Decavanadate Doped Polyaniline for Aqueous Zinc Batteries

Supramolecular channels via crown ether functionalized polyaniline for proton-self-doped cathode in aqueous zinc-ion battery

Polyaniline (PANI) has been widely used as a cathode in aqueous zinc-ion batteries (AZIBs) because of its attractive conductivity and energy storage capability. However, the extensive application of PANI is limited by spontaneous deprotonation and slow diffusion kinetics. Herein, an 18-crown-6-functionalised PANI pseudorotaxane (18C6@PANI) cathode is successfully developed through a facile template-directed polymerisation reaction. The 18C6@PANI cathode exhibits a high specific capacity of 256 mAh g-1 at 0.2 A/g, excellent rate performance of 134 mAh g-1 at 6 A/g and outstanding cycle stability at a high current density of 3 A/g over 10,000 cycles. Experimental and theoretical analyses demonstrate the formation of the -N-Zn-O- structure. The abundant supramolecular channels in pseudorotaxane, induced by crown ether functional groups, are beneficial for achieving superior cyclability and rate capability. These encouraging results highlight the potential for designing more efficient PANI-based cathodes for high-performance AZIBs.

Bifunctional Potential Structure Design Breaks Electrolyte Limitations of Zinc Ion Battery

Aqueous zinc-ion batteries (ZIBs) are safe and economical for grid applications. However, current ZIBs have limitations in terms of inferior capacity and low output voltage, which are hampered by the electrolyte applicability of the Zn2+ hosts. In this study, we propose a novel organic cathode design strategy with a bifunctional potential region. This polymeric Zn2+ host combines the conjugated polyaniline backbone to tune the molecular surface pH and [Fe(CN)6]3-/4- redox couple for high output voltage and capacity. The polyaniline doped with ferricyanide (PAF) electrode exhibits two forms of charge storage in ZIBs: proton-assisted Zn2+ doping below 1.2 V (mechanism I), and [Fe(CN)6]3-/4- redox pair above 1.8 V (mechanism II). Density functional theory calculations and in situ pH experiments demonstrated that the H+ doping process of mechanism I forms a localized pH regulation on the molecular chain surface, providing a favorable reaction environment for mechanism II. The Zn-polymer battery delivered an outstanding discharge capacity (405.2 mAh g-1) and high output voltage (1.8 V) in the Zn(CF3SO3)2 electrolyte. This study provides a new route for enhancing the structural stability of electrodes and overcoming the electrolyte limitations of ferricyanide in weakly acidic electrolytes.

Trifunctional Rb+-Intercalation Enhancing the Electrochemical Cyclability of Ammonium Vanadate Cathode for Aqueous Zinc Ion Batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) have been highly desired due to their low cost, intrinsic safety, environmental friendliness, and great potential in large-scale power storage systems. However, their practical applications are impeded by unstable long-term electrochemical performances induced by microstructure degradation of the cathode material, hydrogen evolution reaction in the electrolyte, and dendritic growth on the zinc anode upon cycling. In this work, rubidium cations (Rb+) are introduced to synthesize an Rb+-preintercalated NH4V4O10 (NVO-Rb) composite. The contribution of Rb+ ions as pillars in V-O interlayers to facilitating Zn2+ storage is investigated first, and then the influences of partial Rb+ ions from the NVO-Rb cathode on the aqueous electrolyte and zinc anode are specially inspected from different viewpoints. Based on a series of characterization results, it is comprehensively elucidated that the partial Rb+ ions into the electrolyte suppress the generation of byproducts on the cathode and regulate the dendrite growth on the zinc anode, thus effectively promoting the long-term electrochemical performances of NVO-based AZIBs. The assembled Zn∥Zn(CF3SO3)2∥NVO-Rb cell can exhibit a high specific capacity and optimized Zn2+ diffusion kinetics, especially an improved electrochemical cyclability with a capacity retention of 87.6% at 5 A g-1 over 10000 cycles. This study enlightens the multiple roles of cation-preintercalation in the layered structure material and provides a feasible strategy for the development of high-performance aqueous batteries.

Bio-catalyzed oxidation self-charging zinc-polymer batteries

Oxidation self-charging batteries have emerged with the demand for powering electronic devices around the clock. The low efficiency of self-charging has been the key challenge at present. Here, a more efficient autoxidation self-charging mechanism is realized by introducing hemoglobin (Hb) as a positive electrode additive in the polyaniline (PANI)-zinc battery system. The heme acts as a catalyst that reduces the energy barrier of the autoxidation reaction by regulating the charge and spin state of O2. To realize self-charging, the adsorbed O2 molecules capture electrons of the reduced (discharged state) PANI, leading to the desorption of zinc ions and the oxidation of PANI to complete self-charging. The battery can discharge for 12 min (0.5 C) after 50 self-charging/discharge cycles, while there is nearly no discharge capacity in the absence of Hb. This biology-inspired electronic regulation strategy may inspire new ideas to boost the performance of self-charging batteries.

Boosting zinc-ion storage performance by interlayer chemistry modulation on an organic-inorganic hybrid cathode

Aqueous zinc-ion batteries (AZIBs) have triggered a surge of scientific research due to the unique merits of high safety, volumetric specific capacity, and environmental benignity. However, the implementation of this technology is still plagued by the lack of high-performance cathodes that can output high energy density and exceptional cycle life and inadequate Zn reversibility. Here, an organic-inorganic hybrid cathode based on a poly(3,4-ethylenedioxythiophene) (PEDOT) intercalated hydrated vanadium oxide (denoted PVO), which delivers an ultrahigh discharge capacity of 513.1 mAh g-1 (0.5 A g-1) and an ultra-stable cycle with 95.3 % capacity retention and approximately 100 % Coulombic efficiency over 2000 cycles (20 A g-1), is developed. Combining substantive measurements and theoretical calculations, it is demonstrated that favorable structural features with expanded interlayer galleries and robust architecture are believed to be responsible for the enhanced electrochemical performance, which can be further boosted by the improved Zn reversibility because of the introduction of maltitol electrolyte additive. This work provides a new attempt to achieve organic-inorganic composites for high-performance cathode materials of AZIBs and new insights into the charge storage behavior under the synergistic regulation of bilateral interfaces.

Proton-self-doped PANI@CC as the cathode for high-performance aqueous zinc-ion battery

Aqueous zinc-ion batteries (AZIB) have several advantages such as low cost, large theoretical capacity and good safety. However, the development of polyaniline (PANI) cathode materials has been limited by slow diffusion kinetics. Herein, proton-self-doped polyaniline@carbon cloth (CC) (PANI@CC) was prepared via in-situ polymerization, where polyaniline was deposited on an activated carbon cloth. The PANI@CC cathode exhibits a high specific capacity of 234.3 mA h g-1 at 0.5 A g-1, and excellent rate performance, delivering a capacity of 143 mA h g-1 at 10 A g-1. Furthermore, the reversible redox conversion during the charge-discharge process was studied using ex-situ X-ray photoelectron spectroscopy (XPS) and ex-situ Raman spectra. The results show that the excellent performance of the PANI@CC battery can be attributed to the formation of a conductive network between the carbon cloth and polyaniline. Also, a mixing mechanism involving insertion/extraction of Zn2+/H+ and a double-ion process is proposed. PANI@CC electrode is a novel idea for developing high-performance batteries.

Layered porous Mn0.18V2O5@C with manganese and carbon provided by a metal-organic framework precursor as a cathode material for aqueous zinc-ion batteries

At present, vanadium-based cathodes for aqueous zinc-ion batteries (AZIBs) are limited by their slow reaction kinetics, poor electrical conductivity, and low capacity retention. To overcome these problems, here, we design a layered porous Mn0.18V2O5@C as the cathode material for AZIBs using a manganese-containing metal-organic framework as a template through a simple solvothermal method. Such an electrode delivers an excellent specific capacity (380 mA h g-1 at 0.1 A g-1) accompanied by superior cycling stability (about 85% capacity retention for 2000 cycles at 6 A g-1). The excellent electrochemical performance of Mn0.18V2O5@C is ascribed to the improved interface activity including smooth zinc ion transport, abundant ion reaction active sites and accelerated charge transfer resulting from the coordination of the porous structure, doped conductive carbon, and the stable channel structure derived from the pillar effect of doping manganese ions, preventing a premature collapse of the electrode structure. It is also revealed by structural evolution analysis that the residual zinc ions also combine with the original Mn0.18V2O5 to form a ZnxMnyV2O5 phase, which serves as an additional structural pillar and in the meantime, also participates in the following cycles. These favorable electrochemical results suggest that Mn0.18V2O5@C is a suitable cathode material for AZIBs.

Polyaniline-Coated Porous Vanadium Nitride Microrods for Enhanced Performance of a Lithium-Sulfur Battery

To solve the slow kinetics of polysulfide conversion reaction in Li-S battery, many transition metal nitrides were developed for sulfur hosts. Herein, novel polyaniline-coated porous vanadium nitride (VN) microrods were synthesized via a calcination, washing and polyaniline-coating process, which served as sulfur host for Li-S battery exhibited high electrochemical performance. The porous VN microrods with high specific surface area provided enough interspace to overcome the volume change of the cathode. The outer layer of polyaniline as a conductive shell enhanced the cathode conductivity, effectively blocked the shuttle effect of polysulfides, thus improving the cycling capacity of Li-S battery. The cathode exhibited an initial capacity of 1007 mAh g^-1 at 0.5 A g^-1, and the reversible capacity remained at 735 mAh g^-1 over 150 cycles.

Functionalization of decavanadate anion by coordination to cobalt(II): Binding to proteins, cytotoxicity, and water oxidation catalysis

A series of five decavanadates (V₁₀) using a simple, one-pot synthesis, adhering to the model template: transition metal ion - decavanadate - ligands:(Hnicotinamide)₂{[Co(H₂O)₃(nicotinamide)₂]₂[μ-V₁₀O₂₈]}.6H₂O (1), {[Co(H₂O)₄(isonicotinamide)₂]₃}V₁₀O₂₈·4H₂O (2), {[Co(H₂O)₄]₂[Co(H₂O)₂(μ-pyrazinamide)₂][μ-V₁₀O₂₈]}·4H₂O (3) {[Co(H₂O)₄(μ-pyrazinamide)]₃.V₁₀O₂₈}·4H₂O (4), and (NH₄)₂{[Ni(H₂O)₄(2-hydroxyethylpyridine)]₂}V₁₀O₂₈·2H₂O (5) was synthesized. X-ray analysis reveals that 1 and 3 are decavanadato complexes, while 2, 4 and 5 are decavanadate complex salts. Moreover, 3 is the first example of a polymeric decavanadato complex, employing direct coordination with the metal center and the organic ligand, in toto. From the solution studies using ⁵¹V NMR spectroscopy, it was decoded that 1 and 3 stay stable in the model buffer solution and aqueous media. Binding to model proteins, cytotoxicity and water oxidation catalysis (WOC) was studied primarily for 1 and 3 and concluded that neither 1 nor 3 have an interaction with the model proteins thaumatin, lysozyme and proteinase K, because of the presence of the organic ligands in the Co(II) center, any further interplay with the proteins was blocked. Cytotoxicity studies reveal that 1 is 40% less toxic (0.05 mM) and 26% less toxic (0.1 mM) than the uncoordinated V₁₀ with human cell lines A549 and HeLa respectively. In WOC, 1 performed superior activity, by evolving 143.37 nmol of O₂ which is 700% (9-fold) increase than the uncoordinated V₁₀.

Fabrication of Polyaniline/graphene oxide composites for implementing it in humidity sensing

This work reports the measurement of impedance variations under various humidity conditions at frequency ranges between 100 Hz to 5 MHz. The electrochemical polymerization process has been used to synthesize by varying the mass ratios of graphene oxide (GO) in polyaniline (PAni). The electrochemical deposition method has been used to make samples film on an Indium Tin Oxide (ITO) glass slide. The percentage relative humidity (RH) of the samples was estimated to be 20 to 90%. It has been found that impedance and humidity show an inverse relation, i.e., the impedance value decreases with an increase in humidity. In contrast with platitudinous capacitive humidity sensors (PC-HS), the GO-based humidity sensor has a sensitivity of 75 to 99%, which is approximately ten times more elevated than traditional sensors. It has been observed with three different paraments weight % of GO; the frequency ranges between 100 Hz to 5 MHz and RH % between 20 to 90%. Moreover, it has been demonstrated that the humidity sensor shows a fast response and recovery time. Therefore, GO appears to be a consummate material for building a humidity sensor with high sensing for a comprehensive approach.