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In this work, the compositional series of sulfide and mixed oxysulfide (MOS) glasses 0.56Li2S + 0.44[(0.33-x)PS5/2 + xPO5/2 + 0.67SiS2] was prepared, where 0 ≤ x ≤ 0.33, and their short range order (SRO) structures and their thermal properties have been investigated. Powder x-ray diffraction (XRD) confirmed that the MOS glasses were free from crystallization, with only very minor diffraction peaks in the x = 0 glass being observed. Fourier transform infrared (FT-IR), Raman, and 29Si and 31P magic angle spinning (MAS) NMR spectroscopies were used to identify the SRO structures present in these glasses. These spectra revealed oxygen migration from P to Si during synthesis. Although oxygen was introduced in the form of phosphorus oxide, the majority of the oxygen in these glasses ends up being bonded to silicon, thereby creating sulfur-rich SROs centered by phosphorus and MOS SROs centered by silicon. It was further found that the P-S SRO species were predominantly charged non-bridging sulfurs (NBS). The Si SRO species were comprised of neutral bridging oxygens (BOs) and charged non-bridging oxygens (NBOs) and neutral bridging sulfurs (BS) and charged non-bridging sulfurs with the neutral BO and BS species being larger in fraction than the NBO and NBS. These results suggest that the preponderance of the mobile Li+ cations in these glasses are located near the more negatively charged P centers and not near the more neutrally charged Si centers. The average negative charge of the P SRO structures was found to be ∼ − 3.0 with ∼97% of the phosphorous species in the P0 SRO while the average negative charge of the Si SRO structures was found to be −2.3. Consistent with the creation of the large numbers of NBS on the P and more BOs and BSs on the Si, these values are more negative and more positive, respectively, than the compositionally expected average value of −2.55. Differential scanning calorimetry (DSC) measurements of their glass transition (Tg) and crystallization (Tc) temperatures showed that the Tgs of these glasses are higher than 300 °C and their working ranges, ΔT ≡ Tc – Tg, are ∼100 °C. 

Abstract While much of the current research on glassy solid electrolytes (GSEs) has focused on the binary Li₂S+P₂S₅system, compositions with Si are of interest because Si promotes stronger glass formation and allows low‐cost melt‐quenching (MQ) synthesis under ambient pressure. Another advantage is that they can be formed in homogeneous and continuous glass forms, as a result they are free of grain boundaries. In this work, we have examined the structures and electrochemical properties of bulk glass pieces of sulfide and oxy‐sulfide GSE compositions and have also expanded the study by using LiPON glass as a dopant to produce an entirely new class of nitrogen doped mixed oxy‐sulfide nitride (MOSN) GSEs. Upon doping with oxygen and nitrogen, the solid electrolyte interface (SEI) is stabilized and the doped MOSN GSE exhibits a critical current density (CCD) of 1.8 mA cm⁻²at 100 °C. We also report on improving the glass quality, the SEI engineering and its limitations, and future plans of improving the electrochemical performance of these homogeneous MQ MOSN GSEs. These fundamental results can help to understand the structures and doping effects of the bulk GSEs, and as such can provide a guide to design improved homogeneous grain‐boundary‐free GSEs.