DES Electrolyte Interlayers for Low-Resistance Solid-State Battery Cathodes
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Solution Overview
Problem
Conventional solid-state batteries face high interfacial resistance and poor cycling performance due to the rigid nature of ceramic solid-state electrolytes, which limits Li-ion conductivity and accessibility at the cathode/solid-state electrolyte interface, and existing solutions like gel polymer electrolytes or ionic liquid electrolytes are either impractical or costly.
Innovation Solution
The use of deep eutectic solvent-based electrolytes, comprising lithium salts and amide compounds with a molar ratio of 1:1 to 1:50, which form intermolecular hydrogen bonds to maintain a liquid state at room temperature, reducing interfacial resistance and enhancing cycling stability by providing continuous ion paths at the cathode/solid-state electrolyte interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ceramic solid-state electrolytes are used, then high safety and stability against Li metal are achieved, but high interfacial resistance and poor Li-ion accessibility at the cathode/SSE interface occur
Solution Approach 1:
A liquid electrolyte interlayer comprising lithium salt and nitrile compound is introduced between the cathode and solid-state electrolyte. This intermediary layer mediates the interface by providing good wetting to cathode particles, establishing continuous Li-ion conduction paths, and reducing interfacial resistance while maintaining the stability benefits of the solid-state electrolyte.
Solution Approach 2:
The battery employs a composite structure combining liquid electrolyte (with lithium salt and nitrile compound) and solid-state electrolyte. The liquid component provides ionic conductivity and interface wetting, while the solid component provides structural stability and safety, creating a composite system that achieves both low interfacial resistance and high reliability.
2Object-generated harmful factors
If gel polymer electrolytes or ionic liquid electrolytes are used to reduce interfacial resistance, then Li-ion conductivity is improved, but device complexity or cost increases
Solution Approach 1:
The invention changes the chemical composition parameters of the liquid electrolyte by selecting specific lithium salts (LiPF6, LiBF4, LiCF3SO3) and nitrile compounds (acetonitrile, propionitrile, butyronitrile) with specific ratios. This parameter optimization achieves low interfacial resistance and high ionic conductivity while maintaining a simple single-layer configuration, avoiding the complexity of gel polymer or ionic liquid systems.
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
This approach significantly reduces cathode/solid-state electrolyte interfacial resistance to ~130 Ω cm2 at room temperature and maintains ~80% capacity retention for over 400 cycles, offering high ionic conductivity, low cost, non-flammability, and biodegradability.
Implementation Method 1
comprising lithium salts and amide compounds with a molar ratio of 1:1 to 1:50, which form intermolecular hydrogen bonds to maintain a liquid state at room temperature
Data Source
AI summary
A battery includes a substrate; a cathode disposed on the substrate; at least one interlayer disposed on the cathode; a solid-state electrolyte (SSE) disposed on the interlayer; and a lithium anode disposed on the solid-state electrolyte, such that the at least one interlayer is a deep-eutectic-solvent-based (DES) electrolyte.