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This research elucidates novel insights into the electrochemical properties and degradation phenomena of propylene carbonate (PC)-based supercapacitors at a large-scale 18650 cylindrical jelly-roll cell level. Central to our findings is the identification of 2-ethyl-4-methyl-1,3-dioxolane (EMD) as a hitherto undocumented decomposition by-product, highlighting the nuanced complexity of PC electrolyte stability. We further demonstrate that elevated operational voltages precipitate accelerated electrolyte degradation, underscoring the criticality of defining the operational voltage window for maximizing device longevity. Employing advanced analytical techniques, including gas chromatography-mass spectrometry (GC-MS), this study meticulously analyzes electrolyte decomposition mechanisms. The outcomes offer pivotal insights into the operational constraints and chemical resilience of PC-based supercapacitors, contributing significantly to the optimization of supercapacitor design and application. By delineating a specific decomposition pathway, this investigation enriches the understanding of electrochemical dynamics in supercapacitor systems, providing a foundation for future research and technological advancement in energy storage devices., (© 2024 Wiley-VCH GmbH.)

The pursuit of high-performing cathode materials for next-generation lithium ion batteries has focused on increasing the nickel content of the material. However, this study reveals that particle size uniformity is a more decisive factor in battery performance than the nickel content alone. Using in operando X-ray diffraction, in situ gas evolution, and Atlung intercalant diffusion, we compared two promising cathode materials: LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC80) and LiNi 0.9 Mn 0.05 Co 0.05 O 2 (NMC90). We found that the NMC90 cell, with its more uniform particle size, exhibits a remarkable accumulation energy density of 558 kW h kg NMC -1 , which is 22% higher than that of the NMC80 cell. Also, the NMC90 cell unexpectedly has a 20% better capacity retention, a 50-fold higher discharge capacity at the 5C rate, and an Atlung lithium diffusion coefficient that is one order of magnitude higher after 1000 cycles. In situ gas analysis at a high voltage of 4.5 V reveals that the NMC80 cell generates 1.75 times more CO 2 than the NMC90 cell. These findings illuminate the intricate relationship between the nickel content, particle size uniformity, and battery performance. They offer vital insights for optimizing cathode materials in future lithium ion batteries., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)

The demand for lithium-ion batteries has significantly increased due to the increasing adoption of electric vehicles (EVs). However, these batteries have a limited lifespan, which needs to be improved for the long-term use needs of EVs expected to be in service for 20 years or more. In addition, the capacity of lithium-ion batteries is often insufficient for long-range travel, posing challenges for EV drivers. One approach that has gained attention is using core-shell structured cathode and anode materials. That approach can provide several benefits, such as extending the battery lifespan and improving capacity performance. This paper reviews various challenges and solutions by the core-shell strategy adopted for both cathodes and anodes. The highlight is scalable synthesis techniques, including solid phase reactions like the mechanofusion process, ball-milling, and spray-drying process, which are essential for pilot plant production. Due to continuous operation with a high production rate, compatibility with inexpensive precursors, energy and cost savings, and an environmentally friendly approach that can be carried out at atmospheric pressure and ambient temperatures. Future developments in this field may focus on optimizing core-shell materials and synthesis techniques for improved Li-ion battery performance and stability., (© 2023 Wiley-VCH GmbH.)

Li-S batteries with a sulphur loading content of 5 mg cm -2 were produced as large-scale 18 650 cylindrical cells. We have found that a key failure mode of cylindrical Li-S battery cells is the severe capacity fading during the galvanostatic charge-discharge process due to the corrosion of the electrodes, the electrolyte decomposition, and the severe polysulphide shuttling effect.

This study investigates the use of a hierarchical porous carbon electrode derived from oil palm leaves in a "water-in-salt" supercapacitor. The impact of anion identity on the electrical performance of the carbon electrode was also explored. The results show that the prepared carbon had a hierarchical porous structure with a high surface area of up to 1840 m 2 g -1 . When a 20 m LiTFSI electrolyte was used, the carbon electrode had a specific capacitance of 176 F g -1 with a wider potential window of about 2.6 V, whereas the use of a cheaper 20 m LiCl electrolyte showed a higher specific capacitance of 331 F g -1 due to the smaller size of the Cl - anion, which enabled inner capacitance. Therefore, the anion identity has an effect on the electrochemical performance of porous carbon, and this research contributes to the understanding of using "water-in-salt" electrolytes in carbon-based supercapacitors. The study's findings provide insights into developing low-cost, high-performance supercapacitors that can operate in a wider voltage range., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

This manuscript presents the design and facile production of screen-printed arrays (SPAs) for the internally validated determination of raised levels of serum procalcitonin (PCT). The screen-printing methodology produced SPAs with six individual working electrodes that exhibit an inter-array reproducibility of 3.64% and 5.51% for the electrochemically active surface area and heterogenous electrochemical rate constant respectively. The SPAs were modified with antibodies specific for the detection of PCT through a facile methodology, where each stage simply uses droplets incubated on the surface, allowing for their mass-production. This platform was used for the detection of PCT, achieving a linear dynamic range between 1 and 10 ng mL -1 with a sensor sensitivity of 1.35 × 10 -10 NIC%/ng mL -1 . The SPA produced an intra- and inter-day %RSD of 4.00 and 5.05%, with a material cost of £1.14. Internally validated human serum results (3 sample measurements, 3 control) for raised levels of PCT (>2 ng mL -1 ) were obtained, with no interference effects seen from CRP and IL-6. This SPA platform has the potential to offer clinicians vital information to rapidly begin treatment for "query sepsis" patients while awaiting results from more lengthy remote laboratory testing methods. Analytical ranges tested make this an ideal approach for rapid testing in specific patient populations (such as neonates or critically ill patients) in which PCT ranges are inherently wider. Due to the facile modification methods, we predict this could be used for various analytes on a single array, or the array increased further to maintain the internal validation of the system., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Potassium-based energy storage devices are attracting increasing attention as an alternative to lithium and sodium systems. In addition, metal-organic frameworks (MOFs) can be considered as promising electrode materials for this type of device due to their advantageous properties. Herein, the anionic MOF JUMP-1 and its analog with pre-loading of potassium cations, namely JUMP-1(K), were synthesized and characterized. The anionic framework of JUMP-1 is found to be extremely stable towards the exchange of the dimethylammonium cations by potassium ions. These MOFs were tested in composite electrodes in combination with conventional organic electrolytes as anode materials in a potassium-based system, including the full cell assembly of a potassium ion capacitor (KIC). The results show the significant improvement in capacity between the pristine JUMP-1 and the potassium-exchanged analog JUMP-1(K) as electrode materials. KICs containing JUMP-1(K) coupled with activated carbon (AC) display a promising stability over 4000 cycles. According to the results from these studies, the composite MOF electrode with the potassium-exchange analog JUMP-1(K) presents a promising approach, for which the electrochemical performance compared to the pristine anionic MOF is significantly enhanced., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The rapidly increasing adoption of electric vehicles (EVs) worldwide is causing high demand for production of lithium-ion batteries (LIBs). Tremendous efforts have been made to develop different components of LIBs in addition to design of battery pack architectures as well as manufacturing processes to make better batteries with affordable prices. Nonetheless, sustainable use of LIBs relies on the availability and cost of rare metals, which are naturally concentrated in a few countries. In addition, toxic electrolytes used in LIBs pose concerns on environmental impacts if LIBs are not handled properly after decommissioned from EVs. Therefore, it is paramount to realize effective utilization of spent LIBs, where their remaining capacities can be reused in less demanding applications. Finally, electrode materials and other valuable components of LIBs can be recovered via recycling, completing their circular life cycle. In this review, available options of LIBs after their retirement from EV applications, including battery second use, repair of electrode materials by direct regeneration, and material recovery by hydrometallurgical or pyrometallurgical processes are discussed. Throughout the review, the discussion is based around current available technologies, their environmental impacts, and economic feasibility as well as provided examples of pilot and industrial scale adoption of the processes., Competing Interests: The authors declare no conflict of interest., (© 2023 The Authors. Global Challenges published by Wiley‐VCH GmbH.)

Zero-emission hydrogen and oxygen production are critical for the UK to reach net-zero greenhouse gasses by 2050. Electrochemical techniques such as water splitting (electrolysis) coupled with renewables energy can provide a unique approach to achieving zero emissions. Many studies exploring electrocatalysts need to "electrically wire" to their material to measure their performance, which usually involves immobilization upon a solid electrode. We demonstrate that significant differences in the calculated onset potential for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) can be observed when using screen-printed electrodes (SPEs) of differing connection lengths which are immobilized with a range of electrocatalysts. This can lead to false improvements in the reported performance of different electrocatalysts and poor comparisons between the literature. Through the use of electrochemical impedance spectroscopy, uncompensated ohmic resistance can be overcome providing more accurate Tafel analysis., Competing Interests: There are no conflicts of interest to declare.

There is a controversial issue based on the particle cracking of the Ni-rich layered oxide cathode materials whether it occurs at the primary particles or the grain boundary. Herein, we found that the microcracking of NMC811 does not occur at single crystalline primary particles even abused at a severe upper cell voltage of 4.7 V having a lot of gas evolution since the single-crystal NMC811 has superior mechanical stability. The capacity retentions determined at 1C rate and a 100% state of charge (SOC) are 80% and 50% after 1000 cycles for single crystal and polycrystal NMC811, respectively.

Although the LiMn 2 O 4 cathode can provide high nominal cell voltage, high thermal stability, low toxicity, and good safety in Li-ion batteries, it still suffers from capacity fading caused by the combination of structural transformation and transition metal dissolution. Herein, a carbon-coated LiMn 2 O 4 cathode with core@shell structure (LMO@C) was therefore produced using a mechanofusion method. The LMO@C exhibits higher cycling stability as compared to the pristine LiMn 2 O 4 (P-LMO) due to its high conductivity reducing impedance growth and phase transition. The carbon shell can reduce direct contact between the electrolyte and the cathode reducing side reactions and Mn dissolution. Thus, the cylindrical cell of LMO@C//graphite provides higher capacity retention after 900 cycles at 1 C. The amount of dissoluted Mn for the LMO@C is almost 2 times lower than that of the P-LMO after 200 cycles. Moreover, the LMO@C shows smaller change in lattice parameter or phase transition than P-LMO, indicating to the suppression of λ-MnO 2 phase from the mixed phase of Li 1-δ Mn 2 O 4  + λ-MnO 2 when Li-delithiation at highly charged state leading to an improved cycling reversibility. This work provides both fundamental understanding and manufacturing scale demonstration for practical 18650 Li-ion batteries., (© 2022. The Author(s).)

The safety of Li-ion batteries is one of the most important factors, if not the most, determining their practical applications. We have found that free carbonate-based solvent molecules in the hybrid electrolyte system can cause severe safety concerns. Mixing ionic liquids with a carbonate-based solvent as the co-solvent at a fixed salt concentration of 1 M LiPF 6 can lead to free carbonate-based molecules causing poor charge storage performance and safety concerns.

The specific cell capacitance, equivalent series resistance (ESR) and equivalent distributed resistance (EDR) of porous carbon-based supercapacitors linearly depend on the cationic molecular length of room-temperature ionic liquids.

Although cobalt hydroxide (Co(OH) 2 ) has been attracting attention in several applications, its photoelectrochemical property has not yet been fully investigated. In this work, tuning the energy band gap of Co(OH) 2 nanosheets with silver atoms and enhancing their electrical conductivity with silver nanoparticles were then focused. A Ag-doped α-Co(OH) 2 thin film was successfully synthesized via an electrodeposition method. The optical properties of the as-prepared materials were characterized by UV-vis and fluorescence lifetime spectroscopies and further confirmed by density functional theoretical calculation. It was found that Ag atoms between adjacent layers of Co(OH) 2 can reduce its electronic band gap to 2.45 eV (α-Co(OH) 2 ) as compared to 2.85 eV of β-Co(OH) 2 . In terms of electrochemical properties, silver nanoparticles (AgNPs) can enhance the electrical conductivity of Co(OH) 2 nanosheets, leading to faster charge transfer reducing the internal resistance and significantly increasing the overall charge storage performance. Interestingly, under light illumination, Ag-doped α-Co(OH) 2 exhibits ca. 0.8 times lower charge storage capacity as compared to that under the dark condition. This is because the photoelectrons can be recombined with the generated holes in the conduction band. The charge storage mechanisms of Ag-doped α-Co(OH) 2 operated under dark conditions and light irradiation were further studied and confirmed using in situ electrochemical X-ray absorption spectroscopy (XAS). Overall, the in situ XAS supports the electrochemical result. This finding may pave a way to further develop photoactive advanced functional materials of metal hydroxides and oxides., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Transport phenomena and the solvation structure of lithium ions (Li + ) and hexafluorophosphate anions (PF 6 - ) in electrolytes with different fluoroethylene carbonate (FEC) concentrations as well as the electrochemical performance and safety of Ni-rich Li-ion battery cells at the 18650 cylindrical cell level are investigated. We have found that the electrolyte with an optimized FEC concentration (25% v/v) can effectively enhance the transport property in terms of the Li + transference number and contact ion pair (CIP) ratio leading to high performance and safety of practical 18650 cylindrical LIBs.

The microstructure of the electrodes in lithium-ion batteries (LIBs) strongly affects their gravimetric and volumetric energy and power as well as their cycle life. Especially, the effect of the microstructure in the case of next-generation Ni-rich cathode materials has not yet been investigated. A comprehensive understanding of the calendering process is therefore necessary to find an optimal level of the electrode microstructure that can enhance lithium-ion transportation, minimize plastic deformation, and improve conductivity. This work therefore aims to investigate the effect of microstructure and wettability on the electrode kinetics of next-generation Ni-rich LiNi 0.88 Co 0.09 Al 0.03 O 2 -based 18650 cylindrical cells, which were produced at the semiautomation scale of the pilot plant. Thus, all materials, electrodes, and the battery production are in quality control as the same level of commercial LIBs. With the optimized microstructure and other properties including a finely tuned compaction degree of 17.54%, a thickness of 188 μm, a sheet resistivity of 36.47 mΩ cm -2 , a crystallite size of 88.85 nm, a porosity of 26.03%, an electrode Brunauer-Emmett-Teller (BET) surface area of 1.090 m 2 g -1 , an electrode density of 2.529 g cm -3 , and an electrolyte uptake capability of 47.8%, the optimized LiNi 0.88 Co 0.09 Al 0.03 O 2 18650 cylindrical cells exhibit excellent high-rate capacity retention, fast Li-ion diffusion, and low internal resistance. The optimized electrode microstructure of next-generation Ni-rich cathode materials could be an effective strategy toward the real application of next-generation Ni-rich LIBs.

Scalable aqueous-based supercapacitors are ideal as future energy storage technologies due to their great safety, low cost, and environmental friendliness. However, the corrosion of metal current collectors e.g., aluminium (Al) foil in aqueous solutions limits their practical applications. In this work, we demonstrate a low-cost, scalable, and simple method to prepare an anti-corrosion current collector using a concept of hydrophobicity by coating the hydrophobic graphite passivation layer on the Al foil via a roll-to-roll coating technology at the semi-automation scale of production pilot plant of 18,650 cylindrical supercapacitor cells. All qualities of materials, electrodes, and production process are therefore in the quality control as the same level of commercial supercapacitors. In addition, the effects of the graphite coating layer have been fundamentally evaluated. We have found that the graphite-coated layer can improve the interfacial contact without air void space between the activated carbon active material layer and the Al foil current collector. Importantly, it can suppress the corrosion and the formation of resistive oxide film resulting in better rate capability and excellent cycling stability without capacitance loss after long cycling. The scalable supercapacitor prototypes here in this work may pave the way to practical 18,650 supercapacitors for sustainable energy storage systems in the future.

Recently, graphene-based materials have become ubiquitous in electrochemical devices including electrochemical sensors, electrocatalysts, capacitive and membrane desalination and energy storage devices. However, many of the electrochemical properties of graphene (particularly the capacitance and ionic transport) are not yet fully understood. This paper explores the capacitance and ionic transport properties of size dependent graphene (from 100 nm to 1 μm) prepared through the liquid phase exfoliation of graphite in which the size of graphene was finely selected using a multi-step centrifugation technique. Our experiment was then expanded to include basal plane graphene using highly ordered pyrolytic graphite as a model electrode, describing the assumed theoretical graphene capacitance (quoted as 550 F g-1 or 21 μF cm-2) and the electrochemical surface area of the carbon-based materials. This work improves our understanding of graphene electrochemistry (capacitance and ion transport), which should lead to the continuing development of many high-performance electrochemical devices, especially supercapacitors, capacitive desalination and ion-based selective membranes.

Deposition of redox-active metal-organic frameworks (MOFs) as thin films on conductive substrates is of great importance to improve their electrochemical performance and durability. In this work, a series of metalloporphyrinic MOF crystals was successfully deposited as thin films on carbon fiber paper (CFP) substrates, which is an alternative to rigid glass substrates. The specific dimensions of the obtained films could be adjusted easily by simple cutting. Metalloporphyrinic MOFs on CFP with different active metal species have been employed for electrochemical conversion of the carcinogenic nitrite into the less toxic nitrate. The MOFs on CFP exhibit remarkable improvement in terms of the electrocatalytic performance and reusability compared with the electrodes prepared from MOF powder. The contribution from metal species of the porphyrin units and reaction mechanisms was elucidated based on the findings from X-ray photoelectron spectroscopy (XPS) and in situ X-ray absorption near edge structure (XANES) measured during the electrochemical reaction. By integrating the redox-active property of metalloporphyrinic MOFs and high conductivity of CFP, MOF thin films on CFP provided a significant improvement of electrocatalytic performance to detoxify the carcinogenic nitrite with good stability., (© 2020 Wiley-VCH GmbH.)

Hydrazine is a common reducing agent widely used in many industrial and chemical applications; however, its high toxicity causes severe human diseases even at low concentrations. To detect traces of hydrazine released into the environment, a robust sensor with high sensitivity and accuracy is required. An electrochemical sensor is favored for hydrazine detection owing to its ability to detect a small amount of hydrazine without derivatization. Here, we have investigated the electrocatalytic activity of layered birnessite manganese oxides (MnO 2 ) with different intercalants (Li + , Na + , and K + ) as the sensor for hydrazine detection. The birnessite MnO 2 with Li + as an intercalant (Li-Bir) displays a lower oxidation peak potential, indicating a catalytic activity higher than the activities of others. The standard heterogeneous electron transfer rate constant of hydrazine oxidation at the Li-Bir electrode is 1.09- and 1.17-fold faster than those at the Na-Bir and K-Bir electrodes, respectively. In addition, the number of electron transfers increases in the following order: K-Bir (0.11 mol) < Na-Bir (0.17 mol) < Li-Bir (0.55 mol). On the basis of the density functional theory calculation, the Li-Bir sensor can strongly stabilize the hydrazine molecule with a large adsorption energy (-0.92 eV), leading to high electrocatalytic activity. Li-Bir also shows the best hydrazine detection performance with the lowest limit of detection of 129 nM at a signal-to-noise ratio of ∼3 and a linear range of 0.007-10 mM at a finely tuned rotation speed of 2000 rpm. Additionally, the Li-Bir sensor exhibits excellent sensitivity, which can be used to detect traces of hydrazine without any effect of interference at high concentrations and in real aqueous-based samples, demonstrating its practical sensing applications.

A new approach using graphene as a conductive binder in electrical supercapacitors has recently been proposed. Graphene shows outstanding properties as a conductive binder, and can be used to replace conductive, additive, and polymer binders. However, graphene follows an EDLC behaviour, which may limit its electrochemical performance. In the process described in this work, we introduced WSe 2 nanoflakes as a new approach to using pseudocapacitive materials as binders. The WSe 2 nanoflakes were produced through liquid phase exfoliation of bulk WSe 2 , and the flake size was finely selected using a controlled centrifugation speed. The physical and electrochemical properties of the exfoliated WSe 2 flakes were analysed; it was found that the smallest flakes (an average flake size of 106 nm) showed outstanding electrochemical properties, expanding our understanding of transition metal dichalcogenide (TMD) materials, and we were able to demonstrate the applicability of using WSe 2 as a binder in supercapacitor electrodes. We also successfully replaced conductive additives and polymer binders with WSe 2 . The overall performance was improved: capacitance was enhanced by 35%, charge transfer resistance reduced by 73%, and self-discharge potential improved by 9%. This study provides an alternative application of using TMD materials as pseudo capacitive binders, which should lead to the continued development of energy storage technology., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Exploring electrochemically chapped graphite/graphene composites derived from the bulk carbon rod of the spent Zn/carbon primary cell is for the advanced high-capacity lithium-ion battery anode. It is found that the synthesized graphitic carbon has grain boundary defects with multilayered exfoliation. Such material exhibits an average specific capacity of 458 mA h g -1 at 0.2 C, which is higher than the theoretical specific capacity (372 mA h g -1 ) of graphite. The differential specific capacity calculations also show no significant difference in lithiation and delithiation potentials for the exfoliated sample at the low voltage. However, two additional plateaus have also been observed at ∼1.2 and 2.5 V, which confirms the formation of the LiC 3 phase similar to lithiation of graphene. Hence, the superior lithiation ability and thecycling stability of defected graphite/graphene flakes may be useful for the sustainable development of next-generation high energy lithium-ion batteries. Also, waste recovery tends to reduce the risk of environmental pollution and the cost of raw materials., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

A simple and chemical-free recycled carbon-ZnMn 2 O 4 powder (composite) from the spent Zn-carbon batteries is proposed as an effective active material for the supercapacitor. This approach may amplify the economic and environmental benefits of the recycling process. We also synthesized the spherical MnO x nanoparticles by the calcination followed by the chemical treatment. Recycled composite and the MnO x nanoparticles were comprehensively characterized. Symmetrical supercapacitors with the composite and the MnO x nanoparticles show specific capacitances of 118 F g -1 and 88 F g -1 at 0.1 A g -1 , respectively. Also, the supercapacitor with the composite offers a specific energy of 8.0Whkg -1 at 0.1A g -1 while 4.3Whkg -1 is obtained for MnO x nanoparticles. The stable cell potential limits of 1.4 V and 1.2 V were established for the supercapacitors of the composite and MnO x nanoparticles with the capacitance retention of 83% and 96%, respectively at the end of 100,000 cycles at 2.5Ag -1 . Also, the excellent energy efficiencies of 80% and 72% with the coulombic efficiency of 100% are estimated for the supercapacitors of the composite and the MnO x nanoparticles, respectively. Finally, in situ gas analysis of the symmetrical supercapacitors are carried out using the differential electrochemical mass spectrometry. The proposed approach may be more economical and the environmentally benign recycling of spent Zn-carbon battery for circular economy and sustainability., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The charge storage mechanism of mixed cobalt oxysulphide/hydroxide materials having electrochromic properties was investigated. The cobalt oxysulphide/hydroxide materials exhibit a dual reversible redox reaction and electrochromic properties in 1 M KOH during charging and discharging., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A modified hydrolysed polyethylene with polyaniline was used as a dual functional interlayer/separator for high-performance lithium-sulphur batteries (LSBs) to reduce the migration of soluble polysulphide intermediates. Also, the sulphur cathode was encapsulated with carbon nanoparticles with a S@C core-shell structure using a solvent-free coating process. The chemical interaction between the imine group of the quinoid ring in the PANI structure and the polysulphides reducing the shuttle effect as well as the high electrical conductivity and less volume change of the carbon encapsulated sulphur can provide high-performance Li-S@C core-shell batteries.

The interaction between the reactive lithium metal surface and LiNO3 results in the formation of LixNOy clusters, which can protect the Li metal anode and suppress the shuttling effect of lithium polysulfides via the dipole-dipole interaction called the lithium bond.

Manganese oxide nanoparticles decorated on 3D reduced graphene oxide aerogels (3D MnO x /rGO ae ) for neutral electrochemical capacitors were successfully produced by a rapid microwave reduction process within 20 s. The symmetric electrochemical capacitor of 3D MnO x /rGO ae (Mn 3.0 at%) storing charges via both electric double layer capacitance (EDLC) and pseudocapacitance mechanisms exhibits a specific capacitance of 240 F g -1 as compared with 190 F g -1 of that using the bare 3D rGO ae at 0.5 A g -1 in 1 M Na 2 SO 4 (aq.) electrolyte. It retains 90% of the initial capacitance after 10 000 cycles, demonstrating high cycling stability. In addition, the charge storage mechanism of 3D MnO x /rGO ae was investigated using an electrochemical quartz crystal microbalance. In situ gas analysis using differential electrochemical mass spectrometry (DEMS) shows the CO 2 evolution at a cell potential over 1 V indicating that the positive electrode is possibly the voltage limiting electrode in the full cell. This finding may be useful for further development of practical high power and energy supercapacitors., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Nickel-rich layered, mixed lithium transition-metal oxides have been pursued as a propitious cathode material for the future-generation lithium-ion batteries due to their high energy density and low cost. Nevertheless, acute side reactions between Ni 4+ and carbonate electrolyte lead to poor cycling as well as rate performance, which limits their large-scale applications. Here, core-shell like LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA)-carbon composite synthesized by a solvent-free mechanofusion method is reported to solve this issue. Such a core-shell structure exhibits a splendid rate as well as stable cycling when compared to the physically blended NCA. In operando X-ray diffraction studies show that both materials experience anisotropic structural change, i.e., stacking c -axis undergoes a gradual expansion followed by an abrupt shrinkage; meanwhile, the a -axis contracts during the charging process and vice versa. Interestingly, the core-shell material displays a significantly high reversible capacity of 91% in the formation cycle at 0.1C and a retention of 84% at 0.5C after 250 cycles, whereas pristine NCA retains 71%. The robust mechanical force assisted dry coating obtained by the mechanofusion method shows improved electrochemical performance and demonstrates its practical feasibility.

Spinel-type cobalt oxide (Co 3 O 4 ) was synthesized and used as a photoactive bifunctional electrocatalyst towards the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) at the air cathode of zinc-air batteries (ZABs). The Co 3 O 4 having direct and indirect band gap energies of ca. 2.20 eV and ca. 1.35 eV can absorb visible light, generating photogenerated carriers and photoelectrons via the photoelectric effect. Upon exposure to visible light, the Co 3 O 4 electrode exhibits ca. 30% higher current density than that under dark conditions and provides around 10-20% lower OER and ORR overpotentials than those under the dark conditions. Under visible light, the specific capacity of the as-fabricated photoactive ZAB cell is improved by ca. 10% as compared to that under dark conditions.

A 3D free-standing lithiophilic silver nanowire aerogel (AgNWA) can stop the dendritic growth of lithium metal at the initial nucleation process. The 3D structure can also suppress the infinite volume expansion of lithium during cycling. The active AgNWA scaffold can serve as a Li reservoir to compensate for the irreversible consumption of Li. The lithiated AgNWA anode was coupled with a lithium iron phosphate (LFP) cathode in a full-cell configuration providing much higher performance than the Li//LFP cell.

New insight into the influence of Li+, Na+, and K+ cations between adjacent layers of birnessite-type manganese oxides (MnOx) towards the intercalation/deintercalation charge storage mechanism as a neutral electrochemical capacitor (1 M Na2SO4) is demonstrated. These structural cations play a major role in both the kinetic electron transfer in a faradaic redox reaction and the accessibility of the compensating electrolyte ions. Li-MnOx shows the highest Mn utilization of 51% followed by Na-MnOx (40%) and K-MnOx (31%), respectively.

Rational design and synthesis of a new silicon carbide/titanium carbide@silicon oxide/titanium dioxide (SiC/TiC@SiO x /TiO 2 ) porous core-shell nanostructured material could significantly enhance the specific capacity, rate capability, and cycle stability of electrodes. The results demonstrate that the specific capacities are 387, 300, 252, 210, 174 and 151 mA h g -1 at 100, 200, 500, 1000, 1500 and 2000 mA g -1 , respectively. The newly designed electrode still exhibits a larger specific capacity of 217 mA h g -1 at 1000 mA g -1 after the 1000th cycle.

Hydrogen can be the potential substitute energy carrier for fuel while electrolysis water with hydrogen evolution reaction (HER) is an efficient way to produce hydrogen. Highly active and robust electrocatalysts composed by earth abundant elements are required. Herein, nickel-copper-phosphorus (Ni-Cu-P) electrocatalysts are designed and synthesized by a facile one-step electrodeposition method. A unique pine-needle-like dendrite nanotube morphology of Ni-Cu-P electrocatalyst can be synthesized when copper content changed and impressive HER activity obtained in alkaline and acidic media. Briefly, the overpotential reaches 120 mV in 1 M KOH and 150 mV in 0.5 M H 2 SO 4 at the current density of 10 mA cm -2 , with the corresponding Tafel slope reaching 69 mV dec -1 . The results are close to that of commercial Pt/C catalysts (37 mV in 1 M KOH). Furthermore, the density functional theory calculations also demonstrate that P-incorporated Ni-Cu, Cu-incorporated Ni-P, and Ni-incorporated Cu-P have the optimized hydrogen adsorption free energy (Δ G H* ) of -0.066, -0.157, and -0.003 eV, respectively, which are more suitable than those of Ni-Cu, Ni-P, and Cu-P, respectively. The Ni-incorporated Cu-P even has a much smaller Δ G H* of -0.003 than that of Pt (∼-0.09 eV). We believe that our study will provide a new strategy to design non-noble metal alloy materials for practical applications in catalysis and energy fields.

We report the influence of electrolyte on the electrical contact between graphene nanoplatelets (GNPs) and an electrode via a single entity electrochemical technique. The current "steps" were observed in the absence of electrolyte due to the GNPs impacting on and bridging across an interdigitated gold electrode array (IDE); in contrast, current spikes of short duration were obtained in the presence of electrolyte. This result indicates that in the latter case the constant short-circuit bridging current was switched off and replaced solely by impacts of GNPs with single electrodes. These observed current spikes measured in the presence of electrolyte are evidenced to be of a capacitative nature, demonstrating the high sensitivity of the electronic properties of the GNP/metal junction to the ionic strength of the electrolytic solution.

A single hybrid energy conversion and storage (HECS) cell of alpha-cobalt hydroxide (α-Co(OH) 2 ) in ionic liquid was fabricated and operated under light illumination. The α-Co(OH) 2 , which is unstable in an aqueous electrolyte (i.e. KOH), is surprisingly stable in 1-butyl-1-methyl-pyrrolidinium dicyanamide ionic liquid. The as-fabricated HECS cell provides 100% coulombic efficiency and 99.99% capacity retention over 2000 cycles. Under a photo-charging condition, the dicyanamide anion of ionic liquid can react with a generated α-Co(OH) 2 + hole at the positive electrode since the HOMO energy level of the anion is close to the valence band of α-Co(OH) 2 . The excited photoelectron will transfer to the current collector and move to the negative electrode. At the negative electrode, the 1-butyl-1-methyl-pyrrolidinium cations of ionic liquid do electrostatically adsorb on the surface and intercalate into the interlayer of active material stabilizing the whole cell. The HECS cell having both energy conversion (photovoltaic effect) and energy storage (supercapacitor) properties may be an ideal device for future renewable energy.

The effect of the intercalated alkaline cations between the adjacent layers of multilayered manganese oxide (MnO x ) towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) was investigated. Li-MnO x , Na-MnO x , K-MnO x , Rb-MnO x , and Cs-MnO x provide OER overpotentials of 1.64, 1.70, 1.79, 1.83, and 1.84 V vs. RHE, respectively as well as ORR overpotentials of 0.71, 1.06, 1.13, 1.15, and 1.14 V vs. RHE, respectively. Li-MnO x shows the highest bifunctional catalytic activity towards both the ORR and OER. In addition, the Gibbs free energy change of *OH adsorption is found to be the largest throughout the reaction pathways determining the rate of the whole ORR and OER.

The aerobic epoxidation of propylene over the metal-organic framework Fe 3 (btc) 2 (btc = 1,3,5-benzentricarboxylate) as catalyst has been investigated by means of density functional calculations. The mechanisms of the reaction towards propylene oxide, carbonylic products (acetone and propanal) and a pi-allyl radical were investigated to assess the efficiency of Fe 3 (btc) 2 for the selective formation of propylene oxide. Propylene oxide and carbonylic products are formed on Fe 3 (btc) 2 by proceeding via propyleneoxy intermediates in the first step. Subsequently, the intermediates can then either be transformed to propylene oxide by way of ring closure of the intermediate or to the carbonylic compounds of propanal and acetone via 1,2-hydride shift. The results show that the formation of propylene oxide is favored over the formation of carbonylic products mainly due to the activation barriers being 2-3 times smaller. The activation barriers for the formation of the propyleneoxy intermediates on the Fe 3 (btc) 2 catalyst for the first and second reaction cycle are also lower than the barriers obtained for the formation of the pi-allyl radical that acts as the precursor to combustion products. On the basis of these computational results, we therefore expect a high catalytic selectivity of the Fe 3 (btc) 2 catalyst with respect to the formation of propylene oxide. We also compared the catalytic activities of Fe 3 (btc) 2 and Cu 3 (btc) 2 . The activation energy of the rate-determining step is almost 2 times lower for Fe 3 (btc) 2 than that for Cu 3 (btc) 2 , due to a larger charge transfer from the catalytic site to the O 2 molecule in the case of Fe 3 (btc) 2 .

Here, an impedimetric biosensor for determination and quantification of an aflatoxin B1 (AFB1) level using a reduced graphene oxide aerogel labeled with a single strand DNA (ss-HSDNA/rGO ae ) modified on a rotating disk electrode (RDE) is presented. Owing to the large biomolecule biding on the electrode, an electron transfer is interrupted and not easily accessible to a target molecule. To address this issue, we aim to study two effects; one considers electro-redox mediators and the other considers the hydrodynamic effect. By observing a cyclic voltammetric response from the ss-HSDNA/rGO ae electrode in three different charges of the redox mediators (i.e., neutral FcCH 2 OH, cationic Ru(NH 3 ) 6 3+ , and anionic Fe(CN) 6 4- ) in a phosphate buffer solution (PBS) containing AFB1, the magnitude of anodic current at 50 mV s -1 is 825, 615, and 550 mA cm -1 , respectively, which is significant dominated by the charge of the redox probe. The effect of hydrodynamic diffusion of the ss-HSDNA/rGO ae rotating disk electrode (RDE) toward AFB1 detection using FcCH 2 OH as the redox mediator was recorded by applying a range of rotating speed from 500 to 4000 rpm. Increasing rotating speed reduces the charge transfer resistance resulting in the lower detectable level for AFB1 quantification. In the case of 4000 rpm, the AFB1 can be detected with a limit of detection of 0.04 ng/mL and a linear range of 1 × 10 -10 to 7 × 10 -8 g/mL.

We design the Janus-like interlayer with two different functional faces for suppressing the shuttle of soluble lithium polysulfides (LPSs) in lithium-sulfur batteries (LSBs). At the front face, the conductive functionalized carbon fiber paper (f-CFP) having oxygen-containing groups i.e., -OH and -COOH on its surface was placed face to face with the sulfur cathode serving as the first barrier accommodating the volume expansion during cycling process and the oxygen-containing groups can also adsorb the soluble LPSs via lithium bonds. At the back face, a crystalline coordination network of [Zn(H 2 PO 4 ) 2 (TzH) 2 ] n (ZnPTz) was coated on the back side of f-CFP serving as the second barrier retarding the left LPSs passing through the front face via both physical confinement and chemical adsorption (i.e. Li bonding). The LSB using the Janus-like interlayer exhibits a high reversible discharge capacity of 1,416 mAh g -1 at 0.1C with a low capacity fading of 0.05% per cycle, 92% capacity retention after 200 cycles and ca. 100% coulombic efficiency. The fully charged LSB cell can practically supply electricity to a spinning motor with a nominal voltage of 3.0 V for 28 min demonstrating many potential applications.

Although metal-organic frameworks (MOFs) or porous coordination polymers have been widely studied, their antimicrobial activities have not yet been fully investigated. In this work, antifungal activity of copper-based benzene-tricarboxylate MOF (Cu-BTC MOF), which is water stable and industrially interesting, is investigated against Candida albicans , Aspergillus niger , Aspergillus oryzae and Fusarium oxysporum . The Cu-BTC MOF can effectively inhibit the growth rate of C. albicans and remarkably inhibit the spore growth of A. niger , A. oryzae and F. oxysporum . This finding shows the potential of using Cu-BTC MOF as a strong biocidal material against representative yeasts and moulds that are commonly found in the food and agricultural industries., Competing Interests: We have no competing interests.

Manganese dioxide (MnO 2 ) has been widely used as an active material for high-performance supercapacitors due to its high theoretical capacitance, high cycling stability, low cost, and environmental friendliness. However, the effect of its crystallographic phase on charge storage performances and mechanisms is not yet clear. Herein, MnO 2 -based supercapacitors with different structures including nanospheres, nanorods, nanotubes, and nanosheets have been fabricated and investigated. Among such structures, δ-MnO 2 nanosheets exhibit the highest specific capacitance of 194.3 F g -1 at 1 A g -1 when compared with other phases and shapes. The maximum specific energy of the δ-MnO 2 nanosheet supercapacitor is 23.4 W h kg -1 at 971.6 W kg -1 and the maximum specific power is 4009.2 W kg -1 at 15.9 W h kg -1 with a capacity retention of 97% over 15 000 cycles. The δ-MnO 2 nanosheet mainly stores charges via a diffusion-controlled mechanism at the scan rates of 10-100 mV s -1 , whilst the α-MnO 2 with different morphologies including nanospheres, nanorods, and nanotubes store charges via a non-faradaic or non-diffusion controlled process especially at fast scan rates (50-100 mV s -1 ). Understanding the charge storage performance and mechanism of the MnO 2 nanostructures with different crystallographic phases and morphologies may lead to the further development of supercapacitors.

A proton-conducting coordination polymer of anionic one-dimensional (1D) chains of Zn 2+ phosphate and protonated imidazole with the formula of [Zn(HPO 4 )(H 2 PO 4 ) 2 ](ImH 2 ) 2 has been used as a novel supercapacitor material in aqueous electrolytes. This material stores charges via a proton-hopping mechanism.

We report the use of an electroactive species, acetaminophen, to modify the electrical connection between a carbon nanotube (CNT) and an electrode. By applying a potential across two electrodes, some of the CNTs in solution occasionally contact the electrified interface and bridge between two electrodes. By observing a single CNT contact between two microbands of an interdigitated Au electrode in the presence and absence of acetaminophen, the role of the molecular species at the electronic junction is revealed. As compared with the pure CNT, the current magnitude of the acetaminophen-modified CNTs significantly increases with the applied potentials, indicating that the molecule species improves the junction properties probably via redox shuttling.

Carbon black nanospheres were turned to hollow carbon nanospheres (HCNs) and were used as the conductive additive in the cathodes of Li-ion batteries (LIBs). The results show that 10 wt % HCN added to the LIB cathodes, such as LiMn 2 O 4 , LiCoO 2 , LiNiMnCoO 2 , and LiFePO 4 , can provide significantly higher specific capacity than those using spherical carbon black. For example, a specific capacity of the LiMn 2 O 4 /HCN/PVDF cathode at 80:10:10 wt % with a bulk electrical conductivity of 1.07 Ω cm -2 is 125 mA h g -1 at 0.1 C from 3.0 to 4.3 V versus Li + /Li, which is 3.85-fold higher than that using Super P. The stability tested at 1 C remains over 95% after 800 charge/discharge cycles with 100% Coulombic efficiency. Replacing the present carbon black conductive additive with HCN in this work may be one of the best choices to increase the charge storage performance of LIBs rather than only focusing on the development of active cathode materials., Competing Interests: The authors declare no competing financial interest.

Although Nickel-Cadmium (NiCd) and Nickel-metal hydride (NiMH) batteries have been widely used, their drawbacks including toxic Cd and expensive La alloy at the negative electrodes, low energy density (40-60 Wh/kg for NiCd and 140-300 Wh/L for NiMH), low power density (150 W/kg for NiCd and 1000 W/kg for NiMH), and low working potential (1.2 V) limit their applications. In this work, Cd and La alloy were replaced with N-doped reduced graphene oxide aerogel (N-rGO ae ) providing a hybrid energy storage (HES) having the battery and supercapacitor effects. The HES of Ni(OH) 2 -coated N-rGO ae //N-rGO ae provides 1.5 V, a specific energy of 146 Wh/kg, a maximum specific power of 7705 W/kg, and high capacity retention over 84.6% after 5000 cycles. The mass change at the positive electrode during charging/discharging is 8.5 µg cm -2 owing to the insertion/desertion of solvated OH - into the α-Ni(OH) 2 -coated N-rGO ae . At the negative electrode, the mass change of the solvated K + , physically adsorbed/desorbed to the N-rGO ae , is 7.5 μg cm -2 . In situ X-ray absorption spectroscopy (XAS) shows highly reversible redox reaction of α-Ni(OH) 2 . The as-fabricated device without using toxic Cd and expensive La alloy has a potential as a candidate of NiCd and NiMH.