Redox-active π-conjugated polymers
exhibit great
potential
in energy storage applications. However, how the location of redox-active
sites affects the electrochemistry and battery performance remains
elusive. In this study, three isomeric conjugated polymers with redox-active
azo units linked with thiophene were designed and synthesized. The
impact of the location of azo units (para vs meta linkage, main chain vs side chain) in the conjugated
polymers on the properties of electrochemistry and battery performance
were systematically studied. Experimental and theoretical studies
clearly demonstrate that “redox-pendant” and “meta junction” are two effective features to design
redox-conjugated polymers for high-performance energy storage. By
merging the two features, the polymer exhibits a high azo utilization
of close to 100% and displays the highest specific capacity of 215
mAh g–1 at 0.1 A g–1, along with
a long and flat charge/discharge plateau appearing at 1.7 V. Moreover,
the as-fabricated full battery using polymers with such a design as
the anode coupled with LiFePO4 or LiCoO2 as
the cathode delivers satisfactory discharge specific capacities of
110 and 95 mA h g–1 at 0.1 A g–1, along with output voltages of 1.9 and 2.3 V, respectively. The
practical application of the full battery to power an LED bulb was
also demonstrated. The present study provides useful insights into
the tuning of the structures for high-performance batteries.
Organic compounds are desirable alternatives for sustainable lithium-ion battery electrodes. Vat orange 3 (VO3, 4,10dibromoanthanthrone) is a highly cost-effective organic dye containing two conjugated carbonyl groups, which can reversibly accept two electrons. The skeleton also contains two bromine atoms, which allows easy incorporation of the anthanthrone unit into polymers through simple reactions. In this work, we report the preparation of organic cathodes derived from the low-cost VO3 dye for lithium-organic batteries (LOBs). The results show that polymeric VO3-based materials exhibit remarkably high cyclability and rate performance, because of their effective suppression of dissolution. In particular, the sulfide polymer poly(anthanthrone sulfide) (PATS) shows an initial large-current (0.2 A g À 1 ) discharge capacity of 133 mAh g À 1 at a potential near 2.4 V. The capacity reaches a maximum capacity of 147 mAh g À 1 after 24 cycles and is maintained at 132 mAh g À 1 after 300 cycles. Moreover, a full battery cell with the structure: PATS cathode j j graphite anode, further delivers an impressive electrochemical performance with an energy density up to 237 Wh kg À 1 along with an output voltage of 2.3 V. The present study initiates the use of VO3based organics, which show promising potential for future application in LOBs on a large scale.
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