Core-Shell Sulfide Solid Electrolytes for Wider Voltage Stability
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Solution Overview
Problem
Solid state electrolytes, such as Li10SiP2S12, face stability issues due to incompatibility with lithium chemical potentials, leading to decay at voltages below or above their stability window, limiting their practical use in batteries.
Innovation Solution
A core-shell morphology is introduced in solid state electrolytes containing an alkali metal and sulfide, with a shell that reduces core expansion during electrical cycling, enhancing stability, and a method of fabricating these electrolytes by mixing sulfur, phosphorus, and alkali metal sources and annealing under controlled conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If solid state electrolytes like LSPS are used to achieve high Li ion conductivity, then ion conductivity is improved, but voltage stability deteriorates due to decay at voltages outside the narrow stability window
Solution Approach 1:
The solid state electrolyte is divided into core and shell regions with different compositions. The core maintains high Li ion conductivity while the shell provides enhanced voltage stability and prevents decay reactions at the electrodes, effectively segmenting the functional requirements of conductivity and stability into separate regions.
Solution Approach 2:
The invention uses a composite structure combining different sulfide-based materials with distinct properties. The core material (e.g., LSPS) provides high ionic conductivity, while the shell material (e.g., LGPS or other stable sulfides) provides broad voltage stability, creating a composite electrolyte that exhibits both high conductivity and wide electrochemical stability window.
2Stability of the object's composition
If external pressure is applied to stabilize solid state electrolytes, then voltage stability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The stabilizing shell structure is incorporated into the electrolyte during the synthesis process itself, rather than requiring post-synthesis pressure application. The annealing process simultaneously forms the core-shell structure and stabilizes the material, eliminating the need for separate pressurization steps and reducing manufacturing complexity.
Solution Approach 2:
The invention replaces the need for external mechanical pressure systems with an intrinsic structural solution. Instead of applying continuous external pressure to stabilize the electrolyte, the core-shell morphology provides inherent structural stability that prevents volume expansion and maintains voltage stability without requiring complex pressure application systems.
3Use of energy by moving object
If core expansion is allowed during electrical cycling, then Li ion conductivity is maintained, but voltage stability deteriorates
Solution Approach 1:
Different regions of the electrolyte are assigned different functional qualities: the core region allows volume changes and maintains high ionic conductivity pathways, while the shell region provides mechanical constraint and structural stability. This local differentiation of properties enables simultaneous optimization of conductivity and cycle reliability.
Solution Approach 2:
The shell acts as a flexible constraint that accommodates minor volume changes during Li ion insertion/extraction while preventing excessive expansion. The shell structure is designed to be sufficiently compliant to allow necessary ion transport but rigid enough to maintain overall structural integrity and prevent decay reactions during battery cycling.
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 core-shell structure significantly improves voltage stability and battery cycle performance, expanding the stability window without the need for excessive external pressures, enabling more reliable battery operation.
Implementation Method 1
the shell increases the stability of the solid state electrolyte during electrical cycling by reducing expansion of the core
Implementation Method 2
annealing the mixture to form a sulfide solid state electrolyte having alkali metal atoms and halogen atoms incorporated therein. The annealing occurs, e.g., under conditions to produce a solid state electrolyte with a core-shell morphology
Data Source
AI summary
The invention provides compositions containing a solid state electrolyte (SSE) containing an alkali metal and a sulfide for use as the electrolyte matrix in a solid state rechargeable battery. The SSE compositions may further contain phosphorous, silicon, or a dopant atom, such as a halogen. These compositions are advantageous as they use Earth-abundant elements, have high voltage stability, excellent battery cycle performance, and are fabricated and used under conditions that do not require excessive external pressures which would otherwise limit their use in a production battery. In particular, the SSEs have a controllable microstructure, e.g., core-shell structure, that enhances their inherent stability while obviating the need for excessively large pressures to control the electrolyte stability. Methods of producing the compositions and rechargeable batteries including the composition are also provided.