A rechargeable aqueous manganese-ion battery based on intercalation chemistry

Abstract

Aqueous rechargeable metal batteries are intrinsically safe due to the utilization of low-cost and non-flammable water-based electrolyte solutions. However, the discharge voltages of these electrochemical energy storage systems are often limited, thus, resulting in unsatisfactory energy density. Therefore, it is of paramount importance to investigate alternative aqueous metal battery systems to improve the discharge voltage. Herein, we report reversible manganese-ion intercalation chemistry in an aqueous electrolyte solution, where inorganic and organic compounds act as positive electrode active materials for Mn2+ storage when coupled with a Mn/carbon composite negative electrode. In one case, the layered Mn0.18V2O5·nH2O inorganic cathode demonstrates fast and reversible Mn2+ insertion/extraction due to the large lattice spacing, thus, enabling adequate power performances and stable cycling behavior. In the other case, the tetrachloro-1,4-benzoquinone organic cathode molecules undergo enolization during charge/discharge processes, thus, contributing to achieving a stable cell discharge plateau at about 1.37 V. Interestingly, the low redox potential of the Mn/Mn2+ redox couple vs. standard hydrogen electrode (i.e., −1.19 V) enables the production of aqueous manganese metal cells with operational voltages higher than their zinc metal counterparts.

A Binary Hydrate‐Melt Electrolyte with Acetate‐Oriented Cross‐Linking Solvation Shells for Stable Zinc Anodes

“…In our case, PCHL was selected as the cathode material since it can provide reversible Zn 2+ storage and the introduction of electron‐withdrawing groups (–Cl) in quinones will improve their operating voltage. [ 42 ] In the CV curves of Zn||PCHL batteries, a pair of peaks is observed. It is ascribed to the reversible structural evolution between CO and C–O – groups in PCHL (Figure 5b).…”

Proton‐Assisted Aqueous Manganese‐Ion Battery Chemistry

“…The relationship between peak currents (i) and scan rates (v) is as follows [Eq. ( 4)]: [13] i ¼ av b (4) where b value could reflect the charge/discharge behavior. When b value approaches 0.5, the energy storage process is controlled by ionic diffusion.…”

“…However, in common aqueous metal (Al, Zn and Fe) battery systems, their discharge voltages are generally hindered due to the high redox potentials of these metals in mild electrolytes [3] . Compared with these common metal anodes, Mn metal has a lower redox potential (−1.19 V vs. standard hydrogen electrode), indicating that aqueous manganese‐ion batteries (MIBs) could provide higher discharge voltages [4] . Besides, Mn metal also has other distinctive merits, in terms of its high abundance, low cost, nontoxicity, and high theoretical capacity (7250 mAh cm −3 and 976 mAh g −1 , based on Mn/Mn 2+ transition), endowing MIBs with cost‐effectiveness and high energy density [5]…”

Proton‐Assisted Aqueous Manganese‐Ion Battery Chemistry

“…Recently, we designed aqueous rechargeable MIBs, where Mn 2+ ion could be reversibly intercalated/extracted in cathode materials [4] . However, these cathodes exhibit low capacities of less than 150 mAh g −1 since the divalent Mn 2+ ions possess a high charge density and a large solvated ionic radius.…”