Tailoring the phase evolution of molybdenum-based nanocrystals in carbon nanofibers for enhanced performance of lithium-ion batteries

The design and development of flexible and free-standing molybdenum (Mo)-based composite nanoma-terials have aroused intensive attention in the fields of electrocatalysis, energy storage, and wearable electronics. In this study, novel nanocomposite membranes constructed with Mo-based compound nano -crystals loaded carbon nanofibers (CNFs) were successfully generated by a combination of electrospinning molybdenum acetylacetone-contained polyacrylonitrile (PAN) solution and subsequent annealing process from 580 to 900 C. The relationship and mechanisms between the generation of different types of Mo-based nanocrystals and the annealing temperature were systematically explored. It was found that MoO2 nanocrystals were formed when the annealing temperature was 580 degrees C. With the temperature increasing, Mo2N nanocrystals began to form due to the reaction between the formed MoO2 and the N atoms in the PAN macromolecules. At higher temperature like 669 degrees C, Mo2C nanocrystals started to form due to the reaction between Mo2N and C atoms in the carbonized PAN macromolecules, and single-phase Mo2C nanocrystals were produced in CNFs at 900 C. Then, a series of flexible CNF-based nanocomposite membranes em-bedded with various different types of Mo-based compound nanocrystals were generated by effectively controlling the annealing temperature, which were all utilized as anodes for the construction of lithium-ion batteries. Electrochemical measurements showed that the anode materials annealed at 600 oC possessed the highest specific capacity, which were due to the high theoretical specific capacity of MoO2 and sig-nificantly improved conductivity of Mo2N. Moreover, all the as-developed electrodes exhibited excellent cycling stability during the charge-discharge process. The present study provides a facile and broadly -ap-plicable routine to tailor the component, structure, and electrochemical properties of Mo-based nano -crystals in CNFs, which finds huge application potential in the fields of various flexible electrochemical devices.(c) 2022 Elsevier B.V. All rights reserved.