Highly stable aqueous zinc-ion batteries enabled by suppressing the dendrite and by-product formation in multifunctional Al³⁺ electrolyte additive

Rechargeable aqueous zinc-ion batteries (ZIBs) have gained extensive attention owing to the high safety, low cost, and high power/energy densities. But unfortunately the ZIBs universally suffer from the highly damaging series of side reactions, majorly including the insulating products formation, dendritic growth of zinc, and hydrogen evolution. To date there are few reports on the effective strategy that can solve the problems at the same time. Here we propose a novel hybrid electrolyte with Al³⁺ as additive to construct an aqueous ZIB composed of metallic zinc anode and K_0.51V₂O₅ (KVO) nanoplate cathode. The highly reversible multistep K⁺/Zn²⁺-ions co-insertion/extraction in the lamellar structure with large interlayer spacing is clearly evidenced by systematical characterizations. In the presence of Al³⁺, the insulating basic zinc salts on the cathode surface have been reduced greatly, and the electrochemical potential window has been significantly expanded from 3 to 4.35 V. More interestingly, the Al³⁺ acts as a dopant embedded into the lattice that strengthens the crystal structure. Benefits from the suppressed zinc dendrite growth, the symmetrical Zn/Zn battery exhibited a satisfactory cycling life over 1,500 h at a high rate of 3 mA·cm^–2 in the hybrid electrolyte. As a result, the Zn/KVO batteries delivered a high specific capacity of 210 mAh·g^–1 and retained high capacity retention of 91% after 1,600 h at a low current of 100 mA·g^–1.