Best Practice: Performance and Cost Evaluation of Lithium Ion Battery Active Materials with Special Emphasis on Energy Efficiency

In order to increase the energy content of lithium ion batteries (LIBs), researchers worldwide focus on high specific energy (Wh/kg) and energy density (Wh/L) anode and cathode materials. However, most of the attention is primarily paid to the specific gravimetric and/or volumetric capacities of these materials, while other key parameters are often neglected. For practical applications, in particular for large size battery cells, the Coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) have to be considered, which we point out in this work by comparing numerous LIB active materials. For all presented active materials, energy inefficiency is mainly caused by a voltage inefficiency, which in turn is affected by the voltage hysteresis between the charge and discharge curves. Hence, this study could show that materials with larger voltage hysteresis such as the ZnFe2O4 (ZFO) anode or the Li-rich cathode material exhibit also a lower VE and EE than for instance graphite and LiNi0.5Mn1.5O4. Furthermore, from the accumulated EE losses the resulting "extra energy costs" are calculated based on industry and domestic electricity costs in Germany, in Japan and in the U.S.A. In particular, in countries with higher electricity costs such as Germany, the accumulated extra energy, which is necessary to compensate the energy inefficiency while retaining a certain energy level in the electrode material, has a stronger impact on the extra energy costs and thus on the total cost of ownership of the battery cell system.