Composite Separator Structure for Aqueous Batteries Against Dendrites
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Solution Overview
Problem
Aqueous electrolyte batteries face challenges with water electrolysis and dendrite formation, leading to reduced charge/discharge efficiency and safety concerns due to the narrow potential window and susceptibility to internal short circuits.
Innovation Solution
A secondary battery design incorporating a composite separator with bimodal particle size distribution of inorganic solid particles and a polymeric material, which reduces water movement and proton conduction, enhancing charge/discharge efficiency and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aqueous electrolyte is used instead of a non-aqueous electrolyte, then safety is improved by eliminating flammability, but water electrolysis occurs leading to reduced charge/discharge efficiency
Solution Approach 1:
A gel polymer electrolyte is introduced as an intermediary medium between the aqueous electrolyte and the electrodes. This gel polymer electrolyte contains hydrophobic groups that repel water molecules, preventing water from reaching the electrodes and causing electrolysis, while still allowing ion transport for charge/discharge reactions
Solution Approach 2:
The chemical composition and physical state of the electrolyte are changed from liquid aqueous electrolyte to gel polymer electrolyte. This parameter change modifies the electrolyte's properties to reduce water activity and prevent water electrolysis while maintaining ionic conductivity
2Productivity
If a porous separator is used to allow ion transport, then charge/discharge efficiency is improved, but dendrites can penetrate through leading to internal short circuits
Solution Approach 1:
A composite separator structure is created combining a porous base layer for ion transport with a water-repellent gel polymer coating layer. This composite structure maintains porosity for efficient ion transport while the hydrophobic gel layer blocks dendrite penetration and prevents water electrolysis
3Quantity of substance
If the potential window is expanded to increase energy density, then energy storage capacity is improved, but water decomposition occurs more readily
Solution Approach 1:
The gel polymer electrolyte acts as an intermediary barrier that decouples the electrode potential from water activity. By containing hydrophobic groups, it creates a water-free interface at the electrode surface, allowing operation at higher potentials without water decomposition while maintaining stable ion transport
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 battery exhibits high charge/discharge efficiency and extended lifetime performance by minimizing water decomposition and dendrite formation, while maintaining flexibility and energy density.
Implementation Method 1
a composite separator comprising a porous substrate and a water-repellent layer formed on the porous substrate
Implementation Method 2
designed to minimize water electrolysis and dendrite formation
Implementation Method 3
an aqueous electrolyte containing a electrolyte salt
Data Source
AI summary
According to one embodiment, a secondary battery provided with a negative electrode including a negative electrode active material-containing layer, a positive electrode including a positive electrode active material-containing layer, a separator located between the negative electrode and the positive electrode, and an aqueous electrolyte is provided. The separator includes a composite layer containing inorganic solid particles and a polymeric material. A particle size distribution of the inorganic solid particles in the composite layer has at least two peaks. A frequency FPS of a peak top PS of a peak on a smallest particle diameter side and a frequency FPL of a peak top PL of a peak on a largest particle diameter side in the particle size distribution have a relationship of 0.9≤FPS/FPL≤5. A porosity of the composite layer is less than both of a porosity of the negative electrode active material-containing layer and a porosity of the positive electrode active material-containing layer, and is 1% or more and less than 15%.