  A flexible, light weight and high conductivity current collector is the key
element that enables fabrication of high performance flexible lithium ion
battery. Here we report a thin, light weight and flexible lithium ion battery
that uses graphite paper enhanced with a nano-sized metallic layers as the
current collector, LiFePO4 and Li4Ti5O12 as the cathode and anode materials,
and PE membrane soaked in LiPF6 as a separator. Using thin and flexible
graphite paper as a substrate for the current collector instead of a rigid and
heavy metal foil enables us to demonstrate a very thin Lithium-Ion Battery into
ultra-thin (total thickness including encapsulation layers of less than 250
{\mu}m) that is also light weight and highly flexible.
