Stabilizing anionic redox processes in electrospun NiS2–based cathode towards durable aluminum-ion batteries

Abstract

Rechargeable aluminum-ion batteries (AIBs) are receiving considerable attention as a desirable device for large-scale energy storage owing to high theoretical capacity and abundance of aluminum. However, due to strong charge of Al3+, the state-of-the-art AIBs often show sluggish electrode reaction kinetics and rapid capacity fading and the available cathode materials always demonstrate poor structural stability, thereby greatly hindering their practical use. NiS2 with anion redox species (S22– dimers) and favorable electronic conductivity is a promising cathode to boost the performance of AIBs in terms of reversible capacity, rate capability and cycling stability. Here, we report a systematic investigation of the Al storage behavior and mechanism of NiS2/S-doped carbon (NiS2/SC) cathode based on a series of electrochemical tests and ex situ measurements. We further develop electrospun NiS2/S-doped carbon@S-doped carbon nanofiber (NiS2/SC@SCNF) structure as the cathode of AIBs. The as-fabricated AIB delivers an unprecedented Al3+ storage performance with a stable capacity of 76 mAh/g at 0.5 A/g CV 500 cycles and a superior cycling Coulombic efficiency of 97 %. This study reveals that NiS2/SC@SCNF undergoes a reversible evolution of initial Al3+ insertion followed by anionic redox between S22– and S2–, paving the road for the futher development of NiS2–based cathodes for AIBs.