Bromine-Substituted Argodite Solid Electrolyte for Low Activation Energy
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Solution Overview
Problem
Current solid electrolytes for all-solid secondary batteries, particularly those with an argyrodite crystal structure, face challenges with high activation energy, leading to poor temperature stability and varying ion conductivity depending on use temperature.
Innovation Solution
A solid electrolyte composition represented by Li7-xPS6-xBrx, where 1.2<x<1.75, is developed, which maintains high ion conductivity while reducing activation energy by substituting sulfur atoms with bromine, and is prepared through mechanical milling and heat-treating a mixture of Li2S, P2S5, and LiBr, resulting in a solid electrolyte with an argyrodite crystal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte with argyrodite crystal structure is used, then ion conductivity is improved (about 10^-4 to 10^-3 S/cm), but activation energy becomes too high (30 kJ/mol or greater) causing poor temperature stability
Solution Approach 1:
The patent modifies the chemical composition parameters of the solid electrolyte by introducing a specific formula Li6.5-xPS4.5-xBrx with controlled x values (0.25≤x≤1.5). This compositional parameter change allows simultaneous achievement of high ion conductivity and low activation energy, resolving the contradiction between conductivity and temperature stability.
Solution Approach 2:
The patent creates a composite solid electrolyte system combining Li2S, P2S5, and LiBr in specific ratios to form the Li6.5-xPS4.5-xBrx composition. This composite approach enables tuning of both ion conductivity and activation energy characteristics, achieving both high reliability and temperature stability.
2Stability of the object's composition
If sulfur atoms are substituted with bromine to reduce activation energy, then temperature stability is improved, but ion conductivity may decrease
Solution Approach 1:
The patent optimizes the bromine substitution level by controlling the x parameter in the formula Li6.5-xPS4.5-xBrx. By precisely adjusting x within the range 0.25≤x≤1.5, the patent achieves the optimal balance where activation energy is reduced (improving temperature stability) while ion conductivity remains sufficiently high (maintaining reliability).
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 new solid electrolyte achieves an ion conductivity of 1.6×10−3 S/cm or greater at 27°C and an activation energy of 29 kJ/mol or less, enhancing temperature stability and performance across a wide temperature range.
Implementation Method 1
the solid electrolyte may have an ion conductivity of about 1.6×10−3 Siemens per centimeter (S/cm) or greater at a temperature of 27° C.
Implementation Method 2
the solid electrolyte may have an activation energy of about 29 kilojoules per mole (kJ/mole) or less
Data Source
AI summary
A solid electrolyte for an all-solid secondary battery, wherein the solid electrolyte has a composition represented by Formula (1):Li7-xPS6-xBrx (1)wherein 1.2<x<1.75, the solid electrolyte has an argyrodite crystal structure, and the solid electrolyte has at least one peak at a position of a 29.65±0.50° 2θ when analyzed by X-ray diffraction using CuKα radiation.