Built-in Electric Field Formed In Situ and Sulfur Vacancy Synergistically Promoting Copper Sulfide Anode Efficient Sodium Storage
Wei Shuang, Fuyou Chen, Jun Xu, Yujun Wu, Lin Yang, Zhengyu Bai
Abstract
Copper sulfides with abundant redox active sites are hailed as a great promising anode material for sodium-ion batteries. However, sluggish reaction kinetics, poor conductivity, and structural stability affect their electrochemical performance. Here, in situ formation of built-in electric field and vacancy strategies were adapted to synergistically promote copper sulfide anode material efficient sodium storage. First, S/CuS 1– x @PANI with S vacancies was synthesized, and then Cu 2 S/CuS 1– x heterogeneous interface was formed in situ during the discharge–charge process. The experimental and theoretical calculation results indicate that sulfur vacancies provide additional reaction sites for storage of Na + ions, and accelerate the transfer of Na + ions. The built-in electric field from the Cu 2 S/CuS 1– x heterogeneous interface can effectively improve its stability and electronic conductivity. Polyaniline (PANI) serves as a strong protective layer to effectively ease the volume effects and boost conductivity during the cycle. The anode material shows excellent rate performance (493 mA h g –1 at 15 A g –1 ) and long cycle stability (620.5 mA h g –1 with a high-capacity preservation ratio of 98.4% after 3000 cycles at 5 A g –1 ), which exceeds the theoretical specific capacity of CuS and Cu 2 S. Our study proposes a promising idea for developing sustainable and high-performance sodium-ion battery anode materials.