A biomass-based protective layer with rigid structure and ion conductivity for high-performance lithium metal batteries

Lithium (Li) metal has been considered as an effective anode material because of its high theoretical capacity, but the uncontrolled dendrite growth and the unstable electrode/electrolyte interface limit its practical application. In this work, proanthocyanidin (PA), a natural extracted biomass, was designed and developed as a coating material to guide homogeneous deposition and restrain side reaction for lithium metal batteries. The rigid benzene ring structure of PA can increase the mechanical strength to restrain dendrite growth on Li surface. Moreover, the spontaneous formation of organolithium (PA-Li) structure from the reaction of phenolic hydroxyl group with Li metal increase the ion transportation ability of PA layer and induce the uniform deposition of Li + ions to hinder the growth of Li dendrites, as well as prevent the direct contact of organic electrolyte with Li metal to suppress the interface side reaction. As a result, Li metal anode with PA-Li exhibits stable cycling properties for 2800 h at 2 mA cm -2 and 2 mAh cm -2 , better that of bare Li (200 h). Li-sulfur full battery with PA-Li can still achieve a capacity of 570 mAh g -1 after 300 cycles. This work provides an effective strategy for the construction a natural functional layer on Li surface to enhance the electrochemical performance, as well as the implementation of high-value utilization for natural biomass.