In recent years, a rechargeable aluminum-ion battery based on ionic liquid electrolyte is being extensively explored due to three-electron electrochemical reactions, rich resources, and safety. Herein, a rechargeable Al-ion battery composed of MoS microsphere cathode, aluminum anode, and ionic liquid electrolyte has been fabricated for the first time. It can be found that Al intercalates into the MoS during the electrochemical reaction, whereas the storage mechanisms of the electrode material interface and internal are quite different. This result is confirmed by ex situ X-ray photoelectron spectroscopy and X-ray diffraction etching techniques. Meanwhile, this aluminum-ion battery also shows excellent electrochemical performance, such as a discharge specific capacity of 253.6 mA h g at a current density of 20 mA g and a discharge capacity of 66.7 mA h g at a current density of 40 mA g after 100 cycles. This will lay a solid foundation for the commercialization of aluminum-ion batteries.

Herein, a novel graphite-graphite dual ion battery (GGDIB) based on a AlCl /1-ethyl-3-methylimidazole Cl ([EMIm]Cl) room temperature ionic liquid electrolyte, using conductive graphite paper as cathode and anode material is developed. The working principle of the GGDIB is investigated, that is, metallic aluminum is deposited/dissolved on the surface of the anode, and chloroaluminate ions are intercalated/deintercalated in the cathode material. The self-discharge phenomenon and pseudocapacitive behavior of the GGDIB are also analyzed. The GGDIB shows excellent rate performance and cycle performance due to the high ionic conductivity of ionic liquids. The initial discharge capacity is 76.5 mA h g at a current density of 200 mA g over a voltage window of 0.1-2.3 V, and the capacity remains at 62.3 mA h g after 1000 cycles with a corresponding capacity retention of 98.42% at a current density of 500 mA g . With the merits of environmental friendliness and low cost, the GGDIB has a great advantage in the future of energy storage application.

The modification of lithium-rich layered cathode materials has been widely studied by surface coating, doping and chemical treatment for lithium-ion batteries.

Salphen-type nickel Schiff bases Ni(salphen), Ni(CH 3 -salphen), and Ni(CH 3 O-salphen) are synthesized and electropolymerized on stable ITO electrode, respectively. The morphologies of the three polymer electrodes were evaluated by field emission scanning electron microscopy (FESEM). X-ray photoelectron spectroscopy (XPS) measurements were carried out to shed light on the polymerization mode and energy storage mechanism. Meanwhile, kinetic analysis of the redox reactions was used to verify the pseudocapacitive mechanisms of charge storage. The result signals that the polymerization mode and the mechanism of energy storage are related to the reversible conversion of the azomethine nitrogen group (−NCH−) in the six-membered ring of Schiff base instead of the Ni 2+ /Ni 3+ process. Meanwhile, the azomethine nitrogen group was found to be directly affected by the addition of the electron-donating group methyl and methoxy so that additional peaks of the CV curve are generated, making polyNi(CH 3 -salphen) and polyNi(CH 3 O-salphen) have higher doping level, charge transfer ability, and better pseudocapacitive energy storage property than the pristine polyNi(salphen) polymer. At the current density of 0.05 mA cm −2 , the specific capacity of the polyNi(CH 3 Osalphen) electrode was about 216 F g −1 , higher than the specific capacity of 85 F g −1 for polyNi(salphen) and 133 F g −1 for polyNi(CH 3 -salphen). In the meantime, the conductivity of polyNi(CH 3 O-salphen) is 108.7 S cm −1 higher than that of the other two polymers. Therefore, the addition of the stronger methoxy group for electron-donating substituents makes polyNi(CH 3 Osalphen) have more excellent electrochemical kinetics and pseudocapacitive characteristics.

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