Surficial grafting of organoimido moieties enhances the capacity performance of oxometallic clusters

Abstract

Molybdenum trioxide (MoO₃) with a theoretical specific capacity of 1117 mA h g⁻¹ is widely considered a promising anode material for lithium-ion batteries. However, the irreversible conversion reactions, low electrical conductivity, and detrimental volume expansion upon Li intercalation between the one-dimensional layered structures of MoO₃ hinder its practical implementation. Herein, we report a facile synthetic protocol that allows surficial modification by replacing the terminal and bridging oxo groups of molybdenum oxide clusters. Successful organoimido functionalization resulted in a large cathodic shift in Mo(VI/V) reduction by 0.6 V, pronounced electronic communication between the organic moiety and the metal–oxide unit, and significant increase in electrical conductivity (80–100 Ω interfacial charge-transfer resistance). Combined with the enlarged active surface area due to the structural hindrance induced by the organic functionality, the steady specific capacity of the organoimido-modified molybdenum oxide clusters was greater than 1200 mA h g⁻¹ at 900 mA g⁻¹ at the end of 360 cycles, where the best value of 1653 mA h g⁻¹ was achieved for the nitroaniline-substituted species. The steady capacity of 480 mA h g⁻¹ was achieved in the fast charge–discharge process (3000 mA g⁻¹) over 1400 cycles. The results indicate that the surficial modification of metal oxides with organo moieties using our facile synthetic method has broad application potential for metal oxides to be used as high-capacity electrode materials in the future.