Electric-Field Assisted Deposition of Carbon Nanostructures as a Binder-Free Approach to Fabricate High-Efficiency Li-S Batteries

Compared with the conventional li-ion batteries, lithium-sulfur (Li-S) batteries have been recognized as one of the most promising energy storage systems for the next-generation of lithium batteries regarding their high theoretical specific capacity (1675 mAhg^-1) and energy density (2600 Whkg⁻¹) [1]. In the present study, the multi-step electrophoretic deposition (EPD) method [2] was successfully employed as a facile approach to deposit a layered structure of conductive agents on the surface of Al sheet (as current collector). For this purpose, uniform DC electric fields in the range of 20-100 V were applied to stable suspensions of carbon black and MWCNTs in acetone for certain durations to obtain crack-free uniform layers. In the first step, a thick layer of carbon black was deposited on Al sheet serving as a 3-D framework for the following CNT layer. The obtained Al/CB/CNT cathode was impregnated with sulfur using a facile vapor-phase infusion technique at 200 ̊C. The galvanostatic charge-discharge profiles of the coin cells containing liquid organic electrolyte and lithium metal anode exhibited an initial discharge capacity of around 1000 mAhg^-1 along with an improved capacity retention rate after up to 50 cycles and coulombic efficiency of 94% at 0.1 C. The obtained results clearly show that cathode structures with significantly high discharge capacity and enhanced cycling behavior can be fabricated by simultaneous application of EPD technique and the sulfur vapor infusion method. The rate-capability tests carried out at 0.1C, 0.5C, 1C, and 2C also revealed relatively high cyclability of the cells. As a result, the EPD method can be applied as a facile binder-free and flexible method to fabricate layered/composite cathode structures for Li-S batteries.