Chestnut shell-derived oxygen-rich porous carbon as a stable framework for dendrite-free Na metal anode

Abstract

Metallic Na has a higher theoretical specific capacity (1165 mAh/g) and the lowest electrode potential (−2.71 vs. standard hydrogen electrode), which is conducive to the improvement of the energy density of Na secondary batteries. Nevertheless, dendrite growth and volume expansion caused by non-uniform Na deposition limit the development of Na metal anode. Here, the resource-rich and environmentally friendly chestnut shells are selected as the precursor, and oxygen-rich porous carbon is prepared by a one-step chemical activation method to solve the above issues. The high electronegativity of oxygen atom improves the polarity of the porous carbon, enhances the adsorption capacity of Na⁺, and reduces the Na nucleation barrier. Meanwhile, the massive polar sites facilitate the regulation of the distribution of Na⁺ on the carbon framework and directs uniform Na deposition. The porous structure increases the specific surface area, reduces the local current density and inhibits dendrite growth. The density functional theory calculations indicate that the oxygen-containing polar functional group (C=O, C-OH, and C-O-C) increases the binding energy to Na⁺. Thus, the full cell with Na₃V₂(PO₄)₃ cathode displays a high reversible capacity (88.6 mA h g⁻¹) at 1C after 300 cycles. The results show that the application of chestnut shell-derived biocarbon materials on Na metal anode plays a positive role in achieving their commercialisation in battery systems.