Maximized lithiophilic carbonyl units in covalent organic frameworks as effective Li ion regulators for lithium metal batteries

• The covalent organic framework (COF) with maximized carbonyl groups was synthesized. • The lithiophilic active sites were optimized in the porous skeleton. • The smart COF interlayer were introduced into the lithium metal batteries (LMBs). • The lithium ionic flux was regulated uniformly and the random Li deposition was suppressed. Li metal batteries (LMBs) have been intensively investigated in recent years due to the ultrahigh theoretical capacity of Li metal anodes. However, the random nucleation of Li ions and the proliferation of Li filaments originated from the concentration polarization and space charge region would consume both liquid electrolyte and Li metal, and simultaneously undermine the work life and cycling performance of LMBs. Herein, we develop covalent organic framework (COF) interlayer with maximized lithiophilic carbonyl groups as the ionic regulator in LMBs. The maximized carbonyl groups with aligned arrangement bring about maximized Li affinity and ideal homogeneous Li ion flux, and subsequently avoid the formation of ramified Li metal. With introducing this maximized lithiophilic polymer backbone, both half batteries and full cells exhibit extraordinary cycling performance. The symmetric cells exhibit stable polarization voltage more than 600 h under current density of 4 mA cm −2 , and the Li–LiFePO 4 batteries with this interlayer achieve high reversible capacity up to 163 mAh g −1 and limited capacity loss in more than 700 cycles.