Fluorinated Ester Additive for Lithium Battery Electrolyte
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Solution Overview
Problem
Lithium secondary batteries face issues with the decomposition of electrolytic solutions, leading to deteriorated battery performance, including reduced capacity and cycle life, due to solvent decomposition on electrodes and gas generation, which worsens with increased power consumption.
Innovation Solution
Incorporating an ester compound with an alkoxy group and a fluorine atom on a benzene ring, such as propargyl 3-methoxy-2,4,5-trifluorobenzoate, into the nonaqueous electrolytic solution to enhance initial battery capacity and cycle properties, and using specific ester compounds in the electrolyte to prevent reductive decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytic solutions are used in lithium secondary batteries, then the batteries can operate, but the solvent decomposes on the electrodes through reduction and oxidation, leading to deteriorated battery performance and reduced cycle life
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance in the electrolytic solution. This compound acts as a mediator that preferentially reacts with the electrode surfaces to form stable protective films, preventing the direct contact and harmful reactions between the conventional electrolyte solvents and the electrodes. The fluorinated compound serves as a buffer layer that protects the system from degradation.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolytic solution by incorporating fluorinated cyclic carbonate compounds with specific molecular structures and fluorine content ratios. By changing the chemical parameters (adding compounds with 20-70% fluorine by mass), the stability and performance characteristics of the electrolyte are improved, reducing decomposition and enhancing cycle life.
2Power
If the capacity of lithium secondary batteries is increased to meet higher power consumption demands, then the battery power increases, but the electrolytic solution becomes more easily decomposable, worsening cycle property
Solution Approach 1:
The fluorinated cyclic carbonate compound performs preliminary protective action by forming stable films on the electrode surfaces before the main electrolyte decomposition can occur. This pre-formed protective layer prevents subsequent degradation reactions, allowing the battery to maintain high capacity and power output without suffering from accelerated electrolyte decomposition that would normally worsen cycle properties.
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 lithium secondary battery exhibits improved initial battery capacity and cycle properties, maintaining performance over a long period by preventing solvent decomposition and gas generation, thus addressing the limitations of existing battery technologies.
Implementation Method 1
the solvent in the nonaqueous electrolytic solution decomposes through reduction on the surface of the negative electrode in charging
Implementation Method 2
when the solvent in the nonaqueous electrolytic solution has a high temperature in a charged state, then it partly decomposes through oxidation locally in the interface between the positive electrode material and the nonaqueous electrolytic solution
Data Source
AI summary
The present invention includes (1) an ester compound having a specific structure, (2) a nonaqueous electrolytic solution for lithium secondary battery comprising an electrolyte dissolved in a nonaqueous solvent and containing an ester compound having a specific structure in an amount of from 0.01 to 10% by weight of the nonaqueous electrolytic solution, which is excellent in initial battery capacity and cycle property, and (3) a lithium secondary battery comprising a positive electrode, a negative electrode and a nonaqueous electrolytic solution of an electrolyte salt dissolved in a nonaqueous solvent, wherein the nonaqueous electrolytic solution contains an ester compound having a specific structure in an amount of from 0.01 to 10% by weight of the nonaqueous electrolytic solution.