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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 (≈100 %) and fast charging (≈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. [ABSTRACT FROM AUTHOR]

• Defect engineered hexagonal boron nitride (hBN) anode to overcome the safety and performance limitations of current generation Li-ion batteries. • Reversible LiF formation catalyzed by defects in hBN to enable the pseudocapacitive type Li-ion storage on the hBN surface. • Non-flammability and excellent thermal tolerance of hBN allows a high specific capacity (880 mAh/g @ 25 mA/g), rate performance (480 mAh/g @ 5 A/g) and stable cycling (5000 cycles) at 60 °C. • The power and energy density are 3–4 times improved in the full cell with the defective hBN anode. The mass market adoption of electric vehicles has increased the risk of safety concerns, such as overheating and flammability. Rational design of fire-safe and high-capacity anodes with thermal tolerance, capable of fast-charging and long cycle-life, is crucial for the development of next generation Li-ion batteries operating under extreme conditions. Here we report a defect engineered hexagonal boron nitride (hBN) anode to mediate the safety dilemma. We demonstrate that the defects generated via cryomilling catalyze the reversible LiF formation and enable the pseudocapacitive type Li-ion storage on hBN. The non-flammability and excellent thermal tolerance of hBN allows high specific capacity (880 mAh/g @ 25 mA/g), rate performance (480 mAh/g @ 5 A/g) and stable cycling (5000 cycles) at 60 °C. The Li-ion full-cell with the defective hBN anode and the conventional cathode (LiNiMnCoO 2) delivers significantly higher energy (400 Wh kg−1) and power density (1 kW kg−1) when compared to graphite/LiNiMnCoO 2 full-cells (121 Wh kg−1 and 250 W kg−1). First-principles calculations confirm that nitrogen antisite (N B V N) defects are responsible for the electrochemical activation of otherwise inactive hBN. The strategy of defect-induced electrochemical activation opens up new avenues in the design of high-performance electrode materials for numerous secondary batteries. [ABSTRACT FROM AUTHOR]

Although secondary Li-ion batteries are widely used for electrochemical energy storage, low energy (100–300 Wh kg−1) and power density (250–400 W kg−1) are limiting their applications in several areas including long-range electric vehicles. Herein, we demonstrate high energy (400 Wh kg−1) and power density (1 kW kg−1) Li-ion batteries (considering the weight of both electrodes) based on extremely pseudocapacitive interface engineered CoO@3D-NRGO hybrid anodes. These values are 2.8 and 2.3-fold higher respectively compared to graphite‖LiNiMnCoO 2 full-cells under similar experimental conditions. Three-dimensional anode architecture presented here composed of ultrafine CoO nanoparticles (∼10 nm) chemically bonded to nitrogen-doped reduced graphene-oxide. This hybrid anode demonstrated excellent pseudocapacitance (∼92%), specific capacity (1429 mAh g−1 @ 25 mA g−1), rate performance (906 mAh g−1 @ 5 A g−1), and cycling stability (990 mAh g−1 after 7500 cycles @ 5 A g−1). Outstanding electrochemical performance of CoO@3D-NRGO‖LiNiMnCoO 2 full-cells is credited to the extreme pseudocapacitance of CoO@3D-NRGO anode resulting from Li 2 O/Co/NRGO nanointerfaces and Co–O–C bonds. The demonstrated strategy of interfacial engineering can also be extended for other environmental friendly/inexpensive transition metal oxide (Fe 2 O 3 , MnO 2 etc.) anodes for high energy/power density and ultra-long-life Li-ion batteries. Image 1 • Extremely pseudocapacitive CoO@3D-NRGO hybrid Li-ion battery anodes are developed. • Li-ion battery exhibited high energy (400 Wh kg−1) and power density (1 kW kg−1). • These values are 2.8 and 2.3-fold higher compared to graphite anode based system. • Li 2 O/Co/NRGO nanointerfaces and Co–O–C bonds caused extreme pseudocapacitance. • This strategy provides new opportunities to design advanced Li-ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fast-charging and ultralong-life Mg-Na hybrid battery is presented. • Hierarchical TiO 2- B nanosheet cathode exhibited outstanding pseudocapacitance. • In-situ XRD measurements revealed unique Mg-Na dual-ion storage mechanism. • This strategy present new opportunities to design advanced Mg-Na hybrid batteries. Despite of their inexpensive and sustainable characteristics, practical application of Mg-Na hybrid batteries are limited due to the lack of high performance dual-ion compatible cathode materials. This is mainly due to the increased size of Na-ions and improved electrostatic repulsion resulting from the high charge density of Mg-ions. Herein, we report for the first time a fast charging and ultralong-life Mg-Na hybrid battery based on an extremely pseudocapacitive hierarchical bronze TiO 2 (TiO 2 -B) nanosheet cathode. This two dimensional cathode exhibited outstanding pseudocapacitance (up to 94%), specific capacities (195 mAh/g @ 25 mA/g), rate performance (140 mAh/g @ 1A/g), cycling stability (∼76% after 6000 cycles @ 1A/g), coulombic efficiency (∼100%) and fast-charging (∼8 min). These performances are vastly superior to the previously reported metal oxide type Mg-Na hybrid battery cathodes. Mechanistic investigations revealed Mg-Na dual-ion intercalation pseudocapacitance with no significant structural changes. Exceptional electrochemical performance of the TiO 2 -B nanosheet cathode is credited to the dominant pseudocapacitive Mg-Na dual-ion diffusion through the nanointerfaces resulting from the hierarchical microstructure of TiO 2 -B nanosheets. High surface area, ultrathin nature and mesoporous structure are also contributed as secondary factors by facilitating superior contact with the electrolyte solution. The demonstrated method of nanointerfaces induced pseudocapacitive Mg-Na dual-ion intercalation provides new opportunities for the development of high-performance Mg-Na hybrid batteries. [ABSTRACT FROM AUTHOR]

Although Mg–Li hybrid batteries are proposed as an alternative to Mg-batteries, the lack of dual-ion compatible cathodes are limiting their practical application. Herein, we report a high-rate and ultralong-life Mg–Li hybrid battery based on a dual-phase TiO 2 cathode. Highly pseudocapacitive hierarchical two-dimensional TiO 2 consists of anatase (60%) and bronze (40%) nanocrystallites forming interfaces due to crystal structure mismatch. This dual-phase hierarchical cathode exhibits excellent pseudocapacitance (up to 92%), specific capacities (235 mAh/g @ 25 mA/g), rate performance (120 mAh/g @ 1A/g) cycling stability (~87% after 3000 cycles @ 1A/g) and coulombic efficiency (~100%). These results are vastly superior to the previously reported values for TiO 2 based Mg–Li hybrid battery cathodes. Only minimal structural changes are observed during the charge-discharge of two-dimensional TiO 2 electrode. Outstanding electrochemical performance of dual-phase TiO 2 nanosheet cathode is attributed to the superior pseudocapacitive Mg/Li-ion diffusion through nanointerfaces between anatase and bronze crystallites. While other structural features such as 2D-morphology, ultrathin nature, mesoporosity, and high surface area act as secondary factors. The demonstrated approach for efficient pseudocapacitive Mg/Li-ion intercalation enhanced by nanointerfaces can be further exploited in the development of other high performance electrodes for advanced Mg–Li hybrid batteries. [Display omitted] • High-rate and ultralong-life Mg–Li hybrid battery is presented. • Dual-phase TiO 2 nanosheet cathode exhibited outstanding Mg/Li-ion storage. • Anatase-bronze nanointerfaces caused excellent pseudocapacitance. • This tactic provides new opportunities to design advanced Mg–Li hybrid batteries. [ABSTRACT FROM AUTHOR]