This study develops room-temperature sodium-sulphur (RT Na-S) batteries as a sustainable, cost-effective alternative to lithium-ion technologies. The research achieves high performance by optimising electrolytes and cathode design, making these batteries a promising solution for grid-scale energy storage, such as for solar power.

A key contribution was identifying the optimal electrolyte: 1M NaTFSI + 0.3M NaNO₃ in TEGDME. This formulation balances polysulphide solubility and anode stability, outperforming solvents typically used in lithium-sulphur batteries. The study also established the full Na-S redox reaction chain, revealing that reactions proceed despite low-solubility sulphides because the TEGDME solvent swells their precipitates, enabling ion transport in a semi-solid state. Innovative cell design features were critical to this success: Cathode Engineering: A cathode composed of sulphur-infiltrated hollow porous carbon (Ketjenblack) and a PEDOT:PSS conductive binder, which effectively traps active materials. Functional Interlayer: A thin BN-doped-graphene layer sprayed on the cathode surface, which polysulphides, provides excellent electronic contact, and acts as an electrocatalyst and Strategic Additives: Gelatine in the electrolyte and vanadyl phthalocyanine (VOPc) in the catholyte enhance polysulphide retention and reaction kinetics, with VOPc networks reducing cell resistance enough to enable operation at 1C rates.

However, challenges remain. The batteries exhibit low discharge voltages (~1V) due to sluggish Na⁺ transport through semi-solid sulphides, and the cathode suffers from fragmentation caused by expansion during cycling. The study also confirmed that sodium metal remains the preferred anode, as silicon-based alternatives were impractical due to slow reaction kinetics.

In conclusion, the configured RT Na-S battery - featuring an optimised sulphur-carbon cathode, a functional interlayer, and a tailored electrolyte system—represents significant progress toward commercial viability, with projected material costs below $5/kWh. Future work must focus on mitigating cathode expansion and improving anode stability to enhance cyclability, but this study provides a critical foundation for sustainable energy storage.