Current collector interphase design for high-energy and stable anode-less sodium batteries

Sodium-ion batteries have emerged as one of the most promising next-generation energy storage systems. However, their widespread application is hindered by the low energy density and high cost of hard carbon anodes. Anode-free designs offer a potential solution but typically suffer from poor cycling performance due to uncontrolled Na plating and inefficient stripping. Here we report a hard-carbon-derived interphase on an aluminium current collector to construct an anode-less sodium battery (ALSB) that maintains high energy density, reduces costs and enhances cycling stability. Remarkably, the interphase layer with a low dielectric constant and strong Na interaction enables homogeneous Na nucleation, crack-free plating and efficient stripping, thereby minimizing active Na loss during cycling. As a result, our ALSB maintains good stability for up to 900 cycles and 2.3-Ah-level ALSBs show an energy density of 203 Wh kg−1. Our findings pave the way for more sustainable batteries with competitive energy density, extended cycle life and lower costs.