No abstract

Garnet-structured LiLaZrO is a promising solid Li-ion electrolyte for all-solid-state Li-metal batteries and Li-redox-flow batteries owing to its high Li-ion conductivity at room temperature and good electrochemical stability with Li metal. However, there are still three major challenges unsolved: (1) the controversial electrochemical window of garnet, (2) the impractically large resistance at a garnet/electrode interface and the fast lithium-dendrite growth along the grain boundaries of the garnet pellet, and (3) the fast degradation during storage. We have found that these challenges are closely related to a thick LiCO layer and the Li-Al-O glass phase on the surface of garnet materials. Here we introduce a simple method to remove LiCO and the protons in the garnet framework by reacting garnet with carbon at 700 °C; moreover, the amount of the Li-Al-O glass phase with a low Li-ion conductivity in the grain boundary on the garnet surface was also reduced. The surface of the carbon-treated garnet pellets is free of LiCO and is wet by a metallic lithium anode, an organic electrolyte, and a solid composite cathode. The carbon post-treatment has reduced significantly the interfacial resistances to 28, 92 (at 65 °C), and 45 Ω cm at Li/garnet, garnet/LiFePO, and garnet/organic-liquid interfaces, respectively. A symmetric Li/garnet/Li, an all-solid-state Li/garnet/LiFePO, and a hybrid Li-S cell show small overpotentials, high Coulombic efficiencies, and stable cycling performance.

The TiN-S composite cathode exhibits superior performance because of higher electrical conductivity and the capture of the soluble intermediate species of the electrode reactions by 2-5 nm mesopores and strong N-S surface bonding.

NASICON (Na super ionic conductor) structures of NaMV(PO) (M = Mn, Fe, Ni) were prepared, characterized by aberration-corrected STEM and synchrotron radiation, and demonstrated to be durable cathode materials for rechargeable sodium-ion batteries. In NaMnV(PO), two redox couples of Mn/Mn and V/V are accessed with two voltage plateaus located at 3.6 and 3.3 V and a capacity of 101 mAh g at 1 C. Furthermore, the NaMnV(PO) cathode delivers a high initial efficiency of 97%, long durability over 1000 cycles, and good rate performance to 10 C. The robust framework structure and stable electrochemical performance makes it a reliable cathode materials for sodium-ion batteries.

Indium-oxide (InO) nanobelts coated by a 5-nm-thick carbon layer provide an enhanced photocatalytic reduction of CO to CO and CH, yielding CO and CH evolution rates of 126.6 and 27.9 μmol h, respectively, with water as reductant and Pt as co-catalyst. The carbon coat promotes the absorption of visible light, improves the separation of photoinduced electron-hole pairs, increases the chemisorption of CO, makes more protons from water splitting participate in CO reduction, and thereby facilitates the photocatalytic reduction of CO to CO and CH.