To keep pace with the increasing pursuit of portable and wearable electronics, it is urgent to develop advanced flexible power supplies. In this context, Zn‐ion batteries (ZIBs) have garnered ...increasing attention as favorable energy storage devices for flexible electronics, owing to the high capacity, low cost, abundant resources, high safety, and eco‐friendliness. Extensive efforts have been devoted to developing flexible ZIBs in the last few years. This work summarizes the recent achievements in the design, fabrication, and characterization of flexible ZIBs. Representative structures, such as sandwich and cable type, are particularly highlighted. Special emphasis is put on the novel design of electrolyte and electrode, which aims to endow reliable flexibility to the fabricated ZIBs. Moreover, current challenges and future opportunities for the development of high‐performance flexible ZIBs are also outlined.
The recent development of electrode materials, gel electrolytes, and device configurations for flexible zinc‐ion batteries (ZIBs) is reviewed. Recent progresses in flexible ZIBs are discussed by briefly categorizing into Zn–Mn based, Zn–V based, Zn–Prussian blue analog based, and the other ZIBs. The current challenges and future opportunities for the development of flexible ZIBs are also discussed.
The current boom of safe and renewable energy storage systems is driving the recent renaissance of Zn‐ion batteries. However, the notorious tip‐induced dendrite growth on the Zn anode restricts their ...further application. Herein, the first demonstration of constructing a flexible 3D carbon nanotube (CNT) framework as a Zn plating/stripping scaffold is constituted to achieve a dendrite‐free robust Zn anode. Compared with the pristine deposited Zn electrode, the as‐fabricated Zn/CNT anode affords lower Zn nucleation overpotential and more homogeneously distributed electric field, thus being more favorable for highly reversible Zn plating/stripping with satisfactory Coulombic efficiency rather than the formation of Zn dendrites or other byproducts. As a consequence, a highly flexible symmetric cell based on the Zn/CNT anode presents appreciably low voltage hysteresis (27 mV) and superior cycling stability (200 h) with dendrite‐free morphology at 2 mA cm−2, accompanied by a high depth of discharge (DOD) of 28%. Such distinct performance overmatches most of recently reported Zn‐based anodes. Additionally, this efficient rechargeability of the Zn/CNT anode also enables a substantially stable Zn//MnO2 battery with 88.7% capacity retention after 1000 cycles and remarkable mechanical flexibility.
A flexible 3D carbon nanotube (CNT) network is proposed as a highly conductive skeleton for Zn deposition to achieve a dendrite‐free Zn/CNT anode. Taking the advantages of low Zn nucleation overpotential and homogeneously distributed electric field, the Zn/CNT anode exhibits a prolonged cycling life over 200 h at high depth of discharge of 28%, which also enables a stable Zn//MnO2 battery.
Flexible energy‐storage devices are attracting increasing attention as they show unique promising advantages, such as flexibility, shape diversity, light weight, and so on; these properties enable ...applications in portable, flexible, and even wearable electronic devices, including soft electronic products, roll‐up displays, and wearable devices. Consequently, considerable effort has been made in recent years to fulfill the requirements of future flexible energy‐storage devices, and much progress has been witnessed. This review describes the most recent advances in flexible energy‐storage devices, including flexible lithium‐ion batteries and flexible supercapacitors. The latest successful examples in flexible lithium‐ion batteries and their technological innovations and challenges are reviewed first. This is followed by a detailed overview of the recent progress in flexible supercapacitors based on carbon materials and a number of composites and flexible micro‐supercapacitors. Some of the latest achievements regarding interesting integrated energy‐storage systems are also reviewed. Further research direction is also proposed to surpass existing technological bottle‐necks and realize idealized flexible energy‐storage devices.
Flexible energy‐storage devices are indispensable to the development of flexible electronics. This review surveys recent achievements, focusing on flexible lithium‐ion batteries and flexible supercapacitors combined with integrated energy‐storage systems.
With the fast development in flexible electronic technology, power supply devices with high performance, low‐cost, and flexibility are becoming more and more important. Potassium ion batteries (KIBs) ...have a brilliant prospect for applications benefiting from high voltage, lost cost, as well as similar electrochemistry to lithium ion batteries (LIBs). Although carbon materials have been studied as KIBs anodes, their rate capability and cycling stability are still unsatisfactory due to the large‐size potassium ions. Herein, a nitrogen (N) and phosphorus (P) dual‐doped vertical graphene (N, P‐VG) uniformly grown on carbon cloth (N, P‐VG@CC) is reported as a binder‐free anode for flexible KIBs. With the combined advantages of rich active sites, highly accessible surface, highly conductive network, larger interlayer spacing as well as robust structural stability, this binder‐free N, P‐VG@CC anode exhibits high capacity (344.3 mAh g−1), excellent rate capability (2000 mA g−1; 46.5% capacity retention), and prominent long‐term cycling stability (1000 cycles; 82% capacity retention), outperforming most of the recently reported carbonaceous anodes. Moreover, a potassium ion full cell is successfully assembled on the basis of potassium Prussian blue (KPB)//N, P‐VG@CC, exhibiting a large energy density of 232.5 Wh kg−1 and outstanding cycle stability.
A nitrogen and phosphorus dual‐doped vertical graphene uniformly grown on carbon cloth is reported as a binder‐free anode for flexible potassium ion batteries. Benefiting from the large surface, sufficient active sites, enhanced electronic and ionic conductivities, and increased interlayer distance, the material performs excellently in rate performance and cycling durability. Moreover, a flexible potassium ion full cell is assembled and exhibits exceptional electrochemical performance.
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–MnO2 battery is constructed by engineering MnO2 electrodes and gel electrolyte. Benefiting from a poly(3,4‐ethylenedioxythiophene) (PEDOT) buffer layer and a Mn2+‐based neutral electrolyte, the fabricated Zn–MnO2@PEDOT battery presents a remarkable capacity of 366.6 mA h g−1 and good cycling performance (83.7% after 300 cycles) in aqueous electrolyte. More importantly, when using PVA/ZnCl2/MnSO4 gel as electrolyte, the as‐fabricated quasi‐solid‐state Zn–MnO2@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–MnO2 battery achieves an admirable energy density of 504.9 W h kg−1 (33.95 mW h cm−3), together with a peak power density of 8.6 kW kg−1, substantially higher than most recently reported flexible energy‐storage devices. With the merits of impressive energy density and durability, this highly flexible rechargeable Zn–MnO2 battery opens new opportunities for powering portable and wearable electronics.
A highly flexible rechargeable quasi‐solid‐state Zn–MnO2@PEDOT battery is demonstrated for the first time. The battery affords a prominent energy density of 504.9 W h kg−1 (33.95 mW h cm−3), substantially outstripping most of the recently reported batteries and supercapacitors. Additionally, benefiting from a protective layer and modified electrolyte, such a Zn–MnO2@PEDOT battery delivers a good durability of 77.7% after 300 cycles.
A facile and efficient electrochemical oxidation method to directly activated carbon cloth as an excellent electrode material for supercapacitors is reported. Flexible asymmetric supercapacitor ...devices based on activated carbon cloth anodes reach a remarkable energy density and excellent long‐term durability.
Hydrogen, a clean energy carrier with high energy capacity, is a very promising candidate as a primary energy source for the future. Photoelectrochemical (PEC) hydrogen production from renewable ...biomass derivatives and water is one of the most promising approaches to producing green chemical fuel. Compared to water splitting, hydrogen production from renewable biomass derivatives and water through a PEC process is more efficient from the viewpoint of thermodynamics. Additionally, the carbon dioxide formed can be re-transformed into carbohydrates via photosynthesis in plants. In this review, we focus on the development of photoanodes and systems for PEC hydrogen production from water and renewable biomass derivatives, such as methanol, ethanol, glycerol and sugars. We also discuss the future challenges and opportunities for the design of the state-of-the-art photoanodes and PEC systems for hydrogen production from biomass derivatives and water.
The kinetically sluggish rate of oxygen reduction reaction (ORR) on the cathode side is one of the main bottlenecks of zinc‐air batteries (ZABs), and thus the search for an efficient and ...cost‐effective catalyst for ORR is highly pursued. Co3O4 has received ever‐growing interest as a promising ORR catalyst due to the unique advantages of low‐cost, earth abundance and decent catalytic activity. However, owing to the poor conductivity as a result of its semiconducting nature, the ORR activity of the Co3O4 catalyst is still far below the expectation. Herein, we report a controllable N‐doping strategy to significantly improve the catalytic activity of Co3O4 for ORR and demonstrate these N doped Co3O4 nanowires as an additive‐free air‐cathode for flexible solid‐state zinc‐air batteries. The results of experiments and DFT calculations reveal that the catalytic activity is promoted by the N dopant through a combined set of factors, including enhanced electronic conductivity, increased O2 adsorption strength and improved reaction kinetics. Finally, the assembly of all‐solid‐state ZABs based on the optimized cathode exhibit a high volumetric capacity of 98.1 mAh cm‐3 and outstanding flexibility. The demonstration of such flexible ZABs provides valuable insights that point the way to the redesign of emerging portable electronics.
A novel additive‐free design of the air‐cathode for flexible zinc–air batteries consists of directly growing and neatly assembling mesoporous Co3O4 nanowires on a carbon cloth. To optimize the catalytic activity of Co3O4 for the oxygen reduction reaction, a controllable N‐doping strategy is developed giving rise to enhanced electronic conductivity and increased O2 adsorption strength.
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−1) electrolytes. Moreover, a peak energy density of 6.6 µWh cm−2, together with a remarkable power density of 20.2 mW cm−2, 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.
An ultrastable, flexible fiber‐shaped Ni–Zn battery with impressive electrochemical performance is rationally demonstrated by employing Ni–NiO heterostructured nanosheets as the cathode. This Ni–NiO//Zn battery exhibits 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−1) electrolytes.
