Self-assembled asymmetric membrane containing micron-size germanium for high capacity lithium ion batteries

Here we report the formation of novel asymmetric membrane electrode containing micron-size (∼5 μm) germanium powders through a self-assembly phase inversion method for high capacity lithium ion battery anode. 850 mA h g^-1 capacity (70%) can be retained at a current density of 600 mA g^-1 after 100 cycles with excellent rate performance. Such a high retention rate has rarely been seen for pristine micron-size germanium anodes. Scanning electron microscope studies reveal that germanium powders are uniformly embedded in a networking porous structure consisting of both nanopores and macropores. It is believed that such a unique porous structure can efficiently accommodate the ∼260% volume change during germanium alloying and de-alloying process, resulting in an enhanced cycling performance. These porous membrane electrodes can be manufactured in large scale using a roll-to-roll processing method.