Structural Isomers: Small Change with Big Difference in Anion Storage

A donor-acceptor (D-A) conjugated polymer for fast storage of anions

Organic electrode materials have attracted a lot interest in batteries in recent years. However, most of them still suffer from low performance such as low electrode potential, slow reaction kinetics, and short cycle life. In this work, we report a strategy of fabricating donor-acceptor (D-A) conjugated polymers for facilitating the charge transfer and therefore accelerating the reaction kinetics by using the copolymer (p-TTPZ) of dihydrophenazine (PZ) and thianthrene (TT) as a proof-of-concept. The D-A conjugated polymer as p-type cathode could store anions and exhibited high discharge voltages (two plateaus at 3.82 V, 3.16 V respectively), a reversible capacity of 152 mAh g-1 at 0.1 A g-1 , excellent rate performance with a high capacity of 124.2 mAh g-1 at 10 A g-1 (≈50 C) and remarkable cyclability. The performance, especially the rate capability was much higher than that of its counterpart homopolymers without D-A structure. As a result, the p-TTPZ//graphite full cells showed a high output voltage (3.26 V), a discharge specific capacity of 139.1 mAh g-1 at 0.05 A g-1 and excellent rate performance. This work provides a novel strategy for developing high performance organic electrode materials through molecular design and will pave a way towards high energy density organic batteries.