Lithium-Phosphate-Coated LLZO Electrolyte for Lower Resistance
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Solution Overview
Problem
Conventional liquid electrolytes are volatile, prone to leakage, and unstable at high temperatures, while solid electrolytes have high electrical resistance, limiting their ion conductivity in batteries.
Innovation Solution
A composite solid electrolyte comprising lithium lanthanum zirconium oxide particles with a protective layer of lithium phosphate, and optionally a fluorine-containing colloid, to enhance ion conductivity and mechanical strength while reducing electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid electrolyte is used to replace liquid electrolyte, then stability is improved, but electrical resistance increases
Solution Approach 1:
The patent uses a composite structure consisting of lithium lanthanum zirconium oxide particles (LLZO) as the solid electrolyte base and lithium phosphate as a protective coating layer. This composite approach combines the high stability of solid electrolytes with the beneficial surface properties of lithium phosphate, reducing interfacial resistance while maintaining the inherent stability advantages of solid-state materials.
Solution Approach 2:
The protective layer of lithium phosphate is applied specifically on the surface of the LLZO particles rather than throughout the entire material. This local modification addresses the interfacial resistance issue at the particle surface while preserving the bulk properties of the solid electrolyte, including its high stability and low electrical resistance characteristics.
2Reliability
If protective layer is added to solid electrolyte particle, then ion conductivity is improved, but manufacturing complexity increases
Solution Approach 1:
The lithium phosphate protective layer is formed on the LLZO particle surfaces during the sintering process itself, rather than requiring a separate coating step. The precursor materials are mixed with the LLZO powder before sintering, allowing the protective layer to form in-situ during the standard solid electrolyte manufacturing process, thereby avoiding additional manufacturing complexity.
Solution Approach 2:
The formation of the protective layer is merged with the sintering process of the solid electrolyte. By incorporating lithium phosphate precursor into the particle mixture before sintering, the protective layer formation and the electrolyte densification occur simultaneously in the same thermal processing step, reducing the number of separate manufacturing operations required.
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 composite solid electrolyte achieves high ion conductivity, mechanical strength, and stability with reduced electrical resistance, maintaining performance over long-term use and increasing battery cycle numbers.
Implementation Method 1
The lithium lanthanum zirconium oxide particle is mixed with phosphoric acid to form a protective layer containing lithium phosphate covering an outer surface of the lithium lanthanum zirconium oxide particle by an acid-base reaction
Implementation Method 2
the solid electrolyte may have a higher electrical resistance, making the solid electrolyte used in the battery have poor ion conductivity
Data Source
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AI summary
The present disclosure provides a composite solid electrolyte. The composite solid electrolyte includes a lithium lanthanum zirconium oxide particle and a protective layer containing lithium phosphate. An average particle size of the lithium lanthanum zirconium oxide particle is smaller than 500 nm and larger than 50 nm. The protective layer containing lithium phosphate covers an outer surface of the lithium lanthanum zirconium oxide particle.