A New Germanium-Based Anode Material with High Stability for Lithium-Ion Batteries

The anode materials based on conversion or alloying reaction typically show a large specific capacity and suitable working potential in lithium-ion batteries (LIBs). However, the large volume change and relatively low ionic/electronic conductivity lead to poor reversibility and cycle life. In the present work, we report a new lithium–niobium germanate LiNbGeO5 material as the anode material for LIBs in which the in situ formed intermediate LiNbO3 with high ionic/electronic conductivity was introduced during the discharge/charge process. In situ X-ray diffraction and synchrotron-based X-ray absorption near edge spectroscopy proved that conversion and alloying mechanisms were combined. In situ transmission electron microscopy shows a volume change of 30% in the lithiation of carbon-coated LiNbGeO5 (LNGO@C). As a consequence, the LNGO@C anode exhibits a reversible discharge specific capacity of 785 mAh g–1 with a corresponding initial Coulombic efficiency of 76%, and great cycling stability without capacity loss after 5000 cycles at 10 A g–1 (∼75 C). Paired with a LiNi0.5Mn1.5O4 cathode, a full cell was assembled and exhibited a maximum energy density of 368 Wh kg–1 and a power density of 618.7 W kg–1 with an average output voltage of 3.65 V. The work develops a new reaction mechanism for conversion-type materials for LIBs.