CN107293792A - A kind of nonaqueous electrolytic solution and nickelic tertiary cathode material battery - Google Patents

Abstract

The invention provides a kind of electrolyte, including lithium salts, organic solvent and additive A；The additive A includes the one or more in alkyl amine compound, silicon nitrogen compound and siloxane compound.The present invention starts with terms of the improvement of electrolyte, propose the nonaqueous electrolytic solution containing at least one of alkyl amine, the key classes of N containing Si compound (silicon nitrogen compound) and siloxane compound, the nonaqueous electrolytic solution that the present invention is provided has extremely low free acid content, it is applied in the lithium ion battery of nickelic tertiary cathode material, can effectively improve the cycle performance, high temperature cyclic performance and high-temperature storage performance of lithium ion battery.

Description

A kind of non-aqueous electrolyte and high-nickel ternary positive electrode material battery

technical field

The invention relates to the technical field of lithium-ion batteries, in particular to an electrolyte and a lithium-ion battery, in particular to a non-aqueous electrolyte and a high-nickel ternary positive electrode material battery.

Background technique

As the "engine" part of electric vehicles, the specific energy of lithium-ion power batteries is a key factor determining the mileage of a single charge of pure electric vehicles, which directly affects the technological development and popularization of electric vehicles. The specific energy of current lithium-ion power batteries largely depends on the specific energy of the cathode material. Increasing the discharge specific capacity of the positive electrode is one of the effective ways to increase the specific energy of the battery.

Among many positive electrode materials, high nickel ternary lithium ion battery positive electrode materials mainly include nickel cobalt lithium manganate LiNi _{1-x- y} Co _x Mn _y O ₂ (NCM) (0<x<1,0<y<1) and lithium nickel cobalt aluminate LiNi _1-xy Co _x Al _y O ₂ (NCA) (0<x<1,0<y<1), because of its advantages of high specific capacity, low cost and excellent safety, etc. It is considered to be a positive electrode material for lithium-ion power batteries with great application prospects, and has become the main development direction of many power battery companies. However, with the increase of Ni content, the specific discharge capacity of high-nickel ternary materials increases from 160mAh g ^-1 to more than 220mAh g ^-1 , but its capacity retention, thermal stability and high-temperature storage performance all decrease, which greatly limits Its industrial development and application. The study found that the reasons for these problems of high-nickel ternary materials are complex, mainly divided into two major problems: the material itself and the interface. The problems of the material itself are: first, the Ni/Li mixing during the cycle produces a phase transition reaction, which in turn induces the stress-strain effect, resulting in capacity decay during the material cycle; the second is that Ni ⁴⁺ tends to reduce When Ni ³⁺ is generated, oxygen will be released from the material, which will deteriorate the thermal stability of the material. On the other hand, the interface problem refers to the instability of the electrode/electrolyte interface in the actual electrochemical environment, which is easily corroded by free acid in the electrolyte, resulting in low battery capacity retention and poor high temperature performance. For high-nickel ternary materials (Ni content ≥ 0.6), even in the air, the surface of the material easily reacts with CO ₂ and H ₂ O in the air, and Li ₂ CO ₃ and LiOH, Li ₂ CO ₃ will cause severe gas swelling during high-temperature storage, and LiOH reacts with LiPF ₆ in the electrolyte to generate HF, which directly affects the capacity retention rate during the material cycle. Of course, for batteries with other positive electrode materials, the above-mentioned problems also exist more or less.

In order to improve the cycle performance and thermal stability of lithium-ion battery cathode materials, especially high-nickel ternary cathode materials, existing research usually starts from three aspects: material modification, ion doping, material surface coating, and development of electrolyte additives. A lot of exploratory research work has been carried out. By doping elements such as Mg and F in the ternary material lattice; by coating the surface of the material with some metal oxides (such as Al ₂ O ₃ , ZnO, etc.), fluorides (such as AlF ₃ , etc.) or some Some phosphates can physically isolate the direct contact between the active material and the electrolyte, reduce the occurrence of side reactions, and so on. But there are still imperfections.

In recent years, the development of electrolytes suitable for high-nickel ternary materials has also become an important research direction. But so far, the research direction of this type of material electrolyte is mainly to improve the conventional LiPF ₆ -based carbonate electrolyte. However, these measures have a very limited effect on improving the cycle performance of high-nickel ternary cathode materials. Stability is still not ideal.

Therefore, how to improve the electrochemical performance of lithium-ion batteries, especially the electrochemical performance of lithium-ion batteries with high-nickel ternary materials, has become one of the urgent problems to be solved in frontier disciplines in this field.

Contents of the invention

In view of this, the present invention provides a kind of electrolytic solution and lithium ion battery, particularly a kind of non-aqueous electrolytic solution and high-nickel ternary positive electrode material battery, adopt the lithium ion battery of electrolytic solution provided by the present invention, can effectively improve Cycle performance, high temperature cycle performance and high temperature storage performance, etc.

The invention provides an electrolyte, including a lithium salt, an organic solvent and an additive A;

The additive A includes one or more of alkylamine compounds, silicon nitrogen compounds and siloxane compounds.

Preferably, the volume percentage of the additive A in the electrolyte is 0.05% to 10%;

The molar concentration of the lithium salt in the electrolyte is 0.1-20 mol/L.

Preferably, the alkylamine compound is selected from one or more of the alkylamine compounds having the structure of formula I,

Wherein, R ₁ , R ₂ and R ₃ are independently selected from C1-C6 straight-chain or branched-chain alkyl groups.

Preferably, the silicon-nitrogen compound is selected from one or more of the disilamine compounds with the structure of formula II, and/or one of the silane imidazole compounds with the structure of formula III or more,

Wherein, R ₄ , R ₅ , R ₆ , R ₈ , R ₉ and R ₁₀ are independently selected from hydrogen atoms, halogens, C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups, _R7 is independently selected from a hydrogen atom, a halogen, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C6-C20 aromatic group, and an alkali metal atom;

Wherein, R ₁₁ , R ₁₂ and R ₁₃ are independently selected from hydrogen atoms, halogens, C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups.

Preferably, the siloxane compound is selected from one or more of the linear siloxane compounds represented by the structure of formula IV, and/or, the cyclic siloxane compounds represented by the structure of formula V one or more of the compounds,

Wherein, R ₁₄ , R ₁₅ , R ₁₆ and R ₁₇ are independently selected from C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups;

Wherein, R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ and R ₂₃ are independently selected from C1-C6 straight-chain or branched-chain alkyl groups;

n is an integer of 1-6.

Preferably, the lithium salts include lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium trifluorooxalate phosphate, lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, di One or more of lithium (trifluoromethylsulfonyl)imide and lithium bisfluorosulfonylimide;

The organic solvents include fluorine-free or fluorine-substituted carbonate solvents, fluorine-free or fluorine-substituted ether solvents, fluorine-free or fluorine-substituted carboxylate solvents, fluorine-free or fluorine-substituted phosphate solvents and ion One or more of one or more of liquid-based solvents.

Preferably, the electrolyte also includes additive B;

The additive B includes one or more of Li ₂ CO ₃ , CaCO ₃ , Al ₂ O ₃ , ZnO, MgO, BaO, AlF ₃ , MgF ₂ , AlOF, LiPF ₆ , LiBF ₄ and LiBOB;

The mass percentage of the additive B in the electrolyte solution is 0.005%-10%.

Preferably, the electrolyte also includes additive C;

The additive C includes propylene sulfate, vinyl sulfite, propylene sulfite, 1-propyl phosphoric acid cyclic anhydride, tris(trimethylsilyl) phosphate, trimethyl phosphate, tris(1,1, 1,3,3,3-Hexafluoroisopropyl) phosphate, fluoroethylene carbonate, anisole, vinylene carbonate, vinylphenatate, acrylocyanide, vinylethylene carbonate, 1,3- One or more of propane sultone, succinonitrile, 1,3-propenyl-sultone, divinyl sulfone, lithium dioxalate borate and lithium difluoro(oxalate) borate;

The mass percentage of the additive C in the electrolyte solution is 0.005%-10%.

The invention provides a lithium ion battery, comprising a positive electrode and an electrolyte;

The electrolyte is the electrolyte described in any one of the above technical solutions.

Preferably, the positive electrode includes a high-nickel ternary positive electrode material.

The invention provides an electrolytic solution, which includes a lithium salt, an organic solvent and an additive A; the additive A includes one or more of alkylamine compounds, silicon nitrogen compounds and siloxane compounds. Compared with the prior art, the present invention aims at the defects of existing lithium-ion battery positive electrode materials, especially the cycle performance and thermal stability of high-nickel ternary positive electrode materials, and starts from the improvement of electrolyte, especially It is aimed at adding a small amount of functional additives to the conventional LiPF ₆ -based carbonate electrolyte. Through the oxidative decomposition of the additive molecules during the first week of charging of the battery, it participates in the formation of a stable positive electrode interface film on the surface of the positive electrode material, reducing the interaction between the active material and the battery. The reaction of the electrolyte to improve the electrochemical performance of the material, etc., is insufficient in improving the cycle stability and the improvement effect is limited. The present invention creatively proposes a non-aqueous electrolytic solution containing at least one of alkylamines, Si-N bond-containing compounds (silicon-nitrogen compounds) and siloxane compounds. The non-aqueous electrolytic solution provided by the present invention has The extremely low content of free acid can effectively improve the cycle performance, high-temperature cycle performance and high-temperature storage performance of lithium-ion batteries when applied to lithium-ion batteries with high-nickel ternary cathode materials.

The experimental results show that the lithium-ion battery prepared by using the electrolyte provided by the invention has good cycle stability and high-temperature storage performance at room temperature and high temperature, and the capacity retention rate of the battery is 65% to 90% after charging and discharging at room temperature for 200 cycles; After 100 cycles of charging and discharging at high temperature, the capacity retention rate of the battery is 51% to 81%. After 30 days of storage at high temperature, the open circuit voltage OCV decline rate is 1.7% to 11%, and the capacity retention rate of the battery is 62% to 89%.

Description of drawings

FIG. 1 is an appearance view of a 1000mAh soft-pack laminated battery used for testing in an embodiment of the present invention and a comparative example.

detailed description

In order to further understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

All raw materials in the present invention have no particular limitation on their sources, they can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

All raw materials in the present invention have no special limitation on their purity, and the present invention preferably adopts analytical purity or conventional purity in the field of lithium-ion batteries.

In the present invention, there is no particular limitation on the definition of the specific groups of R ₁ to R ₂₃ , and the conventional definitions of substituents well known to those skilled in the art can be used. In principle, the groups described in the present invention may include substituted group and/or unsubstituted group.

The invention provides an electrolyte, including a lithium salt, an organic solvent and an additive A;

The additive A includes one or more of alkylamine compounds, silicon nitrogen compounds and siloxane compounds.

The present invention has no special limitation on the electrolyte, and the lithium battery electrolyte well known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The electrolyte of the present invention It is preferably a non-aqueous electrolyte solution for lithium-ion batteries, more preferably an electrolyte solution for lithium-ion batteries with ternary cathode materials, and most preferably an electrolyte solution for lithium-ion batteries with high-nickel ternary cathode materials.

In the present invention, the alkylamine compounds are not particularly limited, and the alkylamine compounds well-known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The present invention The alkylamine compound is preferably selected from one or more of the alkylamine compounds represented by the structure of formula I;

Wherein, R ₁ , R ₂ and R ₃ are independently selected from C1-C6 straight-chain or branched-chain alkyl groups.

In the present invention, R ₁ , R ₂ and R ₃ are independently preferably selected from C1-C6 straight-chain alkyl or branched-chain alkyl, more preferably from C2-C5 straight-chain or branched-chain alkyl, more preferably from C3-C4 straight-chain or branched-chain alkyl.

The present invention has no special limitation on the silicon-nitrogen compound, and the silicon-nitrogen compound or the compound containing Si-N bond well known to those skilled in the art can be used according to the application situation, product performance and quality requirements. Selection and adjustment, the silicon-nitrogen compounds described in the present invention are preferably selected from one or more of the disilamine compounds represented by the structure of formula II, and/or, among the silane imidazole compounds represented by the structure of formula III One or more, that is, the silicon nitrogen compound can be selected from one or more of the disilamine compounds shown in the structure of formula II, and can also be selected from the silane imidazoles shown in the structure of formula III One or more of the compounds can also be selected from one or more of the disilamine compounds shown in the structure of formula II and one of the silane imidazole compounds shown in the structure of formula III or more.

Wherein, R ₄ , R ₅ , R ₆ , R ₈ , R ₉ and R ₁₀ are independently selected from hydrogen atoms, halogens, C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups, R ₇ is independently selected from a hydrogen atom, a halogen, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C6-C20 aryl group, and an alkali metal atom.

In the present invention, R ₄ , R ₅ , R ₆ , R ₈ , R ₉ and R ₁₀ are independently preferably selected from hydrogen atom, halogen, C1-C6 alkyl, C1-C6 alkoxy, C6-C20 aromatic group, more preferably from hydrogen atom, halogen, C2-C5 alkyl group, C2-C5 alkoxy group, C8-C16 aryl group, more preferably from hydrogen atom, halogen, C3-C4 alkyl group, C3-C4 The alkoxyl group of C10-C14, the aryl group of C10-C14 can specifically be a hydrogen atom, halogen, alkyl group of C1-C3, alkoxyl group of C1-C3, aryl group of C6-C8.

In the present invention, _R7 is independently preferably selected from hydrogen atom, halogen, C1-C6 alkyl group, C1-C6 alkoxyl group, C6-C20 aryl group, alkali metal atom, more preferably from hydrogen atom, halogen, C2 ~C5 alkyl group, C2~C5 alkoxy group, C8~C16 aryl group, alkali metal atom, more preferably selected from hydrogen atom, halogen, C3~C4 alkyl group, C3~C4 alkoxy group, C10~ The C14 aryl group and alkali metal atom may specifically be hydrogen atom, halogen, C1-C3 alkyl group, C1-C3 alkoxy group, C6-C8 aryl group, and alkali metal atom.

Wherein, R ₁₁ , R ₁₂ and R ₁₃ are independently selected from hydrogen atoms, halogens, C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups.

In the present invention, R ₁₁ , R ₁₂ and R ₁₃ are preferably independently selected from hydrogen atoms, halogens, C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups, more preferably hydrogen atoms, halogen groups , C2-C5 alkyl group, C2-C5 alkoxy group, C8-C16 aryl group, more preferably selected from hydrogen atom, halogen, C3-C4 alkyl group, C3-C4 alkoxy group, C10-C14 The aryl group may specifically be a hydrogen atom, a halogen, a C1-C3 alkyl group, a C1-C3 alkoxy group, or a C6-C8 aryl group.

The present invention has no special limitation on the siloxane compound, and the siloxane compound well-known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The present invention The siloxane compound is preferably selected from one or more of the linear siloxane compounds represented by the structure of formula IV, and/or, one or more of the cyclic siloxane compounds represented by the structure of formula V One or more, that is, the siloxane compound can be selected from one or more of the linear siloxane compounds shown in the structure of formula IV, and can also be selected from the rings shown in the structure of formula V One or more of the linear siloxane compounds can also be selected from one or more of the linear siloxane compounds shown in the structure of formula IV and the cyclic silicon compounds shown in the structure of formula V One or more of the oxane compounds.

Wherein, R ₁₄ , R ₁₅ , R ₁₆ and R ₁₇ are independently selected from C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups.

In the present invention, R ₁₄ , R ₁₅ , R ₁₆ and R ₁₇ are independently selected from C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups, more preferably from C2-C5 alkyl groups , C2-C5 alkoxyl group, C8-C16 aryl group, more preferably selected from C3-C4 alkyl group, C3-C4 alkoxyl group, C10-C14 aryl group, specifically C1-C6 straight chain The alkyl group or branched chain alkyl group may also be a C1-C4 straight-chain alkyl group or branched-chain alkyl group, or a C1-C2 straight-chain alkyl group or branched chain alkyl group.

Wherein, R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ and R ₂₃ are independently selected from C1-C6 straight-chain or branched-chain alkyl groups;

n is an integer of 1-6.

In the present invention, R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ and R ₂₃ are independently preferably selected from C1-C6 straight-chain or branched-chain alkyl groups, more preferably C2-C5 straight-chain alkyl groups Or branched chain alkyl, more preferably straight chain alkyl or branched chain alkyl from C3～C4, also can be C1～C4 straight chain alkyl or branched chain alkyl, or C1～C2 straight chain alkyl or branched chain alkyl. In the present invention, n is preferably an integer of 1-6, more preferably an integer of 2-5, more preferably an integer of 3-4, specifically an integer of 1-4, or an integer of 1-2.

The present invention has no particular limitation on the specific structure of the additive A, and those skilled in the art can select and adjust it within the above range according to the application situation, product performance and quality requirements. The present invention is a further optimized technical solution. The additive A The specific structural formula can be the following formula 1 to formula 9:

The present invention has no special limitation on the addition amount of the additive A, just the conventional addition amount well known to those skilled in the art, and those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The volume percentage of additive A in the electrolyte solution is preferably 0.05%-10%, more preferably 0.1%-8%, more preferably 0.5%-6%, more preferably 1%-5%.

The present invention has no special restrictions on the lithium salt, and the lithium salt for lithium battery electrolyte well known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The lithium salts preferably include lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium trifluorooxalate phosphate, lithium difluorooxalate phosphate, lithium tetrafluorooxalate phosphate, bis(trifluorooxalate lithium One or more of lithium methylsulfonyl imide and lithium bisfluorosulfonimide, more preferably lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bisoxalate borate, lithium difluorooxalate borate, Lithium trifluorooxalate phosphate, lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, lithium bis(trifluoromethylsulfonyl)imide, or lithium bisfluorosulfonylimide.

The present invention has no special limitation on the addition amount of the lithium salt, the conventional lithium salt addition amount well known to those skilled in the art can be used, and those skilled in the art can select and adjust according to the application situation, product performance and quality requirements, the present invention The molar concentration of the lithium salt in the electrolyte is preferably 0.1-20 mol/L, more preferably 0.5-5 mol/L, more preferably 0.6-2.5 mol/L, more preferably 0.8-1.5 mol/L.

The present invention has no special restrictions on the organic solvent, and the organic solvent for lithium battery electrolyte well known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The organic solvents preferably include fluorine-free or fluorine-substituted carbonate solvents, fluorine-free or fluorine-substituted ether solvents, fluorine-free or fluorine-substituted carboxylate solvents, fluorine-free or fluorine-substituted phosphate solvents and ion One or more of one or more of liquid solvents, more preferably fluorine-free or fluorine-substituted carbonate solvents, fluorine-free or fluorine-substituted ether solvents, fluorine-free or fluorine-substituted carboxylic acids Ester solvents, fluorine-free or fluorine-substituted phosphate solvents or ionic liquid solvents, which can be ethylene carbonate + dimethyl carbonate, fluoroethylene carbonate + dimethyl carbonate + methyl ethyl carbonate + hexafluoroiso Propyl methyl ether, fluorocarbonate + methyl trifluoropropionate, trimethyl phosphate + fluoroethylene carbonate or N-methyl-N-butyl-piperidine-bistrifluoromethylsulfonamide PP ₁₄ TFSI ionic liquid + hexafluoroisopropyl methyl ether, the specific ratio can be ethylene carbonate + dimethyl carbonate (3:7, v/v), fluoroethylene carbonate + dimethyl carbonate + carbonic acid Ethyl methyl ester + hexafluoroisopropyl methyl ether (2:3:1:4, v/v/v/v), fluorocarbonate + methyl trifluoropropionate (3:7, v/v) , trimethyl phosphate + fluoroethylene carbonate (9:1, v/v) or N-methyl-N-butyl-piperidine-bistrifluoromethylsulfonamide PP ₁₄ TFSI ionic liquid + hexafluoro Isopropyl methyl ether (9:1, v/v).

In order to further improve the performance of the lithium battery, especially when the lithium salt is a lithium salt centered on the N atom, in order to prevent the corrosion of the Al current collector, the electrolyte preferably also includes additive B, more preferably capable of making Al Additive B for current collector surface passivation.

The present invention has no particular limitation on the specific selection of the additive B, and the commonly used additives for lithium battery electrolyte well known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The additive B in the invention preferably includes one or more of Li ₂ CO ₃ , CaCO ₃ , Al ₂ O ₃ , ZnO, MgO, BaO, AlF ₃ , MgF ₂ , AlOF, LiPF ₆ , LiBF ₄ and LiBOB, more preferably Li ₂ CO ₃ , CaCO ₃ , Al ₂ O ₃ , ZnO, MgO, BaO, AlF ₃ , MgF ₂ , AlOF, LiPF ₆ , LiBF ₄ or LiBOB.

The present invention has no special limitation on the addition amount of the additive B, just the conventional addition amount well known to those skilled in the art, and those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The mass percentage of additive B in the electrolyte solution is preferably 0.005% to 10%, more preferably 0.01% to 8%, more preferably 0.05% to 6%, more preferably 0.1% to 4%, and more preferably 0.5% %~2%.

In order to further improve the performance of the lithium battery and stabilize the positive electrode interface film and the negative electrode SEI film, the electrolyte solution preferably further includes additive C.

The present invention has no particular limitation on the specific selection of the additive C, and the commonly used additives for lithium battery electrolytes well known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The additive C described in the invention preferably includes propylene sulfate, vinyl sulfite, propylene sulfite, 1-propyl phosphoric acid cyclic anhydride, tris(trimethylsilyl) phosphate, trimethyl phosphate, tris(1, 1,1,3,3,3-Hexafluoroisopropyl) phosphate, fluoroethylene carbonate, anisole, vinylene carbonate, vinylinhibinate, acrylocyanide, vinylethylene carbonate, 1, One or more of 3-propane sultone, succinonitrile, 1,3-propenyl-sultone, divinyl sulfone, lithium dioxalate borate and lithium difluoro(oxalate) borate, more Preferred are propylene sulfate, vinyl sulfite, propylene sulfite, 1-propyl phosphate cyclic anhydride, tris(trimethylsilyl) phosphate, trimethyl phosphate, tris(1,1,1,3 , 3,3-hexafluoroisopropyl) phosphate, fluoroethylene carbonate, anisole, vinylene carbonate, vinylphenatate, acrylocyanide, vinylethylene carbonate, 1,3-propanesulfonic acid Lactone, succinonitrile, 1,3-propenyl-sultone, divinylsulfone, lithium dioxalate borate or lithium difluoro(oxalate)borate.

The present invention has no special limitation on the addition amount of the additive C, and the conventional addition amount well known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The mass percentage of additive C in the electrolyte solution is preferably 0.005% to 10%, more preferably 0.01% to 8%, more preferably 0.05% to 6%, more preferably 0.1% to 4%, and more preferably 0.5% ~2%.

The present invention has no special limitation on the free acid content of the electrolyte, and those skilled in the art can select and adjust according to the application situation, product performance and quality requirements. The present invention further optimizes the positive electrode material in order to improve the performance of the lithium battery , the free acid content of the electrolyte is preferably less than or equal to 50ppm, more preferably less than or equal to 40ppm, more preferably less than or equal to 30ppm.

The present invention is aimed at the poor acid corrosion resistance of high-nickel ternary materials. Even in the air, the surface of high-nickel materials is very easy to react with CO ₂ and H ₂ O in the air to generate Li ₂ CO ₃ and LiOH. These by-products are very easy Reaction with LiPF ₆ -based carbonate electrolyte, Li ₂ CO ₃ will cause severe gas swelling during high temperature storage, LiOH reacts with LiPF ₆ in the electrolyte to produce HF, which directly affects the capacity retention rate during the material cycle , and the current LiPF ₆ -based carbonate electrolyte is prone to produce free acids such as HF, especially at high temperatures, which will acidify the electrolyte, resulting in acidification corrosion of electrode materials and sharp deterioration of battery performance. The surface coating is also an electrolyte additive. Its function is to reduce the direct contact between the material and the electrolyte. The surface of the material prevents the corrosion of free acids such as HF, but it cannot completely prevent the inherent defects of the generation of HF in the electrolyte.

Starting from the above defects, the present invention proposes a non-aqueous electrolyte, creatively using additive A, which reacts with H ₂ O (and/or free acids such as HF) to effectively capture a small amount of water in the electrolyte And a small amount of free acid such as HF, which greatly reduces the content of free acid in the electrolyte, thereby preventing the acidification corrosion of the electrode material, stabilizing the electrolyte/electrode interface, and finally maintaining the cycle stability of the electrode material.

The present invention also provides a lithium ion battery, including a positive electrode and an electrolyte; the electrolyte is the electrolyte described in any one of the above technical solutions.

The present invention has no special restrictions on the positive electrode material or lithium ion battery, and the lithium battery positive electrode material and lithium ion battery well known to those skilled in the art can be selected and selected according to the application situation, product performance and quality requirements. Adjustment, the positive electrode material of the present invention is preferably a ternary positive electrode material, that is, the lithium ion battery is preferably a ternary positive electrode material lithium ion battery, more preferably a high-nickel ternary positive electrode material, that is, the lithium ion battery is more preferably High nickel ternary cathode material lithium ion battery.

The present invention has no special restrictions on other compositions or parameters of the lithium-ion battery, and the conventional composition or parameters of the lithium-ion battery well-known to those skilled in the art can be used, and those skilled in the art can carry out according to the application situation, product performance and quality requirements. Optionally and adjusted, the lithium-ion battery of the present invention preferably further includes a negative electrode, a separator, a battery casing, and the like.

The invention provides a non-aqueous electrolyte and a high-nickel ternary positive electrode material battery. The invention starts from the improvement of the electrolyte and creatively adds alkylamine compounds and Si-N bond-containing compounds into the non-aqueous electrolyte. At least one of compound (silicon-nitrogen compound) and siloxane compound, the non-aqueous electrolytic solution provided by the invention has extremely low free acid content, and it is applied in the lithium-ion battery with high-nickel ternary positive electrode material , can effectively improve the cycle performance, high-temperature cycle performance and high-temperature storage performance of lithium-ion batteries.

Experimental results show that the lithium-ion battery prepared by the electrolyte provided by the invention has better normal temperature, high-temperature cycle stability and high-temperature storage performance, and the charge-discharge cycle is 200 cycles at a room temperature of 25° C., and the capacity retention rate of the battery is 65%- 90%; after 100 cycles of charging and discharging at a high temperature of 60°C, the capacity retention rate of the battery is 51% to 81%; 62% to 89%. However, for a lithium-ion battery equipped with an existing conventional carbonate electrolyte, after 200 cycles of charging and discharging at room temperature at 25°C, the capacity retention rate of the battery is only 23% to 54%; after 100 cycles of charging and discharging at a high temperature of 60°C, The capacity retention rate of the battery is only 16% to 32%; after storage at 55°C for 30 days, the decrease rate of the open circuit voltage OCV is only 18% to 34%, and the capacity retention rate of the battery is 51% to 60%.

In order to further illustrate the present invention, an electrolyte solution and a lithium-ion battery provided by the present invention are described in detail below in conjunction with examples, but it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and detailed descriptions are given. The embodiments and the specific operation process are only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.

All reagents used in the following examples of the present invention are commercially available.

The kind of additive A used in the following examples has:

Examples 1-10

The organic solvent is selected from carbonate solvents, that is, a mixture of ethylene carbonate EC and dimethyl carbonate DMC, and its volume ratio is 3:7.

The lithium salts are respectively selected from LiPF ₆ and lithium salt LiTFSI centered on the N atom, so that the molar concentration is 1 mol L ^-1 .

Additive A is selected from the above formulas 1-9, additive B is preferably LiPF ₆ (2% by mass), additive C is preferably 1,3-propane sultone (PS, 1% by mass), and finally lithium Ion battery electrolyte.

Comparative example 1～2

The conventional lithium-ion battery electrolyte is used, and the organic solvent is selected from carbonate solvents, that is, a mixture of ethylene carbonate EC and dimethyl carbonate DMC, and the volume ratio is 3:7.

The lithium salts are respectively selected from LiPF ₆ and lithium salt LiTFSI centered on the N atom, so that the molar concentration is 1 mol L ^-1 .

Example 11

Parallel performance detection is carried out to the electrolyte solutions shown in Examples 1-10 of the present invention and Comparative Examples 1-2,

Referring to FIG. 1 , FIG. 1 is an appearance view of a 1000mAh pouch laminated battery used for testing in an embodiment of the present invention and a comparative example.

The lithium-ion battery electrolytes prepared above were respectively injected into 1000mAh soft-pack laminated batteries. carry out testing.

The positive electrode is high-nickel ternary material NCM nickel cobalt lithium manganese oxide (811), the negative electrode is artificial graphite, and the diaphragm is Celgard2075.

Test conditions: charge and discharge voltage range is 2.5 ~ 4.3V;

Normal temperature cycle performance: 200 charge and discharge cycles at 30°C and 1C rate at room temperature;

High temperature performance test: charge and discharge cycle 100 times at 60°C high temperature and 1C rate;

High-temperature storage performance: Store the battery under test at 55°C for 30 days in a fully charged state, and test the OCV drop rate and capacity retention rate of the battery after storage.

See Table 1, Table 1 is the electrolyte formula and performance test results in the lithium-ion battery prepared in Example 11 of the present invention

Table 1

From the test data in Table 1, it can be seen that the room temperature, high temperature cycle performance and high temperature storage performance of the high-nickel ternary positive electrode battery using the electrolyte of additive A are significantly better than the battery of Comparative Example 1 without additive. When the lithium salt in the electrolyte is a lithium salt centered on N atoms, compared with Comparative Example 2, the combined use of additives A, B, and C can significantly improve the performance of the battery.

A kind of non-aqueous electrolytic solution provided by the present invention and the high-nickel ternary positive electrode material battery have been introduced in detail above. In this paper, specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above examples is only used It is used to help understand the method and its core idea of the present invention, including the best mode, and also enables anyone skilled in the art to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements close to the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal expressions of the claims.

Claims (10)

1. An electrolyte, is characterized in that, comprises lithium salt, organic solvent and additive A; The additive A includes one or more of alkylamine compounds, silicon nitrogen compounds and siloxane compounds. 2. The electrolyte according to claim 1, wherein the volume percentage of the additive A in the electrolyte is 0.05% to 10%; The molar concentration of the lithium salt in the electrolyte is 0.1-20 mol/L. 3. The electrolyte according to claim 1, wherein the alkylamine compound is selected from one or more of the alkylamine compounds shown in the structure of formula I, Wherein, R ₁ , R ₂ and R ₃ are independently selected from C1-C6 straight-chain or branched-chain alkyl groups. 4. The electrolyte solution according to claim 1, wherein the silicon-nitrogen compound is selected from one or more of the disilamine compounds shown in the structure of formula II, and/or, has the formula One or more of the silane imidazole compounds shown in structure III, Wherein, R ₄ , R ₅ , R ₆ , R ₈ , R ₉ and R ₁₀ are independently selected from hydrogen atoms, halogens, C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups, _R7 is independently selected from a hydrogen atom, a halogen, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C6-C20 aromatic group, and an alkali metal atom; Wherein, R ₁₁ , R ₁₂ and R ₁₃ are independently selected from hydrogen atoms, halogens, C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups. 5. The electrolyte according to claim 1, wherein the siloxane compound is selected from one or more of the linear siloxane compounds shown in the structure of formula IV, and/or, One or more of the cyclic siloxane compounds represented by the structure of formula V, Wherein, R ₁₄ , R ₁₅ , R ₁₆ and R ₁₇ are independently selected from C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C20 aryl groups; Wherein, R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ and R ₂₃ are independently selected from C1-C6 straight-chain or branched-chain alkyl groups; n is an integer of 1-6. 6. The electrolytic solution according to claim 1, wherein the lithium salt comprises lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxalate borate, lithium difluorooxalate borate, lithium trioxalate phosphate, dioxalate lithium borate, One or more of lithium difluorooxalate phosphate, lithium tetrafluorooxalate phosphate, lithium bis(trifluoromethylsulfonyl)imide and lithium bisfluorosulfonylimide; The organic solvents include fluorine-free or fluorine-substituted carbonate solvents, fluorine-free or fluorine-substituted ether solvents, fluorine-free or fluorine-substituted carboxylate solvents, fluorine-free or fluorine-substituted phosphate solvents and ion One or more of one or more of liquid-based solvents. 7. The electrolytic solution according to any one of claims 1 to 6, characterized in that, the electrolytic solution also includes additive B; The additive B includes one or more of Li ₂ CO ₃ , CaCO ₃ , Al ₂ O ₃ , ZnO, MgO, BaO, AlF ₃ , MgF ₂ , AlOF, LiPF ₆ , LiBF ₄ and LiBOB; The mass percentage of the additive B in the electrolyte solution is 0.005%-10%. 8. The electrolytic solution according to any one of claims 1 to 6, characterized in that, the electrolytic solution also includes additive C; The additive C includes propylene sulfate, vinyl sulfite, propylene sulfite, 1-propyl phosphoric acid cyclic anhydride, tris(trimethylsilyl) phosphate, trimethyl phosphate, tris(1,1, 1,3,3,3-Hexafluoroisopropyl) phosphate, fluoroethylene carbonate, anisole, vinylene carbonate, vinylphenatate, acrylocyanide, vinylethylene carbonate, 1,3- One or more of propane sultone, succinonitrile, 1,3-propenyl-sultone, divinyl sulfone, lithium dioxalate borate and lithium difluoro(oxalate) borate; The mass percentage of the additive C in the electrolyte solution is 0.005%-10%. 9. A lithium ion battery, characterized in that, comprises a positive electrode and an electrolyte; The electrolytic solution is the electrolytic solution described in any one of claims 1-8. 10. The lithium-ion battery according to claim 9, wherein the positive electrode includes a high-nickel ternary positive electrode material.