Over - Discharge Hazards of Rechargeable Lithium - Batteries

　　Over - discharge occurs when a rechargeable lithium - battery is discharged beyond its recommended lower voltage limit. This seemingly simple act can lead to a cascade of detrimental effects on the battery's performance and lifespan.

　　One of the primary issues is the degradation of the battery's capacity. During over - discharge, the chemical reactions within the battery deviate from the normal operating range. The active materials in the electrodes, such as lithium - cobalt oxide in the cathode and graphite in the anode, undergo irreversible changes. For example, the lithium ions may be stripped from the anode in an excessive and unregulated manner, making it difficult for them to be properly intercalated back during the subsequent charging process. As a result, the battery's ability to store and release electrical energy is significantly reduced. A battery that was once able to power a device for several hours may, after repeated over - discharges, only last for a fraction of that time.

　　Over - discharge can also cause the battery to heat up. The abnormal chemical reactions generate heat, and if the heat is not dissipated properly, it can lead to thermal runaway in extreme cases. Thermal runaway is a self - perpetuating process where the increasing temperature causes more rapid chemical reactions, which in turn generate more heat. This can result in the battery swelling, venting, or even catching fire. In addition, the heat generated during over - discharge can damage the battery's internal components, such as the separator that prevents the positive and negative electrodes from short - circuiting. Once the separator is damaged, the risk of an internal short - circuit increases, further exacerbating the battery's problems.

　　Moreover, over - discharge can affect the battery's voltage stability. A severely over - discharged battery may exhibit erratic voltage fluctuations when recharged. This can be a problem for devices that require a stable power supply, as the inconsistent voltage can cause the device to malfunction, reboot unexpectedly, or experience performance issues.

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