Hollow mesoporous hetero-NiCo₂S₄/Co₉S₈ submicro-spindles were fabricated in high yield, and delivered excellent pseudocapacitance with high energy density and desirable cycling duration at high rates for advanced hybrid supercapacitors.

In this study, one-dimensional (1D) CoMoO₄·0.9H₂O nanorods (NRs) with different sizes and crystallinities were controllably fabricated via a facile hydrothermal strategy coupled with the assistance of various surfactants, and further utilized as electroactive materials for supercapacitors. The significant influences of surfactants on the crystalline phases, sizes and electrochemical performance of the resulting CoMoO₄·0.9H₂O were systematically investigated. Physicochemical characterization demonstrated that the 1D NR product (denoted as CMO-CTMAB) synthesized by using hexadecyl trimethyl ammonium bromide (CTMAB) was endowed with the weakest crystallization, minimum size (∼10 nm) and the highest specific surface area (∼98 m² g⁻¹), when compared to other anionic and/or non-ionic surfactants. Benefiting from their weak crystallization, large electroactive surface, and 1D nanoscale architecture, the ultrafine CMO-CTMAB NRs manifested excellent electrochemical capacitance with the largest specific capacitance (SC) of 377 F g⁻¹ and high SC retention (∼93%) in 2 M KOH up to 1000 cycles at a current rate of 0.5 A g⁻¹.

Na₄Fe₃(PO₄)₂P₂O₇ (NFPP) is recognized as a prospective electrode for sodium-ion batteries (SIBs) because of its structure stability, economic viability and environmental friendliness. Nevertheless, its commercialization is constrained by low operating voltage and limited theoretical capacity, which result in a power density significantly inferior to that of LiFePO₄. To address these limitations, in this work, we first designed and synthesized a series of Mn-doped NFPP to enhance its operating voltage, inspired by the successful design of LiFe_1-xMn_xPO₄ cathodes. This approach was implemented to enhance the operating voltage of the material. Subsequently, the optimized Na₄Fe_1.2Mn_1.8(PO₄)₂P₂O₇ (1.8Mn-NFMPP) sample was selected for further Ti-doped modification to enhance its cycle durability and rate performance. The final Mn/Ti co-doped Na₄Fe_1.2Mn_1.7Ti_0.1(PO₄)₂P₂O₇ (0.1Ti-NFMTPP) material exhibited a high operating voltage of ~3.6 V (vs. Na⁺/Na) in a half cell, with an outstanding reversible capacity of 122.9 mAh g⁻¹ at 0.1 C and remained at 90.6% capacity retention after 100 cycles at 0.5 C. When assembled into a coin-type full cell employing a commercial hard carbon anode, the optimized cathode material exhibited an initial capacity of 101.7 mAh g⁻¹, retaining 86.9% capacity retention over 50 cycles at 0.1 C. These results illustrated that optimal Mn/Ti co-doping is an effective methodology to boost the electrochemical behavior of NFPP materials, achieving mitigation of the Jahn–Teller effect on the Mn³⁺ and Mn dissolution problem, thereby significantly improving structural stability and cycling performance.