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.
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.
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