Cross-linked polyaniline for production of long lifespan aqueous iron||organic batteries with electrochromic properties

Fe3+ intercalated hierarchical structured hydrated vanadate cathode for flexible iron ion hybrid supercapacitor

Energy storage devices are the core hub in constructing the modern energy system and have become an indispensable factor in driving the development of new electronic devices. In this work, we synthesized a flexible cathode of Fe3+ intercalated V2O5·3H2O (VOH) on carbon cloth (FeVOH@CC) and explored an advanced iron ion hybrid supercapacitor (IIHS). The presence of V4+/V5+ electrons in FeVOH@CC enhances the material's conductivity, while Fe3+ acts as a stabilizing pillar to accommodate structural expansion and contraction, thereby ensuring improved ion diffusion dynamics and cycling stability. Additionally, the growth of the material directly on the carbon cloth, eliminates the negative effects of conductive agents, binders, and other additives, and the prepared FeVOH@CC maintains structural flexibility, which is crucial for the effective insertion/extraction of Fe2+. As a result, the aqueous IIHS exhibits excellent areal capacitance (882.4 mF cm-2 at 1 mA cm-2) and energy density (176.5 μWh·cm-2 at 606.4 μW·cm-2). After 20,000 cycles, it retains 85.7 % of its capacity, significantly outperforming VOH. Meanwhile, we have developed a polyacrylamide/sodium alginate/glycerol-Fe2+ gel electrolyte for flexible IIHS, and the device exhibits outstanding performance by retaining 85.9 % of its capacity after 5,000 cycles. Therefore, FeVOH@CC cathode based flexible IIHS opens up new exploratory possibilities for next-generation energy storage devices.

Doping assisted interfacial engineering improves the photoelectrochemical performance of titanium dioxide photoanodes

Titanium dioxide (TiO2) is a widely studied photoanode material for photoelectrochemical (PEC) water splitting, however, its performance is often hindered by severe charge carrier recombination. To address this limitation, a novel composite photoanode comprising indium-doped TiO2 (In-TiO2), polyaniline (PANI), and cobalt phosphate (CoPi) was developed. In this material system, In3+ doping effectively modulates the electronic structure of TiO2, elevating its work function and facilitating bulk charge separation while mitigating Fermi level pinning. The PANI interlayer functions as an efficient hole transport medium, and CoPi acts as an oxygen evolution reaction (OER) co-catalyst, providing abundant active sites and accelerating surface reaction kinetics. Moreover, the formation of strong Co-N interactions between PANI and CoPi enhances interfacial charge transfer, further boosting PEC activity. As a result, the optimized In-TiO2/PANI/CoPi photoanode delivers a photocurrent density of 4.0 mA·cm-2 at 1.23 V vs. RHE and achieves a solar-to-hydrogen (STH) efficiency of 1.72 %. This synergistic design strategy offers a promising pathway for the development of efficient and stable photoanodes for solar-driven water splitting.

Atomically Dispersed Fe Confined into MnO Nanoclusters Enhances Alkaline Oxygen Reduction Activity and Stability

Transition metal oxide electrocatalysts are promising alternatives to expensive noble metals for the oxygen reduction reaction (ORR). Here, we present a simple metal-atom localization strategy to confine the atomically dispersed Fe into MnO nanoclusters, which are dispersed and immobilized on high-conductivity carbon support (MF/CN). The experimental and theoretical calculation results reveal that the trace Fe(III) ions doped into MnO nanoclusters can induce charge transfer and spin state transition to trigger a butterfly effect, obtaining abundant active Mn(III) with single-electron eg configuration and strengthened built-in electric field (BIEF), which is greatly helpful to balance the adsorption and desorption of ORR O-containing intermediates, facilitate the interfacial electron transfer, and improve the electrical conductivity. As a result, the optimized MF0.04/CN exhibits compelling alkaline ORR activity (half-wave potential 0.79 V vs. RHE) and stability (nearly 100% current retention rate for 30 h). Finally, the MF0.04/CN realizes a remarkable power density (138 mW cm-2) and durability (>666 h at 10 mA cm-2) in Zn-air batteries. This finding not only helps to design high-performance metal oxide heterointerfaces by tuning eg orbital occupancy and BIEF strength, but also deepens the understanding of the reaction mechanism.

Regulating the Interfacial Solvation Environment by a Pyran-Based Polymer for High-Areal-Capacity and Low-Temperature-Endurable Magnesium Metal Batteries

Regulating the artificial solid electrolyte interphase (SEI) and interfacial solvation structure of the electrolyte is crucial for developing rechargeable magnesium batteries (RMBs) with long cycling life, high current density tolerance, and fast ion transport capability operated under extreme environments, such as low temperatures. Herein, an effective strategy using oligomeric poly(3,4-dihydro-2H-pyran) (polyDHP) is proposed to modulate the interfacial solvation structure of RMBs, with the construction of an artificial SEI with rapid Mg-ion conductivity. The steric hindrance of polyDHP and its electrostatic interaction with Mg2+ reduce the solvent molecules in the first solvation shell, allowing polyDHP molecules to participate in coordination, thus lowering the desolvation energy barrier of Mg2+ and facilitating their deposition and stripping. Furthermore, due to the glass transition behavior, oligomeric polyDHP exhibits a more ordered structure with more continuous internal ion transport channels at -20 °C, therefore enabling stable RMB operation at lower temperatures for the first time. The corresponding Mg symmetric cells display a much lower overpotential (400 mV) and excellent cycling stability at both room temperature (over 5000 h at 5 mA cm-2 and 10 mA h cm-2) and a low temperature of -20 °C (over 1300 h at 3 mA cm-2 and 3 mA h cm-2). This strategy supports the stable cycling of CuS∥Mg full cells for over 200 cycles at -20 °C. This work reveals the importance of regulating the interfacial solvation structure, promoting the realistic applications of RMBs under extreme conditions.

An Air-Operated, High-Performance Fe-Ion Secondary Battery Using Acidic Electrolyte

Fe2+ have emerged as the ideal charge carriers to construct aqueous batteries as one of the most competitive candidates for next-generation low-cost and safe energy storage. Unfortunately, the fast oxidation of Fe2+ into Fe3+ at ambient conditions inevitably requires the assembly process of the cells in an oxygen-free glovebox. Up to date, direct air assembly of aqueous Fe-ion battery remains very desirable yet highly challenge. Here oxidation of Fe2+ is found at ambient condition and is completely inhibited in an acidic electrolyte. A proton/O2 competitive mechanism in the acidic electrolyte is revealed with reduced coordinated O2 in the Fe2+ solvated shell for this unexpected finding. Based on this surprise, for the first time, air-operated assembly of iron-ion batteries is realized. Meanwhile, it is found that the acidic environment induces the in situ growth of active α-FeOOH derivate on the VOPO4·2H2O surface. Strikingly, the acidic electrolyte enables an air-operated Fe-ion battery with a high specific capacity of 192 mAh g-1 and ultrastable cycling stability over 1300 cycles at 0.1 A g-1. This work makes a break through on the air-assembly of Fe-ion battery without oxygen-free glovebox. It also reveals previously unknown proton/O2 competitive mechanisms in the Fe2+ solvated shell and cathode surface chemistry for aqueous Fe2+ storage.

Dual-Functional Photonic Battery Enabling Dynamic Radiative Thermal Management and Power Supply

Dynamic thermal management materials are pivotal for advancing energy-efficient buildings and promoting global sustainability. However, existing materials typically offer only a single-function of temperature regulation, lacking the integrated power supply capability essential for sustaining indoor activities and building sustainability, particularly in the face of frequent power outages. A photonic battery that combines all-season dynamic radiative thermoregulation with electrical power supply in a single silicon-based unit is demonstrated. This device delivers dual functionality with high infrared emissivity regulation (0.53 at 8-13 µm) and superior energy storage performance, featuring a high specific capacity (≈3271 mAh g-1), areal capacity (≈0.38 mAh cm-2), and efficient energy recycling (71.6%). A reversible ion-interaction-induced phase change mechanism, enabling continuous and non-volatile electro-optical-thermal transformation and significant infrared tunability, is proposed. Our simulations indicate that the implementation of these dynamic materials into buildings could significantly reduce energy consumption by up to 18.4%, equating to 544.8 GJ, and achieve an annual reduction in CO2 emissions of 124.1 tons. This work paves the way for the development of energy-saving electro-driven dynamic materials, marking a significant step forward in global sustainability initiatives.

Ultrafast, Targeting Fluorion-Capture Electrochemical Nanosystem Assembled with Polymeraldine Salt-Modulated Ti3C2Tx MXene

Fluoride-containing groundwater has become a major concern since it serves as a source of drinking water for over half the world's population. Here, we develop an ion-selective polymeraldine salt (PANI-Clx; PANI = polyaniline) modulated Ti3C2Tx MXene electrode as a mediator for electrochemical capture of fluoride ion (F-) from groundwater. The single-stage configuration equipped with PANI-Clx/Ti3C2Tx electrode as anode and activated carbon as cathode exhibits an ultrafast removal rate of 4.7 mg-F- g-1 min-1 toward F- and high selectivity coefficients. Density-functional theory calculations and characterizations reveal that PANI-Clx/Ti3C2Tx can lower the charge-transfer resistance and activation energy, promoting the synergy of high selectivity of nitrogen-related motifs in PANI-Clx and a fast rate of ion intercalation in Ti3C2Tx. A stack-based multi-stage configuration operated at a staircase descent voltage mode is applied to produce freshwater from practical groundwater with low energy consumption (0.92 kWh kg-1-F-). Our findings pave the way for the electrochemical production of potable water from fluorine-containing groundwater.

Tailored Polymer-Inorganic Bilayer SEI with Proton Holder Feature for Aqueous Zn Metal Batteries

Conventional solid-electrolyte interface (SEI) in aqueous Zn-ion batteries mainly acts as a physical barrier to prevent hydrogen evolution reaction (HER), while such SEI is prone to structural deterioration stemming from uneven Zn deposition at high current densities. Herein, we propose an in situ structural design of polymer-inorganic bilayer SEI with a proton holder feature by aniline-modulated electrolytes. The Zn(OTF)2 exhibits a lower LUMO energy level in comparison to aniline, resulting in the formation of a bilayer structure characterized by an inner ZnF2 layer and an outer polyaniline (PANI) layer. The ZnF2 with high stiffness and strength effectively suppresses Zn dendrites. Meanwhile, the PANI regulates the current distribution, minimizing the concentration gradient, and delays the Sand's time of dendrites growth. Furthermore, the =N- in PANI is capable of reversible proton holder, thereby inhibiting HER. With this bilayer SEI, the Zn anode achieves an impressive cycle life of 126 h under 40 mA cm-2 & 40 mAh cm-2 (depth of discharge, DOD=70.8 %), solving the bottleneck of single-layer inorganic SEI that could not be cycled under these conditions. The Zn || NaVO pouch battery with bilayer SEI exhibits a high capacity of 1.2 Ah and a cycle life of 350 h with 78 % capacity retention. At -30 °C, the same battery delivers a capacity of 335 mAh and a cycle life of 507 h with 72 % capacity retention, attributed to the modulation mechanism of the hydrogen bonding in the electrolyte. Our findings offer profound insights into the design of SEI with tailored structure and functionality, paving the way for the next generation of advanced high-performance batteries.

Optically Decoupling Electrochromic Dynamics and In Situ Morphological Evolution of a Single Soft Polyaniline Nanoentity

Electroresponsive multicolored materials have tremendous potential in flexible electronics and smart wearable devices. Herein, the electrochromic dynamics and in situ morphological evolution of a single soft polyaniline nanoentity can be visualized and decoupled by an opto-electrochemical imaging strategy. The durability, tinting speed, and reversibility down to the single-nanoparticle level are quantified, and the switching of transient intermediate electrochromic states is trapped. The mechanistic studies suggest that the heterogeneity of electrochromic activity is attributed to the nonuniformity of the polymer network interspersed at the nanometric level. Furthermore, the representative Pauli repulsion effect is uncovered from the self-stretching behavior of the conductive state of polyaniline at the oxidized potential. It provides novel insights for advancing high-performance electrochromic devices and flexible strain sensors, which can be dynamically manipulated by external stimuli.

Robust MnO2-WO3 Complementary Electrochromic Device Enabled by Reversible Electrodeposition of MnO2

Reversible electrodeposition and dissolution of manganese oxide (MnO2) represent an emerging electrochromic system. However, challenges such as "dead MnO2" formation, limited optical modulation across a narrow wavelength range, and difficulties in scaling up have significantly hindered the development of MnO2 reversible electrodeposition-based electrochromic windows. In this work, we introduced Fe2+/Fe3+ mediator ions into the electrolyte to suppress the Jahn-Teller effect, thereby preventing the formation of "dead MnO2" and achieving stable and reversible MnO2 deposition/dissolution. Furthermore, by employing WO3 as the counter electrode, we developed a complementary electrochromic device based on ion insertion and metal oxide deposition. This complementary system exhibits color neutrality in the colored state and high optical contrast across the entire visible spectrum, with an average optical modulation of 67.3%, excellent cycling stability (85.0% retention after 3000 cycles), and capability to switch uniformly over areas as large as 100 cm2.

Recycling of Spent Lithium Iron Phosphate Cathodes: Challenges and Progress

The number of spent lithium iron phosphate (LiFePO4, LFP) batteries will increase sharply in the next few years, owing to their large market share and development potential. Therefore, recycling of spent LFP batteries is necessary and urgent from both resource utilization and environmental protection standpoints. In this review, the significance of pretreatment for LFP recycling is first underscored, and its technical challenges and recent advancements are presented. Following that, the current recycling methods for spent LFP cathodes are outlined in terms of the respective treating processes, advantages, and disadvantages. Additionally, the preparation methods of LFP cathode material are reviewed to guide the resynthesis of LFP that uses salts obtained from spent LFP, which are beneficial for closed-loop recycling of LFP batteries. Lastly, we explore the future development direction of spent LFP battery recycling, highlighting the importance of technological innovation to advance the sustainable growth of the LFP battery industry.

An interactive dual energy storage mechanism boosts high-performance aqueous zinc-ion batteries

Organic materials are promising cathodes for aqueous zinc-ion batteries (AZIBs) due to their cost-effectiveness, environmental friendliness, and tunable structures. However, the energy density of AZIBs remains limited by the inherently low capacity and output voltage of organic cathode materials. To address this challenge, we develop a Mn ion-doped polyaniline (PAM) by harnessing the joint merits of the highly reversible doping process of the conjugated backbone and the unique dissolution-deposition behavior of Mn2+ in ZnSO4 electrolyte. The incorporation of Mn2+ into the PANI backbone facilitates the stabilization of PAM at high potentials by lowering the lowest unoccupied molecular orbital (LUMO) energy level, resulting in enhanced output voltage and cycling stability. This new interactive dual energy storage mechanism, illustrated by density functional theory calculations and ex situ characterization, contributes to the improved capacity by employing a dissolution-deposition storage mechanism. The battery showcases a maximum specific capacity of 496.7 mA h g-1 at an ultra-high working voltage of 2.4 V. And the capacity is 213.2 mA h g-1 when the current density reaches 20 A g-1. This molecular design of the pre-doped PANI cathode and the insight into the groundbreaking dual energy storage mechanism offer a new alternative host for high-performance Zn-organic batteries.

Coordination and Hydrogen Bond Chemistry in Tungsten Oxide@Polyaniline Composite toward High-Capacity Aqueous Ammonium Storage

Aqueous ammonium ion batteries (AAIBs) have garnered significant attention due to their unique energy storage mechanism. However, their progress is hindered by the relatively low capacities of NH4 + host materials. Herein, the study proposes an electrodeposited tungsten oxide@polyaniline (WOx@PANI) composite electrode as a NH4 + host, which achieves an ultrahigh capacity of 280.3 mAh g-1 at 1 A g-1, surpassing the vast majority of previously reported NH4 + host materials. The synergistic interaction of coordination chemistry and hydrogen bond chemistry between the WOx and PANI enhances the charge storage capacity. Experimental results indicate that the strong interfacial coordination bonding (N: →W6+) effectively modulates the chemical environment of W atoms, enhances the protonation level of PANI, and thus consequently the conductivity and stability of the composites. Spectroscopy analysis further reveals a unique NH4 +/H+ co-insertion mechanism, in which the interfacial hydrogen bond network (N-H···O) accelerates proton involvement in the energy storage process and activates the Grotthuss hopping conduction of H+ between the hydrated tungsten oxide layers. This work opens a new avenue to achieving high-capacity NH4 + storage through interfacial chemistry interactions, overcoming the capacity limitations of NH4 + host materials for aqueous energy storage.

A Facile Electrochemical Strategy for Achieving a High-Conductivity Polypyrrole Derivative with Intrinsic Metallic Transport as a High-Performance Electrochromic Conducting Polymer Film

Conjugated polymer electrochromic materials (PECMs) with tailored optical and electrical properties are applied in smart windows, electronic displays, and adaptive camouflage. The limitation in the electrical conductivity results in slow and monotonous color switching. We present a polypyrrole film incorporated with a toluene-p-sulfonic group (PPy-TSO-F), via a one-step electrodeposition technique. The PPy-TSO-F thin film (110 nm) achieves an impressive electrical conductivity of 1011 S cm-1, a high carrier mobility of 82 cm2 V-1 s-1, and intrinsic metallic electronic behavior. It demonstrates exceptionally reversible multicolor switching, transitioning from emerald green (-1.5 V), to bluish green (-1.4 V), bright yellow (-1.2 V), greenish yellow (-0.6 V), reddish brown (0.1 V), dark brown (0.3 V), and atrovirens (0.6 V). The fast charge transport and high carrier mobility render the film with an ultrafast electrochromic switching speed of 0.01 s/0.02 s. This research provides a new route to designing ultrafast multicolor switching PECMs with metallic charge transport.

Insight into Anionic Discrepancies in Bipolar Poly(Thionine) Organic Cathodes for Aqueous Zinc Ion Batteries

Electroactive organic electrode materials exhibit remarkable potential in aqueous zinc ion batteries (AZIBs) due to their abundant availability, customizable structures, sustainability, and high reversibility. However, the research on AZIBs has predominantly concentrated on unraveling the storage mechanism of zinc cations, often neglecting the significance of anions in this regard. Herein, bipolar poly(thionine) is synthesized by a simple and efficient polymerization reaction, and the kinetics of different anions are investigated using poly(thionine) as the cathode of AZIBs. Notably, poly(thionine) is a bipolar organic polymer electrode material and exhibits enhanced stability in aqueous solutions compared to thionine monomers. Kinetic analysis reveals that ClO4 - exhibits the fastest kinetics among SO4 2-, Cl-, and OTF-, demonstrating excellent rate performance (109 mAh g-1 @ 0.5 A g-1 and 92 mAh g-1 @ 20 A g-1). Mechanism studies reveal that the poly(thionine) cathode facilitates the co-storage of both anions and cations in Zn(ClO4)2. Furthermore, the lower electrostatic potential of ClO4 - influences the strength of hydrogen bonding with water molecules, thereby enhancing the overall kinetics in aqueous electrolytes. This work provides an effective strategy for synthesizing high-quality organic materials and offers new insights into the kinetic behavior of anions in AZIBs.

On-Demand Picoliter-Level-Droplet Inkjet Printing for Micro Fabrication and Functional Applications

With the advent of Internet of Things (IoTs) and wearable devices, manufacturing requirements have shifted toward miniaturization, flexibility, environmentalization, and customization. Inkjet printing, as a non-contact picoliter-level droplet printing technology, can achieve material deposition at the microscopic level, helping to achieve high resolution and high precision patterned design. Meanwhile, inkjet printing has the advantages of simple process, high printing efficiency, mask-free digital printing, and direct pattern deposition, and is gradually emerging as a promising technology to meet such new requirements. However, there is a long way to go in constructing functional materials and emerging devices due to the uncommercialized ink materials, complicated film-forming process, and geometrically/functionally mismatched interface, limiting film quality and device applications. Herein, recent developments in working mechanisms, functional ink systems, droplet ejection and flight process, droplet drying process, as well as emerging multifunctional and intelligence applications including optics, electronics, sensors, and energy storage and conversion devices is reviewed. Finally, it is also highlight some of the critical challenges and research opportunities. The review is anticipated to provide a systematic comprehension and valuable insights for inkjet printing, thereby facilitating the advancement of their emerging applications.

Amorphous-Crystalline Interface Induced Internal Electric Fields for Electrochromic Smart Window

Balancing optical modulation and response time is crucial for achieving high coloration efficiency in electrochromic materials. Here, internal electric fields are introduced to titanium dioxide nanosheets by constructing abundant amorphous-crystalline interfaces, ensuring large optical modulation while reducing response time and therefore improving coloration efficiency. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) reveals the presence of numerous amorphous-crystalline phase boundaries in titanium dioxide nanosheets. Kelvin probe force microscopy (KPFM) exhibits an intense surface potential distribution, demonstrating the presence of internal electric fields. Density functional theory (DFT) calculations confirm that the amorphous-crystalline heterointerfaces can generate internal electric fields and reduce diffusion barriers of lithium ions. As a result, the amorphous-crystalline titanium dioxide nanosheets exhibit better coloration efficiency (35.1 cm2 C-1) than pure amorphous and crystalline titanium dioxide nanosheets.

Highly deformable bi-continuous conducting polymer hydrogels for electrochemical energy storage

Conducting polymer hydrogels with inherent flexibility, ionic conductivity and environment friendliness are promising materials in the fields of energy storage. However, a trade-off between mechanical and electrochemical properties has limited the development of flexible/stretchable conducting polymer hydrogel electrodes, owing to the intrinsic conflict among mechanical and electrical phases. Here, we report a reliable design to enable conducting polymer with both exceptional mechanical and electrical/electrochemical performance through the construction of bi-continuous conducting polymer crosslinked network. The resultant bi-continuous conducting polymer hydrogels (BCPH) demonstrate significantly improved mechanical and electrochemical properties compared to the conventional conducting polymer hydrogel (CPH) electrode. BCPH presents a high specific capacitance of 715 F g-1 at 0.5 A/g, a high mechanical strength (∼1 MPa) and a large stretchability (∼300%). Enabled by such intrinsically deformability and electrochemical properties, we further demonstrate its utility in flexible solid-state supercapacitor (FSSC), which exhibits an outstanding specific capacitance of 760 mF cm-2 at 2 mA cm-2, excellent electrochemical stability with 81% capacitance retention after 5000 charge/discharge cycles, and superior bending cycle stability. This simple and scalable strategy provides a platform for the fabrication of high-performance conducting hydrogel electrodes for various wearable electronic equipment.

Enhancing Proton Co-Intercalation in Iron Ion Batteries Cathodes for Increased Capacity

Recently, aqueous iron ion batteries (AIIBs) using iron metal anodes have gained traction in the battery community as low-cost and sustainable solutions for green energy storage. However, the development of AIIBs is significantly hindered by the limited capacity of existing cathode materials and the poor intercalation kinetic of Fe2+. Herein, we propose a H+ and Fe2+ co-intercalation electrochemistry in AIIBs to boost the capacity and rate capability of cathode materials such as iron hexacyanoferrate (FeHCF) and Na4Fe3(PO4)2(P2O7) (NFPP). This is achieved through an electrochemical activation step during which a FeOOH nanowire layer is formed in situ on the cathode. This layer facilitates H+ co-intercalation in AIIBs, resulting in a high specific capacity of 151 mAh g-1 and 93% capacity retention over 500 cycles for activated FeHCF cathodes. We found that this activation process can also be applied to other cathode chemistries, such as NFPP, where we found that the cathode capacity is doubled as a result of this process. Overall, the proposed H+/Fe2+ co-insertion electrochemistry expands the range of applications for AIBBs, in particular as a sustainable solution for storing renewable energy.

Self-Charging Aqueous Zn//COF Battery with UltraHigh Self-Charging Efficiency and Rate

Self-charging zinc batteries that combine energy harvesting technology with batteries are candidates for reliable self-charging power systems. However, the lack of rational materials design results in unsatisfactory self-charging performance. Here, a covalent organic framework containing pyrene-4,5,9,10-tetraone groups (COF-PTO) is reported as a cathode material for aqueous self-charging zinc batteries. The ordered channel structure of the COF-PTO provides excellent capacity retention of 98% after 18 000 cycles at 10 A g-1 and ultra-fast ion transfer. To visually assess the self-charging performance, two parameters, namely self-charging efficiency (self-charging discharge capacity/galvanostatic discharge capacity, η) and average self-charging rate (total discharge capacity after cyclic self-charging/total cyclic self-charging time, ν), are proposed for performance evaluation. COF-PTO achieves an impressive η of 96.9% and an ν of 30 mAh g-1 self-charge capacity per hour in 100 self-charging cycles, surpassing the previous reports. Mechanism studies reveal the co-insertion of Zn2+ and H+ double ions in COF-PTO of self-charging zinc batteries. In addition, the C═N and C═O (on the benzene) in COF-PTO are ortho structures to each other, which can easily form metal heterocycles with Zn ions, thereby driving the forward progress of the self-charging reaction and enhancing the self-charging performance.

One-step achieving high performance all-solid-state and all-in-one flexible electrochromic supercapacitor by polymer dispersed electrochromic device strategy

Electrochromic devices (ECD) are widely used to regulate the transmittance of sunlight by applying a small voltage, but the drawbacks like complex layer-by-layer preparation procedures and inconvenient assembling process still exist. To address these problems, gel or solution-type all-in-one ECDs were recently developed for the simple structure, however, the leakage risk and absence of flexible large-area production have limited real applications. Herein, a novel all-solid-state and all-in-one flexible ECD was reported by originally developed polymer dispersed electrochromic device (PDECD) strategy. This all-solid-state flexible ECD could be efficiently prepared only by one step of phase separation without any extra treatment, and demonstrated outstanding stability (92.1 % of original ΔT remained after 10,000 cycles), high coloration efficiency (197 cm2/C), low power consumption (86.4 μW/cm2) and satisfied response time (≤12 s). Meanwhile, the stored power in ECD during coloring process could drive a LED with excellent cyclic stability (93 % of original capacity remained after 3000 cycles), implying that ECD could also serve as an idea electrochromic supercapacitor. What'more, a reported largest viologen-based all-solid-state flexible ECD (17.8 × 13.2 cm2) with robust bending resistance (up to 1000 bending cycles) was successfully fabricated with industrial roller coating technique, which indicated the huge potential in real world.

Long-term stable pH sensor array with synergistic bilayer structure for 2D real-time mapping in cell culture monitoring

Pursuing accurate, swift, and durable pH sensors is important across numerous fields, encompassing healthcare, environmental surveillance, and agriculture. In particular, the emphasis on real-time pH monitoring during cell cultivation has become increasingly pronounced in the current scientific environment-a crucial element being diligently researched to ensure optimal cell production. Both polyaniline (PANi) and iridium oxide (IrOx) show their worth in pH sensing, yet they come with challenges. Single-PANi-layered pH sensors often grapple with diminished sensitivity and lagging responses, while electrodeposited IrOx structures exhibit poor adhesion, leading to their separation from metallic substrates-a trait undesirable for a consistently stable, long-term pH sensor. This paper introduces a bi-layered PANi-IrOx pH sensor, strategically leveraging the advantages of both materials. The results presented here underscore the sensitivity enhancement of binary-phased framework, faster response time, and more robust structure than prior work. Through this synergistic strategy, we demonstrate the potential of integrating different phases to overcome the inherent constraints of individual materials, setting the stage for advanced pH-sensing solutions.

Organic Electrode Materials for Energy Storage and Conversion: Mechanism, Characteristics, and Applications

ConspectusLithium ion batteries (LIBs) with inorganic intercalation compounds as electrode active materials have become an indispensable part of human life. However, the rapid increase in their annual production raises concerns about limited mineral reserves and related environmental issues. Therefore, organic electrode materials (OEMs) for rechargeable batteries have once again come into the focus of researchers because of their design flexibility, sustainability, and environmental compatibility. Compared with conventional inorganic cathode materials for Li ion batteries, OEMs possess some unique characteristics including flexible molecular structure, weak intermolecular interaction, being highly soluble in electrolytes, and moderate electrochemical potentials. These unique characteristics make OEMs suitable for applications in multivalent ion batteries, low-temperature batteries, redox flow batteries, and decoupled water electrolysis. Specifically, the flexible molecular structure and weak intermolecular interaction of OEMs make multivalent ions easily accessible to the redox sites of OEMs and facilitate the desolvation process on the redox site, thus improving the low-temperature performance, while the highly soluble nature enables OEMs as redox couples for aqueous redox flow batteries. Finally, the moderate electrochemical potential and reversible proton storage and release of OEMs make them suitable as redox mediators for water electrolysis. Over the past ten years, although various new OEMs have been developed for Li-organic batteries, Na-organic batteries, Zn-organic batteries, and other battery systems, batteries with OEMs still face many challenges, such as poor cycle stability, inferior energy density, and limited rate capability. Therefore, previous reviews of OEMs mainly focused on organic molecular design for organic batteries or strategies to improve the electrochemical performance of OEMs. A comprehensive review to explore the characteristics of OEMs and establish the correlation between these characteristics and their specific application in energy storage and conversion is still lacking.In this Account, we initially provide an overview of the sustainability and environmental friendliness of OEMs for energy storage and conversion. Subsequently, we summarize the charge storage mechanisms of the different types of OEMs. Thereafter, we explore the characteristics of OEMs in comparison with conventional inorganic intercalation compounds including their structural flexibility, high solubility in the electrolyte, and appropriate electrochemical potential in order to establish the correlations between their characteristics and potential applications. Unlike previous reviews that mainly introduce the electrochemical performance progress of different organic batteries, this Account specifically focuses on some exceptional applications of OEMs corresponding to the characteristics of organic electrode materials in energy storage and conversion, as previously published by our groups. These applications include monovalent ion batteries, multivalent ion batteries, low-temperature batteries, redox flow batteries with soluble OEMs, and decoupled water electrolysis employing organic electrodes as redox mediators. We hope that this Account will make an invaluable contribution to the development of organic electrode materials for next-generation batteries and help to unlock a world of potential energy storage applications.

Non-Metal Ion Storage in Zinc-Organic Batteries

Zinc-organic batteries (ZOBs) are receiving widespread attention as up-and-coming energy-storage systems due to their sustainability, operational safety and low cost. Charge carrier is one of the critical factors affecting the redox kinetics and electrochemical performances of ZOBs. Compared with conventional large-sized and sluggish Zn2+ storage, non-metallic charge carriers with small hydrated size and light weight show accelerated interfacial dehydration and fast reaction kinetics, enabling superior electrochemical metrics for ZOBs. Thus, it is valuable and ongoing works to build better ZOBs with non-metallic ion storage. In this review, versatile non-metallic cationic (H+, NH4 +) and anionic (Cl-, OH-, CF3SO3 -, SO4 2-) charge carriers of ZOBs are first categorized with a brief comparison of their respective physicochemical properties and chemical interactions with redox-active organic materials. Furthermore, this work highlights the implementation effectiveness of non-metallic ions in ZOBs, giving insights into the impact of ion types on the metrics (capacity, rate capability, operation voltage, and cycle life) of organic cathodes. Finally, the challenges and perspectives of non-metal-ion-based ZOBs are outlined to guild the future development of next-generation energy communities.

Multielectron Redox-Bipolar Tetranitroporphyrin Macrocycle Cathode for High-Performance Zinc-Organic Batteries

Bipolar organics fuse the merits of n/p-type redox reactions for better Zn-organic batteries (ZOBs), but face the capacity plafond due to low density of active units and single-electron reactions. Here we report multielectron redox-bipolar tetranitroporphyrin (TNP) with quadruple two-electron-accepting n-type nitro motifs and dual-electron-donating p-type amine moieties towards high-capacity-voltage ZOBs. TNP cathode initiates high-kinetics, hybrid anion-cation 10e- charge storage involving four nitro sites coordinating with Zn2+ ions at low potential and two amine species coupling with SO4 2- ions at high potential. Consequently, Zn||TNP battery harvests high capacity (338 mAh g-1), boosted average voltage (1.08 V), and outstanding energy density (365 Wh kg-1 TNP). Moreover, the extended π-conjugated TNP macrocycle achieves anti-dissolution in electrolytes, prolonging the battery life to 50,000 cycles at 10 A g-1 with 71.6 % capacity retention. This work expands the chemical landscape of multielectron redox-bipolar organics for state-of-the-art ZOBs.

Unveiling the potential of PANI@MnO2@rGO ternary nanocomposite in energy storage and gas sensing

The development of advanced materials for energy storage and gas sensing applications has gained significant attention in recent years. In this study, we synthesized and characterized PANI@MnO2@rGO ternary nanocomposites (NCs) to explore their potential in supercapacitors and gas sensing devices. The ternary NCs were synthesized through a multi-step process involving the hydrothermal synthesis of MnO2 nanoparticles, preparation of PANI@rGO composites and the assembly to the ternary PANI@MnO2@rGO ternary NCs. The structural, morphological, and compositional characteristics of the materials were thoroughly analyzed using techniques such as XRD, FESEM, TEM, FTIR, and Raman spectroscopy. In the realm of gas sensing, the ternary NCs exhibited excellent performance as NH3 gas sensors. The optimized operating temperature of 100 °C yielded a peak response of 15.56 towards 50 ppm NH3. The nanocomposites demonstrated fast response and recovery times of 6 s and 10 s, respectively, and displayed remarkable selectivity for NH3 gas over other tested gases. For supercapacitor applications, the electrochemical performance of the ternary NCs was evaluated using cyclic voltammetry and galvanostatic charge-discharge techniques. The composites exhibited pseudocapacitive behavior, with the capacitance reaching up to 185 F/g at 1 A/g and excellent capacitance retention of approximately 88.54% over 4000 charge-discharge cycles. The unique combination of rGO, PANI, and MnO2 nanoparticles in these ternary NCs offer synergistic advantages, showcasing their potential to address challenges in energy storage and gas sensing technologies.

Six-Electron-Redox Iodine Electrodes for High-Energy Aqueous Batteries

Iodine (I2 ) shows great promising as the active material in aqueous batteries due to its distinctive merits of high abundance in ocean and low cost. However, in conventional aqueous I2 -based batteries, the energy storage mechanism of I- /I2 conversion is only two-electron redox reaction, limiting their energy density. Herein, six-electron redox chemistry of I2 electrodes is achieved via the synergistic effect of redox-ion charge-carriers and halide ions in electrolytes. The redox-active Cu2+ ions in electrolytes induce the conversion between Cu2+ ions and I2 to CuI at low potential. Simultaneously, the Cl- ions in electrolytes activate the I2 /ICl redox couple at high potential. As a result, in our case, I2 -based battery system with six-electron redox is developed. Such energy storage mechanism with six-electron redox leads to high discharge potential and capacity, excellent rate capability, as well as stable cycling behavior of I2 electrodes. Impressively, six-electron-redox I2 cathodes can match various aqueous metal (e.g. Zn, Mn and Fe) anodes to construct metal||I2 hybrid batteries. These hybrid batteries not only deliver enhanced capacities, but also exhibit higher operate voltages, which contributes to superior energy densities. Therefore, this work broadens the horizon for the design of high-energy aqueous I2 -based batteries.

Bidirectional manipulation of iodine redox kinetics in aqueous Fe-I2 electrochemistry

Catalyzing conversion is a promising approach to unlock the theoretical potentials of the I2/I- redox couple in aqueous Fe-I2 electrochemistry. However, most reported results only obtain one-directional efficient iodine conversion and cannot realize a balance of full reduction and reoxidation, thereby resulting in rapid capacity decay and/or low coulombic efficiency. Herein, the concept of bidirectional catalysis based on a core-shell structured composite cathode design, which accelerates the formation and the decomposition of FeI2 simultaneously during battery dynamic cycling, is proposed to regulate the Fe-I2 electrochemical reactions. Notably, the functional matrix integrates N, P co-doping and FeP nanocrystals into a carbon shell to achieve bidirectional catalysis. More specifically, the carbon shell acts as a physical barrier to effectively capture active species within its confined environment, N, P heteroatoms function better in directing the iodine reduction and FeP facilitates the decomposition of FeI2. As confirmed with in situ and ex situ analysis, the Fe-I2 cell operates a one-step but reversible I2/FeI2 pair with enhanced kinetics. Consequently, the composite cathode exhibits a reversible Fe2+ storage capability of 202 mA h g-1 with a capacity fading rate of 0.016% per cycle over 500 cycles. Further, a stable pouch cell was fabricated and yielded an energy density of 146 W h kgiodine-1. Moreover, postmortem analysis reveals that the capacity decay of the Fe-I2 cell originates from anodic degradation rather than the accumulation of inactive iodine. This study represents a promising direction to manipulate iodine redox in rechargeable metal-iodine batteries.

Engineering Polymer-Based Porous Membrane for Sustainable Lithium-Ion Battery Separators

Due to the growing demand for eco-friendly products, lithium-ion batteries (LIBs) have gained widespread attention as an energy storage solution. With the global demand for clean and sustainable energy, the social, economic, and environmental significance of LIBs is becoming more widely recognized. LIBs are composed of cathode and anode electrodes, electrolytes, and separators. Notably, the separator, a pivotal and indispensable component in LIBs that primarily consists of a porous membrane material, warrants significant research attention. Researchers have thus endeavored to develop innovative systems that enhance separator performance, fortify security measures, and address prevailing limitations. Herein, this review aims to furnish researchers with comprehensive content on battery separator membranes, encompassing performance requirements, functional parameters, manufacturing protocols, scientific progress, and overall performance evaluations. Specifically, it investigates the latest breakthroughs in porous membrane design, fabrication, modification, and optimization that employ various commonly used or emerging polymeric materials. Furthermore, the article offers insights into the future trajectory of polymer-based composite membranes for LIB applications and prospective challenges awaiting scientific exploration. The robust and durable membranes developed have shown superior efficacy across diverse applications. Consequently, these proposed concepts pave the way for a circular economy that curtails waste materials, lowers process costs, and mitigates the environmental footprint.