Forming bubble-encapsulated double-shelled hollow spheres towards fast kinetics and superior high rate performance for aqueous rechargeable Zn-ion batteries

Building intricate hollow structures has attracted tremendous interest in energy storage and conversion due to their unique structural features, fascinating physicochemical characteristics and superior electrochemical properties. In this work, we introduce a novel intricate hollow structure, i. e. bubble- encapsulated doubleshelled hollow spheres ( BDHSs), to achieve fast kinetics and a superior high rate performance for rechargeable aqueous Zn- ion batteries. The double- shelled hollow spheres form the bulk architecture, and the small bubbles connect to build an additional outside layer on its surface. This hierarchical structure not only possesses a highly porous skeleton for fast ion transport, but also provides more active sites for electrochemical reaction, and thus is favorable for fast kinetics and high energy storage. For the first time, the process of evolution of the BDHS structure is probed and a dual- template mechanism based on both the colloid and the gas/ liquid interface soft templates is disclosed. In this study, a BDHS structure is constructed for a Zn2V2O7 composite. The unique structure and nanoscale crystals enable better capacitive behavior and superior high rate properties of the Zn2V2O7 BDHS sample over reference samples. Moreover, solid- state batteries are fabricated based on a Zn2V2O7 BDHS/ SWNT cathode and polymer electrolyte. The superior power density, high energy density and good long- term cycling stability confirm their excellent energy storage ability and fast charge/ discharge capability. Therefore, the present work introduces a highly efficient architecture to realize a superior electrochemical performance for electroactive materials, which also provides a new clue to propel the development of functional materials in various fields, such as catalysis, medicine and electronics.