Robust artificial interlayer for columnar sodium metal anode

Metallic Na with high specific capacity is considered as one of the most desirable alternatives for both stationary and portable electrical energy storage. However, uncontrollable dendrite generated from sluggish electrochemical kinetics and chemical instability of the solid-electrolyte interphase (SEI) layer seriously hampers the practical application of Na metal anode. Herein, interface-rich artificial interlayer composed of NaBr/Na3P nano-crystallines (NaBrP) is constructed on Na metal surface to manipulate the Na diffusion behaviors. As assisted theoretically, Na3P phase with rich ionic conductive channels greatly eliminates the diffusion barriers for Na+ permeation, while NaBr phase with low surface diffusion barrier and large band gap ensures fast spread of Na+ along the interface with promoted ionic distribution and interfacial stability. Furthermore, undesirable Na dendrites and electrolyte decomposition are significantly suppressed from the interlayer with high mechanical and chemical stability. In virtue of this robust interlayer, columnar and uniform Na is herein plated beneath NaBrP-protected electrode with a dendrite-free morphology, which achieves a prolonged lifespan of symmetrical cells over 700 h with minor polarization fluctuation and promotes the Na3V2(PO4)3 based full cells with a long-term stability of 500 cycles at 5 C as well as a high rates capacity of 38.4 mAh g−1 at 30 C (13.5 mA cm−2). This work systemically discovers the internal mechanism of Na+ transport within the SEI component, and provides an efficient strategy to realize high-performance sodium metal anode.