Development of printable, flexible nickel‐iron batteries based on composite electrodes

We present flexible nickel‐iron batteries with printable multiwalled carbon nanotube (MWCNTs) based electrodes. All the metal composites are prepared via a single‐step precipitation reaction to synthesize metal hydroxides on the MWCNTs. High loading of the conductive materials enhances reactivity. Compared with Ni(OH)2‐CNT, β‐NiOOH increases output energy due to higher discharge voltage in flexible cells. Cyclic voltammogram shows that the iron electrode underwent a two‐step redox reaction among Fe, Fe(II), and Fe(III). The flexible Ni‐Fe battery has higher charge‐discharge efficiency when using 6 M KOH electrolyte saturated with LiOH, and with 5% Co(NO3)2 added to anode. The anode exhibits a specific capacity of more than 300 mAh g−1. All the components and the flexible cells themselves show good performance under bending conditions and the fabrication methods are also suitable for scale‐up via printing techniques.