Preparation And Study Of Highly Stable Lithium Metal Anodes Based On Metal Compounds Skeleton

Spurred by rapid development of renewable energy,portable electric devices and electric vehicles,rechargeable batteries with high energy densities are in great demand.Lithium metal is regarded as the most promising anode materials for next-generation high-energy batteries due to its high theoretical capacity(3860 m Ah g^-1)and small reduction potential（-3.04 V vs.standard hydrogen electrode）.Nevertheless,inhomogeneous Li plating/stripping results in growth of Li dendrites and formation of “dead Li” causing internal short circuit and safety concerns.Moreover,the big volume changes during Li stripping/plating leads to repeated breakdown/buildup of the solid electrolyte interphase,which consumes the electrolyte and aggravates inhomogeneous Li deposition,giving rise to low Coulombic efficiency（CE）and poor cycling lifespan.To suppress the formation of Li dendrites is the key to building a more stable lithium metal anode.Herein,lithiated NiCo₂O₄ nanorods anchored on Ni foam（LNCO/Ni）and ultralong VN nanowires（VN NWs）is designed and constructed as skeletons of lithium metal,to reveal the mechanism of the skeleton homogenizing lithium metal deposition-stripping and obtaine high-performance lithium metal anode with high areal capacity,high coulombic efficiency and long cycle life.The research contents are as follows:（1）The LNCO/Ni skeleton composed of lithiated NiCo₂O₄ nanorods anchored on Ni foam have been fabricated,which can decrease local current density,homogenize Li nucleates and accommodate volume fluctuations of the anode during cycling.The LNCO/Ni-Li anode exhibites a low voltage hysteresis of 16 m V,high CE of 98.6%,and excellent Li plating/stripping stability for over 1000 hrs at a current density of 1 m A cm^-2 without obvious voltage fluctuation.Moreover,a scalable Li loading of 20 m Ah cm^-2 is achieved without dendrite Li growth and thickness fluctuation at the electrode level.The full-cell consisting of the LNCO/Ni-Li anode and LiFePO₄ cathode also exhibits a higher rate capability and better cycling stability than comparative samples.（2）A highly conductive and lithiophilic 3D membrane was fabricated using single component and ultra-long VN nanowires（VN NWs）as skeleton to form VN-Li composite with infusion of suitable amount of molten Li.After 100 cycles,no dendrites are observed and the electrode thickness fluctuations are small（3.3 %）.During the charging and discharging process,the corresponding composite Li metal anode delivers a long-life span of 1000 hrs at a current density of 0.5 m A cm^-2 with lower nucleation overpotential（almost 0 V）and voltage hysteresis（50 m V）.Specifically,as the current density increases to 5 m A cm^-2,the voltage hysteresis of the VN-Li electrode is only 200 m V.When being assembled into a full-cell battery with LiFePO₄（LFP）as counter electrode,VN-Li composite anode affords capacity of 76 and 58 m Ah g^-1 at 5 C(1 C=152 m A g^-1)and 8 C much higher than pure Li metal anode,showing excellent application potential.