Lithium battery (coin cell): overview, types, uses, and safety

Chemistry and construction

Most coin-type lithium batteries use lithium metal as the negative electrode and a matching cathode chemistry such as manganese dioxide (often indicated by the prefix CR) or other chemistries in specialized cells. The lithium is oxidized in the cell reaction to produce electrons that flow through an external circuit, yielding a nominal voltage commonly around 3 volts for many lithium coin cells. Compared with alkaline button cells, lithium cells offer higher energy density, lower self-discharge, and better performance at low temperatures.

Sizes, codes and common types

Manufacturers mark coin cells with alphanumeric codes that indicate chemistry and physical size. Common formats include the CR series (lithium manganese dioxide). The numeric part of codes is related to diameter and thickness so that different codes correspond to different physical dimensions and capacity. Examples of widely used codes appear in consumer electronics and watches; many size charts and compatibility lists are consolidated in device manuals or online guides such as manufacturer pages.

Typical uses and importance

Lithium coin cells are chosen for applications that need long service life with low continuous current draw: quartz wristwatches, computer real-time clocks and CMOS memory back-up, small transmitters and sensors, glucose monitors, and some hearing aids. Their long shelf life (often several years) and stable voltage profile make them suitable where infrequent replacement is expected. Because they are compact and lightweight, they are also common in portable medical devices and IoT sensors.

Safety, handling and disposal

Although small, lithium coin batteries present important safety concerns. Ingestion by children or pets can cause severe internal burns within hours; any suspected swallowing requires immediate medical attention. Cells can short, leak, or, if mistreated or improperly charged, rupture or ignite. Primary lithium coin cells are not rechargeable; attempting to recharge them risks fire or explosion. End-of-life cells should be recycled or disposed of according to local hazardous-waste rules to prevent environmental release of reactive materials and to recover valuable metals—see local recycling programs and information at official guidance.

Distinctions and notable facts

• Primary vs rechargeable: "Lithium battery" commonly means a primary lithium metal cell; this is distinct from lithium-ion (rechargeable) cells used in phones and laptops.
• Voltage and capacity: Lithium coin cells usually have higher nominal voltage than alkaline button cells and can store more energy for their size, but capacity depends on both chemistry and physical size.
• Compatibility: When replacing a cell, match the device’s recommended code and polarity; physical fit and voltage are critical to safe operation.