Li-Ion Cell Electrolyte and Separator for Heat-Treated Stability
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Solution Overview
Problem
Lithium-ion secondary batteries face degradation of charging and discharging characteristics and safety concerns due to heat treatment, requiring high heat resistance and flexibility in power storage devices for integration with electronic devices.
Innovation Solution
A power storage device comprising a positive electrode, negative electrode, first separator, and electrolyte with specific components such as polyphenylene sulfide or cellulosic fiber separators and a solvent system of propylene carbonate, ethylene carbonate, and vinylene carbonate, along with lithium hexafluorophosphate and lithium bis(pentafluoroethanesulfonyl)amide, to enhance thermal stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes and separators are used in lithium-ion secondary batteries, then the batteries can achieve basic charging and discharging functions, but the charging and discharging characteristics are degraded by heat treatment and safety concerns arise
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by using a specific mixture of cyclic carbonate (15-30 vol%), chain carbonate (40-70 vol%), and carboxylate (10-40 vol%). This parameter optimization ensures the electrolyte maintains stability during heat treatment while preserving charging and discharging characteristics. The separator composition is also optimized with polyolefin (3-20 mass%) and non-polyolefin (80-97 mass%) to achieve thermal stability without degrading performance
Solution Approach 2:
The patent employs composite materials in both the electrolyte and separator. The electrolyte is a composite of three different carbonate types (cyclic, chain, and carboxylate) that work synergistically to provide heat resistance. The separator is a composite of polyolefin and non-polyolefin materials, where the polyolefin provides thermal shutdown functionality and the non-polyolefin maintains structural integrity. This composite approach resolves the contradiction by combining materials with complementary properties
2Object-affected harmful factors
If the power storage device is designed for high heat resistance, then safety is improved, but flexibility is reduced
Solution Approach 1:
The patent uses a thin-film separator with optimized composition (polyolefin 3-20 mass%, non-polyolefin 80-97 mass%) that provides both thermal safety and flexibility. The thin-film structure inherently offers flexibility while the carefully controlled composition ensures heat resistance through the polyolefin content that provides thermal shutdown functionality. This resolves the contradiction between safety and flexibility by achieving both through material composition and structural design
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 provides a power storage device with improved heat resistance, safety, and flexibility, preventing degradation of charging and discharging characteristics even under heat treatment, suitable for integration with electronic devices.
Implementation Method 1
The electrolyte includes propylene carbonate, ethylene carbonate, and vinylene carbonate, lithium hexafluorophosphate, and lithium salt expressed by General Formula (G1)
Implementation Method 2
The first separator is positioned between the positive electrode and the negative electrode. The first separator includes polyphenylene sulfide or cellulosic fiber
Data Source
AI summary
Provided is a power storage device whose charging and discharging characteristics are unlikely to be degraded by heat treatment or a power storage device that is highly safe against heat treatment. The power storage device includes a positive electrode, a negative electrode, a separator, an electrolyte, and an exterior body. The separator is positioned between the positive electrode and the negative electrode and includes polyphenylene sulfide or cellulosic fiber. The electrolyte includes propylene carbonate, ethylene carbonate, and vinylene carbonate, lithium hexafluorophosphate, and lithium bis(pentafluoroethanesulfonyl)amide. A concentration of lithium hexafluorophosphate with respect to the electrolyte is more than or equal to 0.01 wt % and less than or equal to 1.9 wt % in a weight ratio.