Effect Of Metal Lithium Modification And Lithium-rich Silicide Interface Modification On Electrochemical Performance Of Lithium Anode

Lithium metal has been considered as one of the most promising anode materials in high-energy-density rechargeable batteries due to its extremely high specific capacity,low density and the lowest reduction potential of all possible candidates.However,Li dendrite formation and low Coulombic efficiency of lithium metal anode in long-term cycles have greatly plagued the practical applications of Li metal in secondary batteries.In this work,we synthesized the lithium rich silicide with high activity,and the solvent compatibility of the silicide was studied.Then it was applied to the interface modification of lithium metal anode by drop coating.At the same time,the de-texturing of lithium and its effect on the performance of lithium anode were also studied.The lithium rich silicide was prepared by solid-phase hydrogen evolution reaction using silicon powder and LiH as raw materials.The solvent compatibility was studied by analyzing the influence of different solvents in the preparation of the slurry on the electrochemical performance of lithium-rich silicide.It was found that the lithium-rich silicide can reach the delithiation specific capacity of 1485 mAh g^-1 at the current density of 0.5 A g^-1 in the first cycle when toluene was used as the solvent,showing the best electrochemical properties.The failure mechanism of lithium-rich silicide in incompatible solvents was also analyzed by XRD,XPS and other methods.And then,as-prepared lithium-rich silicide was applied to the interface modification of lithium anode.In situ observation of lithium plating was conducted by using optical microscope.It was found lithium was deposited in a planar growth on the surface of the modified electrode.The interaction of these lithium-rich silicide with Li atom were performed through first-principle density functional theory（DFT）calculations.The results showed that Li₂₁Si₅ and Li have strong interaction,indicating that lithium-rich silicide provides uniform nucleation sites for lithium deposition and improves the deposition of lithium.The voltage hysteresis of the symmetrical battery was still lower than 30 mV after 500 h cycling at the current density of 1 mA cm^-2.The half-cells matched with the commercial cathode electrodes also showed good cycle performance and rate performance.The modified lithium electrodes were prepared by melt quenching.It was found that the surface of the lithium become flat and clean,the grain size and crystallinity of lithium decrease,and the preferential orientation of lithium surface becomes weaker,which promotes the uniform nucleation of lithium on its surface.The quenched-treated lithium metal in symmetrical battery showed stable cycling at the current density of 1 mA cm^-2 over 800 h.In addition,the half-battery assembled with LiFePO₄ cathode remained capacity of 132 mAh g^-1 after 300 cycles at 1 C and the average capacity attenuation per cycle was only 0.093 mAh,which showed stable cycle performance.