Green synthesis of zinc sulfide-reduced graphene oxide composite and its application in sodium-ion batteries

Abstract

A green chemistry synthesis of a sodium-ion battery (SIB) anode is described. The anode comprises nanometric Sphalerite (ZnS) film, coated uniformly on reduced graphene oxide. Compliance of an energy storage component with sustainability goals requires the following attributes: i) exclusive use of abundant and non-toxic raw materials; ii) energy-minimized processing that uses cheap materials of construction, and involves a minimal waste generation, and no hazardous wastes, and iii) high energy efficiency without compromising power performance. Only low-cost, abundant raw materials are used in this synthesis: zinc acetate, 1 wt% hydrogen peroxide solution, and in-situ generated hydrogen sulfide. The synthesis protocol is based on hydrogen peroxide sol-gel (HPSG) processing, i.e. synthesis of zinc peroxide sol followed by a delicate pH change to deposit the zinc peroxide on dispersed graphene oxide. HPSG is a wet-chemistry process that does not rely on energy-rich hydrothermal/solvothermal steps, water or solvent evaporation, or the use of dispersing organic solvents, and the zinc precursor is fully converted to ZnS. We show film deposition from as low as 1 wt% aqueous hydrogen peroxide solution. The anode exhibits excellent electrochemical characteristics: 550 mAh g −1 at 0.1 A g −1 after 150 cycles between 0 and 2.5 V vs. Na reference, and a high-rate capability of 420 mAh g −1 at 2 A g −1 (ca 5 C rate). Despite being a conversion type anode, ZnS exhibits similar voltage hysteresis (and energy efficiency) to tin sulfide - graphene-oxide composite, a conversion-alloying anode. Despite being a SIB anode, it compares favorably with the Fe 3 O 4 and MnO LIB conversion anodes, commended for their high energy efficiency. SYNOPSIS: A green chemistry synthesis of a sodium ion battery anode based on ZnS-rGO. • A green chemistry synthesis of a sodium ion battery anode based on ZnS-rGO. • ZnS-rGO anode revealed a high specific capacitance of 543 mAh g −1 . • Anodes show lower voltage hysteresis, higher 1st cycle discharging–charging efficiency.