Protection Devices in Commercial 18650 Lithium-Ion Batteries

Bin Xu,Guangrui Wen,Michael G Pecht,Lingxi Kong

doi:10.1109/access.2021.3075972

Abstract

18650 Lithium-ion batteries are wildly used as power sources for portable electronics because of the standardized format and economical manufacturing cost. However, commercial 18650 cells come in various designs due to the implementation of different protection devices. The current interrupt device and top vent are mandatory protection devices for all commercial 18650 Li-ion batteries. In contrast, the positive temperature coefficient thermistor, bottom vent, and protection circuit are optional protection devices that can be non-installed, installed separately, or combined in commercial 18650 batteries. Four representative commercial 18650 Li-ion batteries were disassembled and compared in terms of the similarities and differences of the protection devices. This paper overviews the working mechanism, advantages, and drawbacks of each protection device. Recommendations on battery selection and potential future trends are then provided.

Highlights

18650 cylindrical battery was first released as a standard Lithium-ion (Li-ion) battery model in 1994 [1]
CURRENT INTERRUPT DEVICE In commercial 18650 cells, the current interrupt device (CID) consists of the top disk, second plastic insert, bottom disk, and metallic foil
The overall safety could be significantly improved after integrating with some protection devices, such as the protection circuit, while other protection devices contribute less to battery safety, such as the positive temperature coefficient (PTC)

Summary

INTRODUCTION

18650 cylindrical battery was first released as a standard Lithium-ion (Li-ion) battery model in 1994 [1]. CID and top vent are mandatory protection devices in commercial 18650 cells. Other three safety devices, including PTC, bottom vent, and protection circuit, can only be found in one of the batteries. MANDATORY PROTECTION DEVICES The CID and top vent are mandatory protection devices in commercial 18650 cells and installed in the battery cap. A. CURRENT INTERRUPT DEVICE In commercial 18650 cells, the CID consists of the top disk, second plastic insert, bottom disk, and metallic foil. In commercial 18650 cells, both the top vent and the CID are pressure-responsive protection devices. Like the CID, the top vent involves a ‘‘weak point’’ for safely releasing internal pressure, which is the ‘‘C’’ shape scorings on the top disk. Battery manufacturers have introduced new cylindrical cell designs with a bottom vent for better venting

OPTIONAL PROTECTION DEVICES

Findings

DISCUSSION

CONCLUSION