Electrolyte containing fluoro-boron ester compound and application thereof

Abstract

The invention provides a fluoro-boron-containing ester electrolyte and application thereof.The fluoro-boron-containing ester electrolyte comprises an electrolyte, an organic solvent and a fluoro-boron-containing ester compound shown in the formula I. According to the electrolyte, by adding the components shown in the formula I, when the electrolyte is used in a battery, the rate charge and rate discharge performance and the cycle performance of the obtained battery are improved, and the performance of the battery is improved. The high-temperature storage performance and the low-temperature discharge performance are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a fluorinated boron ester electrolyte and applications thereof. Background Art

[0002] Battery electrolytes have a crucial impact on battery service life, storage life, capacity utilization, high and low temperature performance, and safety performance. Currently, commercial electrolytes are primarily binary or ternary mixed solvent systems of cyclic carbonates and chain carbonates dissolved in lithium hexafluorophosphate (LiPF6). This system has the characteristics of good solubility, high ionic conductivity, and the ability to form a stable solid electrolyte interface film (SEI film) on the surface of the graphite anode, and is considered the best choice for electrolyte solvent systems. However, organic carbonate solvents have defects such as high volatility, flammability, and insufficient antioxidant properties, which lead to reduced battery safety.

[0003] Adding a small amount of non-energy storage substances to the electrolyte can effectively improve certain battery properties, such as electrolyte conductivity, positive and negative electrode matching performance, battery capacity, cycle efficiency, cycle life, reversible capacity and safety performance. According to their mechanism of action, additives can be divided into SEI film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, additives to improve the low-temperature performance of the electrolyte, additives to improve the thermal stability of the electrolyte, and additives to control the acid and water content in the electrolyte.

[0004] CN110911750A discloses a high-voltage lithium-ion battery electrolyte, an additive, and a method for preparing the additive. The additive disclosed is a thiourea derivative salt. The disclosed additive preparation method comprises the following steps: (1) first placing a solvent, a catalyst, and thiourea in 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; (2) separating the by-products through a water separator and high-temperature reduced-pressure distillation to obtain a crude thiourea ester compound; (3) extracting the product with a solvent, recrystallizing and purifying it, and drying it to obtain the thiourea ester compound. The thiourea ester compound can be used as an additive for high-voltage lithium-ion battery electrolytes, can capture oxygen free radicals generated by the positive electrode material under high voltage, and can also form an SEI film. CN103094616A discloses an electrolyte additive, a high-voltage electrolyte containing the electrolyte additive, and a lithium-ion battery. The disclosed electrolyte additive is maleic anhydride C4H2O3 or one of its derivatives. The disclosed high-voltage electrolyte can form a stable interface film on the positive and negative electrode surfaces, inhibit the reactivity of the electrode surfaces, reduce the oxidative decomposition of the electrolyte, and effectively inhibit flatulence, thereby improving the safety performance, cycle performance under normal pressure and high voltage, and service life of the lithium-ion battery.

[0005] However, the demand for high energy density and large-capacity and high-voltage electrode materials for batteries is increasing, so it is crucial to develop a material and electrolyte that improves the battery's rate charge and rate discharge performance, cycle performance, high-temperature storage performance, and low-temperature discharge performance. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention aims to provide a fluorinated boron ester electrolyte and its application.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In one aspect, the present invention provides a fluoroboryl ester electrolyte, comprising an electrolyte, an organic solvent, and a fluoroboryl ester compound represented by formula I;

[0009]

[0010] Among them, R n Any one selected from C2-C3 alkenylene or C2-C3 alkynylene.

[0011] In the present invention, the C2-C3 alkenylene group may be a C2 or C3 alkenylene group, and the C2-C3 alkynylene group may be a C2 or C3 alkynylene group.

[0012] By adding the component shown in formula I, the electrolyte of the present invention can improve the rate charge and rate discharge performance, cycle performance, high temperature storage performance and low temperature discharge performance of the resulting battery when used in a battery.

[0013] Preferably, R n Selected from vinylene, allyl or ethynylene.

[0014] Preferably, the fluoroboryl ester compound represented by formula I is selected from any one of the following compounds:

[0015]

[0016] Preferably, based on the total weight of the fluorinated boryl ester electrolyte as 100%, the content of the fluorinated boryl ester compound is 0.1-10%, for example, 0.1%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 7%, 8% or 10%.

[0017] Preferably, the electrolyte comprises any one of XClO4, XPF6, XBF4, XTFSI, XFSI, XBOB, XODFB, XCF3SO3 or XAsF6, or a combination of at least two thereof; wherein X is any one of Li, Na or K.

[0018] Preferably, based on 100% of the total weight of the fluorinated boron ester electrolyte, the content of the electrolyte is 8-20%, for example, 8%, 10%, 13%, 15%, 18% or 20%.

[0019] Preferably, the organic solvent is selected from any one or a combination of at least two of carbonates, carboxylates, fluorocarboxylates, propionates, fluoroethers or aromatic hydrocarbons.

[0020] Preferably, the carbonate includes a halogenated carbonate and / or a non-halogenated carbonate.

[0021] Preferably, the non-halogenated carbonate includes any one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate, or a combination of at least two thereof.

[0022] 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, trifluoromethylethylene carbonate, 4-trifluoromethylethylene carbonate, chloroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, methyl trifluoropropionate, 3,3,3-trifluoroethyl acetate, methyl 2-trifluoromethylbenzoate, ethyl 4,4,4-trifluorobutyrate or 1,1,1,3,3,3-hexafluoroisopropyl acrylate.

[0023] Preferably, the carboxylic acid ester includes a halogenated carboxylic acid ester and / or a non-halogenated carboxylic acid ester.

[0024] Preferably, the halogenated carboxylic acid ester includes any one of propyl fluorobutyrate, propyl fluoroacetate, isopropyl fluoroacetate, butyl fluoropropionate, isopropyl fluoropropionate, ethyl fluorobutyrate, methyl fluoropropionate, ethyl fluoropropionate or propyl fluoropropionate, or a combination of at least two thereof.

[0025] Preferably, the non-halogenated carboxylic acid ester includes 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.

[0026] Preferably, the fluoroether has 7 or less carbon atoms.

[0027] Preferably, the aromatic hydrocarbon includes a halogenated aromatic hydrocarbon and / or a non-halogenated aromatic hydrocarbon.

[0028] Preferably, the halogenated aromatic hydrocarbon includes any one of monofluorobenzene, difluorobenzene, 1,2,3-trifluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene or 2,4-dichlorotrifluorotoluene, or a combination of at least two thereof.

[0029] Preferably, based on the total weight of the fluorinated boron ester electrolyte as 100%, the content of the organic solvent is 1-85%, for example, 1%, 3%, 5%, 8%, 10%, 15%, 18%, 20%, 25%, 28%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or 85%.

[0030] In another aspect, the present invention provides a battery comprising the fluorinated boron ester electrolyte described above.

[0031] Preferably, the battery comprises a lithium ion battery, a sodium ion battery or a potassium ion battery.

[0032] Preferably, the negative electrode material of the battery is any one of metallic lithium, metallic sodium, metallic potassium, graphite, soft carbon, hard carbon, a composite material of single crystal silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate or niobium pentoxide, or a combination of at least two thereof.

[0033] In another aspect, the present invention provides a capacitor comprising the fluorinated boron ester electrolyte as described above.

[0034] In the present invention, the capacitor is a supercapacitor.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] By adding the component represented by formula I, the electrolyte of the present invention improves the rate charge and rate discharge performance, cycle performance, high-temperature storage performance and low-temperature discharge performance of the resulting battery when used in a battery. The battery of the present invention has a 3C charge rate of more than 85.5% at room temperature, a 1C discharge rate of more than 84.6% at -20°C, a capacity retention rate of more than 84.1% after 800 1C charge / 1C discharge cycles at room temperature, and a capacity retention rate of more than 82.1% after 800 1C charge / 1C discharge cycles at a high temperature of 45°C, showing excellent comprehensive performance. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] In the following examples, the structure of the compound II is used, which was customized from Shijiazhuang Shengtai Chemical (purity 99.5%):

[0039]

[0040] The preparation reaction equation is:

[0041]

[0042] The preparation reaction equation is:

[0043]

[0044] Comparative compounds:

[0045]

[0046] The compositions of the electrolytes provided in Examples 1-11 and Comparative Examples 1-2 are shown in Table 1:

[0047] The compositions of the electrolytes provided in Examples 1-11 and Comparative Examples 1-2 are all by weight, and both contain 1% VC and 1% PS, as shown in Table 1.

[0048] Comparative Examples 3-4 represent the substitution of Compound A and Compound B for Compound II in Example 2, respectively.

[0049] Table 1 (All percentages are by weight)

[0050]

[0051] The electrolytes described in Examples 1-11 and Comparative Examples 1-2 were tested as follows:

[0052] The electrolytes described in Examples 1-7, 9-11 and Comparative Examples 1, 3, and 4 were added to a 1.67Ah lithium-ion battery with a silicon-carbon negative electrode material (Bai Te Rui S420) and a 4.2V lithium nickel cobalt manganese oxide positive electrode material;

[0053] The electrolytes described in Example 8 and Comparative Example 2 were added to a battery whose negative electrode material was graphite material (Shanshan P15) and whose positive electrode material was 4.5V lithium cobalt oxide to prepare a 1.67Ah lithium-ion battery;

[0054] Perform the following test:

[0055] (1) Charge rate performance: 1C current is 1.67A, 3C current is 5.01A; the charge and discharge potential range is 2.75V to 4.50V. The 3C charge rate at room temperature is the ratio of the 3C constant current charging capacity C2 to the 1C constant current charging capacity C1.

[0056] (2) Cyclic performance: The charge and discharge potential range is 2.75V to 4.50V, the charging current is 1C (1.67A) to 4.50V, and the battery is charged at a constant voltage of 4.50V to a cut-off current ≤0.02C (0.0334A). After standing for 5 minutes, the battery is discharged at 1C (1.67A) to 2.75V and allowed to stand for 5 minutes. The charge and discharge cycle is repeated in this way.

[0057] (3) Low-temperature discharge performance: The discharge capacity at 1C (1.67A) at room temperature (25°C) is recorded as C1. After fully charging to 4.5V, the battery is frozen at -20°C for 4 hours and then discharged at 1C (1.67A) to 2.75V. The discharge capacity is recorded as C2. The discharge rate at -20°C is C2 / C1.

[0058] The test results are summarized in Tables 2 to 4.

[0059] Table 2

[0060]

[0061]

[0062] Table 3

[0063]

[0064]

[0065] Table 4

[0066]

[0067] Analysis of the data in Tables 2 to 4 shows that the electrolyte of the present invention improves various performance aspects of the battery when used in a battery by adding the compound represented by Formula II. The battery of the present invention has a 3C discharge rate of more than 85.5% at room temperature, a 1C discharge rate of more than 84.6% at -20°C, a capacity retention rate of more than 84.1% after 800 1C charge / 1C discharge cycles at room temperature, and a capacity retention rate of more than 82.1% after 800 1C charge / 1C discharge cycles at a high temperature of 45°C, indicating excellent overall performance.

[0068] Analysis of Comparative Example 1, Example 2, and Example 11 shows that the performance of Comparative Example 1 is not as good as that of Example 2 and Example 11, proving that adding the electrolyte containing the compound represented by Formula II can improve the overall performance of the battery.

[0069] Analysis of Comparative Example 2 and Example 8 shows similar results, demonstrating that the addition of the compound represented by Formula II to the electrolyte is beneficial to the charge-discharge cycle performance and low-temperature discharge performance of the battery containing silicon material or graphite as the negative electrode.

[0070] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the electrolyte and its applications. However, the present invention is not limited to the above-mentioned embodiments, which does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for various raw materials in the products of the present invention, addition of auxiliary components, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A fluorinated boron ester electrolyte, characterized in that: The fluorinated boron ester electrolyte comprises an electrolyte, an organic solvent and a fluorinated boron ester compound represented by formula I; Among them, R n Any one selected from C2-C3 alkenylene or C2-C3 alkynylene.

2. The fluorinated boron ester electrolyte according to claim 1, characterized in that R n Selected from vinylene, allylene, ethynylene or propargylene.

3. The fluorinated boron ester electrolyte according to claim 1 or 2, characterized in that The fluoroboryl ester compound represented by formula I is selected from any one of the following compounds: Preferably, based on 100% of the total weight of the fluorinated boryl ester electrolyte, the content of the fluorinated boryl ester compound is 0.1-10%.

4. The fluorinated boron ester electrolyte according to any one of claims 1 to 3, characterized in that The electrolyte comprises any one of XClO4, XPF6, XBF4, XTFSI, XFSI, XBOB, XODFB, XCF3SO3 or XAsF6, or a combination of at least two thereof; wherein X is any one of Li, Na or K; Preferably, based on the total weight of the fluorinated boron ester electrolyte being 100%, the content of the electrolyte is 8-49%.

5. The fluorinated boron ester electrolyte according to any one of claims 1 to 4, characterized in that The organic solvent is selected from any one or a combination of at least two of carbonates, carboxylates, fluorocarboxylates, propionates, fluoroethers or aromatic hydrocarbons.

6. The fluorinated boron ester electrolyte according to claim 5, characterized in that The carbonates include halogenated carbonates and / or non-halogenated carbonates; Preferably, the non-halogenated carbonate comprises any one or a combination of at least two of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate; Preferably, the halogenated carbonate comprises any one or a combination of at least two of fluoroethylene carbonate, difluoroethylene carbonate, difluoropropylene carbonate, trifluoroethyl acetate, trifluoroethyl methyl carbonate, trifluoromethylethylene carbonate, 4-trifluoromethylethylene carbonate, chloroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, methyl trifluoropropionate, 3,3,3-trifluoroethyl acetate, methyl 2-trifluoromethylbenzoate, ethyl 4,4,4-trifluorobutyrate or 1,1,1,3,3,3-hexafluoroisopropyl acrylate; Preferably, the carboxylic acid ester comprises a halogenated carboxylic acid ester and / or a non-halogenated carboxylic acid ester; Preferably, the halogenated carboxylic acid ester includes any one of propyl fluorobutyrate, propyl fluoroacetate, isopropyl fluoroacetate, butyl fluoropropionate, isopropyl fluoropropionate, ethyl fluorobutyrate, methyl fluoropropionate, ethyl fluoropropionate or propyl fluoropropionate, or a combination of at least two thereof. Preferably, the non-halogenated carboxylic acid ester includes 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; Preferably, the fluoroether has 7 or fewer carbon atoms; Preferably, the aromatic hydrocarbon comprises a halogenated aromatic hydrocarbon and / or a non-halogenated aromatic hydrocarbon; Preferably, the halogenated aromatic hydrocarbon includes any one of monofluorobenzene, difluorobenzene, 1,2,3-trifluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene or 2,4-dichlorotrifluorotoluene, or a combination of at least two thereof.

7. The fluorinated boron ester electrolyte according to any one of claims 1 to 6, characterized in that Based on the total weight of the fluorinated boron ester electrolyte being 100%, the content of the organic solvent is 1-85%.

8. A battery, characterized in that: The battery comprises the fluorinated boron ester electrolyte according to any one of claims 1 to 7.

9. The battery according to claim 8, characterized in that The battery includes a lithium ion battery, a sodium ion battery or a potassium ion battery; Preferably, the negative electrode material of the battery is any one of metallic lithium, metallic sodium, metallic potassium, graphite, soft carbon, hard carbon, a composite material of single crystal silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate or niobium pentoxide, or a combination of at least two thereof.

10. A capacitor, characterized in that: The capacitor comprises the fluorinated boron ester electrolyte according to any one of claims 1 to 7.

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