Neutral-pH Eutectic Electrolyte for Zinc Redox Cells
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Solution Overview
Problem
Existing zinc-based rechargeable energy storage devices face issues with aqueous and eutectic electrolytes, including capacity fading, poor cyclic ability, gas evolution, and internal pressure buildup, which are not adequately addressed by conventional alkaline or acidic electrolytes, leading to safety concerns and inefficiencies.
Innovation Solution
A eutectic electrolyte comprising specific inorganic transition metal salts, metal hydroxides, and a eutectic solvent with a pH range of 5 to 7, formed by mixing derivatives of methanesulfonic acid, ammonium salts, and hydrogen bond donors, which prevents hydrogen and oxygen evolution, enhancing stability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional aqueous electrolytes (alkaline/acidic) are used in Zn based energy storage devices, then the devices can operate with simple electrolyte composition, but they suffer from capacity fading, poor cyclic ability, and gas evolution leading to internal pressure buildup
Solution Approach 1:
The patent changes the pH parameter of the electrolyte from conventional alkaline (pH>10) or acidic (pH<3) ranges to a neutral range (pH 5-7). This parameter change prevents gas evolution reactions while maintaining electrochemical activity, thereby improving cyclic ability and capacity stability without significantly increasing device complexity
Solution Approach 2:
The patent employs a composite electrolyte system combining eutectic solvents (choline chloride-urea or choline chloride-glycerol) with metal salts (ZnSO4, MnSO4, NiSO4). This composite approach creates a stable electrolyte environment that prevents capacity fading and improves cyclic performance while maintaining reasonable compositional simplicity
2Quantity of substance
If conventional aqueous electrolytes are used, then the electrolyte can provide good ionic conductivity, but they cause water evaporation leading to electrode dryness and faster capacity fading
Solution Approach 1:
The patent changes the physical state parameter of the electrolyte from purely aqueous liquid to a eutectic solvent system with controlled viscosity and boiling point. The eutectic composition (choline chloride with urea or glycerol) raises the boiling point and reduces water evaporation, thereby extending shelf life and capacity retention while maintaining adequate ionic conductivity through optimized metal salt concentrations
Solution Approach 2:
The eutectic solvent acts as an intermediary between water and the metal salts, creating a stable medium that prevents water evaporation while facilitating ion transport. The hydrogen bonding network in the eutectic system mediates between the conflicting requirements of ionic conductivity and evaporation resistance
3Ease of operation
If alkaline electrolytes with pH above 10 are used, then the electrolyte can facilitate zinc ion dissolution, but they form irreversible products like zinc oxide and hydroxide causing dendrite formation
Solution Approach 1:
The patent changes the pH parameter from alkaline (pH>10) to neutral (pH 5-7), which prevents the formation of irreversible zinc oxide and hydroxide products that cause dendrites. The neutral pH maintains sufficient zinc ion dissolution efficiency while eliminating the harmful side reactions associated with high pH environments
Solution Approach 2:
The patent converts the potential harm of high pH by using it to create a stable eutectic solvent system where the basicity of choline chloride is balanced by the acidity of the added metal salts, achieving neutral pH. This converts the harmful alkaline environment into a beneficial neutral environment that prevents dendrite formation while maintaining zinc ion dissolution
4Stability of the object's composition
If acidic electrolytes with pH below 3 are used, then the electrolyte can prevent zinc oxide formation, but they facilitate hydrogen and oxygen gas evolution leading to pitting and explosion risks
Solution Approach 1:
The patent changes the pH parameter from highly acidic (pH<3) to neutral (pH 5-7), which eliminates gas evolution reactions while preventing zinc oxide formation through the stable eutectic environment. The neutral pH achieved through eutectic composition balancing provides sufficient protection against zinc oxide without the harmful gas evolution effects of strong acids
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 eutectic electrolyte provides thermal and chemical stability, improved shelf life, and high ionic conductivity, with minimal dendrite formation and efficient electrochemical reactions, achieving >99% coulombic efficiency and >90% energy efficiency.
Implementation Method 1
The eutectic electrolyte provides thermal and chemical stability, improved shelf life, and high ionic conductivity
Implementation Method 2
efficient electrochemical reactions, achieving >99% coulombic efficiency and >90% energy efficiency
Data Source
AI summary
An electrolyte is provided for the zinc based rechargeable redox static energy storage devices, the electrolyte comprising one or more inorganic transition metal salt(s) of zinc; one or more Metal hydroxide(s); a eutectic solvent comprising one or more derivative(s) of methanesulfonic acid selected from its salts, one or more ammonium salt(s) one or more hydrogen bond donor(s). The electrolyte is thermally and chemically stable and has pH ranging from 5 to 7, and therefore does not facilitate evolution of hydrogen and oxygen during its application.