Buffer-Layer Cathode Material for Stable Sulfide Solid Electrolytes
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Solution Overview
Problem
Sulfide solid electrolytes in all-solid-state batteries face performance deterioration due to side reactions with the cathode, leading to increased interfacial resistance.
Innovation Solution
A composite cathode active material is developed with a secondary particle structure containing a nickel lithium transition metal oxide and a buffer layer of metal oxide, which includes a metal oxide with a different crystal structure, forming a conformal coating to reduce side reactions and enhance stability at high voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a sulfide solid electrolyte is used in an all-solid-state battery, then high energy density is achieved, but side reactions with the cathode occur leading to increased interfacial resistance
Solution Approach 1:
A buffer layer comprising a metal oxide (such as TiO2, ZrO2, HfO2, Nb2O5, Ta2O5, WO3, MoO3, or their mixtures) is introduced as an intermediary between the cathode active material and the sulfide solid electrolyte. This buffer layer acts as a mediator that prevents direct contact and harmful side reactions between the cathode and electrolyte, thereby reducing interfacial resistance while allowing the sulfide solid electrolyte to maintain its high energy density benefits.
Solution Approach 2:
The invention creates a composite structure consisting of three components: cathode active material, buffer layer, and sulfide solid electrolyte. This composite architecture combines the high energy density advantage of sulfide solid electrolytes with the chemical stability of metal oxide buffer layers, resolving the contradiction between energy density and interfacial stability.
2Use of energy by moving object
If the cathode operates at high voltages, then energy density is improved, but stability and reaction stability with the sulfide solid electrolyte deteriorate
Solution Approach 1:
The buffer layer serves as a protective intermediary that shields the sulfide solid electrolyte from high-voltage stress and chemical reactions with the cathode material. By positioning this chemically stable metal oxide layer between the cathode and electrolyte, the system can operate at high voltages necessary for high energy density while the buffer layer maintains compositional stability and prevents degradation.
Data Source
AI summary
A composite cathode active material, a preparation method thereof, a cathode layer for an all-solid-state battery, and an all-solid-state battery including the cathode layer, the composite cathode active material for the all-solid-state battery including a secondary particle including a plurality of primary particles; and a buffer layer on a surface of the secondary particle, wherein the secondary particle includes a nickel lithium transition metal oxide represented by Formula 1, and the buffer layer includes a metal oxide represented by Formula 2,LiaNi1-bMbO2 Formula 1LixAy-1Ey2Oz. Formula 2