Carbon-Based Materials for Lithium-Ion Batteries, Electrochemical Capacitors, and Their Hybrid Devices

TiN as Radical Scavenger in Fe─N─C Aerogel Oxygen Reduction Catalyst for Durable Fuel Cell

Fe─N─C is the most promising alternative to platinum-based catalysts to lower the cost of proton-exchange-membrane fuel cell (PEMFC). However, the deficient durability of Fe─N─C has hindered their application. Herein, a TiN-doped Fe─N─C (Fe─N─C/TiN) is elaborately synthesized via the sol-gel method for the oxygen-reduction reaction (ORR) in PEMFC. The interpenetrating network composed by Fe─N─C and TiN can simultaneously eliminate the free radical intermediates while maintaining the high ORR activity. As a result, the H2O2 yields of Fe─N─C/TiN are suppressed below 4%, ≈4 times lower than the Fe─N─C, and the half-wave potential only lost 15 mV after 30 kilo-cycle accelerated durability test (ADT). In a H2─O2 fuel cell assembled with Fe─N─C/TiN, it presents 980 mA cm-2 current density at 0.6 V, 880 mW cm-2 peak power density, and only 17 mV voltage loss at 0.80 A cm-2 after 10 kilo-cycle ADT. The experiment and calculation results prove that the TiN has a strong adsorption interaction for the free radical intermediates (such as *OH, *OOH, etc.), and the radicals are scavenged subsequently. The rational integration of Fe single-atom, TiN radical scavenger, and highly porous network adequately utilize the intrinsic advantages of composite structure, enabling a durable and active Pt-metal-free catalyst for PEMFC.

Onion husk-derived high surface area graphene-like carbon for supercapacitor electrode material application

In this study, we report the synthesis of graphene-like carbon derived from onion husk, with potential application as an electrode material in energy storage devices. Graphene-like carbon (GLC) was synthesized from onion husk (OH) by preliminary carbonization at 550 °C, followed by thermochemical activation at various temperatures to determine the optimal activation parameters. The surface morphology of graphene-like carbon from onion husk (GLC-OH) samples after carbonization shows distinct thermal exfoliation of the material. This layering upon activation in KOH promotes the formation of highly porous graphene-like carbon flakes. According to the Brunauer-Emmett-Teller (BET) method, the specific surface area at 850 °C was 1924 m2/g. The X-ray diffraction (XRD) and Raman spectroscopy results reveal the emergence of few-layer graphene with a significant amount of structural defects at 850 °C. As the temperature increases, the formation shifts towards multilayer graphene, which leads to a decrease in the specific surface area of the carbon material. The electrochemical characterization of the assembled GLC-OH-based supercapacitor synthesized at 850 °C revealed a markedly higher specific capacitance value of 131 F/g, along with a Coulombic efficiency of 98 % at a gravimetric current density of 1 A/g. Additionally, it exhibited a low charge transfer resistance (RCT) of approximately 1.4 Ω. Our study investigates the influence of structural changes on the electrochemical performance of biomass-derived activated carbon, highlighting the potential of graphene-like carbon from onion husk as a promising and low-cost material for future energy storage devices.

Synthesis and Characterization of Titanium Nitride-Carbon Composites and Their Use in Lithium-Ion Batteries

This work focuses on the synthesis of titanium nitride-carbon (TiN-carbon) composites by the thermal decomposition of a titanyl phthalocyanine (TiN(TD)) precursor into TiN. The synthesis of TiN was also performed using the sol-gel method (TiN(SG)) of an alkoxide/urea. The structure and morphology of the TiN-carbon and its precursors were characterized by XRD, FTIR, SEM, TEM, EDS, and XPS. The FTIR results confirmed the presence of the titanium phthalocyanine (TiOPC) complex, while the XRD data corroborated the decomposition of TiOPC into TiN. The resultant TiN exhibited a cubic structure with the FM3-M lattice, aligning with the crystal system of the synthesized TiN via the alkoxide route. The XPS results indicated that the particles synthesized from the thermal decomposition of TiOPC resulted in the formation of TiN-carbon composites. The TiN particles were present as clusters of small spherical particles within the carbon matrix, displaying a porous sponge-like morphology. The proposed thermal decomposition method resulted in the formation of metal nitride composites with high carbon content, which were used as anodes for Li-ion half cells. The TiN-carbon composite anode showed a good specific capacity after 100 cycles at a current density of 100 mAg-1.

Recent Progress in Improving Rate Performance of Cellulose-Derived Carbon Materials for Sodium-Ion Batteries

Cellulose-derived carbon is regarded as one of the most promising candidates for high-performance anode materials in sodium-ion batteries; however, its poor rate performance at higher current density remains a challenge to achieve high power density sodium-ion batteries. The present review comprehensively elucidates the structural characteristics of cellulose-based materials and cellulose-derived carbon materials, explores the limitations in enhancing rate performance arising from ion diffusion and electronic transfer at the level of cellulose-derived carbon materials, and proposes corresponding strategies to improve rate performance targeted at various precursors of cellulose-based materials. This review also presents an update on recent progress in cellulose-based materials and cellulose-derived carbon materials, with particular focuses on their molecular, crystalline, and aggregation structures. Furthermore, the relationship between storage sodium and rate performance the carbon materials is elucidated through theoretical calculations and characterization analyses. Finally, future perspectives regarding challenges and opportunities in the research field of cellulose-derived carbon anodes are briefly highlighted.

WS2-Graphene van der Waals Heterostructure as Promising Anode Material for Lithium-Ion Batteries: A First-Principles Approach

In this work, we report the results of density functional theory (DFT) calculations on a van der Waals (VdW) heterostructure formed by vertically stacking single-layers of tungsten disulfide and graphene (WS2/graphene) for use as an anode material in lithium-ion batteries (LIBs). The electronic properties of the heterostructure reveal that the graphene layer improves the electronic conductivity of this hybrid system. Phonon calculations demonstrate that the WS2/graphene heterostructure is dynamically stable. Charge transfer from Li to the WS2/graphene heterostructure further enhances its metallic character. Moreover, the Li binding energy in this heterostructure is higher than that of the Li metal's cohesive energy, significantly reducing the possibility of Li-dendrite formation in this WS2/graphene electrode. Ab initio molecular dynamics (AIMD) simulations of the lithiated WS2/graphene heterostructure show the system's thermal stability. Additionally, we explore the effect of heteroatom doping (boron (B) and nitrogen (N)) on the graphene layer of the heterostructure and its impact on Li-adsorption ability. The results suggest that B-doping strengthens the Li-adsorption energy. Notably, the calculated open-circuit voltage (OCV) and Li-diffusion energy barrier further support the potential of this heterostructure as a promising anode material for LIBs.

Lithiation of Anodic Magnetite-Hematite Nanotubes Formed on Iron

Electrochemically active iron oxide nanotubes formed by anodization are of high interest as battery components in various battery systems due to their 1D geometry, offering high volume expansion tolerance and applications without the use of binders and conductive additives. This work takes a step forward toward understanding lithium-ion storage in 1D nanotubes through the analysis of differential capacity plots d(Q - Q0)·dE-1 supported by in situ Raman spectroscopy observations. The iron oxide nanotubes were synthesized by anodizing polycrystalline iron and subsequently modified by thermal treatment in order to control the degree of crystallinity and the ratio of hematite (Fe2O3) to magnetite (Fe3O4). The electrochemical fingerprints revealed a quasi-reversible lithiation/delithiation process through Li2O formation. Significant improvement in electrochemical performance was found to be related to the high degree of crystallinity and the increase of the hematite (Fe2O3) to magnetite (Fe3O4) ratio. In situ mechanistic studies revealed a reversible reduction of iron oxide to metallic iron simultaneously with Li2O formation.

Carbon Electrode Materials for Advanced Potassium-Ion Storage

Tremendous progress has been made in the field of electrochemical energy storage devices that rely on potassium-ions as charge carriers due to their abundant resources and excellent ion transport properties. Nevertheless, future practical developments not only count on advanced electrode materials with superior electrochemical performance, but also on competitive costs of electrodes for scalable production. In the past few decades, advanced carbon materials have attracted great interest due to their low cost, high selectivity, and structural suitability and have been widely investigated as functional materials for potassium-ion storage. This article provides an up-to-date overview of this rapidly developing field, focusing on recent advanced and mechanistic understanding of carbon-based electrode materials for potassium-ion batteries. In addition, we also discuss recent achievements of dual-ion batteries and conversion-type K-X (X=O2 , CO2 , S, Se, I2 ) batteries towards potential practical applications as high-voltage and high-power devices, and summarize carbon-based materials as the host for K-metal protection and possible directions for the development of potassium energy-related devices as well. Based on this, we bridge the gaps between various carbon-based functional materials structure and the related potassium-ion storage performance, especially provide guidance on carbon material design principles for next-generation potassium-ion storage devices.

Hydrogen-Type Binding Sites in Carbonaceous Electrodes for Rapid Lithium Insertion

Direct pyrolysis of coronene at 800 °C produces low-surface-area, nanocrystalline graphitic carbon containing a uniquely high content of a class of lithium binding sites referred to herein as "hydrogen-type" sites. Correspondingly, this material exhibits a distinct redox couple under electrochemical lithiation that is characterized as intermediate-strength, capacitive lithium binding, centered at ∼0.5 V vs Li/Li+. Lithiation of hydrogen-type sites is reversible and electrochemically distinct from capacitive lithium adsorption and from intercalation-type binding between graphitic layers. Hydrogen-type site lithiation can be fully retained even up to ultrafast current rates (e.g., 15 A g-1, ∼40 C) where intercalation is severely hampered by ion desolvation kinetics; at the same time, the bulk nature of these sites does not require a large surface area, and only minimal electrolyte decomposition occurs during the first charge/discharge cycle, making coronene-derived carbon an exceptional candidate for high-energy-density battery applications.

Ultrafast and Ultralarge Lithium-Ion Storage Enabled by Fluorine-Nitrogen Co-Implanted Carbon Tubes

As a holy grail in electrochemistry, both high-power and high-energy electrochemical energy storage system (EES) has always been a pursued dream. To simultaneously achieve the "both-high" EES, a rational design of structure and composition for storage materials with characteristics of battery-type and capacitor-type storage is crucial. Herein, fluorine-nitrogen co-implanted carbon tubes (FNCT) have been designed, in which plentiful active sites and expanded interlayer space have been created benefiting from the heteroatom engineering and the fluorine-nitrogen synergistic effect, thus the above two-type storage mechanism can get an optimal balance in the FNCT. The implanted fluorine heteroatoms can not only amplify interlayer spacing, but also induce the transformation of nitrogen configuration from pyrrole nitrogen to pyridine nitrogen, further promoting the activity of the carbon matrix. The extraordinary electrochemical performance as results can be witnessed for FNCT, which exhibit fast lithium-ion storage capability with a high energy density of 119.4 Wh kg-1 at an ultrahigh power density of 107.5 kW kg-1 .

Recent Advances in Carbon-Based Electrodes for Energy Storage and Conversion

Carbon-based nanomaterials, including graphene, fullerenes, and carbon nanotubes, are attracting significant attention as promising materials for next-generation energy storage and conversion applications. They possess unique physicochemical properties, such as structural stability and flexibility, high porosity, and tunable physicochemical features, which render them well suited in these hot research fields. Technological advances at atomic and electronic levels are crucial for developing more efficient and durable devices. This comprehensive review provides a state-of-the-art overview of these advanced carbon-based nanomaterials for various energy storage and conversion applications, focusing on supercapacitors, lithium as well as sodium-ion batteries, and hydrogen evolution reactions. Particular emphasis is placed on the strategies employed to enhance performance through nonmetallic elemental doping of N, B, S, and P in either individual doping or codoping, as well as structural modifications such as the creation of defect sites, edge functionalization, and inter-layer distance manipulation, aiming to provide the general guidelines for designing these devices by the above approaches to achieve optimal performance. Furthermore, this review delves into the challenges and future prospects for the advancement of carbon-based electrodes in energy storage and conversion.

Achieving Practical Venue Recycle of Waste Oil-Based Drilling Fluids with Vacuum Distillation Technology

Drilling fluids are essential operating additives for extracting oil and shale gas. Thus, their pollution control and recycling utilization are significant to petrochemical development. Vacuum distillation technology was used in this research to handle waste oil-based drilling fluids and achieve reutilization. Briefly, recycled oil and recovered solids can be obtained from waste oil-based drilling fluids whose density is 1.24-1.37 g/cm³ by vacuum distillation under the condition of an external heat transfer oil temperature of 270 ± 5 °C and a reaction pressure below 5 × 10³ Pa. Meanwhile, recycled oil has excellent apparent viscosity (AV, 21 mPa·s) and plastic viscosity (PV, 14 mPa·s), which could be used as a substitute for 3# white oil. Furthermore, PF-ECOSEAL prepared by recycled solids exhibited better rheological properties (27.5 mPa·s AV, 18.5 mPa·s PV, and 9 Pa yield point) and plugging performance (32 mL V₀, 1.90 mL/min^1/2V_sf) than drilling fluids prepared with the conventional plugging agent PF-LPF. Our work confirmed that vacuum distillation is a valid technology in innocuity treatment and resource utilization of drilling fluids and has great value in industrial applications.

Guest Ion-Dependent Reaction Mechanisms of New Pseudocapacitive Mg3 V4 (PO4 )6 /Carbon Composite as Negative Electrode for Monovalent-Ion Batteries

Polyanion-type phosphate materials, such as M₃ V₂ (PO₄ )₃ (M = Li/Na/K), are promising as insertion-type negative electrodes for monovalent-ion batteries including Li/Na/K-ion batteries (lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and potassium-ion batteries (PIBs)) with fast charging/discharging and distinct redox peaks. However, it remains a great challenge to understand the reaction mechanism of materials upon monovalent-ion insertion. Here, triclinic Mg₃ V₄ (PO₄ )₆ /carbon composite (MgVP/C) with high thermal stability is synthesized via ball-milling and carbon-thermal reduction method and applied as a pseudocapacitive negative electrode in LIBs, SIBs, and PIBs. In operando and ex situ studies demonstrate the guest ion-dependent reaction mechanisms of MgVP/C upon monovalent-ion storage due to different sizes. MgVP/C undergoes an indirect conversion reaction to form Mg⁰ , V⁰ , and Li₃ PO₄ in LIBs, while in SIBs/PIBs the material only experiences a solid solution with the reduction of V³⁺ to V²⁺ . Moreover, in LIBs, MgVP/C delivers initial lithiation/delithiation capacities of 961/607 mAh g^-1 (30/19 Li⁺ ions) for the first cycle, despite its low initial Coulombic efficiency, fast capacity decay for the first 200 cycles, and limited reversible insertion/deinsertion of 2 Na⁺ /K⁺ ions in SIBs/PIBs. This work reveals a new pseudocapacitive material and provides an advanced understanding of polyanion phosphate negative material for monovalent-ion batteries with guest ion-dependent energy storage mechanisms.

Activated Biocarbon from Paper Mill Sludge as Electrode Material for Supercapacitors: Comparative Performance Evaluation in Two Aqueous Electrolytes

The valorization of a South African paper mill waste sludge into an activated biocarbon electrode material for energy storage application is reported. The valorization method is a two-step synthesis that comprises hydrothermal carbonization and NaOH activation of paper mill waste at 700 °C to produce activated biocarbon. The development of high porosity carbon material with a surface area of 1139 m²/g was observed. The synthesized biocarbon electrode exhibited good specific capacitance (C _sp) values of 206 and 157 Fg^-1, from a three-electrode cell in neutral (1 M Na₂SO₄) and alkali (3 M KOH) electrolytes, respectively. The electrolyte concentration purportedly has a considerable effect on specific capacitance. In both electrolytes, symmetric triangular curves in galvanostatic charge-discharge point to a quick charge-discharge process. Synthesized material testing with a two-electrode cell in 3 M KOH and 1 M Na₂SO₄ electrolytes, respectively, delivered specific capacitances of 125 and 152 Fg^-1, with the corresponding energy densities of 17.4 and 21.1 Wh kg^-1. The material had capacity retention efficiencies of 83 and 92% after 5000 cycles in 3 M KOH and 1 M Na₂SO₄ electrolytes, respectively. The electrode material performance of the activated biocarbon from paper sludge clearly shows its potential for electrochemical energy storage. The reported results present an exciting potential contribution of the pulp and paper industry toward the transition to green energy.

Advances in high-voltage supercapacitors for energy storage systems: materials and electrolyte tailoring to implementation

To achieve a zero-carbon-emission society, it is essential to increase the use of clean and renewable energy. Yet, renewable energy resources present constraints in terms of geographical locations and limited time intervals for energy generation. Therefore, there is a surging demand for developing high-performance energy storage systems (ESSs) to effectively store the energy during the peak time and use the energy during the trough period. To this end, supercapacitors hold great promise as short-term ESSs for rapid power recovery or frequency regulation to improve the quality and reliability of power supply. In particular, the electrical double layer capacitor (EDLC) which offers long and stable cycle retention, high power densities, and fast charge/discharge characteristics with a moderate operating voltage window, is a suitable candidate. Yet, for implementation of the EDLC in ESSs, further research effort is required in terms of increasing the operating voltage and energy densities while maintaining the long-term cycle stability and power densities which are desirable aspects for ESS operation. Here, we examine the advances in EDLC research to achieve a high operating voltage window along with high energy densities, covering from materials and electrolytes to long-term device perspectives for next-generation supercapacitor-based ESSs.

Investigation of Amorphous Carbon in Nanostructured Carbon Materials (A Comparative Study by TEM, XPS, Raman Spectroscopy and XRD)

Amorphous carbon (AC) is present in the bulk and on the surface of nanostructured carbon materials (NCMs) and exerts a significant effect on the physical, chemical and mechanical properties of NCMs. Thus, the determination of AC in NCMs is extremely important for controlling the properties of a wide range of materials. In this work, a comparative study of the effect of heat treatment on the structure and content of amorphous carbon in deposited AC film, nanodiamonds, carbon black and multiwalled carbon nanotube samples was carried out by TEM, XPS, XRD and Raman spectroscopy. It has been established that the use of the 7-peak model for fitting the Raman spectra makes it possible not only to isolate the contribution of the modes of amorphous carbon but also to improve the accuracy of fitting the fundamental G and D₂ (D) modes and obtain a satisfactory convergence between XPS and Raman spectroscopy. The use of this model for fitting the Raman spectra of deposited AC film, ND, CB and MWCNT films demonstrated its validity and effectiveness for investigating the amorphous carbon in various carbon systems and its applicability in comparative studies of other NCMs.

Improved Electrochemical Performance of NTs-WS2@C Nanocomposites for Lithium-Ion and Sodium-Ion Batteries

Even though WS₂ nanotubes (NTs-WS₂) have great potential as anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) thanks to their unusual layered structure, their conductivity and cycling stability are far from satisfactory. To tackle these issues, carbon-coated WS₂ (NTs-WS₂@C) nanocomposites were prepared through a facile synthesis method that involved precipitating a carbon precursor (20% sucrose) on WS₂ nanotubes, followed by annealing treatment under an argon environment. Thanks to the presence of highly conductive and mechanically robust carbon on the outer surface, NTs-WS₂@C nanocomposites show improved electrochemical performance compared with bare NTs-WS₂. After 60 cycles at 80 mA g^-1 current density, the cells display high capacities of 305 mAh g^-1 in LIBs and 152 mAh g^-1 in SIBs, respectively. As the current density increases to 600 mA g^-1, it provides specific capacities of 209 and 115 mAh g^-1, correspondingly. The enhanced electrochemical performance in LIBs and SIBs is primarily attributed to the synergistic effects of the tubular architecture of WS₂, carbon network and stable nanocomposite structure, which can effectively constrain volume variation during the metal ions intercalation/deintercalation processes.

Two Birds with One Stone: Prelithiated Two-Dimensional Nanohybrids as High-Performance Anode Materials for Lithium-Ion Batteries

As an inexpensive and naturally abundant two-dimensional (2D) material, molybdenum disulfide (MoS₂) exhibits a high Li-ion storage capacity along with a low volume expansion upon lithiation, rendering it an alternative anode material for lithium-ion batteries (LIBs). However, the challenge of using MoS₂-based anodes is their intrinsically low electrical conductivity and unsatisfied cycle stability. To address the above issues, we have exploited a wet chemical technique and integrated MoS₂ with highly conductive titanium carbide (Ti₃C₂) MXene to form a 2D nanohybrid. The binary hybrids were then subjected to an n-butyllithium (n-Buli) treatment to induce both MoS₂ deep phase transition and MXene surface functionality modulation simultaneously. We observed a substantial increase in 1T-phase MoS₂ content and a clear suppression of -F-containing functional groups in MXene due to the prelithiation process enabled by the n-Buli treatment. Such an approach not only increases the overall network conductivity but also improves Li-ion diffusion kinetics. As a result, the MoS₂/Ti₃C₂ composite with n-Buli treatment delivered a high Li-ion storage capacity (540 mA h g^-1 at 100 mA g^-1), outstanding cycle stability (up to 300 cycles), and excellent rate capability. This work provides an effective strategy for the structure-property engineering of 2D materials and sheds light on the rational design of high-performance LIBs using 2D-based anode materials.

Tailoring thermal insulation architectures from additive manufacturing

Tailoring thermal transport by structural parameters could result in mechanically fragile and brittle networks. An indispensable goal is to design hierarchical architecture materials that combine thermal and mechanical properties in a continuous and cohesive network. A promising strategy to create such a hierarchical network targets additive manufacturing of hybrid porous voxels at nanoscale. Here we describe the convergence of agile additive manufacturing of porous hybrid voxels to tailor hierarchically and mechanically tunable objects. In one strategy, the uniformly distributed porous silica voxels, which form the basis for the control of thermal transport, are non-covalently interfaced with polymeric networks, yielding hierarchic super-elastic architectures with thermal insulation properties. Another additive strategy for achieving mechanical strength involves the versatile orthogonal surface hybridization of porous silica voxels retains its low thermal conductivity of 19.1 mW m⁻¹K⁻¹, flexible compressive recovery strain (85%), and tailored mechanical strength from 71.6 kPa to 1.5 MPa. The printed lightweight high-fidelity objects promise thermal aging mitigation for lithium-ion batteries, providing a thermal management pathway using 3D printed silica objects.

Nanoscale porous building blocks hold great promise for a range of thermal management technologies but often porous nanoparticle assemblies are intrinsically brittle. Here, the authors report 3D printing of porous silica voxels with polymeric additives to enable the coupling between additive manufacturing and hierarchical assembly for superior machinability and structural controllability.

Influence of sequential HTC pre-treatment and pyrolysis on wet food-industry wastes: Optimisation toward nitrogen-rich hierarchical carbonaceous materials intended for use in energy storage solutions

Due to elevated protein content, the food-industry bio-wastes are promising feedstock to produce hierarchical (micro-mesoporous) carbonaceous materials with the intended use as electrodes in the energy storage solutions. However, the high initial water content, makes their direct activation through high-temperature processes costineffective due to significant heat requirements. In this study, the influence of pretreatment with hydrothermal carbonization (HTC) on wet food-industry bio-wastes, further pyrolysed, was investigated. Selected wastes (brewer's spent grains, spent coffee grains and spent sugar beets) were pre-treated by HTC at 180 °C or 240 °C, and then pyrolysed at 500 °C or 700 °C. Obtained materials were examined using elemental analysis, gas adsorption (N₂ and CO₂) and FT-IR. Besides minor differences caused by the bio-composition of wastes, the general trends were similar for feedstock. The pre-treatment had a beneficial influence on the properties of all wastes. The HTC at 180 °C and pyrolysis at 700 °C for all wastes show the most promising total specific surface area 560 ± 10 m²/g and accessible specific surface area 96 m²/g. Those conditions simultaneously did not reduce the total solid yield in comparison to the one-step process. The pre-treatment at 240 °C led to elevated nitrogen incorporation in the carbonaceous structure compared to HTC at 180 °C. However, it formed a hierarchical structure that was not stable for the thermal treatment. Study proves the HTC pre-treatment at 180 °C is beneficial for the conversion of food-industry bio-wastes into hierarchical carbonaceous material for their use in the energy storage systems application.

Synthesis and Electrochemical Properties of TiNb2O7 and Ti2Nb10O29 Anodes under Various Annealing Atmospheres

In this study, two compounds of TiNb2O7 and Ti2Nb10O29 were successfully synthesized by mechanochemical method and post-annealing as an anode material for lithium-ion batteries. The effect of annealing atmosphere on the morphology, particle size, and electrochemical characteristics of two compounds was investigated. For these purposes, the reactive materials were milled under an argon atmosphere with a certain mole ratio. Subsequently, each sample was subjected to annealing treatment in two different atmospheres, namely argon and oxygen. Phase and morphology identifications were carried out by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) to identify the phases and evaluate the morphology of the synthesized samples. The charging and discharging tests were conducted using a battery-analyzing device to evaluate the electrochemical properties of the fabricated anodes. Annealing in different atmospheres resulted in variable discharge capacities so that the two compounds of TiNb2O7 and Ti2Nb10O29 annealed under the argon atmosphere showed a capacity of 60 and 66 mAh/g after 179 cycles, respectively, which had a lower capacity than their counterpart under the oxygen atmosphere. The final capacity of the annealed samples in the oxygen atmosphere is 72 and 74 mAh/g, respectively.

Modifying Metastable Sr1-xBO3-δ (B = Nb, Ta, and Mo) Perovskites for Electrode Materials

The presence of surface/deep defects in 4d- and 5d-perovskite oxide (ABO3, B = Nb, Ta, Mo, etc.) nanoparticles (NPs), originating from multivalent B-site cations, contributes to suppressing their metallic properties. These defect states can be removed using a H2/Ar thermal treatment, enabling the recovery of their electronic properties (i.e., low electrical resistivity, high carrier concentration, etc.) as expected from their electronic structure. Therefore, to engineer the electronic properties of these metastable perovskites, an oxygen-controlled crystallization approach coupled with a subsequent H2/Ar treatment was utilized. A comprehensive study of the effect of the post-treatment time on the electronic properties of these perovskite NPs was performed using a combination of scattering, spectroscopic, and computational techniques. These measurements revealed that a metallic-like state is stabilized in these oxygen-reduced NPs due to the suppression of deep rather than surface defects. Ultimately, this synthetic approach can be employed to synthesize ABO3 perovskite NPs with tunable electronic properties for application into electrochemical devices.

3D tremella-like nitrogen-doped carbon encapsulated few-layer MoS2 for lithium-ion batteries

MoS₂ is regarded as an attractive anode material for lithium-ion batteries due to its layered structure and high theoretical specific capacity. Its unsatisfied conductivity and the considerable volume change during the charge and discharge process, however, limits its rate performance and cycling stability. Herein, 3D tremella-like nitrogen-doped carbon encapsulated few-layer MoS₂ (MoS₂@NC) hybrid is obtained via a unique strategy with simultaneously poly-dopamine carbonization, and molybdenum oxide specifies sulfurization. The three-dimensional porous nitrogen-doped carbon served both as a mechanical supporting structure for stabilization of few-layers MoS₂ and a good electron conductor. The MoS₂@NC exhibits enhanced high rate performance with a specific capacity of 208.7 mAh g^-1 at a current density of 10 A g^-1 and stable cycling performance with a capacity retention rate of 85.7% after 1000 cycles at 2 A g^-1.

High-Performance and High-Voltage Supercapacitors Based on N-Doped Mesoporous Activated Carbon Derived from Dragon Fruit Peels

Designing the mesopore-dominated activated carbon electrodes has witnessed a significant breakthrough in enhancing the electrolyte breakdown voltage and energy density of supercapacitors. Herein, we designed N-doped mesoporous-dominated hierarchical activated carbon (N-dfAC) from the dragon fruit peel, an abundant biomass precursor, under the synergetic effect of KOH as the activating agent and melamine as the dopant. The electrode with the optimum N-doping content (3.4 at. %) exhibits the highest specific capacitance of 427 F g-1 at 5 mA cm-2 and cyclic stability of 123% capacitance retention until 50000 charge-discharge cycles at 500 mA cm-2 in aqueous 6 M KOH electrolytes. We designed a 4 V symmetric coin cell supercapacitor cell, which exhibits a remarkable specific energy and specific power of 112 W h kg-1 and 3214 W kg-1, respectively, in organic electrolytes. The cell also exhibits a significantly higher cycle life (109% capacitance retention) after 5000 GCD cycles at the working voltage of ≥3.5 V than commercial YP-50 AC (∼60% capacitance retention). The larger Debye length of the diffuse ion layer permitted by the mesopores can explain the higher voltage window, and the polar N-doped species in the dfAC enhance capacitance and ion transport. The results endow a new path to design high-capacity and high-working voltage EDLCs from eco-friendly and sustainable biomass materials by properly tuning their pore structures.

Lithium-Ion Capacitors: A Review of Design and Active Materials

Lithium-ion capacitors (LICs) have gained significant attention in recent years for their increased energy density without altering their power density. LICs achieve higher capacitance than traditional supercapacitors due to their hybrid battery electrode and subsequent higher voltage. This is due to the asymmetric action of LICs, which serves as an enhancer of traditional supercapacitors. This culminates in the potential for pollution-free, long-lasting, and efficient energy-storing that is required to realise a renewable energy future. This review article offers an analysis of recent progress in the production of LIC electrode active materials, requirements and performance. In-situ hybridisation and ex-situ recombination of composite materials comprising a wide variety of active constituents is also addressed. The possible challenges and opportunities for future research based on LICs in energy applications are also discussed.

Review on carbonaceous materials and metal composites in deformable electrodes for flexible lithium-ion batteries

With the rapid propagation of flexible electronic devices, flexible lithium-ion batteries (FLIBs) are emerging as the most promising energy supplier among all of the energy storage devices owing to their high energy and power densities with good cycling stability. As a key component of FLIBs, to date, researchers have tried to develop newly designed high-performance electrochemically and mechanically stable pliable electrodes. To synthesize better quality flexible electrodes, based on high conductivity and mechanical strength of carbonaceous materials and metals, several research studies have been conducted. Despite both materials-based electrodes demonstrating excellent electrochemical and mechanical performances in the laboratory experimental process, they cannot meet the expected demands of stable flexible electrodes with high energy density. After all, various significant issues associated with them need to be overcome, for instance, poor electrochemical performance, the rapid decay of the electrode architecture during deformation, and complicated as well as costly production processes thus limiting their expansive applications. Herein, the recent progression in the exploration of carbonaceous materials and metals based flexible electrode materials are summarized and discussed, with special focus on determining their relative electrochemical performance and structural stability based on recent advancement. Major factors for the future advancement of FLIBs in this field are also discussed.

Carbon materials for ion-intercalation involved rechargeable battery technologies

The development of carbon electrode materials for rechargeable batteries is reviewed from the perspective of structural features, electrochemistry, and devices.

Natural biomass derived hard carbon and activated carbons as electrochemical supercapacitor electrodes

With every moving day, the aspect that is going to be the most important for modern science and technology is the means to supply sufficient energy for all the scientific applications. As the resource of fossil fuel is draining out fast, an alternative is always required to satisfy the needs of the future world. Limited resources also force to innovate something that can utilise the resource more efficiently. This work is based on a simple synthesis route of biomass derived hard carbon and to exploring the possibility of using it as electrochemical supercapacitors. A cheap, eco-friendly and easily synthesized carbon material is utilized as electrode for electrochemical energy-storage. Four different hard carbons were synthesized from KOH activated banana stem (KHC), phosphoric acid treated banana stem derived carbons (PHC), corn-cob derived hard carbon (CHC) and potato starch derived hard carbons (SHC) and tested as supercapacitor electrodes. KOH-activated hard carbon has provided 479.23 F/g specific capacitance as calculated from its cycle voltammograms. A detailed analysis is done to correlate the results obtained with the material property. Overall, this work provides an in depth analysis of the science behind the components of an electrochemical energy-storage system as well as why the different characterization techniques are required to assess the quality and reliability of the material for electrochemical supercapacitor applications.

Photo-Supercapacitors Based on Third-Generation Solar Cells

Photopowered energy systems (PPESs), which simultaneously achieve power conversion and energy storage, are one of the most promising auxiliaries to fulfill the giant and diversified power demand in modern society. Devices with a low cost, wearable, compact structure and the potential to add a variety of features (such as photochromic, flexible, textile, and wearable) have received extensive research attention. Photo-supercapacitors are becoming one of the most extensively researched PPESs due to their ease of fabrication, mitigation of solar irradiation discontinuities, and the promotion of renewable energy utilization, and these devices have been fabricated with different combinations of photovoltage devices and energy-storage technologies. This review summarizes the development of photo-supercapacitors that integrate third-generation solar cells and supercapacitors, with a focus on materials alignment, performance, structure design, and application. Finally, current challenges, possible solutions, and future perspectives are discussed.

Rational Design of Carbon Nanomaterials for Electrochemical Sodium Storage and Capture

Electrochemical sodium storage and capture are considered an attractive technology owing to the natural abundance, low cost, safety, and cleanness of sodium, and the higher efficiency of the electrochemical system compared to fossil-fuel-based counterparts. Considering that the sodium-ion chemistry often largely deviates from the lithium-based one despite the physical and chemical similarities, the architecture and chemical structure of electrode materials should be designed for highly efficient sodium storage and capture technologies. Here, the rational design in the structure and chemistry of carbon materials for sodium-ion batteries (SIBs), sodium-ion capacitors (SICs), and capacitive deionization (CDI) applications is comprehensively reviewed. Types and features of carbon materials are classified into ordered and disordered carbons as well as nanodimensional and nanoporous carbons, covering the effect of synthesis parameters on the carbon structure and chemistry. The sodium storage mechanism and performance of these carbon materials are correlated with the key structural/chemical factors, including the interlayer spacing, crystallite size, porous characteristics, micro/nanostructure, morphology, surface chemistry, heteroatom incorporation, and hybridization. Finally, perspectives on current impediment and future research directions into the development of practical SIBs, SICs, and CDI are also provided.