Positive Electrode Active Material Withstand High Compression
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in achieving high capacity and enhanced cycle characteristics due to particle cracking when subjected to high pressures, which compromises the cycle characteristics of the positive electrode active material.
Innovation Solution
Incorporating Ta and Nb into the positive electrode active material and employing a two-stage calcination process to adjust the hardness and grain size, ensuring the particles have a compression fracture strength of 500 MPa or more and a grain diameter in the (110) vector direction of 100 nm to 300 nm, allowing for high compression without cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a pressure of 500 MPa or more is applied to particles to increase the density of the positive electrode, then the filling properties are improved, but the particles are cracked and cycle characteristics deteriorate
Solution Approach 1:
The invention changes the physical parameters of the positive electrode active material particles by controlling grain size to 100 nm to 300 nm and adjusting compression fracture strength to 300 MPa to 500 MPa. These parameter changes enable the particles to withstand high compression pressures (500 MPa or more) during electrode manufacturing without cracking, thereby achieving both high filling properties and excellent cycle characteristics
Solution Approach 2:
The invention uses composite positive electrode active material particles containing multiple metal elements (at least one selected from Ta and Nb) combined with lithium, nickel, cobalt, and manganese. This composite structure enhances the mechanical strength and fracture resistance of the particles, allowing them to maintain integrity under high compression pressure while achieving high density and excellent cycle characteristics
2Quantity of substance
If the grain size of the positive electrode active material is reduced to improve capacity density, then the capacity density increases, but the particle strength decreases and particles crack under compression
Solution Approach 1:
The invention optimizes the grain size parameter to a specific range of 100 nm to 300 nm, which is large enough to maintain particle strength and resistance to cracking, yet small enough to achieve high capacity density. This precise parameter control resolves the contradiction between increasing capacity density through grain size reduction and maintaining sufficient particle strength
Solution Approach 2:
The composite structure with multiple metal elements (Ta, Nb, Li, Ni, Co, Mn) creates a mechanically robust particle architecture that maintains high strength even at reduced grain sizes. The synergistic combination of these elements enhances both the strength and capacity density, allowing the particles to withstand compression while achieving high capacity density
Data Source
AI summary
A positive electrode active material for use in nonaqueous electrolyte secondary batteries. The active material is composed of particles each formed by the gathering of grains that comprises at least one metal element selected from the group consisting of Ta and Nb. One of the particles has a compression fracture strength of 500 MPa or more. The grain diameter in the (110) vector direction of the particles is 100 nm to 300 nm.