Separator Thermal Shrinkage Evaluation by Four-Point Imaging
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Solution Overview
Problem
Existing methods for evaluating the thermal shrinkage rate of separators in batteries suffer from low accuracy and reliability, particularly when the separator does not maintain a square shape, making it difficult to measure the shrinkage rate accurately.
Innovation Solution
A separator thermal shrinkage rate evaluation device and method that uses a mounting table, lighting units to illuminate the separator sample, an imaging unit to capture images, and an evaluation unit to determine shrinkage by comparing measured lengths with reference values based on four reference points, setting first and second measurement ranges in the X and Y-axis directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a gel electrolyte is used in a lithium ion secondary battery, then Li ion mobility is improved, but thermal run-away resistance deteriorates due to separator shrinkage at elevated temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the gel electrolyte by incorporating specific concentrations of LiPF6 (1-3 mol/L), cyclic carbonates (15-30 vol%), chain carbonates (65-80 vol%), and gum arabic (0.1-5 wt%). These parameter adjustments optimize both Li ion mobility and thermal stability, preventing separator shrinkage at elevated temperatures while maintaining fast ion transport.
Solution Approach 2:
The patent creates a composite gel electrolyte system combining multiple components: lithium salts (LiPF6), cyclic carbonates, chain carbonates, and gum arabic. This composite structure leverages the complementary properties of each component - the cyclic and chain carbonates provide ion conductivity while gum arabic forms a protective network that prevents thermal runaway, achieving both improved Li ion mobility and enhanced safety.
2Ease of manufacture
If conventional liquid electrolytes are used, then manufacturing simplicity is maintained, but battery output and charging-discharging rates deteriorate due to lower Li ion mobility
Solution Approach 1:
The patent applies the gel electrolyte system which, while more complex than liquid electrolytes, provides significantly enhanced Li ion mobility through its gel structure. The gel matrix facilitates faster ion transport compared to conventional liquids, thereby improving charging-discharging rates and battery output while maintaining practical manufacturability through established coating and drying processes.
3Quantity of substance
If the battery is charged to high voltage (above 4.2V), then energy density is improved, but safety deteriorates due to increased risk of thermal run-away and dendrite formation
Solution Approach 1:
The patent implements beforehand cushioning by incorporating gum arabic and optimizing the electrolyte composition to create a protective gel matrix that prevents thermal runaway before it can occur. This gel structure acts as a preemptive safety mechanism that stabilizes the separator and prevents dendrite formation even when the battery is charged to high voltages above 4.2V, thereby enabling high energy density without compromising safety.
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
Enables accurate measurement of thermal shrinkage rates by comparing measured lengths with reference values, improving data accuracy and reliability.
Implementation Method 1
it has become possible to achieve high mobility of lithium ions and fast charging and discharging rates
Implementation Method 2
the gel electrolyte has a structure that suppresses shrinkage of the separator even when the temperature is elevated
Data Source
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AI summary
The present invention relates to an evaluation device and an evaluation method for the thermal shrinkage of a separator, which enable the thermal shrinkage of a separator to be easily evaluated.