A Single-Phase Mixed Ion-Electron Conducting Metal-Organic Framework.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Mixed ionic-electronic conductors (MIECs) are crucial for electrochemical devices, enabling simultaneous charge and mass transport.
• Structurally defined single-phase MIECs are rare, with most systems relying on physical mixtures of components.

Purpose of the Study:

• To introduce a cation-rich design strategy for creating solid-state mixed ionic-electronic conductors.
• To engineer tunable transport properties in a two-dimensional copper-catecholate metal-organic framework (MOF).

Main Methods:

• A cation-rich design strategy was employed using a 2D copper-catecholate MOF, Cu 3 (HOTAT) 2 .
• Controlled fractional reduction of the MOF generated a series of Li x Cu 3 (HOTAT) 2 phases with varying Li content.
• Electronic-structure calculations were used to analyze transport properties.

Main Results:

• The Li-rich phase, Li 7.50 Cu 3 (HOTAT) 2 , demonstrated intrinsic mixed conduction at room temperature.
• Achieved electronic conductivity of 2.8 × 10 -3 S cm -1 and Li + conductivity of 1.1 × 10 -3 S cm -1 .
• As a cathode in all-solid-state Li batteries, it delivered 100 mAh g -1 over 100 cycles with high Coulombic efficiency.

Conclusions:

• Cation-rich reduction of redox-active 2D MOFs is an effective method for engineering solid-state mixed ionic-electronic conductors.
• This approach opens new avenues for developing dual-conducting porous materials for advanced electrochemical technologies.
• The developed material shows promise for high-performance, stable solid-state lithium-ion batteries.