Nitrogen and oxygen co-doped porous carbon nanosheets as high-rate and long-lifetime anode materials for high-performance Li-ion capacitors

Abstract

Abstract The rational design and sustainable synthesis of high-performance electrode materials are crucial for the practical applications of Li-ion capacitors. Herein, we demonstrate a sustainable strategy for the synthesis of N and O co-doped porous carbon nanosheets via the extraction of gelatin from the fish scales by KCl aqueous solution, lyophilization, and carbonization followed by water washing. With the help of ice/KCl double templates, the resulting sample possesses porous nanosheet structure with the thickness of ca. 4\u202fnm, numerous N and O heteroatoms (8.2\u202fat.% for N, 8.4\u202fat.% for O) derived from gelatin and good electric conductivity (111\u202fS\u202fm−1). When used as the anode material for Li-ion storage, it shows surprising rate capability (249 mAh g−1 at 50\u202fA\u202fg−1) and cycling performance (without decay in 10,000 cycles) in half cells. Consequently, a hybrid Li-ion capacitor based on the carbon nanosheet anode delivers a high energy density (184\u202fWh kg−1), an ultrahigh power density (78.1\u202fkW\u202fkg−1), and an ultralong lifetime (with energy retention of 70% after 10\u202f000 cycles).