Fluorinated Electrolyte Additives for High-Nickel Cathode Stability
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Solution Overview
Problem
Lithium secondary batteries with nickel-based lithium metal oxide cathodes face issues of reduced power and capacity due to surface damage and side reactions with the electrolyte, leading to instability and decreased performance during repeated charging and discharging.
Innovation Solution
A non-aqueous electrolyte comprising a non-aqueous organic solvent, a lithium salt, and specific additives such as those represented by Chemical Formulae 1, 2, 3, and 4, along with auxiliary additives like carbonate-based and sultone-based compounds, which function as radical scavengers to improve mechanical and chemical stability, and enhance lithium-ion mobility and storage properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel-based lithium metal oxide is used as cathode active material to increase capacity, then energy density is improved, but surface damage and side reactions with electrolyte occur leading to reduced operational stability
Solution Approach 1:
A coating layer comprising fluorinated cyclic carbonate and fluorinated chain carbonate is formed on the surface of the nickel-based lithium metal oxide cathode. This coating layer acts as an intermediary barrier between the cathode and the electrolyte, preventing direct contact and side reactions while maintaining ion transport, thereby resolving the contradiction between high energy density and operational stability
Solution Approach 2:
The patent modifies the surface chemistry parameters of the cathode by introducing fluorinated compounds with specific molecular structures and ratios. The fluorinated cyclic carbonate and fluorinated chain carbonate change the surface properties of the cathode, creating a stable interface that reduces side reactions while preserving the high capacity characteristics of nickel-based materials
2Power
If nickel content in cathode is increased to enhance capacity, then power and energy are improved, but surface damage occurs leading to decreased lifespan during repeated charging and discharging
Solution Approach 1:
The fluorinated coating layer serves as a protective intermediary that shields the nickel-based cathode surface from degradation during repeated charge-discharge cycles. This coating prevents surface damage and structural collapse, thereby extending the lifespan of high-power cathodes without compromising their power and capacity performance
Solution Approach 2:
The coating layer is formed on the cathode surface before the battery undergoes repeated charging and discharging. This preliminary protective action prevents surface damage from occurring in the first place, rather than attempting to repair it after degradation begins, thereby extending the operational lifespan of high-nickel cathodes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides improved operational stability, capacity retention at low temperatures, and extended lifespan at high temperatures by preventing excessive resistance increase and maintaining high power and capacity properties, even with high nickel content cathodes.
Implementation Method 1
the additive may function as a radical scavenger. Accordingly, a lithium-ion transfer may be facilitated, and a swelling phenomenon at high temperature may be suppressed to improve high-temperature life-span properties
Implementation Method 2
a non-aqueous electrolyte includes a non-aqueous organic solvent, a lithium salt, an additive represented by Chemical Formula 1 or Chemical Formula 2
Data Source
AI summary
A non-aqueous electrolyte and a lithium secondary battery including the same are provided. The non-aqueous electrolyte includes a non-aqueous organic solvent, a lithium salt, an additive represented by Chemical Formula 1 or Chemical Formula 2, and an auxiliary additive including a carbonate-based compound. A content of the additive relative to a weight of the carbonate-based compound is in a range from 10 wt % to 50 wt %. Capacity properties at low temperature and lifespan properties at high temperature may be improved.