Flexible energy storage devices are at the forefront of next‐generation power supplies, one of the most important components of which is the gel electrolyte. However, shortcomings exist, more or ...less, for all the currently developed hydrogel electrolytes. Herein, a facile and cost‐effective method is developed to construct an all‐round hydrogel electrolyte by using cotton as the raw material, tetraethyl orthosilicate as the crosslinker, and glycerol as the antifreezing agent. The obtained hydrogel electrolyte has high ionic conductivity, excellent mechanical properties (e.g., high tensile strength and elasticity), ultralow freezing point, good self‐healing ability, high adhesion, and good heat‐resistance ability. Remarkably, this hydrogel electrolyte can provide a record‐breaking high ionic conductivity of 19.4 mS cm−1 at −40 °C compared with previously reported aqueous electrolytes for zinc‐ion batteries. In addition, this hydrogel electrolyte can significantly inhibit zinc dendritic growth and parasitic side reactions from −40 to 60 °C. With this hydrogel electrolyte, a flexible quasi‐solid‐state Zn–MnO2 battery is assembled, which shows remarkable energy densities from −40 to 60 °C. The battery also exhibits outstanding cycling durability and has high endurance under various harsh conditions. This work opens new opportunities for the development of hydrogel electrolytes.
A hydrogel electrolyte with high ionic conductivity, ultralow freezing point, excellent mechanical properties, good self‐healing ability, high adhesion, and good heat‐resistance ability is constructed. It can effectively suppress the growth of zinc dendrites and the occurrence of parasitic side reactions, thereby enabling a high‐performance flexible quasi‐solid‐state Zn–MnO2 battery that can work normally in a wide temperature range.
Owing to the growing heat removal issue in modern electronic devices, electrically insulating polymer composites with high thermal conductivity have drawn much attention during the past decade. ...However, the conventional method to improve through‐plane thermal conductivity of these polymer composites usually yields an undesired value (below 3.0 Wm−1 K−1). Here, construction of a 3D phonon skeleton is reported composed of stacked boron nitride (BN) platelets reinforced with reduced graphene oxide (rGO) for epoxy composites by the combination of ice‐templated and infiltrating methods. At a low filler loading of 13.16 vol%, the resulting 3D BN‐rGO/epoxy composites exhibit an ultrahigh through‐plane thermal conductivity of 5.05 Wm−1 K−1 as the best thermal‐conduction performance reported so far for BN sheet‐based composites. Theoretical models qualitatively demonstrate that this enhancement results from the formation of phonon‐matching 3D BN‐rGO networks, leading to high rates of phonon transport. The strong potential application for thermal management has been demonstrated by the surface temperature variations of the composites with time during heating and cooling.
An oriented phonon‐matching skeleton is developed based on two kinds of 2D materials for efficient thermal conduction in polymer composites via ice‐templated assembly technology. This development leads to significantly improved through‐plane thermal conductivity for polymer composites when compared with traditional strategies, suggesting strong potential in thermal management. The results would benefit the design of novel thermal‐management materials.
Recent success in achieving highly stable Rb‐containing organolead halide perovskites has indicated the possibility of incorporating small monovalent cations, which cannot fit in the lead‐halide cage ...with an appropriate tolerance factor, into the perovskite lattice while maintaining a pure stable “black” phase. In this study, through a combined experimental and theoretical investigation by density functional theory (DFT) calculations on the incorporation of extrinsic alkali cations (Rb+, K+, Na+, and Li+) in perovskite materials, the size‐dependent interstitial occupancy of these cations in the perovskite lattice is unambiguously revealed. Interestingly, DFT calculations predict the increased ion migration barriers in the lattice after the interstitial occupancy. To verify this prediction, ion migration behavior is characterized through hysteresis analysis of solar cells, electrical poling, temperature‐dependent conductivity, and time‐dependent photoluminescence measurements. The results collectively point to the suppression of ion migration after lattice interstitial occupancy by extrinsic alkali cations. The findings of this study provide new material design principles to manipulate the structural and ionic properties of multication perovskite materials.
Interstitial occupancy in a perovskite lattice by small alkali cations is proposed and verified through a combined experimental and theoretical investigation. Density functional theory calculations and ion‐migration characterization further reveal increased ion‐migration barriers due to the presence of interstitial alkali cations. These findings provide new material design principles to manipulate the structural and ionic properties of the multication perovskite materials.
Owing to the growing heat removal issue of modern electronic devices, polymer composites with high thermal conductivity have drawn much attention in the past few years. However, a traditional method ...to enhance the thermal conductivity of the polymers by addition of inorganic fillers usually creates composite with not only limited thermal conductivity but also other detrimental effects due to large amount of fillers required. Here, novel polymer composites are reported by first constructing 3D boron nitride nanosheets (3D‐BNNS) network using ice‐templated approach and then infiltrating them with epoxy matrix. The obtained polymer composites exhibit a high thermal conductivity (2.85 W m−1 K−1), a low thermal expansion coefficient (24–32 ppm K−1), and an increased glass transition temperature (Tg) at relatively low BNNSs loading (9.29 vol%). These results demonstrate that this approach opens a new avenue for design and preparation of polymer composites with high thermal conductivity. The polymer composites are potentially useful in advanced electronic packaging techniques, namely, thermal interface materials, underfill materials, molding compounds, and organic substrates.
Polymer composites are fabricated by constructing 3D boron nitride nanosheet (3D‐BNNS) networks using an ice‐templated approach. The polymer composites exhibit a high thermal conductivity, low coefficient of thermal expansion, and an increased glass transition temperature at relatively low BNNS loading (9.29 vol%). This approach finds uses in the preparation of the polymer composites with high thermal conductivity.
Nitrogen‐doped graphene (NG) is a promising metal‐free catalyst for the oxygen‐reduction reaction (ORR). A facile and low‐cost synthesis of NG via the pyrolysis of graphene oxide and urea is ...reported. The N content in NG can be up to 7.86%, with a high percentage of graphitic N (≈24%), which gives rise to an excellent catalytic activity toward the ORR.
Flexible aqueous zinc-ion batteries (AZIBs) are promising to satisfy the emerging wearable electronics. However, conventional hydrogel electrolytes are unable to work at subzero temperatures because ...they inevitably freeze. In this work, a borax-crosslinked polyvinyl alcohol (PVA)/glycerol gel electrolyte is developed, in which glycerol can strongly interact with PVA chains, thus effectively prohibiting the formation of ice crystals within the whole gel network. Thanks to this, the freezing point of this gel electrolyte is below −60 °C, which allows it to work in extremely cold environments. Even at −35 °C, it still exhibits a high ionic conductivity of 10.1 mS cm−1 and great mechanical properties. On the basis of this anti-freezing gel electrolyte, a flexible quasi-solid-state aqueous Zn–MnO2 battery is assembled and realizes an impressive energy density of 46.8 mW h cm−3 (1330 μW h cm−2) at a power density of 96 mW cm−3 (2.7 mW cm−2) at 25 °C, outperforming nearly all the reported AZIBs. More importantly, when the temperature is reduced to −35 °C, a rather high energy density (25.8 mW h cm−3, 732 μW h cm−2) can still be achieved, and 53.3% of that value can be retained when the power density is increased to about 10-fold. This battery also shows excellent cycling durability (around 90% capacity retention over 2000 cycles) and great tolerance to various extreme conditions even when the temperature is down to −35 °C. These findings provide valuable insights into designing aqueous batteries/supercapacitors that can work in cold climates and high-altitude areas.
Metal‐based materials with exceptional intrinsic conductivity own excellent electromagnetic interference (EMI) shielding performance. However, high density, corrosion susceptibility, and poor ...flexibility of the metal severely restrict their further applications in the areas of aircraft/aerospace, portable and wearable smart electronics. Herein, a lightweight, flexible, and anticorrosive silver nanowire wrapped carbon hybrid sponge (Ag@C) is fabricated and employed as ultrahigh efficiency EMI shielding material. The interconnected Ag@C hybrid sponges provide an effective way for electron transport, leading to a remarkable conductivity of 363.1 S m−1 and superb EMI shielding effectiveness of around 70.1 dB in the frequency range of 8.2–18 GHz, while the density is as low as 0.00382 g cm−3, which are among the best performances for electrically conductive sponges/aerogels/foams by far. More importantly, the Ag@C sponge surprisingly exhibits super‐hydrophobicity and strong corrosion resistance. In addition, the hybrid sponges possess excellent mechanical resilience even with a large strain (90% reversible compressibility) and an outstanding cycling stability, which is far better than the bare metallic aerogels, such as silver nanowire aerogels and copper nanowire foams. This strategy provides a facile methodology to fabricate lightweight, flexible, and anticorrosive metal‐based sponge for highly efficient EMI shielding applications.
Anticorrosive, ultralightweight, and flexible silver nanowire wrapped with carbon hybrid sponge is designed and employed as electromagnetic interference (EMI) shielding material with ultrahigh efficiency. The interconnected hybrid sponge shows superb EMI shielding effectiveness of 70.1 dB, while the density is as low as 0.00382 g cm−3, which are among the best performances for electrically conductive sponges/aerogels/foams by far.
Laser‐induced graphene (LIG) has emerged as a promising and versatile method for high‐throughput graphene patterning; however, its full potential in creating complex structures and devices for ...practical applications is yet to be explored. In this study, an in‐situ growing LIG process that enables to pattern superhydrophobic fluorine‐doped graphene on fluorinated ethylene propylene (FEP)‐coated polyimide (PI) is demonstrated. This method leverages on distinct spectral responses of FEP and PI during laser excitation to generate the environment preferentially for LIG formation, eliminating the need for multistep processes and specific atmospheres. The structured and water‐repellant structures rendered by the spectral‐tuned interfacial LIG process are suitable as the electrode for the construction of a flexible droplet‐based electricity generator (DEG), which exhibits high power conversion efficiency, generating a peak power density of 47.5 W m−2 from the impact of a water droplet 105 µL from a height of 25 cm. Importantly, the device exhibits superior cyclability and operational stability under high humidity and various pH conditions. The facile process developed can be extended to realize various functional devices.
Monolithic fabrication of a flexible droplet‐based electricity generator (DEG) is demonstrated by in situ growth of laser‐induced graphene electrodes with different hydrophobicity in a fluorinated ethylene propylene‐coated polyimide bilayer structure. The DEG exhibits high power conversion efficiency, lighting up 480 LEDs with one water droplet. More importantly, the DEG exhibits superior cyclability and operational stability under high humidity and various pH conditions.
With the rapid development of wearable electronics, there arises an urgent need to exploit flexible, bendable, and even self-reparative energy storage devices. In order to realize this goal, one ...should construct suitable gel electrolytes. Herein, a zinc-salt-containing borax-crosslinked polyvinyl alcohol/nanocellulose hydrogel electrolyte is developed, and shows great mechanical properties, intriguing self-healing feature, and high ionic conductivity. To demonstrate the feasibility of this hydrogel electrolyte, a flexible quasi-solid-state zinc-ion hybrid supercapacitor is assembled from the hydrogel electrolyte, cellulose paper cathode, and zinc metal anode. This device can combine the advantages of both zinc-ion batteries and supercapacitors. It exhibits high capacity (56.1 mA h g
−1
, 504.9 mF cm
−2
, and 224.4 μA h cm
−2
at 0.5 mA cm
−2
), great rate capability (22.1 mA h g
−1
at 10 mA cm
−2
), and excellent cyclability (95.3% capacity retention over 5000 cycles). It can also be folded, bent, compressed, and even self-healed while sacrificing only a small portion of its capacity. This work opens the door to new possibilities in flexible energy storage.
The quasi-solid-state zinc-ion hybrid supercapacitor based on borax-crosslinked polyvinyl alcohol/nanocellulose hydrogel electrolyte displays not only great electrochemical performances but also high flexibility and self-healing ability.
A hybrid nanoparticle, consisting of BaTiO3 nanoparticles tightly embedded in bronnitride (BN) nanosheets, has been fabricated based on a daring supposition that BN may act as a host to incorporate ...ferroelectric nanoparticles to improve insulation and polarization under a high electric field. Using the hybrids as fillers in poly(vinylidene fluoride) (PVDF) composites, a high electric breakdown strength (Eb ≈580 kV/mm), which is 1.76 times of the PVDF film, is obtained when the filler content is 5 wt%. A large displacement (9.3 µC/cm2 under 580 kV/mm) is observed so as to obtain a high discharged energy density (Ud ≈17.6 J/cm3) of the BT@BN/PVDF composites, which is 2.8 times of the PVDF film. The enhancement ratio of Eb achieved in this study demonstrates the highest among the reported results. This hybrid structure of fillers provides an effective way to adjust and improve the energy storage properties of the polymer‐based dielectrics.
BaTiO3@BN hybrids with the structure of barium titanate nanoparticles embedded in bronnitride nanosheets are fabricated, which act as fillers in poly(vinylidene fluoride)‐based composites. The electric breakdown strength and discharged energy density of the composites are significantly enhanced owing to the reduced surface charge density and the enhanced displacement.
