High Entropy Metal Phosphide Activated Fluorinated Carbon as Electroactive Host for Extra High Cathode Capacity in Lithium–Sulfur Batteries

Abstract

Lithium–sulfur (Li–S) batteries are one of the most promising high-energy battery systems due to the high theoretical energy density (2600 Wh kg⁻¹). However, a large proportion of electro-inert host materials are typically employed in cathode composites, which severely reduces the practical performance of Li–S batteries. In this study, a novel approach is proposed using fluorinated activated carbon (CF) as an electroactive host of sulfur for the first time, which can release extra capacity during the initial operation. Specifically, with the activation effect of in situ deposited high entropy metal phosphide (HEP) catalyst Pd_0.34Sn_0.15Ni_0.05Co_0.09Cu_0.29P_0.08, the extra capacity of the HEP/CF host is almost 1.5 times higher than pristine CF. Consequently, the S/HEP/CF cathode exhibits high initial discharge capacity (1059.2 mAh g⁻¹_−composite at 0.1C), high rate performance (476.5 mAh g⁻¹_−composite at 2C) and long-term cycling stability. Moreover, the as-prepared cathode retains high initial discharge capacity of 492.6 mAh g⁻¹_−composite under harsh conditions (sulfur loading of 3.2 mg cm⁻² and lean electrolyte/sulfur ratio of 10 µL mg⁻¹). This work demonstrates a new strategy for designing electroactive sulfur hosts to improve the performance of Li–S batteries.