Nanocomposite Cathode Material for Stable High-Capacity Li-Ion Cycling
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high capacity and structural stability over multiple cycles, leading to structural collapse and reduced electrochemical performance due to irreversible reactions and volume expansion of primary particles.
Innovation Solution
A positive electrode active material is developed with a nanocomposite structure comprising rocksalt and layered structures, where primary particles have a specific size and distribution, and a doping element is used to enhance particle strength and maintain crystallinity, reducing irreversible reactions and volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If primary particles are used as positive electrode active material, then capacity can be increased, but structural stability deteriorates leading to particle collapse after multiple cycles
Solution Approach 1:
The positive electrode active material is divided into secondary particles that aggregate multiple primary particles. Each secondary particle maintains structural integrity while containing the primary particles that provide high capacity. This segmentation allows the primary particles to deliver high capacity without causing overall structural collapse, as the secondary particle structure provides stability during cycling.
2Quantity of substance
If particle size is increased to improve capacity, then electrochemical performance improves, but particle strength decreases leading to microcracks
Solution Approach 1:
The invention creates a heterogeneous structure where the secondary particle aggregate has different properties from its constituent primary particles. The secondary particle structure provides enhanced strength and stability, while the primary particles maintain their high-capacity characteristics. This local quality differentiation allows the material to simultaneously achieve high capacity and high particle strength, preventing microcrack formation during cycling.
3Productivity
If high nickel content is used to increase capacity, then electrochemical efficiency improves, but structural stability deteriorates due to volume expansion
Solution Approach 1:
High-nickel primary particles that provide high electrochemical efficiency are segmented and aggregated into secondary particles. The secondary particle structure acts as a stable framework that accommodates volume expansion of the nickel-rich primary particles during lithium insertion/extraction cycles. This segmentation allows the high-nickel material to maintain both high electrochemical efficiency and structural stability over multiple cycles.
Data Source
AI summary
A positive electrode active material for a lithium secondary battery is disclosed. The positive electrode active material includes a secondary particle composed of an aggregate of a plurality of primary particles, in which the primary particle includes a nanocomposite structure in which rocksalt (Fm3m) structures and layered (R-3m) structures coexist as a physical mixture.