Promoting\nCathodic Kinetics and Anodic Stability in\nPractical Room-Temperature Sodium–Sulfur Batteries with Bifunctional\nElectrolytes

The\ndevelopment of room-temperature (RT) sodium–sulfur (Na–S)\nbatteries is severely hindered due to the slow kinetics of the S cathode\nand the instability of the Na-metal anode. To overcome this, we introduced\na dual-functional electrolyte cosolvent, trifluoromethanesulfonamide\n(TFMSA). Short-chain Na<sub>2</sub>S<sub><i>x</i></sub> (1\n≤ <i>x</i> ≤ 2) can be effectively dissolved\ndue to the strong H–S bond interaction between TFMSA and sulfides,\nwhich changes the S conversion process, thereby effectively enhancing\nthe conversion kinetics of the cathode. Meanwhile, TFMSA can generate\na stable solid electrolyte interphase on the Na-metal surface to protect\nit from soluble polysulfide attack. Therefore, the RT Na–S\nbatteries using the ether electrolyte show a high initial discharge\ncapacity of 896.6 mAh g<sup>–1</sup> and a capacity retention\nrate of 73% after 150 cycles at 0.2C, and the pouch cell also demonstrates\nits practical performance. This work proposes a dual-functional electrolyte\ncosolvent selection principle to inspire the practical application\nof high-performance RT Na–S batteries.