To solve the wetting capability issue of commercial polypropylene (PP) separators in lithium-ion batteries (LIBs), we developed a simple dipping surface-coating process based on tannic acid (TA), a natural plant polyphenol. Fourier transform infrared and X-ray photoelectron measurements indicate that the TA is coated successfully on the PP separators. Scanning electron microscopy images show that the TA coating does not destroy the microporous structure of the separators. After being coated with TA, the PP separators become more hydrophilic, which not only enhances the liquid electrolyte retention ability but also increases the ionic conductivity. The battery performance, especially for power capability, is improved after being coated with TA. It indicates that this TA-coating method provides a promising process by which to develop an advanced polymer membrane separator for lithium-ion batteries.

A versatile, facile method is reported for preparation of core–shell nano-structured carbon composites using tannic acid as the carbon source.

A polymer lithium–oxygen battery based on lithiated perfluorinated sulfonic conducting ionomers swollen with non-aqueous solvents operates at room temperature, showing good cycling stability, rate capability and a capacity as high as 1500 mA h gcarbon−1.

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Triethylene glycol dimethyl ether (G3) is evaluated as an electrolyte solvent for non-aqueous lithium-oxygen (Li-O 2 ) batteries. A liquid electrolyte of 1 M LiTFSI in G3 shows lower viscosity, higher oxygen solubility and diffusion, higher ionic conductivity and lithium ionic transference number compared to the conventional liquid electrolyte of 1 M LiTFSI in tetraethylene glycol dimethyl ether (G4). Then the Li-O 2 battery using the G3-based electrolyte shows better cycling stability and higher rate capability compared to the battery using the G4-based electrolyte. At a higher current density of 2.5 A g carbon −1 , the discharge capacity of the battery using the G3-based electrolyte is about 1472 mAh g carbon −1 , which is about four times higher than that of the battery using the G4-based electrolyte. At current density of 1 A g carbon −1 with a fixed capacity of 1000 mAh g carbon −1 , the battery using the G3-based electrolyte can be operated stably for 80 cycles, while only 20 cycles are achieved by using the G4-based electrolyte. Therefore, we think the G3-based electrolyte could be a proper alternative electrolyte to the conventional G4-based electrolyte for the development of Li-O 2 batteries.