Nonaqueous Electrolyte Solution for High-Temperature Battery Stability
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Solution Overview
Problem
Conventional lithium secondary batteries face challenges in maintaining performance at high temperatures, particularly in terms of discharge capacity retention and low-temperature input characteristics after high-temperature storage, especially with high-density electrodes.
Innovation Solution
A nonaqueous electrolytic solution containing four or more kinds of lithium salts, including a main electrolyte salt like LiPF6 and additional salts with oxalate, phosphate, and S=O groups, which suppress decomposition and enhance thermal stability, forming a firm surface film to improve electrochemical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional electrolyte solutions are used at high temperature, then the battery can operate at elevated temperatures, but the discharge capacity retention and low-temperature input characteristics deteriorate due to solvent decomposition
Solution Approach 1:
The patent introduces a film-forming additive as an intermediary substance that mediates between the electrolyte solvent and the electrode surface. This additive preferentially decomposes to form a protective film that prevents further decomposition of the main electrolyte solvent, thereby maintaining battery performance at high temperatures. The additive acts as a sacrificial protective layer that shields the electrode from harmful reactions.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte solution by adding specific compounds (e.g., fluoroethylene carbonate, other fluorinated carbonates) to change the properties of the surface film formed on the electrode. This parameter change in the electrolyte composition leads to the formation of a more stable and protective surface film that maintains ion permeability while preventing solvent decomposition at high temperatures.
2Temperature
If the battery is stored at high temperature for extended periods, then thermal energy is maintained, but low-temperature input characteristics worsen due to decomposition products blocking ion movement
Solution Approach 1:
The patent applies preliminary action by having the film-forming additive decompose first during initial high-temperature exposure to create a protective surface film before the main electrolyte solvent can decompose. This preliminary decomposition of the additive prevents the formation of harmful decomposition products that would otherwise block ion movement and degrade low-temperature performance during subsequent storage.
Solution Approach 2:
The patent converts the potentially harmful decomposition reaction into a beneficial protective mechanism. The film-forming additive is designed to decompose preferentially at high temperatures, and this decomposition product forms a protective film that benefits the battery by preventing further decomposition and maintaining performance. The harmful decomposition is thus transformed into a useful protective action.
3Volume of moving object
If thin laminate film packaging is used to reduce device size, then the battery becomes more compact, but the battery deforms easily due to outer packaging expansion at high temperature
Solution Approach 1:
The patent converts the thermal expansion of the outer packaging from a harmful factor causing deformation into a beneficial effect. By forming a stable surface film through the film-forming additive, the battery can accommodate the expansion of the thin laminate packaging at high temperatures without deforming. The protective film acts as a buffer that allows the packaging to expand while maintaining overall battery structural integrity.
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 discharge capacity retention, low-temperature output, and input characteristics after high-temperature storage, ensuring better battery performance across a wide temperature range.
Implementation Method 1
forming a firm surface film to improve electrochemical characteristics
Implementation Method 2
a nonaqueous electrolytic solution containing a lithium salt and a nonaqueous solvent
Data Source
AI summary
Provided are a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent, the electrolyte salt including at least one first lithium salt selected from LiPF6, LiBF4, LiN(SO2F)2, LiN(SO2CF3)2, and LiN(SO2C2F5)2, and at least one second lithium salt selected from a lithium salt having an oxalate structure, a lithium salt having a phosphate structure, and a lithium salt having an S=O group, with a sum total of the first lithium salt and the second lithium salt being four or more, and an energy storage device using the same. This nonaqueous electrolytic solution is not only able to improve electrochemical characteristics at a high temperature and much more improve a discharge capacity retention rate and low-temperature output characteristics after a high-temperature storage test but also able to improve low-temperature input characteristics even for high-density electrodes.