Layered Oxide-Sulfide Electrolytes for Stable Solid-State Batteries
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Solution Overview
Problem
Current solid-state batteries face challenges in achieving high ionic conductivity, mechanical strength, and commercial viability due to the limitations of single ion conducting solid-state electrolytes, leading to design tradeoffs and deficiencies such as low capacity and capacity fade over time.
Innovation Solution
A solid-state electrochemical cell design incorporating a positive electrode layer with a sulfide catholyte, a single ion conducting buffer, a borohydride bonding layer, and a lithium-stuffed garnet layer, where the buffer is mixed within or in contact with the positive electrode layer, and the borohydride layer is between the lithium-stuffed garnet and the positive electrode, enhancing lithium ion conductivity and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single monolithic solid-state electrolyte is used, then the device complexity is reduced, but the ionic conductivity and mechanical strength are insufficient
Solution Approach 1:
The electrolyte is divided into multiple functional layers: a sulfide-based solid electrolyte layer in contact with the cathode for high ionic conductivity, an oxide-based solid electrolyte layer for mechanical strength and stability, and a bonding layer for interface connection. This segmentation allows each layer to optimize its specific function rather than requiring a single material to satisfy all requirements.
Solution Approach 2:
The patent employs composite material structures combining different solid electrolyte types (sulfide and oxide) with distinct properties. The sulfide layer provides high Li-ion conductivity while the oxide layer provides mechanical robustness and voltage stability, creating a composite electrolyte system that achieves properties superior to individual materials.
2Reliability
If sulfide solid electrolyte is used, then the lithium ion conductivity is improved, but the mechanical strength and voltage stability deteriorate
Solution Approach 1:
The electrolyte structure separates the conductivity function (sulfide layer) from the mechanical support function (oxide layer), allowing the sulfide layer to be optimized for ion transport without needing to provide mechanical strength.
Solution Approach 2:
The bonding layer acts as an intermediary between the sulfide and oxide layers, ensuring good interfacial contact and mechanical coupling while allowing each electrolyte layer to maintain its optimal properties for its specific function.
3Strength
If oxide solid electrolyte is used, then the mechanical strength and voltage stability are improved, but the lithium ion conductivity deteriorates
Solution Approach 1:
The electrolyte is segmented into layers where the oxide layer provides mechanical strength and voltage stability without needing to provide high ionic conductivity, as this function is fulfilled by the adjacent sulfide layer.
Solution Approach 2:
Different regions of the electrolyte structure have different local properties: the sulfide layer region has high ionic conductivity while the oxide layer region has high mechanical strength, with each layer's properties optimized for its specific location and function in the overall structure.
4Reliability
If a bonding layer is added between electrolyte layers, then the interfacial contact is improved, but the device complexity increases
Solution Approach 1:
The bonding layer serves as an intermediary component that facilitates good interfacial contact between the sulfide and oxide electrolyte layers, ensuring effective ion transport across the interface while providing mechanical adhesion.
Solution Approach 2:
The bonding layer performs multiple functions simultaneously: providing mechanical adhesion between layers, ensuring good interfacial contact for ion transport, and potentially serving as an additional ion conduction pathway, thereby justifying its inclusion despite increased structural complexity.
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 design achieves an area-specific resistance of less than 50 Ω-cm² at room temperature, with improved lithium ion conductivity and mechanical strength, leading to enhanced performance and stability of solid-state batteries.
Implementation Method 1
a bonding layer comprising a borohydride, is used to bond an oxide electrolyte separator and a sulfide electrolyte separator
Implementation Method 2
Batteries are referred to as solid-state batteries when they include a solid-state electrolyte separator between the positive and negative electrodes of the battery cell
Data Source
AI summary
Provided herein solid-state battery architectures that include an oxide electrolyte in contact with the anode of an electrochemical cell and a sulfide electrolyte in contact with the cathode of an electrochemical cell.