Microstructured nitrogen-doped graphene-Sn composites as a negative electrode for high performance lithium-ion hybrid supercapacitors

Herein, we report a simplistic single-step synthesis of nitrogen-doped graphene decorated with tin particles suitable as a negative (battery-type) electrode for lithium-ion hybrid capacitors. An activated carbon derived from a graphene–carbon composite is used as a positive (capacitor-type) electrode. The excellent features of the nitrogen-doped graphene matrix combined with the homogeneous distribution and high theoretical capacity (994 mA h g−1) of the submicrometer-sized tin particles lead to an improved performance of the negative electrode, especially at high current densities. An optimized dual-carbon lithium-ion capacitor with 2 : 1 positive to negative mass ratio delivers high energy and power densities (133 W h kg−1 at 142 W kg−1 and 51 W h kg−1 at 25 600 W kg−1). Furthermore, within a discharge time of 1 min, the device reaches 19 000 cycles with full capacity retention, delivering ca. 100 W h kg−1 at 5600 W kg−1.