Nanocrystalline Moo2/C Microspheres Anchored in Interconnected Rgo Frameworks: Improved Bifunctional Anode Materials for Lithium-Ion Batteries

Abstract

Both crystalline and amorphous MoO2 exhibit distinct advantages for lithium-ion battery applications, with the former favoring lithium-ion intercalation and the latter undergoing complete lithiation via a conversion reaction. However, their sluggish lithium-ion insertion rates and inadequate charge transfer kinetics hinder their full potential. To address these challenges, we have developed a groundbreaking approach that integrates freeze-drying with the combination of well-dispersed HxMoO3/C precursors and graphene oxide (GO), followed by calcination in an inert atmosphere. This innovative method results in the formation of bubble-sheet-like MoO2/C@rGO composites, where the strategic inclusion of GO and the unique properties of HxMoO3/C effectively mitigate recrystallization and surface oxidation, enabling the creation of highly tunable nanocrystalline structures. Furthermore, the reduction of HxMoO3/C precursors into MoO2/C within these composites creates a flexible void space between the microspheres and the rGO coating, accommodating volume variations. These structural merits endow the MoO2/C@rGO composite with high initial coulombic efficiency (ICE, e.g., up to 71.3% at 100 mA g−1), impressive rate performance (e.g., achieving 60 mAh g−1 at 1 A g−1, and 34.1% retention from 0.1 to 2 A g−1) and excellent cyclability (e.g., retaining 98.9% of its capacity after 200 cycles) when employed as an intercalation-type anode material. Remarkably, the MoO2/C@rGO composite, especially the sample containing 15%wt rGO, demonstrates exceptional performance as a conversion-type anode material. It displays enhanced ICE (e.g., up to 76.9% at 100 mA g−1), accelerated activation (e.g., achieving peak performance within 10 cycles at 100 mA g−1), superior rate performance (e.g., achieving 446 mAh g−1 at 2 A g−1), and remarkable cyclability (e.g., maintaining 510 mAh g−1 with 88.9% capacity retention over 600 cycles at 1 A g−1). Additionally, the observed pseudocapacitive behavior underscores the significant improvements achieved through nano-crystallization and conductive interconnected rGO frameworks, positioning them as promising bifunctional anode materials for advanced lithium-ion battery applications.

Keywords: Nanocrystalline MoO2/C microspheres, Interconnected rGO frameworks, MoO2/C@rGO composites, Intercalation-type lithiation reaction, Pseudocapacitive lithium storage, Conversion-type lithiation activation