Difluoro Ionic Complex Electrolyte for Low-Temperature Battery Performance
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Solution Overview
Problem
Conventional nonaqueous electrolytic solutions for lithium secondary batteries face challenges in maintaining high output characteristics at low temperatures and ensuring safety, as they tend to degrade over time and are prone to expansion and overcharging issues.
Innovation Solution
A nonaqueous electrolytic solution comprising a difluoro ionic complex in a cis configuration and specific compounds such as cyclic phosphazene, siloxane, or fluorinated ether, which enhances ion conductivity, stability, and safety by preventing expansion and overcharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional nonaqueous electrolytic solutions are used in lithium secondary batteries, then the batteries can operate with standard ion conductivity, but the output characteristics deteriorate at low temperatures and cycle durability decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolytic solution by introducing a difluoro ionic complex with specific molecular structure (formula 1) containing P, As, or Sb central atom coordinated with fluorine atoms and oxygen-containing or nitrogen-containing ligands. This parameter change in electrolyte composition improves ion conductivity at low temperatures while maintaining cycle durability through stable SEI formation.
Solution Approach 2:
The patent creates a composite electrolytic system by combining the difluoro ionic complex (formula 1) with conventional electrolyte components including lithium salts (LiPF6, LiBF4), cyclic carbonates (EC, PC), and chain carbonates (DMC, DEC). This composite approach leverages the synergistic effects of the ionic complex for low-temperature performance and conventional components for overall stability.
2Temperature
If the battery operates at low temperatures, then cold environment performance is improved, but ion conductivity and electrochemical reactions are hindered
Solution Approach 1:
The difluoro ionic complex modifies the electrolyte's physical parameters including viscosity and dielectric constant, enabling maintained ion conductivity at low temperatures. The complex's molecular structure with fluorine atoms and coordinated ligands reduces solution viscosity and enhances ion mobility even in cold conditions.
3Quantity of substance
If the battery capacity is increased for large-sized applications, then energy storage capability is improved, but expansion and overcharging issues arise
Solution Approach 1:
The difluoro ionic complex acts as an intermediary substance that mediates between the electrode and electrolyte interface. It forms a protective intermediate layer that prevents direct harmful interactions, suppresses expansion by controlling SEI growth, and prevents overcharging by regulating ion transport at high states of charge.
Solution Approach 2:
The patent converts the potential harm of solvent decomposition and electrode degradation into beneficial effects. The ionic complex promotes controlled formation of stable SEI layers that protect electrodes from further degradation, and the decomposition products form protective films that prevent overcharging and expansion.
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 maintains high output characteristics at low temperatures, improves cycle durability, and enhances safety by preventing expansion and overcharging, thus extending the battery's lifespan and performance.
Implementation Method 1
enhances ion conductivity
Implementation Method 2
a nonaqueous solvent in a nonaqueous electrolytic solution may be reductively decomposed on the surface of a negative electrode upon charging
Implementation Method 3
This film on the surface of the electrode which is called a Solid Electrolyte Interface (SEI) may, in nature, have significant impacts on battery performance. For example, it may reduce reductive decomposition of a solvent to prevent deterioration of battery performance.
Implementation Method 4
a nonaqueous solvent in a nonaqueous electrolytic solution may partly undergo local oxidative decomposition at the interface between a positive electrode material and the nonaqueous electrolytic solution when the temperature is increased during charging
Data Source
AI summary
An object of the present invention is to provide a nonaqueous electrolytic solution and a nonaqueous electrolytic solution secondary battery capable of showing high output characteristics at a low temperature even after the battery is used to some extent, and capable of showing good high-rate properties, and further capable of improving safety of batteries. The nonaqueous electrolytic solution includes a nonaqueous solvent, an electrolyte dissolved in the nonaqueous solvent, (I) a difluoro ionic complex (1) represented by the general formula (1), and (II) at least one compound selected from the group consisting of a specific cyclic phosphazene compound, siloxane compound, aromatic compound, cyclohexene compound, phosphoric acid ester compound, fluorinated linear ether compound, fluorinated cyclic ether compound, and boric acid ester compound, and 95 mol % or more of the difluoro ionic complex (1) is a difluoro ionic complex (1-Cis) in a cis configuration represented by the general formula (1-Cis).