Germanium nanoparticles encapsulated in flexible carbon nanofibers as self-supported electrodes for high performance lithium-ion batteries.

Germanium is a promising high-capacity anode material for lithium ion batteries, but still suffers from poor cyclability due to its huge volume variation during the Li-Ge alloy/dealloy process. Here we rationally designed a flexible and self-supported electrode consisting of Ge nanoparticles encapsulated in carbon nanofibers (Ge-CNFs) by using a facile electrospinning technique as potential anodes for Li-ion batteries. The Ge-CNFs exhibit excellent electrochemical performance with a reversible specific capacity of ∼1420 mA h g(-1) after 100 cycles at 0.15 C with only 0.1% decay per cycle (the theoretical specific capacity of Ge is 1624 mA h g(-1)). When cycled at a high current of 1 C, they still deliver a reversible specific capacity of 829 mA h g(-1) after 250 cycles. The strategy and design are simple, effective, and versatile. This type of flexible electrodes is a promising solution for the development of flexible lithium-ion batteries with high power and energy densities.