Charge-discharge Cycles Research Articles

Highly Durable Sn-Ni Alloy Anode Pretreated in Vinylene Carbonate-Containing Electrolyte for Lithium-Ion Capacitors

Abstract Lithium-ion capacitors (LICs) are promising energy storage devices for electric vehicles because they rank between LIBs and EDLCs in terms of energy and power density. In a previous work, an LIC with a Sn-Ni alloy anode was proven to be superior in terms of energy and power density compared to that with a graphite anode. To improve the cycle durability at a practical level, the effect of vinylene carbonate (VC), which positively affects LIBs, was investigated. VC demonstrates a positive effect during the pre-treatment process, but also a negative effect during charge-discharge cycling. The difference between these effects is discussed in terms of the potential and morphology changes of the anode, revealing that the VC forms a polymer-like solid electrolyte interphase during the pre-treatment process, suppressing the deactivation of Sn caused by crack growth and peeling off during charge-discharge cycling. In contrast, VC continuously decomposes during charge-discharge cycling while consuming pre-treated lithium. Finally, an excellent cycle durability (10,000 cycles with a capacity retention of 72.3%) is here demonstrated for the first time for the LIC with a high volumetric energy density of 38.9 Wh/L at 120 W/L.

A General Sol-Gel Route to Fabricate Large-Area Highly-Ordered Metal Oxide Arrays Toward High-Performance Zinc-Air Batteries.

A universal method is demonstrated for the fabrication of large-area highly ordered microporous arrayed metal oxides based on a high-quality self-assembly opal template combined with a sucrose-assisted sol-gel technique. Sucrose as a chelating agent optimizes precursor infiltration and regulates both oxide formation and the melting process of polystyrene templates, thus preventing crack formation during infiltration and calcination. As a result, over 20 metal element-based 3DOM oxides with arbitrary compositions are successfully prepared. Therein, a champion electrocatalyst RuCoOx-IO exhibits outstanding bifunctional oxygen activity with an ultra-narrow oxygen potential gap of 0.598V, and the Zn-air batteries based on RuCoOx-IO air cathode operates for 1380h under fast-charging cycling (50mA cm-2), and reaches a high energy efficiency of 69.5% in discharge-charge cycling. In situ spectroscopy characterizations and density functional theory reveal that the rational construction of Ru─O─Co heterointerface with decoupled multi-active sites and mutual coupling of RuO2 and Co3O4 facilitate interfacial electron transfer, leading to an optimized d-band centers of active Ru/Co and a weakened spin interaction between oxygen intermediates and Co sites, so as to enhance the adsorption ability of *OOH on interfacial Co sites for fast ORR kinetics while favoring the desorption of oxygen intermediates on interfacial Ru during OER.

Restructuring of Sodium-Lead Alloys during Charge-Discharge Cycling in Sodium-Ion Batteries

Abstract Sodium-ion batteries (NIBs) are of growing interest due to their expected lower cost than many lithium-ion batteries (LIBs). However, most NIBs suffer from lower volumetric energy density than LIBs. Lead (Pb) can replace hard carbon in the NIB negative electrode to substantially increase its volumetric energy density and has been shown to have no capacity fade over hundreds of cycles in half cells. Pb also experiences 387% volume expansion upon full sodiation, which presumably leads to significant changes in the electrode morphology. In this work, the morphology of Pb and Pb-hard carbon blended electrodes is tracked using scanning electron microscopy. As well, each Na-Pb phase is examined to analyze their physical properties. These analyses show that the Pb particles restructure into ~1 µm particles, even after just a single cycle, and surprisingly do not pulverize the hard carbon in a blended electrode. Single-walled carbon nanotubes appear to be necessary to maintain active material electrical connection.

Rational Design of Hierarchical Structure Electrodes to Suppress Shuttle Diffusion in Redox-Enhanced Supercapacitors.

In carbon-based supercapacitors, redox couples can effectively improve the energy density of supercapacitors; however, most redox couples still suffer from serious shuttle diffusion. Currently, there is no universal strategy to effectively constrain their shuttle diffusion. Therefore, developing a simple, effective, and universal method to suppress shuttle diffusion remains a great challenge. Herein, we designed and prepared a hierarchical structure electrode composed of three functional layers (inner conductive layer, intermediate storage layer, and outer confinement layer) for redox-enhanced supercapacitors. The hierarchical electrode can be fabricated on a large scale in three simple steps based on commercial carbon felt. The rationally designed three functional layers endow the hierarchical structure electrode with excellent conductivity, adsorption capacity, and confinement ability. Long-term charge-discharge cycle results prove that the hierarchical structure electrode exhibits an outstanding restriction effectiveness on three redox media with different molecular sizes (anthraquinone (AQ), naphthoquinone (NQ), and p-benzoquinone (PQ)). Specifically, for AQ, NQ, and PQ, the hierarchical structure electrodes showed CV peak current attenuation rates of only 5.64%, 3.54%, and 10.34% after 5,000 cycles of charge-discharge, while common electrodes exhibited attenuation rates of 10.44%, 15.02%, and 20.20%, respectively. Moreover, the soft-pack supercapacitors composed of hierarchical electrodes still had a capacitance retention of 86.6% after 5,000 cycles of charge-discharge. All the results demonstrate that the structure design is reasonable and the hierarchical structure electrode has a great potential to be the universal electrode for suppressing the shuttle diffusion of redox media in supercapacitors and other energy storage devices.

Thermodynamics analyses on a novel CHP system integrated with multi-grade thermal energy storage

The high penetration level of intermittent renewable power necessitates the crucial requirement for combined heat and power systems to possess both high efficiency and flexibility. However, the heat-controlled operation modes of traditional combined heat and power systems impose limitations on their efficiency and flexibility. Therefore, it is of great significance to develop a heat-power decoupling technology that exhibits exceptional efficiency and flexibility. A novel combined heat and power system integrated with multi-grade thermal energy storage is proposed in this study. Thermodynamic analysis models of all operational conditions are developed, and the comprehensive characteristics of efficiency and operational flexibility for the proposed system are assessed by taking a 330 MW system as an example. Results show that the proposed system can decrease/increase 16.05 MW/30.96 MW power loads comparing with the reference system during the charging/discharging periods under the design condition. Energy efficiency of the proposed system can reach 49.40 %, which is improved by 1.66 percentage points. Exergy analysis reveals the exergy destruction order for the proposed system, and shows that the combustion and heat transfer in the boiler are the major process of exergy dissipation. Moreover, operation strategies of the proposed system during charging-discharging cycle are explored and formulated under off-design condition, suggesting that thermodynamic performances of the novel system under various conditions even extreme conditions exhibits exceptional properties. The maximum heat load of the proposed system can be improved by 46.78 % comparing with the reference system, and the maximum improvement of power load capacity during charging-discharging cycle is 14.58 percentage points. This study provides a promising approach for multi-grade thermal energy storage to improve the comprehensive characteristics of combined heat and power systems.

Electrochemical Impedance Spectroscopy Analysis of Dendrite Growth on the Lithium Metal Surface in Polysulfide-Insoluble Electrolytes

Abstract Lithium has been widely investigated owing to its high theoretical specific capacity and low electrochemical potential. This is required for high-energy-density lithium batteries such as lithium–sulfur (Li–S) batteries. Recently, Li–S batteries with polysulfide-insoluble electrolytes, such as sulfolane (SL) and triglyme (G3), have attracted research attention because they suppress the dissolution of lithium polysulfide intermediates. However, lithium dendrite growth on the Li metal anode during the charging–discharging process causes an internal short-circuit, which may lead to serious accidents. To realize a Li–S battery, a fail-safe system to prevent short-circuits is essential. In this study, we investigated the cycle degradation mechanism of a Li metal anode in SL and G3 electrolytes using electrochemical impedance spectroscopy. The changes in charge transfer resistance (Rct) and solid electrolyte interphase resistance (RSEI) of Li-Li symmetrical cells in SL and G3 electrolytes was measured under charge–discharge cycling in detail down to internal short-circuits. Consequently, in both the electrolyte systems, the RSEI and Rct behaviors were disparate during cycling, and a mechanism for the short-circuit process was proposed. In addition, before the short-circuit process occurred, the change in the trend of Rct from stable to increasing was indicative of an imminent short-circuit.

A Promising Approach to Ultra-Flexible 1 Ah Lithium-Sulfur Batteries Using Oxygen-Functionalized Single-Walled Carbon Nanotubes.

Lithium-sulfur (Li-S) batteries represent a promising solution for achieving high energy densities exceeding 500Wh kg-1, leveraging cathode materials with theoretical energy densities up to 2600Wh kg-1. These batteries are also cost-effective, abundant, and environment-friendly. In this study, an innovative approach is proposed utilizing highly oxidized single-walled carbon nanotubes (Ox-SWCNTs) as a conductive fibrous scaffold and functional interlayer in sulfur cathodes and separators, respectively, to demonstrate large-area and ultra-flexible Li-S batteries with enhanced energy density. The free-standing sulfur cathodes in the Li-S cells exhibit high energy density maintaining 806 mAh g-1 even after 100 charge-discharge cycles. Additionally, oxygen-containing functional groups on the SWCNTs significantly improve electrochemical performance by promoting the adsorption of lithium polysulfides. Employing Ox-SWCNTs in both cathodes and interlayers, the study achieves high-capacity Li-S pouch cells that consistently deliver a capacity of 1.06 Ah and a high energy density of 909 mAh g-1 over 50 charge-discharge cycles. This strategy not only significantly enhances the electrochemical performance of Li-S batteries but also maintains excellent mechanical flexibility under severe deformation, positioning this Ox-SWCNT-based architecture as a viable, light-weight, and ultra-flexible energy storage solution suitable for commercializing rechargeable Li-S batteries.

O−O Radical Coupling in Ultrathin Reconstructed Co6.8Se8 Nanosheets for Effective Oxygen Evolution and Zinc‐Air Batteries

AbstractDesigning ultrathin transition metal electrocatalysts with optimal surface chemistry state is crucial for oxygen evolution reaction (OER). However, the structure‐dependent electrochemical performance and the underlying catalytic mechanisms are still not clearly distinguished. Herein, we synthesize ultrathin Co6.8Se8 nanosheets (NSs) with subnanometer thickness by incorporating catalytically inactive selenium (Se) into ultrathin Co(OH)2, thereby switching the OER reaction pathway from adsorbate evolution mechanism (AEM) to oxide path mechanism (OPM). The prepared ultrathin Co6.8Se8 NSs exhibit an overpotential of 253 mV at 10 mA/cm2, outperforming the mostly reported Co‐based electrocatalysts. Advanced operando synchrotron spectroscopies and X‐ray absorption spectroscopy reveal the ultrathin Co6.8Se8 NSs, whose surface is reconstructed into Se‐doped Co(OH)2 during the OER process, could trigger direct O*−O* radical coupling rather than OOH* intermediates within AEM pathway thus lowering the energy input. Density functional theory calculations confirm that Co6.8Se8 NSs with shorter Co−Co bond length and stable Co−Se bond could optimize the rate‐determining step barrier via OPM pathway. Besides, rechargeable zinc‐air batteries based on Co6.8Se8 NSs exhibit excellent stability for more than 500 h of continuous charge–discharge cycles at 4 mA/cm2. The present study highlights the structural‐dependent switch of OER pathways and provides valuable insights for further development of ultrathin OER catalysts.

Polythiophene side chain chemistry and its impact on advanced composite anodes for lithium-ion batteries.

In the development of high-performance lithium-ion batteries (LIBs), the design of polymer binders, particularly through manipulation of side-chain chemistry, plays a pivotal role in optimizing electrode stability, ion transport, and adaptability to the volume changes during cycling. In particular, poly[3-(potassium-4-butanoate)thiophene-2,5-diyl] (P3KBT) increases magnetite and silicon capacity and cycling stability. This work explores the impact of polythiophene alkyl sidechain length on anode characteristics, aiming to enhance performance in LIBs. P3KBT and its alkyl chain alternatives, poly[3-(potassium-5-pentanoate)thiophene-2,5-diyl] (P3KPT) and poly[3-(potassium-6-hexanoate)thiophene-2,5-diyl] (P3KHT) were systematically investigated over 300 charge-discharge cycles. The experiments were designed to assess how varying side-chain length affects the stability, ion transport, and capacity retention of the electrodes. The results revealed that P3KHT, with its longer alkyl chain, exhibited superior capacity retention and reduced charge-transfer resistance after 300 cycles compared to its shorter chain analogs. The findings demonstrate that tailored side chains can improve ion transport, structural integrity, and capacity retention, addressing critical challenges in LIBs such as capacity fade and electrode degradation. This research contributes to the development of next-generation LIBs with enhanced performance and reliability.

Estimation of the RUL of Alkaline Batteries in EV by using Machine Learning Algorithm

The attention on battery longevity and performance has increased due to the quick uptake of electric cars (EVs) as a sustainable substitute for conventional internal combustion engine vehicles. The foundation of EV technology, batteries control the vehicle's dependability, efficiency, and range. With their distinct chemical characteristics, alkaline. Batteries are one of the various battery varieties that may be advantageous for specific EV applications. However, a variety of variables, including charge-discharge cycles, temperature fluctuations, and usage patterns, affect their life cycle and efficiency. To maximize performance, lower maintenance costs, and guarantee user safety, it is crucial to precisely calculate these batteries' Remaining Useful Life (RUL). Conventional approaches to RUL prediction frequently depend on statistical methods or empirical models, which might not take into consideration the intricate relationships between the factors influencing battery deterioration. For a potential solution to this issue machine learning (ML) algorithms, which can examine big datasets and reveal hidden patterns. This study intends to provide a reliable framework for forecasting the RUL of alkaline batteries in EVs by utilizing cutting-edge machine learning models. This will ultimately help to enhance battery management systems and encourage the wider use of EV technology.

Studies on Multifunctional Nanostructured Materials

Multifunctional materials are of today’s quest. Miniaturization, i.e. development of these materials in the form of nanomaterials is of primary need considering their application in devices. Moreover, if these are obtained in nanostructured form, they can bring wonders. We have adopted a method for developing multiferroic BiFeO3 (BFO) with simultaneous antiferromagnetic, ferroelectric & ferroelastic behaviour in form of nanostructures like nanorods, nanowire etc. by employing Anodised Alumina (AAO) template with various pore sizes from 20nm with solution route followed by controlled vacuum filtration and sintering. Diameters of nanorods are in the range of 20-100 nm as observed by FESEM. Capacitance assayed by cyclic voltammetry (CV) and charge discharge processes reveals a very high value of specific capacitance of 450F/gm. Capacitance has been estimated by extrapolating the charge collected at the electrode to that at scanning rate of infinity which is relevant for the charge collected at the nanorods protruding out of the template. Charging and discharging times are quite constant over a large number of cycles. This large value of specific capacitance can be attributed to the nanostructure form of BFO nanorod. The high value of specific capacitance of BFO nanorods brings forth its use as electrode in storage energy devices. Also, a high value of polarization as well as a significant magnetic susceptibility are observed in multiferroic Bismuth Ferrite (BFO) in the form of nanorods protruding out. The high values of polarization and magnetic susceptibility are attributed to the structured form of BFO nanorods giving rise to the directionality. There is no leakage current in P-E loop examined at various fields and frequencies. Magnetocapacitance measurements reflect a significant enhancement in magnetoelectric coupling also.

Novel multi-modular power conditioning system and decoupling control strategy for SMES with coupled superconducting coil

The high-temperature superconducting magnetic energy storage system (HTS-SMES) utilizes a superconducting coil (SC) to store electric energy in a magnetic field. It has several advantages such as high efficiency, fast response, and infinite charge–discharge cycles. Coupling two SCs made of different HTS materials, known as coupled SC (CSC), can enhance the utilization rate of HTS tapes, reduce manufacturing costs, increase the energy storage density of the SC, and lower magnetic leakage. However, the presence of a coupled magnetic field in CSC makes precise power and current regulation of the individual SC challenging. Additionally, the self-inductances of the individual SCs, composed of different materials, typically differ from each other. Consequently, the current variation induces electromotive force in each SC that differs from the others, necessitating the design of power converters with different voltage ratings connected to each SC. To address the difficulties associated with SMES implementation using CSC, this paper proposes novel modular power conditioning system (MPCS) and decoupling control strategy for SMES. The MPCS enables the flexible design of individual SC power ratings by selecting the appropriate number of power modules. The decoupling control ensures precise current control of each individual SC, which significantly reduces the current ripple of the SCs. Moreover, by employing carrier phase shift modulation, the total harmonic distortion (THD) of the PCS output current is as low as 0.79%. Furthermore, the feedforward power control is proposed to reduce the power control overshoot, and the current sharing control is presented to ensure precise current sharing between each SC. Simulation results verify the efficacy of the proposed approaches.

Pre-magnetization smashing hydrated vanadium ions to improve redox flow batteries performance

The vanadium redox flow battery (VRFB) has received extensive attention due to its intrinsic safety and high scalability. Currently, there are still deficiencies of low energy efficiency and higher unit capacity cost in VRFB energy storage. Continuously optimizing the battery performance through reducing electrode polarization losses is a necessary way to achieve efficient VRFB energy storage technology. In this study, a method of pre-magnetizing the electrolyte to improve the performance of the battery was proposed. A permanent magnet with an intensity of 0.9 T was used to pre-magnetize the vanadium-ion aqueous electrolyte before feed into the battery stack and working-on, it was found that the diffusion capacity of vanadium ions increased by 133.6 % after pre-magnetized even if the external magnetic field was removed. Meanwhile, both of the charge transfer and concentration polarization resistance of the electrode were reduced. The energy efficiency (EE) of the battery was increased by 6.4 % in the charge–discharge test at current density of 300 mA cm−2. The power density increased by 6.19 % with current density 400 mA cm−2 at most, and it prefers to continuously increase as current larger. The electrolyte pre-magnetization showed significant positive improvements on the electrode reaction kinetics and battery charge–discharge cycle.

Ternary metal oxide carbon composite as high-performance electrode material for supercapacitor applications

Recently, ternary metal oxides carbon composites recognized as metal organic frameworks (MOFs) have gained striking attention for supercapacitor electrode material due to high surface area, porosity, chemical stability, tunable properties, redox activity, and eco-friendly material. ZIF-67 is a novel MOF possessing these characteristics. Therefore, the present work reports the development of ternary iron-nickel–cobalt ZIF-67 composites (FeNiCo ZIF-67) using co-precipitation method with the variation in molar concentration of iron oxide, nickel oxide, and cobalt oxide. Physico-chemical characterizations of developed materials were investigated through X-ray diffraction (XRD), Raman spectroscopy, energy dispersive X-ray (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) to confirm the successful formation of composites and structure, morphology. Then, the electrodes were fabricated for all three synthesized composites and electrochemical analyses such as cyclic voltammetry (CV), galvanic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed. The results revealed the porous polyhedral structure of FeNiCo ZIF-67 with different compositions consisting of interconnected nanoparticles played an important role in increasing the charge storage capacity of the material. Among the composites, FeNiCo ZIF-67 (1:2:1) electrode material achieved the highest specific capacitance of 532.7 F/g at a current density of 1 A/g. FeNiCo ZIF-67 (1:2:1) exhibited maximum electrochemical active surface area 89.12. Electrochemical impedance spectroscopy (EIS) demonstrated the minimal resistance of 7.8 Ω by FeNiCo ZIF-67 (1:2:1) composite electrode compared to the other two electrode materials. Cyclic stability study revealed the capacitance retention of 91 % after 10,000 continuous charge discharge cycles at a current density of 10 A/g. Electrode material demonstrated an outstanding electrochemical performance, and this work could provide a simple strategy to fabricate FeNiCo ZIF-67 nanostructured electrode materials for supercapacitors.

Assessment of Internal Short-Circuit Risks in Overdischarged Lithium Batteries Under Various Charging Conditions

This study analyzes the internal short-circuit behavior of an overdischarged secondary lithium-ion cell (OD-cell) under subsequent charging conditions. The results revealed that Cu ions dissolved from the anode Cu substrate during overdischarge were initially deposited on the cathode, migrated back to the anode, and deposited there during subsequent charging. These Cu deposits on the anode maintained their shape throughout normal charge–discharge cycles. Post-charging destructive analysis of the OD-cells revealed that the morphology of the Cu deposits on the anode surface varied significantly with the charging current. Cu formed coarse spherical particles at low currents (< 0.2 C-rate). As the current increased, a mixture of spherical and dendritic structures appeared. Only dendritic structures were observed above a certain threshold (> 3 C-rate). The leakage currents in OD-cells charged at various rates were measured to calculate their internal short-circuit resistance (ISR), and the relationship between Cu morphology and self-discharge was investigated. The “ISR decrease rate” was defined to compare the calculated ISR with the ISR of a normal cell, which was used as an indicator of the internal short circuit of the cell. The OD-cells charged at low currents (< 0.2 C-rate) maintained an ISR similar to that of normal cells (ISR decrease rate < 10%) with minimal self-discharge. However, high-current charging (> 3 C-rate) significantly reduced the ISR (decrease rate of > 97%) and introduced severe self-discharge. These findings suggest that high-rate charging immediately after overdischarge may exacerbate the internal short circuit and self-discharge owing to Cu-bridge formation.

Ultra-small CoxSy nanoparticles adhered to 3D-reduced graphene oxide as attractive anodes for lithium-ion batteries

A novel composite anode material, CoxSy/G, has been developed through a novel hydrothermal synthesis method complemented by an innovative high-temperature vulcanization technique. This process facilitates the deposition of CoxSy nanoparticles, each less than 10nm in size, onto a substrate of 3D rGO. This composite material combines the robust lithium storage capacity of CoxSy nanoparticles with the exceptional electrical conductivity and mechanical resilience of the 3D rGO framework, resulting in a significantly enhanced specific surface area and optimized mesoporous structure for CoxSy/G. Furthermore, it exhibits excellent electrochemical performance in lithium-ion batteries. Specifically, the CoxSy/G composites achieve a discharge capacity of 748.5mAh g⁻¹ at 50mAg⁻¹, notably exceeding the 647mAh g⁻¹ capacity demonstrated by pure CoxSy. Furthermore, these composites maintain an extraordinary cycle retention rate of 112.4% after undergoing 500 charge-discharge cycles at a continuous rate of 0.5Ag⁻¹. The reduced charge transfer resistance noted after cycling underscores the material’s enhanced performance attributes. This innovative creation of CoxSy/G composites offers critical insights and potential strategies for further development in the field of lithium-ion cobalt-sulfur electrodes.

Enhanced photocatalytic and supercapacitor performance of CeO2 nano foam integrated MWCNT and rGO nanocomposites

In this study, Cerium oxide nanoparticles (CeO2 NPs) with foam like morphology were prepared using the Moringa Oleifera seed extract-assisted green synthesis method. The prepared CeO2 NPs were integrated respectively with reduced graphene oxide (CeO2/rGO) and multi-walled carbon nanotubes (CeO2/MWCNT) via a simple one-pot reflex method. The structural and morphological features and elemental characteristics, including the physico-chemical and thermal characteristics of the samples, were assessed. The photocatalytic degradation ability of the catalyst was tested against Alizarin Red (AR) and Safranin (SF) dyes. Under sunlight, degradation efficiencies of 92.62%, 95.46%, and 99.62% were achieved against Safranin dye by CeO2, CeO2/MWCNT, and CeO2/rGO, respectively. The XRD analysis shows the structural phase stability of the nanocatalyst even after five cycles. The supercapacitor characteristics of all anode electrode samples were assessed. Moreover, the specific capacitance values of 370, 413, and 554 Fg-1 were measured using cyclic voltammetry at a scan rate of 5 mV/s for CeO2, CeO2/MWCNT, and CeO2/rGO, respectively. After undergoing 3000 charge-discharge cycles, the hybrid CeO2/rGO nanocomposite revealed admirable cycling stability with an 8.6% decrease in its specific capacitance. According to the results, the green-mediated CeO2/rGO heterojunction nano semiconducting materials are promising candidates for twin applications in photocatalysis and supercapacitors.

Bamboo waste derived hard carbon as high performance anode for sodium-ion batteries

Biomass-derived hard carbon stands out as one of the most promising anode materials for advancing the commercial viability of sodium-ion batteries (SIBs). In this study, we harnessed a straightforward and eco-friendly two-step carbonization approach to fabricate high-performance hard carbon materials, ingeniously repurposing industrial bamboo waste. Concurrently, we delved into the impact of carbonization temperature on the microstructure and properties of the hard carbon derived from bamboo waste. The findings revealed that the as-prepared hard carbon at 1400 °C (HCB-1400) showcased the most desirable sodium-ion storage capabilities. The HCB-1400 material not only can deliver a substantial reversible capacity of 328.4 mAh g−1 at 30 mA g−1 in its maiden charge-discharge cycle but also display remarkable cycling stability. Moreover, the HCB-1400//Na3V2(PO4)3 full cell, when assembled, exhibited an impressive energy density of 249.25 Wh kg−1, with a capacity retention rate of 93 % after enduring 200 cycles at a current density of 1.0 C. This research underscores the potential of transforming biomass waste into high-performance hard carbon, heralding a sustainable path for SIB applications.

Cerium oxide anchored free-standing silicon nanowires as potential anode materials for electrochemical supercapacitor

Free-standing 1 D silicon nanowires (Si-NWs) were synthesized by the metal-assisted chemical etching (MACE) technique and subsequently decorated with cerium oxide (CeO2) nanoparticles synthesized by a solvothermal process. Morphological characterization of the CeO2/Si-NWs nanocomposite validates the homogeneous growth of spherical CeO2 nanoparticles around the Si-NWs, while the N2 adsorption-desorption study indicates a large specific surface area (SSA) and the presence of ink-bottle-shaped pores possessing a significant portion of mesopores. This CeO2/Si-NWs composite electrode demonstrates excellent electrochemical behavior, attaining an impressive specific capacitance (Csp) of 830 F g–1 at a current density of 1.0 A g–1, the anodic material delivers an energy density of 19 Wh kg–1 at a power density of 2.5 kW kg–1, along with exceptional durability, retaining 94% of its capacitance after 2000 charge-discharge cycles. The results show that the CeO2/Si-NWs composite electrode has great potential as an emerging category of anodic material for supercapacitors.

Inspired by plant body frameworks bionics: Fabrication of self-healing polyvinyl alcohol/cellulose nanocrystals composite hydrogels reinforced by polyurethane sponges for flexible supercapacitors

With the booming development of electronic technology, ultra-toughness and self-healing supercapacitors have drawn substantial attentions. In this work, inspired by plant body frameworks, a novel method was proposed to prepare self-healing conductive hydrogels based on self-healing polyurethane sponge (PUS) network. First, a self-healing PUS based on multiple hydrogen bonding interactions and disulfide bonds was prepared. Subsequently, PUS was combined with polyvinyl alcohol (PVA)/cellulose nanocrystals (CNF) composite hydrogels crosslinked by borate ester bonds and hydrogen bonding interactions to manufacture the sponge network reinforced self-healing conductive hydrogels. Due to the reinforcement of PUS, the composite hydrogels had excellent mechanical properties, with a tensile strength of 1.81 MPa and a compressive strength of 1.96 MPa. After 400 times of charge-discharge cycles under bending deformation, the supercapacitor could maintain 90.1 % of the original specific capacitance value. Furthermore, the hydrogels could be healed at room temperature due to the hydrogen bonds and reversible borate bonds in PVA/CNF matrix, as well as the disulfide bonds and multiple hydrogen bonds in PUS. The healed supercapacitor could maintain 75.2 % of the original specific capacitance value after 400 times of charge-discharge cycles. Therefore, the as-prepared self-healing and tough conductive hydrogels may have promising prospects in electronic devices.