Biphenylene network as sodium ion battery anode material

Sodium ion batteries possess several advantages for large-scale energy storage, such as low cost and enhanced safety. However, graphite or other anode materials are not satisfactory because the large radius of Na⁺ hinders their embedding and removal in the charge and discharge processes. Recently, a biphenylene network (BPN), a two-dimensional (2D) carbon allotrope, has been synthesized. In this paper, we reveal the potential possibility of BPN as a Na storage material. The theoretical results indicate the advantages of BPN as a sodium battery anode. The maximum specific capacity (413 mA h g^-1) is larger than that of the graphite-Li system (372 mA h g^-1). With low Na⁺ diffusion barrier (<0.6 eV) and small volume expansion in the charging process (∼26%), BPN presents superiority to the graphite-Na system. Our findings show new insights into Na storage in BPN and provide guidance for the use of a BPN anode in sodium ion batteries.