Air Electrode-LDH Separator Assembly for Stacked Zinc-Air Cells
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Solution Overview
Problem
Zinc-air secondary batteries face issues with short circuits due to zinc dendrite penetration and carbon dioxide ingress, which degrade battery performance, and constructing stacked-cell batteries is challenging due to gas and water impermeability of LDH separators.
Innovation Solution
An air electrode/LDH separator assembly is developed, comprising a rigid porous layer with air permeability and an LDH separator, allowing for efficient construction of stacked-cell batteries that supply high voltage or large current without compromising the original functions of the LDH separator and air electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an LDH separator is used to prevent zinc dendrite penetration and carbon dioxide ingress, then battery reliability is improved, but gas and water impermeability makes it difficult to construct stacked-cell batteries
Solution Approach 1:
The air electrode is divided into multiple independent assemblies, each comprising an LDH separator and air electrode layer combination. This segmentation allows each assembly to function as a complete unit with integrated CO2 blocking capability, enabling modular construction of stacked-cell batteries without requiring the entire battery structure to be gas-tight.
Solution Approach 2:
The air electrode layer is directly formed on the LDH separator, creating a nested structure where the functional layer is integrated with the barrier layer. This nesting eliminates the need for separate gas-tight encapsulation layers, as the LDH separator itself serves as both the barrier and the substrate for the electroactive material.
2Reliability
If a dense LDH separator is used to block zinc dendrites, then battery reliability is improved, but air permeability is reduced
Solution Approach 1:
The LDH separator exhibits selective permeability with different properties for different substances: it is impermeable to gases (CO2) and liquid water while maintaining ion conductivity for hydroxide ions. This local quality differentiation allows the separator to block harmful factors (CO2, dendrites) while permitting necessary transport (ion flow, air access to electrode sites).
Solution Approach 2:
The air electrode assembly functions as a composite structure combining the LDH separator material with the air electrode layer containing catalysts and conductive materials. This composite configuration allows the dense LDH separator to provide barrier functionality while the porous electrode layer structure facilitates air access and electrochemical reactions.
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 assembly enables the construction of zinc-air secondary batteries in a stacked-cell form, effectively preventing short circuits and carbon dioxide ingress, while ensuring efficient air intake and maintaining battery performance.
Implementation Method 1
a layered double hydroxide (LDH) separator that blocks the penetration of zinc dendrite while selectively permeating hydroxide ions
Implementation Method 2
a rigid porous layer having rigidity and air permeability
Implementation Method 3
Upon discharge, O2 is reduced on an air electrode (positive electrode) side to generate OH−
Implementation Method 4
zinc is oxidized on a negative electrode to generate ZnO
Implementation Method 5
carbon dioxide in the air passes through the air electrode, dissolves in the electrolyte, and precipitates an alkali carbonate
Data Source
AI summary
Provided is an air electrode/LDH separator assembly including: a rigid porous layer having rigidity and air permeability, wherein the rigidity is defined as a proportion of displacement in a compression direction of less than 3% when pressurized at 0.1 MPa; an air electrode layer that covers both sides of the rigid porous layer, or both sides and end faces of the rigid porous layer provided that at least one end face is excluded; and a layered double hydroxide (LDH) separator that covers an outside of the air electrode layer; wherein i) the rigid porous layer is made of a metal or an electrically conductive ceramic, whereby the rigid porous layer itself functions as a positive electrode current collector, or ii) the rigid porous layer is made of an insulating material and is covered with a porous metal layer, whereby the porous metal layer functions as a positive electrode current collector.