Designing a carbon nanofiber-encapsulated iron carbide anode and nickel-cobalt sulfide-decorated carbon nanofiber cathode for high-performance supercapacitors

Three-dimensional NiCoS nanotubes@NiCo-LDH nanosheets core-shell heterostructure for high-rate capability alkaline zinc-based batteries

Aqueous alkaline zinc-based batteries (AAZBs) are promising for large-scale applications due to their high working voltage, safety, and low cost. However, the further development of AAZBs has been significantly hindered by the low electronic conductivity and poor cycling stability of traditional nickel/cobalt-based cathode materials. In this work, a binder-free electrode was successfully designed by electrodepositing NiCo-LDH nanosheets on NiCoS nanotube arrays that were grown on nickel foam (NiCoS@NiCo-LDH). The unique three-dimensional core-shell heterostructures not only enhance electrical conductivity but also offer abundant active sites and rapid ion/electron transport channels, thereby improving its electrochemical performance. The as-fabricated NiCoS@NiCo-LDH electrode delivers a capacity of 312 mA h g-1 (0.624 mA h cm-2) at 2 mA cm-2 and exhibits high rate capability with 90% capacity retention at 10 mA cm-2. Additionally, the assembled NiCoS@NiCo-LDH//Zn battery exhibits a high energy density of 435.3 W h kg-1 at a power density of 4.1 kW kg-1 and maintains 95.9% of its capacity after 3000 cycles at a current density of 20 mA cm-2.

Controllable synthesis of Fe3C-reinforced petal-like lignin microspheres with boosted electrochemical performance and its application in high performance supercapacitors

One more effective measure to solve the energy crisis caused by the shortage of fossil energy is to convert natural renewable resources into high-value chemical products for electrochemical energy storage. Lignin has broad application prospects in this field. In this paper, three kinds of lignin with different molecular weights were obtained by the ethanol/water grading of Kraft lignin (KL). Then, different surface morphology lignin microspheres were prepared by spray drying. Finally, petal-like microspheres were successfully prepared by mixing and grinding the above four kinds of surface morphology lignin microspheres with potassium ferrate and cyanogen chloride and carbonizing at 800 °C and were later used as electrode materials for supercapacitors. Compared with the other microspheres, LMS-F3@Fe3C has the highest specific surface area (1041.42 m2 g-1), the smallest pore size (2.36 nm) and the largest degree of graphitization (ID/IG = 1.06). At a current density of 1 A g-1, the maximum specific capacitance is 786.7 F g-1. At a power density of 1000 W kg-1, the high energy density of 83.3 Wh kg-1 is displayed. This work provides a novel approach to the modulation of surface morphology and structure of lignin microspheres.

Inhabiting Inactive Transition by Coupling Function of Oxygen Vacancies and Fe─C Bonds achieving Long Cycle Life of an Iron-Based Anode

Fe-based battery-type anode materials with many faradaic reaction sites have higher capacities than carbon-based double-layer-type materials and can be used to develop aqueous supercapacitors with high energy density. However, as an insurmountable bottleneck, the severe capacity fading and poor cyclability derived from the inactive transition hinder their commercial application in asymmetric supercapacitors (ASCs). In this work, driven by the "oxygen pumping" mechanism, oxygen-vacancy-rich Fe@Fe3 O4 (v) @Fe3 C@C nanoparticles that consist of a unique "fruit with stone"-like structure are developed, and they exhibit enhanced specific capacity and fast charge/discharge capability. Experimental and theoretical results demonstrate that the capacity attenuation in conventional iron-based anodes is greatly alleviated in the the Fe@Fe3 O4 (v) @Fe3 C@C anode because the irreversible phase transition to the inactive γ-Fe2 O3 phase can be inhibited by a robust barrier formed by the coupling of oxygen vacancies and Fe─C bonds, which promotes cycle stability (93.5% capacity retention after 24 000 cycles). An ASC fabricated using this Fe-based anode is also observed to have extraordinary durability, achieving capacity retention of 96.4% after 38 000 cycles, and a high energy density of 127.6 W h kg-1 at a power density of 981 W kg-1 .