In Situ Growth of\nCarbon Nanotubes on Iron Phosphate\nand Doped with Nitrogen and Selenium for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S)\nbatteries have been\nconsidered\nas one of the effective alternative energy systems to commercial lithium-ion\nbatteries (LIBs) due to their high theoretical energy density (2600\nWh kg<sup>–1</sup>), high theoretical specific capacity (1675\nmAh g<sup>–1</sup>), low cost, and abundant reserves of sulfur.\nHowever, intrinsic challenges, such as severe shuttle effect, low\nconductivity, and significant volume expansion, hinder their large-scale\napplication. In this study, a novel composite (CNT/FP-N, Se), which\nin situ grown with carbon nanotubes (CNTs) and doped with N, Se elements,\nhas been synthesized by utilizing commercial ferric phosphate (FP)\nas a precursor. Benefitting from the synergistic effects of abundant\nadsorption active sites of CNTs and the catalytic effects of N and\nSe, the shuttle effect of lithium polysulfides (LPS) can be effectively\ninhibited, leading to an enhancement of Li–S batteries when\nthe CNT/FP-N, Se is utilized as separator modifier. The charge/discharge\nplatforms can be well maintained from 0.1 to 5 C, and a capacity of\n617 mAh g<sup>–1</sup> at 5 C can be acquired. Notably, an\ninitial capacity of 990.7 mAh g<sup>–1</sup> at 1 C can be\nobtained, with a retention of 711.3 mAh g<sup>–1</sup> after\n500 cycles, corresponding to a capacity loss rate of only 0.056% per\ncycle. This work provides a feasible scheme for FP application in\nnext-generation low-cost energy systems.