Abstract:
Lithium-ion battery (LIB) proves to be one of the most important energy storage systems for portable electronics and vehicles. High volumetric lithium storage is becoming increasingly necessary as the market for nanotechnology of electrochemical energy storage devices grows. Since the conventional carbonaceous-based electrodes have already surpassed the theoretical efficiency limits the Transition Metal Oxides (TMOs) have a bright future as high-energy anodes in emerging lithium-ion batteries.1 In recent years ZnCo2O4 has been among the widely used anode materials as compared to other binary TMOs, owing to its high performance, cost-efficiency, high thermal stability, and environmental friendliness. Due to the mutually advantageous matrix of Zn and Co, ZnCo2O4 is among the strongest oxide materials for Lithium recyclability. 2 Even so, LIBs with this conversion reaction anode also have a poor coulombic efficiency accompanied by the generation of the solid electrolyte interface layer and sudden volume transition during charge/discharge leads to significant capacity loss. Thus, fabricating practical TMO anodes with adequate electrochemical performance continues to be a challenge. To address these deficits, graphitic-C3N4, a semiconducting material with a small bandgap of 2.3eV and abundant pores has been a promising nanomaterial as it easily absorbs Li+ ions. 3 Unambiguously, it acts as a Li+ ion transport bridge, resulting in increased Li+ diffusivity. The high nitrogen content of g-C3N4 strengthens the electrode's wettability with liquid electrolytes and enhances the lithium charge transfer process. 4 In this work, a graphitic-C3N4 supported ZnCo2O4 composite is successfully synthesized by a simple hydrothermal method. The crystalline structure and surface morphology are investigated by XRD, SEM, TEM and BET analyses. The discharge (Li+ insertion) and charge (Li+ extraction) profiles of pristine ZnCo2O4 and g-C3N4@ZnCo2O4 are measured using LiPF6/ethylene carbonate (EC) and diethylene carbonate (DMC) electrolyte in the voltage window of 0. 01�3 V. When employed as an anode material for LIBs, pristine ZnCo2O4 showed a moderate capacity (686 mAhg?1 at 0.5Ag-1). Whereas, for g-C3N4@ZnCo2O4, the g-C3N4 nanofibers not only serve as a bridge between ZnCo2O4 nanoparticles allowing rapid electron transport, but also act as connectors to avoid extreme volume variation. Thus, owing to the synergistic effects, g-C3N4@ZnCo2O4 the composite showed an excellent reversible capacity of 1429 mAhg?1 at 5 Ag-1. The initial coulombic efficiency for g-C3N4@ZnCo2O4 composite is 88 %, which could be attributed to the high discharge potential of the electrodes along with low interfacial surface area. Our findings indicate that an interlayer design approach leads to improved reversible capacity and stability in compacted conversion-type anodes for practical applications.