Suppressing polysulfide shuttle in lithium-sulfur batteries using CNTs/C3N4/S cathodes

To suppressing the shuttle effect of lithium polysulfides during cycling, a synergism strategy is proposed to prepare CNTs/C3N4-X composites with an adjustable ratio of carbon nanotubes (CNTs) to carbon nitride (C3N4). When the mass of C3N4 is 10% of the total mass of CNTs/C3N4-X composites, the sulfur loading is high up to about 70%. Evaluated as cathodic host material of lithium-sulfur (Li-S) batteries, CNTs/C3N4-10/S cathode exhibits superior cyclical stability and rate capability. The first cycle discharge specific capacity is as high as 1074.3 mA h g−1 at 0.1 C, and it persists 830.3 mA h g−1 after 100 cycles. Even at 0.5 C, the discharge specific capacitance still retains 559.2 mA h g−1 after 650 cycles with a capacity retention ratio of 73.0%. The discharge specific capacities are 890.3, 783.9, 625.9 and 510.1 mA h g−1 at 0.2, 0.5, 1.0 and 2.0 C, indicating high rate capability. The superior performances are mainly ascribed to the synergism of CNTs and C3N4, which restricts the dissolution of lithium polysulfide, relieves volume expansion and improves the electrical conductivity, leading to enhanced cycle stability and rate capability of Li-S batteries.