Controlled Bottom-up growth of Li by a gradient lithiophobic?lithiophilic 3D Cu foam structure

초록

With the rapid development of electric vehicles (EVs) and energy storage systems (ESS) demanding for high energy density over 400 Wh kg-1, lithium metal is a regarded competitive anode material to replace the commercial graphite anode for next generation lithium batteries due to its high theoretical capacity (3860 mAh g-1), low redox potential (-3.04 V versus standard hydrogen electrode), and low gravimetric density (0.59 g cm-3). However, the practical application of Li metal anode has faced tremendous challenges including cracking of the solid electrolyte interface (SEI) due to the large volume change of Li metal during repeated cycling, and the internal short-circuiting of batteries caused by the uncontrollable growth of Li dendrites.[1] Although the application of 3D framework electrode with large surface areas and high porosity have been applied to reduce local current densities with increased tolerance to volume variation, Li preferentially grows on the top of the framework electrode due to the ionic resistance that inhibits diffusion of Li+ to the bottom of the electrode. In this study, we demonstrated the controlled bottom?up growth of Li using a gradient lithiophobic?lithiophilic 3D Cu foam framework. The upper passive layer of Polyvinylidene fluoride (PVDF) with lithiophobic property was attained by spin?coating method to prevent the deposition of Li at the interfaces.[2,3] In addition, the bottom lithiophilic layer of skeleton is achieved by decorating Tin (Sn) via spin?coating or magnetron sputtering approaches for preferred reduction of Li+ without formation of dendrite structures. Benefiting from the distinct structure with gradient lithiophobic?lithiophilic properties, 3D Cu foam framework exhibits improved electrochemical performances resulting from bottom?up growth of Li compared to traditional Cu host.