Non-aqueous electrolyte additive, non-aqueous electrolyte, and secondary battery

Abstract

The application belongs to the technical field of secondary batteries, and particularly relates to a borate non-aqueous electrolyte additive, and further discloses a prepared non-aqueous electrolyte and a secondary battery. The additive comprises a compound shown in the following formula I: Formula I The non-aqueous electrolyte additive disclosed in the application, based on the borate basic structure, by selecting a selected substitution structure, forms a functional additive which can be used in a non-aqueous electrolyte of a secondary battery, and the borate compound of this type of structure has a higher probability of forming a coordination lithium with a lower activation energy with a solvated metal ion to promote desolvation, can effectively reduce the internal impedance of the battery in the SEI film and improve the low-temperature and high-temperature performance, and can make the metal ion embed into the negative electrode with lower energy loss, and finally achieve the purpose of reducing and improving the impedance performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a borate ester-based non-aqueous electrolyte additive, and further disclosing the non-aqueous electrolyte and secondary battery prepared therefrom. Background Technology

[0002] Currently, rechargeable batteries have attracted widespread attention and become the mainstream power batteries due to their high operating voltage, high specific energy, long cycle life, and lack of memory effect. With the rapid development of the new energy field, the performance requirements for rechargeable batteries are also increasing, with lithium-ion power batteries facing numerous challenges, particularly in high-temperature performance, low-temperature performance, and internal impedance performance. During the charging process of a rechargeable battery, metal ions in the positive electrode material undergo intercalation and deintercalation, embedding into the carbon negative electrode material through the electrolyte. In current rechargeable battery systems, various functional additives are added to improve battery performance. Research shows that traditionally used additives play a crucial role, especially film-forming additives.

[0003] Film-forming additives can form an SEI film on the negative electrode, which can slow down the chemical reaction between the electrode material and the electrolyte, improve metal ion permeability, and reduce electronic conductivity. However, existing additives such as VC, FEC, and ES derivatives that form SEI films all have drawbacks, including uneven film thickness, poor high-temperature stability, low lithium-ion conductivity, and high impedance, which negatively impact battery life and high-rate discharge. Furthermore, the impedance of metal ion migration increases at low temperatures, leading to a corresponding increase in the battery's internal impedance. Research indicates that the desolvation process of solvated metal ions crossing the SEI in the electrolyte should dominate the internal impedance of the secondary battery, rather than originating from the overall electrolyte conductivity. Therefore, developing an electrolyte additive that can further reduce the activation energy of the desolvation process while simultaneously generating a stable SEI film, thereby improving the battery's impedance performance, high-temperature performance, and low-temperature performance, is of positive significance for improving the performance of secondary batteries. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a non-aqueous electrolyte additive that enables the secondary battery to form a stable SEI film during charging and discharging, thereby improving the high-temperature performance, low-temperature performance and reducing impedance of the secondary battery.

[0005] The second technical problem to be solved by the present invention is to provide a non-aqueous electrolyte prepared by the above-mentioned non-aqueous electrolyte additive, wherein the additive can significantly improve the impedance and low-temperature performance of the secondary battery at the initial stage, and effectively improve the performance of the secondary battery.

[0006] To address the above problems, the present invention provides a non-aqueous electrolyte additive having the structure shown in Formula I:

[0007]

[0008] Wherein, A1, A2, and A3 are independently selected from the structure shown in equation (AE), and A1, A2, and A3 are not simultaneously selected from the structure shown in equation (E); where * represents the bonding position;

[0009]

[0010] R1 and R2 are each independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl, or substituted or unsubstituted C2-C5 alkynyl.

[0011] a, b, and c are independent integers selected from 0 to 3.

[0012] Preferably, in the non-aqueous electrolyte additive:

[0013] R1 is selected from substituted or unsubstituted C1-C2 alkyl groups, and R2 is selected from substituted or unsubstituted C1-C2 alkyl groups.

[0014] a is an integer between 0 and 2, b is an integer between 0 and 2, and c is an integer between 1 and 3.

[0015] Preferably, in the non-aqueous electrolyte additive, at least two of A1, A2 and A3 have the same substitution structure.

[0016] Preferably, in the non-aqueous electrolyte additive, at least two of A1, A2 and A3 have the structure shown in option (B).

[0017] More preferably, the non-aqueous electrolyte additive is selected from compounds with the following structures:

[0018]

[0019] The present invention also discloses a non-aqueous electrolyte, comprising an organic non-aqueous solvent, an electrolyte salt, and the non-aqueous electrolyte additives.

[0020] Specifically, in the non-aqueous electrolyte of the present invention, based on the total mass of the non-aqueous electrolyte being 100%, the content of the non-aqueous electrolyte additive is 0.05-10 wt%.

[0021] In a preferred embodiment, the content of the compound represented by Formula I is 0.1-5 wt%, based on 100% of the total mass of the non-aqueous electrolyte.

[0022] Specifically, the mass percentage of the compound represented by Formula I 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%.

[0023] When the content of the compound shown in Formula I 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 Formula I is too low, it will be difficult to significantly improve the battery performance. If the content of the compound shown in Formula I is too high, it may affect the function of other substances in the electrolyte due to the excessive decomposition products.

[0024] In a specific embodiment, the concentration of the electrolyte salt in the non-aqueous electrolyte is 0.1 mol / L to 8 mol / L. In a preferred embodiment, the concentration of the electrolyte salt is 0.5 mol / L to 2.5 mol / L. Specifically, the concentration of the electrolyte salt can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L.

[0025] In non-aqueous electrolytes, alkali metal ions formed by the dissociation of electrolyte salts undergo intercalation and deintercalation between the positive and negative electrodes to complete charge-discharge cycles. The concentration of the electrolyte salt directly affects the transfer rate of alkali metal ions, which in turn affects the potential change at the negative electrode. During fast charging, it is necessary to maximize the movement speed of alkali metal ions to prevent the negative electrode potential from dropping too quickly, which could lead to the formation of lithium dendrites and pose a safety hazard to the battery. This also helps prevent the battery's cycle capacity from decaying too rapidly. If the electrolyte salt content is too low, the intercalation and deintercalation efficiency of alkali metal ions between the positive and negative electrodes will be reduced, failing to meet the requirements of fast charging. Conversely, if the electrolyte salt content is too high, the viscosity of the non-aqueous electrolyte will increase, which is also detrimental to improving the intercalation and deintercalation efficiency of alkali metal ions and increases the battery's internal resistance.

[0026] In some embodiments, the electrolyte salt is selected from one or more lithium salts and sodium salts.

[0027] 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 Cl10 At least one of the following: lithium salts of lower aliphatic carboxylic acids.

[0028] The electrolyte salt is selected from at least one of NaBF4, NaFSI, NaTFSI, NaPF6, NaClO4, NaAsF6, NaSbF6, NaPOF4, NaPO2F2, NaC4BO8, NaC2BF2O4, NaODFB, NaN(SO2C2F5)2, NaN(SO2CF3)(SO2C4F9)2, NaC(SO2CF3), and Na(C2F5)PF3. In a preferred embodiment, the sodium salt is selected from at least one of sodium perchlorate (NaClO4), sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium bis(fluorosulfonyl)imide (NaFSI), and sodium bis(trifluoromethylsulfonyl)imide (NaTFSI).

[0029] In some embodiments, the non-aqueous electrolyte further includes auxiliary additives selected from at least one of cyclic carbonates, fluorocyclic carbonates, sulfonyl lactones, cyclic sulfates, phosphates, borate esters, and nitrile compounds.

[0030] In some preferred embodiments, the cyclic carbonate compound is selected from at least one of vinylene carbonate (VC), ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, and compounds represented by Formula II below:

[0031]

[0032] In equation II shown, R 31 R 32 R 33 R 34 R 35 R 36 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group. Specifically, the compounds represented by Formula II include... At least one of them.

[0033] In some preferred embodiments, the fluorocyclic carbonate is selected from one or more of fluoroethylene carbonate, trifluoromethyl ethylene carbonate, and difluoroethylene carbonate.

[0034] The sulfonyl lactone compounds are selected from 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, propenyl-1,3-sulfonyl lactone, and others. At least one of the following. In some preferred embodiments, the cyclic sulfate compound is selected from vinyl sulfate (DTD), 4-methylvinyl sulfate, propylene sulfate, etc.

[0035] At least one of them;

[0036] In some preferred embodiments, the phosphate ester compound is selected from at least one of saturated phosphate ester compounds and unsaturated phosphate ester compounds; wherein the saturated phosphate ester compound includes tris(trimethylsilane) phosphate; and the unsaturated phosphate ester compound includes at least one of the compounds represented by Formula III:

[0037]

[0038] In Equation III, R 41 R 42 R 43 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -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 them is an unsaturated hydrocarbon group; specifically, the compound represented by Formula III includes at least one of the following: triargyl 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, diallyl 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.

[0039] In some preferred embodiments, the borate ester is tris(trimethylsilane)borate ester and / or tris(triethylsilane)borate ester.

[0040] In some preferred embodiments, the nitrile compound includes at least one selected from succinic anhydride, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octanilide, nonadionitrile, and sebaconitrile.

[0041] It should be noted that, unless otherwise specified, the content of any one of the optional substances in the auxiliary additives in the non-aqueous electrolyte is generally less than 10%, preferably 0.1-5%, and more preferably 0.1% to 3%. Specifically, the content of any one of the optional substances in the auxiliary additives 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%.

[0042] In some embodiments, when the auxiliary additive is selected from fluoroethylene carbonate, the content of fluoroethylene carbonate is 0.05% to 30% based on 100% of the total mass of the non-aqueous electrolyte.

[0043] In the non-aqueous electrolyte, compared with a single additive or a combination of other existing additives, the compound shown in Formula I, when added together with the auxiliary additive, exhibits a significant synergistic effect in improving battery performance. This indicates that the compound shown in Formula I and the auxiliary additive, when forming a film together on the electrode surface, can compensate for the film-forming defects of a single additive, resulting in a more stable passivation film.

[0044] In some embodiments, the non-aqueous organic solvent includes one or more of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

[0045] In some embodiments, the ether solvent includes cyclic ethers or chain ethers. Specifically, the cyclic ether may be, but is not limited to, one or more of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF); the chain ether may be, but is not limited to, one or more of dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), and diethylene glycol dimethyl ether (TEGDME). The nitrile solvent may be, but is not limited to, one or more of acetonitrile, glutaronitrile, and malononitrile. Carbonate solvents include cyclic carbonates or chain carbonates. Cyclic carbonates may specifically include, but are not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and butylene carbonate (BC). Chain carbonates may specifically include, but are not limited to, one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). Carboxylic acid ester solvents may specifically include, but are not limited to, one or more of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate. Preferably, the non-aqueous electrolyte for the secondary battery also includes one or more of vinylene carbonate (VC), ethylene ethylene carbonate (VEC), and fluoroethylene carbonate (FEC).

[0046] The present invention also provides a secondary battery comprising a positive electrode, a negative electrode, and the non-aqueous electrolyte.

[0047] Because the secondary battery uses the non-aqueous electrolyte described above, it can form a high-performance passivation film on the positive and negative electrodes, thereby effectively improving the battery's high-temperature storage performance and high-temperature cycle performance, and enhancing the battery's power characteristics.

[0048] In a specific embodiment, the secondary battery is a lithium metal battery, a lithium-ion battery, or a sodium-ion battery, etc.

[0049] In some embodiments, the positive electrode includes a positive electrode material layer, and the positive electrode material layer includes a positive electrode active material. The type and content of the positive electrode active material are not particularly limited and can be selected according to actual needs. It can be any positive electrode active material or conversion type positive electrode material that can reversibly insert / deintercalate metal ions (lithium ions or sodium ions, etc.).

[0050] In a preferred embodiment, the secondary battery is a lithium-ion battery, and its positive electrode active material can be selected from LiFe. 1-x 'M' x 'PO4, LiMn 2-y 'M y 'O4 and LiNix Co y Mn z M 1-x-y-z One or more of O2, wherein M' is selected from one or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and M is selected from one or more 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 electrode active material may also be selected from one or more of sulfides, selenides, and halides. More preferably, the positive electrode active material may be selected from 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 One or more of O2.

[0051] In a preferred embodiment, the secondary battery is a sodium-ion battery, and its positive electrode active material is selected from one or more of metallic sodium, carbon materials, alloy materials, over-plated metal oxides, over-plated metal sulfides, phosphorus-based materials, titanate materials, and Prussian blue-based materials. The carbon material is selected from one or more of graphite, soft carbon, and hard carbon. The alloy material is selected from an alloy composed of at least two of Si, Ge, Sn, Pb, and Sb. The alloy material can also be selected from an alloy composed of at least one of Si, Ge, Sn, Pb, and Sb with C. The chemical formula of the over-plated metal oxide and the over-plated metal sulfide is M1. x N y M1 can be selected from one or more of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V; N is selected from O or S; the phosphorus-based material can be selected from one or more of red phosphorus, white phosphorus, and black phosphorus; and the titanate material can be selected from Na2Ti3O7 and Na2Ti6O7. 13 Na4Ti5O 12 Li4Ti5O12 One or more of NaTi2(PO4)3, wherein the molecular formula of the Prussian blue-like material is

[0052] Na x M[M'(CN)6] y ·zH₂O, where M is a transition metal, M' is a transition metal, and 0 <x≤2,0.8≤y<1,0<z≤20。

[0053] In some embodiments, the positive electrode further includes a positive electrode current collector, and the positive electrode material layer is disposed on the surface of the positive electrode current collector.

[0054] The positive electrode current collector is selected from a metallic material that can conduct electrons. Preferably, the positive electrode current collector includes one or more of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

[0055] In some embodiments, the positive electrode active material layer further includes 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.

[0056] The positive electrode binder includes one or more of the following: polyvinylidene fluoride (PVDF), copolymers of PVDF, polytetrafluoroethylene (PTFE), copolymers of PVDF-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ethers, copolymers of ethylene-tetrafluoroethylene, copolymers of PVDF-tetrafluoroethylene, copolymers of PVDF-trifluoroethylene, copolymers of PVDF-trichloroethylene, copolymers of PVDF-fluorinated vinylidene, copolymers of PVDF-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; and styrene-butadiene rubber.

[0057] The positive electrode conductive agent includes one or more of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide.

[0058] In some embodiments, the negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes one or more of carbon-based negative electrodes, silicon-based negative electrodes, tin-based negative electrodes, and lithium negative electrodes. The carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.; the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials, etc.; the tin-based negative electrode may include tin, tin-carbon, tin oxide, and tin metal compounds; the lithium negative electrode may include metallic lithium or lithium alloys. Specifically, the lithium alloy may be at least one of lithium-silicon alloys, lithium-sodium alloys, lithium-potassium alloys, lithium-aluminum alloys, lithium-tin alloys, and lithium-indium alloys.

[0059] In some embodiments, the negative electrode further includes a negative electrode current collector, and the negative electrode material layer is disposed on the surface of the negative electrode current collector. The material of the negative electrode current collector may be the same as that of the positive electrode current collector, and will not be described in detail here.

[0060] In some embodiments, the negative electrode material layer further includes 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, and will not be described in detail here.

[0061] In some embodiments, the secondary battery further includes a separator located between the positive electrode and the negative electrode.

[0062] The diaphragm can be a conventional diaphragm, such as a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, or an inorganic-organic composite diaphragm, including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP, and triple-layer PP / PE / PP diaphragms.

[0063] The present invention also discloses the use of the non-aqueous electrolyte additive in the preparation of non-aqueous electrolytes for secondary batteries or secondary batteries.

[0064] The non-aqueous electrolyte additive of this invention, based on the basic structure of borate esters, forms a functional additive that can be used in non-aqueous electrolytes for secondary batteries by selecting appropriate substitution structures. This type of borate ester compound has a higher probability of forming coordination metals with solvated metal ions with lower activation energy, thus promoting desolvation. In the SEI film, it can effectively reduce the internal impedance of the battery and improve low-temperature and high-temperature performance. It also allows metal ions to embed into the negative electrode with lower energy loss. The linear structure is more conducive to desolvation than the cyclic structure, ultimately achieving the goal of reducing and improving battery impedance performance. Compared with traditional electrolyte additives, the borate ester compounds of this invention enable the secondary battery to form a stable SEI film during charging and discharging, thereby improving the high-temperature performance, low-temperature performance, and reducing initial impedance of the secondary battery, and significantly improving the application performance of the secondary battery. Detailed Implementation

[0065] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0066] Those skilled in the art, knowing the structural formula of the compound shown in Formula I, can understand the preparation method of the above compound based on common knowledge in the field of chemical synthesis.

[0067] The preparation method of the compounds described in the following embodiments of the present invention can be obtained according to known synthetic methods in the prior art, and suitable substances are selected as raw materials for reaction based on the substitution structures of A1, A2, and A3 in the selected compounds. For example, when A1 is selected from the substitution structure shown in formula (AE), boron trichloride can be used to react with the selected substituted compound raw material in a ratio of one or two equivalents in the presence of an acid-binding agent (such as triethylamine, pyridine, N,N-diisopropylethylamine, 4-dimethylaminopyridine, triethanolamine, tetrabutylammonium bromide, potassium carbonate, ammonium carbonate, or sodium carbonate, etc.), and then reacted sequentially with the selected hydroxyalkyl sulfonate in the presence of an acid-binding agent (triethylamine, pyridine, N,N-diisopropylethylamine, 4-dimethylaminopyridine, triethanolamine, tetrabutylammonium bromide, potassium carbonate, ammonium carbonate, or sodium carbonate, etc.) to obtain the compound shown in formula I.

[0068] The present application will be further illustrated by the following examples.

[0069] Table 1

[0070]

[0071]

[0072] Note: The compounds used in the following examples and comparative examples are selected from Table 1.

[0073] Examples 1-17

[0074] Examples 1-17 of this invention illustrate the preparation method of the non-aqueous electrolyte and lithium-ion battery described in this invention. The preparation methods are identical except for the different additives used in the non-aqueous electrolyte. The specific preparation methods are as follows:

[0075] (1) Preparation of non-aqueous electrolyte

[0076] Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a mass ratio of EC:DEC:EMC = 1:1:1. Then, lithium hexafluorophosphate (LiPF6) was added to a molar concentration of 1 mol / L. Based on the total weight of the non-aqueous electrolyte being 100%, the additives and their contents as shown in Table 2 were added.

[0077] (2) Preparation of positive electrode plate

[0078] The positive electrode active material, lithium nickel cobalt manganese oxide (LiNiO), was prepared in a mass ratio of 93:4:3. 0.5Co 0.2 Mn 0.3 O2, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) are mixed and then dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) to obtain the positive electrode slurry. The obtained slurry is uniformly coated on both sides of aluminum foil, and after drying, rolling and vacuum drying, aluminum leads are welded on using an ultrasonic welding machine to obtain the positive electrode plate. The thickness of the electrode plate is between 120-150 μm.

[0079] (3) Preparation of negative electrode plate

[0080] According to the mass ratio of 94:1:2.5:2.5, artificial graphite, conductive carbon black Super-P, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) are mixed and dispersed in an appropriate amount of deionized water to obtain a negative electrode slurry. The slurry is coated on both sides of a copper foil, dried, rolled, and vacuum dried, and nickel leads are welded on using an ultrasonic welding machine to obtain a negative electrode plate with a thickness between 120-150 μm.

[0081] (4) Cell fabrication

[0082] A three-layer separator with a thickness of 20 μm is placed between the positive and negative plates prepared above. Then, the sandwich structure composed of the positive plate, negative plate and separator is wound up, and the wound body is flattened and placed in an aluminum foil packaging bag. It is then vacuum baked at 75°C for 48 hours to obtain the cell to be injected with electrolyte.

[0083] (5) Electrolyte injection and formation of the battery cell

[0084] In a glove box where the dew point is controlled below -40°C, the electrolyte prepared above is injected into the battery cell, vacuum sealed, and left to stand for 24 hours.

[0085] The initial formation was then performed as follows: constant current charging at 0.05C for 180 minutes, constant current charging at 0.2C to 3.95V, followed by a second vacuum sealing. Then, it was further charged at a constant current of 0.2C to 4.2V, left to stand at room temperature for 24 hours, and finally discharged at a constant current of 0.2C to 3.0V to obtain a LiNi alloy. 0.5 Co 0.2 Mn 0.3 O2 / Artificial Graphite Secondary Battery

[0086] Comparative Examples 1-7

[0087] This comparative example is used to illustrate the non-aqueous electrolyte and battery method disclosed in this invention. It includes most of the operation steps in the above embodiments. The difference is that in the preparation of the non-aqueous electrolyte, the components with the mass percentages shown in Comparative Examples 1-7 in Table 2 are added as additives based on the total weight of the non-aqueous electrolyte as 100%, and the test results are filled in Table 2.

[0088] Performance testing

[0089] The lithium-ion batteries prepared in Examples 1-17 and Comparative Examples 1-7 were subjected to the following performance tests.

[0090] 1. High-temperature storage performance test

[0091] The formed lithium-ion battery was charged at room temperature with a constant current of 1C to 4.2V, then charged with a constant current and constant voltage until the current dropped to 0.05C. It was then discharged at a constant current of 1C to 3.0V. The initial discharge capacity and initial battery volume were measured. The battery was then fully charged and stored at 60℃ for 30, 60, and 90 days, respectively. Afterward, it was discharged at 1C to 3V, and the retention capacity, recovery capacity, and battery volume after storage were measured. The calculation formula is as follows:

[0092] Battery capacity retention rate (%) = Retained capacity / Initial capacity × 100%;

[0093] Battery capacity recovery rate (%) = Recovered capacity / Initial capacity × 100%;

[0094] Volume expansion rate (%) = (Battery volume after storage - Initial battery volume) / Initial battery volume × 100%.

[0095] 2. DC Impedance Test (DCIR Test)

[0096] DCRch = (Charging cutoff voltage - Starting voltage) / Current

[0097] DCRdis = (Discharge cutoff voltage - Start-up voltage) / Current

[0098] At 25°C, the battery is charged and discharged at a rate of 0.5C for 3 cycles, and the average capacity of the 3 discharge cycles is taken as the rated capacity. Then, it is charged at a rate of 0.5C to 50% of the rated capacity.

[0099] 25℃ DCIR test: After placing the battery with a constant capacity of 50% at 25℃ for 4 hours, charge it at a constant current rate of 0.5C for 10 seconds, let it rest for 40 seconds and test the charging DCRch. Then discharge it at a constant current rate of 0.5C for 10 seconds, let it rest for 40 seconds and test the discharging DCRdis.

[0100] 0℃ DCIR test: After placing the battery with a constant capacity of 50% at 0℃ for 4 hours, charge it at a constant current rate of 0.5C for 10 seconds, let it rest for 40 seconds and test the charging DCRch. Then discharge it at a constant current rate of 0.5C for 10 seconds, let it rest for 40 seconds and test the discharging DCRdis.

[0101] 3. Low temperature performance

[0102] Low-temperature discharge performance test: At 25℃, the formed battery was charged to 4.35V using a 1C constant current and constant voltage method, and then discharged to the full discharge voltage of 3.0V using a 1C constant current and constant voltage method, and the discharge capacity was recorded. Then, it was charged to the full voltage using a 1C constant current and constant voltage method, placed in an environment at -20℃ for 12 hours, and then discharged to the corresponding voltage of 2.5V using a 0.5C constant current method, and the discharge capacity was recorded.

[0103] The low-temperature discharge efficiency value at -20℃ = 0.5C discharge capacity (-20℃) / 1C discharge capacity (25℃) × 100%.

[0104] The test results are shown in Table 2 below.

[0105] Table 2. Electrochemical performance test results of lithium-ion batteries

[0106]

[0107]

[0108]

[0109] Comparing the test results of Examples 1-6 and Comparative Example 1, it can be seen that adding the structure shown in Formula I to the electrolyte can effectively reduce the internal impedance of lithium-ion batteries and improve their low-temperature and high-temperature performance. Furthermore, compared with the test results of Comparative Examples 2-4, Examples 1-6, compared with traditional vinylene carbonate (VC), vinyl sulfate (DTD), and 1,3-propanesulfonate lactone (PS), using the structure shown in Formula I of this application as an additive enables the lithium-ion battery to form a stable SEI film during charging and discharging, thereby improving the high-temperature performance, low-temperature performance, and reducing the initial impedance of the lithium-ion battery.

[0110] Comparing the test results of Examples 1-6 and Comparative Examples 6-7, it can be seen that adding the structure shown in Formula I to the electrolyte, the borate ester compound of this type has a higher probability of forming a coordination metal with solvated metal ions with a lower activation energy to promote their desolvation. In the SEI film, it can effectively reduce the internal impedance of the battery and improve the low-temperature and high-temperature performance. It can also enable metal ions to be inserted into the negative electrode with lower energy loss. The linear structure is more likely to promote desolvation than the cyclic structure, ultimately achieving the purpose of reducing and improving the battery impedance performance.

[0111] Comparing the test results of Example 2 and Comparative Example 6, it can be seen that the cycle performance and impedance reduction effect of Example 2 are better than those of Comparative Example 6. This is mainly because, compared with the perfluoroalkyl structure of Compound 7, the additive of Compound 2 contains a sulfate ester group, which has a higher probability of forming a coordination metal with solvated metal ions with a lower activation energy to promote their desolvation. This results in a more stable SEI film, improving the high-temperature performance, low-temperature performance, and initial impedance reduction of the lithium-ion battery. Comparing the test results of Example 5 and Comparative Example 7, it can be seen that the cycle performance and impedance reduction effect of Example 5 are better than those of Comparative Example 7. This is mainly because the additive of Compound 5 used in Example 5 has a higher probability of forming a coordination metal with solvated metal ions with a lower activation energy to promote their desolvation. In the SEI film, this can effectively reduce the internal impedance of the battery and improve high-temperature and low-temperature performance.

[0112] Comparing the test results of Examples 1 and 7-14, it can be seen that adding the structure shown in Formula I to the electrolyte can significantly improve the high-temperature performance, low-temperature performance, and battery impedance performance of lithium-ion batteries within a wide range of addition. In particular, the lithium-ion battery exhibits the best overall performance when the compound content is 1 wt%. This may be because when the content of the compound shown in Formula I is in the range of 0.1-5 wt%, the stability of the SEI film formed on the electrode surface is better, which further contributes to improving battery performance.

[0113] Comparing the test results of Examples 1, 15-17, and Comparative Example 5, it can be seen that, compared to the individual addition of the structure shown in Formula I, the combination of the structure shown in Formula I with traditional vinylene carbonate (VC), vinyl sulfate (DTD), and 1,3-propanesulfonate lactone (PS) can better improve the high and low temperature performance and impedance performance of lithium-ion batteries. Furthermore, compared to combinations of traditional additives, the combination of the structure shown in Formula I with traditional additives yields even better results, further demonstrating that the passivation film formed by the structure shown in Formula I has superior high and low temperature performance and impedance performance.

[0114] Examples 18-34

[0115] Examples 18-34 illustrate the preparation method of the non-aqueous electrolyte and sodium-ion battery of the present invention. The preparation methods are identical except for the different additives used in the non-aqueous electrolyte. The specific preparation methods are as follows:

[0116] (1) Preparation of non-aqueous electrolyte

[0117] Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a mass ratio of EC:DEC:EMC = 1:1:1. Then, sodium hexafluorophosphate (NaPF6) was added to a molar concentration of 1 mol / L. Based on the total weight of the non-aqueous electrolyte being 100%, the types and amounts of additives shown in Table 3 were added.

[0118] (2) Preparation of positive electrode plate

[0119] The layered metal oxide NaNi of the positive electrode active material was taken in a mass ratio of 93:4:3. 1 / 3 Fe 1 / 3 Mn 1 / 3 O3, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) are mixed and then dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) to obtain the positive electrode slurry. The obtained slurry is uniformly coated on both sides of aluminum foil, and after drying, rolling and vacuum drying, aluminum leads are welded on using an ultrasonic welding machine to obtain the positive electrode plate. The thickness of the electrode plate is between 120-150 μm.

[0120] (3) Preparation of negative electrode plate

[0121] According to the mass ratio of 94:1:2.5:2.5, artificial graphite, conductive carbon black Super-P, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) are mixed and dispersed in an appropriate amount of deionized water to obtain a negative electrode slurry. The slurry is coated on both sides of a copper foil, dried, rolled, and vacuum dried, and nickel leads are welded on using an ultrasonic welding machine to obtain a negative electrode plate with a thickness of 120-150 μm.

[0122] (4) Cell fabrication

[0123] A three-layer separator with a thickness of 20 μm is placed between the positive and negative plates prepared above. Then, the sandwich structure composed of the positive plate, negative plate and separator is wound up, and the wound body is flattened and placed in an aluminum foil packaging bag. It is then vacuum baked at 75°C for 48 hours to obtain the cell to be injected with electrolyte.

[0124] (5) Electrolyte injection and formation of the battery cell

[0125] In a glove box where the dew point is controlled below -40°C, the electrolyte prepared above is injected into the battery cell, vacuum sealed, and left to stand for 24 hours.

[0126] Then, the first charge was performed using the following steps: constant current charging at 0.05C for 180 minutes, constant current charging at 0.2C to 3.95V, vacuum sealing, and then further constant current charging at 0.2C to 4.2V. After being left at room temperature for 24 hours, constant current discharge at 0.2C to 3.0V was obtained, resulting in a sodium-ion secondary battery.

[0127] Comparative Examples 8-11

[0128] This comparative example is used to illustrate the non-aqueous electrolyte and battery method disclosed in this invention. It includes most of the operation steps in the above embodiments. The difference is that in the preparation of the non-aqueous electrolyte, the components with the mass percentages shown in Comparative Examples 8 to 11 in Table 3 are added as additives based on the total weight of the non-aqueous electrolyte as 100%, and the test results are filled in Table 3.

[0129] Performance testing

[0130] The sodium-ion batteries prepared in Examples 18-34 and Comparative Examples 8-11 were subjected to the following performance tests.

[0131] 1. High-temperature storage performance test

[0132] The sodium-ion batteries, after formation, were charged at room temperature with a constant current of 0.5C to 3.9V (cutoff current 0.03C), and then left to rest for 5 minutes. They were then discharged at a constant current of 0.5C to 1.5V, left to rest for 5 minutes, and then charged at a constant current and voltage of 0.5C to 3.9V (cutoff current 0.03C). The initial discharge capacity and initial battery volume were measured. After being fully charged, the batteries were stored at 60℃ for 30, 60, and 90 days, respectively. They were then discharged at 0.3C to 1.5V, and then charged at a constant current and voltage of 0.5C to 3.9V. The retention capacity, recovery capacity, and battery volume after storage were measured under these conditions. The calculation formula is as follows: Battery capacity retention rate (%) = Retention capacity / Initial capacity × 100%;

[0133] Battery capacity recovery rate (%) = Recovered capacity / Initial capacity × 100%;

[0134] Volume expansion rate (%) = (Battery volume after storage - Initial battery volume) / Initial battery volume × 100%.

[0135] 2. DC Impedance Test (DCIR Test)

[0136] DCRch = (Charging cutoff voltage - Starting voltage) / Current

[0137] DCRdis = (Discharge cutoff voltage - Start-up voltage) / Current

[0138] At 25°C, the battery is charged and discharged at a rate of 0.3C for 3 cycles, and the average capacity of the 3 discharge cycles is taken as the rated capacity. Then, it is charged at a rate of 0.3C to 50% of the rated capacity.

[0139] 25℃ DCIR Test: After placing the battery, which has been capacitated to 50%, at 25℃ for 4 hours, it was charged at a constant current rate of 0.3C for 10 seconds, and then rested for 40 seconds to test the charging DCIR (DCRch). Then, it was discharged at a constant current rate of 0.3C for 10 seconds, and then rested for 40 seconds to test the discharging DCIR (DCRdis). The test results are shown in Table 3 below.

[0140] Table 3. Electrochemical performance test results of sodium-ion batteries

[0141]

[0142]

[0143] Comparing the test results of Examples 18-23 and Comparative Example 8, it can be seen that adding the structure shown in Formula I to the electrolyte can effectively reduce the internal impedance of sodium-ion batteries and improve high-temperature performance. Furthermore, compared with the test results of Comparative Examples 9-11, Examples 18-23, compared with traditional vinylene carbonate (VC), vinyl sulfate (DTD), and 1,3-propanesulfonate lactone (PS), using the structure shown in Formula I of this application as an additive enables the sodium-ion battery to form a stable SEI film during charging and discharging, thereby improving the high-temperature performance of the sodium-ion battery and reducing the initial impedance.

[0144] Comparing the test results of Examples 18 and 24-31, it can be seen that adding the structure shown in Formula I to the electrolyte can effectively improve the high-temperature performance and battery impedance performance of sodium-ion batteries over a wide range of addition. In particular, the sodium-ion battery exhibits the best overall performance when the compound content is 1 wt%. This may be because when the content of the compound shown in Formula I is in the range of 0.1-5 wt%, the stability of the SEI film formed on the electrode surface is better, which further contributes to improving battery performance.

[0145] Comparing the test results of Examples 18 and 32-34, it can be seen that, compared with the individual addition of the structure shown in Formula I, the combination of the structure shown in Formula I with the traditional vinylene carbonate (VC), vinyl sulfate (DTD) and 1,3-propanesulfonate lactone (PS) can better improve the high-temperature performance and impedance performance of sodium-ion batteries.

[0146] In summary, the borate ester compounds with the structure described in this application, when used as electrolyte additives for secondary batteries, enable the formation of a stable SEI film during charging and discharging, thereby improving the high-temperature performance, low-temperature performance, and reducing impedance of the secondary battery. Compared to traditional electrolyte additives, they offer superior functional improvements to secondary batteries and possess significant industrial value. The electrolyte additives of this application also enhance the chemical performance of both lithium-ion and sodium-ion batteries to a certain extent, indicating that the non-aqueous electrolyte additives of this application are suitable for various secondary batteries.

[0147] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. A non-aqueous electrolyte additive, characterized in that, The non-aqueous electrolyte additive has the structure shown in Formula I: Formula I In formula I, A1, A2, and A3 are each independently selected from the structure shown in formula (AD), wherein at least two of A1, A2, and A3 have the same substitution structure, and A1, A2, and A3 are not simultaneously selected from the structure shown in formula (D); For bonding positions; ； R1 and R2 are each independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl, or substituted or unsubstituted C2-C5 alkynyl. a and b are each independent integers selected from 0 to 3.

2. The non-aqueous electrolyte additive according to claim 1, characterized in that, The non-aqueous electrolyte additive is selected from compounds with the following structures: 。 3. A non-aqueous electrolyte, characterized in that, It includes organic non-aqueous solvents, electrolyte salts, and non-aqueous electrolyte additives as described in any one of claims 1-2.

4. The non-aqueous electrolyte according to claim 3, characterized in that, Based on the total mass of the non-aqueous electrolyte being 100%, the content of the non-aqueous electrolyte additive is 0.05-10 wt%.

5. The non-aqueous electrolyte according to claim 4, characterized in that, Based on the total mass of the non-aqueous electrolyte being 100%, the content of the non-aqueous electrolyte additive is 0.1-5 wt%.

6. The non-aqueous electrolyte according to claim 3, characterized in that, The concentration of the electrolyte salt is 0.1 mol / L to 8 mol / L.

7. The non-aqueous electrolyte according to claim 6, characterized in that, The concentration of the electrolyte salt is 0.5 mol / L to 2.5 mol / L.

8. The non-aqueous electrolyte according to claim 3, characterized in that, The electrolyte salt is selected from one or more lithium salts and sodium salts; 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, Li2B 10 Cl 10 At least one of the following: lower aliphatic lithium carboxylate salts; The sodium salt is selected from at least one of NaBF4, NaFSI, NaTFSI, NaPF6, NaClO4, NaAsF6, NaSbF6, NaPOF4, NaPO2F2, NaC4BO8, NaC2BF2O4, NaODFB, NaN(SO2C2F5)2, NaN(SO2CF3)(SO2C4F9)2, NaC(SO2CF3) and Na(C2F5)PF3.

9. The non-aqueous electrolyte according to claim 3, characterized in that, The non-aqueous electrolyte further includes auxiliary additives, which are selected from at least one of cyclic carbonates, fluorocyclic carbonates, sulfonyl lactones, cyclic sulfates, phosphates, borate esters, and nitrile compounds; The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, and compounds shown in Formula II below: Formula II In equation II shown, R 31 R 32 R 33 R 34 R 35 R 36 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group; The fluorocyclic carbonate is selected from one or more of fluoroethylene carbonate, trifluoromethyl ethylene carbonate and difluoroethylene carbonate; The sulfonyl lactone compounds are selected from 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, propenyl-1,3-sulfonyl lactone, and others. At least one of them; The cyclic sulfate compounds are selected from vinyl sulfate, 4-methylvinyl sulfate, propylene sulfate, etc. , , , , At least one of them; The phosphate ester compound is selected from at least one of saturated phosphate ester compounds and unsaturated phosphate ester compounds; wherein the saturated phosphate ester compound includes tris(trimethylsilane) phosphate; and the unsaturated phosphate ester compound includes at least one of the compounds shown in Formula III below: Formula III In Equation III, R 41 R 42 R 43 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -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 them is an unsaturated hydrocarbon group; The borate ester compound is selected from at least one of tris(trimethylsilane)borate ester and tris(triethylsilane)borate ester; The nitrile compound is selected from at least one of succinic acid, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octanilide, nonadionitrile, and sebaconitrile.

10. The non-aqueous electrolyte according to claim 3, characterized in that, The non-aqueous organic solvents include one or more of the following: ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

11. A secondary battery, characterized in that, It includes a positive electrode, a negative electrode, and the non-aqueous electrolyte as described in any one of claims 3-10.

12. The secondary battery according to claim 11, characterized in that, The secondary battery is a lithium-ion battery, a lithium metal battery, or a sodium-ion battery.

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