Nanostructured Li-Ion Cathode Material for High-Rate Discharge
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Solution Overview
Problem
Lithium manganese iron phosphate-based positive electrode active materials in lithium ion secondary batteries suffer from low electron conductivity and ion conductivity, limiting high-speed discharge characteristics and energy density, and are prone to sintering issues during carbon coating, leading to coarse particle formation and deteriorated performance.
Innovation Solution
A positive electrode active material with primary particle diameters between 10 nm and 80 nm and a number ratio of particles above 100 nm of 5% or less, combined with a carbon cover layer, to enhance electron and ion conductivity and prevent sintering, resulting in improved high-speed discharge characteristics and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium manganese iron phosphate is formed into a battery, then high energy density can be achieved, but low ion conductivity and electron conductivity prevent high-speed discharge
Solution Approach 1:
The positive electrode active material is divided into primary particles with a diameter of 100 nm or less, creating a segmented structure that reduces ion diffusion distance and improves conductivity while maintaining high energy density
Solution Approach 2:
A carbon coating layer is applied to the surface of the lithium manganese iron phosphate particles, creating a composite material structure that enhances electron conductivity and ion conductivity while preserving the high capacity of the olivine-based material
2Productivity
If carbon coating is applied to enhance conductivity, then electron conductivity improves, but sintering occurs during firing leading to coarse particle formation
Solution Approach 1:
The carbon coating is applied before the final firing process, and the primary particles are pre-formed with a diameter of 100 nm or less. This preliminary preparation ensures that even after high-temperature firing, the particles remain fine-grained rather than sintering into coarse structures
Solution Approach 2:
The particle size parameter is strictly controlled to 100 nm or less, and the carbon coating thickness is optimized to balance conductivity enhancement with prevention of excessive sintering during the firing process
3Productivity
If particle size is reduced to improve conductivity, then ion conductivity increases, but surface energy increases promoting sintering
Solution Approach 1:
The carbon coating layer acts as an intermediary substance between the primary particles, reducing surface energy and preventing direct contact and sintering between particles, thereby maintaining the fine particle size structure that provides high ion conductivity
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 solution achieves excellent high-speed discharge characteristics and energy density while maintaining safety by optimizing particle size and conductivity, reducing sintering, and ensuring uniform carbon coverage.
Implementation Method 1
enhancing the electron conductivity
Implementation Method 2
decrease the in-solid diffusion distance of electrons and lithium ions
Implementation Method 3
prevent sintering
Data Source
AI summary
The purpose of the present invention is to provide positive electrode active substance particles for a lithium ion secondary battery, such particles being capable of producing a lithium ion secondary battery having excellent high-speed discharge properties. The present invention is a granulated body of a positive electrode active substance for a lithium ion secondary battery, wherein the primary particle average diameter is 10 to 80 nm and the number of primary particles having a diameter of 100 nm or greater is no more than 5.0%.