Lithium–sulphur batteries are one very appealing power source with high energy density. But their practical use is still hindered by several issues including short lifespan, low efficiency and safety concern from the lithium anode. Polysulphide dissolution and insulating nature of sulphur are generally considered responsible for the capacity degradation. However, the detachment of discharge products, that is, highly polar lithium sulphides, from nonpolar carbon matrix (for example, graphene) has been rarely studied as one critical factor. Here we report the strongly covalent stabilization of sulphur and its discharge products on amino-functionalized reduced graphene oxide that enables stable capacity retention of 80% for 350 cycles with high capacities and excellent high-rate response up to 4 C. The present study demonstrates a feasible and effective strategy to solve the long-term cycling difficulty for lithium–sulphur batteries and also helps to understand the capacity decay mechanism involved.

Lithium metal batteries have been considerably limited by the problems of uncontrolled dendritic lithium formation and the highly reactive nature of lithium with electrolytes. Herein, we have developed functional porous bilayer composite separators by simply blade-coating polyacrylamide-grafted graphene oxide molecular brushes onto commercial polypropylene separators. Our functional porous bilayer composite separators integrate the lithiophilic feature of hairy polyacrylamide chains and fast electrolyte diffusion pathways with the excellent mechanical strength of graphene oxide nanosheets and thus enable molecular-level homogeneous and fast lithium ionic flux on the surfaces of electrodes. As a result, dendrite-free uniform lithium deposition with a high Coulombic efficiency (98%) and ultralong-term reversible lithium plating/stripping (over 2600 h) at a high current density (2 mA cm⁻²) are achieved for lithium metal anodes. Remarkably, lithium metal anodes with an unprecedented stability of more than 1900 h cycling at an ultrahigh current density of 20 mA cm⁻² are demonstrated.