Advanced flexible batteries with high energy density and long cycle life are an important research target. Herein, the first paradigm of a high-performance and stable flexible rechargeable quasi-solid-state Zn-MnO battery is constructed by engineering MnO electrodes and gel electrolyte. Benefiting from a poly(3,4-ethylenedioxythiophene) (PEDOT) buffer layer and a Mn -based neutral electrolyte, the fabricated Zn-MnO @PEDOT battery presents a remarkable capacity of 366.6 mA h g and good cycling performance (83.7% after 300 cycles) in aqueous electrolyte. More importantly, when using PVA/ZnCl /MnSO gel as electrolyte, the as-fabricated quasi-solid-state Zn-MnO @PEDOT battery remains highly rechargeable, maintaining more than 77.7% of its initial capacity and nearly 100% Coulombic efficiency after 300 cycles. Moreover, this flexible quasi-solid-state Zn-MnO battery achieves an admirable energy density of 504.9 W h kg (33.95 mW h cm ), together with a peak power density of 8.6 kW kg , substantially higher than most recently reported flexible energy-storage devices. With the merits of impressive energy density and durability, this highly flexible rechargeable Zn-MnO battery opens new opportunities for powering portable and wearable electronics.

Currently, the main bottleneck for the widespread application of Ni-Zn batteries is their poor cycling stability as a result of the irreversibility of the Ni-based cathode and dendrite formation of the Zn anode during the charging-discharging processes. Herein, a highly rechargeable, flexible, fiber-shaped Ni-Zn battery with impressive electrochemical performance is rationally demonstrated by employing Ni-NiO heterostructured nanosheets as the cathode. Benefiting from the improved conductivity and enhanced electroactivity of the Ni-NiO heterojunction nanosheet cathode, the as-fabricated fiber-shaped Ni-NiO//Zn battery displays high capacity and admirable rate capability. More importantly, this Ni-NiO//Zn battery shows unprecedented cyclic durability both in aqueous (96.6% capacity retention after 10 000 cycles) and polymer (almost no capacity attenuation after 10 000 cycles at 22.2 A g ) electrolytes. Moreover, a peak energy density of 6.6 µWh cm , together with a remarkable power density of 20.2 mW cm , is achieved by the flexible quasi-solid-state fiber-shaped Ni-NiO//Zn battery, outperforming most reported fiber-shaped energy-storage devices. Such a novel concept of a fiber-shaped Ni-Zn battery with impressive stability will greatly enrich the flexible energy-storage technologies for future portable/wearable electronic applications.

Supercapacitors (SCs) have great promise as the state‐of‐the‐art power source in portable electronics and hybrid vehicles. The performance of SCs is largely determined by the properties of the electrode material, and numerous efforts have been devoted to the explorations of novel electrode materials. Recently, iron‐based materials, including Fe2O3, Fe3O4, FeOOH, FeOx, CoFe2O4, and MnFe2O4, have received considerable attention as very promising electrode materials for SCs due to their high theoretical specific capacitances, natural abundance, low cost, and non‐toxicity. However, most of these Fe‐based SC electrodes suffer from poor conductivity and/or electrochemical instability, which seriously impede their implementation as high‐performance electrodes for SCs. To settle these issues, substantial efforts have been made in improving their conductivity and cycling stability, and great processes have been achieved. Here, recent research advances in the rational design and synthesis of diverse Fe‐based nanostructured electrodes and their capacitive performance for SCs are presented. Besides, challenges and prospects of Fe‐based materials as advanced negative electrodes for SCs are also discussed.

A new type of ultrafast Ni//Bi battery with high flexibility and impressive electrochemical performance is demonstrated for the first time based on an as-prepared Bi electrode as the anode and a NiCo O nanowire electrode as the cathode. The NiCo O //Bi battery is able to deliver a remarkable energy density of 85.8 W h kg at a power density of 1.02 kW kg , and still retains 55.4 W h kg when the power density is increased to 21.2 kW kg .

Alkali metals are ideal anodes for high-energydensity rechargeable batteries, while seriously hampered by limited cycle life and low areal capacities. To this end, rationally designed frameworks for dendrite-free and volume-changeless alkali-metal deposition at both high current densities and capacities are urgently required. Herein, a general 3D conductive Ti 3 C 2 T X MXene-melamine foam (MXene-MF) is demonstrated as an elastic scaffold for dendrite-free, high-areal-capacity alkali anodes (Li, Na, K). Owing to the lithiophilic nature of F-terminated MXene, conductive macroporous network, and excellent mechanical toughness, the constructed MXene-MF synchronously achieves a high current density of 50 mA cm −2 for Li plating, high areal capacity (50 mAh cm −2 ) with high Coulombic efficiency (99%), and long lifetime (3800 h), surpassing the Li anodes reported recently. Meanwhile, MXene-MF shows flat voltage profiles for 720 h at 10 mA cm −2 for the Na anode and 800 h at 5 mA cm −2 for the K anode, indicative of the wide applicability. Notably, the high current density of 20 mA cm −2 for 20 mAh cm −2 for the Na anode, accompanying good recyclability was rarely achieved before. When coupled with sulfur or Na 3 V 2 (PO 4 ) 3 cathodes, the assembled MXene-MF alkali (Li, Na)-based full batteries showcase enhanced rate capability and cycling stability, demonstrating the potential of MXene-MF for advanced alkali-metal batteries.