Regulating the d-p band center of FeP/Fe2P heterostructure host with built-in electric field enabled efficient bidirectional electrocatalyst toward advanced lithium-sulfur batteries

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2023-05, Vol.463, p.142397, Article 142397
• Main Authors: Zhao, Zhenxin, Yi, Zonglin, Duan, Yunrui, Pathak, Rajesh, Cheng, Xiaoqin, Wang, Yongzhen, Elam, Jeffrey W., Wang, Xiaomin
• Format: Article
• Language: English
• Subjects: Built-in electric field; Heterostructure; Lithium-sulfur batteries; Phosphides
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2023.142397

•A favorable preparation strategy toward FeP/Fe2P heterostructure is proposed by regulating the calcination temperature of phosphating process.•Deciphering the role of energy gap between cation 3d and anion 2p band in regulating the adsorption and catalysis of polysulfides.•The charge migration and an internal electric field of FeP and Fe2P are induced after reaching a thermodynamic equilibrium state. Exploring advanced electrocatalysts and understanding their mechanism in regulating polysulfides-transformation is of great importance but a challenging task for lithium-sulfur batteries (LSBs). Herein, FeP/Fe2P heterostructure nanoparticles with an internal electric field, prepared by a temperature-controlled phosphating process, can effectively improve the electrocatalytic activities of the bidirectional Li2S deposition/dissolution. This improvement can be attributed to the modulating absorptivity of lithium polysulfides (LiPSs) and propelling charge transfer. The reduced d-p band center between bonding and antibonding orbitals of the Fe 3d and P 2p band in the heterostructure enables bonding with LiPSs to achieve a higher electronic concentration at the Fermi level. This regulates the adsorption-diffusion-conversion process, reduces the activation energy, and improves the Li+ diffusion. Benefiting from the boosted kinetics of the FeP/Fe2P heterostructure, the cells exhibit a high reversible capacity of 1412 mAh g−1 at 0.1 C and outstanding energy efficiency of ∼ 90% from 0.1 C to 2 C. Furthermore, the cell with high sulfur loading of 4 mg cm−2 demonstrates a high capacity of 786 mAh g−1 after 100 cycles at 0.5 C. This work presents an effective method and favorable guidance for developing advanced heterostructures in LSBs.