Two Birds with One Stone: A NaCl-Assisted Strategy toward MoTe2 Nanosheets Nanoconfined in 3D Porous Carbon Network for Sodium-Ion Battery Anode

The larger van der Waals interlayer distance of MoTe2 is favorable for Na+ insertion/extraction when MoTe2 is used as sodium-ion battery (SIB) anode. However, engineering of stoichiometric 2D MoTe2 and high-conductivity carbon networks with robust interfacial bonding for SIB anodes is still a great challenge and rarely reported. In this work, high-crystallized 2D MoTe2 nanosheets nanoconfined by interconnected 3D porous carbon networks (indicated with 2D-MoTe2@3DPCN) for SIB anode is successfully constructed via a facile NaCl-assisted strategy. During the synthesis process, the NaCl demonstrates the two birds with one stone effect: the template effect for the formation of interconnected 3D hierarchical porous carbon networks, and the promoting effect of chalcogen atom exchange for in situ conversion from 2D-MoS2 to 2D-MoTe2, which was validated by both experimental results and first-principles simulations. The as-constructed unique architecture not only facilitates both ions and electrons transportation and diffusion throughout the overall electrode, but also can effectively prevent the aggregation of MoTe2 nanosheets and buffer their volume change during the insertion and extraction of Na+. As a result, 2D-MoTe2@3DPCN as SIB anode displays high reversible discharge specific capacity (∼412 mA h g−1 at 100 mA g−1), excellent rate capability (213.8 mA h g−1 at 20 A g−1) and outstanding long cycle life even at high charge/discharge current density (the capacity retention after 3000 cycles is 77.4% at 20 A g−1). This work provides a new path to construct MoTe2-based composites for application in energy-storage fields and beyond.