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Microsized porous SiO@C composites used as anode for lithium-ion batteries (LIBs) are synthesized from rice husks (RHs) through low-temperature (700 °C) aluminothermic reduction. The resulting SiO@C composite shows mesoporous irregular particle morphology with a high specific surface area of 597.06 m/g under the optimized reduction time. This porous SiO@C composite is constructed by SiO nanoparticles uniformly dispersed in the C matrix. When tested as anode material for LIBs, it displays considerable specific capacity (1230 mAh/g at a current density of 0.1 A/g) and excellent cyclic stability with capacity fading of less than 0.5% after 200 cycles at 0.8 A/g. The dramatic volume change for the Si anode during lithium-ion (Li) insertion and extraction can be successfully buffered because of the formation of LiO and LiSiO during initial lithiation process and carbon coating layer on the surface of SiO. The porous structure could also mitigate the volume change and mechanical strains and shorten the Li diffusion path length. These characteristics improve the cyclic stability of the electrode. This low-cost and environment-friendly SiO@C composite anode material exhibits great potential as an alternative for traditional graphite anodes.

The synthesized LiBH4−MgH2−Al (4:1:1 mole ratio) composite exhibits reversible de/rehydrogenation properties. Thermogravimetry and differential scanning calorimetry indicate that the dehydrogenation onset temperature is reduced by 100 K from that of 2LiBH4−MgH2 and 2LiBH4−Al systems. The major dehydrogenation pathway for the 4LiBH4−MgH2−Al complex system can be identified as 4LiBH4 + MgH2 + Al → 4LiH + MgAlB4 + 7H2 by means of X-ray diffraction (XRD) measurements on the as-dehydrogenated samples. The isothermal dehydrogenation measurements exhibit that the maximum dehydrogenation amount (9.4 wt % H2, 673 K) approaches the theoretical value (9.9 wt % H2) of the reaction. Through pressure−composition isotherms (P−C−T) and the van’t Hoff equation, the dehydrogenation enthalpy and entropy of the 4LiBH4−MgH2−Al system can be determined as 57 kJ/mol-H2 and 75 J/K·mol-H2, respectively. The system is slightly destabilized from pristine LiBH4 (ΔH de ° = 68 kJ/mol-H2) by coadditives of MgH2 and Al. The XRD measurements on the rehydrogenated samples suggest that the above reaction is partially reversible and the backward reaction takes place in two steps as 4LiH + MgAlB4 + 6H2 → Mg + 4LiBH4 + Al and Mg + H2 → MgH2. Because of the alloying of Mg with Al, MgH2 in the complex system cannot be fully recovered below the temperature of 673 K. The isothermal rehydrogenation measurements exhibit significantly enhanced kinetics for the LiH−MgAlB4 system compared with LiH−MgB2 and LiH−AlB2 systems.