Graphene–Li₂S–Carbon Nanocomposite\nfor Lithium–Sulfur Batteries

Abstract

Lithium\nsulfide (Li₂S) with a high theoretical specific\ncapacity of 1166mAh g^–1 is a promising cathode material\nfor next-generation Li–S batteries with high specific energy.\nHowever, low conductivity of Li₂S and polysulfide dissolution\nduring cycling are known to limit the rate performance and cycle life\nof these batteries. Here, we report on the successful development\nand application of a nanocomposite cathode comprising graphene covered\nby Li₂S nanoparticles and protected from undesirable interactions\nwith electrolytes. We used a modification of our previously reported\nlow cost, scalable, and high-throughput solution-based method to deposit\nLi₂S on graphene. A dropwise infiltration allowed us to\nkeep the size of the heterogeneously nucleated Li₂S particles\nsmaller and more uniform than what we previously achieved. This, in\nturn, increased capacity utilization and contributed to improved rate\nperformance and stability. The use of a highly conductive graphene\nbackbone further increased cell rate performance. A synergetic combination\nof a protective layer vapor-deposited on the material during synthesis\nand <i>in situ</i> formed protective surface layer allowed\nus to retain ∼97% of the initial capacity of ∼1040 mAh\ng_s^–1 at <i>C</i>/2 after over\n700 cycles in the assembled cells. The achieved combination of high\nrate performance and ultrahigh stability is very promising.