Solid LiI Electrolyte for Crack-Resistant Molten Batteries
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Solution Overview
Problem
Conventional thermal batteries with fluid electrodes face significant safety issues due to brittle solid electrolytes, which can crack and lead to dangerous fire or explosion conditions, and previous attempts to address these issues have compromised energy density or increased complexity and cost.
Innovation Solution
A solid non-brittle electrolyte, such as lithium iodide (LiI), is used to separate fluid electrodes, maintaining a solid state near its melting point to minimize cracking and provide effective sealing while allowing the electrodes to remain in a fluid state, thereby enhancing safety and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brittle solid electrolytes are used in thermal batteries, then the battery structure is simple and manufacturing is easy, but the electrolyte can crack and lead to fire or explosion hazards
Solution Approach 1:
The patent changes the physical and chemical parameters of the electrolyte material by operating it near its melting point temperature. This parameter change transforms the electrolyte from a brittle solid at low temperatures to a soft, non-brittle solid at operating temperature, eliminating cracking hazards while maintaining structural simplicity
Solution Approach 2:
The patent employs composite material strategies by selecting electrolyte compositions (such as lithium iodide or specific glass compositions) that exhibit contrasting properties at different temperatures - brittle at room temperature for handling safety, but soft and ductile at operating temperature for operational safety
2Reliability
If solid electrolytes are used to separate fluid electrodes, then safety is improved by preventing direct contact between electrodes, but the electrolyte may crack due to brittleness
Solution Approach 1:
The patent utilizes temperature as a critical parameter to change the mechanical properties of the electrolyte. By maintaining the electrolyte near its melting point, the material transitions from a brittle state prone to cracking to a soft, ductile state that can withstand mechanical stresses without fracturing
Solution Approach 2:
The patent introduces dynamic properties to the electrolyte by operating it in a temperature regime where it exhibits time-dependent mechanical behavior. The electrolyte becomes soft and adaptable at operating temperature, allowing it to dynamically respond to stress without catastrophic failure
3Quantity of substance
If high energy density electrochemical couples are used in thermal batteries, then energy density is improved, but safety risks of fire and explosion increase
Solution Approach 1:
The patent introduces the soft solid electrolyte as an intermediary barrier between the high-energy-density fluid electrodes. This intermediary maintains electrical isolation while accommodating thermal expansion and mechanical stresses, preventing the harmful interaction between electrodes that would cause fire or explosion
Solution Approach 2:
The patent converts the potential harm of high-energy-density materials into benefit by using the electrolyte's softness near its melting point to absorb and dissipate energy that would otherwise cause catastrophic failure. The same thermal conditions that enable high energy density also soften the electrolyte to prevent failure
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 use of a solid non-brittle electrolyte like LiI in thermal batteries significantly reduces the risk of electrolyte failure, maintaining high energy density and power density while ensuring safety, making thermal batteries viable for applications like electric vehicles.
Implementation Method 1
maintaining a solid state near its melting point to minimize cracking and provide effective sealing
Data Source
AI summary
A battery includes a fluid negative electrode and a fluid positive electrode separated by a solid electrolyte at least when the electrodes and electrolyte are at an operating temperature. The solid electrolyte comprises a salt formed by ions of the negative electrode material forming the fluid negative electrode. In one example, the fluid negative electrode comprises lithium (Li), the fluid positive electrode comprises sulfur (S) and the solid electrolyte comprises lithium iodide (LiI).