Conventionally, rechargeable batteries with a fast charge-discharge rate, while being able to be implemented in large-scale applications with low prices, are critical for new energy storage systems. In this work, first-principles simulations were employed to theoretically investigate the insertion of sodium into the Na(2)Ti(3)O(7) structure. The result discovered that the theoretical capacity of Na(2)Ti(3)O(7) was 311 mA h g(-1). Furthermore, a microspheric Na(2)Ti(3)O(7) material consisting of tiny nanotubes of ca. 8 nm in outside diameter and a few hundred nanometers in length has been synthesized. The galvanostatic charge-discharge measurements, using the as-prepared Na(2)Ti(3)O(7) nanotubes as a working electrode with a voltage range of 0.01-2.5 V vs. Na(+)/Na, disclosed that a high capacity was maintained even under an ultrafast charge-discharge rate. At a current density of 354 mA g(-1), the discharge capacity was maintained at 108 mA h g(-1) over 100 cycles. Even at a very large current density of 3540 mA g(-1), the discharge capacity was still 85 mA h g(-1). HRTEM analysis and electrochemical tests proved that sodium ions could not only intercalate into the Na(2)Ti(3)O(7) crystal, but could also be stored in the intracavity of the nanotubes. All of the results disclose that the as-prepared Na(2)Ti(3)O(7) nanotubes are able to be used as anode materials in large-scale applications for rechargeable sodium-ion batteries at low cost while maintaining excellent performance.

Single crystalline Na 2 Ti 3 O 7 rods were prepared through sintering a precursor synthesized in a reverse micelle. Charge/discharge measurements were performed in the potential range 0.01-2.5 V versus Na/Na + under different C-rates. The tested capacity was maintained at 103 mA h g 21 , even after 20 cycles at a rate of 0.1 C.The results exhibited that the as-prepared single crystalline Na 2 Ti 3 O 7 rods had a very low voltage plateau (around 0.3 V), and were suitable to use as anode materials for sodium-ion batteries.

A general synthetic route to the resonance-stabilized pyrazine-bridged bisdithiazolyl framework, involving the reductive deprotection of 2,6-diaminopyrazine-bisthiocyanate and cyclization with thionyl chloride, has been developed. An N-methyl bisdithiazolyl radical, 4-methyl-4H-bis[1,2,3]dithiazolo[4,5-b:5',4'-e]pyrazin-3-yl, has been prepared and characterized in solution by electron paramagnetic resonance spectroscopy and cyclic voltammetry. Its crystal structure has been determined at several temperatures. At 295 K, the structure belongs to the space group Cmca and consists of evenly spaced radicals pi-stacked in an alternating ABABAB fashion along the x-direction. At 123 K, the space group symmetry is lowered by loss of C-centering to Pccn, so that the radicals are no longer evenly spaced along the pi-stack. At 88 K, a further lowering of space group symmetry to P21/c is observed. Extended Hückel Theory band structure calculations indicate a progressive opening of a band gap at the Fermi level in the low-temperature structures. Magnetic susceptibility measurements over the range 4-300 K reveal essentially diamagnetic behavior below 120 K. Variable-temperature single-crystal conductivity (sigma) measurements indicate that the conductivity is activated, even at room temperature, with a room-temperature value sigma RT=0.001 S cm-1 and a thermal activation energy Eact=0.19 eV. Under an applied pressure of 5 GPa, sigma RT is increased by 3 orders of magnitude, but the conductivity remains activated, with Eact being lowered to 0.11 eV at 5.5 GPa.