Study On The Surface Modification And Electrochemical Performance Of Lithium Metal Anode

Lithium metal anode is considered as the next generation ideal energy storage material for rechargeable batteries,due to its ultra-high theoretical specific capacity(3860 m Ah g^-1),low density(0.59 g cm^-3)and lowest redox potential?-3.04 V vs.standard hydrogen electrode?.Unfortunately,the uncontrollable lithium dendrite growth during the charging/discharging process has caused a series of problems such as extremely low coulombic efficiency,consumption of electrolyte and volume expansion,which severely restricted the commercial production of lithium metal anodes.In order to suppress the growth of lithium dendrites,a composite lithium metal anode with excellent cycling performance was prepared by coating the surface of the bare Li disc with a lithiophilic material.Lithophilic materials guide the uniform distribution of lithium ions.During the lithium ions deposition and stripping process,the surface of the lithium anode is flatter,thereby inhibiting the growth of lithium dendrites.Firstly,in the article,Ag metal was evaporated on the bare Li disc by using the thermal evaporation technique to obtain an Ag/Li metal anode.The characterization test methods were used to explore the mechanism of the significant improvement in the electrochemical performance of lithium metal anodes.The results show that,compared with the bare Li,the Ag/Li metal electrode exhibits more excellent electrochemical performance.This is mainly due to the strong affinity between Ag and Li.During the charge/discharge process of Ag/Li metal anode,lithium nucleation energy can be reduced,and lithium dendrite growth caused by local accumulation of lithium ions can be avoided.At a current density of 1 m A cm^-2 and a deposition capacity of 1 m Ah cm^-2,the silver/lithium electrode achieved a cycle life of more than 250 h,and the polarization voltage was only 38 m V.At a current of 0.5 C,a full cell assembled with the Li Fe PO₄ as a cathode and the Ag/Li as an anode exhibits excellent cycle stability.The first discharge has a specific capacity of 142 m Ah g^-1,and there is still a reversible specific capacity of 131 m Ah g^-1 after 300 cycles.Although the Ag/Li anode has great cycle stability and service life,since metallic silver is a noble metal,it is limited in preparation cost.For this reason,we subsequently choose cheap and readily available metal Al as the modified Li metal anode material.An Ag/Li metal anode was prepared by depositing Al on the bare Li disc using the magnetron sputtering method.The results show that the electrochemical performance of aluminum on lithium metal anodes has also improved significantly.Characterization results show that during the Al spatter,some Li reacts with Al to produce Al-Li alloy.During the cycling,the Al-Li alloy induces the lithium ions uniform deposition,thereby inhibiting the growth of lithium dendrites.At a current density of up to 5 m A cm^-2,the Al/Li symmetric cell still has a cycle lifespan of more than 140 h,and the polarization voltage remains stable.In a full cell assembled with the Ag/Li as an anode and the Li Fe PO₄ as a cathode,the discharge specific capacity of 86 m Ah g^-1 is maintained at a rate of 10 C,showing good rate performance.This work proposes that lithiophilic metals are used as surface-modified lithium anode materials to inhibit the growth of lithium dendrites and improve the electrochemical performance of lithium metal anodes.A variety of physical characterization techniques were used for the prepared composite electrode,and the electrochemical performance was studied.The possible mechanism of the lithium-philic protective layer on inhibiting the growth of lithium dendrites was discussed.The research work also provides a feasible path for large-scale production of lithium metal anode materials.