Electrolyte composition
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Solution Overview
Problem
Aqueous zinc-ion batteries face issues with free water in their electrolyte causing instability during the deposition process, leading to passivation, gas production, and rapid capacity decay, as well as potential short-circuiting due to accumulated passivated zinc products.
Innovation Solution
An electrolyte composition comprising zinc chloride, an alkali metal chloride, and acetonitrile, which forms coordinate bonds to reduce free water content and enhance the solubility of zinc chloride, thereby improving charge-discharge cycling performance and preventing battery aging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If free water is present in the aqueous electrolyte, then the electrolyte maintains good ionic conductivity, but the zinc ion becomes unstable during deposition leading to passivation and side reactions
Solution Approach 1:
The patent introduces a water-soluble polymer as an intermediary substance that mediates between water and zinc ions. The polymer binds to zinc ions through coordination chemistry, forming a protective complex that prevents direct interaction between free water and zinc ions, thereby maintaining ionic conductivity while stabilizing zinc ion deposition
Solution Approach 2:
The electrolyte is designed as a composite system combining water, zinc salt, and water-soluble polymer. This composite structure allows the polymer component to modify the local environment around zinc ions, creating a stable coordination sphere that prevents passivation while maintaining the aqueous nature of the electrolyte for good ionic conductivity
2Ease of operation
If free water is present in the aqueous electrolyte, then the electrolyte maintains solvent properties, but the positive electrode material dissolves easily and gas is produced
Solution Approach 1:
The water-soluble polymer acts as a mediator between water and the positive electrode material. By forming a protective layer or modifying the electrolyte structure, the polymer reduces the direct solvating action of water on the electrode material, preventing dissolution and gas evolution while preserving the overall solvent properties of the aqueous electrolyte
3Quantity of substance
If passivated zinc product accumulates during cycling, then the battery shows initial capacity, but the passivated product pierces the separator and contacts the positive electrode causing short-circuit
Solution Approach 1:
The water-soluble polymer provides beforehand cushioning by forming a protective coordination complex around zinc ions before deposition. This pre-formed protective layer prevents the formation of passivated zinc products that could pierce the separator, thus preventing short-circuits while allowing the battery to maintain its capacity
Solution Approach 2:
The polymer serves as an intermediary that modifies the deposition morphology of zinc. By controlling the deposition process through coordination chemistry, the polymer ensures that zinc deposits as a stable, non-passivating structure that does not grow into dendrites or pierce the separator, thereby maintaining both capacity and safety
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 composition effectively reduces free water content, enhancing the stability and performance of secondary batteries by improving charge-discharge cycling and preventing aging, as evidenced by clear solutions and better battery performance in tests.
Implementation Method 1
acetonitrile, which forms coordinate bonds to reduce free water content and enhance the solubility of zinc chloride
Implementation Method 2
Coordination of water molecules to the alkali metal ions reduces the number of water molecules available to coordinate with Zn2+ ions
Data Source
AI summary
Disclosed herein is an electrolyte composition that includes zinc chloride, an alkali metal chloride, acetonitrile, and water.