LAUSR

The current insertion anode chemistries are approaching their capacity limits, thus alloying reaction anode materials with high theoretical specific capacity are investigated as potential alternative for lithium ions batteries. However, their performance is far from being satisfactory because of large volume change and severe capacity decay occurring upon lithium alloying and de-alloying processes. To address these problems, we propose and demonstrate a versatile strategy making use of the electrodic reaction confinement via the synthesis of ultra-small Ge nanoparticles (10 nm) uniformly confined in a matrix of larger spherical carbon particles (Ge⊂C spheres). This architecture provides free pathways for electron transport and Li+ diffusion, allowing for the alloying reaction of the Ge nanoparticles. The thickness change of electrodes containing such a material, monitored by in-situ electrochemical dilatometer, is rather limited and reversible, confirming the excellent mechanical integrity of the confined electrode. As a result, these electrodes exhibit high reversible capacity (1310 mAh g-1 at 0.1C) and very impressive cycling ability (92% after 1000 cycles at 2C). A prototype device employing such an alloying electrode material in combination with LiNi0.8Mn0.1Co0.1O2 offers an estimated practical energy density of 250 Wh kg-1.