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Mechanical properties of Li10.35Ge1.35P1.65S12 (LGPS) solid electrolytes with different grain sizes were investigated via indentation tests. Hand-milled LGPS (HM LGPS, d50: 1.32 μm) and wet-milled LGPS (WM LGPS, d50: 0.46 μm) powders were uniaxially pressed to obtain pellet samples. The HM LGPS and WM LGPS pellets had a similar bulk density of 1.63 g cm-3. At the initial loading/unloading, the WM LPGS pellet showed a large deformation owing to a decrease in cavities compared with the HM LGPS. In the subsequent cycles, both pellets exhibited elastic deformation behavior in the pressure range up to 20 N. The elastic modulus and relative residual depth of HM LGPS and WM LGPS were 21.7 GPa and 15.0 GPa and 0.75 and 0.71, respectively. This result revealed that WM LGPS is more elastically deformable and less plastically deformable than HM LGPS, which could be associated with the grain boundary strengthening interpreted by the Hall-Petch relation. Based on these mechanical properties, the superior cycle stability at the In-Li electrode/WM LGPS electrolyte interface during charging/discharging was discussed. Controlling the mechanical properties of sulfide solid electrolytes by the grain size is important for suppressing physical degradation in all-solid-state batteries. [ABSTRACT FROM AUTHOR]

No design rules have yet been established for producing solid electrolytes with a lithium-ion conductivity high enough to replace liquid electrolytes and expand the performance and battery configuration limits of current lithium ion batteries. Taking advantage of the properties of high-entropy materials, we have designed a highly ion-conductive solid electrolyte by increasing the compositional complexity of a known lithium superionic conductor to eliminate ion migration barriers while maintaining the structural framework for superionic conduction. The synthesized phase with a compositional complexity showed an improved ion conductivity. We showed that the highly conductive solid electrolyte enables charge and discharge of a thick lithium-ion battery cathode at room temperature and thus has potential to change conventional battery configurations. [ABSTRACT FROM AUTHOR]

All solid-state batteries are of key importance in the development of next-generation energy storage devices with high energy density. Herein, we report the fabrication and operation of bulk-type 5 V-class all solid-state batteries consisting of LiNi0.5Mn1.5O4 cathode, Li10GeP2S12 solid-electrolyte, and Li metal anode. The 1st discharge capacity is about 80 mAh g-1 with an average voltage of 4.3 V. The discharge capacity gradually decreases during the subsequent cycles. X-ray diffraction and electrochemical impedance spectroscopy measurements reveal that the capacity fading results from the growth of a resistive interfacial layer on the cathode composite. The development of suitable conductive additive and sulfide solid electrolyte materials is essential for the development of high-voltage all solid-state batteries. [ABSTRACT FROM AUTHOR]