Li-MOF-based ions regulator enabling fast-charging and dendrite-free lithium metal anode

Abstract

Li metal has been regarded as the holy grail for the next-generation Li-ion battery. Li dendrites issues, however, impede its practical application. In general, prolonging the sand time of Li nucleation and regulating homogeneous Li+ flux are effective approaches to suppress the dendrites formation and growth. Regarding this view, a functional polypropylene (PP) separator is developed to regulate ion transportation via a newly designed Li-based metal-organic framework (Li-MOF) coating. The Li-MOF crystallizes in the orthorhombic space group P212121 and features a double-walled three-dimensional (3D) structure with 1D channels. The well-defined intrinsic nanochannels of Li-MOF and the steric-hinerance effect both restrict free migration of anions, contributing to a high Li+ transference number of 0.65, which improve the Sand time of Li nucleation. Meanwhile, the Li-MOF coating with uniform porous structure promotes homogeneous Li+ flux at the surface of Li metal. Furthermore, the Li-MOF coating layer helps to build solid-electrolyte interphase (SEI) layer that comprises of inorganic LiF and Li3N, which further prohibits the dendrites growth. Consequently, a highly stable Li plating/stripping cycling for over 1000 h is achieved. The functional separator also enables high-performance full lithium metal cells, the high-rate and long-stable cycling performance of LiNi0.8Mn0.1Co0.1 (NMC811)-Li and LiCoO2 (LCO)-Li cells further demonstrate the feasibility of this concept.