Electrolyte, battery, and electrical device

Abstract

An electrolyte, a battery, and an electrical device, relating to the technical field of batteries. The electrolyte comprises: a first solvent, the first solvent comprising an amide solvent and / or a sulfonamide solvent; a second solvent, the second solvent comprising a linear ether and / or a cyclic ether; a lithium salt; and an additive. By optimizing the ratio of the first solvent to the second solvent, the solvation structure of Li+ can be effectively adjusted, and an SEI film is generated on the surface of the negative electrode while a uniform and dense CEI film is formed on the positive electrode side, thereby suppressing side effects and structural damage to the high-voltage positive electrode and effectively improving the high-voltage cycling stability of the battery. The lithium salt and the additive are added into a mixed solvent system, so that the fast-charging performance of the battery at room temperature is improved. In addition, the ratio of the first solvent with high-voltage resistance characteristics to the second solvent with low viscosity can be adjusted according to actual needs, significantly reducing electrolyte viscosity and improving battery wettability.

Description

An electrolyte, a battery, and an electrical device

[0001] This application claims priority to Chinese Patent Application No. 202410704501.1, filed on May 31, 2024, entitled “An Electrolyte, Battery and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of batteries, and more particularly to an electrolyte, a battery, and an electrical device. Background Technology

[0003] In the field of batteries, such as lithium-ion batteries, energy density and fast-charging efficiency are two important indicators for evaluating lithium-ion battery performance. To further improve energy density and fast-charging efficiency, the cutoff voltage of lithium-ion batteries is typically increased. However, at high cutoff voltages (>4.3V), the electrolyte suffers from oxidative decomposition. Furthermore, ternary cathode materials (LiNi...) x Mn y Co z O2 still suffers from structural and interfacial instability at high cutoff voltages (>4.4V). Solving the problems of continuous oxidative decomposition of the electrolyte and the growth of a non-uniform positive electrode electrolyte interface (CEI) under high cutoff voltages is key to improving energy density and fast-charging efficiency. Summary of the Invention

[0004] In view of the technical problems in the prior art, this application provides an electrolyte, a battery, and an electrical device to optimize battery performance.

[0005] An electrolyte comprising:

[0006] The first solvent includes amide solvents and / or sulfonamide solvents;

[0007] The second solvent; the second solvent includes linear ethers and / or cyclic ethers;

[0008] Lithium salts;

[0009] additive.

[0010] Optionally, the amide solvent includes at least one of 2,2,2-trifluoro-N,N-dimethylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-dimethylpropionamide, formamide, N,N-diethylacetamide, N,N-dimethylisobutyramide, N,N-diethylacetylacetamide, N-methyl-N-vinylacetamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide.

[0011] Optionally, the sulfonamide solvent has a structure as shown in Formula I and / or Formula II;

[0012] R1 is a fluorinated alkyl group with 1 to 8 carbon atoms;

[0013] R2, R3, and R4 are one of pyrrolidinyl, piperidinyl, or linear alkyl groups having 1 to 10 carbon atoms; or R3 and R4 are one of pyrrolidinyl or piperidinyl.

[0014] Optionally, the sulfonamide solvent includes at least one of N,N-dimethyltrifluoromethanesulfonamide (DMTMSA), 1-((trifluoromethyl)sulfonyl)piperidine (TFSPP), N-methyltrifluoromethanesulfonamide, N,N-diethyl-1,1,1-trifluoromethanesulfonamide, 1,1-difluoro-N,N-dimethylmethanesulfonamide, and 1,1-difluoro-N-methylmethanesulfonamide.

[0015] Optionally, the second solvent includes at least one of 2-dimethoxyethane (DME), ethylene glycol dimethyl ether (EDG), dimethoxydimethyl ether (DMM), diethylene glycol dimethyl ether (DG), 1,3-dioxocyclopentane (DOL), triethylene glycol monoethyl ether (Trig), tetrahydrofuran (THF), and 2-methyl-tetrahydrofuran (2-Me-THF).

[0016] Optionally, the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bisfluorosulfonylimide (LiFSI), lithium trifluoromethanesulfonyl-perfluorobutylsulfonylimide (LiTNFSI), lithium fluorosulfonyl-perfluorobutylsulfonylimide (LiFNFSI), lithium bis(oxalatoborate)borate (LiBOB), and lithium difluorophosphate (LiPO2F2).

[0017] Optionally, the additive includes at least one of fluoroethylene carbonate (FEC), 1,3-propane sulpholol (PSL), vinylene carbonate (VEC), ethylene sulfate (SES), lithium nitrate (LiNO3), lithium borate (LiBF4), lithium difluorooxalate borate (LiDFOB), and lithium difluoro(bis(oxalate) phosphate).

[0018] Optionally, the additive includes at least one of lithium nitrate, lithium borate, lithium difluorooxalate borate, and lithium difluoro(bis(oxalate) phosphate).

[0019] Optionally, the volume ratio of the first solvent to the second solvent is (0.5–9.5):(0.5–9.5).

[0020] Optionally, the concentration of the lithium salt in the electrolyte is 0.5 mol / L to 3 mol / L.

[0021] Optionally, the amount of the additive is 0.01 wt% to 10 wt% of the sum of the masses of the first solvent and the second solvent.

[0022] A battery comprising a positive electrode, a negative electrode, a separator, and any one of the above-mentioned electrolytes.

[0023] Optionally, the positive electrode includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, ternary materials, lithium-rich manganese-based materials, lithium nickel manganese oxide, and lithium vanadium oxide phosphate.

[0024] Optionally, the negative electrode includes at least one of graphite negative electrode, silicon-oxygen negative electrode, silicon-carbon negative electrode, silicon negative electrode, tin negative electrode, tin oxide negative electrode, tin alloy negative electrode, lithium metal negative electrode, lithium alloy negative electrode and lithium-free negative electrode.

[0025] Optionally, the diaphragm includes at least one of polypropylene, polyethylene, PP / PE / PP composite membrane, polyvinylidene fluoride, polyacrylonitrile, ceramic diaphragm, ceramic polyamide, aramid, and nonwoven fabric.

[0026] A battery includes a positive electrode, a negative electrode, a separator, and an electrolyte; the electrolyte includes any one of the above-mentioned electrolyte solutions; the content of the electrolyte solution in the electrolyte is 0.5 wt.% to 50 wt.%.

[0027] Optionally, the electrolyte is a gel electrolyte or a solid electrolyte; the solid electrolyte is an inorganic solid electrolyte, a polymer solid electrolyte, or a composite solid electrolyte.

[0028] An electrical device that uses any of the above-mentioned batteries as a power source.

[0029] The electrolyte, battery, and power supply device provided in this application can solve the high-voltage failure problem of traditional carbonate electrolytes. Firstly, by optimizing the ratio of the first solvent (amide-based solvent and / or sulfonamide-based solvent) to the second solvent, the Li... + The solvation structure generates an SEI film on the negative electrode surface and a uniform and dense CEI film on the positive electrode side, which suppresses side reactions and structural damage to the high-voltage positive electrode, effectively improving the high-voltage cycle stability of the battery. Secondly, the addition of lithium salt and additives to the mixed solvent system improves the fast-charging performance of the battery under room temperature conditions. In addition, the ratio of the first solvent with high-voltage resistance and the second solvent with low viscosity can be adjusted according to actual needs, which significantly reduces the electrolyte viscosity and improves the wettability of the battery. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0031] This application discloses an electrolyte comprising:

[0032] The first solvent includes amide solvents and / or sulfonamide solvents;

[0033] The second solvent; the second solvent includes linear ethers and / or cyclic ethers;

[0034] Lithium salts;

[0035] additive.

[0036] Understandably, the electrolyte provided in this embodiment is applicable to lithium batteries, sodium-ion batteries, etc., and belongs to a non-aqueous electrolyte. The first solvent can be an amide solvent and / or a sulfonamide solvent, such as 2,2,2-trifluoro-N,N-dimethylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethyltrifluoromethanesulfonamide, 1-((trifluoromethyl)sulfonyl)piperidine, etc. The second solvent can be a linear ether and / or a cyclic ether, such as 2-dimethoxyethane, ethylene glycol dimethyl ether, tetrahydrofuran, etc.

[0037] The first and second solvents work synergistically to effectively regulate Li + The solvation structure of Li, on the one hand, through the strong electron-withdrawing inductive effect of amide or thioamide groups, enables Li to... + The preferential reduction and decomposition on the negative electrode surface effectively regulates the formation of the electrolyte interphase (SEI) film. On the other hand, the solvation structure, influenced by solvent solubility, balances the potentials of the negative and positive electrodes, mitigating electrolyte decomposition under high voltage conditions and forming a stable CEI film on the positive electrode. This effectively covers the nickel-rich NCM positive electrode particles, reduces side reactions in the electrolyte, and weakens the adverse electrochemical reactions caused by lithium dendrite growth in the battery, achieving excellent cycle performance and high coulombic efficiency. The mixed solvent system formed by the first and second solvents generates stable SEI and CEI through solvation structure regulation, providing a stable cycle foundation for the battery system under high voltage conditions.

[0038] Lithium salts can be selected from inorganic or organic lithium salts suitable for batteries, such as lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Lithium salts can effectively improve the ionic conductivity of the electrolyte, enhance its voltage resistance, and improve lithium metal / graphite compatibility. Firstly, after dissolving in a mixed solvent, lithium salts dissociate into lithium ions and corresponding anions. These lithium ions act as charge carriers, moving within the electrolyte and providing channels for charge transfer within the battery. Therefore, adding lithium salts can improve the ionic conductivity of the electrolyte, contributing to improved charge-discharge efficiency and power performance of the battery. Secondly, lithium salt anions possess high electrochemical stability; within the battery's operating voltage range, these anions are less prone to oxidation or reduction reactions, reducing the occurrence of side reactions. This prevents the electrolyte from decomposing under high voltage, thereby improving the electrolyte's voltage resistance and ensuring stable battery operation over a wide voltage range. Third, during the initial battery cycles, the lithium salt anions or their reduction products can form a stable solid electrolyte interphase (SEI) film on the electrode surface (SEI on the negative electrode, CEI on the positive electrode), especially for active electrode materials such as lithium metal and graphite. This interphase film can prevent other components in the electrolyte from further reacting with the electrodes, reduce lithium dendrite growth, protect the electrode materials from electrolyte corrosion, enhance the compatibility of lithium metal and graphite, and improve battery safety and cycle stability.

[0039] Additives suitable for batteries can be selected, such as fluoroethylene carbonate (FEC), 1,3-propane sulphol (PSL), vinylene carbonate (VC), ethylene sulfate (SES), lithium nitrate, lithium borate, lithium difluorooxalate borate, and lithium difluoro(bis(oxalate) phosphate). Additives are used to improve battery performance. For example, FEC can form a more stable and dense SEI on the negative electrode surface; PSL can provide specific chemical stability and improve interfacial properties at high voltages.

[0040] The electrolyte provided in this embodiment can solve the high-voltage failure problem of traditional carbonate electrolytes. Firstly, by optimizing the ratio of the first solvent (amide-based solvent and / or sulfonamide-based solvent) to the second solvent, the Li... + The solvation structure generates an SEI film on the negative electrode surface and a uniform and dense CEI film on the positive electrode side, which suppresses side reactions and structural damage to the high-voltage positive electrode, effectively improving the high-voltage cycle stability of the battery. Secondly, the addition of lithium salt and additives to the mixed solvent system improves the fast-charging performance of the battery under room temperature conditions. In addition, the ratio of the first solvent with high-voltage resistance and the second solvent with low viscosity can be adjusted according to actual needs, which significantly reduces the electrolyte viscosity and improves the wettability of the battery.

[0041] In some embodiments, the amide solvent includes at least one of 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), N,N-diethylformamide (DEFA), N,N-dimethylpropionamide (DMA), formamide (FA), N,N-diethylacetamide (DEAC), N,N-dimethylisobutyramide (DMSA), N,N-diethylacetylacetamide (DEAC), N-methyl-N-vinylacetamide (MVAC), N,N-dimethylacrylamide (DMAA), and N,N-diethylacrylamide (DEAA).

[0042] Understandably, amide solvents possess excellent ionic conductivity, which promotes the rapid migration of lithium ions in the electrolyte, thereby improving the battery's charge-discharge efficiency and power performance. They also exhibit high chemical and electrochemical stability, capable of withstanding the high potentials during battery operation, reducing electrolyte decomposition, and enhancing battery safety and cycle stability. Furthermore, they can improve the compatibility between the electrolyte and electrode materials, especially for high-energy-density electrode materials such as graphite or lithium metal anodes. Reaction products on the electrode surface can promote the formation of a stable and ion-transport-friendly solid electrolyte interphase (SEI) or cathode electrolyte interphase (CEI). By using specific amide-based electrolytes, the composition and structure of the SEI can be effectively controlled, reducing lithium dendrite formation, protecting electrode materials, and improving battery cycle life and safety. Amide solvents typically have low melting points and high boiling points, allowing them to remain liquid over a wide temperature range, contributing to improved battery performance under high and low temperature conditions. Compared to traditional carbonate solvents, amide solvents offer better environmental compatibility and biodegradability, meeting the requirements of sustainable development.

[0043] In some embodiments, the sulfonamide solvent has a structure as shown in Formula I and / or Formula II;

[0044] R1 is a fluorinated alkyl group with 1 to 8 carbon atoms;

[0045] R2, R3, and R4 are one of pyrrolidinyl, piperidinyl, or linear alkyl groups having 1 to 10 carbon atoms; or R3 and R4 are one of pyrrolidinyl or piperidinyl.

[0046] Understandably, sulfonamide solvents can be fluorosulfonamide solvents having a structure as shown in Formula I or Formula II. In some examples, sulfonamide solvents include at least one of N,N-dimethyltrifluoromethanesulfonamide, 1-((trifluoromethyl)sulfonyl)piperidine, N-methyltrifluoromethanesulfonamide, N,N-diethyl-1,1,1-trifluoromethanesulfonamide, 1,1-difluoro-N,N-dimethylmethanesulfonamide, and 1,1-difluoro-N-methylmethanesulfonamide.

[0047] Sulfonamide solvents have higher flash points and ignition points than traditional carbonate solvents, which significantly reduces the fire risk of electrolytes under high-temperature conditions and can significantly improve the flame retardant properties of electrolytes, making batteries safer under overheating or abuse conditions. They also have excellent chemical and electrochemical stability, resisting oxidation at high potentials and reducing electrolyte decomposition, which is particularly important for lithium batteries using high-voltage cathode materials, helping to improve battery energy density and cycle life. They help improve the battery's performance under extreme temperatures, maintaining good conductivity at low temperatures and electrolyte stability at high temperatures, thus broadening the battery's application range. They participate in the formation of the solid electrolyte interphase (SEI) film on the electrode surface, helping to build a more stable, dense, and highly ion-conductive SEI layer, protecting the electrode from electrolyte corrosion and reducing resistance to lithium-ion transport. In addition to flame retardant properties, fluorosulfonamide solvents can further improve the overall safety of batteries by reducing the release of harmful gases and enhancing tolerance to mechanical damage.

[0048] The sulfonamide solvent used in this embodiment is particularly suitable for high-voltage electrolyte systems, which greatly improves the overall performance of the battery.

[0049] In some embodiments, the second solvent includes at least one selected from 2-dimethoxyethane, ethylene glycol dimethyl ether, dimethoxydimethyl ether, diethylene glycol dimethyl ether, 1,3-dioxocyclopentane, triethylene glycol monoethyl ether, tetrahydrofuran, and 2-methyl-tetrahydrofuran.

[0050] Understandably, the second solvent can be a linear ether, such as 2-dimethoxyethane (DME), ethylene glycol dimethyl ether (EDG), dimethoxydimethyl ether (DMM), diethylene glycol dimethyl ether (DG), etc., or a cyclic ether, such as 1,3-dioxolane (DOL), triethylene glycol monoethyl ether (Trig), tetrahydrofuran (THF), 2-methyl-tetrahydrofuran (2-Me-THF), etc. The second solvent has low viscosity and low dielectric constant, which facilitates the rapid migration of lithium ions in the electrolyte, thereby improving the electrolyte conductivity and enhancing the battery's charge-discharge efficiency and power performance. When used in conjunction with the first solvent, it provides stable electrochemical performance, broadens the electrochemical stability window of the electrolyte, and is suitable for high-voltage battery systems. It also has a low melting point and good low-temperature fluidity, improving the battery's low-temperature start-up performance and cycle life. Furthermore, it can optimize the desolvation process of lithium ions on the electrode surface, improving compatibility with electrode materials, such as reducing co-intercalation problems on graphite anodes or promoting Na+ in sodium-ion batteries. + It facilitates the transport of electrolytes and controls the reaction of solvents on the electrode surface. This helps to form a more stable and suitable solid electrolyte interphase (SEI) and positive electrode electrolyte interphase (CEI), reduces side reactions, protects electrode materials, and improves the cycle stability and safety of the battery.

[0051] In some embodiments, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, lithium trifluoromethanesulfonyl-perfluorobutylsulfonylimide, lithium fluorosulfonyl-perfluorobutylsulfonylimide, lithium bis(oxalato)borate, lithium difluorooxalato)borate, and lithium difluorophosphate.

[0052] Understandably, lithium salts can be selected from inorganic or organic lithium salts suitable for batteries, such as lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bisfluorosulfonylimide (LiFSI), lithium trifluoromethanesulfonyl-perfluorobutylsulfonylimide (LiTNFSI), lithium fluorosulfonyl-perfluorobutylsulfonylimide (LiFNFSI), lithium bis(oxalatoborate)borate (LiBOB), lithium difluorophosphate (LiPO2F2), etc.

[0053] The lithium salt provided in this embodiment can effectively improve the ionic conductivity of the electrolyte, enhance the electrolyte's voltage resistance, and improve lithium metal / graphite compatibility.

[0054] In some embodiments, the additive includes at least one of fluoroethylene carbonate, 1,3-propane sulpholol, vinylene carbonate, vinyl sulfate, lithium nitrate, lithium borate, lithium difluorooxalate borate, and lithium difluoro(bis(oxalate) phosphate).

[0055] Understandably, the additives can be selected from those suitable for batteries, such as one or more of fluoroethylene carbonate, 1,3-propane sulpholactone, vinylene carbonate, ethylene sulfate, lithium nitrate, lithium borate, lithium difluorooxalate borate, and lithium difluoro(bisoxalate) phosphate, preferably lithium nitrate, lithium borate, lithium difluorooxalate borate, and lithium difluoro(bisoxalate) phosphate. Lithium nitrate can form lithium-nitrogen compounds with fast ion conduction characteristics on the positive and negative electrodes. The resulting rapid interfacial kinetics significantly reduce electrode overpotential and improve lithium-ion transport at the positive and negative electrode interfaces, resulting in excellent cycle stability of the battery system at high cutoff voltages.

[0056] In some embodiments, the volume ratio of the first solvent to the second solvent is (0.5–9.5):(0.5–9.5).

[0057] Understandably, the volume ratio of the first solvent and the second solvent can be determined according to actual needs, such as (0.5 to 9.5):(0.5 to 9.5).

[0058] In some embodiments, the concentration of the lithium salt in the electrolyte is 0.5 mol / L to 3 mol / L.

[0059] Understandably, the lithium salt concentration can be determined according to actual needs, such as 0.5 mol / L to 3 mol / L. Preferably, the concentration of lithium salt in the electrolyte can be 1 mol / L or 1.5 mol / L.

[0060] In some embodiments, the amount of the additive is 0.01 wt% to 10 wt% of the sum of the masses of the first solvent and the second solvent.

[0061] An embodiment of this application also provides a battery, including a positive electrode, a negative electrode, a separator, and any one of the above-described electrolytes.

[0062] Understandably, the electrolyte provided in the previous embodiment can be used in conjunction with a positive electrode, a negative electrode, and a separator to prepare a battery. The positive electrode is one of the core components of the battery, significantly affecting its energy density. The positive electrode can be selected from at least one of lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel oxide (LNO), ternary materials (NCM, NCA), lithium-rich manganese-based materials (LMR), lithium nickel manganese oxide (LNMO), and lithium vanadium oxide phosphate (Li3V2(PO4)3, LiVOPO4). The negative electrode is also one of the core components of the battery, interacting with the electrolyte to promote the insertion and extraction of metal cations. The negative electrode can be selected from at least one of the following: graphite negative electrode, silicon-oxygen negative electrode, silicon-carbon negative electrode, silicon negative electrode, tin negative electrode, tin oxide negative electrode, tin alloy negative electrode (Sn-Fe, Sn-Co, Sn-Cu, etc.), lithium metal negative electrode, lithium alloy negative electrode (Li-Ag, Li-Al, Li-Sn, Li-Mg, Li-Zn, Li-In, Li-Ga, etc.), and lithium-free negative electrode. The separator is a very thin porous material located between the positive and negative electrodes of the battery, and can be selected from at least one of the following: polypropylene (PP), polyethylene (PE), PP / PE / PP composite membrane, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ceramic separator, polyimide (PI), aramid (AF), and nonwoven fabric.

[0063] The battery provided in this embodiment can be manufactured as a liquid stacked battery, a liquid wound battery, or a liquid cylindrical battery. Due to the use of a higher-performance electrolyte, the battery system has excellent cycle stability at high cutoff voltage.

[0064] One embodiment of this application also provides a battery, including a positive electrode, a negative electrode, a separator, and a gel electrolyte; the gel electrolyte includes any of the above-mentioned electrolytes; the content of the electrolyte in the electrolyte is 0.5 wt.% to 50 wt.%. In this embodiment, the battery can be a semi-solid battery, such as a semi-solid stacked battery, a semi-solid wound battery, or a semi-solid cylindrical battery, wherein the electrolyte can be a gel electrolyte composed of a solid electrolyte and an electrolyte, and the content of the electrolyte in the electrolyte is 0.5 wt.% to 50 wt.%. The solid electrolyte can be selected from inorganic solid electrolytes (oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes), polymer solid electrolytes, and composite solid electrolytes (inorganic filler + polymer matrix). Solid electrolytes have higher mechanical strength and thermal stability, can better resist deformation and temperature changes, and can provide better safety performance. Compared with liquid electrolytes, gel electrolytes reduce the risk of leakage and improve safety.

[0065] One embodiment of this application also provides an electrical device that uses any of the above-described batteries as a power source.

[0066] Example

[0067] Preparation of electrolyte

[0068] Mix the first and second solvents as shown in Table 1 in the specified proportions, add the corresponding lithium salts to achieve the lithium salt concentrations shown in Table 1, and finally add the additives. Stir at room temperature for 12 hours before use.

[0069] Table 1 Electrolyte Formulation

[0070] Preparation of positive electrode

[0071] The positive electrode active material NCM811, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 93:4:3, and then dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) to obtain the positive electrode slurry. The obtained slurry is uniformly coated on both sides of an aluminum foil, and after drying, calendering, and vacuum drying, aluminum leads are welded on using an ultrasonic welding machine to obtain the positive electrode sheet with a thickness between 120-150 μm.

[0072] Preparation of negative electrode

[0073] The negative electrode uses a lithium metal negative electrode.

[0074] Cell manufacturing

[0075] A ceramic-coated separator with a thickness of 6 μm is placed between the positive and negative electrode sheets prepared above. Then, the sandwich structure consisting of the positive electrode sheet, negative electrode sheet and separator is stacked and packaged with aluminum-plastic film to produce a soft-pack battery cell with a capacity of 1Ah ready for liquid injection.

[0076] The cells are injected with electrolyte and formed to obtain lithium batteries.

[0077] Performance testing

[0078] The following performance tests were performed on the batteries prepared in Examples 1-11 and Comparative Examples 1-3:

[0079] (1) Electrolyte oxidation potential test: The oxidation potential of the electrolyte membrane was tested using the linear scanning potential method and an EC-Lab electrochemical workstation. The test voltage range was 2.5–6 V, and the scan rate was 1 mV·s. -1 The method uses a 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.

[0080] (2) Electrolyte-membrane composite system conductivity test: The ionic conductivity of the electrolyte membrane was determined by electrochemical impedance spectroscopy (EIS). The battery was assembled into a stainless steel sheet | membrane | stainless steel sheet structure. The test was conducted using an EC-Lab electrochemical workstation with a frequency range of 100kHz to 10mHz, an oscillation voltage of 5mV, and a test temperature of 25±3℃. The ionic conductivity was calculated using the following formula: σ=l / RA

[0081] l is the thickness of the electrolyte membrane (cm), R is the impedance value of the electrolyte membrane measured by EIS (Ω), and A is the effective contact area between the stainless steel sheet and the electrolyte membrane (cm²). 2 ).

[0082] (3) Cell cycle performance test: The battery was tested in a voltage range of 3.0V to 4.3V and a temperature of 25℃, using a 0.5C / 0.5D cycle charge and discharge test. The capacity retention rate of the battery was recorded after 100 cycles.

[0083] The test results are shown in Table 2.

[0084] Table 2 Electrochemical performance of lithium batteries

[0085] As can be seen from Table 2, the experimental results above show that the amide and ether solvents provided in this embodiment synergistically optimize the solvation structure of the electrolyte, effectively improving the ionic conductivity and oxidation stability of the electrolyte system. Under the action of appropriate additives within the range provided in this embodiment, the cycle life of the battery system is effectively improved.

[0086] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrolyte, characterized in that, include: First solvent; The first solvent includes amide solvents and / or sulfonamide solvents; The second solvent; the second solvent includes linear ethers and / or cyclic ethers; Lithium salts and additives.

2. The electrolyte as described in claim 1, characterized in that, The amide solvents include at least one of 2,2,2-trifluoro-N,N-dimethylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-dimethylpropionamide, formamide, N,N-diethylacetamide, N,N-dimethylisobutyramide, N,N-diethylacetylacetamide, N-methyl-N-vinylacetamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide.

3. The electrolyte as described in claim 1, characterized in that, The sulfonamide solvents have structures as shown in Formula I and / or Formula II; R1 is a fluorinated alkyl group with 1 to 8 carbon atoms; R2, R3, and R4 are one of pyrrolidinyl, piperidinyl, or linear alkyl groups having 1 to 10 carbon atoms; or R3 and R4 are one of pyrrolidinyl or piperidinyl.

4. The electrolyte as described in claim 3, characterized in that, The sulfonamide solvents include at least one of N,N-dimethyltrifluoromethanesulfonamide, 1-((trifluoromethyl)sulfonyl)piperidine, N-methyltrifluoromethanesulfonamide, N,N-diethyl-1,1,1-trifluoromethanesulfonamide, 1,1-difluoro-N,N-dimethylmethanesulfonamide, and 1,1-difluoro-N-methylmethanesulfonamide.

5. The electrolyte as described in claim 1, characterized in that, The second solvent includes at least one of 2-dimethoxyethane, ethylene glycol dimethyl ether, dimethoxydimethyl ether, diethylene glycol dimethyl ether, 1,3-dioxocyclopentane, triethylene glycol monoethyl ether, tetrahydrofuran, and 2-methyl-tetrahydrofuran.

6. The electrolyte as described in claim 1, characterized in that, The lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, lithium trifluoromethanesulfonyl-perfluorobutylsulfonylimide, lithium fluorosulfonyl-perfluorobutylsulfonylimide, lithium bis(oxalatoborate), and lithium difluorophosphate.

7. The electrolyte as described in claim 1, characterized in that, The additives include at least one of fluoroethylene carbonate, 1,3-propane sulpholol, vinylene carbonate, vinyl sulfate, lithium nitrate, lithium borate, lithium difluorooxalate borate, and lithium difluoro(bis(oxalate) phosphate).

8. The electrolyte as described in claim 7, characterized in that, The additives include at least one of lithium nitrate, lithium borate, lithium difluorooxalate borate, and lithium difluoro(bis(oxalate) phosphate).

9. The electrolyte as described in claim 1, characterized in that, The volume ratio of the first solvent to the second solvent is (0.5–9.5):(0.5–9.5).

10. The electrolyte as described in claim 1, characterized in that, The concentration of the lithium salt in the electrolyte is 0.5 mol / L to 3 mol / L.

11. The electrolyte as described in claim 1, characterized in that, The amount of the additive is 0.01 wt% to 10 wt% of the sum of the masses of the first solvent and the second solvent.

12. A battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte as described in any one of claims 1 to 11.

13. The battery as claimed in claim 12, characterized in that, The positive electrode includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, ternary materials, lithium-rich manganese-based materials, lithium nickel manganese oxide, and lithium vanadium oxide phosphate.

14. The battery as claimed in claim 12, characterized in that, The negative electrode includes at least one of graphite negative electrode, silicon-oxygen negative electrode, silicon-carbon negative electrode, silicon negative electrode, tin negative electrode, tin oxide negative electrode, tin alloy negative electrode, lithium metal negative electrode, lithium alloy negative electrode and lithium-free negative electrode.

15. The battery as claimed in claim 12, characterized in that, The diaphragm includes at least one of polypropylene, polyethylene, PP / PE / PP composite membrane, polyvinylidene fluoride, polyacrylonitrile, ceramic diaphragm, ceramic polyamide, aramid, and nonwoven fabric.

16. A battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte; the electrolyte includes the electrolyte as described in any one of claims 1 to 11; the content of the electrolyte in the electrolyte is 0.5 wt.% to 50 wt.%.

17. The battery as claimed in claim 16, characterized in that, The electrolyte is a gel electrolyte or a solid electrolyte; the solid electrolyte is an inorganic solid electrolyte, a polymer solid electrolyte, or a composite solid electrolyte.

18. An electrical appliance, characterized in that, The battery described in any one of claims 12 to 17 is used as the power source.

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