Perylenetetracarboxylic Diimide Composite Electrodes as Organic Cathode Materials for Rechargeable Sodium-Ion Batteries: A Joint Experimental and Theoretical Study.

The organic semiconductor 3,4,9,10-perylenetetracarboxylic diimide (PTCDI), a widely used industrial pigment, has been identified as a diffusion-less Na-ion storage material, allowing for exceptionally fast charging/discharging rates. The elimination of diffusion effects in electrochemical measurements enables the assessment of interaction energies from simple cyclic voltammetry experiments through the theoretical work of Laviron and Tokuda. In this work, the two N-substituted perylenes, N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic diimide (Me2PTCDI) and N,N'-diphenyl-3,4,9,10-perylenetetracarboxylic diimide (Ph2PTCDI), as well as the parent molecule 3,4,9,10-perylenetetracarboxylic diimide (H2PTCDI) are investigated as thin-film composite electrodes on carbon fibers for sodium-ion batteries. The composite electrodes are analyzed with Raman spectroscopy. Interaction parameters are extracted from cyclic voltammetry measurements. The stability and rate capability of the three PTCDI derivatives are examined through galvanostatic measurements in sodium-ion half-cell batteries and the influence of the interactions on those parameters is evaluated. In addition, self-consistent charge density function tight binding calculations of the different PTCDI systems interacting with graphite have been carried out. The results show that the binding motif displays notable deviations from an ideal ABA stacking, especially for the neutral state. In addition, data obtained for the electron-transfer integrals show that the difference in performance between different PTCDI thin-film batteries cannot be solely explained by the electron-transfer properties and other factors such as H-bonding have to be considered.

Perylenetetracarboxylic Diimide as Diffusion-Less Electrode Material for High-Rate Organic Na-Ion Batteries.

In this work 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) is investigated as electrode material for organic Na-ion batteries. Since PTCDI is a widely used industrial pigment, it may turn out to be a cost-effective, abundant, and environmentally benign cathode material for secondary Na-ion batteries. Among other carbonyl pigments, PTCDI is especially interesting due to its high Na-storage capacity in combination with remarkable high rate capabilities. The detailed analysis of cyclic voltammetry measurements reveals a diffusion-less mechanism, suggesting that Na-ion storage in the PTCDI film allows for exceptionally fast charging/discharging rates. This finding is further corroborated by galvanostatic sodiation measurements at high rates of 17 C (2.3 A g-1 ), showing that 57 % of the theoretically possible capacity of PTCDI, or 78 mAh g-1 , are attained in only 3.5 min charging time.