Electrode Assembly Separator Pore Diameter Design
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Solution Overview
Problem
Conventional electrode assemblies face issues with stress accumulation due to electrode expansion and contraction, leading to deformation, uneven spacing, and reduced productivity, as well as poor electrolyte impregnation and gas management, which affect battery performance and safety.
Innovation Solution
The electrode assembly features a stack-folded structure with unit cells having a first separator between cathode and anode, surrounded by a second separator with a larger average pore diameter and higher porosity, enhancing wettability and degassing properties to prevent electrolyte leakage and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a jelly-roll type electrode assembly is prepared by winding cathode and anode sheets, then the battery can be manufactured with continuous winding process, but stress accumulation from electrode expansion and contraction causes deformation and uneven spacing
Solution Approach 1:
The electrode assembly is divided into multiple unit cells, each surrounded by an outer separator. This segmentation allows each unit cell to independently accommodate expansion and contraction stresses without transmitting them to adjacent cells, preventing cumulative stress and deformation while maintaining the compact jelly-roll structure.
2Stability of the object's composition
If a stack type electrode assembly is prepared by laminating multiple cathode and anode units, then the structure is more stable, but it requires separate transfer procedures and sequential laminating which reduces productivity
Solution Approach 1:
The invention merges the advantages of both jelly-roll and stack types by combining the continuous winding process with the stable stacked structure. Multiple cathode and anode units are laminated together and then continuously wound into a compact jelly-roll form, achieving both high productivity and structural stability.
3Reliability
If the first separator has small pore diameter for good separation, then the separator performance is improved, but electrolyte impregnation is slow and gas management is poor
Solution Approach 1:
The outer separator surrounding each unit cell has a different pore size structure compared to the first separator between electrodes. The outer separator has larger pores optimized for electrolyte impregnation and gas management, while the first separator maintains smaller pores for effective electrode separation. This local differentiation allows each separator to perform its specific function optimally.
4Volume of moving object
If the electrode assembly is compactly wound, then the battery size is reduced, but gas buildup from side reactions cannot be effectively managed
Solution Approach 1:
The outer separator acts as an intermediary structure between unit cells, providing dedicated pathways for gas management. Its larger pore structure and surrounding configuration allow it to collect and channel gases generated from side reactions away from the compact electrode assembly, preventing gas buildup while maintaining compact battery dimensions.
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 configuration improves battery performance by ensuring effective electrolyte impregnation, preventing gas buildup, and maintaining structural integrity under external impacts, thus enhancing stability and safety.
Implementation Method 1
the second separator has an average pore diameter (d2) larger than the average pore diameter (d1) of the first separator in the unit cells... enhancing wettability
Implementation Method 2
enhancing wettability and degassing properties
Implementation Method 3
degrading properties to prevent electrolyte leakage and deformation
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The present disclosure provides an electrode assembly comprising a plurality of unit cells, each unit cell having a full-cell or a bi-cell structure comprising a cathode, an anode, and a first separator interposed between the cathode and the anode, and the plurality of unit cells being stacked by surrounding each unit cell with a second separator, wherein the second separator has an average pore diameter (d2) larger than the average pore diameter (d1) of the first separator in the unit cells.