Bipolar Battery Current Collecting Plates Thermal Shrinkage
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Solution Overview
Problem
Conventional bipolar secondary batteries face performance degradation due to internal short circuits caused by electrical conductors penetrating the exterior body, leading to continuous short-circuit current flow through current collecting plates.
Innovation Solution
The use of current collecting plates with an electrically conductive layer on a resin film, where the resin film has a thermal shrinkage percentage of 2% or greater at 150°C, and separators with a higher thermal shrinkage start temperature than the resin film, preventing short-circuit current flow by thermally separating the conductor from the plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current collecting plates are used without thermal shrinkage properties, then electrical conductivity is maintained, but short-circuit current continues to flow when an electrical conductor penetrates the battery case
Solution Approach 1:
The current collecting plate is constructed as a composite structure with a resin film substrate and an electrically conductive layer. The resin film provides thermal shrinkage capability while the conductive layer maintains electrical conductivity, resolving the contradiction between reliability improvement and structural complexity by integrating multiple material functions into a single composite component.
Solution Approach 2:
The resin film is selected with specific thermal properties (thermal shrinkage percentage of 2% or more at 150°C) to enable automatic separation from penetrating conductors through thermal shrinkage when exposed to short-circuit heat. This parameter-based solution allows the current collecting plate to transition from a static conductor to an active safety component that responds to temperature changes.
2Reliability
If the resin film has high thermal shrinkage percentage at 150°C, then short-circuit current is interrupted, but the separator may be damaged by heat before shrinkage occurs
Solution Approach 1:
The resin film is pre-engineered with specific thermal shrinkage properties that activate at 150°C, creating a preliminary protective mechanism. When a conductor penetrates and generates heat, the resin film automatically shrinks at this temperature threshold to separate the conductor from the current collecting plate, interrupting the short-circuit current path before the separator is exposed to damaging temperatures.
Solution Approach 2:
The thermal shrinkage of the resin film acts as a cushioning protective mechanism that activates beforehand to prevent the more severe damage of separator thermal decomposition. By interrupting the short-circuit current at the current collecting plate level, the system prevents heat propagation to the separator, providing beforehand protection against catastrophic failure.
3Strength
If the separator has high thermal shrinkage start temperature, then it maintains structural integrity during short-circuit, but it cannot provide early thermal protection
Solution Approach 1:
The thermal protection function is segmented between two components: the resin film in the current collecting plate handles early thermal response at 150°C through shrinkage, while the separator maintains structural integrity at higher temperatures. This segmentation allows each component to specialize in different temperature ranges, with the resin film providing early protection and the separator providing sustained structural support.
Solution Approach 2:
The resin film acts as an intermediary protective layer between the external conductor and the separator. When thermal shrinkage occurs, it creates physical separation that protects the separator from direct contact with hot conductors, allowing the separator to maintain its high thermal shrinkage start temperature without compromising overall system reliability.
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 prevents short-circuit currents and reduces heat generation, thereby avoiding thermal damage to the separators and maintaining battery performance during nail penetration tests.
Implementation Method 1
the resin film having a thermal shrinkage percentage of 2% or greater at a temperature of 150° C.
Implementation Method 2
each of the separators has a higher thermal shrinkage start temperature than the resin film
Data Source
AI summary
The bipolar secondary battery includes a power generation element including unit power generation elements stacked together and including bipolar electrodes stacked via separators, and current collecting plates arranged at both ends of the power generation element in the stacked direction of the unit power generation elements so as to be in contact with the power generation element, wherein the current collecting plates each include an electrically conductive layer and a resin film, the electrically conductive layer being formed on the resin film having a thermal shrinkage percentage of 2% or greater at a temperature of 150° C., and the separators have a higher thermal shrinkage start temperature than the resin films.