Separator Heat-Resistant Layer Crush Safety
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Solution Overview
Problem
Existing energy storage devices face challenges in restraining temperature rise when crushed, as specifying the tensile elongation percentage of the positive electrode alone is insufficient to prevent short circuits and subsequent temperature increases.
Innovation Solution
The energy storage device incorporates a positive electrode with a composite layer, a negative electrode with a composite layer, and a separator with a heat-resistant layer containing heat-resistant particles, where the separator's tensile elongation ratios and thickness ratios are optimized to ensure the positive electrode fractures before the separator, reducing direct contact between electrodes and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tensile elongation percentage of the positive electrode is specified, then the safety against crush is improved, but the short circuit between electrodes cannot be sufficiently restrained
Solution Approach 1:
The separator is divided into multiple layers including a heat-resistant layer containing inorganic particles and a base layer, creating a segmented structure that provides both thermal stability and mechanical strength to prevent electrode contact during crush
Solution Approach 2:
The separator uses a composite structure combining organic base material with inorganic heat-resistant particles, achieving both flexibility for electrode fracture accommodation and thermal resistance to maintain integrity under heat and pressure
2Ease of manufacture
If only the positive electrode structure is optimized, then the manufacturing process is simple, but the temperature rise when crushed cannot be sufficiently restrained
Solution Approach 1:
The heat-resistant layer is pre-formed on the separator before assembly, providing advance protection against thermal runaway and crush-induced temperature rise, cushioning the harmful effects before they occur
Solution Approach 2:
The heat-resistant layer acts as an intermediary barrier between the electrodes, absorbing and dissipating heat during crush events, mediating the thermal energy transfer to prevent excessive temperature rise
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
This configuration effectively restricts the flow of short circuit current and subsequent temperature rise in the energy storage device when it is crushed, enhancing safety and stability.
Implementation Method 1
the heat-resistant layer is formed so as to restrain thermal shrinkage of the separator
Implementation Method 2
the separator's tensile elongation ratios and thickness ratios are optimized to ensure the positive electrode fractures before the separator
Data Source
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AI summary
In the state where a positive electrode (18) and a separator (21) are held in a case, the value of the ratio of the tensile elongation in a first direction of the separator to the tensile elongation in the first direction of a positive electrode substrate (22) is from 4 to 68. In the same state, the value of the ratio of the tensile elongation in a second direction of the separator to the tensile elongation in the second direction of the positive electrode substrate is from 4 to 68. The value of the ratio of the thickness of a heat-resistant layer (31) to the thickness of the positive electrode substrate is from 0.25 to 0.70. The proportion by mass of heat-resistant particles contained in the heat-resistant layer is from 30 to 99% by mass of the heat-resistant layer.