Co3 O4 Nanosheets as Active Material for Hybrid Zn Batteries.

The rapid development of electric vehicles and modern personal electronic devices is severely hindered by the limited energy and power density of the existing power sources. Here a novel hybrid Zn battery is reported which is composed of a nanostructured transition metal oxide-based positive electrode (i.e., Co3 O4 nanosheets grown on carbon cloth) and a Zn foil negative electrode in an aqueous alkaline electrolyte. The hybrid battery configuration successfully combines the unique advantages of a Zn-Co3 O4 battery and a Zn-air battery, achieving a high voltage of 1.85 V in the Zn-Co3 O4 battery region and a high capacity of 792 mAh gZn-1 . In addition, the battery shows high stability while maintaining high energy efficiency (higher than 70%) for over 200 cycles and high rate capabilities. Furthermore, the high flexibility of the carbon cloth substrate allows the construction of a flexible battery with a gel electrolyte, demonstrating not only good rechargeability and stability, but also reasonable mechanical deformation without noticeable degradation in performance. This work also provides an inspiring example for further explorations of high-performance hybrid and flexible battery systems.

Integration of Zn-Ag and Zn-Air Batteries: A Hybrid Battery with the Advantages of Both.

We report a hybrid battery that integrates a Zn-Ag battery and a Zn-air battery to utilize the unique advantages of both battery systems. In the positive electrode, Ag nanoparticles couple the discharge behaviors through the two distinct electrochemical systems by working as the active reactant and the effective catalyst in the Zn-Ag and Zn-air reactions, respectively. In the negative electrode, in situ grown Zn particles provide large surface areas and suppress the dendrite, enabling the long-term operating safety. The battery first exhibits two-step voltage plateaus of 1.85 and 1.53 V in the Zn-Ag reaction, after which a voltage plateau of 1.25 V is delivered in the Zn-air reaction, and the specific capacity reaches 800 mAh gZn-1. In addition, excellent reversibility and stability with maintaining high energy efficiency of 68% and a capacity retention of nearly 100% at 10 mA cm-2 are demonstrated through 100 cycles, outperforming both conventional Zn-air and Zn-Ag batteries. This work brings forth a conceptually novel high-performance battery, and more generally opens up new vistas for developing hybrid electrochemical systems by integrating the advantages from two distinct ones.