CN113675473A - Electrolyte and battery containing same - Google Patents

Abstract

The invention relates to an electrolyte and a battery containing the electrolyte, wherein the electrolyte comprises an electrolyte, an organic solvent and an additive shown in a formula I; wherein R is₁、R₂、R₃And R₄Each independently comprises: any one of C1-C10 alkyl, C6-C20 aromatic hydrocarbon group, C3-C10 alkoxy, C2-C10 alkenyl or C2-C10 alkynyl; the R is₁、R₂、R₃And R₄At least one is C2-C10 alkenyl or C2-C10 alkynyl; the R is₅Comprises one of difluoride sulfonyl imide, bistrifluoromethane sulfonyl imide, difluoro oxalic acid borate, bisoxalic acid borate, difluoro oxalic acid phosphate radical or hexafluorophosphoric acid radical. The electrolyte can improve the rate discharge performance, the cycle performance and the low-temperature discharge performance of the battery.

Description

Electrolyte and battery containing same

Technical Field

The invention relates to the technical field of batteries, in particular to an electrolyte and a battery containing the electrolyte.

Background

The battery electrolyte has a crucial influence on the service life, storage life, capacity exertion, high and low temperature, safety performance and the like of the battery. Currently, commercial electrolytes are predominantly dissolved with lithium hexafluorophosphate (LiPF)₆) The binary or ternary mixed solvent system of the cyclic carbonate and the chain carbonate has the characteristics of good solubility, high ionic conductivity, capability of forming a stable solid electrolyte interface film (SEI film) on the surface of a graphite cathode and the like, and is considered as the optimal choice of the electrolyte solvent system. However, organic carbonate solvents have the defects of high volatility, flammability, insufficient oxidation resistance and the like, resulting in the reduction of the safety of the battery.

A small amount of non-energy-storage substances are added into the electrolyte, so that certain properties of the battery, such as the conductivity of the electrolyte, the anode and cathode matching performance, the capacity of the battery, the cycle efficiency, the cycle life, the reversible capacity, the safety performance and the like, can be effectively improved. According to the action mechanism, the additives can be classified into SEI film-forming additives, conductive additives, flame-retardant additives, overcharge protection additives, additives for improving the low-temperature performance of the electrolyte, additives for improving the thermal stability of the electrolyte, additives for controlling the acid and water contents in the electrolyte, and the like.

CN110911750A discloses a high voltage lithium ion battery electrolyte, an additive and a preparation method of the additive, wherein the disclosed additive is thiourea derivative salt, and the disclosed preparation method of the additive comprises the following steps: (1) firstly, placing a solvent, a catalyst and thiourea in a reaction container, gradually dropwise adding organic acid, and carrying out polycondensation reaction in an ice-water bath to obtain a thiourea lipid compound; (2) separating the by-product by a water separator and high-temperature reduced pressure distillation to obtain a crude product of the thiourea ester compound; (3) and extracting the product by using a solvent, recrystallizing, purifying and drying to obtain the thiourea lipid compound. The thiourea ester compound can be used as an additive of high-voltage lithium ion battery electrolyte, can capture oxygen free radicals generated by a positive electrode material under high voltage, and can also form an SEI film.

CN103094616A discloses an electrolyte additive and a high voltage battery containing the electrolyte additiveThe electrolyte additive is maleic anhydride C₄H₂O₃Or one of the derivatives thereof, the disclosed high-voltage electrolyte can form a stable interfacial film on the surfaces of a positive electrode and a negative electrode, inhibit the reaction activity of the surfaces of the electrodes, reduce the oxidative decomposition of the electrolyte and effectively inhibit the flatulence, thereby improving the safety performance, the cycle performance under normal pressure and high voltage and the service life of the lithium ion battery.

However, the demand for high energy density and the demand for high-capacity and high-voltage electrode materials are increasing, and therefore, it is important to develop an electrolyte capable of improving the rate discharge performance, cycle performance and low-temperature discharge performance of a battery.

Disclosure of Invention

In view of the defects of the prior art, the invention aims to provide an electrolyte and a battery comprising the electrolyte, wherein the electrolyte can improve the rate discharge performance, the cycle performance and the low-temperature discharge performance of the battery.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides an electrolyte comprising an electrolyte, an organic solvent and an additive of formula i;

wherein R is₁、R₂、R₃And R₄Each independently comprises: any one of C1-C10 (e.g., C2, C4, C6, C8, etc.) alkyl, C6-C20 (e.g., C8, C10, C12, C14, C16, C18, etc.) aromatic hydrocarbon group, C3-C10 (e.g., C4, C6, C8, etc.) alkoxy, C2-C10 (e.g., C2, C4, C6, C8, etc.) alkenyl, or C2-C10 (e.g., C2, C4, C6, C8, etc.) alkynyl;

the R is₁、R₂、R₃And R₄At least one is C2-C10 alkenyl or C2-C10 alkynyl;

the R is₅Including bis-Fluorosulfonylimide (FSI), bis-trifluoromethanesulfonylIminium (TFSI), difluorooxalato borate (DFOB), bisoxalato borate (BOB), difluorodioxaoxalato phosphate (DFOP) or hexafluorophosphate (PF)₆) Any one of them.

The compound shown in the formula I is adopted as an additive, so that the compound is beneficial to the polymerization of a positive electrode to form a film, the multiplying power discharge performance, the cycle performance and the low-temperature discharge performance of the battery can be improved, and particularly, the compound material of graphite, monocrystalline silicon and graphite or the compound material of silicon monoxide and graphite is adopted as a negative electrode material of a lithium ion battery.

The C1-C10 refers to the corresponding group with the number of carbon atoms of 1-10, and the C6-C10 are equivalent.

Preferably, said R is₁、R₂、R₃And R₄Each independently comprises: any one of methyl, ethyl, propyl, isopropyl, allyl, and propargyl;

the R is₁、R₂、R₃And R₄At least one of which is allyl or propargyl.

Preferably, the structural formula of the additive is shown as a formula II;

the R is₁、R₂、R₃And R₄Each independently comprises: any one of methyl, ethyl, propyl, isopropyl, allyl or propargyl;

the R is₁、R₂、R₃And R₄At least one of which is allyl or propargyl;

the R is₅Comprises one of difluoride sulfonyl imide, bistrifluoromethane sulfonyl imide, difluoro oxalic acid borate, bisoxalic acid borate, difluoro oxalic acid phosphate radical or hexafluorophosphoric acid radical.

R is as defined above₅The structural formulas are respectively as follows:

preferably, the structural formula of the additive comprises any one of a formula III or a formula IV;

the R is₅Is one of difluoride sulfonyl imide radical, bistrifluoromethane sulfonyl imide radical or hexafluorophosphate radical.

Preferably, the additive comprises any one of compounds of the structures shown in formula iii or formula iv or a combination of at least two of them, for example, the additive includes but is not limited to the following compounds:

preferably, the electrolyte comprises any one of a lithium salt, a sodium salt or a potassium salt or a combination of at least two thereof.

Preferably, the electrolyte comprises XClO₄、XPF₆、XBF₄、XTFSI、XFSI、XBOB、XODFB，XCF₃SO₃Or XAsF₆Any one or a combination of at least two of which typical but non-limiting combinations include: XClO₄And XPF₆In combination of (A), XBF₄XTFSI, XFSI and XBOB, XBF₄、XTFSI、XFSI、XBOB、XODFB，XCF₃SO₃And XAsF₆Combinations of (a), (b), (c), (d);

wherein, X comprises any one of Li, Na or K.

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

Preferably, the organic solvent comprises any one of, or a combination of at least two of, a carbonate, a carboxylate, a propionate, a fluoroether, or an aromatic hydrocarbon, wherein typical but non-limiting combinations include: combinations of carbonates and carboxylates, combinations of carboxylates, propionates, and fluoroethers, combinations of carboxylates, propionates, fluoroethers, and aromatic hydrocarbons, and the like.

Preferably, the carbonate includes a halogenated carbonate and/or a non-halogenated carbonate.

Preferably, the non-halogenated carbonate includes any one of Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC) or Ethyl Methyl Carbonate (EMC) or a combination of at least two thereof.

Preferably, the halogenated carbonate includes any one or a combination of at least two of fluoroethylene carbonate (FEC), difluoroethylene carbonate, difluoropropylene carbonate, trifluoroethyl acetate, trifluoroethyl methyl carbonate, trifluoromethyl ethylene carbonate, 4-trifluoromethylethylene carbonate, chloroethylene carbonate, bis (2,2, 2-trifluoroethyl) carbonate, methyl trifluoropropionate, ethyl 3,3, 3-trifluoroacetate, methyl 2-trifluoromethylbenzoate, ethyl 4,4, 4-trifluorobutyrate, or 1,1,1,3,3, 3-hexafluoroisopropyl acrylate.

Preferably, the carboxylic acid ester includes any one of 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 thereof.

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

Preferably, the aromatic hydrocarbon comprises a halogenated aromatic hydrocarbon and/or a non-halogenated aromatic hydrocarbon.

Preferably, the halogenated aromatic hydrocarbon comprises any one of monofluorobenzene, difluorobenzene, 1,3, 5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene or 2, 4-dichlorotrifluorotoluene or a combination of at least two of the above.

Preferably, the weight percentage of the electrolyte in the electrolyte is 8% -49%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc.

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

Preferably, the weight percentage of the additive represented by formula i in the electrolyte is 0.01% to 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%, etc.

The electrolyte obtained by the additive in the range of 0.01-5% by weight in the electrolyte is more beneficial to improving the comprehensive performance of the battery, when the additive is less than 0.01%, the improvement effect is not obvious, the content of the additive exceeds 5%, the performance is improved, and the cost is too expensive.

Preferably, the electrolyte further comprises other additives.

The other additives of the present invention refer to additives other than the additives represented by formula I, such as vinylene carbonate, 1, 3-propane sultone, vinyl sulfate, and the like.

In a second aspect, the present invention provides a battery comprising the electrolyte of the first aspect.

Preferably, 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 comprises any one or a combination of at least two of graphite, soft carbon, hard carbon, a composite material of monocrystalline silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate or niobium pentoxide.

Compared with the prior art, the invention has the following beneficial effects:

by adding the additive shown in the formula I, when the electrolyte is used in a battery, the charge-discharge cycle performance and the low-temperature discharge performance of the obtained battery are improved, the 3C discharge rate at normal temperature in the battery is more than 80.6%, the 1C discharge rate at-20 ℃ is more than 81.0%, the 1C rate capacity retention rate after 1000 times of normal-temperature cycle is more than 80.01%, the 1000 times capacity retention rate after 1C cycle at 45 ℃ is more than 74.12%, and the comprehensive performance is excellent.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

The compositions of the electrolytes provided in examples 1 to 12 and comparative examples 1 to 2 are shown in table 1:

TABLE 1

Performance testing

The electrolytes described in examples 1 to 12 and comparative examples 1 to 2 were subjected to the following tests:

the electrolyte described in examples 1-9, 11-12 and comparative example 1 was added to a 1.67Ah lithium ion battery containing a silicon-carbon negative electrode material (fibrate S420) and a positive electrode material of NCM811 nickel cobalt manganese ternary material (batch S85 ES);

the electrolyte described in example 10 and comparative example 2 was added to a battery whose negative electrode material was graphite (fir P15) and whose positive electrode material was NCM811 nickel cobalt manganese ternary (r 85ES) to prepare a 1.67Ah lithium ion battery;

the following tests were performed:

(1) discharge rate performance: the 1C current is 1.67A, and the 3C current is 5.01A; the charge and discharge potential range is 2.75V-4.20V. The discharge rate at room temperature of 3C was the ratio of the capacity C2 of 3C discharge to the 1C discharge capacity C1.

(2) Cycle performance: the range of charging and discharging potential is 2.75V-4.20V, the charging current is 1C (1.67A) to 4.20V, the charging is carried out at a constant voltage of 4.20V until the cut-off current is less than or equal to 0.02C (0.0334A), after standing for 5 minutes, the 1C (1.67A) is discharged to 2.75V, and the standing is carried out for 5 minutes; thus, the charge and discharge are cycled.

(3) Low-temperature discharge performance: the 1C (1.67A) discharge capacity at 25 ℃ at room temperature was C1, and after full charge at 4.2V and freezing at-20 ℃ for 4 hours, the discharge was 1C (1.67A) to 2.75V, and the discharge capacity was C2. The discharge rate at-20 ℃ was C2/C1.

The test results are summarized in tables 2 to 4.

TABLE 2

	3C discharge rate at room temperature	Discharge rate at-20 ℃ 1C
			Example 1	85.3％	89.0％
Example 2	82.1％	86.4％
			Example 3	84.2％	87.5％
Example 4	83.9％	87.0％
			Example 5	82.3％	86.1％
Example 6	81.5％	85.7％
			Example 7	82.4％	86.3％
Example 8	83.2％	86.1％
			Example 9	82.5％	85.9％
Example 10	85.6％	85.2％
			Example 11	80.6％	81.0％
Example 12	82.7％	84.6％
			Comparative example 1	80.0％	80.0％
Comparative example 2	81.1％	79.1％

TABLE 3

TABLE 4

The data in tables 2-4 show that when the electrolyte disclosed by the invention is used in a battery, the charge-discharge cycle performance and the low-temperature discharge performance of the battery are improved by adding the additive shown in the formula I, the 3C discharge rate of the battery obtained by the invention at normal temperature is more than 80.6%, the 1C discharge rate at-20 ℃ is more than 81.0%, the capacity retention rate of 1C multiplying power at 1000 times of normal-temperature cycle is more than 80.01%, the capacity retention rate of 1000 times of 1C cycling at 45 ℃ is more than 74.12%, and the comprehensive performance is excellent.

As can be seen from the analysis of comparative example 1 and example 1, the performance of comparative example 1 is inferior to that of example 1, and the electrolyte added with the additive shown in formula I can improve the comprehensive performance of the battery.

Analysis of comparative example 2 and example 10 revealed similar results, demonstrating that the electrolyte added with the additive of formula i is advantageous for the charge-discharge cycle performance and low-temperature discharge performance of the battery using a silicon-containing material or graphite as the negative electrode.

As can be seen from the analysis of examples 11-12 and comparative examples 1 and 2, the performance of comparative examples 1 and 12 is inferior to that of examples 2 and 11, and the fact that the emphasis percentage of the additive shown in formula I in the electrolyte is in the range of 0.01% -5% is beneficial to the improvement of the comprehensive performance of the battery.

The present invention is illustrated in detail by the examples described above, but the present invention is not limited to the details described above, i.e., it is not intended that the present invention be implemented by relying on the details described above. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (10)

1. The electrolyte is characterized by comprising an electrolyte, an organic solvent and an additive shown as a formula I;

wherein R is₁、R₂、R₃And R₄Each independently comprises: any one of C1-C10 alkyl, C6-C20 aromatic hydrocarbon group, C3-C10 alkoxy, C2-C10 alkenyl or C2-C10 alkynyl;

the R is₁、R₂、R₃And R₄At least one is C2-C10 alkenyl or C2-C10 alkynyl;

the R is₅Comprises one of difluoride sulfonyl imide, bistrifluoromethane sulfonyl imide, difluoro oxalic acid borate, bisoxalic acid borate, difluoro oxalic acid phosphate radical or hexafluorophosphoric acid radical.

2. The electrolyte of claim 1, wherein R is₁、R₂、R₃And R₄Each independently comprises: any one of methyl, ethyl, propyl, isopropyl, allyl or propargyl;

the R is₁、R₂、R₃And R₄At least one of which is allyl or propargyl.

3. The electrolyte of claim 1 or 2, wherein the additive has a formula as shown in formula ii;

the R is₁、R₂、R₃And R₄Each independently comprises: any one of methyl, ethyl, propyl, isopropyl, allyl, and propargyl;

the R is₁、R₂、R₃And R₄At least one of which is allyl or propargyl;

the R is₅Comprises one of difluoride sulfonyl imide, bistrifluoromethane sulfonyl imide, difluoro oxalic acid borate, bisoxalic acid borate, difluoro oxalic acid phosphate radical or hexafluorophosphoric acid radical.

4. The electrolyte of any one of claims 1-3, wherein the additive has a structural formula comprising any one of formula III or formula IV;

the R is₅Is one of difluoride sulfonyl imide radical, bistrifluoromethane sulfonyl imide radical or hexafluorophosphate radical.

5. The electrolyte of any one of claims 1-4, wherein the additive comprises any one of a compound having a structure represented by formula III or formula IV, or a combination of at least two of the compounds.

6. The electrolyte of any one of claims 1-5, wherein the electrolyte comprises any one of a lithium salt, a sodium salt, or a potassium salt, or a combination of at least two thereof;

preferably, theThe electrolyte comprises XClO₄、XPF₆、XBF₄、XTFSI、XFSI、XBOB、XODFB，XCF₃SO₃Or XAsF₆Any one or a combination of at least two of;

wherein, X comprises any one of Li, Na or K.

7. The electrolyte of any one of claims 1-6, wherein the organic solvent comprises a non-aqueous organic solvent;

preferably, the organic solvent comprises any one of carbonate, carboxylate, propionate, fluoroether or aromatic hydrocarbon or a combination of at least two thereof;

preferably, the carbonate includes a halogenated carbonate and/or a non-halogenated carbonate;

preferably, the non-halogenated carbonate comprises any one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate or a combination of at least two of the same;

preferably, the halogenated carbonate includes any one or a combination of at least two of fluoroethylene carbonate, difluoroethylene carbonate, difluoropropylene carbonate, trifluoroethyl acetate, trifluoroethyl methyl carbonate, trifluoromethyl ethylene carbonate, 4-trifluoromethylethylene carbonate, chloroethylene carbonate, bis (2,2, 2-trifluoroethyl) carbonate, methyl trifluoropropionate, ethyl 3,3, 3-trifluoroacetate, methyl 2-trifluoromethylbenzoate, ethyl 4,4, 4-trifluorobutyrate, or 1,1,1,3,3, 3-hexafluoroisopropyl acrylate;

preferably, the carboxylic acid ester comprises any one of propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate or propyl propionate or a combination of at least two thereof;

preferably, the fluoroether has 7 or less carbon atoms;

preferably, the aromatic hydrocarbon comprises halogenated aromatic hydrocarbon and/or non-halogenated aromatic hydrocarbon;

preferably, the halogenated aromatic hydrocarbon comprises any one of monofluorobenzene, difluorobenzene, 1,3, 5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene or 2, 4-dichlorotrifluorotoluene or a combination of at least two of the above.

8. The electrolyte of any one of claims 1 to 7, wherein the electrolyte is present in the electrolyte in an amount of from 8% to 49% by weight;

preferably, the weight percentage of the organic solvent in the electrolyte is 40-85%;

preferably, the weight percentage of the additive shown in the formula I in the electrolyte is 0.01-5%;

preferably, the electrolyte further comprises other additives.

9. A battery comprising the electrolyte of any one of claims 1-8.

10. The battery of claim 9, wherein 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 comprises any one or a combination of at least two of graphite, soft carbon, hard carbon, a composite material of monocrystalline silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate or niobium pentoxide.