A rGO-Based Fe2O3 and Mn3O4 Binary Crystals Nanocomposite Additive for High Performance Li-S Battery

Abstract Chemical anchor effect is an efficient route for polysulfides immobilization to enhance the performance of Li-S battery. Transition metal oxides are suitable chemical anchor matrix as Lewis acid coordinated with sulfur atoms in the form of Lewis base. Ion bonds may also be formed between anions in transition metal compounds and lithium ions in lithium polysulfides alleviating the shuttle effect. Reducing their crystal sizes to expose more surface active sites and expand surface areas is pivotal to sufficiently immobilize polysulfides. Here, an optimized GFM-2 composite was fabricated, where the 20 nm metal oxide particles aggregated by the 3-5 nm Fe2O3 and Mn3O4 binary crystals are uniformly distributed on the reduced graphene oxide (rGO) nanosheets. A high specific surface area up to 144.9 m2 g-1 was obtained for the GFM-2. The modified sulfur@rGO (S@G) cathode obtained by mixing S@G and GFM-2 additive with the mass ratio of 20: 1, presented high specific discharge capacities of 1356.3 and 770.2 mAh g-1, respectively, at scan rates of 0.1 and 5 C (1 C = 1675 mAh g-1) under conventional electrolyte dosage with electrolyte/sulfur (E/S) = 30 mL g(S)-1 and sulfur loading of 1.1 mg cm-2. The capacity was 1053.5 mAh g-1 at 1 C and maintained at 530.1 mAh g-1 after 1000 cycles with the low average capacity decay rate of each cycle of 0.049%. Under low electrolyte dosages of E/S = 15 and 8 mL g(S)-1, the high capacities of 1308.0 and 1230.4 mAh g-1 could be still obtained at 0.1 C, respectively. When the sulfur loading was increased to 2.8 mg cm-2 and E/S was reduced to 10 mL g(S)-1, the good capacity of 1163.6 mAh g-1 was gotten at 0.1 C. The high capacity and high cyclic property under different E/S and sulfur loading amounts indicate the potential for practical application of this simple but effective modified sulfur cathode.