Multiphase Energy Storage Of Carbon Aerogel/molybdenum Dioxide Nanocomposites Based On Alginate Carbon Source

Sodium alginate,a natural macromolecular polysaccharide polymer extracted from brown seaweeds,has been used in textile,printing,dyeing and medical dressing areas because of its biocompatibility and Ionic complexation.We extended the Sodium alginate into electrochemistry area using its characteristic of Ionic complexation by annealing the sodium alginate aerogels(SAC),which was made from the hydrogels dehydrate via a freeze-drying process.We found that sodium alginate can be used in new energy fields as a carbon precursor with advantages of high conductivity and environment-friendly,and the main research contents and conclusions are as follows.We synthetized SAC@MoO2 composite by annealing at a high temperature,and we studied the phase transformation of ammonium molybdate at different temperatures.We found that ammonium molybdate can completely turn to be MoO3 at 350?,and the crystallinity would be influenced at higher temperature.The SAC could be entirely oxided when the oxidation temperature come to 400 ? or higher.We present a one step in situ method to synthesize MoO2/Carbon aerogels composite with MoO2 nanoparticles embedded in carbon aerogels matrix using an environmental friendly alginate as the carbon precursor.The composite prepared at optimum conditions,namely stabilization temperature at 375 ?,exhibited a brilliant cycle stability with a reversible capacity of 490 mAh g-1 at a current density of 200 mA g-1 for 120 cycles,which was far better than the pure SAC.Porous carbon aerogels were synthetized with the KOH chemical activation,and we loaded various proportion MoO2 on the porous carbon aerogels with ex situ method.The sample contained 15 wt% MoO2 exhibited the best Li-S performance with a specific capacity of 632 mAh g-1 at a current density of 1 C(1 C=1675 mAhg-1)after 100 cycles,which was superior to the samples with different proportion MoO2(5 wt%,10 wt%,20 wt%)and pure active SAC.