OxygenVacancy Engineering Boosts the Rate Performanceof Li/MnO₂ Primary Batteries

Abstract

Although Li/MnO₂ primary batteries have been extensively utilized, their practical specific capacity and rate performance are limited, requiring a better understanding of the limiting factors and the development of effective improvement strategies. In this study, MnO₂ samples were annealed under oxygen and various characterization techniques were applied to assess the morphology, particle size, specific surface area, crystal structure, composition, valence states, and oxygen vacancy content of MnO₂. Annealed MnO₂ showed increased oxygen vacancies, while the O₂ atmosphere raised its phase transition temperature, resulting in significantly higher specific capacity and rate performance, as well as a more stable structure even at high oxygen vacancy concentrations. The MnO₂ sample annealed in O₂ at 500 °C achieved a high specific capacity of 301 mAh·g^–1 at 0.1 C and 186.8 mAh·g^–1 at 5 C, outperforming pristine MnO₂ (243 and 75.4 mAh·g^–1, respectively). Cyclic voltammetry tests, first-principles calculations, and molecular dynamics simulations further revealed that oxygen vacancy engineering enhanced ion diffusion kinetics, leading to improved specific capacity and energy density in MnO₂. This study provides valuable theoretical insights into oxygen vacancy effects and offers a practical route to improving primary battery performance.