Rational Design and Controllable Synthesis of Multishelled Fe2O3@SnO2@C Nanotubes as Advanced Anode Material for Lithium-/Sodium-Ion Batteries

Template-Assisted Epitaxial Growth of Ordered SnO2 Nanorods Arrays with Different Hollow Structures for High-Performance Sodium Storage

Anode materials for sodium ion batteries (SIBs) are confronted with severe volume expansion and poor electrical conductivity. Construction of assembled structures featuring hollow interior and carbon material modification is considered as an efficient strategy to address the issues. Herein, a novel template-assisted epitaxial growth method, ingeniously exploiting lattice matching nature, is developed to fabricate hollow ordered architectures assembled by SnO2 nanorods. SnO2 nanorods growing along [100] direction can achieve lattice-matched epitaxial growth on (110) plane of α-Fe2O3. Driven by the lattice matching, different α-Fe2O3 templates possessing different crystal plane orientations enable distinct assembly modes of SnO2, and four kinds of hollow ordered SnO2@C nanorods arrays (HONAs) with different morphologies including disc, hexahedron, dodecahedron and tetrakaidecahedron (denoted as Di-, He-, Do-, and Te-SnO2@C) are achieved. Benefiting from the synergy of hollow structure, carbon coating and ordered assembly structure, good structural integrity and stability and enhanced electrical conductivity are realized, resulting in impressive sodium storage performances when utilized as SIB anodes. Specifically, Te-SnO2@C HONAs exhibit excellent rate capability (385.6 mAh·g-1 at 2.0 A·g-1) and remarkable cycling stability (355.4 mAh·g-1 after 2000 cycles at 1.0 A·g-1). This work provides a promising route for constructing advanced SIB anode materials through epitaxial growth for rational structural design.

Highly stable Fe2O3@SnO2@HNCS hollow nanospheres with enhanced lithium-ion battery performance

Hollow Fe2O3@SnO2@HNCS nanospheres recombined the merits of the synergistic effect of metal oxides, rigid hollow structure and highly conductive N-doping.

Hierarchical Fe2O3 hexagonal nanoplatelets anchored on SnO2 nanofibers for high-performance asymmetric supercapacitor device

Metal oxide heterostructures have gained huge attention in the energy storage applications due to their outstanding properties compared to pristine metal oxides. Herein, magnetic Fe₂O₃@SnO₂ heterostructures were synthesized by the sol-gel electrospinning method at calcination temperatures of 450 and 600 °C. XRD line profile analysis indicated that fraction of tetragonal tin oxide phase compared to rhombohedral hematite was enhanced by increasing calcination temperature. FESEM images revealed that hexagonal nanoplatelets of Fe₂O₃ were hierarchically anchored on SnO₂ hollow nanofibers. Optical band gap of heterogeneous structures was increased from 2.06 to 2.40 eV by calcination process. Vibrating sample magnetometer analysis demonstrated that increasing calcination temperature of the samples reduces saturation magnetization from 2.32 to 0.92 emu g^-1. The Fe₂O₃@SnO₂-450 and Fe₂O₃@SnO₂-600 nanofibers as active materials coated onto Ni foams (NF) and their electrochemical performance were evaluated in three and two-electrode configurations in 3 M KOH electrolyte solution. Fe₂O₃@SnO₂-600/NF electrode exhibits a high specific capacitance of 562.3 F g^-1 at a current density of 1 A g^-1 and good cycling stability with 92.8% capacitance retention at a high current density of 10 A g^-1 after 3000 cycles in three-electrode system. The assembled Fe₂O₃@SnO₂-600//activated carbon asymmetric supercapacitor device delivers a maximum energy density of 50.2 Wh kg^-1 at a power density of 650 W kg^-1. The results display that the Fe₂O₃@SnO₂-600 can be a promising electrode material in supercapacitor applications.

Innovative Materials for Energy Storage and Conversion

The metal chalcogenides (MCs) for sodium-ion batteries (SIBs) have gained increasing attention owing to their low cost and high theoretical capacity. However, the poor electrochemical stability and slow kinetic behaviors hinder its practical application as anodes for SIBs. Hence, various strategies have been used to solve the above problems, such as dimensions reduction, composition formation, doping functionalization, morphology control, coating encapsulation, electrolyte modification, etc. In this work, the recent progress of MCs as electrodes for SIBs has been comprehensively reviewed. Moreover, the summarization of metal chalcogenides contains the synthesis methods, modification strategies and corresponding basic reaction mechanisms of MCs with layered and non-layered structures. Finally, the challenges, potential solutions and future prospects of metal chalcogenides as SIBs anode materials are also proposed.

Engineering a ternary one-dimensional Fe2P@SnP0.94@MoS2 mesostructure through magnetic-field-induced self-assembly as a high-performance lithium-ion battery anode

Engineering energy-storage materials possessing high-speed electronic and ionic transport properties for secondary batteries is significant. Here, we develop a ternary one-dimensional mesostructured anode composed of MoS₂ nanosheets grown in situ on SnP_0.94 nanotubes infilled with Fe₂P nanospheres, which is prepared by magnetic-field-induced self-assembly. The mesostructure provides fast transport pathways for electrons, as verified through a galvanostatic intermittent titration technique; and the voids effectively alleviate the volume change, enabling long-term cycling stability. The Fe₂P@SnP_0.94@MoS₂ anode displays a high capacity of 797.5 mA h g^-1 after cycling 800 times at 2 A g^-1, a coulombic efficiency of 99.4%, and stable rate-performance after three rounds of cycling. Furthermore, the anode shows high capacities at different temperatures, indicating that the composite presented here has a promising potential for use in real conditions.

Heterostructure Fe2O3 nanorods@imine-based covalent organic framework for long cycling and high-rate lithium storage

Fe₂O₃ as an anode for lithium-ion batteries has attracted intense attention because of its high theoretical capacity, natural abundance, and good safety. However, the inferior cycling stability, low-rate performance, and limited composite varieties hinder the application of Fe₂O₃-based materials. In this work, an Fe₂O₃@COF-LZU1 (FO@LZU1) anode was prepared via an imine-based covalent organic framework (COF-LZU1) covering on the exterior surface of Fe₂O₃ after rational optimization. With its unique heterostructure, the COF-LZU1 layer not only effectively alleviated the volume expansion during cycling but also improved the charge-transfer capability because of the π-conjugated system. Moreover, the organic functional group (CN, benzene ring) for COF-LZU1 provided more redox-active sites for Li⁺ storage. Under the contributions of both Fe₂O₃ nanorods and COF-LZU1, the FO@LZU1_50% exhibited an ultrahigh initial capacity and long-term cycling performance with initial discharge capacities of 2143 and 2171 mA h g^-1 after 300 cycles under 0.1 A g^-1, and rate performance of 1310 and 501 mA h g^-1 at 0.3 and 3 A g^-1, respectively. In addition, a high retention capacity of 1185 mA h g^-1 was achieved at 1 A g^-1 after 500 cycles. Furthermore, a full-cell with the FO@LZU1_50% anode and LiCoO₂ cathode exhibited superior cycling and rate performance, which still maintained a reversible capacity of 260 mA h g^-1 after 200 cycles even at a current density of 1 A g^-1. The proposed strategy offers a new perspective for exploring the high-rate capability and designability of Fe₂O₃-based electrode materials.

A Lamellar Yolk-Shell Lithium-Sulfur Battery Cathode Displaying Ultralong Cycling Life, High Rate Performance, and Temperature Tolerance

The shuttling behavior and slow conversion kinetics of the intermediate lithium polysulfides are the severe obstacles for the application of lithium-sulfur (Li-S) batteries over a wide temperature range. Here, an engineered lamellar yolk-shell structure of In2 O3 @void@carbon for the Li-S battery cathode is developed for the first time to construct a powerful barrier that effectively inhibits the shuttling of polysulfides. On the basis of the unique nanochannel-containing morphology, the continuous kinetic transformation of sulfur and polysulfides is confined in a stable framework, which is demonstrated by using X-ray nanotomography. The constructed Li-S battery exhibits a high cycling capability over 1000 cycles at 1.0 C with a capacity decay rate as low as 0.038% per cycle, good rate performance, and temperature tolerance at -10, 25, and 50 °C. A nondestructive in situ monitoring method of the interfacial reaction resistance in different cycling stages is proposed, which provides a new analysis perspective for the development of emerging electrochemical energy-storage systems.

Optimizing SnO2- x /Fe2 O3 Hetero-Nanocrystals Toward Rapid and Highly Reversible Lithium Storage

Engineering oxygen vacancy and boosting Li₂ O reversibility on oxides-based electrode are of significance but remains a challenge in high-power lithium-ion batteries. Herein, the heterogenous SnO_{2- x} /Fe₂ O_{3- y} nanocrystals are demonstrated with tailorable x and y values enabled by a glucose-assisted spray combustion technique. Density functional theory calculations unveil the SnO_{2- x} /Fe₂ O₃ with a maximum x value has the optimal electronic structure, the metallic Fe generated from Fe₂ O₃ can markedly reduce the free energy to break Li-O bonds for accelerating subsequent delithiation process of Li₂ O. Consequently, the optimized SnO_{2- x} /Fe₂ O₃ exhibits a remarkably enhanced electrochemical reversibility and reaction kinetics. After stabilized by reduced graphene oxide, the hybrid delivers a high reversible specific capacity of 1113 mAh g^-1 with superior rate performance (474 mAh g^-1 at 20 A g^-1 ) and long cycle life (negligible loss after 500 cycles at 5 A g^-1 ), the oxygen vacancy and microstructure are well-maintained after cycles. This work provides the possibilities for skillfully regulating oxygen vacancy and meantime enhancing Li₂ O reversibility.

Encapsulating Fe2 O3 Nanotubes into Carbon-Coated Co9 S8 Nanocages Derived from a MOFs-Directed Strategy for Efficient Oxygen Evolution Reactions and Li-Ions Storage

The development of high-efficiency, robust, and available electrode materials for oxygen evolution reaction (OER) and lithium-ion batteries (LIBs) is critical for clean and sustainable energy system but remains challenging. Herein, a unique yolk-shell structure of Fe₂ O₃ nanotube@hollow Co₉ S₈ nanocage@C is rationally prepared. In a prearranged sequence, the fabrication of Fe₂ O₃ nanotubes is followed by coating of zeolitic imidazolate framework (ZIF-67) layer, chemical etching of ZIF-67 by thioacetamide, and eventual annealing treatment. Benefiting from the hollow structures of Fe₂ O₃ nanotubes and Co₉ S₈ nanocages, the conductivity of carbon coating and the synergy effects between different components, the titled sample possesses abundant accessible active sites, favorable electron transfer rate, and exceptional reaction kinetics in the electrocatalysis. As a result, excellent electrocatalytic activity for alkaline OER is achieved, which delivers a low overpotential of 205 mV at the current density of 10 mA cm^-2 along with the Tafel slope of 55 mV dec^-1 . Moreover, this material exhibits excellent high-rate capability and excellent cycle life when employed as anode material of LIBs. This work provides a novel approach for the design and the construction of multifunctional electrode materials for energy conversion and storage.

Engineering tin dioxide quantum dots in a hierarchical graphite and graphene oxide framework for lithium-ion storage

The spontaneous aggregation and poor electronic conductivity are widely recognized as the main challenges for practically applied nano-sized tin dioxide-based anode candidates in lithium-ion batteries. This work describes a hierarchical graphite and graphene oxide (GO) framework stabilized tin dioxide quantum dot composite (SnO₂@C/GO), which is synthesized by a solid-state ball-milling treatment and a water-phase self-assembly process. Characterization results demonstrate the engineered inside nanostructured graphite and outside GO layers from the SnO₂@C/GO composite jointly contribute to a good immobilization effect for the SnO₂ quantum dots. The hierarchical carbonaceous matrix supported SnO₂ quantum dots could maintain good structure stability over a long cycling life under high current densities. As an anodic electrochemically active material for lithium-ion batteries, the SnO₂@C/GO composite shows a high reversible capacity of 1156 mAh·g^-1 at the current density of 1000 mA·g^-1 for 350 continual cycles as well as good rate performance. The large pseudocapacitive behavior in this electrode is favorable for promoting the lithium-ion storage capability under higher current densities. The whole synthetic route is simple and effective, which probably has good potential for further development to massively fabricate high-performance electrode active materials for energy storage.

A Review of Battery Materials as CDI Electrodes for Desalination

The world is suffering from chronic water shortage due to the increasing population, water pollution and industrialization. Desalinating saline water offers a rational choice to produce fresh water thus resolving the crisis. Among various kinds of desalination technologies, capacitive deionization (CDI) is of significant potential owing to the facile process, low energy consumption, mild working conditions, easy regeneration, low cost and the absence of secondary pollution. The electrode material is an essential component for desalination performance. The most used electrode material is carbon-based material, which suffers from low desalination capacity (under 15 mg·g−1). However, the desalination of saline water with the CDI method is usually the charging process of a battery or supercapacitor. The electrochemical capacity of battery electrode material is relatively high because of the larger scale of charge transfer due to the redox reaction, thus leading to a larger desalination capacity in the CDI system. A variety of battery materials have been developed due to the urgent demand for energy storage, which increases the choices of CDI electrode materials largely. Sodium-ion battery materials, lithium-ion battery materials, chloride-ion battery materials, conducting polymers, radical polymers, and flow battery electrode materials have appeared in the literature of CDI research, many of which enhanced the deionization performances of CDI, revealing a bright future of integrating battery materials with CDI technology.