JP2023026280A - Electrolyte and battery containing electrolyte - Google Patents

Abstract

To provide an electrolyte capable of improving the discharge rate performance, the cycle performance, and the low-temperature discharge performance of a battery.SOLUTION: An electrolyte comprises an electrolyte, an organic solvent, and an additive represented by the formula (I). (R1, R2, R3, and R4 each independently include at least any one of a C1-C10 alkyl group, a C6-C20 aromatic hydrocarbon group, a C3-C10 alkoxy group, a C2-C10 alkenyl group or a C2-C10 alkynyl group, and at least one of R1, R2, R3, and R4 is a C2-C10 alkenyl group or a C2-C10 alkynyl group, and R5 includes any one of bisfluorosulfonylimide group, bistrifluoromethanesulfonylimide group, difluoro(oxalato)boric acid group, bis(oxalato)boric acid group, difluorobis(oxalato)phosphate group, and hexafluorophosphate group).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to the technical field of batteries, and more particularly to an electrolyte and a battery containing the electrolyte.

The battery electrolyte has a great influence on the service life, storage life, capacity performance, high and low temperature and safety performance of the battery. At present, commercial electrolyte solutions are mainly binary or ternary mixed solvent systems of cyclic carbonates and chain carbonates in which lithium hexafluorophosphate (LiPF ₆ ) is dissolved. It has properties such as high ionic conductivity and the ability to form a stable solid electrolyte interfacial film (SEI film) on the graphite negative electrode surface, and is considered to be an optimal choice for the electrolyte solvent system. However, organic carbonate-based solvents have drawbacks such as volatility, flammability, and insufficient oxidation resistance, which cause deterioration in battery safety.

Adding a small amount of non-energy storage materials to the electrolyte can effectively improve certain performance of the battery, such as electrolyte conductivity, cathode and anode matching performance, battery capacity, cycle efficiency, cycle life, reversible capacity and safety performance. can be improved to Additives, depending on their mechanism of action, include SEI film formation additives, conductive additives, flame retardant additives, overcharge prevention additives, electrolyte low temperature performance improvement additives, and electrolyte thermal stability improvement additives. , acid and water content control additives in the electrolyte, etc.

CN110911750A discloses an electrolyte for high voltage lithium ion batteries, an additive and a method for preparing the additive, the additive disclosed therein is a thiourea derivative salt, disclosed therein The method for preparing the additive includes step (1) of first putting a solvent, a derivative and thiourea into a reaction vessel, gradually adding an organic acid dropwise, and conducting a polycondensation reaction in an ice water bath to obtain a thiourea ester compound. , the step (2) of separating the by-products by a water separator and high-temperature vacuum distillation to obtain a crude product of a thiourea ester-based compound; and then obtaining a thiourea ester compound (3). The thiourea ester-based compound can be used as an additive in high-voltage lithium-ion battery electrolytes, and can scavenge oxygen radicals generated by positive electrode materials under high voltage or form SEI films.

CN103094616A discloses an electrolyte additive and a high voltage electrolyte _and lithium ion battery containing the electrolyte additive, wherein the disclosed electrolyte additive is maleic anhydride _{C4H2O 3} or one of its derivatives, and the high-voltage electrolyte disclosed therein forms a stable interfacial film on the surfaces of the positive electrode and the negative electrode, suppresses the reaction activity of the electrode surface, and prevents the oxidative decomposition of the electrolyte. and effectively suppressing gas expansion, the safety performance, cycle performance under normal pressure and high voltage, and service life of the lithium-ion battery can be improved.

However, in industrial production, the demand for high energy density and the demand for large-capacity, high-voltage electrode materials is increasing more and more. is very important.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolyte and a battery containing the electrolyte that can improve the discharge rate performance, cycle performance and low temperature discharge performance of the battery.

In order to achieve this object, the present invention employs the following technical solutions.
In a first aspect, the present invention provides an electrolytic solution comprising an electrolyte, an organic solvent and an additive of Formula I.

provided that R ₁ , R ₂ , R ₃ and R ₄ are each independently a C1-C10 (eg C2, C4, C6, C8 etc.) alkyl group, a C6-C20 (eg C8, C10, C12, C14 , C16, C18, etc.) aromatic hydrocarbon group, C3-C10 (e.g., C4, C6, C8, etc.) alkoxy group, C2-C10 (e.g., C2, C4, C6, C8, etc.) alkenyl group or C2-C10 ( For example, C2, C4, C6, C8, etc.) containing any one of alkynyl groups,
at least one of R ₁ , R ₂ , R ₃ and R ₄ is a C2-C10 alkenyl group or a C2-C10 alkynyl group;
R ₅ is a bisfluorosulfonylimide group (FSI), a bistrifluoromethanesulfonylimide group (TFSI), a difluoro(oxalato)boric acid group (DFOB), a bis(oxalato)boric acid group (BOB), a difluorobis(oxalato) It contains either one of a phosphate group (DFOP) or a hexafluorophosphate group (PF6).

The present invention uses the compound represented by formula I as an additive to contribute to the polymerization and film formation of the positive electrode, and the discharge rate performance, cycle performance and low temperature discharge performance of the battery, especially the negative electrode material is graphite, single crystal silicon and graphite. or a composite material of silicon monoxide and graphite.

"C1-C10" according to the present invention means that the number of carbon atoms in the corresponding group is 1-10, and "C6-C10" etc. are equivalent.

Preferably, each of R ₁ , R ₂ , R ₃ and R ₄ independently contains any one of methyl group, ethyl group, propyl group, isopropyl group, allyl group and propargyl group,
At least one of R ₁ , R ₂ , R ₃ and R ₄ is an allyl group or a propargyl group.

Preferably, the structural formula of said additive is shown in Formula II.

each of R ₁ , R ₂ , R ₃ and R ₄ independently contains any one of a methyl group, an ethyl group, a propyl group, an isopropyl group, an allyl group and a propargyl group;
at least one of R ₁ , R ₂ , R ₃ and R ₄ is an allyl group or a propargyl group;
R ₅ is any one of a bisfluorosulfonylimide group, a bistrifluoromethanesulfonylimide group, a difluoro(oxalato)boric acid group, a bis(oxalato)boric acid group, a difluorobis(oxalato)phosphate group, or a hexafluorophosphate group Includes 1 species.

The structural formulas of _R5 are as follows.

Preferably, the structural formula of said additive comprises either one of Formula III or Formula IV.

_R5 is one of a bisfluorosulfonylimide group, a bistrifluoromethanesulfonylimide group and a hexafluorophosphoric acid group.

Preferably, said additive comprises any one or a combination of at least two compounds of the structure shown in Formula III or Formula IV, for example additives include, but are not limited to:

Preferably, the electrolyte comprises any one or a combination of at least two of lithium, sodium or potassium salts.

Preferably, said electrolyte comprises any one or a combination of at least two of _XClO4 , _XPF6 , _XBF4 , XTFSI, XFSI, XBOB, XODFB, _{XCF3SO3 or XAsF6} , although typical but non-limiting combinations include combinations of _XClO4 and _XPF6 , combinations of _XBF4 , XTFSI, XFSI and XBOB, _combinations of XBF4, XTFSI, XFSI, XBOB, XODFB, _XCF3SO3 and _XAsF6 , and _the like. ,
However, X contains any one of Li, Na and K.

Preferably, said organic solvent comprises a non-aqueous organic solvent.

Preferably, said organic solvent comprises any one or a combination of at least two of carbonates, carboxylates, propionates, fluoroethers or aromatic hydrocarbons, although typical but non-limiting combinations include carbonates and carboxylates, combinations of carboxylates, propionates and fluoroethers, combinations of carboxylates, propionates, fluoroethers and aromatic hydrocarbons, and the like.

Preferably, said carbonate comprises a halogenated carbonate and/or a non-halogenated carbonate.

Preferably, said non-halogenated carbonate is any one or a combination of at least two of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC) or methyl ethyl carbonate (EMC) including.

Preferably, said halogenated carbonate is fluoroethylene carbonate (FEC), difluoroethylene carbonate, bisfluoropropylene carbonate, ethyl trifluoroacetate, trifluoroethylmethyl carbonate, trifluoromethylethylene carbonate, 4-trifluoromethylethylene carbonate, chloro Ethylene carbonate, di(2,2,2-trifluoroethyl) carbonate, methyl trifluoropropionate, ethyl 3,3,3-trifluoroacetate, methyl 2-trifluoromethylbenzoate, 4,4,4-tri Any one or a combination of at least two of ethyl fluorobutyrate or 1,1,1,3,3,3-hexafluoroisopropyl acrylate.

Preferably, said carboxylates are propyl butyrate (PB), propyl acetate (PA), isopropyl acetate (IPA), butyl propionate (BP), isopropyl propionate (IPP), ethyl butyrate (EB), methyl propionate (EM ), ethyl propionate (EP) or propyl propionate (PP), or a combination of at least two.

Preferably, the fluoroether has 7 (eg, 5, 6, etc.) or less carbon atoms.

Preferably, said aromatic hydrocarbons comprise halogenated aromatic hydrocarbons and/or non-halogenated aromatic hydrocarbons.

Preferably, said halogenated aromatic hydrocarbon is any one of monofluorobenzene, bisfluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene or 2,4-dichlorotrifluorotoluene. species or a combination of at least two species.

Preferably, the weight percent of said electrolyte in said electrolyte is between 8% and 49%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%.

Preferably, the weight percent of said organic solvent in said electrolyte is between 40% and 85%, such as 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc. .

Preferably, the weight percentage of the additive of Formula I in the electrolyte is between 0.01% and 5%, such as 0.04%, 0.06%, 0.08%, 0.1%. , 0.3%, 0.5%, 0.6%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4. 5%, and so on.

The electrolyte obtained with the weight percentage of the additive in the electrolyte according to the present invention in the range of 0.01% to 5% contributes more to the improvement of the overall performance of the battery, and the additive is 0.01%. If the content is less than 5%, the improvement effect is not significant, and if the content exceeds 5%, the improvement in performance decreases and the cost is too high.

Preferably, the electrolytic solution further contains other additives.

Other additives according to the present invention are additives other than those of Formula I, such as vinylene carbonate, 1,3-propanesultone and ethylene sulfate.

In a second aspect, the invention provides a battery comprising an electrolyte according to the first aspect.

Preferably, said battery comprises a lithium ion battery, a sodium ion battery, a potassium ion battery or a supercapacitor.

Preferably, the negative electrode material of the lithium ion battery is any one of graphite, soft carbon, hard carbon, monocrystalline silicon-graphite composite material, silicon monoxide-graphite composite material, lithium titanate or niobium pentoxide. or a combination of at least two.

Compared with the prior art, the present invention has the following beneficial effects.
By adding an additive represented by formula I, the electrolytic solution according to the present invention improves both the charge-discharge cycle performance and the low-temperature discharge performance of the resulting battery when used in a battery, and is obtained by the present invention. The battery has a 3C discharge rate of 80.6% or more at room temperature, a 1C discharge rate of 81.0% or more at -20°C, and a 1C rate capacity retention rate of 80.01% or more after 1000 cycles at room temperature. , the capacity retention rate after 1000 cycles of 1C at a high temperature of 45° C. is 74.12% or more, and the overall performance is excellent.

Hereinafter, the technical solution of the present invention will be further described through specific embodiments. It should be understood by those skilled in the art that the following examples are for the understanding of the present invention only and should not be considered as specific limitations on the present invention.

The compositions of the electrolytic solutions according to Examples 1-12 and Comparative Examples 1-2 are shown in Table 1.

Performance Test The electrolyte solutions according to Examples 1 to 12 and Comparative Examples 1 and 2 were subjected to the following tests.
The electrolyte solutions according to Examples 1 to 9, 11 to 12 and Comparative Example 1 were prepared by using a silicon-carbon-containing negative electrode material (Better our World S420) as a negative electrode material and a NCM811 nickel-cobalt-manganese ternary material (RONBAY TECHNOLOGY S85ES) as a positive electrode material. to obtain a 1.67 Ah lithium ion battery.
The electrolyte solutions according to Example 10 and Comparative Example 2 were added to a battery in which the negative electrode material was graphite material (ShanShan Corporation P15) and the positive electrode material was NCM811 nickel-cobalt-manganese ternary material (RONBAY TECHNOLOGY S85ES) to prepare 1.67 Ah. of lithium-ion batteries were obtained.

I did the following tests:
(1) Discharge rate performance: 1C current is 1.67A, 3C current is 5.01A, and the charge/discharge potential range is 2.75V to 4.20V. The 3C discharge rate at room temperature is the ratio of the 3C discharge capacity C2 and the 1C discharge capacity C1.
(2) Cycle performance: The charge/discharge potential range is 2.75 V to 4.20 V, the charge current is 1 C (1.67 A), and the cutoff current is ≤ 0.02 C (0.0334 A). The battery was charged at a constant voltage of 4.20 V, allowed to stand for 5 minutes, discharged to 2.75 V at 1 C (1.67 A) and left to stand for 5 minutes, thus repeating charging and discharging.
(3) Low-temperature discharge performance: The discharge capacity of 1C (1.67A) at room temperature 25°C is denoted as C1, and after being fully charged at 4.2V, it is frozen at -20°C for 4 hours and then 1C (1.67A). 67 A) to 2.75 V, and the discharge capacity was noted as C2. The discharge rate at -20°C is C2/C1.

The test results are summarized in Tables 2-4.

Analysis of the data in Tables 2 to 4 shows that the electrolytic solution according to the present invention, by adding an additive represented by formula I, when used in a battery, the charge-discharge cycle performance and low-temperature discharge performance of the resulting battery are improved. Both are improved, and the battery obtained in the present invention has a 3C discharge rate at room temperature of 80.6% or more, a 1C discharge rate at -20 ° C. of 81.0% or more, and a 1C rate after 1000 cycles at room temperature. 80.01% or more, and the capacity retention after 1000 cycles of 1C at a high temperature of 45° C. was 74.12% or more, indicating excellent overall performance.

By analyzing Comparative Example 1 and Example 1, it can be seen that the performance of Comparative Example 1 is inferior to that of Example 1. This is because the electrolyte with the additive represented by Formula I can improve the overall performance of the battery. proved.

Analysis of Comparative Example 2 and Example 10 show similar results, which show that the electrolyte solution with the additive represented by Formula I was subjected to charge-discharge cycles of batteries in which the negative electrode was a silicon-containing material or graphite. It has been proved to contribute to performance and low temperature discharge performance.

Analysis of Examples 11-12, Comparative Example 1 and Example 2 reveals that the performance of Comparative Example 1 and Example 12 is inferior to that of Example 2 and Example 11, which corresponds to Formula I in the electrolyte. Weight percentages of the indicated additives within the range of 0.01% to 5% have proven to contribute to improved overall battery performance.

Although the present invention describes the detailed method of the present invention by means of the above examples, the present invention is not limited to the above detailed method, which means that the present invention can only be carried out with the above detailed method. not something to do. For those skilled in the art, any modification to the present invention, equivalent substitution and addition of auxiliary ingredients for each raw material of the product of the present invention, selection of specific forms, etc. are all within the protection scope and disclosure scope of the present invention. You should know.

Claims (10)

An electrolytic solution comprising an electrolyte, an organic solvent and an additive of Formula I.

(where R ₁ , R ₂ , R ₃ and R ₄ are each independently a C1-C10 alkyl group, a C6-C20 aromatic hydrocarbon group, a C3-C10 alkoxy group, a C2-C10 alkenyl group or a C2-C10 containing any one of alkynyl groups,
at least one of R ₁ , R ₂ , R ₃ and R ₄ is a C2-C10 alkenyl group or a C2-C10 alkynyl group;
R ₅ is any one of a bisfluorosulfonylimide group, a bistrifluoromethanesulfonylimide group, a difluoro(oxalato)boric acid group, a bis(oxalato)boric acid group, a difluorobis(oxalato)phosphate group, or a hexafluorophosphate group Includes 1 species. ) each of R ₁ , R ₂ , R ₃ and R ₄ independently contains any one of a methyl group, an ethyl group, a propyl group, an isopropyl group, an allyl group and a propargyl group;
2. The electrolytic solution according to claim 1, wherein at least one of _R1 , _R2 , _R3 and _R4 is an allyl group or a propargyl group. 3. Electrolyte solution according to claim 1 or 2, characterized in that the structural formula of the additive is given by formula II.

(the R ₁ , R ₂ , R ₃ and R ₄ each independently contain any one of a methyl group, an ethyl group, a propyl group, an isopropyl group, an allyl group and a propargyl group,
at least one of R ₁ , R ₂ , R ₃ and R ₄ is an allyl group or a propargyl group;
R ₅ is any one of a bisfluorosulfonylimide group, a bistrifluoromethanesulfonylimide group, a difluoro(oxalato)boric acid group, a bis(oxalato)boric acid group, a difluorobis(oxalato)phosphate group, or a hexafluorophosphate group Includes 1 species. ) Electrolyte solution according to any one of claims 1 to 3, characterized in that the structural formula of the additive comprises either one of Formula III or Formula IV.

(The above _R5 is any one of a bisfluorosulfonylimide group, a bistrifluoromethanesulfonylimide group and a hexafluorophosphoric acid group.) 5. The electrolytic solution according to any one of claims 1 to 4, wherein the additive comprises any one or a combination of at least two compounds having a structure represented by Formula III or Formula IV. the electrolyte comprises any one or a combination of at least two of lithium salt, sodium salt or potassium salt;
Preferably, said electrolyte comprises any one or a combination of at least two of _XClO4 , _XPF6 , _XBF4 , XTFSI, XFSI, XBOB, _XODFB , _XCF3SO3 or _XAsF6 ,
The electrolytic solution according to any one of claims 1 to 5, wherein X contains any one of Li, Na or K. the organic solvent comprises a non-aqueous organic solvent;
Preferably, said organic solvent comprises any one or a combination of at least two of carbonates, carboxylates, propionates, fluoroethers or aromatic hydrocarbons,
Preferably, said carbonate comprises a halogenated carbonate and/or a non-halogenated carbonate,
Preferably, said non-halogenated carbonate comprises any one or a combination of at least two of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or methyl ethyl carbonate,
Preferably, said halogenated carbonate is fluoroethylene carbonate, difluoroethylene carbonate, bisfluoropropylene carbonate, ethyl trifluoroacetate, trifluoroethylmethyl carbonate, trifluoromethylethylene carbonate, 4-trifluoromethylethylene carbonate, chloroethylene carbonate, Di(2,2,2-trifluoroethyl) carbonate, methyl trifluoropropionate, ethyl 3,3,3-trifluoroacetate, methyl 2-trifluoromethylbenzoate, ethyl 4,4,4-trifluorobutyrate or any one or a combination of at least two of 1,1,1,3,3,3-hexafluoroisopropyl acrylate,
Preferably, said carboxylate is any one or a combination of at least two of propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate or propyl propionate. including
Preferably, the fluoroether has 7 or less carbon atoms,
Preferably, said aromatic hydrocarbons comprise halogenated aromatic hydrocarbons and/or non-halogenated aromatic hydrocarbons,
Preferably, said halogenated aromatic hydrocarbon is any one of monofluorobenzene, bisfluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene or 2,4-dichlorotrifluorotoluene. Electrolyte solution according to any one of claims 1 to 6, characterized in that it comprises a species or a combination of at least two species. the weight percentage of the electrolyte in the electrolyte is 8% to 49%;
Preferably, the weight percentage of said organic solvent in said electrolyte is between 40% and 85%,
Preferably, the weight percent of the additive of formula I in the electrolyte is between 0.01% and 5%,
Electrolyte solution according to any one of claims 1 to 7, characterized in that it preferably further comprises other additives. A battery comprising the electrolytic solution according to any one of claims 1 to 8. the battery comprises a lithium ion battery, a sodium ion battery, a potassium ion battery or a supercapacitor;
Preferably, the negative electrode material of the lithium ion battery is any one of graphite, soft carbon, hard carbon, monocrystalline silicon-graphite composite material, silicon monoxide-graphite composite material, lithium titanate or niobium pentoxide. or a combination of at least two.