Flexible Ion Conductive Membrane for Lithium Sulfur Batteries
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Solution Overview
Problem
Current lithium sulfur batteries face challenges such as short cycle life, low cycling efficiency, high self-discharge rates, and safety concerns due to the dissolution of polysulfide ions in the electrolyte, which existing solid-state electrolyte membranes fail to adequately address due to thickness, brittleness, low ionic conductivity, high cost, and manufacturing difficulties.
Innovation Solution
A flexible ion selective membrane composed of a microporous substrate and a thin Prussian blue dense layer, combined with an ion conductive polymer layer, is developed to block polysulfide ions while maintaining high lithium ion conductivity, achieved through electrochemical deposition and sequential adsorption techniques, resulting in a thinner, more cost-effective, and flexible membrane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid state lithium ion conductive non-porous glass electrolyte is used to block polysulfide ions, then polysulfide ion blocking capability is improved, but membrane thickness increases (>150 μm) and brittleness increases
Solution Approach 1:
The patent replaces thick rigid glass electrolyte with a thin film composite membrane consisting of a porous substrate coated with Prussian blue particles and ion conductive polymer. This thin film structure (micrometer scale thickness) provides both flexibility and effective polysulfide ion blocking through the Prussian blue layer's selective ion transport properties.
Solution Approach 2:
The patent creates a composite membrane structure combining three components: porous substrate (for mechanical support and ion transport), Prussian blue particles (for polysulfide ion blocking via size exclusion and electrostatic repulsion), and ion conductive polymer (for enhanced lithium ion conductivity). This composite approach achieves superior performance compared to single-material solutions.
2Reliability
If solid state lithium ion conductive non-porous glass electrolyte is used to block polysulfide ions, then polysulfide ion blocking capability is improved, but ionic conductivity decreases (∼0.1-1 mS/cm)
Solution Approach 1:
The patent assigns different functional properties to different layers of the composite membrane: the porous substrate provides mechanical support and baseline ion transport, the Prussian blue layer provides selective polysulfide ion blocking while maintaining lithium ion conductivity through its open zeolitic structure, and the ion conductive polymer coating enhances overall lithium ion conductivity. This localized functional distribution optimizes both blocking and conductivity performance.
3Reliability
If solid state lithium ion conductive non-porous glass electrolyte is used to block polysulfide ions, then polysulfide ion blocking capability is improved, but manufacturing cost increases (>$4000/m2)
Solution Approach 1:
The patent replaces expensive glass electrolyte (>4000/m2) with a cost-effective composite membrane using abundant, low-cost materials: porous substrates from standard battery manufacturing, Prussian blue particles that can be synthesized economically, and common ion conductive polymers. This dramatically reduces material costs while maintaining or improving performance.
Solution Approach 2:
The patent utilizes porous substrates with well-established manufacturing processes from existing lithium ion battery production, avoiding the need for complex glass processing equipment. The porous structure also facilitates efficient ion transport while providing mechanical integrity at reduced cost.
4Reliability
If solid state lithium ion conductive non-porous glass electrolyte is used to block polysulfide ions, then polysulfide ion blocking capability is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent divides the membrane into separate functional layers that can be manufactured and assembled independently: the porous substrate can be produced using existing battery manufacturing techniques, the Prussian blue particles can be synthesized separately and then deposited onto the substrate, and the ion conductive polymer coating can be applied as a final layer. This modular approach simplifies manufacturing compared to producing monolithic glass electrolyte.
Solution Approach 2:
The patent replaces the complex mechanical processing required for glass electrolyte (cutting, polishing, sealing) with chemical deposition methods for applying the Prussian blue and polymer layers onto flexible porous substrates. This substitution enables easier manufacturing and integration into battery assemblies.
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
This membrane effectively blocks polysulfide ions, enhances lithium ion conductivity, and reduces costs, enabling the development of high energy density, low-cost, and safe lithium sulfur batteries suitable for long-range electric vehicles.
Implementation Method 1
PB and its analogues are known to exhibit an open zeolitic structure with channel size of 0.32 nm. The specific capability to intercalate the alkali ions has led to its applications for sensors, ion selective electrode coating as well as battery materials. Because of its small rigid channel size, only small alkali ions (e.g., Li+) can pass through the structure, PSs cannot pass through since the diameter of the smallest PS ions (i.e., S2−:0.38 nm) is bigger than the zeolitic channel size.
Implementation Method 2
Recent publications have shown that Li+ or Na+ have very fast diffusivity inside the zeolitic channel of PB, as evidenced by super high rate capability (80° C.) of the cell. Li+ diffusivity in PB is ̃2×10−9 cm2·s−1, which is 2-3 orders of magnitude higher than that in (Li2S)7—(P2S5) glass SSE (10−11-10−12 cm2·s−1).
Implementation Method 3
our proposed membrane is made of microporous substrate, Prussian blue (PB) dense membrane layer and thin ion conductive polymer layer
Data Source
AI summary
In an improved lithium sulfur battery, an improvement comprises an effective Prussian blue dense membrane interposed between the anode and the cathode.