Phendione–Transition‐Metal Complexes with Bipolar Redox Activity for Lithium Batteries

Abstract

1,10-Phenanthroline-5,6-dione (phendione)-based transitionmetal complexes are known for their use in pharmacological and catalysis applications. However, their application in electrochemicale nergy storageh as not been investigated thus far. Herein, the feasibility of employing phendione-transitionmetal complexes was investigated for electrochemical charge storageb yt aking advantage of the reversible redox activity of both carbonyl groups and transition metal center, contributing to augmented charges torage. Interestingly,t he chemistry of the counter ion in the studied complexes effectively tuned the solubility and improved the cycling stability. Although further studies are required to limit the solubility and active-species shuttle,t his study explores the bottlenecks of phendione-transition-metal complexes as electrode materials for solid-electrode-format batteries.Quinone derivatives constitute an importantc lass of naturally occurring compounds found in plants, fungi, and bacteria, with an important role as charge-transfer mediators in photosynthesis and the respiratory chain of chloroplasts and mitochondria (plastoquinones and ubiquinones). [1] The redox activity of quinones is also well-established in molecular electrochemistry, [2] with interesting characteristics manifestedb y multi-electron redox reactions and fast kinetics. Owing to these properties, quinone derivatives have attracted significant interesti nt he electrochemical charge-storage research community.T he first mention of the use of quinones as active material in batteriesc an be traced back to 1972, when Alt et al. [3] reported the use of simple benzoquinone as electrode material for lithium storage.T he cell provided an output voltage of 2.50 Vv s. Li + /Li for at heoretical capacity of 496 mAh g À1 with an energy density as high as 1kWh g À1 .S ince then, many different molecular designs have been proposed, [4] with the use of quinone derivatives in many forms to fit with the desired energy-storage device requirements. So far,q uinones have been used as dissolved or bulky solid active material, but also in different molecular architectures such as smallm olecules (mainly in oxidized but also in reduced state:m etal-reservoir cathode), polymers, or hybrid frameworks.Quinone-based smallm olecules are usually privileged owing to their highere nergy density and easier structuralf lexibility. Indeed, their redox potential can be effectively modified by incorporating electron-withdrawing or -donating groups. [5] Along the same principles, fusing with heteroaromatic rings [6] or switching the isomerism to foster electrostatic interaction [7] was also shown to cause ap ositives hift of the redox potential. Althougha ni ncreaseo ft he redox potential achieves higher energy-density metrics,c ycling stability is still am ajor concern when integratingq uinoned erivatives in lithium cells. Indeed, solubility remains at opic of concern when dealingw ith small molecules, requiring various approaches to be applied. For example,i ntegration of ionic g...

Through-Space Charge Modulation Overriding Substituent Effect: Rise of the Redox Potential at 3.35 V in a Lithium-Phenolate Stereoelectronic Isomer

“…For all these reasons, the organic battery field has experienced flourishing developments over the past decade. Many classes of redox chemistries have been explored, and the number of these investigations is continuously increasing as a result of the high versatility of organic chemistry. ,− Moreover, capacity and energy performance metrics are steadily increasing with values that verge on competitiveness. ,− However, despite all the progress achieved up to date, this emerging field still misses flagship chemistries that would once and for all put it on the map of EES systems by fulfilling the paramount criteria of conventional Li-ion battery technology: Li-ion positive electrode materials prepared in their lithiated (reduced) state stable to ambient air, so that these can be handled and processed in the same way as conventional Li-ion positive electrode materials.…”

An Electrically Conducting Li-Ion Metal–Organic Framework

“…The irreversible process observed with Mn-CPO-27 (Figure A) might have a more complex origin, with Mn 3+ species disproportionation , and MOF degradation (black path in Scheme A, supported by experimental analysis in Figure A). The incorporation of Mn 2+ in Li 2 - Mn -DOBDC induces a significant increase in redox potential by nearly 800 mV with respect to Li 4 -DOBDC, ,− attributed to the high ionic potential and polarizing power of Mn 2+ . ,, Upon second Mn 2+ (or Mg 2+ ) incorporation, further redox potential increase is expected, and the Mn 2+/3+ mediation might not be possible (Scheme B, the case for Mn 2 -DOBDC). This also corroborates the use of strong oxidizing agents applied for Fe-CPO-27 (Fe 2 -DOBDC) and Mn-CPO-27 .…”

“…The incorporation of Mn 2+ in Li 2 -Mn-DOBDC induces a significant increase in redox potential by nearly 800 mV with respect to Li 4 -DOBDC, 36,40−43 attributed to the high ionic potential and polarizing power of Mn 2+ . 18,36,62 Upon second Mn 2+ (or Mg 2+ ) incorporation, further redox potential increase is expected, and the Mn 2+/3+ mediation might not be possible (Scheme 2B, the case for Mn 2 -DOBDC). This also corroborates the use of strong oxidizing agents applied for Fe-CPO-27 (Fe 2 -DOBDC) 32 and Mn-CPO-27.…”

“…Over the past years, hybrid metal–organic frameworks (MOFs) have flourished as electrode materials for next-generation electrochemical energy storage devices. − Thanks to their superior functionality, unique morphology, design flexibility, and structural integrity, MOFs are capable of fitting into the required parameters for an efficient electrode material. At the material level, high gravimetric energy could be achieved thanks to the hybrid nature, allowing the charge storage from both metal cations and organic ligands, whereas cycling stability and facile ion transport are inherent to the polymer-like robust network and the porous structure, respectively. Additionally, MOFs with intrinsic electronic conductivity can also be designed, ,, resulting in enhanced power density, and allow electrode fabrication with a minimum amount of conductive carbon additives …”

Recent progress in metal–organic framework/graphene-derived materials for energy storage and conversion: design, preparation, and application

“…Owing to the easily tunable chemical compositions of the organic linkers and metal nodes (metal ions/clusters), more than 20 000 different MOFs have been designed and synthesized in the past two decades. Their unique structures and properties make them potential candidates in many applications, such as environmental protection, 1-3 drug delivery, 4,5 gas adsorption and separation, [6][7][8][9] sensors, 10-12 catalysis, [13][14][15] electrochemical energy storage, [16][17][18][19][20][21] etc. Nevertheless, it should be noted that most pristine MOFs still suffer from the intrinsic drawbacks of low structural stability and poor electrical conductivity, which hinder their practical applications, especially in the eld of electrochemical energy storage and conversion.…”