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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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