Multipolar Conjugated Polymer Framework Derived Ionic Sieves via Electronic Modulation for Long‐Life All‐Solid‐State Li Batteries

Abstract

AbstractHere, we build a tunable multipolar conjugated polymer framework platform via pore wall chemistry to probe the role of electronic structure engineering in improving the Li+ conduction by theoretical studies. Guided by theoretical prediction, we develop a new cyano‐vinylene‐linked multipolar polymer framework namely CNF‐COF, which can act as efficient ion sieves to modify solid polymer electrolytes to simultaneously tune Li+ migration and stable Li anodes for long‐lifespan all‐solid‐state (ASS) Li metal batteries at high rate. The dual‐decoration of cyano and fluorine groups in CNF‐COF favorably regulates electronic structure via multipolar donor‐acceptor electronic effects to afford proper energy band structure and abundant electron‐rich sites for enhanced oxidative stability, facilitated ion‐pair dissociation and suppressed anion movements. Thus, the CNF‐COF incorporation into poly (ethylene oxide) (PEO) electrolytes not only renders fast selective Li+ transport but also facilitates the Li dendrite suppression. Specifically, the constructed PEO composite electrolyte with an ultra‐low CNF‐COF content of only 0.5 wt % is endowed with a wide electrochemical window, a high ionic conductivity of 0.634 mS cm−1 at 60 °C and a large Li+ transference number of 0.81—remarkably outperforming CNF‐COF‐free counterparts (0.183 mS cm−1 and 0.22). As such, the Li symmetric cell delivers stable Li plating/stripping over 1400 h at 0.1 mA cm−2. Impressively, by coupling with LiFePO4 (LFP) cathodes, the assembled ASS Li battery under 60 °C allows for stable cycling over 2000 cycles at 1 C and over 1000 cycles even at 2 C with a large capacity retention of ~75 %, surpassing most reported ASS Li batteries using PEO‐based electrolytes.