Studies Of Gallium-oxide-based Noble Anode Materials For Lithium Ion Batteries

Rechargeable Li-ion batteries(LIBs)represent one of the most widely applicable technologies for electrochemical energy storage.The rapid evolution of personal consumer electronics,vehicle power battery and large-scale energy storage has proposed advanced demand for LIBs.Development and optimization of new-type anode materials and cathode materials of LIBs is the key to fulfill the increasing demand.The anode materials of commercial LIBs implement the lithium storage through the intercalation reaction of Li+ in graphite layers.This mechanism bases on the LiC6(lithium-graphite intercalation compounds)with a theoretical specific capacity of 372 mAh g-1.To improve anode performance,great efforts have been devoted to the investigation of alternative materials that can store lithium through intercalation reaction,conversion reactions and reversible alloying reactions.Comparing with graphite anode material,the anode materials employed with conversion reactions and reversible alloying reactions generally obtain higher capacity in lithium storage.Nevertheless,the volume change effect hinders the structure stability of those materials during charging-discharging cycling.Given that gallium(Ga)is a metal that melts near room temperature and has low volatility.The self-healing peculiarity of Ga can reduce the negative influence of the volume change effect towards electrode structure.However,Ga nanoparticles(NPs),when directly applied,tended to aggregate upon charge/discharge cycling.To address this issue,Ga2O3 is aimed as active materials for lithium storage instead.The major progress is summarized as follows:1.The assessment and screen for the potential of Ga-based compounds as anode materials for LIBs.?-Ga2O3/C,GaP/C and GaSb/C composites were synthesized via ball-milling method.The initial delithiation capacity of those composites is 940.1 mAh g-1,944.3 mAh g-1 and 577.3 mAh g-1 respectively.By controlling the condition of ball-milling method,the optimized a-Ga2O3/C is over 688.6 mAh g-1 for delithiation capacity.2.The construction of stable structure of Ga2O3 encapsulated by carbon component(Ga2O3@C).By controlling the pH of the precursor solution,highly dispersed and ultra-fine Ga2O3 NPs,embedded in carbon shells,could be synthesized through a hydrothermal carbonization(HTC)method which is a convenient and environmentally friendly process.The particle size of the Ga2O3 NPs was 2.6 nm,with an extremely narrow size distribution,as determined by high-resolution transmission electron microscopy(HRTEM)and Brunner-Emmet-Teller(BET)measurements.A LIB anode based on this material exhibited stable charging and discharging,with a capacity.of 721 mAh g-1 after 200 cycles.The high cyclability is due to the formation of Ga0 during the lithiation process,as indicated by operando X-ray absorption near-edge spectroscopy(XANES).3.Carbon substrate supported gallium oxides with a series of different crystal forms.Tailoring the synthesis methods and corresponding conditions has obtained a-Ga2O3/RGO,?-Ga2O3/RGO and y-Ga2O3/RGO.The delithiation capacity after 12 cycles of those composites is 379.9 mAh g-1,253.4 mAh g-1 and 598.4 mAh g-1 respectively.This result preliminary indicates that ?-Ga2O3 with spinel structure display superior perform for lithium storage among gallium oxide isomers.4.The optimization of gallate with spinel structure with RGO.NiGa2O4 and ZnGa2O4 are chosen as candidates for anode materials of LIB s basing on the density of state curve and the practical measurements of powder electric conductivity.NiGa2O4/RGO and ZnGa2O4/RGO with uniform distribution structure are synthesized through two-step method and one-pot reaction respectively.NiGa2O4/RGO exert preferable performance in lithium storage.The delithiation capacity is over 621.1 mAh g-1 after 2000 cycles at 2.0 A g-1.The full-cell test and ex-situ XRD test furtherly prove the maintaining ability of electrode during charging and discharging.5.The preparation of Ga2O3/C with hierarchical structure.Hierarchical Ga2O3/C nanosheets with micrometer-scale 2D planar construction and combing the short Li+ solid phase transmission distance are prepared through NaCl-template method.The delithiation capacity of Ga2O3/C nanosheets is over 1025.9 mAh g-1 after 500 cycles at 0.5 A g-1 and 378.1 mAh g-1 at 10 A g-1 in rate-test.The performance advancement towards Ga2O3@C structure demonstrates the progressiveness of hierarchical structure.Utilizing the order structure of micrometer-scale microfiber from bamboo fiber has synthesized Ga2O3/C micrometer-scale sticks.This structure maintains the hierarchy of microfiber Ga2O3/C micrometer-scale sticks exert the lithium storage capacity of 401.6 mAh g-1 after 1500 cycles at 1.0 A g-1.Galvanostatic intermittent titration technique(GITT)measurement has analyzed the reversibility of the conversion reaction for Ga2O3,which describes the extensible performance space for gallium oxides as anode materials for LIBs.