Core-Shell Electrolyte Additive for High-Temperature Battery Protection
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Solution Overview
Problem
Rechargeable lithium batteries face issues with thermal stability and safety due to the decomposition of LiPF6, leading to electrolyte depletion and increased resistance, which compromises high-temperature performance and safety.
Innovation Solution
An additive with a core of polyethylene wax and a shell of a polymer with a melting point of 90 °C to 120 °C, such as PVDF-HFP, is used to form fibers through electrospinning, which releases the core material at high temperatures to prevent short circuits and maintain battery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as lithium salt in electrolyte, then battery performance is improved, but thermal stability deteriorates due to decomposition at high temperatures
Solution Approach 1:
A polymer-coated lithium salt additive serves as an intermediary substance in the electrolyte. The polymer coating (melting point 90-120°C) protects the lithium salt core from direct thermal decomposition while allowing ionic conductivity. When temperature exceeds the polymer melting point, the coating breaks down to release the lithium salt, providing a controlled release mechanism that improves thermal stability while maintaining performance.
Solution Approach 2:
The invention changes the physical state and release timing of the lithium salt by encapsulating it in a polymer matrix. The polymer's melting point (90-120°C) is specifically selected to be higher than normal operating temperatures but lower than decomposition temperatures of lithium salts. This parameter change enables the system to maintain stability during operation and only activate when needed for safety.
2Reliability
If electrolyte components are used to maintain battery characteristics, then resistance increases at high temperatures causing short circuits
Solution Approach 1:
The polymer-coated lithium salt additive performs preliminary protective action by preventing direct contact between electrolyte components and high-temperature conditions. The polymer coating acts as a thermal barrier that prevents premature reactions and resistance increase. Only when the temperature exceeds the polymer melting point does the protective layer break down, at which point the released lithium salt helps maintain proper electrolyte composition and prevents short circuits.
3Reliability
If additive amount is increased to improve safety, then electrolyte composition is altered affecting battery performance
Solution Approach 1:
The invention uses parameter changes in the polymer's melting point (selected between 90-120°C) to control the activation and release of the lithium salt additive. This allows a small amount of additive to have a amplified effect - remaining dormant during normal operation (maintaining electrolyte composition) and then releasing concentrated lithium salt when thermal runaway is detected, thus improving safety without permanently altering electrolyte composition.
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 additive enhances electrolyte impregnation and suppresses short circuits, improving safety and maintaining battery performance without increasing resistance, thereby enhancing cycle-life characteristics and high-temperature reliability.
Implementation Method 1
the shell includes a polymer having a melting point of 90 °C to 120 °C
Implementation Method 2
The additive may be in a form of fibers formed using electrospinning
Data Source
Figure 1~2
AI summary
Provided are an additive for a rechargeable lithium battery, an electrolyte a rechargeable lithium battery including the same, and a rechargeable lithium battery, the additive including a core including polyethylene wax, and a shell surrounding the core, wherein the shell includes a polymer having a melting point of 90 °C to 120 °C.