Sulfur is a promising cathode for lithium batteries due to its high theoretical specific capacity (1673 mAh/g), low cost, and environmental friendliness. With a high specific energy density of 2500 Wh/kg, which is a five times greater energy density than a conventional Li-ion battery, Li-S batteries hold great potential for next-generation high-energy storage systems. However, wide-scale commercial use has been limited because some key challenges, such as the dissolution of the intermediate discharge product (Li2Sx, 2<X<8) in conventional liquid electrolytes, remain unsolved. On the other hand, all-solid-state batteries (SSBs) are considered to be the ultimate power supply for pure electric vehicles (EVs). SSB systems demonstrate a new approach for novel Li-S batteries. Replacing the organic electrolyte with solid-state electrolytes (SSEs) will intrinsically eliminate the dissolution of polysulfide. However, all of the solidstate Li-S batteries incorporating current state-of-the-art SSEs suffer from high interfacial impedance due to their low surface area.
A novel 3D Li-S battery was developed that is based on a tri-layer solid-state electrolyte structure. The battery consists of three components: a tri-layer solid-state electrolyte, cathode, and lithium metal anode. The tri-layer solid-state electrolytes have a supported thin-film dense layer in the middle, and a thicker porous scaffold support layer on the cathode side and anode side. The porous scaffold on the cathode side is designed to host sulfur-based materials, and Li metal is infiltrated into the pores of the anode scaffold. This highly porous scaffold provides a large interface area to enable better contact with the cathode and anode, which can significantly decrease cell impedance. This solid-state Li-S battery can effectively increase the energy density of batteries, and prevent lithium dendrite penetration through the dense solid-state electrolyte.
Conductive contents are added in the two outer layers of the SSE scaffold to improve electron transport. These conductive materials can be conductive polymers or porous carbon nanotube (CNT) fibers, or other conducting carbon materials. Charge/discharge cycles in the 3D networked SSE scaffolds occur by pore filling/emptying, thus removing electrode cycling fatigue and allowing for tight cell dimensional tolerances since electrodes don't expand or shrink when cycled.
Applications include electric vehicles, consumer electronics, unmanned aerial vehicles, and wind and solar energy storage.