Positive Electrode Composition for High-Capacity Cycle Stability
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Solution Overview
Problem
Conventional positive electrode active materials for secondary batteries, such as lithium ion batteries, struggle to simultaneously achieve high capacity and high durability, particularly in terms of charge-discharge cycle characteristics.
Innovation Solution
Employing a combination of first and second lithium nickel composite oxides with different particle sizes and surface modifications with Ca and Sr, where the second lithium nickel composite oxide has a higher content of Ca and Sr, to enhance reaction resistance and improve cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional positive electrode active materials are used, then high capacity can be achieved, but charge-discharge cycle characteristic deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains lithium nickel composite oxide with high nickel content for high capacity, while the outer shell region contains lithium nickel composite oxide with lower nickel content and higher Ca/Sr content for stability. This spatial differentiation of composition allows each region to perform its specific function optimally.
Solution Approach 2:
The patent uses composite materials by combining two different lithium nickel composite oxides with distinct compositions and properties into a single positive electrode active material system. The first lithium nickel composite oxide (core) and second lithium nickel composite oxide (shell) form a composite structure that integrates the high capacity advantage of high-nickel materials with the high stability advantage of low-nickel materials.
2Quantity of substance
If particle size is increased to improve capacity, then reaction resistance increases and cycle characteristic deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the positive electrode active material into two distinct particle size populations: large particles (8-30 μm) for high capacity contribution and small particles (≤6 μm) for low reaction resistance. The small particles provide abundant active sites for rapid lithium ion insertion/extraction, reducing overall reaction resistance while the large particles maintain high capacity.
Solution Approach 2:
The patent creates local quality differences in particle size distribution, where small particles are strategically present to provide low reaction resistance pathways, while large particles dominate the capacity contribution. This non-uniform particle size distribution optimizes both capacity and reaction kinetics.
Data Source
AI summary
A positive electrode active material for secondary batteries which is one example of the embodiment comprises a first lithium-nickel composite oxide having a volume-based D50 value of 8 μ82 m to 30 μm inclusive and a second lithium-nickel composite oxide having a volume-based D50 value of 6 μm or less. At least one component selected from Ca and Sr is present on the surfaces of primary particles constituting the second lithium-nickel composite oxide. The total content of Ca and Sr in the second lithium-nickel composite oxide is larger than that in the first lithium-nickel composite oxide.