Materials, Electrodes, and Electrolytes Advances for Next Generation Lithium-based Anode-Free Batteries

The high volumetric stack energy density (∼ 750Wh L−1) is a must for grasping the practical application of electric vehicles with more than 100 km per day driving range. Such achievement requires significant advances in state-of-the-art battery technologies. The anode-free, derived from the metal-battery concept, germinates as one of the future potential battery configurations due to the highest, nearly theoretical gravimetric and volumetric energy density. Thus, moving from the graphite-based anode, where lithium is stored as ions, to anode-free cells, wherein lithium is plated as metal, can change the scenario of the electrochemical energy storing devices both in terms of energy density and fundamental mechanism. Although an anode-free battery theoretically provides higher stack energy density than a Li-ion battery, current developments are still underoptimized as these can barely hold for several cycles at room temperature due to the absence of an active lithium reservoir and still severe losses at the anode side. Hence electrolyte engineering with suitable electrode material choice is highly desirable and extremely challenging in realizing next-generation anode-free batteries. Herein, we summarize the current developments and achievements in the direction of anode-free batteries. Central emphasis is set on electrolyte chemistries that should on one hand allow for high-efficiency initial nucleation, followed by subsequent electrodeposition and electrodissolution of lithium metal, while also forming stable anodic interphases with the high energy cathode materials currently in use. We also prospect for better batteries with higher energy density beyond the present status.