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The rechargeable zinc–air battery is a clean technology for energy storage applications but is impeded by the slow kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during its cycling. Herein, a series of lanthanum cobaltate based perovskites are synthesised with the B-site cation deficiencies in the structure occupied by Ru substitution: LaCo1−xRuxO3−δ (x = 0, 0.1, 0.2, 0.3 and 0.5). These compositions were designed to enhance the OER/ORR activities, which are two vital reactions for rechargeable Zn–air batteries. Powder X-ray diffraction analysis revealed that increasing the Ru substitution >20% (x > 0.2) alters the LaCoO3 crystal structure from rhombohedral to orthorhombic. Photoelectron spectroscopy studies reveal that the surface oxygen vacancies increased in the Ru substituted catalyst, a property important for enhancing the OER/ORR efficiency. The LaCo0.8Ru0.2O3−δ (LCRO82) catalyst exhibits promising electrocatalytic activities in both the OER and the ORR in 0.1 M KOH solution. Furthermore, the LCRO82 catalyst was evaluated as a cathode for rechargeable Zn–air battery applications displaying a high power density of 136 mW cm−2 at a current density of 175 mA cm−2 and a stable charge–discharge voltage gap of 0.78 V after 1440 cycles, with excellent cycling stability over 240 h. [ABSTRACT FROM AUTHOR]

The Li+ transport kinetics at the solid–solid electrode‖electrolyte interfaces are crucial for the stable and durable performance of solid-state batteries (SSBs). A poor interface due to mechanical problems and/or (electro-)chemical instabilities will curtail the performance of such batteries. Herein, we present a detailed study on the interfaces of a lithium–sulfur (Li–S) SSB with a Li anode, Li–garnet (LLZO) solid electrolyte (SE), and a sulfur–carbon composite as the cathode. Interlayer gels based on ionic liquids were introduced to improve the interfacial properties of the system. For Li symmetric cells, the strategy resulted in a decrease in cell resistance by about a factor of five and stable voltage profiles with low overpotentials (∼300 mV at 0.4 mA cm−2 after >450 hours). Furthermore, the LLZO SE efficiently blocked the polysulfide shuttle to the Li anode. Due to the advantageous features of the design, good electrochemical performance was obtained, where the Li–S SSB delivered an initial discharge capacity of ca. 1360 mA h gsulfur−1 and a discharge capacity of ca. 570 mA h gsulfur−1 after 100 cycles. Detailed electrochemical and compositional characterization of the interphase layers was performed at the Li anode and sulfur cathode interfaces through X-ray photoelectron spectroscopy (XPS), applying depth-profiling techniques, and scanning transmission electron microscopy (STEM). The results revealed the presence of interphase nano-layers with varying thicknesses on the LLZO surface which contained organic and inorganic species. [ABSTRACT FROM AUTHOR]

Rechargeable zinc-air batteries are considered to be more sustainable and efficient candidates for safe, low-cost energy storage because of their higher energy density and the abundance of zinc resources. Recently Zn-air batteries have aroused significant research attention, however, because an unresolved impediment due to the notorious instability of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) kinetics of the cathode catalyst limit their practical application. Herein, we report the synthesis of non-precious MnCo 2 O 4 nanospheres synergized with a graphene sheet as a bi-functional cathode catalyst for rechargeable Zn-air battery application using a one-pot probe sonochemical method. Structural characterization confirms that the MnCo 2 O 4 nanospheres successfully anchored on graphene sheet. X-ray photoelectron spectroscopy revealed that the Mn and Co in the MnCo 2 O 4 are in mixed valence states on the graphene sheet surface and the MnCo 2 O 4 -graphene sheet (MCO-GS) hybrid catalyst exhibits excellent OER and ORR activity compared with their individual counterparts. A rechargeable Zn-air battery using an MCO-GS catalyst reveals unique small charge-discharge overpotential, cycling stability and higher rate capability than a bare MnCo 2 O 4 (MCO) catalyst. This superiority in electrocatalytic activity combined with simplicity of material synthesis, turn the MCO-GS hybrid into a promising catalyst for a rechargeable Zn-air battery., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)