Deformable sodium metal current collectors for lithium solid-state batteries

Anode-free solid-state batteries could enhance energy density by eliminating excess Li metal from the battery cell. However, their performance is hindered by exacerbated contact loss at the deposited Li/solid-state electrolyte interface. Here, we introduce the use of a plastically deformable current collector to accommodate morphological irregularities during Li deposition and stripping by employing mechanically soft Na metal. The Na metal current collector is shown to establish and maintain conformal interfacial contact with both the solid-state electrolyte and the dynamically evolving Li layer. This behavior enables highly reversible Li plating and stripping on the Na current collector in cells with both Li and LiNi_0.6Co_0.2Mn_0.2O₂ counter electrodes, demonstrating superior performance compared to conventional Cu current collectors. Our findings offer a new materials design paradigm for anode-free batteries, replacing the prevailing strategy of using hard current collectors that constrain Li growth with soft current collectors to allow Li morphology to freely evolve.