Rechargeable Magnesium Hybrid Ion Batteries

Rechargeable magnesium batteries have achieved widespread concern because of high volume energy density,low cost and good safety.However,the divalent magnesium ion shows a low intercalation level and low diffusion rate for most of the cathode materials due to the serious solvation and high charge density of Mg2+.To solve this problem,researchers have designed magnesium hybrid batteries,which contain a Li+(Na+)intercalation cathode material,a magnesium anode,and a hybrid Mg2+-Li+(Na+)electrolyte,aiming at combining the advantages of two kinds of batteries,building a stable battery system with high energy densities.In this paper,commercial lithium titanate(LTO)was used as the cathode material of hybrid Mg2+-Li batteries to study its electrochemical performance in Mg(BH4)2-based mixed electrolyte and APC-based mixed electrolyte.LTO showed higher specific capacities and better cycling performance in APC-based mixed electrolyte.Futhermore,both of the rate capability andcycling performance of the batteries were improved by adding graphene into LTO.The optimum ratio of LTO/GNS was determined as 8:2.Moreover,a hyrid Mg2+-Na+battery system NaFeFe(CN)6|0.3 M NaBH4+0.3 M Mg(BH4)2/TG:DME:PP14TFSI=1:1:4 |Mg was established.The addition of ionic liquid PP14TFSI effectively widened the electrochemical window of the electrolyte to 3.0 V.With hastelloy C-276 as the current collector,PVA was determined experimentally as the binder because of its high oxidation potential.Combined with NaFeFe(CN)6 as cathode material,a high voltage magnesium hybrid battery system has been designed.The battery voltage can reach up to 2.5 V,and own the first discharge specific capacity of 70 mAh/g at a current density of 0.05C However,the cycying ability of the battery needs to be further enhanced.