ALD Metal Oxide Coating for High-Nickel Cathode Surface Stability
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Solution Overview
Problem
High-nickel positive electrode active materials for lithium secondary batteries face issues with surface stability, increased resistance, and lifetime degradation due to side reactions with electrolytes, necessitating a method to enhance surface stability and minimize film resistance.
Innovation Solution
A method involving the preparation of a lithium composite transition metal oxide with a high nickel content, where a thin and uniform metal oxide coating layer is formed using atomic layer deposition (ALD) on the surface, incorporating a moisture absorbent and coating metal precursor to improve reaction yield and suppress interfacial side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content in the lithium composite transition metal oxide is increased to achieve high capacity, then the capacity is improved, but surface stability deteriorates and side reactions with electrolyte increase
Solution Approach 1:
A coating layer comprising aluminum oxide, aluminum hydroxide, or both is formed on the surface of the high-nickel lithium composite transition metal oxide particles. This coating layer acts as an intermediary barrier between the high-nickel active material and the electrolyte, preventing direct contact and suppressing side reactions while maintaining high capacity. The coating layer specifically addresses the surface stability issue without compromising the high nickel content (60 mol% or more) that provides high capacity.
2Reliability
If a coating layer is formed on the surface of high-Ni positive electrode active material to improve surface stability, then surface stability and suppression of side reactions are improved, but film resistance increases
Solution Approach 1:
The coating process parameters are precisely controlled to form a thin coating layer with optimal thickness. By adjusting deposition conditions and controlling the amount of coating material, the layer is made thin enough to minimize film resistance while still providing sufficient coverage to improve surface stability and suppress side reactions. The coating layer thickness is optimized to balance protection and conductivity.
Solution Approach 2:
The coating layer is formed selectively on the surface of the particles rather than throughout the bulk material. This localized coating approach provides surface stability and electrolyte isolation only where needed at the particle surface, while the interior high-nickel material maintains its excellent electrochemical properties and conductivity, minimizing overall resistance.
3Reliability
If a thick coating layer is formed to suppress interfacial side reactions, then side reactions are reduced, but reaction yield decreases due to excessive coating material and increased resistance
Solution Approach 1:
Instead of forming a thick coating layer that would excessively cover the particles and increase resistance, a thin but sufficient coating layer is formed. This partial action approach applies just enough coating material to achieve the necessary surface protection and suppress side reactions, without excessive coating that would reduce reaction yield. The coating is applied uniformly but minimally to achieve the desired effect.
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 approach effectively improves the structural and chemical stability of the high-nickel positive electrode active material, reducing resistance and extending the battery's lifespan by forming a uniform coating layer that minimizes contact with the electrolyte and prevents side reactions.
Implementation Method 1
adding a coating metal precursor into an atomic layer deposition (ALD) reactor, and forming a metal oxide coating layer on surfaces of particles of the lithium composite transition metal oxide by atomic layer deposition (ALD)
Implementation Method 2
adding a moisture absorbent and the lithium composite transition metal oxide into an atomic layer deposition (ALD) reactor
Data Source
AI summary
A method of preparing a positive electrode active material for a secondary battery includes preparing a lithium composite transition metal oxide which includes nickel, cobalt, and manganese and contains 60 mol % or more of the nickel among all metals except lithium, adding a moisture absorbent and the lithium composite transition metal oxide into an atomic layer deposition (ALD) reactor, and adding a coating metal precursor into the atomic layer deposition (ALD) reactor and forming a metal oxide coating layer on surfaces of particles of the lithium composite transition metal oxide by atomic layer deposition (ALD).