Nonaqueous Battery Separator Recess for Controlled Overcharge Shutdown
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in preventing rapid temperature increases during overcharge, leading to potential internal short-circuits and safety hazards due to the rapid melting of separators, which can cause excessive heat generation before the shutdown function effectively stops charging.
Innovation Solution
A nonaqueous electrolyte secondary battery design featuring a separator with a recessed short-circuit promoting portion, strategically positioned to induce an internal short-circuit between the electrode mixture layer and the current collector foil when excessive current is supplied, thereby controlling the occurrence of internal short-circuits and preventing rapid temperature increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator is designed with a shutdown function to close micropores by melting at early stage overcharge, then charging can be stopped before high-temperature range starts, but when excessive current is supplied at early stage of overcharge, the separator might melt rapidly causing internal short-circuit and rapid temperature increase to high-temperature range
Solution Approach 1:
The separator is divided into different functional regions: a first region with a shutdown function that melts at a first temperature to close micropores, and a second region with a different melting point that melts at a second temperature. This segmentation allows the separator to provide staged protection, preventing rapid temperature increase even when excessive current is supplied.
Solution Approach 2:
The patent changes the melting point parameter of different regions of the separator. The first region has a lower melting point for early shutdown, while the second region has a different melting point to prevent rapid temperature increase. This parameter variation ensures reliable shutdown function while preventing harmful rapid temperature increases.
2Speed
If the separator melts rapidly to stop charging, then the shutdown function works quickly, but internal short-circuit might occur due to contact between positive and negative electrodes before charging is stopped, causing rapid temperature increase to high-temperature range
Solution Approach 1:
The separator is pre-designed with regions having different melting points. The first region with lower melting point acts as a preliminary protection mechanism that melts first to close micropores and stop charging. The second region with different melting point provides backup protection to prevent internal short-circuit and rapid temperature increase, ensuring reliable operation even if the first region melts too rapidly.
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 design effectively prevents battery temperatures from rising to hazardous levels by intentionally causing a short-circuit in a controlled position, ensuring safer operation by stopping charging before a high-temperature range is reached, thus enhancing safety and efficiency.
Implementation Method 1
The separator having the shutdown function is configured to close the micropores by melting due to a temperature increase at an early stage of overcharge
Implementation Method 2
A short-circuit promoting portion constituted by a recessed portion having a depth of 30% or more of a thickness of the separator is formed in the separator provided between the electrode sheets in the mixture layer non-facing portion
Data Source
AI summary
An electrode body of a secondary battery described herein includes: a core portion where electrode mixture layers of a plurality of electrode sheets are laminated; terminal connecting portions where respective current collector foil exposed portions are laminated, and a mixture layer non-facing portion where the electrode mixture layer faces the current collector foil exposed portion, the mixture layer non-facing portion being formed in a boundary between the terminal connecting portion and the core portion. In the secondary battery described herein, a short-circuit promoting portion having a predetermined depth (d) is formed in a separator provided between the electrode sheets in the mixture layer non-facing portion. Hereby, before a battery temperature rapidly increases to a high-temperature range due to occurrence of internal short-circuit between the electrode mixture layers, internal short-circuit is caused between the electrode mixture layer and the current collector foil exposed portion, so that charging can be stopped.