Suppressing cathode dissolution via guest engineering for durable aqueous zinc-ion batteries

Rechargeable aqueous zinc ion batteries (AZIBs) have attracted increasing attention because of high ionic conductivity and non-flammable electrolytes. The spontaneous reaction of vanadium dissolution in aqueous electrolytes is a major problem for vanadium-based cathodes, since the water molecules with strong polarity could easily attack the vanadium-based cathodes crystal structure and directly lead to capacity deterioration. Here, a strategy of guest engineering is used to regulate the interlayer binding energy between vanadium oxide layers, thus thermodynamically suppressing vanadium dissolution. First-principles calculations indicate that a large interlayer binding energy of up to 208.1 meV angstrom(-2) between vanadium oxide layers is obtained with NH4+ and H2O co-intercalation, which is more than tenfold that of V2O5. The as-prepared compound (NH4)(2)V6O16.1.5H(2)O (NH-V) restrains the vanadium dissolution effectively as expected. The electrolyte with NH-V immersion remains colorless even after 200 days, and the vanadium concentration of this electrolyte is thirty-seven times less than that of V2O5. Moreover, benefiting from this ultra-good chemical stability, the NH-V cathode shows an impressive recharge capacity retention of 98.5% after the open circuit voltage test for three days, which is 23% higher than that of V2O5. These results demonstrate that the guest engineering strategy could be a feasible way to construct robust layer structures, suppress the cathode dissolution, restrain self-discharge and improve the battery storage time. This work can provide new insights to understand the cathode dissolution behavior and it will be helpful to develop cathode materials with robust structures for suppressing cathode dissolution in aqueous batteries and beyond.