|dc.description.abstract||Magnesium is an attractive anode material for secondary batteries because of low cost, low pollution, abundance, high energy density and high safety. However, there are two major obstacle in developing ideal magnesium ion batteries (MIBs). The first one is the formation of passivation layer on the surface due to the high chemical activity of magnesium. This result in restrictions on selecting suitable electrolytes. The other one is the strong coulombic interaction between Mg2+ and the intercalation host, which makes the ion diffusion sluggish, creating a barrier for the development of the cathode materials for MIBs.
In this study, MoS2 is chosen as the active material which Mg2+ ion cannot intercalate/deintercalate into the host structure in the presence of APC electrolyte. After adding the lithium salt (LiCl) in the APC electrolyte, the Mg//MoS2 cell starts storing energy and its electrochemical behavior is very similar to MoS2 in lithium-ion battery system. The electrochemical performances significantly increase with the increase of lithium-ion concentration. At low concentration (0.1 M), the cell delivers reversible capacity of 45 mAh/g (at 25 mA/g), whereas at high concentration (0.7 M) the cell delivers superior capacity of 166 mAh/g. Similarly, the cell with high concentration of Li salt showed excellent high rate retention of 64% at 1000 mA/g, whereas the cell with low concentration of Li salt showed poor retention of 31%. The ion mobility is believed to play important role in electrochemical performance.
After showing the remarkable benefits of dual-salts electrolyte, it is worth expanding this concept to other electrolytes, which have the nature of high safety and environmental friendliness. Therefore, we introduce Mg(BH4)2 salt and Glyme-based solvents as electrolyte. The present study indicate that substrates, temperature, concentration, solvent and the additive effects the reversibility of Magnesium deposition and dissolution. The study showed addition of LiBH4 and NaBH4 can improve the electrochemical performance of MIBs to a greater extent. To investigate the properties of different dual-salts Mg(BH4)2 (MBH) electrolyte, MoS2/Graphene composite is chosen as the active material. Among them, MBH-diglyme electrolyte delivered highest capacity, whereas MBH-triglyme and MBH-tetraglyme electrolytes showed slightly decreased capacity owing to their high viscosity. Despite the electrochemical performance between MBH and APC electrolyte are similar, MBH electrolyte is expected to replace APC electrolyte for practical application.
This study reports the possibility of Na/Mg hybrid battery based on intercalated cathode material for the first time. Compared to lithium-ion and Li/Mg hybrid battery, the high rate retention of Na/Mg hybrid battery is much higher (up to 76%) but the capacity at low current density needs to be further improved. These results provide insight for further development of Na/Mg hybrid battery.||en_US|