Sulfur-Rich (NH₄)₂Mo₃S₁₃ as a Highly Reversible Anode for Sodium/Potassium-Ion Batteries

Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have attracted much attention owing to the inexpensive Na/K metal and satisfactory performance. Currently, there are still difficulties in research anode materials that can insert/extract Na/K ions quickly and stably. Herein, the sulfur-rich (NH₄)₂Mo₃S₁₃ is proposed as the anode for SIBs/PIBs and is obtained by a hydrothermal method. The sulfur-rich (NH₄)₂Mo₃S₁₃ with a three-dimensional structure shows a high capacity and long lifespans for Na⁺ (at 10 A g^-1 the capacity of 165.2 mAh g^-1 after 1100 cycles) and K⁺ (120.7 mAh g^-1 at 1 A g^-1 retained after 500 cycles) storage. In addition, the (NH₄)₂Mo₃S₁₃ electrode exhibits excellent electrochemical performance at low temperatures (0 °C). The mechanism of Na⁺ storage in (NH₄)₂Mo₃S₁₃ can be innovatively revealed through the combined use of electrochemical kinetic analysis and a series of ex situ characterization tests. It is believed that the present work identifies (NH₄)₂Mo₃S₁₃ as a promising anode for the SIBs/PIBs and will be of broad interest in research on engineering sulfur-rich transition metal sulfide and on energy storage devices.