Simple and scalable gelatin-mediated synthesis of a novel iron sulfide/graphitic carbon nanoarchitecture for sustainable sodium-ion storage

Transition metal sulfide (TMS)-based sodium-ion batteries (SIBs) are inherently different from traditional intercalation-based ones because of their ability to store more than one Na ⁺ per transition metal ion via conversion reaction. Iron sulfide (FeS) is an attractive conversion electrode material with a high theoretical capacity. Apart from the extensive availability and cost-effectiveness, many issues deter the development of iron sulfide-based SIBs. Huge volume changes accompanied by polysulfide generation and dissolution with long-term electrochemical cycling of FeS result in tremendous deterioration in capacity. To resolve these complex concerns, we herein present the strategic design of a porous, three-dimensional (3D) interconnected network of carbon nanosheets consisting of well-confined FeS nanoparticles via a simple and scalable gelatin-mediated sol-gel method utilizing the coordination capability of carboxylic and amino acid groups in biomass precursor gelatin with Fe ³⁺. While the in-situ generated nano FeS shortens the Na ⁺ diffusion pathway, the heteroatom (N, S) doped graphitic carbon network improves the ion/electron transport, buffers the volume change in FeS, and simultaneously immobilizes the polysulfide species dissolved in ether electrolyte. The as-synthesized novel composite delivers a high specific capacity of 303.4 mAh g ⁻¹ after 1200 cycles at a high current rate of 10 A g ⁻¹, with a low capacity-decay rate of 0.029% per cycle, delivering stable, long-term sodium-ion storage. Additionally, a full sodium-ion battery assembled with Na ₃V ₂(PO ₄) ₃ cathode and this composite achieve a stable specific capacity of 347.9 mAh g ⁻¹ after 100 cycles at 0.5 A g ⁻¹ with a capacity retention of ∼86.5% demonstrating the competence for practical applications.