Rechargeable lithium–iodine (Li–I2) batteries are a promising electrochemical energy storage candidate due to their high energy and power density. However, the high solubility of iodine in electrolytes seriously deteriorates the electrochemical performance of Li–I2 batteries. In addition, the low iodine content in the cathode impedes the enhancement of energy density. Active graphene (AG) has a large specific surface area, abundant micropores and mesopores, free inter-particle voids and unimpeded ion diffusion channels, making it a promising substrate for loading a high content of iodine. In this study, I2–AG composites were fabricated through an in situ iodine deposition route. The facile synthesis process can introduce a high content of iodine into the nanopores of AG effectively. The microstructure and morphology of the I2–AG composites were characterized using Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The results show that iodine is well dispersed in the nanopores of AG. The as-prepared I2–AG composites exhibit high specific capacity, excellent cyclic performance and high rate performance. In particular, the I2–AG composite, with a high iodine content of 56 wt%, delivers a high capacity of 218 mA h g−1 at a 1C rate, and maintains 161 mA h g−1 after 500 cycles, corresponding to a low capacity fading of only 0.023% per cycle. Especially, the I2–AG composite exhibits outstanding high-rate performance. Even at 20C, an appreciable discharge capacity of 184 mA h g−1 can still be obtained. The results indicate that the high content of soluble iodine can be well constrained in the nanopores of AG during charging and discharging processes, making Li–I2 batteries a promising alternative energy storage device with both high energy and high power density.

The hydrogen storage properties and catalytic mechanism of FeCl2-doped LiAlH4 were investigated in minute details. LiAlH4-2 mol% FeCl2 samples start to release hydrogen at 76 °C, which is 64 °C lower than that of as-received LiAlH4. Isothermal desorption measurements show that the 2 mol% FeCl2-doped sample releases 7.0 wt% of hydrogen within 17 min at 250 °C. At lower temperatures of 110 °C and 80 °C, the sample can release 4.4 wt% and 3 wt% of hydrogen, respectively. The apparent activation energy of LiAlH4-2 mol% FeCl2 samples for R2 is 105.02 kJ/mol, which is 67 kJ/mol lower than that of pure LiAlH4. The reaction between LiAlH4 and FeCl2 during ball milling was found by analyzing the X-ray diffraction results, and Fe-Al particles formed in-situ from the reaction act as the real catalyst for the dehydrogenation of LiAlH4.The dopant FeCl2 react with LiAlH4 to produce Fe–Al particles in-situ, which act as the real catalyst for dehydrogenation of LiAlH4. Download high-res image (83KB)Download full-size image

Rechargeable lithium–iodine (Li–I2) batteries are a promising electrochemical energy storage candidate due to their high energy and power density. However, the high solubility of iodine in electrolytes seriously deteriorates the electrochemical performance of Li–I2 batteries. In addition, the low iodine content in the cathode impedes the enhancement of energy density. Active graphene (AG) has a large specific surface area, abundant micropores and mesopores, free inter-particle voids and unimpeded ion diffusion channels, making it a promising substrate for loading a high content of iodine. In this study, I2–AG composites were fabricated through an in situ iodine deposition route. The facile synthesis process can introduce a high content of iodine into the nanopores of AG effectively. The microstructure and morphology of the I2–AG composites were characterized using Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The results show that iodine is well dispersed in the nanopores of AG. The as-prepared I2–AG composites exhibit high specific capacity, excellent cyclic performance and high rate performance. In particular, the I2–AG composite, with a high iodine content of 56 wt%, delivers a high capacity of 218 mA h g−1 at a 1C rate, and maintains 161 mA h g−1 after 500 cycles, corresponding to a low capacity fading of only 0.023% per cycle. Especially, the I2–AG composite exhibits outstanding high-rate performance. Even at 20C, an appreciable discharge capacity of 184 mA h g−1 can still be obtained. The results indicate that the high content of soluble iodine can be well constrained in the nanopores of AG during charging and discharging processes, making Li–I2 batteries a promising alternative energy storage device with both high energy and high power density.