Cathode Coating for Solid-State Batteries With Low Interfacial Resistance
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Solution Overview
Problem
Conventional layered positive electrode active materials for all-solid-state batteries react with sulfide-based solid electrolytes, forming high-resistance interfacial layers that deteriorate battery capacity and cycle life due to lithium depletion and side reactions.
Innovation Solution
A positive electrode active material with a thin and uniformly formed lithium zirconium composite oxide coating layer on the surface of a lithium nickel-based transition metal oxide, controlled through precise coating methods to suppress high-resistance layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional layered positive electrode active material (high nickel content) is used, then high capacity is achieved, but a high-resistance interfacial layer forms with sulfide-based solid electrolyte, deteriorating cycle life
Solution Approach 1:
A lithium zirconium composite oxide coating layer is introduced as an intermediary between the high-nickel layered positive electrode active material and the sulfide-based solid electrolyte. This coating layer prevents direct harmful reactions between the active material and electrolyte, reducing interfacial resistance and improving cycle life while maintaining high capacity.
Solution Approach 2:
The patent uses a composite material structure consisting of a layered lithium nickel-based transition metal oxide core combined with a lithium zirconium composite oxide coating shell. This composite structure combines the high capacity characteristics of high-nickel materials with the protective and conductive properties of the lithium zirconium oxide coating.
2Reliability
If a coating layer is formed on the positive electrode active material to prevent reaction with solid electrolyte, then cycle life is improved, but coating thickness must be precisely controlled to avoid increasing interfacial resistance
Solution Approach 1:
The patent optimizes specific parameters including the molar ratio of lithium to zirconium (1:1 to 1:3), coating layer thickness (1-10 nm), and heat treatment temperature (400-600°C) to achieve the desired coating properties. By precisely controlling these parameters, the coating provides protection without significantly increasing interfacial resistance.
Solution Approach 2:
The coating layer is applied with a thickness that is sufficient to prevent direct contact between the active material and electrolyte (excessive action for protection), but controlled to remain thin (1-10 nm) to minimize resistance increase. This partial application ensures adequate protection while maintaining good ionic conductivity.
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 coating layer improves battery capacity and cycle life characteristics by reducing interfacial resistance and preventing the formation of high-resistance layers.
Implementation Method 1
The coating layer improves battery capacity and cycle life characteristics by reducing interfacial resistance and preventing the formation of high-resistance layers
Data Source
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AI summary
The present invention relates to a positive electrode active material for an all-solid-state battery, comprising a layered lithium nickel-based transition metal oxide and a coating layer disposed on a surface of the lithium nickel-based transition metal oxide, wherein the coating layer comprises a lithium zirconium composite oxide and is formed to have a uniform thickness of 5 nm or less over the entire surface of the lithium nickel-based transition metal oxide.