A non-aqueous electrolyte additive and its application

Abstract

This invention belongs to the field of secondary battery technology, specifically relating to heterocyclic compounds containing lactone structures as cores as additives for non-aqueous electrolytes and their applications. The additives include at least one compound shown in structural formulas 1 and 2. The inventors have discovered that the passivation film formed by these additives exhibits superior high-temperature stability, effectively improving the storage and cycle performance of secondary batteries, especially lithium-ion and sodium-ion batteries, while simultaneously reducing the battery's DC internal resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary batteries, and particularly relates to a non-aqueous electrolyte additive and application thereof. BACKGROUND

[0002] At present, lithium ion batteries have become the mainstream power battery on the market. Sodium ion batteries have similar working principles as lithium ion batteries, and the element sodium is more widely distributed in the earth's crust and is much cheaper. The abundant reserves and insertion mechanism of sodium make sodium ion batteries an ideal substitute for lithium ion batteries in large-scale applications. Due to the wide application of secondary batteries, people's performance requirements for them are also increasingly high. The performance of secondary batteries, especially the high-temperature performance, low-temperature performance, internal impedance performance and cycle performance, has been challenged. Taking lithium ion batteries as an example, during the charging process of the secondary battery, lithium ions in the positive electrode material are deintercalated and inserted into the negative electrode material through the electrolyte. In the current lithium ion battery, various additives play a very important role, especially the film-forming additive. The film-forming additive can form a SEI film on the negative electrode, which can slow down the chemical reaction between the electrode material and the electrolyte and improve the lithium ion permeability and reduce the electronic conductivity. However, the SEI film formed by the existing additives on the market such as VC, FEC and ES derivatives has the disadvantages of uneven film surface thickness, poor high-temperature stability, low ion conductivity, high impedance and the like, which has an adverse effect on the battery life and high-rate discharge. At the same time, the impedance of lithium ion migration at low temperature will increase accordingly, so the internal impedance of the battery will also increase. Studies have shown that the desolvation process of solvated lithium ions crossing the SEI film should dominate the internal impedance of the secondary battery, rather than the electrolyte conductivity of the whole battery.

[0003] Therefore, how to develop an electrolyte additive that can significantly improve the impedance, high-temperature storage and cycle performance of the battery and apply it to the electrolyte and the battery is the direction of continuous efforts of the battery industry, and has become a problem that needs to be solved with the large-scale industrialization of the battery. SUMMARY

[0004] Based on this, the purpose of the present application is to provide a non-aqueous electrolyte additive which can significantly improve the storage performance of the secondary battery at high temperature, reduce the impedance of the battery and improve the cycle performance.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows.

[0006] A non-aqueous electrolyte additive, comprising at least one of the compounds shown in structural formula 1 and structural formula 2:

[0007]

[0008] wherein X and Y are independently selected from any one of the following structures, and the * represents a bonding position:

[0009]

[0010] Preferably, X and Y are simultaneously selected from the same structure.

[0011] Preferably, at least one of X and Y is selected from structure b or structure c.

[0012] Preferably, the additive comprises at least one of the following compounds:

[0013]

[0014]

[0015] In some preferred embodiments, the additive is selected from at least one of the following compounds:

[0016]

[0017] The present application also provides a non-aqueous electrolyte, which comprises the above-mentioned non-aqueous electrolyte additive.

[0018] Preferably, the content of the non-aqueous electrolyte additive is 0.01% to 7% based on the total mass of the non-aqueous electrolyte, more preferably, the content of the non-aqueous electrolyte additive is 0.05% to 5%, and further preferably, the content of the non-aqueous electrolyte additive is 0.1% to 2%.

[0019] The present application also provides a secondary battery, which comprises a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and the above-mentioned non-aqueous electrolyte.

[0020] The inventors have found that, by using a heterocyclic compound with a lactone structure as a core, as shown in structural formula 1 or structural formula 2, as an additive of a non-aqueous electrolyte, a SEI film formed on the surface of an electrode has a uniform thickness and has more excellent high-temperature stability, which can significantly improve the storage performance and impedance performance of a secondary battery at high temperatures. Especially when used in lithium-ion batteries and sodium-ion batteries, the capacity retention rate and the capacity recovery rate of the lithium-ion battery during high-temperature storage can be effectively improved, and the direct current resistance of the lithium-ion battery at 0°C and 25°C can be reduced; similarly, the additive can also significantly improve the cycle life of the sodium-ion battery, while reducing the direct current resistance of the battery, thereby accelerating the reaction kinetics of the sodium-ion battery. DETAILED DESCRIPTION

[0021] The experimental methods in the following examples of the present application, unless otherwise specified, are generally carried out according to the conventional conditions, or according to the conditions suggested by the manufacturers. The various common chemical reagents used in the examples are commercially available products.

[0022] The technical solutions of the present application will be described clearly and completely in the following specific examples. Obviously, the described examples are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all the other examples obtained by the ordinary skilled in the art without making any creative efforts are within the protection scope of the present application.

[0023] The present embodiment provides a non-aqueous electrolyte additive, which includes at least one of the compounds shown in structural formula 1 and structural formula 2:

[0024]

[0025] In some embodiments, the X and Y are simultaneously selected from the same structure, which includes but is not limited to the following compounds:

[0026]

[0027] In some embodiments, the X and Y are simultaneously selected from the same structure, which includes but is not limited to the following compounds:

[0028]

[0029] In some embodiments, at least one of the X and Y is selected from structure b or structure c, which includes but is not limited to the following compounds:

[0030]

[0031]

[0032] The skilled in the art can know the preparation method of the above-mentioned compounds according to the common knowledge in the field of chemical synthesis, based on the structural formula of the compound of structural formula 1 or structural formula 2. For example:

[0033] It can be obtained by reacting gulonolactone or ascorbic acid with two equivalents of dimethyl carbonate in the presence of an acid binding agent;

[0034] It can be obtained by reacting gulonolactone or ascorbic acid with two equivalents of dichlorosulfoxide.

[0035] The present embodiment provides a non-aqueous electrolyte, which includes the non-aqueous electrolyte additive described above.

[0036] In some embodiments, the content of the non-aqueous electrolyte additive is 0.01 to 10% based on the total mass of the non-aqueous electrolyte as 100%.

[0037] In some embodiments, the content of the non-aqueous electrolyte additive is 0.01 to 7% based on 100% of the total mass of the non-aqueous electrolyte.

[0038] In a preferred embodiment, the content of the non-aqueous electrolyte additive is 0.05-5% based on the total mass of the non-aqueous electrolyte as 100%.

[0039] In a more preferred embodiment, the content of the non-aqueous electrolyte additive is 0.1-2% based on the total mass of the non-aqueous electrolyte as 100%.

[0040] Specifically, the mass percentage of the compound represented by structural formula 1 or structural formula 2 can be 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, or 10%.

[0041] When the content of the compound shown in Structural Formula 1 or Structural Formula 2 is within the above range, it can effectively maintain the stability of the film formed on the electrode surface and improve the battery performance. If the content of the compound shown in Structural Formula 1 or Structural Formula 2 is too low, it will be difficult to significantly improve the battery performance. If the content of the compound shown in Structural Formula 1 or Structural Formula 2 is too high, the film may be too thick, resulting in an increase in the battery internal resistance.

[0042] In some embodiments, the non-aqueous electrolyte further includes an electrolyte salt selected from at least one of lithium salts, sodium salts, potassium salts, magnesium salts, zinc salts, and aluminum salts.

[0043] In a preferred embodiment, the electrolyte salt is selected from lithium salts or sodium salts.

[0044] In a preferred embodiment, the lithium salt is selected from LiPF6, LiBOB, LiDFOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO2F)2, LiClO4, LiAlCl4, LiCF3SO3, and Li2B. 10 Cl 10at least one of LiBF4, LiPF6, LiSbF6, LiAsF6, LiClO4, LiAlCl4, LiCF3SO3, LiCF3CO2, Li2B10Cl10, LiI, Li2DTPP (dithio- phosphate), LiSO2F, LiTOP (lithium trifluoromethanesulfonate), LiDODFP (lithium difluorophosphate), LiOTFP (lithium tetrafluorophosphate), and lithium salts of lower aliphatic carboxylic acids.

[0045] In preferred embodiments, the sodium salt is at least one of NaPF6, NaClO4, NaAsF6, NaSbF6, NaPOF4, NaPO2F2, NaC4BO8, NaC2BF2O4, NaODFB, NaN(SO2C2F5)2, NaN(SO2CF3)(SO2C4F9)2, NaC(SO2CF3), and Na(C2F5)PF3.

[0046] The alkali metal ions dissociated from the electrolyte salt in the non-aqueous electrolyte solution are deintercalated and intercalated between the positive electrode and the negative electrode to complete the charge and discharge cycle, and the concentration of the electrolyte salt directly affects the transfer speed of the alkali metal ions, and the transfer speed of the alkali metal ions affects the potential change of the negative electrode. During the fast charging of the battery, it is necessary to try to increase the moving speed of the alkali metal ions to prevent the negative electrode potential from falling too fast to cause the formation of lithium dendrites, which brings potential safety hazards to the battery, and also prevents the rapid decay of the cycle capacity of the battery. When the content of the electrolyte salt is too low, the intercalation and deintercalation efficiency of the alkali metal ions between the positive electrode and the negative electrode will be reduced, which cannot meet the demand of fast charging of the battery; when the content of the electrolyte salt is too high, the viscosity of the non-aqueous electrolyte will increase, which is also not conducive to the improvement of the intercalation and deintercalation efficiency of the alkali metal ions, and increases the internal resistance of the battery.

[0047] In some embodiments, the concentration of the lithium salt in the non-aqueous electrolyte solution is 0.1 mol / L to 8 mol / L. In preferred embodiments, the concentration of the lithium salt in the non-aqueous electrolyte solution is 0.5 mol / L to 2.5 mol / L. Specifically, the concentration of the lithium salt in the non-aqueous electrolyte solution can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L.

[0048] In some embodiments, the concentration of the sodium salt in the non-aqueous electrolyte solution is 0.1 mol / L to 2 mol / L. In preferred embodiments, the concentration of the sodium salt in the non-aqueous electrolyte solution is 0.4 mol / L to 1.5 mol / L. Specifically, the concentration of the sodium salt in the non-aqueous electrolyte solution can be 0.1 mol / L, 0.4 mol / L, 0.5 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, or 2 mol / L.

[0049] In some embodiments, the nonaqueous electrolyte further comprises an auxiliary additive, the auxiliary additive comprising at least one of a cyclic sulfate compound, a sulfonic acid lactone compound, a cyclic carbonate compound, an unsaturated phosphate compound, a borate compound, and a nitrile compound.

[0050] In some embodiments, the cyclic sulfate compound is selected from at least one of vinyl sulfate, 4-methyl vinyl sulfate, propylene sulfate, In some embodiments, the cyclic sulfate compound is selected from at least one of vinyl sulfate, 4-methyl vinyl sulfate, propylene sulfate,

[0051] In some embodiments, the sulfonic acid lactone compound is selected from at least one of 1,3-propane sulfonic acid lactone, 1,4-butane sulfonic acid lactone, propylene-1,3-sulfonic acid lactone,

[0052] In some embodiments, the cyclic carbonate compound is selected from at least one of vinylene carbonate, vinyl ethylene carbonate, methylene vinylene carbonate, fluoro vinylene carbonate, trifluoromethyl vinylene carbonate, difluoro vinylene carbonate, and a compound represented by structural formula 3 as shown below:

[0053]

[0054] In structural formula 3 as shown above, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 are each independently selected from one of a hydrogen atom, a halogen atom, and a C1-C5 group. Specifically, the compound represented by structural formula 3 includes at least one of In structural formula 3 as shown above, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 are each independently selected from one of a hydrogen atom, a halogen atom, and a C1-C5 group. Specifically, the compound represented by structural formula 3 includes at least one of

[0055] In some embodiments, the phosphate compound is selected from at least one of a saturated phosphate compound and an unsaturated phosphate compound; wherein the saturated phosphate compound includes tris(trimethylsilyl) phosphate; and the unsaturated phosphate compound includes at least one of a compound represented by structural formula 4 as shown below:

[0056]

[0057] wherein R 41 , R 42 , R 43 are each independently selected from a C1-C5 saturated hydrocarbon group, an unsaturated hydrocarbon group, a halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 41 , R 42R 43 Specifically, the compounds represented by structural formula 4 include at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

[0058] In some embodiments, the borate compound is selected from at least one of tris(trimethylsilyl) borate and tris(triethylsilyl) borate.

[0059] In some embodiments, the nitrile compound is selected from at least one of butanedinitrile, pentanedinitrile, ethylene glycol bis(propionitrile) ether, hexanetristitnile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile, and decanedinitrile.

[0060] It should be noted that, unless otherwise specified, the content of any optional substance in the auxiliary additive is generally less than 10%; preferably, the content is 0.1-5%; more preferably, the content is 0.1-3%.

[0061] Specifically, the content of any optional substance in the auxiliary additive can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, or 10%.

[0062] In some embodiments, when the auxiliary additive is selected from fluoroethylene carbonate, the content of the fluoroethylene carbonate is 0.05-30% based on the total mass of the non-aqueous electrolyte solution.

[0063] Compared with single addition or combination of other existing additives, the compound represented by structural formula 1 or structural formula 2 exhibits obvious synergistic effect in improving battery performance when added together with the auxiliary additive, which indicates that the compound represented by structural formula 1 or structural formula 2 and the auxiliary additive can form a film together on the electrode surface to compensate for the film-forming defects of single addition, and a more stable passivation film is obtained.

[0064] In some embodiments, the non-aqueous electrolyte further comprises a non-aqueous organic solvent, which comprises one or more of an ether solvent, a nitrile solvent, a carbonate solvent, a carboxylate solvent, and a sulfone solvent.

[0065] In some embodiments, the ether solvent comprises a cyclic ether or a chain ether, which specifically but not exclusively can be one or more of 1,3-dioxolane (DOL), 1,4-dioxane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), 2-trifluoromethyltetrahydrofuran (2-CF3-THF); the chain ether specifically but not exclusively can be one or more of dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), diglyme (TEGDME). The nitrile solvent specifically but not exclusively can be one or more of acetonitrile, glutaronitrile, malononitrile. The carbonate solvent comprises a cyclic carbonate or a chain carbonate, which specifically but not exclusively can be one or more of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), butylene carbonate (BC); the chain carbonate specifically but not exclusively can be one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC). The carboxylate solvent specifically but not exclusively can be one or more of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate.

[0066] Another embodiment of the present application provides a secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte as described above.

[0067] The secondary battery, due to the adoption of the non-aqueous electrolyte as described above, can form a passivation film with excellent performance on the positive electrode and the negative electrode, and further effectively improve the high-temperature storage performance and the high-temperature cycle performance of the battery, and improve the power characteristics of the battery.

[0068] In preferred embodiments, the secondary battery is a lithium metal battery, a lithium ion battery, a lithium-sulfur battery, a sodium ion battery, a magnesium ion battery.

[0069] In more preferred embodiments, the secondary battery is a lithium ion battery, a sodium ion battery.

[0070] In some embodiments, the positive electrode comprises a positive electrode material layer, which comprises a positive electrode active material, the kind and content of which are not particularly limited and can be selected according to actual needs, as long as it is a positive electrode active material or a conversion-type positive electrode material capable of reversibly intercalating / deintercalating metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.).

[0071] In preferred embodiments, when the secondary battery is a lithium ion battery, the positive active material thereof can be selected from at least one of LiFe 1-x’ M’ x’ PO4, LiMn 2-y’ M y’ O4, and LiNi x Co y Mn z M 1-x-y-z O2, wherein M’ is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0≤x’<1, 0≤y’≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1, the positive active material can also be selected from at least one of sulfides, selenides, halides. More preferably, the positive active material can be selected from at least one of LiCoO2, LiFePO4, LiFe 0.8 Mn 0.2 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O2, LiNi 0.5 Co 0.2 Al 0.3 O2.

[0072] In preferred embodiments, when the secondary battery is a sodium ion battery, the positive active material thereof includes but is not limited to at least one of transition metal oxides, Prussian blue analogs, phosphates, sulfates, titanate materials. The chemical formula of the transition metal oxide can be Na z M x O y , M can be selected from at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V, more preferably, the transition metal oxide is NaNi m Fe n Mn pO2(m+n+p = 1, 0≤m≤1, 0≤n≤1, 0≤p≤1) or NaNi m Co n Mn p O2(m+n+p = 1, 0≤m≤1, 0≤n≤1, 0≤p≤1); the Prussian-type material has a formula of Na x M[M'(CN)6] y ■zH2O, wherein M is a transition metal, M' is a transition metal, 0 < x < 2, 0.8 < y < 1, 0 < z < 20, more preferably, the Prussian-type material is Na x Mn[Fe(CN)6] y ■nH2O (0 < x < 2, 0 < y < 1, 0 < z < 10) or Na x Fe[Fe(CN)6] y ■nH2O (0 < x < 2, 0 < y < 1, 0 < z < 10); the phosphate has a formula of Na3(MO 1- x PO4)2F 1+2x , 0 < x < 1, M is selected from at least one of Al, V, Ge, Fe, Ga, more preferably, the phosphate is Na3(VPO4)2F3 or Na3(VOPO4)2F; the phosphate has a formula of Na2MPO4F, M is selected from at least one of Fe, Mn, more preferably, the phosphate is Na2FePO4F or Na2MnPO4F; the titanate material can be selected from at least one of Na2Ti3O7, Na2Ti6O 13 , Na4Ti5O 12 , Li4Ti5O 12 , NaTi2(PO4)3; the sulfate has a formula of Na2M(SO4)2■2H2O, M can be selected from at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V.

[0073] In some embodiments, the positive electrode further comprises a positive electrode current collector, and the positive electrode material layer is disposed on a surface of the positive electrode current collector.

[0074] The positive electrode current collector is selected from a metal material that can conduct electrons, preferably, the positive electrode current collector comprises at least one of Al, Ni, tin, copper, stainless steel, in more preferred embodiments, the positive electrode current collector is selected from an aluminum foil.

[0075] In some embodiments, the positive electrode active material layer further comprises a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder and the positive electrode conductive agent are blended to obtain the positive electrode material layer.

[0076] The positive electrode binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-vinyl fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a thermoplastic polyimide, a thermoplastic resin such as polyethylene and polypropylene, an acrylic resin, and a styrene butadiene rubber.

[0077] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

[0078] In some embodiments, the negative electrode includes a negative electrode material layer, and the negative electrode material layer includes a negative electrode active material. The kind and content of the negative electrode active material are not particularly limited and can be selected according to actual needs.

[0079] In preferred embodiments, when the secondary battery is a lithium ion battery, the negative electrode active material includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode. The carbon-based negative electrode can include graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads, etc. The silicon-based negative electrode can include silicon material, silicon oxide, silicon-carbon composite material, and silicon alloy material, etc. The tin-based negative electrode can include tin, tin-carbon, tin oxide, tin metal compound. The lithium negative electrode can include metal lithium or lithium alloy. The lithium alloy can be at least one of lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy, and lithium-indium alloy.

[0080] In preferred embodiments, when the secondary battery is a sodium ion battery, the negative electrode active material includes at least one of metal sodium, graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbead, silicon-based material, tin-based material, lithium titanate, or other alloy material capable of forming an alloy with sodium, etc. The alloy material can be an alloy material composed of at least one of Si, Ge, Sn, Pb, and Sb and C. The graphite can be at least one of artificial graphite, natural graphite, and modified graphite. The silicon-based material can be at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, and silicon alloy. The tin-based material can be at least one of elemental tin, tin oxide compound, and tin alloy.

[0081] In some embodiments, the negative electrode further includes a negative electrode current collector, and the negative electrode material layer is arranged on a surface of the negative electrode current collector. The material of the negative electrode current collector can be the same as that of the positive electrode current collector, which is not described herein again.

[0082] In some embodiments, the negative electrode material layer further comprises a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer. The negative electrode binder and the negative electrode conductive agent can be the same as the positive electrode binder and the positive electrode conductive agent respectively, which will not be described herein again.

[0083] In some embodiments, the secondary battery further comprises a separator between the positive electrode and the negative electrode.

[0084] The separator can be a conventional separator, which can be a ceramic separator, a polymer separator, a non-woven fabric, an inorganic-organic composite separator, etc., including but not limited to a single-layer PP (polypropylene) separator, a single-layer PE (polyethylene) separator, a double-layer PP / PE separator, a double-layer PP / PP separator and a three-layer PP / PE / PP separator, etc.

[0085] The application will be further described by the following examples. The compounds 1-6 used in the following examples and comparative examples are shown in Table 1.

[0086] Table 1

[0087]

[0088] Examples 1-18

[0089] Examples 1-18 are used to illustrate the non-aqueous electrolyte, the lithium ion battery and the preparation method thereof. In the preparation method, except that the non-aqueous electrolyte additive is different, the others are the same, and the specific preparation method is as follows:

[0090] 1) Preparation of non-aqueous electrolyte:

[0091] Vinyl carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EC) are mixed in a mass ratio of EC:DEC:EC = 1:1:1, then lithium hexafluorophosphate (LiPF6) is added to a molar concentration of 1 mol / L, and additives are added and uniformly mixed. The types and contents of each additive are shown in Table 2, based on 100% of the total weight of the non-aqueous electrolyte.

[0092] 2) Preparation of positive electrode plate:

[0093] The positive electrode active material lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3O2, conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF), and then disperse them in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The slurry is uniformly coated on both sides of an aluminum foil, dried, calendered and vacuum dried, and then an aluminum lead wire is welded on the positive electrode plate using an ultrasonic welding machine to obtain the positive electrode plate, the thickness of the electrode plate being between 12 and 15 μ.

[0094] 3) Preparation of the negative electrode plate:

[0095] The negative electrode active material artificial graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SB) and carboxymethyl cellulose (CC) are mixed in a mass ratio of 94:1:2.5:2.5, and then dispersed in deionized water to obtain a negative electrode slurry. The slurry is coated on both sides of a copper foil, dried, calendered and vacuum dried, and then a nickel lead wire is welded on the negative electrode plate using an ultrasonic welding machine to obtain the negative electrode plate, the thickness of the electrode plate being between 12 and 15 μ.

[0096] 4) Preparation of the battery cell:

[0097] A three-layer separator with a thickness of 2 μ is placed between the positive electrode plate and the negative electrode plate, and then the sandwich structure of the positive electrode plate, the negative electrode plate and the separator is wound, and the wound body is flattened and placed in an aluminum foil packaging bag, and vacuum baked at 75°C for 48 h to obtain a battery cell to be injected with electrolyte.

[0098] 5) Injection of electrolyte and formation of the battery cell:

[0099] The electrolyte prepared above is injected into the battery cell in a glove box with the dew point controlled below -4°C, and vacuum packaged, and allowed to stand for 24 h.

[0100] The battery cell is then subjected to the conventional formation of the first charge in the following steps: 0.5C constant current charging for 180 min, 0.2C constant current charging to 3.95 V, secondary vacuum sealing, further constant current charging to 4.2 V at a current of 0.2C, standing at room temperature for 24 h, and constant current discharging to 3.95 V at a current of 0.2C to obtain a LiNi 0.5 Co 0.2 Mn 0.3 O2 / artificial graphite lithium ion battery.

[0101] Comparative Examples 1 to 5

[0102] Comparative Examples 1 to 5 are used to illustrate the non-aqueous electrolyte and lithium ion battery of the present application. The preparation method thereof includes most of the operation steps in the preparation method of the above examples, and the only difference is that the types and contents of the various additives are shown in Table 2, based on 100% of the total weight of the non-aqueous electrolyte.

[0103] Performance test

[0104] The lithium ion batteries prepared from Examples 1-18 and Comparative Examples 1-5 were subjected to the following performance tests:

[0105] (1) High-temperature storage performance

[0106] The lithium ion batteries after formation were charged at room temperature to 4.2 V at a current of 1 C, then charged at a constant current and constant voltage until the current dropped to 0.05 C, and then discharged at a current of 1 C to 3.0 V. The initial discharge capacity and the initial battery volume were measured, and then the batteries were charged to full charge and stored at 60°C for 30 days, 60 days, and 90 days, respectively. After that, the batteries were discharged at 1 C to 3 V, and the retention capacity and recovery capacity and the battery volume after storage were measured. The calculation formulae are as follows:

[0107] Battery capacity retention rate (%) = retention capacity / initial capacity x 1%;

[0108] Battery capacity recovery rate (%) = recovery capacity / initial capacity x 1%;

[0109] Volume expansion rate (%) = (battery volume after storage-initial battery volume) / initial battery volume x 1%.

[0110] (2) DC internal resistance

[0111] At 25°C, the batteries were charged and discharged at a rate of 0.5 C for 3 cycles, and the average capacity of 3 cycles was taken as the rated capacity. Then the batteries were charged at a rate of 0.5 C to 50% of the rated capacity.

[0112] 25°C DCIR test: The battery with a capacity of 50% was placed at 25°C for 4 h, then charged at a rate of 0.5 C for 10 s, rested for 40 s to test the charging DCR ch , then discharged at a rate of 0.5 C for 10 s, rested for 40 s to test the discharging DCR dis .

[0113] 0°C DCIR test: The battery with a capacity of 50% was placed at 0°C for 4 h, then charged at a rate of 0.5 C for 10 s, rested for 40 s to test the charging DCR ch , then discharged at a rate of 0.5 C for 10 s, rested for 40 s to test the discharging DCR dis .

[0114] The test results are shown in Table 2.

[0115] (3) High-temperature cycle performance

[0116] The lithium ion batteries after formation were charged at 45°C to 4.3 V at a constant current and constant voltage, then charged at a constant voltage until the current dropped to 0.05 C, and then discharged at a current of 1 C to 3.0 V. The discharge capacity in the first week and the discharge capacity in the 500th week were recorded.

[0117] The capacity retention rate of high temperature cycle was calculated as follows:

[0118] The capacity retention rate = (discharge capacity in the 500th week / discharge capacity in the 1st week) x 100%.

[0119] Table 2

[0120]

[0121]

[0122] From the performance test results of Examples 1-6 and Comparative Example 1, it can be seen that the additive of the present application can make the lithium ion battery have higher capacity retention rate and capacity recovery rate, and lower direct current internal resistance. It is illustrated that the additive can significantly improve the storage performance and impedance performance of the lithium ion battery at high temperature.

[0123] From the test results of Comparative Example 1 and Examples 7-15, it can be seen that the content of compound 1 has a significant influence on the performance of the lithium ion battery. With the increase of the content of compound 1, the high temperature cycle performance and high temperature storage performance of the lithium ion battery first increase and then decrease. When the content of the non-aqueous electrolyte additive in the non-aqueous electrolyte is 0.1% to 7%, the lithium ion battery has good high temperature storage performance; especially when the content of the non-aqueous electrolyte additive is 0.5% to 2%, the lithium ion battery has the best high temperature storage performance. When the content of the non-aqueous electrolyte additive is less than 0.1%, it may not form a SEI film with sufficient area for coating, resulting in the loss of active lithium ions, and the electrolyte solvent preferentially forms a non-uniform SEI on the electrode, which is easy to cause the precipitation of lithium dendrites, thereby affecting the performance of the overall SEI; when the content of the non-aqueous electrolyte additive is higher than 7%, the formed SEI film has a tendency to be too thick, causing the electrode dynamics performance to deteriorate.

[0124] From the test results of Comparative Examples 1-6 and Comparative Examples 1-5, it can be seen that compared with the traditional vinyl carbonate (VC), vinyl sulfate (DTD) and 1,3-propane sulfone lactone (PS) additives, using the compound represented by structural formula 1 or structural formula 2 as an additive can more obviously improve the storage performance of the lithium ion battery at high temperature, which illustrates that the heterocyclic compound containing lactone structure as the mother nucleus in the present application has a more stable structure in the passivation film obtained by decomposition on the electrode surface, so the passivation film formed by the compound represented by structural formula 1 or structural formula 2 has more excellent high temperature stability and lower internal resistance.

[0125] The test results of Comparative Examples 16-18 and Comparative Examples 2-5 show that, compared to the combination of the traditional vinylene carbonate (VC) and vinyl sulfonate (DTD) additives, the performance of the lithium ion battery is further improved by using the combination of the compound 1 and the vinyl sulfonate (DTD), indicating that the decomposition product shown in the structural formula 1 or the structural formula 2 has good affinity with the decomposition product of the vinyl sulfonate (DTD), and the combination product obtained by the combination of the two has higher stability than the single decomposition product at high temperature, and therefore the passivation film formed by the compound shown in the structural formula 1 and the vinyl sulfonate has more excellent high-temperature stability.

[0126] In summary, the passivation film formed by the additive of the present application has more excellent high-temperature stability, and can significantly improve the storage performance and impedance performance of the lithium ion battery at high temperature.

[0127] Examples 19-36

[0128] Examples 19-36 are used to illustrate the non-aqueous electrolyte, sodium ion battery and preparation method thereof. In the preparation method, except that the non-aqueous electrolyte additive is different, the others are the same, and the specific preparation method is as follows:

[0129] 1) Preparation of non-aqueous electrolyte:

[0130] Vinyl carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EC) are mixed in a mass ratio of EC:DEC:EC=1:1:1, then sodium hexafluorophosphate (NaPF6) is added to a molar concentration of 1.12 mol / L, and the additives are mixed uniformly, and the types and contents of the additives are shown in Table 3, based on the total weight of the non-aqueous electrolyte being 100%.

[0131] 2) Preparation of positive plate:

[0132] The layered transition metal oxide (NaNi 0.6 Fe 0.25 Mn 0.15 O2) is used as the positive active material, carbon black (Super P) is used as the conductive agent, and polyvinylidene fluoride is used as the binder, and the ratio is 97:2:1, and the slurry tank is filled, and the mixture is fully stirred and uniformly coated on the aluminum foil current collector, and then dried, rolled and die cut to obtain the positive plate, and the thickness of the plate is between 12-15μ.

[0133] 3) Preparation of negative plate:

[0134] The negative electrode sheet was obtained by coating the slurry into aluminum foil current collector, drying, rolling, and die cutting, in which hard carbon was used as negative active material, carbon black (Super P) was used as conductive agent, sodium carboxymethyl cellulose and butadiene-styrene rubber were used as binder, and the ratio of the above components was 95.5:1:1.5:2.

[0135] 4) Preparation of the battery cell:

[0136] The three-layer separator with a thickness of 6 μm was placed between the positive electrode plate and the negative electrode plate, and then the sandwich structure of the positive electrode plate, the negative electrode plate, and the separator was wound, and the wound body was flattened and placed in an aluminum foil packaging bag, and vacuum baked at 75 °C for 48 h to obtain the battery cell to be injected with electrolyte. The electrolyte prepared above was injected into the battery cell in a glove box with the dew point controlled below -4 °C, vacuum packaged, and allowed to stand for 24 h before being subjected to formation to obtain the sodium ion battery.

[0137] Comparative Examples 6-10

[0138] Comparative Examples 6-10 were used to illustrate the non-aqueous electrolyte and the sodium ion battery of the present application. The preparation method included most of the operation steps in the preparation method of Examples 19-36 described above, and the only difference was that the types and contents of the additives were as shown in Table 3, based on 100% of the total weight of the non-aqueous electrolyte.

[0139] The sodium ion batteries prepared from Examples 19-36 and Comparative Examples 6-10 were subjected to the following performance tests:

[0140] (1) DC internal resistance

[0141] At 25 °C, the battery was charged and discharged at 0.3C rate for 3 cycles, and the average capacity of 3 cycles was the rated capacity, and then the battery was charged at 0.3C rate to 50% of the rated capacity.

[0142] 25 °C DCIR test: the battery with a capacity of 50% was placed at 25 °C for 4 h, and then charged at 0.3C rate for 10 s, and rested for 40 s to test the charging DCR ch , and then discharged at 0.3C rate for 10 s, and rested for 40 s to test the discharging DCR dis .

[0143] (2) 25 °C cycle test

[0144] The battery was charged at 1C constant current and constant voltage to 3.8 V, and the cutoff current was 0.05C, and then discharged at 1C constant current to 1.8 V, and the cycle was repeated, and the cycle capacity retention rate was calculated, and the cycle capacity retention rate (%) = test cycle week discharge capacity / average value of the first 3 cycle discharge capacities x 100%.

[0145] The test results are shown in Table 3.

[0146] Table 3

[0147]

[0148]

[0149] As can be seen from the test results of Table 3, the performance test results of Examples 19-26 and Comparative Example 6 show that the additive of the present application can make the sodium ion battery have higher cycle performance and lower direct current resistance, indicating that the additive can significantly improve the cycle performance and impedance performance of the sodium ion battery at high temperature.

[0150] As can be seen from the comparison of Example 19 and Examples 25-33, the content of the additive of the present application in the electrolyte will affect the cycle performance of the prepared sodium ion battery. Controlling the mass percentage of the additive in the range of 0.5% to 2% can significantly improve the cycle life of the battery.

[0151] As can be seen from the comparison of Examples 34-36 and Comparative Examples 6-10, the additive of the present application can form a dense and stable SEI film on the surface of the positive and negative electrode materials, reducing the degradation of the positive and negative electrode interface film during the cycle of the battery, thereby significantly improving the cycle life of the sodium ion battery. At the same time, the use of other auxiliary film-forming additives reduces the direct current resistance of the battery, thereby accelerating the reaction kinetics of the sodium ion battery.

[0152] The above has further described the present application with the aid of specific examples, but it should be understood that the specific description here should not be understood as limiting the essence and scope of the present application. Various modifications made by those of ordinary skill in the art after reading the present specification to the above examples all belong to the scope of protection of the present application.

Claims

1. A nonaqueous electrolyte additive, characterized by comprising: The non-aqueous electrolyte additive comprises at least one of the compounds shown in structural formula 2: ； Wherein, X and Y are independently selected from any one of the following structures, and the * represents the bonding position: 。 2. The nonaqueous electrolyte additive according to claim 1, characterized by The X and Y are simultaneously selected from the same structure.

3. The nonaqueous electrolyte additive according to claim 1, characterized by At least one of the X and Y is selected from structure b or structure c.

4. The nonaqueous electrolyte additive according to claim 1, characterized by The additive comprises at least one of the compounds shown as follows: 。 5. A nonaqueous electrolyte characterized by comprising: The non-aqueous electrolyte comprises the non-aqueous electrolyte additive according to any one of claims 1-4, and the content of the non-aqueous electrolyte additive is 0.01%-7% based on the total mass of the non-aqueous electrolyte being 100%.

6. The nonaqueous electrolyte according to claim 5, wherein The content of the non-aqueous electrolyte additive is 0.1%-2%.

7. The nonaqueous electrolyte according to claim 5, wherein The non-aqueous electrolyte further comprises an electrolyte salt, and the electrolyte salt is selected from at least one of lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt and aluminum salt.

8. The nonaqueous electrolyte according to claim 7, wherein The electrolyte salt is selected from lithium salt or sodium salt.

9. The nonaqueous electrolyte according to claim 7, wherein said lithium salt is selected from at least one of LiPF6, LiBOB, LiDFOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO2F)2, LiClO4, LiAlCl4, LiCF3SO3, Li2B 10 Cl 10 , LiSO2F, LiTOP, LiDODFP, LiOTFP and a lithium salt of a lower aliphatic carboxylic acid; The sodium salt is selected from at least one of NaPF6, NaClO4, NaAsF6, NaSbF6, NaPOF4, NaPO2F2, NaC4BO8, NaC2BF2O4, NaODFB, NaN(SO2C2F5)2, NaN(SO2CF3)(SO2C4F9)2, NaC(SO2CF3) and Na(C2F5)PF3.

10. The nonaqueous electrolyte according to claim 5, wherein The non-aqueous electrolyte further comprises an auxiliary additive, and the auxiliary additive comprises at least one of cyclic sulfate compound, sulfonic acid lactone compound, cyclic carbonate compound, unsaturated phosphate compound, borate compound and nitrile compound.

11. The nonaqueous electrolyte according to claim 5, wherein the cyclic sulfate compound is selected from at least one of ethylene sulfate, 4-methyl ethylene sulfate, propylene sulfate, , , , , , the sulfolane compound is selected from at least one of 1,3-propane sulfolane, 1,4-butane sulfolane, propenyl-1,3-sulfonic acid lactone, ​ The cyclic carbonate compound is selected from at least one of vinylene carbonate, vinyl ethylene carbonate, methylene vinyl carbonate, fluorinated vinyl carbonate, trifluoromethyl vinyl carbonate, difluorinated vinyl carbonate and the compound shown in structural formula 3 as follows: Structural Formula 3 in the structural formula 3 shown below, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 each is independently selected from one of a hydrogen atom, a halogen atom, a C1-C5 group; The phosphate compound is selected from at least one of saturated phosphate compound and unsaturated phosphate compound; wherein the saturated phosphate compound comprises tris(trimethylsilyl) phosphate; and the unsaturated phosphate compound comprises at least one of the compounds shown in structural formula 4 as follows: Structural Formula 4 wherein R 41 , R 42 , R 43 are each independently selected from the group consisting of C1-C5 saturated hydrocarbon group, unsaturated hydrocarbon group, halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 41 , R 42 , R 43 at least one of which is an unsaturated hydrocarbon group; The borate compound is selected from at least one of tris(trimethylsilyl) borate and tris(triethylsilyl) borate; The nitrile compound is selected from at least one of butanedinitrile, pentanedinitrile, ethylene glycol bis(propionitrile) ether, hexanetristitnile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile and decanedinitrile.

12. A secondary battery comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, characterized by, The non-aqueous electrolyte according to any one of claims 5-11 is further included.

13. The secondary battery according to claim 12, characterized by The secondary battery is a lithium metal battery, a lithium ion battery, a lithium sulfur battery, a sodium ion battery or a magnesium ion battery.

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