Practical sodium metal batteries (SMBs) require ultrathin Na anodes. However, bulk Na is hard to thin, and Na-lean electrodes suffer from rapid failure once dead Na forms. Herein, a unique reaction-induced rheological transition strategy is reported to fabricate ∼8 μm ultrathin Na metal anodes. Through in situ interfacial reaction between room-temperature Na-based liquid metal (RT Na-LM) and the substrate, the fluidic Na-LM spontaneously spreads while being anchored by the reaction products, transitioning into a stable quasi-solid electrode. The resulting rheo-transformable ultrathin Na (RTUT-Na) reduces Na waste by ∼90% versus conventional Na electrodes (>500 μm). Additionally, the quasi-solid composite synergizes self-healing with high ionic-electronic transport, guiding homogeneous Na deposition and effectively suppressing dendrites. As a result, the RTUT-Na||NVP@C cell exhibits an initial capacity of 93 mAh g–1 and delivers 84% of capacity retention after 2000 cycles at 2 A g–1. This scalable route advances Na-lean, dendrite-resistant Na anodes.
Qin et al. (2026) studied this question.