Adsorption Of Electrolytes Research Articles

Exploring Electrolyte Adsorption on the Different Types of Layered Cathode Surfaces in Lithium-Ion Batteries via a Universal Neural Network Potential Method.

LiNi x Mn y Co z O2 (NCM) is a promising cathode material for lithium-ion batteries. Their long-term stability and impedance growth as cycles are strongly influenced by the properties of the cathode electrolyte interface (CEI), formed by the reaction between the electrolyte and electrode surface. Understanding of these interactions at the atomic level of the NCM electrode surface and electrolyte will provide a new strategic approach for the design of a highly functional CEI layer. In this study, we explored the influence of Ni content in transition metal layers on surface energies under different synthetic conditions and terminations using a density functional theory (DFT) validated universal neural network potential (UNNP) method. Furthermore, we investigated the adsorption of ethylene carbonate (EC) and dimethyl carbonate (DMC) on the most favorable NCM surfaces. EC and DMC displayed similar adsorption energy trends; however, differences were observed in the preferred configurations, which can affect the formation of the CEI.

Viscoelastic Properties of Electrospray‐Deposited Polymer Shells via Quartz Crystal Microbalance With Dissipation (QCM‐D)

AbstractMultilayer polymer films are extensively used in multiphase separation. Electrospray deposition (ESD) is an important technique for fabricating such films with tunable morphology. Viscoelastic properties of polystyrene (PS) nanoshell coatings produced by ESD on gold and spin‐coated PS surfaces are evaluated using Quartz Crystal Microbalance with Dissipation (QCM‐D). The thickness of PS films on gold increases with flow rate from ∼200 nm at 0.5 to ∼400 nm at 1.5 mL h−1, accompanied by an order‐of‐magnitude increase in dissipation due to larger particle sizes from shorter droplet flight times. This effect is absent on spin–coated PS films, suggesting the onset of the self‐limiting effect of charges. Although the shear moduli for ESD films calculated from Voigt models is only 0.08%–0.20% of the bulk PS modulus, the stiffness ratio of spray‐coated PS to a single shell is (5.00–13.3) × 103 m−1, due to shell–shell and shell–substrate interactions. These are novel results related to the interparticle friction obtained using QCM‐D for the first time. This work demonstrates that mechanical properties of particulate viscoelastic films with potential applications in high surface area sensors, such as size‐selective membranes for protein or electrolyte adsorption, can be evalauted by QCM‐D with nanograms of material.

Electrolytes at Uncharged Liquid Interfaces: Adsorption, Potentials, Surface Tension, and the Role of the Surfactant Monolayer.

The article summarizes the results of our research on the behavior of ions at uncharged fluid interfaces, with a focus on moderately to highly concentrated aqueous electrolytes. The ion-specific properties of such interfaces have been analyzed. The ion-specificity series are different for water|air and water|oil; different for surface tension σ, surface Δχ potential and electrolyte adsorption, and they change with concentration. A methodology has been developed that allows to disentangle the multiple factors controlling the ion order. The direct ion-surface interactions are not always the most significant factor behind the observed ion sequences: indirect effects stemming from conjugate bulk properties are often more important. For example, the order of the surface tension with the nature of the anion (σKOH > σKCl > σKNO3 for potassium salts) is often the result of bulk nonideality and follows the order of the bulk activity coefficients (γKOH > γKCl > γKNO3) rather than that of a specific ion-surface interaction potential. The surface Δχ potential of aqueous solutions is, in many cases, insensitive to the ion distribution in the electric double layer but reflects the orientation of water at the surface, through the ion-specific dielectric permittivity ε of the solution. Even the sign of Δχ is often the result of the decrement of ε in the presence of electrolyte. A whole new level of complexity appears when the ions interact with an uncharged surfactant monolayer. A method has been developed to measure the electrolyte adsorption isotherms on monolayers of varying area per surfactant molecule via a combination of experiments-compression isotherms and surface pressure of equilibrium spread monolayers. The obtained isotherms demonstrate that the ions exhibit a maximum in their adsorption on monolayers of intermediate density. The maximum is explained with the interplay between ion-surfactant complexation, volume exclusion and osmotic effects.

Fabrication of single-ion conductive quasi-solid-state electrolyte membrane for high-performance lithium-ion batteries

The aim of this work is to develop new quasi-solid-state electrolyte materials for lithium-ion batteries (LIBs) to improve their safety and comprehensive electrochemical performance. Herein, helical mesoporous silica nanofibers were synthesized by a sol–gel method. After grafting lithium salt onto their surfaces, a single-ion conductor (SL) was obtained. Then, using poly(vinylidene fluoride-co-hexafluoropropylene) as the polymer matrix, SL as the filler, a porous composite film was prepared by solution casting method. After soaking organic electrolyte with low concentration Li salt till saturation, one quasi-solid-state electrolyte membrane (PSLE) was achieved. It showed high electrolyte adsorption rate of 660 % and good thermal stability. A high lithium-ion transfer number of 0.85 indicated typical single-ion conductivity. Moreover, a high electrochemical stability window of up to 5.5 V and an ionic conductivity of 2.5 × 10−3 S·cm−1 at 25 °C were gained. The assembled LFP|PSLE|Li battery exhibited excellent rate performance and cycle stability, indicating that the PSLE has great application prospect in solid-state LIBs.

Self-extinguishing polyimide sandwiched separators for high-safety and fast-charging lithium metal batteries

Developing fast-charging lithium metal battery (LMB) with high specific capacity arouses enormous attentions. Unfortunately, during the operation of fast-charging LMB, substantial amount of Joule heat generated within battery often induces inhomogeneous heat accumulation that concomitantly deteriorates the lithium dendrite growth issues, resulting in rapid capacity fading and potentially fatal thermal runaway. It is critically essential to develop advanced separator that possesses high ionic conductivity, effective dendrite inhibition and self-extinguishing property for fast-charging LMB with high-safety. Here, we report a facile approach to fabricate polyimide composite separator (denoted as PIFAP), where the polyimide fiber (PIF) membrane is sandwiched by aerogel layers of polyimide/ammonium polyphosphate composite. Notably, compared with PIF, the PIFAP features significant enhancement in flame retardance, electrolyte affinity, electrolyte adsorption and ionic conductivity. Moreover, beneficiating from the aerogel layers with uniform nanopores of ∼100 nm, the optimized PIFAP separator can enable homogeneous lithium deposition, achieving a dendrite-free lithium deposition on the surface of anode for over 1600 h, superior to the PIF and Celgard separators. The resulting “LiFePO4/PIFAP/Li” cell can exhibit a remarkably high cycling stability with 99.1 % of capacity retention after long-term cycling at a current density of 10 C.

Electrochemical Investigation of Lithium Perchlorate-Doped Polypyrrole Growing on Titanium Substrate

Lithium perchlorate-doped polypyrrole growing on titanium substrate (LiClO4-PPy/Ti) has been fabricated to act as electroactive electrode material for feasible electrochemical energy storage. A theoretical and experimental investigation is adopted to disclose the conductivity, electroactivity properties and interfacial interaction-dependent capacitance of LiClO4-PPy/Ti electrode. The experimental measurement results disclose that LiClO4-PPy/Ti reveals lower ohmic resistance (0.2226 Ω cm−2) and charge transfer resistance (2116 Ω cm−2) to exhibit higher electrochemical conductivity, a more reactive surface, and feasible ion diffusion to present higher double-layer capacitance (0.1930 mF cm−2) rather than LiClO4/Ti (0.3660 Ω cm−2, 65,250 Ω cm−2, 0.0334 mF cm−2). LiClO4-PPy/Ti reveals higher Faradaic capacitance caused by the reversible doping and dedoping process of perchlorate ion on PPy than the electrical double-layer capacitance of LiClO4/Ti caused by the reversible adsorption and desorption process of the LiClO4 electrolyte on Ti. Theoretical simulation calculation results prove that a more intensive electrostatic interaction of pyrrole N···Ti (2.450 Å) in LiClO4-PPy/Ti rather than perchlorate O···Ti (3.537 Å) in LiClO4/Ti. LiClO4-PPy/Ti exhibits higher density of states (57.321 electrons/eV) at Fermi energy and lower HOMO-LUMO molecule orbital energy gap (0.032 eV) than LiClO4/Ti (9.652 electrons/eV, 0.340 eV) to present the enhanced electronic conductivity. LiClO4-PPy/Ti also exhibits a more declined interface energy (−1.461 × 104) than LiClO4/Ti (−5.202 × 103 eV) to present the intensified interfacial interaction. LiClO4-PPy/Ti accordingly exhibits much higher specific capacitances of 0.123~0.0122 mF cm−2 at current densities of 0.01~0.10 mA cm−2 rather than LiClO4/Ti (0.010~0.0095 mF cm−2, presenting superior electroactivity and electrochemical capacitance properties. LiClO4-PPy/Ti could well act as the electroactive supercapacitor electrode for feasible energy storage.

Ir metal nanoparticles and IrO2 for acidic oxygen evolution reaction: Insight from Raman spectroscopy

Due to their high activity and stability, Ir-based materials are state-of-the-art electrocatalysts for oxygen evolution reaction (OER) under acidic conditions. However, many factors such as the influence of the activation/conditioning protocol and the resulting oxidation state or the effect of electrolyte adsorption on activity are still debated or overlooked. Herein, Raman spectroscopy was performed on commercial Ir black and IrO2 nanopowders to reveal differences in the samples after activation, as well as adsorption of perchlorates. Specifically, three different activation protocols were performed, 0.05 to 1.45 VRHE (activated), 0.05 to 1.6 VRHE (activated-long range (l.r.)), and 1.1 to 1.6 VRHE (activated-short range (s.r.)), resulting in different OER activity as well as different Raman spectra. However, only Ir(IV) bands remain visible in the ex situ Raman experiments, which was not sufficient to reveal the hydrated phases in the iridium samples. Therefore, mimicked in situ experiments were performed, which allowed the observation of the hydrated phase, particularly for Ir black, but also showed adsorption of perchlorate anions. In addition, the influence of solvation on Raman band shifts is revealed - along with DFT calculations. Overall, this work paves the way for our future in situ Raman spectroscopy experiments with iridium-based electrocatalysts during activation and OER.

Microstructure and Electrochemical Performance of Supercapacitor Based on Nickel/Activated Carbon Composite Electrode

Supercapacitors are promising electrochemical energy storage devices because they have higher energy than conventional capacitors and higher power than rechargeable batteries. Based on material for supercapacitors, activated Carbon (AC) has large specific surface area, high conductivity, and chemical stability, but still shows less than optimal specific capacitance and energy density. In this work, AC was composited with nickel (Ni) and Carbon Black (CB) to modify microstructure and optimize its electrochemical performance. Initially, synthesis of Ni-AC (cathode) and AC (anode) slurry was carried out by blending method in different mass percentages of Ni (5, 10, 15, 20, 25 %). The slurry was coated using doctor blade on aluminum foil. Then, Ni-AC//AC was fabricated and tested by Galvanostatic Charge-Discharge (GCD) instrument to analyze the electrochemical performance changes of supercapacitor. Based on XRD pattern, AC peak was found at 26.5° and Ni-AC composite had additional peaks in 44.4°, 51.7°, and 76.2°. The crystal size and porosity of electrode were in range of 23.2 – 45.4 nm and 66.6 – 75.7%, respectively. Based on the electrochemical evaluation, addition of 20% Ni mass in activated carbon electrode has the optimum performance, which increases active sites of the electrode and ion electrolyte adsorption capacity. Further, the GCD revealed that the prepared Ni-AC//AC electrode have excellent capacitive behavior with specific capacitance of 56.6 F/g, power density of 308.8 W/kg, energy density of 20.8 Wh/kg, and specific retention of 69.6% until 50 cycles.

A high-efficient stable surface-prelithiated Li1.2Ni0.13Co0.13Mn0.54O2 cathode enabled by sacrificial lithium nitrides for high-energy-density lithium-ion batteries

Lithium-rich cathode materials with superior practical specific capacity over 250 mAh g−1 are considered as one of the resolutions for high-energy-density lithium-ion batteries, while the intrinsic capacity loss caused by solid electrolyte interface (SEI) formation on the anode impedes the increase of energy density. To address this issue, we propose a composite cathode prelithiation strategy including a carbon-incorporated lithium phosphorus oxynitride (LiCPON) layer and a sacrificial Li3N (Sac. Li3N) layer, which can not only compensate for the capacity loss effectively and controllably with a high lithium utilization rate over 85% but also provide outstanding atmosphere stability with an 80.2% lithium utilization rate after exposed in dry air for 8 hours. The energy densities achieve 489.5 Wh kg−1 and 497.3 Wh kg−1 initially after cathode prelithiation in full cells paired with Si/C and SiOx/C anodes, corresponding to a 11.9% and 11.6% increase, respectively. The energy densities still remain 318.7 Wh kg−1 and 319.7 Wh kg−1 after 50 cycles with an increase of 13.7% and 11.7%, respectively. The cathode electrolyte interface (CEI) and SEI layers are mutually optimized and the electrolyte adsorption and degradation are suppressed after cathode prelithiation. Our work has demonstrated that such a composite cathode prelithiation strategy provides the possibility for large-scale industrial production, transportation, and conservation of prelithiated lithium-rich cathodes to achieve high-energy-density lithium-ion batteries.

Wood and PAN-derived hierarchically porous low-tortuosity carbon electrodes for high-areal-performance supercapacitors

Carbonized wood not only well retains the original hierarchical pore structure and full openly straight channels of wood, but also has structural stability and conductivity, which make it considered as a low tortuosity 3D self-support porous carbon networks electrode material with conductive-free and binder-free for supercapacitor. However, carbonized wood as a self-support electrode of supercapacitor still has some problems, such as relatively low specific surface area, not effective use of pore structure and excessive absorption of electrolyte, which seriously affects the performance of its supercapacitor. Herein, a 3D porous network of pure carbon PCN/CW electrode with high specific surface area was prepared by effective filling and re‑carbonization of the polymer PAN in carbonized wood. The PCN/CW electrode not only realized the effective filling and regulation of the carbonized wood channel solved the problem of excessive adsorption of electrolyte by the electrode, but also improved the specific surface area without introducing other substances. The obtained PCN/CW electrode exhibits high areal capacitance up to 5547 mF cm−2 at 5 mA cm−2, its symmetrical supercapacitor (PCN/CW//PCN/CW-60) delivers a maximum areal energy density of 0.26 mWh cm−2 at power density of 1.19 mW cm−2 with an outstanding capacitance retention of 97.4 % after 10,000 cycles.

Regulating the Oxygen Vacancy and Electronic Structure of NiCo Layered Double Hydroxides by Molybdenum Doping for High-Power Hybrid Supercapacitors.

Amelioration of nickel-cobalt layered double hydroxides (NiCo-LDH) with a high specific theoretical capacitance is of great desire for high-power supercapacitors. Herein, a molybdenum (Mo) doping strategy is proposed to improve the charge-storage performance of NiCo-LDH nanosheets growing on carbon cloth (CC) via a rapid microwave process. The regulation of the electronic structure and oxygen vacancy of the LDH is consolidated by the density functional theory (DFT) calculation, which demonstrates that Mo doping narrows the band gap, reduces the formation energy of hydroxyl vacancies, and promotes ionic and charge transfer as well as electrolyte adsorption on the electrode surface. The optimal Mo-doped NiCo-LDH electrode (MoNiCo-LDH-0.05/CC) has an amazing specific capacity of 471.1mA h g-1 at 1 A g-1 , and excellent capacity retention of 84.8% at 32 A g-1 , far superior to NiCo-LDH/CC (258.3mA h g-1 and 76.4%). The constructed hybrid supercapacitor delivers an energy density of 103.3W h kg-1 at a power density of 750W kg-1 and retains the cycle retention of 85.2% after 5000 cycles. Two assembled devices in series can drive thirty LED lamps, revealing a potential application prospect of the rationally synthesized MoNiCo-LDH/CC as an energy-storage electrode material.

Scalable Preparation of Polyimide Sandwiched Separator for Durable High-Rate Lithium-Metal Battery.

The ever-growing demands for efficient energy storage accelerate the development of high-rate lithium-metal battery (LMB) with desirable energy density, power density, and cycling stability. Nevertheless, the practical application of LMB is critically impeded by internal temperature rise and lithium dendrite growth, especially at high charge/discharge rates. It is highly desired but remains challenging to develop high-performance thermotolerant separators that can provide favorable channels to enable fast Li+ transport for high-rate operation and simultaneously homogenize the lithium deposition for dendrite inhibition. Polyimide-based separators with superior thermal properties are promising candidate alternatives to the commercial polyolefin-based separators, but previous strategies of designing either nanoporous or microporous channels in polyimide-based separators often meet a dilemma. Here, a facile and scalable approach is reported to develop a polyimide fiber/aerogel (denoted as PIFA) separator with the microporous polyimide fiber membrane sandwiched between two nanoporous polyimide aerogel layers, which can enable LMBs with remarkable capacity retention of 97.2% after 1500 cycles at 10 C. The experimental and theoretical studies unravel that the sandwiched structure of PIFA can appreciably enhance the electrolyte adsorption and ionic conductivity; while, the aerogel coating can effectively inhibit dendrite growth to realize durable high-rate LMBs.

Potential-Dependent Competitive Adsorption of Electrolytes Kinetically Inhibits High-Current Hydrogen Oxidation in Non-Aqueous Media

Performing electrochemical transformations in non-aqueous media can unlock new reactivities and selectivities unattainable in aqueous media. For instance, non-aqueous media (e.g. acetonitrile (MeCN), dimethylformamide (DMF), dimethylsulfoxide (DMSO)) allow the dissolution of organic compounds and enable water-incompatible organic electrosynthesis reactions. On the other hand, the lithium-mediated nitrogen reduction reaction (NRR) carried out electrochemically in tetrahydrofuran (THF) is one of the most promising routes towards electrifying the Haber-Bosch reaction and thus eliminating the need for hundreds of atmospheres of pressure and high temperatures. However, many cathodic non-aqueous electrochemical reactions either do not operate with well-defined anodic reactions (e.g. unproductive solvent and/or electrolyte oxidation) or are often coupled with the sacrificial oxidation of a dissolving metal electrode (e.g. magnesium, zinc). Hence, the development of a non-sacrificial anodic reaction is essential for engineering practical, sustainable non-aqueous electrochemical transformations. In this study, we investigate the hydrogen oxidation reaction (HOR) in a variety of non-aqueous solvents (MeCN, DMF, DMSO, THF) and buffers (AcO-/AcOH, Cl-/HCl, etc.) whose base serves as the proton acceptor for HOR. The reason why HOR can be sustainable is because it produces protons, which can be paired with a number of proton-demanding electro-reductions such as NRR, carbon dioxide reduction (CDR) to form oxalic acid or carboxylic acids, and more. Hydrogen is also stoichiometrically cheaper and less greenhouse-emitting than sacrificial metals, making HOR both cheaper and greener. First, we demonstrate a fabricated gas diffusion electrode (GDE) architecture that supports high H2 transport-limited current densities in non-aqueous solvents at ambient pressure. We find that the maximum HOR current density obtained is not H2 transport-limited but instead depends on the kinetics influenced by the pKa and steric profile of the buffer electrolytes present. By also varying the buffer electrolyte concentration and H2 partial pressure and conducting voltametric studies in the absence of H2, we demonstrate that the HOR current density reaches a maximum due to a competitive adsorption mechanism of the buffer electrolytes, limiting the surface concentration of adsorbed hydrogen atoms from H2 dissociative adsorption and thus inhibiting HOR. Based on these findings, we outline strategies for mitigating HOR inhibition via this competitive adsorption mechanism to unlock higher HOR current densities.

Microplastics as an adsorption and transport medium for per- and polyfluoroalkyl substances in aquatic systems: Polystyrene and undecafluorohexanoic acid interactions

The assessment of possible interactions between microplastic particles (MPP) and other emerging contaminants such as per- and polyfluoroalkyl substances (PFAS) is of great importance due to their potentially conjunctive harmful effects on the environment. Here, the colloidal behaviour of a polystyrene MPP in the presence of undecafluorohexanoic acid (UFHA), an alternative to the widely used C8 PFAS, was studied in aqueous dispersions. Adsorption of UFHA on MPP was confirmed, where it induced charge neutralization with overcharging at higher UFHA concentrations. Rates of MPP aggregation were rapid with neutral particles, while slow at low and high UFHA doses, where considerable, alternate surface charge persisted and hence, fine particle dispersion was maintained. The addition of multivalent ions influenced the surface charge and aggregation features of MPP, in both their native form and in the presence of UFHA. Concurrent adsorption of electrolytes and UFHA was observed and strongly affected the rate of MPP aggregation under some experimental conditions. This study provides new insights into the possible interactions of PFAS with MPP, which may fundamentally influence the migration of these contaminants in aqueous environments. Aggregated particles will more likely accumulate in the sediments or at the air–water interface, while individual, highly stable MPP-PFAS composites have the potential to migrate together in the water column.

Prediction of alkaline earth metal ion adsorption on goethite for various background electrolytes with the CD-MUSIC model

As water scarcity drives the use of more saline water sources, contaminant fate and transport models must capture the impact of high concentrations of alkaline earth metal ions (AEMs) and background electrolytes in these more complex waters. By utilizing macroscopic adsorption data from various electrolyte systems, a Charge Distribution – Multisite Complexation (CD-MUSIC) model, capable of incorporating electrolyte adsorption, was able to accurately simulate the adsorption behavior of alkaline earth metal ions onto goethite. The modeling effort was guided by previous spectroscopic and surface complexation modeling of alkaline earth metal adsorption and built on previous CD-MUSIC modeling that accounted for changes in crystal face contributions to the surface site density as a function of specific surface area. The model was constrained to consider only two dominant surface complex species for each metal ion adsorption reaction. These two species were selected from 44 possible species through objective curve fitting of single-solute macroscopic adsorption data. While most of the alkaline earth metal surface complexes formed outer-sphere complexes at the goethite surface, an inner-sphere species was utilized for Mg2+. With the surface complex species and equilibrium constants obtained from this study, the calibrated model successfully predicted alkaline earth metal ion adsorption over a wide range of solution and surface conditions; the model predictions encompassed a wide range of pH (5–11), solute/solid ratio (1.37 × 10−5– 8.33 × 10−4 mol-solute/g-solid), ionic strengths (0.01 M – 0.7 M), and background electrolytes (Na+, Cs+, Rb+, Cl−, and NO3−) using the same crystal face contribution methodology for site density, capacitance values, and surface acidity constants adopted for proton and cadmium adsorption in previous work (Han and Katz, 2019). Model simulations for a range of background water chemistries demonstrated the potential for Mg2+ to reduce Cd2+ adsorption to goethite in model seawater and oil- and gas-produced waters.

Measuring the Adsorption of Electrolytes on Lipid Monolayers.

The interactions between ions and lipid monolayers have captivated the attention of biologists and chemists alike for almost a century. In the absence of experimentally accessible concentration profiles, the electrolyte adsorption remains the most informative quantitative characteristic of the ion-lipid interactions. However, there is no established procedure to obtain the electrolyte adsorption on spread lipid monolayers. As a result, in the literature, the ion-lipid monolayer interactions are discussed qualitatively, based on the electrolyte effect on more easily accessible variables, e.g., surface tension. In this letter, we demonstrate how the electrolyte adsorption on lipid monolayers can be obtained experimentally. The procedure requires combining surface pressure versus molecular area compression isotherms with spreading pressure data. For the first time, we report an adsorption isotherm of NaCl on a lipid monolayer as a function of the density of the monolayer. The leading interactions seem to be the osmotic effect from the lipid head groups in the surface layer and ion-lipid association.

Interactions between Small Inorganic Ions and Uncharged Monolayers on the Water/Air Interface.

The interaction of several simple electrolytes with uncharged insoluble monolayers is studied on the basis of tensiometric and potentiometric data for the surface electrolyte solution|air. The induced adsorption of electrolyte on the monolayer is determined via a combination of data for equilibrium spreading pressure and surface pressure versus area isotherms. We show that the monolayer-induced adsorption of electrolyte is not only strongly ion-specific but also surfactant-specific. The comparison between the ion-specific effects on a carboxylic acid monolayer at low pH and an ester monolayer shows that the anion series follows the same order while the cation series reverses. The effect of the electrolyte on the chemical potential of the monolayer shows attraction between the surfactant and the ions at low monolayer densities, but at high surface densities, repulsion seems to come into play. In nearly all investigated cases, a maximum of monolayer-induced electrolyte adsorption is observed at intermediate monolayer densities. This suggests specific interactions between the surfactant headgroup and the ions. The Volta potential data for the monolayers are analyzed on the basis of the equations of quadrupolar electrostatics. The analysis suggests that the ion-specific effect on the Volta potential is due to the ion-specific decrement of the bulk dielectric constant of the electrolyte solution. Moreover, we present evidence that in most cases the effect of the electrolyte on the orientation of the adsorbed dipoles cannot be neglected. Instead, the change in the ion distribution in the electric double layer seems to have a small effect on the Volta potential.

Grown of flower-like polyaniline nanosheet clusters on carbon cloth for enhanced electrochemical energy storage

Layered nanomaterials with hierarchically porous structure are reported to exhibit superior capacitive properties due to the facilitated electrolyte adsorption and migration process. In this work, polyaniline (PANI) nanosheet assembled flowers were successfully grown on carbon cloth (CC) through a simple repeated-deposition method. In this research, it is found that the affinity between the pre-loaded PANI and the new aniline monomer play an decisive role in the formation of product with nanosheet morphology. The typical hierarchically porous structure and the high redox activity of PANI endow CC/PANI4 with high specific capacitances of 1421.9 mF cm−2 (643.4 F g−1) at 1 mA cm−2 and 1101.2 mF cm−2 (498.3 F g−1) at 50 mA cm−2 in three-electrode system, as well as a stable charge-discharge behavior with 68.75% capacitance retention after 5000 cyclic tests. This research provides a new strategy for the construction of PANI with optimized sheet-assembled structures and also high electrochemical performances on flexible substrates.

In situ synthesis of integrated dodecahedron NiO/NiCo2O4 coupled with N-doped porous hollow carbon capsule for high-performance supercapacitors

NiO and NiCo2O4 exhibit excellent synergistic effects and broad application prospects in electrochemical applications. However, the apparent interfacial instability between NiO and NiCo2O4 limits ion transport kinetics, charge/ion transfer, and electrochemical stability. In response, we developed and designed an integrated dodecahedron NiO/NiCo2O4 by a facile in-situ calcination method. Moreover, by utilizing the porous hollow structure of nitrogen-doped carbon capsules (N-Cc) as a conductive network, the N-Ccx@NiO/NiCo2O4 heterostructures with stable interface structure, excellent electrolyte adsorption, and electron transfer pathways were carefully designed. The N-Cc1.0@NiO/NiCo2O4 heterostructures are found to deliver an outstanding specific capacitance of 658.8 F g−1, and a high energy density of 101.40 Wh kg−1 at a power density of 775.03 W kg−1, along with capacitance retention of more than 93.5% after 8000 cycles. Based on the DFT calculations and electrochemical experimental results, this work provides an effective in situ route for the construction of high-performance metal oxide heterostructure electrode materials for new energy storage devices.

Biochar for Supercapacitor Application: A Comparative Study.

Biochar is a carbon-rich solid that can be prepared through heat treatment of biomass under an inert atmosphere. In the present work, biochar prepared from different feedstocks, namely, Litchi chinensis (Litchi) seeds, Syzygium cumini (Jamun) seeds, and pine cone, were evaluated for charge storage in the form of supercapacitors. The physicochemical and electrochemical properties of the biochar were highly dependent on the preparation temperature and the choice of feedstock. Among the three feedstocks, Litchi seed-derived biochar showed the highest specific capacitance of 190 F g-1 at 1 A g-1 in a symmetric cell configuration. N and O heteroatom functionalities in the Litchi seed-derived biochar, higher specific surface area, and pore volume for electrolyte adsorption were responsible for its superior capacitive performance as compared to Jamun seeds and pine cone biochar.