Monoclinic Fluoride Solid Electrolyte for Safer Li-Ion Conduction
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Solution Overview
Problem
Existing solid electrolytes for lithium-ion batteries, particularly those based on fluorine compounds, suffer from insufficient lithium-ion conductivity and safety issues due to the generation of toxic hydrogen sulfide gas when exposed to moisture.
Innovation Solution
A solid electrolyte composed of a monoclinic phase compound containing Li, F, and a metallic or metalloid element M, with a content of the monoclinic phase quantitatively determined by RIR method exceeding 65%, and optionally including Cl, Br, or I, is developed to enhance lithium-ion conductivity and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte consisting of a sulfide is used, then lithium-ion conductivity can be achieved, but toxic hydrogen sulfide gas is generated when reacting with moisture in the air
Solution Approach 1:
The patent changes the chemical composition parameters by replacing sulfide-based materials with fluorine-based materials (specifically Li3MF6-aXa compounds where M is Ga, Al, or Zr). This fundamental parameter change eliminates the harmful hydrogen sulfide gas generation while maintaining solid electrolyte functionality, directly resolving the contradiction between conductivity and safety.
Solution Approach 2:
The patent employs composite material design by combining multiple elements (Li, F, M, and optionally Cl/Br/I) to create a new class of solid electrolyte materials. The specific composition Li3MF6-aXa represents a composite approach that achieves both high lithium-ion conductivity and improved safety by avoiding sulfide-related hazards.
2Object-generated harmful factors
If a solid electrolyte of a fluorine compound is used, then safety is improved by avoiding hydrogen sulfide gas, but lithium-ion conductivity remains insufficient at the order of 10^-6 S/cm
Solution Approach 1:
The patent optimizes the stoichiometric parameters of the fluorine-based compound by controlling the ratios of Li, M, F, and halogen elements (Cl/Br/I). By adjusting these compositional parameters within specific ranges, the patent achieves lithium-ion conductivity exceeding 10^-5 S/cm, which is an order of magnitude improvement over conventional fluorine compounds, while maintaining the safety advantages of non-sulfide materials.
Solution Approach 2:
The patent introduces local compositional variations by incorporating different halogen elements (Cl, Br, or I) at specific positions in the crystal structure, represented by the parameter 'a' in the formula Li3MF6-aXa. This local quality adjustment allows optimization of ion transport pathways while maintaining the overall safety and structural integrity of the fluorine-based electrolyte.
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 proposed electrolyte achieves high lithium-ion conductivity exceeding 1 × 10 -5< S/cm and ensures high safety by avoiding the generation of hydrogen sulfide gas, with the monoclinic phase content correlating positively with conductivity.
Implementation Method 1
a solid electrolyte with high safety and high lithium-ion conductivity
Implementation Method 2
In an X-ray diffraction pattern obtained by an X-ray diffraction measurement, a content of the monoclinic phase quantitatively determined by an RIR method is higher than or equal to 65%
Data Source
Figure 1~2
AI summary
A solid electrolyte includes, as a main phase, a monoclinic phase of a compound containing Li, F, and M that is a metallic element(s) other than Li or a metalloid element(s). In an X-ray diffraction pattern obtained by an X-ray diffraction measurement, a content of the monoclinic phase quantitatively determined by an RIR method is higher than or equal to 65%. This provides the solid electrolyte with high safety and high lithium-ion conductivity.