Nickel nanoparticles embedded N-doped mesoporous graphitized carbon nanoflake as multifunctional sulfur host for high-performance lithium-sulfur batteries

Abstract

The practical application of lithium-sulfur (Li-S) batteries has long been obstructed by the critical problems of the lithium polysulfides shuttle effect and the intrinsically sluggish sulfur redox kinetics. In this study, nickel nanoparticles were embedded in N-doped mesoporous graphitized carbon nanoflakes (Ni-NMC) through the pyrolysis of polydopamine-coated nickel flakes followed by an acidic etching process. Homogeneous mesopores and highly graphitized carbon are formed by the thermal aggregation and catalytic effect of the nickel nanoparticles during the high-temperature pyrolysis. The nickel nanoparticles remain embedded in the substrate after the acidic etching process due to the protection provided by the carbon layer. The obtained Ni-NMC consists of ca. 3-nm thickness nanoflake, with a high specific surface area of 812.2 m2 g–1, a pore volume of 1.59 cm3 g–1, and a pore size distribution of 6–8 nm. When used as a multifunctional sulfur host, the as-synthesized Ni-NMC, due to its mesoporous and thin-flake architecture, high conductivity, and catalytic effect, is simultaneously able to confine sulfur species within the carbon host and bidirectionally promote the conversion of sulfur to the final lithium sulfide. As a result, a high-performance Li-S battery with a reversible capacity of 869 mA h g–1 at 0.2 C after 100 cycles and a remarkable specific capacity of 705 mA h g–1 at 1.0 C after 200 cycles with a decay rate of 0.05 % per cycle, was realized.