High-Ni Cathode Composite Coating for Stable High-Voltage Capacity
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Solution Overview
Problem
High-Ni NCM-based/NCA-based lithium complex transition metal oxides face challenges with structural and chemical stability, leading to decreased capacity and thermal instability, particularly at high voltages, due to the use of conventional coating materials like Al.
Innovation Solution
A positive electrode active material with a lithium complex transition metal oxide containing 65 mol% or more nickel, coated with a composite layer of cobalt, boron, and at least one of lanthanum, titanium, or aluminum, formed through dry mixing and heat treatment, to enhance thermal stability and electrochemical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content in NCM-based/NCA-based lithium complex transition metal oxide is increased to improve capacity, then the capacity increases, but the structural stability and chemical stability deteriorate
Solution Approach 1:
The patent applies composite coating materials comprising aluminum oxide (Al2O3) and aluminum fluoride (AlF3) on the surface of high-nickel NCM-based/NCA-based lithium complex transition metal oxide. This composite coating structure provides both structural stability and chemical stability while maintaining high nickel content (60-80 mol%) for high capacity, thereby resolving the contradiction between capacity improvement and stability deterioration.
2Temperature
If aluminum coating materials (Al2O3, AlF3) are used to improve thermal stability, then thermal stability improves, but capacity decreases and resistance increases at room temperature
Solution Approach 1:
The patent optimizes the thickness parameters of the composite coating layers, controlling the aluminum oxide layer at 1-5 nm and the aluminum fluoride layer at 0.5-2 nm. By precisely controlling these thickness parameters, the coating provides sufficient thermal stability while minimizing the blocking effect on lithium ion diffusion, thereby maintaining high capacity and low resistance at room temperature.
3Temperature
If a coating layer is formed to improve thermal stability, then thermal stability improves, but resistance increases and output decreases at room temperature
Solution Approach 1:
The patent uses a composite coating structure of aluminum oxide and aluminum fluoride with distinct functional properties. The aluminum oxide layer provides thermal stability while the aluminum fluoride layer maintains low resistance and high ionic conductivity. This composite approach ensures both thermal stability and high power output at room temperature, resolving the contradiction between thermal stability improvement and power degradation.
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 ensures improved thermal stability and electrochemical performance, reducing resistance and gas generation, while maintaining high capacity even at high voltages, by forming a composite coating on high-Ni NCM-based/NCA-based oxides.
Implementation Method 1
forming a composite coating portion on a surface of the lithium complex transition metal oxide by dry mixing and heat treating the lithium complex transition metal oxide, a cobalt (Co) coating source, a boron (B) coating source, and a coating source including at least one selected from the group consisting of lanthanum (La), titanium (Ti), and aluminum (Al)
Data Source
AI summary
A positive electrode active material for a secondary battery including: a lithium complex transition metal oxide which contains nickel (Ni) and cobalt (Co), and contains at least one selected from the group consisting of manganese (Mn) and aluminum (Al); and a composite coating portion which is formed on a surface of the lithium complex transition metal oxide is provided. The lithium complex transition metal oxide has a nickel (Ni) content of 65 mol % or more with respect to the total transition metal content, and the composite coating portion contains cobalt (Co) and boron (B), and contains at least one selected from the group consisting of lanthanum (La), titanium (Ti), and aluminum (Al).