Research Of Interface Modification In Lithium Metal Battery Based On Traditional Lithium Ion Electrolyte

The development and utilization of solar energy and the development of smart grid have put forward an urgent demand for the development of high-performance energy storage technologies.Lithium-ion batteries（LIBs）with high energy density and long cycle life have been widely used in portable electronic equipment and electric vehicles.However,with the rapid development of new energy vehicles and3C electronic consumer products,higher requirements for lithium energy battery energy storage technologies have been proposed.Traditional LIBs are subject to the insufficient theoretical specific capacities due to the relatively low theoretical specific capacity of graphite anode(372 m Ah g^-1),and their overall energy densities tend to be less than 300 Wh kg^-1.In contrast,the lithium metal anode has an ultrahigh theoretical specific capacity(3860 m Ah g^-1)ten times than graphite.In addition,the lithium metal anode has the lowest electrochemical redox potential（-3.04 V vs standard electrode potential）,enables the lithium ion batteries with higher working voltage,and can effectively promote the energy density of lithium ion batteries.Therefore,lithium metal anode have been considered to be the most potential anode material in LIBs.However,applied in lithium ion batteries,lithium metal anode is facing a key technical bottleneck of lithium dendrite growth,which leads to the short circuit of LIBs and thus thermal runaway.As a result,the application of lithium metal anode can bring about serious safety risks.In order to alleviate the safety problems caused by lithium dendrite growth,different design strategies have been proposed to suppress their growth,such as structural design of lithium metal anode,artificial SEI construction on the surface of lithium anode,electrolyte optimization design,etc.However,the aforementioned strategies generally suffer from complex procedure,or the poor compatibility with electrodes,etc.Therefore,the key to developing high-performance LIBs based on lithium metal anode is to explore the design strategy that is compatible with the electrodes and electrolytes in battery systems and meantime can effectively inhibit the growth of lithium dendrites.1,3-dioxolane（DOL）and lithium hexafluorophosphate was used as the monomer material and the initiator for the surface modification of lithium metal anode,which lead to the in-situ formation of a polymer transition layer（DPTL）with high mechanical strength,and thus inhibited the growth of lithium branch crystals.Moreover,DOL is a commonly used electrolyte sovant in LIBs and has a good interface compatibility with the electrode and electrolyte.Moreover,DPTL has excellent affinity performance with the electrolyte,which can effectively enhance the infiltration of the electrolyte on the surface of lithium metal anode and enhance the kinetics of ion transfer across the anode/electrolyte interface.Following the research idea,the structure and properties of polymer transition layer were analyzed by XRD,SEM,EDS,FTIR,NMR and Nano Indentor.Then,the symmetric battery and the full battery were prepared based on the lithium metal anode with and without the DPTL modification.The comparison between their electrochemical properties showed that the protection of DPTL could suppress the growth of lithium dendrites on the lithium metal anode.Finally,with the modification of DPTL,the cycle life of the symmetrical lithium metal battery was increased from 410h to 1170h,the corresponding full battery based on Li Fe PO₄cathode presented an enhanced cycling performance of 550cycles（vs.250 cycles for the counterpart without the protection of DPTL）,and the Coulombic efficiency was stable above 99.6%.