Dual Carbon Design Strategy for Anodes of Sodium-Ion Battery: Mesoporous CoS<sub>2</sub>/CoO on Open Framework Carbon-Spheres with rGO Encapsulating
Ran Sui, Guangtao Zan, Ming Wen, Weina Li, Zihui Liu, Qingsheng Wu, Yongqing Fu
Abstract
Transition metal sulfides and oxides with high theoretical capacities have been regarded as promising anode candidates for a sodium-ion battery (SIB); however, they have critical issues including sluggish electrochemical kinetics and poor long-term stability. Herein, a dual carbon design strategy is proposed to integrate with highly active heterojunctions to overcome the above issues. In this new design, CoS2/CoO hollow dodecahedron heterojunctions are sandwiched between open framework carbon-spheres (OFCs) and a reduced graphene oxide (rGO) nanomembrane (OFC@CoS2/CoO@rGO). The CoS2/CoO heterojunctions effectively promote electron transfer on their surface and provide more electrochemical active sites through their hierarchical hollow structures assembled by nanodots. Meanwhile, the dual-carbon framework forms a highly conductive network that enables a better rate capability. More importantly, the dual carbon can greatly buffer volume expansion and stable reaction interfaces of electrode material during the charge/discharge process. Benefitting from their synergistical effects, the OFC@CoS2/CoO@rGO electrode achieves a high reversible capacity of 460 mAh g–1 at 0.05 A g–1 and still maintains 205.3 mAh g–1 even when current density is increased by 200 times when used as an anode material for SIBs. Their cycling property is also remarkable with a maintained capacity of 161 mAh g–1 after 3500 charging/discharging cycles at a high current density of 1 A g–1. The dual-carbon strategy is demonstrated to be effective for enhanced reaction kinetics and long-term cycling property, providing siginificant guidance for preparing other high-performance electrode materials.