Targeted synthesis of ionic liquid-polyoxometalate derived Mo-based electrodes for advanced electrochemical performance

Abstract

Rational design of advanced electrode materials with high capacity and long cycle stability is a great challenge for both lithium and sodium storage. In this work, we report a versatile strategy for the synthesis of N/P-codoped MoO₂@carbon (N/P-MoO₂@C) electrodes via a simple pyrolysis of ionic liquid-based polyoxometalate (IL-POM) molecular precursors. The contents of C, N, and P, and the pore geometry of N/P-MoO₂@C networks can be easily tailored by adjusting the position of cyano groups in the IL-POM precursor. Benefiting from this novel design, the optimized N/P-MoO₂@C4 electrode with cross-linked porous tunnels and abundant defects exhibits excellent lithium storage performance, with a high reversible capacity of 1381 mA h g⁻¹ after 100 cycles at 0.5 A⁻¹, and 346 mA h g⁻¹ after 5000 cycles at 20 A g⁻¹. The Li⁺ storage performance of this N/P-MoO₂@C4 is dominated by pseudocapacitance behavior, which contributed to the high reversible capacity and long cycle stability. Exceptional sodium storage performance is also observed in the N/P-MoO₂@C4 electrode with 0.02% capacity decay per cycle over 1100 cycles at 1.0 A g⁻¹. The present approach provides some insight into the design and synthesis of task-specific Mo-based materials towards applications in energy storage and conversion.