LiMSO4F Cathode Coating for Deliquescence Control
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Solution Overview
Problem
Lithium ion secondary battery positive electrode materials with high energy density are prone to deliquescence due to moisture, leading to degraded performance and reduced operational potential.
Innovation Solution
A positive electrode active material with a coating layer containing LiM′PO4, where M′ is Fe, Mn, or Co, is applied to LiMSO4F particles, suppressing deliquescence and maintaining high operational potential by controlling the coating layer's mass percentage and thickness, thereby enhancing charge and discharge cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Li(Fe, Mn)SO4F with high operation potential is used to achieve higher energy density, then energy density is improved, but deliquescence occurs due to moisture leading to degraded properties
Solution Approach 1:
A coating layer comprising LiFePO4 or LiMnPO4 is applied on the surface of Li(Fe, Mn)SO4F particles. This coating layer acts as an intermediary barrier that prevents direct contact between the high-potential Li(Fe, Mn)SO4F and moisture, thereby suppressing deliquescence while maintaining the high operation potential and energy density benefits
Solution Approach 2:
The positive electrode active material is designed as a composite structure combining Li(Fe, Mn)SO4F core particles with a LiFePO4 or LiMnPO4 coating layer. This composite material approach allows the inner core to provide high operation potential for energy density while the outer coating provides moisture resistance, resolving the contradiction between energy density improvement and reliability maintenance
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 solution effectively prevents deliquescence, improves energy density, and maintains high operational potential, resulting in enhanced charge and discharge cycle performance of nonaqueous electrolyte batteries.
Implementation Method 1
These positive electrode materials, however, have a high deliquescence, and thus have a defect in which their properties are degraded due to moisture in the air in production of a battery, or moisture generated inside a battery
Data Source
AI summary
According to one embodiment, a positive electrode active material includes particles and a coating layer. The particles includes a first compound represented by the general formula LiMSO4F wherein M is at least one element selected from the group consisting of Fe, Mn, and Zn. The coating layer coats at least one part of surfaces of the particles. The coating layer includes a second compound represented by the general formula LiM′PO4 wherein M′ is at least one element selected from the group consisting of Fe, Mn, Co, and Mg.