Highly Conductive Two-Dimensional Metal-Organic Frameworks for Resilient Lithium Storage with Superb Rate Capability

Abstract

Redox-active organic cathode materials have drawn growing attention because of the broad availability of raw materials, eco-friendliness, scalable production, and diverse structural flexibility. However, organic materials commonly suffer from fragile stability in organic solvents, poor electrochemical stability in charge/discharge processes, and insufficient electrical conductivity. To address these issues, using Cu(II) salt and benzenehexathiolate (BHT) as the precursors, we synthesized a robust and redox-active 2D metal-organic framework (MOF), [Cu₃(C₆S₆)]_n, namely, Cu-BHT. The Cu-BHT MOFs have a highly conjugated structure, affording a high electronic conductivity of 231 S cm^-1, which could further be increased upon lithiation in lithium-ion battery (LIB) applications. A reversible four-electron reaction reveals the Li storage mechanism of the Cu-BHT for a theoretical capacity of 236 mAh g^-1. The as-prepared Cu-BHT cathode delivers an excellent reversible capacity of 175 mAh g^-1 with ultralow capacity deterioration (0.048% per cycle) upon 500 cycles at a high current density of 300 mA g^-1. Therefore, we believe this work would provide a practical strategy for the development of high-power energy storage materials.

Keywords: Cu-BHT; LIBs; benzenehexathiolate; cathode; conductive 2D metal−organic frameworks (MOFs); high-rate.