Halide-Hydrate Sulfide Solid Electrolyte for Stable Battery Interfaces
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Solution Overview
Problem
Solid-state batteries with sulfide solid electrolytes face increased reaction resistance between the active material and the electrolyte, leading to deterioration in battery characteristics due to the formation of a resistive layer at their interface, which existing solutions like surface coatings or oxide layers are not economically practical.
Innovation Solution
A sulfide solid electrolyte with specific diffraction peak ranges and a lithium halide hydrate composition is used, reducing reaction resistance through X-ray diffraction measurement and exposure to a water-containing atmosphere, or by mixing with a compound containing water of crystallization, to enhance lithium ionic conductivity and battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a sulfide solid electrolyte is used in a solid-state battery, then the battery can achieve higher voltage and simplified safety devices, but reaction resistance increases between the active material and the sulfide solid electrolyte, leading to deterioration in battery characteristics
Solution Approach 1:
The patent changes the chemical composition parameters of the sulfide solid electrolyte by introducing specific halogen elements (Cl, Br, I) to form new compounds like Li3PS4, Li2SiO3, and their mixtures. This compositional modification reduces reaction resistance at the interface between the active material and electrolyte, thereby maintaining battery characteristics while preserving the high voltage capability of sulfide solid electrolytes
2Reliability
If the surface of the positive electrode active material is coated with specific compounds to restrain increase in reaction resistance, then reaction resistance can be controlled, but expensive substances such as lithium niobate, lithium titanate, lithium lanthanum zirconate, lithium tantalate, or lithium tungstate must be used
Solution Approach 1:
The patent replaces expensive coating materials (lithium niobate, lithium titanate, etc.) with a cost-effective sulfide solid electrolyte composition containing halogen elements. The electrolyte itself forms a protective interface layer through controlled reaction, eliminating the need for expensive external coatings while maintaining low reaction resistance
Solution Approach 2:
The sulfide solid electrolyte composition serves multiple functions: it acts as the electrolyte medium for lithium ion transport, forms a protective interface layer with active materials, and provides structural stability. This multi-functionality eliminates the need for separate expensive coating layers, reducing manufacturing cost
3Reliability
If an oxide layer is formed on the surface of a sulfide solid electrolyte material to restrain formation of a high-resistance section, then reaction resistance can be reduced, but moisture must be avoided as much as possible during exposure to the atmosphere and a drying step is needed
Solution Approach 1:
The sulfide solid electrolyte composition containing halogen elements self-forms a protective interface layer when contacted with moisture in the atmosphere. This self-passivation mechanism eliminates the need for controlled oxide layer formation processes and drying steps, simplifying the manufacturing process while reducing reaction resistance
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 solution results in improved discharge capacity and rate characteristics for solid-state batteries by reducing reaction resistance, achieving favorable battery characteristics without the need for expensive surface coatings or stringent moisture control.
Implementation Method 1
Patent Literature 2 discloses an attempt to restrain formation of a high-resistance section by forming an oxide layer on a surface of a sulfide solid electrolyte material, the oxide layer resulting from oxidation of the sulfide solid electrolyte material itself
Implementation Method 2
diffraction peak A observed within a range of 2θ = 20.0° to 24.0°; and diffraction peak B observed within a range of 2θ = 24.4° to 26.4°, diffraction peak A and diffraction peak B being observed by performing X-ray diffraction measurement using CuKα1 radiation
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Provided is a sulfide solid electrolyte having: diffraction peak A observed within a range of 2θ = 20.0° to 24.0°; and diffraction peak B observed within a range of 2θ = 24.4° to 26.4°, diffraction peak A and diffraction peak B being observed by performing X-ray diffraction measurement using CuKα1 radiation, and the ratio of IA to IB, IA/IB, being 2.0 or less, wherein IA is an intensity of diffraction peak A and IB is an intensity of diffraction peak B. Preferably, the sulfide solid electrolyte contains elemental lithium, elemental phosphorus, elemental sulfur, and an elemental halogen. It is also preferable that the sulfide solid electrolyte has an argyrodite-type crystal structure. It is also preferable that the sulfide solid electrolyte contains a lithium halide hydrate.