Cycling Durability Research Articles

Efficient Bifunctional Oxygen Electrocatalysts for Rechargeable Zn−air Batteries Derived from Ni‐modified Prussian Blue

AbstractThe rational design and exploration of efficient, low‐cost and durable bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key to the development of rechargeable metal−air batteries. Here, we report a novel approach to in‐situ synthesize Fe0.64Ni0.36 nanoalloy encapsulated in nitrogen‐doped porous carbon nanotubes (FeNi@N−CNTs) as bifunctional electrocatalyst derived from Ni‐modified Prussian blue, on which the ORR/OER can be promoted by the N−CNTs surface due to the electron modulation caused by electron transfer from the inner FeNi nanoalloy to the N−CNTs surface. The abundant wide‐size range of mesopores in N−CNTs can offer rapid mass transport channels to facilitate the catalytic reactions. In addition, the encapsulation structure endows the outer N−CNTs acting as a “shield” to prevent the inner FeNi nanoalloy from corrosion in strong basic medium. Thanks to the synergistic effect between the N−CNTs and FeNi nanoalloy, the obtained FeNi@N−CNTs exhibits excellent bifunctional oxygen catalytic activity together with outstanding performance and cycling durability in rechargeable Zn−air battery. This work will open new avenues for the development of advanced bifunctional electrocatalysts for other metal−air batteries.

Preparation and Performance Investigation of Epoxy Resin-Based Permeable Concrete Containing Ceramsite.

Permeable concrete is an innovative type of concrete that provides a sustainable solution for stormwater management by allowing water to seep through and be filtered naturally. This study focuses on the preparation and performance investigation of an epoxy resin-based permeable concrete containing ceramsite. In this study, ceramsite, a lightweight aggregate, is used as a substitute for conventional aggregates in the concrete mixture. The epoxy resin is then added to improve the strength and durability of the concrete. A series of tests, including compressive strength, water permeability, and freeze-thaw resistance tests, are conducted to evaluate the performance of the epoxy resin-based permeable concrete. The results show that with an increasing epoxy resin binder-aggregate ratio, the compressive strength of the epoxy resin-based permeable concrete significantly increases while the permeability coefficient decreases. Different types of aggregates have varying effects on the compressive strength and permeability coefficient of epoxy resin-based permeable concrete, with high-strength clay ceramsite providing the highest compressive strength and lightweight ceramsite having the highest permeability coefficient. In addition, the discrete element simulation method effectively and feasibly determines the ultimate load and accurately simulates the compressive strength of the permeable cement-based mixture, consistent with the measured compressive strength. A quadratic polynomial regression analysis yielded an R2 value of around 0.93, showing a strong relationship between durability and freeze-thaw cycles. The findings contribute to the development of sustainable construction materials for stormwater management and offer potential applications in various infrastructure projects.

Mixed-valence system with near-infrared electrochromism of Fe(II)-based metal-organic coordination polymers

Near-infrared electrochromic materials have garnered great attention due to their potential applications in optical data storage and military camouflage. Herein, a networked metal-organic coordination polymer bearing multi-redox centra (Fe-MCP) was successfully prepared by coordination interaction of Fe ions with D-A-D-structure ligands through the liquid-liquid interface self-assembly strategy. The resultant uniform film exhibits improved NIR electrochromic attributed to the construction of mixed-valence system. Furthermore, a sandwich-structured electrochromic device was fabricated by combining Fe-MCP electrochromic layer, a gel composed of LiClO4, PMMA, and PC as the electrolyte layer, and anodically coloring PB as an ion storage layer. The resultant device illustrated an optical contrast of 31.4 % at 800 nm and 34.2 % at 1000 nm, a response speed of 4.0 s/8.3 s at 800 nm and 7.6 s/2.7 s at 1000 nm, and good cycling durability. The design principles proposed in this study provide a new insight for the preparation of high-performance NIR electrochromic materials.

Building oxygen-rich vacancy coating for fast Li-ion diffusion kinetics and stable cycling of lithium-rich layered oxide cathode at wide-temperature

As a cathode with a high energy density for Li-ion batteries, Li-rich layered oxide (LLO) cathodes suffer from short lifespans and poor rate performance, mainly due to their irreversible lattice oxygen evolution leading to severe structural degradation and oxygen release. Herein, we propose the use of Zn-doped SnO2 coated with LLO cathode to tackle these issues. Compared to the traditional method of coating oxides on the surface of lithium-rich cathodes, Zn doping of SnO2 coating can artificially create abundant oxygen vacancies for LLO cathode, which can provide a buffer boundary for active oxygen generated by lithium-rich cathode during circulation, effectively promoting the reversible reaction of oxygen redox couple and stabilizing lattice oxygen. The experimental results show that the surface of the LLO cathode's Zn-doped SnO2 is rich in oxygen vacancies could significantly boost the kinetics of lithium ion transfer, and effectively inhibit layer-to-spinel phase transition, and lattice oxygen release. By taking advantage of the Zn-doped SnO2 coating, the capacity stability of LLO cathode is raised from 58.1 % to 86.7 % at 1C after 500 cycles and also obtains outstanding rate performance and cycling durability at wide-temperature (−10 to 55 °C).

Upgrading the electrochemical performance of Li-rich Mn-based cathodes through additional fast Li storage assisted by few-layer MXene

Li-rich Mn-based [xLi2MnO3·(1-x)LiMO2] (LR) cathodes are low cost and have high energy density, indicating high commercialization potential. However, the low initial coulombic efficiency, poor rate performance, and inferior cycling durability of LR cathodes confer difficulty in such commercialization. Herein, we proposed the use of a few-layer MXene (Ti3C2) to improve electrochemical performance. We found that the few-layer MXene can improve the conductivity and provide additional capacity at low voltage (2.25 V), thereby greatly increasing the initial coulombic efficiency, rate, and cycle performance. The additional capacity may have originated from an interface space-charge storage with capacitive properties, that is, the storage and transport of ions and electrons at the interface of Ti3C2 and LR particles. The modified sample exhibited an initial coulombic efficiency of 94.3 % and 158 mAh g–1 at 5C. Even after 300 cycles at 5C, it retained 87.3 % of its capacity. This novel strategy can serve as a reference for the modification of other electrode materials and can also expand the application of MXene in the field of batteries.

Zn-induced formation of polymetallic carbonate hydroxide cathodes with high mass loading for high performance aqueous alkaline Zn-based batteries

Developing high mass loading cathodes with high capacity and durable life cycles is greatly worthwhile and challenging for alkaline aqueous rechargeable Zn-based batteries (AAZBs). Herein, we demonstrate an efficient zinc-induced strategy to rationally develop Zn-Ni-Co carbonate hydroxides/hydroxides heterostructure nanosheet array with an extremely high mass loading of 9.2 mg cm−2 on Ni foam (ZNC/NF) as such a superior cathode for AAZBs. It is discovered that Ni-Co hydroxide nanowires can be transformed into Zn-Ni-Co carbonate hydroxides/hydroxides heterostructure nanosheet with rich defect structures after the introduction of Zn during the synthetic process. The formed heterostructures and rich defect structures can enhance ion and electron transfer efficiency, thus ensuring the excellent electrochemical performance under high loading condition. Consequently, the ZNC/NF//Zn battery shows an outstanding areal capacity of 2.1 mAh cm−2 at 5 mA cm−2, with an ultrahigh energy density of 3.6 mWh cm−2. Moreover, the battery can still retain a high capacity of 0.42 mAh cm−2 after 5000 cycles at 50 mA cm−2, suggesting strong long-term cycling stability. This research enables pave the way for the rational design and manufacture of advanced electrode materials with large mass loadings.

Nitrogen-doped coal-based microporous carbon material co-activated by HCOOK and urea for high performance supercapacitors

The doping of heteroatoms can adjust the surface chemical state of porous carbons, which is conducive to improving the surface activity, and enhancing the hydrophicity and conductivity of carbon electrodes. Herein, we developed a facile and green strategy to obtain nitrogen-doped coal-derived porous carbon dominated by micropores for high performance supercapacitor. The hydrothermal treatment of coal and urea can not only achieve the doping of nitrogen atoms, but also conducive to the subsequent activation process. Benefiting from the large micropore volume and specific surface area (0.68 cm3 g−1 and 1563 m2 g−1), suitable micropore size, and high content of surface CO, N-Q and N-5, the optimal sample exhibits a large capacitance of 371 F g−1 (1 A g−1), high capacitance retention of 67% (50 A g−1), and outstanding cyclic durability in a three-electrode system (aqueous electrolyte). Furthermore, the symmetrical supercapacitor in neat EMIM BF4 shows a high energy density of 40 Wh kg−1 (625 W kg−1). This work proposes a facile and potential strategy for preparing nitrogen-doped porous carbon materials with outstanding electrochemical property for supercapacitors and provides a novel insight for the efficient and low carbonization utilization of coal resources.

Large scale preparation of Na3V2(PO4)2F3 with cross-linked double carbon network for high energy density sodium ion batteries at −20 °C

Na3V2(PO4)2F3 (NVPF) is considered as one of the most promising cathode materials for high-voltage sodium ion batteries, because of its high energy density and rapid ion diffusion ability. Yet, the insulating nature of (PO4)3− and the perishable F− cause the NVPF suffers from poor rate performance and short cycle durability. Herein, a particular three-dimensional double carbon network-intertwined NVPF nanospheres (notated as NVPF/CNTs) are successfully prepared by spray drying method. The coting carbon on the surface of NVPF can collect electrons at same time effectively improve lattice stability. And the unique conductive three-dimensional CNTs network framework has significantly improved the electrical conductivity between particles and enlarged the contact area between the cathode and electrolyte. Thanks to the unique structure, the electrochemical properties of NVPF/CNTs electrode has been significantly improved, showing awesome rate capability (127.7 mAh g−1 at 0.1 A g−1 and 77.7 mAh g−1 at 10 A g−1) and ultra-long cycle life (92.1 % capacity reminded after 20,000 cycles at 10 A g−1). In addition, it has excellent adaptability to low temperature (96.8 mAh g−1 at 0.1 A g−1, 98 % capacity retention after 500 cycles at −20 °C) and considerable energy density of 353.4 Wh kg−1 in NVPF/CNTs||hard carbon full-cells. These excellent properties further enhance the competitiveness of NVPF/CNTs to achieve high performance of sodium-ion batteries.

Exploring the Potential of Carbonized Nano-Si within G@C@Si Anodes for Lithium-Ion Rechargeable Batteries.

This study presents the synthesis, characterization, and electrochemical performance evaluation of carbon@silicon (C@Si) and graphite@carbon@silicon (G@C@Si) nanocomposites as potential anode materials for lithium-ion batteries (LIBs). Employing a combination of mechanical milling and carbonization using citric acid, we developed nanocomposites exhibiting unique core-shell structures, as confirmed by detailed SEM and TEM analysis. The G@C@Si nanocomposite displayed superior electrochemical performance, delivering an initial discharge capacity of 1724 mAh g-1 and a high initial Coulombic efficiency of 87.37%. The nanocomposite demonstrated remarkable cycling durability with a discharge capacity of 1248 mAh g-1 over 200 cycles and an average Coulombic efficiency of 99.1% and high-capacity retention of about 83%. Notably, a high capacity of 1325 mAh g-1 was observed at a high 3C rate, and the electrode showed excellent resilience by rapidly recovering to a discharge capacity of 1637 mAh g-1 when the C rate was reduced back to 0.5C. Electrochemical impedance spectra revealed a reduced charge transfer resistance of approximately 43 Ω in the G@C@Si nanocomposite as compared to that of C@Si (∼56 Ω) and nano-Si (105 Ω), indicating enhanced lithium-ion diffusion due to the integration of graphite. Postcycle electrode analysis revealed excellent structural integrity, with minimized volume changes in both C@Si and G@C@Si. XPS studies revealed a thinner SEI layer formation in the G@C@Si electrode compared to C@Si. The C@Si core-shell formation through the citric acid treatment of nano-Si and integration of graphite by mechanical milling significantly boosts the electrochemical performance of the G@C@Si nanocomposite. These findings suggest that the G@C@Si nanocomposite offers immense potential for utilization in high-capacity and high-efficiency LIBs.

Durability of clayey soil stabilized with calcium sulfoaluminate cement and polypropylene fiber under extreme environment

Calcium Sulfo-Aluminate Cement (CSAC) is gaining interest among researchers, consultants, engineers, and environmentalists as a prospective replacement of Ordinary Portland Cement (OPC) across many construction industries. The main reason is that the production of CSAC generates a lower carbon footprint as compared to OPC cement production. Other benefits of CSAC include quick bonding & strength development, and less shrinkage. Many studies are available and ongoing on the advantages and limitations of CSAC in concrete. However, only a few studies are available on its application in soil stabilization. Therefore, the efficiency of CSAC for soil stabilization is a topic of discussion in geotechnical engineering. In this research, a locally sourced highly compressible clayey soil was stabilized with different combinations of CSAC and polypropylene fiber (e.g., 5.0%, 7.5% & 10.0% of CSAC and 0.5% & 1.0% polypropylene fiber), and its effectiveness was observed and evaluated in terms of durability (Wetting-Drying and Freezing-Thawing tests) against extreme environments and also checked Unconfined Compressive Strength (UCS) as per American Society of Testing and Materials (ASTM) guidelines. The findings of this research are evaluated in terms of percentage of soil loss, change in moisture content and volume, and loss of strength after durability exposure. Moisture content and bulk unit weight were determined after each stage in the Freezing-Thawing durability cycles. Samples prepared with 10.0% of CSAC and 1.0% of fiber were able to survive all durability cycles of Wetting-Drying with PCA (Portland Cement Association) soil-loss percentage criteria. On the other hand, samples prepared with 10.0% cement with 0.5% as well as 1.0% fiber were able to survive all durability cycles of Freezing-Thawing with PCA soil-loss percentage criteria. These survived samples showed a significant amount of unconfined compressive strength even after being subjected to these durability cycles.

An electron/ion pathway reconstruction strategy enabling fast aqueous Zn2+ storage

Aqueous Zn-ion batteries (ZIBs) are considered ideal alternatives for scalable energy storage due to their reliable safety, affordable cost, and sustainability. However, the further development of ZIBs is limited by the design of the cathode, especially with the kinetic coupling of electron transfer and ion diffusion. Here, we develop an electron/ion pathway reconstruction strategy to enhance the kinetics of Zn storage by designing a composite of reduced graphene oxide-wrapped polyaniline/vanadium oxide superlattices. The superlattice structure of V–O layers stacked with polyaniline enables rapid Zn2+ diffusion due to the enlarged interlayer spacing and redistributed electron structure. Meanwhile, the lamellar superlattices wrapped with rGO optimize the electron transfer pathway and enhance mechanical stability. Therefore, the synergistic optimization between ion migration inside superlattices and charge transport in bulk materials achieves double acceleration for Zn2+ storage kinetics, showing superior rate capability (≥100 mAh/g at 20 A/g) and cycling durability. Moreover, the electrochemical mechanism investigation shows that the as-obtained composite cathode presents highly reversible Zn diffusion behavior and good structural stability through a series of in-situ spectroscopic characterizations. It is hoped that this electron/ion pathway reconstruction strategy can provide a new perspective for the development of high-performance cathodes for aqueous batteries.

Investigating the role of 3D hierarchical Ni-CAT/NiFe-LDH/CNFs in enhancing the oxygen evolution reaction and Zn-air battery performance

NiFe layered double hydroxide (NiFe-LDH) is an efficient and widely available catalyst for the oxygen evolution reaction (OER), but further improvement of its OER property remains a challenge. Therefore, a conductive Ni-organic framework is triumphantly synthesized in-situ on NiFe-LDH/carbon nanofibers (Ni-CAT/NiFe-LDH/CNFs) through a hydrothermal treatment. This configuration utilizes the exposed surface area and the electron transfer pathways of Ni-CAT and CNFs, resulting in exceptional OER kinetics in alkaline conditions. A low overpotential of 370 mV at 10 mA cm−2 and a small Tafel slope of 79 mV dec−1 are achieved. The liquid-state Zn-air batteries, featuring Ni-CAT/NiFe-LDH/CNFs catalyst as an air cathode, indicate a significant peak power density of 292.1 mW cm−2 and an extended cycle durability of over 66 h. Solid-state Zn-air batteries demonstrate stable cycling at various flat/bent/flat states, showing great potential for flexible electronic device applications. According to experimental measurements and computational analysis, the in-situ growth of Ni-CAT on the NiFe-LDH matrix can optimize intermediate adsorption and alter hydrophilicity, resulting in improved performance of Zn-air batteries.

Facile synthesis of nanostructured sodium and MoS2 incorporated Ni-MOFs with excellent cyclic durability for symmetric supercapacitor application

Highly porous and nanostructured metal-organic frameworks (MOFs) have fascinated enormous interest as electrode active materials for electrochemical energy storage systems, whereas their practical applications are significantly hindered by their relative inferior energy density and cyclability. In this study, MoS2 with layered structure was successfully incorporated onto hierarchical Ni-MOFs via a facile hydrothermal approach. Moreover, sodium cations were introduced to improve electronic conductivity. The resulting nanocomposites (sodium ions and MoS2 incorporated Ni-MOFs) exhibited hierarchical porous structures with varying dimensions, offering increased volume for charge storage and diffusion channels for electrolyte ions. Benefiting from the unique topological architectures, the as-synthesized porous nanocomposites delivered an excellent supercapacitive performance, achieving a superlative energy of 33.33 Wh kg−1 and a power density of 3390 W kg−1. Furthermore, the as-fabricated symmetric supercapacitor device delivered a remarkable cycling durability where the acquired outstanding capacitance retention was 97.42% and coulombic efficiency was 97.82% respectively over more than 10,000 cycles in an aqueous electrolyte.

Oxygen vacancy defect engineering of porous single-crystal VO2 nanobelts for aqueous zinc ion battery cathodes

Aqueous zinc ion batteries (AZIBs) have received considerable attention due to their high safety, low cost, environmental friendliness, and high theoretical capacities. However, the energy/power density and cost efficiency of AZIBs are still limited by cathode materials, so the exploration of advanced cathode materials plays a key role in their further practical development. Herein, porous single-crystal VO2 nanobelts with adjustable oxygen vacancy defects (Od-VO2 NBs) are obtained by precise regulation of chemical synthesis. Collective results reveal that the defect engineering designed Od-VO2–2 NBs as the optimized cathode exhibit excellent electrochemical performance due to the suitable oxygen vacancy defects, showing a high discharging capacity of 202.8 mAh g–1 after 500 cycles at 0.5 A g–1, durable cycling stability over 1000 cycles at 1.0 A g–1, and impressive rate performance. The electrode design can effectively improve the electrical conductivity and structural stability of Od-VO2 cathodes to accelerate reaction kinetics, and provide more activated sites for reversible Zn2+ storage. Besides this, the porous single-crystal structure favors rapid ions/electrons transport and buffers the volume change. This work demonstrates a simple method to design vanadium-based cathodes for high-performance AZIBs, making it a promising candidate for next-generation energy storage devices.

NixB/rGO as the cathode for high-performance aqueous alkaline zinc-based battery

Aqueous alkaline zinc batteries (AZBs) exhibit great potential due to their high capacity, high safety and low cost. However, despite these advantages, the lack of high stability and high utilization rate makes the search for high-performance cathode materials a great challenge. Here, an amorphous nickel boride/rGO (NixB/rGO) complex structure was designed. As a result of abundant unsaturated active sites and synergistic electronic effects, amorphous NixB exhibits excellent energy storage properties. As well as having high electrical conductivity, rGO avoids aggregation of NixB nanoparticles, ensuring that NixB/rGO electrodes have a high energy storage capacity. The structure has a strong adhesion between NixB and rGO, which protects its stable structure and extends its life. More importantly, the NixB/rGO//Zn full battery shows remarkable capacity (228.4 mAh/g at 2 A/g), extraordinary cycle durability (93.7% retained after 1000 cycles) and strong energy density 399.7 Wh/kg, when coupled with NixB/rGO cathode. This work will also shed light on other nickel-zinc batteries in order to achieve super durability and capacity.

Electrochemically alternating voltage induction and in-situ preparation of tin-based multiphase structures anode for sodium-ion batteries

Tin-based materials possess a high-capacity as a potential anode for Na-ion batteries (SIBs), but the inferior electric conductivity and sluggish reaction kinetics limit their further development. In this paper, we have successfully constructed multiphase structure SnO2/SnS/SnS2 by combining the electrochemical induction and in-situ hydrothermal method to effectively alleviate these problems. The continuous addition of sulfur source (thioacetamide, TAA) results in the formation of a transition from pure product (SnO2) to double structure (SnO2/SnS), and finally multiphase structure (SnO2/SnS/SnS2). Compared to single or bimetal chalcogenides, the tri-metal chalcogenides have strengthened synergistic effects between diverse components. Additionally, the SnO2/SnS/SnS2 composites exhibit small grain size and abundant mesoporous structure, which aid to shorten the distance of ions transfer and increase surface active sites for Na-ions storage. The SnO2/SnS/SnS2 anode displays optimal diffusion coefficient (1.94 × 10−15 cm2 s−1) and cycling durability, with a recoverable specific discharge ability of 401 mA h g−1 over 100 cycles at 100 mA g−1 and a maintenance overpasses 77 %. These results indicate that the construction of multiphase structures is a prospective way to improve the reaction kinetics of Sn-based materials for SIBs.

Potassium-Based Dual-Ion Batteries Operating at -60 °C Enabled By Co-Intercalation Anode Chemistry.

Battery performance at subzero is restricted by sluggish interfacial kinetics. To resolve this issue, potassium-based dual-ion batteries (K-DIBs) based on the polytriphenylamine (PTPAn) cathode with anion storage chemistry and the hydrogen titanate (HTO) anode with K+ /solvent co-intercalation mechanism are constructed. Both the PTPAn cathode and the HTO anode do not undergo the desolvation process, which can effectively accelerate the interfacial kinetics at subzero. As revealed by theoretical calculations and experimental analysis, the strong K+ /solvent binding energy in the dilute electrolyte, the charge shielding effect of the crystal water, and the uniform SEI layer with high content of the flexible organic species synergically promote HTO to undergo K+ /solvent co-intercalation behavior. The special co-intercalation mechanism and anion storage chemistry enable HTO||PTPAn K-DIBs with superior rate performance and cycle durability, maintaining a capacity retention of 94.1% after 6000 cycles at -40 °C and 91% after 1000 cycles at -60 °C. These results provide a step forward for achieving high-performance energy storage devices at low temperatures.

Hierarchically Porous Carbon Rods Derived from Metal-Organic Frameworks for Aqueous Zinc-Ion Hybrid Capacitors.

Aqueous zinc-ion hybrid capacitors (ZIHCs), as ideal candidates for high energy-power supply systems, are restricted by unsatisfied energy density and poor cycling durability for further applications. The construction of a surface-functionalized carbon cathode is an effective strategy for improving the performance of ZIHCs. Herein, a high-performance ZIHC is achieved using oxygen-rich hierarchically porous carbon rods (MDPC-X) prepared by the pyrolysis of a metal-organic framework (MOF) assisted by KOH activation. The MDPC-X samples displayed high electric double-layer capacitance (EDLC) and pseudocapacitance owing to their oxygen-rich surfaces, abundant electroactive sites, and short ions/electron transfer lengths. The surface oxygen functional groups for the reversible chemical adsorption/desorption of Zn2+ are identified using ex situ X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Consequently, the as-assembled ZIHC exhibited a high capacity of 323.4 F g-1 (161.7mA h g-1) at 0.5 A g-1 and a retention of 147 F g-1 (73.5mA h g-1) at an ultrahigh current density of 50Ag-1, corresponding to high energy and power densities of 145.5W h kg-1 and 45kW kg-1, respectively. Furthermore, an excellent cycling life with 96.5% of capacity retention is also maintained after 10 000 cycles at 10 A g-1, demonstrating its promising potential for applications.

A New Ternary Co-Free Layered Cathode, Li[Ni1-x-yTixAly]O2, for High-Energy Lithium-Ion Batteries

For the sustainable development of Li[NixCoyMn1−x−y]O2 and Li[NixCoyAl1−x−y]O2 cathodes, reducing the reliance on cobalt, which is extremely expensive with a fluctuating price and supply uncertainty, is considered essential. In this study, we propose a highly stable Co-free Ni-rich layered cathode developed through a new doping strategy that incorporates heteroelements at different doping stages, including the introduction of Ti during Ni(OH)2 synthesis and doping excess amounts of Al during the lithiation step. The multi-stage engineering strategy guarantees structural durability and electrochemical cycling stability of the inherently unstable LNO to a commercially viable level. Combined with particle surface protection, the Li[Ni0.951Ti0.008Al0.041]O2 cathode retains 72.0% of its initial capacity after 3500 cycles, which is unprecedented among previously reported Co-free cathodes. The proposed Co-free cathodes can meet the energy density required for next-generation electric vehicles, as the cathode delivers 890 Wh kgcathode-1, and presents a clear breakthrough for the development of commercially viable LNO cathode.

Locally graphitized biomass-derived porous carbon nanosheets with encapsulated Fe3O4 nanoparticles for supercapacitor applications

Waste biomass-derived porous carbons offer significant application prospects, especially in the field of carbon-based supercapacitors, while simultaneously reducing carbon emissions. However, their relatively low conductivity and charge storage capacity have resulted in a low energy density for supercapacitor applications, thereby significantly impeding their large-scale commercial application. At present, comprehensively enhancing the performance of biomass-derived carbon-based supercapacitors (BC-SCs), including energy density, power density, cyclic stability, and rate capability, remains a challenge. To overcome this challenge, Fe3O4 nanoparticles with high conductivity are successfully encapsulated within biomass-derived carbon nanosheets. In conjunction with a localized graphitization strategy, a novel electrode material, locally graphitized biomass-derived hierarchical porous carbon nanosheets with encapsulated Fe3O4 nanoparticles, possessing high specific surface area and conductivity, is successfully prepared. Coupled with TFA electrolyte featuring a high working voltage of 1.4 V, a significant enhancement in the energy density is achieved for BC-SCs, along with ultra-long cyclic durability and excellent fast-charging capabilities. The BC-SCs assembled achieves a high energy density of 15.80 kW kg−1 at a power density of 483 W kg−1. Even at a high power density of 16.40 kW kg−1, the energy density remains at 11.4 Wh kg−1. After 100,000 cycles, the capacitance retention remains remarkably high at 99.6 %. By utilizing hydroquinone as a redox additive, the energy density can be further improved to 32.0 Wh kg−1. This work would pave the way for the large-scale commercialization of BC-SCs.