Layered Solid-State Battery Electrolytes for Conductivity and Strength
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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 discrete layers including a lithium-stuffed garnet layer and a sulfide solid electrolyte layer, each optimized for specific functions. This segmentation allows the garnet layer to provide mechanical strength while the sulfide layer provides high ionic conductivity, resolving the contradiction between structural simplicity and performance requirements.
Solution Approach 2:
The patent employs a composite electrolyte structure combining lithium-stuffed garnet (providing mechanical stability) with sulfide solid electrolyte (providing high ionic conductivity). This composite approach enables the system to simultaneously achieve both mechanical strength and high ionic conductivity that neither material could provide alone.
2Ease of manufacture
If a single monolithic solid-state electrolyte is used, then the manufacturing process is simplified, but the mechanical strength is insufficient
Solution Approach 1:
The electrolyte system is segmented into multiple manufacturable layers that can be processed and assembled separately. The lithium-stuffed garnet layer and sulfide layer are fabricated as distinct components and then combined, allowing each layer to be optimized for its specific manufacturing requirements while achieving superior overall mechanical strength.
Solution Approach 2:
The composite structure of lithium-stuffed garnet and sulfide electrolyte layers provides enhanced mechanical strength compared to single-material electrolytes. The garnet layer specifically contributes mechanical robustness while maintaining compatibility with standard solid-state battery manufacturing processes.
3Reliability
If oxide-sulfide composite electrolytes are used, then the ionic conductivity is improved, but the capacity fade over time increases
Solution Approach 1:
The patent applies different electrolyte materials to different regions of the battery system based on local requirements. The sulfide electrolyte is positioned where high ionic conductivity is most critical (near the cathode), while the lithium-stuffed garnet layer provides mechanical stability and interfacial protection. This spatial differentiation of material properties reduces capacity fade while maintaining high conductivity.
Solution Approach 2:
The lithium-stuffed garnet layer acts as an intermediary between the sulfide electrolyte and other battery components, protecting the sulfide layer from degradation and preventing direct contact between incompatible materials. This intermediary layer stabilizes the interfaces, reducing capacity fade over time while preserving the high ionic conductivity of the sulfide layer.
4Reliability
If solid-state electrolytes are used, then the safety is improved, but the energy density is reduced compared to liquid electrolytes
Solution Approach 1:
The composite electrolyte structure combines the safety advantages of solid-state electrolytes with the high ionic conductivity of sulfide materials. The lithium-stuffed garnet provides mechanical stability and safety, while the sulfide layer maintains high ion transport efficiency, thereby preserving energy density closer to liquid electrolyte systems while retaining solid-state safety benefits.
Solution Approach 2:
The patent optimizes parameters such as layer thickness, composition ratios, and microstructure of the composite electrolyte to minimize resistance to ion transport. By carefully controlling these parameters, the system achieves energy density levels comparable to liquid electrolytes while maintaining the inherent safety advantages of solid-state construction.
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 single ion conducting solid-state buffer... achieving an area-specific resistance of less than 50 Ω-cm² at room temperature, with improved lithium ion conductivity
Implementation Method 2
a borohydride bonding layer... between the lithium-stuffed garnet and the positive electrode
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.