Sacrificial cathode additives for enhanced cycle performance for liquid and all–solid–state anode–free lithium secondary batteries

Li metal anodes have been intensively studied due to the high capacity of 3860 mA h g–1 to increase the energy density of batteries. However, inevitable Li dendrite growth and poor cycle life prevent the practical use of Li metal anodes. The anode-free batteries (AFBs), constructed with a cathode and a current collector as an anode without Li metal, have many advantages in energy density, cost-effectiveness, and processability in cell fabrication. However, AFBs present continuous capacity fading due to the zero excess Li reservoir. Here, we report Li2Cu0.6Ni0.4O2 (LCNO) as a sacrificial cathode additive to provide an additional Li to the anode current collector to improve the cyclability of AFBs. LCNO, a solid solution of Li2NiO2 and Li2CuO2, presents a striking difference in electrochemical properties depending on the critical voltage windows. LCNO shows a high initial charging capacity of 393.3 mA h g–1 with a very low initial Coulombic efficiency of 5.6 %, and could not contribute to later electrochemical reactions at 4.3 – 3.0 V. We demonstrate significantly improved cyclability of AFBs with LCNO as a sacrificial cathode additive in liquid and all solid-state AFBs.