Lithium Ion Battery Electrode Assembly Uniform Thickness Design
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in preventing short circuits due to uneven thickness and heat generation, which can cause the separator to melt and shrink, leading to potential short circuits between the positive and negative electrode plates.
Innovation Solution
The electrode assembly is designed with optimally aligned uncoated areas and active material layers to ensure uniform thickness, with the negative electrode active material layer positioned within the positive electrode uncoated area and vice versa, and the positive and negative electrode taps are strategically placed to manage heat and prevent direct contact between the electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrode plates are wound with uncoated areas and active material layers in conventional alignment, then the battery can be manufactured with standard processes, but the thickness becomes uneven and heat generation causes separator melting and short circuits
Solution Approach 1:
The patent applies preliminary action by pre-aligning the uncoated areas and active material layers in a specific configuration before winding the electrode plates. The uncoated areas are positioned to overlap with active material layers of the opposite electrode, creating a predetermined heat dissipation pathway that prevents separator melting before short circuits can occur. This advance arrangement ensures uniform thickness distribution throughout the wound structure.
Solution Approach 2:
The uncoated areas serve as an intermediary element between the active material layers of positive and negative electrodes. By positioning uncoated areas to overlap with opposite electrode's active material layers, the patent creates a thermal buffer zone that mediates heat transfer, preventing direct thermal contact between active material layers and reducing the risk of separator melting and short circuits.
2Quantity of substance
If the separator is made thinner to increase energy density, then the battery capacity increases, but the separator becomes more susceptible to melting and shrinking from heat generation
Solution Approach 1:
The patent applies beforehand cushioning by creating overlapping uncoated area regions that serve as thermal buffer zones before heat can reach the separator. These pre-positioned uncoated areas act as protective cushions against thermal runaway, allowing the use of thinner separators for increased energy density while maintaining reliability through the advance thermal protection mechanism.
3Power
If the electrode taps are positioned to facilitate electrical connection, then the internal resistance decreases, but heat generation increases at the tap locations
Solution Approach 1:
The patent applies local quality by creating spatial variation in the electrode structure, specifically positioning uncoated areas at strategic locations where they can overlap with active material layers. This local structural modification allows for optimized electrical connection at tap positions while simultaneously providing localized heat dissipation pathways, addressing both low internal resistance and heat generation concerns through location-specific design features.
Data Source
AI summary
An electrode assembly and a lithium ion secondary battery using the same capable of preventing a short circuit from being created in an outer peripheral portion of the electrode assembly. Uncoated areas of positive and negative electrode plates and an active material layer in the inner and outer peripheral portions of the electrode assembly are optimally aligned such that the thickness of the electrode assembly is uniformly formed widthwise along the electrode assembly.