Benzene-1,2-dithiolato complexes as cathode materials for rechargeable lithium batteries

Highlights: • Benzene-1,2-dithiolato complexes (M-BDTs) are synthesized and used as cathode materials. • The M-BDTs are colored solids and insoluble in liquid ether electrolyte. • The volumetric specific capacities and energy densities of M-BDTs are increased. • The separate electron/lithium ion storage processes are highly reversible. -- Abstract: Organosulfides are a class of promising cathode materials for rechargeable lithium batteries. In order to overcome their disadvantages of solubility and low mass density, we prepare benzene-1,2-dithiolato complexes with metal ions (Sn⁴⁺ and Cu²⁺) by a facile method, which are designated as Sn-(BDT)₂ and Cu-BDT, respectively. The synthesized compounds are colored solids and insoluble in liquid ether electrolyte. Their mass densities are about 2.0 mg cm⁻³, which are much higher than that (1.2 mg cm⁻³) of the starting material 1,2-benzenedithiol. When evaluated in Li half cells, Sn-(BDT)₂ delivers a capacity of 221.2 mAh g⁻¹ rendering a volumetric energy density of 973.2 Wh L⁻¹. Cu-BDT can deliver a capacity of 234.2 mAh g⁻¹ and its volumetric energy density is 1044.5 Wh L⁻¹. Both volumetric capacities and energy densities are higher than those of the starting material. In the discharge, the metal ions serve as electron receptors and 1,2-benzenedithiolate holds lithium ions. The separate electron/lithium ion storage process is highly reversible, which is evidenced by the cycling performances of 200 and 500 cycles for the Li/Sn-(BDT)₂ and Li/Cu-BDT cells, respectively. This strategy is promising to overcome the intrinsic disadvantages of organosulfides as cathode materials for lithium batteries.