Mesoporous MnO/C–N Nanostructures Derived from a Metal–Organic Framework as High-Performance Anode for Lithium-Ion Battery

N-Containing Porous Carbon-Based MnO Composites as Anode with High Capacity and Stability for Lithium-Ion Batteries

MnO has attracted much attention as the anode for Li-ion batteries (LIBs) owing to its high specific capacity. However, the low conductivity limited its large application. An effective solution to solve this problem is carbon coating. Biomass carbon materials have aroused much interest for being low-cost and rich in functional groups and hetero atoms. This work designs porous N-containing MnO composites based on the chemical-activated tremella using a self-templated method. The tremella, after activation, could offer more active sites for carbon to coordinate with the Mn ions. And the as-prepared composites could also inherit the special porous nanostructures of the tremella, which is beneficial for Li+ transfer. Moreover, the pyrrolic/pyridinic N from the tremella can further improve the conductivity and the electrolyte wettability of the composites. Finally, the composites show a high reversible specific capacity of 1000 mAh g-1 with 98% capacity retention after 200 cycles at 100 mA g-1. They also displayed excellent long-cycle performance with 99% capacity retention (relative to the capacity second cycle) after long 1000 cycles under high current density, which is higher than in most reported transition metal oxide anodes. Above all, this study put forward an efficient and convenient strategy based on the low-cost biomass to construct N-containing porous composite anodes with a fast Li+ diffusion rate, high electronic conductivity, and outstanding structure stability.

A Lignin-Based Carbon Anode with Long-Cycle Stability for Li-Ion Batteries

Due to its wide source and low cost, biomass-based hard carbon is considered a valuable anode for lithium-ion batteries (LIBs). Lignins, as the second most abundant source in nature, are being intensively studied as candidate anode materials for next generation LIBs. However, direct carbonization of pure lignin usually leads to low specific surface area and porosity. In this paper, we design a porous carbon material from natural lignin assisted by sacrificing a metal-organic framework (MOF) as the template. The MOF nanoparticles can disperse the lignin particles uniformly and form abundant mesopores in the composites to offer fast transfer channels for Li+. The as-prepared carbon anode shows a high specific capacity of 420 mAh g-1 with the capacity retention of 99% after 300 cycles at 0.2 A g-1. Additionally, it keeps the capacity retention of 85% after long cycle of 1000 cycles, indicating the good application value of the designed anode in LIBs. The work provides a renewable and low-cost candidate anode and a feasible design strategy of the anode materials for LIBs.

Metal-organic frameworks and their derivatives as electrode materials for Li-ion batteries: a mini review

In recent decades, in order to obtain more excellent performance and wider application of rechargeable lithium-ion batteries (LIBs), researchers have been exploring potential electrode materials. MOFs possess attractive features, such...

MOF-derivated MnO@C nanocomposite with bidirectional electrocatalytic ability as signal amplification for dual-signal electrochemical sensing of cancer biomarker

Dual-signal strategy has great potential in improving the accuracy and sensitivity of cancer biomarker determination. However, most sensors based on nanomaterials as signal amplification usually output single detectable signal. It is still a challenge to achieve dual-signal sensing of biomarkers with nanomaterials as signal amplification. Herein, MnO@C nanocomposite was prepared with Mn-MOF-74 as precursor by pyrolysis. It possesses bidirectional electrocatalytic ability toward both oxidation and reduction of H₂O₂ for its fully exposed crystal facets. After loading AuNPs, MnO@C@AuNPs can connect aptamer (Apt) via Au-S and then as a signal amplification for the construction of sandwich-type aptasensor for dual-signal electrochemical sensing of cancer biomarker. Thus, taking mucin 1 (MUC1) as a model system. The aptasensor has the parallel output of differential pulse voltammetry (DPV) and chronoamperometry responses based on oxidation and reduction of H₂O₂, respectively, which implemented sensitive and accurate measurements to avoid false results. The linear response ranges of 0.001 nM-100 nM (detection limit of 0.31 pM) for DPV technique and 0.001 nM-10 nM (detection limit of 0.25 pM) for chronoamperometry technique were obtained. It opens up a new way to design elegant dual-signal aptasensors with potential applications in early disease diagnosis.

The encapsulation of MnFe2O4 nanoparticles into the carbon framework with superior rate capability for lithium-ion batteries

Binary transition metal oxides (BTMOs) have been regarded as one of the most hopeful anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacity, excellent electrochemical activity and abundant electrochemical reactions. However, BTMOs still suffer from two main problems, which are poor conductivity and large volume expansion during the charge/discharge processes. In order to address the above-mentioned problems, mesoporous MnFe2O4@C nanorods have been successfully synthesized in this work. The synergistic effect of the cross-linked carbon framework and mesoporous structure greatly improves the electrochemical performances. As expected, the mesoporous MnFe2O4@C electrode manifests discharge capacities of 987.5 and 816.6 mA h g-1 at the current densities of 100 and 2000 mA g-1, respectively, with the capacity retention ratio of 82.7%, exerting distinguished rate capabilities for LIBs.

Structural Diversity of Zinc(II), Manganese(II), and Gadolinium(III) Coordination Polymers Based on Two Isomeric N-Heteroaromatic Polycarboxylate Ligands: Structures and Their Derived Mn2O3 for Lithium Storage Applications

Tuning the coordination sites of two isomeric semirigid ligands, 5-(4-pyridin-3-yl-benzoylamino)isophthalic acid (3-H₂PBI) and 5-(4-pyridin-4-yl-benzoylamino)isophthalic acid (4-H₂PBI), afforded six new coordination polymers (CPs), [Zn(3-PBI)(H₂O)]_n (1), {[Mn₂(3-PBI)₂(H₂O)]·DMF·2H₂O}_n (2), {[Gd₂(3-PBI)₃(H₂O)₃]·DMF·3H₂O}_n (3), {[Zn₂(4-PBI)₂]·H₂O}_n (4), {[Mn₂(4-PBI)₂(H₂O)₂]·4H₂O}_n (5), and {(Me₂NH₂)[Gd(4-PBI)₂]·H₂O}_n (6). Structural analysis shows that 1 consists of 2D honeycomb (6,3) net, three sets of networks interlace mutually, generating an unexpected 2D + 2D + 2D → 3D polycatenating interesting system. 2 exhibits a 3D pcu topology. 3 presents a unique 3D with 3,3,6T13 network topology. 4 possesses 3D 2-fold interpenetrated structure with rutile topology. 5 presents an alluring 2D architecture comprising two distinct topologies (kgd and hcb), stacked arrangement in an unexpected ABBABB mode. 6 displays 2D (4,4)-grid network. A differentiation of these structural features indicate that coordination connectivity of metals, together with binding modes of two ligands are accountable for the fascinating structural contrast. In addition, 2 and 5 were then transformed into Mn₂O₃ via a simple heat treatment. Electrochemical test results show that both of the obtained Mn₂O₃ moieties exhibit stable lithium storage properties and excellent rate capabilities.

Enhanced photocatalytic activity of g-C3N4/MnO composites for hydrogen evolution under visible light

In this work, a range of g-C3N4/MnO composites were constructed using g-C3N4 nanosheets modified with MnO, and the photocatalytic performance for hydrogen evolution was evaluated by using these as-prepared g-C3N4/MnO composites as photocatalysts. It was found that the photocatalytic activity of the g-C3N4/MnO composites for hydrogen evolution is significantly enhanced compared with that of pristine g-C3N4 since the formation of heterojunctions between the MnO nanoparticles and g-C3N4 nanosheets through coordination covalent bonds promotes the charge carrier transfer and separation abilities of the composites. The loading mass of MnO also has a large influence on the photocatalytic activity of the g-C3N4/MnO composites. Particularly, the g-C3N4/MnO-5 composite with 5 wt% MnO shows superior photocatalytic activity with a hydrogen evolution rate of 559 μmol h-1 g-1 under visible light, which is about 9 times that of the bulky g-C3N4. These findings demonstrate that the combination of metal oxides and g-C3N4 to construct composite photocatalysts is an effective method to improve the photocatalytic performance.

MnO@graphene nanopeapods derived via a one-pot hydrothermal process for a high performance anode in Li-ion batteries

Although transition metal oxide-carbon (TMO-C) composites exhibit high Li storage capacity, the weak bonding between TMO particles and carbon mainly via van der Waals' force and the limited internal void space result in poor rate capability and cycling performance. Herein, MnO@graphene nanopeapods are produced by calcination of hydrothermally-synthesized MnO2-C composites. The flexible graphene shells provide superior conductivity and excellent structural stability to the MnO cores, and the enough internal void space can significantly buffer the drastic volume expansion. The MnO@graphene nanopeapods exhibit high Li storage capacity (1168 mA h g-1 at 50 mA g-1 and 945 mA h g-1 at 500 mA g-1) at a voltage platform of ∼1.2 V, excellent rate capability (728 mA h g-1 at 1000 mA g-1 and 505 mA h g-1 at 3000 mA g-1), high initial coulombic efficiency (85.9%) and remarkable long-life cycling performance (undiminished after 1000 cycles). The MnO@graphene nanopeapods have been successfully used as the anode to assemble a full battery with LiFePO4 as the cathode. Our results provide a useful and rational strategy to design high performance graphene-supported MnO composites for Li ion batteries.

Four new Zn(ii) and Cd(ii) coordination polymers using two amide-like aromatic multi-carboxylate ligands: synthesis, structures and lithium–selenium batteries application

Four new coordination polymers, {[Zn(3-PBI)(H₂O)]·2DMF}_n (1), [Cd(3-PBI)(DMF)]_n (2), {[Zn₄(μ₄-O)(4-PBI)₃]·3DMF}_n (3), {[Cd₄(4-PBI)₄(H₂O)₆]·13H₂O}_n (4), have been constructed from two isomeric flexible multi-carboxylate ligands, 3-H₂PBI = 5-(3-(pyridin-3-yl)benzamido)isophthalic acid and 4-H₂PBI = 5-(3-(pyridin-4-yl)benzamido)isophthalic acid. Structural analysis reveals that compound 1 is a one-dimensional (1D) ladder-like chain assembled by Zn(ii) ions and 3-PBI²⁻ ligands, which further extend into a 3D supramolecular structure through π⋯π stacking and interlayer (O–H⋯O) hydrogen bonding interactions. In compound 2, Cd²⁺ metal ions are connected by carboxylate groups to form [Cd₂(COO)₄] secondary building units (SBUs). The whole framework possesses a quadrilateral channel and constitutes a unique 3D (3,6)-connected rutile net with the Schläfli symbol of (4²·6¹⁰·8³)(4·6²)₂. As for 3, Zn(ii) ions are bridged by one μ₄-O and six carboxylate groups to form a tetranuclear [Zn₄(μ₄-O)(COO)₆] cluster, resulting in a rare (3,9)-connected 3D network. Compound 4 has an appealing 2D layered architecture involving two distinct topologies in the crystal structure, stacking in an unusual ABBABB mode (where A represents (4·8²) topology and B denotes kgd topology). Moreover, compound 2 is prepared as a support for active selenium through a melt-diffusion method. The obtained Cd-CP/Se electrode can be tested for lithium–selenium batteries and shows an initial capacity of 514 mA h g⁻¹ and a reversible capacity of 200 mA h g⁻¹ at 1C after 500 cycles. The good storage performance of Cd-CP/Se demonstrates it to be a prospective cathode material for lithium–selenium batteries.

Four new coordination polymers were constructed and compound 2 was used as a host to active selenium for Li–Se batteries.

Green and Rational Design of 3D Layer-by-Layer MnO x Hierarchically Mesoporous Microcuboids from MOF Templates for High-Rate and Long-Life Li-Ion Batteries

Rational design and delicate control on the textural properties of metal-oxide materials for diverse structure-dependent applications still remain formidable challenges. Here, we present an eco-friendly and facile approach to smartly fabricate three-dimensional (3D) layer-by-layer manganese oxide (MnO _x) hierarchical mesoporous microcuboids from a Mn-MOF-74-based template, using a one-step solution-phase reaction scheme at room temperature. Through the controlled exchange of metal-organic framework (MOF) ligand with OH^- in alkaline aqueous solution and in situ oxidation of manganese hydroxide intermediate, the Mn-MOF-74 template/precursor was readily converted to Mn₃O₄ or δ-MnO₂ counterpart consisting of primary nanoparticle and nanosheet building blocks, respectively, with well-retained morphology. By X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy, high-resolution TEM, N₂ adsorption-desorption analysis and other techniques, their crystal structure, detailed morphology, and microstructure features were unambiguously revealed. Specifically, their electrochemical Li-ion insertion/extraction properties were well evaluated, and it turns out that these unique 3D microcuboids could achieve a sustained superior lithium-storage performance especially at high rates benefited from the well-orchestrated structural characteristics (Mn₃O₄ microcuboids: 890.7, 767.4, 560.1, and 437.1 mAh g^-1 after 400 cycles at 0.2, 0.5, 1, and 2 A g^-1, respectively; δ-MnO₂ microcuboids: 991.5, 660.8, 504.4, and 362.1 mAh g^-1 after 400 cycles at 0.2, 0.5, 1, and 2 A g^-1, respectively). To our knowledge, this is the most durable high-rate capability as well as the highest reversible capacity ever reported for pure MnO _x anodes, which even surpass most of their hybrids. This facile, green, and economical strategy renews the traditional MOF-derived synthesis for highly tailorable functional materials and opens up new opportunities for metal-oxide electrodes with high performance.

Porosity- and content-controlled metal/metal oxide/metal carbide@carbon (M/MO/MC@C) composites derived from MOFs: mechanism study and application for lithium-ion batteries

Facile method for morphology-preserved transformation of MOFs to porosity and content-controlled M/MO/MC@C composites is presented.