Sn modified nanoporous Ge for improved lithium storage performance.

Although high-capacity germanium (Ge) has been regarded as the promising anode material for lithium ion batteries (LIBs), its actual performance is far from expectation because of low electrical conductivity and rapid capacity decay during cycling. In this work, Sn modified nanoporous Ge materials with different Ge/Sn atomic ratios in precursors were synthesized by a simple melt-spinning and dealloying strategy. As the anodes of LIBs, Sn modified nanoporous Ge materials display improved cycling stability compared with Sn-free nanoporous Ge, revealing a potential role of Sn in improving electrochemical properties of Ge-based anodes. In particular, Sn modified nanoporous Ge with Ge/Sn atomic ratio of 3:1 presents the best Li storage performance among measured electrodes, delivering a reversible capacity of 974 mA h g-1 after 500 cycles at 200 mA g-1. It is found that the introduction of appropriate amount of Sn can not only regulate the nanoporous structure of Ge to better alleviate volume expansion, but also improves the conductivity and activity of the electrode material. This improvement is demonstrated by density functional theory calculations. The study uncovers a route to improve Li storage properties by rationally modify Ge-based anodes with Sn, which may facilitate the development of high-performance LIBs.