Halogen-Tuned Sulfide Solid Electrolyte for Moisture Stability
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Solution Overview
Problem
Current lithium ion batteries using sulfide solid electrolytes face challenges in achieving high ionic conductivity and suppressing the generation of hydrogen sulfide when exposed to moisture, while also requiring complex safety devices due to the use of flammable organic solvents.
Innovation Solution
A novel sulfide solid electrolyte composed of lithium, phosphorus, sulfur, chlorine, and bromine, characterized by specific diffraction peaks and molar ratios, which enhances ionic conductivity and reduces hydrogen sulfide generation, is developed. This electrolyte is synthesized using a method that applies mechanical stress and heat treatment to optimize halogen distribution within the argyrodite crystal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a sulfide solid electrolyte is used in a lithium ion battery, then the energy density is improved, but the battery generates hydrogen sulfide when exposed to moisture
Solution Approach 1:
The patent modifies the chemical composition parameters of the sulfide solid electrolyte by incorporating both chlorine and bromine in specific molar ratios (0.1 ≤ x ≤ 1.5 in Li6-a-bPS5-c-dClxBr1-x-y where a+b≤0.6 and c+d≥1.4). This compositional parameter change optimizes the electrolyte's stability against moisture while maintaining high ionic conductivity, thereby reducing hydrogen sulfide generation without sacrificing energy density.
2Reliability
If an electrolyte containing flammable organic solvent is used, then the ionic conductivity is improved, but the battery requires complex safety devices
Solution Approach 1:
The patent transitions from liquid organic electrolytes to solid sulfide electrolytes by changing the physical state parameter. The specific compositional parameters (Li6-a-bPS5-c-dClxBr1-x-y with controlled halogen content) provide solid-state ionic conductivity comparable to or exceeding liquid electrolytes, while eliminating flammability risks and enabling safety device simplification.
3Reliability
If the halogen content in the sulfide solid electrolyte is increased, then the ionic conductivity is improved, but the stability against moisture is reduced
Solution Approach 1:
The patent creates a composite electrolyte system by combining multiple halogen elements (chlorine and bromine) in specific proportions within the Li6-a-bPS5-c-dClxBr1-x-y structure. This composite approach leverages the complementary properties of different halogens: chlorine provides structural stability while bromine enhances ionic conductivity, achieving both high conductivity and moisture stability simultaneously.
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 sulfide solid electrolyte exhibits improved ionic conductivity and reduced hydrogen sulfide generation, potentially simplifying safety devices and reducing production costs, while maintaining high energy density.
Implementation Method 1
Some of argyrodite type crystal structures have high lithium ion conductivity
Implementation Method 2
in powder X-ray diffraction analysis using CuKα rays, it has a diffraction peak A at 2θ=25.2±0.5 deg and a diffraction peak B at 2θ=29.7±0.5 deg
Data Source
AI summary
A sulfide solid electrolyte that contains lithium, phosphorus, sulfur, chlorine and bromine, wherein in powder X-ray diffraction analysis using CuKα rays, it has a diffraction peak A at 2θ=25.2±0.5 deg and a diffraction peak B at 2θ=29.7±0.5 deg, the diffraction peak A and the diffraction peak B satisfy the following formula (A), and a molar ratio of the chlorine to the phosphorus “c (Cl/P)” and a molar ratio of the bromine to the phosphorus “d (Br/P)” satisfies the following formula (1):1.2<c+d<1.9 (1)0.845<SA/SB<1.200 (A)where SA is an area of the diffraction peak A and SB is an area of the diffraction peak B.