Continuous wet chemical synthesis of Mo(C,N,O)x as anode materials for Li-ion batteries

Abstract

Molybdenum carbides, oxides, and mixed anionic carbide–nitride–oxides Mo(C,N,O)_x are potential anode materials for lithium-ion batteries. Here we present the preparation of hybrid inorganic–organic precursors by a precipitation reaction of ammonium heptamolybdate ((NH₄)₆Mo₇O₂₄) with para-phenylenediamine in a continuous wet chemical process known as a microjet reactor. The mixing ratio of the two components has a crucial influence on the chemical composition of the obtained material. Pyrolysis of the precipitated precursor compounds preserved the size and morphology of the micro- to nanometer-sized starting materials. Changes in pyrolysis conditions such as temperature and time resulted in variations of the final compositions of the products, which consisted of mixtures of Mo(C,N,O)_x, MoO₂, Mo₂C, Mo₂N, and Mo. We optimized the reaction conditions to obtain carbide-rich phases. When evaluated as an anode material for application in lithium-ion battery half-cells, one of the optimized materials shows a remarkably high capacity of 933 mA h g⁻¹ after 500 cycles. The maximum capacity is reached after an activation process caused by various conversion reactions with lithium.