Scalable mechanochemical synthesis of selenite (MSeO₃, M for Ni, Co, Mn, Cu) anodes for high-performance lithium-ion batteries and their lithium storage mechanism

Transition metal selenites (TMS) are considered effective anode materials for lithium-ion batteries (LIBs). However, their development has been limited by low production yields, high laboratory synthesis costs, and imperfect lithium storage mechanisms. Here, we present a simple, efficient, and scalable mechanochemical synthesis method for TMS (MSeO₃, where M stands for Co, Ni, Cu, or Mn) for the first time. The optimized process produces MSeO₃ with high lithium storage capacity (2459.6 mAh g⁻¹ at 0.2 A g⁻¹ for 400 cycles), remarkable high-current charge/discharge capability (15 A g⁻¹), and excellent cycling stability (1500 and 1740 cycles at 5 and 10 A g⁻¹, respectively) when used as a lithium anode. Cyclic voltammetry (CV), in-situ Raman spectroscopy, ex-situ transmission electron microscopy (TEM), and X-ray diffraction (XRD) confirmed the decomposition of TMS during the first lithiation to form metal oxide and selenium oxide heterostructures. The reduction product metal monomers were found to be involved in an irreversible alloying process, which leads to capacity decay in the initial stage, using dQ/dV and post X-ray photoelectron spectroscopy (XPS). Subsequently, selenium oxide dominates, leading to an increase in specific capacity. Density functional theory (DFT) calculations suggest that the mismatched band structure of these materials may cause the capacity fluctuations prevalent in TMS. This study paves the way for the large-scale production of selenite and sheds new light on the lithium storage mechanism in TMS.