Pretreatment Methods Of Lithium Anodes For High-stability Li-O₂ Batteries

In the background of energy crisis and environment pollution,optimizing the energy structure has become the strategic plan of China,with the development of the wind power industry,the photovoltaic industry and electrical vehicles.However,to achieve this goal,it is necessary to develop advanced energy storage technology.The lithium-oxygen battery has a very high theoretic energy density of 3458 Wh·kg^-1.It is widely considered as a potential next-generation electrochemical energy storage device.However,its high overpotential,short cycle life and open-system condition greatly limit its further development.At this stage,the cathode,the electrolyte and the anode of lithium-oxygen batteries all have serious problems.Especially,the lithium metal anode suffers from extremely serious side-reactions in oxygen existing environment,which greatly hampers the normal discharge/charge reactions.To solve this problem,this thesis proposes to pretreat the lithium anode with two metal halide solutions,so that the stability of lithium anodes is improved and the cycle life of lithium-oxygen batteries is elongated.The major research contents are as follows:?1?Improvement of lithium anode stability with AgF/DMSO solution pretreatment.Taking advantage of the replacement reaction between AgF and Li,a thin layer of LiF/Ag protection film would form on the Li surface.The LiF would effectively improve the passivation effect of the SEI film.The Ag component,which has high Li affinity,would serve as nucleation sites during Li deposition.This effect would lower the nucleation overpotential,induce the uniform Li growth and depress the Li dendrite growth.With the protection of the Li/AgF layer,the lithium-oxygen battery can cycle 90 rounds with fixed capacity of 1000 mAh·g^-1 at current density of 300 mAh·g^-1.The cycle life is elongated 4-folds comparing with untreated reference sample.?2?Improvement of lithium anode stability with AuCl₃/DME solution pretreatment.Taking advantage of the replacement reaction between AuCl₃ and Li,a layer of LiCl/Au film would form on the lithium surface.Such protection layer composes of uniformly distributed LiCl,Li₂CO₃ and Au nanoparticles.It can also depress the lithium dendrite growth.It is able to prevent the corrosion of lithium anodes by the electrolyte.So that the stability of the SEI layer is improved and the cycle performance of the lithium anode is improved.With the LiCl/Au protection layer,the lithium-oxygen battery can cycle 120rounds with fixed capacity of 1000 mAh·g^-1 at current density of 300 mAh·g^-1.