Research Projects

The global drive for decarbonizing the energy and transport sector has pushed our dependency on renewable resources like solar, wind, and hydro energy. However, the current energy storage requirements of the grid storage and EV applications cannot be met by conventional Lithium-ion batteries (LIBs) due to their low energy density (<250 Wh kg-1). By contrast, Lithium–sulfur batteries (Li-S) using sulfur cathode (1600 mAh g-1), and Lithium metal (3600 mAh g-1) can offer higher energy density (>350 Wh kg-1). Despite the high-capacity electrodes, a practical Li-S battery cannot be realized due to instability issues in electrodes. The low electronic conductivity of S cathode (5 X 10-28 S m-1), sluggish conversion kinetics (S to Li2S), polysulfide shuttling, highly reactive/dendritic Li anode remains the major obstacle for commercialization. The realistic energy density of Li–S is much lower due to (i) low elemental sulfur loading (mg cm-2), (ii) high N/P ratio, and (iii) high electrolyte/sulfur (E/S) mass ratio in prototypes. To achieve energy density >350 Wh kg−1, a Li-S battery performing efficiently at high sulfur loading (8-12 mg cm-2), and Li anode with low N/P ratio, E/S mass ratio (<5) must be developed. Therefore, the global objective of the project is to develop high density and fast charging Li-S prototypes with high energy density (>350 Wh kg-1) and long stability. The current research will identity the pathways for practical Li-S batteries (>350 Wh kg-1) by engineering: sulfur cathode, and Li metal anode, and separator. Strategies involving interface engineering of Li anode, heterostructure cathode host, and electrolyte engineering will be employed. The poor S cathode utilization and sluggish kinetics, that leads to low discharge capacity will be addressed by newly developed carbon-based sulfur host. The hosts with high porosity will efficiently confine large amount of sulfur cathode (>75 wt. %), helping to achieve high S mass loading. The electrocatalytic compounds, and redox mediators in cathode host will favor rapid polysulfide conversion kinetics, helping to achieve high capacity at high C rates. Dual functional separators employing several ceramic coatings will be employed to overcome polysulfide shuttling issues and improve the stability. The dendrite formation and SEI instability issues in Li anode are addressed by introducing the Li+ ion-conductive artificial SEI layer that exbibits negligible electronic conductivity and strong mechanical strength. An artificial SEI layer will be developed over thinner Li metal anode, and alloy type artificial SEI layers will also be studied to enable low N/P ratio. At the end of the project, a Li-S prototype pouch cell battery will be studied by coupling newly engineered cathode and Li metal anode in pouch-cell configuration. The research proposal will output a new-class of energy storage system with high energy density at pack cell (>350 Wh kg-1), fast charging ability, and high cycle life.