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 Li2S x 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.