Encapsulating sodium deposition into carbon rhombic dodecahedron guided by sodiophilic sites for dendrite-free Na metal batteries

Abstract

Uncontrollable growth of sodium dendrite during repeated sodium plating/stripping process results in low Coulombic efficiency, short cycle life and safety problem of sodium metal batteries. Herein, cobalt-based metal organic frameworks (Co-MOFs) was chosen as precursor, a porous nitrogen-anchored carbon rhombic dodecahedron (CoNC) embedded with Co nanoparticles is designed to uniform Na nucleation and deposition for sodium metal anodes, integrating high surface area and high conductivity. Both DFT calculations and experiment results demonstrate that the CoNC can enhance the sodiophilic for sodium nucleation and deposition, encapsulating sodium into CoNC nanoparticles and realize a dendrite-free Na plating and stripping process. CoNC@Na symmetric cell exhibits stable cycle performance for 1200 ​h ​at 1.0 ​mA ​cm−2 for 1.0 ​mAh cm−2 with low nucleation overpotential. The CoNC@Na half cell can operate stable cycling with a superhigh average Coulombic efficiency of 99.6% for 400 cycles. Moreover, full cell paired with Na3V2(PO4)2F3 (NVPF) cathode exhibits excellent cycling performance with a high reversible specific capacity of 113 ​mAh g−1 and capacity retention of 90%. This offers a sight into the design of electrode for encapsulating sodium into carbon matrix by sodiophilic sites to uniform Na nucleation and growth for dendrite-free Na metal anodes.