1：Experimental Design and Method Selection:

The synthesis of NixSn2xS4x and M–NixSn2xS4x nanocomposites was carried out by a one-pot hydrothermal method using nickel chloride hexahydrate, tin chloride dehydrate, and thiourea as precursors, with sodium dodecyl sulfate (SDS) as a structure directing agent. The composites were characterized by XRD, SEM, FE-SEM, HR-TEM, SAED, XPS, EDAX, and Raman spectroscopy.

2：Sample Selection and Data Sources:

The samples were synthesized at different temperatures (140, 160, and 180 °C) to study the effect of temperature on morphology and crystallinity.

3：List of Experimental Equipment and Materials:

Equipment used includes Shimadzu XRD-6000 for XRD, JEOL-6390 for SEM, FEI quanta 250-FESEM for FE-SEM, JEOL JEM 2100 for HR-TEM and SAED, ESCALAB 250XI for XPS, and Bruker for EDAX. Materials include NiCl

4：6H2O, SnCl2H2O, thiourea, SDS, and MWCNTs. Experimental Procedures and Operational Workflow:

The synthesis involved dissolving SDS in water, adding precursors, stirring, transferring to a Teflon-lined autoclave, and maintaining at specified temperatures. The products were washed and dried.

5：Data Analysis Methods:

Data were analyzed using DFT calculations for theoretical interpretation, and electrochemical performance was evaluated using CV, EIS, and Tafel polarization measurements.