Fluorinated Nonaqueous Electrolyte for Low-Temperature Li-Ion Cycling
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges in improving low-temperature cycle performance, capacity retention rate, and safety performance, particularly in extreme conditions such as electric vehicles and high-altitude electric aircraft.
Innovation Solution
A nonaqueous electrolyte solution comprising compounds A and B, where compound A includes a saturated ring with 1 or 2 oxygen atoms and fluorine-containing substituents, and compound B has fluorine atoms replacing ring carbon atoms adjacent to oxygen, combined with a lithium salt and optionally a phosphate ester additive, to enhance stability and capacity release at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used to improve low-temperature cycle performance, then capacity retention rate improves, but safety performance deteriorates due to increased oxidative decomposition
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by introducing fluorinated cyclic carbonates (compound A) and fluorinated cyclic carboxonates (compound B) with specific fluorine substitution patterns. This chemical parameter change enables the electrolyte to maintain low-temperature performance while improving oxidation resistance, resolving the contradiction between cycle performance and safety.
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate (compound A) and fluorinated cyclic carboxonate (compound B) in specific ratios (0.3:0.7 to 0.7:0.3 by volume). This composite approach synergistically improves both low-temperature capacity retention and oxidation resistance, addressing the safety-performance contradiction.
2Object-affected harmful factors
If fluorine atoms are increased in the electrolyte compounds to improve oxidation resistance, then safety performance improves, but low-temperature capacity release deteriorates
Solution Approach 1:
The patent applies fluorine substitution locally at specific positions (ring carbon atoms adjacent to oxygen atoms) rather than throughout the entire molecule. This localized fluorination provides oxidation resistance at the critical interface with lithium ions while preserving the bulk molecular properties needed for low-temperature ionic conductivity and capacity release.
Solution Approach 2:
The patent optimizes the fluorine content parameter by limiting substitution to specific ring positions adjacent to oxygen atoms, rather than complete fluorination. This parameter optimization maintains the balance between oxidation resistance (improved by fluorine) and low-temperature capacity release (maintained by preserving molecular mobility and ionic conductivity).
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 significantly prolongs cycle life and capacity retention of lithium secondary batteries at low temperatures while improving safety by reducing oxidative decomposition and maintaining high energy density.
Implementation Method 1
The nonaqueous electrolyte solution formed by using the mutually coordinating compound A and compound B as a solvent in the secondary battery
Implementation Method 2
improving safety by reducing oxidative decomposition
Data Source
AI summary
This application discloses a nonaqueous electrolyte solution, a secondary battery containing the nonaqueous electrolyte solution, and an electrical device. The nonaqueous electrolyte solution includes: a compound A including a saturated five-membered ring or six-membered ring and at least one fluorine-containing substituent, where the ring contains 1 or 2 oxygen atoms as ring atoms, and a ring carbon atom connected to the oxygen atom in the ring is not directly replaced by fluorine; and a compound B including a saturated five-membered ring or six-membered ring that contains 1 or 2 oxygen atoms as ring atoms, where at least one ring carbon atom connected to the oxygen atom in the ring is directly replaced by at least one fluorine atom.