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

Abstract

The\nanode materials based on conversion or alloying reaction typically\nshow a large specific capacity and suitable working potential in lithium-ion\nbatteries (LIBs). However, the large volume change and relatively\nlow ionic/electronic conductivity lead to poor reversibility and cycle\nlife. In the present work, we report a new lithium–niobium\ngermanate LiNbGeO₅ material as the anode material for LIBs\nin which the in situ formed intermediate LiNbO₃ with high\nionic/electronic conductivity was introduced during the discharge/charge\nprocess. In situ X-ray diffraction and synchrotron-based X-ray absorption\nnear edge spectroscopy proved that conversion and alloying mechanisms\nwere combined. In situ transmission electron microscopy shows a volume\nchange of 30% in the lithiation of carbon-coated LiNbGeO₅ (LNGO@C). As a consequence, the LNGO@C anode exhibits a reversible\ndischarge specific capacity of 785 mAh g^–1 with\na corresponding initial Coulombic efficiency of 76%, and great cycling\nstability without capacity loss after 5000 cycles at 10 A g^–1 (∼75 C). Paired with a LiNi_0.5Mn_1.5O₄ cathode, a full cell was assembled and exhibited a\nmaximum energy density of 368 Wh kg^–1 and a power\ndensity of 618.7 W kg^–1 with an average output voltage\nof 3.65 V. The work develops a new reaction mechanism for conversion-type\nmaterials for LIBs.