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As anode materials for lithium-ion batteries, transition metal oxides show usually high theoretic specific lithium ion storage capacities, but their electrical conductivity remains to be improved and their structural pulverizations during lithiation/delithiation need to be suppressed, which affect severely their lithiation/delithiation rate capability and also the cycling stability. Herein, NiO/Co 3 O 4 nanotubes encapsulated with graphene sheets are designed and assembled. It is demonstrated that as anode for lithium-ion batteries, the as-obtained NiO/Co 3 O 4 nanotubes encapsulated with graphene show excellent electrochemical performance, including large lithium ion storage capability (∼1206 mA h g −1 at 0.1 A g −1 after 100 cycles), high rate capability, and cycling stability. The electrochemical kinetics analyses reveal that the tubular structure not only facilitates lithium ion transportation, but also provides even more spaces for lithium ion storage. The external encapsulated graphene sheets can improve the electrical conductivity of NiO/Co 3 O 4 nanotubes, and afford also certain lithium ion storage capacity. Those structural and component factors synergistically account for their improved electrochemical performances.

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The adhesion of a gel electrolyte to the electrode is one of the key factors to the electrochemical performance of lithium-ion batteries (LIBs). Herein, gel electrolyte is prepared on the LiFePO 4 electrode through in situ electrospinning the poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) nanofiber matrix, followed by lithium salt solution loading. The interfacial interactions between the in situ electrospun PVdF-HFP matrix and LiFePO 4 electrode before and after gelation are studied using dynamic thermomechanical analysis and scanning electron microscopy. The results demonstrate that the as-prepared gel electrolyte can adhere tightly onto the LiFePO 4 electrode. LIBs (half coin cells) are assembled using the as-obtained gel electrolyte to evaluate their electrochemical properties. The results show that the lithium-ion and electron transfer rates crossing the interface between gel electrolyte and LiFePO 4 electrode are enhanced. The electrochemical performances of the half coin cells, including specific capacity, rate capability, and cycle stability, are improved significantly.

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