Mn incorporated BiOCl anode for high performance sodium ion batteries

Abstract

The layered bismuth oxychloride (BiOCl), with a theoretical capacity of 618 mAh g⁻¹, offers advantages such as favorable redox potential and efficient sodium ion diffusion pathways. However, its performance is impeded by the limited electrical conductivity and significant volume changes during cycling. To overcome these challenges, this study introduces Mn-doped BiOCl nanosheets (Mn-BiOCl) as a hopeful anode material for sodium-ion batteries (SIBs). The incorporation of Mn into the BiOCl structure strengthens the Mn-O bonds and enhances the stability of sodium ion adsorption, as validated by density functional theory calculations. This modification leads to improved capacity and superior electrochemical stability. In-situ XRD analysis reveals that Mn-BiOCl experiences an irreversible conversion reaction to Na₃Bi during the initial discharge cycle, followed by an invertible alloying and dealloying process between Bi and NaBi/Na₃Bi in subsequent cycles. Electrochemical tests demonstrate that Mn-BiOCl delivers an impressive capacity of 347.8 mAh g⁻¹, with 79.1 % capacity retention after 10,000 cycles at 10 A g⁻¹, highlighting its exceptional durability for practical applications. Furthermore, a full cell incorporating Mn-BiOCl as the anode and Na₃V₂(PO₄)₃ as the cathode achieves a notable energy density of 250.6 Wh kg⁻¹ at a power density of 783 W kg⁻¹. This study presents an innovative approach for identifying effective anode materials for SIBs.