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

Abstract

Lithium−sulfur (Li−S) batteries have been considered as one of the effective alternative energy systems to commercial lithium-ion batteries (LIBs) due to their high theoretical energy density (2600 Wh kg −1 ), high theoretical specific capacity (1675 mAh g −1 ), low cost, and abundant reserves of sulfur. However, intrinsic challenges, such as severe shuttle effect, low conductivity, and significant volume expansion, hinder their large-scale application. In this study, a novel composite (CNT/FP-N, Se), which in situ grown with carbon nanotubes (CNTs) and doped with N, Se elements, has been synthesized by utilizing commercial ferric phosphate (FP) as a precursor. Benefitting from the synergistic effects of abundant adsorption active sites of CNTs and the catalytic effects of N and Se, the shuttle effect of lithium polysulfides (LPS) can be effectively inhibited, leading to an enhancement of Li−S batteries when the CNT/FP-N, Se is utilized as separator modifier. The charge/ discharge platforms can be well maintained from 0.1 to 5 C, and a capacity of 617 mAh g −1 at 5 C can be acquired. Notably, an initial capacity of 990.7 mAh g −1 at 1 C can be obtained, with a retention of 711.3 mAh g −1 after 500 cycles, corresponding to a capacity loss rate of only 0.056% per cycle. This work provides a feasible scheme for FP application in next-generation low-cost energy systems.