Most of the existing flexible lithium
ion batteries (LIBs) adopt the conventional cofacial cell configuration
where anode, separator, and cathode are sequentially stacked and so
have difficulty in the integration with emerging thin LIB applications,
such as smart cards and medical patches. In order to overcome this
shortcoming, herein, we report a coplanar cell structure in which
anodes and cathodes are interdigitatedly positioned on the same plane.
The coplanar electrode design brings advantages of enhanced bending
tolerance and capability of increasing the cell voltage by in series-connection
of multiple single-cells in addition to its suitability for the thickness
reduction. On the basis of these structural benefits, we develop a
coplanar flexible LIB that delivers 7.4 V with an entire cell thickness
below 0.5 mm while preserving stable electrochemical performance throughout
5000 (un)bending cycles (bending radius = 5 mm). Also, even the pouch
case serves as barriers between anodes and cathodes to prevent Li
dendrite growth and short-circuit formation while saving the thickness.
Furthermore, for convenient practical use wireless charging via inductive
electromagnetic energy transfer and solar cell integration is demonstrated