Spine-like lithium-ion battery can be flexed and twisted

February 05, 2018 //By Julien Happich
Spine-like lithium-ion battery can be flexed and twisted
Trying to go beyond the traditional limitations of flexible batteries which are typically made ultrathin but then suffer from a low energy density, researchers from Columbia University have shaped a lithium-ion battery so as to mimic the flexibility of a vertebral spinal column.

While the Li-ion battery is initially built from a conventional anode/separator/cathode/ separator stack, the spine-inspired design involves cutting strips that extends from a common backbone, then wrapping those strips around their connecting backbone, forming thicker stacks flexibly connected to one another.

The result described in a paper titled "Bioinspired, Spine-Like, Flexible, Rechargeable Lithium-Ion Batteries with High Energy Density" published in the Advanced Materials journal shares some similarities with a spinal column. The thick stacks (with a high energy density) are akin to the vertebra in the spine, while the thin unwound backbone connecting all the stacks could be compared with the soft marrow of the spinal cord, the whole assembly remaining flexible.

The spine-like battery is made of multilayers of electrodes cut into extending strips that can then be wrapped around the connecting backbone. 1 – copper current collectors, 2 – Graphite anode, 3 and 6 – separators, 4 – lithium cobalt dioxide cathode, 5 – Aluminium current collectors, 7 – Polyethylene supporting film.

In their paper, the researchers describe a LiCoO2/graphite flexible cell, which, although non-optimized, boasted an energy density of 242Wh L−1 including the package, nearly on par (over 86%) with that of conventional prismatic cells, but with the added flexibility. Under various mechanical tests (flexing and twisting at 90º), the fabricated samples exhibited stable charge/discharge cycles, even under continuous dynamic load.

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