Wei Weng,Hongli Wan,Gaozhan Liu,Liping Wu,Jinghua Wu,Xiayin Yao
The nanosized Na11Sn2PS12 solid electrolyte with a particle size of around 200 nm is synthesized using the liquid-phase method using 1,2-dimethoxyethane. The sintering conditions for Na11Sn2PS12 crystallization are systematically optimized to maximize ionic conductivity. The highest room temperature ionic conductivity of the liquid-phase-synthesized Na11Sn2PS12 electrolytes (LP-Na11Sn2PS12) is 1.73 × 10–4 S cm–1, which is comparable with that of ball-milling samples (BM-Na11Sn2PS12) of 2.16 × 10–4 S cm–1. Both Na11Sn2PS12 electrolytes show an electrochemical window of 0.3–3.2 V. Moreover, the as-synthesized Na11Sn2PS12 electrolytes are employed as solid electrolytes in TiS2/Na11Sn2PS12/Na all-solid-state batteries. The TiS2/LP-Na11Sn2PS12/Na battery shows a higher reversible capacity of 142.4 mAh g–1 compared with 110.5 mAh g–1 for the TiS2/BM-Na11Sn2PS12/Na battery after 10 cycles under 20 mA g–1 at 25 °C. The better performance of the TiS2/LP-Na11Sn2PS12/Na battery can be ascribed to improved solid–solid contact between the electrolyte and the electrode arising from the nanosized particles of LP-Na11Sn2PS12 electrolytes.
While sulfide solid electrolytes such as Na 11 Sn 2 PS 12 can allow fast transport of Na + ions, their utilization in solid sodium ion batteries is rather unsuccessful since they are not electrochemically compatible to both high-voltage cathodes and sodium metal anode. In this work, we devise an effective approach toward realizing solid sodium ion batteries, using the Na 11 Sn 2 PS 12 electrolyte and slurry-coated NASICON-type Na 3 MnTi(PO 4 ) 3 @C as high-voltage cathode, highly beneficial for low processing cost and high content/loading of active cathode matter. We report that through significantly improved integrity of electrolyte-cathode interface, such solid sodium ion batteries can deliver outstanding cycling and rate performance, with a charge voltage resilience up to 4.1 V, a high cathode discharge capacity of 128.7 mAh g −1 against the Na 3 MnTi(PO 4 ) 3 @C in cathode is achieved at 0.05 C, and capacity retention ratio of 82% with a rate of 0.1 C is realized after prolonged cycling at room temperature. Besides, we demonstrate that such a solid sodium ion battery can even perform at a sub-zero Celsius temperature of −10°C, when the conventional control cell using liquid electrolyte completely fail to function. This work is to offer a dependable avenue in engineering next generation of safe solid ion batteries based on highly sustainable and much cheaper material resources.
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