and storage performance of the battery.

[0004] The first aspect of the present application provides an electrolyte. According to the embodiments of the present application, the electrolyte comprises a first additive, a lithium salt and a solvent, and the first additive comprises at least one of a sulfur-containing imidazolidinone compound containing a carbon-carbon double bond.

[0005] According to the electrolyte provided in the embodiments of the present application, the electrolyte comprises a first additive, the first additive has the multifunctional effects of forming films on the positive and negative electrodes and complexing transition metal ions, so that the interface films formed on the positive and negative electrodes have excellent ion conductivity and film stability, and the DCR increase during the charging and discharging process can be effectively inhibited, and the dissolution and deposition of transition metal ions in the positive electrode material under high temperature / high pressure can be effectively inhibited, thereby improving the high-temperature cycle performance and storage performance of the battery.

[0006] In addition, the electrolyte provided in the embodiments of the present application can have the following additional technical features.

[0007] In some embodiments of the present application, the first additive is selected from at least one of the compounds shown in Formula I, Formula II and Formula III.

[0008]

[0009] wherein R1 and R4 are independently selected from hydrogen, halogen, C1-C8 alkyl, C1-C8 halogenated alkyl, C1-C4 alkenyl, C1-C4 alkynyl, amine group, cyano group or isocyanate group, and R2 and R3 are independently selected from hydrogen, C1-C8 alkyl, C1-C8 halogenated alkyl or alkyl amine.

[0010] In some embodiments of the present application, the compound shown in Formula I comprises at least one of the following compounds:

[0011]

[0012] In some embodiments of the present application, the compound shown in Formula II comprises at least one of the following compounds:

[0013]

[0014] In some embodiments of the present application, the compound shown in Formula III comprises at least one of the following compounds:

[0015]

[0016] In some embodiments of the present application, the mass fraction of the first additive is 0.2% to 5% based on the total mass of the electrolyte.

[0017] In some embodiments of the present application, the electrolyte further comprises a second additive, and the second additive comprises a thermal initiator.

[0018] In some embodiments of the present application, the mass ratio of the first additive to the second additive is 100:(0.01-0.3); and / or, the thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, lauroyl peroxide, and diisopropyl peroxydicarbonate.

[0019] In some embodiments of the present application, the electrolyte further includes: a third additive, wherein the third additive includes at least one of an S-containing additive, a double bond-containing additive, an F-containing additive, a B-containing additive, a P-containing additive, a CN-containing ester additive, and a lithium salt additive.

[0020] In some embodiments of the present application, the S-containing additive includes at least one of 1,3-propane sultone, propenyl-1,3-sultone, vinyl sulfate, and methylene methanedisulfonate; and / or, the double bond-containing additive includes at least one of vinylene carbonate, vinyl ethylene carbonate, and triallyl phosphate; and / or, the F-containing additive includes at least one of fluoroethylene carbonate and tris(2,2,2-trifluoroethyl)phosphite; and / or, the B-containing additive includes at least one of lithium bis(oxalatoborate), lithium bis(oxalatoborate), and tris(trimethylsilyl)borate; and / or, the P-containing additive includes at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, lithium difluorophosphate, and lithium difluorobis(oxalatophosphate); and / or, the CN-containing ester additive includes at least one of hexanetrinitrile, succinonitrile, adiponitrile, 1,2-bis(cyanoethoxy)ethane, and tricyanoethoxypropane.

[0021] In some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the third additive is 0.5% to 10%.

[0022] In some embodiments of the present application, the molar concentration of the lithium salt is 0.7 mol / L to 1.5 mol / L.

[0023] In a second aspect, this application provides a battery. According to an embodiment of this application, the battery includes the electrolyte of the first aspect. As a result, the battery of this application exhibits excellent high-temperature cycling performance, high-temperature storage performance, and dynamic performance, and can effectively suppress the increase in the battery's DCR during charge and discharge.

[0024] In some embodiments of the present application, the battery includes a positive electrode active material, the positive electrode active material including at least one of lithium manganese iron phosphate and a nickel-cobalt-manganese ternary material with a high nickel content; the chemical formula of the lithium manganese iron phosphate is LiMn x Fe 1-x PO4, wherein x is 0.4 to 0.8; the chemical formula of the nickel-cobalt-manganese ternary material with high nickel content is LiNi yCo z Mn 1-y-z O2, wherein y is 0.6 to 0.95, and z is 0.05 to 0.2.

[0025] In a third aspect of the present application, an electrical device is provided. According to an embodiment of the present application, the electrical device includes the battery described in the above embodiment. As a result, the electrical device has all the advantages of the battery, which will not be elaborated here.

[0026] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. DETAILED DESCRIPTION

[0027] The embodiments of the present application are described in detail below, which are intended to explain the present application and should not be construed as limiting the present application.

[0028] The first aspect of the present application proposes an electrolyte. According to an embodiment of the present application, the above-mentioned electrolyte includes a first additive, a lithium salt and a solvent, and the first additive includes at least one of thioimidazole compounds containing a carbon-carbon double bond. Therefore, the electrolyte of the present application includes a first additive, and the first additive has the multifunctional effect of both positive and negative electrode film formation and complexing transition metal ions, so that the interface film formed by the positive and negative electrodes has both excellent ion conductivity and film formation stability, and can also effectively inhibit the DCR growth during the charge and discharge process, and can effectively inhibit the dissolution and deposition of transition metal ions in the positive electrode material under high temperature / high pressure, thereby improving the high temperature cycle performance and storage performance of the battery.

[0029] The following is a detailed explanation of the principle by which the electrolyte proposed in this application can achieve the above beneficial effects:

[0030] The application provides a novel electrolyte, which comprises a first additive containing a thioimidazolidone heterocyclic group, which can be decomposed at the positive and negative electrodes to form an SEI / CEI interface film rich in various inorganic matter combinations (such as Li3N, Li2O, Li2S, etc.), the inorganic matter with excellent ion conductivity and the crystal boundary between different inorganic matters are beneficial to the transmission of lithium ions at the interface, so that the ion transmission kinetics of the system can be effectively improved; and the inorganic matter combination has good high-temperature stability, which can effectively inhibit the dissolution and decomposition of unstable components of SEI at high temperature and inhibit the increase of DCR in the charging and discharging process. Meanwhile, the first additive also contains a N-containing group with a lone pair of electrons, which can effectively complex transition metal ions and inhibit the dissolution of positive transition metal ions. Meanwhile, the first additive also contains a strong electron-withdrawing S element, which endows the interface film with higher oxidation resistance and improves the high-voltage stability of the positive electrode interface film. In addition, the first additive also contains a carbon-carbon double bond, so that the first additive can preferentially undergo redox reaction at the positive and negative electrodes, and decompose and polymerize to form a uniform and dense organic flexible interface film, which can effectively adapt to the volume change of the negative material in the charging and discharging process and enhance the resistance of SEI to the deposition damage of transition metal ions. Therefore, the first additive of the application has multiple functional groups which work together to make the formed interface film have excellent ion conductivity and film stability. Meanwhile, the first additive can complex transition metal ions, protect the positive and negative electrodes, avoid direct contact with the electrolyte, inhibit the electrolyte side reaction at the interface, effectively alleviate the dissolution and deposition of transition metal ions in the positive material at high temperature / high pressure, and improve the high-temperature cycle performance and storage performance of the lithium battery.

[0031] According to some specific embodiments of the application, the first additive comprises at least one of the compounds shown in formula I, formula II and formula III.

[0032]

[0033] wherein R1 is selected from hydrogen, halogen, C1-C8 alkyl, C1-C8 haloalkyl, alkenyl, alkynyl, amine group, cyano group or isocyanic acid group, R2 and R3 are respectively selected from hydrogen, C1-C8 alkyl, C1-C8 haloalkyl or alkylamine, and R4 is selected from hydrogen, halogen, C1-C8 alkyl, C1-C8 haloalkyl, alkenyl, alkynyl, amine group, cyano group or isocyanic acid group.

[0034] According to some specific embodiments of the application, the compound shown in formula I comprises at least one of the following compounds:

[0035]

[0036] Therefore, the compound of formula I with the above structure further has the multifunctional effects of forming films on the positive and negative electrodes and complexing transition metal ions, so that the interface film formed has excellent ion conductivity and film stability, and can further effectively inhibit the dissolution and deposition of transition metal ions in the positive electrode material under high temperature / high pressure, thereby further improving the high temperature stability of the lithium battery.

[0037] According to some specific embodiments of the present application, the compound of formula II includes at least one of the following compounds:

[0038]

[0039]

[0040] Therefore, the compound of formula II with the above structure further has the multifunctional effects of forming films on the positive and negative electrodes and complexing transition metal ions, so that the interface film formed has excellent ion conductivity and film stability, and can further effectively inhibit the dissolution and deposition of transition metal ions in the positive electrode material under high temperature / high pressure, thereby further improving the high temperature stability of the lithium battery.

[0041] According to some specific embodiments of the present application, the compound of formula III includes at least one of the following compounds:

[0042]

[0043] Therefore, the compound of formula III with the above structure further has the multifunctional effects of forming films on the positive and negative electrodes and complexing transition metal ions, so that the interface film formed has excellent ion conductivity and film stability, and can further effectively inhibit the dissolution and deposition of transition metal ions in the positive electrode material under high temperature / high pressure, thereby further improving the high temperature stability of the lithium battery.

[0044] According to some specific embodiments of the present application, the mass percentage of the first additive is 0.2% to 5%, preferably 0.5% to 2%, based on the total mass of the electrolyte, so that the interface film formed by the positive and negative electrodes has excellent ion conductivity and film stability, and can further effectively inhibit the dissolution and deposition of transition metal ions in the positive electrode material under high temperature / high pressure, thereby further improving the high temperature stability of the lithium battery.

[0045] According to some specific embodiments of the present application, the electrolyte further includes a second additive, and the second additive includes a thermal initiator that can effectively reduce the polymerization temperature of the first additive in the formation of the SEI / CEI interface film on the positive and negative electrodes, thereby reducing the preparation difficulty.

[0046] It should be noted that by adding the above-mentioned first additive and an optional second additive to the electrolyte, injecting the electrolyte into the battery cell and encapsulating it, and heating it at high temperature for a certain period of time, a layer of artificial interface passivation film can be polymerized on the surface of the positive / negative electrode. When the electrolyte does not contain the second additive, the polymerization temperature for forming the SEI / CEI interface film at the positive / negative electrode is approximately above 80°C. When the electrolyte contains the second additive, the polymerization temperature for forming the SEI / CEI interface film at the positive / negative electrode is approximately 40°C to 60°C. This shows that the second additive can effectively reduce the polymerization temperature of the first additive to form the SEI / CEI interface film at the positive / negative electrode.

[0047] According to some further specific embodiments of the present application, the mass ratio of the first additive to the second additive is 100:(0.01-0.3), thereby further effectively reducing the polymerization temperature of the first additive in forming the SEI / CEI interface film at the positive / negative electrode.

[0048] In the embodiments of the present application, the specific type of the above-mentioned thermal initiator is not particularly limited, and those skilled in the art can select it according to actual needs. As some preferred embodiments, the above-mentioned thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, lauroyl peroxide, and diisopropyl peroxydicarbonate.

[0049] According to further specific embodiments of the present application, the electrolyte further includes a third additive, the third additive including at least one of a S-containing additive, a double bond-containing additive, a F-containing additive, a B-containing additive, a P-containing additive, a CN-containing ester additive, and a lithium salt additive. The third additive facilitates the formation of an SEI / CEI interface film at the positive / negative electrode, improves the uniformity of the film formation, and improves the interfacial impedance.

[0050] In the embodiments of the present application, the specific type of the above-mentioned S-containing additive is not particularly limited. As some preferred embodiments, the S-containing additive includes at least one of 1,3-propane sultone (PS), propenyl-1,3-sultone (PST), diethylene sulfate (DTD), and methylene methane disulfonate (MMDS).

[0051] In the embodiments of the present application, the specific type of the above-mentioned double bond-containing additive is not particularly limited. As some preferred embodiments, the double bond-containing additive includes at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and triallyl phosphate (TAP).

[0052] In the embodiments of the present application, the specific type of the above-mentioned F-containing additive is not particularly limited. As some preferred embodiments, the F-containing additive includes at least one of fluoroethylene carbonate (FEC) and tris(2,2,2-trifluoroethyl)phosphite (TTFP).

[0053] In the embodiments of the present application, the specific type of the above-mentioned B-containing additive is not particularly limited. As some preferred embodiments, the B-containing additive includes at least one of lithium dioxalatoborate (LiBOB), lithium dioxalatoborate (LiODFB), and tris(trimethylsilyl)borate (TMSB).

[0054] In the embodiments of the present application, the specific type of the above-mentioned P-containing additive is not particularly limited. As some preferred embodiments, the P-containing additive includes at least one of tris(trimethylsilyl) phosphate (TMSP), tris(trimethylsilyl) phosphite (TMSPi), lithium difluorophosphate (LiPO2F2), and lithium difluorobis(oxaloyl)phosphate (LiODFP).

[0055] In the embodiments of the present application, the specific type of the above-mentioned CN-containing ester additive is not particularly limited. As some preferred embodiments, the CN-containing ester additive includes at least one of hexane trinitrile (HTCN), succinonitrile (SN), adiponitrile (ADN), 1,2-bis(cyanoethoxy)ethane (DENE), and tricyanoethoxypropane (TCP).

[0056] According to some other specific embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the third additive is 0.5% to 10%, which can further facilitate the formation of SEI / CEI interface film at the positive / negative electrode, further improve the film formation uniformity of the interface film, further improve the interface impedance, etc.

[0057] According to further specific embodiments of the present application, the molar concentration of the lithium salt in the electrolyte is 0.7 mol / L to 1.5 mol / L, thereby enabling the electrolyte to have a high ionic conductivity. The organic solvent in the electrolyte serves as an important carrier for ion transport, and when the electrolyte lithium salt is dissolved, it can have a high electronic conductivity.

[0058] In the embodiments of the present application, the specific type of the above-mentioned solvent is not particularly limited. As some preferred embodiments, the above-mentioned solvent is selected from at least one of a carbonate solvent and a carboxylate solvent. The carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and various fluorinated cyclic and linear carbonates; the carboxylate solvent includes at least one of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate and various fluorinated cyclic and linear carboxylates.

[0059] In the embodiments of the present application, the specific type of the above-mentioned lithium salt is not particularly limited. As some preferred embodiments, the above-mentioned lithium salt includes at least one of LiPF6, LiClO4, LiBF4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI, and LiTDI.

[0060] A second aspect of this application provides a battery. According to an embodiment of this application, the battery includes the electrolyte of the second aspect. As a result, the battery of this application exhibits excellent high-temperature cycling performance, high-temperature storage performance, and dynamic performance, and can effectively suppress the increase in the battery's DCR during charge and discharge.

[0061] The type of battery of the present application is not particularly limited and can be a lithium-ion battery or a sodium-ion battery. The electrolyte additive of the present application is particularly suitable for lithium-ion batteries, and can effectively improve the ion conductivity and stability of the positive and negative electrode interface films of lithium-ion batteries, and can also effectively inhibit the increase of DCR during charging and discharging. At the same time, it can effectively inhibit the dissolution and deposition of transition metal ions in the positive electrode materials (especially lithium manganese iron phosphate and nickel-cobalt-manganese ternary materials with high nickel content) under high temperature / high pressure, thereby improving the high-temperature cycle performance and storage performance of the battery.

[0062] According to some specific embodiments of the present application, the battery includes a positive electrode active material, the positive electrode active material includes at least one of lithium manganese iron phosphate and a nickel-cobalt-manganese ternary material with a high nickel content; the chemical formula of the lithium manganese iron phosphate is LiMn x Fe 1-x PO4, wherein x is 0.4 to 0.8; the chemical formula of the nickel-cobalt-manganese ternary material with high nickel content is LiNi y Co z Mn 1-y-z O2, wherein y is 0.6 to 0.95, and z is 0.05 to 0.2.

[0063] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts the active ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing the active ions to pass through.

[0064] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material. The positive electrode active material is preferably a lithium manganese iron phosphate material or a nickel-cobalt-manganese ternary material with a high nickel content.

[0065] In some embodiments of the present application, the positive current collector can include a metal foil or a composite positive current collector. For example, the metal foil can employ an aluminum foil. The composite positive current collector can include a polymer material base layer and a metal layer formed on at least one side surface of the polymer material base layer. For example, the composite negative current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material base material (e.g., a polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0066] In some embodiments of the present application, the positive active material layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0067] In some embodiments of the present application, the positive active material layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin.

[0068] In some embodiments of the present application, the positive electrode sheet can be prepared by dispersing the above-described components for preparing the positive electrode sheet, e.g., the positive active material, the conductive agent, the binder, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive current collector, and then performing drying, cold pressing, etc. to obtain the positive electrode sheet.

[0069] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side surface of the negative current collector, the negative active material layer including a negative active material.

[0070] In some embodiments of the present application, the negative current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material base material (e.g., a polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0071] In some embodiments of the present application, the negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material can include at least one of graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can include at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can include at least one of elemental tin, tin oxide compound, and tin alloy.

[0072] In some embodiments of the present application, the negative active material layer can further optionally include a binder. The binder can include at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0073] In some embodiments of the present application, the negative active material layer can further optionally include a conductive agent. The conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0074] In some embodiments of the present application, the negative active material layer can further optionally include other auxiliary agents, such as thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0075] In some embodiments of the present application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative current collector, and after processes such as drying, cold pressing, etc., the negative electrode sheet can be obtained.

[0076] The type of the separator film is not particularly limited in the present application, and any known porous structure separator film having good chemical stability and mechanical stability can be selected. In some embodiments of the present application, the material of the separator film can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride.

[0077] The battery of the present application can include a battery monomer form, a battery module form, and a battery pack form. In some embodiments, the battery monomer can be assembled into a battery module, and the number of battery monomers contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module. In some embodiments, the battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0078] The third aspect of the present application provides a power consuming device comprising the battery of the second aspect. Thus, the power consuming device has excellent service life and safety performance.

[0079] The battery cell, the battery module and the battery pack can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device (such as a mobile phone, a notebook computer, etc.), 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., but is not limited thereto.

[0080] As the power consuming device, the battery, the battery module or the battery pack can be selected according to the use requirement thereof.

[0081] As an embodiment of the power consuming device, it can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the battery for the power consuming device, the battery pack or the battery module can be used.

[0082] As another embodiment of the device, it can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the battery cell can be used as a power source.

[0083] It should be noted that the features and advantages described above for the battery are also applicable to the power consuming device, which will not be described herein.

[0084] The embodiments of the present application will be described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. In addition, if not specifically stated, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods, and the reaction conditions not listed are also easily obtained by those skilled in the art.

[0085] Example 1

[0086] 1) Preparation of the positive electrode tab

[0087] The positive electrode active material (LiNi 0.8 Co 0.1 Mn 0.1The positive electrode slurry was obtained by mixing the positive electrode active material LiFePO4, conductive agent carbon black and binder polyvinylidene fluoride (PVDF) in a solvent N-methyl-2-pyrrolidone (NMP) under stirring in a vacuum state (the solid content in the positive electrode slurry was 56%), the positive electrode slurry was uniformly coated on both sides of the current collector aluminum foil, and after drying in a 120°C oven for 8 hours, cold pressing was performed, then after edge cutting, piece cutting and striping, the positive electrode piece was prepared.

[0088] 2) Preparation of the negative electrode piece

[0089] The negative electrode slurry was obtained by mixing the negative electrode active material graphite, conductive agent carbon black, binder styrene-butadiene rubber and thickening agent sodium carboxymethyl cellulose (CMC) in deionized water in a mass ratio of 95:1.5:1.5:3 under stirring in a vacuum state (the solid content in the negative electrode slurry was 55%), the negative electrode slurry was uniformly coated on both sides of the current collector copper foil, and after drying, calendering and vacuum drying, cold pressing, edge cutting, piece cutting and striping were performed, and the negative electrode piece was prepared.

[0090] 3) Preparation of the electrolyte

[0091] In a glove box with qualified oxygen content, ethylene carbonate (EC) and methyl ethyl carbonate (EMC) were mixed in a mass ratio of 30:70, and then lithium hexafluorophosphate (LiPF6) was added and stirred uniformly to serve as the base electrolyte. The molar concentration of lithium hexafluorophosphate (LiPF6) was 1.0 mol / L based on the total mass of the base electrolyte.

[0092] The electrolyte functional additives shown in Table 1 were added to the above base electrolyte.

[0093] 4) Separator

[0094] The separator was a PE ceramic-coated separator with a thickness of 20 μm purchased from Star Source Material.

[0095] 5) Preparation of the lithium ion battery

[0096] The positive electrode piece, the separator and the negative electrode piece were stacked in order, with the separator between the positive and negative electrode pieces to serve as a separator for the positive and negative electrodes, and a bare cell was obtained by winding. The bare cell was welded with tabs, placed in an outer package, and the electrolyte prepared above was injected into the dried cell. After packaging, the cell was allowed to stand at 25°C for 24 h to allow the electrolyte to fully soak.

[0097] The battery was heated to 45-80°C and allowed to stand for 2.5 h (the specific polymerization heating temperature of the battery is shown in Table 2), so that the first additive polymerizes at the positive / negative electrode interface to form an SEI / CEI interface film. The battery was then subjected to conventional formation and capacity distribution, and the performance of the cell after capacity distribution was tested.

[0098] Examples 2-20

[0099] The preparation methods of the lithium-ion batteries of Examples 2 to 20 are the same as those of Example 1, except that the composition of the additives in the electrolyte is different, as shown in Table 1.

[0100] Comparative Example 1

[0101] The preparation method of the lithium ion battery of Comparative Example 1 is the same as that of Example 1, except that: the first additive is not added in Comparative Example 1.

[0102] Comparative Example 2

[0103] The preparation method of the lithium ion battery of Comparative Example 2 is the same as that of Example 19, except that the first additive is not added in Comparative Example 2.

[0104] Table 1

[0105]

[0106]

[0107] The high temperature cycle, cycle DCR growth and cycle gas generation of the lithium ion batteries of Examples 1 to 20 and Comparative Examples 1 to 2 were tested respectively. The results are shown in Table 2.

[0108] Performance tests:

[0109] The performance test was performed as follows, and the test results are shown in Table 2.

[0110] (1) High temperature cycle performance test: At 45°C, the battery was cycled and charged to 4.25V at a constant current of 1C, then charged at a constant voltage until the current reached 0.05C. After standing for half an hour, it was discharged at a constant current of 1C. The initial capacity of the battery in the first cycle was obtained and recorded as C1. After that, the charge and discharge cycle was repeated in the CCCV / DC mode of the first cycle. The capacity after the 400th cycle was recorded as C 400 , then the capacity retention rate after 400 cycles of high temperature cycling (%) = C 400 / C1×100%. Before and after high-temperature cycling, the DC internal resistance (DCR) value of the battery cell at 50% SOC is tested using the following current pulse method and recorded.

[0111] (2) DCR test: After cooling the cell before or after high temperature cycling to room temperature, charge it at a constant current of 0.5C to 4.25V, charge it at a constant voltage to a current of 0.05C, leave it for 1 hour, discharge it at 0.5C for 1 hour (50% SOC), continue to leave it for 1 hour, and record the voltage V1 at the end; then discharge it at 2C for 10 seconds, and record the voltage V2 at the end. The DCR of the cell before or after cycling = (V1-V2) / (I 1C -I 0.1C), the DCR growth rate after cycling is (DCR 循环后 -DCR 循环前 ) / DCR 循环前 ×100%.

[0112] (3) Cycling gas production test: after cooling the battery cell to room temperature before or after high-temperature cycling, the battery volume is tested by the drainage method, and the specific operation is as follows: place a container containing deionized water on an electronic scale, use a fixed clamp to fix the tab at the upper end of the soft package battery, and completely immerse the soft package battery in the liquid, and record the weight change displayed by the electronic scale. By measuring the change in the volume of deionized water after the soft package battery is immersed in deionized water, the volume of the soft package battery can be calculated. The specific calculation formula is: V = (m1-m2) / p, wherein m1 is the weight of the soft package battery after being completely immersed in deionized water, m2 is the weight of the soft package battery when it is not immersed in deionized water, and p is the density of deionized water (1 g / L). The volume V 循环前 before cycling and the volume V 循环后 after cycling are measured respectively, and the cycling gas production is calculated by the following formula: (V 循环后- V 循环前 ) / V 循环前 ×100%.

[0113] Table 2

[0114]

[0115]

[0116] As can be seen from Table 2, compared with Comparative Example 1, the high-temperature cycling performance of Examples 1-20 has an improved cycle capacity retention rate of 2%-6%, a reduced cycle DCR growth of 3%-15%, and a reduced cycle gas production of 8%-20%. It can be seen that the first additive can effectively improve the high-temperature cycling of the lithium ion battery, inhibit the cycle DCR growth, and inhibit the cycle gas production.

[0117] As can be seen from Table 2, compared with Comparative Example 2, the high-temperature cycling performance of Example 19 has an improved cycle capacity retention rate of 3.7%, a reduced cycle DCR growth of 10.1%, and a reduced cycle gas production of 14%. It can be seen that the first additive can effectively improve the high-temperature cycling of the lithium ion battery, inhibit the cycle DCR growth, and inhibit the cycle gas production.

[0118] As can be seen from Table 2, compared with Examples 1, 5-6, the high-temperature cycling performance of Examples 2-4 has an improved cycle capacity retention rate of 1.6%-4%, a reduced cycle DCR growth of 1.6%-6.9%, and a reduced cycle gas production of 1.5%-7%. It can be seen that the mass ratio of the first additive based on the total mass of the electrolyte is preferably 0.5%-2%.

[0119] It can also be seen from Table 2 that compared with Examples 1 to 14, the polymerization heating temperature of the batteries of Examples 15 to 20 is significantly lower. It can be seen that the second additive can effectively reduce the polymerization temperature of the first additive to form the SEI / CEI interface film at the positive / negative electrode, thereby reducing the difficulty of preparation.

[0120] It can also be seen from Table 2 that compared with Example 16, the high temperature cycle performance cycle capacity retention rate of Examples 18 to 20 is increased by 0.5%-1%, the cycle DCR growth is reduced by 1%-2.9%, and the cycle gas production is reduced by 1%-3.3%. It can be seen that the third additive can further improve the high temperature cycle of the lithium-ion battery, inhibit the cycle DCR growth, and inhibit the cycle gas production.

[0121] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0122] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An electrolyte, characterized in that: The electrolyte includes a first additive, a lithium salt and a solvent, wherein the first additive includes at least one thioimidazole-based compound containing a carbon-carbon double bond.

2. The electrolyte according to claim 1, characterized in that The first additive is selected from at least one of the compounds represented by formula I, formula II and formula III; Among them, R1 and R4 are independently selected from hydrogen, halogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C4 alkenyl, C1-C4 alkynyl, amine, cyano or isocyanate, and R2 and R3 are independently selected from hydrogen, C1-C8 alkyl, C1-C8 haloalkyl or alkylamine.

3. The electrolyte according to claim 2, characterized in that The compound represented by formula I includes at least one of the following compounds:

4. The electrolyte according to claim 2, characterized in that The compound represented by formula II includes at least one of the following compounds:

5. The electrolyte according to claim 2, characterized in that The compound represented by formula III includes at least one of the following compounds:

6. The electrolyte according to claim 1, characterized in that Based on the total mass of the electrolyte, the mass proportion of the first additive is 0.2% to 5%.

7. The electrolyte according to any one of claims 1 to 6, characterized in that Also includes: A second additive, wherein the second additive comprises a thermal initiator.

8. The electrolyte according to claim 7, characterized in that The mass ratio of the first additive to the second additive is 100:(0.01-0.3); And / or, the thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, lauroyl peroxide, and diisopropyl peroxydicarbonate.

9. The electrolyte according to any one of claims 1 to 6, characterized in that Also includes: The third additive includes at least one of an S-containing additive, a double bond-containing additive, an F-containing additive, a B-containing additive, a P-containing additive, a CN-containing ester additive, and a lithium salt additive.

10. The electrolyte according to claim 9, characterized in that The sulfur-containing additive includes at least one of 1,3-propane sultone, propenyl-1,3-sultone, vinyl sulfate, and methylene methanedisulfonate; And / or, the double bond-containing additive includes at least one of vinylene carbonate, vinyl ethylene carbonate, and triallyl phosphate; And / or, the F-containing additive includes at least one of fluoroethylene carbonate and tris(2,2,2-trifluoroethyl)phosphite; and / or, the B-containing additive includes at least one of lithium bis(oxalatoborate), lithium bis(oxalatoborate), and tris(trimethylsilyl)borate; And / or, the P-containing additive includes at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, lithium difluorophosphate, and lithium difluorobis(oxalophosphate); And / or, the CN-containing ester additive includes at least one of hexanetrinitrile, succinonitrile, adiponitrile, 1,2-bis(cyanoethoxy)ethane, and tricyanoethoxypropane.

11. The electrolyte according to claim 9, characterized in that Based on the total mass of the electrolyte, the mass proportion of the third additive is 0.5% to 10%.

12. The electrolyte according to any one of claims 1 to 6, characterized in that The molar concentration of the lithium salt in the electrolyte is 0.7 mol / L to 1.5 mol / L.

13. A battery, characterized in that: The electrolyte according to any one of claims 1 to 12 is included.

14. The battery according to claim 13, characterized in that The battery includes a positive electrode active material, wherein the positive electrode active material includes at least one of lithium manganese iron phosphate and a nickel-cobalt-manganese ternary material with a high nickel content; The chemical formula of the lithium manganese iron phosphate is LiMn x Fe 1-x PO4, where x is 0.4 to 0.8; The chemical formula of the nickel-cobalt-manganese ternary material with high nickel content is LiNi y Co z Mn 1-y-z O2, wherein y is 0.6 to 0.95, and z is 0.05 to 0.

2.

15. An electrical device, characterized in that: A battery according to claim 13 or 14.

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