What are the Different Types of 21700 Positive Caps?
Blog | Published by Alex on July 29, 2025
The positive caps of 21700 cells mainly come in several types, with slight variations depending on their application, manufacturing process, and manufacturer.
Three Main Common Types
| Type Name |
Description |
| ① Flat Top |
The top is flat without any protrusion. Commonly used in electric vehicles, battery packs, and power modules. Ideal for spot welding and compact stacking. |
| ② Button Top |
The positive terminal has a small protruding bump. Typically used in flashlights, power tools, and other spring-contact devices. |
| ③ Welded Tab Cap |
The cap has pre-welded nickel strips or tabs for easy integration into battery packs. |
Special Types (Less Common)
| Type |
Description |
| ④ Safety Valve Cap |
Integrated with a PTC thermistor or explosion-proof valve. Used in high-safety applications such as electric vehicles. |
| ⑤ Vent Cap |
Designed with a small vent hole for gas release or inspection. Common in experimental or specialized cells. |
Application Recommendations
- Power Battery Packs (e.g., EVs, energy storage): Mostly use flat top with spot welding.
- Consumer Electronics (e.g., flashlights, toys): Prefer button top.
- Automated Welding Lines: Use welded tab caps or cells with pre-welded nickel strips.
- Customized Designs: Choose cap types with vent holes or pressure valves based on BMS or module requirements.
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21700 and 18650 NCM lithium cells.
You can take a look at JOINSUN's products.
