Influence of synthesis parameters on crystallization behavior and ionic conductivity of the Li4_{4}PS4_{4}I solid electrolyte

Superionic solid electrolytes are key to the development of advanced solid-state Li batteries. In recent years, various materials have been discovered, with ionic conductivities approaching or even exceeding those of carbonate-based liquid electrolytes used in high-performance Li-ion batteries. Among the different classes of inorganic solid electrolytes under study, lithium thiophosphates are one of the most promising due to their high Li-ion conductivity at room temperature and mechanical softness. Here, we report about the effect of synthesis parameters on the crystallization behavior and charge-transport properties of Li$_{4}$PS$_{4}$I. We show that thermally induced crystallization of Li$_{4}$PS$_{4}$I (P4/nmm), starting from the glassy phase 1.5Li$_{2}$S–0.5P$_{2}$S$_{5}$–LiI, adversely affects the material’s conductivity. However, both conductivity and crystallization temperature can be significantly increased by applying pressure during the preparation

Investigations into the superionic glass phase of Li4_{4}PS4_{4}I for improving the stability of high-loading all-solid-state batteries

In recent years, investigations into improving the performance of bulk-type solid-state batteries (SSBs) have attracted much attention. This is due, in part, to the fact that they offer an opportunity to outperform the present Li-ion battery technology in terms of energy density. Ni-rich Li$_{1+x}$(Ni$_{1-y-z}$Co$_{y}$Mn$_{z}$)$_{1-x}$O$_{2}$ (NCM) and lithium-thiophosphate-based solid electrolytes appear to be a promising material combination for application at the cathode side. Here, we report about exploratory investigations into the 1.5Li$_{2}$S/0.5P$_{2}$S$_{5}$/LiI phase system and demonstrate that a glassy solid electrolyte has more than an order of magnitude higher room-temperature ionic conductivity than the crystalline counterpart, tetragonal Li$_{4}$PS$_{4}$I with the P4/nmm space group (∼1.3 versus ∼0.2 mS cm$^{-1}$). In addition, preliminary results show that usage of the glassy 1.5Li$_{2}$S–0.5P$_{2}$S$_{5}$–LiI in pellet stack SSB cells with an NCM622 (60% Ni content) cathode and a Li$_{4}$Ti$_{5}$O$_{12}$ anode leads to enhanced capacity retention when compared to the frequently employed argyrodite Li$_{6}$PS$_{5}$Cl solid electrolyte. This indicates that, apart from interfacial instabilities, the stiffness (modulus) of the solid electrolyte and associated mechanical effects may also impact significantly the long-term performance. Moreover, SSB cells with the glassy 1.5Li$_{2}$S–0.5P$_{2}$S$_{5}$–LiI and high-loading cathode (∼22 mg$_{NCM622}$ cm$^{-2}$) manufactured using a slurry-casting process are found to cycle stably for 200 cycles at C/5 rate and 45 °C, with areal capacities in excess of 3 mA h cm$^{-2}$

Effect of surface carbonates on the cyclability of LiNbO3_{3}-coated NCM622 in all-solid-state batteries with lithium thiophosphate electrolytes

While still premature as an energy storage technology, bulk solid-state batteries are attracting much attention in the academic and industrial communities lately. In particular, layered lithium metal oxides and lithium thiophosphates hold promise as cathode materials and superionic solid electrolytes, respectively. However, interfacial side reactions between the individual components during battery operation usually result in accelerated performance degradation. Hence, effective surface coatings are required to mitigate or ideally prevent detrimental reactions from occurring and having an impact on the cyclability. In the present work, we examine how surface carbonates incorporated into the sol–gel-derived LiNbO$_{3}$ protective coating on NCM622 [Li$_{1+x}$(Ni$_{0.6}$Co$_{0.2}$Mn$_{0.2}$)$_{1-x}$O2] cathode material affect the efficiency and rate capability of pellet-stack solid-state battery cells with β-Li$_{3}$PS$_{4}$ or argyrodite Li$_{6}$PS$_{5}$Cl solid electrolyte and a Li$_{4}$Ti$_{5}$O$_{12}$ anode. Our research data indicate that a hybrid coating may in fact be beneficial to the kinetics and the cycling performance strongly depends on the solid electrolyte used

Dark state experiments with ultracold, deeply-bound triplet molecules

We examine dark quantum superposition states of weakly bound Rb2 Feshbach molecules and tightly bound triplet Rb2 molecules in the rovibrational ground state, created by subjecting a pure sample of Feshbach molecules in an optical lattice to a bichromatic Raman laser field. We analyze both experimentally and theoretically the creation and dynamics of these dark states. Coherent wavepacket oscillations of deeply bound molecules in lattice sites, as observed in one of our previous experiments, are suppressed due to laser-induced phase locking of molecular levels. This can be understood as the appearance of a novel multilevel dark state. In addition, the experimental methods developed help to determine important properties of our coupled atom / laser system.Comment: 20 pages, 9 figure

Transition-metal interdiffusion and solid electrolyte poisoning in all-solid-state batteries revealed by cryo-TEM

Using scanning transmission electron microscopy, along with electron energy loss spectroscopy, under cryogenic conditions, we demonstrate transition-metal dissolution from a layered Ni-rich oxide cathode material and subsequent diffusion into the bulk of a lithium thiophosphate solid electrolyte during electrochemical cycling. This problem has previously only been considered for liquid-electrolyte-based batteries