A modified electrolyte

Abstract

The present invention relates to a modified electrolyte, wherein in Formula 1, R1 and R6 are independently selected from one of a fluoroalkyl group, a fluoroalkoxy group, a fluoroalkenyl group, a fluoroalkenyloxy group, a fluoroaryl group, and a fluoroaryloxy group, and R2, R3, R4, and R5 are independently selected from one of an alkyl group, an alkoxy group, an alkenyl group, an alkenyloxy group, an aryl group, and an aryloxy group. In Formula 2, R1 is one of C or O, and R2 is one of a C2-C5 hydrocarbon group or a halogenated hydrocarbon group. The present invention generates a high-strength and low-impedance composite interface protective film through the synergistic effect of a specific content of a cyano-containing biphenyl sulfone compound and a cyclic sulfate compound additive. The composite interface protective film can improve the interfacial compatibility between the composite current collector and the electrolyte and effectively inhibit side reactions between the composite current collector and the electrolyte.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytes, in particular to a modified electrolyte. Background Art

[0002] As an important component of lithium-ion batteries, electrolyte plays an important role in the transmission of lithium ions in the battery and the formation of solid electrolyte membrane at the interface of positive and negative electrodes. It is one of the core materials of lithium-ion batteries. The electrolyte is composed of three parts: electrolyte lithium salt, solvent and additives. The current mainstream electrolyte lithium salt is lithium hexafluorophosphate, which is responsible for providing lithium source and affecting the battery's rate and cycle performance; solvents mainly include carbonates and carboxylates, which are mainly responsible for solvating the electrolyte lithium salt to ensure the transmission of lithium ions; additives are used to improve battery performance.

[0003] The current collector is one of the indispensable electrode materials for lithium-ion batteries. It has the important functions of carrying active substances (carrying capacity) and collecting microcurrents (conductivity). Thinning and functionalization are the main development directions of current collectors. The composite current collector is a "sandwich" structure with an inner layer of a polymer high molecular layer (such as PET, PP or PI) and metal conductive layers (such as Al or Cu) on both sides. The composite copper foil in the current industrial mass production of composite current collectors uses 4.5um OPP (polypropylene) as the substrate. First, a 50nm copper layer is magnetron sputtered on both sides of the substrate, and then water electroplating is performed on the surface of the copper layer to thicken the copper layer to about 1um. Composite aluminum foil usually uses 6um PET (polyethylene terephthalate) as the substrate, and then a 1um aluminum layer is evaporated on both sides of the substrate.

[0004] Due to its high concentration of ester bonds, PET is unstable in strongly acidic and alkaline electrolytes, prone to dissolution, swelling, and reaction. Methanol dissociates into protons and methanol anions, which attack the electrophilic reaction centers of PET, severing the ester bonds of the PET polymer. Reaction with adjacent protons produces dimethyl terephthalate monomer and ethylene glycol, effectively depolymerizing the PET. Dissolving in the electrolyte increases electrolyte viscosity, slowing ion transport and increasing the internal resistance of the lithium-ion battery. Over extended cycling, the PET swelling and dissolution reactions cause the chemical bonds between the metal layer and PET to gradually degrade over time. This weakens the interfacial adhesion and peel strength between the metal layer and the substrate, leading to a decrease in cycling capacity. To address this issue, PET research and development should focus on breakthroughs in electrolyte and electrode material engineering. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a modified electrolyte with better safety performance, enhance the interface adhesion and peel strength between the metal layer and the substrate, and reduce the shedding of the metal layer when the composite film is immersed in the electrolyte.

[0006] To achieve the above objectives, the present invention provides the following technical solutions.

[0007] A modified electrolyte includes a cyano-containing biphenyl sulfone compound additive as shown in the following structural formula 1 and a cyclic sulfate compound as shown in the following structural formula 2.

[0008]

[0009] In Formula 1, R1 and R6 are independently selected from one of fluoroalkyl, fluoroalkoxy, fluoroalkenyl, fluoroalkenyloxy, fluoroaryl, and fluoroaryloxy; R2, R3, R4, and R5 are independently selected from one of alkyl, alkoxy, alkenyl, alkenyloxy, aryl, and aryloxy; in Formula 2, R1 is one of C or O, and R2 is one of C2-C5 hydrocarbon groups or halogenated hydrocarbon groups.

[0010] The cyano-containing biphenyl sulfone compound additive includes at least one of the compounds represented by the following structural formulas 3-6:

[0011]

[0012] The sulfate ester compound includes at least one of the compounds shown in the following structural formulas 7-9,

[0013]

[0014] Furthermore, based on the total weight of the composite current collector non-aqueous electrolyte being 100%, the weight percentage of the cyano-containing biphenyl sulfone compound is 0.1-8%, and the weight percentage of the cyclic sulfate compound is 0.1-8%.

[0015] Furthermore, the composite current collector nonaqueous electrolyte further comprises at least one of a cyclic carbonate compound or a cyclic sultone compound. The weight percentage of the cyclic carbonate compound is 0.1-16% based on the total weight of the composite current collector nonaqueous electrolyte as 100%; and / or the weight percentage of the cyclic sultone compound is 0.1-6% based on the total weight of the composite current collector nonaqueous electrolyte as 100%.

[0016] Furthermore, the cyclic carbonate includes at least one of fluorocarbonate, vinylene carbonate, and vinylethylene carbonate; and / or the cyclic sultone includes at least one of 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone, and methylene methanedisulfonate.

[0017] In an embodiment of the present invention, the non-aqueous electrolyte further includes an organic solvent. Specifically, the organic solvent includes but is not limited to at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate. The non-aqueous electrolyte further includes a lithium salt. Specifically, the lithium salt includes but is not limited to at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide. In addition, an embodiment of the present invention further provides a composite current collector material, comprising a PET-Al-PET structure arranged in an electrolyte, and the electrolyte is the above-mentioned composite current collector non-aqueous electrolyte.

[0018] Compared with the prior art, the present invention has the following beneficial effects.

[0019] 1. The present invention generates a high-strength and low-impedance composite interface protective film through the synergistic effect of specific content of cyano-containing biphenyl sulfone compounds and cyclic sulfate compound additives. The composite interface protective film can improve the interfacial compatibility between the composite current collector and the electrolyte and effectively inhibit the side reactions between the composite current collector and the electrolyte. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] The present invention is achieved by providing a composite current collector non-aqueous electrolyte comprising a cyano-containing biphenyl sulfone compound additive as shown in the following structural formula 1 and a cyclic sulfate compound as shown in the following structural formula 2.

[0022]

[0023] In the formula, R1 and R6 are each independently selected from a fluoroalkyl group, a fluoroalkoxy group, a fluoroalkenyl group, a fluoroalkenyloxy group, a fluoroaryl group, and a fluoroaryloxy group; R2, R3, R4, and R5 are each independently selected from an alkyl group, an alkoxy group, an alkenyl group, an alkenyloxy group, an aryl group, and an aryloxy group. In Formula 2, R1 is C or O, and R2 is a C2-C5 hydrocarbon group or a halogenated hydrocarbon group.

[0024] The cyano-containing biphenyl sulfone compound additive includes at least one of the compounds represented by the following structural formulas 1-4:

[0025]

[0026] Based on the total weight of the composite current collector non-aqueous electrolyte as 100%, the weight percentage of the cyano-containing biphenyl sulfone compound is 0.1-8%, more preferably 0.5-4%. Within this weight percentage range, the cyano-containing biphenyl sulfone compound can significantly reduce the reaction between the current collector material and the electrolyte at high temperatures, thereby improving the cycle performance of the composite current collector. When the weight percentage of the cyano-containing biphenyl sulfone compound is less than 0.1%, its film-forming effect on the material surface is reduced, and its effect on improving the binding force of the current collector is reduced. When the weight percentage of the cyano-containing biphenyl sulfone compound is greater than 8%, the viscosity of the non-aqueous electrolyte is significantly increased, reducing the permeability of the non-aqueous electrolyte to the electrode.

[0027] In view of this, a cyclic sulfate ester compound is added to the non-aqueous electrolyte of the embodiment of the present invention. In the present invention, a high-strength and low-impedance composite interface protective film is generated by combining the cyclic sulfate ester compound with the aforementioned cyano-containing biphenyl sulfone compound, effectively suppressing the side reaction between the composite current collector and the electrolyte. Preferably, the cyclic sulfate ester compound includes at least one of the compounds shown in the following structural formulas 7-9:

[0028]

[0029] Based on the total weight of the composite current collector non-aqueous electrolyte as 100%, the weight percentage of the cyclic sulfate ester compound is 0.1-8%, more preferably 0.5-4%. Within this weight percentage range, the cyclic sulfate ester compound can significantly improve the cycling performance of the composite current collector. When the weight percentage of the cyclic sulfate ester compound is less than 0.1%, its effect on improving the cycling performance of the lithium-ion battery decreases; when the weight percentage of the cyclic sulfate ester compound is greater than 8%, its effect on improving the binding force of the current collector decreases.

[0030] The composite current collector nonaqueous electrolyte further includes at least one of a cyclic carbonate compound or a cyclic sultone compound. The weight percentage of the cyclic carbonate compound is 0.1-16% based on the total weight of the composite current collector nonaqueous electrolyte as 100%; and / or the weight percentage of the cyclic sultone compound is 0.1-6% based on the total weight of the composite current collector nonaqueous electrolyte as 100%.

[0031] The cyclic carbonate includes at least one of fluorocarbonate, vinylene carbonate and vinylethylene carbonate; and / or the cyclic sultone includes at least one of 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone and methylene methanedisulfonate.

[0032] In an embodiment of the present invention, the non-aqueous electrolyte further includes an organic solvent. Specifically, the organic solvent includes but is not limited to at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate. The non-aqueous electrolyte further includes a lithium salt. Specifically, the lithium salt includes but is not limited to at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide. In addition, an embodiment of the present invention further provides a composite current collector material, comprising a PET-Al-PET structure arranged in an electrolyte, and the electrolyte is the above-mentioned composite current collector non-aqueous electrolyte.

[0033] The above is a detailed description of the present invention in conjunction with specific embodiments, and the specific implementation methods of the present invention should not be considered to be limited to these descriptions. For those skilled in the art to which the present invention relates, any equivalent substitutions or obvious modifications that do not depart from the concept of the present invention and have the same performance or use should be considered to fall within the scope of patent protection of the present invention as determined by the submitted claims.

Claims

1. A modified electrolyte, characterized in that: It includes a cyano-containing biphenyl sulfone compound additive as shown in the following structural formula 1 and a cyclic sulfate compound as shown in the following structural formula 2; In Formula 1, R1 and R6 are independently selected from one of fluoroalkyl, fluoroalkoxy, fluoroalkenyl, fluoroalkenyloxy, fluoroaryl, and fluoroaryloxy; R2, R3, R4, and R5 are independently selected from one of alkyl, alkoxy, alkenyl, alkenyloxy, aryl, and aryloxy; in Formula 2, R1 is one of C or O, and R2 is one of a C2-C5 hydrocarbon group or a halogenated hydrocarbon group; The cyano-containing biphenyl sulfone compound additive includes at least one of the compounds shown in the following structural formulas 3-6: The sulfate ester compound includes at least one of the compounds shown in the following structural formulas 7-9, 2. A modified electrolyte according to claim 1, characterized in that: Based on the total weight of the composite current collector non-aqueous electrolyte being 100%, the weight percentage of the cyano-containing biphenyl sulfone compound is 0.1-8%, and the weight percentage of the cyclic sulfate compound is 0.1-8%.

3. A modified electrolyte according to claim 1, characterized in that: The composite current collector non-aqueous electrolyte further includes at least one of a cyclic carbonate compound or a cyclic sultone compound, wherein the weight percentage of the cyclic carbonate compound is 0.1-16% based on the total weight of the composite current collector non-aqueous electrolyte being 100%; and / or the weight percentage of the cyclic sultone compound is 0.1-6% based on the total weight of the composite current collector non-aqueous electrolyte being 100%.

4. A modified electrolyte according to claim 1, characterized in that: The cyclic carbonate includes at least one of fluorocarbonate, vinylene carbonate and vinylethylene carbonate; and / or the cyclic sultone includes at least one of 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone and methylene methanedisulfonate.

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