Research On The Electrode Materials And Systems Of High Energy Density Aqueous Rechargable Lithium Batteries

Solar, wind and other renewable energy sources are gaining ground as nations work to lower greenhouse gas emissions and reliance on petroleum. But sunlight and wind are not constant, so consumers can't count on them 24-7. Storing energy can make renewables more reliable, but current technologies such as lithium-ion batteries are limited by safety issues, high costs and other factors. Aqueous rechargeable batteries ?ARLBs? have brought the dawn to energy storage industry. They have been widely studied for they possess many advantages, such as low cost, easy to assemble, safe and environmentally friendly and good rate capacity. But current ARLBs can't meet the requirement of the electric vehicle and smart grid for high voltage, high power density and high energy density. There are two main reasons:1) The specific capacity of currently used anode materials is quite limited; 2) The electrochemical stability window of aqueous solution is limited. Two solutions could be taken to solve this problem:??? to improve the specific discharge capacity of the electrode materials; ??? broaden the electrochemical stability window of the battery.The main researching contents and results are as follows:?1? Reserches on the ARLB using a dual core-shell structured MWCNTs@S@PPy nanocomposite as a high capacity anode. A dual core-shell structured MWCNTs@S@PPy nanocomposite was prepared and tested in aqueous saturated Li Ac electrolyte as anode material for the first generation ARLBs. And then, an ARLB system was built up consisting of the MWCNTs@S@PPy nanocomposite anode and the nanorod LiMn₂O₄ cathode using saturated LiAc electrolyte. The results showed that:The nanocomposite exhibits a high capacity and good rate performance. The MWCNTs and PPy net work provides structural stability for Li+ ion insertion and extraction reaction with sulfur, and slow down the dissolution of polysulfide out of the anode. The alkalescence of aqueous saturated LiAc electrolyte can also improve the the redox reversibility of sulfur in aqueous electrolytes. The MWCNTs@S@PPy//LiMn₂O₄ battery was tested at the current density of 0.5 A.g^-1. Its average discharge voltage is about 1.25 V, and the energy density is 110 Wh.kg^-1, higher than those of the reported for the first generation ARLBs. It shows good cycling performance, which indicates that this ARLB system is very promising for applications in large-scale EES systems.?2? Reserches on the preparation and electrochemical performance of nanorod LiMn₂O₄ which has high power performance. LiMn₂O₄ nanorod was prepared through a two-step method. The results showed that the nanorod LiMn₂O₄ presents an excellent rate capacity and cycling performance:the nanorod LiMn₂O₄ shows a discharge capacity of 124 mAh.g^-1 at the charge and discharge current densities of 1 A.g^-1 and 94 mAh.g^-1 even at those of 20 A.g^-1; the cycling behavior is excellent and there is no evident capacity fading after 1000 cycles at the current density of 2 A.g^-1. Then a series of" quick-charge/slow-discharge " experiment were designed to test the LiMn₂O₄ nanorod electrode, and results showed that the LiMn₂O₄ nanorod electrode has present a excellent quick charge and slow discharge performance:at the charging rate of 400 C ?6.3 s?,70.9% of the capacity could be obtained at the discharge current density of 6.75 C.?3? Reserches on the high voltage and high energy density Zn/Zn?OH?42-//LiMn₂O₄ ARLB system. The results showed that:With the increase of the concentration of the KOH solution, oxidation reduction potential of zinc electrode shift toward negative potential, and the working voltage of the battery will increase; when the concentration ofthe KOH solution is about 6 M, the average discharge voltage can be up to 2.4 V, and the energy density is as high as 251 Wh.kg^-1. The Zn/?1 M KOH?//?1 M LiNO3?/LiMn₂O₄ battery system possess a ultrahigh energy density and presents an exllent rate performance and cycling performance:it's average discharge voltage can be up to 2.24 V, and the energy density as high as 236 Wh.kg^-1 at the current density of 1 A.g^-1; and when the current density is up to 3 A.g^-1, the average discharge voltage is 2.07 V, and the energy density still has 191 Wh.kg^-1; the cycling behavior is excellent, the initial discharge capacity is 117 mAh.g^-1, and there is no evident capacity fading after 1000 cycles at the current density of 2 A.g^-1. The high voltage high energy density and exellent cycling performance of this ARLB system indicates that it's very promising for applications for advanced technologies such as electric and hybrid electric vehicles and smart grids.