Sodiophilic Au-diamane Polypropylene Separators Enabled Dendrite-Free Sodium Metal Batteries

Abstract

Sodium metal is considered as a promising anode material for sodium metal batteries (SMBs) owing to its high theoretical specific capacity and low electrochemical potential. Nevertheless, its practical application is hindered by the challenge of dendrite formation. To address this issue, a separator modification strategy was adapted to enhance the performance of sodium metal anodes (SMAs) by using Au nanoparticle-decorated two-dimensional diamane on a commercial polypropylene substrate (Au-diamane/PP) separator. The sodiophilic Au-diamane/PP separator facilitates improved Na⁺ ion diffusion kinetics and induces a dendrite-free deposition morphology, effectively suppressing dendrite growth. The dendrite-free deposition behavior was systematically characterized using in-situ optical microscopy and ex-situ scanning electron microscopy. Symmetric Na||Na cell incorporating the Au-diamane/PP separator exhibits exceptional cycling stability, maintaining operation for more than 2100 h at 2 mA cm-2 with 1 mAh cm-2. The sodiophilicity is originated from the in-situ formed AuNa2 alloy formed on the surface of diamane during the discharging process. Additionally, a full cell configuration with a Na3V2(PO4)3@C cathode, Au-diamane/PP separator, and Na metal anode delivers a high reversible capacity of 88.4 mAh g-1 more than 300 cycles. Our work underscores the potential of the Au-diamane/PP separator in advancing the development of SMBs with extended cycle life and enhanced performance.