High performance Mg-Li dual metal-ion batteries based on highly pseudocapacitive hierarchical TiO2-B nanosheet assembled spheres cathodes.

Although Mg-Li dual metal-ion batteries are proposed as a superior system that unite safety of Mg-batteries and performance of Li-ion based systems, its practical implantation is limited due to the lack of reliable high-performance cathodes. Herein, we report a high-performance Mg-Li dual metal-ion battery system based on highly pseudocapacitive hierarchical TiO₂-B nanosheet assembled spheres (NS) cathode. This 2D cathode displayed exceptional pseudocapacitance (a maximum of 93%) specific capacity (303 mAh g^-1at 25 mA g^-1), rate performance (210 mAh g^-1at 1 A g^-1), consistent cycling (retain ∼100% capacity for 3000 cycles at 1 A g^-1), Coulombic efficiency (nearly 100%) and fast-charging (∼12.1 min). These properties are remarkably dominant to the existing Mg-Li dual metal-ion battery cathodes. Spectroscopic and microscopic mechanistic studies confirmed negligible structural changes during charge-discharge cycles of the TiO₂-B nanosheet assembled spheres electrodes. Exceptional electrochemical properties of the 2D electrode is ascribed to remarkable pseudocapacitive Mg-Li dual metal-ion diffusion via the numerous nanointerfaces of TiO₂-B caused by its hierarchical microstrucrure. Large surface area, nanosheet morphology, mesoporous structure and ultrathin nature also acted as secondary factors facilitating improved electrode-electrolyte contact. Demonstrated approach of pseudocapacitive type Mg-Li dual metal-ion intercalation through hierarchical nanointerfaces may be further utilized for the designing of numerous top-notch electrode materials for futuristic Mg-Li dual metal-ion batteries.