Secondary battery

Abstract

The present invention provides a secondary battery including a positive electrode active material, a negative electrode active material, and a non-aqueous electrolyte solution, and having a charging voltage of not less than 4.45 V. The non-aqueous electrolyte comprises an electrolyte salt, a non-aqueous organic solvent and an additive, and the non-aqueous organic solvent at least comprises carbonic ester. The additive comprises a compound A and a compound B, the structural formula of the compound A is shown as a structural formula I, and the structural formula of the compound B is shown as a structural formula II or a structural formula III. Wherein R1 is selected from hydrogen, substituted or unsubstituted C1-C6 alkyl groups, R2 is selected from hydrogen, substituted or unsubstituted C1-C6 alkyl groups and nitrile groups, R3 is selected from nitrile groups, C1-C6 alkyl ether groups, substituted or unsubstituted C1-C6 alkyl groups and substituted or unsubstituted acylamino groups, R4, R5, R6, R7, R8 and R9 are respectively and independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl groups, and R is a chain-shaped tertiary amino group or a cyclic tertiary amino group. The secondary battery still has better high-temperature storage performance and high-temperature cycle performance under high voltage of 4.45 V and above. The structural formula I, the structural formula II and the structural formula III are shown in the description

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, and in particular relates to a secondary battery. Background Technology

[0002] Rechargeable batteries, as efficient and environmentally friendly energy storage devices, have been widely used in electric vehicles, portable electronic devices, and energy storage systems due to their high energy density and long cycle life. Their core performance mainly relies on the synergistic effect of the cathode material, anode material, and electrolyte system. Among these, medium-nickel cathode materials have become one of the mainstream cathode materials due to their high specific capacity and moderate cost. To improve the energy density of rechargeable batteries, the industry tends to increase the battery's operating voltage (e.g., ≥4.4V vs. Li / Li). + This is to fully unleash the capacity potential of medium-nickel cathode materials (such as NCM523 and NCM622). However, under high-voltage conditions, traditional electrolyte (carbonate-based) systems are prone to severe decomposition, leading to rapid performance degradation of the battery, which has become a key bottleneck restricting the commercial application of medium-nickel cathode material systems in secondary batteries.

[0003] Electrolyte systems for secondary batteries using medium-nickel cathode materials face multiple challenges: First, under high-voltage conditions, electrolyte solvents (such as ethylene carbonate EC, diethyl carbonate DEC, and other carbonate solvents) are easily oxidized and decomposed, producing gases (CO2, alkanes, etc.) and acidic substances (such as HF), leading to battery expansion, a surge in interfacial impedance, and the dissolution of transition metal ions. Second, it is difficult to form a dense and stable high-voltage compatible CEI film on the surface of medium-nickel cathode materials, resulting in continuous side reactions between the medium-nickel cathode material and the electrolyte, accelerating capacity decay. Third, the dissolved transition metal ions (such as Ni...) 2+ Co 3+ Transition metal ions migrate to the negative electrode surface, disrupting the SEI film structure and catalyzing lithium dendrite growth, threatening battery safety. Currently, additives are used in the industry to improve battery performance; however, while conventional additives (such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC)) can partially improve film-forming properties, their antioxidant capacity is insufficient, and they are prone to generating excessively high-impedance interface layers or introducing harmful byproducts at high voltages, making it difficult to meet the stringent requirements of long-cycle and high-safety secondary batteries using medium-nickel cathode materials. Therefore, developing novel electrolyte systems that combine high voltage stability with transition metal ion suppression has become a core issue urgently needing breakthroughs in this field. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a secondary battery, which is a secondary battery based on a medium-nickel cathode material system. This secondary battery still exhibits excellent high-temperature storage performance and high-temperature cycling performance at high voltages of 4.45V and above.

[0005] To achieve the above object, the present invention provides a secondary battery, comprising a positive electrode active material, a negative electrode active material and a non-aqueous electrolyte, and the charging voltage is not less than 4.45V. The positive electrode active material includes a medium-nickel positive electrode material, and the chemical formula of the medium-nickel positive electrode material is LiNi x Co y Mn z M 1-x-y-z O2, where M is selected from at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0.5≤x<1.0, 0<y<0.5, 0<z<0.5, x + y + z≤1. The non-aqueous electrolyte includes an electrolyte salt, a non-aqueous organic solvent and an additive. The non-aqueous organic solvent at least includes a carbonate, and the additive includes compound A and compound B. The structural formula of compound A is as shown in Structural Formula I, and the structural formula of compound B is as shown in Structural Formula II or Structural Formula III. Among them, R1 is selected from hydrogen, a substituted or unsubstituted C1-C6 alkyl group, R2 is selected from hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a nitrile group, R3 is selected from a nitrile group, a C1-C6 alkoxy group, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted amide group, and R4, R5, R6, R7, R8, R9 are each independently selected from hydrogen, a substituted or unsubstituted C1-C6 alkyl group, and R is a chain tertiary amine group or a cyclic tertiary amine group.

[0006]

[0007] Structural Formula I

[0008] Structural Formula II Structural Formula III In the secondary battery of the present invention, the additive contains compound A as shown in Structural Formula I. Compound A is a thiazole compound, and the CEI layer formed on the surface of the medium-nickel positive electrode material can inhibit the release of lattice oxygen (O 2- ) at a high voltage of 4.45V and above, so as to improve the cycle stability and high-temperature performance of the battery. However, when the thiazole compound participates in SEI film formation, side reactions occur on the negative electrode surface, resulting in an increase in the negative electrode interface impedance and affecting lithium ion transmission. Therefore, the present invention further introduces compound B into the non-aqueous electrolyte. Compound B is a benzenesulfonyl fluoride compound containing a tertiary amine group as shown in Structural Formula II, and its reduction potential is higher than that of compound A, and it can undergo a reduction reaction on the negative electrode side in advance to generate a high Li-containing sulfur and fluorine +The electrolyte contains an inorganic SEI component with high conductivity and blocks HF corrosion of the cathode surface, reducing the breakage of transition metal-oxygen bonds. Benzenesulfonyl fluoride compounds containing tertiary amine groups can form a CEI layer containing lithium sulfonate / lithium fluoride at high voltages of 4.45V and above, inhibiting further oxidation by carbonate solvents. Furthermore, the benzenesulfonyl fluoride compounds containing tertiary amine groups and thiazole compounds synergistically passivate surface oxygen vacancies. The decomposition product Li₂SO₃ of the benzenesulfonyl fluoride compounds fills these vacancies, and the nitrogen atoms of the thiazole compounds form NO coordination bonds with surface oxygen, doubly inhibiting lattice oxygen evolution, thereby improving the high-voltage stability, cycle life, and high-temperature performance of the medium-nickel cathode material system secondary battery. Therefore, the electrolyte of this invention, through the combination of compounds A and B, enables the medium-nickel cathode material system secondary battery to maintain excellent high-temperature storage and high-temperature cycling performance at high voltages of 4.45V and above.

[0009] As one technical solution of the present invention, R1 is selected from hydrogen, C1-C3 alkyl, C1-C3 fluoroalkyl, R2 is selected from hydrogen, C1-C3 alkyl, C1-C3 fluoroalkyl, nitrile, R3 is selected from nitrile, C1-C3 alkyl ether, C1-C3 alkyl, C1-C3 fluoroalkyl, amide, C1-C3 alkyl-substituted amide, R4, R5, R6, R7, R8, and R9 are each independently selected from hydrogen, C1-C3 alkyl, C1-C3 fluoroalkyl, and R is a C1-C3 alkyl-substituted tertiary amine, a C1-C3 fluoroalkyl-substituted tertiary amine, a five-membered ring tertiary amine, or a six-membered ring tertiary amine.

[0010] As one technical solution of the present invention, R is a C1~C3 alkyl-substituted tertiary amine group, a C1~C3 fluoroalkyl-substituted tertiary amine group, a five-membered ring imide, or a six-membered ring imide.

[0011] As a technical solution of the present invention, compound A is selected from at least one of compounds one to four.

[0012]

[0013] Compound 1 Compound 2

[0014] Compound 3 Compound 4 As a technical solution of the present invention, compound B is selected from at least one of compounds five to eight.

[0015]

[0016] Compound Five Compound Six

[0017] Compound Seven, Compound Eight As a technical solution of the present invention, based on the sum of the masses of the electrolyte salt, the non-aqueous organic solvent and the additive being 100%, the mass ratio of Compound A is 0.05 to 3.00%, and the mass ratio of Compound B is 0.05 to 3.00%.

[0018] As a technical solution of the present invention, the electrolyte salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalato)borate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium difluoro(dioxalato)phosphate and lithium bis(fluorosulfonyl)imide.

[0019] As a technical solution of the present invention, the non-aqueous organic solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, pentylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl n-propyl carbonate, ethyl n-propyl carbonate and propylene carbonate.

[0020] As a technical solution of the present invention, the non-aqueous organic solvent further includes at least one of γ-butyrolactone, γ-valerolactone, δ-valerolactone, methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, propyl propionate, propyl butyrate, 1,3-dioxolane, 1,4-dioxane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2-trifluoromethyltetrahydrofuran, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether and diethylene glycol dimethyl ether.

[0021] As a technical solution of the present invention, the negative electrode active material is selected from at least one of artificial graphite, natural graphite, soft carbon, hard carbon, lithium titanate, silicon-carbon composite material and silicon-oxygen composite material Detailed Embodiments The secondary battery of the present invention includes a positive electrode active material, a negative electrode active material and an electrolyte, and the charging voltage is not lower than 4.45V.

[0022] The positive electrode active material includes a medium-nickel positive electrode material, and the chemical formula of the medium-nickel positive electrode material is LiNi x Co y Mn z M 1-x-y-z O2, where M is selected from at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0.5 ≤ x < 1.0, 0 < y < 0.5, 0 < z < 0.5, and x + y + z ≤ 1. As an example, the medium-nickel positive electrode material can be NCM523, NCM622.

[0023] The negative electrode active material is selected from at least one of artificial graphite, natural graphite, soft carbon, hard carbon, lithium titanate, silicon-carbon composite material, and silicon-oxygen composite material. The negative electrode active material may use only one of the above, or a combination of two or more of the above.

[0024] The electrolyte comprises an electrolyte salt, a non-aqueous organic solvent, and additives. With the total mass of the electrolyte salt, non-aqueous organic solvent, and additives being 100%, the mass percentage of the electrolyte salt is 5% to 25%. Further, the mass percentage of the electrolyte salt is 8% to 20%, and even further, it is 10% to 15%. As examples, the mass percentage of the electrolyte salt may be, but is not limited to, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, and 25%. The electrolyte salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorooxalateborate, lithium difluorodioxalate phosphate, and lithium bis(fluorosulfonyl)imide.

[0025] The non-aqueous organic solvent comprises 65-90% by mass, further comprising 70-88% by mass, and even further comprising 80-88% by mass. As examples, the mass percentage of the non-aqueous organic solvent may be, but is not limited to, 65%, 67%, 69%, 70%, 72%, 74%, 75%, 77%, 79%, 80%, 81%, 84%, 85%, 88%, 89%, and 90%. The non-aqueous organic solvent includes at least one carbonate. The carbonate may be a chain carbonate and / or a cyclic carbonate. Further, the carbonate may be at least one selected from ethylene carbonate (EC), propylene carbonate, butyl carbonate (BC), amyl carbonate, vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (EMC), methyl ethyl carbonate (EMC), methyl n-propyl carbonate, ethyl n-propyl carbonate, and propylene carbonate (PC). The non-aqueous organic solvent may also include lactones, carboxylic acid esters, or ether compounds. Furthermore, the non-aqueous organic solvent may also include at least one of γ-butyrolactone, γ-valerolactone, δ-valerolactone, methyl acetate (MA), ethyl acetate (EA), ethyl propionate (EP), butyl acetate (n-Ba), propyl propionate (n-PP), butyl propionate, 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), 2-trifluoromethyltetrahydrofuran (2-CF3-THF), dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

[0026] The additives include compound A and compound B. The structural formula of compound A is shown in structural formula I, and the structural formula of compound B is shown in structural formula II or structural formula III.

[0027]

[0028] Structural Formula I

[0029] Structure II Structure III Wherein, R1 is selected from hydrogen, substituted or unsubstituted C1-C6 alkyl groups. Further, R1 is selected from hydrogen, C1-C3 alkyl groups, and C1-C3 fluoroalkyl groups. As an example, R1 is selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, monofluoromethyl, monofluoroethyl, monofluoropropyl, monofluoroisopropyl, monofluorobutyl, monofluoroisobutyl, monofluoropentyl, monofluorohexyl, polyfluoromethyl, polyfluoroethyl, polyfluoropropyl, polyfluoroisopropyl, polyfluorobutyl, polyfluoroisobutyl, polyfluoropentyl, and polyfluorohexyl.

[0030] R2 is selected from hydrogen, substituted or unsubstituted C1-C6 alkyl groups, and nitrile groups. Further, R2 is selected from hydrogen, C1-C3 alkyl groups, C1-C3 fluoroalkyl groups, and nitrile groups. As an example, R2 is selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, monofluoromethyl, monofluoroethyl, monofluoropropyl, monofluoroisopropyl, monofluorobutyl, monofluoroisobutyl, monofluoropentyl, monofluorohexyl, polyfluoromethyl, polyfluoroethyl, polyfluoropropyl, polyfluoroisopropyl, polyfluorobutyl, polyfluoroisobutyl, polyfluoropentyl, polyfluorohexyl, and nitrile groups.

[0031] R3 is selected from nitrile, C1-C6 alkyl ether, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted amide. Further, R3 is selected from nitrile, C1-C3 alkyl ether, C1-C3 alkyl, C1-C3 fluoroalkyl, amide, and C1-C3 alkyl-substituted amide. As an example, R3 is selected from nitrile, methyl ether, diethyl ether, propyl ether, isopropyl ether, butyl ether, isobutyl ether, pentyl ether, hexyl ether, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, monofluoromethyl, monofluoroethyl, monofluoropropyl, monofluoroisopropyl, monofluorobutyl, monofluoroisobutyl, monofluoropentyl, monofluorohexyl, polyfluoromethyl, polyfluoroethyl, polyfluoropropyl, polyfluoroisopropyl, polyfluorobutyl, polyfluoroisobutyl, polyfluoropentyl, polyfluorohexyl, aminomethyl, aminoethyl, aminopropyl, aminoisopropyl, aminobutyl, aminoisobutyl, aminopentyl, aminohexyl, amide, methylamide.

[0032] R4, R5, R6, R7, R8, and R9 are each independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl groups. Further, R4, R5, R6, R7, R8, and R9 are each independently selected from hydrogen, C1-C3 alkyl groups, and C1-C3 fluoroalkyl groups. As an example, R4, R5, R6, R7, R8, and R9 are each independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, monofluoromethyl, monofluoroethyl, monofluoropropyl, monofluoroisopropyl, monofluorobutyl, monofluoroisobutyl, monofluoropentyl, monofluorohexyl, polyfluoromethyl, polyfluoroethyl, polyfluoropropyl, polyfluoroisopropyl, polyfluorobutyl, polyfluoroisobutyl, polyfluoropentyl, and polyfluorohexyl.

[0033] R is a chain-like tertiary amine group or a cyclic tertiary amine group. Further, R is a C1-C3 alkyl-substituted tertiary amine group, a C1-C3 fluoroalkyl-substituted tertiary amine group, a five-membered ring tertiary amine group, or a six-membered ring tertiary amine group. Even further, R is a C1-C3 alkyl-substituted tertiary amine group, a C1-C3 fluoroalkyl-substituted tertiary amine group, a five-membered ring imide, or a six-membered ring imide. For example, R is dimethyl tertiary amino, diethyl tertiary amino, dipropyl tertiary amino, methyl ethyl tertiary amino, methyl propyl tertiary amino, ethyl propyl tertiary amino, monofluorodimethyl tertiary amino, monofluorodiethyl tertiary amino, monofluorodipropyl tertiary amino, monofluoromethyl ethyl tertiary amino, monofluoromethyl propyl tertiary amino, monofluoroethyl propyl tertiary amino, polyfluorodimethyl tertiary amino, polyfluorodiethyl tertiary amino, polyfluorodipropyl tertiary amino, polyfluoromethyl ethyl tertiary amino, polyfluoroethyl propyl tertiary amino, succinimide, N-bromosuccinimide, glutarimide, and maleimide.

[0034] Furthermore, compound A is selected from at least one of compounds one through four.

[0035]

[0036] Compound 1 Compound 2 CAS:1261677-60-4 CAS:1452-16-0

[0037] Compound 3 Compound 4 CAS: 55661-33-1 CAS: 16733-85-0 The mass percentage of compound A is 0.05% to 3.00%. Further, the mass percentage of compound A is 0.10% to 2.00%. Even further, the mass percentage of compound A is 0.10% to 1.00%. As examples, the mass percentage of compound A may be, but is not limited to, 0.05%, 0.50%, 1.00%, 1.50%, 2.00%, 2.50%, and 3.00%.

[0038] Furthermore, compound B is selected from at least one of compounds five through eight.

[0039]

[0040] Compound Five Compound Six CAS: 6162-22-7 CAS: 34523-28-9

[0041] Compound 7 Compound 8 CAS:1403672-31-0CAS:84348-87-8 The mass percentage of compound B is 0.05~3.00%. Further, the mass percentage of compound B is 0.10~2.00%. Even further, the mass percentage of compound B is 0.10~1.00%. As examples, the mass percentage of compound B may be, but is not limited to, 0.05%, 0.50%, 1.00%, 1.50%, 2.00%, 2.50%, and 3.00%.

[0042] To better illustrate the purpose, technical solution, and beneficial effects of the present invention, specific embodiments are provided below to further illustrate the purpose, technical solution, and beneficial effects of the present invention. However, these embodiments do not constitute any limitation on the present invention. Unless otherwise specified, specific conditions may be followed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products that can be obtained commercially.

[0043] Example 1 In an argon atmosphere and a vacuum glove box with a moisture content of <1ppm, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a weight ratio of EC:EMC=3:2. Then, various additives are added, dissolved, and stirred thoroughly before LiPF6 is added. After mixing evenly, a non-aqueous electrolyte is obtained.

[0044] (2) Preparation of positive electrode LiNi nickel cobalt manganese oxide material LiNi 0.6 Co 0.2 Mn 0.2 The binder PVDF and the conductive agent SuperP are mixed evenly at a mass ratio of 95:3:2 to prepare a lithium secondary battery positive electrode slurry with a certain viscosity. After the mixed slurry is coated on both sides of aluminum foil, it is dried and rolled to obtain the positive electrode sheet.

[0045] (3) Preparation of negative electrode Artificial graphite, binder PVDF and conductive agent SuperP are mixed evenly in a mass ratio of 92:2:6 to prepare a lithium secondary battery negative electrode slurry with a certain viscosity. The mixed slurry is coated on both sides of copper foil, dried and rolled to obtain the negative electrode sheet.

[0046] (4) Preparation of lithium-ion batteries The positive electrode, separator, and negative electrode are stacked in sequence, and then layered as needed. After the tabs are welded, they are placed in the aluminum-plastic film of the battery outer packaging. The prepared non-aqueous electrolyte is injected into the dried bare cell. Vacuum sealing, standing, formation (0.05C constant current charging to 3.9V, then 0.1C constant current charging to 4.45V), shaping, and capacity testing are carried out in sequence to finally obtain a 1Ah soft-pack lithium secondary battery.

[0047] The non-aqueous electrolyte formulations for Examples 1-11 and Comparative Examples 1-5 are shown in Table 1. The steps for preparing the electrolyte and manufacturing the battery are the same as in Example 1.

[0048] Table 1. Non-aqueous electrolyte formulations for Examples 1-11 and Comparative Examples 1-5

[0049] The lithium-ion batteries prepared in Examples 1-11 and Comparative Examples 1-5 were subjected to high-temperature storage tests and high-temperature cycling tests, respectively. The specific test conditions are as follows, and the performance test results are shown in Table 2.

[0050] (1) High-temperature storage performance test Under normal temperature (25℃) conditions, a lithium-ion battery was subjected to one 0.3C / 0.3C charge and discharge cycle (battery discharge capacity recorded as C0), with an upper limit voltage of 4.45V. The battery was then placed in a 60℃ oven for 30 days, removed, and placed in a 25℃ environment for a 0.3C discharge, with the discharge capacity recorded as C1. The lithium-ion battery was then subjected to another 0.3C / 0.3C charge and discharge cycle (battery discharge capacity recorded as C2). The capacity retention rate and capacity recovery rate of the lithium-ion battery were calculated using the following formulas.

[0051] Capacity retention rate = C1 / C0 × 100% Capacity recovery rate = C2 / C0 × 100% (2) High-temperature cycling performance test The lithium-ion battery was placed in a 45°C constant temperature chamber and allowed to stand for 30 minutes to reach a constant temperature. It was then charged at a constant current of 4C until the voltage reached 4.45V, followed by constant voltage charging at 4.45V until the current reached 0.05C. Next, it was discharged at a constant current of 4C until the voltage reached 2.5V. The first discharge capacity was recorded as C0. This constitutes one charge-discharge cycle. Then, 1000 cycles of 1C / 1C charge and discharge were performed at 45°C, and the discharge capacity was recorded as C1. The capacity retention rate of the lithium-ion battery was calculated using the following formula.

[0052] Capacity retention rate = C1 / C0 × 100% Table 2 Performance test results of lithium-ion batteries in Examples 1-11 and Comparative Examples 1-5

[0053] Based on the results of Examples 1-11 and Comparative Examples 2-5 in Table 2, it can be seen that the lithium-ion batteries of Examples 1-11 have better high-temperature cycling and high-temperature storage performance. This is because the synergistic effect of compound A and compound B can avoid the capacity decay caused by the structural collapse of the nickel cathode material, reduce the side reactions between the electrolyte and the anode material, reduce the consumption of active lithium, and thus improve the cycle stability and high-temperature storage performance of the battery.

[0054] A comparison of Examples 1-4 shows that Compound A exhibits superior performance. This is because Compound A forms a cathode electrolyte interface / solid electrolyte interface film rich in N and S on the surface of the nickel cathode material, which can suppress lattice oxygen (O) at high voltages of 4.45V and above. 2- The release of ) improves the cycle stability and high-temperature performance of the battery.

[0055] A comparison of Examples 1 and 5-7 shows that compound B, being compound five, exhibits superior performance. This is because compound five preferentially undergoes redox reactions, producing a homogeneous and mechanically stable CEI rich in LiF and Li₂SO₄, and altering the Li... + The solvation structure of the CEI, rich in LiF, can suppress the degradation of the cathode material and the growth of lithium dendrites. Simultaneously, the Li₂SO₄ component with high ionic conductivity promotes the growth of Li in the SEI / CEI. + The migration.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A secondary battery, comprising a positive electrode active material, a negative electrode active material, and a non-aqueous electrolyte, characterized in that, The charging voltage is not less than 4.45V, and the positive electrode active material includes a medium nickel positive electrode material. The chemical formula of the medium nickel positive electrode material is LiNi x Co y Mn z M 1-x-y-z O2, where M is selected from at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, 0.5 ≤ x < 1.0, 0 < y < 0.5, 0 < z < 0.5, x + y + z ≤ 1. The non-aqueous electrolyte includes an electrolyte salt, a non-aqueous organic solvent, and an additive. The non-aqueous organic solvent includes at least a carbonate. The additive includes compound A and compound B. The structural formula of compound A is as shown in structural formula I, and the structural formula of compound B is as shown in structural formula II or III. Among them, R1 is selected from hydrogen, a substituted or unsubstituted C1-C6 alkyl group, R2 is selected from hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a nitrile group, R3 is selected from a nitrile group, a C1-C6 alkoxy group, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted amide group, R4, R5, R6, R7, R8, R9 are each independently selected from hydrogen, a substituted or unsubstituted C1-C6 alkyl group, and R is a chain-like tertiary amine group or a cyclic tertiary amine group. Structural Formula I Structure II and Structure III.

2. The secondary battery according to claim 1, characterized in that, R1 is selected from hydrogen, C1-C3 alkyl, and C1-C3 fluoroalkyl; R2 is selected from hydrogen, C1-C3 alkyl, C1-C3 fluoroalkyl, and nitrile; R3 is selected from nitrile, C1-C3 alkyl ether, C1-C3 alkyl, C1-C3 fluoroalkyl, amide, and C1-C3 alkyl-substituted amide; R4, R5, R6, R7, R8, and R9 are each independently selected from hydrogen, C1-C3 alkyl, and C1-C3 fluoroalkyl; R is a C1-C3 alkyl-substituted tertiary amine, a C1-C3 fluoroalkyl-substituted tertiary amine, a five-membered ring tertiary amine, or a six-membered ring tertiary amine.

3. The secondary battery according to claim 2, characterized in that, R is a C1-C3 alkyl-substituted tertiary amine group, a C1-C3 fluoroalkyl-substituted tertiary amine group, a five-membered ring imide, or a six-membered ring imide.

4. The secondary battery according to claim 1, characterized in that, Compound A is selected from at least one of compounds one through four. Compound 1 Compound 2 Compound 3 and Compound 4.

5. The secondary battery according to claim 1, characterized in that, Compound B is selected from at least one of compounds five to eight. Compound Five Compound Six Compound 7 and Compound 8.

6. The secondary battery according to claim 1, characterized in that, With the total mass of the electrolyte salt, the non-aqueous organic solvent, and the additive being 100%, the mass percentage of compound A is 0.05~3.00%, and the mass percentage of compound B is 0.05~3.00%.

7. The secondary battery according to claim 1, characterized in that, The electrolyte salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate-borate), lithium difluorophosphate, lithium di(oxalate-borate), lithium di(difluorodioxalate-phosphate), and lithium bis(oxalate-imide).

8. The secondary battery according to claim 1, characterized in that, The non-aqueous organic solvent includes at least one of ethylene carbonate, propylene carbonate, butyl carbonate, pentylenetene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl n-propyl carbonate, ethyl n-propyl carbonate, and propylene carbonate.

9. The secondary battery according to claim 1, characterized in that, The non-aqueous organic solvent further includes at least one of γ-butyrolactone, γ-valerolactone, δ-valerolactone, methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, propyl propionate, butyl propionate, 1,3-dioxolane, 1,4-dioxolane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2-trifluoromethyltetrahydrofuran, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

10. The secondary battery according to claim 1, characterized in that, The negative electrode active material is selected from at least one of artificial graphite, natural graphite, soft carbon, hard carbon, lithium titanate, silicon-carbon composite material, and silicon-oxygen composite material.

Images