Experimental and computational analysis of SnSx encapsulated into carbonized chitosan as electrode material for potassium ion batteries

Tin sulphide compounds (SnS_x, x = 1, 2) are potential anode materials for potassium-ion batteries (PIBs) due to their characteristic layered structure, high theoretical capacity, non-toxicity and low production cost. However, they suffer from significant volume changes resulting in poor performance of such anodes. In this work incorporation of SnS_x into the carbon structure was expected to overcome these disadvantages. Two SnS-based electrode materials encapsulated into chitosan, as a natural carbon source, are fabricated by two different synthesis routes: (a) solvothermal, and (b) solvothermal followed by pyrolysis. The results indicate that the synthesis route is a crucial factor affecting the composition and electrochemical performance of the negative electrode. The electrode material, exhibiting a high reversible capacity (304 mAh/g at 50 mA/g), and good rate capability (128 mAh/g at 1000 mA/g for 500 cycles) is produced by the solvothermal method. The relationship between specific capacity and synthesis procedure is analyzed using the results obtained from XRD, XPS. Additionally, density functional theory is employed to provide deeper insights into the underlying mechanisms governing the electrochemical performance of the SnS_x@C electrode materials.