WO2023104038A1

WO2023104038A1 - Secondary battery

Info

Publication number: WO2023104038A1
Application number: PCT/CN2022/136962
Authority: WO
Inventors: 钱韫娴; 刘中波; 邓永红; 王勇; 黄雄
Original assignee: 深圳新宙邦科技股份有限公司
Priority date: 2021-12-07
Filing date: 2022-12-06
Publication date: 2023-06-15
Also published as: CN114373980A; CN114373980B

Abstract

In order to overcome the problem of an insufficient high-temperature performance of existing secondary batteries, the present invention provides a secondary battery. The secondary battery comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises a cobalt-containing compound; the negative electrode comprises a negative electrode material layer; and the non-aqueous electrolyte comprises a solvent, an electrolyte salt and a compound as represented by structural formula 1, wherein R1 is selected from an unsaturated hydrocarbyl group having 3-6 carbon atoms, R2 is selected from an alkylene group having 2-5 carbon atoms, and n = 1 or 2. The secondary battery satisfies the condition (aa). The secondary battery provided in the present invention effectively reduces the damage, to a highly compacted negative electrode, of Co ions dissolved out from the cobalt-containing compound during a cycling process of the battery, reduces the capacity loss of the secondary battery during high-temperature cycling, and improves the high-temperature cycling performance of the secondary battery.

Description

a secondary battery

technical field

The invention belongs to the technical field of energy storage battery devices, and in particular relates to a secondary battery.

Background technique

Due to the advantages of high working voltage, wide working temperature range, high energy density and power density, no memory effect and long cycle life, lithium-ion batteries have been widely used in the field of 3C digital products such as mobile phones and notebook computers, as well as in the field of new energy vehicles. Applications. In recent years, with the continuous development of thinner and thinner 3C digital products, the battery industry has higher and higher requirements for high energy density of lithium-ion batteries. At the same time, for the consideration of users, fast charging has become a basic requirement for batteries. Therefore, there is an urgent need to increase the energy density of lithium-ion batteries and improve the fast charging performance.

In terms of the positive electrode, the volume energy density of the battery can be effectively increased by using the positive electrode active material containing cobalt, and a good rate performance can be maintained. However, as the battery voltage gradually increases, the positive electrode material enters a higher delithiation state, and the material The structural stability will be deteriorated, the Co in the positive electrode is prone to disproportionation reaction, dissolves in the electrolyte in the form of ions, and migrates to the interface of the negative electrode, and undergoes ion exchange with lithium in the negative electrode, occupying the lithium intercalation position of the negative electrode, and is not easy to come out , leading to a decrease in the lithium storage capacity of the negative electrode, resulting in a loss of capacity, resulting in a deterioration in the performance of the lithium-ion secondary battery. The specific manifestations are: the battery generates gas, the internal resistance increases rapidly, and the capacity drops sharply. Gas production in the battery will lead to an increase in internal pressure, which may further develop into dangerous situations such as explosion and combustion of the battery. Therefore, high-voltage batteries need to be matched with an electrolyte with better high-voltage resistance.

From the perspective of the negative electrode, in order to increase the energy density, high-pressure compaction has become a commonly used method in the industry. By reducing the porosity of the negative electrode, it can achieve the purpose of carrying more active materials. However, the higher the compaction density of the negative electrode material of lithium-ion batteries, the higher the requirements for the electrolyte. The electrolyte suitable for conventionally compacted negative electrodes is prone to a series of problems such as lithium deposition in the battery, reduced cycle life, and reduced rate performance in a high-pressure system, and the Co ions dissolved from the positive electrode will damage the negative electrode under high-pressure conditions. It is more serious, resulting in a significant drop in the high-temperature cycle performance of the battery.

Therefore, in a battery system that uses a high-voltage cobalt-containing positive electrode combined with a high-pressure negative electrode, how to configure the electrolyte to ensure the normal operation of the battery at high temperature is an urgent problem to be solved.

Contents of the invention

Aiming at the problem of insufficient high-temperature performance of existing secondary batteries, the invention provides a secondary battery.

The technical solution adopted by the present invention to solve the problems of the technologies described above is as follows:

On the one hand, the present invention provides a kind of secondary battery, comprise positive pole, negative pole and nonaqueous electrolytic solution, described positive pole comprises positive pole material layer, and described positive pole material layer comprises positive pole active material, and described positive pole active material comprises cobalt-containing compound , the negative electrode includes a negative electrode material layer, and the non-aqueous electrolytic solution includes a compound shown in solvent, electrolyte salt and structural formula 1:

Wherein, R1 is selected from unsaturated hydrocarbon groups with 3-6 carbon atoms, R2 is selected from alkylene groups with 2-5 carbon atoms, and n is 1 or 2;

The secondary battery satisfies the following conditions:

Wherein, a is the ratio of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer;

b is the mass percent content of Co element in the positive electrode material layer, and the unit is %;

m is the mass percentage of the compound shown in structural formula 1 in the non-aqueous electrolyte, in %;

p is the compacted density of the negative electrode material layer, and the unit is g/cm ³ .

Optionally, the secondary battery meets the following conditions:

Optionally, the compound represented by the structural formula 1 is selected from one or more of the following compounds:

Optionally, the ratio a of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer is 0.10 to 0.70; preferably, the ratio a of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer The ratio a is 0.15-0.60.

Optionally, the mass percentage b of Co element in the positive electrode material layer is 5% to 60%; preferably, the mass percentage b of Co element in the positive electrode material layer is 5% to 30%.

Optionally, the mass percentage m of the compound represented by structural formula 1 in the nonaqueous electrolyte is 0.05% to 5%; preferably, the mass percentage m of the compound represented by structural formula 1 in the nonaqueous electrolyte The content m is 0.1% to 3%.

Optionally, the compacted density p of the negative electrode material layer is greater than or equal to 1.5 g/cm ³ ; preferably, the compacted density p of the negative electrode material layer is 1.55˜1.8 g/cm ³ .

Optionally, the non-aqueous electrolyte also includes auxiliary additives, the auxiliary additives include cyclic sulfate ester compounds, sultone compounds, cyclic carbonate compounds, unsaturated phosphoric acid ester compounds and nitrile at least one of the compounds.

Optionally, based on 100% of the total mass of the nonaqueous electrolyte, the auxiliary additive is added in an amount of 0.01%-30%.

Optionally, the cyclic sulfate ester compound is selected from at least one of vinyl sulfate, propylene sulfate or vinyl methyl sulfate;

The sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone or 1,3-propene sultone;

The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate or the compound shown in structural formula 2,

In the structural formula 2, R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , and R ₂₆ are each independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group;

The unsaturated phosphate compound is selected from at least one of the compounds shown in structural formula 3:

In the structural formula 3, R ₃₁ , R ₃₂ , and R ₃₃ are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C _m H _2m+1 ) ₃ , m is 1 to A natural number of 3, and at least one of R ₃₁ , R ₃₂ , and R ₃₃ is an unsaturated hydrocarbon group;

Described nitrile compound comprises succinonitrile, glutaronitrile, ethylene glycol two (propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile one or more.

According to the secondary battery provided by the present invention, a high-pressure negative electrode and a cobalt-containing positive electrode are used, so that the secondary battery has a higher initial energy density, and at the same time, in order to avoid the degradation of the cycle performance of the battery, a structural formula 1 is added to the non-aqueous electrolyte. For the compounds shown, the inventors have found through a large number of experiments that the compound shown in structural formula 1 has the effect of improving the high-temperature cycle performance and its addition amount, the ratio of the quality of the electrolyte to the total mass of the positive electrode material layer, and the ratio of the Co element in the positive electrode material layer. The mass percentage content and the compaction density of the negative electrode material layer are closely related. When the positive and negative electrodes and the electrolyte in the secondary battery satisfy the relationship

At the same time, it can effectively suppress the dissolution of Co ions in the positive electrode at high temperature, and at the same time form a denser and more stable SEI film on the surface of the negative electrode, effectively reducing the impact of Co ions leached from the cobalt-containing compound on the high-pressure negative electrode during the battery cycle. damage, reducing the capacity loss of the secondary battery under high-temperature cycle, and improving the high-temperature cycle performance of the secondary battery.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

An embodiment of the present invention provides a secondary battery, including a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material includes a cobalt-containing compound, The negative electrode includes a negative electrode material layer, and the non-aqueous electrolytic solution includes a compound shown in solvent, electrolyte salt and structural formula 1:

Wherein, R1 is selected from unsaturated hydrocarbon groups with 3-6 carbon atoms, R2 is selected from alkylene groups with 2-5 carbon atoms, n=1 or 2;

The secondary battery satisfies the following conditions:

The secondary battery adopts a high-pressure negative electrode and a cobalt-containing positive electrode, so that the secondary battery has a higher initial energy density, and at the same time, in order to avoid the degradation of the cycle performance of the battery, a compound shown in structural formula 1 is added to the non-aqueous electrolyte , the inventor found through a large number of experiments that the compound shown in structural formula 1 can improve the high-temperature cycle performance and its addition amount, the total mass percentage of the positive electrode and the electrolyte, the mass percentage of Co element in the positive electrode material layer, and the content of the negative electrode material layer. The compacted density is closely related, when the relationship between the positive and negative electrodes and the electrolyte in the secondary battery satisfies the relationship

In a preferred embodiment, the secondary battery satisfies the following conditions:

In the secondary battery provided by the present invention, the compound shown in structural formula 1 is combined with the design parameters of the positive electrode and the negative electrode in the secondary battery (the total mass percentage of the positive electrode and the electrolyte, the mass percentage of Co element in the positive electrode material layer, The compaction density of the negative electrode material layer) is correlated, and the influence of the positive electrode, the negative electrode and the compound shown in structural formula 1 on the performance of the battery can be integrated to a certain extent, and a battery with a high initial energy density and excellent high-temperature cycle performance can be obtained. secondary battery.

In some embodiments, the compound represented by the structural formula 1 is selected from one or more of the following compounds:

In some embodiments, the ratio a of the mass of the electrolyte solution to the total mass of the positive electrode material layer is 0.10˜0.70.

In a preferred embodiment, the ratio a of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer is 0.15-0.60.

The capacity of the secondary battery depends on the interaction of the positive electrode material layer, the negative electrode material layer and the non-aqueous electrolyte. When the ratio of the quality of the electrolyte to the total mass of the positive electrode material layer in the secondary battery is too high, the When the ratio of the quality of the electrolyte in the secondary battery to the total mass of the positive electrode material layer is too low, there is a lack of insertion sites for the positive electrode material layer for electrolyte ion insertion, so the quality of the electrolyte in the secondary battery Too high or too low a ratio to the total mass of the positive electrode material layer is not conducive to the improvement of the capacity of the secondary battery.

In some embodiments, the mass percentage b of the Co element in the positive electrode material layer is 5%-60%.

In a preferred embodiment, the mass percentage b of Co element in the positive electrode material layer is 5%-30%.

The mass percentage content of the Co element in the positive electrode material layer can be regulated correspondingly by selecting a specific type of cobalt-containing compound for the positive electrode active material and adjusting the content of the positive electrode active material in the positive electrode material layer. Only when the mass percentage of Co element in the positive electrode material layer reaches a certain value can the secondary battery have better rate performance, but when the mass percentage of Co element in the positive electrode material layer is too large, it is easy to Under certain conditions, the positive electrode active material reacts with the non-aqueous electrolyte, resulting in the dissolution of Co element, and migrates to the negative electrode interface, and ion exchange occurs with lithium in the negative electrode, occupying the lithium intercalation position of the negative electrode, and is not easy to come out, resulting in the lithium storage capacity of the negative electrode. Reduced, resulting in capacity loss, leading to poor performance of lithium-ion secondary batteries.

In a preferred embodiment, the secondary battery is a lithium ion battery.

In this embodiment, the positive electrode active material includes a compound represented by the following formula;

Li _1+x Ni _a Co _b M _1-ab O _2-y A _y

Wherein, -0.1≤x≤0.2, 0≤a<1, 0<b≤1, 0≤y<0.2, M includes one or more of Mn and Al, and optionally includes Sr, Mg, Ti , Ca, Zr, Zn, Si, Fe, zero, one or more of Ce, A includes one or more of S, N, F, Cl, Br and I.

In some embodiments, the positive electrode material layer also includes a positive electrode binder and a positive electrode conductive agent, the positive electrode active material, the compound represented by the structural formula 1, the positive electrode binder and the positive electrode conductive agent blending to obtain the positive electrode material layer.

Based on the total mass of the positive electrode material layer as 100%, the mass percentage of the positive electrode binder is 1-2%, and the mass percentage of the positive electrode conductive agent is 0.5-2%.

The positive electrode binder includes polyvinylidene fluoride, copolymer of vinylidene fluoride, polytetrafluoroethylene, copolymer of vinylidene fluoride-hexafluoropropylene, copolymer of tetrafluoroethylene-hexafluoropropylene, tetrafluoroethylene- Copolymer of perfluoroalkyl vinyl ether, copolymer of ethylene-tetrafluoroethylene, copolymer of vinylidene fluoride-tetrafluoroethylene, copolymer of vinylidene fluoride-trifluoroethylene, copolymer of vinylidene fluoride-trichloroethylene Copolymers, vinylidene fluoride-fluorinated vinyl copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, thermoplastic polyimides, thermoplastic resins such as polyethylene and polypropylene; acrylic resins; methylol One or more of sodium cellulose; polyvinyl butyral; ethylene-vinyl acetate copolymer; polyvinyl alcohol; and styrene butadiene rubber.

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

In some embodiments, the positive electrode sheet further includes a positive electrode current collector, and the positive electrode material layer covers the surface of the positive electrode current collector. It should be noted that, in the present application, the part of the positive electrode other than the positive electrode current collector is referred to as the positive electrode material layer.

The positive electrode current collector is selected from metal materials 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 The current collector is selected from aluminum foil.

In some embodiments, the mass percentage m of the compound represented by structural formula 1 in the non-aqueous electrolyte is 0.05%-5%.

In a preferred embodiment, the mass percentage m of the compound represented by structural formula 1 in the non-aqueous electrolyte is 0.1%-3%.

The positive electrode active material includes a cobalt-containing compound so that the secondary battery has a good rate performance, but when the mass percentage of Co element in the positive electrode material layer is too large, it is easy to cause the positive electrode active material and the non-aqueous electrolyte to be separated under high voltage conditions. The reaction takes place to cause the stripping of Co element. By adding the compound shown in structural formula 1, the stability of the non-aqueous electrolyte can be improved, and then the stripping of Co element in the positive electrode active material can be suppressed. However, if the compound added in the structural formula 1 is too large, it will It leads to the formation of some unnecessary side reaction products, which further deteriorates other performances of the secondary battery.

In some embodiments, the compacted density p of the negative electrode material layer is greater than or equal to 1.5 g/cm ³ ; preferably, the compacted density p of the negative electrode material layer is 1.55˜1.8 g/cm ³ .

The compaction density p of the negative electrode material layer has a certain influence on the capacity of the secondary battery. Generally, if the compaction density is too low, the negative electrode active material available for lithium ion intercalation in the negative electrode per unit volume will be less, which is not conducive to The improvement of energy density, but the compaction density of the negative electrode material layer is too large, indicating that the pores used for lithium ion intercalation and extraction in the negative electrode are severely compacted, the negative electrode sheet is dense, and the porosity is smaller, so the negative electrode active material particles They will be more tightly attached to each other, and the active sites exposed to the electrolyte will be reduced, so that the negative porous electrode has fewer active sites that can participate in the reaction. In addition, the compaction density of the negative electrode material layer is related to the compound shown in structural formula 1. After adding the compound shown in structural formula 1 in the non-aqueous electrolyte, its ionic conductivity and viscosity etc. will change, affecting the non-aqueous electrolyte for the negative electrode. The permeability of the material layer affects the intercalation and extraction efficiency of lithium ions; the compaction density of the negative electrode material layer also affects the density of the SEI film formed by the decomposition of the compound shown in structural formula 1 on the surface of the negative electrode material layer, affecting the SEI The protective effect of the membrane against free Co.

The above analysis is only based on the impact of each parameter or multiple parameters on the battery alone, but in the actual battery application process, the above four parameters are interrelated and inseparable. The relational formula given by the present invention relates the four, and the four jointly affect the electrochemical performance of the battery, so adjust the addition amount m of the compound shown in structural formula 1, the ratio a of the mass of the electrolyte to the total mass of the positive electrode material layer, the positive electrode The mass percent content b of the Co element in the material layer, the compaction density p of the negative electrode material layer, make

The high-temperature cycle performance and high-temperature storage performance of the secondary battery can be effectively improved on the premise of ensuring that the secondary battery has a high energy density. like

When the value is too high or too low, the kinetics of the battery will deteriorate, which will shorten the service life of the battery under high temperature conditions, and even cause safety problems.

In some embodiments, the anode material layer includes an anode active material, and the anode active material is selected from at least one of a silicon-based anode, a carbon-based anode, and a tin-based anode.

In a preferred embodiment, the carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesocarbon microspheres, and the like. The graphite includes but not limited to one or more of natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite, and resin-coated graphite. The natural graphite may be flaky graphite, flaky graphite, soil graphite, and/or graphite particles obtained by using these graphites as raw materials and subjecting them to spheroidization, densification, and the like. The artificial graphite can be p-coal tar pitch, coal heavy crude oil, atmospheric residue, petroleum heavy crude oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride , polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene ether, furfuryl alcohol resin, phenolic resin, imide resin and other organic substances are obtained by graphitization at high temperature. The amorphous carbon may be obtained by heat-treating once or more in a temperature range (400 to 2200° C.) in which graphitization does not occur, using a graphitizable carbon precursor such as tar or pitch as a raw material. Particles, amorphous carbon particles obtained by heat treatment using a non-graphitizable carbon precursor such as a resin as a raw material. The carbon-coated graphite may be obtained by mixing natural graphite and/or artificial graphite with a carbon precursor that is an organic compound such as tar, pitch, resin, etc., and performing heat treatment at 400-2300° C. once or more. A carbon-graphite composite is obtained by using the obtained natural graphite and/or artificial graphite as core graphite and covering it with amorphous carbon. The carbon-graphite composite may be a form in which the entire or part of the surface of core graphite is coated with amorphous carbon, or may be a form in which a plurality of primary particles are composited using carbon derived from the carbon precursor described above as a binder. In addition, a carbon-graphite composite can also be obtained by reacting hydrocarbon gases such as benzene, toluene, methane, propane, and volatile components of aromatics with natural graphite and/or artificial graphite at high temperature to deposit carbon on the graphite surface. The graphite-coated graphite may be natural graphite and/or artificial graphite mixed with carbon precursors of easily graphitizable organic compounds such as tar, pitch, resin, etc., and heat-treated at a range of about 2400-3200°C for more than one time. The obtained natural graphite and/or artificial graphite is used as the core graphite, and the entire or part of the surface of the core graphite is coated with graphitized substances, so that graphite-coated graphite can be obtained. The resin-coated graphite can be mixed with natural graphite and/or artificial graphite and resin, and dried at a temperature lower than 400°C, and the natural graphite and/or artificial graphite thus obtained is used as core graphite, and the resin is used and so on to coat the core graphite. Organic compounds such as tar and pitch resin mentioned above are selected from heavy crude oil of coal type, heavy crude oil of direct flow type, heavy crude oil of decomposition type petroleum, aromatic hydrocarbon, N-ring compound, S-ring compound, polyphenylene, organic synthesis Carbonizable organic compounds in polymers, natural polymers, thermoplastic resins and thermosetting resins, etc.

In a preferred embodiment, the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, silicon alloy materials, and the like. The added amount of the silicon-based material is greater than 0 and less than 30%. Preferably, the upper limit of the added amount of the silicon-based material is 10%, 15%, 20% or 25%; the lower limit of the added amount of the silicon-based material is 5%, 10% or 15%. The silicon material is one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon films, 3D porous silicon, and hollow porous silicon.

In a preferred embodiment, the tin-based negative electrode may include tin, tin-carbon, tin oxide, tin-based alloy, tin metal compound; the tin-based alloy refers to tin and Cu, Ag, Co, Zn, Sb, Bi and An alloy composed of one or more of In.

In some embodiments, the negative electrode material layer includes one or more of lithium negative electrodes, sodium negative electrodes, potassium negative electrodes, magnesium negative electrodes, zinc negative electrodes and aluminum negative electrodes. The lithium negative electrode may include metallic lithium or a lithium alloy. Specifically, the lithium alloy may be at least one of lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy and lithium-indium alloy.

In some embodiments, the negative electrode further includes a negative electrode current collector, and the negative electrode material layer covers the surface of the negative electrode current collector. It should be noted that the part of the negative electrode in this application other than the negative electrode current collector is referred to as the negative electrode material layer.

The negative electrode current collector is selected from metal materials that can conduct electrons. Preferably, the negative electrode current collector includes one or more of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode The current collector is selected from aluminum foil.

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 includes polyvinylidene fluoride, copolymer of vinylidene fluoride, polytetrafluoroethylene, copolymer of vinylidene fluoride-hexafluoropropylene, copolymer of tetrafluoroethylene-hexafluoropropylene, tetrafluoroethylene- Copolymer of perfluoroalkyl vinyl ether, copolymer of ethylene-tetrafluoroethylene, copolymer of vinylidene fluoride-tetrafluoroethylene, copolymer of vinylidene fluoride-trifluoroethylene, copolymer of vinylidene fluoride-trichloroethylene Copolymers, vinylidene fluoride-fluorinated vinyl copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, thermoplastic polyimides, thermoplastic resins such as polyethylene and polypropylene; acrylic resins; methylol sodium cellulose; and one or more of styrene butadiene rubber.

The negative electrode conductive agent includes one or more of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene or reduced graphene oxide.

In some embodiments, the non-aqueous electrolyte also includes auxiliary additives, and the auxiliary additives include cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, unsaturated phosphate compounds and at least one of nitrile compounds.

Preferably, the cyclic sulfate ester compound is selected from at least one of vinyl sulfate, propylene sulfate or vinyl methyl sulfate;

In the structural formula 2, R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , and R ₂₆ are each independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group.

In the structural formula 3, R ₃₁ , R ₃₂ , and R ₃₃ are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C _m H _2m+1 ) ₃ , m is 1 to 3, and at least one of R ₃₁ , R ₃₂ , and R ₃₃ is an unsaturated hydrocarbon group.

In a preferred embodiment, the unsaturated phosphoric acid ester compound may be 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, diallyl hexafluoroisopropyl phosphate at least one of the

In other embodiments, the auxiliary additives may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, specifically flame retardant additives such as fluorophosphate esters and cyclophosphazene, or tert-amyl Benzene, tert-butylbenzene and other anti-overcharge additives.

In some embodiments, based on 100% of the total mass of the non-aqueous electrolyte, the amount of the auxiliary additive is 0.01%-30%.

It should be noted that, unless otherwise specified, in general, the addition amount of any optional substance in the auxiliary additive in the non-aqueous electrolyte is less than 10%, preferably, the addition amount is 0.1-5%, more Preferably, the added amount is 0.1%-2%. Specifically, the addition amount 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%, 10%.

In some embodiments, when the auxiliary additive is selected from fluoroethylene carbonate, based on 100% of the total mass of the non-aqueous electrolyte, the added amount of the fluoroethylene carbonate is 0.05%-30%.

In some embodiments, the electrolyte salt includes one or more of lithium salts, sodium salts, potassium salts, magnesium salts, zinc salts and aluminum salts. In a preferred embodiment, the electrolyte salt is selected from lithium salts or sodium salts.

In a preferred embodiment, _the electrolyte salt is selected from LiPF ₆ , LiPO ₂ F ₂ , LiBF ₄ , LiBOB, LiSbF 6 , LiAsF ₆ , LiCF ₃ SO ₃ , LiDFOB, LiN(SO ₂ CF ₃ ) ₂ , LiC(SO ₂ CF ₃ ) ₃ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(SO ₂ F) ₂ , LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ At least one of lithium chloroborane, lower aliphatic lithium carboxylate having 4 or less carbon atoms, lithium tetraphenylborate, and lithium imide. Specifically, the electrolyte salt can be inorganic electrolyte salts such as LiBF ₄ , LiClO ₄ , LiAlF ₄ , LiSbF ₆ , LiTaF ₆ , LiWF ₇ ; fluorophosphate electrolyte salts such as LiPF ₆ ; tungstate electrolyte salts such as LiWOF ₅ ; HCO ₂ Li , CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF _{3 CF 2 CO 2 Li, CF 3} _CF ₂ _CF ₂ _CO ₂ Li , CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ Li and other carboxylic acid electrolyte salts; CH ₃ SO ₃ Li and other sulfonic acid electrolyte salts; LiN(FCO ₂ ) ₂ , LiN(FCO)(FSO ₂ ), LiN(FSO ₂ ) ₂ , LiN(FSO ₂ )(CF ₃ SO ₂ ), LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , cyclic 1,2-perfluoroethanedisulfonylimide Lithium, cyclic 1,3-perfluoropropanedisulfonylimide lithium, LiN(CF ₃ SO ₂ )(C ₄ F ₉ SO ₂ ) and other imide electrolyte salts; LiC(FSO ₂ ) ₃ , LiC( CF ₃ SO ₂ ) ₃ , LiC(C ₂ F ₅ SO ₂ ) ₃ and other methyl electrolyte salts; lithium difluorooxalatoborate, lithium di(oxalato)borate, lithium tetrafluorooxalatophosphate, di Oxalic acid electrolyte salts such as lithium fluorodi(oxalato)phosphate and lithium tri(oxalato)phosphate; and LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiBF ₃ C ₃ F ₇ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) _2. LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ and other fluorine-containing organic electrolyte salts, etc.

If the electrolyte salt is selected from other salts such as sodium salt, potassium salt, magnesium salt, zinc salt or aluminum salt, the lithium in the above lithium salt can be replaced with sodium, potassium, magnesium, zinc or aluminum.

In a preferred embodiment, the sodium salt is selected from sodium perchlorate (NaClO ₄ ), sodium hexafluorophosphate (NaPF ₆ ), sodium tetrafluoroborate (NaBF ₄ ), sodium trifluoromethanesulfonate (NaFSI), At least one of sodium trifluoromethanesulfonate (NaTFSI).

Usually, the electrolyte salt in the electrolyte is the transfer unit of lithium ions. The concentration of the electrolyte salt directly affects the transfer speed of lithium ions, and the transfer speed of lithium ions will affect the potential change of the negative electrode. During the fast charging process of the battery, it is necessary to increase the moving speed of lithium ions as much as possible to prevent the formation of lithium dendrites caused by the rapid decrease in the potential of the negative electrode, which brings safety hazards to the battery, and at the same time prevent the cycle capacity of the battery from decaying too quickly. Preferably, the total concentration of the electrolyte salt in the electrolyte can be 0.5mol/L-2.0mol/L, 0.5mol/L-0.6mol/L, 0.6mol/L-0.7mol/L, 0.7mol/L ～0.8mol/L, 0.8mol/L～0.9mol/L, 0.9mol/L～1.0mol/L, 1.0mol/L～1.1mol/L, 1.1mol/L～1.2mol/L, 1.2mol/L ～1.3mol/L, 1.3mol/L～1.4mol/L, 1.4mol/L～1.5mol/L, 1.5mol/L～1.6mol/L, 1.6mol/L～1.7mol/L, 1.7mol/L ～1.8mol/L, 1.8mol/L～1.9mol/L, or 1.9mol/L～2.0mol/L, more preferably 0.6mol/L～1.8mol/L, 0.7mol/L～1.7mol/L L, or 0.8mol/L～1.5mol/L.

In some embodiments, the solvent includes one or more of ether solvents, nitrile solvents, carbonate solvents and carboxylate solvents.

In some embodiments, ether solvents include cyclic ethers or chain ethers, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms. The cyclic ethers can specifically be but not limited to It is 1,3-dioxolane (DOL), 1,4-dioxane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH ₃ -THF), 2-tri One or more of fluoromethyltetrahydrofuran (2-CF ₃ -THF); the chain ether can be, but not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane , Ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which are low in viscosity and impart high ion conductivity, are particularly preferred because the solvation ability of chain ethers with lithium ions is high and ion dissociation can be improved. methyl methane. One kind of ether compound may be used alone, or two or more kinds may be used in any combination and ratio. The addition amount of the ether compound is not particularly limited, and it is arbitrary within the scope of not significantly destroying the effect of the high-compression lithium-ion battery of the present invention. When the volume ratio of the non-aqueous solvent is 100%, the volume ratio is usually more than 1%, preferably 1% by volume. The ratio is 2% or more, more preferably 3% or more by volume, and usually 30% or less by volume, preferably 25% or less by volume, more preferably 20% or less by volume. When two or more ether compounds are used in combination, the total amount of the ether compounds may satisfy the above range. When the addition amount of the ether compound is within the above-mentioned preferred range, it is easy to ensure the effect of improving the ion conductivity by increasing the lithium ion dissociation degree of the chain ether and reducing the viscosity. In addition, when the negative electrode active material is a carbon material, co-intercalation of the chain ether and lithium ions can be suppressed, so that input-output characteristics and charge-discharge rate characteristics can be brought into appropriate ranges.

In some embodiments, the nitrile solvent may specifically be, but not limited to, one or more of acetonitrile, glutaronitrile, and malononitrile.

In some embodiments, the carbonate solvents include cyclic carbonates or chain carbonates, and the cyclic carbonates can specifically be, but not limited to, ethylene carbonate (EC), propylene carbonate (PC), gamma-butyrolactone One or more of (GBL), butylene carbonate (BC); the chain carbonate can specifically be, but not limited to, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC ), one or more of dipropyl carbonate (DPC). The content of cyclic carbonate is not particularly limited, and it is arbitrary within the scope of not significantly destroying the effect of the high-pressure lithium-ion battery of the present invention, but the lower limit of its content is relative to that of the non-aqueous electrolyte when one is used alone. The volume ratio of the total solvent is usually 3% or more, preferably 5% or more. By setting this range, it is possible to avoid a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte, and it is easy to make the large-current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery reach a good range. In addition, the upper limit is usually 90% or less by volume, preferably 85% or less by volume, and more preferably 80% or less by volume. By setting this range, the oxidation/reduction resistance of the non-aqueous electrolytic solution can be improved, thereby contributing to the improvement of stability during high-temperature storage. The content of the chain carbonate is not particularly limited, but is usually 15% or more by volume, preferably 20% or more by volume, and more preferably 25% or more by volume relative to the total amount of solvent in the nonaqueous electrolyte. In addition, the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less. By making the content of the chain carbonate within the above range, it is easy to make the viscosity of the non-aqueous electrolytic solution in an appropriate range, suppress the decrease in ion conductivity, and contribute to making the output characteristics of the non-aqueous electrolyte battery a good range. When two or more chain carbonates are used in combination, the total amount of the chain carbonates may satisfy the above-mentioned range.

In some embodiments, chain carbonates having fluorine atoms (hereinafter simply referred to as “fluorinated chain carbonates”) may also be preferably used. The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, these fluorine atoms may be bonded to the same carbon or to different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.

Carboxylate solvents include cyclic carboxylates and/or chain carbonates. Examples of cyclic carboxylic acid esters include one or more of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonates include: methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate one or more of .

In some embodiments, the sulfone solvent includes cyclic sulfone and chain sulfone, but preferably, in the case of cyclic sulfone, it usually has 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms. In the case of chain sulfone, it is usually a compound having 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. The amount of sulfone solvent added is not particularly limited, and it is arbitrary within the scope of not significantly destroying the effect of the high-compression lithium-ion battery of the present invention. With respect to the total amount of solvent in the non-aqueous electrolyte, the volume ratio is usually more than 0.3%, preferably The volume ratio is 0.5% or more, more preferably 1% or more, and usually 40% or less, preferably 35% or less, more preferably 30% or less. When using two or more sulfone-based solvents in combination, the total amount of the sulfone-based solvent may satisfy the above range. When the added amount of the sulfone solvent is within the above range, an electrolytic solution having excellent high-temperature storage stability tends to be obtained.

In a preferred embodiment, the solvent is a mixture of cyclic carbonates and chain carbonates.

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

The diaphragm can be an existing conventional diaphragm, which can be a polymer diaphragm, non-woven fabric, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP /PP and three-layer PP/PE/PP separators.

The present invention is further described by way of examples below.

Each parameter design of table 1 embodiment and comparative example

Note: LCO refers to LiCoO ₂ , NCM811 refers to LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , NCM622 refers to LiNi _0.6 Co _0.2 Mn _0.2 O ₂ .

Example 1

This embodiment is used to illustrate the battery disclosed in the present invention and its preparation method, including the following steps: (1) Preparation of positive electrode sheet

Disperse the Co-containing positive electrode active material LiCoO ₂ (subsequently referred to as LCO), the conductive agent and the binder PVDF into the solvent NMP and mix uniformly to obtain the positive electrode slurry; evenly coat the positive electrode slurry on the aluminum foil of the positive electrode current collector , after drying, rolling, and cutting, the positive pole piece is obtained, and the mass ratio of the positive active material, conductive carbon black and binder PVDF is 96:2:2.

(2) Preparation of negative pole piece

Disperse the negative electrode active material graphite, conductive agent, binder CMC and SBR in deionized water according to the mass ratio of 96:1:1:2 and stir to obtain the negative electrode slurry; evenly coat the negative electrode slurry on the negative electrode current collector copper foil, after drying, rolling, and cutting, a negative electrode sheet with a compacted density of 1.6 g/cm ³ was obtained.

(3) Preparation of electrolyte

Mix ethylene carbonate (EC) and diethyl carbonate (DEC) uniformly at a mass ratio of 30:70, and mix 1 mol/L of LiPF ₆ and a compound represented by structural formula 1 in an amount of 0.1 wt% of the electrolyte Dissolve in the above-mentioned non-aqueous organic solvent to obtain an electrolytic solution.

(4) Preparation of lithium-ion secondary battery

Using the stacking process, the positive pole piece, the separator and the negative pole piece are stacked in sequence, and then the pouch battery is made after top-side sealing and injection of a certain amount of electrolyte.

Examples 2-28

Examples 2-28 are used to illustrate the battery disclosed in the present invention and its preparation method, including most of the operation steps in Example 1, the differences are:

The positive electrode parameters, negative electrode parameters and electrolyte addition components shown in Table 1 were adopted.

Comparative example 1-12

Comparative Examples 1-12 are used to illustrate the battery disclosed in the present invention and its preparation method, including most of the operation steps in Example 1, the difference being:

Performance Testing

The high-temperature cycle performance test of the lithium-ion battery is carried out on the lithium-ion battery prepared above:

At 45°C, charge the formed battery with 1C constant current and constant voltage to the cut-off voltage, then charge it with constant voltage until the current drops to 0.05C, and then discharge it with a constant current of 1C to 3.0V. The discharge capacity and volume of the first discharge and the discharge capacity and volume of the last discharge.

Calculate the capacity retention rate of high temperature cycle according to the following formula:

Capacity retention ratio = last discharge capacity / first discharge capacity × 100%.

Volume growth rate = (volume of the last time - volume of the first time) / volume of the first time × 100%

(1) The performance test results of the lithium-ion batteries made in Examples 1 to 20 and Comparative Examples 1 to 7 are shown in Table 2:

Table 2

From the test results of Examples 1 to 20 and Comparative Examples 1 to 7, it can be seen that when the lithium ion battery provided by the present invention is used, the ratio of the amount m of the compound shown in Structural Formula 1, the mass of the electrolyte to the total mass of the positive electrode material layer a, the mass percentage of Co element in the positive electrode material layer b and the compaction density p of the negative electrode material layer satisfy the relational expression

, lithium-ion batteries have better cycle performance at high temperatures, while

If the value is too large or too small, it is not conducive to the improvement of the high-temperature performance of the lithium-ion battery. In particular, it can be seen from Examples 13-20 that when the cobalt content in the positive electrode active material increases, the compacted density of the negative electrode is reduced and the structural formula 1 is increased. The content of the compound shown and the mass ratio of the electrolyte to the positive electrode material layer can maintain the high temperature capacity retention and volume growth rate of the battery at a similar level, indicating that the above factors have a mutual effect on the adjustment of the cobalt content of the positive electrode active material. By adjusting the above factors, the negative impact of the increase in the cobalt content of the positive electrode on the battery cycle performance can be effectively suppressed.

At the same time, it can be seen from Comparative Examples 2 and 3 that when the cobalt content in the positive electrode active material is low, the content of the compound shown in structural formula 1 in the non-aqueous electrolyte is too high, which also leads to the degradation of the high-temperature cycle performance of the lithium-ion battery; It can be seen from Comparative Example 4 and Comparative Example 5 that when the content of cobalt in the positive electrode active material is high, the content of the compound shown in structure 1 in the non-aqueous electrolyte is too low, which is also not conducive to the high-temperature cycle performance of the lithium-ion battery. , indicating that when the cobalt content in the positive electrode active material is low or high, the compound shown in structural formula 1 needs to be added in the non-aqueous electrolyte at a low or high content.

Comparing the test results of Examples 1 to 20, it can be seen that when the relational expression satisfies

Lithium-ion batteries have the best high-temperature storage performance and high-temperature cycle performance.

(2) The performance test result of the lithium-ion battery that embodiment 1, 21～23 makes is as shown in table 3:

table 3

From the test results of Examples 1 and 21 to 23, it can be seen that when using different compounds shown in structural formula 1 as additives for non-aqueous electrolytes, the relational formula

At the same time, the improvement effects of different compounds represented by structural formula 1 on battery high-temperature capacity retention and high-temperature volume growth rate are similar, indicating that the relationship provided by the present invention is universally applicable to compounds represented by different structural formula 1 sex.

(3) The performance test results of the lithium-ion batteries made in Examples 1, 24-28 and Comparative Examples 8-12 are shown in Table 4:

Table 4

From the test results of Examples 1 and 24 to 28, it can be seen that in the lithium ion battery provided by the present invention, adding cyclic sulfate ester compounds, sultone compounds, cyclic carbonate compounds, unsaturated phosphate esters Compounds or nitrile compounds as auxiliary additives can further improve the high-temperature cycle performance and high-temperature storage performance of the battery. Compounds, unsaturated phosphate compounds or nitrile compounds interact to form a passivation film on the electrode. Among them, when the auxiliary additive is vinyl sulfate, the performance improvement of the battery is most obvious.

From the comparative results of Example 1 and Comparative Examples 8 to 12, it can be seen that when cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, unsaturated phosphoric acid ester compounds or nitrile compounds are used to replace non- When the compound represented by structural formula 1 is present in the water electrolyte, the effect that can be achieved by adding the compound represented by structural formula 1 cannot be achieved.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims

A secondary battery, characterized in that it includes a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes a cobalt-containing compound, the The negative pole comprises a negative electrode material layer, and the non-aqueous electrolytic solution comprises a compound shown in solvent, electrolyte salt and structural formula 1:

Wherein, R1 is selected from unsaturated hydrocarbon groups with 3-6 carbon atoms, R2 is selected from alkylene groups with 2-5 carbon atoms, n=1 or 2;

The secondary battery satisfies the following conditions:

Wherein, a is the ratio of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer;

b is the mass percent content of Co element in the positive electrode material layer, and the unit is %;

m is the mass percentage of the compound shown in structural formula 1 in the non-aqueous electrolyte, in %;

p is the compacted density of the negative electrode material layer, and the unit is g/cm 3 .
The secondary battery according to claim 1, wherein the secondary battery satisfies the following conditions:
The secondary battery according to claim 1, wherein the compound represented by the structural formula 1 is selected from one or more of the following compounds:
The secondary battery according to claim 1, characterized in that the ratio a of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer is 0.10-0.70.
The secondary battery according to claim 4, characterized in that the ratio a of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer is 0.15-0.60.
The secondary battery according to claim 1, characterized in that the mass percentage b of Co element in the positive electrode material layer is 5%-60%.
The secondary battery according to claim 6, characterized in that, the mass percentage b of the Co element in the positive electrode material layer is 5%-30%.
The secondary battery according to claim 1, characterized in that the mass percentage m of the compound represented by structural formula 1 in the non-aqueous electrolytic solution is 0.05%-5%.
The secondary battery according to claim 8, characterized in that the mass percentage m of the compound represented by structural formula 1 in the non-aqueous electrolytic solution is 0.1%-3%.
The secondary battery according to claim 1, wherein the compacted density p of the negative electrode material layer is greater than or equal to 1.5 g/cm 3 .
The secondary battery according to claim 10, characterized in that, the compacted density p of the negative electrode material layer is 1.55˜1.8 g/cm 3 .
The secondary battery according to claim 1, wherein the non-aqueous electrolytic solution also includes auxiliary additives, and the auxiliary additives include cyclic sulfate ester compounds, sultone compounds, and cyclic carbonate compounds. At least one of compounds, unsaturated phosphate ester compounds and nitrile compounds.
The secondary battery according to claim 12, characterized in that, based on the total mass of the non-aqueous electrolyte solution as 100%, the amount of the auxiliary additive added is 0.01%-30%.
The secondary battery according to claim 12, wherein the cyclic sulfate ester compound is at least one selected from vinyl sulfate, propylene sulfate or vinyl methyl sulfate.
The secondary battery according to claim 12, wherein the sultone compound is selected from 1,3-propane sultone, 1,4-butane sultone or 1,3- at least one of propene sultones.
The secondary battery according to claim 12, characterized in that, the cyclic carbonate compound is selected from at least A sort of,

In the structural formula 2, R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group.
The secondary battery according to claim 12, wherein the unsaturated phosphate compound is selected from at least one of the compounds shown in structural formula 3:

In the structural formula 3, R 31 , R 32 , and R 33 are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 ) 3 , m is 1 to 3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group.
The secondary battery according to claim 12, wherein the nitrile compound comprises succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, heptanedinitrile One or more of nitrile, suberonitrile, azelanitrile, sebaconitrile.