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.

The zinc-rich epoxy cathodic protection coating is the most widely used anticorrosion material for marine steel. However, traditional conductive fillers lack the intelligent self-healing effect, which limits the long-term anticorrosion performance. Herein, with uniform carbon-coated ZnS (ZnS@C) nanoballs as the smart active release filler, we propose an anticorrosive and self-healing zinc-rich maleic anhydride epoxy coating. Due to the high pore filling efficiency of the nanoballs, the water vapor transmission rate of the coating with an initial corrosion efficiency of 99.92% and a low-frequency impedance of |Z|_f=10mHz = 3.88 × 10¹⁰ Ω·cm², was reduced by 52%. The carbon-shell of the nanoball increases electron transmission paths in the coating and improves conductivity by nearly two orders of magnitude, which effectively activates more Zn-sites and extends the cathodic protection time. Moreover, once the steel-substrate undergoes regional corrosion, the SO₄²⁻ hydrolyzes from the ZnS-core of the nanoball and reacts with iron ions on the corroded area accurately and intelligently to fill the gap and self-heals into a new dense barrier layer (Fe₂(SO₄)₃, etc.), which significantly improves the shielding protection ability during the long-term usage of the coating. The effective anticorrosion time of the proposed coating could be up to 3,400 h.