Cylindrical Electrode Assembly Layout to Prevent Coating Exposure
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Solution Overview
Problem
Conventional cylindrical batteries face issues with current collection efficiency and heat generation due to concentrated current flow in strip-shaped electrode tabs, leading to potential ignition during rapid charging, especially when scaled for electric vehicles. Additionally, the exposure of coated portions during handling can cause internal short circuits and reduce energy density.
Innovation Solution
A tab-less cylindrical battery design with optimally positioned fixing members on the separator's winding end to prevent coated portions from exposure, using a minimum folding angle and reduced separator usage to enhance safety and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If strip-shaped electrode tabs are used for current collection, then the battery structure is simple, but current collection efficiency is poor due to large resistance and large heat generation
Solution Approach 1:
The single strip-shaped electrode tab is segmented into multiple electrode tabs distributed around the cylindrical battery. This segmentation divides the current collection function across multiple contact points, reducing the current density and resistance at each tab while improving overall current collection efficiency and reducing heat generation.
2Quantity of substance
If the cylindrical battery form factor is increased for electric vehicle application, then the energy capacity is improved, but heat generation around the electrode tab increases leading to potential ignition during rapid charging
Solution Approach 1:
The current collection function is segmented into multiple electrode tabs distributed around the battery cylinder. This distributes the heat generation across multiple locations rather than concentrating it at a single tab, preventing localized overheating and potential ignition during rapid charging of large-capacity batteries.
Solution Approach 2:
The electrode tabs are arranged in a circular distribution around the cylindrical battery, transitioning from a single-point (0D) or linear (1D) connection to a two-dimensional circular arrangement. This spatial distribution in another dimension effectively disperses heat generation and improves thermal management.
3Stability of the object's composition
If the separator winding end corner is secured to prevent unwinding, then the electrode assembly stability is improved, but the coated portion may be exposed to the outside causing internal short circuits
Solution Approach 1:
An insulating coating layer is introduced as an intermediary between the separator winding end corner and the external environment. This coating layer prevents direct exposure of the coated portion while allowing the separator to remain secured, thus eliminating the risk of internal short circuits without compromising assembly stability.
Solution Approach 2:
A thin insulating coating layer is applied to the separator winding end corner. This inexpensive, simple protective layer effectively prevents exposure and short circuits without adding significant complexity or cost to the battery structure.
4Reliability
If the separator extends further to cover the coated portion, then the protection against exposure is improved, but the amount of separator used increases reducing energy density
Solution Approach 1:
Instead of extending the separator, a thin insulating coating layer is applied only to the winding end corner area that requires protection. This minimal protective measure provides adequate protection against exposure without the material cost and energy density penalty of extending the entire separator.
Solution Approach 2:
The insulating coating is applied locally only to the specific area (winding end corner) that requires protection, rather than extending the separator globally. This localized approach provides necessary protection while minimizing the amount of additional material and preserving energy density.
Data Source
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AI summary
Disclosed is an electrode assembly, a cylindrical battery, a battery pack and a vehicle. The electrode assembly has a structure in which a first electrode, a second electrode, and a separator interposed therebetween are wound. An outermost coated portion is the coated portion of the first electrode. A winding end of the separator extends further from the winding end of the coated portion of the first electrode. A fixing member is attached to the winding end of the separator along the axial direction from a point spaced apart from the axial end of the separator. When the winding end corner of the separator is folded as much as possible with the axial end of the fixing member acting as a folding bias point so that its outer surface faces the outer circumference, the winding end corner of the coated portion of the first electrode is not exposed to the outside.