Core-Shell NCM Positive Electrode Active Material for Secondary Battery
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Solution Overview
Problem
Conventional NCM-based lithium composite transition metal oxide positive electrode active materials face limitations due to high specific surface area, low particle strength, excessive lithium by-product, and poor thermal and structural stability, particularly in high-Ni compositions, which affect the performance and safety of lithium secondary batteries.
Innovation Solution
A method involving the preparation of NCM-based lithium composite transition metal oxide particles with a core-shell structure, where the core has a layered crystal structure and the shell has a cubic rock-salt structure, achieved through specific sintering temperatures and processes to reduce surface area and enhance particle strength, thereby reducing side reactions and improving thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional NCM-based lithium composite transition metal oxide is used with high nickel content to secure high capacity, then capacity is improved, but structural and chemical stabilities are reduced and thermal stability becomes difficult to secure
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high nickel content (0.6-0.8 mol fraction) for high capacity, while the shell region contains lower nickel content (0.3-0.5 mol fraction) for structural stability. This spatial differentiation of composition allows simultaneous achievement of high capacity and structural/chemical stability that cannot be obtained with uniform composition.
2Quantity of substance
If conventional NCM-based lithium composite transition metal oxide is used with high nickel content, then capacity is improved, but thermal stability is difficult to secure
Solution Approach 1:
The patent creates a compositional gradient where the shell region has lower nickel content (0.3-0.5 mol fraction) compared to the core (0.6-0.8 mol fraction). Since nickel content correlates with thermal instability, the low-nickel shell provides thermal stability while the high-nickel core delivers high capacity, resolving the contradiction between capacity and thermal stability.
3Quantity of substance
If NCM-based lithium composite transition metal oxide is used, then high capacity is achieved, but specific surface area is large and particle strength is low, resulting in poor stability
Solution Approach 1:
The patent creates a compositional gradient from core to shell, with nickel content decreasing from 0.6-0.8 in the core to 0.3-0.5 in the shell. This local quality variation provides high capacity from the high-nickel core while the low-nickel shell provides structural integrity and reduced specific surface area effects, improving overall stability.
Solution Approach 2:
The patent creates a composite material structure with distinct core and shell regions having different compositions. The core-shell composite architecture combines the high capacity characteristics of high-nickel NCM with the structural stability of low-nickel NCM, achieving both high capacity and improved stability simultaneously.
4Quantity of substance
If conventional NCM-based lithium composite transition metal oxide is used, then capacity is achieved, but amount of lithium by-product is large, causing increased resistance and side reactions with electrolyte solution
Solution Approach 1:
The patent reduces lithium by-product formation by creating a low-nickel shell region (0.3-0.5 mol fraction Ni) that is less prone to generating lithium by-products during electrochemical cycling. The shell protects the high-nickel core from excessive side reactions, allowing high capacity utilization while minimizing harmful lithium by-product generation.
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 results in reduced gas generation, suppressed resistance increase, and enhanced thermal stability, making the NCM-based positive electrode active material suitable for high-voltage lithium secondary batteries with improved stability and performance.
Implementation Method 1
performing primary sintering on the mixture at a sintering temperature of 980°C or more to form a primary sintered product; and performing secondary sintering on the primary sintered product at a sintering temperature of 900°C or less to form a lithium composite transition metal oxide
Data Source
AI summary
A positive electrode active material for a secondary battery is provided, which includes a lithium composite transition metal oxide including nickel (Ni), cobalt (Co), and manganese (Mn), wherein a particle of the lithium composite transition metal oxide includes a core portion and a resistance portion formed on a surface of the core portion, and is composed of a single particle, wherein the core portion has a layered crystal structure of space group R-3m, and the resistance portion has a cubic rock-salt structure of space group Fm-3m.