O2-Type Cathode Particles With Surface Doping for Cycle Stability
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Solution Overview
Problem
Conventional positive electrode active materials with O2-type structures face challenges in achieving both high capacity and cycling properties, particularly when used at high potentials, due to instability and capacity deterioration.
Innovation Solution
The development of positive electrode active material particles with an O2-type structure, comprising elements like Mn, Ni, Co, Li, and an element M (such as Al or Ga) with a higher molar concentration of M in the surface layer than in the central portion, achieved by ion-exchanging Na-containing transition metal oxide particles and doping element M in the surface layer, stabilizing the O2-type structure and enhancing charge/discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional O2-type positive electrode active materials are used, then high capacity can be achieved, but cycling properties deteriorate due to structural instability at high potentials
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of element M within the particle structure. The surface layer portion contains a higher concentration of element M (0.05-0.20 mol) compared to the central portion (0.00-0.05 mol), resulting in a concentration gradient that stabilizes the O2-type structure at the surface where structural degradation typically initiates, while preserving high capacity in the central region
Solution Approach 2:
The patent employs composite material strategy by combining multiple elements (Mn, Ni, Co, Li, and element M) in a specific configuration. The surface layer acts as a composite structure with enhanced stability due to the presence of element M, while the central portion maintains the high-capacity O2-type composition, creating a core-shell like structure that integrates both stability and high capacity characteristics
2Reliability
If element M is uniformly distributed throughout the particles, then structural stability improves, but charge/discharge capacity decreases due to reduced active material content
Solution Approach 1:
The patent resolves this contradiction by making the distribution of element M non-uniform. The surface layer portion contains higher concentrations of element M (0.05-0.20 mol) for structural stability, while the central portion contains lower concentrations (0.00-0.05 mol) to maximize charge/discharge capacity. This localized differentiation allows each region to optimize its function
Solution Approach 2:
The patent segments the particle into two distinct regions: a surface layer portion and a central portion, each with different concentrations of element M. This segmentation allows the surface to provide structural stability while the central region provides high capacity, avoiding the capacity loss that would occur with uniform distribution throughout the entire particle
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
These particles demonstrate improved stability and high capacity retention even at high potentials, achieving both high charge/discharge capacity and cycling characteristics by concentrating the stabilizing element M in the surface layer.
Implementation Method 1
ion-exchange of Li for at least a portion of the Na in a Na-containing transition metal oxide with a P2-type structure
Implementation Method 2
doping at least one element M selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W in the surface layer of the particle
Data Source
AI summary
Disclosed are positive electrode active material particles having both high-capacity and cycling properties. The positive electrode active material particles of the present disclosure have an O2-type structure, and comprise: at least one element selected from Mn, Ni and Co; Li; an element M; and O, wherein the element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W, and the molar concentration of the element M in the surface layer portion of the particles is higher than the molar concentration of the element M in the central portion of the particles.