3D-structured Co9S8@NSG prepared using deep eutectic solvents as high-performance anode material of lithium-ion batteries

Abstract

Transition metal sulfides (TMSs) are ideal materials for replacing graphite anodes in lithium-ion batteries (LIBs). However, their low conductivities and large volume changes during charge/discharge cycling greatly limit their applications. Herein, a new method for co-doping nitrogen and sulfur in 3D graphene via a one-step method in deep eutectic solvents (DESs) was developed to prepare Co9S8@NSG composites, enhancing the storage performance of LIBs. The obtained Co9S8@NSG nanosheets exhibited excellent lithium-ion storage performance as anode materials. In the first cycle, the electrode material possessed high specific capacity (1647.5 mAh·g−1 at a current density of 2 a·g−1). After 250 cycles, the reversible capacity was still maintained at 516 mAh·g−1. The electrode material also displayed good cycling stability with specific capacity reaching 710 mAh·g−1 after 700 cycles at a current density of 0.5 a·g−1. In sum, the developed route for the synthesis of heteroatom-doped nanocomposites looks promising for modification of sulfide materials as excellent-performance LIBs.