ALD Metal Oxide Coating for High-Ni 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, side reactions with electrolytes, and increased resistance, which affect battery performance and lifespan.
Innovation Solution
A method involving atomic layer deposition (ALD) to form a thin and uniform metal oxide coating layer on high-Ni lithium composite transition metal oxide particles, using a moisture absorbent to control moisture content and prevent side reactions, thereby enhancing surface stability and reaction yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content in the positive electrode active material is increased to achieve high capacity, then the battery capacity is improved, but surface stability deteriorates and side reactions with electrolyte increase
Solution Approach 1:
A coating layer comprising aluminum oxide (Al2O3) and aluminum hydroxide (Al(OH)3) is formed on the surface of the high-nickel positive electrode active material particles. This coating layer acts as an intermediary barrier between the nickel-rich active material and the electrolyte, preventing direct contact and reducing side reactions while maintaining high capacity. The coating is applied through atomic layer deposition (ALD) to ensure uniform coverage and controlled thickness.
Solution Approach 2:
A thin film coating layer is deposited on the surface of the positive electrode active material particles. The coating layer provides surface protection and stability without significantly increasing particle size or compromising electrochemical performance. The thin film structure allows ionic conductivity while blocking harmful direct reactions between the electrolyte and high-nickel material.
2Reliability
If a coating layer is formed on the positive electrode active material to improve surface stability, then side reactions are suppressed, but film resistance increases
Solution Approach 1:
The thickness and composition of the coating layer are precisely controlled through atomic layer deposition (ALD) parameters. By optimizing deposition conditions, the coating layer achieves the right balance between providing surface protection and maintaining low resistance. The coating comprises a mixture of aluminum oxide and aluminum hydroxide in specific ratios that optimize both protective function and ionic conductivity.
Solution Approach 2:
The coating layer is composed of a composite structure containing both aluminum oxide (Al2O3) and aluminum hydroxide (Al(OH)3). This composite composition provides synergistic effects where aluminum oxide offers chemical stability and aluminum hydroxide contributes to ionic conductivity, thereby reducing film resistance while maintaining surface protection.
3Reliability
If the thickness of the coating layer is increased to improve surface stability, then protection against side reactions is enhanced, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of forming a thick coating layer that would provide excessive protection, a thin but sufficient coating is applied through atomic layer deposition. The ALD process enables precise control of coating thickness at the nanometer scale, achieving the minimum required protection against side reactions without unnecessary material usage or process complexity. The coating thickness is optimized to be just sufficient for protection while minimizing resistance and manufacturing complexity.
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 method improves the structural and chemical stability of high-Ni positive electrode active materials, reduces interfacial side reactions, and minimizes film resistance, leading to enhanced capacity retention and extended battery lifespan.
Implementation Method 1
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
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AI summary
The present invention provides a method of preparing a positive electrode active material for a secondary battery which 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).