Asymmetric organic-inorganic bi-functional composite solid-state electrolyte for long stable cycling of high-voltage lithium battery

Abstract

Poly(ethylene oxide) (PEO)-based solid-state electrolyte is difficult to achieve high voltage and energy density due to low ionic conductivity and narrow electrochemical stabilization window. Therefore, an urgent demand exists to construct a composite solid-state electrolyte that is resistant to both Li dendrite and high-voltage cathode oxidation. Here, we design and prepare an asymmetric bi-functional composite solid-state electrolyte achieving compatibility with Li anode and high-voltage anode to extend the cycle life of batteries. The F-containing hierarchically structured polyamide acids nanofibers towards the cathode side enhance interfacial compatibility with the cathode and provide excellent oxidation resistance. The rigid two-dimensional alumina nanosheets on the anode side further improve the interfacial stability with the Li anode and effectively inhibit the growth of Li dendrites. The synergistic effect of asymmetric organic-inorganic composite solid-state electrolyte is exploited to improve the cycling stability of different cathode (LiFePO4 (LFP) and LiNi0.8Mn0.1Co0.1O2 (NMC811))/Li batteries, greatly broaden the electrochemical stability window (5.3 V) and significantly enhance lithium dendrite inhibition. Based on density functional theory, the introduction of F-containing groups reduces the highest occupied molecular orbitals of the polyamide acids and that there is a strong binding between alumina and both the PEO terminal group and TFSI−. The result suggests that the composite solid-state electrolyte enhances the stability of PEO with the high-voltage cathode and Li anode, and inhibits the movement of anions. Therefore, it is noteworthy that the excellent electrochemical stability of this composite solid-state electrolyte with the NMC811/Li electrodes ensures long cycle of more than 800 cycles.