High-performance germanium nanowire-based lithium-ion battery anodes extending over 1000 cycles through in situ formation of a continuous porous network.

Here we report the formation of high-performance and high-capacity lithium-ion battery anodes from high-density germanium nanowire arrays grown directly from the current collector. The anodes retain capacities of ∼ 900 mAh/g after 1100 cycles with excellent rate performance characteristics, even at very high discharge rates of 20-100C. We show by an ex situ high-resolution transmission electron microscopy and high-resolution scanning electron microscopy study that this performance can be attributed to the complete restructuring of the nanowires that occurs within the first 100 cycles to form a continuous porous network that is mechanically robust. Once formed, this restructured anode retains a remarkably stable capacity with a drop of only 0.01% per cycle thereafter. As this approach encompasses a low energy processing method where all the material is electrochemically active and binder free, the extended cycle life and rate performance characteristics demonstrated makes these anodes highly attractive for the most demanding lithium-ion applications such as long-range battery electric vehicles.