Single-Particle High-Ni NCM Cathode for Low Gas Generation
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Solution Overview
Problem
High-Ni NCM-based lithium composite transition metal oxide positive electrode active materials face challenges with low structural and chemical stability, high specific surface area, particle breakage, and excessive lithium by-product generation, limiting their use in high-capacity lithium secondary batteries.
Innovation Solution
A method to produce a high-Ni NCM-based lithium composite transition metal oxide with a single particle structure, comprising nickel, cobalt, and manganese, involving pre-sintering and secondary sintering processes to reduce specific surface area and enhance particle strength, while maintaining high manganese content and low cobalt content, resulting in improved thermal stability and reduced gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-Ni NCM-based lithium composite transition metal oxide is used to achieve high capacity, then capacity characteristics are improved, but structural and chemical stability deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the particle interior maintains high Ni content (65-95 mol%) for high capacity, while the particle surface has a different composition with lower Ni content and higher Co content (5-30 mol% Co) for improved stability. This spatial differentiation of composition allows simultaneous optimization of capacity (core) and stability (surface).
Solution Approach 2:
The patent creates a composite particle structure consisting of a core region (high-Ni NCM) and a shell region (modified NCM with lower Ni, higher Co). This composite structure combines the high capacity advantage of high-Ni materials with the stability advantage of lower-Ni, higher-Co materials, resolving the contradiction between capacity and stability.
2Ease of manufacture
If conventional NCM-based lithium composite transition metal oxide in secondary particle form is used, then manufacturing is easier, but specific surface area increases and particle strength decreases
Solution Approach 1:
The patent segments the particle structure into primary particles (5-20 μm) that are sintered to form secondary particles (10-50 μm). This segmentation allows control of specific surface area through primary particle size while maintaining manufacturability through the secondary particle aggregation structure. The controlled segmentation reduces excessive surface area compared to fully fine-particle structures.
3Device complexity
If conventional NCM-based lithium composite transition metal oxide is used, then production process is simpler, but particle strength is low and lithium by-product increases
Solution Approach 1:
The patent applies preliminary action by performing a pre-sintering step before the main sintering process. The pre-sintering (first sintering at 800-900°C for 5-10 hours) preliminarily forms the particle structure and strengthens the particles before the final sintering with Li source. This preliminary structural development improves particle strength and reduces lithium by-product formation during the main sintering, while adding only one process step.
4Quantity of substance
If high-Ni NCM-based lithium composite transition metal oxide is used, then capacity is high, but thermal stability deteriorates and gas generation increases
Solution Approach 1:
The patent applies local quality by concentrating the high-Ni content (65-95 mol% Ni) in the particle core where it provides high capacity, while the particle surface has lower Ni content (5-35 mol% Ni) and higher Co content (5-30 mol% Co) that provides thermal stability. This spatial separation allows the core to deliver high capacity while the surface protects against thermal degradation and gas generation.
Solution Approach 2:
The patent uses Co as a protective shell material that sacrificially stabilizes the particle surface. The higher Co content at the surface (5-30 mol% Co) creates a more thermally stable phase that protects the high-Ni core from thermal degradation and electrolyte reaction, reducing gas generation. The Co-rich surface acts as a protective barrier that can be consumed or modified without compromising the high-Ni core's capacity.
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 effectively reduces side reactions with the electrolyte, enhances particle strength, and secures thermal stability, enabling high-capacity performance while minimizing gas generation and lithium by-products, thus addressing the stability and performance limitations of high-Ni NCM-based materials.
Implementation Method 1
pre-sintering and secondary sintering processes
Implementation Method 2
pre-sintering and secondary sintering processes
Data Source
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AI summary
The present invention relates to a positive electrode active material for a secondary battery which is a lithium composite transition metal oxide including nickel (Ni), cobalt (Co), and manganese (Mn), wherein the lithium composite transition metal oxide includes the nickel (Ni) in an amount of 65 mol% or more and the manganese (Mn) in an amount of 5 mol% or more based on a total amount of transition metals, and wherein the electrode positive active material is composed of a single particle, and has a crystallite size of 180 nm or more.