Towards Durable and High-Rate Rechargeable Aluminum Dual-ion Batteries via a Crosslinked Diphenylphenazine-based Conjugated Polymer Cathode.

Rechargeable aluminum battery (RAB) is expected to be a promising energy storage technique for grid-scale energy storage. However, the development of RABs is seriously plagued by the lack of suitable cathode materials. Herein, we report two p-type conjugated polymers of L-PBPz and C-PBPz with the same building blocks of diphenylphenazine but different linkage patterns of linear and crosslinked structures as the cathode materials for Al dual-ion batteries. Compared to the linear polymer skeleton in L-PBPz, the crosslinked structure endows C-PBPz with amorphous nature and low dihedral angles of the polymer chains, which severally contribute to the fast diffusion of AlCl4 - with large size and the electron transfer during the redox reaction of diphenylphenazine. As a result, C-PBPz delivers a much better rate performance than L-PBPz. The crosslinked structure also leads to a stable cyclability with over 80000 cycles for C-PBPz. Benefiting from the fast kinetics, meanwhile, the C-PBPz cathode could realize a high redox activity of 117 mAh g-1, corresponding to an areal capacity of 2.30 mAh cm-2, even under a high mass loading of 19.7 mg cm-2 and a low content of 10 wt% conductive agent. These results might boost the development of polymer cathodes for RABs.