Electrophoretically Deposited MnO₂/CNT Composite As Host Material for Efficient Li-S Batteries

Over the past few decades, lithium-sulfur (Li-S) batteries have gained growing attention as the next generation energy storage devices owing to their low cost, relative safety as well as higher theoretical capacity (1675 mAh g^-1) and energy density (2600 Wh kg^-1) [1]. This work employs the multi-step electrophoretic deposition (EPD) method [2] to fabricate a layered structure of conductive agents on the surface of micron-sized 3D carbon fiber paper (as the current collector).
For this purpose, a homogeneous and crack-free film of MnO₂/CNT was deposited as the host material (HM) on carbon fiber paper (CFP) by applying uniform DC electric fields of 30-80 V to the stable suspensions of manganese dioxide (MnO₂) and carbon nanotubes (MWCNTs) in acetone. The obtained CFP/MnO₂/CNT cathode was then impregnated with sulfur using a facile vapor-phase infusion technique at 200 ̊C.
The galvanostatic charge-discharge behavior of the coin cells containing CFP/MnO₂/CNT as cathode exhibited an initial discharge capacity of around 1000 mAh g^-1 and an improved capacity retention rate after up to 50 cycles at 0.1 C. Also, a coulombic efficiency of above 96% was achieved. It is shown that the EPD-deposited carbon and metal oxide-based host materials, as lithium-sulfur cathode, can achieve high discharge capacity and enhanced cycling behavior. In addition, the rate performance tests conducted at 0.1C, 0.5C, 1C, and 2C revealed relatively high capacities at current rates below 2C, implying excellent conductivity and reaction kinetics of the CFP/MnO₂/CNT/S composite. It is concluded that the EPD can be employed as a facile binder-free method to fabricate composite cathode structures for Li-S batteries.