Dynamic Alloying Codeposition/Costripping for Dendrite-Less Multivalent Metal Batteries

Multivalent metal batteries are promising for next-generation large-scale energy storage due to the high abundance and low cost of these metals. Aluminum metal batteries operating with molten salt electrolytes are gaining particular traction for the rapid desolvation but are still hindered by dendritic aluminum growth at practical temperatures and current densities/capacities. Here, we describe an electrochemically driven dynamic alloying codeposition/costripping strategy to suppress aluminum dendrites at these practical conditions. Enabled by the formation of unique bimetal Al-Mn-Cl-active clusters in the chloroaluminate electrolyte, we realize dynamic Al-Mn codeposition in the form of substitutional solid solution and Al₆Mn intermetallic, and importantly, reversible and dynamic Al-Mn costripping. As opposed to the conventional sequential deposition mechanism, the dynamic codeposition/costripping serves to reduce the surface energy and facilitates adatom diffusion constantly at the dynamic front of the reaction, instead of merely at the initiation of deposition, therefore enabling a smooth, dendrite-free aluminum anode at high current and capacity. As a result, the Al metal anode exhibits unprecedented cycling stability over 1000 h with a high current density of 10 mA cm^-2 and an areal capacity of 20 mA h cm^-2, and the Al|graphite cells achieve 4000-cycle life with a current of 24.6 mA cm^-2. Our strategy here paints a rational path for designing stable, high-rate, and dendrite-less multivalent metal anodes.