Single-Particle Cathode Active Material for Crack-Resistant Li-Ion Cells
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Solution Overview
Problem
Lithium secondary batteries face issues with mechanical and chemical stability due to cracks in lithium metal oxide particles during the manufacturing process and repetitive charging/discharging, leading to reduced lifespan and high-temperature instability.
Innovation Solution
A cathode for lithium secondary batteries is developed using lithium metal oxide particles with a single particle shape and single or poly-crystalline structure, where the average crystal size is controlled between 1 μm and 3 μm, and the particles contain nickel, enhancing mechanical and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithium metal oxide particles with secondary particle shape and polycrystalline structure are used, then manufacturing process is simpler, but cracks occur during pressing and charging/discharging leading to reduced lifespan
Solution Approach 1:
The patent changes the crystallographic parameters by controlling crystal size to 0.3 μm or less and adjusting the ratio of single crystal to polycrystal regions. This parameter optimization prevents crack formation during pressing and charging/discharging cycles while maintaining manufacturing feasibility, thereby improving lifespan properties without completely redesigning the manufacturing process
Solution Approach 2:
The patent creates a composite cathode active material layer combining single crystal regions and polycrystal regions in specific ratios. This composite structure leverages the advantages of both single crystals (crack resistance) and polycrystals (manufacturing ease), resolving the contradiction between ease of manufacture and reliability
2Reliability
If nickel-cobalt-based lithium metal oxide particles with single particle shape are used, then lifespan properties are improved, but mechanical and chemical stability deteriorates
Solution Approach 1:
The patent applies local quality by creating regions with different crystal structures (single crystal and polycrystal) in specific proportions within the cathode active material layer. The single crystal regions provide mechanical stability while the polycrystal regions contribute to chemical stability, achieving both improved lifespan and enhanced overall stability through spatial distribution of different material properties
3Ease of operation
If lithium metal oxide particles are used in high-temperature environment, then battery operation is maintained, but side reactions with electrolyte solution increase causing gas generation and lifespan deterioration
Solution Approach 1:
The patent employs beforehand cushioning by pre-optimizing the crystal structure and size of lithium metal oxide particles before battery operation. The controlled crystal structure (0.3 μm or less) and composition ratio create a more stable material that resists side reactions with the electrolyte solution even in high-temperature environments, preventing gas generation and lifespan deterioration before they can occur
Data Source
AI summary
A cathode for a lithium secondary battery includes a cathode current collector, and a cathode active material layer satisfying a specific formula formed on the cathode current collector. The cathode active material layer includes lithium metal oxide particles that have a single particle shape, and a single crystalline structure or a poly-crystalline structure including two or more single crystals. A lithium secondary battery including the cathode, and a method of preparing a cathode active material are also provided.