Basic Research On High-Performance Rechargeable Lithium Air/Carbon Dioxide Batteries

The theoretical energy density of Lithium?Li?-air batteries is much higher than that of lithium-ion batteries,so Lithium-air batteries are frequently advocated as a solution toward next-generation electrochemical energy storage for applications including electric vehicles or grid energy storage.However,they have not fulfilled their full potential because of challenges associated with the electrolyte,Li anode,and air cathode.These challenges will have to be properly resolved before Li-air batteries can become a practical reality and be deployed on a large scale.In this work,the effects of polymer electrolytes,lithium anode materials,and different catalytic electrode materials on Li–air/carbon dioxide batteries were investigated.The main study results are as follows:?1?Generally,the liquid electrolyte is volatile,poor in safety,and easily decomposed by superoxide molecules?O₂^-?attack,which will cause the performance degradation of the lithium-air battery.Hence,a novel gel polymer electrolyte?GPE?by taking advantages of the stability of polymethyl methacrylate?PMMA?to superoxide molecules and the non-volatility of 1-Ethyl-3-methylimidazolium tetrafluoroborate?EMIMBF₄?is proposed.This novel GPE possesses the excellent ion conductivity and superior leakproof property.In addition,the as-assembled Li–air battery containing the novel GPE and binder-free Ru-based cathode shows effectively improved reaction kinetics and coulomb efficiency?97.1%?.When operated at the limited capacity,this battery can run for over 120 cycles with the low overpotential of?2 V.The improvement of electrochemical performance of the battery is mainly because of the unique design of the GPE and the binder-free structure of Ru-based cathode.?2?The application of gel electrolytes still cannot avoid the lithium dendrites formed during cycling.So designed the graphene oxide?GO?decorated Ni foam?GO-Ni?,and further used thermal-infusion method to prestore Li into GO-Ni framework to form Li-based reduced?r?GO-Ni?Li/rGO-Ni?anode.GO-Ni matrix not only has abundant pores to effectively accommodate huge dimensional expansion and reduce formation of dendritic Li,but also shows superior heating and cycling stability during thermal-infusion and cell operation processes.Additionally,lithiophilic GO addition can obviously accelerate infusion of molten Li into GO-Ni and further realize uniform Li dissolution/deposition in Li/rGO-Ni over cycles.Hence,Li/rGO-Ni anodes in symmetric batteries have higher cycling stability and smaller voltage hysteresis than bare Li electrodes at various current densities.Furthermore,Li/rGO-Ni based Li-air full batteries have been constructed and can steadily run for 100 cycles with low overpotential?1.9 V?,which are much better compared with Li-based cells.More interestingly,Li/rGO-Ni electrodes have good flexibility and thus are introduced into flexible Li-air batteries which exhibit good performances after different bending conditions.?3?In the process of studying lithium-air batteries,it was found that carbon dioxide also has electrochemical reversible charging and discharging properties,so a preliminary study was conducted on Lithium-carbon dioxide batteries.The Ru nanosheets were directly grown on one side of the nickel foam through a galvanic replacement reaction to form the Ru/Ni electrode,which was further used in the Lithium-carbon dioxide batteries.The highly dispersed Ru nanosheets in the Ru/Ni cathode effectively promote the decomposition of discharge product Li₂CO₃ and thus reduce the charge overpotential.Moreover,the typical porous and binder-free Ru/Ni electrode not only has a stable construction to suppress the side reaction in the Lithium-carbon dioxide batteries,but also enables the rapid permeation of carbon dioxide and electrolyte/electron into the active sites of the Ru/Ni electrode.As a result,the Ru/Ni cathode-based Lithium-carbon dioxide battery exhibits the superior discharge capacity(9502 mAh g^-1),good coulombic efficiency?95.4%?and excellent rate performance(3177 mAh g^-1 at 500 mA g^-1)at the full discharge/charge condition.When operated at the limited capacity of 1000 mAh g^-1,this cell can run for over 100 cycles with the charge potential below 4.1 V.