Spherical O2-Type Cathode Particles for High-Rate Li-Ion Capacity
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Solution Overview
Problem
Positive electrode active materials with an O2-type structure exhibit low rate characteristics and reduced capacity during high-speed charge-discharge compared to slow charge-discharge.
Innovation Solution
Development of spherical positive electrode active material particles with an O2-type structure comprising transition metal elements like Mn, Ni, and Co, featuring a shell with crystallites and voids along the inner wall, which increases the contact area with electrolytes and reduces reaction resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a positive electrode active material with an O2-type structure is used, then it can be obtained by ion-exchange of Li for Na in a Na-containing transition metal oxide with a P2-type structure, but it exhibits low rate characteristic and reduced capacity during high-speed charge-discharge
Solution Approach 1:
The patent applies spheroidality by transforming the conventional laminar-shaped positive electrode active material into a spherical shape. This spherical morphology reduces tortuosity for lithium ion diffusion and provides uniform stress distribution during charge-discharge cycles, thereby improving rate characteristics while maintaining ease of manufacture through controlled synthesis processes
Solution Approach 2:
The patent introduces a porous hollow internal structure within the spherical particles, creating void spaces that facilitate electrolyte penetration and lithium ion diffusion. This porous architecture increases the effective surface area for electrochemical reactions, significantly enhancing rate characteristics without compromising the structural integrity or manufacturability of the material
2Ease of manufacture
If a positive electrode active material with an O2-type structure is used, then it can be obtained by ion-exchange of Li for Na in a Na-containing transition metal oxide with a P2-type structure, but it tends to have lower capacity during high-speed charge-discharge compared to slow charge/discharge
Solution Approach 1:
The spherical external shape reduces diffusion path lengths for lithium ions and minimizes polarization effects during high-speed charge-discharge, enabling the material to achieve higher capacity utilization at elevated rates while maintaining straightforward synthesis procedures
Solution Approach 2:
The hollow porous internal structure provides additional pathways for lithium ion insertion and extraction, increasing the accessible capacity during high-speed operations. The porous architecture allows electrolyte to penetrate deeper into the particle, enabling more complete utilization of the active material's capacity even at high discharge rates
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 spherical particles with shell and void structures demonstrate improved rate characteristics and higher capacity retention during high-speed charge-discharge, enhancing the performance of lithium ion secondary batteries.
Implementation Method 1
A positive electrode active material with an O2-type structure can be obtained by ion-exchange of Li for at least a portion of the Na in a Na-containing transition metal oxide with a P2-type structure
Data Source
AI summary
The rate characteristic of O2-type positive electrode active material particle is improved. The positive electrode active material particle of the first mode have an O2-type structure, comprise at least one transition metal elements from among Mn, Ni and Co, with Li and O, as constituent elements, and are spherical. The positive electrode active material particle of the second mode have at least one shell and at least one void in the cross-sectional structure, wherein the shell has an O2-type structure, the shell comprises at least one transition metal element from among Mn, Ni and Co, with Li and O, as constituent elements, the surface of the shell comprises crystallites, and the void is present along the inner wall of the shell.