Aluminum is a naturally abundant, trivalent charge carrier with high theoretical specific capacity and volumetric energy density, rendering aluminum-ion batteries a technology of choice for future large-scale energy storage. However, the frequent collapse of the host structure of the cathode materials and sluggish kinetics of aluminum ion diffusion have thus far hampered the realization of practical battery devices. Here, we synthesize AlxMnO2·nH2O by an in-situ electrochemical transformation reaction to be used as a cathode material for an aluminum-ion battery with a configuration of Al/Al(OTF)3-H2O/AlxMnO2·nH2O. This cell is not only based on aqueous electrolyte chemistry but also delivers a high specific capacity of 467 mAh g−1 and a record high energy density of 481 Wh kg−1. The high safety of aqueous electrolyte, facile cell assembly and the low cost of materials suggest that this aqueous aluminum-ion battery holds promise for large-scale energy applications.

No abstract

Anion-effects are embodied in: (1) halogen anions resulting from different halogenated imidazole salt species, which is the critical factor for electrochemical windows; (2) aluminum chloride anions resulting from different AlCl3/imidazole salt mole ratios, which is the determinant of electrochemical activities.

As a promising post-lithium battery, rechargeable aluminum battery has the potential to achieve a three-electron reaction with fully use of metal aluminum. Alternative electrolytes are strongly needed for further development of rechargeable aluminum batteries, since typical AlCl3-contained imidazole-based ionic liquids are moisture sensitive, corrosive, and with low oxidation voltage. In this letter, a kind of non-corrosive and water-stable ionic liquid obtained by mixing 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM]OTF) with the corresponding aluminum salt (Al(OTF)3) is studied. This ionic liquid electrolyte has a high oxidation voltage (3.25V vs Al3+/Al) and high ionic conductivity, and a good electrochemical performance is also achieved. A new strategy, which first use corrosive AlCl3-based electrolyte to construct a suitable passageway on the Al anode for Al3+, and then use non-corrosive Al(OTF)3-based electrolyte to get stable Al/electrolyte interface, is put forward.

Understanding the properties of polysulfide intermediates is crucial for explaining and optimizing metal−sulfur batteries. Unlike the unstable or inseparable low-order polysulfide intermediates in Li−S systems, the K−S phase diagram displays a series of stable phases of K 2 S n (n = 1, 2, 3, 4, 5, 6), which provides the accessibility of an individual polysulfide to investigate the mechanism using pure-phase polysulfides. Herein, we synthesized two key intermediate polysulfides, K 2 S 2 and K 2 S 3 , and probed their electrochemical pathways. When K 2 S 2 and K 2 S 3 are coated directly on a current collector, both species can be further reduced. However, when K 2 S 2 and K 2 S 3 are electrically isolated from the current collector, no further reduction is observed, showing the reduction occurs through a solid-state conversion pathway. Interestingly, K 2 S 2 and K 2 S 3 can be charged even when they are electrically isolated from the current collector, proving solution-mediated charging pathways. Only K 2 S is the "dead" sulfur species that cannot be charged.