High‐Performance Mg−Li Hybrid Batteries Based on Pseudocapacitive Anatase Ti<sub>1‐<i>x</i></sub>Co<sub><i>x</i></sub>O<sub>2‐<i>y</i></sub> Nanosheet Cathodes
Mewin Vincent, Venkata Sai Avvaru, Maciej Harańczyk, Vinodkumar Etacheri
Abstract
Abstract 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 TiO 2 cathode was developed. Extremely pseudocapacitance‐type Ti 1‐ x Co x O 2‐ 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 (≈100 %) and fast charging (≈11 min). This performance was superior to the TiO 2 ‐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 TiO 2 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.