Coated NCA/NCM Cathode Material for Stable High-Energy Li Batteries
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density, cycle-life characteristics, and structural stability, particularly in hybrid or electric vehicles, due to limitations in positive electrode active materials.
Innovation Solution
The development of a positive electrode active material comprising a lithium nickel-cobalt-aluminum composite oxide with radially oriented primary particles and a coating layer of ZrO2 and Li6Zr2O7, combined with a lithium nickel-cobalt-aluminum-manganese composite oxide, optimized through a co-firing process and dry mixing with zirconium raw material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lithium nickel-cobalt-aluminum composite oxide is used as positive electrode active material, then energy density is improved, but structural stability and cycle-life characteristics deteriorate
Solution Approach 1:
The patent uses a composite material system consisting of lithium nickel-cobalt-aluminum composite oxide particles combined with lithium nickel-cobalt-aluminum-manganese composite oxide particles. This composite structure allows the high energy density NCA component to contribute to capacity while the NCM component provides structural stability, resolving the contradiction between energy density and structural stability.
Solution Approach 2:
The patent creates particles with non-uniform composition distribution, where the aluminum content varies between the surface layer and internal portion. The surface layer has higher aluminum content for structural stability, while the internal portion maintains higher nickel content for energy density, thus resolving the contradiction through spatial differentiation of material properties.
2Use of energy by moving object
If a lithium nickel-cobalt-aluminum composite oxide is used as positive electrode active material, then energy density is improved, but cycle-life characteristics deteriorate
Solution Approach 1:
The composite of NCA and NCM particles creates a synergistic effect where the NCM component with higher structural stability improves cycle-life characteristics while the NCA component maintains high energy density, thus resolving the contradiction between energy density and cycle-life.
Solution Approach 2:
The aluminum-rich surface layer acts as a protective barrier that enhances structural stability during cycling, while the nickel-rich interior maintains high capacity. This local quality differentiation protects the high-energy-density material from degradation during repeated charge-discharge cycles.
3Quantity of substance
If particle size of positive electrode active material is increased, then volumetric capacity is improved, but charge/discharge efficiency deteriorates
Solution Approach 1:
The patent divides the positive electrode active material into secondary particles that are agglomerates of multiple primary particles. This segmentation allows the electrode to achieve high volumetric capacity through dense packing of secondary particles while maintaining short lithium ion diffusion paths within each primary particle, thus resolving the contradiction between volumetric capacity and charge/discharge efficiency.
4Stability of the object's composition
If aluminum content in positive electrode active material is increased, then structural stability is improved, but capacity deteriorates
Solution Approach 1:
The patent implements a concentration gradient of aluminum within the particles, with higher aluminum content at the surface layer for structural stability and lower aluminum content (higher nickel content) in the internal portion for capacity. This local quality differentiation allows simultaneous achievement of structural stability and high capacity.
Solution Approach 2:
The composite system combines NCA particles (high capacity) with NCM particles (high stability), allowing the overall electrode to achieve both structural stability and high capacity through the synergistic combination of different material compositions rather than requiring uniform high aluminum content throughout.
Data Source
AI summary
A positive electrode active material, including a first positive electrode active material including secondary particles including a lithium nickel-cobalt-aluminum composite oxide, wherein the secondary particles include an agglomeration of a plurality of primary particles and at least a portion of the plurality of primary particles are oriented radially, and a coating layer on a surface of the secondary particles, the coating layer including ZrO2 and Li6Zr2O7; and a second positive electrode active material including secondary particles including a lithium nickel-cobalt-aluminum-manganese composite oxide, wherein the secondary particles include an agglomeration of a plurality of primary particles, and a coating layer on a surface of the secondary particles, the coating layer including ZrO2 and Li6Zr2O7, wherein an average particle diameter of the secondary particles of the first positive electrode active material is larger than an average particle diameter of the secondary particles of the second positive electrode active material.