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EP-4246638-B1 - ELECTROLYTIC SOLUTION AND NON-AQUEOUS ELECTROLYTIC SOLUTION SECONDARY BATTERY

EP4246638B1EP 4246638 B1EP4246638 B1EP 4246638B1EP-4246638-B1

Inventors

  • CHO, Taehyung
  • TAKAHASHI, RYOUSUKE
  • ANDO, TSUTOMU

Dates

Publication Date
20260506
Application Date
20211222

Claims (6)

  1. An electrolytic solution comprising: a carboxylic acid ester; and a hydroxy group-containing compound and an ether group-containing compound, the electrolytic solution comprising the hydroxy group-containing compound and the ether group-containing compound in an amount of 50 mass ppm or less, and having a mass ratio of the hydroxy group-containing compound to the ether group-containing compound of 0.1 or greater and 10 or less.
  2. The electrolytic solution according to claim 1, wherein the amount of the carboxylic acid ester is 3% by mass or greater and 40% by mass or less.
  3. The electrolytic solution according to either of claims 1 or 2, wherein the hydroxy group-containing compound is at least one selected from the group consisting of a primary alcohol, a secondary alcohol, and a tertiary alcohol.
  4. The electrolytic solution according to any one of claims 1 to 3, wherein the ether group-containing compound contains a diether compound.
  5. The electrolytic solution according to any one of claims 1 to 4, wherein the carboxylic acid ester has a structure represented by the general formula R-COOR' wherein R represents a hydrogen atom or a C1-C10 linear or branched hydrocarbon group, and R' represents a C1-C10 linear or branched hydrocarbon group.
  6. A non-aqueous electrolytic solution secondary battery comprising the electrolytic solution according to any one of claims 1 to 5.

Description

TECHNICAL FIELD The present invention relates to an electrolytic solution and a non-aqueous electrolytic solution secondary battery including the electrolytic solution. BACKGROUND ART With the rapid expansion of the market of laptop computers, mobile phones, and electric vehicles, etc., high energy density secondary batteries are needed. Lithium secondary batteries with high electromotive force that use non-aqueous electrolytic solutions, which contain solutes dissolved in non-aqueous solvents, and utilize lithium oxidation and reduction, have been used as new secondary batteries with high energy density. CN109 119 598 A discloses a non-aqueous electrolytic solution for secondary battery, comprising a carboxylic acid ester as (co-)solvent and a monohydric alcohol as additive contained in an amount of 20 to 2000 ppm. KR 100 467 430 B1 describes an electrolyte for lithium-sulfur battery, comprising a lithium salt mixture dissolved in an ether-based solvent, to which an alcohol is added in an amount of 50 to 500 ppm by volume. JP H01 122566 A refers to a non-aqueous electrolytic solution comprising a solvent mixture including a diether and a cyclic ester, with an extremely reduced amount of impurities like water or propylene glycol. JP 2005 050585 A discloses a non-aqueous electrolytic solution for lithium secondary battery, comprising an ether-based solvent and at least one additive selected from alcohols, aldehydes and carboxylic acid esters. WO 2019/065196 A1 is directed to an electrolytic solution for secondary battery, comprising an ester compound C of an alcohol compound A and a carboxylic acid compound B, and further containing at least one of the alcohol compound A and the carboxylic acid compound B in an amount of 15 ppm or more, relative to a mass of the electrolytic solution. CITATION LIST - Patent Literature Patent Literature 1: JP 2005-50585 A SUMMARY OF INVENTION - Technical problem However, conventional lithium secondary batteries may not have sufficient storage properties because the negative electrode reacts with the non-aqueous electrolytic solution during storage in a charged state. Especially in recent years, the above lithium secondary batteries have been used as, for example, power sources for memory backup in electronic devices such as mobile phones. Such lithium secondary batteries are exposed to high temperature, resulting in a greater decrease in storage properties. In response to this, for example, Patent Literature 1 discloses a method of adding at least one additive compound selected from an alcohol, an aldehyde, and a carboxylic acid ester to a non-aqueous electrolytic solution. However, adding the additive compound of Patent Literature 1 may cause the discharge capacity of the secondary battery to decrease as the current value increases. Especially at high current values, the capacity retention may significantly decrease. The present invention aims to provide an electrolytic solution that is less likely to cause a decrease in discharge capacity even under high-current conditions and enables high capacity retention, and a non-aqueous electrolytic solution secondary battery including the electrolytic solution. - Solution to problem The present invention relates to an electrolytic solution containing a carboxylic acid ester; and a hydroxy group-containing compound and/or an ether group-containing compound, the electrolytic solution containing the hydroxy group-containing compound and/or the ether group-containing compound in an amount of 50 mass ppm or less, and having a mass ratio of the hydroxy group-containing compound to the ether group-containing compound of 0.1 or greater and 10 or less. The present invention is described in detail below. As a result of intensive studies, the present inventors have found out that adding a predetermined amount of a compound having a predetermined functional group to a carboxylic acid ester can provide an electrolytic solution that is less likely to cause a decrease in discharge capacity even under high-current conditions and enables high capacity retention. The inventors thus completed the present invention. The electrolytic solution that is an embodiment of the present invention contains a carboxylic acid ester. The electrolytic solution, having the feature that it contains a carboxylic acid ester, enables high capacity retention not only at room temperature but also at low temperature. The carboxylic acid ester is not limited, but preferably has a structure represented by the general formula R-COOR' wherein R represents a hydrogen atom or a C1-C10 linear or branched hydrocarbon group, and R' represents a C1-C10 linear or branched hydrocarbon group. R and R' are each more preferably a linear alkyl group. One carboxylic acid ester or a mixture of two or more carboxylic acid esters may be used. R and R' each preferably have a carbon number of 1 or greater and 8 or less, more preferably 5 or less, still more preferably 3 or less, particularly pre