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The CO2 treatment on argyrodite sulfide-based solid electrolyte Li6PS5Cl (LPSC) can effectively improve the interfacial stability between the Li and LPSC.

LiGe2(PO4)3 (LGP), a NASICON-type solid electrolyte, has many advantages such as its superior electrochemical and thermal stability for use in all solid-state lithium batteries. However, its low ionic conductivity is one of the challenges that can hinder its practical application commercially. In this work, the influence of adding different amounts of scandium and aluminum on the Li+ conductivity of LGP was investigated computationally and experimentally. Substituting 25% of Ge4+ ions in the LGP structure with Al3+ and/or Sc3+ ions to obtain doped LGP in the form of Li1+x+yAlxScyGe2−x−y(PO4)3, where x + y = 0.5, led to more Li+ ions in the 36f vacant sites (M2) and resulted in enhanced ionic conductivity of the material. In both approaches, the highest bulk Li+ conductivity of 5.826 mS cm−1 was obtained for Li1.5Al0.33Sc0.17Ge1.5(PO4)3 from the experimental measurement. The activation energy was also investigated theoretically using the nudged elastic band method, and the lowest value (0.279 eV) was obtained for this composition. Furthermore, the Li1+x+yAlxScyGe2−x−y(PO4)3 electrolytes were synthesized using a melt-quenching method and subsequently transformed into a glass–ceramic material through heat treatment. X-ray diffraction, electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize the structure, measure the Li+ conductivity and determine the electrochemical window of the synthesized glass–ceramic material, respectively. There was a remarkable agreement between the computationally calculated and experimentally measured values of ionic conductivity, activation energy and electrochemical window. Finally, its applicability in a solid-state battery was tested, and it showed good electrochemical performance.

Li1.5Al0.5Ge1.5(PO4)3 (LAGP) is a promising solid electrolyte for use in next-generation lithium batteries. Nevertheless, its lower bulk and grain-boundary ionic conductivities are major restrictions preventing its practical utilization. Mg was introduced into LAGP to form Li1.6Al0.4Mg0.1Ge1.5(PO4)3 (LAMGP) based on computational analysis. The doping of LAGP with Mg results in advantages such as increasing the Li+ concentration and expanding the material dimensions due to the larger ionic radius of Mg, leading to enhanced ionic conductivity. Mg had a two-birds-with-one-stone effect in the LAMGP electrolyte, not only generating super high bulk ionic conductivity of 7.435 mS cm−1, compared to 2.896 mS cm−1 in LAGP, but also generating low grain-boundary resistance due to improved densification. The lowering of the grain-boundary resistance and the increased densification are related to choosing the right precursor for the dopant. Using LAMGP as a hybrid solid electrolyte, a solid battery delivered great electrochemical performance in comparison to when LAGP was used. Interfacial analysis was also conducted, which revealed that the formation of an interface prevented the reduction of components in LAMGP by Li metal, therefore ensuring the long-term durability of LAMGP in liquid electrolyte. These results suggest that LAMGP is an auspicious solid electrolyte for achieving practical solid-state lithium batteries.

Rechargeable aqueous zinc-ion batteries (ZIBs) are emerging as an alternative to lithium-ion batteries in large-scale energy storage applications due to their safety and environmental friendliness. However, their application is hindered by the lack of suitable cathode materials that provide high capacity and long cycling stability. In this work, we have designed Cu–MnO nanospheres with abundant manganese/oxygen defects as a cathode material via calcination and reduction of manganese dioxide (MnO2) in an Ar/H2 atmosphere. Investigation of the electrochemical mechanism showed that the spinel-type Cu–MnO electrode started to transform into layered-type Cu–MnO2·nH2O nanoflowers upon initial charging, and thus, the subsequent Zn2+ intercalation and H+ conversion reactions took place in the Cu–MnO2·nH2O material. The underlying phase transformation of the Cu–MnO nanospheres and energy storage mechanism of the Cu–MnO2·nH2O nanoflowers were systematically investigated using a broad range of characterization techniques. Manganese vacancy was also observed in Cu–MnO2·nH2O, which interestingly triggered the lattice oxygen redox reaction. As a result, when employed as a cathode material in zinc-ion batteries, Cu–MnO2·nH2O delivered a high specific capacity of 320 mA h g−1 and long-term cycling stability with a capacity retention of over 70% after 1000 cycles. This work not only provides insight into the design of transition-metal-modified manganese monoxide cathodes but also broadens the horizon for understanding the electrochemical properties and energy-storage mechanism of low-valance manganese-based cathode materials in rechargeable zinc-ion batteries.