Design And Preparation Of Hybrid Li-Ion/ Li-Oxygen Batteries

Modern society consumes a huge quantity of fossil fuels at a relatively low apparent cost but creates other environmental and societal costs. Pursuing for green, clean and low carbon energy is now becoming urgency especially in large-scale applications. Rechargeable energy storage systems with high energy density and round-trip efficiency are therefore desired to capture and deliver renewable energy for applications suc h as electric transportation. Among the modern electrochemical power sources, lithium- ion batteries(LIB) already power the portable electronic devices such as cell phones and laptops, and they may soon power your car. However, all of today's lithium- ion positive electrodes are based on intercalation reactions, in which the crystal structure of the electrode is essentially maintained during charge and discharge. This inherently limits the possible stored energy. The Li-air(O2) battery(LOB) is widely considered as the next generation secondary battery because its theoretical specific energy far exceeds that of lithium- ion batteries. the energy density of a typical non-aqueous Li-O2 cell is as high as 3460 Wh kg-1 based on the molecular weight of Li2O2.We design a novel strategy to take advantage of both LIB and LOB in one battery, i.e., a hybrid mode of LIB and LO B. LiCoO2(LCO) cathode with optimized electrolyte is charged/discharged in oxygen. In the potential range from 3.0 to 4.2 V, LCO acts as normal LIB cathode with excellent cyclability. If the discharge goes deeper, an additional capacity of more than 200 mAh g-1 will appear at about 2.6 V vs. Li+/Li due to the LOB discharge mode. When TEGDME is used as the electrolyte, the battery capacity suffers severe decay resulting from decomposition of TEGDME.Ionic liquid is replaced with TEGDME because of its excellent nonvolatility, high hydrophobicity against water, high thermal stability, and broad electrochemical window. Unlike the lithium carbonate proble m in TEGDME electrolyte, the incomplete decomposition of Li2O2 is mainly because of the poor solid-solid contact. The Li2O2 particles that are closely touched with the LCO surface can still be oxidized. So the accumulation of Li2O2 does not block the Li- ion intercalation pathway, instead it only hinders the oxygen diffusion and the Li2O2 formation in the next cycle.In order to effectively decompose Li2O2, we change the operation mode of the battery. Since the LIB discharge and charge potential plateaus at 3.8?4.2 V are higher than the decomposition potential of Li2O2(or even Li2CO3), running the battery in LIB mode can actually help to decompose the residual LOB discharge products. Therefore, if the battery is just occasionally deep-discharged to 2.0 V, we can still renew the cathode by running a few cycles in solo LIB mode. The cycle life of the hybrid battery is prolonged. The “LIB+LOB” capacity is still higher than 220 mAh g-1 after 10 times deep discharge and 18 times shal ow discharge.RuO2/Fe2O3 nanofiber was synthesized by electrostatic spinning method. The heat treatment on the nanofiber precursor can affect the structure and morphology of RuO2/Fe2O3 nanofiber. By XRD and SEM analysis, we conclude that the optimum heat treatment condition is 500 oC, 1 h, the RuO2/Fe2O3 nanofiber material can catalyze O RR and OER reaction by observing the charge and discharge curves. The initial discharge voltage increases 500 mV than that of super P, and the charge voltage can reduce to 4 V. when the capacity is limited to 1000 mAh g-1, the batteries can run 20 cycles steadily.