Superior Specific Capacitance Research Articles

Nano ZnO modified amorphous carbon materials enabling long-cycle performance and high-capacity for lithium/sodium-ion batteries

Zinc-modified carbon materials exhibit high specific capacity, good safety, and low self-discharge, making them promising anode materials for lithium-ion and sodium-ion batteries. However, the high cost of raw materials, complex fabrication processes, and limited cycle life remain significant challenges to their further development. In this study, we elucidated a two-step process, simple in technique and suitable for large-scale production, for in-situ zinc modification of amorphous carbon. The synthesized carbon material exhibited superior reversible specific capacity (maintaining 780.27 mAh·g−1 capacity after 80 cycles at 50 mA·g−1 current density), high cycling stability (maintaining Coulombic efficiency at 100.06 % after 15,000 cycles at 10 A·g−1 current density), and good application value (achieving a capacity of 89.67 mAh·g−1 after 1000 cycles at 200 mA·g−1 current density for the assembled MFAC-Zn||NVP full cell). Through our investigation, we discovered that Nano ZnO not only directly participate in electrochemical reactions but also effectively improve the microstructure of amorphous carbon, increasing its three-dimensional axial stacking and providing more reaction sites. The enrichment of open pores significantly enhances the diffusion efficiency of ions within the carbon-based matrix. The superior diffusion ability of alkali metal-ion in the electrode is the reason for the excellent electrochemical performance of Zinc-modified amorphous carbon. Moreover, the incorporation of Nano ZnO aids in the formation of a robust and thin SEI layer. This significantly enhances the stability of the electrode materials during cycling and improves charge transfer efficiency during the charge-discharge process. Our study provides a new strategy for adjusting the internal microstructure of amorphous carbon materials to achieve high-performance lithium/sodium storage.

Recycling of activated carbons from spent supercapacitors to refabricate improved supercapacitors

The growing market of commercial electric double-layer capacitors (EDLCs) will lead to a vast accumulation of waste as they arrive out of operation. Recycling the spent electrode activated carbon is a closed-loop solution to provide environmental and economic advantages for EDLC use. However, effectively regenerated methods of high-purity activated carbons are still lacked despite their considerable expense. Herein, a simple steam physical activation method is developed to regenerate high-class activated carbons from spent EDLCs. The process is first demonstrated that can effectively eliminate few electrolytes and complex organics as well as regenerate electrode carbon materials. The activation-recycled carbon materials preserve the physicochemical properties of fresh activated carbons and enhance their mesopore ratios, which contributes to improved EDLC performance, obviously surpassing recycled carbon materials by calcination method, including superior specific capacitance of 103.3 F g−1 at 0.5 A g−1, rate performance and cycling stability, equal to fresh activated carbons. Moreover, the assembled activation-recycled carbon material EDLC delivers low self-discharge rate (89 % of initial voltage after 72 h), wide temperature range (−40 to 85 °C), excellent cycling stability (92.2 % capacitance retention after 10,000 cycles) even at elevated voltages (3.0 V) and temperature (65 °C) test. The present work provides an effective and economic method of recycling high-grade activated carbons for sustainable EDLCs.

A two-pronged strategy to boost the capacitive deionization performance of nitrogen-doped porous carbon nanofiber membranes

Carbon-based capacitive deionization (CDI) systems are universally subject to the limited desalination capacity, due to the electrosorption characteristics and undesirable pore structures. Herein, a two-pronged strategy is proposed to boost the desalination performance of the electrospun carbon nanofibers (CNFs), where silicalite-1 nanoparticles as the internal porogen create mesopores and macropores, and zeolitic imidazolate framework (ZIF-L) leaves as the external carbon source provide micropores and mesopores. This combination results in the large surface area, well-developed graded pore structure, and increased nitrogen content of the core-shell polyacrylonitrile/silicalite-1@ZIF-L-derived CNFs (defined as PCNFs-SZ) electrode, which delivers a superior specific capacitance of 145.4 F g−1 in a neutral electrolyte. The symmetric CDI cell assembled by the self-supporting PCNFs-SZ membrane electrodes holds a prominent desalination capacity of 37.09 mg g−1 and a rapid salt removal rate of 10.36 mg g−1 min−1 at 1.2 V (initial NaCl concentration: 500 mg L−1), and demonstrates significant potential for real-world applications in the desalination and purification of reclaimed water. Furthermore, theory calculations confirm the enhanced Na+-capture capability of PCNFs-SZ. The present work highlights an effective and viable approach to enhance the desalination performance of carbon-based CDI cells.

Multifunctional RGO-Gd2O3:Eu3+ nanocomposites for supercapacitor and biosensor application

This study successfully synthesized pristine RGO-Gd2O3:Eu3+ nanocomposites (NCs) using a hydrothermal method, as confirmed by X-ray diffraction and TEM analysis. Cyclic voltammetry (CV) demonstrated that RGO-Gd2O3:Eu3+ NCs exhibited a superior specific capacitance (Csp) of 340 Fg⁻1 at a scan rate of 2 mV s⁻1. Impressively, the synthesized nanocomposites displayed high energy and power densities of 41 Wh/kg and 30000 W/kg, respectively, along with excellent capacity retention (91.12%) and Coulombic efficiency (95.77%). Modified glassy carbon electrodes (MGCEs) fabricated using these NCs showed promising electrochemical responses for dopamine (DA) detection at pH 7. These findings highlight the potential of the developed electrode for both supercapacitor applications and DA sensing.

Enhancing the electrochemical efficiency of Ni3V2O8 NPs synthesised by hydrothermal methods for supercapattery applications

A key challenge in renewable energy production is the persistent gap between energy supply and demand. Developing and optimizing materials for energy storage devices offers a promising solution to this issue. The Ni3V2O8 Nanoparticles (NPs) were prepared using a simple hydrothermal process and their structural, morphology, functional and elemental properties were confirmed with special analytical tools like PXRD, SEM, FTIR and EDX with mapping correspondingly. Ensuring the redox peaks and electrochemical interaction, charge/discharge cycles and conductivity of electrode materials were examined through the CV, GCD and EIS studies. The prepared Ni3V2O8 electrode exhibits a superior specific capacity of 581.07 at 5 mV/s. The cyclic stability of the electrode attained 72 % specific-capacity retention completing 10,000 cycles with 5 A/g. The supercapatteries belong to the electrode configuration of Ni3V2O8||AC fabricated and also investigated its properties with capacitive and diffusive mechanisms. Additionally essentially, fabricated asymmetric supercapatteries with a notable power density (PD) and energy density (ED) 1976 W kg and 45.5 Wh/kg and outstanding cycle stability performance above 92 % specific capacity retention after 10,000 cycles is accrued effectively by using the Ni3V2O8 as electrode material for supercapattery applications.

α-Bi2Mo3O12: A Dual-Functional Material for Electrocatalytic Water Splitting and Supercapacitor Applications.

This study explores the functionality of α-Bi2Mo3O12 (BMO) as an electrocatalyst for water splitting and its suitability for supercapacitor applications. BMO was synthesized by the solvothermal method and characterized in pre-calcination [BMO (BC)], post-calcination [BMO (AC)], and base-etched forms [BMO (BE)]. Structural analysis confirmed the formation of α-Bi2Mo3O12 with well-defined crystallographic planes. Electrochemical analysis revealed that BMO (AC) exhibited the lowest overpotential for hydrogen evolution reactions (HER) and BMO (BC) exhibited the lowest overpotential for oxygen evolution reactions (OER), indicating its superior electrocatalytic activity. The Tafel slope and electrochemical impedance spectroscopy results confirmed the superior kinetics and charge transfer properties of BMO material. Furthermore, BMO samples demonstrated excellent stability during prolonged chronoamperometry (CA) testing for 12 h. For supercapacitor performances, the BMO (BE) exhibits a superior specific capacitance value of 398 F/g at 2.0 A/g. Thus, the BMO material delivers prominent electrocatalytic activity as well as supercapacitor performance. Overall, this study demonstrates the potentiality of α-Bi2Mo3O12 in different forms as a dual-functional material for efficient energy storage and conversion.

P-Block-metal bismuth embedded in N/P co-doped carbon nanorods for kinetics-enhanced rechargeable lithium-oxygen batteries

Rechargeable lithium-oxygen batteries (LOBs) are considered one of the most promising electrochemical energy storage devices due to their extremely high theoretical energy density. However, the slow redox kinetics of the oxygen cathode leads to low coulombic efficiency and poor cycling performance, which limits the development of high-performance LOBs. Herein, Bi@NPC heterostructure nanorods are designed with the assistance of p-block metal Bi and successfully synthesized as bifunctional cathode catalysts for LOBs. Experimental and theoretical calculations show that Bi@NPC electrode can significantly reduce overpotential during discharge/charge processes due to the easily tunable localized p-orbitals and resulting versatile electronic structures. Benefiting from p-orbital electrons regulation of Bi atoms, the Bi@NPC electrode exhibited superior specific capacity over 11852.6 mAh g−1, outstanding rate capabilities, and ultralong cycle stability over 83 cycles at 200 mA g−1 with the fixed capacity of 500 mAh g−1. This work reveals an efficient pathway to synthesize p-block metal-based catalysts for high-performance LOBs.

Hollow-porous carbon microspheres with hierarchically micromesoporous shells and superhydrophilic surfaces for high-performance aqueous supercapacitors

Hollow-porous carbon microspheres (SPC-MnO2) are synthesized using sucrose as a carbon source and MnO2 microspheres with a porous and rough surface as a template, followed by activation with KHCO3. The activation process involves anchoring carbon onto the MnO2 template while simultaneously creating pores in the carbon shell. The SPC-MnCO3 sample, which utilizes well-defined MnCO3 microspheres as a template, exhibits disintegrated grains with irregular shapes owing to the substantial decomposition of MnCO3 during activation. The SPC-MnO2 sample demonstrates a large surface area of 1589 m² g⁻¹ and a pore volume of 2.52 cm³ g⁻¹, featuring substantial amounts of mesopores ranging from 3 to 30 nm in size. The micromesoporous structure of SPC-MnO2 provides a hydrophilic surface, thereby enhancing wettability in aqueous KOH electrolytes and improving charge-storage capabilities. The SPC-MnO2 electrode exhibits superior specific capacitance (317 F g⁻¹ at 1 A g⁻¹) and high-rate performance (202 F g⁻¹ at 50 A g⁻¹) in 6 M KOH compared with microporous carbon produced without a template. The notable enhancement in supercapacitor performance can be attributed to the hollow structural integrity of the microspheres, the superhydrophilic surface, high electrical conductivity, and the hierarchical micromesoporous nature. These features facilitate efficient ion/electron transport and surface-controlled redox kinetics.

Improved electrochemical performance of the iron-doped NiO nanoparticles at varying calcination temperatures and examination of their supercapacitor applications

The scientific community is interested in increasing oxide electrochemical characteristics for supercapacitor applications. The present research explores the development of supercapacitor electrodes using Fe-doped NiO nanoparticles synthesised via chemical co-precipitation method with varied calcination temperatures (350, 550, and 750 °C). The key innovation of the work lies in the systematic investigation of the effects of calcination temperature on the electrochemical properties and structural characteristics of the Fe-doped NiO nanoparticles. X-ray diffraction (XRD) analysis revealed a trend of increasing crystallite size with rising temperatures, and optical studies indicated a decreasing trend in the energy band gap from 3.67 eV to 3.23 eV. Fourier transform infrared (FTIR) spectroscopy confirmed the metal-oxygen bond in the molecules. Scanning electron microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM) analysis showed the mesoporous spherical morphology of the nanoparticles. Energy-dispersive X-ray spectroscopy (EDX) ensured the samples' elemental composition purity. Brunauer–Emmett–Teller (BET) shows a specific surface area of around 180.8 m2/g was obtained for Fe-doped NiO nanoparticles at 350 °C. Electrochemical tests demonstrated that the Fe-doped NiO electrodes, especially calcined at 350 °C, exhibit superior specific capacitance values (635 F/g) and impressive cycle stability with 93.29 % capacitance retention after 5000 cycles. The present demonstrates the potential of optimizing calcination temperatures to enhance the electrochemical performance and stability of Fe-doped NiO supercapacitor electrodes, marking a significant advancement in supercapacitor technology.

Mn─O Covalency as a Lever for Na⁺ Intercalation Kinetics: The Role of Oxygen Edge-Sharing Co Octahedral Sites in MnO₂.

The strategic enhancement of manganese-oxygen (Mn─O) covalency is a promising approach to improve the intercalation kinetics of sodium ions (Na⁺) in manganese dioxide (MnO2). In this study, an augmenting Mn─O covalency in MnO2 by strategically incorporating cobalt at oxygen edge-sharing Co octahedral sites is focused on. Both experimental results and density functional theory (DFT) calculations reveal an increased electron polarization from oxygen to manganese, surpassing that directed toward cobalt, thereby facilitating enhanced electron transfer and strengthening covalency. The synthesized Co-MnO2 material exhibits outstanding electrochemical performance, demonstrating a superior specific capacitance of 388Fg-1 at 1Ag-1 and maintaining 97.21% capacity retention after 12000 cycles. Additionally, an asymmetric supercapacitor constructed using Co-MnO2 achieved a high energy density of 35Whkg-1 at a power density of 1000Wkg-1, underscoring the efficacy of this material in practical applications. This work highlights the critical role of transition metal-oxygen interactions in optimizing electrode materials and introduces a robust approach to enhance the functional properties of manganese oxides, thereby advancing high-performance energy storage technologies.

MXene-based materials composite with phytic acid for potassium-ion battery anodes

MXenes, with their metallic conductivity and complex surface chemistry, are emerging as promising newcomers in the field of energy storage materials. In this work, we present innovative iterations of MXene synthesised by phytic acid selective etching and self-assembly, denoted P-MXene, with phytic acid adhered tightly to the surface and increased the interlayer spacing of the MXene, which was beneficial to the embedment/desorption of K+, and etched more active sites. When used as an anode material for potassium ion batteries, P-MXene exhibits superior specific capacity of 135 mAh*g−1, long-term cycling stability capacity of 128.8 mAh*g−1 and higher rate performance (the final capacity of 110.0 mAh*g−1). This transformative development not only establishes a new paradigm for MXene derivatives, but also paves the way for the exploration of high-performance MXene-based energy storage materials.

Exploring the role of transition metal ions doping on the optical, magnetic and energy storage properties of Bi0.96Eu0.04FeO3 nanoparticles

Bismuth ferrite has been quite extensively studied because of its unique multiferroic properties. The introduction of dopants strategically at the ‘A’ and ‘B’ sites has been known to improve the multiferroic properties of bismuth ferrite. This study focuses on the detailed investigation of the structural, morphological, optical, magnetic, and electrochemical properties of sol-gel synthesized bismuth ferrite as well as Bi0.96Eu0.04Fe0.95M0.05O3(M=Mn, Cu, Co, Zn) nanoparticles. The crystal structure and morphological analysis are done using XRD, Rietveld refinement, and FESEM. The XRD analysis and Rietveld Refinement have confirmed a structural transition to the orthorhombic phase upon simultaneous co-doping of ‘Eu’ and ‘M’(M= Mn, Cu, Co, Zn) ions at the ‘A’ and ‘B’ sites respectively. The evidence of different ratios of mixed valence states of ‘Fe’ and oxygen vacancies in the co-doped nanoparticles dictates the enhanced magnetic properties. There is a significant decrease in the band-gap of co-doped nanoparticles obtained from Tauc’s plot, with the lowest achieved band-gap of 1.8 eV in the case of ‘Eu’ and ‘Mn’ doped nanoparticles. Room-temperature M-H loops have recorded an increase in the value of maximum magnetization from 0.1 emu/g in case of pristine bismuth ferrite to 0.79 emu/g for ‘Eu’ and ‘Co’ doped bismuth ferrite nanoparticles. The unsaturated loops, however, have confirmed the presence of anti-ferromagnetic component along with the ferromagnetic part. The electrochemical studies have shown superior specific capacitance in co-doped bismuth ferrite, with the maximum specific capacitance of 273 F/g for ‘Eu’ and ‘Zn’ doped bismuth ferrite. It has also shown remarkable capacitive retention of 84.8 % after 5000 cycles at 10 A/g.

Novel design of nickel cobalt boride nanosheets-decorated molybdenum disulfide hollow spheres as efficient battery-type materials of hybrid supercapacitors

Transition metal borides (TMBs) with high theoretical capacitances and excellent electronic properties have attracted much attention as a promising active material of supercapacitors (SCs). However, TMB nanoparticles are prone to conduct self-aggregation, which significantly deteriorates the electrochemical performance and structural stability. To address the severe self-aggregation in TMBs and improve the active material utilization, it is imperative to provide a conductive substrate that promotes the dispersion of TMB during growths. In this work, sheet-like nickel cobalt boride (NCB) was grown on molybdenum disulfide (MoS2) hollow spheres (H-MoS2) by using simple template growth and chemical reduction methods. The resultant NCB/H-MoS2-50 was observed with uniform NCB nanosheets structure on the surface of the H-MoS2 and stronger MB bonding. After optimizing the loading amount of H-MoS2, the optimal composite (NCB/H-MoS2-50) modified nickel foam (NF) exhibits a superior specific capacity (1302 C/g) than that of the NCB electrode (957 C/g) at 1 A/g. Excellent rate capability of 84.8% (1104 C/g at 40 A/g) is also achieved by the NCB/H-MoS2-50 electrode. The extraordinary electrochemical performance of NCB/H-MoS2-50 is credited to the unique nanosheet-covered hollow spheres structure for facilitating ion diffusion and versatile charge storage mechanisms from the pseudocapacitive behavior of H-MoS2 and the Faradaic redox behavior of NCB. Furthermore, a hybrid SC is assembled with NCB/H-MoS2-50 and activated carbon (AC) electrodes (NCB/H-MoS2-50//AC), which operates in a potential window up to 1.7 V and delivers a high energy density of 76.8 W h kg−1 at a power density of 850 W kg−1. A distinguished cycling stability of 93.2% over 20,000 cycles is also obtained for NCB/H-MoS2-50//AC. These findings disclose the significant potential of NCB/H-MoS2-50 as a highly performed battery-type material of SCs.

Defect-rich hard carbon designed by heteroatom escape assists sodium storage performance for sodium-ion batteries

Sodium-ion batteries (SIBs) avoids the use of expensive cobalt element, and the abundance of sodium element is high, so it shows great application potential, and the development of sodium-ion battery materials is of great value. Biomass precursors have the advantages of low cost and widely and sufficiently distributed resources, and embody the environmental concept of waste utilization, however, the poor reversible specific capacity and initial coulombic efficiency (ICE) of pristine corn stover-derived hard carbons (CSHCs) limit their practical application value. In this paper, we propose a method to increase the reversible specific capacity of hard carbon and maintain high ICE, introduce heteroatoms into graphene-like nanosheets at low carbonization temperature, then escape heteroatoms through high pyrolysis temperature, create defects in the graphene-like carbon layer and expand the (002) layer spacing. Density functional theory (DFT) calculations show that defects are beneficial to the adsorption of Na+ on graphene-like nanosheets, and Na+ have a lower diffusion barrier between layers rich in defects and extended (002) layer spacing. Compared with the conventional low pyrolysis temperature heteroatom doping process, the present method exhibits superior ICE. In the ester-based electrolyte, the modified hard carbon (D-CSHC) exhibits a superior specific capacity of 284.5 mAh/g and an ICE of 85.9 % as compared to the pristine corn stover-derived hard carbon (233.5 mAh/g, 72.7 %). In addition, the capacity retention rate was 92.6 % after 500 turns of constant current cycles at 0.15 A/g.

Nanosized hyperbranched cobalt and metal-free phthalocyanine intercalated with Pd–C matrix using PVA-TEOS as binder for admirable supercapacitor properties

The expanding global economy resulted mainly from consuming fossil fuels, which are scarce and cause prodigious environmental harm. Mankind is shifting towards sustainable, efficient and clean energy sources known as green energy. The storage of green energy is an urge of time, to fulfil the energy requirements. Supercapacitors are gaining popularity in the field of energy storage due to their excellent safety, cost-effectiveness, and environmental friendliness. The forthright strategy of using a nitrogen-rich phthalocyanine macrocycle as a nanosized particle is to increase surface area resulting in a high specific capacitance. Herein, an innovative approach has been made by synthesising nanosized hyperbranched metal-free/Co-Phthalocyanine characterized by various analytical and spectroscopic techniques. The morphology of the composite was confirmed through physicochemical characterization like BET, SEM, XRD and electrochemical features were studied through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The electrode modification was carried out using the binder Poly (vinyl alcohol)-Tetraethyl orthosilicate (PVA-TEOS) crosslinked hybrid solution. The intercalated nanosized palladium on carbon matrix with HBCoPc and HBPc at different ratios enhanced the performance of capacitance. Amongst all the ratios, HBCoPc: Pd–C with 30:70 ratio has demonstrated superior specific capacitance of 824.25 F g−1 at 0.5 A g−1. Additionally, the fabricated electrode of HBCoPc: Pd–C and HBPc: Pd–C has exhibited good capacitance retention of 84.03 % and 81.01 % over 5000 cycles, respectively. This work delivers a promising approach towards the development of high-performance supercapacitors using metal phthalocyanine/metal-carbon composites as a new way to manufacture devices for conversion and energy storage.

Charge storage mechanism and pseudocapacitance performance of NiO and Ce-doped NiO synthesized via modified combustion technique

Supercapacitors, as promising energy storage devices, have gained significant attention due to their ability to deliver high power and efficient charge storage mechanisms. In this work, we report the synthesis and electrochemical characterization of pristine NiO and Ni1-xCexO (x = 0.01, 0.02, 0.03) nanoparticles using a single-step auto ignition combustion method. Preliminary investigations indicate that Ni1-xCexO (x = 0.02) nanoparticles (2 % Ce doping) exhibit superior specific capacitance compared to other compositions. Therefore, we focused on structural, morphological, and vibrational studies on pristine and 2 % Ce-doped NiO. XPS and BET techniques were explored to assess the electronic state and porosity of the samples. Subsequent electrochemical performance evaluations included Cyclic Voltammetry (CV) at various scan rates, Galvanostatic Charge-Discharge (GCD), and Electrochemical Impedance Spectroscopic (EIS) techniques. From CV at a scan rate of 5 mVs−1, specific capacitance values of 419 Fg-1 and 604 Fg-1 were obtained for pristine and 2 % Ce-doped NiO, respectively. GCD studies revealed a specific capacitance of 381 Fg-1 for 2 % Ce-doped NiO at a current density of 1 Ag-1 and demonstrated capacitance retention of 95.1 % over 3000 GCD cycles for a current density of 4 Ag-1. The symmetric two-electrode supercapacitor cell demonstrates exceptional electrochemical performance, exhibiting a high specific capacitance of 122 Fg-1, an impressive energy density of 8.17 WhKg−1, a power density of 700 WKg-1 at 1 Ag-1, and a remarkable 88 % capacitance retention after 5000 GCD cycles. DFT calculations suggest that Ce doping significantly alters pristine NiO's electronic and structural features due to lattice strain. Our work highlights the enhanced electrochemical performance of 2 % Ce-doped NiO and its potential as a good-quality supercapacitor material.

Controllable Synthesis of Manganese Organic Phosphate with Different Morphologies and Their Derivatives for Supercapacitors.

Morphological control of metal-organic frameworks (MOFs) at the micro/nanoscopic scale is critical for optimizing the electrochemical properties of them and their derivatives. In this study, manganese organic phosphate (Mn-MOP) with three distinct two-dimensional (2D) morphologies was synthesized by varying the molar ratio of Mn2+ to phenyl phosphonic acid, and one of the morphologies is a unique palm leaf shape. In addition, a series of 2D Mn-MOP derivatives were obtained by calcination in air at different temperatures. Electrochemical studies showed that 2D Mn-MOP derivative calcined at 550 °C and exhibited a superior specific capacitance of 230.9 F g-1 at 0.5 A g-1 in 3 M KOH electrolyte. The aqueous asymmetric supercapacitor and the constructed flexible solid-state device demonstrated excellent rate performance. This performance reveals the promising application of 2D Mn-MOP materials for energy storage.

Effect of Ce-Doping on the Structural, Morphological, and Electrochemical Features of Co3O4 Nanoparticles Synthesized by Solution Combustion Method for Battery-Type Supercapacitors

This study investigates the potential of cerium (Ce) doping to improve the performance of cobalt oxide (Co₃O₄) nanoparticles as battery-type supercapacitor electrodes. Pure Co₃O₄ nanoparticles were synthesized via a solution combustion method and then doped with 2.5% (Ce-Co3O4) and 5% Ce (CeO2-Co3O4). Comprehensive characterization, including X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM), was used to analyze the impact of Ce doping on the material properties. XRD analysis confirmed the successful incorporation of Ce into the Co₃O₄ structure, with distinct CeO2 phases forming at higher doping levels. Ce doping resulted in decreased crystallite size and peak intensity, indicating reduced crystallinity and increased defect concentration. Raman spectroscopy corroborated these findings, showing a redshift that suggests weakened metal-oxygen bonds and smaller grain sizes due to Ce³⁺ incorporation. FESEM images demonstrated that Ce doping effectively reduced nanoparticle agglomeration, with 2.5% doping leading to smaller particles and 5% doping promoting a 2D flake-like morphology with increased porosity. Nitrogen adsorption-desorption measurements revealed a significant increase in surface area and pore volume for CeO2-Co₃O₄, facilitating improved electrolyte diffusion and reduced resistance, thereby enhancing electrochemical performance. Evaluation of the electrochemical properties of undoped and Ce-doped Co₃O₄ materials revealed a battery-like response in a three-electrode configuration. Notably, the CeO2-Co3O4 exhibited a superior specific capacity of 603.3 C g-1 at a current density of 1 A g-1, significantly exceeding the values of 368.5 C g-1 and 127.1 C g-1 achieved by Ce-Co3O4 and undoped Co3O4, respectively. Furthermore, the CeO2-doped Co3O4 demonstrated exceptional cyclic stability, retaining 87% of its initial capacity after undergoing 5000 charge-discharge cycles at a high current density of 10 A g-1. These results suggest that Ce doping is a promising strategy for optimizing Co₃O₄-based battery-type electrode materials, potentially leading to the development of high-performance and cost-effective energy storage systems.

Effect of oxygen-substituted lattice carbon in Ti3C2 MXene as anchoring material for Li-S battery: DFT calculations and experiments

Electrochemical processes involving the adsorption/desorption of polysulfides are usually related to the composition of adsorbed-sulfur electrode material. Here, we investigate the moderate influence of non-metallic O and C elements on anchoring property towards lithium polysulphides (LiPSs), whereby the adsorption behavior of 2D-Ti3C2 MXene with continuous O-substitution into C site is analyzed via density functional theory (DFT) calculations in concerning of reported inevitable oxygen in the lattice. The introduction of O into 2D-Ti3C2 lattice reduces the density of states of Ti elements near the Fermi level, thus weakening the Ti-S binding interaction. Ti3C2 MXene with C/O ratio of 3:1 (Ti3C2-C12O4 model) exhibits moderate adsorption superior to other compositions, where the calculated binding energies of S8 and Li2Sn (n = 8, 6, 4) are −2.88, −2.57, −2.31 and −2.19 eV atom−1, respectively. The substitution of O atom theoretically hinders the transfer of Li+ and reduces the energy barrier of S-migration, thus promoting the anchoring and transformation of LiPSs. Notably, consistent result is obtained from the comparative study on electrochemical performance of titanium oxycarbide with precisely different C/O ratios as alternative, considering the unpractical controlling of O-content in 2D-Ti3C2 and the homologous crystal structure. Titanium oxycarbide with C/O ratio of 3:1 (Ti(C,O)-C12O4) as anchoring material in Li-S battery exhibits a superior initial specific capacity of 841 mAh/g at 1C and fasten ion diffusion coefficients (1.92 cm2 s−1 and 2.94 cm2 s−1). This study suggest attention on regulatory effect of non-metallic elements in lattice instead of surface towards performance optimization of titanium-carbide-based material as host for sulfur cathode utilized in Li-S battery.

Synthesis and electrochemical properties of microcanals Mg-S-Cu-S as an electrode material for energy storage applications

The synthesis of novel nanostructured electrode materials is the community demand to overcome energy crises. Herein, the nanostructured copper-sulfide, copper-cadmium-sulfide and copper-magnesium-sulfide (Cu-S, Cd-S-Cu-S and Mg-S-Cu-S) electrodes are synthesized by chemical vapor deposition technique. The changes in crystal growth and surface morphologies of Cu-S, Cd-S-Cu-S and Mg-S-Cu-S electrodes are associated with the formation of heterostructures and change in energy fluxes. The weight % of Ni, Cu, S; Ni, Cd, Cu, S; and Ni, Mg, Cu, S are found to be 8, 62, 30; 6, 16, 48, 30; 15, 14, 45, 26 are observed in Cu-S, Cd-S-Cu-S and Mg-S-Cu-S electrodes respectively. The Mg-S-Cu-S electrode showed superior specific capacitance of 4393 and 5657 F/g at 1 mV/s and 1.0 A/g respectively. The maximum energy density and power density of Mg-S-Cu-S electrode are found to be 141 Wh/kg and 2120 W/kg respectively. The cyclic retention after 3000 cycles of Cu-S, Cd-S-Cu-S and Mg-S-Cu-S electrodes are found to be 80.8, 87.5 and 96.2 % respectively. The simulation results show that the Cd-S-Cu-S followed more capacitive-controlled while Mg-S-Cu-S followed more diffusive controlled process. Result show that the Mg-S-Cu-S electrode is comparatively more suitable for portable energy storage devices.