Nonaqueous Battery Separator Welding for Low Resistance
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face increased resistance due to adhesive coatings on separators, which hinder ion movement and electrolyte flow, leading to poor performance during repeated charging and discharging.
Innovation Solution
A stacked-type electrode body configuration with a second active material layer non-formation section and through-hole design allows for welding of separators without bonding to the active material layers, reducing initial resistance and preventing electrolyte flow obstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separators are coated with adhesive to bond electrodes and separators, then misalignment is prevented, but ion movement is hindered and resistance increases
Solution Approach 1:
The separator is divided into multiple regions: a bonding region with adhesive coating for securing electrodes, and a non-bonding region without adhesive that allows free ion movement. This segmentation enables the separator to simultaneously provide both mechanical bonding function and ionic conduction function without mutual interference.
Solution Approach 2:
Different regions of the separator have different properties: the bonding region has adhesive characteristics for structural stability, while the non-bonding region has high ionic permeability for low resistance. This local differentiation allows each region to optimize its specific function.
2Stability of the object's composition
If adhesive is applied to bond separators and electrodes, then structural stability is improved, but electrolyte flow is obstructed and resistance increases upon repeated charging/discharging
Solution Approach 1:
The separator surface is segmented into bonding areas and non-bonding areas, allowing the adhesive to secure the electrode-separator structure while leaving channels open for electrolyte penetration and ion transport during cycling.
Solution Approach 2:
The non-bonding region acts as an intermediary pathway that facilitates electrolyte flow between the bonded regions, ensuring that the adhesive bonding does not completely block ionic transport during battery operation.
3Area of stationary object
If the area of separators is made larger than active material layers, then bonding coverage is improved, but ion transport pathways are reduced
Solution Approach 1:
The larger separator area is differentially treated: portions overlapping with active material layers have adhesive for bonding, while other portions remain adhesive-free to provide extended ion transport pathways, thus reconciling the need for both coverage and transport.
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
The configuration results in a battery with low initial resistance and suppressed resistance increases during repeated charging and discharging, enhancing ion flow and electrolyte impregnation efficiency.
Implementation Method 1
the first separator and the second separator are welded at the missing portion of the second active material layer non-formation section
Data Source
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AI summary
Provided is a nonaqueous electrolyte secondary battery having low initial resistance and in which increases in resistance upon repeated charging and discharge are suppressed. The nonaqueous electrolyte secondary battery disclosed herein has a stacked-type electrode body that includes cell units in which a first electrode, a first separator, a second electrode and a second separator are laid up. The first electrode has a first collector and a first active material layer. The second electrode has a second collector and a second active material layer. The areas of main surfaces of the first separator and the second separator are respectively larger than the areas of main surfaces of the first active material layer and of the second active material layer. A second active material layer non-formation section at which the second active material layer is not formed and the second collector is exposed, is provided in the second electrode. The second active material layer non-formation section has a missing portion. The first separator and the second separator are not bonded to the second active material layer of the second electrode; and the first separator and the second separator are welded at the missing portion of the second active material layer non-formation section.