High Electrochemical Performance Research Articles

Superior conductive 1D and 2D network structured carbon-coated Ni-rich Li1.05Ni0.88Co0.08Mn0.04O2 as high-ion-diffusion cathodes for lithium-ion batteries.

Numerous studies have addressed the low electrical conductivity of Li1.05Ni0.88Co0.08Mn0.04O2 (Ni-rich NCM). Among these approaches, surface treatment using multiwalled carbon nanotubes (MWCNTs) has emerged as a promising strategy for enhancing the depolarization of Ni-rich NCM and improving its electrochemical performance. However, MWCNT coatings applied by various methods often result in agglomeration and increase the ion-transfer resistance of the coating layer, leading to degraded electrochemical performance. In this study, 1D and 2D network structures are assembled on Ni-rich NCM surfaces using a MWCNT solution dispersed in ethanol solvent by an incipient method. The resulting highly conductive network structure facilitates electron movement without interfering with Li-ion transport, enhancing the depolarization of Ni-rich NCM and enabling high electrochemical performance. The 1D and 2D network structure coated Ni-rich NCM exhibits an excellent rate capability of 87.64% at 3C/0.2C and a cycle retention of 94.53% after 50 cycles at 1C/1C. Moreover, the incipient method used herein effectively maximizes the electrochemical performance with less coating weight than other methods. These findings highlight the potential of the 1D and 2D network structure coated Ni-rich NCM for advanced energy storage applications.

Direct solid–vapor approach to 2D FeCoNiP@N-graphene-CNTs as robust electrode material for high-performance supercapacitors

Carbon supported bi(tri)-metallic phosphides are well known high-active electrode nanomaterials as it poses multiple redox sites, excellent electrochemical reversibility, and stability. In spite of that the synthesis of metal phosphides are limited as it involves multiple steps, harsh preparation conditions and often pose poor metal-support interactions. Herein, a simple and direct one-step solvent-free solid–vapor method was developed for the fabrication of bi(tri)-metallic phosphides supported N-graphene/N-CNTs 2D-nanosandwidch, first report to the best of our knowledge. Unique surface morphology, high surface area, good thermal stability and strong metal-support interaction, were confirmed for the as prepared electrocatalysts (FeNiP/NCNTs, FeCoP/NCNTs and FeNiCoP/NCNTs). In three electrode system, the FeNiCoP/NCNTs showed highest specific capacitance of 1479F/g at 1 A/g in 3 M KOH and excellent cycling stability, with capacitance retention of 90.8 % over 5000 cycles. Interestingly in the two-electrode system, the FeNiCoP/NCNTs demonstrated impressive capacitance of 245F/g at 1 A/g, power density of 10567 W/kg and energy density of 66.7 Wh/kg, with excellent retention of 91.5 % over 5000 cycles. The direct one-step preparation and high electrochemical performance inclusively promote the present FeNiCoP/NCNTs (with low metal loading of less than 10 wt%) as a promising supercapacitor electrode nanomaterial for energy storage applications.

Biomaterial-derived porous carbon doped with heteroatoms as a separator coating for high-energy–density Zn-I batteries

Chitin and phytic acid are abundant sustainable resources commonly found in shrimp shells, crab shells, and various plants. However, they are underutilized, and their biomass value is frequently underestimated. To address this, the current study developed a strategy to synthesize efficient separator coatings for zinc-iodine (Zn-I) batteries using chitin and phytic acid as carbon sources (biochar). First, nanosheets of porous carbon doped with N and P (NP-PC), featuring multiple active sites, are synthesized through in situ carbonization of chitin and phytic acid. Subsequently, the synthesized materials are coated onto the surfaces of glass fiber (GF) separators, effectively addressing several persistent challenges associated with Zn-I batteries. Notably, the modified separator (NP-PC@GF) enhanced the rapid-discharge capability of the involved battery, effectively inhibited the diffusion of intermediate polyiodide species, stabilized the electrolyte interface, suppressed irreversible dendrite formation, and increased I utilization efficiency. Consequently, the battery demonstrated high electrochemical performance, with an initial capacity of 7.8 mAh cm–2 at 20 mA cm–2, an initial specific capacity of 8.9 mAh cm–2 under high I loading, and a retention rate of 56% (5.1 mAh cm–2) at the 174th cycle. Overall, this research demonstrates the effective use of biochar for separator modification, facilitating the development of high-performance Zn-I batteries.Graphical

Small Molecule‐Assisted Thermal Radiation Synthesis of Super‐Sb Toward Ultrafast and Ultrastable Sodium Storage

AbstractNanostructure engineering of alloying‐type anodes is a key approach to achieving high electrochemical performance in sodium‐ion batteries (SIBs). Despite intensive efforts in traditional calcination methods, synthesizing high‐quality nanomaterials while maintaining ultrafine and homogeneous nanostructure under high temperature remains a key challenge. Herein, a one‐step small molecule‐assisted thermal radiation (MTR) method that fabricates ultrafine Sb nanoparticles with uniform dispersion across heteroatom‐doped carbon supports (Super‐Sb) is reported. This MTR method features the nonequilibrium synthetic conditions induced by ultrafast heating/cooling rate. Additionally, in situ, high‐temperature synchrotron X‐ray diffraction (SXRD) characterization of the MTR synthetic process demonstrates that the formation and stabilization of ultrasmall Sb nanoparticles can be ascribed to the simultaneous thermolysis of small‐molecule additives into defect‐rich carbon nanosheets. The as‐obtained Super‐Sb nanocomposite exhibits superior sodium‐ion storage performance in terms of ultralong cycling stability of 15 000 cycles at 20.0 A g−1 and ultrahigh rate capability of 152.8 mAh g−1 at 50.0 A g−1. Furthermore, in situ laboratory XRD and finite element analysis (FEA) demonstrate the structural advantages of the ultrafine nanoparticles in stress‐buffering effect. This study provides an effective strategy to manufacture high‐performance and high‐quality energy‐storage nanomaterials for advanced SIBs.

Cobalt-nickel sulfide hierarchical hollow microspheres to boost electrochemical activity for supercapacitors

Cobalt-nickel bimetallic sulfides are promising candidates for supercapacitors due to their high theoretical specific capacity, good electrical conductivity and fast redox kinetics. Nevertheless, they confront challenges such as poor cycling stability, volume expansion, and complicated synthesis methods. To address these issues, in this work, a MOF-assisted synthesis strategy is developed to achieve the one-pot formation cobalt-nickel sulfide hollow microspheres. The 2D nanosheet-constructed hierarchical hollow configuration promotes rapid electron/ion transfer, provides more active sites and effectively mitigates volume expansion during cycling. The optimized Co1Ni4S exhibits high electrochemical performance, such as a specific capacity of 277.2 mA h/g (2217 F g−1) at 1 A g−1, remarkable cycling stability with ∼100 % retention after 5000 cycles, and favorable rate capability with 84.8 % retention at 20 A g−1. Furthermore, an aqueous asymmetric supercapacitor (ASC) assembled with the Co1Ni4S and active carbon (AC) derived from lotus pollen achieves an energy density of 86.9 Wh kg−1 at 800.1 W kg−1, along with significant cycling stability (97.1 % retentions over 30,000 cycles). These superior results showcase a simple one-step method for developing superior-performing electrode materials applicable to advanced supercapacitors.

Composite Solid-State Electrolyte with Vertical Ion Transport Channels for All-Solid-State Lithium Metal Batteries.

Composite solid electrolytes (CSEs) consisting of polymers and fast ionic conductors are considered a promising strategy for realizing safe rechargeable batteries with high energy density. However, randomly distributed fast ionic conductor fillers in the polymer matrix result in tortuous and discontinuous ion channels, which severely constrains the ion transport capacity and restricts its practical application. Here, CSEs with highly loaded vertical ion transport channels are fabricated by magnetically manipulating the alignment of Li0.35La0.55TiO3 nanowires. The construction of densely packed, vertically aligned ion transport channels can effectively enhance the ion transport capacity of the electrolyte, thereby significantly increasing ionic conductivity. At room temperature (RT), the presented CSE exhibits a remarkable ionic conductivity of up to 2.5 × 10-4 S cm-1. The assembled LiFePO4/Li cell delivers high capacities of 118 mAh g-1 at 5 C at 60°C and a RT capacity of 115 mAh g-1 can be achieved at a charging rate of 0.5 C. This work paves an encouraging avenue for further development of advanced CSEs that favor lithium metal batteries with high energy density and electrochemical performance.

Composite Gel Polymer Electrolyte for High-Performance Flexible Zinc-Air Batteries.

Enhancing ionic conductivity and electrolyte uptake is of significance for gel polymer electrolytes (GPEs) for flexible zinc-air batteries (FZABs). Herein, a composite mesoporous silica/polyacrylamide (5 wt.% mPAM) GPE is constructed with comparable ionic conductivity to aqueous electrolytes, where the ionic conductivity is up to 337 mS cm-1, and the weight loss after exposing in air 72h is less than 18%, owing to the excellent electrolyte uptake and continuous ion migration network provided by the mesoporous silica fillers. When used as a quasi-solid-electrolyte, the rechargeable FZAB exhibited high electrochemical performance and structural stability, where the peak power density is up to 162.8mW cm-2, and the initial charge-discharge potential gap is as low as 0.62V, resulting in a long lifespan exceeding 110h, showcasing the combination of high durability, cost-effectiveness and easy production for practical applications.

Mechanically Robust Polyimide Binder Realizes Stable and High Electrochemical Performance for Micro-Silicon Anodes in Lithium-Ion Batteries.

Silicon anodes have been considered one of the most promising candidates for Li-ion batteries due to their high theoretical specific capacity. However, the practical use of silicon anodes is impeded due to side reactions and volumetric change (from 300~400%) charge/discharge process. Binders played a crucial role in Li-ion batteries by effectively mitigating the stress resulting from the volumetric expansion in silicon-based anodes. Herein, we developed a mechanically stable polyimide binder PI-CF3 that introduced trifluoromethyl and hydroxyl groups for commercial microparticular silicon anodes. With a highest Young's modulus of ~921.1 MPa, the binder presented the maximum resilience during the charging and discharging of Micro-Si, integrating the morphology, and reducing the degree to which the electrode disrupted ion and electric pathways. Moreover, -OH and -CF3 groups of the binder could potentially interact with oxide layer at the surface of silicon through hydron bonds, and thereby results in a cross-linking network to improve interface stability during cycling. The as-prepared PI-CF3 binder with excellent intrinsic mechanical and electro-rich groups stabilizes the electrode structure and facilitates fast Li+ transportation. Consequently, micro-Si anode delivered initial specific capacity of 1838 mAh g-1 (at 0.6 A g-1), and at high mass (Si loading = 0.78 mg cm-2) these was retained about 1219 mAh g-1 after 330 cycles (only -0.061% capacity reduction per cycle).

The role of ion beam in modification of CuO@NiO@ZnO/GO electrode for supercapacitor application

Recently, mixed transition metals oxides became emerging electrode materials for energy storage devices such as supercapacitors, batteries, etc. due to their high electrochemical performances. In this study, mixed transition metals including Copper oxide (CuO), Nickel oxide (NiO) and Zinc oxide (ZnO) in conjunction with graphene oxide (GO) were used to fabricate electrode materials for the supercapacitor applications adopting hydrothermal process. The features of the as-fabricated electrodes were further modified by irradiating them with 5.0 MeV C++ ions with varying fluence rates. Monte Carlo-based Stopping and Range of Ions in Matter (SRIM) simulation code was utilized to analyze the ion implantation-induced processes inside the target electrode. Electrodes' crystal features, morphologies, elemental compositions, and vibrational and optical characteristics were examined employing X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and UV–visible spectroscopy, respectively. Electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD), and cyclic voltammetry (CV) were among various techniques engaged to analyze the electrochemical properties of the pristine and post-implanted electrode materials. The electrochemical findings from CV and GCD for the electrode implanted with 5.0 × 1015 ionscm−2, which offered the best result presented enhanced specific capacitances of 1250 and 1350 Fg−1 at a scan rate 1.0 mVs−1 and current density 0.5 Ag−1 respectively. This study revealed that carbon ion implantation at a fluence 5.0 × 1015 ionscm−2 could prompt the enhancement of the electrochemical properties of this fabricated electrode material.

Reinforcement and toughening of the self‐piercing riveted bonded joints induced by the pre‐embedded adhesive in rivet cavities

AbstractSelf‐piercing riveted bonded (SPRB) joints are widely used in body‐in‐white (BIW) to connect dissimilar materials owing to their high fatigue and electrochemical performance. However, the strength of the SPRB joint has been found to be inferior to that of self‐piercing riveted (SPR) joints, owing to the reduction in undercut induced by the introduction of an adhesive, especially under pull‐out loading conditions. Interestingly, the mechanical strength improved when the rivet cavity was pre‐embedded with an adhesive. Before the riveting process, the rivet cavities in SPRB joints were pre‐embedded with 0.01, 0.02, and 0.03 mL of adhesive, namely them PSPRB‐V1–V3, respectively. Finite element (FE) models of SPRB and PSPRB joints were developed to analyze their formability and mechanical properties. The simulated and experimental results showed that the hydraulic pressure in the rivet cavity increased as the pre‐embedded adhesive volume in the rivet cavity increased during the riveting process, which further improved the undercut, microhardness, effective bearing area, and mechanical properties of joints. Among the prepared PSPRB joints, the PSPRB‐V3 joint exhibited the best undercut and optimal mechanical properties. Specifically, its undercut and peak force increased by 16.43% and 12.87% compared with those of SPRB joints. These findings provide important guidance for designing steel‐aluminum SPRB joints that require high‐bearing capabilities.Highlights The effect of pre‐embedded adhesive on the SPRB joint cross‐section was studied. Failure mechanisms of the SPRB and PSPRB joints were investigated via FEM. The better PSPRB joint performance over SPRB joints was elucidated. The stress–strain history was considered in the FE model of the joint failure process. Strengthening mechanism of pre‐embedded adhesive in the rivet cavity was discussed.

High ionic conductive sodium β-alumina (SBA) and SBA-NaPF6 composite solid electrolytes prepared by cold sintering process

Sodium β-alumina (SBA) electrolytes are among the most excellent candidates for all-solid-state batteries due to their high electrochemical performances and low cost of sodium resources. However, thermally sintering at above 1400 °C is required to fabricate high dense SBA electrolytes, thus giving rise to a huge energy consumption. Here, dense SBA electrolytes and (1-x)SBA-xNaPF6 (x = 5, 10, 15, 20 wt%) composites were fabricated using cold sintering process (CSP) below 300 °C with 2 mol/L NaOH solution as transient chemistry. The ionic conductivity of SBA electrolytes is significantly enhanced from 5.53×10-6 S cm-1 to 5.91 × 10−4 S cm−1 as 15 wt% NaPF6 was introduced to the composite, which is comparable with the SBA sintered above 1400 °C. CSP may provide a promising approach for the fabrication of solid-state electrolytes by avoiding the detrimental impact of high temperature heat treatment.

Facile synthesis and first principles calculations of Li-MoS2/rGO nanocomposite for high-performance supercapacitor applications

Two-dimensional (2D) nanostructured materials such as graphene oxide nanosheets and molybdenum disulfide (MoS2) are potential candidates for electrochemical energy storage applications. The layered structure of MoS2 makes it a promising active electrode material for supercapacitors. Lithium (Li) interacted with MoS2/reduced graphene oxide (Li-MoS2/rGO) nanocomposite has been synthesized in two steps using a sonochemical dispersion method, and a one-pot hydrothermal method resulting in few-layered MoS2/rGO nanosheets of 2D heterointerfaces. The Li-MoS2/rGO nanocomposite exhibits a high specific capacitance of 173.3 F g−1 at a current density of 1 A g−1. Furthermore, an asymmetric supercapacitor device fabricated with Li-MoS2/rGO achieves a good energy density of 10.6 Wh kg−1 at a power density of 686.3 W kg−1 and outstanding cycling stability with 81.2 % capacity retention over 10,000 cycles. The dispersion of 2D-MoS2 in water is due to the strong electrostatic interface. The structural and electronic properties are theoretically calculated for pristine and Li-interacted MoS2/rGO heterostructure using density functional theory. A comparison of the density of states plots of the two heterostructures and the difference charge density plot of Li-MoS2/rGO heterostructure clearly brings out the importance of the presence of Li. A value of 64 μF cm−2 for the quantum capacitance for pristine MoS2/graphene heterostructure increases to a value 99 μF cm−2 corroborating the experimental observations and we assign this change to the transfer of charge from the Li atom to the outer S atoms in the MoS2/graphene heterostructure. This comprehensive approach, combining experimental synthesis with computational modelling, significantly advances the development and optimization of high-performance supercapacitor materials in the energy storage field. The Li-MoS2/rGO nanocomposite has excellent electrochemical specific capacitance and long-term cyclic stability and has been effectively used for supercapacitor applications with high electrochemical performance.

Elucidating the effect of annealing temperature on the atomic-level surface structure evolution and electrochemical performance of Mo doped LiMn2O4 cathode materials

Critical barriers to the extensive applications of the spinel LiMn2O4 cathodes include grievous capacity degradation and structural collapse. Bulk elemental doping combining surface modification, which is a common approach to address these challenges. Here, synchronous bulk Mo-doped and in-situ surface reconstructed layer coated LiMo0.02Mn1.98O4 cathodes are prepared by tuning the annealing temperatures. Using the spherical aberration-corrected scanning transmission microscopy (Cs-STEM) technique, we demonstrate that part of Mo6+ ions dopes into the octahedral Mn 16d sites to form LiMo0.02Mn1.98O4 that strengthens bulk structural stability. The other part of Mo6+ ions or the Mn atom occupying the Mn 16c sites of the spinel to form a surface reconstructed layer on the outermost surface that suppresses the side reaction and slows down the decomposition of the electrolyte. Specifically, the LiMo0.02Mn1.98O4 cathode calcined at 750 °C with an appropriate surface reconstructed layer exhibits an outstanding capacity retention of 76.28 % after 1000 cycles at 10C at 25 °C. Our work provides a simple and novel way toward high electrochemical performance tuning for spinel LiMn2O4 cathodes.

Amino Acid Supported Conductive Nanocomposite for Developing Flexible Electrode Material for Energy Storage

Introduction: This study focused on synthesizing biocompatible, flexible and wearable electrode materials for energy storage applications. The unique zwitterionic structure of L-proline provides numerous interesting properties to the nanocomposite such as high ionic interactions through the various ion migration channels, and strong hydration characteristics. These features are key to thehigh performance of energy deposition systems.Methods: Binary nanocomposites containing L-proline (Pro) amino acid and polypyrrole (Ppy) were produced on rGO modified carbon textile (rGO-CC) to develop electroactive materials. Two step hydrothermal method was used to produce flexible electrodes. DRIFT spectroscopy andAFM analysis were performed to clarify the structural and the morphological characterization. Electrochemical behavior was evaluated utilizing CV, GCD and EIS methods.Results: ProPpy@rGO-CC electrode materials exhibit high electrochemical performances in aqueous electrolytes (0.1 M NaCl). The prepared electrode shows high specific capacitance of 500.4 Fg-1 (at 25 mVs−1) at the ambient conditions. Additionally, after 5,000 charge/discharge cycles the specific capacitance retains a high level of 95% confirming the good cycle stability. The energy and the power densities were found to be 278 Wh kg−1 and 12.5 kW kg−1, respectively.Conclusion: The results indicate that the ProPpy@rGO-CC electrode is a promising candidate for next-generation high-performance energy deposition systems. The unique structural features of L-proline contribute to the formation of a large number of electroactive sites and short diffusion pathways.

Fluorine-Free Cycloaliphatic Epoxy-Based Siloxane Nanohybrid Binder with High Polar Hydroxyl Group Content Enabling LiFePO4-Type Battery with High Electrochemical Performance and Stability.

LiFePO4-type (LFP) batteries have attracted significant attention in most battery manufacturing industries due to their long lifespan, high-temperature safety, and low cost of raw materials. However, as an active material, LFP still suffers from several intrinsic drawbacks, including poor conductivity, a low Li+ diffusion coefficient, low capacity, and a lack of electrochemical stability, primarily due to conventional fluorine-based binders. Here, we report a simple yet effective approach to developing a fluorine-free binder based on a robust cycloaliphatic epoxy-based siloxane nanohybrid material (CES) to achieve high electrochemical stability in LFP batteries. The high content of silanol moieties in CES induces a strong affinity for the active material and conductive agent, significantly improving rheological (thixotropy) and mechanical (adhesion and cohesion) properties, which enable the formation of a uniformly coated electrode. As a result, we achieved superior electrochemical performance and stability in CES-applied electrodes compared to those with conventional fluorine-based binders. We investigate the reasons behind the contribution of CES to the electrochemical stability of LFP batteries through various analyses. The high thermal and oxidation stability of CES effectively prevents degradation of LFP-based active materials. Our binder development strategy offers a significant breakthrough in replacing conventional fluorine-based binders, advancing the development of high-performance and stable secondary batteries.

Regulation plateau capacity and initial coulombic efficiency of furfural residues-derived hard carbon via components engineering

The scale-up application of biomass-based hard carbon (HC) in sodium-ion battery (SIB) is hampered by low initial coulombic efficiency (ICE) and specific capacity, especially for the plateau capacity. By taking advantage of furfural residues (FRs), which are mainly constructed with lignin and cellulose, a component modulation engineering strategy is adopted to prepare high performance HC. In this work, the microstructure of FR-derived HCs can be well-regulated after component modulation. Specifically, the introduction of oxygen functional groups during low-temperature oxidation process promotes the recombination of cellulose and lignin in FRs and produces more C=O in oxidized FRs, which is favorable to suppress the carbon structure from melting and rearranging during the high-temperature carbonization process, leading to a well-balanced pseudo-graphitized/disordered microstructure and excellent corresponding electrochemical performance. Experiment results reveal that the sample underwent component engineering delivers a high capacity of 302.5 mAh g−1 and excellent ICE of 90.9 %, which are higher than that of the sample direct carbonized (225.0 mAh g−1 and 75.6 %). Notably, the plateau capacity increases from 147.0 mAh g−1 to 204.2 mAh g−1, accounting for nearly 100 % of the reversible capacity increase. Our work provides a new insight of microstructure regulation of biowaste-based HC with high electrochemical performance.

Iron and Nitrogen-Doped Wheat Straw Hierarchical Porous Carbon Materials for Supercapacitors.

In this paper, we prepared a new type of iron and nitrogen co-doped porous carbon material (WSC-Fe/N) using a carbonization-activation process with wheat straw as a precursor and FeCl3 and NH4Cl as co-doping agents and analyzed the electrochemical properties of the resulting electrode material. Through precise control of the doping elements and carbonization temperature (900 °C), the resulting WSC-Fe/N-900 material exhibits abundant micropores, uniform mesopores, a significant specific surface area (2576.6 m2 g-1), an optimal level of iron doping (1.7 wt.%), and excellent graphitization. These characteristics were confirmed through X-ray diffraction and Raman spectroscopy. Additionally, the WSC-Fe/N-900 electrode demonstrated a specific capacitance of 400.5 F g-1 at a current density of 0.5 A g-1, maintaining a high capacitance of 308 F g-1 even at 10 A g-1. The solid-state symmetric supercapacitor in an aqueous electrolyte achieved an energy density of 9.2 Wh kg-1 at a power density of 250 W kg-1 and maintained an energy density of 6.5 Wh kg-1 at a power density of 5000 W kg-1, demonstrating remarkable synergistic energy-power output characteristics. In terms of structural properties, the porous characteristics of WSC-Fe/N-900 not only enhance the specific surface area of the electrode but also improve the diffusion capability of electrolyte ions within the electrode, thereby enhancing capacitance performance. The reliability of the electrode material demonstrated good performance in long-term cycling tests, maintaining a capacitance retention rate of 93% after 10,000 charge-discharge cycles, indicating excellent electrochemical stability. Furthermore, over time, the aging effect of the WSC-Fe/N-900 electrode material is minimal, maintaining high electrochemical performance even after prolonged use, suggesting that this material is suitable for long-term energy storage applications. This study introduces a novel strategy for producing porous carbon materials for supercapacitors, advancing the development of economically efficient and environmentally friendly energy storage solutions.

Architecting V2O5 with a Triune Crystal Water-Amorphous-Crystalline Feature for Robust Zinc-Ion Batteries.

The notorious collapse of the electrode structure and strong electrostatic interactions in aqueous zinc-ion batteries (AZIBs) limit the achievement of a long cycle life. Herein, by designing an ordered/disordered hybrid structure, we have effectively preserved the integrity of the V2O5·1.6H2O (VOH) electrode. Moreover, our approach facilitates the release of stress concentration contributed to by the amorphous component, alleviating the strong electrostatic interaction merited by crystal water and promoting the diffusion kinetics of Zn2+ assisted by the crystalline component. Noteworthy, the crystal water serves as an interlayer pillar significantly enhancing the structural stability of the electrode. As a result, our VOH electrode exhibits high electrochemical performance. It delivered 227.8 mAh g-1 at a higher current density of 2 A g-1, and a high cycle life of 1000 cycles with 95% capacity retention was achieved at a current density of 1 A g-1.

Microstructure reconstruction via confined carbonization achieves highly available sodium ion diffusion channels in hard carbon

Hard carbon is considered as the main candidate negative electrode material for sodium-ion batteries (SIBs) due to its high stability and electrochemical performance. However, the complex carbon structure and composition of hard carbon are difficult to achieve precise control during the preparation process, which leads to difficulties in accurately determining the attribution of electrochemical behavior. Here, we propose a confined carbonization strategy to achieve microstructure reconstruction of hard carbon, characterized by the anchoring of polymers in the mesopores of porous carbon to generate ordered carbon structures at high temperatures. The stacking of ordered carbon on micropores in porous carbon achieves the transition from exposed pores to closed pores (nano cleithral pores). Through mechanism detection, it is found that the ordered carbon structure provides sub nanochannels for sodium ion migration, which contributes to high slope capacity. In addition, the nano cleithral pores are sites filled with sodium ions and provide high plateau capacity. Benefiting from theses available sodium ion transport channels, carbon materials have achieved a transition from surface-controlled process to diffusion-controlled process in the sodium storage process via confined carbonization. The as-prepared carbon delivers a superior capacity of 356.2 mAh g–1 (215.6 mAh g–1 for plateau capacity) at 20 mA g–1 with excellent rate and cycling performance. This work reveals the correlation between structure and electrochemical performance for carbon electrode, providing profound guidance for the precise preparation of high-performance carbon materials.

Tip effect of NiCo-LDH with low crystallinity for enhanced energy storage performance of yarn-shaped supercapacitors

Layered double hydroxides (LDHs) are considered promising materials for supercapacitor applications. However, the development of yarn-shaped supercapacitors (YSCs) with high electrochemical performance utilizing LDHs remains challenging. In this study, the NiCo-LDHs with various morphologies (nano-needles, nano-sheets, needle-sheet composites, and nano-flowers) were grown on carbon nanotubes (CNTs)-functionalized cotton yarn via a co-precipitation technique for YSC applications. Among these, the yarn incorporating nano-needle NiCo-LDHs exhibited reduced crystallinity yet demonstrated a superior areal capacitance compared to other morphologies, following a diffusion-controlled process. Finite element simulations were subsequently conducted to investigate this phenomenon, revealing that the lower-crystallinity nano-needle NiCo-LDHs accumulated a greater charge at their tips, thereby enhancing redox reactions and achieving higher energy storage capacitance. Subsequently, the yarns with nano-needle NiCo-LDHs were assembled into flexible quasi-solid-state symmetric YSCs, achieving a peak areal capacitance of 124.27 mF cm−2 and an exceptionally high energy density of 39.4 μWh cm−2 at a current density of 0.2 mA cm−2. Furthermore, our YSCs can be scaled up through serial or parallel connections and integrated into fabrics, making them suitable for wearable energy storage applications. This work provides an efficient method for fabricating high-performance YSCs and demonstrates significant potential for wearable energy storage devices.