Phase and Structural Evolution in Molten Inorganic Salts of Molybdenum Borides for Electrochemical Applications

Due to the increasing demand for high-performance, sustainable, and reliable energy, the pursuit of advanced electrode materials for lithium-ion capacitors (LICs) has attracted great attention within the field of energy storage. Among various candidates, molybdenum borides (MoB_X, where X = 1 or 2) have emerged as promising anode materials owing to their remarkable electrical conductivity, chemical stability, and high theoretical capacity. However, the synthesis of phase-pure crystalline MoB_X nanoparticles remains a challenge. This study investigates the ionothermal route as an efficient synthesis method to overcome this obstacle while also exploring the lithium-ion energy storage mechanism of MoB_X nanoparticles and their potential as LIC anodes. The MoB and MoB₂ electrodes exhibit excellent cycling stability, with capacities reaching 159 and 207 mAh g^-1, respectively, after 800 cycles at 0.1 A g^-1. Additionally, LICs using MoB and MoB₂ as anodes, paired with commercial activated carbon as cathodes, demonstrate exceptional capacity retention rates of 51.5% and 72.1%, respectively, after 10,000 cycles. These results not only confirm the potential of MoB_X nanoparticles as superior anode materials for LICs, but also provide a foundation for future research aimed at developing high-performance and long-lasting energy storage systems.