Li-M-O Coated Positive Electrode Active Material for All-Solid-State Batteries
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Solution Overview
Problem
Conventional lithium secondary batteries using sulfide-based solid electrolytes face high interfacial resistance at the interface of the positive electrode active material and the solid electrolyte due to space charge layer formation and interfacial impurity layers, which hinder capacity utilization and safety.
Innovation Solution
A positive electrode active material for all-solid-state batteries is developed, comprising a lithium metal oxide core coated with a compound represented by Formula 1 (Li 3+x Al [1-(1/3)x-y] Ga y F 6) or Formula 2 (Li 3+z Ga [1-(1/3)z] F 6), which reduces interfacial resistance by preventing direct contact and enhancing lithium ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfide-based solid electrolyte is used to replace liquid electrolyte, then safety is improved, but interfacial resistance at the positive electrode interface increases
Solution Approach 1:
A coating layer comprising Li-M-O (where M is B, Al, Zr, P, Ti, Nb, or W) is introduced at the interface between the positive electrode active material and the sulfide-based solid electrolyte. This intermediary coating layer prevents direct contact between the two materials, reducing interfacial resistance caused by space charge layer formation and chemical reactions, while maintaining the safety benefits of the solid electrolyte.
Solution Approach 2:
The positive electrode structure is designed as a composite system with three components: the positive electrode active material, the coating layer comprising Li-M-O, and the sulfide-based solid electrolyte. This composite structure combines the high voltage characteristics of the positive electrode material with the low interfacial resistance of the coating layer and the high safety of the solid electrolyte.
2Productivity
If coating layer of Li-M-O is introduced to reduce interfacial resistance, then capacity utilization is improved, but manufacturing complexity increases
Solution Approach 1:
The coating layer of Li-M-O is formed on the surface of the positive electrode active material before assembling the battery. This preliminary coating action prevents interfacial reactions during battery operation, ensuring high capacity utilization from the first cycle without requiring complex post-processing steps.
Solution Approach 2:
The coating layer composition is optimized by selecting specific metals (B, Al, Zr, P, Ti, Nb, or W) and controlling their ratios to achieve the desired balance between reducing interfacial resistance and maintaining manufacturability. The coating thickness and composition parameters are tuned to maximize capacity utilization while keeping the manufacturing process feasible.
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 coated positive electrode active material reduces interfacial resistance, improving the lifetime characteristics and discharge capacity of all-solid-state batteries.
Implementation Method 1
a coating portion located on a surface of the core portion and comprising a compound represented by Formula 1 or 2
Implementation Method 2
reduces the interfacial resistance between the positive electrode active material and the solid electrolyte
Data Source
AI summary
The present invention relates to a positive electrode active material for an all-solid-state battery, a method of preparing same, and a positive electrode for an all-solid-state battery and an all-solid-state battery comprising same.