Germanium (Ge) has aroused great attention due to its
high theoretical
capacity, benign lithium diffusion, and low working potential. However,
application of the Ge anode is hindered by volume expansion and the
unstable solid electrolyte interphase (SEI) during the (de)lithiation
process. Herein, Ge particles encapsulated tightly on an N-doped porous
carbon matrix structure are obtained via a simple
one-step in situ thermally driven reduction reaction
of poly(vinylpyrrolidone) and carboxyethyl germanium sesquioxide.
A protective N-doped carbon layer of suitable thickness is further
rationally designed to improve the conductivity as well as enhance
the transfer of lithium ions while alleviating the volume stress of
Ge particles. The adsorption energy for the N-doped carbon obtained
by density function theory (DFT) calculation has verified that heteroatom
doping is helpful to considerable decrease the energy barrier of lithium
ions and a remarkable electrochemical performance of the Ge electrode
is achieved with this optimal designing. This facile easy-to-control
method can further be applied for electrodes of silicon, tin, phosphorus etc., which have the volume expansion issue.
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