One-way voltaic and energy efficiency analysis for lithium-ion batteries

This paper focuses on experimental research of the efficiency of lithium-ion batteries, an important but often overlooked metric that can be used to assess charging and discharging energy losses. Two widespread lithium-ion technologies are compared: Lithium-Nickel-Manganese-Cobalt-Oxide and Lithium-Iron-Phosphate. The batteries are cycled using different charging/discharging rates using the constant-current-constant-voltage method, as well as the constant-power-constant-voltage method. The two methods are compared and the influence of a particular mode (constant current, constant power and constant voltage) on battery efficiency is analyzed. Determination of one-way voltaic and energy efficiencies is based on the batteries' open-circuit voltage characteristics which are determined experimentally. An in-depth analysis of the voltaic efficiency and its dependence on the charging/discharging rate and the battery's state-of-charge is given. An accurate information about the battery's one-way efficiencies potentially increases accuracy of various battery models.