Vanadium doping inhibit the Jahn−Teller effect of Mn3+ for high-performance aqueous zinc ion battery

The Jahn-Teller effect of Mn 3+ brings drastic structural changes to MnO 2 -based materials and accelerates the destruction and deactivation of the internal structure of the materials, thus leading to severe capacity fading and phase change of MnO 2 -based materials in aqueous zinc ion batteries (AZIBs). Here, this study doped high valent vanadium ions into MnO 2 (VMO-x) to inhibit manganese's Jahn−Teller effect. Through a series of characterizations, such as X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM), it was discovered that the introduction of vanadium ions effectively increased the interlayer spacing of MnO 2 , facilitating the transport of ions into the interlayer. Additionally, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) demonstrated vanadium doped could effectively adjust the electronic structure, decreasing the average oxidation state of manganese, thereby inhibiting the Jahn−Teller effect and significantly enhancing the stability of the VMO-x cathode. The theoretical calculation showed that introducing vanadium ions enhanced the interaction between the main material and Zn 2+ , optimized its electron transport capacity, and led to better electrical conductivity and reaction kinetics of the VMO-5. Benefiting from this, the VMO-5 cathode exhibited an outstanding capacity of 283 mAh/g and maintained a capacity retention rate of 79% after 2000 cycles, demonstrating excellent electrochemical performance. Furthermore, the mechanism of H + /Zn 2+ co-intercalation/deintercalation was demonstrated through mechanism analysis. Finally, the test results of the pouch cell demonstrated the excellent flexibility and safety exhibited by the VMO-5 make it have great potential in flexible devices. This work presented a novel approach to doping high valence metal ions into manganese-based electrodes for AZIBs. Here, high valence vanadium ions were doped into MnO 2 . The low substitution energy of vanadium was used to reduce the oxidation state of Mn, thereby effectively suppressing the Jahn−Teller effect and enhancing the structural stability of MnO 2 . In addition, the multivalent transition of vanadium ions also brought additional capacity to MnO 2 , making it exhibited unexpected results in terms of electrochemical performance.