Nonaqueous Electrolyte with Fluorinated Carbonate and Dinitrile
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Solution Overview
Problem
Lithium secondary batteries face deterioration in electrochemical properties across a broad temperature range due to decomposition of nonaqueous electrolytic solutions, which affects lithium ion migration and battery performance, especially in vehicles used in varying climates.
Innovation Solution
A nonaqueous electrolytic solution is developed with 0.001 to 5% by mass of a branched dinitrile compound and a fluorine atom-containing cyclic carbonate, or a linear dinitrile compound, to improve electrochemical properties by forming a coating film that suppresses oxidative decomposition and enhances Li ion permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a nonaqueous electrolytic solution is used in lithium secondary batteries, then the batteries can operate with high energy density, but the electrolytic solution decomposes at high temperatures and deposits on electrodes, worsening electrochemical properties in broad temperature ranges
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance that mediates between the electrolytic solution and the electrode surface. This compound preferentially decomposes to form a protective coating film that acts as a barrier, preventing the harmful decomposition and deposition of the main electrolytic solution components on the electrodes, thereby maintaining electrochemical performance across broad temperature ranges while preserving high energy density
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolytic solution by adding fluorinated cyclic carbonate compounds with specific molecular structures and concentrations (0.01-5% by volume). This parameter change alters the decomposition behavior and surface properties of the electrolytic solution, enabling it to form stable protective films that prevent electrode degradation and maintain reliable electrochemical properties in both high and low temperature conditions
2Productivity
If the electrolytic solution is reduced in volume to increase electrode density, then battery capacity is increased, but decomposition of the electrolytic solution is accelerated, worsening electrochemical characteristics
Solution Approach 1:
The fluorinated cyclic carbonate compound serves as a protective intermediary that forms a stable coating film on the electrode surface. This intermediary layer prevents direct contact and harmful reactions between the concentrated electrolytic solution and the electrode, allowing the battery to achieve high capacity through increased electrode density without suffering from accelerated electrolytic solution decomposition
3Ease of operation
If decomposed products are deposited on the negative electrode, then lithium cannot smoothly be absorbed and released, but preventing decomposition requires reducing electrolytic solution volume
Solution Approach 1:
The fluorinated cyclic carbonate compound acts as a sacrificial intermediary that decomposes first to form a protective coating film on the electrode surface. This intermediary decomposition prevents the decomposition and deposition of main electrolytic solution components, ensuring that lithium can smoothly be absorbed and released from the negative electrode without forming harmful deposits, while maintaining adequate electrolytic solution volume
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 improves the electrochemical properties of lithium batteries, particularly at low temperatures after storage at high temperatures, maintaining performance across a broad temperature range without excessive coating film formation on electrodes.
Implementation Method 1
decomposed products and gases generated from a solvent in a nonaqueous electrolytic solution which is reduced and decomposed on a surface of a negative electrode
Implementation Method 2
forming a coating film that suppresses oxidative decomposition
Implementation Method 3
enhances Li ion permeability
Implementation Method 4
lithium can not smoothly be absorbed onto and released from a negative electrode
Data Source
AI summary
The object of the present invention is to provide a nonaqueous electrolytic solution that can improve the electrochemical properties in a broad temperature range and an electrochemical device using the same. A nonaqueous electrolytic solution prepared by dissolving an electrolyte salt in a nonaqueous solvent, wherein the nonaqueous solvent includes 0.1 to 30% by volume of a fluorine atom-containing cyclic carbonate, and further the nonaqueous electrolytic solution includes 0.001 to 5% by mass of a branched dinitrile compound in which the main chain of an alkylene chain linking the two nitrile groups has 2 or more and 4 or less of the carbon number.