How Depth of Discharge Affects the Cycle Life of Lithium-Metal-Polymer Batteries

Batteries used as energy storage in telecommunications applications do not usually cycle over their full rated capacity. These batteries spend most of the time floating at full charge, and during discharges, only a fraction of the battery capacity is used depending on the time of the power outage. The cycle life of a battery is often reported at 100% depth of discharge (DOD) of the capacity and it usually corresponds to a worst-case scenario. In this paper, the impact of cycling at different DODs on LMP battery cycling performances was investigated. The depth of discharge was correlated to capacity fade and coulombic efficiency. Various cycling protocols covering a range of DODs have been applied to LMP cells at 43 degC and 60 degC. Analysis of the data was made considering both depth of discharge and cumulative discharge capacity throughout the test. We will report on the beneficial effect of decreasing DOD on the cycle life performances of LMP technology, resulting in a significant cycle life improvement