The Research On Several Critical Issues Of Non-aqueous Lithium-air Batteries

Lithium-air batteries as “beyond Li-on” battery technology is sufficient to meet the energy requirements for electric vehicles. If exclude cathode oxidant, O2that comes from the surrounding environment, the theoretical specific energy of lithium-air battery can achieve11140Wh/kg. Although the lithium-air battery is a very attractive system, there are still many challenges that need to be overcome before practical applications, such as the decomposition of electrolyte in the oxygen-rich environment, the blocking of pores within air electrodes by the insoluble discharge product, slow oxygen reduction reaction and oxygen evolution reaction on the air electrode, poor discharge-charge cycling performance and so on.First, air electrodes were prepared with different carbon materials to study the relationship between morphology, specific surface area, pore volume of carbon material and discharge performance. The results showed that the air electrode using GNSs as cathode material exhibited a high specific discharge capacity of3023mAhg-1. The morphology of carbon material had no influence on the discharge performance. And the discharge platform was mainly affected by the specific surface area of carbon material, while the specific capacity was mainly affected by the pore volume. The effect of carbon loading and binder content on the discharge performance of lithium-air battery was investigated. It was found that the specific discharge capacity decreased with the increase of carbon loading and binder content.a novel catalyst of Pd-coated α-MnO2(α-MnO2@Pd) catalyst with a core-shell structure for rechargeable lithium-air batteries was prepared by reduction reaction of PdCl2with NaBH4on a homemade hollow α-MnO2micro-sphere with a high specific surface area of145m2g-1in a aqueous solution at room temperature. Compared to the α-MnO2catalyst, both the energy conversion efficiency and the charge-discharge cycling performance of the air electrode have been improved obviously by using the α-MnO2@Pd catalyst. The initial specific discharge capacity of an air electrode composed of Super P carbon and the α-MnO2@Pd catalyst is1220mAh g-1at a current density of0.1mA cm-2, and the capacity retention rate of the α-MnO2@Pd/Super P air electrode is about47.3%after13charge-discharge cycles.Last, LiTFSI electrolyte salt with esters(PC), ethers(TEGDME), sulfoxde(DMSO,sulfolane), ionic liquid(PyP14TFSI，EMITFSI) were investigated on the influence of discharge-charge performance of lithium-air batteries. It demonstrated that DMSO as solvent delivered the best electrochemical performance. DMSO electrolyte with for lithium salts including LiTFSI、LiTFS、LiBF4、LiClO4were also investigated. It was found that LiTFSI/DMSO delivered the best cycling performance. In addition, the influence of discharge depth on the discharge performance of lithium-air batteries was studied by limiting the specific discharge capacity. When limiting the specific discharge capacity within500mAh g-1, the cycling performance of lithium-air batteries has been great improved, compared to that with discharge cut-off voltage of2V.