Rambutan‐like hollow carbon spheres decorated with vacancy‐rich nickel oxide for energy conversion and storage

Transition metal oxides hold great promise for lithium‐ion batteries (LIBs) and electrocatalytic water splitting because of their high abundance and high energy density. However, designing and fabrication of efficient, stable, high power density electrode materials are challenging. Herein, we report rambutan‐like hollow carbon spheres formed by carbon nanosheet decorated with nickel oxide (NiO) rich in metal vacancies (denoted as h ‐NiO/C) as a bifunctional electrode material for LIBs and electrocatalytic oxygen evolution reaction (OER). When being used as the anode of LIBs, the h ‐NiO/C electrode shows a large initial capacity of 885 mA h g −1 , a robust stability with a high capacity of 817 mA h g −1 after 400 cycles, and great rate capability with a high reversible capacity of 523 mA h g −1 at 10 A g −1 after 600 cycles. Moreover, working as an OER electrocatalyst, the h ‐NiO/C electrode shows a small overpotential of 260 mV at 10 mA cm −2 , a Tafel slope of 37.6 mV dec −1 along with good stability. Our work offers a cost‐effective method for the fabrication of efficient electrode for LIBs and OER.