Redox Targeting-Based Aqueous Redox Flow Lithium Battery

Abstract

Redox flow batteries (RFBs) have been extensively investigated because of their great operation flexibility and scalability for large-scale energy storage, yet they suffer from low energy density and relatively high cost when price per kWh is considered. Here, we report an aqueous redox flow lithium battery (RFLB) system based on the concept of Nernstian potential-driven redox targeting reactions of battery materials to address the above issues. With [Fe­(CN)6]4–/[Fe­(CN)6]3– and S2–/S2 2– as the redox mediators in the catholyte and anolyte, the cell reveals an anodic and cathodic volumetric capacity up to 305 and 207 Ah L–1 when LiFePO4 and LiTi2(PO4)3 are respectively loaded into the cathodic and anodic tank as energy storage materials. These are 4–6 times as high as that of the vanadium redox flow battery (VRB). In addition, with water-based electrolytes, the system presents notably enhanced Li+ conductivity in the membrane and consequently much improved power performance as compared to its nonaqueous counterpart. We anticipate that this work would be a paradigm and pave the way for the deployment of redox targeting-based flow battery technology for large-scale applications.

Na3V2(PO4)3 as the Sole Solid Energy Storage Material for Redox Flow Sodium‐Ion Battery

“…[27,30] Benefit from the multivalence of vanadium, NVP exhibits the ability as both the cathode (117 mAh g −1 at 3.40 V vs Na) and anode (58.5 mAh g −1 at 1.63 V vs Na) to further simplify the system (see the CV curves in Figure 1B), the reaction of which corresponds to the valence change of two V 3+ to V 4+ and one V 3+ to V 2+ , respectively. [27,30] Benefit from the multivalence of vanadium, NVP exhibits the ability as both the cathode (117 mAh g −1 at 3.40 V vs Na) and anode (58.5 mAh g −1 at 1.63 V vs Na) to further simplify the system (see the CV curves in Figure 1B), the reaction of which corresponds to the valence change of two V 3+ to V 4+ and one V 3+ to V 2+ , respectively.…”

“…[27,30] Benefit from the multivalence of vanadium, NVP exhibits the ability as both the cathode (117 mAh g −1 at 3.40 V vs Na) and anode (58.5 mAh g −1 at 1.63 V vs Na) to further simplify the system (see the CV curves in Figure 1B), the reaction of which corresponds to the valence change of two V 3+ to V 4+ and one V 3+ to V 2+ , respectively. [27,34] For the cathodic side, 10-methylphenothiazine (MPTZ), with a robust aromatic core that can readily be oxidized to its radical cation state, is chosen to demonstrate the SMRT reaction with NVP (V 3+ ↔V 4+ ). Ideally, to realize SMRT reaction in both directions, E E RM O NVP O − should equal to 0.…”

“…Generally, different solid materials are required to build a full cell. [27,30] Benefit from the multivalence of vanadium, NVP exhibits the ability as both the cathode (117 mAh g −1 at 3.40 V vs Na) and anode (58.5 mAh g −1 at 1.63 V vs Na) to further simplify the system (see the CV curves in Figure 1B), the reaction of which corresponds to the valence change of two V 3+ to V 4+ and one V 3+ to V 2+ , respectively. [31,32] In terms of the reported crystal structure (ICSD #248 140 [33] ) of NVP, the above redox reactions correspond to a concentration of the V-redox sites of around 14.7 m for the cathodic side and 7.4 m for the anodic side (see the Supporting Information for details).…”

“…[26,27] The SMRT reaction, driven by Nernstianpotential difference, enables a much simplified electrolyte composition and improved voltage efficiency. [26,27] The SMRT reaction, driven by Nernstianpotential difference, enables a much simplified electrolyte composition and improved voltage efficiency.…”

“…Recently, a second-generation redox targeting-based flow battery system based on single molecule redox targeting (SMRT) reaction has been proposed to mitigate the aforementioned free energy loss. [26,27] The SMRT reaction, driven by Nernstianpotential difference, enables a much simplified electrolyte composition and improved voltage efficiency. The success of this concept relies on paring suitable redox mediator with the solid material, both of which should share identical potential.…”