Double‐site Substitution Doping by Anion/Cation Breaking the Jahn–Teller Effects of MnO ₂ for High‐Performance Aqueous Zinc‐Ion Batteries

ABSTRACT Aqueous zinc‐ion batteries (AZIBs) provide a new scheme for large‐scale electrochemical energy storage systems by virtue of high safety and cost‐effectiveness. However, the application of MnO 2 cathodes in AZIBs is hindered by the irreversible structural collapse originating from the Jahn–Teller effects of Mn 3+ and the sluggish diffusion kinetics. Herein, an Al/N co‐doping strategy is proposed to overcome these limitations. Partial Mn 3+ is substituted by Al 3+ in the Al/N co‐doped MnO 2 (Al/N‐MO), where the Al 3+ ions disrupt the long‐range ordering of Mn 3+ and exert a pinning effect within the lattice to restrain the axial deformation of [Mn 3+ O 6 ] units during discharge, thereby mitigating the Jahn–Teller effects. The substitution of lattice oxygen by less electronegative N atoms counteracts the lattice strain induced by Al‐doping and reduces the diffusion resistance for carriers within the tunnels, simultaneously triggering the optimization of the band gap. Furthermore, the substitutional co‐doping of Al and N induces grain refinement, provides abundant grain boundaries, and widens tunnel size, significantly boosting pseudocapacitive storage. The tailored Al/N‐MO cathode demonstrates decent electrochemical performance (315.3 mAh g −1 at 2 A g −1 and a residual capacity of 292.6 mAh g −1 over 3000 cycles), as well as stable cycling over 130 days with a quasi‐solid‐state electrolyte.