Electrolyte additive, electrolyte, and battery

Abstract

The application discloses an electrolyte additive, an electrolyte and a battery, the electrolyte additive comprising a first additive and a second additive, the first additive comprising a compound shown in formula 1: wherein R1 and R2 are each independently selected from at least one of H, a phenyl group, a halogen, a C1-C6 hydrocarbon group, a C1-C6 halogenated hydrocarbon group, wherein R1 and R2 are not H at the same time; R3, R4 and R5 are each independently selected from at least one of a C1-C3 hydrocarbyl group, an oxygen atom, O=S=O, C=O and S=O, at least one of R3, R4 and R5 is selected from O=S=O, C=O and S=O, and at least one of R3, R4 and R5 is selected from an oxygen atom; and the second additive comprising a compound shown in formula 2: thereby, adding the electrolyte additive to the electrolyte of the battery can improve the fast-charging performance of the battery and can improve the high-temperature cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular, to an electrolyte additive, an electrolyte and a battery. BACKGROUND

[0002] With the development of new energy vehicles, consumers' demand for power supply and energy storage is also increasing day by day. Secondary batteries such as lithium ion batteries and sodium ion batteries gradually replace traditional batteries such as lead-acid batteries and are widely used in the fields of electronics, new energy vehicles and energy storage. Although lithium ion batteries have been successful in commerce, the fast charging performance and service life of lithium ion batteries still need to be further improved to meet the fast charging and long endurance needs of users.

[0003] The electrolyte, as an important component of the secondary battery, plays a key role in improving performance. However, the current high energy density battery has a rapid temperature rise inside the battery during fast charging cycle, which deteriorates the rate charging performance of the battery, and the battery performance decays faster under high temperature cycle conditions, thereby affecting the service life of the battery.

[0004] Therefore, there is an urgent need to develop a battery with high rate charging performance and excellent high temperature cycle performance. SUMMARY

[0005] The present application aims to at least partially alleviate or solve at least one of the above-mentioned problems.

[0006] In one aspect of the present application, an electrolyte additive is provided. In some embodiments of the present application, the electrolyte additive comprises a first additive and a second additive, the first additive comprising a compound represented by Formula 1:

[0007]

[0008] wherein R1 and R2 are each independently selected from H, phenyl, halogen, C1-C6 hydrocarbyl, C1-C6 halogenated hydrocarbyl, at least one of R1 and R2 is not H; R3, R4 and R5 are each independently selected from at least one of C1-C3 hydrocarbylene, oxygen atom, O=S=O, C=O and S=O, at least one of R3, R4 and R5 is selected from O=S=O, C=O and S=O, and at least one of R3, R4 and R5 is selected from oxygen atom;

[0009] the second additive comprising a compound represented by Formula 2:

[0010] Therefore, by adding the above-mentioned electrolyte additive to the electrolyte of the battery, the fast charging performance of the battery can be improved, and the high temperature cycle performance can be improved.

[0011] In some embodiments of the present application, the first additive comprises at least one of the following substances:

[0012]

[0013] The first additive described above can preferentially form a good SEI film on the negative electrode by being reduced, thereby inhibiting the co-intercalation and reduction of solvent molecules on the negative electrode, and can preferentially form a good CEI film on the positive electrode by being oxidized, thereby inhibiting the oxidative decomposition of electrolyte components on the positive electrode, thereby inhibiting the reaction of the electrolyte at the interface, and in particular, reducing the degree of exacerbation of the reaction induced under high temperature conditions.

[0014] In some embodiments of the present application, the mass ratio of the first additive to the second additive in the electrolyte additive is (0.25-10):1. Thereby, the fast charging performance and high temperature cycle performance of the battery can be further improved.

[0015] In another aspect of the present application, the present application provides an electrolyte. In some embodiments of the present application, the electrolyte comprises the electrolyte additive described above. Thereby, the electrolyte has all the features and advantages of the electrolyte additive described above, which will not be repeated here. In general, when the electrolyte is used in a battery, the increase in battery impedance during the cycle process can be inhibited, and the fast charging performance and high temperature cycle performance of the battery can be improved.

[0016] In some embodiments of the present application, the mass fraction of the first additive based on the total mass of the electrolyte is 0.1%-5%, which can be optionally 0.5%-2%. The first additive in the above amount can form a SEI film and a CEI film with excellent quality, and can more effectively slow down the interface reaction, thereby effectively improving the high temperature cycle performance of the battery.

[0017] In some embodiments of the present application, the mass fraction of the second additive based on the total mass of the electrolyte is 0.1%-3%, which can be optionally 0.2%-2%. The second additive in the above amount can effectively reduce the initial impedance of the battery and inhibit the increase in battery impedance during the cycle process, thereby improving the fast charging performance of the battery.

[0018] In some embodiments of the present application, the electrolyte further comprises a solvent and an electrolyte salt, the mass fraction of the electrolyte salt based on the total mass of the electrolyte is 12%-18%, which can be optionally 12%-16%, and the mass fraction of the solvent based on the total mass of the electrolyte is 69%-87.2%. The content of the solvent and the electrolyte salt meets the above conditions, which is beneficial to improve the overall performance of the battery.

[0019] In some embodiments of the present application, the solvent comprises at least one of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl propionate, propyl propionate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate. The above-mentioned solvent can maintain good stability during the charge and discharge cycle, which is conducive to improving the fast charging and high-temperature cycle performance of the battery.

[0020] In some embodiments of the present application, the electrolyte further comprises a third additive, the third additive comprises at least one of a high-temperature additive, a negative electrode film-forming additive, and a water and acid removal additive, and the mass fraction of the third additive is 0.1%-5%. Thus, it is conducive to further improving the fast charging and high-temperature cycle performance of the battery.

[0021] In some embodiments of the present application, the high-temperature additive comprises at least one of 1,3-propane sultone, 1,3-propene sulfonic acid lactone, ethylene sulfate, ethylene sulfite, and tetra-vinyl silane.

[0022] In some embodiments of the present application, the negative electrode film-forming additive comprises at least one of vinylene carbonate and vinyl ethylene carbonate.

[0023] In some embodiments of the present application, the water and acid removal additive comprises at least one of tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, and tris-(vinyl dimethylsilyl)phosphate. Thus, it is conducive to further improving the fast charging and high-temperature cycle performance of the battery.

[0024] In another aspect of the present application, the present application provides a battery. In some embodiments of the present application, the battery comprises the electrolyte described above. Thus, the battery has all the features and advantages of the electrolyte described above, which will not be repeated here.

[0025] In some embodiments of the present application, the battery is a lithium ion battery.

[0026] In some embodiments of the present application, the electrolyte salt in the electrolyte of the lithium ion battery comprises at least one of lithium hexafluorophosphate and lithium bisfluorosulfonylimide.

[0027] In some embodiments of the present application, the electrolyte of the lithium ion battery further comprises a lithium salt additive, and the lithium salt additive comprises at least one of lithium bis-oxalate borate, lithium difluoro-oxalate borate, lithium difluoro-di-oxalate phosphate, lithium tetrafluoroborate, lithium tetrafluoro-oxalate phosphate, lithium bis-trifluoromethylsulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium difluorophosphate.

[0028] In some embodiments of the present application, the lithium ion battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer on at least one surface of the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises LiNi 0.5 Mn 1.5 O4, LiMn2O4, Li 1+a Mn 1-x M 1 x O2, LiCo 1- y M 2 y O2, LiFe 1-z M 3 z PO4, Li2Mn 1-b O4, M 1 , M 2 , M 3 each independently comprises one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, F, 0≤a<0.2, 0≤x<1, 0≤y<1, 0≤z<1, 0≤b<1.

[0029] In some embodiments of the present application, the battery is a sodium ion battery.

[0030] In some embodiments of the present application, the electrolyte salt in the electrolyte of the sodium ion battery comprises at least one of sodium hexafluorophosphate, sodium bisfluorosulfonylimide.

[0031] In some embodiments of the present application, the electrolyte of the sodium ion battery further comprises a sodium salt additive, the sodium salt additive comprises at least one of sodium bisoxalate borate, sodium difluoro oxalate borate, sodium tetrafluoroborate, sodium difluorophosphate. DETAILED DESCRIPTION

[0032] Embodiments of the present application are described in detail below, 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.

[0033] In one aspect of the present application, the present application proposes an electrolyte additive. In some embodiments of the present application, the electrolyte additive can comprise a first additive and a second additive. The first additive can comprise a compound shown in Formula 1: Formula 1, wherein R1and R2are each independently selected from H, phenyl, halogen, C1-C6 hydrocarbon group, C1-C6 halogenated hydrocarbon group, at least one of C1-C3 alkylene, an oxygen atom, O=S=O, C=O and S=O, at least one of R3, R4 and R5 is selected from O=S=O, C=O and S=O, and at least one of R3, R4 and R5 is selected from an oxygen atom.

[0034] The second additive can include a compound shown in Formula 2:

[0035] For lithium ion batteries, the second additive can effectively improve the film-forming components of SEI and CEI. Due to the structure containing elements such as F, P and S, inorganic components such as LiF, LiSO3 and P=O anion groups can be formed during the film-forming stage, which can effectively reduce the initial impedance of the battery and inhibit the increase of impedance during the cycle process, improve the conduction rate of lithium ions in SEI and CEI, and thus improve the fast charging performance of the battery. However, due to the large amount of inorganic components in the interface film formed by the second additive, the film-forming stability may be affected under high temperature cycling, so the addition of the first additive can effectively improve the film-forming components and improve the high temperature stability of the film. The first additive has a lower LUMO (lowest unoccupied molecular orbital) energy level, which can be preferentially reduced on the negative electrode side to form a good SEI (solid electrolyte film), thereby inhibiting the co-intercalation and reduction of solvent molecules on the negative electrode. At the same time, the first additive has a higher HOMO (highest occupied molecular orbital) energy level, which can be preferentially oxidized on the positive electrode side to form a good CEI (positive electrode-electrolyte interface film). The formed ROSO3Li / ROSO2Li, Li2SO4 / Li2SO3 replace lithium alkyl carbonate as the main component of SEI and CEI, so that the toughness of the interface film is improved, and the structure remains relatively stable at high temperature, thereby improving the high temperature cycle performance of the battery.

[0036] The mechanism of the first additive and the second additive to improve the fast charging performance and the high temperature cycle performance of the lithium ion battery is described in detail above. The electrolyte additive containing the first additive and the second additive added to the sodium ion battery electrolyte can also improve the fast charging performance and the high temperature cycle performance of the sodium ion battery, and the mechanism is similar to that of the lithium ion battery, which will not be described here.

[0037] In some embodiments of the present application, the first additive can include at least one of the following substances:

[0038]

[0039] In some embodiments, the second additive can be The second additive can effectively improve the film-forming components of the SEI film and the CEI film, increase the content of inorganic small molecules, thereby reducing the initial impedance of the battery and inhibiting the increase of the impedance of the battery during the cycle process, and improving the fast-charging performance of the battery.

[0040] In some embodiments of the present application, the mass ratio of the first additive to the second additive in the electrolyte additive can be (0.25-10):1, for example, the mass ratio of the first additive to the second additive can be 0.25:1, 0.5:1, 1:1, 3:1, 5:1, 8:1, 10:1, etc. Thus, the initial impedance of the battery can be further reduced and the impedance increase during the cycle process can be inhibited, and the fast-charging performance and high-temperature cycle performance of the battery can be improved.

[0041] In another aspect of the present application, the present application provides an electrolyte. In some embodiments of the present application, the electrolyte can include the electrolyte additive described above. Thus, the electrolyte has all the features and advantages of the electrolyte additive described above, which will not be repeated here.

[0042] In some embodiments of the present application, the mass fraction of the first additive based on the total mass of the electrolyte can be 0.1%-5%, i.e., 0.1g-5g of the first additive is included in 100g of the electrolyte. Specifically, the mass fraction of the first additive can be selected from 0.1%, 0.2%, 0.5%, 1%, 3%, 5%, or a range consisting of any two of them. The film-forming quality can be effectively improved, and the high-temperature stability of SEI and CEI can be improved, thereby improving the high-temperature cycle performance.

[0043] In some embodiments of the present application, the mass fraction of the first additive based on the total mass of the electrolyte can be 0.5%-2%, for example, the mass fraction of the first additive can be 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.7%, or 2%. Thus, the film-forming quality can be significantly improved, and the high-temperature cycle performance of the battery can be improved. If the content of the first additive is lower than this range, the film-forming effect is not obvious, and the high-temperature cycle performance is not obvious. Higher than this range can cause the impedance of the battery to increase too much, affecting the fast-charging performance of the battery.

[0044] In some embodiments of the present application, the mass percentage of the second additive can be 0.1%-3% based on the total mass of the electrolyte, i.e. 0.1g-3g of the second additive is included in 100g of the electrolyte, and specifically, the mass percentage of the second additive can be selected from 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% or a range consisting of any two of them. In this way, the impedance can be reduced, and the fast charging performance of the battery can be improved. If the content of the second additive is lower than this range, the effect of improving the impedance is not obvious, and the fast charging performance is not obviously improved. If the content of the second additive is higher than this range, it can cause adverse effects, and the impedance can be negatively affected.

[0045] In some embodiments of the present application, the mass percentage of the second additive can be 0.2%-2% based on the total mass of the electrolyte, for example, the mass percentage of the second additive can be 0.2%, 0.3%, 0.5%, 0.8%, 1.0%, 1.3%, 1.4%, 1.7% or 2%. The impedance of the battery can be significantly reduced, and the fast charging performance of the battery can be significantly improved.

[0046] In some embodiments of the present application, the electrolyte can further include a solvent, and the mass percentage of the solvent can be 50%-85% based on the total mass of the electrolyte, for example, the mass percentage of the solvent can be 50%, 55%, 60%, 65%, 70%, 75%, 80% or 85%.

[0047] In some embodiments of the present application, the solvent can include at least one of ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethyl propionate, propyl propionate, methyl acetate, ethyl acetate, propyl acetate, and methyl propionate. In some embodiments of the present application, the solvent can include at least two of the above-mentioned solvents.

[0048] In some embodiments of the present application, the electrolyte can further include an electrolyte salt, and the mass percentage of the electrolyte salt can be 12%-18% based on the total mass of the electrolyte, i.e. 12g-18g of the electrolyte salt is included in 100g of the electrolyte, and specifically, the mass percentage of the electrolyte salt can be selected from 12%, 13%, 14%, 15%, 16%, 17%, 18% or a range consisting of any two of them.

[0049] In some embodiments of the present application, the mass percentage of the electrolyte salt can be 12%-16% based on the total mass of the electrolyte.

[0050] In some other embodiments of the present application, the electrolyte can further include a third additive, and the third additive can include at least one of a high-temperature additive, a negative electrode film-forming additive, and a water and acid removal additive.

[0051] In some embodiments of the present application, the mass percentage of the third additive can be 0.1%-5% based on the total mass of the electrolyte, for example, the mass percentage of the third additive can be 0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 4% or 5%. The content of the third additive in the above range is beneficial to further improve the high-temperature cycle performance of the battery.

[0052] In some embodiments of the present application, the high-temperature additive can include at least one of 1,3-propane sultone, 1,3-propene sultone, ethylene sulfate, ethylene sulfite, tetraethenylsilane. The above-mentioned additives can form organic components such as lithium alkyl sulfonate and silane on the negative electrode sheet, improve the high-temperature stability of the SEI film, and thus improve the high-temperature cycle performance of the battery.

[0053] In some embodiments of the present application, the negative electrode film-forming additive can include at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate. The above-mentioned additives can be reduced to form SEI film on the negative electrode prior to solvent molecules, thereby further inhibiting the co-intercalation and reduction of solvent molecules on the negative electrode, and thus more effectively avoiding the generation of reducing gas.

[0054] In some embodiments of the present application, the water and acid removal additive can include at least one of tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, and tris-(vinyl dimethylsilyl)phosphate. It can react with trace water in the battery to reduce the generation of HF and inhibit the interface side reaction triggered by moisture and HF.

[0055] In another aspect of the present application, the present application provides a battery. In some embodiments of the present application, the battery can include the electrolyte described above. Thus, the battery has good fast charging performance and high-temperature cycle performance.

[0056] In some embodiments of the present application, the battery can be a lithium ion battery.

[0057] In some embodiments of the present application, the electrolyte salt in the electrolyte of the lithium ion battery can include at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide.

[0058] In some embodiments of the present application, the electrolyte of the lithium ion battery can further include a lithium salt additive, and the lithium salt additive can include at least one of lithium bisoxalate borate, lithium difluoro oxalate borate, lithium difluoro di-oxalate phosphate, lithium tetrafluoroborate, lithium tetrafluoro oxalate phosphate, lithium bis-trifluoromethyl sulfonimide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate.

[0059] In some embodiments of the application, the lithium-ion battery can include a positive electrode sheet, the positive electrode sheet can include a positive electrode current collector and a positive electrode active material layer on at least one surface of the positive electrode current collector, the positive electrode active material layer can include a positive electrode active material, and the positive electrode active material can include LiNi 0.5 Mn 1.5 O4, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4. 1+a Mn 1-x M 1 x O2, LiCo 1-y M 2 y O2, LiFe 1-z M 3 z PO4, Li2Mn 1-b O4, M 1 , M 2 , M 3 each independently includes one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, F, 0≤a<0.2, 0≤x<1, 0≤y<1, 0≤z<1, 0≤b<1.

[0060] In some embodiments, 0≤a≤0.19, 0.05≤a≤0.15, 0.08≤a≤0.13, or 0.1≤a≤0.12.

[0061] In some embodiments, 0≤x≤0.9, 0.1≤x≤0.8, 0.2≤x≤0.7, 0.3≤x≤0.6, or 0.4≤x≤0.5.

[0062] In some embodiments, 0≤y≤0.9, 0.1≤y≤0.8, 0.2≤y≤0.7, 0.3≤y≤0.6, or 0.4≤y≤0.5.

[0063] In some embodiments, 0≤z≤0.9, 0.1≤z≤0.8, 0.2≤z≤0.7, 0.3≤z≤0.6, or 0.4≤z≤0.5.

[0064] In some embodiments, 0≤b≤0.9, 0.1≤b≤0.8, 0.2≤b≤0.7, 0.3≤b≤0.6, or 0.4≤b≤0.5.

[0065] In some embodiments of the application, the positive electrode active material of the lithium-ion battery can include NCM, LiNi 0.5 Mn 1.5 O4, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4.

[0066] In some embodiments of the present invention, the battery may be a sodium-ion battery.

[0067] The electrolyte salt in the electrolyte of a sodium-ion battery may include at least one of sodium hexafluorophosphate and sodium difluorosulfonamide.

[0068] In some embodiments of the present invention, the electrolyte of the sodium-ion battery may further include sodium salt additives, which may include at least one of sodium bis(oxalateborate), sodium difluorooxalateborate, sodium tetrafluoroborate, and sodium difluorophosphate.

[0069] In some embodiments of the present invention, the sodium-ion battery may include a positive electrode sheet, which may include a positive current collector and a positive active material layer located on at least one surface of the positive current collector. The positive active material layer includes a positive active material, which may include a polyanionic material Na+. c M 4 d (X 1 e O f )X 2 g M 4 X is a transition metal. 1 For phosphorus, sulfur, silicon, tungsten, etc., X 2 It is at least one of F, OH, etc. In some specific embodiments, the positive electrode active material may include Na4Fe3(PO4)2(P2O7).

[0070] In some embodiments of the present invention, the battery may include a positive electrode, a negative electrode, a separator, and the electrolyte described above. During the charging and discharging process, active ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor of ions between the positive and negative electrode. The separator is disposed between the positive and negative electrode, primarily to prevent short circuits between the positive and negative electrodes, while simultaneously allowing ions to pass through.

[0071] In some embodiments of the present invention, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil. The composite positive electrode current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. For example, the composite negative electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0072] In some embodiments of the application, the positive active material layer of the positive electrode tab 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.

[0073] In some embodiments of the 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.

[0074] In some embodiments of the application, the positive electrode tab can be prepared by dispersing the positive active material, the conductive agent, and the binder in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive current collector, and then drying, cold-pressing, and the like to obtain the positive electrode tab.

[0075] In some embodiments of the application, the negative electrode tab can include a negative current collector and a negative active material layer on at least one surface of the negative current collector, and the negative active material layer can include a negative active material.

[0076] In some embodiments of the application, the negative current collector can be a metal foil or a composite current collector. For example, as an example, the metal foil can be a copper foil. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (e.g., a polypropylene (PP) substrate, a polyethylene terephthalate (PET) substrate, a polybutylene terephthalate (PBT) substrate, etc.).

[0077] In some embodiments of the application, the negative active material can be a negative active material known in the art for use in a battery. As an example, the negative active material can include at least one of graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate, etc. Among them, the silicon-based material can include at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy; the tin-based material can include at least one of elemental tin, a tin oxide compound, and a tin alloy.

[0078] In some embodiments of the present application, the negative active material layer can optionally further include a binder, which 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).

[0079] In some embodiments of the present application, the negative active material layer can optionally further include a conductive agent, which can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0080] In some embodiments of the present application, the negative active material layer can optionally further include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0081] In some embodiments of the present application, the negative electrode sheet can be prepared by dispersing the negative active material, the conductive agent, the binder, and any other components (e.g., thickening agents) in a solvent (e.g., deionized water) to form a negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector, and then performing processes such as drying, cold pressing, and the like to obtain the negative electrode sheet.

[0082] In the present application, the type of the separation film is not particularly limited, and any known porous structure separation film with good chemical stability and mechanical stability can be selected by those skilled in the art according to actual needs.

[0083] In some embodiments of the present application, the material of the separation film can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride.

[0084] In some embodiments of the present application, the thickness of the separation film can be 10 μm-12 μm, for example, 10 μm, 11 μm, 12 μm, and the like.

[0085] The battery proposed in the present application can be used in an electrical device or an energy storage device, thereby the electrical device or the energy storage device has a longer service life and good high temperature resistance. In some embodiments of the present application, the electrical device can include, but is not limited to, a mobile phone, a notebook computer, a pure electric vehicle, a hybrid electric vehicle, and the like.

[0086] The present application is illustrated below by specific examples, and those skilled in the art can understand that the specific examples below are only for illustrative purposes, and do not limit the scope of the present application in any way. In addition, in the following examples, unless otherwise specified, the materials and equipment used are commercially available. If the specific processing conditions and processing methods are not explicitly described in the following examples, the conditions and methods known in the art can be used for processing.

[0087] Example 1

[0088] 1. Preparation of positive electrode sheet

[0089] The positive electrode active material NCM613 (molar ratio of Ni, Co, and Mn in ternary material is 6:1:3), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were added to N-methyl pyrrolidone (NMP) in a mass ratio of 96:2:2 to prepare a positive electrode slurry (the solid content in the positive electrode slurry is 68wt%, i.e., the mass content of solids in the positive electrode slurry is 68%). The positive electrode slurry was coated on the upper and lower surfaces of an aluminum foil, dried, and then cold-pressed. After edge cutting, sheet cutting, and striping, a positive electrode sheet was prepared.

[0090] 2. Preparation of negative electrode sheet

[0091] The negative electrode active material graphite, conductive agent conductive carbon black, thickening agent carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) were added to deionized water in a mass ratio of 95:1.5:1.5:2 to prepare a negative electrode slurry (the solid content in the negative electrode slurry is 49wt%). The negative electrode slurry was coated on the upper and lower surfaces of a copper foil and dried, and then cold-pressed, edge-cut, sheet-cut, and striped to prepare a negative electrode sheet.

[0092] 3. Preparation of electrolyte

[0093] In a high-purity argon glove box with oxygen content and water content not higher than 0.1 ppm, electrolyte additives including a first additive and a second additive were added to an organic solvent (in the organic solvent, the mass ratio of ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) is EC:DMC:EMC=3:3:4), mixed uniformly, and then lithium hexafluorophosphate (LiPF6) was slowly added (based on the total mass of the electrolyte, the mass ratio of LiPF6 is 13%). After the lithium salt was completely dissolved, an electrolyte was obtained.

[0094] 4. Separation film

[0095] A polyethylene film with a thickness of 10 μm was used as a separation film.

[0096] 5. Preparation of lithium ion battery

[0097] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet, to separate the positive electrode sheet and the negative electrode sheet, to obtain a bare battery cell, to weld the tabs, to place the bare battery cell in an outer package, to inject the electrolyte prepared above into the dried battery cell, and to complete the preparation of the lithium ion battery through packaging, standing, formation, shaping, and other steps.

[0098] The differences between Examples 2-16, Comparative Examples 1 and 2, and Example 1 are recorded in Table 1, and the remaining parameters and steps remain the same as in Example 1.

[0099] Example 17

[0100] 1. Electrolyte preparation: EC and EMC are mixed in a mass ratio of 3:7, and after mixing, sodium hexafluorophosphate (NaPF6), the first additive, and the second additive are added according to the mass fraction of each component. After uniform mixing, the electrolyte is obtained.

[0101] 2. Positive electrode sheet preparation: Na4Fe3(PO4)2(P2O7) (abbreviated as NFPP) positive electrode material, conductive agent Super P (conductive carbon black), carbon nanotube, and adhesive PVDF (polyvinylidene fluoride) are added to N-methylpyrrolidone in a mass ratio of 94.5:2.5:0.5:2.5 and mixed uniformly. After vacuum stirring to a certain viscosity and uniform flowability, the slurry is uniformly coated on both sides of the aluminum foil. After drying at 85°C, cold pressing, edge cutting, sheet cutting, striping, and vacuum drying at 85°C for 10 hours, the positive electrode sheet with a surface density of 33 mg / cm 2 is obtained after welding the tabs.

[0102] 3. Negative electrode sheet preparation: hard carbon negative electrode material, conductive agent Super P (conductive carbon black), thickening agent CMC (sodium carboxymethyl cellulose), and adhesive SBR (styrene-butadiene rubber) are added to deionized water in a mass ratio of 95:1.5:2.0:1.5, and the mixture is thoroughly mixed into a uniform slurry. After coating on both sides of the aluminum foil, drying at 85°C, cold pressing, edge cutting, sheet cutting, and striping, the negative electrode sheet with a surface density of 14.2 mg / cm 2 is obtained after vacuum drying at 85°C for 12 hours and welding the tabs.

[0103] 4. Separator: a 9μm thick polyethylene porous polymer film is used as the base material, and a 2μm adhesive coating is applied to both sides of the base material.

[0104] 5. Sodium ion battery preparation:

[0105] The positive electrode sheet, the separator and the negative electrode sheet are sequentially stacked and then subjected to a winding process to produce a bare cell having a theoretical capacity of 1000 mAh. The bare cell is placed in an outer packaging aluminum foil, vacuum baked at 75°C for 10 hours, and then the above-mentioned electrolyte is injected. After vacuum packaging, standing, formation, aging, and capacity distribution, the sodium ion battery is completed.

[0106] The differences between Examples 18-20, Comparative Examples 3 and 4, and Example 17 are recorded in Table 1. The remaining parameters and steps are consistent with Example 17.

[0107] Table 1

[0108]

[0109]

[0110] The batteries of each example and comparative example were tested, including direct current impedance, fast charging performance, high temperature cycle performance, etc., and the test results are recorded in Table 2. The test methods for lithium ion batteries are as follows:

[0111] Test method of direct current impedance (DCR): at 25°C, 1C constant current and constant voltage charging to 4.4V full charge, cutoff current 0.05C, 1C constant current discharging to 50% SOC for 30min, standing for 60min, recording the last voltage data point V1, 7C constant current discharging for 10S, recording the last voltage data point V2, the DCR of 7C constant current discharging for 10S is calculated as follows: DCR=(V1-V2) / 7C.

[0112] Test method of fast charging cycle performance: at 25°C, 5C constant current and constant voltage charging to 4.4V, standing for 5min, then 1C constant current discharging to 2.75V, calculating the capacity retention rate after 500 cycles, the calculation method is as follows: capacity retention rate (%)=(500th discharge capacity / 1st discharge capacity) x 100%.

[0113] Test method of high temperature cycle performance: at 45°C, 1C constant current and constant voltage charging to 4.4V, standing for 5min, then 1C constant current discharging to 2.75V, calculating the capacity retention rate after 500 cycles, the calculation method is as follows: capacity retention rate (%)=(500th discharge capacity / 1st discharge capacity) x 100%.

[0114] The test methods for sodium ion batteries are as follows:

[0115] The test method of direct current resistance (DCR) is as follows: at 25℃, 1C constant current and constant voltage charging to 3.6V full charge, the cutoff current is 0.05C, discharging at 1C constant current for 30min to 50% SOC, after standing for 60min, recording the last voltage data point V1, discharging at 2C constant current for 10S, recording the last voltage data point V2, the calculation method of DCR of discharging at 2C constant current for 10S is: DCR=(V1-V2) / 2C.

[0116] The test method of fast charging cycle performance is as follows: at 25℃, charging to 3.6V by 5C constant current and constant voltage, after standing for 5min, discharging to 1.5V by 2C constant current, after 500 cycles, the capacity retention rate is calculated, the calculation method is: capacity retention rate (%)=(the 500th discharge capacity / the 1st discharge capacity)×100%.

[0117] The test method of high temperature cycle performance is as follows: at 45℃, charging to 3.6V by 1C constant current and constant voltage, after standing for 5min, discharging to 1.5V by 1C constant current, after 500 cycles, the capacity retention rate is calculated, the calculation method is: capacity retention rate (%)=(the 500th discharge capacity / the 1st discharge capacity)×100%.

[0118] Table 2

[0119]

[0120]

[0121] For lithium ion batteries, from table 1 and table 2, it can be seen that the fast charging performance and high temperature cycle performance of lithium ion batteries are poor in the electrolyte of comparative example 1 and comparative example 2, only adding the first additive or the second additive; compared with example 1, example 2, example 6, example 7 and example 13, the content of the first additive and the second additive in example 3-5 and example 8-12 is more appropriate, and the fast charging performance and high temperature cycle performance are also more excellent; in example 14-16, the first additive and the second additive are added, and the third additive is also added, and the battery has excellent fast charging performance and high temperature cycle performance.

[0122] For sodium ion batteries, from table 1 and table 2, it can be seen that the direct current resistance of sodium ion batteries in comparative example 3 and comparative example 4 is larger, and the fast charging performance and high temperature cycle performance are poor in the electrolyte of comparative example 3 and comparative example 4, only adding the first additive or the second additive, compared with example 17-20. Therefore, it can be known that the direct current resistance of sodium ion battery can be reduced, and the fast charging performance and high temperature cycle performance of sodium ion battery can be improved by adding the first additive and the second additive in the electrolyte at the same time.

[0123] In the description of the specification, the description of the terms "some embodiments", "other embodiments", and the like are intended to indicate that the specific features, structures, materials, or characteristics described in connection with the embodiments are included in at least one embodiment of the application. Illustrative expressions of the above terms in the specification do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in one or more embodiments or examples. Furthermore, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples, without contradiction. In addition, it should be noted that in the specification, the terms "first", "second" are for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated.

[0124] Although the embodiments of the application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the application, and that those ordinarily skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the application.

Claims

1. An electrolyte additive characterized in that, comprising a first additive and a second additive, the first additive comprising a compound represented by Formula 1: Formula 1, wherein R1and R2are each independently selected from at least one of H, phenyl, halogen, C1-C6alkyl, C1-C6haloalkyl, , and R1and R2are not simultaneously H; R3, R4, and R5are each independently selected from at least one of C1-C3alkylene, an oxygen atom, O=S=O, C=O, and S=O, at least one of R3, R4, and R5is selected from O=S=O, C=O, and S=O, at least one of R3, R4, and R5is selected from an oxygen atom; The second additive comprises a compound shown in Formula 2: Formula 2; The mass percentage of the first additive in the electrolyte is 0.1%-5%, and the mass percentage of the second additive in the electrolyte is 0.1%-3%.

2. The electrolyte additive according to claim 1, characterized in that The first additive comprises at least one of the following substances: Formula 1-1, Formula 1-2, Formula 1-3, Formula 1-4.

3. The electrolyte additive according to claim 1 or 2, characterized in that, The mass ratio of the first additive to the second additive in the electrolyte additive is (0.25-10):

1.

4. An electrolyte, characterized by The electrolyte additive comprises the electrolyte additive according to any one of claims 1-3.

5. The electrolyte according to claim 4, characterized in that The mass percentage of the first additive in the electrolyte is 0.5%-2% based on the total mass of the electrolyte.

6. The electrolyte of claim 4, wherein, The mass percentage of the second additive in the electrolyte is 0.2%-2% based on the total mass of the electrolyte.

7. The electrolyte according to any one of claims 4 to 6, characterized in that, The electrolyte further comprises a solvent and an electrolyte salt, and the mass percentage of the electrolyte salt in the electrolyte is 12%-18% based on the total mass of the electrolyte. The mass percentage of the solvent in the electrolyte is 69%-87.2% based on the total mass of the electrolyte.

8. The electrolyte of claim 7, wherein, The mass percentage of the electrolyte salt in the electrolyte is 12%-16% based on the total mass of the electrolyte. And / or, the solvent comprises at least one of vinyl carbonate, fluorinated vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl propionate, propyl propionate, methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.

9. The electrolyte of claim 7, wherein, The electrolyte further comprises a third additive, and the third additive comprises at least one of a high-temperature additive, a negative electrode film-forming additive, and a water and acid removal additive, and the mass percentage of the third additive is 0.1%-5%.

10. The electrolyte of claim 9, wherein, At least one of the following conditions is met: The high-temperature additive comprises at least one of 1,3-propane sultone, 1,3-propylene sulfone, ethylene sulfate, ethylene sulfite, and tetraethenylsilane; The negative electrode film-forming additive comprises at least one of vinylene carbonate and vinyl ethylene carbonate; The water and acid removal additive comprises at least one of tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, and tris-(vinyl dimethylsilyl)phosphate.

11. A battery, characterized by The battery comprises the electrolyte according to any one of claims 4-10.

12. The battery of claim 11, wherein, The battery is a lithium ion battery.

13. The battery of claim 12, wherein, The electrolyte salt in the electrolyte of the lithium ion battery comprises at least one of lithium hexafluorophosphate and lithium bisfluorosulfonylimide. And / or, the electrolyte of the lithium ion battery further comprises a lithium salt additive, and the lithium salt additive comprises at least one of lithium bisoxalate borate, lithium difluoro oxalate borate, lithium difluoro di-oxalate phosphate, lithium tetrafluoroborate, lithium tetrafluoro oxalate phosphate, lithium bis-trifluoromethylsulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium difluorophosphate.

14. The battery of claim 12, wherein, The lithium ion battery includes a positive electrode sheet including a positive electrode current collector and a positive electrode active material layer on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material including one or more of LiNi 0.5 Mn 1.5 O4, LiMn2O4, Li 1+a Mn 1- x M 1 x O2, LiCo 1-y M 2 y O2, LiFe 1-z M 3 z PO4, Li2Mn 1-b O4, M 1 , M 2 , M 3 each independently includes one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, F, 0≤a<0.2, 0≤x<1, 0≤y<1, 0≤z<1, 0≤b<1.

15. The battery of claim 11, wherein, The battery is a sodium ion battery.

16. The battery of claim 15, wherein, The electrolyte salt in the electrolyte of the sodium ion battery comprises at least one of sodium hexafluorophosphate and sodium bisfluorosulfonylimide. And / or, the electrolyte of the sodium ion battery further comprises a sodium salt additive, and the sodium salt additive comprises at least one of sodium bisoxalate borate, sodium difluoro oxalate borate, sodium tetrafluoroborate, and sodium difluorophosphate.

Images