Zinc Anode Coating for Secondary Cell Cycle Life
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Solution Overview
Problem
Zinc secondary cells with aqueous electrolytic solutions face short charge-discharge cycle life due to zinc dendrite growth, self-discharge, and decreased discharge capacity, primarily because of zincate anion solubility and hydrogen-generating dissolution reactions in alkaline solutions, which limit their practical application in electric vehicles.
Innovation Solution
A zinc anode material is developed by coating zinc-containing particles with a specific composition of metal oxides such as titanium, zirconium, magnesium, tin, or yttrium oxides, ensuring a surface localization ratio of 1.6 to 16, which enhances chemical and electrochemical stability, prevents zinc oxide deposition, and suppresses hydrogen-generating reactions, thereby improving charge-discharge cycle durability and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strong alkaline aqueous solution saturated with zinc oxide is used as electrolytic solution to prevent zinc dissolution, then zinc electrode stability is improved, but zincate anion still dissolves in supersaturated condition and causes self-discharge
Solution Approach 1:
A gel polymer electrolyte is introduced as an intermediary substance between the zinc electrode and the aqueous electrolytic solution. This gel polymer electrolyte contains zinc ions and acts as a mediator that allows ionic conduction while preventing the dissolution and migration of zincate anions into the bulk electrolyte, thus eliminating self-discharge while maintaining electrode stability
Solution Approach 2:
The invention changes the physical state and composition parameters of the electrolyte system by replacing conventional liquid aqueous electrolyte with a gel polymer electrolyte. This parameter change transforms the electrolyte from a liquid state that allows free ion migration to a gel state that restricts zincate anion dissolution while maintaining ionic conductivity through the gel matrix
2Quantity of substance
If conventional zinc anode material is used to achieve high theoretical capacity density, then energy density is improved, but charge-discharge cycle life becomes very short due to dendrite growth and shape change
Solution Approach 1:
A gel polymer electrolyte film is applied as a flexible protective layer surrounding the zinc anode material. This thin film structure physically constrains the zinc electrode, preventing dendrite growth and shape changes during charge-discharge cycles, while still allowing ionic transport to maintain high capacity density and extend cycle life
3Duration of action of stationary object
If zinc-containing particles are coated with metal oxide to prevent zincate anion diffusion, then charge-discharge cycle durability is improved, but surface localization ratio must be precisely controlled to maintain electrochemical activity
Solution Approach 1:
The invention uses a composite structure consisting of zinc-containing particles coated with metal oxide within a gel polymer electrolyte matrix. This composite material approach provides protective metal oxide coating to prevent zincate anion diffusion while the gel polymer electrolyte ensures ionic conductivity, achieving enhanced cycle durability without excessive complexity in coating composition control
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 coated zinc anode material significantly increases charge-discharge cycle durability and prevents self-discharge, maintaining high charge efficiency and energy density by stabilizing the zinc surface and reducing zincate anion diffusion, thus overcoming the limitations of conventional zinc secondary cells.
Implementation Method 1
a zinc-containing particles coated with a coating layer containing at least one oxide of a metal selected from titanium (Ti), zirconium (Zr), magnesium (Mg), tin (Sn) and yttrium (Y)
Implementation Method 2
By a charge reaction in the zinc anode, zinc oxide species (ZnO or Zn(OH)42-) are electrochemically reduced to produce metal zinc
Implementation Method 3
a hydrogen-generating dissolution reaction of the following Chemical Equation (5) occurs to cause self-discharge that consumes the produced metal zinc
Implementation Method 4
Zn+2OH−+H2O→Zn(OH)42-+H2↑
Implementation Method 5
the zincate anion is deposited as solid zinc oxide by a chemical reaction of the following Chemical Equation (2)
Data Source
AI summary
A zinc anode material for secondary cells includes zinc-containing particles that are coated with a coating composition containing at least one oxide of a metal selected from titanium, zirconium, magnesium, tin and yttrium. The surface localization ratio of the coating composition of Equation (1) ranges from 1.6 to 16. In Equation (1), the surface metal atomic ratio of the coating composition is represented by Equation (2), and the bulk metal atomic ratio of the coating composition is represented by Equation (3).SurfaceLocalizationRatioofCoatingComposition=SurfaceMetalAtomicRatioofCoatingCompositionBulkMetalAtomicRatioofCoatingCompositionEquation(1)SurfaceMetalAtomicRatioofCoatingComposition=MetalAtomicinSurfaceCoatingComposition/mol%MetalAmountinSurfaceCoatingComposition+SurfaceZnAmount/mol%Equation(2)BulkMetalAtomicRatioofCoatingComposition=MetalAtomicinCoatingComposition/molMetalAmountinCoatingComposition+ZnAmount/molEquation(3)