Towards practical Li–S batteries through the combination of a nanostructured graphene composite cathode and a novel sparingly solvating electrolyte

Lithium-sulfur batteries (LSBs) have emerged as promising alternatives to replace Li-ion technology in lightweight applications, but they still face some important challenges that hinder their commercialization. To overcome them, several optimization strategies focusing on each battery component have been investigated. In this work, we have explored the symbiotic combination of an optimized high-sulfur loading graphene-containing cathode with a novel sparingly solvating electrolyte (SSE) consisting of 1,3-dioxolane (DOL) as solvent and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OCTO) as diluent, at an E/S ratio of 7 μL mg−1. The impact of graphene incorporation into the cathode formulation and the physicochemical compatibility between cathode and electrolyte have been evaluated and compared to those obtained for the benchmarking DME/DOL electrolyte. Using the DOL/OCTO SSE enhanced wettability over our graphene-containing electrodes and hampered significant polysulfide dissolution. Most importantly, the electrochemistry of this system showed very promising values at coin cell level, achieving areal discharge capacities of 5.3 mAh cm−2 at C/10, enduring beyond 100 cycles with 65 % capacity retention. The transferability of the system to prototype cells was successfully demonstrated by assembling a monolayer pouch cell which reached initial capacities of 55 mAh and lasted more than 60 cycles, paving the way for real deployment and commercialization of this energy storage technology.