Tuning molecular planarity of donor-acceptor-based polymers to promote charge transfer for symmetric all-organic batteries

Charge separation and transport are regarded as the major challenges limiting the electrochemical activity of polymer electrodes. Herein, two novel linear donor-acceptor conjugated polymers (DA-CPs) with/without intramolecular noncovalent S···O interactions (INSOIs) are synthesized and investigated as bipolar electrode materials. It is revealed that the INSOIs enhance the self-planarity of the n-p fused DA polymer (PSFAQ) backbones, improving charge mobility and making it a promising electrode material. The as-synthesized PSFAQ polymer provides active pyrrolic nitrogen and carbonyl oxygen sites for reversible uptake of PF₆⁻ and Li⁺, respectively. A high discharge capacity of 153.7 mAh g⁻¹ at 0.2 A g⁻¹ (~95 % of the theoretical specific capacity) is achieved, along with excellent cycling stability, retaining 91 % of the capacity after 1000 cycles. It enables a symmetric all-organic battery to operate with an average voltage of 1.5 V and energy density of 102 Wh kg⁻¹, implying its potential applications. This work provides insights into rational design of organic electrode materials for next-generation batteries.