Tailoring Lithiation Behavior by Interface and Bandgap
Engineering at the Nanoscale
- Publication date
- Publisher
Abstract
Controlling the transport of lithium
(Li) ions and their reaction
with electrodes is central in the design of Li-ion batteries for achieving
high capacity, high rate, and long lifetime. The flexibility in composition
and structure enabled by tailoring electrodes at the nanoscale could
drastically change the ionic transport and help meet new levels of
Li-ion battery performance. Here, we demonstrate that radial heterostructuring
can completely suppress the commonly observed surface insertion of
Li ions in all reported nanoscale systems to date and to exclusively
induce axial lithiation along the ⟨111⟩ direction in
a layer-by-layer fashion. The new lithiation behavior is achieved
through the deposition of a conformal, epitaxial, and ultrathin silicon
(Si) shell on germanium (Ge) nanowires, which creates an effective
chemical potential barrier for Li ion diffusion through and reaction
at the nanowire surface, allowing only axial lithiation and volume
expansion. These results demonstrate for the first time that interface
and bandgap engineering of electrochemical reactions can be utilized
to control the nanoscale ionic transport/insertion paths and thus
may be a new tool to define the electrochemical reactions in Li-ion
batteries