The main limitation of aqueous supercapacitors (SCs) lies in their narrow operating voltages, especially when compared with organic SCs. Fundamental understanding of factors relevant to the operating voltage helps providing guidance for the assembly of high-voltage aqueous SCs. In this regard, this concept analyzes the deciding factors for the operating voltage of aqueous SCs. Strategies applied to expand the operating voltage are summarized and discussed from the aspects of electrolyte, electrode, and asymmetric structure. Dynamic factors associated with water electrolysis and maximally using the available potential ranges of electrodes are particularly emphasized. Finally, other promising approaches that have not been explored and their challenges are also elaborated, hoping to provide more insights for the design of high-voltage aqueous SCs.

A facile solvothermal reduction strategy is demonstrated to introduce oxygen defects into ultrathin Co3O4 nanosheets (R–Co3O4), which function as an advanced cathode for Zn//Co batteries.

The exploration of high-energy anodes with good mechanical properties is highly attractive for flexible asymmetric supercapacitors (ASCs) but challenging. Owing to the excellent conductivity and superior mechanical flexibility, carbon fiber textile (CFT) holds great promise as a substrate/ current-collector for fabricating flexible electrodes. Yet, it is rarely used as a flexible active electrode in terms of its low electrochemical reactivity and small accessible area. In this work, an effective surface and structural modulation strategy is developed to directly tune CFT into a highly active anode for flexible ASCs by creating hierarchical pores and numerous pseudocapacitive oxygenic groups. Arising from large surface and increased active sites, the as-prepared activated porous CFT (APCFT) electrode not only achieves a large capacitance (1.2 F cm −2 at 4 mA cm −2 ) and fast kinetics but also shows satisfying cycling durability (no capacitance decay after 25 000 cycles). More importantly, an advanced flexible ASC device with an impressive energy density of 4.70 mWh cm −3 is successfully assembled by employing this APCFT as an anode, outperforming most recently reported ASC devices. This dual modification strategy may throw light on the rational design of new generation advanced carbon electrodes for high-performance flexible supercapacitors.

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Rechargeable alkaline zinc‐ion batteries (ZIBs) have gained extensive attention on account of their inexpensiveness, and high levels of safety and output voltage, but the lack of suitable cathode materials with high energy storage property and long cycle stability limits further development of ZIBs. Herein, we report an effective two‐step electrochemical approach to prepare Ni@NiO core‐shell dendritic architectures as cathode material for rechargeable alkaline ZIBs. Benefiting from the highly active NiO shell and unique core‐shell structure, this Ni@NiO electrode shows an excellent discharge capacity (0.112 mAh cm−2, at 4 mA cm−2) and a high rate capability (63.7 % capacity retention at 40 mA cm−2). Furthermore, the alkaline ZIBs with this Ni@NiO cathode also displays a high energy density of 0.193 mWh cm−2 and a remarkable power density of 65.0 mW cm−2.

Carbon nanomaterials with remarkable capacitance are highly notable. Although electronic double‐layer capacitors exhibit high power density, their low energy density blocks the practical utility of these carbon materials. Herein, a type of porous‐carbon nanoarchitecture with significant capacitive performance is successfully synthesized using a ZnO template and KOH activation. Benefiting from its excellent conductivity, ultrahigh surface area, and porous architecture, the as‐prepared porous carbon delivers a high capacitance of 245.4 mF cm−2 at a current density of 2 mA cm−2 with impressive rate performance. Moreover, it shows superior cycling durability with more than 99% capacitance retention after 10 000 cycles. A cost‐effective, eco‐friendly, and promising strategy is proposed for the large‐scale preparation of porous‐carbon nanomaterial electrodes.

Implementation of aqueous supercapacitors (SCs) in industrial production is within reach and will be facilitated through further expanding their operating voltages. This Concept article by X. Lu et al. on page 3639 ff. deals with the recent understanding of factors relevant to the operating voltages of SCs, and novel strategies that have been identified to increase the stable voltages of SCs. From the aspect of suppressing water electrolysis, important roles of both electrolyte and electrode surface are evident.