Nickel-Rich NCM Cathode Sintering for Stable Single Particles
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Solution Overview
Problem
Nickel-rich NCM-based lithium composite transition metal oxides face challenges in thermal stability and performance deterioration due to increased nickel content, leading to degradation of charge/discharge efficiency and resistance, which conventional methods struggle to address effectively.
Innovation Solution
A method for preparing a nickel-rich NCM-based lithium composite transition metal oxide as a single particle by using a specific combination of firing additives, including a lithium-containing compound, a carbonate ion-containing compound, and a boron-containing compound, at a relatively low firing temperature, minimizing the interface of secondary particles and enhancing control over the over-firing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content is increased to improve capacity, then the capacity increases, but thermal stability degrades and side reactions increase
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high nickel content (0.8-0.95) for high capacity, while the surface region contains nickel-poor spinel phase for thermal stability. This spatial differentiation of composition allows simultaneous achievement of high capacity and thermal stability that cannot be obtained with uniform composition.
Solution Approach 2:
The patent uses composite materials by forming a composite structure consisting of a nickel-rich layered oxide core and a nickel-poor spinel phase shell. The two phases have complementary properties: the layered oxide provides high capacity while the spinel phase provides thermal stability, and their combination creates a material that exhibits both properties simultaneously.
2Manufacturing precision
If the firing temperature is increased to minimize secondary particle interfaces, then the particle interface is reduced, but charge/discharge efficiency degrades and resistance increases
Solution Approach 1:
The patent applies parameter changes by optimizing the firing temperature to a specific range (700-900°C) that is sufficiently high to minimize secondary particle interfaces but not so high as to cause performance degradation. Additionally, the patent changes the chemical composition parameters by controlling the ratio of nickel to other metals (cobalt, manganese) to achieve the desired core-shell structure with appropriate phase formation at this moderate temperature range.
3Reliability
If conventional doping or coating techniques are used to improve thermal stability, then some improvement is achieved, but the improvement is limited
Solution Approach 1:
The patent merges the functions of doping and coating into a single integrated process. Instead of separately doping the material and then coating it, the patent uses a one-step firing process that simultaneously forms both the doped core and the protective spinel shell layer, achieving the benefits of both techniques while simplifying the overall processing.
Solution Approach 2:
The patent applies self-service by allowing the material to self-organize into the desired core-shell structure during the firing process. The nickel-rich layered oxide core spontaneously forms a nickel-poor spinel phase shell on its surface during firing, without requiring separate coating steps. The material essentially self-assembles the protective layer that improves thermal stability.
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
This approach enhances thermal stability, reduces side reactions, and minimizes performance deterioration, such as degradation of charge/discharge efficiency and increased resistance, while maintaining high capacity and nickel content.
Implementation Method 1
performing primary firing
Implementation Method 2
performing over-firing while increasing a firing temperature
Data Source
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AI summary
Provided is a method of preparing a positive electrode active material for a secondary battery, which includes: providing a positive electrode active material precursor containing nickel, cobalt, and manganese and having a nickel content accounting for 60 mol% or more of total metals; and forming a lithium transition metal oxide by mixing the positive electrode active material precursor, a lithium source material, a first firing additive, a second firing additive, and a third firing additive and performing primary firing, wherein the first firing additive is a lithium-containing compound, the second firing additive is a carbonate ion-containing compound, and the third firing additive is a boron-containing compound.