Semi-solid polymer electrolyte for safe lithium metal batteries
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Solution Overview
Problem
Lithium ion/metal batteries face safety concerns due to flammable organic electrolytes, which can lead to thermal chain reactions and fires, and existing solutions either do not completely eradicate fire risks or compromise performance and production costs. Additionally, solid-state electrolytes have lower ionic conductivities at room temperature, requiring higher operating temperatures and affecting energy efficiency.
Innovation Solution
Development of fast cure semi-solid polymer electrolytes (SSPEs) with a phosphate backbone that form a stable, non-flammable, and highly conductive network, providing a wide operational temperature range and compatibility with existing manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flammable organic electrolytes are used to achieve high ionic conductivity, then ionic conductivity is improved, but safety deteriorates due to fire hazards
Solution Approach 1:
The patent uses composite materials by combining polymer matrices with liquid electrolyte components to create gel polymer electrolytes. This composite structure provides both the structural integrity and ion conduction pathways needed for high ionic conductivity while the polymer network suppresses flammability, achieving a balance between conductivity and safety
Solution Approach 2:
The patent changes the physical state parameter of the electrolyte from purely liquid to semi-solid gel form. This parameter change maintains the liquid-like ion mobility necessary for high conductivity while introducing solid-like structural properties that reduce flammability and improve safety
2Object-affected harmful factors
If solid-state electrolytes are used to improve safety, then fire hazard is reduced, but ionic conductivity deteriorates at room temperature
Solution Approach 1:
The patent changes the physical state from fully solid to semi-solid gel form, which maintains structural safety benefits while restoring liquid-like ion mobility. The gel structure provides sufficient mechanical strength for safety while the incorporated liquid electrolyte components ensure high ionic conductivity at room temperature
Solution Approach 2:
The gel polymer electrolyte combines solid polymer matrices with liquid electrolyte components, creating a composite that exhibits both solid-like mechanical properties for safety and liquid-like ionic conductivity for performance
3Reliability
If gel polymer electrolytes are used to achieve high ionic conductivity, then ionic conductivity is improved, but safety deteriorates due to flammable volatiles
Solution Approach 1:
The patent modifies the electrolyte formulation by incorporating flame-retardant components and adjusting the ratio of liquid to polymer phases. This parameter change reduces the concentration of flammable volatiles while maintaining sufficient ion conduction pathways for high ionic conductivity
Solution Approach 2:
The patent converts the potentially harmful flammable volatiles into beneficial flame-retardant species by incorporating phosphorus-containing compounds that decompose to form protective char layers. This transforms the fire hazard into a safety feature while maintaining electrolyte functionality
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 SSPEs achieve comparable or better ionic conductivity to conventional liquid electrolytes at room temperature, maintain stability over a wide temperature range, and integrate seamlessly into existing battery manufacturing processes, enhancing safety and performance while avoiding the limitations of flammable electrolytes.
Implementation Method 1
the state-of-the-art SSEs, including polymers, oxides, and sulfides, have lower ionic conductivities than liquid-based rivals at room temperature
Implementation Method 2
liquid organic phosphates, including trimethyl phosphate, tri-ethyl phosphate, and diethyl ethylphosphonate, have been used as electrolyte solvents to absorb hydrogen radicals that cause the combustion chain reactions
Data Source
AI summary
Described herein are semi-solid polymer electrolytes (SSPEs) based on a polymer backbone incorporating a flame-retardant crosslinker and fluorinated counterions that are useful in the production of high energy rechargeable lithium metal batteries. The described SSPEs are not liquid electrolytes, are not solid state electrolytes (SSEs), and are differentiated from standard state-of-the-art gel polymer electrolytes (GPEs). The described SSPEs are formed from a first solvent, an optional second solvent, a crosslinker, a lithium salt, and an initiator. The unique coordination structure of the described SSPEs yields non-flammable, low-volatility, non-vaporizable, high Coulombic efficiency (CE), stable solid-electrolyte-interphase (SEI)-forming electrochemical devices, such as lithium metal rechargeable batteries, that are easily adaptable to existing mass-production lines.