  We have demonstrated a fiber lithium ion battery (LIB) fabricated by
co-twisting a LiFePO4 composite-coated copper wire (cathode) together with an
aluminum wire (anode). An all-solid LiPF6 composite layer functioning both as
the electrolyte and battery separator is deposited onto the two electrode wires
before twisting. To characterize the electrochemical properties of the battery,
charge-discharge tests with different C-rates are performed. The fiber LIB has
an open-circuit voltage of ~3.4 V, and the typical specific capacity is found
to be ~87 mAhg-1 at 0.5 C charge-discharge rate. Besides, the proposed battery
has a Coulombic efficiency of more than 82% throughout all the charge-discharge
tests. We also find that bending of the fiber battery has insignificant
influence on the battery electrochemical properties.
