Modified novel electrolyte

Abstract

The invention relates to a modified novel electrolyte, in the formula 1, R1 and R6 are respectively and independently selected from one of fluoroalkyl, fluoroalkoxy, fluoroalkenyl, fluoroalkenyloxy, fluoroaryl and fluoroaryloxy, R2, R3, R4 and R5 are respectively and independently selected from one of alkyl, alkoxy, alkenyl, alkenyloxy, aryl and aryloxy, in the formula 2, R1 is one of C or O, R2 is one of C or O, R3 is one of C or O, and R5 is one of C or O; and R2 is one of alkyl or halogenated alkyl of C2-C5. Through the synergistic effect of the specific content of the additive containing the cyanobiphenyl sulfone compound and the cyclic sulfate compound, the high-strength and low-impedance composite interface protection film is generated, the interface compatibility of the composite current collector and an electrolyte can be improved through the composite interface protection film, and the side reaction between the composite current collector and the electrolyte is effectively inhibited.

Description

Technical Field

[0001] The invention relates to the technical field of electrolytes, and in particular to a modified novel 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. The inner layer is a polymer high molecular layer (such as PET, PP or PI), and the two sides are metal conductive layers (such as Al or Cu). 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 the large number of ester bonds, PET is not stable in strong acidic and alkaline electrolytes, and is easy to dissolve, swell or react. Methanol dissociates into protons and methanol anions, and attacks the electrophilic reaction center of PET, cuts off the ester bond of the PET polymer, and produces dimethyl terephthalate monomer and ethylene glycol by reacting with adjacent protons, thereby effectively depolymerizing PET. If dissolved in the electrolyte, it will increase the viscosity of the electrolyte, slow down the ion transmission rate, and increase the internal resistance of the lithium-ion battery. As the cycle time increases, PET swells and dissolves, causing the chemical bonds between the metal layer and PET to gradually age during long-term use, and the interface adhesion and peel strength between the metal layer and the substrate gradually weaken, resulting in a decrease in cycle capacity. To solve this problem, the research and development of PET should make 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 new electrolyte with better safety performance, enhance the interface adhesion and peeling 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 object, the present invention provides the following technical solutions.

[0007] A modified novel electrolyte comprises a cyano-containing biphenyl sulfone compound additive as shown in the following structural formula 1 and a cyclic sulfate ester 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 groups; R2, R3, R4, and R5 are independently selected from one of alkyl, alkoxy, alkenyl, alkenyloxy, aryl, and aryloxy groups; 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 shown in 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 cyanobiphenyl 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 non-aqueous 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 non-aqueous 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 non-aqueous electrolyte as 100%.

[0016] Further, the cyclic carbonate includes at least one of fluorocarbonate, vinylene carbonate and ethylene 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 methane disulfonate.

[0017] In an embodiment of the present invention, the non-aqueous electrolyte also 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 also 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, including 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 beneficial effects of the present invention are as follows.

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

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 work 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 independently selected from one of fluoroalkyl, fluoroalkoxy, fluoroalkenyl, fluoroalkenyloxy, fluoroaryl, and fluoroaryloxy, and 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 or halogenated hydrocarbon.

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

[0025]

[0026] Taking 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%. The weight percentage of the cyano-containing biphenyl sulfone compound within this range can significantly reduce the reaction between the current collector material and the electrolyte at high temperature, 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 surface of the material decreases, and the effect of improving the binding force of the current collector decreases; 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, and the permeability of the non-aqueous electrolyte on the electrode is reduced.

[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, thereby effectively inhibiting 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] Taking 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%. When the weight percentage of the cyclic sulfate ester compound is within this range, the cycle performance of the composite current collector can be significantly improved. When the weight percentage of the cyclic sulfate ester compound is less than 0.1%, its effect of improving the cycle performance of the lithium ion battery decreases; when the weight percentage of the cyclic sulfate ester compound is greater than 8%, the effect of improving the binding force of the current collector decreases.

[0030] The composite current collector non-aqueous 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 non-aqueous 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 non-aqueous 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 methane disulfonate.

[0032] In an embodiment of the present invention, the non-aqueous electrolyte also 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 also 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, including 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 combination with specific embodiments, and it cannot be determined that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, making several equivalent substitutions or obvious modifications without departing from the concept of the present invention, and having the same performance or use, should be regarded as belonging to the patent protection scope of the present invention determined by the submitted claims.

Claims

1. A modified novel electrolyte, characterized in that: The invention comprises a cyano-containing biphenyl sulfone compound additive as shown in the following structural formula 1 and a cyclic sulfate ester 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 groups; R2, R3, R4, and R5 are independently selected from one of alkyl, alkoxy, alkenyl, alkenyloxy, aryl, and aryloxy groups; in Formula 2, R1 is one of C or O, and R2 is one of C2-C5 hydrocarbon groups or halogenated hydrocarbon groups. 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 novel electrolyte according to claim 1, characterized in that: Taking 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%, and the weight percentage of the cyclic sulfate ester compound is 0.1-8%.

3. A modified novel electrolyte according to claim 1, characterized in that: The composite current collector non-aqueous 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 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 novel electrolyte according to claim 1, characterized in that: The cyclic carbonate includes at least one of fluorocarbonate, vinylene carbonate and ethylene 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 methane disulfonate.

Images