Self-assembled monolayers of diphenyl disulphide: a novel cathode material for rechargeable lithium batteries

Abstract

The use of self-assembled monolayers (SAM) of organic disulfide as novel cathode materials for high specific energy, rechargeable, lithium batteries is demonstrated for the first time. The suitability of monolayer films of diphenyl disulfide (DDS) as cathode materials for facilitating reversible insertion and de-insertion of Li⁺ ions is examined by means of cyclic voltammetry (CV), infra-red spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and charge-discharge measurements. The SAM-based cathodes on coupling with Li-metal anodes in 0.1 M LiClO₄ and tetrahydrofuran (THF) show good thermodynamic feasibility along with an open-circuit voltage of 2.9 V. The electrochemical capacity obtained is found, however, to fade during continuous cycling. This indicates a loss of electroactivity concomitant with the destruction of the monolayer functionalized cathode. The reasons for the coulombic efficiency of these rechargeable SAM-based cathodes are explained in terms of two different mechanistic modes of interaction of Li⁺ ions with the monomolecular film.