Overall structural modification, integrating coating and doping, was developed to enhance the structural stability and Li+ transport kinetics in a layered Ni-rich cathode, which significantly improves the electrochemical performance at high voltage.

Despite the high specific capacity of LiÀ S battery, shuttle effect of lithium polysulfides (LiPSs) and safety issue pose a great challenge to realize its commercial application. Replacing liquid electrolyte with poly (ethylene oxide) (PEO) -based solid-state electrolyte is considered as a promising method to boost the safety, but the shuttle effect of LiPSs cannot be completely eliminated. In this work, a new kind of double-layer PEO-based polymer electrolyte is designed to restrict the LiPSs. The layer next to cathode consists of PEO and poly(vinylpyrrolidone) (PVP). The other layer consists of PEO. PVP with abundant of amide groups has been proved to have strong affinity to LiPSs. The strong interaction between LiPSs and carbonyl groups in amide is verified by Attenuated Total Reflection-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy tests. As a result, the assembled LiÀ S battery exhibits a specific capacity of 1100 mAh g À 1 and capacity retention of 347 mAh g À 1 after 200 cycles at 60 °C and 0.05 C, while the capacity retention of the battery without PVP-blended PEO electrolyte remains only 27 % at the same conditions.

Li−S batteries are recognized as one of the most promising energy storage and conversion devices because of the high theoretical energy density and acceptable financial and environmental costs but suffer from sluggish sulfur reduction. Herein, the g-C 3 N 4 /g-C 3 N 4 heterojunction is synthesized using two kinds of precursors, aiming to adjust the electron cloud structure of g-C 3 N 4 and the interface adhesion energy. This intimate interface of g-C 3 N 4 /g-C 3 N 4 endows a significantly accelerated reaction kinetics and enhanced transportation of ions and electrons. Furthermore, the abundant N element of g-C 3 N 4 allows physical confinement and chemical interactions with lithium polysulfides (LiPSs). As a result, a Li−S cell with a g-C 3 N 4 /g-C 3 N 4 heterojunction as the sulfur host provides an initial discharge capacity of 1200 mAh/g at 0.1 C and retains 464 mAh/g after 150 cycles at 1 C. It also exhibits a stable rate capability of 350 mAh/g after 500 cycles at 2 C. This study may provide insights into functionalizing g-C 3 N 4 for application in Li−S batteries.

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