A proton (H+) and zinc ion (Zn2+) co-insertion model is put forward in this study to elucidate the capacity origin of an aqueous zinc ion battery (ZIB) based on a heavily loaded (∼15 mg cm-2) cathode, which consists of Na2V6O16·3H2O (NVO) embedded particularly in the macropores of activated carbon cloth (ACC), coupled with a highly stable Zn/In anode. The confinement effect of these porous channels not only prevents the detachment of NVO from ACC but also well mitigates its volume change resulting from H+ and Zn2+ co-intercalation, which collectively render the stability of NVO/ACC markedly enhanced. Moreover, the bicontinuous structure of NVO/ACC, as a result of the self-interlacing of intrapore NVO, which is first engineered into the nanobelts, and their interlocking with the carbon fibers of ACC, simultaneously giving rise to a solid and a holey framework, is favorable to the electron and ion transport throughout the entire electrode. The synergistic effect of such facile charge transfer kinetics and the high packing density of NVO in the cathode endows ZIBs with not only a good rate performance but also an exceptional areal capacity amounting to 4.6 mAh cm-2, far surpassing those reported for additional vanadium-based counterparts reported in the literature.
Keywords: dual-ion co-insertion charge storage mechanism; high areal capacity; high mass loading; in situ Raman spectroscopy; zinc ion battery.