Lithium Ferrites@Polydopamine Core-Shell Nanoparticles as a New Robust Negative Electrode for Advanced Asymmetric Supercapacitors

Spinel ferrites hold great promise as attractive electrode materials for high-performance supercapacitors owing to their multiple valence states and abundant choice of metal cation. However, the main bottleneck for most of the currently reported spinel ferrite-based electrodes is relatively low specific capacitance. Herein, a new kind of lithium ferrites (Li0.5Fe2.5O4, LFO)@polydopamine (PDA) (denoted as LFO@PDA) core-shell nanoparticles with extraordinary capacitive performance as negative electrodes for aqueous asymmetric supercapacitors (ASCs) are reported first. Taking advantage of increased active sites, improved conductivity, enhanced hydrophilicity, and good strain accommodation in terms of the interesting core-shell architecture and PDA shell, the as-obtained LFO@PDA electrode reaches a remarkable capacitance of 276.4 F g(-1) and prominent durability (no any capacitance loss after 15 000 cycles). Moreover, a robust aqueous 1.8 V-ASC device with a preferable energy density of 33.9 Wh kg(-1) is also achieved based on the LFO@PDA electrode as negative electrode.