1 research outputs found
Mixed Ionic–Electronic Conduction Increases the Rate Capability of Polynaphthalenediimide for Energy Storage
Conjugated polymers offer a number of unique and useful
properties
for use as battery electrodes, and recent work has reported that conjugated
polymers can exhibit excellent rate performance due to electron transport
along the polymer backbone. However, the rate performance depends
on both ion and electron conduction, and strategies for increasing
the intrinsic ionic conductivities of conjugated polymer electrodes
are lacking. Here, we investigate a series of conjugated polynapthalene
dicarboximide (PNDI) polymers containing oligo(ethylene glycol) (EG)
side chains that enhance ion transport. We produced PNDI polymers
with varying contents of alkylated and glycolated side chains and
investigated the impact on rate performance, specific capacity, cycling
stability, and electrochemical properties through a series of charge–discharge,
electrochemical impedance spectroscopy, and cyclic voltammetry measurements.
We find that the incorporation of glycolated side chains results in
electrode materials with exceptional rate performance (up to 500C,
14.4 s per cycle) in thick (up to 20 μm), high-polymer-content
(up to 80 wt %) electrodes. Incorporation of EG side chains enhances
both ionic and electronic conductivities, and we found that PNDI polymers
with at least 90% of NDI units containing EG side chains functioned
as carbon-free polymer electrodes. This work demonstrates that polymers
with mixed ionic and electronic conduction are excellent candidates
for battery electrodes with good cycling stability and capable of
ultra-fast rate performance