The drastic need for development
of power and electronic equipment
has long been calling for energy storage materials that possess favorable
energy and power densities simultaneously, yet neither capacitive
nor battery-type materials can meet the aforementioned demand. By
contrast, pseudocapacitive materials store ions through redox reactions
with charge/discharge rates comparable to those of capacitors, holding
the promise of serving as electrode materials in advanced electrochemical
energy storage (EES) devices. Therefore, it is of vital importance
to enhance pseudocapacitive responses of energy storage materials
to obtain excellent energy and power densities at the same time. In
this Review, we first present basic concepts and characteristics about
pseudocapacitive behaviors for better guidance on material design
researches. Second, we discuss several important and effective material
design measures for boosting pseudocapacitive responses of materials
to improve rate capabilities, which mainly include downsizing, heterostructure
engineering, adding atom and vacancy dopants, expanding interlayer
distance, exposing active facets, and designing nanosheets. Finally,
we outline possible developing trends in the rational design of pseudocapacitive
materials and EES devices toward high-performance energy storage.
Aqueous zinc ion batteries are promising secondary batteries
for
next-generation electrochemical energy storage. In this work, we report
a hybrid electrolyte system with 3 M Zn(OTf)2 as zinc salt
and 1 M urea + 0.3 M LiOAc as hybrid solute additives for highly reversible
aqueous zinc ion batteries. In this electrolyte system, partial coordinated
water molecules of Zn2+ are replaced, and the original
hydrogen bond network of the bulk electrolyte also suffers from interruption.
Moreover, the introduction of lithium acetate solves the aggravated
self-corrosion caused by urea on the one hand and inhibits the growth
of dendrites through the electrostatic shielding effect on the other.
Benefiting from this multifunctional synergistic effect, dendrite-free
Zn plating/stripping for 600 h at 4.8 mA cm–2 (20%
depth of discharge) and highly reversible plating/stripping at ∼99.7%
Coulombic efficiency with a high cumulative plating capacity of 1600
mAh is achieved.
Wearable strain sensors with the ability of detecting physiological activities play an important role in personalized healthcare. Electrospun fibers have become a popular building block for wearable strain sensors due to their excellent mechanical properties, breathability, and light weight. In this review, the structure and preparation process of electrospun fibers and the conductive layer are systematically introduced. The impact of materials and structures of electrospun fibers on the wearable strain sensors with a following discussion of sensing performance optimization strategies is outlined. Furthermore, the applications of electrospun fiber‐based wearable strain sensors in biomonitoring, motion detection, and human‐machine interaction are presented. Finally, the challenges and promising future directions for the community of wearable strain sensors based on electrospun fibers are pointed out.
The current energy crises and imminent danger of global warming severely limit the ability to scale societal development sustainably. As such, there is a pressing need for utilizing renewable, green energy sources, such as wind energy, which is ubiquitously available on Earth. In this work, a fundamentally new wind‐energy‐harvesting technology is reported, which is based on the giant magnetoelastic effect in a soft composite system, namely, magnetoelastic generators. Its working principle is based on wind‐induced mechanical deformation, which alters the magnetic field in a soft system converting the wind energy into electricity via electromagnetic induction from arbitrary directions. The wind‐energy‐harvesting system features a low internal impedance of 68 Ω, a high current density of 1.17 mA cm–2, and a power density of 0.82 mW cm–2 under ambient natural wind. The system is capable of sustainably driving small electronics and electrolytically splitting water. The system can generate hydrogen at a rate of 7.5 × 10–2 mL h–1 with a wind speed of 20 m s−1. Additionally, since magnetic fields can penetrate water molecules, the magnetoelastic generators are intrinsically waterproof and work stably in harsh environments. This work paves a new way for wind‐energy harvesting with compelling features, which can contribute largely to the hydrogen economy and the sustainability of human civilization.
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