Exceptional Rate Performance Research Articles

Dynamic Lock-And-Release Mechanism Enables Reduced ΔG at Low Temperatures for High-Performance Polyanionic Cathode in Sodium-Ion Batteries.

Low-temperature synthesis of polyanionic cathodes for sodium-ion batteries is highly desirable but often plagued by prolonged reaction times and suboptimal crystallinity. To address these challenges, a novel self-adaptive coordination field regulation (SACFR) strategy based on a dynamic lock-and-release (DLR) mechanism is introduced. Specifically, urea is used as a DLR carrier during synthesis, which dynamically "locks" and "releases" vanadium ions for controlled release, simultaneously "locking" H+ ions to enhance phosphate group release, thereby creating a self-adaptive coordination field that can intelligently respond to real-time demands of the reaction system. This dynamic coordination behavior contributes to both an improvement in reaction kinetics and a significant reduction in Gibbs free energy change (ΔG). As a result, the kinetic efficiency and thermodynamic spontaneity of the reaction are greatly enhanced, enabling the efficient synthesis of high-crystalline Na3V2O2(PO4)2F (NVOPF) at 90 °C within just 3 hours. The as-prepared NVOPF cathode exhibits exceptional rate performance and ultra-stable cycling stability across a broad temperature range. Furthermore, the successful kilogram-scale synthesis underscores the practical potential of the innovative strategy. This work pioneers the regulation of coordination field chemistry for polyanionic cathode synthesis, providing transformative insights into material design.

Selection of high rate capability and cycling stability MnO anode material for lithium-ion capacitors: Effect of the carbon source

The N-doped carbon modified MnO composites were successfully prepared using K2MnO4 as the manganese source, CH4N2O as the nitrogen source, and glucose, sucrose, or reduced graphene oxide as the carbon sources. Among them, the composite (MPN) prepared using glucose as the carbon source exhibited excellent electrochemical performance, attributed to its relatively small particle size (6.4 nm), high specific surface area of 199.4 m2·g−1, and a high ID/IG ratio of 0.86. The MnO in MPN contained a significant amount of Mn3+, ∼16.8 %, which is ascribed to the incomplete reduction of high valence Mn during the process of synthesis. With the formation of Mn3+, a large number of cationic vacancies were generated, which increased the diffusion coefficient of Li+ from 2.12 × 10−14 cm2 s −1 to 5.94 × 10−13 cm2 s−1. The carbon layer with appropriate thickness, doped N and mesoporous structure suitable for electrolyte transport provide a fast ion/electron transport channels for MnO, and ensure a stable interface structure in the electrochemical reactions. Consequently, the MPN anode material exhibited remarkable high current discharge capacity (769.5 mAh·g−1 at a high current density of 2 A·g−1) and excellent cycling performance (882.2 mAh·g−1 after 200 cycles at 1 A·g−1), indicating its exceptional rate performance and cycle stability. Furthermore, the lithium ion capacitor constructed with MPN as anode and activated carbon as cathode demonstrated a high specific energy of 190 Wh·kg−1, a high specific power of 205.3 W·kg−1, and an impressive cycling lifespan of up to 3000 cycles without obvious degradation.

Structural modulation of Na4Fe3(PO4)2P2O7 via cation engineering towards high-rate and long-cycling sodium-ion batteries

Mixed iron-based phosphate Na4Fe3(PO4)2P2O7/C (NFPP) has gradually emerged as a promising cathode material for sodium-ion batteries (SIBs) owing to its affordability and convenient preparation. However, poor electrical conductivity and inadequate sodium-ion diffusion limit the exertion of its electrochemical properties. Herein, a structural modulation strategy based on Cd doping is applied to NFPP to address the above limitations. In situ X-ray diffraction analysis reveals that Cd-doped NFPP (NFCPP) undergoes an incomplete solid-solution reaction driven by Fe2+/Fe3+ redox. Cd doping effectively stabilises the crystal structure, resulting in a minimal 1 % change in unit cell volume during cycling. Density of state calculations indicate that Cd doping reduces the band gap, increases the local electron density and significantly improves electron conductivity. Benefitting from the enhanced electrochemical kinetics and intercalation pseudocapacitance, the optimised Na4Fe2.91Cd0.09(PO4)2P2O7/C (NFCPP@3%) exhibits exceptional rate performance (capacity of 62 mAh/g at 20 C) and ultra-long cycling life (82.7 % after 6000 cycles at 20 C). A full SIB prepared using NFCPP@3% and hard carbon, display a 91 % capacity retention rate at a current density of 130 mA g−1 over 200 cycles. This work demonstrates that doping can effectively enhance electrochemical performance and offers insights into future development of SIBs.

Nanosizing strategy to fabricate uniformly dispersed NiO/Ni/lignin porous carbon composites for high lithium storage

Nickel oxide is considered a promising anode material for lithium-ion batteries. Nevertheless, its performance is hindered by significant volume expansion and low electrical conductivity, particularly at larger particle sizes, which lead to a notable decrease in lithium storage capacity and rate performance. To address these challenges, we introduce a nanocomposite strategy to synthesise nickel oxide and lignin-derived porous carbon composites (LPC/Ni/NiO). Through in situ polymerization, lignin macromolecules form a uniform 3D network with nickel carbonate, which, during the subsequent carbonisation process, results in the formation of nickel oxide within a conductive carbon network. This approach reduces the nickel oxide to nanosize and enhances the composite's electrical conductivity, effectively integrating the buffering framework of porous carbon with the high storage capacity of nickel oxide. As a result, the LPC/Ni/NiO composite exhibited significantly improved lithium storage capacity. Notably, when employed as an anode material in lithium-ion half-cells, the optimized composite maintained an excellent specific capacity of 1065 mAh/g after 100 cycles at a current density of 0.2 A/g. It also shown exceptional rate performance, delivering a specific discharge capacity of 505 mAh/g at a current density of 2 A/g, with stable cycling performance. The electrochemical reaction process was further validated using in ex-situ EIS. This study offers valuable insights into scalable synthesis methods for oxide nanocomposites, highlighting their potential as promising anode materials for lithium-ion batteries.

Facile synthesis of MWCNT hexagonal needles grown on interconnected honeycombs like MnCo2O4/MnO2 nanoporous electrode for high-performance asymmetric supercapacitor

The construction of a honeycomb-like structure composed of MnCo2O4/MnO2was effectively achieved using a combination of hydrothermal processing and heat treatment. The whole surface of the MnCo2O4/MnO2 honeycomb is coated with neatly arranged hexagonal nano needles made of MWCNT, leading to a substantial enhancement in the specific surface area. At 1 A/g, the supercapacitor electrode composed of MnCo2O4/MnO2@MWCNT composite exhibited an exceptional specific capacitance of around 1539 F/g. Furthermore, it maintained approximately 95.5 % of its capacity even after undergoing 10,000 cycles. The asymmetric capacitor device, with MnCo2O4/MnO2@MWCNT and AC electrode, has a power density of 1537.8 W kg−1 and an energy density of 48.78 Wh kg−1. The MnCo2O4/MnO2composite exhibits exceptional rate performance, significant capacitance, and excellent cycle performance due to the synergistic effect between MnCo2O4/MnO2 and MWCNT, as well as the high specific surface area and unique structure. Consequently, it presents a viable option for the advancement of high-efficiency electrochemical super capacitors in the next generation.

Internal Space Modulation of Yolk-Shell FeSe2@Carbon Anode with Peanut-Shaped Morphology Enabling Ultra-Stable and Fast Potassium-Ion Storage.

The poor cycling stability and rate performance of transition metal selenides (TMSs) are caused by their intrinsic low conductivity and poor structural stability, which hinders their application in potassium-ion batteries (PIBs). To address this issue, encapsulating TMSs within carbon nanoshells is considered a viable strategy. However, due to the lack and uncontrollability of internal void space, this structure cannot effectively mitigate the volume expansion induced by large K+, resulting in unsatisfactory electrochemical performance. Herein, peanut-shaped FeSe2@carbon yolk-shell capsules are prepared by modulation of the internal space. The active FeSe2 is encapsulated within a robust carbon shell and an optimal void space is retained between them. The outer carbon shell promotes electronic conductivity and avoids FeSe2 aggregation, while the internal void mitigates volume expansion and effectively ensures the structural integrity of the electrode. Consequently, the FeSe2@carbon anode demonstrates exceptional rate performance (242 mAh g-1 at 10 A g-1) and long cycling stability (350 mAh g-1 after 500 cycles at 1 A g-1). Furthermore, the effect of internal space modulation on electrochemical properties is elucidated. Meanwhile, ex situ characterizations elucidate the K+ storage mechanism. This work provides effective guidance for the design and the internal space modulation of advanced TMSs yolk-shell structures.

One-step in situ doping of Sb achieves enhanced performance of [001]-oriented nano-LiFe0.6Mn0.4PO4/C cathode high-rate materials

The LiFe0.6Mn0.4PO4/C composite has become a cost-effective and reliable material for lithium battery storage in commercial applications, due to its significant safety benefits. However, its industrial application is limited by its suboptimal high-rate capacity and unsatisfactory cycling performance. To address this issue, Li(Fe0.6Mn0.4)1-xSbxPO4 (x = 0, 0.01, 0.03, 0.04, 0.05) materials were synthesized using a one-step solvothermal method in this study, aiming to modulate the microstructure and achieve Sb doping, thereby enhancing the electrochemical performance. The electrochemical test results indicate that LFMP/C doped with Sb (designated as LFMP/C-Sb0.04) displays exceptional electrochemical performance, with remarkable capacities of 166.6 mAh·g−1 and 146.8 mAh·g−1 at 0.2C and 1C, respectively. Notably, it achieves a capacity of 126.1 mAh·g−1 at a high rate (5C) and maintains an impressive capacity retention rate of 93.6 % after 300 cycles, outperforming the original LMFP/C (109.5 mAh·g−1), which retains only 61.5 % of its initial capacity. Further characterization of the samples reveals that in situ Sb doping promotes the growth of the [001] crystal orientation, enhancing the lithium-ion diffusion rate and effectively reducing electrode polarization and charge transfer resistance, thereby contributing to its exceptional rate performance. Moreover, Sb doping increases the M − O binding energy, strengthens the metal-oxygen framework, mitigates the Jahn-Teller effect caused by Mn3+ dissolution, and enhances its cycling stability.

Luffa vines-derived N, O doped porous carbon with high surface area for supercapacitors

Considerable attention has been devoted to creating porous carbons with exceptional surface area and porosity from biomass waste for energy storage devices. Herein, we employed a straightforward high-temperature carbonization and KOH activation method to synthesize nitrogen (N) and oxygen (O) co-doped porous activated carbons derived from luffa vines (LVACs). The impact of varying KOH concentrations on the morphology, structure, and electrochemical properties of LVACs was thoroughly investigated. The optimal mass ratio of KOH to LVACs at 1:6 achieved the maximum specific surface area of 3369 m2 g−1. At a current density of 1 A g−1, the LASC-6 electrode exhibits an impressive specific capacitance of 348.5 F g−1. It also demonstrates exceptional rate performance, retaining 70.6 % of its capacitance at a current density of 20 A g−1. The electrode possesses robust cycling stability, retaining 90 % of the initial capacitance after 5000 cycles. We assessed the practicality of LVAC-6 by constructing symmetric supercapacitors (SSCs) using KOH and [BMIM]BF4 electrolytes. The KOH and [BMIM]BF4 SSCs achieved specific capacitances of 86.75 and 50.31 F g−1, respectively, at a current density of 0.25 A g−1. Moreover, the [BMIM]BF4 SSC exhibited an impressive energy density of 51.05 Wh kg−1 at a power density of 346.15 W kg−1. Therefore, we propose a simple and cost-effective strategy to produce porous carbon materials with excellent electrochemical performance from discarded biomass waste, facilitating the preparation of environmentally friendly electrode materials for high-performance supercapacitors.

Binder‐induced inorganic‐rich solid electrolyte interphase and physicochemical dual cross‐linked network for high‐performance SiOx anode

AbstractSilicon oxide (SiOx) is heralded as the forefront anode material for high‐energy density lithium‐ion batteries, owing to its exceptional specific capacity. Nevertheless, the traditional combination of polyacrylic acid binder and acetylene black conductive carbon continues to struggle with the immense stress induced by the repetitive volume expansion and contraction processes. Here we report a high ionic conductivity, sulfonyl fluoro‐containing binder for SiOx anode via free radical copolymerization reaction between perfluoro (4‐methyl‐3,6‐dioxaoct‐7‐ene) sulfonyl fluoride and acrylic acid. The electrode fabrication process incorporated amino‐functionalized carbon nanotubes (CNT‐NH2) as the conductive agent. A three‐dimensional conductive network structure is constructed through physical and chemical double cross‐linking interactions between the ‐COOH and ‐SO2F functional groups of PAF0.1 binder, the ‐NH2 groups of CNT‐NH2, and the ‐OH groups on the surface of SiOx, including hydrogen bonds and covalent bonds. In addition, the binder induces the formation of a solid electrolyte interphase (SEI) rich in inorganic components such as Li2O, Li2SO3, Li2CO3, and LiF. Benefiting from the synergistic effects of the physically and chemically double cross‐linked three‐dimensional conductive network constructed by the PAF0.1 binder and CNT‐NH2, coupled with the rich‐inorganic SEI, the SiOx anode delivers exceptional rate performance, cycle stability, and lithium‐ion diffusion dynamics.

Formation of hollow stepped FePBA@rGO anode for high-performance lithium-ion batteries

Prussian blue and its analogues (PBAs) have been considered promising anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacity and cost-effectiveness. However, they often encounter challenges such as poor electronic conductivity and structural instability. Herein, we introduce a hollow stepped FePBA framework structure coated with reduced graphene oxide (FePBA@rGO). This sophisticated design significantly improves electronic conductivity and optimizes the diffusion pathways for lithium ions, leading to exceptional cycling stability and rate performance. The FePBA@rGO-15 anode developed in this study shows a notable rate capability of 294 mAh g−1 at a current density of 2 A g−1. More significantly, it demonstrates exceptional lithium storage performance, maintaining a capacity of 1245 mAh g−1 after 600 cycles at a current density of 1 A g−1. Density functional theory simulations further support our findings by illustrating that the robust interface between FePBA and rGO significantly accelerates the reactions kinetics of Li+ within the FePBA framework. This study represents a significant advancement towards improving the capacity and cycling stability of PBA-based anode materials, offering promising prospects for future battery applications.

Facilitating ion transport in porous chemically bonded black phosphorene/MXene heterostructured films for flexible high-rate supercapacitors

Developing thick MXene-based electrodes for supercapacitors (SCs) that possess both high specific capacitance and exceptional rate performance has become a critical research focus. However, MXene-based electrodes often face challenges related to the complex and elongated ion diffusion pathway caused by their large aspect ratio and nanosheet restacking, limiting the rate performance. Herein, we propose fabricating porous chemically bonded black phosphorene/Ti3C2Tx heterostructured films co-doped with S/N heteroatoms via electrostatic self-assembly followed by thermal foaming. The incorporation of black phosphorene serves to effectively prevent the restacking of Ti3C2Tx, while the porous structure enhances ion transport. Additionally, the doped heteroatoms significantly boost the electrochemical activity of Ti3C2Tx. The porous films of approximately 50 μm thickness demonstrate a high capacitance of 374 F g-1 at 0.5 A g-1, retaining 84% of the capacitance at 20 A g-1, thereby enabling the assembled SCs to deliver excellent rate performance. This work presents a promising and innovative approach for the development of high-rate MXene-based SCs.

Synthesis and electrochemical characteristics of metal nanoparticles decorated composite anode made of domestic alloy, used in lithium ion batteries

In this work, appropriate material selection and process design enable the succesful production of high energy density electrode active material in the form of XAZ (where X, A and Z stand for electrochemically active, electrochemically inactive and carbon materials, respectively). Herein, the precipitates rich in iron and chromium are extracted selectively from a local ferrochromium alloy utilizing hydrometallurgy procedures. The precipitates are then exposed to separate calcination to get iron-rich and chromium-rich oxides seperately. In the end, a composite (XAZ) is fabricated under the mild synthesis conditions by combining these oxides with activated carbon and aluminum powder in a planetary ball mill. The composite's morphological, structural, and chemical properties are all optimized. The galvanostatic test results clearly demonstrate that the powder made of XAZ composite with embedded metal nanoparticles delivers 798 mAh g-1 after 100th cycle under a current load of 50 mA g-1 and high capacity (600 mAh g−1) over 300 cycles with an exceptional rate performance. It is anticipated that this research will create novel opportunities for producing high-value electrode active materials from accessible, low-cost raw ingredients.

High-Performance Optimised Porosity Iron Electrode for Hybrid Battery Electrolyzer

The growing demand for efficient, cost-effective and sustainable energy systems has prompted significant research into the development of advanced electrochemical devices. Hybrid battery electrolyzer, integrating the capabilities of both battery and electrolyzer, is a groundbreaking technology aiming to enhance both energy conversion efficiency and storage capacity. [1] Iron with large earth-abundance, low-cost, robustness, and high capacity is a promising electrode material for such hybrid energy systems. [2-4]This study focuses on the design, fabrication, and performance evaluation of a novel porous iron electrode tailored for use in a hybrid battery electrolyzer system. The proposed electrode exhibits superior electrocatalytic activity, enhanced mass transport properties, and increased surface area, contributing to improved overall performance. The electrode's porosity and pore structure are tuned to facilitate efficient mass transport and electrolyte penetration, addressing common challenges associated with conventional electrodes. The electrochemical performance of the optimised porosity iron electrode is investigated through comprehensive characterization techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and charge-discharge cycling tests. Results indicate superior electrochemical properties, showcasing enhanced specific capacity, faster charge/discharge kinetics, and prolonged cycle life compared to conventional electrodes. The incorporation of conducting nanocarbon and sintering at optimized temperature of 800 ℃ led to the achievement of a stable and elevated capacity exceeding 500 mAh/g for these advanced iron electrodes. The iron electrodes exhibit outstanding porosity (65 - 70%), along with a pore size of 5-10 µm. This configuration results in exceptional current rate performance, achieving a discharge capacity of 350 mAh/cm2 at a current density of 35 mA/cm2 and 245 mAh/cm2 at 50 mA/cm2. Furthermore, the iron electrodes exhibit superior performance in high-current electrolysis, showcasing an HER potential of -1.25, -1.34, and -1.50 V (vs Hg/HgO) at a current density of 200, 500 and 1000 mA/cm2 respectively.These findings highlight the potential of optimised porosity iron electrodes as a key component in the development of high-performance and cost-effective hybrid battery electrolyzer systems. The integration of such advanced materials holds promise for unlocking new frontiers in energy storage and green hydrogen technology, contributing to the realization of efficient and sustainable energy systems.

Synergetic effects of S, N co-doping and surface concave-pores rich in lotus-leaf-like carbon nanosheets enabled threefold lithium storage mechanisms

Carbon-based materials based on structural and dimensional optimization are appealing as anode materials in lithium-ion batteries (LIBs). However rational design of high-efficiency low-dimensional carbon-based electrodes is still challenging. Therefore, a synthesis strategy based on Schiff base reaction has been devised for S, N co-doped and surface-enriched concave pores coupled with two-dimensional lotus-leaf-like carbon nanosheets (S, N-SCP/LCN). Experimental and theoretical results disclose that the synergetic effect of S, N co-doping and surface concave pores synergistically contribute to the improved lithium storage efficiency. The numerous concave pores within the defective carbon substrates significantly enhance the specific surface area and boost the quantity of active sites. Furthermore, S, N co-doping induces additional surface and structural defects and widens the crystallographic spacing. Herein, the formed threefold lithium storage mechanisms work synergistically to increase the active lithium storage sites and ion diffusion channels, promoting ion diffusion and charge transfer during lithium storage. As expected, the S, N-SCP/LCN exhibits remarkably high lithium storage capacity (1250 mAh/g at 0.1 A/g) and exceptional rate performance (445.65 mAh/g at a high rate of 10 A/g).

Artificial aluminum-doped SiO2 aerogel coating layer regulating zinc ions flow for highly reversible dendrite-free zinc anodes

As a sustainable, safe, and cost-effective alternative to conventional lithium-ion batteries, aqueous rechargeable zinc-metal-based batteries have attracted significant attention in large-scale energy storage. However, their practical application is hindered by zinc anode degradation, primarily dendrite growth and corrosion, which compromise battery performance and lifespan. Herein, we present an aluminum-doped silica (Al-SiO2) aerogel coating layer to address these issues. The aluminum-doped silica aerogel coating layer offers improved hydrophilicity and zinc ion adsorption capabilities because of its porous structure, high surface area, and functional groups. By facilitating uniform zinc ion deposition and providing a physical barrier against corrosion, the Al-SiO2 aerogel coating layer significantly mitigates dendrite formation and extends the electrochemical stability and operational lifespan of aqueous rechargeable zinc-metal-based batteries. Symmetric cell tests reveal that zinc anodes coated with Al-SiO2 can achieve stable cycling over 3000 h, indicating exceptional reversibility and rate performance, much better than that of the bare Zn anode. Furthermore, the Al-SiO2 aerogel-coated zinc anode coupled with MnO2 cathode forms a stable rechargeable full battery. This work contributes to the body of knowledge on advanced materials for energy storage, highlighting the potential of aerogel coatings as a scalable and effective solution for improving the performance and durability of zinc metal anode for aqueous rechargeable zinc-metal-based batteries.

Gel biopolymer electrolyte for high-voltage, durable, and flexible Zn/K dual-ion pouch cells

Zinc-ion rechargeable battery (ZIRB) is a promising candidate for future energy storage systems due to its cost-effectiveness, operational safety, and environmental friendliness. However, the commercial-scale application of ZIRB is hindered by its insufficient energy efficiency, poor rate capability, and inferior cycling stability. Here, we introduce a gel biopolymer electrolyte (GBE) empowered Zn/K dual-ion battery with exceptional cycling and rate performance. Calling for sustainability, this cellulose-encapsulated bisalt electrolyte presents strong mechanical robustness that inhibits Zn dendrite growth and promotes anodic plating/stripping reversibility. Sandwiching the GBE between a potassium manganese hexacyanoferrate (KMnHCF) cathode and a Zn anode, the coin-cell configuration of KMnHCF|GBE|Zn demonstrates a high voltage discharge plateau of 1.80 V, an initial capacity of up to 65 mAh g−1, and excellent cycling stability with capacity retention of 92 % after 1,000 cycles. Furthermore, the superior durability, flexibility, safety, and endurance with extreme conditions (e.g., bending, puncturing, and cutting) demonstrated by KMnHCF|GBE|Zn pouch-cell enables its future application in wearable electronics.

In Situ Polymerization of a Self-Healing Polyacrylamide-Based Eutectogel as an Electrolyte for Zinc-Ion Batteries.

Gel electrolytes have attracted extensive attention in flexible batteries. However, the traditional hydrogel electrolyte is not enough to solve the fundamental problems of zinc anodes, such as dendrite growth, side reactions, and freezing failure at temperatures below zero, which seriously restricts the development of zinc-ion batteries. As a flexible energy storage device, the zinc-ion battery inevitably undergoes multiple stretches, bends, folds, or twists in daily use. Here, a self-healing and stretchable eutectogel, designated as deep eutectic solvent-acrylamide eutectic gel (DA-ETG), was developed as a solid-state electrolyte for zinc-ion batteries. This gel was prepared by immobilizing a high-concentration ZnCl2 deep eutectic solvent (DES) into a polyacrylamide matrix through in situ polymerization under ultraviolet light. The eutectogel electrolyte showed exceptional mechanical properties with a maximum fracture strength of 0.6 MPa and a high ionic conductivity of 6.4 × 10-4 S cm-1. The in situ polymerization of the DA-ETG electrolyte in the assembly of a full solid-state zinc-ion battery increased the electrode-electrolyte interface area contact, reduced the ion transport distance between the electrode and electrolyte, minimized the internal resistance, and enhanced the battery's long-term cycling stability. Using the DA-ETG electrolyte, a remarkably high capacity of 580 mAh g-1 at 0.1 A g-1 was achieved by the zinc-ion battery, and a considerable capacity of 234 mAh g-1 was maintained even at 5 A g-1, showing exceptional rate performance. After 2000 cycles at 2 A g-1, the cell with the eutectogel retained a capacity of 85% with a cycling efficiency close to 98%, which demonstrated excellent cycling stability. The self-healing function enabled the prepared soft battery to be reused multiple times, with full contact between the electrode and electrolyte interface, and without device failures.

Cu single atoms regulating nitrogen active-sites of g-C3N4 for sodium ion storage

Nitrogen-rich material of graphitic carbon nitride (g-C3N4) with cost-effectiveness and easy accessibility has been considered as one of the most promising anode materials for sodium ion batteries (SIBs). However, the excessive presence of non-stable nitrogen sites in low crystallinity carbon nitrides would result in significant irreversibility, inadequate ion conductivity and structural instability, thereby limiting its practical application. Herein, a novel low-temperature strategy is proposed to stabilize the g-C3N4 by modulating the nitrogen configuration with single-atoms copper. The formed copper single atoms serving as anchors effectively regulate the coordination environment of nitrogen atoms in carbon nitride, thereby constructing stable nitrogen active sites for Na+ storage and conductive networks for rapid Na+ transport. Therefore, the Cu1.0/NC exhibits superior capacity (350.4 mAh g−1 at 50 mA g−1), exceptional rate performance (252.3 mAh g−1 at 1000 mA g−1), and long-cycle stability (capacity retention rate of 80.3 % after 1000 cycles at 5A g−1). Furthermore, in-situ Raman, ex-situ XANES and XPS technologies jointly reveal that the Cu atoms significantly influence the charge transfer process of Na+ and change the storage mode of sodium through redox effects during the sodiation/desodiation process. This work proves that single-atom engineering is a novel and feasible strategy to optimize the high-performance electrode materials for rechargeable batteries.

In situ preparation of MOF-74 for compact zincophilic surfaces enhancing the stability of aqueous zinc-ion battery anodes

Zinc-ion batteries (ZIBs), while celebrated for their environmental friendliness, abundant material availability, and inherent safety, face significant challenges that curtail their performance and lifecycle. These challenges include the formation of zinc dendrites, susceptibility to electrolyte corrosion, and the propensity for hydrogen evolution reactions. Addressing these critical issues, our research introduces an innovative surface modification strategy for zinc anode of ZIB with mild electrolyte, by the in-situ synthesis of Metal-Organic Framework (MOF-74) facilitated by the mild acidity of a 2,5-dihydroxyterephthalic acid (DHTA) methanol solution. The zincophilic sites and pore structure introduced by MOF-74 to substantially enhance the surface properties of zinc anodes and accelerate the solvation process, enabling uniform zinc deposition, inhibiting dendrite growth, and significantly bolstering corrosion resistance and electrochemical stability. Combination of physical and electrochemical characterization techniques are employed to validate the successful implementation of MOF-74 on the zinc anode surface and its resultant benefits. When tested in full cell setups with α-MnO2 as the cathode, the MOF-74 modified zinc anodes displayed exceptional cyclic stability and rate performance, surpassing those of unmodified counterparts. This investigation highlights the potential of MOF materials to address the electrochemical challenges facing zinc anodes, offering a straightforward yet efficacious strategy to enhance the performance and longevity of ZIBs.

High volumetric performance of functional carbon material enabled by co-pyrolysis of mango branches and Faradaic active N-enriched doping

Restricted by the poor volumetric performance, biomass-based supercapacitors are challenging to meet the rapid development of miniaturization and portability of energy storage devices, and the Faraday active nitrogen-doping strategy proves to be an efficient approach to address this concern. This study successfully synthesizes functional carbon materials with significant Faraday activity through a straightforward and environmentally friendly co-pyrolysis method. Mango branches served as the primary raw material, NH4B5O8∙4H2O acted as a template, and NH4Cl and NH4B5O8∙4H2O were utilized as the multiple nitrogen-enriched agents. A surface micro-NH3 environment can be achieved by modulating the addition of NH4Cl, and the decomposed NH3 is adsorbed on the biomass surface by the electrostatic adsorption of NH4B5O8∙4H2O. MA1.5N1.5-T700 showcases a compact self-supported structure with micro/mesopores, boasting a substantial nitrogen content of 2.95 %. It achieves a notable volumetric capacitance of 320 F/cm3 (368 F/g) at 0.5 A/g and maintains an exceptional rate performance of 72.9 % at 20 A/g. The constructed symmetrical supercapacitor also reveals an ultra-high energy density of 13.01 Wh/L (14.95 Wh/kg) and an impressive capacitance retention of 94.03 % undergoing 10,000 cycles. This study offers theoretical insights into fabricating electrode materials for high volumetric energy density supercapacitors through the pyrolysis of forestry waste.