Combining Structural Modification and Electrolyte Regulation to Enable Long-Term Cyclic Stability of MoO_3-x @TiO₂ as...

Orthorhombic MoO₃ (α-MoO₃ ) with multivalent redox couple of Mo⁶⁺ /Mo⁴⁺ and layered structure is a promising cathode for rechargeable aqueous Zn-ion batteries (AZIBs). However, pure α-MoO₃ suffers rapid capacity decay due to the serious dissolution and structural collapse. Meanwhile, the growth of byproduct and dendrite on the anode also lead to the deterioration of cyclic stability. This article establishes the mechanism of proton intercalation into MoO₃ and proposes a joint strategy combining structural modification with electrolyte regulation to enhance the cyclic stability of MoO₃ without sacrificing the capacity. In ZnSO₄ electrolyte with Al₂ (SO₄ )₃ additive, TiO₂ coated oxygen-deficient α-MoO₃ (MoO_3-x @TiO₂ ) delivers a reversible capacity of 93.2 mA h g^-1 at 30 A g^-1 after 5000 cycles. The TiO₂ coating together with the oxygen deficiency avoids structural damage while facilitating proton diffusion. Besides, the additive of Al₂ (SO₄ )₃ , acting as a pump, continuously supplements protons through dynamic hydrolysis, avoiding the formation of Zn₄ SO₄ (OH)₆ ·xH₂ O byproducts at both MoO_3-x @TiO₂ and Zn anode. In addition, Al₂ (SO₄ )₃ additive facilitates uniform deposition of Zn owing to the tip-blocking effect of Al³⁺ ion. The study demonstrates that the joint strategy is beneficial for both cathode and anode, which may shed some light on the development of AZIBs.