In situ synthetic C encapsulated δ-MnO₂ with O vacancies: a versatile programming in bio-engineering

In this study, we successfully synthesized a δ-MnO₂ cathode with O vacancies, encapsulated by C derived from pyromellitic acid, using a facile hydrothermal method followed by annealing in an Ar atmosphere. The cathode's structural stability and charge transfer kinetics are enhanced by inhibiting the formation of the by-product Zn₄SO₄(OH)₆·4H₂O, regulating the Mn valence state, and suppressing the Jahn-Teller effect through the synergy of C encapsulation and O vacancies. This results in remarkable electrochemical performance, including a large capacity of 421.2 mAh g^-1 at 0.1 A g^-1, a high specific energy density of 595.53 Wh kg^-1, and exceptional long-cycle life stability with 90.88% over 4000 cycles at 10 A g^-1, together with superior coulombic efficiency (∼100%) in pure ZnSO₄ electrolyte. Moreover, the cathode materials demonstrate specific antitumor efficacy. In brief, this work introduces an in situ synthetic C encapsulated δ-MnO₂ with O vacancies expected to be applied in both large-scale energy storage and biomedicine.