Cis Difluoro Ionic Complex for Low-Temp Battery Output
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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 high-rate properties after prolonged use or high-temperature storage, with existing solutions failing to adequately prevent decomposition and gas generation that affects battery performance.
Innovation Solution
A nonaqueous electrolytic solution comprising a difluoro ionic complex in the cis configuration, combined with specific salts and silane compounds, which enhances ion conductivity and stability, thereby improving output characteristics and high-rate performance even after extensive charge-discharge cycles and high-temperature storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nonaqueous electrolytic solutions are used in lithium secondary batteries, then the batteries can operate with basic charge-discharge functionality, but the output characteristics deteriorate at low temperatures and after prolonged use or high-temperature storage
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolytic solution by introducing a specific difluoro ionic complex with cis configuration and controlling its content within 0.01-5 mass% relative to the electrolyte. This parameter change enables the solution to maintain high ion conductivity across a wide temperature range while preventing decomposition, thereby resolving the contradiction between low-temperature output characteristics and high-temperature storage stability
Solution Approach 2:
The patent creates a composite electrolytic solution system by combining the difluoro ionic complex with specific components including chain carbonates (ethyl methyl carbonate, diethyl carbonate), cyclic carbonates (ethylene carbonate, propylene carbonate), and lithium salts (LiPF6, LiBF4). This composite formulation synergistically improves both low-temperature output characteristics and high-temperature storage performance, achieving reliability across varying operating conditions
2Productivity
If the battery undergoes extensive charge-discharge cycles, then the battery capacity is utilized, but cycle durability decreases due to decomposition products and gas generation
Solution Approach 1:
The difluoro ionic complex acts as a protective agent that preemptively prevents the decomposition of conventional electrolytic solution components during charge-discharge cycles. By being present in the electrolytic solution from the beginning, it suppresses the formation of decomposition products and gases that would otherwise accumulate and degrade cycle characteristics, thereby maintaining productivity over extended cycling
Solution Approach 2:
The difluoro ionic complex serves as an intermediary substance between the electrode materials and the bulk electrolytic solution. It mediates the electrochemical reactions by facilitating ion transport while protecting the electrode surfaces from direct contact with aggressive electrolyte components, thus improving cycle durability without sacrificing charge-discharge capacity
3Quantity of substance
If metal lithium or alloy materials are used as negative electrode material to achieve high initial capacity, then the initial capacity is high, but pulverization is promoted during cycles leading to decreased charge/discharge efficiency
Solution Approach 1:
The difluoro ionic complex provides beforehand cushioning protection for metal lithium or alloy negative electrodes by forming a stable protective interface layer during initial cycles. This layer cushions the electrode material against mechanical stress and chemical degradation during subsequent cycling, preventing pulverization and maintaining charge/discharge efficiency while preserving the high initial capacity benefits of metal lithium or alloy materials
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 achieves high output characteristics at low temperatures and maintains performance after storage at high temperatures, with improved cycle durability and reduced irreversible capacity, ensuring stable battery operation.
Implementation Method 1
enhances ion conductivity and stability, thereby improving output characteristics and high-rate performance
Implementation Method 2
a nonaqueous solvent in a nonaqueous electrolytic solution may be reductively decomposed on the surface of a negative electrode upon charging, resulting in generation of decomposition products or gases
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 showing sufficient performance again at low temperature even after stored at a high temperature. 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 difluorophosphate salt, a monofluorophosphate salt, a specific salt having an imide anion, and a specific silane 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).