Wet Chemistry Route to Li3InCl6: Microstructural Control Render High Ionic Conductivity and Enhanced All-Solid-State Battery Performance.

Thanks to superionic conductivity and compatibility with >4 V cathodes, halide solid electrolytes (SEs) have elicited tremendous interest for application in all-solid-state lithium batteries (ASSLBs). Many compositions based on groups 3, 13, and divalent metals, and substituted stoichiometries have been explored, some displaying requisite properties, but the Li+ conductivity still falls short of theoretical predictions and appealing sulfide-type SEs. While controlling microstructural characteristics, namely grain boundary effects and microstrain, can boost ionic conductivity, they have rarely been considered. Moving away from the standard solid-state route, here a scalable and facile wet chemical approach for obtaining highly conductive (>2 mS cm-1) Li3InCl6 is presented, and it is shown that aprotic solvents can reduce grain boundaries and microstrain, leading to very high ionic conductivity of over 4 mS cm-1 (at 22 °C). Minimized grain boundary area renders improved moisture stability and enhances solid-solid interfacial contact, leading to excellent LiNi0.6Mn0.2Co0.2O2-based full-cell performance, exemplified by stable room temperature (22 °C) cycling at a 0.2 C rate with 155 mAh g-1 capacity and 85% retention after 1000 cycles at 60 °C with a high 99.75% Coulombic efficiency. The findings showcase the viability of the aprotic solvent-mediated route for producing high-quality Li3InCl6 for all-solid-state batteries.

Sucrose-templated interconnected meso/macro-porous 2D symmetric graphitic carbon networks as supports for α-Fe2O3 towards improved supercapacitive behavior.

In this study, ultrahigh electrochemical performance for interconnected meso/macro-porous 2D C@α-Fe2O3 synthesized via sucrose-assisted microwave combustion is demonstrated. Hematite (α-Fe2O3) synthesized via the same approach gave an encouraging electrochemical performance close to its theoretical value, justifying its consideration as a potential supercapacitor electrode material; nonetheless, its specific capacitance was still low. The pore size distribution as well as the specific surface of bare α-Fe2O3 improved from 145 m2 g-1 to 297.3 m2 g-1 after it was coated with sucrose, which was endowed with ordered symmetric single-layer graphene (2D graphene). Accordingly, the optimized hematite material (2D C@α-Fe2O3) showed a specific capacitance of 1876.7 F g-1 at a current density of 1 A g-1 and capacity retention of 95.9% after 4000 cycles. Moreover, the material exhibited an ultrahigh energy density of 93.8 W h kg-1 at a power density of 150 W kg-1. The synergistic effect created by carbon-coating α-Fe2O3 resulted in modest electrochemical performance owing to extremely low charge transfer resistance at the electrode-electrolyte interface with many active sites for ionic reactions and efficient diffusion process. This 2D C@α-Fe2O3 electrode material has the capacity to develop into a cost-effective and stable electrode for future high-energy-capacity supercapacitors.