The self-discharge rate is a key factor in energy storage devices like batteries and capacitors, indicating the rate at which they lose stored energy when not in use. It's crucial for applications requiring long-term energy storage, such as emergency backup systems and remote sensors. The self-discharge rate is influenced by factors like temperature, the materials used, and the age of the device. Reducing the self-discharge rate is a focus in battery technology development, as it directly impacts the device's efficiency and longevity. For example, lithium-ion batteries are preferred in many applications for their relatively low self-discharge rate compared to other battery types.