Red phosphorus confined in N-doped multi-cavity mesoporous carbon for ultrahigh-performance sodium-ion batteries

Abstract

Phosphorus-based materials are one of the most promising anodes due to their high theoretical capacity (2596 mAh g−1) and safe working potential for sodium-ion batteries (SIBs). However, they suffer from severe volume changes (≈293–487%) as well as poor electronic conductivity (10−14 S cm−1), resulting in fast capacity decay during cycling. To tackle the aforementioned issues, in this work, N-doped multi-cavity carbon (NMC) connected by porous structured walls is prepared via the surface energy-driven self-assembly strategy. The internal space is divided into multiple small grids connected by multiple porous carbon walls, which helps accommodate the volume change and build interconnected electronic conductive networks. The amorphous red P is encapsulated in the hollow multi-cavity of carbon and forms P@NMC anode. Benefitting from the unique structure in alleviating volume change and enabling fast electron transport, the SIBs assembled with P@NMC anode exhibit excellent cycling stability and outstanding rate capability as well, retaining a high discharge capacity of 923.7 mAh g−1 after 1000 cycles at 0.5 A g−1 and keeping the Coulombic Efficiencies (CEs) as over 98.5%. Furthermore, the mechanism of sodium-ion storage in P@NMC is dynamically investigated, providing a new perspective for figuring out the electrochemical cycling behavior.