High-Performance Mg-Li Hybrid Batteries Based on Pseudocapacitive Anatase Ti1-xCoxO2-y Nanosheet Cathodes

Despite the proposed safety, performance, and cost advantages, practical implementation of Mg-Li hybrid batteries is limited due to the unavailability of reliable cathodes compatible with the dual-ion system. Herein, a high-performance Mg-Li dual ion battery based upon cobalt-doped TiO2 cathode was developed. Extremely pseudocapacitance-type Ti1-xCoxO2-y nanosheets consist of an optimum 3.57 % Co-atoms. This defective cathode delivered exceptional pseudocapacitance (maximum of 93 %), specific capacities (386 mAh g(-1) at 25 mA g(-1)), rate performance (191 mAh g(-1) at 1 A g(-1)), cyclability (3000 cycles at 1 A g(-1)), and coulombic efficiency (approximate to 100 %) and fast charging (approximate to 11 min). This performance was superior to the TiO2-based Mg-Li dual-ion battery cathodes reported earlier. Mechanistic studies revealed dual-ion intercalation pseudocapacitance with negligible structural changes. Excellent electrochemical performance of the cation-doped TiO2 cathode was credited to the rapid pseudocapacitance-type Mg/Li-ion diffusion through the disorder generated by lattice distortions and oxygen vacancies. Ultrathin nature, large surface area, 2D morphology, and mesoporosity also contributed as secondary factors facilitating superior electrode-electrolyte interfacial kinetics. The demonstrated method of pseudocapacitance-type Mg-Li dual-ion intercalation by introducing lattice distortions/oxygen vacancies through selective doping can be utilized for the development of several other potential electrodes for high-performance Mg-Li dual-ion batteries.

Automated summary

This paper presents a high-performance Mg-Li dual-ion battery based on a cobalt-doped TiO2 cathode. The cathode demonstrates exceptional pseudocapacitance, specific capacities, rate performance, cyclability, and coulombic efficiency, with rapid charging capability. Cation doping, lattice distortions, and oxygen vacancies contribute to its excellent electrochemical performance.