Metal Hydride Based Materials for Advanced Lithium Storage Applications

The state of the art, commercial used graphite anode materials are far from meeting the increasing demand for high-energy density devices. It is necessary to develop anode materials with high energy density, low-cost and superior safety. Generally, compared with classical intercalation anodes, conversion type anodes display higher theoretical capacity have been paid widely attention. Some of the emerging metal hydrides demonstrate high specific capacity, small polarization and suitable working potential. This thesis focusing on two metal hydrides both with relatively high specific capacity, sodium alanate (NaAlH4) and mageneisum hydride (MgH2) as anodes materials in LIBs. In order to enhance the electronic conductivity of the material and relieve the volume variation, four methods of carbon doping, nano crystallization, surface modification and process modification were used to raise the lithium storage performance of metal hydride-based anode materials (NaAlH4 and MgH2). By way of self-assembly, gas-solid reaction and other synthesis methods, the multi nanostructure of metal hydride-based anode materials (NaAlH4 and MgH2) were designed, and a variety of composite materials of metal hydride and graphene with different structures were successfully prepared. Through a facile solvent evaporation induced deposition method, NaAlH4 nanoparticles with an average size of ~ 12 nm encapsulated in graphene nanosheets has been developed. The SAH@G-50 electrode exhibits an discharge capacity about 1995 mAh g-1 at 100 mAh g−1 at first cycle, with a coulombic efficiency (CE) of 85.7%. The specific discharge capacity slowly decayed and then was stabilized at ~698 mAh g-1 after 200 cycles. It has been founded in this thesis, graphene could act as an effective platform to tailor the metal-hydrogen bonds of NaAlH4 through their favorable molecular interaction. Theoretical and experimental results confirm that graphene is capable of weakening the Al-H bonds of NaAlH4, thus facilitating the breaking and recombination of Al-H bonds towards advanced lithium storage performance. In addition, The synergistic effects of the favorable molecular interaction between graphene and NaAlH4, and the noticeable decrease in particle size significantly boost the lithium storage performances of NaAlH4