Layer-by-layer stacked nano-CuZn5 for conductivity multi-enhancement and surface engineering of anode current collector in dendrite-free sodium metal batteries

Abstract

Interfacial instability caused by Na dendrite growth on the anode hinders the further development of sodium metal batteries. To prohibit dendrite growth, constructing anode current collectors with excellent conductivity and surface-regularizing capability is an effective strategy. Here, we report a layer-by-layer stacking design of CuZn₅ layer on an Al-based anode current collector. The densely stacked CuZn₅ hexagonal nanosheets, working in synergy with the Al substrate and Cu surface layer, significantly enhance the conductivity (50.63 × 10⁶ S m⁻¹) through size-confinement, tunnelling effect, ordered nanostructure, built-in electric field, and surface engineering. This enables fast electron supply/collection for uniform Na plating. Moreover, the layer-by-layer stacked CuZn₅ nanosheets induce Cu plating into a rough mountain-like structure with amounts of surface defects, providing abundant active sites for rapid formation of NaF-rich solid electrolyte interphase, which also helps uniform Na plating. The assembled symmetric cell of Na@Cu/CuZn₅@Al exhibits low polarization from 0.5 to 5 mA cm⁻², and cycles for over 2000 h. The half cell maintains 98 % CE after 500 cycles, whereas cells using Na‖Al and Na‖Cu all show pronounced CE decay within 110 cycles at 1 mA cm⁻², 1 mAh cm⁻². This work introduces a strategy for fabricating a high-performance, lightweight anode current collector for dendrite-free sodium metal batteries.