Cathode Active Material Pore Control for Initial Battery Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing non-aqueous electrolyte secondary batteries, such as lithium-ion batteries, face challenges in improving initial charge-discharge efficiency due to the use of positive electrode active materials with large pores and high porosity, which deteriorate battery performance.
Innovation Solution
A positive electrode active material comprising lithium-containing composite oxide secondary particles with a specific number of pores per 76.46 μm², average pore circumferential lengths of less than or equal to 600 nm, and porosity of less than or equal to 0.15%, formed by aggregating primary particles, is used to enhance charge-discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If large pores with high porosity are introduced into the positive electrode active material, then capacity retention is improved, but initial charge-discharge efficiency deteriorates
Solution Approach 1:
The patent applies porous materials by controlling the pore structure within secondary particles. Specifically, it maintains a high number of small pores (≥0.3 pores/μm² with area ≥0.01 μm²) to ensure capacity retention, while strictly limiting porosity to ≤1% and controlling pore distribution to prevent excessive electrolyte absorption that would harm initial efficiency. This selective application of porosity resolves the contradiction between capacity retention and initial efficiency.
Solution Approach 2:
The patent applies local quality by creating different pore density distributions within and between secondary particles. The internal structure of secondary particles contains controlled pores for capacity retention, while the overall porosity between particles is limited to ≤1%. This spatial differentiation allows the material to simultaneously achieve good capacity retention through internal pores and maintain high initial efficiency by preventing excessive overall porosity.
2Duration of action of stationary object
If the number of pores per μm2 is increased to improve capacity retention, then more pores are present, but initial charge-discharge efficiency deteriorates due to excessive porosity
Solution Approach 1:
The patent applies parameter changes by precisely controlling multiple pore-related parameters simultaneously: porosity ≤1%, pore area ≥0.01 μm², and pore number ≥0.3 pores/μm². By changing and optimizing these parameters together rather than individually, the patent achieves the dual goal of improving capacity retention through sufficient pore presence while maintaining initial efficiency by limiting overall porosity and controlling pore size distribution.
Data Source
AI summary
A positive electrode active material for non-aqueous electrolyte secondary batteries according to one example of an embodiment comprises a lithium-containing composite oxide that is secondary particles in which primary particles are aggregated. The lithium-containing composite oxide exhibits not fewer than 300 voids per 76.46 μm2, an average void perimeter length of not more than 600 nm, and a porosity of not more than 0.15%, as determined by observation of a secondary particle cross-section.