Ni-Rich NMC Cathode Gradient Structure for Capacity and Thermal Stability
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Solution Overview
Problem
Ni-rich lithium nickel manganese cobalt oxide (NMC) positive electrode active materials in lithium-ion batteries face instability due to high nickel content, leading to degradation and increased production costs, and they have lower thermal stability and first cycle efficiency compared to traditional lithium cobalt oxide (LCO) materials.
Innovation Solution
A Ni-rich NMC positive electrode active material with a concentration gradient of nickel and cobalt from the edge to the center of secondary particles, where the nickel content at the edge is lower and cobalt content is higher, is developed, along with a specific composition range and crystallite size to enhance stability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content is used in NMC to increase reversible capacity, then capacity is improved, but thermal stability and structural integrity deteriorate
Solution Approach 1:
The patent applies local quality by creating a concentration gradient within the particle structure, where the nickel content varies from the core to the surface. The core region has high nickel content (0.7-0.8 mol) to provide high reversible capacity, while the surface region has lower nickel content (0.5-0.6 mol) to maintain thermal stability and structural integrity. This spatial variation in composition allows simultaneous optimization of both capacity and stability.
2Ease of manufacture
If high nickel content is used in NMC to reduce production cost, then cost is reduced, but particle stability and resistance to degradation deteriorate
Solution Approach 1:
The patent implements local quality by establishing a nickel concentration gradient where the core maintains high nickel content (0.7-0.8 mol) for cost-effectiveness while the surface has reduced nickel content (0.5-0.6 mol) for enhanced particle stability. This gradient structure prevents particle cracks and degradation during charge-discharge cycles, thereby improving reliability without sacrificing the cost benefits of high nickel content.
3Quantity of substance
If high nickel content is used in NMC to achieve higher capacity, then capacity is improved, but first cycle efficiency deteriorates
Solution Approach 1:
The patent applies local quality by creating a nickel concentration gradient where the core has high nickel content (0.7-0.8 mol) to provide high reversible capacity while the surface has lower nickel content (0.5-0.6 mol) to improve first cycle efficiency. The reduced nickel content at the surface minimizes polarization effects and improves kinetic performance, thereby reducing energy loss during the first charge-discharge cycles.
4Ease of manufacture
If high nickel content is used in NMC to reduce dependency on cobalt, then cost is reduced, but air atmosphere stability deteriorates
Solution Approach 1:
The patent implements local quality by establishing a nickel concentration gradient where the core maintains high nickel content (0.7-0.8 mol) to reduce cobalt dependency and production cost, while the surface has reduced nickel content (0.5-0.6 mol) to enhance air atmosphere stability. The lower nickel content at the surface reduces susceptibility to oxidation and degradation when exposed to air, thereby improving compositional stability during handling and processing.
Data Source
AI summary
The present invention relates to positive electrode active materials in rechargeable lithium-ion batteries having a difference in cobalt concentration between the center and the edge of particle.