Jelly-Roll Electrode Recesses for Li-Ion Stress Relief
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Solution Overview
Problem
The repeated expansion and contraction of electrode plates in lithium-ion batteries due to delithiation and lithiation cause stress accumulation, leading to potential tearing and reduced battery life.
Innovation Solution
The electrode plates are designed with strategically located recessed portions to provide deformation space and reduce stress concentration, using a jelly-roll structure with specific length and curvature configurations and recessed areas to enhance stress release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the electrode plate is designed with a flat structure to maximize active material area, then the energy density is improved, but stress concentration occurs during expansion and contraction leading to electrode plate tearing
Solution Approach 1:
The electrode plate is designed with recessed portions at specific locations (curved portions and ends) while maintaining a flat structure in the central active area. This local modification creates deformation spaces that relieve stress concentration during expansion and contraction, preventing electrode plate tearing while preserving the majority of the active material area for high energy density
2Volume of stationary object
If the electrode assembly is tightly wound to maximize space utilization, then the volume energy density is improved, but stress accumulation increases during charge-discharge cycles
Solution Approach 1:
Recessed portions are pre-formed on the electrode plate before winding into the jelly-roll structure. These pre-formed deformation spaces allow the electrode assembly to accommodate expansion and contraction stresses during charge-discharge cycles, preventing stress accumulation and electrode plate tearing while maintaining tight winding for high volume energy density
3Quantity of substance
If the electrode plate is made thicker to increase capacity, then the energy density is improved, but the stress during expansion and contraction increases leading to higher tearing risk
Solution Approach 1:
The electrode plate is designed with recessed portions at curved portions and ends where stress concentration occurs, while maintaining uniform thickness in the central active area to maximize capacity. These localized recesses create deformation spaces that relieve stress during expansion and contraction, preventing tearing even in thicker electrode plates with higher capacity
Data Source
AI summary
An electrode assembly includes a first electrode plate, a second electrode plate, and a separator that are wound to form a jelly-roll structure. The electrode assembly includes a first straight portion, a first curved portion, a second straight portion, and a second curved portion. The first straight portion and the second straight portion each include a first part, a second part, and a third part. Along a thickness direction of the first electrode plate, the first electrode plate is locally recessed in at least one of the first curved portion, the second curved portion, the first part, or the third part, so as to form a first recessed portion or portions. The first electrode plate at the first recessed portion is locally recessed to form a second recessed portion or portions. The first recessed portion and the second recessed portion are recessed in the same direction.