Fluorinated Cyclic Carbonate Electrolyte for High-Rate Lithium Batteries
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Solution Overview
Problem
Conventional lithium secondary batteries face challenges in achieving a desirable high-rate characteristic, particularly for applications in automobiles, where improved ionic conductivity and reduced interface resistance are necessary, while also requiring enhanced energy density and long-term reliability.
Innovation Solution
A nonaqueous electrolyte solution comprising a cyclic carbonate with a fluoro group, a chain carbonate, and trimethylacetonitrile, along with a lithium salt, is used to improve the high-rate characteristic of lithium secondary batteries, forming a low-resistance coating at the electrode interface and enhancing ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional mixed solvents (cyclic carbonate and chain carbonate) are used, then the battery has basic electrolyte function, but the ionic conductivity is insufficient and interface resistance is high
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solvent by introducing a fluorinated cyclic carbonate compound with specific molecular structure (fluoro group at specific position), which fundamentally alters the interface resistance characteristics and ionic conductivity of the electrolyte system
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate (5-70 vol%), chain carbonate (20-45 vol%), and cyclic carbonate (5-45 vol%), where the synergistic interaction between different components achieves both low interface resistance and high ionic conductivity
2Quantity of substance
If energy density is improved by using high-voltage electrodes, then the battery capacity increases, but the electrolyte stability deteriorates due to reductive and oxidative degradation
Solution Approach 1:
The fluorinated cyclic carbonate compound acts in advance to form a stable protective interface film on the electrode surface before degradation can occur, preventing both reductive degradation at the negative electrode and oxidative degradation at the positive electrode during high-voltage operation
Solution Approach 2:
The patent uses a small amount of fluorinated cyclic carbonate (5-70 vol%) as a sacrificial additive that forms a durable protective layer, sacrificing the additive itself to protect the main electrolyte system from degradation over long-term operation
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 effectively improves the high-rate characteristic of lithium secondary batteries by reducing interface resistance and maintaining long-term reliability, making them suitable for high-energy density applications such as electric vehicles.
Implementation Method 1
forming a low-resistance coating at the electrode interface
Implementation Method 2
Ionic conductivity of nonaqueous electrolyte solution is high
Data Source
AI summary
A nonaqueous electrolyte solution for a secondary battery includes: a nonaqueous solvent including a cyclic carbonate having at least one fluoro group on a side chain thereof, a chain carbonate, and trimethylacetonitrile; and a lithium salt dissolved in the nonaqueous solvent.