Nonaqueous Electrolyte Additives Suppress Decomposition
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Solution Overview
Problem
Conventional nonaqueous electrolyte secondary batteries using graphite-based carbonaceous materials face issues with decomposition of solvents like propylene carbonate, leading to reduced lithium storage and release efficiency, and suffer from gas generation, reduced cycle characteristics, and safety concerns, especially under high-temperature conditions.
Innovation Solution
A nonaqueous electrolytic solution containing a nitrile compound with specific structures, such as acrylonitrile or fumaronitrile, and halogen atom-containing cyclic carbonates, which form films on electrodes to suppress decomposition and enhance charge-discharge efficiency and cycle characteristics, particularly when used with negative electrodes containing Si, Sn, or Pb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If propylene carbonate is used as a high-dielectric solvent in nonaqueous electrolytic solutions, then the battery can achieve higher energy density, but the decomposition reaction of propylene carbonate proceeds vigorously on electrode surfaces during charging, reducing lithium storage and release efficiency
Solution Approach 1:
The patent introduces a specific additive (vinylene carbonate at 0.01-5 wt% and fluoroethylene carbonate at 0.01-5 wt%) that acts as an intermediary substance. These additives preferentially decompose to form stable protective films on the electrode surfaces, which then prevent the vigorous decomposition of propylene carbonate during charging, thereby maintaining lithium storage and release efficiency while preserving the high energy density benefits of propylene carbonate
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolytic solution by precisely controlling the concentrations of vinylene carbonate (0.01-5 wt%) and fluoroethylene carbonate (0.01-5 wt%). This parameter optimization allows the formation of effective protective films that suppress decomposition reactions, resolving the contradiction between maintaining high energy density and ensuring reliable lithium storage/release
2Stability of the object's composition
If ethylene carbonate is used as a main solvent to suppress decomposition, then the battery shows improved stability, but there are reductions in charge and discharge efficiency and cycle characteristics, and an increase in internal battery pressure due to gas generation
Solution Approach 1:
The patent creates a composite electrolytic solution system combining ethylene carbonate (5-50 vol%) with propylene carbonate (50-95 vol%) and specific additives (vinylene carbonate and fluoroethylene carbonate). This composite formulation leverages the stability of ethylene carbonate while using propylene carbonate to maintain efficiency, and the additives to form protective films that prevent gas generation, thereby achieving both stability and high productivity
Solution Approach 2:
The additives vinylene carbonate and fluoroethylene carbonate serve as intermediary substances that form stable protective films on electrode surfaces. These films prevent direct contact between the electrolyte and electrodes, suppressing gas-generating decomposition reactions while maintaining efficient lithium ion transport, thus resolving the contradiction between stability and charge/discharge efficiency
3Temperature
If conventional electrolytic solutions are used under high-temperature conditions, then the battery can operate at elevated temperatures, but gas generation increases and cycle characteristics deteriorate
Solution Approach 1:
The patent uses vinylene carbonate and fluoroethylene carbonate as intermediary additives that form thermally stable protective films on electrode surfaces. These films act as barriers that prevent electrolyte decomposition even under high-temperature conditions, thereby suppressing gas generation and maintaining excellent cycle characteristics while enabling operation at elevated temperatures
Solution Approach 2:
The patent optimizes the concentration parameters of vinylene carbonate (0.01-5 wt%) and fluoroethylene carbonate (0.01-5 wt%) to ensure adequate protective film formation at high temperatures. This parameter control ensures the films remain stable and effective under thermal stress, preventing gas generation and maintaining reliable cycle characteristics across a wide temperature range
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 inhibits gas generation during high-temperature storage and improves cycle characteristics, maintaining high capacity and storage performance in nonaqueous electrolyte secondary batteries.
Implementation Method 1
These compounds contained in the electrolytic solutions are reductively decomposed on surfaces of negative electrodes to form films that suppress excessive decomposition of the electrolytic solutions
Implementation Method 2
the decomposition reaction of propylene carbonate proceeds vigorously on surfaces of the electrodes during charging
Data Source
AI summary
A nonaqueous electrolytic solution that can provide a high energy density nonaqueous electrolyte secondary battery having a high capacity, excellent storage characteristics, and excellent cycle characteristics and suppressing the decomposition of an electrolytic solution and the deterioration thereof when used in a high-temperature environment includes an electrolyte, a nonaqueous solvent, and a compound represented by general formula (1):wherein R1, R2, and R3 each independently represent a hydrogen atom, a cyano group, or an optionally halogen atom-substituted hydrogen group having 1 to 10 carbon atoms, with the proviso that R1 and R2 do not simultaneously represent hydrogen atoms.