Improvement of Li-metal battery performance by surface nanostructure control of anode current collectors

Abstract

Due to the ever-growing demand for high energy density energy storage systems, the intensive studies have been carried out on the next generation rechargeable batteries. Among them, lithium (Li)-metal battery has been considered as one of the most promising rechargeable battery due to the properties of Li metal, which are extremely high specific capacity (3860 mAh g–1), low gravimetric density (0.53 g cm-3) and the lowest reduction potential (–3.04 V vs. SHE). Despite of these advantages, dendritic Li growth is the major factor hindering the practical use of Li metal anode due to the safety hazard and poor electrochemical performance. Thus, suppressing the Li dendrite formation is a key factor for the Li metal battery performance. In this work, the surface of Cu substrates are modified to suppress dendritic Li growth by introducing uniform surface and boundary formation. In chapter 2, a Cu anode structure with sharp wrinkles with uniformly distributed [100]-oriented facet is prepared for the dendrite-free Li deposition. The results reveal that the wrinkled Cu surface and uniform [100] facet play an important role in regulating Li+ flux and unifying Li adsorption energy, which allows long-term cycles of Li-metal batteries under carbonate-based electrolytes. In chapter 3, a new design of seed structure comprising a wrinkled Cu/graphene substrate surrounded by copper(I) oxide (Cu2O) on a graphene grain boundary over a large area is prepared for the dendrite-free Li deposition. In this work, the boundary effect derived from two-step Li deposition has been demonstrated. The first Li deposition occurs on Cu2O due to the most lithiophilic nature creates boundaries composed of Li2O and Cu. The second Li deposition occurs on the wrinkled Cu/graphene due to the second best lithiophilicity, and the previously created boundaries prevent Li agglomeration, resulting in high-performance Li metal batteries. This researches provide in-depth insights into the anode design for the development of high-performance Li-metal batteries.