Anion-immobilized solid composite electrolytes based on metal-organic frameworks and superacid ZrO2 fillers for high-performance all solid-state lithium metal batteries

Anion-immobilized solid composite electrolytes (SCEs) are important to restrain the propagation of lithium dendrites for all solid-state lithium metal batteries (ASSLMBs). Herein, a novel SCEs based on metal-organic frameworks (MOFs, UiO-66-NH2) and superacid ZrO2 (S-ZrO2) fillers are proposed, and the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), thermo-gravimetric analyzer (TGA) and some other electrochemical measurements. The -NH2 groups of UiO-66-NH2 combines with F atoms of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) chains by hydrogen bonds, leading to a high electrochemical stability window of 5 V. Owing to the incorporation of UiO-66-NH2 and S-ZrO2 in PVDF-HFP polymer, the open metal sites of MOFs and acid surfaces of S-ZrO2 can immobilize anions by strong Lewis acid-base interaction, which enhances the effect of immobilization anions, achieving a high Li-ion transference number (t(+)) of 0.72, and acquiring a high ionic conductivity of 1.05x10(-4) S center dot cm(-1) at 60 degrees C. The symmetrical Li/Li cells with the anion-immobilized SCEs may steadily operate for over 600 h at 0.05 mA center dot cm(-2) without the short-circuit occurring. Besides, the solid composite Li/LiFePO4 (LFP) cell with the anion-immobilized SCEs shows a superior discharge specific capacity of 158 mAh center dot g(-1) at 0.2 C. The results illustrate that the anion-immobilized SCEs are one of the most promising choices to optimize the performances of ASSLMBs.

Automated summary

The novel anion-immobilized solid composite electrolytes based on metal-organic frameworks (MOFs, UiO-66-NH2) and superacid ZrO2 (S-ZrO2) fillers show high electrochemical stability and ionic conductivity, leading to enhanced performance in solid-state lithium metal batteries (ASSLMBs). The incorporation of UiO-66-NH2 and S-ZrO2 in PVDF-HFP polymer results in a high Li-ion transference number (t(+)) of 0.72 and a high ionic conductivity of 1.05x10(-4) S center dot cm(-1) at 60 degrees C.