High-Density and Robust Charge Storage with Poly(anthraquinone-substituted
norbornene) for Organic Electrode-Active Materials in Polymer–Air
Secondary Batteries
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Abstract
An excellent functional group tolerance
of ruthenium complex catalysts
for olefin metathesis gave rise to ring-opening polymerization of
norbornene functionalized with redox-active anthraquinone (AQ) pendants,
yielding a high-molecular-weight and processable polynorbornene with
large redox capacity. A thin layer of the polymer cast on current
collectors showed reversible redox reaction at −0.85 V vs Ag/AgCl
when immersed in basic aqueous electrolyte solutions. Good cycle performance
was observed with a capacity comparable to the formula weight-based
theoretical density of 212 mAh/g, which was the largest among those
for the previously reported redox-active polynorbornenes. This suggested
that all of the AQ units in the layer were redox-active, that electroneutralization
was accomplished by successive compensation of counterions throughout
the layer, and that the mechanical strength of the polymer layer prevented
dissolution or exfoliation from the current collector surface. A robust
polymer–air secondary battery with the high capacity was fabricated
by using the polymer layer as the anode-active material. The battery
showed a discharge voltage of 0.68 V and long life of over 300 cycles
of charging/discharging, maintaining the moderate energy density of
143 mWh/g