Nonaqueous Battery Electrolyte Additives for High-Temperature Stability
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Solution Overview
Problem
Nonaqueous secondary batteries face issues with electrolyte decomposition at the negative electrode, leading to increased impedance and impaired cycle properties, especially at high temperatures, due to the reductive decomposition of organic solvents and the formation of gas, which affects charging efficiency and battery stability.
Innovation Solution
Incorporating a nonaqueous electrolyte containing a vinyl ethylene carbonate (VEC) derivative, a cyclic acid anhydride, and a cyclic ether derivative such as 1,3-dioxane or its derivatives, which synergistically enhances lithium ion conductivity and suppresses oxidative decomposition, forming a stable surface coating that reduces impedance and gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic solvents are used as nonaqueous electrolyte, then high dielectric constant and ion-conductivity are achieved, but reductive decomposition occurs on negative electrode surface leading to increased impedance and gas generation
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance that mediates between the electrolyte and the negative electrode. This compound preferentially decomposes to form a protective coating layer that prevents direct contact and harmful reactions between the organic solvent and the carbonaceous negative electrode material, thereby reducing gas generation and impedance increase while maintaining electrolyte functionality
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating fluorinated cyclic carbonate compounds with specific molecular structures and fluorine content ratios. This parameter change alters the decomposition behavior and surface coating properties, transforming the harmful reductive decomposition into a controlled process that forms beneficial protective layers
2Reliability
If conventional electrolyte additives are used to suppress decomposition, then some protection is achieved, but charging load property and high-temperature cycle property remain impaired
Solution Approach 1:
The patent optimizes the concentration ratio parameters of the fluorinated cyclic carbonate compound in the electrolyte, specifically setting it within 0.01-5% by mass relative to total electrolyte mass. This precise parameter control ensures sufficient protective coating formation while maintaining adequate ion conductivity and charging performance, resolving the trade-off between decomposition suppression and charging load property
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate compounds with conventional electrolyte components. This composite approach integrates the decomposition suppression benefits of fluorinated compounds with the established performance characteristics of conventional electrolytes, achieving both protection and high charging load property
3Ease of operation
If battery is stored in charged state at high temperature, then convenient storage is achieved, but remaining capacity decreases and gas generation increases
Solution Approach 1:
The patent applies beforehand cushioning by pre-forming a stable protective coating layer on the negative electrode surface during initial electrolyte decomposition. This pre-formed coating acts as a cushion that prevents subsequent harmful reactions during high-temperature charged storage, maintaining remaining capacity and suppressing gas generation throughout the storage period
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 results in improved charging load and cycle properties at both room temperature and high temperatures, with a larger remaining capacity and reduced gas generation when the battery is stored in a charged state, maintaining battery performance and stability.
Implementation Method 1
an organic solvent is reductively decomposed on an electrode surface during a charging or discharging process
Implementation Method 2
forming a stable surface coating that reduces impedance and gas generation
Implementation Method 3
a nonaqueous electrolyte having high ion-conductivity in a wide range of temperatures
Implementation Method 4
a material including a lithium compound oxide capable of reversibly intercalating and deintercalating lithium
Data Source
AI summary
A nonaqueous secondary battery includes a negative electrode using a negative electrode active material containing a carbonaceous material; a positive electrode using a positive electrode active material capable of reversibly intercalating and deintercalating lithium; and a nonaqueous electrolyte. The nonaqueous electrolyte contains:(1) a vinyl ethylene carbonate derivative represented by Formula (I):wherein R1 to R6 independently represent a hydrogen atom or an alkyl group having a carbon number of 1 to 4;(2) a cyclic acid anhydride; and(3) at least one cyclic ether derivative selected from the group consisting of 1,3-dioxanes, 1,3-dioxolanes and derivatives thereof.Accordingly, a nonaqueous secondary battery can be obtained which is excellent in charging load property and cycle property at room temperature and at high temperatures and in which even when the battery is preserved in a charged state in a high temperature atmosphere, not only remaining capacity is large, but also the amount of generated gas is small.