Intrinsic conductivity optimization of bi-metallic nickel cobalt selenides toward superior-rate Na-ion storage

Abstract

Enhancing the conductivity of electrode materials is critically important for improving the high-rate performance of Na-ion batteries (NIBs). Herein, we report a multifaceted strategy for optimizing the conductivity and electrochemical properties of nickel cobalt selenides via the combination of fine component regulation and C coating. The electrical conductivity of C@Ni_0.33Co_0.67Se₂/C nanofiber (CNF) (Co_0.67) hybrids achieved in this study was 0.3733 S mm⁻¹, a conductivity five-fold higher than that of selenides with a Ni/Co ratio of 2 : 1. Coupled with desirable three-dimensional (3D) nanobrush morphology and the 1D conducting path of CNFs, the Co_0.67 electrode achieved a superior rate performance of 413.1 mA h g⁻¹, even at 2 A g⁻¹. Furthermore, the Co_0.67 electrode exhibited an impressive cycling performance of 499 mA h g⁻¹ after 100 cycles (exhibiting an 89.5% capacity retention of the second cycle). Finally, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry analysis at different sweep rates were conducted to demonstrate the Co_0.67 electrode's fast charge/ion transport ability and increased electrode kinetics.