Ta-doped Li7La3Zr2O12 (LLZTO) solid-state electrolytes (SEs) show great promise for solid-state batteries due to its high conductivity and safety. However, one of the challenges it faces is lithium dendrite propagation upon long-term cycling. To address this issue, we propose the incorporation of fumed silica (FS) at the grain boundaries of LLZTO to modify the properties of the garnet pellet, which effectively inhibits the dendrite growth. The introduction of FS has demonstrated several beneficial effects. Firstly, it reduces the migration barrier of lithium ions, which helps prevent dendrite formation and propagation. Additionally, FS reduces the electronic conductivity of the SEs pellet, suppressing the dendrite formation. Moreover, the formed lithium silicates from FS might also be acted as electron inhibitor, thus inhibiting the lithium dendrite growth upon cycling. By investigating the use of FS as a modifier in LLZTO-based electrolytes, our study contributes to advancing dendrite-free solid-state electrolytes and thus the development of high-performance all-solid-state batteries.

The Li3MX6 compounds (M=Sc, Y, In; X=Cl, Br) are known as promising ionic conductors due to their compatibility with typical metal oxide cathode materials. In this study, we have successfully synthesized γ-Li3ScCl6 using high pressure for the first time in this family. Structural analysis revealed that the high-pressure polymorph crystallizes in the polar and chiral space group P63mc with hexagonal close-packing (hcp) of anions, unlike the ambient-pressure α-Li3ScCl6 and its spinel analog with cubic closed packing (ccp) of anions. Investigation of the known Li3MX6 family further revealed that the cation/anion radius ratio, rM/rX, is the factor that determines which anion sublattice is formed and that in γ-Li3ScCl6, the difference in compressibility between Sc and Cl exceeds the ccp rM/rX threshold under pressure, enabling the ccp-to-hcp conversion. Electrochemical tests of γ-Li3ScCl6 demonstrate improved electrochemical reduction stability. These findings open up new avenues and design principles for lithium solid electrolytes, enabling routes for materials exploration and tuning electrochemical stability without compositional changes or the use of coatings.

The Li+-ion conductivity (σLi) in an electrolyte is an important parameter with respect to the performance of all-solid-state lithium-ion batteries (LIBs). However, little is known about how σLi in a porous electrolyte differs from that in a highly dense electrolyte. In this study, the relationship between the bulk density (dbulk) and apparent σLi (σLiapp) in a porous electrolyte of Li[Li1/3Ti5/3]O4 (LTO) was examined by theoretical and experimental approaches. The theoretical calculations demonstrated that dbulk and σLi have a simple relationship irrespective of the radius of the spherical pores in the electrolyte; i.e., σLi increases almost linearly with increasing ζ,where ζ is the ratio of d bulk to the theoretical density. In fact, the observed σLiapp of LTO, which was determined by four-probe alternating-current impedance measurements, increased with increasing ζ. Hence, with this relationship, σLiapp can be estimated by ζ and intrinsic σLi (σLiint) and vice versa; such estimations provide critical information for determining the optimum compositions of composite electrodes for all-solid-state LIBs. The temperature dependence of σLiapp in LTO and differences between the calculated and experimental results are also discussed.