SnO2@PANI Core-Shell Nanorod Arrays on 3D Graphite Foam: A High-Performance Integrated Electrode for Lithium-Ion Batteries

Designing 3D SnS@Cu-Ni Nanoporous Column Array Electrode for High-Capacity and High-Rate Lithium-Ion Batteries

Sn-based materials with high capacity showcase great potential for next-generation lithium-ion batteries (LIBs). Yet, the large volume change and limited ion/electron transfer efficiency of Sn-based materials upon operation significantly compromises the battery performance. In this study, a unique 3D copper-nickel nanoporous column array current collector is rationally developed via a facile template-free galvanostatic electrodeposition method, followed by electrodepositing SnS active material onto it (denoted as 3D SnS@CNCA). Excitingly, the morphology of the 3D SnS@CNCA electrode perfectly inherited the nanoporous column array structure of the 3D current collector, which not only endows the electrode with a large specific surface area to provide more active sites and sufficient ion/electron transport pathways, but also effectively alleviates the volume expansion of SnS upon repeated charge-discharge cycles. Therefore, the binder-free 3D SnS@CNCA electrode showcases a significantly enhanced Li storage performance, showing a high initial reversible capacity of 1019.7 mAh g-1 with noteworthy cycling stability (a capacity retention rate of 89.4% after 200 cycles). Moreover, the designed electrode also manifests high rate performance with a high capacity of 570.6 mAh g-1 at 4 A g-1. This work provides a novel design idea for the preparation of high-performance electrodes beyond LIBs.

High-Resolution Nanoanalytical Insights into Particle Formation in SnO2/ZnO Core/Shell Nanowire Lithium-Ion Battery Anodes

Tin oxide (SnO₂)/zinc oxide (ZnO) core/shell nanowires as anode materials in lithium-ion batteries (LIBs) were investigated using a combination of classical electrochemical analysis and high-resolution electron microscopy to correlate structural changes and battery performance. The combination of the conversion materials SnO₂ and ZnO is known to have higher storage capacities than the individual materials. We report the expected electrochemical signals of SnO₂ and ZnO for SnO₂/ZnO core/shell nanowires as well as unexpected structural changes in the heterostructure after cycling. Electrochemical measurements based on charge/discharge, rate capability, and electrochemical impedance spectroscopy showed electrochemical signals for SnO₂ and ZnO and partial reversibility of lithiation and delithiation. We find an initially 30% higher capacity for the SnO₂/ZnO core/shell NW heterostructure compared to the ZnO-coated substrate without the SnO₂ NWs. However, electron microscopy characterization revealed pronounced structural changes upon cycling, including redistribution of Sn and Zn, formation of ∼30 nm particles composed of metallic Sn, and a loss of mechanical integrity. We discuss these changes in terms of the different reversibilities of the charge reactions of both SnO₂ and ZnO. The results show stability limitations of SnO₂/ZnO heterostructure LIB anodes and offer guidelines on material design for advanced next-generation anode materials for LIBs.

Carbon- and metal-based mediators modulate anaerobic methanogenesis and phenol removal: Focusing on stimulatory and inhibitory mechanism

In this study, anaerobic batch experiments were conducted to investigate the effect of carbon-based (biochar) and metal-based (nanoscale zero-valent iron, NZVI and zero valent iron, ZVI) mediators on the AD process treating phenolic wastewater. Fresh apricot shell- and wood-derived biochar (BiocharA, BiocharB) could remove the phenol efficiently (77.1% and 86.2%), suggesting that biodegradation cooperated with adsorption had advantage in phenol removal. BiocharB, NZVI and ZVI enhanced the methane production by 17.6%, 23.7% and 23.2%, respectively. Apart from serving as carrier for microbial growth, BiocharB might promote the direct interspecies electron transfer (DIET) since the Anaerolineaceae/Clostridium sensu stricto, which have potential for DIET, were enriched. NZVI and ZVI added systems mainly enhanced the abundance of Clostridium sensu stricto (24.5%, 37.6%) and Methanosaeta. Interestingly, BiocharA inhibited the methanogenesis completely. An inhibitory mechanism was proposed: the exposure of absorbed microbes on the BiocharA to the highly concentrated phenol in biochar' pores resulted in the inhibition of methanogens, especially for Methanosarcina. In conclusion, this study showed that suitable biochar (BiocharB) could serve as an alternative redox mediator for realizing simultaneously the efficient phenol removal and methane production.

A SnOx Quantum Dots Embedded Carbon Nanocage Network with Ultrahigh Li Storage Capacity

Tin-based materials with high specific capacity have been studied as high-performance anodes for energy storage devices. Herein, a SnO_x (x = 0, 1, 2) quantum dots@carbon hybrid is designed and prepared by a binary oxide-induced surface-targeted coating of ZIF-8 followed by pyrolysis approach, in which SnO_x quantum dots (under 5 nm) are dispersed uniformly throughout the nitrogen-containing carbon nanocage. Each nanocage is cross-linked to form a highly conductive framework. The resulting SnO_x@C hybrid exhibits a large BET surface area of 598 m² g^-1, high electrical conductivity, and excellent ion diffusion rate. When applied to LIBs, the SnO_x@C reveals an ultrahigh reversible capacity of 1824 mAh g^-1 at a current density of 0.2 A g^-1, and superior capacities of 1408 and 850 mAh g^-1 even at high rates of 2 and 5 A g^-1, respectively. The full cell assembled using LiFePO₄ as cathode exhibits the high energy density and power density of 335 Wh kg^-1 and 575 W kg^-1 at 1 C based on the total active mass of cathode and anode. Combined with in situ XRD analysis, the superior electrochemical performance can be attributed to the SnO_x-ZnO-C asynchronous and united lithium storage mechanism, which is formed by the well-designed multifeatured construction composed of SnO_x quantum dots, interconnected carbon network, and uniformly dispersed ZnO nanoparticles. Importantly, this designed synthesis can be extended for the fabrication of other electrode materials by simply changing the binary oxide precursor to obtain the desired active component or modulating the type of MOFs coating to achieve high-performance LIBs.

Phosphorus-Doped 3D RuCo Nanowire Arrays on Nickel Foam with Enhanced Electrocatalytic Activity for Overall Water Splitting

It is especially significant to design and construct high-performance and stable three-dimensional (3D) bifunctional nanoarchitecture electrocatalysts toward overall water splitting. Herein, we have constructed 3D self-supported phosphorus-doped ruthenium-cobalt nanowires on nickel foams (RuCoP/NF) via a simple hydrothermal reaction followed by a low-temperature phosphating reaction. Doping P can not merely enhance the intrinsic activity of electrocatalysts for overall water splitting but at the same time increase electrochemical surface areas (ECSAs) to expose more accessible active sites. As a 3D bifunctional catalyst, RuCoP/NF demonstrates superior performance for HER (44 mV@10 mA cm^-2) and OER (379 mV@50 mA cm^-2) in 1.0 M KOH electrolyte solution. The overall water-splitting system was assembled using RuCoP/NF as both anode and cathode. Besides, it exhibits a voltage of 1.533 V at a current density of 10 mA cm^-2 and long-term durability within 24 h. P-dopant changes the electron structure of Ru and Co, which is conducive to the formation of Ru^δ- and Co^δ+, resulting in the adjustment of binding H*/OH* and the improvement of the overall water-splitting reaction kinetics. This work provides a facile method to produce heteroatom-doped and high-performance catalysts for efficient overall water splitting.

Smart-Fabric-Based Supercapacitor with Long-Term Durability and Waterproof Properties toward Wearable Applications

The rapid development of wearable electronics and smart textiles has dramatically motivated the generation of flexible textile-based supercapacitors (SCs). However, the rapid evaporation of water moisture in gel electrolyte substantially limits the working durability and performance enhancements of the flexible devices. Therefore, a high-performance multifunctional textile-based SC with long-term durability is highly desired. Herein, a poly(vinyl alcohol) (PVA)/polyacrylamide (PAM) composite gel electrolyte was developed to fabricate multifunctional device with water-retaining and water-proofing properties based on multidimensional hierarchical fabric. And the assembled SC based on composite gel exhibited a superior water-retaining property and long-term working durability (93.29% retention rate after operation for 15 days), whereas the performance of SC based on pure PVA gel declined sharply and only 43.2% capacitance remained. In addition, the assembled SC exhibited enhanced specific capacitance of 707.9 mF/cm² and high energy density of 62.92 μWh/cm² and maintained a good stability of 80.8% even after 10 000 cyclic tests. After water repellency treatment, the integrated device immersed in water could still work normally. What's more, the assembled devices could be charged by a portable hand generator, which could be potentially applied for field rescue and military applications. We foresee that this strategy would be a potential route to prepare high-performance multifunctional textile-based SCs for wearable electronic systems and smart textile applications.

Improving Lithium-Ion Half-/Full-Cell Performance of WO3 -Protected SnO2 Core-Shell Nanoarchitectures

Anodes derived from SnO₂ offer a greater specific capacity comparative to graphitic carbon in lithium-ion batteries (LIBs); hence, it is imperative to find a simple but effective approach for the fabrication of SnO₂ . The intelligent surfacing of transition metal oxides is one of the favorite strategies to dramatically boost cycling efficiency, and currently most work is primarily aimed at coating and/or compositing with carbon-based materials. Such coating materials, however, face major challenges, including tedious processing and low capacity. This study successfully reports a new and simple WO₃ coating to produce a core-shell structure on the surface of SnO₂ . The empty space permitted natural expansion for the SnO₂ nanostructures, retaining a higher specific capacity for over 100 cycles that did not appear in the pristine SnO₂ without WO₃ shell. Using WO₃ -protected SnO₂ nanoparticles as anode, a coin half-cell battery was designed with Li-foil as counter-electrode. Furthermore, the anode was paired with commercial LiFePO₄ as cathode for a coin-type full cell and tested for lithium storage performance. The WO₃ shell proved to be an effective and strong enhancer for both current rate and specific capacity of SnO₂ nanoarchitectures; additionally, an enhancement of cyclic stability was achieved. The findings demonstrate that the WO₃ can be used for the improvement of cyclic characteristics of other metal oxide materials as a new coating material.

Electrodeposition Technologies for Li-Based Batteries: New Frontiers of Energy Storage

Electrodeposition induces material syntheses on conductive surfaces, distinguishing it from the widely used solid-state technologies in Li-based batteries. Electrodeposition drives uphill reactions by applying electric energy instead of heating. These features may enable electrodeposition to meet some needs for battery fabrication that conventional technologies can rarely achieve. The latest progress of electrodeposition technologies in Li-based batteries is summarized. Each component of Li-based batteries can be electrodeposited or synthesized with multiple methods. The advantages of electrodeposition are the main focus, and they are discussed in comparison with traditional technologies with the expectation to inspire innovations to build better Li-based batteries. Electrodeposition coats conformal films on surfaces and can control the film thickness, providing an effective approach to enhancing battery performance. Engineering interfaces by electrodeposition can stabilize the solid electrolyte interphase (SEI) and strengthen the adhesion of active materials to substrates, thereby prolonging the battery longevity. Lastly, a perspective of future studies on electrodepositing batteries is provided. The significant merits of electrodeposition should greatly advance the development of Li-based batteries.

Facile Synthesis of Flower-Like MnCo2 O4 @PANi-rGO: A High-Performance Anode Material for Lithium-Ion Batteries

Flower-like MnCo₂ O₄ was prepared in a self-assembly process and used in the formation of MnCo₂ O₄ @polyaniline (MnCo₂ O₄ @PANi) that proceeds by a simple in situ polymerization. The MnCo₂ O₄ @PANi-reduced graphite oxide (MnCo₂ O₄ @PANi-rGO) composite was then synthesized by introducing rGO into MnCo₂ O₄ @PANi. This modification improves the overall electronic conductivity of the MnCo₂ O₄ @PANi-rGO because of the dual conductive functions of rGO and PANi; it also provides a buffer for the changes in electrode volume during cycling, thus improving the lithium-storage performance of MnCo₂ O₄ @PANi-rGO. The electrochemical performance of the samples was evaluated by charge/discharge cycling testing, cyclic voltammetry, and electrochemical impedance spectroscopy. MnCo₂ O₄ @PANi-rGO delivers a discharge capacity of 745 mAh g^-1 and a Coulombic efficiency of 100 % after 1050 cycles at a current density of 500 mA g^-1 , and is a promising anode material for lithium-ion batteries.

In situ growth of urchin-like cobalt–chromium phosphide on 3D graphene foam for efficient overall water splitting

The CoCr-P@3DGF composite shows excellent activity and durability for overall water splitting due to Cr-doping and the 3DGF substrate.

NiMoS4 nanocrystals anchored on N-doped carbon nanosheets as anode for high performance lithium ion batteries

Owing to the excellent electrical conductivity and high theoretical capacity, binary transition metal sulfides have attracted extensive attention as promising anodes for lithium ion batteries (LIBs). However, the relatively poor electrical conductivity and serious capacity fading originated from large volume change still hinder their practical applications. Herein, binary NiMoS₄ nanoparticles are deposited on N doped carbon nanosheets (NC@NiMoS₄) through a facile hydrothermal method. The N doped carbon nanosheets and the strong chemical bonding between NC and NiMoS₄ can accommodate the volume change, keep the structural integrity and promote the ion/electron transfer during electrochemical reaction. The extra voids between NiMoS₄ nanoparticles enlarge the contact area and reduce the lithium migration barriers. As anode for LIBs, the NC@NiMoS₄ exhibits the excellent cycle stability with 834 mAh g^-1 after 100 cycles at the current density of 100 mA g^-1. Even at high rate of 2000 mA g^-1, the specific capacity of 544 mAh g^-1 can be achieved after 500 cycles.

Synthesis and Electrochemical Energy Storage Applications of Micro/Nanostructured Spherical Materials

Micro/nanostructured spherical materials have been widely explored for electrochemical energy storage due to their exceptional properties, which have also been summarized based on electrode type and material composition. The increased complexity of spherical structures has increased the feasibility of modulating their properties, thereby improving their performance compared with simple spherical structures. This paper comprehensively reviews the synthesis and electrochemical energy storage applications of micro/nanostructured spherical materials. After a brief classification, the concepts and syntheses of micro/nanostructured spherical materials are described in detail, which include hollow, core-shelled, yolk-shelled, double-shelled, and multi-shelled spheres. We then introduce strategies classified into hard-, soft-, and self-templating methods for synthesis of these spherical structures, and also include the concepts of synthetic methodologies. Thereafter, we discuss their applications as electrode materials for lithium-ion batteries and supercapacitors, and sulfur hosts for lithium–sulfur batteries. The superiority of multi-shelled hollow micro/nanospheres for electrochemical energy storage applications is particularly summarized. Subsequently, we conclude this review by presenting the challenges, development, highlights, and future directions of the micro/nanostructured spherical materials for electrochemical energy storage.

Application of Polyaniline for Li-Ion Batteries, Lithium-Sulfur Batteries, and Supercapacitors

Conducting polyaniline (PANI) exhibits interesting properties, such as high conductivity, reversible convertibility between redox states, and advantageous structural feature. It therefore receives ever-increasing attention for various applications. This Minireview evaluates recent studies on application of PANI for Li-ion batteries (LIBs), Li-S batteries (LSBs) and supercapacitors (SCPs). The flexible PANI is crucial for cyclability, especially for buffering the volumetric changes of electrode materials, in addition to enhancing the electron/ion transport. Furthermore, PANI can be directly used as an electroactive component in electrode materials for LIBs or SCPs and can be widely applied in LSBs due to its physically and chemically strong affinity for S and polysulfides. The evaluation of studies herein reveals significant improvements of electrochemical performance by physical/chemical modification and incorporation of PANI.

Bi2MoO6 Microsphere with Double-Polyaniline Layers toward Ultrastable Lithium Energy Storage by Reinforced Structure

Given its competitive theoretical capacity, Bi₂MoO₆ is deemed as a promising anode material for the realization of efficient Li storage. Considering the severe capacity attenuation caused by the lithiation-induced expansion, it is essential to introduce effective modification. Remarkably, in this work, Bi₂MoO₆ microsphere with double-layered spherical shells are successfully prepared, and the polyaniline are coated on both inner and outer surfaces of double-layered spherical shells, working as buffer layers to strain the volume expansion during electrochemical cycling. Inspiringly, when utilized as anode in LIBs, the specific capacity of Bi₂MoO₆@PANI is maintained at 656.3 mAh g^-1 after 200 cycles at 100 mA g^-1, corresponding to a high capacity of 82%. However, the counterpart of individual Bi₂MoO₆ is only 36%. This result confirms that the polyaniline layer can dramatically promote stable cycling performances. Supported by in situ EIS and ex situ technologies followed by detailed analysis, the enhanced pseudocapacitance-dominated contributions and electron/ion transfer rate, benefiting from the combination with polyaniline, are further proved. This work confirms the significant effect of polyaniline on the ultrastable energy storage, further providing an in-depth sight on the impacts of polyaniline coating to the electrical conductivity as well as the resistances of electron/ion transport.

MoO3 nanosheet arrays as superior anode materials for Li- and Na-ion batteries

MoO3 is a promising anode material for energy storage, but its electrochemical performance is still unsatisfactory. Herein, α-MoO3 nanosheets vertically grown on activated carbon fiber cloth as superior anode materials for Li- and Na-ion batteries were achieved by the method of controlled preparation. For Li-ion batteries, the resulting MoO3 array electrodes exhibit a high discharge capacity of 4.48 mA h cm-2 (1780 mA h g-1) at 0.1 mA cm-2 and outstanding cycling stability at 0.5 mA cm-2 (94% capacity retention after 200 cycles). Moreover, for Na-ion batteries, they also show an excellent electrochemical performance with a discharge capacity of 2.5 mA h cm-2 (1621 mA h g-1) at 0.1 mA cm-2 and capacity retention of 90% after 200 cycles at 0.2 mA cm-2. This study suggests that MoO3 array electrodes can be hopefully used as promising anode materials for energy storage applications.

A novel route to prepare N-graphene/SnO2 composite as a high-performance anode for lithium batteries

In this study, we report a simple method to prepare nitrogen-doped graphene, with which a nitrogen-doped graphene/SnO₂ composite was successfully fabricated and employed as a lithium battery anode.

Controlling the Sn-C bonds content in SnO2@CNTs composite to form in situ pulverized structure for enhanced electrochemical kinetics

The Sn-C bonding content between the SnO₂ and CNTs interface was controlled by the hydrothermal method and subsequent heat treatment. Electrochemical analysis found that the SnO₂@CNTs with high Sn-C bonding content exhibited much higher capacity contribution from alloying and conversion reaction compared with the low content of Sn-C bonding even after 200 cycles. The high Sn-C bonding content enabled the SnO₂ nanoparticles to stabilize on the CNTs surface, realizing an in situ pulverization process of SnO₂. The in situ pulverized structure was beneficial to maintain the close electrochemical contact of the working electrode during the long-term cycling and provide ultrafast transfer paths for lithium ions and electrons, which promoted the alloying and conversion reaction kinetics greatly. Therefore, the SnO₂@CNTs composite with high Sn-C bonding content displayed highly reversible alloying and conversion reaction. It is believed that the composite could be used as a reference for design chemically bonded metal oxide/carbon composite anode materials in lithium-ion batteries.

Synthesis and Electrochemical Reaction of Tin Oxalate-Reduced Graphene Oxide Composite Anode for Rechargeable Lithium Batteries

Unlike for SnO₂, few studies have reported on the use of SnC₂O₄ as an anode material for rechargeable lithium batteries. Here, we first introduce a SnC₂O₄-reduced graphene oxide composite produced via hydrothermal reactions followed by a layer-by-layer self-assembly process. The addition of rGO increased the electric conductivity up to ∼10^-3 S cm^-1. As a result, the SnC₂O₄-reduced graphene oxide electrode exhibited a high charge (oxidation) capacity of ∼1166 mAh g^-1 at a current of 100 mA g^-1 (0.1 C-rate) with a good retention delivering approximately 620 mAh g^-1 at the 200th cycle. Even at a rate of 10 C (10 A g^-1), the composite electrode was able to obtain a charge capacity of 467 mAh g^-1. In contrast, the bare SnC₂O₄ had inferior electrochemical properties relative to those of the SnC₂O₄-reduced graphene oxide composite: ∼643 mAh g^-1 at the first charge, retaining 192 mAh g^-1 at the 200th cycle and 289 mAh g^-1 at 10 C. This improvement in electrochemical properties is most likely due to the improvement in electric conductivity, which enables facile electron transfer via simultaneous conversion above 0.75 V and de/alloy reactions below 0.75 V: SnC₂O₄ + 2Li⁺ + 2e^- → Sn + Li₂C₂O₄ + xLi⁺ + xe^- → Li_xSn on discharge (reduction) and vice versa on charge. This was confirmed by systematic studies of ex situ X-ray diffraction, transmission electron microscopy, and time-of-flight secondary-ion mass spectroscopy.