Nonaqueous Battery Case Insulation for Short-Circuit Safety
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Solution Overview
Problem
Existing nonaqueous electrolyte secondary batteries, such as lithium ion batteries, face challenges in preventing overheating due to internal short-circuits or mechanical damage like nail sticking or crush, especially when using aluminum cases for weight reduction, as increased electric resistance either limits discharge performance or fails to suppress short-circuit currents effectively.
Innovation Solution
The battery design incorporates a positive electrode and negative electrode with a resistance of 1.6 Ω·cm² or more between the current collectors and electrically insulates the battery case from the electrodes, preventing short-circuit currents and thus avoiding overheating by ensuring a high resistance between the positive and negative electrodes and isolating the case from electrical conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric resistance of the active material is increased to suppress short-circuit current, then safety against overheating is improved, but discharge performance is drastically dropped
Solution Approach 1:
The invention divides the battery system into electrically isolated segments by insulating the battery case from the electrodes. This segmentation prevents short-circuit current propagation while maintaining normal electrode function, resolving the contradiction between safety and performance.
Solution Approach 2:
An insulating structure is introduced as an intermediary between the battery case and the electrodes. This intermediary blocks electrical conduction paths that would otherwise allow short-circuit currents, enabling safety improvement without affecting discharge performance.
2Reliability
If the electric resistance of the active material is increased, then short-circuit current is suppressed, but the resistance of the electrode plate becomes too high
Solution Approach 1:
The invention extracts the short-circuit prevention function from the electrode active material and relocates it to the battery case insulating structure. This allows the electrode plate to maintain low resistance for good performance while the insulating structure handles short-circuit suppression.
3Weight of moving object
If a metal case containing aluminum is used for weight reduction, then weight is reduced, but short-circuit current concentrates in the battery case causing overheating
Solution Approach 1:
An insulating layer is introduced as an intermediary between the metal battery case and the electrodes. This intermediary prevents electrical conduction through the lightweight aluminum case, eliminating the overheating hazard while preserving the weight reduction benefit.
Solution Approach 2:
The insulating structure acts as a sacrificial protective element that prevents catastrophic failure. By providing a simple, lightweight insulating barrier, the system achieves safety without compromising the lightweight metal case design.
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 suppresses short-circuit currents and prevents overheating in the battery, even when damaged, ensuring a safe and efficient operation without increasing the entire battery's temperature due to Joule heat.
Implementation Method 1
the battery case is electrically insulated from the positive electrode and the negative electrode
Implementation Method 2
when the separator is removed to bring a surface of the positive electrode mixture layer and a surface of the negative electrode mixture layer in contact with each other, terminals are respectively provided on the positive electrode current collector and the negative electrode current collector and a resistance value between the terminals is measured, the resistance value is 1.6 Ω·cm2 or more
Implementation Method 3
ensuring a safe and efficient operation without increasing the entire battery's temperature due to Joule heat
Data Source
AI summary
A nonaqueous electrolyte secondary battery includes: a positive electrode 4; a negative electrode 6; a separator 5; and a battery case 1 in which an electrode plate group 7 including the positive electrode 4 and the negative electrode 6 spirally wound or stacked with the separator 5 interposed therebetween is stored with an electrolyte. In the nonaqueous electrolyte secondary battery, after charging, when the separator 5 is removed to bring a surface of the positive electrode mixture layer and a surface of the negative electrode mixture layer in contact with each other, terminals are respectively provided on the positive electrode current collector and the negative electrode current collector and a resistance value between the terminals is measured, the resistance value is 1.6 Ω·cm2 or more, and the battery case 1 is electrically insulated from the positive electrode 4 and the negative electrode 6.