Aqueous Energy Storage Device Based on LiMn₂O₄ (Spinel) Positive Electrode and Anthraquinone‐Modified Carbon‐Negative Electrode

Abstract

This article describes the design and tests of aqueous hybrid energy‐storage devices based on activated carbon‐negative electrode and LiMn2O4 (spinel) positive electrode. For this study, activated carbons from two different sources are selected and are further improved by grafting with electroactive anthraquinone molecules. The electrolyte solution is aqueous 1 m Li2SO4 with pH = 7.5. The performances of balanced hybrid devices are characterized by cyclic voltammetry and galvanostatic measurements. It is possible to charge the hybrid cells up to 1.5 V and cycle them with current densities of 40 mA g−1 (mass of positive electrode). These fully balanced cells can achieve thousands of cycles with capacities up to 75 mAh g−1. Preliminary calculations predict that such devices may reach energy density approaching 35 Wh kg−1 (total mass of active materials in both electrodes). Herein, a model of “rocking chair”‐type hybrid systems, comprising carbon anodes with amplified capacity, in which the electrolyte solution can serve as a thin layer of ion carrier, is presented. It is believed that the concept may be extended to the more important Na ions hybrid cells. Such systems may be suitable for load‐leveling applications and large stationary energy‐storage devices operating with very safe aqueous electrolyte solutions.

High-Performance Lithium-Ion Hybrid Supercapacitors Based on Lithium Salt/Imidazolium Ionic Liquid Electrolytes and Ni-Doped LiMn2O4 Cathode Materials

“…These results should be highlighted when compared to other Li-HSCs based on LiMn 2 O 4 , ,,, (Figure c). Recently, Li et al reported a cell based on LiMn 2 O 4 nanorods as the cathode, activated carbon (AC) as the anode, and 1 M lithium hexafluorophosphate (LiPF 6 ) in a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) as the electrolyte .…”

“…The aqueous cell containing this mixed oxide operates at 1.6 V and is capable of reaching 20 W h kg –1 at 264 W kg –1 . Superior performance in aqueous media was reported by Hanna et al using LiMn 2 O 4 as a positive electrode and activated carbon as the negative electrode containing electroactive anthraquinone molecules. This cell operates at 1.5 V in 1 M Li 2 SO 4 (pH = 7.5) and is capable of reaching an energy density of 30–35 W h kg –1 and a power density of 25–33 W kg –1 .…”

“…Conventional battery materials commonly fail after 1200 charge/discharge cycles. Different hybrid devices published in the literature are evaluated around 1000 cycles. ,,, In this work, the cells were subjected to 1500 galvanostatic charge/discharge cycles at 400 mA g –1 and those based on doped spinels clearly showed the best stabilities. The energy density retentions for Li-HSCs containing LiMn 2 O 4 , LiNi 0.01 Mn 1.99 O 4 , and LiNi 0.03 Mn 1.97 O 4 correspond to 48, 79, and 85%, respectively.…”

“…Different hybrid devices published in the literature are evaluated around 1000 cycles. 8,23,63,64 In this work, the cells were subjected to 1500 galvanostatic charge/discharge cycles at 400 mA g −1 and those based on doped spinels clearly…”

Hybrid electrochemical capacitors in aqueous electrolytes: Challenges and prospects

“…Composite of anthraquinone with reduced graphene oxide and carbons with quinone functionalities have demonstrated enhanced capacitance as electrode materials [59e61]. Hybrid device based on LiMn 2 O 4 as a positive electrode and anthraquinone-modified carbon as a negative electrode in 1 mol L À1 Li 2 SO 4 is a good strategy to enhance energy and power parameters [62], and determining correct amount of anthraquinone loading on carbon appears to be key for achieving optimized performance [63]. Redox activity of PPD in aqueous KOH greatly enhances the delivered capacitance of the hybrid cell [26], and high self-discharge in PPD-based cells could be solved by its covalent bonding to carbon surface [64].…”