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Orthorhombic β-LiVOPO4/ketjen black composite is obtained via a two-step chemical synthesis. In the first step, Li3V2(PO4)3-V2O3/ketjen black precursor is obtained by spray-drying process and subsequent heat treatment. Solvent-thermal oxidation of the precursor results in the complete formation of β-LiVOPO4/ketjen black composite. The synthesized composite is characterized by means of X-ray diffraction, scanning electron microscopy, nitrogen sorption, and electrochemical tests. Galvanostatic charge–discharge cycling of the composite shows an initial discharge specific capacity of 305, 289, 276, 242, 157, and 77 mAh·g−1 at C/20, C/10, C/5, C/2, 1C, and 2C rate in a voltage window of 2.0–4.5 V, respectively. At higher current rates, although it exhibits good retention of discharge capacity, the capacity is found to reduce with increasing current rates. The composite displays excellent cycling performance at a current rate of C/5 up to 50 cycles, which yields a high specific capacity of 245 mAh·g−1 at the end of the 50th cycle and a small capacity fading of 0.13% per cycle.

The MnO2/Micro-nano Ni-filled Ni foam (MNFNF) hybrids were systematically studied as supercapacitor electrodes. Micro-nano Ni-filled Ni foam (MNFNF) was prepared via a facile NiC2O4·2H2O coating process on foam, followed by sintering treatment, and then employed as substrate for electrodeposition of MnO2. The morphology of the MNFNF substrate exhibited an obviously second-porous structure, deriving from dehydration, decarboxylation, and the lattice contraction occurred in the sintering treatment process of NiC2O4·2H2O. The structure of pores was irregular with 0.05~2 μm in diameter, and the pore walls were composed of nanoparticles with 200~500 nm in diameter. Such porous MNFNF not only provided a conductive network to enhance the charge transport and mass transfer in the electrochemical process but also achieved a large MnO2 mass loading capacity. Electrochemical test showed the MnO2/MNFNF electrode exhibited a mass specific capacitance (SC) of 723.7 F g−1 and an areal specific capacitance of 1.16 F cm−2 at a current rate of 0.25 A g−1. The asymmetric supercapacitor device based on the MnO2/MNFNF electrode and active carbon electrode could supply an energy density of 24.5 Wh kg−1 at the maximum power density of 4.4 kW kg−1. Meanwhile, the supercapacitor device also exhibited a good cycling stability along with 93.2% specific capacitance retained after 5000 cycles. These results demonstrated that the MnO2/MNFNF electrode could be one of the potential electrode material for energy storage applications.

The preparation and capacitance performances of Mn (OH)2@ secondary porous Ni nano-architecture foam (Mn (OH)2@SPNiNF) hybrids are systematically studied. The SPNiNF structure is simply obtained via a NiC2O4·2H2O in situ growing process on Ni foam surface, combined with a thermally treated process under Ar gas. Then, a layer of Mn (OH)2 film was electrodeposited onto the above SPNiNF sheet by applying a galvanostatical technique. It is shown that the SPNiNF sheet is composed of interconnected nanoparticles with a diameter range of 100–200 nm. The fabricated Mn (OH)2@SPNiNF electrode exhibited a high specific capacitance of 532.7 F g−1 and an areal capacitance of 906 m F cm−2 at a current density of 0.5 A g−1. The Mn (OH)2@SPNiNF electrode also exhibited a low ions diffusion resistance and a good cycling performance along with 85.7% specific capacitance retained after 5000 cycles. An asymmetric Mn (OH)2@SPNiNF //AC super capacitor exhibited an energy density of 69.1 Wh kg−1 at a power density of 0.6 kW kg−1. These results demonstrated that the Mn (OH)2@SPNiNF was a promising electrode material for supercapacitors.