A micro Zn-modified Al current collector inducing uniform sodium nucleation for anode-free sodium batteries

Abstract

Anode-free sodium metal batteries (AFSMBs) are attracting notable attention due to their capability to enhance energy density of sodium batteries and decrease overall costs. However, challenges such as uneven sodium nucleation on the Al current collector and weak adhesion between sodium and the Al current collector lead to a poor sodium reversibility, ultimately resulting in diminished battery performance. Herein, we developed uniform micro-Zn coatings on Al foil (Zn@Al) through a mild and rapid chemical deposition process and then applied them in AFSMBs. Due to the high sodiophilicity of the micro zinc particles and sodium–zinc alloy and the structural stability of the sodium–zinc solid solution alloy, the micro Zn@Al current collector promotes more uniform sodium nucleation and enhances sodium adhesion, effectively reducing sodium loss during long-term cycling. Consequently, the Zn@Al current collector facilitates more uniform sodium deposition with lower overpotentials, resulting in an impressive average coulombic efficiency of 99.99% at a current density of 1.0 mA cm⁻² over 1000 cycles. When paired with a Na₃V₂(PO₄)₃ cathode (10 mg cm⁻²), the Zn@Al-NVP cell demonstrates a high initial coulombic efficiency of 91.1% and maintains stable cycling performance over 600 cycles at 1.0C, with a capacity retention of 61% (decay 0.065% per cycle). This high-efficiency and straightforward design strategy for aluminum current collectors has significant potential to advance the development and industrial application of AFSMBs.