Multifunctional cu-Cu3P heterojunction embedded in hierarchically porous carbon nanofibers to strengthen adsorption and catalytic effects based on built-in electric field for liS cell

Abstract

Lithium sulfur batteries (LSBs) are considered a highly promising next-generation battery system. However, severe shuttle effect and slow redox kinetics of lithium polysulfides (LiPSs) in LSBs are still the main obstacles hindering their rapid developments. In this study, the multifunctional Cu-Cu₃P heterojunction nanoparticles embedded in hierarchically porous carbon nanofibers (PCNFs) are designed and prepared for modifying separator of LSBs. The highly conductive metal Cu and PCNFs can synergistically enhance the conductivity of electrons and ions, and physically suppress “shuttle effect” of lithium LiPSs. Meanwhile, based on the spontaneous built-in electric field at the formed heterogeneous interfaces of Cu-Cu₃P, the heterojunction also can chemically adsorb LiPSs and greatly catalyze conversion of LiPSs, thus further suppressing the “shuttle effect” and excellent reaction kinetics of LiPSs. Based on these merits, the assembled LSBs using the heterojunction Cu-Cu₃P@PCNFs modified separator show outstanding initial specific discharge capacities up to 1009.2 mAh g⁻¹ at 1C and 998.5 mAh g⁻¹ at 2C, and stable cycling with an average capacity decay rate of 0.067 % and 0.084 % at 1C during 800 cycles and at 2C during 580 cycles, respectively. Even at a high sulfur loading of 2.5 mg cm⁻², an excellent specific discharge capacity of 784.6 mAh g⁻¹ after 180 cycles 0.5C still can be realized. The work provides a novel perspective on understanding adsorption and catalytic design in energy storage equipment based on heterojunction engineering and built-in electric field.