Unveiling the synergistic catalysis essence of trimetallic Fe-Co-Ni phosphides for lithium–sulfur chemistry

Lithium–sulfur batteries (LSBs) have emerged as prospective candidates for energy storage systems due to their high energy density and low cost of sulfur. However, the fast capacity degradation stemming from the fatal lithium polysulfide (LiPS) shuttle and sluggish redox reaction kinetic acts as the bottleneck for the real implementation of LSBs. Herein, we propose a well-designed nanosphere functionalized with trimetallic Fe-Co-Ni phosphides (FCNP) to host sulfur and promote the sulfur redox reactions. The well-dispersed trimetallic phosphides can not only enhance polarity and electron conductivity but also supply sufficient conversion sites and short sulfur evolution pathway. Therefore, the elaborated trimetallic phosphides on carbon nanosphere effectively inhibits LiPSs escaping from the cathode to anode. Further, the systematic electrochemical measurements and synchrotron X-ray three-dimensional nano-computed tomography (X-ray 3D nano-CT) results provide clear evidence that FCNP as a bidirectional electrocatalyst smoothly accelerates the generation and decomposition of Li₂S. Accordingly, the S/FCNP cathode exhibits a remarkable discharge capacity of 1172.3 mA h g⁻¹ at 0.2C in coin cell, 1164.0 mA h g⁻¹ at 0.1C in pouch cell and the favorable cycling performance.