Hetero-Doped Cathode Surface Gradient for Capacity and Cycle Life
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in achieving high capacity, long lifespan, and stability of positive electrode active materials, particularly due to the limitations of conventional materials and production methods.
Innovation Solution
A positive electrode active material is developed with a surface portion doped with hetero elements, featuring a unique crystal structure and composition gradient, where the surface portion has a higher concentration of hetero elements compared to the center portion, enhancing the material's stability and discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high content of nickel is used in positive electrode active material, then discharge capacity is improved, but lifespan characteristics deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the center portion contains high nickel content (0.8-0.95) for high discharge capacity, while the surface portion contains lower nickel content (0.5-0.8) and hetero elements for stability. This spatial differentiation of material composition allows simultaneous optimization of both discharge capacity and lifespan characteristics.
2Ease of manufacture
If conventional positive electrode active materials are used, then manufacturing simplicity is maintained, but capacity and lifespan characteristics are limited
Solution Approach 1:
The patent employs preliminary action by pre-forming the core-shell structure during the co-precipitation process before final sintering. The surface portion is doped with hetero elements (W, Mo, Ta, Nb, Hf, Si, Sn, Zr, Ca, Ge, Ga, In, Ru, Te, Sb, Fe, Cr, V, Ti) during precursor formation, which prevents capacity deterioration during subsequent charge/discharge cycles while maintaining manufacturing simplicity.
3Device complexity
If uniform composition is used throughout the positive electrode active material, then manufacturing process is simplified, but cycle characteristics are poor
Solution Approach 1:
The patent implements local quality through a controlled composition gradient where the nickel content decreases from center (0.8-0.95) to surface (0.5-0.8), and hetero elements are concentrated in the surface portion (0.01-0.1 mol%). This non-uniform composition distribution optimizes cycle characteristics by providing a stable surface structure that resists degradation during repeated charge/discharge cycles.
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 proposed active material exhibits improved cycle characteristics, high discharge capacity, and minimized lifespan deterioration, making it suitable for long-term use in lithium secondary batteries.
Implementation Method 1
a positive electrode active material having a surface portion doped with hetero elements
Data Source
AI summary
The present invention pertains to: a positive electrode active material precursor containing first secondary particle composed of an aggregate of a plurality of first primary particles, the positive electrode active material precursor including a first center portion represented by chemical formula 1 and a first surface portion represented by chemical formula 2, wherein the thickness of the first surface portion is 2-20% of the average radius of the positive electrode active material precursor; and a positive electrode active material containing the positive electrode active material precursor.