Innovative Design of Dual Functional Polypyrrole-Coated Zinc Cobalt Sulfide Nanosheets on Carbon Cloth As a Binder-Free Anode of Sodium-Ion Batteries

Sodium-ion battery (SIB) is attractive and cost-effective for energy storage due to the high abundance of sodium. Anodes with complex electrochemical mechanisms significantly impact the performance and safety of battery systems. In recent times, cobalt-based binary metal sulfides have received enormous attention in energy storage applications. However, high volume expansion, limited cycle life, and low initial Coulombic efficiency are major problems of SIB in a practical application perspective. Herein, a novel binder-free electrode is designed by synthesizing polypyrrole-coated zinc cobalt sulfide nanosheets on carbon cloth (PPy/ZnCoS@CC) as the anode of SIB via a hydrothermal process for the first time. The PPy coating on the ZnCoS surface is to control the volume expansion and solve the long-term stability issue. The thickness of PPy on ZnCoS is controlled by using different polymerization reaction times. The optimal PPy/ZnCoS@CC electrode demonstrates a high areal capacity of 2.33 mAh/cm2 at 0.1 mA/cm2 and retains 75% of the areal capacity after 100 cycles. The galvanic intermittent titration technique analysis is also used to measure the diffusion coefficient of anodes. This work brings a blueprint on enhancing the conducing property and control the volume expansion during the charge-discharge process by coating conductive polymer on metallic compounds.