Lithium-Rich Layered Cathode with Ni-Co-Mn Gradient Shell
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-nickel-manganese-cobalt oxide cathode active materials in secondary batteries face issues with rate capability, cycle life, and voltage decay due to phase transitions during life cycling, which hinder their practical application in high-energy storage systems.
Innovation Solution
A cathode active material with a layered structure of overlithiated oxide, featuring a core-shell structure with concentration gradients of nickel, cobalt, and manganese, which suppresses phase transitions and enhances lithium ion mobility and structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If overlithiated layered oxide is applied to increase reversible capacity, then charge/discharge capacity is improved, but phase transition occurs during life cycling causing voltage decay and reduced cycle life
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell has a different composition (enriched in Ni and Co, depleted in Mn) compared to the core. This compositional gradient locally modifies the surface properties to suppress phase transition while maintaining the high capacity characteristics of overlithiated oxide in the bulk material.
Solution Approach 2:
The patent employs composite materials by combining overlithiated layered oxide with a specifically designed shell layer. The shell contains a concentration gradient of transition metals (Ni, Co, Mn) that creates a composite structure resistant to phase transition, while the core maintains high reversible capacity.
2Ease of manufacture
If conventional Li(NixCoyMnz)O2 is used to reduce cost, then manufacturing cost is reduced, but rate capability and high-temperature cycle life are poor
Solution Approach 1:
The patent uses local quality by concentrating Ni and Co elements in the shell region while keeping the core composition optimized for cost. This localized enrichment improves rate capability and high-temperature performance without requiring high Co content throughout the entire material, thus maintaining cost-effectiveness.
Solution Approach 2:
The patent applies parameter changes by modifying the compositional parameters (NCM/M ratio) in the shell region. The shell has a higher Ni and Co content compared to the core, creating a gradient that enhances electrochemical performance parameters such as rate capability and stability without uniformly increasing material cost.
3Duration of action of stationary object
If phase transition is suppressed to extend cycle life, then durability is improved, but lithium ion mobility may be affected
Solution Approach 1:
The patent applies local quality by confining the phase-transition-suppressing shell structure to the particle surface, while the bulk core maintains the overlithiated layered oxide structure that provides high lithium ion mobility. This localized approach protects against degradation without impeding ion transport in the interior.
Solution Approach 2:
The patent uses segmentation by dividing the particle into core and shell regions with different functions. The core is optimized for lithium ion mobility and capacity, while the shell is optimized for structural stability and phase transition suppression, allowing both requirements to be satisfied simultaneously.
Data Source
AI summary
A cathode active material for a lithium secondary battery, according to an embodiment of the present invention, comprises a lithium composite oxide comprising a lithium-rich layered oxide, which is represented by the following chemical formula 1, wherein the lithium composite oxide comprises secondary particles, each of the secondary particles comprises one or more primary particles, each of the primary particles comprises one or more crystallites, at least any one selected from among the secondary particles, the primary particles and the crystallites comprises a core and a shell, which occupies a part of the surface of the core, and, when the mole of at least any one element selected from among nickel (Ni), cobalt (Co) and manganese (Mn) to the total mole of M1 and M2 in the following chemical formula 1 are NCM/M, the NCM/M of the shell and the core in the secondary particles are different from each other. [Chemical formula 1] rLi2M1O3·(1−r)LiaM2O2