Fast magnesium conducting electrospun solid polymer electrolyte

Magnesium Ion based Solid State Batteries (MIBs) are subject of intensive studies due to abundance of magnesium, its advantages in volumetric capacity, and the reduced dendrite growth. Here we report on a true solid polymer electrolyte system without liquid additives or plasticizers that reaches conductivities above 10−5 S cm−1 at room temperature and above 10−4 S cm−1 at 50 °C. An electrospun polymer electrolyte membrane fabricated from a polymer electrolyte featuring a composition of PEO : Mg(TFSI)2 36 : 1 [where PEO stands for poly(ethyleneoxide) and Mg(TFSI)2 for magnesium bis(trifluoromethanesulfonyl) imide] was identified as the best performing system. Magnesium transport was substantiated by different methods, and the electrochemical properties including solid electrolyte interface (SEI) formation were investigated. Electrospinning as a preparation method has been identified as a powerful tool to enhance the electrochemical properties beyond conventional polymer membrane fabrication techniques

Li5SnP3: a member of the series Li10+4xSn2−xP6 for x=0 comprising the fast lithium‐ion conductors Li8SnP4 (x=0.5) and Li14SnP6 (x=1)

The targeted search for suitable solid‐state ionic conductors requires a certain understanding of the conduction mechanism and the correlation of the structures and the resulting properties of the material. Thus, the investigation of various ionic conductors with respect to their structural composition is crucial for the design of next‐generation materials as demanded. We report here on Li(5)SnP(3) which completes with x=0 the series Li(10+4x )Sn(2−x )P(6) of the fast lithium‐ion conductors α‐ and β‐Li(8)SnP(4) (x=0.5) and Li(14)SnP(6) (x=1). Synthesis, crystal structure determination by single‐crystal and powder X‐ray diffraction methods, as well as (6)Li, (31)P and (119)Sn MAS NMR and temperature‐dependent (7)Li NMR spectroscopy together with electrochemical impedance studies are reported. The correlation between the ionic conductivity and the occupation of octahedral and tetrahedral sites in a close‐packed array of P atoms in the series of compounds is discussed. We conclude from this series that in order to receive fast ion conductors a partial occupation of the octahedral vacancies seems to be crucial

A zeolitic imidazolate framework with conformational variety

We show via structural considerations and DFT calculations that for a zeolitic imidazolate framework (ZIF) with sodalite (SOD) topology, [Zn(dcim)2]-SOD (dcim = 4,5-dichloroimidazolate), structural models of an infinite number of hypothetical conformational polymorphs with distinct linker orientations can be generated, which can be interconverted most likely only via reconstructive structural transitions. The relative total energies suggest that some of those polymorphs might be synthetically accessible. Efforts in that direction led to the synthesis of new trigonal 1 and previously known cubic 2 with improved crystallinity. According to structural analyses based on powder X-ray diffraction (PXRD) methods supported by NMR spectroscopy, 1 is the most stable of the theoretically predicted SOD-type framework conformers (isostructural to ZIF-7), whereas 2, at variance with a recent proposal, is a SOD-type material with a high degree of orientational disorder of the dcim linker units. The statistics of the linker orientations in 2 is close to that in 1, indicating that the disorder in 2 is not random. Rather, crystals of 2 are likely twins consisting of nanoscopic domains of trigonal 1 that are deformed to a cubic metric, with linker disorder located in the domain interfaces. As structural differences appear to be more related to characteristics of real as opposed to ideal crystal structures, we propose to not consider 1 and 2 as true conformational polymorphs. Systematic investigations of solvent mixtures led to the discovery of intermediate materials of 1 and 2. The PXRD patterns and SEM images indicate that they belong to a complete series of structural intermediates. Differences in the Ar adsorption/desorption behaviours reveal that 1, in contrast to 2, is a flexible ZIF framework.DFG/Priority Program/141

Lithium‐ion mobility in Li6B18(Li3N) and Li vacancy tuning in the solid solution Li6B18(Li3N)1−x(Li2O)x

All-solid-state batteries are promising candidates for safe energy-storage systems due to non-flammable solid electrolytes and the possibility to use metallic lithium as an anode. Thus, there is a challenge to design new solid electrolytes and to understand the principles of ion conduction on an atomic scale. We report on a new concept for compounds with high lithium ion mobility based on a rigid open-framework boron structure. The host–guest structure Li6B18(Li3N) comprises large hexagonal pores filled with urn:x-wiley:14337851:media:anie202213962:anie202213962-math-0001 Li7N] strands that represent a perfect cutout from the structure of α-Li3N. Variable-temperature 7Li NMR spectroscopy reveals a very high Li mobility in the template phase with a remarkably low activation energy below 19 kJ mol−1 and thus much lower than pristine Li3N. The formation of the solid solution of Li6B18(Li3N) and Li6B18(Li2O) over the complete compositional range allows the tuning of lithium defects in the template structure that is not possible for pristine Li3N and Li2O

Fast Ionic Conductivity in the Most Lithium-Rich Phosphidosilicate Li14SiP6.

Solid electrolytes with superionic conductivity are required as a main component for all-solid-state batteries. Here we present a novel solid electrolyte with three-dimensional conducting pathways based on "lithium-rich" phosphidosilicates with ionic conductivity of σ > 10-3 S cm-1 at room temperature and activation energy of 30-32 kJ mol-1 expanding the recently introduced family of lithium phosphidotetrelates. Aiming toward higher lithium ion conductivities, systematic investigations of lithium phosphidosilicates gave access to the so far lithium-richest compound within this class of materials. The crystalline material (space group Fm3m), which shows reversible thermal phase transitions, can be readily obtained by ball mill synthesis from the elements followed by moderate thermal treatment of the mixture. Lithium diffusion pathways via both tetrahedral and octahedral voids are analyzed by temperature-dependent powder neutron diffraction measurements in combination with maximum entropy method and DFT calculations. Moreover, the lithium ion mobility structurally indicated by a disordered Li/Si occupancy in the tetrahedral voids plus partially filled octahedral voids is studied by temperature-dependent impedance and 7Li NMR spectroscopy

Complex lithium ion dynamics in simulated LiPO3 glass studied by means of multi-time correlation functions

Molecular dynamics simulations are performed to study the lithium jumps in LiPO3 glass. In particular, we calculate higher-order correlation functions that probe the positions of single lithium ions at several times. Three-time correlation functions show that the non-exponential relaxation of the lithium ions results from both correlated back-and-forth jumps and the existence of dynamical heterogeneities, i.e., the presence of a broad distribution of jump rates. A quantitative analysis yields that the contribution of the dynamical heterogeneities to the non-exponential depopulation of the lithium sites increases upon cooling. Further, correlated back-and-forth jumps between neighboring sites are observed for the fast ions of the distribution, but not for the slow ions and, hence, the back-jump probability depends on the dynamical state. Four-time correlation functions indicate that an exchange between fast and slow ions takes place on the timescale of the jumps themselves, i.e., the dynamical heterogeneities are short-lived. Hence, sites featuring fast and slow lithium dynamics, respectively, are intimately mixed. In addition, a backward correlation beyond the first neighbor shell for highly mobile ions and the presence of long-range dynamical heterogeneities suggest that fast ion migration occurs along preferential pathways in the glassy matrix. In the melt, we find no evidence for correlated back-and-forth motions and dynamical heterogeneities on the length scale of the next-neighbor distance.Comment: 12 pages, 13 figure