A new kind of Al-ion battery with carbon paper as the cathode, high-purity Al foil as the anode and ionic liquid as the electrolyte is proposed in this work. The significance of the presented battery is going to be an extremely high average voltage plateau of ca. 1.8 V vs. Al(3+)/Al.

may offer noteworthy cost saving and safety improvement compared to its counterparts. Additionally, aluminum has a very negative redox potential (≈1.676 V vs standard hydrogen electrode (SHE)) and a small electrochemical equivalent (0.336 g Ah −1 ), which make it one of the ideal elements for rechargeable batteries. However, the previous efforts have encountered numerous issues over the past few years, such as the cathode material disintegration, [12,14] low discharge voltage, [8] capacitive behavior without discharge voltage plateaus. [15,16] There is no doubt that some of recent works have explored a series of new electrode materials, such as V 2 O 5 , [8] TiO 2 , [9] fluorinated natural graphite, [15] polymers, [16] and Prussian blue analogues (PBAs). [12] The previous work has revealed that Al ions can insert into TiO 2 nanotube arrays and PBAs in aqueous solution. But the discharge capacity of these materials is too low. Very recently, the works from our group at University of Science and Technology Beijing (USTB) and Dai and co-workers at Stanford University found that rechargeable aluminum-ion batteries using graphite materials cathode had a very high charge/discharge voltage plateau around 2.0 V versus Al 3+ /Al. [12,17] The charge/discharge reaction happens through the intercalation and deintercalation of AlCl 4 − into interlayer space of graphite materials.Herein, we report for the first time, the design of Ni 3 S 2 / graphene microflakes composite as a novel cathode material for rechargeable aluminum-ion batteries. The battery runs through the electrochemical deposition and dissolution of aluminum at the anode, and the intercalation and deintercalation of Al 3+ cations in the cathode. The unique advantage of Ni 3 S 2 /graphene microflakes composite lies in the low charge-transfer impedance, which represents a high rate of intercalation and deintercalation of ions. Additionally, we find that there is a dissociation process of Al 2 Cl 7 − during charge process, and the active material transforms from monocrystal to polycrystal at the same time. The battery exhibits a high discharge voltage plateau (≈1.0 V vs Al/AlCl 4 − ), a discharge capacity of over 60 mA h g −1 , a high coulombic efficiency of about 99% , and a high rate capability, suggesting that it is a favorable cathode material for high-performance aluminumion batteries.

On the basis of low-cost, rich resources, and safety performance, aluminum-ion batteries have been regarded as a promising candidate for next-generation energy storage batteries in large-scale energy applications. A rechargeable aluminum-ion battery has been fabricated based on a 3D hierarchical copper sulfide (CuS) microsphere composed of nanoflakes as cathode material and room-temperature ionic liquid containing AlCl and 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) as electrolyte. The aluminum-ion battery with a microsphere electrode exhibits a high average discharge voltage of ∼1.0 V vs Al/AlCl, reversible specific capacity of about 90 mA h g at 20 mA g, and good cyclability of nearly 100% Coulombic efficiency after 100 cycles. Such remarkable electrochemical performance is attributed to the well-defined nanostructure of the cathode material facilitating the electron and ion transfer, especially for chloroaluminate ions with large size, which is desirable for aluminum-ion battery applications.

Due to their small footprint and flexible siting, rechargeable batteries are attractive for energy storage systems. A super-valent battery based on aluminium ion intercalation and deintercalation is proposed in this work with VO2 as cathode and high-purity Al foil as anode. First-principles calculations are also employed to theoretically investigate the crystal structure change and the insertion-extraction mechanism of Al ions in the super-valent battery. Long cycle life, low cost and good capacity are achieved in this battery system. At the current density of 50 mAg−1, the discharge capacity remains 116 mAhg−1 after 100 cycles. Comparing to monovalent Li-ion battery, the super-valent battery has the potential to deliver more charges and gain higher specific capacity.

Rechargeable aluminum-ion batteries (AIBs) are regarded as promising candidates for post-lithium energy storage systems (ESSs). For addressing the critical issues in the current liquid AIB systems, here a flexible solid-state AIB is established using a gel-polymer electrolyte for achieving robust electrodeelectrolyte interfaces. Different from utilization of solid-state systems for alleviating the safety issues and enhancing energy density in lithium-ion batteries, employment of polymeric electrolytes mainly focuses on addressing the essential problems in the liquid AIBs, including unstable internal interfaces induced by mechanical deformation and production of gases as well as unfavorable separators. Particularly, such gel electrolyte enables the solid-state AIBs to present an ultra-fast charge capability within 10 s at current density of 600 mA g −1 . Meanwhile, an impressive specific capacity ≈120 mA h g −1 is obtained at current density of 60 mA g −1 , approaching the theoretical limit of graphite-based AIBs. In addition to the well-retained electrochemical performance below the ice point, the solid-state AIBs also hold great stability and safety under various critical conditions. The results suggest that such new prototype of solid-state AIBs with robust electrode-electrolyte interfaces promises a novel strategy for fabricating stable and safe flexible ESSs.