A mesoporous carbon with regular three-dimensionally interconnected 2 nm pore arrays using AlMCM-48 as a template has been synthesised; the mesoporous carbon exhibited excellent performance as an electrochemical double layer capacitor.

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Hybrid supercapacitors (battery-supercapacitor hybrid devices, HSCs) deliver high energy within seconds (excellent rate capability) with stable cyclability. One of the key limitations in developing high-performance HSCs is imbalance in power capability between the sluggish Faradaic lithium-intercalation anode and rapid non-Faradaic capacitive cathode. To solve this problem, we synthesize Nb2O5@carbon core-shell nanocyrstals (Nb2O5@C NCs) as high-power anode materials with controlled crystalline phases (orthorhombic (T) and pseudohexagonal (TT)) via a facile one-pot synthesis method based on a water-in-oil microemulsion system. The synthesis of ideal T-Nb2O5 for fast Li(+) diffusion is simply achieved by controlling the microemulsion parameter (e.g., pH control). The T-Nb2O5@C NCs shows a reversible specific capacity of ∼180 mA h g(-1) at 0.05 A g(-1) (1.1-3.0 V vs Li/Li(+)) with rapid rate capability compared to that of TT-Nb2O5@C and carbon shell-free Nb2O5 NCs, mainly due to synergistic effects of (i) the structural merit of T-Nb2O5 and (ii) the conductive carbon shell for high electron mobility. The highest energy (∼63 W h kg(-1)) and power (16 528 W kg(-1) achieved at ∼5 W h kg(-1)) densities within the voltage range of 1.0-3.5 V of the HSC using T-Nb2O5@C anode and MSP-20 cathode are remarkable.

A mesostructured spinel Li 4 Ti 5 O 12 (LTO)-carbon nanocomposite (denoted asMeso-LTO-C) with large ( > 15 nm) and uniform pores is simply synthesized via block copolymer self-assembly. Exceptionally high rate capability is then demonstrated for Li-ion battery (LIB) negative electrodes. Polyisoprene-blockpoly(ethylene oxide) (PI-b -PEO) with a sp 2 -hybridized carbon-containing hydrophobic block is employed as a structure-directing agent. Then the assembled composite material is crystallized at 700 °C enabling conversion to the spinel LTO structure without loss of structural integrity. Part of the PI is converted to a conductive carbon that coats the pores of the Meso-LTO-C. The in situ pyrolyzed carbon not only maintains the porous mesostructure as the LTO is crystallized, but also improves the electronic conductivity. A Meso-LTO-C/Li cell then cycles stably at 10 C-rate, corresponding to only 6 min for complete charge and discharge, with a reversible capacity of 115 mA h g − 1 with 90% capacity retention after 500 cycles. In sharp contrast, a Bulk-LTO/Li cell exhibits only 69 mA h g − 1 at 10 C-rate. Electrochemical impedance spectroscopy (EIS) with symmetric LTO/ LTO cells prepared from Bulk-LTO and Meso-LTO-C cycled in different potential ranges reveals the factors contributing to the vast difference between the ratecapabilities. The carbon-coated mesoporous structure enables highly improved electronic conductivity and signifi cantly reduced charge transfer resistance, and a much smaller overall resistance is observed compared to Bulk-LTO. Also, the solid electrolyte interphase (SEI)-free surface due to the limited voltage window ( > 1 V versus Li/Li + ) contributes to dramatically reduced resistance.