Hollow carbon sphere with open pore encapsulated MnO2 nanosheets as high-performance anode materials for lithium ion batteries

Co-Existence of Iron Oxide Nanoparticles and Manganese Oxide Nanorods as Decoration of Hollow Carbon Spheres for Boosting Electrochemical Performance of Li-Ion Battery

Here, we report that mesoporous hollow carbon spheres (HCS) can be simultaneously functionalized: (i) endohedrally by iron oxide nanoparticle and (ii) egzohedrally by manganese oxide nanorods (FexOy/MnO2/HCS). Detailed analysis reveals a high degree of graphitization of HCS structures. The mesoporous nature of carbon is further confirmed by N2 sorption/desorption and transmission electron microscopy (TEM) studies. The fabricated molecular heterostructure was tested as the anode material of a lithium-ion battery (LIB). For both metal oxides under study, their mixture stored in HCS yielded a significant increase in electrochemical performance. Its electrochemical response was compared to the HCS decorated with a single component of the respective metal oxide applied as a LIB electrode. The discharge capacity of FexOy/MnO2/HCS is 1091 mAhg-1 at 5 Ag-1, and the corresponding coulombic efficiency (CE) is as high as 98%. Therefore, the addition of MnO2 in the form of nanorods allows for boosting the nanocomposite electrochemical performance with respect to the spherical nanoparticles due to better reversible capacity and cycling performance. Thus, the structure has great potential application in the LIB field.

An amorphous hierarchical MnO2/acetylene black composite with boosted rate performance as an anode for lithium-ion batteries

Amorphization is considered to be an effective way to enhance the electrochemical performances of electrode materials due to the existence of isotropy and numerous defects. Herein, an amorphous hierarchically structured MnO₂/acetylene black (a-MnO₂/AB) composite is successfully fabricated via a redox method and subsequent mechanical ball milling. The a-MnO₂/AB composite is composed of approximately 300 nm flower-like amorphous MnO₂ submicron spheres and acetylene black particles with a diameter of about 50 nm. The a-MnO₂/AB electrode exhibits an initial coulombic efficiency of 73.2%, excellent rate capabilities of 318 mA h g^-1 at 9.6 A g^-1, and high specific capacity retention of 1300 mA h g^-1 after 300 cycles at 1 A g^-1. The amorphous structure can provide more channels for rapid lithium-ion transmission due to the disorder and defects, and the ion-diffusion coefficient (∼5 × 10^-7 cm² s^-1) is higher than those of crystalline materials. Due to the strong interactions (Mn-O-C bonds) between MnO₂ and AB as a result of the ball milling, the composite shows low charge transport resistance and small volume changes during the discharging/charging process. This work provides a facile route for the construction of amorphous hierarchically structured Mn-based oxides as anodes for lithium-ion batteries (LIBs).

Highly conductive triple-layered hollow MnO2@SnO2@NHCS nanospheres with excellent lithium storage capacity for high performance lithium-ion batteries

Multilayered hollow MnO2@SnO2@NHCS nanospheres incorporate the merits of highly conductive N-doping and the synergistic effect of metal oxides.

Hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers with rosary-like structure as a high surface substrate for impedimetric detection of Pseudomonas aeruginosa

The design of hollow mesoporous carbon-based materials has attracted tremendous attention, due to their sizeable intrinsic cavity to load specific chemical and unique physical/chemical properties in various applications. Herein, we have established an effective strategy for the preparation of novel hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers (CNCNF) with rosary-like structure. By embedding ultrafine hollow carbon nanocapsules into electrospun polyacrylonitrile (PAN) skeleton, the as-designed composite CNFs were carbonized into hierarchical porous CNFs, consisted of interconnected nitrogen-doped hollow carbon nanocapsules. Due to its individual structural properties and unique chemical composition, the performance of CNCNF was evaluated in aptasensor application via the detection of Pseudomonas aeruginosa (PA). Under optimized conditions, the aptasensor based on CNCNF has a detection limit of 1 CFU⋅mL^-1 and a linear range from 10¹ CFU ⋅mL^-1 to 10⁷ CFU ⋅mL^-1 (n = 3). Moreover, the designed aptasensor possesses high sensivity, high selectivity, low detection limit, and high reproducibility. These studies showed that the CNCNF material offers a wide variety of enhanced electrochemical features as an electrode material for aptasensor application.

N-doped 3D porous carbon materials derived from hierarchical porous IRMOF-3 using a citric acid modulator: fabrication and application in lithium ion batteries as anode materials

N-doped three-dimensional carbon nanostructured materials were obtained by calcinating hierarchical porous IRMOF-3 materials, and were fabricated in the presence of citric acid as a modulator via the conventional synthetic protocol, at 900 °C in an Ar atmosphere. The resultant carbon materials were used as anode materials for lithium ion batteries, and exhibited excellent lithium storage capacity and cycling stability and maintained a capacity of about 555 mA h g^-1 at the current density of 0.2 A g^-1 after 100 cycles.

Polypyrrole coated δ-MnO2 nanosheet arrays as a highly stable lithium-ion-storage anode

Manganese dioxide (MnO₂) with a conversion mechanism is regarded as a promising anode material for lithium-ion batteries (LIBs) owing to its high theoretical capacity (∼1223 mA h g^-1) and environmental benignity as well as low cost. However, it suffers from insufficient rate capability and poor cyclic stability. To circumvent this obstacle, semiconducting polypyrrole coated-δ-MnO₂ nanosheet arrays on nickel foam (denoted as MnO₂@PPy/NF) are prepared via hydrothermal growth of MnO₂ followed by the electrodeposition of PPy on the anode in LIBs. The electrode with ∼50 nm thick PPy coating exhibits an outstanding overall electrochemical performance. Specifically, a high rate capability is obtained with ∼430 mA h g^-1 of discharge capacity at a high current density of 2.67 A g^-1 and more than 95% capacity is retained after over 120 cycles at a current rate of 0.86 A g^-1. These high electrochemical performances are attributed to the special structure which shortens the ion diffusion pathway, accelerates charge transfer, and alleviates volume change in the charging/discharging process, suggesting a promising route for designing a conversion-type anode material for LIBs.

Electrochemical study of specially designed graphene-Fe3O4-polyaniline nanocomposite as a high-performance anode for lithium-ion battery

In this work, an anode material with improved thermal stability, charge capacity, charge capacity retention, energy density, cyclic performance, operation safety, reversible capacity, and rate capability was synthesized for battery applications. The graphene-magnetite-polyaniline (Gr-Fe3O4-PANI) nanocomposites (NCs) are believed to deliver outstanding performance owing to the collective effect of the layered graphene (Gr) and magnetite (Fe3O4) hollow rods (HRs), as well as the better conductivity of polyaniline (PANI). The Gr-Fe3O4-PANI NCs easily enable the insertion and deinsertion of Li+, the passage of ions in the electrode, fast kinetics of Li+, and low volume expansion. Gr-Fe3O4-PANI NC was prepared by polymerizing aniline in the presence of already prepared Fe3O4 HRs, then dispersing in Gr. Fe3O4 HRs were synthesized by a hydrothermal route. Electrochemical properties were investigated by galvanostatic charge-discharge analysis and cyclic voltammetry. A lithium-ion battery (LIB) based on the Gr-Fe3O4-PANI exhibited a superior reversible current capacity of 1214 mA h g-1, excellent power capability, low volume expansion, high cycling stability and 99.6% coulombic efficiency over 250 cycles.

Structure and Electrochemical Properties of Mn₃O₄ Nanocrystal-Coated Porous Carbon Microfiber Derived from Cotton

Biomorphic Mn₃O₄ nanocrystal/porous carbon microfiber composites were hydrothermally fabricated and subsequently calcined using cotton as a biotemplate. The as-prepared material exhibited a specific capacitance of 140.8 F·g⁻¹ at 0.25 A·g⁻¹ and an excellent cycle stability with a capacitance retention of 90.34% after 5000 cycles at 1 A·g⁻¹. These characteristics were attributed to the introduction of carbon fiber, the high specific surface area, and the optimized microstructure inherited from the biomaterial.

Iron-Catalyzed Graphitic Carbon Materials from Biomass Resources as Anodes for Lithium-Ion Batteries

Graphitized carbon materials from biomass resources were successfully synthesized with an iron catalyst, and their electrochemical performance as anode materials for lithium-ion batteries (LIBs) was investigated. Peak pyrolysis temperatures between 850 and 2000 °C were covered to study the effect of crystallinity and microstructural parameters on the anodic behavior, with a focus on the first-cycle Coulombic efficiency, reversible specific capacity, and rate performance. In terms of capacity, results at the highest temperatures are comparable to those of commercially used synthetic graphite derived from a petroleum coke precursor at higher temperatures, and up to twice as much as that of uncatalyzed biomass-derived carbons. The opportunity to graphitize low-cost biomass resources at moderate temperatures through this one-step environmentally friendly process, and the positive effects on the specific capacity, make it interesting to develop more sustainable graphite-based anodes for LIBs.