Cathode Active Material Coating for Capacity Retention Stability
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Solution Overview
Problem
Lithium-transition metal composite oxides used as cathode active materials in lithium secondary batteries suffer from non-uniform chemical structures due to lithium precipitation, leading to deteriorated life-span stability and capacity retention, especially during repeated charging and discharging.
Innovation Solution
A coating comprising a lithium-sulfur compound and a metal hydroxide is applied to lithium-transition metal composite oxide particles, with the metal hydroxide having a higher binding energy than the metal oxide, to stabilize the structure and enhance ion conductivity, thereby improving battery life-span and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium-transition metal composite oxide is used as cathode active material, then high operational voltage and energy density are achieved, but non-uniform chemical structure due to lithium precipitation occurs leading to deteriorated life-span stability and capacity retention
Solution Approach 1:
A coating layer comprising metal hydroxide and lithium-sulfur compound is introduced as an intermediary between the lithium-transition metal composite oxide particles and the electrolyte. This coating layer mediates the interaction by preventing direct contact and harmful reactions at the particle surface, thereby maintaining structural uniformity and improving life-span stability while preserving the high energy density of the bulk material.
Solution Approach 2:
The surface chemistry parameters of the cathode active material are changed by forming a coating layer with specific composition (metal hydroxide and lithium-sulfur compound). This parameter change at the surface level prevents lithium precipitation and maintains chemical structure uniformity, allowing the bulk material to retain its high energy density characteristics.
2Quantity of substance
If lithium-transition metal composite oxide structure is deformed or damaged during repeated charging and discharging, then capacity is improved, but life-span stability and capacity retention are deteriorated
Solution Approach 1:
The coating layer of metal hydroxide and lithium-sulfur compound serves as a protective cushion applied beforehand to the surface of lithium-transition metal composite oxide particles. This pre-applied protective layer cushions against structural deformation and damage during repeated charging and discharging cycles, preserving both capacity and life-span by preventing harmful surface reactions and structural collapse.
3Reliability
If coating includes sulfur and metal hydroxide, then ion conductivity is enhanced and life-span is improved, but manufacturing complexity increases
Solution Approach 1:
The coating layer's composition parameters are optimized by controlling the ratio of metal hydroxide to lithium-sulfur compound and adjusting the thickness of the coating. By carefully controlling these parameters, the coating provides enhanced ion conductivity and improved life-span while minimizing manufacturing complexity. The specific composition range is designed to achieve maximum benefit with minimal processing steps.
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 effectively reduces residual lithium, prevents structural deformation, and enhances ion conductivity, resulting in improved life-span and capacity retention of lithium secondary batteries.
Implementation Method 1
a coating that includes a lithium-sulfur compound and a metal hydroxide... enhances ion conductivity
Implementation Method 2
A calcination of the mixture is performed to form a coating that includes a lithium-sulfur compound and a metal hydroxide on the surface of the lithium-transition metal composite oxide particles
Data Source
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AI summary
Embodiments of the present invention provide a cathode active material for a lithium secondary battery. The cathode active material for a lithium secondary battery includes lithium-transition metal composite oxide particles, and a coating formed on each of the lithium-transition metal composite oxide particles. The coating includes a lithium-sulfur compound and a metal hydroxide. A residual lithium on a surface of the cathode active material is sufficiently removed to improve an ionic conductivity and low-resistance.