B,N-Co-doped Graphene Supported Sulfur for Superior Stable Li-S Half Cell and Ge-S Full Battery.

B,N-Co-doped graphene supported sulfur (S@BNG) composite is synthesized by using melamine diborate as precursor. XPS spectra illustrates that BNG with a high percentage and dispersive B, N (B = 13.47%, N = 9.17%) and abundant pyridinic-N and N-B/N═B bond, show strong interaction with Li2Sx proved by adsorption simulation experiments. As cathode for Li-S half cell, S@BNG with a sulfur content of 75% displays a reversible capacity of 765 mA h g-1 at 1 C even after 500 cycles (a low fading rate of 0.027% per cycle). Even at a high sulfur loading of 4.73 mg cm-2, S@BNG still shows a high and stable areal capacity of 3.5 mA h cm-2 after 48 cycles. When S@BNG composite as cathode combines with high performance lithiated Ge anode (discharge capacity of 1138 mA h g-1 over 1000 cycles at 1 C in half cell), the assembled Ge-S full battery exhibits a superior capacity of 530 mA h g-1 over 500 cycles at the rate of 1 C.