Capacitor Electrolyte Stability at Low Temperatures

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Solution Overview

Problem

Existing electrolyte solutions for electric double-layer and lithium ion capacitors face issues with high internal resistance, low withstand voltage, and instability at low temperatures, leading to reduced electrostatic capacity and reliability.

Innovation Solution

A quaternary ammonium salt or lithium salt dissolved in an organic solvent mixture containing a chain alkyl sulfone compound, sulfolane, and acetonitrile, which maintains stability and conductivity across a wide temperature range, preventing salt precipitation and coagulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If sulfolane and its derivatives are used as organic solvent to increase withstand voltage, then the maximum voltage increases, but the electrolyte solution coagulates at low temperatures

Engineering Contradiction:

Improvewithstand voltageVSAvoidlow temperature stability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent combines multiple solvents (cyclic carbonate, chain carbonate, and chain sulfone) in specific proportions to create a blended electrolyte solution. This merging of different solvent types allows the solution to achieve both high withstand voltage (from sulfolane content) and low-temperature fluidity (from cyclic and chain carbonate components), resolving the contradiction between voltage resistance and low-temperature stability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent optimizes the proportion parameters of each solvent component, specifically setting sulfolane at 10-60 vol%, cyclic carbonate at 10-60 vol%, and chain sulfone at 5-40 vol%. By adjusting these parameter ranges, the electrolyte achieves the optimal balance between high voltage resistance and low-temperature performance, preventing coagulation while maintaining voltage withstand capability

Inventive Principle:

Principle #35Parameter changes

2Reliability

If propylene carbonate is used as organic solvent, then the electrolyte solution has high conductivity, but the solvent decomposes at applied voltage of 2.6 to 2.8 V

Engineering Contradiction:

ImproveconductivityVSAvoidwithstand voltage

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent creates a composite electrolyte system by combining propylene carbonate (providing high conductivity) with sulfolane (providing high voltage stability) and chain sulfone compounds. This composite approach allows the electrolyte to maintain high conductivity from the carbonate components while achieving withstand voltage above 2.8 V through the stabilizing effect of sulfolane and sulfone, resolving the decomposition issue

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If quaternary ammonium salt is dissolved in sulfolane and ethyl methyl carbonate mixture, then the electrolyte solution can be prepared, but ethyl methyl carbonate reduces the withstand voltage

Engineering Contradiction:

Improveelectrolyte preparationVSAvoidwithstand voltage

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent assigns different functional roles to different solvent components: cyclic carbonate and chain carbonate provide low-temperature fluidity and ease of handling, while chain sulfone compounds (specifically those with 2-4 carbon atoms) provide high voltage stability. By carefully selecting and proportioning these components, the patent achieves both manufacturability and high withstand voltage, counteracting the voltage-reducing effect of carbonate esters

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution provides a highly conductive, voltage-resistant, and stable electrolyte that maintains excellent electrical characteristics and long-term reliability, even at low temperatures, enhancing the performance of capacitors.

Implementation Method 1

an electrolyte solution containing an organic solvent and a quaternary ammonium salt or lithium salt dissolved in the organic solvent

Methodology Applied

Scientific EffectElectrolyte dissociation: Electrolyte

Implementation Method 2

which does not coagulate and is free from precipitation of salts in a wide temperature range, particularly at low temperatures

Methodology Applied

Scientific EffectFreezing point depression: Freezing

Data Source

PatentEP2833383B1Electrolyte solution for capacitors, electric double layer capacitor, and lithium ion capacitor

Publication Date: 2019.08.14 SUMITOMO SEIKA CHEM CO LTD

AI summary

The present invention provides a highly conductive, highly voltage-resistant, and stable liquid electrolyte solution for capacitors which does not coagulate and is free from precipitation of salts in a wide temperature range, particularly at low temperatures, shows excellent electrical characteristics, and has excellent long-term reliability. The present invention also provides an electric double-layer capacitor and a lithium ion capacitor produced using the electrolyte solution for capacitors. The present invention relates to an electrolyte solution for capacitors including: an organic solvent; and a quaternary ammonium salt or lithium salt dissolved in the organic solvent, the organic solvent containing acetonitrile and a chain alkyl sulfonic compound represented by the formula (1): wherein R 1 and R 2 , which may be the same as or different from each other, each independently represent a straight or branched chain C1-C4 alkyl group.