Sodiophilic Modification Of Porous Carbon Materials And Its Application In Sodium Metal Anode

Sodium（Na）metal anodes are attracting extensive attention for large-scale energy storage due to its high theoretical specific capacity(1166 mA h g^-1),low electrode potential（-2.71 V vs S.H.E.）and low cost.However,the ubiquitous side reactions,uncontrollable sodium dendrites growth and volume changes in cyclic processes will deteriorate the electrochemical performance of sodium metal batteries,hindering its practical application.In this paper,porous carbon materials were chosen as hosts for sodium deposition/dissolution.Aiming at the problem of its intrinsic sodiophobic characteristic,a series of 3D sodium metal anodes with high Coulombic efficiency and long cycle life were fabricated by sodiophilic modification.The main contents and conclusions are as follows:（1）Aiming at the problem of poor Na wettability of commercial carbon cloth（CC）,the modified carbon cloth with uniform Bi distribution were obtained by hydrothermal method in which carbon cloth and Bi-MOF were mixed and carbonized.And then,it was compounded with sodium metal to construct sodium metal anode with good reversibility and stability.In half cells,Na-CC@Bi@C electrode delivers CE of99.85%for near 500 cycles at 1.0 mA cm^-2and 1.0 mA h cm^-2.The symmetric cells exhibit approximately 53 m V overpotential for over 300h at 2.0 mA cm^-2for 2.0 mA h cm^-2.When paired with Na₃V₂（PO₄）₃（NVP）for full cells,a specific capacity of 101.0 mA h g^-1and a capacity retention of 95.50%can be obtained after 150 cycles at 0.5 C.（2）Aiming at the problem of continuous consumption of electrolyte and sodium due to the open-structure of carbon cloth when applied for sodium metal anodes,a semi-confined hierarchical porous carbon（HPC）with high specific surface area was fabricated by template method,combining with lithium/sodium metal.The difference in deposition and dissolution behavior of lithium and sodium metals was systematically compared.In half cells,Na-HPC electrode delivers CE of 99.86%for 350cycles at 1.0 mA cm^-2and 1.0 mA h cm^-2.By contrast,The CE of Li-HPC half cells is always less than 99%under the same condition.When the HPC/Na composite anodes were paired with Na₃V₂（PO₄）₃（NVP）for full cells,a specific capacity of 96.5 mA h g^-1and a capacity retention of91.82%can be obtained after 150 cycles at 1 C.（3）Aiming at the problem of poor Na wettability of hierarchical porous carbon（HPC）,it was mixed with Bi precursor solution by hydrothermal method,and then carbonized to obtain the modified HPC with uniform Bi distribution（Bi@HPC）.And then,it was compounded with sodium metal to construct sodium metal anode with good reversibility and stability.In half cells,Na-Bi@HPC can stably cycle 900cycles with CE of 99.78%at 1.0 mA cm^-2for 1.0 mA h cm^-2.When paied with Na₃V₂（PO₄）₃（NVP）for full cells,a specific capacity of 102.4 mA h g^-1and a capacity retention of 95.34%can be obtained after 150 cycles at1 C.