Flexible Gel Polymer Electrolyte for Stable Mg-S Batteries
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Solution Overview
Problem
Existing multivalent metal batteries, particularly magnesium-sulphur (Mg-S) batteries, face challenges with inadequate cycling stability and short battery life due to the formation of magnesium polysulfide intermediates that dissolve and diffuse into liquid electrolytes, leading to self-discharge and rapid capacity degradation.
Innovation Solution
Development of a novel gel polymer electrolyte (GPE) with a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer backbone and polyethylene glycol dimethyl ether (PEGDME) plasticizer, which suppresses the polysulfide shuttle effect and enables efficient Mg-ion transfer, forming a self-standing, flexible membrane that is chloride-free and compatible with various electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid electrolyte is used in Mg-S batteries, then ionic conductivity is achieved, but polysulfide dissolution and diffusion occur leading to self-discharge and rapid capacity degradation
Solution Approach 1:
The patent introduces a gel polymer electrolyte as an intermediary medium between the electrodes. This GPE contains a polymer matrix (PVDF-HFP) that acts as a physical barrier while still allowing Mg2+ ion transport. The gel structure traps polysulfide intermediates, preventing their dissolution and diffusion between electrodes, thereby eliminating the polysulfide shuttle effect while maintaining ionic conductivity.
Solution Approach 2:
The patent employs a gel polymer electrolyte in the form of a flexible thin film membrane. This thin film structure provides mechanical confinement that prevents polysulfide migration while maintaining ion permeability. The flexible gel matrix allows Mg2+ ions to pass through but physically restricts the movement of larger polysulfide species, solving the contradiction between conductivity and polysulfide suppression.
2Reliability
If polymer electrolyte is used to suppress polysulfide dissolution, then cycling stability improves, but Mg2+ ion transport efficiency decreases
Solution Approach 1:
The patent creates a composite gel polymer electrolyte by combining PVDF-HFP polymer matrix with liquid electrolyte components (Mg[B(hfip)4]2 salt in DME). This composite structure provides both the mechanical framework of the polymer for polysulfide suppression and the liquid electrolyte phases for efficient Mg2+ ion conduction. The synergistic combination resolves the contradiction between structural confinement and ionic mobility.
Solution Approach 2:
The patent optimizes the composition parameters of the gel polymer electrolyte, specifically the ratio of polymer to liquid electrolyte components and the concentration of Mg salt. By adjusting these parameters, the GPE achieves optimal balance between mechanical strength (for polysulfide suppression) and ionic conductivity (for Mg2+ transport), transforming the trade-off into an optimized performance state.
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 novel GPE enhances cycling stability from 200 to 300 cycles while maintaining capacity retention, mitigating self-discharge and improving battery lifespan, making it suitable for flexible and reliable energy storage systems.
Implementation Method 1
The volume increase during the conversion from S to MgS is approximately 28%, which is low when compared to other conversion-type cathode materials. Moreover, sulphur has a high theoretical specific capacity (1672 mA h g -1)
Implementation Method 2
With a double positive charge and an ionic radius of 0.72 Å, which is comparable to that of Li +, Mg 2+ is also a suitable candidate for RMBs
Data Source
Figure 1a~2
Figure 3a~3b
Figure 4a~4h
AI summary
The invention relates to novel and improved multivalent metal batteries comprising a novel flexible gel polymer electrolyte. The invention further relates to novel flexible multivalent metal ion gel polymer electrolyte membranes, a process for the preparation thereof and their use in multivalent metal batteries. The novel MMV-GPE membranes of the invention turned out to be particularly suitable for magnesium-based batteries and allow to provide novel and improved flexible magnesium-sulphur batteries (Mg-S batteries).