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We report direct evidence of soluble LiO 2 generation upon Li 2 O 2 oxidation and reveal a strong solvent-controlled Li 2 O 2-oxidation reaction mechanism in Li-O 2 batteries. In high-donicity solvents, Li 2 O 2 oxidation follows a solution pathway by forming soluble LiO 2 intermediate. While in low-donicity solvent, Li 2 O 2 oxidation follows a solid-solution pathway by forming solid Li 2Àx O 2 intermediate. The preferential formation of soluble LiO 2 promotes the charging kinetics but leads to poor cycling stability. Our work shows that bypassing the generation of soluble LiO 2 will improve the stability of Li-O 2 batteries.

Two dimension (2D) layered molybdenum disulfide (MoS2) has emerged as a promising candidate for the anode material in lithium ion batteries (LIBs). Herein, 2D MoSx (2 ≤ x ≤ 3) nanosheet-coated 1D multiwall carbon nanotubes (MWNTs) nanocomposites with hierarchical architecture were synthesized via a high-throughput solvent thermal method under low temperature at 200°C. The unique hierarchical nanostructures with MWNTs backbone and nanosheets of MoSx have significantly promoted the electrode performance in LIBs. Every single MoSx nanosheet interconnect to MWNTs centers with maximized exposed electrochemical active sites, which significantly enhance ion diffusion efficiency and accommodate volume expansion during the electrochemical reaction. A remarkably high specific capacity (i.e., > 1000 mAh/g) was achieved at the current density of 50 mA g−1, which is much higher than theoretical numbers for either MWNTs or MoS2 along (~372 and ~670 mAh/g, respectively). We anticipate 2D nanosheets/1D MWNTs nanocomposites will be promising materials in new generation practical LIBs.

Low temperature aqueous batteries (LT-ABs) have attracted extensive attention recent years. The LT-ABs suffer from electrolyte freezing, slow ionic diffusion and sluggish interfacial redox kinetics at low temperature. In this review, we discuss physicochemical properties of aqueous electrolytes in terms of phase diagram, ion diffusion and interfacial redox kinetics to guide the design of low temperature aqueous electrolytes (LT-AEs). Firstly, the characteristics of equilibrium and nonequilibrium phase diagrams are introduced to analyze the antifreezing mechanisms and propose design strategies for LT-AEs. Then, the temperature/concentration/charge carrier dependence conductivity characteristics in aqueous electrolytes are reviewed to comprehend and regulate the ion diffusion kinetics. Moreover, we introduce interfacial studies in aqueous and non-aqueous batteries and propose potential improvement strategies for interfacial redox kinetics in LT-ABs. Finally, we summarize design strategies of LT-AEs for developing high performance LT-ABs.

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