Wide Voltage Window Research Articles

Flexible Electro‐Optical Perovskite/Electrolyte Synaptic Transistor to Emulate Photoelectric‐Synergistic Neural Learning Rules and Reflex‐Arc Behavior

AbstractThe design and fabrication of a flexible electric‐optical perovskite/electrolyte synaptic transistor are demonstrated for the first time, which emulates important neuromorphic functions under dual‐mode modulation. Benefiting from the bipolar charge transport properties of light‐harvesting perovskite and the high specific capacitance and mechanically robust multi‐ion electrolyte, the device exhibits bidirectional plasticity, better reliability, retaining >70% of the initial current level after 2500 flex per flat laps, and a very wide operating voltage window from 0.04 to 10 V, and responsive to ultralow stimuli down to tens of millivolt level with femtojoule‐level energy consumption. The synergistic high response under dual‐mode modulation enables the device to emulate complex neural learning rules and achieve neuromorphic applications, including classical conditioning and spatiotemporal learning, and image recognition tasks with higher accuracy of 81%. Moreover, an enhanced artificial reflex‐arc behavior is emulated by employing the flexible electro‐optical artificial synapses that serve as key information‐receiving‐processing units to manipulate the actions of electrochemical artificial muscles to a larger extent. These properties show great potential in soft neurorobotic systems and prostheses.

Choline chloride-based deep eutectic solvents as electrolytes for wide temperature range supercapacitors

Deep eutectic solvents (DESs) are a promising new class of environmentally friendly versatile solvent systems. In this work, a new approach for applying choline chloride-based DESs as cost-effective, and anti-corrosion electrolytes for activated carbon-based electrochemical capacitors (ECs) is proposed for the first time. In this regard, DESs of choline chloride/glycerol and choline chloride/propionic acid were prepared with molar ratios of 1:2. Important properties such as viscosity, electrical conductivity, and electrochemical measurements were studied in the range of room temperature up to 373 K. With the rising temperature, the viscosity of DESs decreased and their electrical conductivity increased. High energy is provided by the symmetric ECs in the choline chloride-based electrolytes, which exhibit excellent electrochemical stability at a maximum voltage up to 2.5 V. The electrolyte with DES ChCl/PA under 373 K has a specific capacitance of 198 F g−1 (with an energy density of 110 Wh kg−1), which can be reduced to 145 F g−1 (with an energy density of 16.3 Wh kg−1) at room temperature. In addition, 93 % capacity retention was achieved in the supercapacitor prepared based on DES ChCl/PA up to 5000 cycles at 373 K. According to the results, important implications are presented for expanding the application of green, non-toxic and cheap electrolytes for high-performance ECs with wide voltage windows and superior lifetime.

High performance aqueous asymmetric supercapacitors developed by interfacial engineering wood-derived nanostructured electrodes

Supercapacitors (SCs) are becoming new candidates in the field of sustainable energy supply. Nevertheless, the unsatisfactory energy density due to the narrow voltage window of the supercapacitor is the main barrier to its practical application. Developing appropriate electrode materials to improve the electrochemical performance of SCs and broaden the operating voltage of supercapacitors are imperative. Herein, compatible interfacial engineering wood-derived nanostructured electrodes for aqueous asymmetric supercapacitors (AASCs) are demonstrated. The 3D carbonized wood matrix serves as a high specific surface area current collector and a porous host for the high capacitive active substance, which is composed of manganese dioxide (MnO2) nanowires and polyaniline (PANI) nanoparticles grown uniformly on the porous wall of aligned microchannels (CW@MnO2 and CW@PANI). The resulting electrochemical exchange reactive sites enable the positive electrode to deliver a high areal capacitance of 729 mF cm−2 at 1 mA cm−2 (369 F g−1 at 0.5 A g−1). The negative electrode delivers a high areal capacitance of 1721 mF cm−2 at 1 mA cm−2 (848 F g−1 at 0.5 A g−1). The areal capacitance of two electrodes is superior to most reported supercapacitor electrodes. Additionally, the assembled CW@MnO2//CW@PANI AASC achieves a desirable energy density (170.84 μWh cm−2 at a power density of 0.5 mW cm−2) because a considerable work function difference between electrodes achieved a 2 V wide voltage window. The results of this study provide a critical benchmark and optimistic incentives to adopt natural hierarchical structures to enhance the performance of new-generation energy-related systems.

Processable oligoaniline-functionalized polyamide for electrochromic capacitive windows featuring energy recovery and reuse

Electrochromic capacitive windows (ECW) combining energy storage and electrochromism have attracted considerable interest because of their unique energy-saving and energy-recovery features. Therefore, it is highly desirable to explore an electrode material with excellent electrochromic and energy storage properties simultaneously. Herein, we synthesize an electroactive polyamide containing pentaaniline segments (EPA) in the main chain via oxidative coupling polymerization, which showcases electrochemical optical modulation and high capacitance synchronously. Attributed to non-acidic electrolyte and rational matching with V2O5 ion-storage material, the as-fabricated ECW exhibits good dual-band optical modulation performance with high optical contrast of 56.57% at 650 nm (Visible region) and 53.29% at 1250 nm (NIR region), fast optical switching response (<5 s), as well as effective regulation of indoor temperature. The resultant ECW also possesses practical energy storage properties, along with a wide voltage window of 2 V, a large capacitance of 47.26 mF/cm2, and outstanding electrochemical cycling durability. In its coloring state, the energy stored in ECW could be utilized to drive small-scale electronic equipment, indicating its energy recovery and reuse feature. In conclusion, the ECW in this work functions as a color-switching smart window and a rechargeable supercapacitor, which exhibits great promise for development in green buildings.

Mo-doped MnO2@CC electrode for high-performance 2.4 V aqueous asymmetric supercapacitors

Despite many advantages of supercapacitors based on aqueous electrolytes, the inherently low operating voltage severely limits their energy density and practical applicability to many applications. Thus, it is a key scientific challenge to broaden the potential window of electrode materials for supercapacitors. Here we report our findings in tailoring the Fermi level of MnO2-based electrode by doping with a high-valence Mo6+ ion, thus modulating its overpotential in aqueous electrolytes and potential window. For example, the redox potential of Mo-doped MnO2 is effectively increased, resulting in a wider potential window. When grown on a carbon support, the specific capacitance of Mo-doped MnO2@CC with a mass loading of 15.1 mg cm−2 reaches 3.22 F cm−2 in a wide potential window of 1.2 V. The enhanced performance is attributed to the additional redox behavior induced by the Mo dopant, as confirmed by in situ Raman and ex-situ XPS analyses. When coupled with a C-Ti3C2Tx/WO3@CC negative electrode to construct an ASC with a total mass loading of 35.8 mg cm−2, the ASC exhibits a wide voltage window of 2.4 V, demonstrating a remarkable energy density of 0.89 mWh cm−2 at a power density of 2.56 mW cm−2. In addition, the device is operational in a wide operating temperature range of −10 to 50 °C, and a voltage of ∼ 58% is retained after self-discharge for 48 h. This work provides some new insights into the development of aqueous ASC devices of commercial-grade mass loadings with high output voltage, high energy density, and slow self-discharge rates.

Preparation of Antioxidative MXene by Deep Eutectic Solvent-Assisted Electrochemical Ultrasonic Composite Exfoliation and Its Application in Flexible Solid-State Supercapacitors

In this work, we achieved a novel preparation of Ti3C2 MXene (MXene–DES) with few layers and a high degree of hydroxylation by a deep eutectic solvent (DES)-assisted electrochemical ultrasonic composite exfoliation method which is easy to scale up. The electrochemical process used a mixture of low-cost DES (choline chloride–urea) and water as the electrolyte, in which DES acts as a triple role of intercalation, interlayer expansion, and anti-oxidation. DES attached to the surface and interlayer of layered Ti3C2 formed an antioxidative protective cover, resulting in the layered Ti3C2 being grafted with hydroxyl functional groups instead of forming TiO2 in water during the entire exfoliation process. The prepared MXene–DES exhibits fewer layers, larger interlayer spacing, higher degree of hydroxylation, and stronger oxidation resistance than the MXene prepared by traditional ultrasound in a nitrogen atmosphere (MXene–N2). The symmetric flexible solid-state supercapacitor based on an activated carbon electrode and the composite gel polymer electrolyte composed of MXene–DES, DES, and polyvinyl alcohol exhibits good mechanical properties, a wide voltage window of 2.3 V, and a high specific capacitance of 133.7 F·g–1 (0.1 A·g–1). Our strategy paved a simple, low-cost, and relatively environmentally friendly way to the scalable preparation and application of antioxidative high-quality MXene.

Ni-doped α-MnO2 nanosheets coupled carbontubes for highly efficient Na+ ions capacity storage

Manganese dioxide (MnO2) has been broadly investigated as electrode material candidate for supercapacitors due to its high theoretical capacity and environmental protection. However, MnO2 also suffer from poor electrical conductivity. Herein, nickel-doped MnO2 coupled carbontubes (Ni-MnO2@CTs) material is prepared by one-step hydrothermal method and carbonization processes. Compared with undoped MnO2, Ni-doped MnO2 can improve the electrical conductivity and expand the voltage window of supercapacitors. This is because Ni doping can introduce additional charge states and regulate the reaction kinetics, changing the energy storage mechanism of the material. Additionally, the carbontubes substrate can enhance both the electrical conductivity and surface area of the material. Based on these advantages, Ni-MnO2@CTs can extend the voltage window of the positive to 0–1 V with high specific capacitance of 366 F g−1 at 1 A g−1. To explore the practical application of the materials, the asymmetric supercapacitor is fabricated with Ni-MnO2@CTs positive and Fe3O4/CTs negative (Ni-MnO2@CTs//Fe3O4/CTs) in a wide voltage window of 2 V. The supercapacitor displays excellent rate capability and cycle performance, while also possessing a high energy density of 44.5 Wh kg−1. These results suggest that the materials utilized in this study have the potential to be used in the development of wide-voltage aqueous asymmetric supercapacitors, which can further enhance their energy density.

LiNO3-poly(vinyl alcohol) polymer electrolytes and its applications in electrochemical capacitors with extended operating temperatures

An ion-conducting neutral pH polymer electrolyte based on LiNO3 and poly(vinyl alcohol) (PVA) was developed for solid electrochemical double layer capacitors (EDLCs). Structural characterizations of LiNO3-PVA electrolytes revealed amorphous structure with well-hydrated ions. The polymer electrolytes are functional over a wide range of temperatures even at −40 °C. Although increasing the concentration of ions can improve the ionic conductivity at and above ambient, it imposes adverse effects at lower temperatures likely due to the freezing of water surrounding the hygroscopic nitrate ions. The optimal electrolyte with relatively high ionic conductivity (ca. 40 mS cm−1 at ambient) and good temperature performance was applied for solid EDLC devices with multi-walled carbon nanotube electrodes. The solid EDLC showed comparable performance to its liquid baseline with excellent rate capability and wide voltage window of 1.6 V. It outperformed the liquid counterpart with lower leakage current and retained capacitive behaviour at −40 °C.

Self-healing polymer electrolytes with dynamic-covalent borate for solid-state lithium metal batteries

Developing a solid polymer electrolyte (SPE) combining superior interface stability with high ionic conductivity is still a challenge in the energy storage field. Herein, a series of novel self-healing solid polymer electrolytes were prepared by free radical photopolymerization with poly(ethylene glycol) methyl ether methacrylate and monomers containing borate. The reversible reaction induced by interesterification of borate ester endows the polymer electrolytes with excellent self-healing ability. The comb-like structure based on flexible poly(ethylene glycol) provides an amorphous state, which is conducive to lithium-ion transport. Further benefiting from the strong interaction between electron capture groups and anions of electrolyte salts, the borate-containing comb-shaped solid polymer electrolytes (PPBSPE) films display optimal ionic conductivity of 0.272 mS cm−1 at 60 °C, satisfactory transfer number for lithium ion, wide working voltage window, and remarkable stability towards lithium metal. The initial discharge capacities of the cell based on PPBSPE reach 156.2 mAh g−1 at a current rate of 0.1C, and high Coulombic efficiency (CE) of 99.4 %. This enhancement is due to the introduction of borate to the comb-shaped polymer, which is beneficial to form a more suitable electrolyte that can stabilize and improve the performance of lithium metal batteries.

Biomass-derived hierarchically porous carbon-supported MnOx enable fast ion/electron transport at high operating voltages

Metal oxide/carbon composite systems have been investigated extensively for fabrication of supercapacitors. To obtain high capacitance, a thick pseudocapacitive layer loaded on a conventional carbon support inevitably leads to high dead volume and poor rate/power characteristics. Herein, we propose a strategy with biomass-derived hierarchical porous carbon as supports to bridge two critical but mutually exclusive properties of supercapacitors: high capacitance and rapid ion/charge transport. Highly dispersed deposition of nanosized MnO2 and MnO on hierarchically porous carbon were achieved through slow redox reaction controlled by gradual hydrolysis of fibrous polymers remaining in the hydrothermal carbon. High surface area, ultrathin pseudocapacitance layer, and wide voltage window (1.6–2 V) improve the synergy between the high energy density of MnOx and the high power density of porous carbon. The maximum energy density of 40.95 Wh kg−1 (at 180 W kg−1) and power density of 9000 W kg−1 (at 23.85 Wh kg−1) was realized for the assembled asymmetric/symmetric supercapacitors in aqueous electrolytes. More importantly, a cycle life comparable to that of carbon-based double-layer capacitors (95.6% capacitance retention after 10,000 charge/discharge cycles) could be achieved. Furthermore, density functional theory (DFT) was also conducted to elaborate the differences between manganese valence states for in-depth understanding. The characteristics of low cost, environmental friendliness, and excellent performance highlight the great promise of biomass waste in designing carbon supports for electrochemical applications.

Modification and Supercapacitive Performance Enhancement of Calcium Carbide-Derived Carbon Prepared by a Green Solvent-Free Mechanochemical Route

A solvent-free mechanochemical method is a green and environmentally friendly preparation technology for the preparation of calcium carbide-derived porous carbon (CCDPC). Although CCDPC can be widely used in the fields of energy storage, gas separation, catalysis, and so on, the performance of CCDPC as an electrode material of supercapacitors still needs to be further improved. Based on the in situ chemical oxidation polymerization method, in this paper, polyaniline (PANI) is successfully introduced into CCDPC and covered on the surface and skeleton of CCDPC. It has been found that the as-prepared CCDPC/PANI composite electrode displays a high specific capacitance of 362 F g–1 at 0.5 A g–1, which is approximately 4 times higher than that of the pure CCDPC electrode. When assembling a symmetric supercapacitor by a CCDPC/PANI composite with a wide voltage window of 0–1.1 V, the supercapacitor delivers a higher energy density than CCDPC and reveals excellent capacitance retention of 77% after 10,000 cycles. Therefore, the preparation technology of the CCDPC/PANI composite provides significative exploration for the enhancement of electrochemical performance of high-performance supercapacitors and predicts a promising application prospect in the field of energy storage.

Microwave-Assisted Rational Designed CNT-Mn3 O4 /CoWO4 Hybrid Nanocomposites for High Performance Battery-Supercapacitor Hybrid Device.

Extensive research interest in hybrid battery-supercapacitor (BSH) devices have led to the development of cathode materials with excellent comprehensive electrochemical properties. In this work, carbon nanotube (CNT)-Mn3 O4 /CoWO4 triple-segment hybrid electrode is synthesized by using a two-step microwave-assisted hydrothermal route. Systematic physical characterization revealed that, with the assistance of microwave, granular Mn3 O4 and spheroid-like CoWO4 with preferred orientation, and oxygen vacancies are stacked or arranged on CNTs skeletons to construct a rational designed hybrid nanocomposite with abundant heterointerfaces and interfacial chemical bonds. Electrochemical evaluations show that the synergistic cooperation in CNT-Mn3 O4 /CoWO4 resulted in an ultra-high specific capacity (1907.5Cg-1 /529.8mAhg-1 at 1Ag-1 ), a wide operating voltage window (1.15V), the satisfactory rate capability (capacity maintained at 1016.5Cg-1 /282.3mAhg-1 at 15Ag-1 ), and excellent cycling stability (117.2% initial capacity retention after 13000 cycles at 15Ag-1 ). In addition, the assembled CNT-Mn3 O4 /CoWO4 //N doped porous carbon (NC) BSH device delivered a stable working voltage of 2.05V and superior energy density of 67.5Whkg-1 at power density of 1025Wkg-1 , as well as excellent stability (92.2% capacity retained at 5Ag-1 for 12600 cycles). This work provides a new and feasible tactic to develop high-performance transition metal oxide-based cathodes for advanced BSH devices.

In situ cross-linked fluorinated gel polymer electrolyte based on PEGDA-enabled lithium-ion batteries with a wide temperature operating range

Lithium-ion batteries (LIBs) require a wide operating temperature window to meet their actual demand. Herein, a fluorinated gel polymer electrolyte (F-GPE) was synthesised by in situ thermal polymerisation method using poly (ethylene glycol) diacrylate (PEGDA) as a cross-linking agent. The F-GPE showed excellent electrochemical stability in a wide voltage window in the range of 2–5.6 V, high ionic conductivity (above 1.2 mS cm−1 at –40 °C), superior lithium-ion transfer number (tLi+) of 0.51 at room temperature, and good compatibility with lithium metal. Additionally, the LiCoO2||F-GPE||graphite pouch battery, which the surface density of LiCoO2 was 30 mg cm−2, showed an outstanding discharge capacity in a wide temperature from –40 to 60 °C. The results displayed the retention rate of discharge capacities at –40 and 60 °C were 64.9% and 106.3% of that at room temperature, respectively. F-GPE retained the low-temperature performance of the electrolyte and improved the stability and electrochemical behavior at high temperature, providing a new strategy for the large-scale application of LIBs in a wide operating temperature.

Rational design of hierarchically nanostructured NiTe@CoxSy composites for hybrid supercapacitors with impressive rate capability and robust cycling durableness

The hierarchically nanostructured NiTe@CoxSy composites are constructed on a foamed nickel substrate by a two-step electrode preparation process. Structural characterization shows the dense growing of CoxSy nanosheets around NiTe nanorods forms a hierarchical nanostructure which possesses synergetic effects from both compositional and structural complementarity, more pathways for ion/electrolyte transport, richer redox active sites, and better conductivity. Thanks to the rational design of this hierarchical structure, NiTe@CoxSy delivers a high areal capacitance of 7.7F cm−2 at 3 mA cm−2 and achieves the improved capacitance retention of 97.9% after 10,000 cycles. Of particular importance is the successful fabrication of NiTe@CoxSy//activated carbon hybrid supercapacitors. This hybrid device has a wide operating voltage window, high areal energy density of 0.48 mWh cm−2 at 2.55 mW cm−2, impressive rate capability of 62.3% even after a 20-fold increase of the current density, and a 115.1% of initial capacitance retention after 15,000 cycles. Meanwhile, two tandem such hybrid devices can easily drive a pair of mini fans or light up a heart-like pattern assembled by 10 red LEDs. These experimental results not only demonstrate that the hierarchically nanostructured NiTe@CoxSy composites can serve as a prospective candidate electrode; but also develop a novel strategy about how to achieve high-performance stockpile equipment by rationale designing a desirable nanostructures.

3D‐Printed Graded Electrode with Ultrahigh MnO2 Loading for Non‐Aqueous Electrochemical Energy Storage

AbstractElectrolytic manganese dioxide is one of the promising cathode candidates for electrochemical energy storage devices due to its high redox capacity and ease of synthesis. Yet, high‐loading MnO2 often suffers from sluggish reaction kinetics, especially in non‐aqueous electrolytes. The non‐uniform deposition of MnO2 on a porous current collectors also makes it difficult to fully utilize the active materials at high mass loading. Here, a 3D printed graded graphene aerogel (3D GA) that contains sparsely separated exterior ligaments is developed to create large open channels for mass transport as well as densely arranged interior ligaments providing large ion‐accessible active surface. The unique structural design homogenizes the thickness of electro deposited MnO2 even at an ultrahigh mass loading of ≈70 mg cm−2. The electrode achieves a remarkable volumetric capacity of 29.1 mA h cm−3 in the non‐aqueous electrolyte. A Li‐ion hybrid capacitor device assembled with a graded 3D GA/MnO2 cathode and graded 3D GA/VOx anode exhibits a wide voltage window of 0–4 V and a superior volumetric energy density of 20.2 W h L−1. The findings offer guidance on 3D printed electrode design for supporting ultrahigh loading of active materials and developments of high energy density energy storage devices.

Introducing hydrophilic cellulose nanofiber as a bio-separator for “water-in-salt” based energy storage devices

There has been enormous interest in energy storage devices in recent years, with the emergence of “water-in-salt” based electrolytes coming to the fore in the context of supercapacitors, and lithium-ion batteries. In fact, the “water-in-salt” electrolyte exhibits a wide voltage window; unfortunately, it shows a low intrinsic wettability on the carbon surface, exhibiting hydrophobic properties on the typical separator. In this work, we introduced carboxylate-modified cellulose for utilization as a novel hydrophilic separator in energy storage devices, especially “water-in-salt” electrolytes. The cellulose was modified through the esterification with succinic anhydride followed by microfluidization to obtain cellulose succinate nanofiber (SCNF). The SCNF increases negative surface charges, enhancing the strong electrostatic repulsion between fibrils and facilitating ion transportation. We successfully fabricated the SCNF separators with a high porosity (60%) and the carboxylate content of SCNF (∼3.9 mmol g−1), giving a hydrophilic surface. The applicability of the separator was demonstrated in “water-in-salt” electrolyte, which shows relatively hydrophobic on the commercial separator. Interestingly, the prepared SCNF separator can improve capacitive properties by reducing the cell resistance. It is found that the capacitance can be enhanced up to 2 to 7 times when compared with the supercapacitor fabricated using a commercial separator. This work could strongly advance the research and development of SCNF separators, and “water-in-salt” based electrolytes in the context of energy storage applications.

The Effect of Key Electronic States on Excess Lithium Intercalation in Li2RuyMn1-yO3.

Excess reversible lithium storage is an alternative crucial strategy besides the expansion of redox centers to boost the capacity of layered cathodes. However, the mechanism of excess Li+ intercalation is far from being comprehended, indisputably hindering the development of layered cathodes. Herein, the comparative study of Li2RuyMn1-yO3 and Li2RuyTi1-yO3 by X-ray absorption and photoemission spectroscopies attempts to illustrate the origin. The charge transfer from Ru to Mn through TM-O π bonding interaction with the formation of O holes has been revealed in Li2RuyMn1-yO3, which originates from the inductive effect and the approaching energy level of Mn and Ru bands. The electronic state is thought to reduce the Coulomb repulsion of Li+ with the matrix, promoting excess Li+ intercalation. The results are instructive to the rational design of layered cathodes to achieve a larger reversible capacity in a wide voltage window.

All-MXenes zinc ion hybrid micro-supercapacitor with wide voltage window based on V2CTx cathode and Ti3C2Tx anode

To further improve the electrochemical performance for the wearable and microelectronic devices, we reported an all-MXenes zinc ion hybrid micro-supercapacitor (ZIHMSC) with a wide voltage window (1.60 V) based on V2CTx as the cathode and Ti3C2Tx as the anode. The flexible V2CTx and Ti3C2Tx electrodes are fabricated by the electrophoretic deposition method, which is simple and conducive to the realization of positive and negative electrodes matching. Benefiting from the synergistic effect of the two MXenes and the unique configuration, our ZIHMSCs also achieve fast ion and electron transfer kinetics, showing better rate capability than the MXene/Zn system. And the ZIHMSCs achieve excellent electrochemical performance, with high area capacitance of 200.1 mF cm−2, well stability over 5,000 charge/discharge cycles, and high energy density of 71.6 μWh cm−2 at 400.7 μW cm−2. The reason for the wide voltage window of the ZIHMSC was well revealed by the large work function difference between the two electrode materials of V2CTx and Ti3C2Tx and the redox potential of the electrolyte. And the electrochemical energy storage mechanisms are well investigated by ex-situ XPS and XRD. In addition, the ZIHMSC displays well flexibility and mechanical property, suffering from 15,000 bending cycles under 90°. The ZIHMSCs can successfully drive digital tubes and meters and enable digital meters to operate for more than 600 s, proving their practical application potential.

Hybrid Acid/alkali All Covalent Organic Frameworks Battery.

Covalent organic frameworks (COFs), thanks to their adjustable porous structure and abundant build-in functional motifs, have been recently regarded as promising electrode materials for a variety of batteries. There still remain grand opportunities to further utilizing their merits for developing advanced COFs-based batteries. In this paper, we propose a hybrid acid/alkali all-COFs battery by coupling pyrene-4,5,9,10-tetraone based COF cathode with anthraquinone based COF anode. In such a hybrid acid/alkali all-COFs battery, the cathodic COF favorably works in acid with a relatively positive potential, while the anodic COF preferably runs in alkali with a relatively negative potential. It thus can deliver a decently high discharge capacity of 92.97 mAh g-1 with a wide voltage window of 2.0 V, and exhibit high energy density of 74.2 Wh kg-1 along with a considerable cyclic stability over 300 cycles. The development of the proof-of-concept all-COFs battery may drive forward the improvement of newly cost-effective and performance-reliable energy storage devices.

Hybrid Acid/alkali All Covalent Organic Frameworks Battery

AbstractCovalent organic frameworks (COFs), thanks to their adjustable porous structure and abundant build‐in functional motifs, have been recently regarded as promising electrode materials for a variety of batteries. There still remain grand opportunities to further utilizing their merits for developing advanced COFs‐based batteries. In this paper, we propose a hybrid acid/alkali all‐COFs battery by coupling pyrene‐4,5,9,10‐tetraone based COF cathode with anthraquinone based COF anode. In such a hybrid acid/alkali all‐COFs battery, the cathodic COF favorably works in acid with a relatively positive potential, while the anodic COF preferably runs in alkali with a relatively negative potential. It thus can deliver a decently high discharge capacity of 92.97 mAh g−1 with a wide voltage window of 2.0 V, and exhibit high energy density of 74.2 Wh kg−1 along with a considerable cyclic stability over 300 cycles. The development of the proof‐of‐concept all‐COFs battery may drive forward the improvement of newly cost‐effective and performance‐reliable energy storage devices.