Constructing layered double hydroxide derived heterogeneous Ti₃C₂T_x@S-MCoP (M = Ni, Mn, Zn) with S-vacancies to boost sodium storage performance

Poor conductivity and huge volume changes severely limit the application of layered double hydroxide (LDH) derived transition metal phosphides (TMPs) as anode materials for sodium ion batteries (SIBs). To solve these problems, Ti₃C₂T_x hollow spheres were prepared using PMMA spheres as a sacrificial template, and S-doped NiCoP nanosheets with rich S vacancies were grown on the surface of Ti₃C₂T_x through a stepwise strategy to obtain hollow Ti₃C₂T_x@S-NiCoP spheres. When used as an anode for SIBs, Ti₃C₂T_x@S-NiCoP shows a high reversible capacity of 563 mA h g⁻¹ at 0.2 A g⁻¹, ≈1.9 and 1.4 times that of S-NiCoP and Ti₃C₂T_x@NiCoP, respectively. It also delivers an outstanding cycling stability over 3000 cycles with a capacity decay of 0.005% per cycle. DFT calculations combined with XPS and XANES tests prove that the excellent electrochemical performance can be ascribed to the strong interaction at the hetero-interfaces of Ti₃C₂T_x@S-NiCoP, which can improve the conductivity and structural integrity. Furthermore, the rational hollow structure design can alleviate volume expansion and accelerate the diffusion of the electrolyte to improve the sodium storage kinetics of Ti₃C₂T_x@S-NiCoP. Notably, this work provides a general strategy for the preparation of bimetallic-based Ti₃C₂T_x@S-MCoP (M = Ni, Mn, Zn) with S-vacancies and opens up a new avenue for their application in the field of energy storage and conversion.