Nitrogen-doped carbon-coated transition-metal sulfides (TMS@NCs) have been considered as efficient anodes for sodium-ion batteries. However, the uncontrollable morphology and weak core–shell binding forces significantly limit the sodium storage performance and life. Herein, based on the reversible ring-opening reaction of the epoxy group of the tertiary amino group-rich epoxide cationic polyacrylamide (ECP) at the beginning of hydrothermal process (acidic environment) and the irreversible ring-opening (cross-linking reactions) at the late hydrothermal period (alkaline environment), 47 nm-sized ZnS@NCs were prepared via a one-pot hydrothermal process. During this process, the covalent bonds formed between the ZnS core and elastic carbon shell significantly improved the mechanical and chemical stabilities of ZnS@NC. Benefiting from the nanosize, fast ion/electron transfer, and high stability, ZnS@NC exhibited a high reversible capacity of 421.9 mAh g⁻¹ at a current density of 0.1 A g⁻¹ after 1000 cycles and a superior rate capability of 273.8 mAh g⁻¹ at a current density of 5 A g⁻¹. Moreover, via this universal synthesis strategy, a series of TMS@NCs, such as MoS₂@NC, NiS@NC, and CuS@NC were developed with excellent capacity and cyclability.

Lithium-sulfur battery has become one of the most promising candidates for next generation batteries, and it is still restricted due to the low sulfur conductivity, large volume expansion and severe polysulfide shuttling. Herein, we present a novel hybrid electrode with a ternary nanomaterial based on sulfur-impregnated multiwalled carbon nanotubes filled with ordered tin-monoxide nanoparticles (MWCNT-SnO/S). Using a dry plasma reduction method, a mechanically robust material is prepared as a cathode host material for lithium-sulfur batteries. The MWCNT-SnO/S electrode exhibits high conductivity, good ability to capture polysulfides, and small volume change during a repeated charge–discharge process. In situ transmission electron microscopy and ultraviolet–visible absorption results indicate that the MWCNT-SnO host efficiently suppresses volume expansion during lithiation and reduces polysulfide dissolution into the electrolyte. Furthermore, the ordered SnO nanoparticles in the MWCNTs facilitate fast ion/electron transfer during the redox reactions by acting as connective links between the walls of the MWCNTs. The MWCNT-SnO/S cathode with a high sulfur content of 70 wt.% exhibits an initial discharge capacity of 1, 682.4 mAh·g^–1 at 167.5 mA·g^–1 (0.1 C rate) and retains a capacity of 530.1 mAh·g^–1 at 0.5 C after 1, 000 cycles with nearly 100% Coulombic efficiency. Furthermore, the electrode exhibits the high capacity even at a high current rate of 20 C.