Dual Separator Electrochemical Cell Impact Safety
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Solution Overview
Problem
Current lithium ion polymer batteries face safety issues due to flammability and explosiveness, particularly when subjected to external impacts like crushing, and existing safety measures are inadequate in preventing severe deterioration at temperatures below 90°C.
Innovation Solution
The use of two different types of separators with varying energy to break, where the outermost electrode layer includes a separator with lower energy to break, inducing primary short-circuiting upon external impact, thereby enhancing safety by facilitating heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single type of separator is used in lithium ion polymer batteries, then the device complexity is low, but the safety is insufficient under external impact conditions
Solution Approach 1:
The battery separator structure is divided into multiple segments: an inner separator (first separator) and an outer separator (second separator). The inner separator uses a first reinforcing layer with high strength to maintain structural integrity during normal operation, while the outer separator uses a second reinforcing layer with low strength to break first under external impact, inducing controlled short-circuiting and preventing thermal runaway. This segmentation allows each layer to perform its specific function, resolving the contradiction between safety and structural simplicity.
Solution Approach 2:
Different reinforcing layers are applied to different parts of the separator structure based on local requirements. The inner separator (facing the electrodes) uses a first reinforcing layer with high tensile strength and modulus to prevent electrode damage during normal use. The outer separator (facing the battery exterior) uses a second reinforcing layer with low tensile strength and modulus to break first under external impact. This local differentiation of material properties enables the separator to provide both structural support and impact protection, resolving the safety-complexity contradiction.
2Ease of manufacture
If the separator structure is simplified, then the manufacturing process is easier, but the ability to prevent explosions and ignition under external impact is reduced
Solution Approach 1:
The separator is segmented into an inner separator and an outer separator with distinct reinforcing layers. The inner separator maintains structural integrity during normal operation, while the outer separator is designed to break first under external impact. This segmentation creates a controlled failure mode that prevents thermal runaway, addressing the explosion and ignition risk without requiring complex manufacturing processes.
Solution Approach 2:
The separator uses composite material structures with different reinforcing layers. The first reinforcing layer (inner) provides structural support with high strength properties, while the second reinforcing layer (outer) provides impact protection with low strength properties. This composite approach enables the separator to exhibit different mechanical behaviors under different conditions, preventing explosions and ignition while maintaining manufacturability.
3Strength
If a separator with high strength is used throughout, then the structural integrity is maintained, but the induced short-circuiting upon external impact occurs in inner electrode layers causing severe deterioration
Solution Approach 1:
The separator structure applies different strength characteristics to different locations. The inner separator uses a first reinforcing layer with high tensile strength and modulus to maintain structural integrity during normal operation. The outer separator uses a second reinforcing layer with low tensile strength and modulus to break first under external impact. This local differentiation ensures that short-circuiting occurs in the outer separator rather than inner electrode layers, preventing severe performance deterioration while maintaining overall structural integrity.
Solution Approach 2:
The outer separator with low-strength second reinforcing layer acts as a cushioning element designed to fail first under external impact. This beforehand cushioning prevents the transmission of impact forces to the inner electrode layers, ensuring that any short-circuiting occurs in the outer separator where it causes minimal performance deterioration. The design anticipates potential impact scenarios and prepares a controlled failure path in advance.
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 significantly improves battery safety by preventing explosions and ignition upon external impacts, maintaining performance without substantial deterioration, as demonstrated by reduced temperature and voltage changes during testing.
Implementation Method 1
upon application of external impact
Implementation Method 2
primarily inducing short-circuiting in the outermost electrode layer
Data Source
AI summary
Provided is an electrochemical device comprising two types of separators having different energy to break, wherein the outermost electrode layer of the electrode assembly includes an active material non-coated cathode, an active material non-coated anode, and a separator (second separator) disposed between the cathode and anode and having relatively low energy to break compared to that of separators (first separator) in other electrode layers. Therefore, it is possible to remarkably improve safety of the battery by inducing primary short-circuiting in the outermost electrode layer of a battery, thus facilitating heat dissipation of the battery, upon application of external impact.