Lithium Secondary Battery Cathode Mix for High-Voltage Cycle Stability
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Solution Overview
Problem
Lithium secondary batteries face limitations in cycle characteristics and swelling at high voltage due to side reactions with electrolytes, especially when using mixed positive electrode materials like lithium nickel cobalt manganese-based oxide and lithium cobalt-based oxide.
Innovation Solution
A lithium secondary battery design that incorporates a positive electrode active material layer with a mixture of lithium nickel cobalt manganese-based oxide and lithium cobalt-based oxide, where the average particle diameter of primary particles is 3 μm or more, and the ratio of negative electrode capacity to positive electrode capacity is within the range of 1.06 to 1.15.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel cobalt manganese-based oxide is used as positive electrode material to achieve high capacity characteristics, then battery capacity increases, but side reactions occur at high voltage causing rapid performance degradation and swelling
Solution Approach 1:
The patent uses a composite positive electrode material consisting of lithium nickel cobalt manganese-based oxide and lithium cobalt-based oxide. This composite structure combines the high capacity characteristics of lithium nickel cobalt manganese-based oxide with the excellent cycle characteristics and high voltage stability of lithium cobalt-based oxide, thereby achieving both high capacity and reliable performance without rapid degradation or swelling.
2Duration of action of stationary object
If mixed positive electrode material of lithium nickel cobalt manganese-based oxide and lithium cobalt-based oxide is used to address individual material limitations, then cycle characteristics improve, but positive electrode potential is more reduced causing rapid degradation under high-temperature and high-voltage conditions
Solution Approach 1:
The patent optimizes the particle size parameter of the lithium nickel cobalt manganese-based oxide to 3 μm or more. This parameter change reduces the specific surface area, thereby minimizing side reactions with the electrolyte solution even under high-temperature and high-voltage conditions. The controlled particle size maintains the benefits of mixed material composition while suppressing harmful side reactions that cause rapid degradation.
3Productivity
If smaller particle size lithium nickel cobalt manganese-based oxide is used to increase contact area with electrolyte, then reaction efficiency improves, but side reactions increase causing capacity degradation and swelling
Solution Approach 1:
The patent sets the average particle diameter of lithium nickel cobalt manganese-based oxide to 3 μm or more, which reduces the specific surface area compared to conventional smaller particles. This parameter change decreases the contact area with the electrolyte solution, thereby minimizing side reactions that cause capacity degradation and swelling, while still maintaining adequate reaction efficiency for battery operation.
Data Source
AI summary
A lithium secondary battery having excellent battery performance at high voltage includes a positive electrode which includes a positive electrode active material layer including a lithium nickel cobalt manganese-based oxide having an average particle diameter of primary particles of 3 μm or more and a lithium cobalt-based oxide, a negative electrode which includes a negative electrode active material layer including a negative electrode active material, and an electrolyte, wherein a ratio of negative electrode capacity to positive electrode capacity is in a range of 1.06 to 1.15.