Water-Based Electrolyte for Supercapacitors with Reduced Corrosion

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Solution Overview

Problem

Conventional water-based electrolytes for electric double layer capacitors have limited operating temperature range and energy-storage efficiency due to corrosiveness and breakdown voltage, while organic electrolytes face instability and high internal resistance.

Innovation Solution

A water-based electrolyte comprising a mixture of salts such as lithium nitrate (LiNO3) and lithium hydroxide (LiOH) with specific volume concentrations, which reduces corrosiveness and enhances operating temperature range and energy-storage efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If conventional water-based electrolytes are used, then internal resistance is low and discharging efficacy is good, but working voltage is limited to less than 1V due to breakdown voltage

Engineering Contradiction:

Improvedischarging efficacyVSAvoidworking voltage

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The patent changes the chemical composition parameters of the water-based electrolyte by adding specific concentrations of LiNO3 (0.5-2.0 M) and other salts to LiOH solution, optimizing the electrolyte's electrical and chemical properties to achieve better performance while maintaining water-based stability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite electrolyte system by combining LiOH (providing high conductivity) with LiNO3 and other salts (improving stability and reducing corrosion), achieving a synergistic effect that balances conductivity, stability, and working voltage

Inventive Principle:

Principle #40Composite materials

2Power

If strong alkali or strong acid water-based electrolytes are used to provide better conductivity, then internal resistance decreases, but corrosiveness increases and damages other elements of the capacitor

Engineering Contradiction:

ImproveconductivityVSAvoidcorrosiveness

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent optimizes the pH and concentration parameters by using LiOH solution with controlled concentration (0.5-2.0 M) and adding LiNO3, achieving high conductivity while reducing the strong alkaline corrosiveness through dilution and chemical buffering effects

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces LiNO3 and other salts as intermediary substances that mediate between the LiOH and the capacitor elements, reducing direct corrosive interactions while maintaining ionic conductivity through alternative charge carriers

Inventive Principle:

Principle #24Intermediary (Mediator)

3Use of energy by moving object

If organic electrolytes are used, then working voltage can be higher (2-3V) and working temperature range is broader, but internal resistance is higher and discharging power is hard to improve

Engineering Contradiction:

Improveworking voltageVSAvoidinternal resistance

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

The patent changes the electrolyte from organic to water-based composition, fundamentally altering the solvent properties to achieve lower viscosity and higher ionic mobility, thereby reducing internal resistance while maintaining acceptable working voltage through optimized salt concentrations

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If conventional water-based electrolytes are used, then manufacturing cost is low and non-toxic, but operating temperature range is narrow due to corrosiveness

Engineering Contradiction:

Improvemanufacturing costVSAvoidoperating temperature range

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent optimizes the electrolyte composition parameters including LiOH concentration (0.5-2.0 M), LiNO3 concentration (0.5-2.0 M), and pH value, creating a formulation that maintains stability and low corrosiveness across a broader temperature range while preserving the cost-effective water-based nature

Inventive Principle:

Principle #35Parameter changes

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 electrolyte achieves an energy-storage efficiency greater than 90% after 151 repeated charge-discharge cycles and operates effectively over a wider temperature range (-25°C to 85°C, with improved stability and reduced internal resistance.

Implementation Method 1

When a potential difference is applied across the electrodes, cations in the electrolyte move toward the negative electrode whereas the anions in the electrolyte move toward the positive electrode and thereby forms an ionic current within the electric double layer capacitor

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

Common water-based electrolytes are aqueous solutions of metal salts, such as IA, IIA metal salts or ammonium salts, dissolved in an aqueous solvent such as KOH or H2SO4 aqueous solution

Methodology Applied

Scientific EffectDissolution: Solvation

Data Source

PatentUS8379366B2Water-based electrolyte for electric double layer capacitor and electric double layer capacitor having the same

Publication Date: 2013.02.19 TAIWAN TEXTILE RESEARCH INSTITUTE

AI summary

Disclosed herein is a water-based electrolyte for an electric double layer capacitor. The water-based electrolyte includes a solution having a first salt and a second salt. The cation of the first salt may be Li+, Na+ or K+, whereas the cation of the second salt may be Cl−, SO42−, PO43− or NO3−, whereas the anion of the second salt is OH−.