WO2024131239A1 - Additive for lithium-ion battery, lithium-ion battery, and electrical device - Google Patents

Abstract

The present application discloses an additive for a lithium-ion battery, a lithium-ion battery, and an electrical device. The lithium-ion battery comprises a negative electrode sheet, a positive electrode sheet, a separator, and a non-aqueous electrolyte, and at least one of the positive electrode sheet, the separator, or the non-aqueous electrolyte comprises a compound of formula I, formula IIa, or formula IIb. According to the present application, the compound of formula I, formula IIa, or formula IIb is added into the positive electrode sheet, the electrolyte, or the separator, the compound is an oxide or halide having multiple boron atoms and is prone to an electrochemical passivation reaction first on the surface of a positive electrode during charging and discharging of the lithium-ion battery to form a uniform, dense and stable passivation protective layer rich in BF3 or fluorine-containing borate, and a formed passivation film can effectively inhibit the corrosion of the positive electrode sheet.

Description

Additives for lithium-ion batteries, lithium-ion batteries and electrical equipment

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese patent application No. 2022116427266, filed with the Chinese Patent Office on December 20, 2022, and entitled “Additives for Lithium-ion Batteries, Lithium-ion Batteries and Electrical Equipment,” the entire contents of which are incorporated by reference into this application.

Technical Field

The present invention relates to the technical field of ion batteries, and in particular to an additive for lithium ion batteries, a lithium ion battery and electrical equipment.

Background technique

In recent years, electrochemical components have been widely used as power sources for small electronic devices such as mobile phones and laptop computers, as well as for electric vehicles and power storage. Gradually, lithium-ion secondary batteries with various special properties have entered our daily lives, and their convenience and practicality are increasingly recognized by everyone.

At the same time, people's high demands for lithium-ion batteries such as long battery life, high capacity, fast charging, and wide operating temperature range need to be further addressed, so that lithium-ion secondary batteries can enter more of our lives and provide greater convenience and experience.

Lithium secondary batteries are mainly composed of positive and negative electrode materials that can embed and deintercalate lithium, and non-aqueous electrolytes containing lithium salts and non-aqueous solvents. Generally, non-aqueous solvents include carbonates such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), and propylene carbonate (PC). Additives are usually ethylene sulfate (DTD), vinylene carbonate (VC), 1,3-propane sultone (1,3-PS), etc.

As a highly crystallized material such as natural graphite or artificial graphite as the negative electrode, the advantage of this material is that the working voltage is low, and it can form a lithium-ion secondary battery with a higher output voltage with a positive electrode material containing metal oxides such as Ni/Co/Mn. Inevitably, due to the low potential of graphite, additives and solvents in the electrolyte can easily form a layer of SEI passivation film on the surface of graphite, effectively preventing further reduction and decomposition of lithium-embedded graphite and electrolyte. Due to the special characteristics of SEI in conducting lithium ions, lithium-ion secondary batteries can be charged and discharged normally. At the same time, due to the traditional electrolyte The liquid will be continuously oxidized under higher platform voltage conditions, accompanied by the precipitation of transition metal ions in the positive electrode material causing structural damage, resulting in lower coulombic efficiency and poor cycle life of the lithium battery. As a result, the problem of oxidative decomposition of conventional electrolytes under high voltage has become increasingly prominent, and its bottleneck problem needs to be further resolved.

In view of this, the present invention is proposed.

Summary of the invention

The object of the present invention is to provide an additive for lithium ion batteries, a lithium ion battery and an electrical device.

The present invention is achieved in that:

In a first aspect, the present invention provides an additive for a lithium ion battery, comprising at least one of a compound of formula I, a compound of formula II-a, and a compound of formula II-b, wherein the structure of the compound of formula I is as follows:

In Formula I, R ₁ is selected from one of hydrogen, Li, Be, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb, Cs, NH ₄ , N(R ₃ ) ₄ , alkyl having 1 to 10 carbon atoms, cyclic alkyl, alkenyl, cyclic alkenyl, alkynyl, cyclic alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl having 6 to 10 carbon atoms, and benzyl;

The structure of the compound of formula II-a is as follows:

In formula II-a, n is a positive integer ≥ 1, and _R2 is independently selected from H, F, Cl, Br, I, Li, Be, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb, Cs, an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group;

The structure of the compound of formula II-b is as follows;

In formula II-b, n ₁ is a positive integer ≥ 1, and X is C, Si, N, P, As, O, S or Se;

When X is C or Si, n ₂ =3, R ₃ is selected from H, an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group;

When X is N, P or As, n ₂ =2, R ₃ is selected from H, alkyl having 1 to 10 carbon atoms, cyclic alkyl, alkenyl, cyclic alkenyl, alkynyl, cyclic alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl having 6 to 10 carbon atoms and benzyl;

When X is O, S or Se, _n2 = 1, and _R3 is selected from H, Li, Be, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb, Cs, an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group.

In an optional embodiment, in the compound of formula I, R ₁ is Li, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, phenyl or benzyl.

In an optional embodiment, in the compound represented by formula II-a, R ₂ is F, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, phenyl or benzyl.

In an optional embodiment, in the compound represented by formula II-b, R ₃ is Li, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, phenyl, benzyl, halophenyl, or halobenzyl.

In a second aspect, the present invention provides a lithium ion battery containing the aforementioned additive for lithium ion batteries, comprising a negative electrode plate, a positive electrode plate, a separator and a non-aqueous electrolyte, wherein at least one of the positive electrode plate, the separator or the non-aqueous electrolyte comprises at least one of the compounds of formula I, formula II-a and formula II-b.

In an optional embodiment, the surface of the positive electrode plate is rich in BF ₃ or a passivation protective layer containing fluorine borate.

In an optional embodiment, in the non-aqueous electrolyte, the content of the compound of Formula I, Formula II-a or Formula II-b is 0.01 wt% to 15 wt%.

In an optional embodiment, the content of the compound of Formula I, Formula II-a or Formula II-b is 0.05 wt% to 6 wt%.

In an optional embodiment, the non-aqueous electrolyte further includes an additive, wherein the additive includes vinyl sulfate At least one of esters, fluoroethylene carbonate, bisfluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, 1-propylene-1,3-sultone, methylene methanedisulfonate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite and tris(trimethylsilyl)borate.

In an optional embodiment, the concentration of the additive in the non-aqueous electrolyte is 0.1 wt% to 3 wt%.

In _an optional embodiment, the non-aqueous electrolyte further includes a lithium salt, _and the lithium salt includes _at least one of LiFSI, _{C4BLi3O11 , LiPF6n} ( _CF3 ) _n , LiN[ _{( FSO2C6F4} )( _CF3SO2 )], _LiSO3CF3 , LiTFSI, LiCH( _SO2CF3 ) ₂ , LiTFSM, _LiPF6 , _LiBF4 , LiBOB, _LiDFOB , _LiAsF6 , _LiPO2F2 , LiN( _CF3SO2 ) _{2 , LiCF3SO3} , _LiClO4 and LiN( _{CxF2x + 1SO2} )( _{CyF2y +1SO2 )} , wherein n is an integer of 0 to ₆ , _and x and y are _both natural numbers.

In an optional embodiment, the molar concentration of lithium ions in the non-aqueous electrolyte is 0.1 to 3 mol/L, calculated as lithium ions.

In an optional embodiment, the molar concentration of lithium ions in the non-aqueous electrolyte is 0.2 to 2 mol/L, calculated as lithium ions.

In an optional embodiment, the concentration of lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide in the non-aqueous electrolyte is 0.01 wt % to 23 wt %.

In an optional embodiment, the content of lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide in the non-aqueous electrolyte is 0.2 wt % to 18.4 wt %.

In an optional embodiment, the non-aqueous electrolyte further includes an organic solvent, and the organic solvent is at least one of carbonates, carboxylates, sulfates, phosphates, amides, nitriles and ethers.

In an optional embodiment, the organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, triethyl phosphate, methyl ethyl phosphite, methyl sulfide, diethyl sulfite, dimethyl sulfite, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3 dioxolane, tetrahydrofuran, fluorine-containing cyclic organic esters and sulfur-containing cyclic organic esters.

In an optional embodiment, in the non-aqueous electrolyte, the organic solvent content is 60 wt % to 85 wt %.

In a third aspect, the present invention provides an electrical device comprising the lithium-ion battery described in the aforementioned embodiment.

The present invention has the following beneficial effects:

The present invention adds a compound represented by formula I, formula IIa or formula IIb to the positive electrode sheet, electrolyte or separator. The compound is an oxide having multiple boron atoms and is very likely to preferentially undergo an electrochemical passivation reaction on the positive electrode surface during the charge and discharge process of the lithium ion battery to form a uniform, dense and stable passivation protective layer rich in _BF3 or fluorine-containing borate. The formed passivation film can effectively inhibit the corrosion of the positive electrode sheet.

When the positive electrode material is a low-cobalt ternary positive electrode material, the passivation film on the positive electrode surface further covers the high active sites on the surface of the low-cobalt (Co%≤20%) ternary positive electrode material in the high voltage (≥4.1V) system, thereby improving the defects of this ternary positive electrode material caused by the low cobalt content, such as strong oxidizability, poor structural order and instability, poor material conductivity, poor kinetic properties, and easy Li ⁺ /Ni2 ⁺ mixing in the material bulk to form rock salt phase change.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

FIG1 is a CP diagram (x1000) of aluminum foil passivation after high temperature cycling when the electrolyte contains 1M LiFSI+1% Li ₂ B ₄ O ₇ in Example 11;

Figure 2 is a CP diagram (x1000) showing that the aluminum foil was severely corroded after high-temperature cycling in Comparative Example 3 when the electrolyte contained 1 M LiFSI.

Detailed ways

In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

The present application embodiment provides an additive for a lithium ion battery, comprising at least one of a compound of formula I, a compound of formula II-a, and a compound of formula II-b, wherein the structure of the compound of formula I is as follows:

In Formula I, R ₁ is selected from hydrogen, NH ₄ , N(R ₃ ) ₄ , an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, One of a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group, or at least one of a metal atom such as Li, Be, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb or Cs;

The structure of the compound of formula II-a is as follows:

In formula II-a, n is a positive integer ≥ 1, and _R2 is independently selected from H, F, Cl, Br, I, Li, Be, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb, Cs, an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group;

The structure of the compound of formula II-b is as follows;

In formula II-b, n ₁ is a positive integer ≥ 1, and X is C, Si, N, P, As, O, S or Se;

When X is C or Si, n ₂ =3, R ₃ is selected from H, an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group;

When X is N, P or As, n ₂ =2, R ₃ is selected from H, alkyl having 1 to 10 carbon atoms, cyclic alkyl, alkenyl, cyclic alkenyl, alkynyl, cyclic alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl having 6 to 10 carbon atoms and benzyl;

When X is an atom such as O, S or Se, _n2 = 1, and _R3 is selected from H, Li, Be, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb, Cs, an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group.

In some embodiments of the present application, in the compound represented by Formula I, R ₁ is Li, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, phenyl or benzyl.

In some embodiments, in the compound represented by formula II-a, R ₂ is F, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, phenyl or benzyl, halophenyl, or halobenzyl.

In some embodiments, in the compound represented by formula II-b, R ₃ is Li, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, phenyl, benzyl, halophenyl, or halobenzyl.

In some embodiments, the additive is a compound having one of the following structures:

Another embodiment of the present application provides a lithium ion battery containing the aforementioned lithium ion battery additive, comprising a negative electrode plate, a positive electrode plate, a separator and a non-aqueous electrolyte, wherein the positive electrode plate, the separator or the non-aqueous electrolyte comprises at least one of the compounds of Formula I, Formula II-a and Formula II-b.

In some embodiments, the surface of the positive electrode plate is rich in BF ₃ or a passivation protective layer containing fluorine borate, which has special electrical properties.

In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

In some embodiments, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is arranged on any one or both of the two opposite surfaces of the negative electrode current collector. The negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the negative electrode active material may be one or a combination of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, etc., and the particle size D value of the negative electrode active material is ≥ 0.1um. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys; the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.

In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector includes two opposite surfaces in its thickness direction, and the positive electrode active material is stacked on either or both of the two surfaces of the positive electrode current collector.

In some embodiments, the positive _{electrode plate} includes a positive electrode active material, _and the general structural formula of the positive electrode active material includes _{LiaNixCoyMzO2} , wherein 0.1≤a≤1.2, 0≤x≤1.0, y≤0.2, x+y+z＝1, and M includes one or two of Al _and Mn; or the general structural formula of the positive electrode active material includes _{LiaMnxFeyPO4 ,} wherein 0.1≤a≤1.2, _{0≤x≤1.0 , 0≤y≤1.0} , x+y＝1, and the positive electrode material includes _{LiFePO4 and LiMnxFeyPO4} .

In some embodiments, the lithium metal battery of the present invention has no particular restrictions on the isolation membrane, and a known porous structure isolation membrane with electrochemical stability and chemical stability can be selected, such as a single-layer or multi-layer film of one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).

In the present invention, at least one compound represented by the compounds of formula I, formula II-a and formula II-b is added to the positive electrode sheet, electrolyte or separator, which is an oxide having multiple boron atoms and is very easy to preferentially form on the positive electrode surface during the charge and discharge process of the lithium ion battery. An electrochemical passivation reaction occurs on the surface to form a uniform, dense and stable passivation protective layer rich in _BF3 or fluorinated borate. The formed passivation film can effectively inhibit the corrosion of the positive electrode sheet.

When the positive electrode material is a low-cobalt ternary positive electrode material, the passivation film on the positive electrode surface further covers the high active sites on the surface of the low-cobalt (Co%≤20%) ternary positive electrode material in the high voltage (≥4.1V) system, thereby improving the defects of this ternary positive electrode material caused by the low cobalt content, such as strong oxidizability, poor structural order and instability, poor material conductivity, poor kinetic properties, and easy Li ⁺ /Ni2 ⁺ mixing in the material bulk to form rock salt phase change.

In some embodiments of the present application, the surface of the positive electrode plate has a passivation protective layer rich in _BF3 or containing fluorine borate substances.

In some embodiments of the present application, in the non-aqueous electrolyte, the content of the compound of Formula I, Formula II-a or Formula II-b is 0.01wt% to 15wt%, specifically 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt% or any value between 0.01wt% and 15wt%.

In some embodiments, the content of the compound of Formula I, Formula II-a or Formula II-b is 0.05 wt% to 6 wt%.

When the content of the compounds represented by Formula I, Formula II-a and Formula II-b is less than 0.01%, the concentration is too low to effectively form a uniform and dense passivation film on the surface of the positive electrode aluminum foil, and the strong oxidation corrosion of the aluminum foil caused by high concentration (≥0.3MLiFSI) cannot be improved, and the high-temperature cycle life and high-temperature storage capacity decay are too fast. Problems such as; when the content of the compounds represented by Formula I, Formula II-a and Formula II-b is greater than 6%, it has a very obvious improvement effect on the strong oxidation corrosion of the aluminum foil in the high-concentration LiFSI electrolyte, while taking into account the high cost increase of the electrolyte brought by the high content of Formula I, Formula II-a and Formula II-b compounds. The content of the compounds of Formula I, Formula II-a and Formula II-b is 0.05wt% to 6wt%.

In some embodiments of the present application, the non-aqueous electrolyte also includes an additive, and the additive includes at least one of vinyl sulfate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, 1-propylene-1,3-sultone, methanedisulfonic acid methylene ester, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite and tris(trimethylsilyl)borate.

In some embodiments of the present application, the concentration of the additive in the non-aqueous electrolyte is 0.1wt% to 3wt%, specifically 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt% or any value between 0.1wt% and 3wt%.

In some embodiments of the present application, the lithium salt includes at least one of LiFSI, C ₄ BLi ₃ O ₁₁ , LiPF _6n (CF ₃ ) _n , LiN[(FSO ₂ C ₆ F ₄ )(CF ₃ SO ₂ )], LiSO ₃ CF ₃ , LiTFSI, LiCH(SO ₂ CF ₃ ) ₂ , LiTFSM, LiPF ₆ , LiBF ₄ , LiBOB, LiDFOB, LiAsF ₆ , LiPO ₂ F ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiClO ₄ and LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ), wherein n is an integer of 0 to 6, and x and y are both natural numbers; From the perspective of energy density, power characteristics, cycle life, etc. of the battery, preferred lithium salts are LiPF ₆ , LiN(SO ₂ F) ₂ , and LiBF ₄ .

In some embodiments, the molar concentration of lithium ions in the non-aqueous electrolyte is 0.1 to 3 mol/L, specifically, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt% or any value between 0.1wt% and 3wt%.

In some embodiments, the molar concentration of lithium ions in the non-aqueous electrolyte is 0.2 to 2 mol/L, the lithium salt concentration is relatively high, and the lithium salt is not easy to dissociate in the solvent system; the lithium salt concentration is relatively low, the number of dissociated Li ⁺ is relatively small, and the conductivity is low.

In some embodiments of the present application, the concentration of lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide in the non-aqueous electrolyte is 0.01wt% to 23wt%, specifically 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 10wt%, 15wt%, 20wt%, 23wt% or any value between 0.01wt% and 23wt%.

In some embodiments, the content of lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide in the non-aqueous electrolyte is 0.2 wt % to 18.4 wt %.

The lithium ion conductivity of lithium bis(fluorosulfonyl imide) and lithium bis(trifluoromethanesulfonyl imide) is high, and when used in non-aqueous electrolytes, they have good high-temperature cycle performance and low-temperature discharge capability.

On the other hand, lithium bis(fluorosulfonyl)imide can cause corrosion of the positive electrode sheet, especially when the content is high, which can easily cause strong oxidative corrosion of the positive electrode current collector such as aluminum foil. Therefore, the lithium-ion battery is prone to cycle jump in the later stage of the cycle, and the battery capacity is accelerated to decay.

The present invention introduces compounds of formula I, formula II-a and formula II-b into lithium-ion batteries, which can preferentially form a passivation protective film on the positive electrode surface, inhibiting the corrosion of lithium bis(fluorosulfonyl)imide to aluminum foil, thereby further improving the high-temperature cycle life and high-temperature storage life of the electrolyte system, while taking into account the low-temperature discharge capacity. It should be emphasized that the compounds of formula I, formula II-a and formula II-b in the present patent application can participate in chemical or electrochemical reactions in high-concentration LiFSI electrolytes to generate BF _3- rich or fluorine-containing borate substances, and such substances are preferentially passivated to form films on the surface of the positive electrode aluminum foil, preventing the oxidation protective layer on the surface of the aluminum foil from further reacting with the LiFSI component to continuously generate Al(FSI) ₃ dissolved in the electrolyte, thereby causing the aluminum foil to be continuously corroded, deteriorating the electrochemical performance of the lithium battery, etc. This type of passivation protection mechanism is different from the disclosed mechanism of reducing the negative electrode to generate LiF or borate substances to enhance the toughness of the negative electrode interface film, and the starting point of the improvement is also different.

When the content of the compound shown in LiFSI is less than 0.1%, the electrolyte conductivity is slightly improved, and the high-temperature cycle dynamics and low-temperature DCR performance of the battery cell cannot be significantly improved. When its content reaches 1.2 mol/L, the high-temperature cycle performance is improved to At a higher level, it has excellent low-temperature discharge performance. At the same time, with the increase of LiFSI concentration, the improvement of high-temperature cycle and low-temperature discharge of lithium-ion batteries is limited. Considering the cost of electrolyte, the system containing higher concentration of LiFSI is usually not adopted.

In some embodiments of the present application, the non-aqueous electrolyte further includes an organic solvent, and the organic solvent is at least one of carbonates, carboxylates, sulfates, phosphates, amides, nitriles and ethers.

In some embodiments, the organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, triethyl phosphate, methyl ethyl phosphite, methyl sulfide, diethyl sulfite, dimethyl sulfite, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3 dioxolane, tetrahydrofuran, fluorine-containing cyclic organic esters and sulfur-containing cyclic organic esters.

In some embodiments, in the non-aqueous electrolyte, the organic solvent content is 60wt% to 85wt%, specifically 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt% or any value between 60wt% and 85wt%.

In some embodiments, the carbonate may be a cyclic carbonate or a chain carbonate. The cyclic carbonate may be at least one of ethylene carbonate (EC), fluoroethylene carbonate (FEC), and propylene carbonate (PC); the chain carbonate may be at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).

Other embodiments of the present invention provide an electrical device including the lithium-ion battery described in the aforementioned embodiment.

The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

Examples 1 to 32

The preparation method of the electrolyte in Examples 1 to 33 is as follows: in an argon atmosphere glove box (H ₂ O<0.1ppm, O ₂ <0.1ppm), weighing an organic solvent (ethylene carbonate, diethyl carbonate, ethyl methyl carbonate (mass ratio 3:2:5)) into a sample bottle, adding 15.3% of LiFSI (1M) (LiFSI in Example 24 is 1.2M) and 1% of vinylene carbonate (VC) accounting for the total mass into the sample bottle, and then adding the compound represented by Formula I, Formula IIa or Formula IIb, mixing well to obtain a prepared electrolyte.

The preparation method of the electrolyte in Examples 1 to 32 is:

In an argon atmosphere glove box (H ₂ O<0.1ppm, O ₂ <0.1ppm), organic solvents (ethylene carbonate, diethyl carbonate, ethyl methyl carbonate (mass ratio 3:2:5)) were weighed into a sample bottle, LiFSI (1M and 1.2M) and 1% vinylene carbonate (VC) in different proportions of the total mass were added to the sample bottle, and then the compound represented by Formula I, Formula IIa or Formula IIb was added and mixed evenly to obtain a prepared electrolyte.

Examples 1 to 32 also provide a series of batteries, the preparation method of which is as follows:

Positive electrode preparation:

The positive electrode active material LiNi _0.68 Co _0.03 Mn _0.29 O ₂ (lithium nickel cobalt manganese oxide) and the conductive agent acetylene black (Super P) are mixed evenly in a stirring tank, and then N-methylpyrrolidone (NMP) and a binder polyvinylidene fluoride glue (PVDF) are added thereto and stirred evenly to obtain a black slurry, which is coated on an aluminum foil and baked, rolled and cut into pieces to obtain a positive electrode sheet, wherein the mass ratio of the positive electrode active material, the conductive agent and the binder is (96.5:2:1.5).

The preparation method of the battery series of embodiments 33 to 38 is as follows:

The positive electrode active material LiNi _0.68 Co _0.03 Mn _0.29 O ₂ (lithium nickel cobalt manganese oxide) and the conductive agent acetylene black (Super P) are mixed evenly in a stirring tank, and then N-methylpyrrolidone (NMP) and binder polyvinylidene fluoride glue (PVDF) and polyborate/polyborate are added thereto in a certain mass ratio and stirred evenly to obtain a black slurry, which is coated on an aluminum foil, and then baked, rolled and cut into pieces to obtain a positive electrode sheet, wherein the mass ratio of the conductive agent to the binder is 2% and 1.5% or more.

Negative electrode sheet preparation (Examples 1 to 38 series batteries):

The negative electrode active material graphite and the conductive agent acetylene black (Super P) are mixed evenly in a stirring tank, and then the binder SBR and deionized water are added and stirred evenly to obtain a black slurry, which is coated on a copper foil and then baked, rolled and cut to obtain a negative electrode sheet, in which the ratio of active material, conductive agent and binder is (96.5:2:1.5).

Battery cell production:

The positive electrode sheets, negative electrode sheets and separators obtained above are stacked in the order of positive electrode, separator and negative electrode, and are wound, hot pressed and shaped, and the tabs are welded to obtain bare cells, which are sealed on the top and sides with aluminum-plastic film. After completion, the cells are placed in an oven at 85±10℃ and baked for 24h±12h to ensure that the water content of the electrodes is qualified, and then the electrolyte is injected. After the processes of reduced pressure packaging, standing, formation, shaping and the like, the battery is obtained.

The battery performance obtained in Examples 1 to 33 was tested using the following method. The results are shown in Table 1.

Ⅰ. Cycle test:

Normal temperature cycle: The batteries of Examples 1 to 38 and Comparative Examples 1 to 5 were subjected to charge and discharge cycle tests at 25°C with a charge and discharge rate of 1C/1C in the range of 2.8 to 4.40V, and the initial discharge capacity of the battery and the discharge capacity after each cycle were recorded. The cycle was repeated for 1000 times, and the capacity retention rate = discharge capacity per cycle/initial discharge capacity of the battery * 100%. The cycle termination condition was 80% SOC. The recorded data are shown in Table 1.

High temperature cycle: The batteries of Examples 1 to 38 and Comparative Examples 1 to 5 were respectively placed in a 45°C incubator for 120 min, and then subjected to charge and discharge cycle tests in a 45°C constant temperature box at a charge and discharge rate of 1C/1C in the range of 2.8 to 4.40 V, and the first discharge capacity of the battery and the discharge capacity after each cycle were recorded. The cycle was repeated for 500 cycles, and the capacity retention rate = discharge capacity per cycle/first discharge capacity of the battery * 100%. The cycle termination condition was 80% SOC. The recorded data are shown in Table 1.

Ⅱ. High temperature storage:

The batteries of Examples 1 to 38 and Comparative Examples 1 to 5 were fully charged, stored in a 60°C thermostat, taken out every 10 days, fully charged again and continued to be stored in a 60°C thermostat, and taken out after 120 days to test their recoverable capacity. The recoverable capacity test method is as follows:

1. 1C constant current discharge to 2.8V, let stand for 10 minutes;

2. 1C CC-CV charge to 4.40V, cut-off current is 0.05C, and stand for 10 minutes;

3. Discharge at 1C constant current to 2.8V, and the discharged capacity is recorded as the recoverable capacity.

Capacity retention rate = recoverable capacity after storage / recoverable capacity of fresh battery * 100%, recorded data see Table 1.

III. Volume expansion experiment: The batteries of Examples 1 to 38 and Comparative Examples 1 to 5 were charged to 4.40 V at 1C, and the volume was tested by the drainage method. The initial volume and the volume after storage at 85°C for 7 days were recorded. The volume expansion rate = (volume after storage at 85°C for 7 days - initial volume) / initial volume * 100%. The storage termination condition was 80% SOC. The results are shown in Table 1.

IV. Constant voltage leakage current test:

The batteries of Examples 1 to 38 and Comparative Examples 1 to 5 were charged to 4.40V at 1C CC-CV, with a cut-off current of 0.05C, and then charged at a constant voltage of 0.05C for 36h. After that, the leakage current of the lithium-ion secondary battery was continuously observed and recorded at 25°C to complete the test. The recorded results are shown in Tables 1 to 3.

Table 1 Composition of the electrolyte in Examples 1 to 17 and the test results of the obtained batteries (lithium borate salt)

Table 2 Composition of the electrolyte in Examples 18 to 25 and the test results of the obtained batteries (boric acid esters)

Note: FB ₃ O ₄ is a mixture ② of the compound of formula II in the claims, and its specific structure is described in the previous specific examples.

Examples 26-32

The difference between Examples 26-32 and Example 2 is that the types of compounds represented by Formula I, Formula IIa or Formula IIb are different, and the other components and concentrations are the same. The obtained batteries were tested, and the results are shown in Table 3.

Table 3 Composition of electrolytes in Examples 26 to 32 and test results of the obtained batteries

Note: Example 32 is a 1.2M LiFSI electrolyte solution

Comparative Examples 1 to 5

The difference between Comparative Examples 1 to 5 and Examples 1 to 32 is only that the electrolyte is different. The preparation method of the electrolyte in Comparative Examples 1 to 5 is as follows:

In an argon atmosphere glove box (H ₂ O<0.1ppm, O ₂ <0.1ppm), weigh organic solvents (ethylene carbonate, diethyl carbonate, ethyl methyl carbonate (mass ratio 3:2:5)) in a sample bottle, add different weight ratios of LiPF ₆ +LiFSI (total concentration of 1.0M or 1.2M) and 1% vinylene carbonate (VC) into the sample bottle, then add the compound shown in formula I, mix well, and obtain a prepared electrolyte. The composition of the electrolyte and the test results of the battery performance are shown in Table 4.

Table 4 The composition of the electrolyte in Comparative Examples 1 to 5 and the test results of the obtained batteries

Examples 33-38

The only difference from Comparative Example 3 is that FB ₃ O ₄ is mixed into the positive electrode sheet or the separator material instead of the electrolyte solution. The results are shown in Table 5.

Table 5 Composition of positive electrode sheets or separators in Examples 33 to 38 and test results of the obtained batteries

Note: In embodiments 33/35/37, the amount of FB ₃ O ₄ added is 1%/3%/5% of the active material content of the positive electrode sheet, respectively; in embodiments 34/36/38, the amount of FB ₃ O ₄ added is 1%/3%/5% of the mass of the diaphragm, respectively, and FB ₃ O ₄ is added to the formula as a slurry and attached to one or both sides of the diaphragm by spraying/rolling.

From the data of the above Examples 1 to 38 and Comparative Examples 1-5, it can be seen that the boron-containing compounds represented by Formula I, Formula IIa or Formula IIb undergo electrochemical oxidation reactions on the surface of the positive electrode aluminum foil during the charge and discharge process of the high-voltage 4.4V lithium-ion battery to form a uniform and dense passivation film (see Figures 1 and 2 for the specific passivation effect and corrosion phenomenon of the aluminum foil), which takes precedence over the passivation effect produced by lithium salts such as LiFSI or LiTFSI, and effectively prevents the serious gas production and excessive capacity decay caused by the strong oxidation corrosion of the aluminum foil caused by high-concentration LiFSI or LiTFSI, and effectively reduces the side reactions such as high leakage current and accelerated decay of high-temperature storage capacity caused by high-concentration LiFSI. At the same time, the passivation film formed by the boron-containing substance in the electrolyte greatly reduces the solid-liquid interface impedance, avoids the generation of large polarization factors in the charge and discharge process, and thereby improves the excessive increase in battery impedance caused by high-temperature cycling and high-temperature storage of high-voltage system batteries. Comparison of the experimental results of Examples 1-4 and 5-9 shows that when the boron-containing additive is lithium metaborate, the electrolyte addition amount is less than 1.5% or the content of polyborate/ester additive is less than 0.1%, the additive content is low, and accordingly, the number of boron-containing functional groups in the compound is small, which is difficult to form an effective dense and uniform passivation film, and the effect of improving room temperature cycle and leakage current is not obvious. When the content is >6%, the interface film formed by the electrochemical oxidation reaction of high-concentration boron-containing substances or polyborates on the surface of the positive electrode aluminum foil is rich in BF ₃ , containing inorganic components such as boron fluoride, effectively prevent the serious corrosion of aluminum foil caused by high-concentration LiFSI, improve the electrochemical kinetics of lithium batteries, and at the same time, the positive electrode passivation film formed on the positive electrode surface has the effect of improving the ability to conduct lithium ions, thereby greatly improving the rapid increase in polarization and serious lithium precipitation at the negative electrode caused by high-rate fast charging; By comparing the results of Examples 8 and 9, it can be concluded that after the borate content exceeds 6%, unilaterally increasing the borate content will not further significantly improve the cycle and storage performance of lithium-ion batteries. Considering the cost factor, excessive addition is not recommended. By comparing Examples 6 to 9 with different addition amounts, it is concluded that compounds of Formula I, Formula IIa or Formula IIb added in different proportions can significantly improve the cycle and storage performance of lithium-ion batteries.

From the comparison of the performance data of the above-mentioned Examples 18 to 32 and Comparative Example 3, it can be seen that, compared with LiB ₃ O ₅ (content of 1%) in Example 6, the fluorine atoms, alkyl phosphine, alkyl mercapto groups and silane-type special substituents in the compounds (6) to (7) of the additive molecules are more nucleophilic, and the boron-heteroatom bond formed is more polar. The nucleophilic substituents are easily oxidized and broken to form a more uniform and dense passivation film on the surface of the high-voltage positive electrode aluminum foil, which greatly improves the cycle life of the lithium-ion battery and reduces the leakage current. However, the nucleophilic ability of the substituents on the B atoms in the molecules of compounds (9) and (10) is relatively small, and the formed BX heteroatom polar bonds cannot be well oxidized and broken to form films at the interface of the high-voltage positive electrode aluminum foil, and their effect of improving the strong oxidation corrosion of the aluminum foil is relatively poor. For the compounds of formula IIa and formula IIb, polyborates and polyborate lithium salts have the same passivation improvement effect on the strong oxidative corrosion of aluminum foil containing a high-concentration LiFSI system, and have the same level of improvement in room temperature/high temperature cycle life. In view of the solubility and easy high-temperature storage characteristics of polyborates, they are easy to add to the electrolyte for dissolution and long-distance transportation. Compared with the synthesis cost of polyborate lithium salts, polyborates have many advantages.

From the comparison of the performance data of the above Examples 33 to 38 and the comparative example, it can be concluded that the compound FB ₃ O _4, as a pole piece additive and a separator additive, has the effect of improving the cycle life of the lithium ion battery and reducing the leakage current.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For the personnel, the present invention can have various changes and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (19)

1. An additive for lithium-ion batteries, characterized in that it comprises at least one of a compound of formula I, a compound of formula II-a, and a compound of formula II-b, wherein the structure of the compound of formula I is as follows:
   

   In Formula I, R ₁ is selected from the group consisting of hydrogen, Li, Be, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb, Cs, NH ₄ , N(R ₃ ) ₄ , an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group;

   The structure of the compound of formula II-a is as follows:
   

   In formula II-a, n is a positive integer ≥ 1, and _R2 is independently selected from H, F, Cl, Br, I, Li, Be, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb, Cs, an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group;

   The structure of the compound of formula II-b is as follows;
   

   In formula II-b, n ₁ is a positive integer ≥ 1, and X is C, Si, N, P, As, O, S or Se;

   When X is C or Si, n ₂ =3, R ₃ is selected from H, an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group;

   When X is N, P or As, n ₂ =2, R ₃ is selected from H, alkyl having 1 to 10 carbon atoms, cyclic alkyl, alkenyl, cyclic alkenyl, alkynyl, cyclic alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl having 6 to 10 carbon atoms and benzyl;

   When X is O, S or Se, _n2 = 1, and _R3 is selected from H, Li, Be, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb, Cs, an alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group, an alkenyl group, a cyclic alkenyl group, an alkynyl group, a cyclic alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aryl group having 6 to 10 carbon atoms, and a benzyl group.
2. The additive for lithium-ion batteries according to claim 1, characterized in that, in the compound represented by formula I, _R1 is Li, an alkyl group, an alkenyl group, an alkynyl group, a halogenated alkyl group, a halogenated alkenyl group, a halogenated alkynyl group, a phenyl group or a benzyl group.
3. The additive for lithium-ion batteries according to claim 1 or 2, characterized in that in the compound represented by formula II-a, _R2 is F, alkyl, alkenyl, alkynyl, halogenated alkyl, halogenated alkenyl, halogenated alkynyl, phenyl or benzyl.
4. The additive for lithium-ion batteries according to any one of claims 1 to 3, characterized in that, in the compound represented by formula II-b, X is C, Si, N, P, As, O, S or Se, and _R3 is Li, alkyl, alkenyl, alkynyl, halogenated alkyl, halogenated alkenyl, halogenated alkynyl, phenyl, benzyl, halogenated phenyl or halogenated benzyl.
5. A lithium-ion battery containing the additive according to any one of claims 1 to 4, characterized in that it comprises a negative electrode sheet, a positive electrode sheet, a diaphragm and a non-aqueous electrolyte, and at least one of the positive electrode sheet, the diaphragm or the non-aqueous electrolyte comprises at least one of the compounds of formula I, formula II-a and formula II-b.
6. The lithium-ion battery according to claim 5, characterized in that the surface of the positive electrode plate has a passivation protective layer rich in _BF3 or containing fluorine borate.
7. The lithium-ion battery according to claim 5 or 6, characterized in that the content of the compound of formula I, formula II-a or formula II-b in the non-aqueous electrolyte is 0.01wt% to 15wt%.
8. The lithium-ion battery according to claim 7, characterized in that the content of the compound of formula I, formula II-a or formula II-b is 0.05wt% to 6wt%.
9. The lithium-ion battery according to any one of claims 5 to 8, characterized in that the non-aqueous electrolyte further comprises the following additives, the additives comprising at least one of vinyl sulfate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, 1-propylene-1,3-sultone, methanedisulfonic acid methylene ester, tris(trimethylsilyl)phosphate and tris(trimethylsilyl)phosphite, and tris(trimethylsilyl)borate.
10. The lithium-ion battery according to claim 9, characterized in that the concentration of the additive in the non-aqueous electrolyte is 0.1wt% to 3wt%.
11. The lithium ion battery according to any one of claims 5 to 10, characterized in that the non-aqueous electrolyte further comprises a lithium salt, and the lithium salt comprises at least one of LiFSI, C ₄ BLi ₃ O ₁₁ , LiPF _6n (CF ₃ ) _n , LiN[(FSO ₂ C ₆ F ₄ )(CF ₃ SO ₂ )], LiSO ₃ CF ₃ , LiTFSI, LiCH(SO ₂ CF ₃ ) ₂ , LiTFSM, LiPF ₆ , LiBF ₄ , LiBOB, LiDFOB, LiAsF ₆ , LiPO ₂ F ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiClO ₄ and LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ), wherein n is an integer of 0 to 6, and x and y are both natural numbers.
12. The lithium ion battery according to any one of claims 5 to 11, characterized in that, calculated as lithium ions, the molar concentration of lithium ions in the non-aqueous electrolyte is 0.1 to 3 mol/L.
13. The lithium ion battery according to claim 12, characterized in that, calculated as lithium ions, the molar concentration of lithium ions in the non-aqueous electrolyte is 0.2 to 2 mol/L.
14. The lithium ion battery according to any one of claims 11 to 13, characterized in that the concentration of lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide in the non-aqueous electrolyte is 0.01 wt% to 23 wt%.
15. The lithium-ion battery according to claim 14, characterized in that the content of lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide in the non-aqueous electrolyte is 0.2wt% to 18.4wt%.
16. The lithium-ion battery according to any one of claims 5 to 15, characterized in that the non-aqueous electrolyte further comprises an organic solvent, and the organic solvent is at least one of carbonates, carboxylates, sulfates, phosphates, amides, nitriles and ethers.
17. The lithium ion battery according to claim 16, characterized in that the organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, triethyl phosphate, methyl ethyl phosphite, methyl sulfide, diethyl sulfite, dimethyl sulfite, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3 dioxolane, tetrahydrofuran, fluorine-containing cyclic organic esters and sulfur-containing cyclic organic esters.
18. The lithium ion battery according to claim 16 or 17, characterized in that the content of the organic solvent in the non-aqueous electrolyte is 60wt% to 85wt%.
19. An electrical device, characterized in that it comprises a lithium-ion battery as described in any one of claims 5-18.