Synthesis of nickel@N-doped carbon nanotube foams for high sulfur-loading lithium-sulfur battery

Abstract

The practical applications of lithium sulfur batteries have been greatly restricted by the polysulfide shuttle effect and non-conductivity of sulfur. Here, we report a nickel-catalyzed carbonization method to synthesize three-dimensional (3D) nickel@N-doped carbon-nanotube (CNT) foams for lithium-sulfur batteries. The corresponding carbon/sulfur cathode with a high sulfur loading of 3.71 mg cm−2 possesses a high initial capacity of 855.6 mAh g−1 at 135 mA g−1 and good cyclic stability with a low fading rate of 0.153% per cycle for 100 cycles at 270 mA g−1. The growth of carbon thin layers on the nickel nanoparticles results in the encapsulation of the nanoparticles in the CNTs, which makes the carbon forms highly conductive and prevents the metal nanoparticles from being oxidized by polysulfides. The high conductivity is favorable for the electron transfer between polysulfides and carbon electrode. Moreover, the doped nitrogen atoms on the CNTs have strong chemical adsorption ability for polysulfides, accelerating redox reaction of polysulfides on the carbon electrode (i.e., suppressing the shuttle effect). These unique structural characteristics well explain the excellent electrochemical performance of the assembled batteries. It is believed that the fabricated carbon foam is a promising material for high sulfur-loading lithium-sulfur battery.