Built-in oriented electric field facilitating durable Zn-MnO2 battery

Rechargeable aqueous zinc ion batteries are particularly attractive for large-scale application due to their features including low cost, environmental friendliness, and safety. Herein, we report the use of defect engineering to generate oxygen vacancies in tunneled alpha-MnO2 through surface gradient Ti doping for long-life Zn-MnO2 battery. Interestingly, the introduction of surface gradient Ti doping leads to shrinkage of the interlayer, but simultaneously generates oxygen vacancies as compensated by electron due to the decreased valence state of Mn. Moreover, Ti substitution as well as the created oxygen vacancies open the [MnO6] octahedral walls and result in imbalanced charge distribution and local electric field in the crystal structure, accelerating ion/electron migration rates. Thus, diffusion coefficients of both Zn2+ and H+ ions in Ti-MnO2 nanowires are improved. Consequently, the Ti-MnO2 nanowires show improved both H+ and Zn2+ ions storage capacity in Zn/MnO2 battery and achieved excellent high-rate capability and ultralong cycling stability with a low capacity decay rate of 0.005% per cycle at high rate of 1 A g(-1). It is believed that the intentionally created vacancies in this work opens up approaches to enhance existing materials that may have applications in more efficient and durable multi-valent ion battery and other technologies.