Design Of Rechargeable Lithium Metal Batteries With High-Energy-Density And Long Lifespan

Energy technology revolution to obtain clean energy is of great significance for China to achieve the carbon peaking and carbon neutrality goals.As an important part of the energy technology revolution,advanced battery technology has a great impact on electric industry and energy storage system.In recent years,the development of large-scale equipment such as electric vehicles and unmanned aircrafts has put forward the requirements for new battery chemistry with high-energy-density and high-safety.The energy density of lithium ion intercalation chemical system with graphite as anode and transition metal oxide as cathode is reaching its theoretical capacity,which is not suitable for higher-energy,high-power devices.As a representative of high specific energy anode,lithium metal has been widely studied because of its light weight,low redox potential and high theoretical capacity.However,there are many problems hindering its commercialization,including lithium dendrites growth,low coulomb efficiency,large volume expansion,potential safety hazard etc.Considering these problems,this paper will put forward different modification strategies such as electrode architecture modification,solid-liquid interface regulation and new electrolyte solvation structure.Moreover,we continuously optimize the parameters in the battery in order to realize high-energy-density and high-safety lithium metal batteries(LMBs)system.The main contents of this paper are as follows:1.In the second section,an alkali metal/three-dimensional skeleton integrated anode is proposed to reduce the local current density,decrease the volume expansion and suppress the growth of lithium dendrite.Transition metal oxide nanofibers are used to adjust the affinity of the 3D skeleton to molten alkali metal.The key to making molten alkali metal enter the three-dimensional skeleton is larger Gibbs free energy enthalpy.The cycle stability of threedimensional composite anode was tested by theoretical simulation,symmetrical cell and full battery.This work proposes a new universal method for the construction of three-dimensional composite anode.2.In the third section,aiming at the problem of solid-liquid interface,a "rigid and flexible" artificial solid electrolyte interphase is put forward to regulate the lithium ion flux approaching interface and suppress dendrite growth by the high Young’s modulus.The polymer matrix as the protective film bears the change of volume expansion,and the inorganic particles as the high Young’s modulus component prevent the penetration of lithium dendrites and improve the ionic conductivity.The high mechanical properties and dendrite inhibition ability of the composite films were confirmed by advanced characterization methods such as scanning electron microscope and atomic force microscope.This work puts forward a new solution for interface protection strategy.3.The fourth section of this paper focuses on the derivation of SEI from electrolyte.The dual-additive ester electrolyte system with synergistic effect is prepared by introducing lithium nitrate and tris(pentafluorophenyl)borane(anion-acceptor).The introduced anion receptor containing Lewis acid centre successfully promoted the dissolution of lithium nitrate,which was originally insoluble in ester electrolyte.The prepared dual-additive electrolyte can form a double-layer structure SEI containing lithium oxide and LiNxOy and an amorphous F-,B-containing cathode electrolyte interphase(CEI).This electrolyte is suitable for different cathode system like high-voltage LNMO,LCO and NCM systems.This work proposes an effective electrolyte system for lithium metal battery chemistry.4.The fifth section of this paper focuses on the Li+solvation structure to improves the utilization of lithium metal and the safety.By increasing the concentration of lithium salt,introducing flame retardant components and adding diluents,a safe non-flammable electrolyte system was successfully constructed.The stable cycling of lithium metal pouch cell under the commercial condition was realized.This work proposes a new localized high concentration electrolyte system,which provides a new strategy for accurately regulating the solvation structure and forming a good SEI protective layer.To sum up,this paper puts forward three kinds of methods to construct highenergy-density lithium metal batteries,including lithophilic three-dimensional architecture,rigid-flexible interface and electrolyte modification.As new understanding and innovative strategies springing up,LMBs will no doubt have an ever greater impact on our lives in the years to come.