Notably, many significant breakthroughs for a new generation of supercapacitors have been reported in recent years, related to theoretical understanding, material synthesis and device designs. Herein, we summarize the state-of-the-art progress toward mechanisms, new materials, and novel device designs for supercapacitors. Firstly, fundamental understanding of the mechanism is mainly focused on the relationship between the structural properties of electrode materials and their electrochemical performances based on some in situ characterization techniques and simulations. Secondly, some emerging electrode materials are discussed, including metal–organic frameworks (MOFs), covalent organic frameworks (COFs), MXenes, metal nitrides, black phosphorus, LaMnO₃, and RbAg₄I₅/graphite. Thirdly, the device innovations for the next generation of supercapacitors are provided successively, mainly emphasizing flow supercapacitors, alternating current (AC) line-filtering supercapacitors, redox electrolyte enhanced supercapacitors, metal ion hybrid supercapacitors, micro-supercapacitors (fiber, plane and three-dimensional) and multifunctional supercapacitors including electrochromic supercapacitors, self-healing supercapacitors, piezoelectric supercapacitors, shape-memory supercapacitors, thermal self-protective supercapacitors, thermal self-charging supercapacitors, and photo self-charging supercapacitors. Finally, the future developments and key technical challenges are highlighted regarding further research in this thriving field.

Due to the energy crisis within recent decades, renewable energies such as solar, wind and tide energies have received a lot of attention. However, these renewable energies are dependent on the time and season. Consequently, energy storage systems are needed to fully utilize these energies including their connection with smart grids. Aqueous rechargeable lithium batteries (ARLBs) may be an ideal energy storage system due to its excellent safety and reliability. However, since the introduction of ARLBs in 1994, the progress on improving their performance has been very limited. Recently, their rate performance, especially superfast charging performance, reversible capacity and cycling life of their electrode materials were markedly improved. The present work reviews the latest advances in the exploration of the electrode materials and the development of battery systems. Also the main challenges in this field are briefly commented on and discussed.

A composite membrane of a nonwoven fabric with poly(vinylidene fluoride) exhibiting high safety (self-extinguishing), good mechanical property and low cost is reported. The ionic conductivity of the as-prepared gel membrane saturated with 1 mol l⁻¹ LiPF₆ electrolyte at ambient temperature can be up to 0.30 mS cm⁻¹, higher than that of the corresponding well-used commercial separator (Celgard 2730), 0.21 mS cm⁻¹. Moreover, the lithium ion transference in the gel membrane at room temperature is almost twice that in the commercial separator. Furthermore, the absorbed solvent is difficult to evaporate at elevated temperature. Its electrochemical performance is evaluated by using a LiFePO₄ cathode. The obtained results suggest that this gel-type composite membrane is very attractive for large-capacity battery systems requiring high safety and low cost.

The past decade has witnessed substantial advances in the synthesis of various electrode materials with three-dimensional (3D) ordered macroporous or mesoporous structures (the so-called “inverse opals”) for applications in electrochemical energy storage devices. This review summarizes recent advancements in 3D ordered porous (3DOP) electrode materials and their unusual electrochemical properties endowed by their intrinsic and geometric structures. The 3DOP electrode materials discussed here mainly include carbon materials, transition metal oxides (such as TiO₂, SnO₂, Co₃O₄, NiO, Fe₂O₃, V₂O₅, Cu₂O, MnO₂, and GeO₂), transition metal dichalcogenides (such as MoS₂ and WS₂), elementary substances (such as Si, Ge, and Au), intercalation compounds (such as Li₄Ti₅O₁₂, LiCoO₂, LiMn₂O₄, LiFePO₄), and conductive polymers (polypyrrole and polyaniline). Representative applications of these materials in Li ion batteries, aqueous rechargeable lithium batteries, Li-S batteries, Li-O₂ batteries, and supercapacitors are presented. Particular focus is placed on how ordered porous structures influence the electrochemical performance of electrode materials. Additionally, we discuss research opportunities as well as the current challenges to facilitate further contributions to this emerging research frontier.