Unravelling V₆O₁₃ Diffusion Pathways via CO₂ Modification for High-Performance Zinc Ion Battery Cathode

Vanadium-based oxide is widely investigated as a zinc ion battery (ZIB) cathode due to its ability to react reversibly with Zn²⁺. Despite its successful demonstration, modification with simple molecules has shown some promise in enhancing the performance of ZIBs. Thus, this presents an immense opportunity to explore simple molecules that can dramatically improve the electrochemical performance of electrodes. Thus, the effect of CO₂ modification is studied in this work by decomposing oxalic acid within a hydrated V₆O₁₃ framework. Based on the collective results, the presence of CO₂ drastically lowers the relative energy of Zn²⁺ diffusion through the pathways by forming weak electrostatic interactions between O_CO2 and Zn²⁺. This leads to an enlarged diffusion contribution, which consequently results in enhanced stability and better rate performance. The as-synthesized CO₂-V₆O₁₃ electrode delivers one of the highest specific capacities reported for vanadium-based oxides of ca. 471 mAh g^-1. Furthermore, an excellent cyclic stability of 80% capacity retention after 4000 cycles at 2 A g^-1 is recorded for CO₂-V₆O₁₃, which suggests the importance of simple molecules in the material framework toward the enhancement of ZIB cathode performance.