Porous Olivine Phosphate Cathode Material for Faster Electrolyte Wetting
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Solution Overview
Problem
Existing positive electrode active materials, particularly olivine-type phosphate compounds, suffer from low electrical conductivity and inadequate liquid impregnation rates due to their structure, hindering battery performance.
Innovation Solution
The positive electrode active material is designed with secondary particles that have a high proportion of open pores, specifically 40% or more with a maximum Feret diameter of 5 μm or more, and 70% or more with a diameter of 10 μm or more, enhancing liquid impregnation pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of primary particles is reduced to improve electrical conductivity, then electrical conductivity is improved, but liquid impregnation rate remains insufficient
Solution Approach 1:
The invention segments the secondary particles into multiple primary particles (10-90 nm) aggregated together, creating a hierarchical structure. This segmentation allows each primary particle to maintain good electrical conductivity while the aggregated secondary particle structure provides pathways for liquid impregnation, resolving the contradiction between conductivity and impregnation rate.
Solution Approach 2:
The invention introduces open pores within the secondary particle structure, creating a porous morphology that facilitates electrolyte penetration. The porous structure allows liquid to reach interior primary particles efficiently while maintaining the fine particle size needed for electrical conductivity, thus resolving the contradiction between the two properties.
2Productivity
If secondary particles with open pores are increased to improve liquid impregnation rate, then liquid impregnation rate is improved, but particle size must be maintained at 5 μm or more
Solution Approach 1:
The invention employs a nested structure where multiple nanoscale primary particles (10-90 nm) are aggregated to form microscale secondary particles (5 μm or more). This nesting allows the secondary particles to achieve sufficient size for structural stability and open pore formation while the interior primary particles maintain the fine size necessary for good electrical conductivity and rapid lithium ion diffusion.
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
This design improves the liquid impregnation rate, leading to better electrolyte solution permeation throughout the electrode layer, thereby enhancing battery productivity and rate properties.
Implementation Method 1
a proportion of the secondary particles each having an open pore to the secondary particles each having a maximum Feret diameter of 5 μm or more is 40% or more... the open pores of the secondary particles with sizes of 5 μm or more tend to provide suitable pathways for permeation
Data Source
AI summary
A positive electrode active material comprises powder. The powder includes secondary particles. Each of the secondary particles includes primary particles. Each of the primary particles includes an olivine-type phosphate compound. In an SEM image of the powder, a proportion of the secondary particles each having an open pore to the secondary particles each having a maximum Feret diameter of 5 μm or more is 40% or more.