LiF-Gradient Composite Solid Electrolyte for Low-Resistance Cathode Interfaces
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Solution Overview
Problem
Secondary batteries face challenges with increased interfacial resistance between the cathode and solid electrolytes, leading to reduced stability and performance.
Innovation Solution
A composite solid electrolyte with a first region of oxide solid electrolyte and a second region of LiF, where the LiF content at the surface side is less than at the interface, creating a gradient that reduces interfacial resistance and suppresses lithium dendrite growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte is used to improve stability, then the stability is improved, but the interfacial resistance between cathode and solid electrolyte increases
Solution Approach 1:
The patent employs a composite solid electrolyte consisting of a first region (oxide solid electrolyte) and a second region (LiF-containing layer) with a gradient LiF content. This composite structure combines the stability benefits of oxide solid electrolytes with the low interfacial resistance properties of LiF, resolving the contradiction between stability and interfacial resistance
Solution Approach 2:
The second region features a gradient distribution of LiF content, with higher concentration at the interface with the first region and lower concentration toward the surface. This local variation in composition optimizes both stability (through the oxide-rich first region) and interfacial resistance (through the LiF-rich interface zone), applying the local quality principle to address different functional requirements at different locations
Data Source
AI summary
A composite solid electrolyte and a secondary battery including the same, wherein the composite solid electrolyte includes a first region, and a second region covering at least a portion of the first region. The first region includes an oxide solid electrolyte, the second region includes LiF, and in the second region, a content of the LiF at a surface side of the composite solid electrolyte is less than a content of the LiF at an interface side between the first region and the second region. When a depth profile of the composite solid electrolyte is analyzed by X-ray photoelectron spectroscopy, the second region includes a 2-1 region having a content of the LiF of about 23 atomic percent to about 40 atomic percent based on a total 100 atomic percent of the 2-1 region.