Improved Ionic Diffusion through the Mesoporous Carbon Skin on Silicon Nanoparticles Embedded in Carbon for Ultrafast Lithium Storage

Sensitive and highly rapid electrochemical measurement of airborne coronaviruses through condensation-based direct impaction onto carbon nanotube-coated porous paper working electrodes

Rapid detection of indoor airborne viruses is critical to prevent the spread of respiratory diseases. Herein, we present sensitive, highly rapid electrochemical measurement of airborne coronaviruses through condensation-based direct impaction onto antibody-immobilized, carbon nanotube-coated porous paper working electrodes (PWEs). Carboxylated carbon nanotubes are drop-cast on paper fibers to make three-dimensional (3D) porous PWEs. These PWEs have higher active surface area-to-volume ratios and electron transfer characteristics than conventional screen-printed electrodes. The limit of detection and detection time of the PWEs for liquid-borne coronaviruses OC43 are 65.7 plaque-forming units (PFU)/mL and 2 min, respectively. The PWEs showed sensitive and rapid detection of whole coronaviruses, which can be ascribed to the 3D porous electrode structure of the PWEs. Moreover, water molecules condense on airborne virus particles during air sampling, and these water-encapsulated virus particles (<4 µm) are impacted on the PWE for direct measurement without virus lysis and elution. The whole detection takes ∼10 min, including air sampling, at virus concentrations of 1.8 and 11.5 PFU/L of air, which can be due to the highly enriching and minimally damaging virus capture on a soft and porous PWE, demonstrating the potential for the rapid and low-cost airborne virus monitoring system.

Toward the High-Performance Lithium Primary Batteries by Chemically Modified Fluorinate Carbon with δ-MnO2

Li/CF_x battery is one of the most promising lithium primary batteries (LPBs) which yields the highest energy density but with poor rate capability. This Achilles'' heel hinders the large-scale applications of Li/CF_x batteries. This work first reports a facile chemical modification method of CF_x with δ-MnO₂ . Having benefited from the chemical bonding, the electrochemical performance at high-rate discharge is remarkably enhanced without compromising the specific capacity. The coin cells exhibit an energy density of 1.94 × 10³  Wh kg^-1 at 0.2 C, which is approaching the theoretical energy density of commercial fluorinated graphite (2.07 × 10³  Wh kg^-1 ). A power density of 5.49 × 10⁴  W kg^-1 at 40 C associated with an energy density of 4.39 × 10²  Wh kg^-1 , which is among the highest value of Li/CF_x batteries, are obtained. Besides, the punch batteries achieve an ultrahigh power density of 4.39 × 10⁴  W kg^-1 with an energy density of 7.60 × 10²  Wh kg^-1 at 30 C. The intrinsic reasons for this outstanding electrochemical performance, which are known as the fast Li⁺ diffusion kinetics guided by thin δ-MnO₂ flakes and the low formation energy barrier caused by chemical bonding, are explored by the galvanostatic intermittent titration technique (GITT) and theoretical calculations.

Solvent-Free Soft-Template Synthesis of Highly Ordered Mesoporous Carbons via Self-Assembly Promoted by Mg(NO3)2

To improve the pore uniformity and volume of ordered mesoporous carbons produced by soft templating under solvent-free conditions, magnesium nitrate inorganic salt was incorporated into the precursors during the synthesis. The addition of magnesium nitrate in this procedure lowered the melting point of resorcinol, increased the diffusivity of the resorcinol-Pluronic F127 complex, and promoted self-assembly. The entry of Mg species into the core of the micelle of Pluronic F127 resulted in a modification of the pore structure resembling a channel-like hexagonal structure. In addition, the MgO in the pores effectively prevented the shrinkage of the mesopores under high-temperature conditions. Correspondingly, the uniformity and the mesopore volume of the mesoporous carbon obtained were also enhanced. Moreover, when used as electrodes, this ordered mesoporous carbon was able to significantly increase the capacity of electric double-layer capacitors. Thus, the current study proposes a novel method for regulating the structure and distribution of ordered mesoporous carbons.

Functionally Gradient Silicon/Graphite Composite Electrodes Enabling Stable Cycling and High Capacity for Lithium-Ion Batteries

Silicon (Si) is regarded as one of the most promising anode materials for high-energy-density lithium (Li)-ion batteries (LIBs). However, Li insertion/extraction induced large volume change, which can lead to the fracture of the Si material itself and the delamination/pulverization of electrodes, is the major challenge for the practical application of Si-based anodes. Herein, a facile and scalable multilayer coating approach was proposed for the large-scale fabrication of functionally gradient Si/graphite (Si/Gr) composite electrodes to simultaneously mitigate the volume change-caused structural degradation and realize high capacity by regulating the spatial distributions of Si and Gr particles in the electrodes. Both our experimental characterizations and chemomechanical simulations indicated that, with a parabolic gradient (PG) distribution of Si through the thickness direction that the two Si-poor surface layers guarantee the major mechanical support and the middle Si-rich layer ensures the high capacity, the as-prepared PG-Si/Gr electrode can not only effectively improve the stability of the electrode structure but also efficiently enable high capacity and stable electrochemical reactions. Consequently, the PG-Si/Gr electrode with a mass loading of 3.15 mg cm^-2 exhibited a reversible capacity of 579.2 mAh g^-1 (1.82 mAh cm^-2) after 200 cycles at 0.2C. Even with a mass loading of 8.45 mg cm^-2, the PG-Si/Gr anodes still delivered a high reversible capacity of 4.04 mAh cm^-2 after 100 cycles and maintained excellent cycling stability. Moreover, when paired with a commercial LiNi_0.5Mn_0.3Co_0.2O₂ (NCM532) cathode (9.56 mg cm^-2), the PG-Si/Gr||NCM532 full cell revealed an initial reversible areal capacity of 1.64 mAh cm^-2 and sustained a stable areal capacity of 0.94 mAh cm^-2 at 0.2C after 100 cycles.

UV-ozone contributions towards facile self-assembly and high performance of silicon-carbon fiber materials as lithium-ion battery anodes

Si-carbon composites have been considered as next generation lithium-ion battery anodes, with a view to sufficiently exerting the respective superiorities of high specific capacity of Si as well as excellent mechanical flexibility and electrical conductivity of carbon. However, direct blending of carbon with Si cannot obtain a synergy composite, resulting in inferior cycle properties during charge-discharge due to huge volume changes and deficient electron-conducting channels from the unavoidably aggregated Si. Herein, the composition of carbon fibers (CNFs) with Si nanoparticles (SiNPs) has been performed through UV-ozone surface modification followed by electrostatic self-assembly. It is found that solvent-free UV-ozone exposure of CNFs for 20 min successfully introduces carboxylic groups, as conventional acid treatment for 12 h. Besides UV-ozone surface modification provides an efficient and scalable route, the distribution and functionalization of CNFs can be also modified to effectively combine with amino-functionalized SiNPs. As a result, such Si-CNF composites containing 70.0 wt% SiNPs are able to exhibit excellent cycle performance with high coulombic efficiency of 74.8% at the 1st cycle and high specific discharge capacity of 1063 mAh g^-1 at the 400th cycle.

Ultrafast Li/Fluorinated Graphene Primary Batteries with High Energy Density and Power Density

Lithium/fluorinated carbon (Li/CF_x) primary batteries have essential applications in consumer electronics and medical and high-power military devices. However, their application is limited due to the difficulty in achieving simultaneous high power density and high energy density in the CF_x cathode. The tradeoff between conductivity and fluorine content is the decisive factor. Herein, by rational design, 3D porous fluorinated graphene microspheres (FGS-x) with both high conductivity and a high F/C ratio are successfully synthesized for the first time. FGS-x possesses an F/C ratio as high as 1.03, a nanosheet structure with hierarchical pores, abundant C═C bonds, few inactive C-F₂ bonds, and electrochemically active C-F bonds. The beneficial features that can increase discharge capacity, shorten the diffusion length for both ions and electrons, enhance the Li⁺ intercalation kinetics, and accommodate the volume change are demonstrated. The Li/FGS-1.03 coin cell delivers an unprecedented power density of 71,180.9 W/kg at an ultrahigh rate of 50 C (43.25 A/g), coupled with a high energy density of 830.7 Wh/kg. Remarkably, the Li/FGS-1.03 pouch cell exhibits a record cell-level power density of 12,451.2 W/kg at 20 C. The in-depth investigation by the ex situ method on structural evolution at different discharge depths reveals that the excellent performance benefits from the structural stability and the uniform formation of LiF. The FGS-1.03 cathode also has excellent performance in extreme operating temperatures (0 to 100 °C) and high active material mass loading (4.3 mg/cm²). These results indicate that the engineered fluorinated graphene developed here has great potential in applications requiring both high power density and high energy density.

Effect of dispersant on the synthesis of cotton textile waste-based activated carbon by FeCl2 activation: characterization and adsorption properties

Considering the accumulation and high consumption of activating agents, anhydrous ethanol (AE) could be used to dissolve them to improve the dispersion effect, which was an effective way of improving the practical utilization rate. In this study, FeCl₂ was dissolved in AE and further impregnated cotton textile waste (CTW) to prepare activated carbons (ACs) by pyrolysis. Afterward, ACs prepared in optimal conditions determined by the orthogonal experiment evaluated the physicochemical properties and adsorption capacities for Cr(VI). The results illustrated that AE greatly increased the dispersion of FeCl₂ on CTW, reduced the conventional impregnation dosage, and remarkably improved the activation efficiency. Textural analyses revealed that ACs exhibited excellent porosity properties and graphite carbon structure. FeCl₂ catalyzed the decomposition of volatile substances to produce gaseous products and promoted the transformation of amorphous carbon to graphite carbon that was conducive to pore development, followed by the formation of developed micropores and crystal structures. The adsorption performance of ACs was estimated using Cr(VI), and the adsorption was fitted with the pseudo-second-order kinetic and the Langmuir isotherm. Furthermore, the ACs possessed superior magnetization and reusability. Graphical abstract.

A Review of Recent Advancements in Electrospun Anode Materials to Improve Rechargeable Lithium Battery Performance

Although lithium-ion batteries have already had a considerable impact on making our lives smarter, healthier, and cleaner by powering smartphones, wearable devices, and electric vehicles, demands for significant improvement in battery performance have grown with the continuous development of electronic devices. Developing novel anode materials offers one of the most promising routes to meet these demands and to resolve issues present in existing graphite anodes, such as a low theoretical capacity and poor rate capabilities. Significant improvements over current commercial batteries have been identified using the electrospinning process, owing to a simple processing technique and a wide variety of electrospinnable materials. It is important to understand previous work on nanofiber anode materials to establish strategies that encourage the implementation of current technological developments into commercial lithium-ion battery production, and to advance the design of novel nanofiber anode materials that will be used in the next-generation of batteries. This review identifies previous research into electrospun nanofiber anode materials based on the type of electrochemical reactions present and provides insights that can be used to improve conventional lithium-ion battery performances and to pioneer novel manufacturing routes that can successfully produce the next generation of batteries.

Mesoscopic open-eye core-shell spheroid carved anode/cathode electrodes for fully reversible and dynamic lithium-ion battery models

We report on the key influence of mesoscopic super-open-eye core-shell spheroids of TiO₂- and LiFePO₄-wrapped nanocarbon carved anode/cathode electrodes with uniform interior accommodation/storage pockets for the creation of fully reversible and dynamic Li-ion power battery (LIB) models. The mesoscopic core-shell anode/cathode electrodes provide potential half- and full-cell LIB-CR2032 configuration designs, and large-scale pouch models. In these variable mesoscopic LIB models, the broad-free-access and large-open-eye like gate-in-transport surfaces featured electrodes are key factors of built-in LIBs with excellent charge/discharge capacity, energy density performances, and outstanding cycling stability. Mesoscopic open-eye spheroid full-LIB-CR2032 configuration models retain 77.8% of the 1^st cycle discharge specific capacity of 168.68 mA h g^-1 after multiple cycling (i.e., 1^st to 2000^th cycles), efficient coulombic performance of approximately 99.6% at 0.1C, and high specific energy density battery of approximately 165.66 W h kg^-1 at 0.1C. Furthermore, we have built a dynamic, super-open-mesoeye pouch LIB model using dense packing sets that are technically significant to meet the tradeoff requirements and long-term driving range of electric vehicles (EVs). The full-pouch package LIB models retain a powerful gate-in-transport system for heavy loaded electron/Li⁺ ion storage, diffusion, and truck movement through open-ended out/in and then up/downward eye circular/curvy folds, thereby leading to substantial durability, and remarkable electrochemical performances even after long-life charge/discharge cycling.

Enhancing the Performance of a Self-Standing Si/PCNF Anode by Optimizing the Porous Structure

Embedding silicon nanoparticles into carbon nanofibers is one of the effective methods to fabricate a self-standing and binder-free Si-based anode material for lithium-ion batteries. However, the sluggish Li-ion transport limits the electrochemical performance in the regular strategies, especially under high rate conditions. Herein, a kind of silicon nanoparticle in porous carbon nanofiber structures (Si/PCNFs) has been fabricated through a facile electrospinning and subsequent thermal treatment. By adjusting the mass ratio to 0.4:1, a Si/PCNF anode material with an effective Li⁺-migration pathway and excellent structural stability can be obtained, resulting in an optimal electrochemical performance. Although increasing the mass ratio of PEG to PAN further can lead to a larger pore size and can be beneficial to Li⁺ migration, thus being profitable for the rate capacity, the structural stability will get worse at the same time as more defects will form and lead to a weaker C-C binding, thus decrease the cycling stability. Remarkably, the rate capacity reaches 1033.4 mA h g^-1 at the current density of 5 A g^-1, and the cycling capacity is 933.2 mA h g^-1 at 0.5 A g^-1 after 200 cycles, maintaining a retention rate of 80.9% with an initial coulombic efficiency of 83.37%.

Interfacial Engineering of a Heteroatom-Doped Graphene Layer on Patterned Aluminum Foil for Ultrafast Lithium Storage Kinetics

The design of the interfacial architecture between the electrode and the current collector in lithium-ion batteries (LIB) plays a key role in achieving ultrafast lithium storage kinetics with respect to efficient charge transfer and cycle stability. However, in recent years, despite considerable efforts in the structural and chemical engineering of active materials (anode and cathode materials), interfacial architectures between the electrode and the current collector have received relatively insufficient attention in the case of ultrafast LIBs. Here, the interface architecture of a micropatterned Al current collector with a heteroatom-doped graphene interfacial layer is developed using roll pressing and dip coating processes. The cathode electrode fabricated with the resultant current collector offers increased contact area with enhanced interfacial stability between the electrode and the current collector because of micropatterns with heteroatom-doped graphene formed on the current collector, leading to outstanding ultrafast cycling capacity (105.8 mA h g^-1) at 20 C. Furthermore, at extremely high rate and long-term cycling performance, significant ultrafast cycling stability (specific capacity of 87.1 mA h g^-1 with capacity retention of 82.3% at 20 C after 1000 cycles) is noted. These improved ultrafast and ultra-stable performances are explained in terms of the increased electron collection/provision site with a high contact area between the electrode and the current collector for enhanced ultrafast cycling capacity and the effective corrosion prevention of the current collector with fast charge transfer for ultrafast cycling stability.

Coupling of a conductive Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 metal-organic framework with silicon nanoparticles for use in high-capacity lithium-ion batteries

A composite of Si nanoparticles (SiNPs) and a two-dimensional (2D) porous conductive Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 (Ni3(HITP)2) metal-organic framework (MOF), namely Si/Ni3(HITP)2, is suggested as a potential anode material for Li-ion batteries (LIBs). The Ni3(HITP)2 MOF with a carbon backbone and evenly dispersed Ni and N heteroatoms showed high potential for mitigating the volume expansion of Si and enhancing the electronic conductivity as well as Li storage ability of the Si/Ni3(HITP)2 anode. The Si/Ni3(HITP)2 electrode delivered a reversible capacity of 2657 mA h g-1 after 100 cycles of discharge-charge at a rate of 0.1C. Moreover, at a high rate of 1C, the Si/Ni3(HITP)2 electrode maintained a reversible capacity of 876 mA h g-1 even after 1000 cycles. The different rate capacities were 1655, 1129, and 721 mA h g-1 at 5C, 10C and 20C, respectively. The excellent electrochemical performance of the Si/Ni3(HITP)2 electrode in terms of improved cycle life and rate capability results from the open channels of the MOF network, which are beneficial for the movement of Li+ ions through the electrolyte to the electrode and the mitigation of stress by volume expansion of Si. We believe that the coupling of conductive Ni3(HITP)2 with Si is a potential way to make an anode for high-performance LIBs.

Bimetallic nanoparticles decorated hollow nanoporous carbon framework as nanozyme biosensor for highly sensitive electrochemical sensing of uric acid

An ultrasensitive electrochemical biosensor was developed to identify the low levels of uric acid (UA) in human serum. The gold/cobalt (Au/Co) bimetallic nanoparticles (NPs) decorated hollow nanoporous carbon framework (Au/Co@HNCF) was synthesized as a nanozyme by pyrolysis of the Au (III)-etching zeolitic imidazolate framework-67 (ZIF-67). The external Au NPs combined with internal Co NPs on the hollow carbon framework exhibited enhanced activity for UA oxidation, thereby generating superior signals. Accordingly, the Au/Co@HNCF biosensor presented ranking performances with a low detection limit of 0.023 μM (S/N = 3), an ultrahigh sensitivity of 48.4 μA μM^-1 cm^-2, and an extensive response in the linear region of 0.1-25 μM and the logarithmic region of 25-2500 μM. Owing to the ordered nanoporous framework and carbon interfacial features, the Au/Co@HNCF biosensor displayed adequate selectivity for UA sensing over a series of biomolecules. In addition, the Au/Co@HNCF biosensor was employed to quantify UA in human serum samples. The test results were basically consistent with those of a commercial apparatus, and thus demonstrated that the proposed Au/Co@HNCF biosensor was reliable for UA determination in clinical research.

Direct Growth of MoO2 /Reduced Graphene Oxide Hollow Sphere Composites as Advanced Anode Materials for Potassium-Ion Batteries

Hollow MoO₂ /reduced graphene oxide (MoO₂ /rGO) sub-microsphere composites have been fabricated through a simple hydrothermal approach followed by a heat treatment process. When employed as an anode material for potassium-ion batteries, the as-synthesized MoO₂ /rGO composite can deliver an initial charge specific capacity of 367.2 mAh g^-1 at 50 mA g^-1 , and its reversible capacity is 218.9 mAh g^-1 after 200 cycles. Even when cycled at 500 mA g^-1 , a high charge specific capacity of 104.2 mAh g^-1 is achieved after 500 cycles. The excellent cycling capability and rate performance may be ascribed to the synergistic effects of the reduced graphene oxide and the hollow MoO₂ spheres, which can increase the electrical conductivity of the composite, as well as resisting the strain arising from the repeated discharge-charge processes. These results indicate that the MoO₂ /rGO hollow sphere composites are promising negative electrode materials for potassium-ion batteries.

A facile method to fabricate a porous Si/C composite with excellent cycling stability for use as the anode in a lithium ion battery

Porous Si/C with excellent cycling stability has been fabricated by dehydrating Si/sucrose mixed powder with concentrated H₂SO₄.