Fast Li⁺ Transport of Li−Zn Alloy Protective Layer Enabling Excellent Electrochemical Performance of Li Metal Anode

Abstract

Li alloy film has been developed as an advanced artificial protection layer on Li metal anode, attributed to its tight contact with Li metal and unique transportation capability of mixed ion/electron. Li+ diffusion coefficient of the alloy interphase layer is crucial for Li dendrite growth and rate performance. Here, Zn thin film is sputtered on the surface of Li foil, and Li−Zn alloy buffer layer is spontaneously formed via an alloying reaction. In the process of electrochemical cycling, while Li+ ions are reduced on the interface of the electrolyte and the anode, the fresh Li atoms rapidly diffuse into the alloy layer via fast ion transport channels of the mixed conductor, resulting in the formation of Li metal free surface. As a consequence, Li−Zn layer protected Li electrode can effectively suppress Li dendrite growth and mitigate the deterioration of Li metal, demonstrating the greatly promoted performance at high current density in both the liquid electrolyte and all solid‐state electrolyte systems.

High Performance Lithium Metal Anode with a Nanolayer of LiZn Alloy for All‐Solid‐State Batteries

“…Figure 1(c) shows the photographs for the pristine Li foil (left) and a LiZn‐protected Li foil (right). The bare lithium presents a metallic grey color while after Zn deposition via sputtering, a homogeneous gold color was observed, which is typical of a LiZn alloy [57] . Depending on the deposition conditions, a slight change in the intensity of gold color is observed that suggests a difference of texture for the LiZn layers.…”

“…In this work, the modification of lithium foils with a nanometric layer of Zn deposited by sputtering is reported. Zn has been chosen for its relatively low price and because the LiZn alloy has a high Li + ion diffusion coefficient [57] . The presence of the LiZn alloy was confirmed by XRD analysis.…”

“…In addition, Li‐rich alloys limit the parasitic reactions between the anode and the electrolyte [52] and could be more air‐stable than pure lithium facilitating their manipulation and storage in dry room [53] . Several metals to date have been sputtered on Li metal such as Al, [53] Si, [54] Cu, [55] Au [56] and Zn [56,57] …”

“…In this work, we report the modification of lithium foils with a nanometric layer of Zn deposited by sputtering. Zn has been chosen for its relatively low price and because the LiZn alloy has a high Li + ion diffusion coefficient of 4.7×10 −8 cm 2 s −1 , which is superior to that for pure lithium (i. e., 5.69×10 −11 cm 2 s −1 ) [57] . The formation of a LiZn alloy upon deposition of Zn metal was confirmed by X‐ray diffraction (XRD) analysis.…”

A facile surface alloy-engineering route to enable robust lithium metal anodes

“…Recently, Li-rich alloy SEI layers (featuring compositions of thermodynamically stable Li-alloys and Li) formed by artificial alloying reactions have been adopted on the Li metal surface. 12,13 To date, several alloy SEI layers have been reported, including LiIn, 14 LiZn, 15,16 LiAl, 17 LiCu, 18 and LiGa groups. 19 The experimental results show that the alloy SEI layers effectively reduce the Li nucleation overpotential and lead to dense non-dendrite Li deposition, excellent coulombic efficiency and ultra-long cycling stability of the cell.…”