Effect of the Electroplated Sn Layer with High Lithiophilicity on the Electrochemical Li Deposition Behaviors in Li Metal Anodes

Abstract

Li metal anodes (LMAs) are one of the attractive anode candidates because of the lowest electrochemical redox electrode potential (-3.04 V vs. SHE) and the extremely high theoretical gravimetric capacity (3,860 mAh/g) compared to graphite anode (372 mAh/g). However, uneven Li deposition causes dendritic Li growth leading to low Coulombic efficiency (CE) and safety hazards which impedes the practical use of LMAs. To suppress dendritic Li growth, lithiophilic material on current collector(CC) is one of the facile and effective strategies to increase the lithiophilicity and control intrinsic Li nucleation and growth behaviors. As one of the methods to adopt the lithiophilic materials, the electrodeposition is very attractive, since it can easily control the surface morphology, affecting the Li deposition morphology and the related electrochemical stability. In this regard, we adopted the electroplated Sn on CC of Cu to form highly lithiophilic LixSny alloy sites. At 100 mAs/cm2, an amount of Sn was considered to be suitable because of the smallest Sn capacity and full uniform coverage. In half cell test, Sn@Cu showed reduced Li nucleation overpotential by approximately 5 times and outstanding cyclic stability for 150 cycles compared to bare Cu at 1 mA/cm2. In particular, by formation cycles between 0 and 1 V (vs. Li/Li+), porous LixSny layer was positioned on the top surface as a protective layer which inhibited dendritic growth of Li. Furthermore, in anode-free Li batteries, higher capacity retention of 62.6% was achieved for Sn@Cu for 50 cycles compared to bare Cu (49.2% for 50 cycles).