One-dimensional porous nanostructure composed of few-layered MoSe₂ nanosheets and highly densified-entangled-N-doped CNTs as anodes for Na ion batteries

Porous nanofibers composed of few-layered MoSe₂ nanosheets and highly densified-entangled N-doped carbon nanotubes (N-CNTs) are designed as anodes for Na ion batteries. To maximize the electrical conductivity of the composite nanofibers, amorphous carbon formed by polyacrylonitrile (PAN) decomposition is selectively removed except N-CNTs by intermediate heat treatment. During this step, numerous mesopores are formed between the N-CNTs. Final selenization results in the formation of porous nanofibers composed of few-layered MoSe₂ nanosheets and highly densified-entangled-N-CNTs (P-MoSe₂/N-CNT NF). The discharge capacity of P-MoSe₂/N-CNT NF after 300 cycles is 372 mA h g^-1, which is a 100% capacity retention calculated from the 2^nd cycle onward. P-MoSe₂/N-CNT NF show capacities of 404, 318, 245, 210, 169, 144, 115, and 74 mA h g^-1 at current densities of 0.2, 2, 5, 7, 10, 12, 15, and 20 A g^-1, respectively. Synergetic effects of the N-CNT matrix, uniformly dispersed mesopores, and few-layered MoSe₂ nanosheets result in efficient diffusion of Na⁺ during uptake/removal and rapid transport of electrons by improving the electrical contact between the MoSe₂ nanosheets and electrodes.