LiNi 0.8 Co 0.15 Al 0.05 O 2 is considered as an alternative for commercial LiCoO 2 positive electrode material for lithium ion batteries because of its excellent cycling performance. However, its capacity fading and potential safety hazard still need to be improved. In this study, fluorination has been introduced for the first time to modify the surface of LiNi 0.8 Co 0.15 Al 0.05 O 2 by a one-step facile and dry method. The crystalline structure, morphology, surface information and electrochemical performance were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectronic spectroscopy and electrochemical tests. The surface-fluorinated LiNi 0.8 Co 0.15 Al 0.05 O 2 exhibits a reversible capacitance up to 220.5 mAh g -1 at 0.1C, good rate capability, and an excellent long-term cycling stability with 93.6% capacity retention after 80 cycles at 0.1C, which is much better than the pristine commercial LiNi 0.8 Co 0.15 Al 0.05 O 2 . The main reason is that metal-fluorine (M-F) bond partially replaces the metal-oxygen (M-O) bond at the surface, enhancing the entire bond energy as well as the structure stability. In addition, the interfacial conductivity between the electrolyte and the positive electrode has been increased, leading to a faster kinetic process. These results show that fluorinated LiNi 0.8 Co 0.15 Al 0.05 O 2 is a promising positive electrode material for high performance lithium ion batteries.This journal is

A hydrothermal-oxidation two-step method has been employed to fabricate a composite of CoOOH nanoplates with conducting multiwalled carbon nanotubes (MWCNTs), which present excellent electrochemical performance as a cathode material for a supercapacitor. The conductive nanostructure network of MWCNTs not only provides effective surface area for the contact between the electrode material and the electrolyte but also shortens the diffusion distances for ions and electrons and buffers the volume change, resulting in higher capacitance, faster redox reaction kinetics, and outstanding cycling stability. The maximum specific capacitance of the composite can achieve 270 F g −1 at a current density of 1 A g −1 in 0.5 mol L −1 KOH aqueous solution. It also exhibits good rate capability with a capacitance of 169 F g −1 even at a high current density of 10 A g −1 and outstanding long-term cycling stability, almost 100% retention of its initial capacitance after 10 000 full cycles. In contrast, the virginal CoOOH shows a capacitance of only 124 and 100 F g −1 at 1 and 10 A g −1 , respectively, and its capacitance retention is only 79.4% after 10 000 full cycles. These results, for the first time, indicate that the composite of CoOOH nanoplates with MWCNTs is a promising cathode material for high-performance aqueous supercapacitors.

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