Buffered Nickel Cathode Material for Sulfide Solid-State Interfaces
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Solution Overview
Problem
Lithium secondary batteries using liquid electrolytes are prone to ignition when exposed to moisture, posing safety risks, especially with the increasing use of electric vehicles, and all-solid-state batteries using solid electrolytes are needed to enhance safety.
Innovation Solution
A positive active material for all-solid secondary batteries is developed, comprising a nickel lithium transition metal oxide with a copper compound buffer layer to minimize side reactions with sulfide electrolytes, improving chemical resistance and lithium ion transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liquid electrolyte is used in lithium secondary batteries, then lithium ion conduction is efficient, but safety deteriorates due to ignition risk when exposed to moisture
Solution Approach 1:
The patent changes the physical state parameter of the electrolyte from liquid to solid, specifically using a sulfide-based solid electrolyte. This fundamental parameter change eliminates the ignition risk associated with liquid electrolytes while maintaining lithium ion conduction capability, directly resolving the safety contradiction.
Solution Approach 2:
The patent employs a composite structure consisting of a sulfide solid electrolyte combined with a buffer layer containing copper compound and halogen. This composite material approach enhances the chemical resistance and interfacial stability between the positive active material and electrolyte, further improving safety and performance simultaneously.
2Reliability
If a sulfide solid electrolyte is used in all-solid secondary batteries, then safety is improved, but side reactions occur at the interface with positive active material
Solution Approach 1:
The patent introduces a buffer layer as an intermediary substance between the sulfide solid electrolyte and the positive active material. This buffer layer, containing copper compound and halogen, mediates the interface interactions, preventing direct harmful reactions while allowing efficient lithium ion transfer, thus resolving the chemical resistance issue.
Solution Approach 2:
The buffer layer itself is a composite material combining copper compound and halogen elements. This composite structure provides both chemical stability to prevent side reactions and adequate ionic conductivity to maintain battery performance, solving the contradiction between safety and chemical resistance.
3Reliability
If the interface between positive active material and solid electrolyte is optimized, then lithium ion conduction is improved, but manufacturing complexity increases
Solution Approach 1:
The buffer layer is incorporated during the battery manufacturing process itself, rather than requiring separate post-processing steps. The preliminary inclusion of the buffer layer in the manufacturing process simplifies production while ensuring optimal lithium ion conduction at the interface from the outset.
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 buffer layer enhances the stability and longevity of all-solid secondary batteries by reducing interfacial resistance and maintaining efficient lithium ion conduction, thereby improving safety and performance.
Implementation Method 1
maintaining efficient lithium ion conduction
Implementation Method 2
minimize side reactions with sulfide electrolytes, improving chemical resistance
Data Source
AI summary
A positive active material for an all-solid secondary battery, an all-solid secondary battery including the same, and a method of manufacturing the positive active material for an all-solid secondary battery, the positive active material 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, the buffer layer includes a copper compound represented by Formula 2,LiaNibM1cO2-eAe <Formula 1>LixCuyXz. <Formula 2>