Effects of Conjugated Structure on the Magnesium Storage Performance of Dianhydrides

Abstract

Inorganic cathodes of rechargeable Mg batteries suffer from limited selections, while organic materials provide more options. Herein, three conjugated dianhydrides, pyromellitic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride and 3,4,9,10-perylenetetracarboxylic dianhydride are comparatively investigated to elucidate the effects of conjugated structure on the Mg 2 + storage performances. It is observed that the reversible Mg 2 + storage capacity is more dependent on the conjugated structure than carbonyl numbers. Ex-situ mechanism study illustrates that the extended conjugated structure delocalizes the electron density, hence enhancing carbonyl enolization and increasing the Mg 2 + storage capacity. Furthermore, the largely conjugated structure buffers the charge density change during repeated magnesiation/demagnesiation resulting in better cyclability. Prominently, 3,4,9,10-perylenetetracarboxylic dianhydride shows a high Mg 2 + storage capacity (160 mAh g À 1 ) and a good cycling stability (80 % capacity retention after 100 cycles) with the largest conjugated structure. This work provides a low-cost cathode for rechargeable Mg batteries that can be utilized for designing high-performance organic Mg battery cathodes.

Organic-conjugated polyanthraquinonylimide cathodes for rechargeable magnesium batteries

“…P26 showed a higher capacity than N14 and N26 despite the larger unit formula weight and lower theoretical capacity. This is consistent with our previous report 39 stating that the larger conjugated structure of PTCDA effectively delocalizes the electron density and enhances the carbonyl enolization.…”

Recent Progress on Organic Electrode Materials for Multivalent (Zn, Al, Mg, Ca) Secondary Batteries

“…To further investigate the effect of the conjugated structures of organic compounds on the performance of magnesium batteries, three different degrees of conjugated acid anhydrides were selected. [65] Surprisingly, 3,4,9,10-perylenetetracarboxylic dianhydride with larger conjugated facets displayed higher Mg 2 + storage capacity and better cycling stability in practice, which was the opposite of the theoretical capacity (Figure 10b). Ex-situ X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the large conjugated structure of PTCDA enhanced the carbonyl enolization and played a more important role in the reversible storage capacity of Mg 2 + .…”

“…To further investigate the effect of the conjugated structures of organic compounds on the performance of magnesium batteries, three different degrees of conjugated acid anhydrides were selected [65] . Surprisingly, 3,4,9,10‐perylenetetracarboxylic dianhydride with larger conjugated facets displayed higher Mg 2+ storage capacity and better cycling stability in practice, which was the opposite of the theoretical capacity (Figure 10b).…”

Storing Mg Ions in Polymers: A Perspective

“…Studies have shown that the expansion of conjugated structure would be beneficial for the charge transport and hence the rate capability (Figure 6a). [56][57][58] The molecular design to improve conductivity will be further discussed below.…”