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.

A new Al-ion battery based on an affordable and nontoxic liquid electrolyte made from molten AlCl/urea was assembled. As the cathode material, natural graphite shows two well-defined discharge voltage plateaus at about 1.9 and 1.5 V with a high specific capacity of 93 mA h g and excellent coulombic efficiency (>99%). The attractive capacity (about 78 mA h g) is retained even at a high current density of 1000 mA g. Moreover, no faster fading in capacity is observed after 500 cycles. This electrolyte could provide a new system for Al ion batteries, which can be used for large scale energy storage, owing to its cost advantages, high-rate capability and durability.

A novel cell configuration allows a Te nanowire positive electrode for delivering an ultrahigh discharge capacity in tellurium–aluminum batteries.

An ultrafast rechargeable multi-ions battery is presented, in which multi-ions can electrochemically intercalate into graphite layers, exhibiting a high reversible discharge capacity of ≈100 mAh g and a Coulombic efficiency of ≈99% over hundreds of cycles at a high current density. The results may open up a new paradigm for multi-ions-based electrochemical battery technologies and applications.