As a proof of concept, soft-packaged Li-S batteries were assembled using these electrodes and they displayed stable electrochemical performance at different bending states. More importantly, the composite films can serve as electrodes in flexible Li-S batteries. As a result, the composite films exhibited a high initial specific capacity, remarkable cycling stability, and excellent rate capability. Their interconnected tubular structure allows easy electron transport throughout the network and helps to confine the polysulfides produced during the charge/discharge process. These composite films can serve as self-supporting cathodes for Li-S batteries without additional binders and conductive agents. In this study, we fabricated composite films of freestanding reduced graphene oxide nanotubes wrapped sulfur nanoparticles by pressing composite foams, which were synthesized by combining cold quenching with freeze-drying and a subsequent reduction process. Therefore, flexible Li-S batteries are desired. Lithium-sulfur (Li-S) batteries are considered as promising candidates for high energy density energy-storage devices. Rapid development of flexible electronic devices is promoting the design of flexible energy-storage devices. The improved cycling performance of KMnO 4-LiNi 0.8 Co 0.1 Mn 0.1 O 2 can be attributed to the favorable structural change due to the more oxidized trivalent nickel ion. XPS spectra of NMC electrodes extracted from NMC/LTO cells after the first chargedischarge cycle between 1.45 and 3.05 V at C/20 with a 60 h potentiostatic hold at 3.05 V for NMC111 and 811. Electrochemical measurements demonstrate that KMnO 4-LiNi 0.8 Co 0.1 Mn 0.1 O 2 has better rate capability and cycling stability at cutoff voltages of 4.3 and 4.5 V than Air-LiNi 0.8 Co 0.1 Mn 0.1 O 2. The structure of the KMnO 4-LiNi 0.8 Co 0.1 Mn 0.1 O 2 shows no distinct differences except for a slight expansion along the c-axis and lower cation disorder. X-ray photoelectron spectroscopy analysis of the KMnO 4-treated precursor and LiNi 0.8 Co 0.1 Mn 0.1 O 2 obtained from the KMnO 4-treated precursor in air (KMnO 4-LiNi 0.8 Co 0.1 Mn 0.1 O 2) indicates that the valence states of nickel ions are higher than those in the untreated (pristine) precursor and LiNi 0.8 Co 0.1 Mn 0.1 O 2 obtained from the pristine precursor in air (Air-LiNi 0.8 Co 0.1 Mn 0.1 O 2). In this study, we introduce a technique for preoxidation of the LiNi 0.8 Co 0.1 Mn 0.1 O 2 precursor by KMnO 4 to partially oxidize Ni 2+ in the precursor (KMnO 4-treatment) and eliminate the need for calcination in pure oxygen atmosphere. Moreover, LiNi 0.8 Co 0.1 Mn 0.1 O 2 should be calcined under oxygen flow to promote the oxidation of Ni 2+ to Ni 3+, which makes it costly. However, the inherent poor cycling stability of Ni-rich cathode materials has always been a serious issue limiting their commercialization. The layered Ni-rich oxide LiNi 0.8 Co 0.1 Mn 0.1 O 2 is very attractive as a cathode material owing to its large reversible capacity.
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