High Charge Storage Research Articles

Polycrystalline phases engineered in-situ in polyaniline-graphene composite evoluting an exceptional stability and high charge storage capacity: An EIS investigative approach to evaluate material's stability

Development of electroactive materials exhibiting high performance with superior stability is crucial in the field of supercapacitors and battery research. We report on synthesis of highly stable composite of semi-polycrystalline polyaniline and graphene (SPani-graphene) and its application in supercapacitor electrodes. The electrochemical behavior and device performance of the electrodes were investigated through cyclic voltammetry (CV), galvanostatic charge-discharge GCD) and electrochemical impedance spectroscopy (EIS) in a 3-electrode and a 2-electrode (device) cell configurations, repectively. The cell specific capacitance (Cell Csp) achieved from the 2-electrode symmetric cell configuration was 525.5 F g−1 at 0.1 A g−1 using polymer gel electrolyte (PGE). The PGE in this work is xanthan gum jellied in 1 M aq. Na2SO4. The maximum energy density and power density achieved from the device was 46.7 Wh kg−1 and 16.16 kW kg−1, respectively, at 0.4 A g−1. Furthermore, the device exhibits an excellent retention of cell specific capacitance and coulombic efficiency of 97 % and 94 %, respectively, over 10,000 continuous GCD cycles, indicating an excellent rate capability as well as a promising power management. To investigate the material's electrochemical durability, a detailed EIS study has been carried out using both, 3-electrode, and 2-electrode cell configurations, before and after long cycling test (over 10,000 continuous GCD cycles). Our thorough experimentation delivers satisfactory results and has been explained in detail in the manuscript. Hereby, we propose that the EIS technique can be adopted for investigating materials' electrochemical stability, in addition to long CV and GCD cycles in the field of supercapacitors and battery research.

Synthesis of 3D rice-like BiOCl battery-type electrode material and evaluation of their electrochemical performance in a symmetrical supercapacitor device configuration

3D porous rice-like BiOCl nanostructure was prepared via solvothermal technique with sodium chlorate as a surfactant which serves as electrode material for the supercapacitor applications. The prepared nanoparticles supported on nickel foam textile exhibit high battery-type charge storage ability in a 3 M KOH aqueous electrolyte solution. The dominance of the battery-type charge storage mechanism of the BiOCl electrode was confirmed through the CV study. Furthermore, the GCD study revealed a good specific capacity of 501 C/g at 0.5 A/g current density and cycle stability of 80% over 2500 cycles. In the presence of a 3 M KOH electrolyte, a symmetric supercapacitor device was constructed with two identical 3D rice-like BiOCl electrodes. This configuration unveiled an impressive energy density of 21.8 Wh/kg at 772.5 W/kg power density. To illustrate its practical viability, two BiOCl/BiOCl symmetric devices were connected in series, successfully powering a red LED for approximately 50 s with high light intensity. This underscores the practical potential of the 3D rice-like BiOCl electrode in energy storage systems. In order to maximize the potential of BiOCl material in the future, the focus could be shifted towards mitigating the challenge of potential drop. This hurdle could be tackled by fabricating nanocomposites of BiOCl incorporated with conductive polymers and graphene oxide, thus elevating its overall performance.

Trap-induced hydro-charging polylactic acid nonwovens with high charge storage capability for stable and efficient air filtration

Under the background of carbon neutrality, eco-friendly biodegradable polylactic acid (PLA) melt-blown nonwovens have been developed in air filtration. Nevertheless, the filtration performance of existing PLA melt-blown nonwovens is in an embarrassing situation and fails to meet the requirement of high efficiency air filters. Here, with controllable doping of N, N′-ethylene bis-stearamide (EBS), and barium titanate (BaTiO3) into PLA, through the melt-blown process, the charge-storage capacity of PLA nonwovens enhanced significantly. By utilizing the hydro-charging technology thereafter, we have prepared hydro-charged PLA/EBS/BaTiO3 nonwovens (HCP-EB) with excellent filtration performances. The doped EBS and BaTiO3 could improve the crystallization and charge storage capacity of PLA during the melt-blown process, thus constructing a large number of interfacial traps between crystalline and amorphous regions, leading to more electric charges captured during the hydro-charging process. The HCP-EB exhibited a high filtration efficiency (99.69 %) for PM0.3, a low pressure drop (27.44 Pa), and superior charge storage stability. Furthermore, the HCP-EB, remained at 99.18 % filtration efficiency after 48 h of treatment at 90 % relative humidity. After 3 months of storage, it still possessed an excellent filtration efficiency (99.02 %). Our work will contribute to the practical application of PLA melt-blown nonwovens in air filters and masks, and inspire the research of next-generation biodegradable electret air filtration materials.

Stoichiometrically Optimized Electrochromic Complex [V2O2+ξ(OH)3-ξ] Based Electrode: Prototype Supercapacitor with Multicolor Indicator.

The systematic structure modification of metal oxides is becoming more attractive, and effective strategies for structural tunning are highly desirable for improving their practical color-modulating energy storage performances. Here, the ability of a stoichiometrically tuned oxide-hydroxide complex of porous vanadium oxide, namely [V2O2+ξ(OH)3-ξ]ξ = 0:3 for multifunctional electrochromic supercapacitor application is demonstrated. Theoretically, the pre-optimized oxide complex is synthesized using a simple wet chemical etching technique in its optimized stoichiometry [V2O2+ξ(OH)3-ξ] with ξ=0, providing more electroactive surface sites. The multifunctional electrode shows a high charge storage property of 610Fg-1 at 1Ag-1, as well as good electrochromic properties with high color contrast of 70% and 50% at 428 and 640nm wavelengths, faster switching, and high coloration efficiency. When assembled in a solid-state symmetric electrochromic supercapacitor device, it exhibits an ultrahigh power density of 1066mWcm-2, high energy density of 246mWhcm-2, and high specific capacitance of 290mFcm-2 at 0.2mAcm-2. A prepared prototype device displays red when fully charged, green when half charged, and blue when fully discharged. A clear evidence of optimizing the multifunctional performance of electrochromic supercapacitor by stoichiometrical tuning is presented along with demonstrating a device prototype of a 25cm2 large device for real-life applications.

Battery and/or supercapacitor?—On the merger of two electrochemical storage system families

Similarities and analogies between materials, structures, operating and construction principles of secondary batteries and supercapacitors and their electrodes are presented, named and reviewed in context. On the material level several materials used both in batteries and supercapacitors are addressed, implications from observations made in one application for the other one are highlighted. On the electrode level a continuous change of architectural details is observed when going from an electrode with high charge storage capability to an electrode supporting high currents is detected, again this overlap provides instructive ideas for both fields. On the cell level combinations of electrodes from both fields yielding hybrid devices are an obvious outcome again with implications for both fields. Ideas and suggestions for further research and development based on a deeper exchange between both families are developed.

Ultra-high performance hafnium-based capacitors: Synergistic achievement of high dielectric constant and low leakage current

The relationship between the dielectric constant and leakage current of materials often exhibits a negative correlation. However, to sustain Moore's Law, the semiconductor industry necessitates novel materials that simultaneously possess a high dielectric constant and low leakage current, meeting the shrinking demands of electronic components. In this study, a high-performance hafnium-based thin film capacitor achieved through the collaborative effects of bottom electrode engineering and ion doping. Tungsten (W) as the bottom electrode, with its chemically inert nature and low thermal expansion coefficient, proves advantageous in improving interface quality and promoting the generation of the high-k phase in HfO2. Concurrently, yttrium (Y) ion doping contributes to stabilizing the high-k phase of HfO2, reducing non-lattice oxygen, and enhancing the disorderliness of the dielectric thin film. By synergistically integrating these factors, the hafnium-based thin film capacitor achieves a high dielectric constant of 36.6 while maintaining minimal leakage current (Electric field ∼ 6 MV/cm, J ∼ 10−8 A/cm2) and a high charge storage capacity (Urec ∼ 104.4 J/cm³). These research findings open a promising pathway for the development of novel hafnium-based materials with broad applicability and exceptional dielectric performance.

Synthesis Processes of Carbonaceous Material/Conducting Polymer Nanocomposites in Relation to Grafting and Electrochemical Properties for Supercapacitor Application: A Review

Supercapacitors are the energy storage devices that have gained increased attention due to high charge storage capacity, fast charge-discharge rate, high specific power and excellent cycle stability. Recently, research on supercapacitors is focused on the development of new electrode materials prepared by surface engineering to obtain superior electrochemical performance. Carbonaceous materials (CM) such as graphene, graphene oxide (GO), reduced graphene oxide (rGO) and carbon nanotubes (CNTs) etc. and conducting polymer (CP) based composite materials have gained increased attention for their use in supercapacitors. The nanocomposites obtained by merely mixing these two components pose some serious drawbacks such as low conductivity or poor film forming ability. The conjugation of CPs to CMs through covalent bonds is able to address these drawbacks. This review mainly provide collective information about various synthetic strategies to obtain CP grafted CMs for supercapacitor application. Herein, we provide information on different CP-CM conjugation reactions for obtaining the composites and their effects on electrochemical performances. The analysis revealed the importance of CP-CM grafting is important for tuning the electrochemical properties of the materials.

Atomic‐Scale Study of Dead Layers in Epitaxial Perovskite Dielectric Thin Films with Oxide and Metal Top Electrodes

AbstractPerovskite‐oxide‐based capacitors, which exhibit high charge storage capacity, have attracted considerable attention as a potential candidate for overcoming the limitations of nanoscale integration. Unfortunately, a dead layer forms in these capacitors at the interface between the electrode and the dielectric, which degrades the charge storage capacity; thus, this layer has been extensively investigated. The dead layer in perovskite‐oxide‐based capacitors exhibits different characteristics depending on the electrode materials; however, a method for minimizing this layer is lacking. In this study, the charge storage capacity of a perovskite‐oxide‐based capacitor is evaluated considering the effect of the Ru and SrRuO3 top electrodes on the SrRuO3/Ba0.5Sr0.5TiO3 stack. Dead layers at the interface between each top electrode material and the dielectric are studied on the atomic scale. The results indicate that the Ru metal electrode causes oxygen to diffuse from the dielectric to the electrode, forming elongated perovskite oxide at the interface, which acts as a dead layer. However, minimizing the dead layer at the top interface increases the dielectric permittivity from 667 to 953. Consequently, the phenomenon and mechanism of the dead layer are intuitively identified. This study proposes a method to overcome the limitations of next‐generation dynamic random access memory (DRAM).

Quantum capacitance induced by electron orbital reconstruction of g-C3N4/Co3O4 heterojunction: Improving electrochemical performance

Utilizing diverse material combinations in heterogeneous structures has become an effective approach for regulating interface characteristics and electronic structures. The g-C3N4/Co3O4 heterostructures were fabricated by uniformly modifying Co3O4 nanoparticles onto discrete clusters of g-C3N4 nanosheets. Then, they were subsequently employed as positive electrode materials for assembling hybrid supercapacitors. According to the first-principles calculation, Co3O4 and g-C3N4 formed Co-N ionic bonds, establishing interfacial space symmetry-broken heterojunction and direct exchange and superexchange between ions at the interface and sub-interface. This resulted in a high-density spin–orbit hybrid heterogeneous polarization interface, significantly improving the quantum capacitance of heterojunction materials. Experimental results showed that the heterojunction had a specific capacitance of 2662 F g−1 at 1 A g−1. When the power density was 750 W kg−1, the energy density reached 128 Wh kg−1. Even when the power density was 16850 W kg−1, it could show an energy density of 62.5 Wh kg−1. The g-C3N4/Co3O4 heterojunction could realize high energy density charge storage as the cathode material of supercapacitors. The construction of heterogeneous polarization interfaces for high-energy quantum capacitors provides a new and effective method for the energy storage field.

Cement/Sulfur for Lithium-Sulfur Cells.

Lithium-sulfur batteries represent a promising class of next-generation rechargeable energy storage technologies, primarily because of their high-capacity sulfur cathode, reversible battery chemistry, low toxicity, and cost-effectiveness. However, they lack a tailored cell material and configuration for enhancing their high electrochemical utilization and stability. This study introduces a cross-disciplinary concept involving cost-efficient cement and sulfur to prepare a cement/sulfur energy storage material. Although cement has low conductivity and porosity, our findings demonstrate that its robust polysulfide adsorption capability is beneficial in the design of a cathode composite. The cathode composite attains enhanced cell fabrication parameters, featuring a high sulfur content and loading of 80 wt% and 6.4 mg cm-2, respectively. The resulting cell with the cement/sulfur cathode composite exhibits high active-material retention and utilization, resulting in a high charge storage capacity of 1189 mA∙h g-1, high rate performance across C/20 to C/3 rates, and an extended lifespan of 200 cycles. These attributes contribute to excellent cell performance values, demonstrating areal capacities ranging from 4.59 to 7.61 mA∙h cm-2, an energy density spanning 9.63 to 15.98 mW∙h cm-2, and gravimetric capacities between 573 and 951 mA∙h g-1 per electrode. Therefore, this study pioneers a new approach in lithium-sulfur battery research, opting for a nonporous material with robust polysulfide adsorption capabilities, namely cement. It effectively showcases the potential of the resulting cement/sulfur cathode composite to enhance fabrication feasibility, cell fabrication parameters, and cell performance values.

Flexible electrodes composed of flower-like MoS2 and MXene for supercapacitor applications

Flexible supercapacitors with high charge storage ability are needed for emerging applications in wearable electronics. Here, we introduce a novel flexible supercapacitor electrode by incorporating flower-like MoS2 into MXene via a hydrothermal technique. We mostly focused on the structural design for electrode configuration to enhance the charge storage mechanism. Three different electrodes composed of MoS2, MXene, and MoS2@MXene were fabricated via a versatile drop-casting and drying method. There are unique advantages of incorporating MoS2 with MXene such as the fast electron transfer, hydrophilicity of the interface, and structural stability. The MoS2@MXene // MXene flexible asymmetric supercapacitor device offered a high energy density of 1.21 W h /kg and a power density of 54.45 W /kg. Moreover, the asymmetric device exhibits nearly identical electrochemical behavior following 100 bending cycles at different angles. The high electrochemical activity of MoS2 and MXene and good interaction are ascribed to the superior electrochemical performance of the composite material. Furthermore, this research could guide the development of flexible, high-performance, and low-cost electrodes which will be useful in wearable electronics.

High-Performance Lithium-Ion Batteries with High Stability Derived from Titanium-Oxide- and Sulfur-Loaded Carbon Spherogels.

This study presents a novel approach to developing high-performance lithium-ion battery electrodes by loading titania-carbon hybrid spherogels with sulfur. The resulting hybrid materials combine high charge storage capacity, electrical conductivity, and core-shell morphology, enabling the development of next-generation battery electrodes. We obtained homogeneous carbon spheres caging crystalline titania particles and sulfur using a template-assisted sol-gel route and carefully treated the titania-loaded carbon spherogels with hydrogen sulfide. The carbon shells maintain their microporous hollow sphere morphology, allowing for efficient sulfur deposition while protecting the titania crystals. By adjusting the sulfur impregnation of the carbon sphere and varying the titania loading, we achieved excellent lithium storage properties by successfully cycling encapsulated sulfur in the sphere while benefiting from the lithiation of titania particles. Without adding a conductive component, the optimized material provided after 150 cycles at a specific current of 250 mA g-1 a specific capacity of 825 mAh g-1 with a Coulombic efficiency of 98%.

Rational nanoarchitectonics of polypyrrole/graphene/polyimide composite fibrous membranes with enhanced electrochemical performance as self-supporting flexible electrodes for supercapacitors

Constructing self-supporting electrodes with the combination of excellent flexibility and superior electrochemical properties is essential to the development of high-performance supercapacitors for flexible electronics and wearable devices. Herein, a highly flexible polypyrrole/reduced graphene oxide/modified-polyimide composite fibrous membranes (PPy/RGO/M-PI CFMs) are prepared via electrostatic self-assembly of reduced graphene oxide (RGO) and in-situ deposition of polypyrrole onto SnCl2-modified polyimide electrospun fibrous membranes (M-PI FMs). M-PI FMs ensure rich pore structure and remarkable flexible properties, the electronic conductivity of the sample is greatly promoted by RGO, and polypyrrole (PPy) provide the capability of high redox pseudo capacitive charge storage for the electrode. Benefiting from the compact assembly of RGO and the uniform deposition of polypyrrole on the fiber surface of the M-PI FMs, the synthesized PPy/RGO/M-PI CFMs have a remarkable area capacitance of 1437.1 mF cm−2, a long cycle life of 84.9 % retention over 5000 cycles, and outstanding mechanical stability. And the assembled symmetric supercapacitor with PPy/RGO/M-PI CFMs deliver an exceptional area capacitance of 363.1 mF cm−2, superior energy density of 32.3 μWh cm−2 and 77.6 % capacitance retention after 5000 cycles. Therefore, this flexible and free-standing PPy/RGO/M-PI CFMs can be regarded as a promising candidate for flexible supercapacitor electrodes.

Etching-induced ion exchange engineering of two-dimensional layered NiFeCo-based hydroxides for high energy charge storage.

Efficient and rapid synthesis of transition metal-based hydroxides with tailored microstructures has emerged as a promising approach to fabricate high-performance electrode materials for energy storage devices. However, many conventional synthesis methods are cumbersome, expensive and time-consuming, and the microstructures of electrode materials are usually uncontrollable. Herein, we propose a fast and cost-effective approach to electrochemically in situ grow NiFeCo-based ternary hydroxides (NiFeCo-THs) with layered nanosheet structures on pretreated nickel foam (NF). The in situ grown NiFeCo-THs were in direct contact with the NF to form a monolithic electrode as NiFeCo/NF. By engineering the ion exchange process for controlling the ionic ratio, the monolithic Ni1(Fe/Co = 1/1)0.5/NF electrode was fabricated and found to show the optimum electrochemical behavior with a specific capacitance of 2.32 C cm-2 at 2 mA cm-2 as a result of its characteristic microstructures. Furthermore, a hybrid supercapacitor was constructed utilizing the monolithic Ni1(Fe/Co = 1/1)0.5/NF electrode and activated carbon as the cathode and anode, respectively, and it was found to have an energy density of 81.1 μW h cm-2 at a power density of 808.8 μW cm-2. After 5000 cycles, 84.0% of the initial capacitance of the hybrid supercapacitor was maintained, and the monolithic Ni1(Fe/Co = 1/1)0.5/NF electrode still retained the arrayed nanosheet structure.

Hoffmeister Effect Optimized Hydrogel Electrodes with Enhanced Electrical and Mechanical Properties for Nerve Conduction Studies.

Flexible epidermal electrodes hold substantial promise in realizing human electrophysiological information collections. Conventional electrodes exhibit certain limitations, including the requirement of skin pretreatment, reliance on external object-assisted fixation, and a propensity of dehydration, which severely hinder their applications in medical diagnosis. To tackle those issues, we developed a hydrogel electrode with both transcutaneous stimulation and neural signal acquisition functions. The electrode consists of a composite conductive layer (CCL) and adhesive conductive hydrogel (ACH). The CCL is designed as a laminated structure with high conductivity and charge storage capacity (CSC). Based on the optimization of Hoffmeister effect, the ACH demonstrates excellent electrical (resistivity of 3.56 Ω·m), mechanical (tensile limit of 1,650%), and adhesion properties (peeling energy of 0.28 J). The utilization of ACH as electrode/skin interface can reduce skin contact impedance and noise interference and enhance the CSC and charge injection capacity of electrodes. As a proof of concept, peripheral nerve conduction studies were performed on human volunteers to evaluate the as-fabricated hydrogel electrodes. Compared with the commercial electrodes, our hydrogel electrodes achieved better signal continuity and lower distortion, higher signal-to-noise ratio (~35 dB), and lower stimulation voltages (up to 27% lower), which can improve the safety and comfort of nerve conduction studies.

Peanut Oil Cake Biomass‐Derived Hierarchical Porous Carbon by Dual Step Activation as Potential Electrodes for Fabrication of Prototype Symmetric Supercapacitor Device

Peanut oil cake biomass is a major by‐product of oil industry and can be a suitable precursor for the production of biomass‐based porous carbon. Herein, dual‐stage activation, physical activation at 400°C, and chemical activation using KOH between 600 and 900°C are adopted to prepare hierarchical porous carbons (HPCs) from peanut oil cake biomass for use as electrode material in electrochemical supercapacitors. The textural and structural properties of the HPC were evaluated by N2‐adsorption/desorption, X‐ray diffraction, Raman, FT‐IR spectroscopy, and scanning electron microscopy. The prepared HPC inherited sufficient micropores and mesopores distribution with a maximum BET surface area of 640 m2/g. The electrochemical properties of the HPC electrodes were evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopic analysis. Among different HPC electrodes prepared, the carbon prepared at 800°C (HPC‐P8) electrode material exhibited a high specific capacitance of 187 F/g at 0.5 A/g in 1M Na2SO4 electrolyte in three‐electrode systems. Symmetric supercapacitors were also fabricated using HPC‐P8//HPC‐P8 as positive and negative electrodes using 1M Na2SO4 electrolyte, in a two‐electrode cell configuration via split cell method. Maximum specific capacitance of 30 F/g was achieved with superior cycle stability of 93.8% capacitance retention over 5,000 cycles for the symmetric device. The device operated at a wide potential window (0–2.0 V) resulted in appreciable specific energy and power density of 15.89 Wh/kg and 493 W/kg, respectively. HPC‐P8 had an ion diffusion coefficient of 7.79 × 10−8 cm2/s which is higher than the other prepared carbon samples. The symmetric device showed relatively high charge storage capacity and cyclic stability without any material degradation. The fabricated prototype portable supercapacitor module was tested for red LED glow with maximum intensity brightness up to 4 min. Thus, the present study reveals that HPC derived from peanut oil cake biomass can behave as a promising electrode material for supercapacitor applications.

Ni0.5Co0.5S nano-chains: a high-performing intercalating pseudocapacitive electrode in asymmetric supercapacitor (ASC) mode for the development of large-scale energy storage devices.

Grid-scale energy storage solutions are necessary for using renewable energy sources efficiently. A supercapattery (supercapacitor + battery) has recently been introduced as a new variety of hybrid devices that engage both capacitive and faradaic charge storage processes. Nano-chain architectures of Ni0.5Co0.5S electrode materials consisting of interconnected nano-spheres are rationally constructed by tailoring the surface structure. Nano-chains of the bimetallic sulfide Ni0.5Co0.5S are presented to have a superior charge storage capacity. The Ni0.5Co0.5S nano-chain electrode presents a capacitance of 2001.6 F g-1 at 1 mV s-1, with a specific capacity of 267 mA h g-1 (1920 F g-1) at 1 A g-1 in 4 M KOH aqueous electrolyte through the galvanostatic charge-discharge (GCD) method. The reason behind the high charge storage capacity of the materials is the predominant redox-mediated diffusion-controlled pseudocapacitive mechanism coupled with surface capacitance (electrosorption), as the surface (outer) and intercalative (inner) charges stored by the Ni0.5Co0.5S electrodes are close to 46.0% and 54.0%, respectively. Additionally, a Ni0.5Co0.5S//AC two electrode full cell operating in asymmetric supercapacitor cell (ASCs) mode in 4 M KOH electrolyte exhibits an impressive energy density equivalent to 257 W h kg-1 and a power density of 0.73 kW kg-1 at a current rate of 1 A g-1.

Ni,S co-doped Cu dendrites decorated with core-shell architecture assisted by MOF and Fe0.92Co0.08S nanoflakes on nanocellulose/graphene fibers for fabrication of flexible wire-type micro-supercapacitor.

One-dimensional micro-supercapacitors (1D micro-SCs) have been regarded as an efficient energy storage system to fulfill the ever-growing need for miniaturized electronics. Designing multi-dimensional nanoarchitectures on fibrous microelectrodes is an effective strategy to build a high-performance 1D micro-SC. In this work, Ni,S-doped Cu was firstly prepared on Cu wire as a micro-sized 1D current collector through Cu electrodeposition using a H2 bubble template and then co-doped with nickel and sulfur. Benefiting from the high electrical/thermal conductivity of Cu, and the highly electroactive sites of Ni and S as well as the 3D porous architecture, the deposited Ni,S-doped Cu provided a platform for growing active substances. Thereafter, cobalt carbonate hydroxide (CoCH) pine-like nanoneedle integrated ZIF-67 polyhedrons were synthesized on a foam-like skeleton and converted into NiMoCo-layered triple hydroxide (LTH)/Ni,S-doped Cu shish-kebab type nanoarrays by applying a hydrothermal method. Finally, Ni2Mo3N-CoN/Ni,S-doped Cu was prepared via nitridation. The potent interactions and synergy between components realized a well-organized hybrid nanoarchitecture consisting of dodecahedrons decorated on needle-like arrays within a 3D framework with rich redox properties, rapid ion/electron transfer dynamics and high electroactivity. In comparison to the LTH obtained from the electrodeposition method (without the ZIF-67 precursor) and that derived from leaf-like ZIF-Co, this modified microfiber exhibited a high charge storage capacity of 1.5 mA h cm-2 (149.9 mA h cm-3 and 0.187 mA h cm-1) at 4 mA cm-2 and possesses an excellent durability of 98.4% after 5000 cycles. Additionally, FeCoS nanoflakes were electrodeposited using carbon fiber coated with an rGO-nanocellulose hydrogel (GNCH) and employed as a negative 1D microelectrode, which delivered a high specific capacitance of 1223 mF cm-2 (83 F cm-3, 232.4 mF cm-1) at 4 mA cm-2 with a superior cyclic lifespan. Ultimately, the assembled 1D flexible micro-device (Ni2Mo3N-CoN/Ni,S-doped Cu@CW//FeCoS/GNCH@CF) yielded an energy density of 7.2 mW h cm-3 at a power density of 294 mW cm-3 and outstanding cycling stability in PVA/KOH electrolyte and preserved the capacitive performance under various bending states. This research highlights that assembled 1D micro-SCs have a high potency for next-generation portable/wearable energy-supply microelectronics.

A solid-state electrolyte for electrochemical lithium-sulfur cells.

Post-lithium-ion batteries are designed to achieve high energy density and high safety by modifying their active material and cell configuration. In terms of the active material, lithium-sulfur batteries have the highest charge-storage capacity and high active-material utilization because of the use of a conversion-type sulfur cathode, which involves conversion between solid-state sulfur, liquid-state polysulfides, and solid-state sulfides. In terms of the configuration, solid-state batteries ensure high safety by using a solid-state electrolyte in between the two electrodes. Herein, we use a lithium lanthanum titanate (LLTO) solid-state electrolyte in the lithium-sulfur cell with a polysulfide catholyte electrode. The LLTO, which replaces the conventional liquid electrolyte, is a solid-state electrolyte that offers smooth lithium-ion diffusion and prevents the loss of polysulfides, while the highly active polysulfide electrode, which replaces the solid-state sulfur cathode, improves the reaction kinetics and the active-material utilization. The material and electrochemical analyses confirm the stabilized electrodes exhibit long-lasting lithium stripping/plating stability and limited polysulfide diffusion. Moreover, the morphologically and electrochemically smooth interface between the solid-state electrolyte and catholyte enables fast charge transfer in the cell, which demonstrates a high charge-storage capacity of 1429 mA h g-1, high rate performance, and high electrochemical efficiency.

Investigation of Heteroatom Doped Graphene Anode for High-Capacity Alkali Metal-Ion Batteries

The drastic growth of Li-ion batteries (LIBs) in global electronic market and low crustal abundance of Li demands for more abundant alternatives such as sodium and potassium having similar electrochemical properties. Sodium-ion battery (SIB) and potassium-ion battery (PIB) can be used “side-by-side” to LIB which can help battery technology progress efficiently. 1Graphite has been a commercial anode in LIB due to its low cost, high abundance, high electrical conductivity, with a theoretical storage capacity (LiC6) of 372 mAh g-1. In contrast the utilization of graphite in SIBs and PIBs is challenging. This is due to the large radius and unstable graphite-intercalation compounds (NaC64) giving very low theoretical capacity of 30 mAh g-1. In PIBs, graphite exhibits a theoretical capacity of 279 mAh g-1 but suffers from poor stability due to huge volume expansion (60%) in fully potassiated state (KC8). Thus, focus is now shifted on to class of amorphous carbon materials such as hard carbon, soft carbon, graphene etc. with variations in micro-structures, larger interlayer spacing, and defect rich sites promoting enhanced capacity and stability even at high current densities. 2 In my presentation I will be discussing about the synthesis of heteroatom doped graphene with high charge storage and stability for LIB, SIB and PIB compared to graphite. The heteroatom doped graphene exhibits nearly 1000 mAh g-1 (LIB), 380 mAh g-1 (SIB) and 379 mAh g-1 (PIB) at a low current density of 25 mAg-1. Additionally, the elastic nature of ultrathin graphene nanosheets aids in attaining long term cyclability at 1 A g-1 with high-capacity retention of 83% for 300 cycles (LIB), 73% for 400 cycles (SIB) and 91% for 600 cycles (PIB). The enhanced stability in case of PIB, is attributed to optimizing solid electrolyte interphase (SEI) components and improving interfacial reaction kinetics at high current densities. Choice of high concentrated electrolyte (HCE) over conventional KPF6 in EC:DEC determines the nature of SEI and thereby helps in achieving cycling stability. The stability in SEI is characterized via voltage profile and understanding chemical composition by ex-situ X-ray photoelectron spectroscopy. Robust SEI in HCE is due to difference in anion structure studied by Raman spectroscopy.Furthermore, the charge-discharge mechanism, alkali ion diffusion kinetics and structure-activity relationship of electrode materials was investigated using various techniques like cyclic voltammetry profiles at different scan rates and Galvanostatic intermittent titration technique (GITT). Additionally, deeper insights into the fundamental understanding of interfacial and bulk behavior were provided with the help of in-situ Raman spectroscopy and in-situ potentiostatic electrochemical impedance spectroscopy (PEIS) analysis. The investigation of peak area and shift in D (defect) and G (graphitic) band analyzed from in-situ Raman studies helped in understanding the evolution and reversibility of alkali ion storage behavior during charging and discharging. PEIS analysis gave us a thorough understanding of the evolution of stable SEI on charging-discharging and after cycling, which helps us to understand the long-term stability in LIB, SIB and PIB.