A Tubular Sandwich-Structured CNT@Ni@Ni2(CO3)(OH)2 with High Stability and Superior Capacity as Hybrid Supercapacitor

Development of highly stabile battery-type electrode materials with superior capacity has been a critical challenge for hybrid supercapacitors. We report a high-performance electrode material, tubular sandwich-structured CNT@Ni@Ni2(CO3)(OH)2, synthesized via a scalable, dynamic, controlled in situ reduction–chemical deposition process. Applied as a battery-type electrode material, this novel nanostructure exhibits excellent electrochemical stability, majorly attributed to the Ni midshell serving a dual role as “capacity supplement” and “electron highway”, which, to our knowledge, was incorporated into the nanocomposite electrodes for the first time. Also benefiting from the high conductivity of carbon nanotubes (CNTs) and the high capacity of the amorphous NiOOH ultrathin film [converted from the Ni2(CO3)(OH)2 outer shell], the resulting CNT@Ni@Ni2(CO3)(OH)2 material as a battery-type electrode achieves a superior capacity of 221 mAh·g–1 at 5 A·g–1 with 76% capacity retention at 50 A·g–1 and maintains 81%...