Bimodal Cathode Active Material for High-Temperature Li-Ion Stability
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Solution Overview
Problem
Lithium transition metal oxides used in lithium secondary batteries suffer from poor thermal stability, leading to poor high-temperature life characteristics and storage characteristics.
Innovation Solution
A bimodal positive electrode active material comprising a first lithium transition metal oxide with higher particle strength and smaller crystalline size, and a second lithium transition metal oxide with lower particle strength and larger crystalline size, both having specific compositions, is used to enhance electrode density and minimize particle breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel composite metal oxide (LiNiO2) is used to achieve high reversible capacity, then battery capacity is improved, but thermal stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains nickel-rich composition (LiNi0.8Co0.1Mn0.1O2) for high capacity, while the outer shell region contains aluminum-substituted composition (LiNi0.8Co0.1Mn0.1Al0.1O2) for enhanced thermal stability. This spatial differentiation of material composition allows simultaneous optimization of capacity and stability properties in different regions of the same particle.
Solution Approach 2:
The patent employs composite materials by combining two distinct lithium transition metal oxide phases with different compositional characteristics. The core-shell structure integrates nickel-rich material (providing high reversible capacity) with aluminum-substituted material (providing thermal stability), creating a composite structure that exhibits both high capacity and improved thermal stability that neither component could achieve alone.
2Reliability
If lithium transition metal oxide substituted with Co, Mn, or Al is used to improve thermal stability, then thermal stability is improved, but high-temperature life characteristics deteriorate
Solution Approach 1:
The patent applies parameter changes by systematically varying the aluminum substitution ratio (x in LiNi0.8Co0.1Mn0.1AlxO2) and controlling particle size distribution (bimodal distribution with D50 of 3-6 μm). By optimizing these parameters, the patent achieves a balance where aluminum substitution provides thermal stability while controlled particle size and composition maintain high-temperature life characteristics.
3Quantity of substance
If particle size is reduced to improve electrode density, then electrode density is improved, but particle strength deteriorates
Solution Approach 1:
The patent applies segmentation by implementing a bimodal particle size distribution with two distinct size ranges: fine particles (D50: 3-6 μm) for high electrode density and coarse particles (D50: 8-15 μm) for adequate mechanical strength. This segmentation allows the electrode to achieve high density from fine particles while coarse particles provide structural integrity and resistance to breakage during processing and cycling.
Data Source
AI summary
The present invention relates to a positive electrode active material which may improve high-temperature life characteristics and high-temperature storage characteristics of a lithium secondary battery, and a positive electrode and a lithium secondary battery which include the positive electrode active material. Specifically, the present invention relates to a bimodal positive electrode active material including 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.