POSS-PEG Gel Polymer Electrolyte Balancing Conductivity and Strength
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Solution Overview
Problem
Lithium metal batteries using traditional carbonate-based liquid electrolytes are limited by temperature range, safety hazards, and lithium dendrite growth, while solid polymer electrolytes offer improved safety but suffer from low ionic conductivity and poor interfacial contact, hindering their application in handheld devices.
Innovation Solution
A lithium gel polymer electrolyte composition is developed, featuring a crosslinked network formed by reacting inorganic polyhedral oligomeric silsesquioxane with functionalized poly(ethylene glycol or poly(ethylene oxide) and incorporating an ionic liquid and lithium salts, which provides enhanced mechanical strength and ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid polymer electrolytes are used, then safety is improved and lithium dendrite resistance is enhanced, but ionic conductivity deteriorates and interfacial contact becomes poor
Solution Approach 1:
The patent creates a gel polymer electrolyte that combines solid polymer matrix (providing safety and dendrite resistance) with ionic liquid components (providing high ionic conductivity). This composite structure integrates the advantages of both material types while mitigating their individual drawbacks.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the polymer electrolyte by incorporating ionic liquids and adjusting composition ratios, transforming it from a purely solid state with low conductivity to a gel state with enhanced ionic conductivity while maintaining safety properties.
2Quantity of substance
If ionic liquid content is increased, then ionic conductivity is enhanced, but mechanical strength deteriorates
Solution Approach 1:
The patent optimizes the composition parameters by controlling the ratio of ionic liquid to polymer matrix, achieving a balance where sufficient ionic conductivity is obtained while maintaining adequate mechanical strength for practical application.
Solution Approach 2:
The gel polymer electrolyte forms a composite structure where the polymer matrix provides mechanical support and the ionic liquid phase provides ionic conduction pathways, achieving synergistic properties that resolve the contradiction between conductivity and strength.
3Quantity of substance
If traditional carbonate-based liquid electrolytes are used, then ionic conductivity is maintained, but temperature range is limited and safety hazards increase
Solution Approach 1:
The patent replaces traditional carbonate-based liquid electrolytes with a gel polymer electrolyte composite that uses ionic liquids embedded in a polymer matrix, achieving both high ionic conductivity and improved safety by eliminating the flammable carbonate solvents.
Solution Approach 2:
The patent converts the potential harm of liquid electrolytes (flammability, leakage) into benefit by using the ionic liquid's inherent high conductivity within a solid polymer framework, thereby achieving safety without sacrificing performance.
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 solution achieves stable cycling performance over a wide temperature range, preventing lithium dendrite growth and ensuring mechanical strength, thus enabling the use of lithium metal batteries in handheld devices with improved safety and performance.
Implementation Method 1
a crosslinked network formed by reacting inorganic polyhedral oligomeric silsesquoxane with functionalized poly(ethylene glycol or poly(ethylene oxide)
Implementation Method 2
incorporating an ionic liquid and lithium salts, which provides enhanced mechanical strength and ionic conductivity
Data Source
AI summary
Ionic liquid N-methyl-N-propyl-pyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI) was introduced into a hybrid network to obtain a series of gel polymer electrolytes (GPEs). Mechanical and electrochemical properties of the GPEs were tuned through controlling the network structure and ionic liquid contents, and ionic conductivity higher than 1 mS cm−1 at room temperature was achieved. The newly developed GPEs are flame-retardant and show excellent thermal and electrochemical stability as well as ultra-stability with lithium metal anode. Symmetrical lithium cells with the GPEs exhibit a stable cycling over 6800 h at a current density of 0.1 mA cm−2 and stable lithium stripping-plating at 1 mA cm−2, the highest current density reported for ionic liquid-based GPEs. Moreover, Li/LiFePO4 batteries with the obtained GPEs exhibit desirable cycling stability and rate performance over a wide temperature range from 0° C. to 90° C.