Bimodal Positive Electrode Material for High-Temperature Battery Life
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Solution Overview
Problem
Lithium secondary batteries face limitations in high-temperature life characteristics and storage characteristics due to poor thermal stability of existing positive electrode active materials, such as lithium nickel composite metal oxides, which can lead to particle breakage and ignition during internal short circuits.
Innovation Solution
A bimodal positive electrode active material comprising a first lithium transition metal oxide with higher particle strength and smaller crystalline size, combined with a second lithium transition metal oxide having a smaller average particle diameter, is developed to enhance electrode density, minimize particle breakage, and improve high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel composite metal oxide is used to achieve high reversible capacity, then battery capacity is improved, but thermal stability deteriorates leading to poor high-temperature life characteristics
Solution Approach 1:
The patent applies parameter changes by controlling the particle size distribution to a bimodal pattern with specific parameters: first particles with D50 of 3-10 μm and second particles with D50 of 0.5-3 μm. This parameter optimization resolves the contradiction by achieving both high capacity utilization and improved thermal stability through reduced particle breakage at high temperatures
Solution Approach 2:
The patent uses composite materials by creating a bimodal particle size distribution system where two distinct particle populations work synergistically. The larger particles provide capacity while the smaller particles fill voids and improve packing, resolving the thermal stability issue without sacrificing capacity
2Volume of stationary object
If particle size is reduced to improve electrode density, then electrode density is improved, but particle strength decreases leading to increased particle breakage
Solution Approach 1:
The patent applies segmentation by dividing the particle population into two distinct size segments: first particles (D50: 3-10 μm) that maintain structural strength, and second particles (D50: 0.5-3 μm) that fill interstitial spaces. This segmentation resolves the contradiction by allowing density improvement through small particles while strength is maintained by the larger, stronger first particles
Solution Approach 2:
The patent uses local quality by assigning different functional roles to different particle size regions: larger first particles serve as structural anchors with high strength, while smaller second particles optimize packing density in the interstitial spaces. This local functional differentiation resolves the strength-density contradiction
3Power
If lithium cobalt composite metal oxide is used to achieve high operating voltage, then voltage characteristics are improved, but cost increases and thermal properties deteriorate
Solution Approach 1:
The patent applies parameter changes by optimizing the particle size distribution parameters (bimodal D50 ranges) to achieve better packing density and capacity utilization. This allows the use of more cost-effective lithium nickel composite metal oxide while maintaining performance levels previously requiring expensive lithium cobalt materials
Data Source
AI summary
A bimodal positive electrode active material includes a first lithium transition metal oxide and a second lithium transition metal oxide having an average particle diameter (D50) smaller than that of the first lithium transition metal oxide, wherein the first lithium transition metal oxide has higher particle strength and smaller crystalline size than the second lithium transition metal oxide, and a positive electrode and a lithium secondary battery which include the positive electrode active material. A positive electrode active material may improve high-temperature life characteristics and high-temperature storage characteristics of a lithium secondary battery. A positive electrode and a lithium secondary battery which include the positive electrode active material are also provided.