Battery Cell Top Cap Structure for Faster Electrolyte Injection
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Solution Overview
Problem
Conventional top caps of battery cells experience low liquid injection speed and are prone to electrolyte leakage due to negative pressure inside the cell during electrolyte injection.
Innovation Solution
The top cap design includes a bottom plastic structure with a hollowed-out stop portion that diverges the electrolyte, improving injection speed and preventing leakage by stopping the sealing rivet from being pressed into the cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a straight cylindrical liquid injection hole is used, then the structure is simple, but the liquid injection speed is slow and injection time is long
Solution Approach 1:
The liquid injection hole is divided into multiple segments: the first liquid injection hole in the second plate, the second liquid injection hole in the aluminum sheet, and the hollowed-out stop portion in between. This segmentation allows electrolyte to flow through multiple paths simultaneously, increasing the effective injection area and speed while maintaining structural simplicity.
Solution Approach 2:
The hollowed-out stop portion adds a third dimension (depth) to the injection path, creating a cavity that increases the effective injection area without significantly increasing the footprint. This dimensional change allows the injection area to expand from a simple circular hole to a three-dimensional cavity system.
2Reliability
If vacuumization is performed before liquid injection, then gas inside the battery cell is removed, but negative pressure is formed that presses the sealing rivet into the cell
Solution Approach 1:
The hollowed-out stop portion is designed in advance to counteract the negative pressure effect. By positioning this cavity between the injection holes, it creates a pressure buffer zone that prevents the sealing rivet from being pressed into the cell during vacuumization and injection, thus pre-compensating for the harmful pressure effect.
Solution Approach 2:
The hollowed-out stop portion acts as a cushioning structure that absorbs and distributes the negative pressure before it reaches the sealing rivet. This beforehand cushioning prevents the rivet from being forced into the cell, maintaining sealing integrity without requiring additional protective measures.
3Reliability
If the sealing rivet is mounted at the liquid injection hole, then sealing is achieved, but the rivet is easily pressed into the cell due to negative pressure causing liquid leakage
Solution Approach 1:
The hollowed-out stop portion serves as an intermediary structure between the liquid injection holes and the sealing rivet. It mediates the pressure distribution, preventing the negative pressure from directly acting on the rivet, thus protecting the sealing function while allowing the rivet to remain in place.
Solution Approach 2:
The hollowed-out stop portion provides beforehand cushioning by creating a pressure buffer zone that protects the sealing rivet from negative pressure effects. This cushioning structure prevents the rivet from being pressed into the cell, thereby preventing liquid leakage while maintaining sealing integrity.
Data Source
AI summary
Disclosed is a top cap of a battery cell including an aluminum sheet and a bottom plastic structure. The bottom plastic structure includes a first plate, a second plate, and an intermediate protrusion located between the first plate and the second plate. The intermediate protrusion is protruded with respect to the first plate and the second plate on a bottom side of the bottom plastic structure. The first plate is provided with a first post hole. The second plate is provided with a first liquid injection hole and a second post hole. A stop portion protruding outwardly from a circumference of the first liquid injection hole is provided on the bottom side of the bottom plastic structure, and is of a hollow-out structure. An area of a hollowed-out region of the stop portion is greater than an area of a cross-section of the first liquid injection hole.