Current-Dependent Lithium Metal Microstructure in ‘Anode-Free’ Solid-State Batteries at the Steel|LPSCI Interface

Abstract

Further improvement of energy densities of state-of-the-art batteries could be achieved with the utilization of lithium metal anodes.1 Due to the reactivity of the alkali metal, the fabrication process needs to be monitored carefully. To circumvent degradation during storage as well as the handling of lithium metal, reservoir-free cells (RFCs) are investigated.2 Using accessible lithium stored within lithiated cathode materials, the lithium anode is formed in a formation step during the first charging cycle. The electrochemical properties of the electrodeposited lithium film are strongly dependent on its microstructure, and can, for example, influence the resoluble amount of lithium during subsequent cycling.3,4 Until now, the microstructure of electrodeposited lithium and how to control it is elusive.To observe and characterize the microstructure of electrodeposited lithium at the stainless steel|LPSCl interface, a combination of electrochemical impedance spectroscopy, focused ion beam and scanning electron microscopy as well as electron backscatter diffraction was used. With this setup, the correlation between deposition current density and resulting microstructure of the lithium film was investigated. For higher current densities, a twenty times smaller grain size was observed, while the grain density showed a twelvefold increase, which could have a major influence on the subsequent dissolution of lithium. Furthermore, the microstructural evolution during prolonged lithium deposition was investigated.1 J. Janek and W. G. Zeier, Nat. Energy, 2016, 1, 16141.2 M. J. Wang, E. Carmona, A. Gupta, P. Albertus and J. Sakamoto, Nat Commun., 2020, 11, 1–9.3 S. E. Sandoval and M. T. McDowell, Matter, 2023, 6, 2101–2102.4 D. K. Singh, T. Fuchs, C. Krempaszky, B. Mogwitz, S. Burkhardt, F. H. Richter and J. Janek, Adv. Funct. Mater., 2023, 33, 2211067.