Ming Au

In Situ Electrochemical Lithiation/Delithiation Observation of Individual Amorphous Si Nanorods

In situ electrochemical lithiation and delithiation processes inside a nanobattery consisting of an individual amorphous Si nanorod and ionic liquid were explored. Direct formation of the crystalline Li(22)Si(5) phase due to the intercalation of Li ions was observed. In addition, the role of the electrolyte-nanorod interface was examined. It was observed that the lithiation of Si nanorods is dominated by surface diffusion. Upon the delithiation process, partial decomposition of Li(22)Si(5) particles was observed which can explain the irreversible capacity loss that is generally seen in Si anodes. This study shows that the radial straining due to lithiation does not cause cracking in nanorods as small in diameter as 26 nm, whereas cracks were observed during the lithiation of 55 nm Si nanorods.

Real-time observation of lithium fibers growth inside a nanoscale lithium-ion battery

Formation of lithium dendrite/fibers during charging-discharging cycles not only causes short circuit but is also known as a major safety issue. In this work, an electrochemical cell was constructed inside a transmission electron microscope to observe the real-time nucleation and growth of the lithium fibers inside a nanoscale Li-ion battery. Our results show that during the lithiation process, the lithium ions nucleate at the interface of anode and electrolyte and then grow into fibers. These fibers grew parallel to the direction of the applied electric field. Such observations can assist the nanoscale design of better electrodes and electrolyte materials needed for safe and high power Li-ion batteries.

Nanostructured metal oxides for anodes of Li-ion rechargeable batteries

The aligned nanorods of Co{sub 3}O{sub 4} and nanoporous hollow spheres (NHS) of SnO{sub 2} and Mn{sub 2}O{sub 3} were investigated as the anodes for Li-ion rechargeable batteries. The Co{sub 3}O{sub 4} nanorods demonstrated 1433 mAh/g reversible capacity. The NHS of SnO{sub 2} and Mn{sub 2}O{sub 3} delivered 400 mAh/g and 250 mAh/g capacities respectively in multiple galvonastatic discharge-charge cycles. It was found that high capacity of NHS of metal oxides is sustainable attributed to their unique structure that maintains material integrity during cycling. The nanostructured metal oxides exhibit great potential as the new anode materials for Li-ion rechargeable batteries with high energy density, low cost and inherent safety.

Novel electrolyte chemistries for Mg-Ni rechargeable batteries.

Commercial hybrid electric vehicles (HEV) and battery electric vehicles (BEV) serve as means to reduce the nations dependence on oil. Current electric vehicles use relatively heavy nickel metal hydride (Ni-MH) rechargeable batteries. Li-ion rechargeable batteries have been developed extensively as the replacement; however, the high cost and safety concerns are still issues to be resolved before large-scale production. In this study, we propose a new highly conductive solid polymer electrolyte for Mg-Ni high electrochemical capacity batteries. The traditional corrosive alkaline aqueous electrolyte (KOH) is replaced with a dry polymer with conductivity on the order of 10{sup -2} S/cm, as measured by impedance spectroscopy. Several potential novel polymer and polymer composite candidates are presented with the best-performing electrolyte results for full cell testing and cycling.