Ni-Rich Cathode Material With Co-Rich Shell for Surface Stability
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Solution Overview
Problem
Lithium secondary batteries face issues with operational stability and reliability due to the generation of by-products from side reactions of lithium metal oxide particles when exposed to the atmosphere or electrolyte, leading to reduced lifespan and stability.
Innovation Solution
A cathode active material for lithium secondary batteries is developed, comprising a lithium metal oxide particle with a core part and a shell part, where the shell part has a higher cobalt content than the core part, acting as a surface coating to enhance chemical stability and reduce surface resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal oxide is used as cathode active material to achieve high capacity and high energy density, then the battery performance is improved, but by-products are generated due to side reactions on particle surfaces leading to deteriorated life-span and operational stability
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell part has different composition (higher Co content, lower Ni content) than the core part. This allows the core to provide high capacity while the shell provides stability and protects against side reactions, resolving the contradiction between energy density and operational stability.
Solution Approach 2:
The patent uses composite materials by combining lithium metal oxide particles with a protective shell layer containing different metal ratios. This composite structure maintains the high energy density benefits of lithium metal oxide while adding the stability benefits of the shell material, preventing by-product formation from side reactions.
2Quantity of substance
If high nickel content is used in lithium metal oxide to increase capacity, then the energy density is improved, but chemical stability deteriorates when exposed to atmosphere or electrolyte
Solution Approach 1:
The patent implements local quality by concentrating high nickel content in the core part for maximum capacity while creating a shell part with lower nickel and higher cobalt content for enhanced chemical stability. This spatial distribution of properties allows the particle to simultaneously achieve high capacity and resistance to chemical degradation.
Solution Approach 2:
The shell part acts as an intermediary layer between the high-nickel core and the external environment (atmosphere/electrolyte). This intermediate structure protects the reactive nickel-rich core from direct exposure to degrading conditions while still allowing the core to function at high capacity.
3Reliability
If surface coating is applied to improve chemical stability, then operational stability is enhanced, but surface resistance increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thickness of the shell part (1-10 nm) and the metal ratios within it. By optimizing these parameters, the shell provides sufficient chemical stability to prevent by-product formation while remaining thin enough to minimize surface resistance and maintain good electrical contact.
Solution Approach 2:
The patent uses local quality by creating a shell with specific composition (higher Co, lower Ni) only at the surface region where it is needed for protection, while keeping the bulk core material optimized for electrical conductivity and capacity. This localized modification minimizes the impact on overall surface resistance.
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 cathode active material improves chemical and operational stability by suppressing surface reactions, thereby enhancing capacity and output characteristics while maintaining a uniform crystal structure.
Implementation Method 1
the shell part includes a depth region in a range of 10 to 100 nm from a surface of the lithium metal oxide particle, and a Co content thereof in the depth region is 1.4 to 6 times a Co content of the core part
Implementation Method 2
thereby enhancing capacity and output characteristics while maintaining a uniform crystal structure
Data Source
AI summary
A cathode active material for a lithium secondary battery according to embodiments of the present invention includes a lithium metal oxide particle which includes a core part and a shell part and contains nickel (Ni), cobalt (Co) and manganese (Mn). A total Ni content of the lithium metal oxide particle is 70 mol % or more based on a total 100 mol % of Ni, Co and Mn. The shell part includes a depth region in a range of 10 to 100 nm from a surface of the lithium metal oxide particle, and a Co content thereof in the depth region is 1.4 to 6 times a Co content of the core part. Stability of the lithium secondary battery may be improved through surface treatment using high content of Co.