Secondary Battery Separator Sealing for Thermal Runaway Containment
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Solution Overview
Problem
Secondary batteries face issues with internal short circuits and flame propagation due to separator shrinkage and the inability to block flames within the battery cell, leading to potential explosions and safety risks.
Innovation Solution
A secondary battery design featuring a separator with a double sealing structure and a flame propagation prevention sheet made of silicate materials, which includes a first and second sealing part to prevent separator shrinkage and block flames, using a fire extinguishing agent that shifts phase at 100° C to 300° C, and a silicate sheet with a binder for enhanced safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional battery module uses flame propagation prevention members installed outside each battery cell, then flame propagation between battery cells is prevented, but the electrode assembly inside the battery cell cannot be protected from burning and the flame propagation time remains short
Solution Approach 1:
The flame propagation prevention sheet is nested inside the battery cell, specifically positioned between the electrode assembly and the battery case. This nested structure allows the prevention mechanism to operate at the source of potential flame propagation, blocking flames before they can spread to adjacent cells, thereby extending the flame propagation time while maintaining reliability
Solution Approach 2:
The flame propagation prevention sheet is pre-installed within the battery cell structure during manufacturing, positioned in advance to intercept and block flames before they can propagate between cells. This preliminary positioning ensures that when thermal runaway occurs, the flame is immediately blocked, extending the time available for safety responses
2Quantity of substance
If the separator is made thin to increase energy density, then battery capacity is improved, but the separator shrinks at high temperature causing internal short circuits and explosion risks
Solution Approach 1:
The separator is constructed as a composite material combining a base separator layer with a heat-resistant coating layer. This composite structure maintains the thin profile needed for high energy density while the heat-resistant coating prevents shrinkage at elevated temperatures, thereby preventing internal short circuits and maintaining reliability
Solution Approach 2:
The separator incorporates materials with modified thermal properties, specifically designed to maintain dimensional stability at high temperatures. By changing the thermal parameters of the separator material through selective coating or composite construction, the separator resists shrinkage during thermal runaway, preventing contact between electrodes and avoiding internal short circuits while keeping the separator thin for high energy density
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 effectively suppresses separator shrinkage, prevents internal short circuits, and significantly delays flame propagation, enhancing the safety of secondary batteries and modules by preventing explosions and improving safety characteristics.
Implementation Method 1
the accommodation part may accommodate a fire extinguishing agent of which a phase is shifted to a gas phase at 100° C. to 300° C.
Implementation Method 2
a flame propagation prevention sheet made of silicate materials, which includes a first and second sealing part to prevent separator shrinkage and block flames
Implementation Method 3
the separator included in the electrode assembly includes a first sealing part bonded to end parts of the separator at an outer side of the electrode assembly
Data Source
AI summary
A secondary battery includes a separator in an electrode assembly thereof that has a sealing part for individually sealing a positive electrode and a negative electrode and has a double sealing structure. The double sealing structure including a first sealing part and a second sealing part so that an accommodation part for accommodating a fire extinguishing agent is provided at an end part of the negative electrode. Further, the secondary battery includes a flame propagation prevention part disposed on an outer surface of the electrode assembly so that a flame generated during thermal runaway of the secondary battery can be blocked in a stage in which the electrode assembly is positioned inside the battery cell, and thus a longer flame propagation time can be induced.