High Electrochemical Performance Research Articles

Design and Functionalization of Lignocellulose‐Derived Silicon‐Carbon Composites for Rechargeable Batteries

AbstractSilicon/carbon (Si/C) composites present great potential as anode materials for rechargeable batteries since the materials integrate the high specific capacity and the preferable cycling stability from Si and C components, respectively. Functional Si/C composites based on lignocellulose have attracted wide attention due to the advantages from lignocellulose, including sustainability property, flexible structural tunability, and diverse physicochemical functionality. Although the flourishing development of rechargeable batteries boosts the studies on lignocellulose‐derived Si/C materials with high electrochemical performance, the publications that comprehensively clarify the design and functionalization of these high‐profile materials are still scarce. Accordingly, this review first systematically summarizes the recent advances in the structural design of lignocellulose‐derived Si/C composites after a brief clarification about the Si selection sources based on self and extraneous sources. Afterward, the functionalization strategies, including nanosizing, porosification, and magnesiothermic reduction of Si material as well as heteroatom modification of C material, are specifically highlighted. Besides, the applications of lignocellulose‐derived Si/C‐based materials in rechargeable batteries are elaborated. Finally, this review discusses the challenges and prospects of the application of lignocellulose‐derived Si/C composites for energy storage and provides a nuanced viewpoint regarding this topic.

Reactive crystallization regulation for synthesizing NCM811 precursor by different impellers

The spherical and dense precursors with a narrow particle size distribution are essential to achieve high electrochemical performance in cathode materials. Four newly designed impellers, including the punched-flow turbine (PFT), punched-flow disc turbine (PFDT), curved-inclined-blade disc turbine (CIBDT), and 6-folded-pitched turbine (FPT-6), are applied to prepare the precursors to investigate the interplay among the fluid flow state, precursors’ morphology and growth, and physicochemical properties of cathodes. The flow and mixing features of double impellers are predicted using computational fluid dynamics, indicating that the FPT-6 plays a crucial role in crystal nucleation while PFDT facilitates crystal growth. This concurrence can be corroborated by examining the performance of precursors synthesized using these four impellers. It is first found that the electrochemical performance is distinctly enhanced by utilizing different impellers to regulate the specified nucleation and growth stage. By increasing the nucleation rate with double impellers of FPT-6, the tap density and sphericity of the precursor and cathode materials are significantly improved. The discharge capacity of cooperative agitators (FPT-6+PT) is 2.1 times that of the only propeller turbine at a high current density (10 C). The later growth stage is suitably regulated by FPT-6 or PFDT; properly extended reactive time can enhance the sphericity and electrochemical performance. The dual mixed-impeller (PT/CIBDT) combines intense mixing and shear ability, attaining a dense spheroid with a highly smooth surface. The cycle retention of this cathode is increased by 10.35% after 200 cycles at 1 C compared to a commercial counterpart. A regulatory strategy for the reactive co-precipitation process to enhance precursor stability is proposed here. Furthermore, the optimal operation parameters derived from this strategy can be effectively applied to commercial cathode materials.

Enhanced dopamine detection using Ti3C2Tx/rGO/Pt ternary composite synthesized via microwave-assisted hydrothermal method

A novel electrochemical sensing platform for dopamine (DA) detection was developed by fabricating the ternary composite of Ti3C2Tx MXene (M) and reduced graphene oxide (rGO) with platinum nanoparticles (Pt NPs) through microwave-assisted hydrothermal heating. The exceptional electrical conductivity and rich surface chemistry of MXene provide abundant active catalytic sites for electrochemical reactions, while the large surface area of rGO facilitates ion and electron pathways. The integration of rGO in the MXene sheet, forming MXene-rGO (M_rGO) heterostructure composite, imparts long-term stability to the 2D heterostructure while providing additional electron pathways and significantly enhancing conductivity. Pt NPs synergistically increased the electrocatalytic activity of the electrochemical sensor's performance. Ternary nanocomposites were fabricated with different weight percentages (wt.%) of Pt NPs, ranging from 5 to 20. Characterizations of the samples (rGO, M, M_rGO, and 5–20 wt% Pt@M_rGO) were conducted through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy (RAMAN), and X-ray spectroscopy (XPS). Electrochemical evaluations of the samples were investigated in 0.1 M phosphate buffer solution (PBS) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analyses. The analysis revealed that the ternary composite with 5 wt% of Pt NPs (5% Pt@M_rGO) exhibited a uniform well-distribution of Pt NPs and the highest oxidation peak for DA oxidation in CV studies. The presence of metal nanoparticles, aided by the synergistic effects between the MXene and rGO, resulted in an excellent DA sensor with a 0.147 μM detection limit from 1 to 14 μM linearity range. The sensor demonstrated outstanding selectivity, reproducibility (RSD values of 8.10%), repeatability (RSD value of 2.46%) and, excellent stability over 14 days. In human urine samples, the sensor exhibited excellent DA recovery (88.62–110.65%). This study significantly advances the development of electrochemical sensors for DA detection by introducing a rapid, facile and, efficient method for fabricating ternary composites. The fabricated sensor exhibited high sensitivity, excellent selectivity, and robust electrochemical performance, offering valuable insights into human and behavioral health advancements.

Collaborative interface optimization strategy guided Fe3C/MnO-NC electrocatalysts for rechargeable flexible zinc-air batteries

The flexible zinc-air batteries characterized by heightened flexibility, durability, and high electrochemical performance have been recognized as the most promising candidates for the next-generation wearable electronic products. Herein, a novel Fe3C/MnO heterostructure coupled with nitrogen-doped carbon (Fe3C/MnO-NC) derived from metal-organic frameworks (MOFs) is innovatively designed as a highly active bifunctional electrocatalyst. The Fe3C/MnO heterostructure in Fe3C/MnO-NC can effectively regulate the electronic structure to optimize the free energy of the related intermediates in the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), consequently improving the catalytic properties of liquid Zn-air battery with impressive power density and outstanding stability. The theoretical calculations reveal that the design of the heterogeneous Fe3C/MnO interface effectively tunes the electron distribution to optimize the adsorption energy of ORR/OER related intermediates and significantly promotes intrinsic ORR/OER activities. Notably, the flexible Zn-air battery was also assembled with the bifunctional Fe3C/MnO-NC electrocatalyst and the prepared polyacrylamide polyacrylic acid-glycerin composite gel polymer electrolyte (PAM-PAA-Gly GPE). The electrochemical results reveal that the constructed flexible Zn-air battery can achieve a remarkable open-circuit voltage of 1.50 V and sustain stable cycling for 48 h (288 cycles). This work not only sheds light on the effective utilization of Fe3C/MnO-NC catalysts but also highlights the potential of hydrogels in achieving high-performance wearable Zn-air batteries.

LaMnO3-Mn3O4 nanocomposite: Synergetic effect towards high electrochemical performance

Metal oxides have been a focus of research for energy storage devices. Herein, xLaMnO3 – (100-x) Mn3O4 (LMO-MO) composites (xwt%: 100, 90, 70, and 50) were prepared via one-pot synthesis to elucidate the synergistic effect of the composite constituents on composite’s electrochemical performance. The X-ray diffraction analysis confirmed the presence of individual compounds in the desired ratio and phase. The X-ray photoelectron spectroscopy confirmed the presence of Mn2+ and Mn3+ oxidation states, indicating the presence of both LaMnO3 (LMO) and Mn3O4 (MO) in the composite. The electrochemical performance of composite electrodes prepared using nickel foam was assessed in 1 and 6 M KOH solutions. High specific capacitance measured via cyclic voltammetry of ∼ 770 Fg−1 at a scan rate of 1 mVs−1 was recorded for the composite of LMO-MO (70 %: 30 %) in 6 M KOH. At the same time, charge-discharge curves revealed a maximum specific capacitance of around 405 Fg−1 for an x =70 % sample at a current density of 0.5 Ag−1. The EIS studies show a reduction in the internal resistance of the composite due to the interconnected structure and reversible faradic process at the interface with a high degree of Coulombic efficiency. A higher overall electrochemical performance of the electrode was recorded in a 6 M KOH electrolyte. The enhanced electrochemical performance of the composite is attributed to efficient charge transfer kinetics through the electrode-electrolyte interface via easy electron hopping pathways between LMO and MO in the composite. These findings suggest that the studied LMO-MO composites could be a potential material for pseudocapacitor energy devices.

Modification of polypropylene separator with multifunctional layers to achieve highly stable sodium metal anode

Separator modification is an effective approach to suppress dendrite growth to realize high-energy sodium metal batteries (SMBs) in practical applications, however, its success is mainly subject to surface modification. Herein, a separator with multifunctional layers composed of N-doped mesoporous hollow carbon spheres (HCS) as the inner layer and sodium fluoride (NaF) as the outer layer on commercial polypropylene separator (PP) is proposed (PP@HCS-NaF) to achieve stable cycling in SMB. At the molecular level, the inner HCS layer with a high content of pyrrolic-N induces the uniform Na+ flux as a potential Na+ redistributor for homogenous deposition, whereas its hollow mesoporous structure offers nano-porous buffers and ion channels to regulate Na+ ion distribution and uniform deposition. The outer layer (NaF) constructs the NaF-enriched robust solid electrolyte interphase layer, significantly lowering the Na+ ions diffusion barrier. Benefiting from these merits, higher electrochemical performances are achieved with multifunctional double-layered PP@HCS-NaF separators compared with single-layered separators (i.e. PP@HCS or PP@NaF) in SMBs. The Na||Cu half-cell with PP@HCS-NaF offers stable cycling (280 cycles) with a high CE (99.6%), and Na||Na symmetric cells demonstrate extended lifespans for over 6000 h at 1 mA cm−2 with a progressively stable overpotential of 9 mV. Remarkably, in Na||NVP full-cells, the PP@HCS-NaF separator grants a stable capacity of ∼81 mA h g−1 after 3500 cycles at 1C and an impressive rate capability performance (∼70 mA h g−1 at 15C).

Nanostructured thin film SrCo0.8Nb0.1Ta0.1O3-δ cathode for low-temperature solid oxide fuel cells

Nanostructured perovskite-type cathodes are considered essential for the realization of high-performance solid oxide fuel cell (SOFC). However, perovskite-type cathode materials demonstrating high electrochemical performance in the low-temperature operating region below 600° are limited. SrCo0.8Nb0.1Ta0.1O3-δ (SCNT) has been identified as a material that exhibits exceptional performance even in the low-temperature region of 500 °C. This paper investigates the growth behavior and electrochemical properties of SCNT thin films for SOFC cathode applications. Pulsed laser deposition (PLD) was employed to fabricate SCNT films under varying chamber pressures: 5 mTorr, 75 mTorr, and 150 mTorr. Systematic analysis through X-ray diffraction and X-ray photoelectron spectroscopy indicates that the structural factors of PLD perovskite oxide nanostructures, such as grain size, porosity, and in-plane connectivity, are intricately influenced by deposition pressure without affecting crystallinity and chemical composition. The findings demonstrate that achieving desired electrochemical properties of the nanostructured PLD perovskite oxide necessitates specific optimal deposition conditions for these structural parameters. Electrochemical assessments revealed an optimal nanostructure achieved with 1200 nm at 75mTorr, demonstrating enhanced power density due to increased active reaction surface area, which significantly reduced resistances in ohmic and polarization. Excessive thickness, however, led to performance decline due to film delamination. Integration of optimized SCNT films into an anodic aluminum oxide supported thin film SOFC exhibited 907 mW/cm2 of peak power density at 550 °C.

Self-Healing fluorinated polymer deep eutectic electrolytes for stable lithium metal batteries

Lithium metal batteries (LMB) have attracted great attention in the last two decades for their high theoretical capacity and ultralow redox potential. However, LMB commercial applications still face safety risks such as electrolyte leakage, short circuits and even spontaneous combustion. Fluorinated polymer electrolytes have the advantages of high thermal stability and wide electrochemical window, endowing them an ideal alternative to liquid electrolytes. This work draws inspiration from the self-healing mechanism by introducing 2-ureido-4-pyrimidinone (UPy) units and successfully demonstrates that the fluorinated polymer deep eutectic electrolytes (FPDE) show high electrochemical performances in LMB. Self-healing structural units can alleviate the volumetric expansion of lithium anode during the charging and discharging process, while the fluorinated group endow the electrolyte wide electrochemical window, high migration number and superior interface stability. The joint effect of deep eutectic electrolytes and fluoroalkane makes FPDE show excellent flame-retardant performance with 0 s self-extinguish time. Symmetric Li||Li cell using the FPDE shows stable performance up to 6000 h. The full cell with Li||FPDE||LFP provides 80.4 % capacity retention after 600 cycles. This work might show some potential for development high safety LMBs.

Self-assembled formation of platinum single atoms and nanoclusters stabilized on MXene as an efficient catalyst for boosting electrocatalytic hydrogen evolution

Atomic isolated and dispersed single atom catalyst is ideal for high-performance industrial catalyst. However, the contribution from small amounts of nanoclusters coexisting with single atoms to the catalytic reaction activity is often neglected. In this work, a MXene-supported uniformly dispersed Pt single atoms and nanoclusters (Pt1+Ptn/MXene) were obtained by self-assembly through an impregnation method. The catalyst exhibits high electrochemical performance in the hydrogen evolution reaction with an overpotential of only 61.3 mV and a Tafel slope of 32.5 mV dec−1 at a current density of 10 mA cm−2 in an acidic environment. The XAFS analysis and further DFT calculation indicate that the synergistic effect between single atoms and nanoclusters can facilitate adsorption of H* and promote the HER reaction. This work provides an efficient method for integrating multiple active sites in noble metal catalysts.

High-energy fiber-shaped calcium-ion batteries enable integrated wearable electronics for human body monitoring

Electronic textiles hold the merits of high conformability with the human body and natural surrounding, possessing large market demand and wide application foreground in smart wearable and portable devices. However, their further application is largely hindered by the shortage of flexible and stable power sources with multifunctional designability. Herein, a free-standing ZnHCF@CF electrode (ZnHCF grown on carbon nanotube fiber) with good mechanical deformability and high electrochemical performance for aqueous fiber-shaped calcium ion battery (FCIB) is reported. Benefiting from the unique Ca2+/H+ co-insertion mechanism, the ZnHCF@CF cathode can exhibit great ion storage capability within a broadened voltage window. By pairing with a polyaniline (PANI)@CF anode, a ZnHCF@CF//PANI@CF FCIB is successfully fabricated, which exhibits a desirable volumetric energy density of 43.2 mWh cm−3 and maintains superior electrochemical properties under different deformations. Moreover, the high-energy FCIB can be harmoniously integrated with a fiber-shaped strain sensor (FSS) to achieve real-time physiological monitoring on knees during long-running, exhibiting great promise for the practical application of electronic textiles.

Effects of surfactants on the morphologies, structures, and electrochemical activities of WO3/Ag2O nanocomposites for supercapacitor electrodes

For energy storage, supercapacitors have been extensively developed. Among them, pseudocapacitors that use faradaic reactions of conductive polymers and transition metal oxides exhibit high electrochemical performance. In this study, WO3-based electrodes for high-performance pseudocapacitors were designed with Ag2O and various surfactants, with the aim to extend of the potential range and shape control of WO3 crystals. The WO3/Ag2O nanocomposites were prepared on a carbon cloth via chemical bath deposition with different types of surfactants: cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Pluronic F-127. Both Ag and the surfactants affected the morphology of the WO3 crystals; their crystal sizes were decreased, and the crystallinity was improved. The specific capacitance of the WO3/Ag2O nanocomposite was 621 F/g at 5 mV/s, whereas that of WO3 was 397 F/g. Furthermore, the specific capacitance of the nanocomposites increased with the use of surfactants: 960 F/g for WO3/Ag2O@Pluronic F-127, 641 F/g for WO3/Ag2O@CTAB, and 846 F/g for WO3/Ag2O@SDS at 5 mV/s. WO3/Ag2O@Pluronic F-127 had superior capacitance and exhibited a charge/discharge capacitance retention rate of 135 % after 2000 cycles at 5 A/g. The symmetric electrode configuration of WO3/Ag2O@Pluronic F-127 exhibited a maximum energy density of 85 W h kg−1 and a power density of 670 W kg−1. These results highlight the significant potential of the WO3/Ag2O@Pluronic F-127 nanocomposite electrode for future energy storage devices.

In-situ cladding PEDOT:PSS on V-doped NCA cathodes for optimized interface and high electrochemical performance of Li-ion battery

The LiNi0.8Co0.15Al0.05O2 (NCA) nickel-rich layered cathode material is widely used for Li-ion batteries because of its excellent structural stability and high specific capacity. However, the Li/Ni mixing effect and the generation of interfacial secondary reactions in NCA cathode materials reduce the electrochemical properties of Li-ion batteries. Herein, we report a series of vanadium (V)-doped NCA cathode (VNCA) materials with different amounts of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) polymers in-situ coated on the surface using a liquid-phase method. The introduction of PEDOT:PSS coating not only improves the conductivity of NCA cathode materials but also protects the surface of cathode materials from cracking during the cycle. Electrochemical results show that the PEDOT:PSS (2 wt%) coating possesses high capacity retention rate (83.58%) after 200 cycles at 1 C, which is better than that of the sample without coating (66.7%). The PEDOT:PSS (2 wt%) coated cathode materials also display superior rate performance to VNCA at high magnification. This work provides new methods and theoretical guidance for the development of efficient ternary cathode materials for Li-ion batteries.

Biomass nanostructure: Cattail leaves derived-porous carbon with high electrochemical performance for Zn-ion hybrid supercapacitors

Biomass-derived porous carbon possesses several advantageous characteristics, such as low cost, inherent properties, and a controllable structure, making it an ideal electrode material for Zn-ion hybrid supercapacitors (ZIHSs). In this investigation, we used cattail leaves (CLs) as the carbon source and employed carbonization and activation techniques to fabricate porous carbon. We aimed to explore the correlation between the morphology, oxygen content, and defects in porous carbon derived from CLs under varying K2CO3 ratios. Remarkably, when the K2CO3/carbon ratio was adjusted to 2:1, the resulting porous carbon from CLs exhibited outstanding electrochemical performance in ZIHSs. These ZIHSs, functioning in an aqueous electrolyte, displayed impressive rate capability, achieving 158.3 mAh g−1 at 0.1 A g−1 and 60.2 mAh g−1 at 20 A g−1, along with a high energy density of 119.5 Wh kg−1. Furthermore, they exhibited exceptional long-term durability with nearly 100 % coulombic efficiency over 10,000 cycles. Additionally, a quasi-solid-state ZIHSs device demonstrated satisfactory specific capacity (148.54 mAh g−1 at 0.1 A g−1) and maintained stability under various orientations. The abundant, renewable, and cost-efficient biomass-derived carbon obtained in this study serves as a valuable guide for the development of portable energy storage devices that are both low in cost and high in performance, thereby contributing to sustainable energy solutions.

Introducing surface adsorption lithium storage mechanism to enhance safety of graphite

The thermal stability of lithiated graphite plays an important role in the thermal safety of lithium-ion batteries (LIBs). However, a safer graphite anode usually leads to a lower energy density. This article starts from multiple hazardous factors of lithiated graphite when thermal runaway occurs, considering the impact of defects on the electrochemical performance and thermal safety of graphite electrodes. In this study, turbostratic graphite was prepared as the anode for LIBs. The stacking of graphite was altered to form narrow pores and spherical aggregates, and introducing defects. By varying the ball-milling time, the structural changes of different ball-milled graphites were analyzed. The impact mechanism of defect structure on electrode electrochemical performance and safety performance was investigated. The results show that the spherical structure and large specific surface area are beneficial to increase the active sites and delay the self-heating of the battery. The formation of defects and pores increases the adsorption sites, which makes the surface adsorption of Li+ dominant and improves the ion diffusion. In addition, the dominance of surface adsorption and desorption effectively suppresses the problem of graphite flake peeling and intensified thermal runaway caused by graphite phase transition and lithium evolution heat release at high temperature. The thermal safety test was carried out by accelerated calorimeter (ARC), and its thermodynamics and reaction kinetics were quantitatively analyzed. It was proved that the introduction of surface adsorption lithium storage method successfully delayed the thermal runaway of the battery, realizing the balance between high electrochemical performance and high safety.

Effect of Functionalized Carbon Nanotubes and Graphene Oxide Nanoribbons on the Supercapacitive Behavior of Zr-Based Metal-Organic Frameworks in Acid Media

Metal-organic frameworks (MOFs) as a kind of crystalline porous materials have attracted much attention due to their high surface area and high electrochemical performance as electrode materials in supercapacitors 1. Recently, there has been a lot of interest in functionalized multiwalled carbon nanotubes (F-MWCNTs) based materials and especially graphene oxide nanoribbons (GONRs), which have unusual characteristics of ultrathin two-dimensional structures and, as promising materials for supercapacitors and other electrochemical energy storage devices. The F-MWCNTs and GONRs' high electrical conductivity, highly changeable surface area, strong chemical stability, excellent mechanical behavior, and capacity to modify attributes for the desired application are behind the reasons for choosing to make a composite of these materials with Zr-MOF 2.In this work, Zr-MOF was synthesized using the solvothermal method 3, MWCNTs were functionalized using acid washing (3 M H2SO4: 1 M HNO3), and GONRs were fabricated using the oxidative unzipping method 4. The Zr-MOF/F-MWCNTs and Zr-MOF/GONRs composites were prepared through physical mixing. The physical and chemical structures of the synthesized Zr-MOF, F-MWCNTs, and GONRs were evaluated using XRD, SEM, TEM, FT-IR, Raman spectroscopy, and XPS. The supercapactive behavior of the prepared composites was evaluated in comparison to their components (Zr-MOF, F-MWCNTs, and GONRs) in 1M H2SO4 utilizing various evaluation systems (three and two-electrode systems). Zr-MOFs showed a high specific capacitance (248 F/g at 1 A/g), making it a promising supercapacitor electrode material. That performance is dramatically improved by the addition of the nanocarbon materials (F-MWCNTs and GONRs). Zr-MOF-GONRs showed the highest specific capacitance (448 F/g at 1 A/g), with a large potential window (1.7 V) in the three-electrode system extended to (2V) in the two-electrode system, and good stability over 10,000 cycles at a high current density of 10 A/g. Reference: (1) Tan, Y.; Zhang, W.; Gao, Y.; Wu, J.; Tang, B. Facile Synthesis and Supercapacitive Properties of Zr-Metal Organic Frameworks (UiO-66). RSC Adv. 2015, 5 (23), 17601–17605. https://doi.org/10.1039/c4ra11896k.(2) Shrivastav, V.; Sundriyal, S.; Tiwari, U. K.; Kim, K. H.; Deep, A. Metal-Organic Framework Derived Zirconium Oxide/Carbon Composite as an Improved Supercapacitor Electrode. Energy 2021, 235, 121351. https://doi.org/10.1016/j.energy.2021.121351.(3) Abdelhamid, H. N. UiO-66 as a Catalyst for Hydrogen Production: Via the Hydrolysis of Sodium Borohydride. Dalton Trans. 2020, 49 (31), 10851–10857. https://doi.org/10.1039/d0dt01688h.(4) Kosynkin, D. V.; Higginbotham, A. L.; Sinitskii, A.; Lomeda, J. R.; Dimiev, A.; Price, B. K.; Tour, J. M. Longitudinal Unzipping of Carbon Nanotubes to Form Graphene Nanoribbons. Nature 2009, 458 (7240), 872–876. https://doi.org/10.1038/nature07872.

Operando chemo-mechanical evolution in LiNi0.8Co0.1Mn0.1O2 cathodes.

Ni-rich LiNi x Co y Mn z O2 (NCMxyz, x+y+z=1, x≥0.8) layered oxide materials are considered the main cathode materials for high-energy-density Li-ion batteries. However, the endless cracking of polycrystalline NCM materials caused by stress accelerates the loss of active materials and electrolyte decomposition, limiting the cycle life. Hence, understanding the chemo-mechanical evolution during (de)lithiation of NCM materials is crucial to performance improvement. In this work, an optical fiber with με resolution is designed to in operando detect the stress evolution of a polycrystalline LiNi0.8Co0.1Mn0.1O2 (P-NCM811) cathode during cycling. By integrating the sensor inside the cathode, the stress variation of P-NCM811 is completely transferred to the optical fiber. We find that the anisotropy of primary particles leads to the appearance of structural stress, inducing the formation of microcracks in polycrystalline particles, which is the main reason for capacity decay. The isotropy of primary particles reduces the structural stress of polycrystalline particles, eliminating the generation of microcracks. Accordingly, the P-NCM811 with an ordered arrangement structure delivered high electrochemical performance with capacity retention of 82% over 500 cycles. This work provides a brand-new perspective with regard to understanding the operando chemo-mechanical evolution of NCM materials during battery operation, and guides the design of electrode materials for rechargeable batteries.

Batch-Scale Synthesis and Interfacially Enhanced Stability of Silicon Suboxide-Based Anodes toward High-Performance Lithium-Ion Batteries.

SiOx anode materials are among the most promising candidates for next-generation high-energy-density lithium-ion batteries (LIBs). However, their commercial application is hindered by poor conductivity, low initial Coulombic efficiency (ICE), and an unstable solid electrolyte interface. Developing cost-effective SiOx anodes with high electrochemical performance is crucial for advanced LIBs. To tackle these issues, this study utilized APTES as a silicon source and carbon nanotubes (CNTs) as additives to prepare a T-SiOx/C/CNTs composite material with N doping and in situ carbon coating using a "molecular assembly combined with controlled pyrolysis" strategy under mild conditions. The in situ carbon coating, formed by the pyrolysis of organic groups on the molecular precursor, effectively protects the inner SiOx active material. The introduced CNTs enhance electron migration and improve the rigidity of the carbon coating layer. The prelithiated T-SiOx@C/CNTs electrode achieves an ICE of 91.6%, with a specific capacity of 622 mAh g-1 after 400 cycles at 1 A g-1 and 475.8 mAh g-1 after 800 cycles. Full cell tests with commercial NCM811 cathodes further demonstrate the potential of T-SiOx@C/CNTs as a highly promising anode material. This work provides some insights into the rational design of advanced anode materials for LIBs, paving the way for their future development and application.

Theoretical study of Jahn Teller effect on ion diffusion in trigonal prismatic 1H-MnO2

The trigonal prismatic MnO6 is a basic structural unit of Mn-based compound which has been seldom explored in theoretical and experimental studies. In this paper, the diffusion potential energy surfaces of Li+, Na+, K+, Mg2+, Al3+, and NH4+ ion in trigonal prismatic 1H-MnO2 are presented, which give an intuitionistic picture of the Jahn-Teller effect on the diffusion process. Based on the nudged elastic band method, it is found that the diffusion of ions in trigonal prismatic MnO2 is accompanied by consecutive structural distortion. The low diffusion barriers indicate trigonal prismatic MnO2 is a fast ion conductor. Band structure calculations show the semimetal characteristic of the intercalated compound, which is fit for high electrochemical performance. The details of the diffusion process are also highlighted. Our theoretical study provides an in-depth understanding and research on the fundamentals of the diffusion process in the special configuration in MnO2 and helps to develop novel high-performance electrodes.

Redox-active hydrogel electrolytes for carbon-based flexible supercapacitors over a wide temperature range

Hydrogel electrolytes are attractive for fabricating flexible supercapacitors (FSCs) due to their relatively high ionic conductivity, adjustable mechanical properties, and easy preparation processes. However, they still face challenges such as a narrow operational temperature range due to the presence of abundant free water molecules, and comparatively less favorable electrochemical properties compared to liquid electrolytes. In this study, a redox-active hydrogel electrolyte was synthesized, consisting of polyvinyl alcohol-H2SO4, TiO2 nanoparticles, carbon nanofibers and a mixture of redox-active species (FeBr3, Fe2(SO4)3 and KBr). The addition of thermally stable TiO2 and carbon nanofibers not only increased the thermal stability but also enhanced the ionic conductivity of the hydrogel. The Faradaic reactions of redox-active species during the charging/discharging processes contributed to improved electrochemical performance. Subsequently, binder-free carbon nanofiber@carbon cloth electrodes were prepared by directly growing carbon nanofibers on carbon cloth. By combining the electrodes with the redox-active hydrogel electrolyte, a redox electrolyte-enhanced FSC was assembled. It exhibited a capacitance of 182.8 mF cm−2 at 3.5 mA cm−2, an energy density of 8.3 Wh kg−1, and a capacitance retention of 84.3 % after 5000 charging/discharging cycles. The device was capable of operating under various temperature conditions (0–60 °C) and bending angles (0–180°). Overall, this work provides a novel but facile approach for fabricating FSCs with high electrochemical performance and versatile applications in different environments.

High voltage electrochemical performance of ultrahigh-Ni cathode via in situ constructed nano-LiF and CNT composite cathode electrolyte interphase layer

Ultrahigh-nickel LiNixCoyMn1-x-yO2 cathode material (Ni content ≥ 0.9) is of great significance for the development of high energy density of lithium-ion batteries. However, its high surface activity leads to more surface residual lithium formation and deterioration of electrochemical performance, especially at high voltage. Here we add NH4F and nitrogen-doped carbon nanotubes (CNT) during the dimethyl carbonate (DMC) washing process, and constructed in situ the nano-LiF and CNT composite cathode electrolyte interphase (CEI) layer while removing part of residual lithium, effectively optimizing the surface environment of LiNi0.9Co0.05Mn0.05O2. The modified LiNi0.9Co0.05Mn0.05O2 has a capacity retention rate of 61.3 % after 200 cycles between 2.8 and 4.5 V at 1C, significantly higher than the 46.7 % of the unwashed sample, and a specific discharge capacity of 146.9 mAh g−1 at 5C, compared to 127.5 mAh g−1 for the unwashed sample. Benefit from the alleviation of polarization and the increase of Li+ diffusion coefficient, the stable CEI layer provides effective protection for LiNi0.9Co0.05Mn0.05O2 under 4.5 V, alleviating surface side reactions. In this paper, a simple and effective strategy is developed to optimize the surface of Ni-rich cathode material, which provides a new insight for the treatment of surface residual lithium.