CN117186113A

CN117186113A - Non-aqueous electrolyte additive and application thereof

Info

Publication number: CN117186113A
Application number: CN202210604461.4A
Authority: CN
Inventors: 向书槐; 刘晋皓; 胡时光; 曹朝伟; 王驰
Original assignee: Shenzhen Capchem Technology Co Ltd
Current assignee: Shenzhen Capchem Technology Co Ltd
Priority date: 2022-05-30
Filing date: 2022-05-30
Publication date: 2023-12-08

Abstract

The application belongs to the technical field of secondary batteries, and particularly relates to a heterocyclic compound with a lactone structure as a mother nucleus as a nonaqueous electrolyte additive and application thereof. The additive comprises at least one of the compounds shown in the structural formula 1 and the structural formula 2:

Description

Non-aqueous electrolyte additive and application thereof

Technical Field

The application belongs to the technical field of secondary batteries, and particularly relates to a nonaqueous electrolyte additive and application thereof.

Background

At present, the lithium ion battery on the market is a mainstream power battery, and the sodium ion battery has a similar working principle to the lithium ion battery, and the sodium element used by the sodium ion battery is widely distributed in the crust, so that the cost is low, and the sodium is abundant in reserve and an insertion mechanism, so that the sodium ion battery becomes an ideal substitute of the lithium ion battery in large-scale application. Due to the wide application of secondary batteries, the performance requirements of the secondary batteries are also increasing. Secondary battery performance, particularly high temperature performance, low temperature performance, internal resistance performance, and cycle performance, are all challenged. Taking a lithium ion battery as an example, lithium ions in a positive electrode material are deintercalated in the process of charging a secondary battery, and are intercalated into a negative electrode material through an electrolyte. In current lithium ion batteries, various additives play a very important role, especially film forming additives. The film forming additive can form SEI film on the negative electrode, can slow down the chemical reaction between the electrode material and the electrolyte, and can improve the lithium ion permeability and reduce the electron conductivity. However, the SEI film formed by the additives such as VC, FEC and ES derivatives in the market at present has the defects of uneven film surface thickness, poor high-temperature stability, lower ion conductivity, higher impedance and the like, and has adverse effects on the service life and high-rate discharge of the battery. Meanwhile, the lithium ion migration resistance at low temperature is correspondingly improved, so that the internal resistance of the battery is correspondingly improved. Studies have shown that desolvation of solvated lithium ions in the electrolyte across the SEI film should dominate the internal resistance of the secondary battery, not the electrolyte conductivity from the battery as a whole.

Therefore, how to develop an electrolyte additive with obviously improved performances such as impedance, high-temperature storage and circulation of a battery, and apply the electrolyte additive to the electrolyte and the battery is a continuous direction of efforts in the battery industry, and becomes a problem to be solved along with the large-scale industrialization of the battery.

Disclosure of Invention

Based on this, an object of the present application is to provide a nonaqueous electrolyte additive capable of significantly improving storage performance of a secondary battery at high temperature, reducing battery resistance, and improving cycle performance.

In order to achieve the above purpose, the present application adopts the following technical scheme.

A nonaqueous electrolyte additive comprising at least one of compounds represented by structural formulas 1 and 2:

wherein X and Y are each independently selected from any one of the following structures, the numbers representing bonding positions:

preferably, X and Y are simultaneously selected from the same structure.

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

Preferably, the additive comprises at least one of the compounds shown below:

in some preferred embodiments, the additive is selected from at least one of the compounds shown below:

the application also provides a non-aqueous electrolyte comprising the non-aqueous electrolyte additive.

Preferably, the content of the nonaqueous electrolyte additive is 0.01% to 7%, more preferably, the content of the nonaqueous electrolyte additive is 0.05% to 5%, and even more preferably, the content of the nonaqueous electrolyte additive is 0.1% to 2%, based on 100% of the total mass of the nonaqueous electrolyte.

The present application also provides a secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and the above-described nonaqueous electrolytic solution.

The inventors have found through research that the use of the heterocyclic compound having a lactone structure as a mother nucleus as shown in the structural formula 1 or 2 of the present application in the nonaqueous electrolyte solution as an additive for the nonaqueous electrolyte solution can form an SEI film on the electrode surface, which is uniform in film thickness and has more excellent high temperature stability, and can significantly improve the storage performance and resistance performance of the secondary battery at high temperature. Particularly, when the lithium ion battery is used for a lithium ion battery and a sodium ion battery, the capacity retention rate and the capacity recovery rate of the lithium ion battery in high-temperature storage can be effectively improved, and meanwhile, the direct current internal resistance of the lithium ion battery at 0 ℃ and 25 ℃ is reduced; likewise, the additive can also obviously prolong the cycle life of the sodium ion battery, and simultaneously reduce the direct current resistance of the battery, thereby accelerating the reaction kinetics of the sodium ion battery.

Detailed Description

The experimental methods of the present application, in which specific conditions are not specified in the following examples, are generally conducted under conventional conditions or under conditions recommended by the manufacturer. The various chemicals commonly used in the examples are commercially available.

The following description of the embodiments of the present application will be made more apparent and fully by reference to the accompanying drawings, in which some, but not all embodiments of the application are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to fall within the scope of the application.

The present embodiment provides a nonaqueous electrolyte additive including at least one of compounds represented by structural formulas 1 and 2:

in some embodiments, the X and Y are simultaneously selected from the same structures, including but not limited to the following compounds:

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

the preparation method of the above-mentioned compound can be known to those skilled in the art from the common general knowledge in the field of chemical synthesis, in the case of knowing the structural formula of the compound of structural formula 1 or structural formula 2. For example:

can be obtained by reacting gulonolactone or ascorbic acid with two equivalent dimethyl carbonate in the presence of an acid binding agent;

can be obtained by reacting gulonolactone or ascorbic acid with two equivalent thionyl chloride.

Another embodiment of the present application provides a nonaqueous electrolyte comprising the nonaqueous electrolyte additive described above.

In some embodiments, the non-aqueous electrolyte additive is present in an amount of 0.01 to 10% based on 100% total mass of the non-aqueous electrolyte.

In some embodiments, the non-aqueous electrolyte additive is present in an amount of 0.01 to 7% based on 100% total mass of the non-aqueous electrolyte.

In a preferred embodiment, the content of the nonaqueous electrolyte additive is 0.05 to 5% based on 100% of the total mass of the nonaqueous electrolyte.

In a more preferred embodiment, the content of the nonaqueous electrolyte additive is 0.1 to 2% based on 100% of the total mass of the nonaqueous electrolyte.

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

When the content of the compound shown in the structural formula 1 or the structural formula 2 is in the range, the stability of film formation on the surface of the electrode can be effectively maintained, and the performance of the battery is improved, and when the content of the compound shown in the structural formula 1 or the structural formula 2 is too small, the obvious improvement effect on the performance of the battery is difficult to generate; if the content of the compound represented by structural formula 1 or structural formula 2 is too large, the film may be formed too thick, resulting in an increase in the internal resistance of the battery.

In some embodiments, the nonaqueous electrolyte further comprises an electrolyte salt selected from at least one of a lithium salt, a sodium salt, a potassium salt, a magnesium salt, a zinc salt, and an aluminum salt.

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

In a preferred embodiment, the lithium salt is selected from LiPF ₆ 、LiBOB、LiDFOB、LiPO ₂ F ₂ 、LiBF ₄ 、LiSbF ₆ 、LiAsF ₆ 、LiN(SO ₂ CF ₃ ) ₂ 、LiN(SO ₂ C ₂ F ₅ ) ₂ 、LiC(SO ₂ CF ₃ ) ₃ 、LiN(SO ₂ F) ₂ 、LiClO ₄ 、LiAlCl ₄ 、LiCF ₃ SO ₃ 、Li ₂ B ₁₀ Cl ₁₀ 、LiSO ₂ F. At least one of LiTOP (lithium trioxalate phosphate), liDODFP (lithium difluorodioxalate phosphate), liOTFP (lithium tetrafluorooxalate phosphate), and a lower aliphatic carboxylic acid lithium salt.

In a preferred embodiment, the sodium salt is selected from the group consisting of NaPF ₆ 、NaClO ₄ 、NaAsF ₆ 、NaSbF ₆ 、NaPOF ₄ 、NaPO ₂ F ₂ 、NaC ₄ BO ₈ 、NaC ₂ BF ₂ O ₄ 、NaODFB、NaN(SO ₂ C ₂ F ₅ ) ₂ 、NaN(SO ₂ CF ₃ )(SO ₂ C ₄ F ₉ ) ₂ 、NaC(SO ₂ CF ₃ ) And Na (C) ₂ F ₅ )PF ₃ At least one of them.

The electrolyte salt in the nonaqueous electrolyte solution is dissociated to form alkali metal ions which are deintercalated and embedded between the positive electrode and the negative electrode to complete charge and discharge circulation, the concentration of the electrolyte salt directly influences the transmission speed of the alkali metal ions, and the transmission speed of the alkali metal ions influences the potential change of the negative electrode. In the process of quick battery charging, the moving speed of alkali metal ions needs to be improved as much as possible, the formation of lithium dendrites caused by too fast negative electrode potential drop is prevented, potential safety hazards are brought to the battery, and meanwhile, the too fast attenuation of the circulating capacity of the battery can be prevented. When the content of the electrolyte salt is too low, the intercalation and deintercalation efficiency of alkali metal ions between the positive electrode and the negative electrode can be reduced, and the requirement of quick charge of the battery can not be met; when the content of the electrolyte salt is too high, the viscosity of the nonaqueous electrolyte is increased, and thus the improvement of the intercalation and deintercalation efficiency of alkali metal ions is also unfavorable, and the internal resistance of the battery is increased.

In some embodiments, the concentration of the lithium salt in the nonaqueous electrolytic solution is 0.1mol/L to 8mol/L. In a preferred embodiment, the concentration of the lithium salt in the nonaqueous electrolytic solution is 0.5mol/L to 2.5mol/L. Specifically, in the nonaqueous electrolytic solution, the concentration of the lithium salt may be 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, 2.5mol/L.

In some embodiments, the concentration of the sodium salt in the nonaqueous electrolytic solution is 0.1mol/L to 2mol/L. In a preferred embodiment, the concentration of the sodium salt in the nonaqueous electrolytic solution is 0.4mol/L to 1.5mol/L. Specifically, in the nonaqueous electrolytic solution, the concentration of the sodium salt may be 0.1mol/L, 0.4mol/L, 0.5mol/L, 0.7mol/L, 0.8mol/L, 0.9mol/L, 1mol/L, 1.2mol/L, 1.5mol/L, 2mol/L.

In some embodiments, the nonaqueous electrolyte further includes an auxiliary additive including at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, an unsaturated phosphate compound, a borate compound, and a nitrile compound.

In some embodiments, the cyclic sulfate compound is selected from the group consisting of vinyl sulfate, vinyl 4-methylsulfate, propylene sulfate, At least one of them.

In some embodiments, the sultone compound is selected from the group consisting of 1, 3-propane sultone, 1, 4-butane sultone, propenyl-1, 3-sultone,At least one of (a) and (b);

in some embodiments, the cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, bis-fluoroethylene carbonate, and a compound represented by the following formula 3:

in the structural formula 3, R ₃₁ 、R ₃₂ 、R ₃₃ 、R ₃₄ 、R ₃₅ 、R ₃₆ Each independently selected from one of a hydrogen atom, a halogen atom, a C1-C5 group. Specifically, the compound represented by the structural formula 3 comprises At least one of them.

In some embodiments, the phosphate compound is selected from at least one of a saturated phosphate compound and an unsaturated phosphate compound; wherein the saturated phosphate compound comprises tris (trimethylsilane) phosphate; the unsaturated phosphate compound comprises at least one of compounds shown in the following structural formula 4:

wherein R is ₄₁ 、R ₄₂ 、R ₄₃ Each independently selected from the group consisting of C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si (C) _m H _2m+1 ) ₃ M is a natural number of 1 to 3, and R ₄₁ 、R ₄₂ 、R ₄₃ At least one of them is an unsaturated hydrocarbon group. Specifically, the compound shown in the structural formula 4 comprises tripropylethyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2, 2-trifluoroethyl phosphate, dipropargyl-3, 3-trifluoropropyl phosphate, and dipropargylAt least one of propyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2, 2-trifluoroethyl phosphate, diallyl-3, 3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

In some embodiments, the borate compound is selected from at least one of tris (trimethylsilane) borate and tris (triethylsilane) borate.

In some embodiments, the nitrile compound is selected from at least one of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetrinitrile, adiponitrile, pimelic nitrile, suberonitrile, nonyldinitrile, and decyldinitrile.

Unless otherwise specified, generally, the content of any one of the optional substances in the auxiliary additive in the nonaqueous electrolytic solution is 10% or less; preferably, the content is 0.1-5%; more preferably, the content is 0.1% -3%.

Specifically, the content of any optional substance in the auxiliary additive may 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%, 8.5%, 9%, 9.5%, 10%.

In some embodiments, when the auxiliary additive is selected from fluoroethylene carbonate, the fluoroethylene carbonate content is 0.05% to 30% based on 100% of the total mass of the nonaqueous electrolytic solution.

In the nonaqueous electrolyte, compared with the single addition or the combination of other existing additives, when the compound shown in the structural formula 1 or the structural formula 2 is added together with the auxiliary additive, the nonaqueous electrolyte has obvious synergistic improvement effect on improving the battery performance, and the fact that the compound shown in the structural formula 1 or the structural formula 2 and the auxiliary additive form a film together on the surface of the electrode can make up the film forming defect of the single addition, so that a more stable passivation film is obtained.

In some embodiments, the nonaqueous electrolyte further comprises a nonaqueous organic solvent comprising one or more of an ether solvent, a nitrile solvent, a carbonate solvent, a carboxylate solvent, and a sulfone solvent.

In some embodiments, the ethereal solvent includes a cyclic ether or a chain ether, and the cyclic ether may be specifically but not limited to one or more of 1, 3-Dioxolane (DOL), 1, 4-Dioxane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH 3-THF), 2-trifluoromethyl tetrahydrofuran (2-CF 3-THF); the chain ether may be specifically, but not limited to, one or more of Dimethoxymethane (DMM), 1, 2-Dimethoxyethane (DME), diglyme (TEGDME). The nitrile solvent may be, but is not limited to, one or more of acetonitrile, glutaronitrile, malononitrile. The carbonate solvent comprises cyclic carbonate or chain carbonate, and the cyclic carbonate can be one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), gamma-butyrolactone (GBL) and Butylene Carbonate (BC); the chain carbonate may be, but is not limited to, in particular, one or more of dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC). The carboxylate solvent may be, but is not limited to, specifically one or more of Methyl Acetate (MA), ethyl Acetate (EA), propyl acetate (EP), butyl acetate, propyl Propionate (PP), butyl propionate.

Another embodiment of the present application provides a secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolytic solution as described above.

The secondary battery adopts the non-aqueous electrolyte, so that a passivation film with excellent performance can be formed on the positive electrode and the negative electrode, thereby effectively improving the high-temperature storage performance and the high-temperature cycle performance of the battery and improving the power characteristic of the battery.

In a preferred embodiment, the secondary battery is a lithium metal battery, a lithium ion battery, a lithium sulfur battery, a sodium ion battery, a magnesium ion battery.

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

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

In a preferred embodiment, when the secondary battery is a lithium ion battery, the positive electrode active material thereof may be selected from LiFe _1-x’ M’ _x’ PO ₄ 、LiMn _2-y’ M _y’ O ₄ And LiNi _x Co _y Mn _z M _1-x-y-z O ₂ Wherein M 'is at least one selected from Mn, mg, co, ni, cu, zn, al, sn, B, ga, cr, sr, V and Ti, M is at least one selected from Fe, co, ni, mn, mg, cu, zn, al, sn, B, ga, cr, sr, V and Ti, x' is 0-1, y is 0-1, x is 0-1, z is 0-1, x+y+z is 1, and the positive electrode active material is at least one selected from sulfide, selenide, and halide. More preferably, the positive electrode active material may be selected from LiCoO ₂ 、LiFePO ₄ 、LiFe _0.8 Mn _0.2 PO ₄ 、LiMn ₂ O ₄ 、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ 、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ 、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ 、LiNi _0.5 Co _0.2 Mn _0.2 Al _0.1 O ₂ 、LiNi _0.5 Co _0.2 Al _0.3 O ₂ At least one of them.

In a preferred embodiment, when the secondary battery is a sodium ion battery, the positive electrode active material thereof includes, but is not limited to, at least one of transition metal oxide, prussian-type material, phosphate, sulfate, titanate material. Wherein the chemical formula of the transition metal oxide can be Na _z M _x O _y M is selected from Cr, fe, co, ni, cu, mn, sn,At least one of Mo, sb and V, more preferably, the transition metal oxide is NaNi _m Fe _n Mn _p O ₂ (m+n+p=1, 0.ltoreq.m.ltoreq.1, 0.ltoreq.n.ltoreq.1, 0.ltoreq.p.ltoreq.1) or NaNi _m Co _n Mn _p O ₂ (m+n+p=1, 0.ltoreq.m.ltoreq.1, 0.ltoreq.n.ltoreq.1, 0.ltoreq.p.ltoreq.1); the molecular formula of the Prussian material is Na _x M[M′(CN) ₆ ] _y ·zH ₂ O, wherein M is a transition metal, M' is a transition metal, 0<x≤2，0.8≤y<1，0<z is less than or equal to 20, more preferably, the Prussian material is Na _x Mn[Fe(CN) ₆ ] _y ·nH ₂ O (x is more than 0 and less than or equal to 2, y is more than 0 and less than or equal to 1, z is more than 0 and less than or equal to 10) or Na _x Fe[Fe(CN) ₆ ] _y ·nH ₂ O (x is more than 0 and less than or equal to 2, y is more than 0 and less than or equal to 1, z is more than 0 and less than or equal to 10); the chemical formula of the phosphate is Na ₃ (MO _1- _x PO ₄ ) ₂ F _1+2x 0.ltoreq.x.ltoreq.1, M is selected from at least one of Al, V, ge, fe, ga, more preferably, the phosphate is Na ₃ (VPO ₄ ) ₂ F ₃ Or Na (or) ₃ (VOPO ₄ ) ₂ F, performing the process; the chemical formula of the phosphate is Na ₂ MPO ₄ F, M is at least one selected from Fe and Mn, more preferably, the phosphate is Na ₂ FePO ₄ F or Na ₂ MnPO ₄ F, performing the process; the titanate material may be selected from Na ₂ Ti ₃ O ₇ 、Na ₂ Ti ₆ O ₁₃ 、Na ₄ Ti ₅ O ₁₂ 、Li ₄ Ti ₅ O ₁₂ 、NaTi ₂ (PO ₄ ) ₃ At least one of (a) and (b); the chemical formula of the sulfate is Na ₂ M(SO ₄ ) ₂ ·2H ₂ O, M may be at least one selected from Cr, fe, co, ni, cu, mn, sn, mo, sb, V.

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

The positive current collector is selected from a metal material that can conduct electrons, preferably, the positive current collector includes at least one of Al, ni, tin, copper, stainless steel, and in a more preferred embodiment, the positive current collector is selected from aluminum foil.

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

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

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

In some embodiments, the anode includes an anode material layer including an anode active material, and the kind and content of the anode active material are not particularly limited and may be selected according to actual requirements.

In a preferred embodiment, when the secondary battery is a lithium ion battery, the negative electrode active material thereof includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode. Wherein the carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, and the like; the silicon-based anode may include a silicon material, an oxide of silicon, a silicon-carbon composite material, a silicon alloy material, or the like; the tin-based negative electrode may include tin, tin carbon, tin oxygen, and tin metal compounds; the lithium negative electrode may include metallic lithium or a lithium alloy. The lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.

In a preferred embodiment, when the secondary battery is a sodium ion battery, the negative electrode active material thereof includes at least one of metallic sodium, graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microsphere, silicon-based material, tin-based material, lithium titanate, or other metal capable of forming an alloy material with sodium, and the like. Wherein the alloy material can also be selected from alloy materials consisting of C and at least one of Si, ge, sn, pb, sb, and the graphite can be selected from at least one of artificial graphite, natural graphite and modified graphite; the silicon-based material can be at least one selected from simple substance silicon, silicon oxygen compound, silicon carbon compound and silicon alloy; the tin-based material can be at least one selected from elemental tin, tin oxide and tin alloy.

In some embodiments, the negative electrode further comprises a negative electrode current collector, and the negative electrode material layer is disposed on a 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 again.

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

In some embodiments, a separator is further included in the secondary battery, the separator being positioned between the positive electrode and the negative electrode.

The membrane can be an existing conventional membrane, and can be a ceramic membrane, a polymer membrane, a non-woven fabric, an inorganic-organic composite membrane and the like, including but not limited to a membrane such as single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP/PP, and three-layer PP/PE/PP.

The application is further illustrated by the following examples. The compounds 1 to 6 used in the following examples and comparative examples are shown in Table 1.

TABLE 1

Examples 1 to 18

Examples 1 to 18 are for explaining the nonaqueous electrolytic solution of the present application, the lithium ion battery and the preparation method thereof. The preparation method is the same except for the non-aqueous electrolyte additives, and the specific preparation method is as follows:

1) Preparation of nonaqueous electrolyte:

mixing Ethylene Carbonate (EC), diethyl carbonate (DEC) and Ethylmethyl Carbonate (EC) according to the mass ratio of EC: DEC: EC=1:1:1, and then adding lithium hexafluorophosphate (LiPF ₆ ) To a molar concentration of 1mol/L, additives were added and mixed uniformly, and the kinds and contents of the respective additives are shown in Table 2, based on 100% by weight of the total nonaqueous electrolytic solution.

2) Preparation of positive plate:

mixing anode active material lithium nickel cobalt manganese oxide LiNi according to the mass ratio of 93:4:3 _0.5 Co _0.2 Mn _0.3 O ₂ Conductive carbon black Super-P and a binder polyvinylidene fluoride (PVDF) are then dispersed in-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The slurry is evenly coated on two sides of an aluminum foil, and the positive plate is obtained after drying, calendaring and vacuum drying, and an aluminum outgoing line is welded by an ultrasonic welder, and the thickness of the positive plate is between 12 mu and 15 mu.

3) Preparation of a negative plate:

the negative electrode active material artificial graphite, conductive carbon black Super-P, binder styrene butadiene rubber (SB) and Carboxymethyl Cellulose (CC) were mixed in a mass ratio of 94:1:2.5:2.5, and then dispersed in deionized water to obtain a negative electrode slurry. Coating the slurry on two sides of a copper foil, drying, calendaring and vacuum drying, and welding a nickel lead-out wire by an ultrasonic welder to obtain a negative plate, wherein the thickness of the negative plate is between 12 and 15 mu.

4) Preparation of the battery cell:

and (3) placing a three-layer diaphragm with the thickness of 2 mu between the positive plate and the negative plate, winding a sandwich structure formed by the positive plate, the negative plate and the diaphragm, flattening the winding body, putting into an aluminum foil packaging bag, and baking for 48 hours at the temperature of 75 ℃ in vacuum to obtain the battery cell to be injected with the liquid.

5) And (3) filling and forming the battery cell:

in a glove box with the dew point controlled below-4 ℃, the prepared electrolyte is injected into a battery cell, and the battery cell is subjected to vacuum packaging and is kept for 24 hours.

Then the first charge is conventionally formed by the following steps: charging at 0.5C constant current for 180min, charging at 0.2C constant current to 3.95V, vacuum sealing, charging at 0.2C constant current to 4.2V, standing at normal temperature for 24 hr, discharging at 0.2C constant current to 3.95V to obtain LiNi _0.5 Co _0.2 Mn _0.3 O ₂ Artificial graphite lithium ion battery.

Comparative examples 1 to 5

Comparative examples 1 to 5 are for comparative illustration of the nonaqueous electrolytic solution of the present application and lithium ion battery. The preparation method comprises most of the operation steps in the preparation method of the embodiment, and the only difference is that: the types and contents of the respective additives are shown in table 2, based on 100% by weight of the total nonaqueous electrolytic solution.

Performance testing

The following performance tests were performed on the lithium ion batteries prepared in examples 1 to 18 and comparative examples 1 to 5:

(1) High temperature storage Property

And (3) charging the lithium ion battery after formation to 4.2V at normal temperature under a constant current of 1C, charging under a constant current and constant voltage until the current is reduced to 0.05C, discharging under a constant current of 1C to 3.0V, measuring the initial discharge capacity and the initial battery volume of the battery, charging until the battery is full of electricity, respectively storing for 30 days, 60 days and 90 days in a 60 ℃ environment, discharging under a constant current to 3V at 1C, and measuring the holding capacity and the recovery capacity of the battery and the battery volume after storage. The calculation formula is as follows:

battery capacity retention (%) =retention capacity/initial capacity×1%;

battery capacity recovery rate (%) =recovery capacity/initial capacity×1%;

volume expansion (%) = (battery volume after storage-initial battery volume)/initial battery volume×1%.

(2) Internal resistance of DC

The battery was charged and discharged at 0.5C rate for 3 cycles at 25C, and the average capacity discharged at 3 cycles was taken as a rated capacity, and then charged to 50% of the rated capacity at 0.5C rate.

DCIR test at 25 ℃): placing the battery with the constant volume of 50% at 25 ℃ for 4 hours, then charging for 10s with constant current at 0.5C multiplying power, and placing for 40s to test the charged DCR _ch Then constant-current discharge is carried out for 10s at a rate of 0.5C, the discharge DCR is tested after 40s is put aside _dis 。

DCIR test at 0 ℃): placing the battery with constant volume to 50% at 0deg.C for 4h, constant-current charging at 0.5C for 10s, and placing for 40s to test charging DCR _ch Then constant-current discharge is carried out for 10s at a rate of 0.5C, the discharge DCR is tested after 40s is put aside _dis 。

The test results are shown in Table 2.

(3) High temperature cycle performance

And (3) charging the lithium ion battery after formation to 4.3V at 45 ℃ with a constant current and a constant voltage of 1C, charging the lithium ion battery again to a constant voltage until the current is reduced to 0.05C, discharging the lithium ion battery to 3.0V with a constant current of 1C, and recording the discharge capacity at the 1 st week and the discharge capacity at the 500 th week in a circulating way.

The capacity retention for the high temperature cycle was calculated as follows:

capacity retention= (discharge capacity at 500 th week/discharge capacity at 1 st week) ×100%.

TABLE 2

From the performance test results of examples 1 to 6 and comparative example 1, it is understood that the additive of the present application can provide lithium ion batteries with higher capacity retention and capacity recovery, and lower direct current internal resistance. The additive is capable of obviously improving the storage performance and the impedance performance of the lithium ion battery at high temperature.

The test results of comparative example 1 and examples 7 to 15 show that the content of the compound 1 has a significant effect on the performance of the lithium ion battery. With the increase of the content of the compound 1, the high-temperature cycle performance and the high-temperature storage performance of the lithium ion battery are improved and then reduced. When the content of the nonaqueous electrolyte additive in the nonaqueous electrolyte is 0.1-7%, the lithium ion battery has better high-temperature storage performance; especially when the content of the non-aqueous electrolyte additive is 0.5% -2%, the lithium ion battery has optimal high-temperature storage performance. When the content of the non-aqueous electrolyte additive is less than 0.1%, an SEI film of a sufficient area may not be formed to be coated, resulting in loss of active lithium ions, and the electrolyte solvent preferentially forms non-uniform SEI on the electrode, which easily results in precipitation of lithium dendrites, thereby affecting the performance of the overall SEI; when the content of the nonaqueous electrolyte additive is more than 7%, the formed SEI film tends to be too thick, resulting in deterioration of electrode dynamic properties.

The test results of comparative examples 1 to 6 and comparative examples 1 to 5 show that the use of the compound represented by structural formula 1 or structural formula 2 of the present application as an additive can more significantly improve the storage performance of lithium ion batteries at high temperatures, compared with the conventional Vinylene Carbonate (VC), vinyl sulfate (DTD) and 1, 3-Propane Sultone (PS) additives, and demonstrate that the heterocyclic compound having a lactone structure as a parent nucleus in the present application has a more stable structure in the passivation film decomposed on the electrode surface, and thus the passivation film formed from the compound represented by structural formula 1 or structural formula 2 has more excellent high temperature stability while having lower internal resistance.

As is apparent from the test results of comparative examples 16 to 18 and comparative examples 2 to 5, the performance of the lithium ion battery is further improved by combining the compound 1 with the vinyl sulfate (DTD) in comparison with the conventional combination of the Vinylene Carbonate (VC) and the vinyl sulfate (DTD) additive, and it is illustrated that the decomposition products of structural formula 1 or structural formula 2 have better affinity with the decomposition products of the vinyl sulfate (DTD), and the combination product obtained by combining the two has higher stability at high temperature than the single decomposition product thereof, so that the passivation film formed by combining the compound of structural formula 1 with the vinyl sulfate exhibits more excellent high temperature stability.

In conclusion, the passivation film formed by the additive has more excellent high-temperature stability, and can obviously improve the storage performance and the impedance performance of the lithium ion battery at high temperature.

Examples 19 to 36

Examples 19 to 36 are for explaining the nonaqueous electrolytic solution of the present application, the sodium ion battery and the production method thereof. The preparation method is the same except for the non-aqueous electrolyte additives, and the specific preparation method is as follows:

1) Preparation of nonaqueous electrolyte:

mixing Ethylene Carbonate (EC), diethyl carbonate (DEC) and Ethylmethyl Carbonate (EC) according to the mass ratio of EC: DEC: EC=1:1:1, and then adding sodium hexafluorophosphate (NaPF ₆ ) The types and contents of the respective additives are shown in Table 3, based on 100% by weight of the total nonaqueous electrolytic solution, after adding the additives and mixing uniformly to a molar concentration of 1.12 mol/L.

2) Preparation of positive plate:

with layered transition metal oxides (NaNi _0.6 Fe _0.25 Mn _0.15 O ₂ ) Carbon black (Super P) is used as a conductive agent, polyvinylidene fluoride is used as a binder, the mixture is fully and uniformly stirred by a slurry mixing tank according to the proportion of 97:2:1, and then the mixture is coated on an aluminum foil current collector, and the mixture is dried, rolled and die-cut to obtain a positive plate, wherein the thickness of the positive plate is between 12 mu and 15 mu.

3) Preparation of a negative plate:

the method comprises the steps of taking hard carbon as a negative electrode active substance, taking carbon black (Super P) as a conductive agent, taking sodium carboxymethylcellulose and styrene-butadiene rubber as binders, passing through a slurry mixing tank according to the proportion of 95.5:1:1.5:2, fully and uniformly stirring, coating the mixture on an aluminum foil current collector, drying, rolling and die cutting to obtain a negative electrode plate, wherein the thickness of the electrode plate is between 12 mu and 15 mu.

4) Preparation of the battery cell:

and (3) placing a three-layer diaphragm with the thickness of 6 mu between the positive plate and the negative plate, winding a sandwich structure formed by the positive plate, the negative plate and the diaphragm, flattening the winding body, putting into an aluminum foil packaging bag, and baking for 48 hours at the temperature of 75 ℃ in vacuum to obtain the battery cell to be injected with the liquid. And (3) injecting the prepared electrolyte into a battery cell in a glove box with the dew point controlled below-4 ℃, vacuum packaging, standing for 24 hours, and then performing formation to obtain the sodium ion battery.

Comparative examples 6 to 10

Comparative examples 6 to 10 are for comparative illustration of the nonaqueous electrolyte of the present application and sodium ion battery. The preparation method comprises most of the operation steps in the preparation methods of the above examples 19 to 36, and the only difference is that: the types and contents of the respective additives are shown in table 3, based on 100% by weight of the total nonaqueous electrolytic solution.

The sodium ion batteries prepared in examples 19 to 36 and comparative examples 6 to 10 were subjected to the following performance tests:

(1) Internal resistance of DC

The battery was charged and discharged for 3 cycles at a rate of 0.3C at 25C, and the average capacity discharged for 3 cycles was taken as a rated capacity, and then charged to 50% of the rated capacity at a rate of 0.3C.

DCIR test at 25 ℃): placing the battery with the constant volume of 50% at 25 ℃ for 4 hours, then charging for 10s with constant current at 0.3C multiplying power, and placing for 40s to test the charged DCR _ch Then constant-current discharge is carried out for 10s at a rate of 0.3C, the discharge DCR is tested after 40s is put aside _dis 。

(2) 25 ℃ cycle test

The battery is charged to 3.8V at a constant current and a constant voltage of 1C, the cut-off current is 0.05C, then the 1C constant current is discharged to 1.8V, the charging and discharging cycles are performed, the cycle capacity retention rate is calculated, and the cycle capacity retention rate (%) = the average value of the discharge capacity at the test cycle/the discharge capacity at the previous 3 times is multiplied by 100%.

The test results are shown in Table 3.

TABLE 3 Table 3

From the test results of Table 3, it can be seen that the additives of the present application can provide sodium ion batteries with higher cycle performance and lower DC internal resistance, indicating that the additives can significantly improve the cycle performance and resistance performance of sodium ion batteries at high temperatures, as shown in the performance test results of examples 19 to 26 and comparative example 6.

The comparison of the embodiment 19 and the embodiments 25 to 33 shows that the content of the additive in the electrolyte can influence the cycle performance of the prepared sodium ion battery, and the mass percent of the additive is controlled within the range of 0.5 to 2 percent, so that the cycle life of the battery can be obviously prolonged.

Compared with comparative examples 6 to 10, examples 34 to 36 show that the additive provided by the application can form a compact and stable SEI film on the surfaces of the anode and cathode materials, and the degradation condition of the anode and cathode interface film in the cycling process of the battery is reduced, so that the cycle life of the sodium ion battery is obviously prolonged, and meanwhile, the direct current resistance of the battery is reduced by the compound use of the additive and other auxiliary film forming additives, so that the reaction kinetics of the sodium ion battery is accelerated.

The application has been further described with reference to specific embodiments, but it should be understood that the detailed description is not to be construed as limiting the spirit and scope of the application, but rather as providing those skilled in the art with the benefit of this disclosure with the benefit of their various modifications to the described embodiments.

Claims

1. A non-aqueous electrolyte additive, characterized in that the non-aqueous electrolyte additive comprises at least one of compounds represented by structural formulas 1 and 2:

2. the nonaqueous electrolyte additive according to claim 1, wherein X and Y are simultaneously selected from the same structures.

3. The non-aqueous electrolyte additive according to claim 1, wherein at least one of X and Y is selected from structure b or structure c.

4. The non-aqueous electrolyte additive according to claim 1, wherein the additive comprises at least one of the following compounds:

5. a nonaqueous electrolyte solution comprising the nonaqueous electrolyte solution additive according to any one of claims 1 to 4.

6. The nonaqueous electrolyte according to claim 5, wherein the content of the nonaqueous electrolyte additive is 0.01% to 7% based on 100% of the total mass of the nonaqueous electrolyte;

preferably, the content of the non-aqueous electrolyte additive is 0.1% -2%.

7. The nonaqueous electrolytic solution according to claim 5, further comprising an electrolyte salt selected from at least one of lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt and aluminum salt;

preferably, the electrolyte salt is selected from lithium salts or sodium salts;

preferably, the lithium salt is selected from LiPF ₆ 、LiBOB、LiDFOB、LiPO ₂ F ₂ 、LiBF ₄ 、LiSbF ₆ 、LiAsF ₆ 、LiN(SO ₂ CF ₃ ) ₂ 、LiN(SO ₂ C ₂ F ₅ ) ₂ 、LiC(SO ₂ CF ₃ ) ₃ 、LiN(SO ₂ F) ₂ 、LiClO ₄ 、LiAlCl ₄ 、LiCF ₃ SO ₃ 、Li ₂ B ₁₀ Cl ₁₀ 、LiSO ₂ F. LiTOP, liDODFP, liOTFP and a lithium salt of a lower aliphatic carboxylic acid;

the sodium salt is selected from NaPF ₆ 、NaClO ₄ 、NaAsF ₆ 、NaSbF ₆ 、NaPOF ₄ 、NaPO ₂ F ₂ 、NaC ₄ BO ₈ 、NaC ₂ BF ₂ O ₄ 、NaODFB、NaN(SO ₂ C ₂ F ₅ ) ₂ 、NaN(SO ₂ CF ₃ )(SO ₂ C ₄ F ₉ ) ₂ 、NaC(SO ₂ CF ₃ ) And Na (C) ₂ F ₅ )PF ₃ At least one of them.

8. The nonaqueous electrolytic solution according to claim 5, further comprising an auxiliary additive comprising at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, an unsaturated phosphate compound, a borate compound and a nitrile compound;

preferably, the cyclic sulfate compound is selected from the group consisting of vinyl sulfate, vinyl 4-methylsulfate, propylene sulfate, and,

At least one of (a) and (b);

the sultone compound is selected from 1, 3-propane sultone, 1, 4-butane sultone, propenyl-1, 3-sultone,At least one of (a) and (b);

the cyclic carbonate compound is at least one selected from ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, bis-fluoroethylene carbonate and a compound shown in the following structural formula 3:

in the structural formula 3, R ₃₁ 、R ₃₂ 、R ₃₃ 、R ₃₄ 、R ₃₅ 、R ₃₆ Each independently selected from one of a hydrogen atom, a halogen atom, a C1-C5 group;

the phosphate compound is at least one of saturated phosphate compound and unsaturated phosphate compound; wherein the saturated phosphate compound comprises tris (trimethylsilane) phosphate; the unsaturated phosphate compound comprises at least one of compounds shown in the following structural formula 4:

wherein R is ₄₁ 、R ₄₂ 、R ₄₃ Each independently selected from the group consisting of C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si (C) _m H _2m+1 ) ₃ M is 1 to 3Natural number, and R ₄₁ 、R ₄₂ 、R ₄₃ At least one of them is an unsaturated hydrocarbon group;

the borate compound is at least one selected from tri (trimethylsilane) borate and tri (triethylsilane) borate;

the nitrile compound is at least one selected from succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanedinitrile, adiponitrile, pimelic nitrile, suberonitrile, nonyldinitrile and decyldinitrile.

9. A secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, characterized by further comprising the nonaqueous electrolytic solution according to any one of claims 5 to 8.

10. The secondary battery according to claim 9, wherein the secondary battery is a lithium metal battery, a lithium ion battery, a lithium sulfur battery, a sodium ion battery, or a magnesium ion battery.