Li-rich Li-Al Alloy As A Novel Anode Material For Lithium Secondary Batteries

Since the exhaustion of non-renewable resources and the pollution caused by fossil fuels becomes more and more serious,it is inevitable that new energy will replace traditional fossil energy.Li-ion batteries have been widely used in various fields due to their high safety,large specific capacity and small size.With the rapid development of portable electronic products（notebook computers,mobile phones,cameras,electric bicycles,etc.）and electric vehicles,it is urgent to develop advanced rechargeable energy storage devices with higher energy density,longer life,excellent safety.Li metal anode is considered as the first choice for the next generation battery due to its extremely high theoretical specific capacity(3860 m Ah g^-1),lowest redox potential（-3.045 V vs.SHE）,high conductivity,and high electrochemical activity.All of these factors have prompted researchers to focus Li metal anode again.However,the Li metal anode suffers from few disadvantages.In the process of cycling,the changeable volume of Li anode could easily lead to the inhomogeneous formation of the solid electrolyte interface（SEI）,pulverization of the electrode,and low coulombic efficiency.And Li⁺cations tend to unevenly deposit on current collectors,resulting in the uncontrollable Li dendrites formation.In order to solve these critical problems,a novel Li-rich dual-phase Li-Al alloy is prepared by a simple thermal melting method for advanced electrochemical performance.The weight ratio of Li and Al in Li-rich dual-phase Li-Al alloys,consisting of Li metal phase and Li₉Al₄ three-dimensional alloy framework,is screened in terms of the electrochemical performance as an anode for Li metal batteries.The Li-Al alloy electrode composed of 20 wt.%Al shows the best electrochemical performance in the configuration of symmetric battery,which is attributed to the efficient suppression of Li dendrite formation and the increased active surface induced by Li₉Al₄ alloy framework.The cell is cycled over 1400 hours,and a smaller voltage hysteresis of 61 m V is recorded at 300th cycle at the current density of 1 m A cm^-2 with the areal capacity of 1 m Ah cm^-2.Moreover,the Li-Al|Li Fe PO₄ full battery gains superior rate performance,exhibiting the promoted cyclic stability with respect to that based on Li metal anode.In the argon atmosphere,the Li-Al liquid alloy is infiltrated into Cu foam to form a Li-Al@Cu composite anode,which further enhances the mechanical strength of the Li₉Al₄ three-dimensional framework and the electrochemical active area for Li nucleation and deposition.Furthermore,the Li₉Al₄ alloy layer can preferably adsorb on the Cu framework,and the modified skeleton is lithiophilic.The synergic effect between the primary Cu framework and the secondary Li₉Al₄ scaffold can further improve the cyclic stability of the anode.The composite anode can be circulated over 1500 hours at the current density of 1 m A cm^-2 and the areal capacity of 1 m Ah cm^-2.