Copper-Buffered Cathode Material for Sulfide Solid-State Batteries
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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 in electric vehicles, and all-solid-state batteries with inorganic solid electrolytes are needed to enhance safety.
Innovation Solution
A positive active material for all-solid secondary batteries is developed, comprising secondary particles with a nickel lithium transition metal oxide core and a copper compound buffer layer, which minimizes side reactions with sulfide electrolytes, improving chemical resistance and lithium ion transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sulfide solid electrolyte is used in an all-solid-state battery, then safety is improved by eliminating combustible organic electrolytes, but high reactivity between the sulfide solid electrolyte and positive active materials causes irreversible lithium loss and reduced long-life characteristics
Solution Approach 1:
A buffer layer comprising a copper compound is introduced as an intermediary between the sulfide solid electrolyte and the positive active material. This buffer layer mediates the interaction between the two materials, preventing direct harmful reactions while maintaining ionic conductivity, thereby resolving the contradiction between safety and long-life characteristics.
Solution Approach 2:
The buffer layer is applied in advance to the surface of the positive active material before contact with the sulfide solid electrolyte. This preliminary protective action prevents irreversible lithium loss and degradation at the interface, ensuring stable long-term performance while maintaining the safety benefits of the sulfide electrolyte.
2Productivity
If the reactivity between sulfide solid electrolyte and positive active material is increased, then charge/discharge rate may be improved, but irreversible lithium loss increases and chemical resistance decreases
Solution Approach 1:
The copper compound buffer layer serves as a mediator that facilitates controlled lithium ion transfer between the positive active material and sulfide solid electrolyte. This intermediary structure enables high charge/discharge rates through efficient ionic conductivity while simultaneously preventing excessive reactivity that would cause irreversible lithium loss.
Solution Approach 2:
The buffer layer modifies the interfacial properties between the positive active material and sulfide solid electrolyte, changing parameters such as chemical resistance and ionic conductivity. By optimizing the composition and structure of the buffer layer, the system achieves both high charge/discharge rates and minimal lithium loss through controlled parameter adjustments.
3Reliability
If a buffer layer is applied to the surface of the positive active material, then chemical resistance and lifetime are improved, but device complexity increases
Solution Approach 1:
The buffer layer is applied locally only at the critical interface between the positive active material and sulfide solid electrolyte, rather than throughout the entire battery structure. This localized approach provides the necessary chemical resistance and protection precisely where needed, minimizing the increase in overall device complexity while maximizing reliability benefits.
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
facilitating efficient lithium ion transfer and charge/discharge processes
Implementation Method 2
the copper compound is applied as a surface protection layer to control reactivity and improve chemical resistance
Data Source
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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, <Formula 1> LiaNibrv11c()2-eAe < Formula 2 > LixCuyXz.