Charge-discharge Current Density Research Articles

Electropolymerization of a Carbonyl-Modified Dihydropyrazine Derivative for Aqueous Zinc Batteries with Ultrahigh Cycling Stability.

The design of aqueous zinc-ion batteries (ZIBs) that have high specific capacity and long-term stability is essential for future large-scale energy storage systems. Cathode materials with extended π-conjugation and abundant active sites are desirable to enhance the charge storage performance and the cycling stability of the aqueous ZIB. Based on this concept, 6,9-dihydropyrazino[2,3-g]quinoxaline-2,3,7,8(1H,4H)-tetrone was chosen as the monomer to be electropolymerized onto carbon cloth (PDHPQ-Tetrone/CC). When used as the cathode material for aqueous ZIBs, an exceptional cycling life (>20,000 cycles) at a current density of 10 A g-1 was achieved, with the specific capacity maintained at 82.8% and with the Coulombic efficiency at around 100% throughout cycling. At the charge-discharge current density of 0.1 A g-1, the ZIB with PDHPQ-Tetrone/CC achieved a high specific capacity of 248 mAh g-1. Kinetic analyses showed that both surface-capacitive-controlled processes and semi-infinite diffusion-controlled processes contribute to the stored charge. The charge storage mechanism was investigated with ex situ characterizations and involves the redox processes of carbonyl/hydroxyl and amino/imino groups coupled with insertion and extraction of both Zn2+ and H+.

Electrodeposited Copper Tin Sulfide/Reduced Graphene Oxide Nanospikes for a High-Performance Supercapacitor Electrode.

Copper tin sulfide, Cu4SnS4 (CTS), a ternary transition-metal chalcogenide with unique properties, including superior electrical conductivity, distinct crystal structure, and high theoretical capacity, is a potential candidate for supercapacitor (SC) electrode materials. However, there are few studies reporting the application of Cu4SnS4 or its composites as electrode materials for SCs. The reported performance of the Cu4SnS4 electrode is insufficient regarding cycle stability, rate capability, and specific capacity; probably resulting from poor electrical conductivity, restacking, and agglomeration of the active material during continued charge-discharge cycles. Such limitations can be overcome by incorporating graphene as a support material and employing a binder-free, facile, electrodeposition technique. This work reports the fabrication of a copper tin sulfide-reduced graphene oxide/nickel foam composite electrode (CTS-rGO/NF) through stepwise, facile electrodeposition of rGO and CTS on a NF substrate. Electrochemical evaluations confirmed the enhanced supercapacitive performance of the CTS-rGO/NF electrode compared to that of CTS/NF. A remarkably improved specific capacitance of 820.83 F g-1 was achieved for the CTS-rGO/NF composite electrode at a current density of 5 mA cm-2, which is higher than that of CTS/NF (516.67 F g-1). The CTS-rGO/NF composite electrode also exhibited a high-rate capability of 73.1% for galvanostatic charge-discharge (GCD) current densities, ranging from 5 to 12 mA cm-2, and improved cycling stability with over a 92% capacitance retention after 1000 continuous GCD cycles; demonstrating its excellent performance as an electrode material for energy storage applications, encompassing SCs. The enhanced performance of the CTS-rGO/NF electrode could be attributed to the synergetic effect of the enhanced conductivity and surface area introduced by the inclusion of rGO in the composite.

One step production of phosphorene from red phosphorus and investigation of their supercapacitor applications with conducting polymers

In this work, phosphorene, which was used as an additive to the conductive polymer (polyaniline), was produced in a single step using the chemical method at 80 °C in 6 h for the first time in the literature. In addition, composites of polyaniline with phosphorene have also been produced for the first time in the literature, and these materials have been used as electrode materials in supercapacitors. The parameters of supporting electrolyte concentration, monomer concentration and cycle number, which are the factors affecting the success of electrochemical synthesis, were optimized and the optimum values for these parameters were determined for polymers. The structural and morphological properties of the produced 2D phosphorene were investigated using spectroscopic and microscopic methods. After that, phosphorene was simultaneously and electrochemically incorporated into the structure of polyaniline (Pani), which was produced by the electrochemical method, likewise. Finally, the phosphorene-based materials produced have been used as electrode components in supercapacitors. Hybrid supercapacitor electrodes (Phosphorene@Pani/PGEs) were characterized by cyclic voltammetry and electrochemical impedance spectroscopy methods and the changes in the capacitive behavior of these systems according to the number of cycles were examined using the galvanostatic charge-discharge technique. Specific capacitance value of phosphorene-doped composite material was 335.54 F·g−1 at a charge-discharge current density of 1.6 A·g−1.Capacitance retention of the composite material was 85 % at end of 1000 cycles with 1.6 A·g−1. It was also around of 80 % after 4000 cycles with 2.5 A·g−1 charge/discharge current densities. A significant increase in specific capacitance of 259.21 % was seen when compared with the electrode without phosphorene added. By adding of phosphorene in the conducting polymer structure, specific capacitance of the system is improved.

High-Rate Nonaqueous Mg-CO2 Batteries Enabled by Mo2 C-Nanodot-Embedded Carbon Nanofibers.

The widespread acceptance of nonaqueous rechargeable metal-gas batteries, known for their remarkably high theoretical energy density, faces obstacles such as poor reversibility and low energy efficiency under high charge-discharge current densities. To tackle these challenges, a novel catalytic cathode architecture for Mg-CO2 batteries, fabricated using a one-pot electrospinning method followed by heat treatment, is presented. The resulting structure features well-dispersed molybdenum carbide nanodots embedded within interconnected carbon nanofibers, forming a 3D macroporous conducting network. This cathode design enhances the volumetric efficiency, enabling effective discharge product deposition, while also improving electrical properties and boosting catalytic activity. This enhancement results in high discharge capacities and excellent rate capabilities, while simultaneously minimizing voltage hysteresis and maximizing energy efficiency. The battery exhibits a stable cycle life of over 250 h at a current density of 200mA g-1 with a low initial charge-discharge voltage gap of 0.72V. Even at incredibly high current densities, reaching 1600mA g-1 , the battery maintains exceptional performance. These findings highlight the crucial role of cathode architecture design in enhancing the performance of Mg-CO2 batteries and hold promise for improving other metal-gas batteries that involve deposition-decomposition reactions.

Bacterial assisted sustainable production of Three-Dimensional defective carbon from rice straw for supercapacitor

Defective carbon nanomaterials with three-dimensional (3D) structure are showing great potential for advanced electrochemical storage and conversion devices, but its application is restricted by the synthesis, which is usually involved with complicate and energy-intensive processes. Herein, pyrolysis of rice straw (RS) residue, of which is collected from the bacterial assisted hydrolysis, is proposed by us here, and the obtained bio-char is defective with 3D structure and rich in oxygen-containing functional groups. Compared to the pristine one, specific surface area of the representative RS carbon (RSC2) was increased from 428.8 to 1131.7 m2 g−1. The assembled supercapacitor with RSC2 showed a high specific capacitance of 331F g−1 at a charge–discharge current density of 0.5 A g−1, and a capacity retention of 97.6% was maintained at 5 A g−1 even after 10,000 cycles.

Electropolymerization of 5-amino-2-naphthalenesulfonic acid and their application as the electrode material for supercapacitors

Electropolymerization is a powerful tool in constructing conducting polymers that can be utilized as the electrode materials for flexible supercapacitors. The 5-amino-2-naphthalenesulfonic acid is electropolymerized at anodic potential on carbon cloth from aqueous perchloric acid solutions. The poly(5-amino-2-naphthalenesulfonic acid) coated carbon cloth electrodes (PANS/CC) are characterized, and are used as the electrode material for supercapacitors. The PANS/CC-40 exhibits the optimum charge storage performance, with the specific capacity of 85.5 mAh g−1 at 1 A g−1 charge-discharge current density in 1 M H2SO4. Specific capacities of 44.8 and 38.5 mAh g−1 are achieved for the PNAS/CC-40 in 1 M ZnSO4 and 1 M (NH4)2SO4, respectively, at 1 A g−1. Kinetic analyses show that the PNAS/CC-40 is a battery-type electrode material, and the surface-controlled processes contribute over 80 % of the stored charge. Evidences of cation (de)intercalation accompanying with the redox of amine/imine groups are given. A symmetric supercapacitor is assembled using two PNAS/CC-40 and the PVA/H2SO4 gel electrolyte, and it can deliver the energy density of 1.1 Wh kg−1 and the power density of 136.9 W kg−1 at 1 A g−1. The capacity retention of the symmetric supercapacitor is 88 % after 10,000 cycles at 5 A g−1.

SPECIFIC CHARACTERISTICS OF SULFUR ELECTRODES IN SALT-SOLVATE ELECTROLYTES

The influence of the technological parameters of the positive electrode and the composition of the salt-solvate electrolyte LiTFSI – TEGDME on the specific characteristics of sulfur electrodes during galvanostatic cycling in lithium-sulfur cells was studied. The dependences of the change in specific capacity on the cathode composition, the charge-discharge current density, and the preservation of the charged state were discussed.
 It was found that the concentration of salt in salt-solvate electrolyte determines the specific characteristics of sulfur and affects its stability during cycling. It was determined that the most stable specific capacity and high Coulombic efficiency of the discharge/charge process of lithium-sulfur cells under long-term cycling conditions were ensured at lithium salt concentration of 0.4 molar fractions (m.f.) in the salt-solvate electrolyte.
 The positive effect of reducing the size of sulfur particles and optimizing its concentration and the composition of conductive additives in the cathode on the specific characteristics of sulfur-containing electrodes during cycling was shown. It was determined that reducing the size of sulfur particles from δS ≤ 150 μm to δS ≤ 40 μm contributes to an increase in the specific capacity of lithium-sulfur cells by approximately 20% and had a positive effect on their stability during cycling.
 It was established that increasing the concentration of sulfur in the cathode from 50% to 70% by mass leads to a significant decreased in the specific capacity of lithium-sulfur cells as a result of accelerated passivation of the electrode by poorly soluble lithium polysulfides.
 It was shown that in salt-solvate electrolytes a high level of retention of specific capacity was achieved under the conditions of long-term storage of a charged sulfur cathode at the temperature of ~30 °C. With a sulfur content of 50% and 70% by mass in the composition of the cathode with a fractional composition of δS ≤ 80 μm, the return of the specific capacity was over 97%.

Investigation the effects of chlorine doped graphene oxide as an electrolyte additive for gel type valve regulated lead acid batteries

In this study, chlorine-doped graphene oxide (Cl-GOP) was used as an additive in the fumed silica-based gel electrolyte system of Valve Regulated Lead Acid (VRLA) batteries for the first time in the literature, and the performance of the gel electrolyte was increased. In this context, chlorine-doped graphene oxide produced by electrochemical methods was characterized using spectroscopic and microscopic methods, and then it was added to the fumed silica based gel electrolyte as an additive. The amount of Cl-GOP in the gel electrolyte system was optimized using electrochemical methods and 0.6 % by mass was determined as the most suitable. Then, the stirring rate and agitation time, which are the most important parameters affecting the performance of the gel electrolyte system, were optimized and the optimum values were determined as 500 rpm and 30 min, respectively. Finally, the prepared fumed silica-based electrolyte systems and aqueous electrolyte systems were subjected to charge-discharge tests and the highest discharge capacity value was determined as 42 mAh.cm−2 in the fumed silica-based gel electrolyte system containing Cl-GOP with 20 mA.cm−2 charge-discharge current densities. The results showed that Cl-GOP is an important additive in the fumed silica-based gel component of gel type VRLA batteries.

Operando neutron imaging study of a commercial Li-ion battery at variable charge-discharge current densities

We report an operando neutron imaging study of a commercial ICR 10440 Li ion battery during charge and discharge. The cylindrical battery with a spiral configuration is composed of a multiphase layered oxide cathode and graphite anode. In spite of a two-dimensional nature of the projection data of this time-resolved study, structural and functional details of the neutron radiography study were successfully uncovered and visualized. The spatially resolved measurements with a resolution of 40 µm enabled to observe Li redistribution between the electrodes as well as a circulation of the electrolyte between the central column and the electrode layers at different states of charge (SoC) and at different current rates. Furthermore, ex-situ tomographic studies of the battery revealed the fine details of the structural inhomogeneity within the cell.

Sulfonated nano-diamonds composite sulfonated reduced graphene oxide: A efficient hydrophilic material for high performance supercapacitors

This paper reports a simple reaction for the synthesis of sulfonated reduced graphene oxide composite with sulfonated diamond nanoparticles, (rGO/ND)-SO3H. It is based on the reaction of a mixture of graphene oxide (GO) and hydroxylated nano-diamonds (ND-OH) with 1,3-propanesultone at 150 °C for 48 h. During this process, ND-OH were converted to sulfonated ND (ND-SO3H) and composite sulfonated rGO formed rGO-SO3H. The electrochemical performance of (rGO/ND)-SO3H in 1 M H2SO4 was compared with that of ND-SO3H, rGO-SO3H and rGO/ND. It could be shown that a maximum specific capacitance of 160.1 F g−1 can be achieved by (rGO/ND)-SO3H at 1 A g−1. 81.5% capacitance retention upon increasing the charge-discharge current density from 0.5 A g−1 to 15 A g−1 was observed, making the material a potent candidate for supercapacitor applications. The high electrochemical surface area and easy accessibility of electrolyte to the electrode material are believed to be the underlying reasons for the improved performance. Furthermore, as-fabricated (rGO/ND)-SO3H shows excellent cycling stability with more the 99.1% retention of the specific capacitance after 6000 galvanostatic charge-discharge cycles, making it a promising matrix for high performance electrochemical capacitors.

Pencil‐Drawing Graphite Nanosheets: A Simple and Effective Cathode for High‐Capacity Aluminum Batteries

Commercial graphite, as an attractive cathode material, has been extensively applied in rechargeable aluminum batteries. However, low capacity and complex cathode preparation procedures limit its further development. Herein, graphite nanosheets as cathode of aluminum battery have been prepared by a novel pencil-drawing strategy, which shows superior capacity of 96 mAh g-1 and excellent stability with almost 100% capacity retention after 2000 cycles at a current density of 0.5 A g-1 . By increasing charge-discharge current density to 2 A g-1 , the battery also exhibits a high capacity of 72 mAh g-1 and retains 90% after 6000 cycles. Furthermore, a stage 3 anion intercalation/deintercalation mechanism has been proposed according to in situ X-ray diffraction and ex situ characterization techniques. This work provides a controllable method for developing a graphite nanosheets cathode with a simplified process and contributes to the development of other kinds of energy storage devices.

Operando Neutron Imaging Study of a Commercial Li-Ion Battery at Variable Charge-Discharge Current Densities

Operando Neutron Imaging Study of a Commercial Li-Ion Battery at Variable Charge-Discharge Current Densities

Ultrahigh capacitance of NiCo2O4/CeO2mixed metal oxide material for supercapacitor applications

Pertaining to research on energy consumption and energy storage systems, new and efficient mixed metal oxides of NiCo2O4/CeO2 as pseudo-capacitor materials have been successfully prepared by sol-gel combustion method. The synthesized unique spinel nanomaterials have been analyzed for structural and morphological characterization by FT-IR, XRD, XPS and electron microscopy techniques. The mesoporous structure and large specific surface area of the synthesized nanomaterials provide an easy channel for ion mobility rendering an effortless redox process at the electrode/electrolyte interface. As a consequence, it is observed that NiCo2O4 mixed with 10% of CeO2 exhibits an excellent specific capacitance of 1355 Fg−1 at 5 Ag−1 along with a high cycling stability with only 4.7% capacity loss at the end of 6000 cycles at a charge-discharge current density of 10 Ag−1. The results obtained are in par with some of the recent electrode materials used for supercapacitors suggesting the possible employment of NiCo2O4/CeO2 mixed metal oxides in energy storage applications.

Degeneration of Key Structural Components Resulting in Ageing of Supercapacitors and the Related Chemical Ageing Mechanism.

The research on supercapacitors (SCs) is one of the hot topics in the field of energy storage, and the intrinsic ageing mechanism of SCs is significant from both the economic and the scientific point of view. In this paper, the negative effects of decay of the key structural components on ageing of SCs were investigated by factorial design and analysis of variance (ANOVA). The ANOVA results showed that the degree of the negative influence on ageing of SCs could be ranked in descending order as anode > separator > cathode. The ageing would be accelerated due to the interaction between the electrode and separator, especially at a high charge-discharge current density. Further, the intrinsic chemical ageing mechanism of SCs was revealed by the morphology, microstructure, and chemical composition analyses of the fresh and aged key components (the electrode carbon materials, current collectors, and separators) with scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectra (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), etc. Moreover, the minimum pore width of electrode carbon materials suitable for electrolyte ion diffusion was obtained by density functional theory (DFT) calculations, which corroborated the assumption that the pore structure deterioration was one of the direct causes of capacitance loss for aged SCs. Generally, the ageing mechanism of key components of SCs could be a reference to develop advanced electrode materials and separators for SCs.

Driving Force of Molecular/Ionic Superfluid Formation

Driving Force of Molecular/Ionic Superfluid Formation

Solution combustion synthesis of a nanometer-scale Co3O4 anode material for Li-ion batteries.

A novel solution combustion synthesis of nanoscale spinel-structured Co3O4 powder was proposed in this work. The obtained material was composed of loosely arranged nanoparticles whose average diameter was about 36 nm. The as-prepared cobalt oxide powder was also tested as the anode material for Li-ion batteries and revealed specific capacities of 1060 and 533 mAh·g−1 after 100 cycles at charge–discharge current densities of 100 and 500 mA·g−1, respectively. Moreover, electrochemical measurements indicate that even though the synthesized nanomaterial possesses a low active surface area, it exhibits a relatively high specific capacity measured at 100 mA·g−1 after 100 cycles and a quite good rate capability at current densities between 50 and 5000 mA·g−1.

Constructing cycle-stable Si/TiSi2 composites as anode materials for lithium ion batteries through direct utilization of low-purity Si and Ti-bearing blast furnace slag

The large volume expansion and poor conductivity leading to the deterioration of electrochemical performance, is a significant challenge for Si-anode materials for practical applications. Previous researches have indicated that introducing a TiSi2 buffer with high conductivity to form Si/TiSi2 composites can effectively improve the electrochemical performance of Si anode. However, the facile and low-cost synthesis of Si/TiSi2 composites remains challenging. In this study, we propose a novel approach to preparing Si/TiSi2 composites as anode materials for lithium-ion batteries by coupling photovoltaic (PV) silicon waste (simulated using inexpensive low-purity Si (98.8%) in experiments) and metallurgical waste (Ti-bearing blast furnace slag, TBBFS) via a new method combining induction melting and mechanical ball milling. A series of Si/TiSi2 materials were obtained using different ratios of raw materials and investigated using SEM, TEM, XRD, XPS and electrochemical performance tests. The results show that TiSi2 not only acts as a buffer for the bulk expansion of Si, but also improves the electrical conductivity; therefore, the Si/TiSi2 materials exhibit enhanced cycling stability when more TiSi2 is introduced. The sample prepared using a low-purity Si and TBBFS with a mass ratio of 1:3 delivered a reversible capacity of 530 mAh g−1 after 200 cycles at a charge-discharge current density of 800 mA g−1. This work not only provides a new strategy and technology for introducing TiSi2 into Si-based anode materials, but also provides a green and sustainable technical route for the high value-added recycling of Ti-bearing blast furnace slag.

Constructing ultrathin TiO2 protection layers via atomic layer deposition for stable lithium metal anode cycling

Uncontrollable dendrite growth during the repeated plating/stripping of Li ions induces short cycle life and safety issues, which has severely impeded the practical application of lithium metal battery. It is acknowledged that the solid electrolyte interphase (SEI) is pivotal for Li metal anode stabilization. Here, a lithium metal anode coated with an artificial SEI film as the working electrode is applied. The TiO2 coating layer is firstly demonstrated for the lithium metal anode protection via atomic layer deposition (ALD) method. Thanks to the ultrathin TiO2 layer, dendritic growth is suppressed and the cycling lifetime is significantly improved. Additionally, the thickness of TiO2 protective layer has been further optimized. Comparing with other different thickness TiO2 layer, 5 nm TiO2 layer is found to be the optimized parameter toward capacity, cycling stability and rate capability in both symmetric battery system and full-cell system. The TiO2 layer promoted uniform deposition of Li+ and effectively inhibited the growth of lithium dendrites. Symmetric Li/50TiO2||Li/50TiO2 battery could cycle stably for more than 1600 h at 1 mA cm−2, and more than 500 h at 3 mA cm−2 and 10 mA cm−2 current density. The Li/50TiO2||NCM622 full-cell exhibited better rate performance and long-cycle performance, which capacity retention was increased by 23.3% compared to bare electrode after 100 cycles at 0.5C charge-discharge current density. Furthermore, the inherent working mechanism of TiO2 artificial SEI film has been proposed. This work provides an effective and new alternative method for lithium metal anodes protection, which is critical for the future design of next-generation Li metal batteries under safe operation.

Real-Time Monitoring of the Thermal Effect for the Redox Flow Battery by an Infrared Thermal Imaging Technology

In this study, a new monitoring method was developed, titled infrared thermal imaging technology, which can effectively evaluate the thermal effect of the charge-discharge test in the vanadium/iodine redox flow battery (V/I RFB). The results show that the all-vanadium redox flow battery (all-V RFB) has a greater molar reaction Gibbs free energy change than that of the V/I RFB, representing a large thermal effect of the all-V RFB than the V/I RFB. The charge-discharge parameters, flow rate and current density, are important factors for inducing the thermal effect, because of the concentration polarization and the ohmic resistor. The new membrane (HS-SO3H) shows a high ion exchange capacity and a good ions crossover inhibitory for the V/I RFB system, and has a high coulomb efficiency that reaches 96%. The voltage efficiency was enhanced from 61% to 86% using the C-TiO2-Pd composite electrode as a cathode with the serpentine-type flow field for the V/I RFB. By adopting the high-resolution images of an infrared thermal imaging technology with the function of the temperature profile data, it is useful to evaluate the key components’ performance of the V/I RFB, and is a favorable candidate in the developing of the redox flow battery system.

Enhancing of Electrochemical Characteristics of Li-S System by Means of Optimization of Sulfur Electrode and Electrolyte Composition

The article discusses the influence of technological parameters of sulfur electrodes and the concentration composition of the salt-solvation electrolytes TEGDME–LiTFSI on the specific characteristics of Li-S cells obtained under galvanostatic cycling conditions. The dependences of the specific capacity on the composition of the cathode, the charge-discharge current density, as well as capacity retention upon storage are discussed.