Perylenedianhydride-Based Polyimides as Organic Cathodes for Rechargeable Lithium and Sodium Batteries

Organic carbonyl molecules have recently been investigated as redox-active electrode materials in rechargeable organic batteries (ROBs), and although redox-active polymers offer high specific energy density and tunable redox potential windows, their undesirable dissolution into aprotic electrolytes during charge/discharge cycling and their poor electronic conductivity compromised their utilization in ROBs. To overcome these challenges, we synthesized, for the first time, two 3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA)-based polyimides, namely, perylenediimide-benzidine (PDI-Bz) and perylenediimide-urea (PDI-Ur), and utilized them as organic cathode materials for lithium-ion batteries and sodium-ion batteries. These cathode materials are synthesized through imidization of a non-bay-substituted PTCDA unit by using bifunctional amine compounds (i.e., benzidine and carbonyl diamine (urea)) via a simple one-step reaction. Our organic metal-ion batteries employing PDI-Bz demonstrate a high discharge capacity of 120 mAh/g (with a reversible capacity of ∼54 mAh/g) vs Li⁺/Li and the second discharge capacity of 111 mAh/g (∼74 mAh/g) vs Na⁺/Na with two discharge voltage plateaus in the range of 1.9-2.4 V. The cells retained a capacity retention of 46% vs Li⁺/Li and 55.2% vs Na⁺/Na over 50 cycles. PDI-Ur exhibits higher lithiation capacity of ∼119 mAh/g at the 14th cycling (increased discharge capacity of ∼118 mAh/g at the 25th cycling). In SIBs, PDI-Ur shows an initial discharge capacity of ∼119 mAh/g with a single discharge voltage plateau around 1.9 V vs Na⁺/Na and the capacity retention of ∼78.7% (∼93 mAh/g) over 50 cycles, both of which are suggesting a potential feasibility of these PTCDA-based polyimides as promising organic cathode materials for high-capacity metal-ions batteries.