Engineering the d-Orbital Energy of Metal–Organic Frameworks-Based Solid-State Electrolytes for Lithium–Metal Batteries

Abstract

Having an orbital-level understanding of the relationship between the electronic state of a central metal in metal−organic frameworks (MOFs) as solid-state electrolytes (SSEs) and Li + ion conductivity is crucial yet challenging for lithium−metal batteries (LMBs). In this study, we report the synthesis of functionalized UiO-66 as a model system to investigate the relationship between the d-band energy of Zr 3d orbitals and Li + ion conductivity. Specifically, the NO 2 group in electron-withdrawing NO 2 -decorated UiO-66 (NO 2 -UiO-66) can capture electron from ZrO 8 sites, resulting the increased energy in 3d z 2 and 3d xz/yz orbitals of Zr atom. The high-energy 3d z 2 and 3d xz/yz orbitals of Zr in NO 2 -UiO-66 hybridize with the 2p z and 2p x/y orbitals of O in ClO 4 − , leading to decreased antibonding orbital energy and resulting in a strong adsorption, ultimately immobilizing the anions and enhancing ion conductivities. Establishing the correlation between the d-orbital energy and Li + ion conductivity may create a descriptor for designing efficient SSEs for LMBs.

Recent progress and perspectives on metal–organic frameworks as solid-state electrolytes for lithium batteries

“…Because the ability of multicationic oligomers (MCOs) in MOFs could restrict the movement of anions and promote the dissociation of Li + , MOF-BZN exhibited an excellent Li + conductivity and t Li + transference number (Table 4). In a recent report, Zhao et al 72 introduced –NH 2 and –NO 2 into the UiO-66 framework, corresponding to electron donating and electron withdrawing groups, in order to investigate the relationship between the d-band energy of Zr 3d orbitals and Li + ion conductivity.…”