Due to their small footprint and flexible siting, rechargeable batteries are attractive for energy storage systems. A super-valent battery based on aluminium ion intercalation and deintercalation is proposed in this work with VO2 as cathode and high-purity Al foil as anode. First-principles calculations are also employed to theoretically investigate the crystal structure change and the insertion-extraction mechanism of Al ions in the super-valent battery. Long cycle life, low cost and good capacity are achieved in this battery system. At the current density of 50 mAg−1, the discharge capacity remains 116 mAhg−1 after 100 cycles. Comparing to monovalent Li-ion battery, the super-valent battery has the potential to deliver more charges and gain higher specific capacity.

We report the observation of a novel phenomenon, the self-retracting motion of graphite, in which tiny flakes of graphite, after being displaced to various suspended positions from islands of highly orientated pyrolytic graphite, retract back onto the islands under no external influences. Reports of this phenomenon have not been found in the literature for single crystals of any kind. Models that include the van der Waals force, electrostatic force, and shear strengths were considered to explain the observed phenomenon. These findings may conduce to create nanoelectromechanical systems with a wide range of mechanical frequency from megahertz to gigahertz.

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Thermoelectric materials can realize significant energy savings by generating electricity from untapped waste heat; however, the coupling of the thermoelectric parameters unfortunately limits their efficiency and practical applications. Herein, rational all-oxide TiC 1-x O x @TiO y -TiO 2 (xo1, 1oyo2) heterostructures with significantly enhanced thermoelectric properties have been designed, and a high dimensionless figure of merit (ZT) value of up to 0.84 at 973 K was achieved in the all-oxide TiC 0.1 O 0.9 @TiO y -TiO 2 heterostructures, which is one of the highest values in n-type oxide bulk thermoelectric materials to date. The TiC 1-x O x @TiO y heterostructures, which include a thin film of approximately 5-10 nm on the surface of TiC 1-x O x compounds prepared by a facile anodization process, exhibit an obvious improvement of the thermoelectric power factor. Furthermore, an excellent dimensionless figure of merit value was obtained in the TiC 1-x O x @TiO y -TiO 2 heterostructures prepared by the anodization process assisted by the sol-gel chemical route, which can be attributed to the decrease in the carrier concentration via the carrier double-barrier filtering effect. This work develops a facile strategy for synthesizing core-shell heterostructures and demonstrates their superior ability to optimize thermoelectric energy harvesting.