Laminate Separator with Metal Layer for Battery Safety
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion secondary batteries face safety issues due to thermal runaway caused by internal or external short circuits, which can lead to rupture or fire, despite measures like oxygen-absorbing separators, as these do not effectively prevent rapid temperature rises during abnormal events.
Innovation Solution
A nonaqueous secondary battery design featuring a laminate separator with a metal layer, a first resin layer having a high thermal shrinkage percentage, and a second resin layer with a lower thermal shrinkage percentage, where the metal layer is opposed to either the positive or negative electrode, interrupting current flow by generating heat and preventing short-circuit area expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a separator with metal coating is used to absorb oxygen, then oxygen absorption capacity is improved, but the ability to prevent rapid temperature rise during short circuit is insufficient
Solution Approach 1:
The separator is divided into multiple functional layers: a base separator layer and a thermal shrinkage layer. Each layer performs a specific function - the base layer provides oxygen absorption through metal coating, while the thermal shrinkage layer provides rapid response to temperature rise by shrinking to close pores and interrupt current flow.
Solution Approach 2:
The separator uses a composite structure combining a base separator material with a thermal shrinkage layer made of heat-shrinkable resin. This composite structure integrates the oxygen absorption function of the base layer with the thermal response function of the shrinkage layer, achieving both oxygen absorption and rapid temperature response.
2Reliability
If the thermal shrinkage percentage of the separator is increased to prevent short circuit area expansion, then safety is improved, but the separator may deform excessively under normal operating conditions
Solution Approach 1:
The thermal shrinkage function is localized to a specific layer (the thermal shrinkage layer) rather than the entire separator. This layer is specifically designed with thermal shrinkage properties, while the base separator layer maintains structural stability. The thermal shrinkage layer only activates under abnormal temperature conditions, preventing excessive deformation during normal operation.
Solution Approach 2:
The separator's thermal response characteristics are controlled by adjusting the thermal shrinkage temperature and shrinkage percentage of the thermal shrinkage layer. By optimizing these parameters, the separator remains stable under normal operating temperatures but undergoes controlled shrinkage only when temperature exceeds the shrinkage threshold, preventing short circuit area expansion.
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 interrupts current flow and prevents short-circuit area expansion, enhancing battery safety by managing thermal shrinkage and resistance, thereby reducing the risk of thermal runaway during external or internal short circuits.
Implementation Method 1
a first resin layer and a second resin layer having a thermal shrinkage percentage smaller than a thermal shrinkage percentage of the first resin layer
Implementation Method 2
The concentrated current causes resistance heating in the battery. The heating causes a chemical reaction of an active material or the electrolytic solution in the battery.
Data Source
AI summary
A nonaqueous secondary battery comprising a pair of electrodes consisting of a positive electrode and a negative electrode, and a separator interposed between the pair of electrodes, wherein the separator is a laminate formed by stacking in sequence a metal layer, a first resin layer and a second resin layer having a thermal shrinkage percentage smaller than a thermal shrinkage percentage of the first resin layer, and the metal layer is opposed to one of the pair of electrodes.