Fe-doped MnxOy with hierarchical porosity as a high-performance lithium-ion battery anode

Deciphering the storage mechanism of biochar anchored with different morphology Mn3O4 as advanced anode material for lithium-ion batteries

Biochar is regarded as a promising lithium-ion batteries anode material, owing to its high cost-effectiveness. However, the poor specific capacity and cycling stability have limited its practical applications. A straightforward and cost-efficient solvothermal method is presented for synthesizing Mn3O4/biochar composites in this study. By adjusting solvothermal temperatures, Mn3O4 with different morphology is prepared and anchored on the biochar surface (MKAC-T) to improve the electrochemical performance. Due to the morphological effect of nanospherical Mn3O4 on the biochar surface, the MKAC-180 anode material demonstrates outstanding reversible capacity (992.5 mAh/g at 0.2 A/g), significant initial coulombic efficiency (61.1 %), stable cycling life (605.3 mAh/g at 1.0 A/g after 1000 cycles), and excellent rate performance (385.8 mAh/g at 1.6 A/g). Moreover, electro-kinetic analysis and ex-situ physicochemical characterizations are employed to illustrate the charge storage mechanisms of MKAC-180 anode. This study provides valuable insights into the "structure-activity relationship" between Mn3O4 microstructure and electrochemical performance for the Mn3O4/biochar composites, illuminating the industrial utilization of biomass carbon anode materials.

Sustainable synthesis of Ni, Mn co-doped FePO4@C cathode material for Na-ion batteries

Olivine FePO4 is widely regarded as an optimal cathode material for sodium-ion batteries due to its impressive theoretical capacity of 177.7 mAh g-1. Nonetheless, the material's limited application stems from its intrinsic low electronic and ionic conductivities and ion diffusion rate. Previously, most modifications of olivine FePO4 are conducted through electrochemical or ion exchange processes in organic solvents, which severely restricted its potential for large-scale applications. In this research, a novel water-based ion exchange method is proposed for the synthesis of Ni-doped, Mn-doped, and Ni, Mn co-doped FePO4@C, which is non-toxic, cost-effective, and demonstrating promising prospects for various applications. Fe2.7Mn0.2Ni0.1PO4@C (0.2Mn0.1Ni-FP@C) is synthesized by a straightforward ion exchange method in aqueous media. The material exhibits a discharge capacity of 154.4 mAh g-1 at 0.1C rate. After 300 cycles at 1C, the capacity retention rate remains at 70.7 %. Numerous tests and calculations conducted in this study demonstrate that 0.2Mn0.1Ni-FP@C, modified through Mn3+ and Ni3+ co-doping, exhibits superior electrochemical performance due to its enhanced electronic conductivity and ion diffusion rate.

Single "Swiss-roll" microelectrode elucidates the critical role of iron substitution in conversion-type oxides

Advancing the lithium-ion battery technology requires the understanding of electrochemical processes in electrode materials with high resolution, accuracy, and sensitivity. However, most techniques today are limited by their inability to separate the complex signals from slurry-coated composite electrodes. Here, we use a three-dimensional "Swiss-roll" microtubular electrode that is incorporated into a micrometer-sized lithium battery. This on-chip platform combines various in situ characterization techniques and precisely probes the intrinsic electrochemical properties of each active material due to the removal of unnecessary binders and additives. As an example, it helps elucidate the critical role of Fe substitution in a conversion-type NiO electrode by monitoring the evolution of Fe₂O₃ and solid electrolyte interphase layer. The markedly enhanced electrode performances are therefore explained. Our approach exposes a hitherto unexplored route to tracking the phase, morphology, and electrochemical evolution of electrodes in real time, allowing us to reveal information that is not accessible with bulk-level characterization techniques.

Facile synthesis of hierarchical MoS2/ZnS @ porous hollow carbon nanofibers for a stable Li metal anode

Lithium metal is considered as an ideal anode candidate for next generation Li battery systems since its high capacity, low density, and low working potential. However, the uncontrollable growth of Li dendrites and infinite volume expansion impede the commercialized applications of Li-metal anodes. In this work, we rationally designed and constructed a hierarchical porous hollow carbon nanofiber decorated with diverse metal sulfides (MS-ZS@PHC). This composite scaffold has three advantages: First, the synergistic effect of multiple-size lithiophilic phases (nano ZnS and micro MoS₂) can regulate Li ions nuclei and grow up homogenously on the scaffold. Second, the enlarged interplanar spacing of MoS₂ microsphere on the fibers can provide abundant channels for Li ions transportation. Third, the porous scaffold can confine the volume expansion of Li metal anode during cycling. Therefore, in a symmetrical cell, the MS-ZS@PHC host presents a homogenous Li plating/stripping behavior and runs steadily for 1100 h at 5 mA cm^-2 with a capacity of 5 mAh cm^-2 and even for 700 h at 10 mA cm^-2 with a capacity of 1 mAh cm^-2. A full cell using MS-ZS@PHC /Li composite as anode and coupled with LiFePO₄ as cathode delivers an excellent cyclic and rate performances.

Nanoparticle-Based Electrodes with High Charge Transfer Efficiency through Ligand Exchange Layer-by-Layer Assembly

Organic-ligand-based solution processes of metal and transition metal oxide (TMO) nanoparticles (NPs) have been widely studied for the preparation of electrode materials with desired electrical and electrochemical properties for various energy devices. However, the ligands adsorbed on NPs have a significant effect on the intrinsic properties of materials, thus influencing the performance of bulk electrodes assembled by NPs for energy devices. To resolve these critical drawbacks, numerous approaches have focused on developing unique surface chemistry that can exchange bulky ligands with small ligands or remove bulky ligands from NPs after NP deposition. In particular, recent studies have reported that the ligand-exchange-induced layer-by-layer (LE-LbL) assembly of NPs enables controlled assembly of NPs with the desired interparticle distance, and interfaces, dramatically improving the electrical/electrochemical performance of electrodes. This emerging approach also demonstrates that efficient surface ligand engineering can exploit the unique electrochemical properties of individual NPs and maximize the electrochemical performance of the resultant NP-assembled electrodes through improved charge transfer efficiency. This report focuses on how LE-LbL assembly can be effectively applied to NP-based energy storage/conversion electrodes. First, the basic principles of the LE-LbL approach are introduced and then recent progress on NP-based energy electrodes prepared via the LE-LbL approach is reviewed.

High-Capacity Interstitial Mn-Incorporated MnxFe3-xO4/Graphene Nanocomposite for Sodium-Ion Battery Anodes

Sodium-ion batteries (SIBs) have attracted wide attention because of their prospects for grid-scale electrical regulation and cost effectiveness of sodium. In this regard, iron oxides (FeO_x) are considered as one of the most promising anode candidates due to their high theoretical capacity and low cost. Unfortunately, the utilization of FeO_x anodes suffers from sluggish reaction kinetics and significant lattice variation, causing insufficient rate performance and fast capacity degradation during the sodiation/desodiation process. In this study, Mn ions are incorporated through interstitial sites into a Fe₃O₄ lattice to form the Mn-incorporated Fe₃O₄/graphene (M-Fe₃O₄/G) composites through a facile hydrothermal method. Confirmed by XRD Rietveld refinement and the first-principles calculation, Mn occupation into the body structure can effectively condense the electron density around the Fermi level and thus contributes to the increased electrical conductivity and improved electrochemical properties. Accordingly, the M_0.1Fe_2.9O₄/G composite demonstrates a high reversible capacity of 439.8 mA h g^-1 at a current density of 100 mA g^-1 over 200 cycles. Even at a high current density of 1 A g^-1, the M-Fe₃O₄/G composites remain stable for over 1200 cycles, delivering a capacity of 210 mA h g^-1. Coupled with a Na₃V₂(PO₄)₃-type cathode, the Mn-incorporated Fe₃O₄/G composites demonstrate good suitability in full SIBs (161.2 mA h g^-1 at the current density of 1 A g^-1 after 100 cycles). The regulation of Mn ions in the Fe₃O₄ lattice provides insights into the optimization of metal oxide anode candidates for their application in SIBs.

Composition Engineering Boosts Voltage Windows for Advanced Sodium-Ion Batteries

Transition-metal selenides have captured sustainable research attention in energy storage and conversion field as promising anodes for sodium-ion batteries. However, for the majority of transition metal selenides, the potential windows have to compress to 0.5-3.0 V for the maintenance of cycling and rate capability, which largely sacrifices the capacity under low voltage and impair energy density for sodium full batteries. Herein, through introducing diverse metal ions, transition-metal selenides consisted of different composition doping (CoM-Se₂@NC, M = Ni, Cu, Zn) are prepared with more stable structures and higher conductivity, which exhibit superior cycling and rate properties than those of CoSe₂@NC even at a wider voltage range for sodium ion batteries. In particular, Zn²⁺ doping demonstrates the most prominent sodium storage performance among series materials, delivering a high capacity of 474 mAh g^-1 after 80 cycles at 500 mA g^-1 and rate capacities of 511.4, 382.7, 372.1, 339.2, 306.8, and 291.4 mAh g^-1 at current densities of 0.1, 0.5, 1.0, 1.4, 1.8, and 2.0 A g^-1, respectively. The composition adjusting strategy based on metal ions doping can optimize electrochemical performances of metal selenides, offer an avenue to expand stable voltage windows, and provide a feasible approach for the construction of high specific energy sodium-ion batteries.

Low-Temperature Assembly of Ultrathin Amorphous MnO2 Nanosheets over Fe2O3 Spindles for Enhanced Lithium Storage

Carbon coating is an effective method to enhance the lithium storage of metal oxides, which, however, suffers from harsh conditions in high-temperature hydrolysis of organic mass at inert atmosphere and compromised capacity due to the presence of low-capacity carbon. We herein report a direct assembly of ultrathin amorphous MnO₂ nanosheets with thickness less than 3 nm over Fe₂O₃ nanospindle backbones at 95 °C as a mild-condition, short-process, and upscalable alternative to the classic carbon-coating method. The assembly of the amorphous MnO₂ nanosheets significantly increases the electrical conductivity of Fe₂O₃ nanospindles. When evaluated as an anode for lithium-ion batteries, the Fe₂O₃@amorphous MnO₂ electrode shows enhanced capacity retention compared to that of the Fe₂O₃ nanospindle electrode. In situ transmission electron microscopy and in situ X-ray diffraction observations of the electrochemically driven lithiation/delithiation of the Fe₂O₃@amorphous MnO₂ electrode indicate that the assembled amorphous MnO₂ nanosheets are in situ transformed into a Fe-Mn-O protection layer for better electrical conductivity, uncompromised Li⁺ penetration, and enhanced structural integration. The Fe₂O₃@amorphous MnO₂ electrode therefore has a reversible capacity of 555 mAh g^-1 after 100 galvanostatic charge/discharge cycles at 1000 mA g^-1, comparable with that of the Fe₃O₄@C electrode derived via the classic carbon-coating route.

Combined Modification of Dual-Phase Li4Ti5O12-TiO2 by Lithium Zirconates to Optimize Rate Capabilities and Cyclability

The low electrical conductivity and ordinary lithium-ion transfer capability of Li₄Ti₅O₁₂ restrict its application to some degree. In this work, dual-phase Li₄Ti₅O₁₂-TiO₂ (LTOT) was modified by composite zirconates of Li₂ZrO₃, Li₆Zr₂O₇ (LZO) to boost the rate capabilities and cyclability. When the homogeneous mixture of LiNO₃, Zr(NO₃)₄·5H₂O and LTOT was roasted at 700 °C for 5 h, the obtained composite achieved a superior reversible capacity of 183.2 mAh g^-1 to the pure Li₄Ti₅O₁₂ after cycling at 100 mA g^-1 for 100 times due to the existence of a scrap of TiO₂. Meanwhile, when the composite was cycled by consecutively doubling the current density between 100 and 1600 mA g^-1, the corresponding reversible capacities are 183.2, 179.1, 176.5, 173.3, and 169.3 mAh g^-1, signifying the prominent rate capabilities. Even undergoing 1400 charge/discharge cycles at 500 mA g^-1, a reversible capacity of 144.7 mAh g^-1 was still attained, denoting splendid cyclability. From a series of comparative experiments and systematic characterizations, the formation of LZO meliorated both the Li⁺ migration kinetics and electrical conductivity on account of the concomitant superficial Zr⁴⁺ doping, responsible for the comprehensive elevation of the electrochemical performance.

Multiscale Interfacial Strategy to Engineer Mixed Metal-Oxide Anodes toward Enhanced Cycling Efficiency

Interconnected macro/mesoporous structures of mixed metal oxide (MMO) are developed on nickel foam as freestanding anodes for Li-ion batteries. The sustainable production is realized via a wet chemical etching process with bio-friendly chemicals. By means of divalent iron doping during an in situ recrystallization process, the as-developed MMO anodes exhibit enhanced levels of cycling efficiency. Furthermore, this atomic-scale modification coherently synergizes with the encapsulation layer across a micrometer scale. During this step, we develop a quasi-gel-state tri-copolymer, i.e., F127-resorcinol-melamine, as the N-doped carbon source to regulate the interfacial chemistry of the MMO electrodes. Electrochemical tests of the modified Fe _xNi_{1- x}O@NC-NiF anode in both half-cell and full-cell configurations unravel the favorable suppression of the irreversible capacity loss and satisfactory cyclability at the high rates. This study highlights a proof-of-concept modification strategy across multiple scales to govern the interfacial chemical process of the electrodes toward better reversibility.

MnWO4 nanoparticles as advanced anodes for lithium-ion batteries: F-doped enhanced lithiation/delithiation reversibility and Li-storage properties

F-Doped MnWO4 nano-particles were synthesized by a one-pot hydrothermal reaction. When evaluated as an electrode material for a Li ion battery, the F-doped nano-MnWO4 delivers a theoretical capacity of 708 mA h g-1 and a long cycle life, as demonstrated by more than 85% capacity retention when cycled for 150 cycles.

Interconnected CoFe2O4-Polypyrrole Nanotubes as Anode Materials for High Performance Sodium Ion Batteries

CoFe₂O₄-coated polypyrrole (PPy) nanotubes (CFO-PPy-NTs) with three-dimensional (3-D) interconnected networks have been prepared through a simple hydrothermal method. The application has been also studied for sodium ion batteries (SIBs). The finely crystallized CoFe₂O₄ nanoparticles (around 5 nm in size) are uniformly grown on the PPy nanotubes. When tested as anode materials for SIBs, the CFO-PPy-NT electrode maintains a discharge capacity of 400 mA h g^-1 and a stable Coulombic efficiency of 98% after 200 cycles at 100 mA g^-1. Even at a higher current density of 1000 mA g^-1, the composite can still retain a discharge capacity of 220 mA h g^-1 after 2000 cycles. The superior electrochemical performance could be mainly ascribed to the uniform distribution of CoFe₂O₄ on the 3-D matrix of PPy interconnected nanotubes, which favors the diffusion of sodium ions and electronic transportation and also buffers the large volumetric expansion during charge/discharge. Thereby our study suggests that such CFO-PPy-NTs have great potential as an anode material for SIBs.

A Novel Phase-Transformation Activation Process toward Ni-Mn-O Nanoprism Arrays for 2.4 V Ultrahigh-Voltage Aqueous Supercapacitors

One of the key challenges of aqueous supercapacitors is the relatively low voltage (0.8-2.0 V), which significantly limits the energy density and feasibility of practical applications of the device. Herein, this study reports a novel Ni-Mn-O solid-solution cathode to widen the supercapacitor device voltage, which can potentially suppress the oxygen evolution reaction and thus be operated stably within a quite wide potential window of 0-1.4 V (vs saturated calomel electrode) after a simple but unique phase-transformation electrochemical activation. The solid-solution structure is designed with an ordered array architecture and in situ nanocarbon modification to promote the charge/mass transfer kinetics. By paring with commercial activated carbon anode, an ultrahigh voltage asymmetric supercapacitor in neutral aqueous LiCl electrolyte is assembled (2.4 V; among the highest for single-cell supercapacitors). Moreover, by using a polyvinyl alcohol (PVA)-LiCl electrolyte, a 2.4 V hydrogel supercapacitor is further developed with an excellent Coulombic efficiency, good rate capability, and remarkable cycle life (>5000 cycles; 95.5% capacity retention). Only one cell can power the light-emitting diode indicator brightly. The resulting maximum volumetric energy density is 4.72 mWh cm^-3 , which is much superior to previous thin-film manganese-oxide-based supercapacitors and even battery-supercapacitor hybrid devices.

Walnut-like Porous Core/Shell TiO2 with Hybridized Phases Enabling Fast and Stable Lithium Storage

TiO₂ is a promising and safe anode material for lithium ion batteries (LIBs). However, its practical application has been plagued by its poor rate capability and cycling properties. Herein, we successfully demonstrate a novel structured TiO₂ anode with excellent rate capability and ultralong cycle life. The TiO₂ material reported here shows a walnut-like porous core/shell structure with hybridized anatase/amorphous phases. The effective synergy of the unique walnut-like porous core/shell structure, the phase hybridization with nanoscale coherent heterointerfaces, and the presence of minor carbon species endows the TiO₂ material with superior lithium storage properties in terms of high capacity (∼177 mA h g^-1 at 1 C, 1 C = 170 mA g^-1), good rate capability (62 mA h g^-1 at 100 C), and excellent cycling stability (∼83 mA h g^-1 was retained over 10 000 cycles at 10 C with a capacity decay of 0.002% per cycle).

Assembly of Ultrathin Gold Nanowires into Honeycomb Macroporous Pattern Films with High Transparency and Conductivity

Because of its promising properties, honeycomb macroporous pattern (HMP) film has attracted increasing attention. It has been realized in many artificial nanomaterials, but the formation of these HMPs was attributed to templates or polymer/supermolecule/surfactant assistant assembly. Pure metal HMP film has been difficult to produce using a convenient colloidal template-free method. In this report, a unique template-free approach for preparation of Au HMP film with high transparency and conductivity is presented. Ultrathin Au nanowires, considered a linear polymer analogue, are directly assembled into HMP film on various substrates using a traditional static breath figure method. Subsequent chemical cross-linking and oxygen plasma treatment greatly enhance the stability and conductivity of the HMP film. The resulting HMP film exhibits great potential as an ideal candidate for transparent flexible conductive nanodevices.

Effects of molecular weight distribution on the self-assembly of end-functionalized polystyrenes

The molecular weight distribution of hydroxyl-end-functionalized polystyrenes shows effects on the self-assembly of patterned porous films and the mechanical strength.

Hierarchically porous materials: synthesis strategies and structure design

This review addresses recent advances in synthesis strategies of hierarchically porous materials and their structural design from micro-, meso- to macro-length scale.

Double-Nanocarbon Synergistically Modified Na3V2(PO4)3: An Advanced Cathode for High-Rate and Long-Life Sodium-Ion Batteries

An advanced cathode material, nitrogen-doped carbon-coated Na3V2(PO4)3 hybriding with multiwalled carbon nanotubes (CNTs) composite, namely double-nanocarbon synergistically modified Na3V2(PO4)3 of sodium ion battery, was fabricated through a simple sol-gel approach. According to the systemical analysis of experimental results on this composite structure, it is found that N-doping not only increases Na-ion migration velocity across the carbon-coated layer but also improves the electric conductivity of the carbon layer. More importantly, the CNTs 3D conducting network could significantly accelerate the electron transport between multiple particles of Na3V2(PO4)3, due to the intimate contacts between active materials and CNTs. Consenquently, the electrochemical properties of this double-nanocarbon-modified Na3V2(PO4)3 are significantly enhanced, especially the high-rate capability and long cycle life. For instance, its initial capacity of 94.5 mAh g(-1) at 0.2 C decreases to 70 mAh g(-1) at 70 C, and the capacity retention is 74%. Moreover, when dischage rate increases to a higher 30 C, the capacity retention is still as high as 87% after 300 cycles.

Employing Synergetic Effect of Doping and Thin Film Coating to Boost the Performance of Lithium-Ion Battery Cathode Particles

Atomic layer deposition (ALD) has evolved as an important technique to coat conformal protective thin films on cathode and anode particles of lithium ion batteries to enhance their electrochemical performance. Coating a conformal, conductive and optimal ultrathin film on cathode particles has significantly increased the capacity retention and cycle life as demonstrated in our previous work. In this work, we have unearthed the synergetic effect of electrochemically active iron oxide films coating and partial doping of iron on LiMn1.5Ni0.5O4 (LMNO) particles. The ionic Fe penetrates into the lattice structure of LMNO during the ALD process. After the structural defects were saturated, the iron started participating in formation of ultrathin oxide films on LMNO particle surface. Owing to the conductive nature of iron oxide films, with an optimal film thickness of ~0.6 nm, the initial capacity improved by ~25% at room temperature and by ~26% at an elevated temperature of 55 °C at a 1C cycling rate. The synergy of doping of LMNO with iron combined with the conductive and protective nature of the optimal iron oxide film led to a high capacity retention (~93% at room temperature and ~91% at 55 °C) even after 1,000 cycles at a 1C cycling rate.

Conversion Reaction-Based Oxide Nanomaterials for Lithium Ion Battery Anodes

Developing high-energy-density electrodes for lithium ion batteries (LIBs) is of primary importance to meet the challenges in electronics and automobile industries in the near future. Conversion reaction-based transition metal oxides are attractive candidates for LIB anodes because of their high theoretical capacities. This review summarizes recent advances on the development of nanostructured transition metal oxides for use in lithium ion battery anodes based on conversion reactions. The oxide materials covered in this review include oxides of iron, manganese, cobalt, copper, nickel, molybdenum, zinc, ruthenium, chromium, and tungsten, and mixed metal oxides. Various kinds of nanostructured materials including nanowires, nanosheets, hollow structures, porous structures, and oxide/carbon nanocomposites are discussed in terms of their LIB anode applications.

Facile synthesis of Mn-doped hollow Fe2O3 nanospheres coated with polypyrrole as anodes for high-performance lithium-ion batteries

Hollow Mn-doped Fe₂O₃/PPy nanospheres have been fabricated, which exhibited excellent electrochemical performance as an anode material for lithium-ion batteries.

Band gap engineering of MnO2 through in situ Al-doping for applicable pseudocapacitors

Band gap engineering was achieved by in situ doping method for high electrical conductivity and chemical activity of MnO₂.

Conformal and non-conformal surface modification of honeycomb-patterned porous films via tunable Cassie–Wenzel transition

We describe here a facile and robust approach to conformal and non-conformal surface modification by tuning the wetting transition between the Wenzel state and the Cassie state.

Ti–Sn–O composite oxides coated with N-doped carbon exhibiting enhanced lithium storage performance

The long-term cycling performance of S1-400C1 and TiO₂-400C1 at different rates.

An unexpected large capacity of ultrafine manganese oxide as a sodium-ion battery anode

MnO2 is shown for the first time to be electrochemically active as a conversion anode for Na-ion batteries (NIBs). Space-confined ultrafine (UF)-MnO2, with an average crystal size of 4 nm, synthesized using a porous silicon dioxide templated hydrothermal process exhibits a high reversible sodiation capacity of 567 mA h g(-1), in contrast to the negligible activity shown by the aggregates of larger (14 nm) MnO2 nanocrystallites. The remarkably enhanced sodiation activity of the UF-MnO2 is attributable to its greatly reduced crystal size, which facilitates diffusion of Na ions, along with high surface energy arising from extensive heterogeneous interfacial bonding with the SiO2 surrounding. The UF-MnO2 anode exhibits an exceptional rate and cycle performance, exhibiting >70% capacity retention after 500 cycles. In operando synchrotron X-ray absorption near-edge structural analysis reveals combined charge-storage mechanisms involving conversion reaction between Mn(III) and Mn(II) oxides, Mn(III)-O1.5 + Na(+) + e(-)- ↔ 1/2Na2O + Mn(II)-O, and non-Mn-centered redox reactions. The finding suggests a new strategy for "activating" the potential electrochemical electrode materials that appear inactive in the bulk form.

Lithium Storage in Microstructures of Amorphous Mixed-Valence Vanadium Oxide as Anode Materials

Constructing three-dimensional (3 D) nanostructures with excellent structural stability is an important approach for realizing high-rate capability and a high capacity of the electrode materials in lithium-ion batteries (LIBs). Herein, we report the synthesis of hydrangea-like amorphous mixed-valence VOx microspheres (a-VOx MSs) through a facile solvothermal method followed by controlled calcination. The resultant hydrangea-like a-VOx MSs are composed of intercrossed nanosheets and, thus, construct a 3 D network structure. Upon evaluation as an anode material for LIBs, the a-VOx MSs show excellent lithium-storage performance in terms of high capacity, good rate capability, and long-term stability upon extended cycling. Specifically, they exhibit very stable cycling behavior with a highly reversible capacity of 1050 mA h g(-1) at a rate of 0.1 A g(-1) after 140 cycles. They also show excellent rate capability, with a capacity of 390 mA h g(-1) at a rate as high as 10 A g(-1) . Detailed investigations on the morphological and structural changes of the a-VOx MSs upon cycling demonstrated that the a-VOx MSs went through modification of the local VO coordinations accompanied with the formation of a higher oxidation state of V, but still with an amorphous state throughout the whole discharge/charge process. Moreover, the a-VOx MSs can buffer huge volumetric changes during the insertion/extraction process, and at the same time they remain intact even after 200 cycles of the charge/discharge process. Thus, these microspheres may be a promising anode material for LIBs.

Recycled Poly(vinyl alcohol) Sponge for Carbon Encapsulation of Size-Tunable Tin Dioxide Nanocrystalline Composites

The recycling of industrial materials could reduce their environmental impact and waste haulage fees and result in sustainable manufacturing. In this work, commercial poly(vinyl alcohol) (PVA) sponges are recycled into a macroporous carbon matrix to encapsulate size-tunable SnO2 nanocrystals as anode materials for lithium-ion batteries (LIBs) through a scalable, flash-combustion method. The hydroxyl groups present copiously in the recycled PVA sponges guarantee a uniform chemical coupling with a tin(IV) citrate complex through intermolecular hydrogen bonds. Then, a scalable, ultrafast combustion process (30 s) carbonizes the PVA sponge into a 3D carbon matrix. This PVA-sponge-derived carbon could not only buffer the volume fluctuations upon the Li-Sn alloying and dealloying processes but also afford a mixed conductive network, that is, a continuous carbon framework for electrical transport and macropores for facile electrolyte percolation. The best-performing electrode based on this composite delivers a rate performance up to 9.72 C (4 A g(-1) ) and long-term cyclability (500 cycles) for Li(+) ion storage. Moreover, cyclic voltammograms demonstrate the coexistence of alloying and dealloying processes and non-diffusion-controlled pseudocapacitive behavior, which collectively contribute to the high-rate Li(+) ion storage.

Bioinspired Carbon/SnO2 Composite Anodes Prepared from a Photonic Hierarchical Structure for Lithium Batteries

A carbon/SnO2 composite (C-SnO2) with hierarchical photonic structure was fabricated from the templates of butterfly wings. We have investigated for the first time its application as the anode material for lithium-ion batteries. It was demonstrated to have high reversible capacities, good cycling stability, and excellent high-rate discharge performance, as shown by a capacitance of ∼572 mAh g(-1) after 100 cycles, 4.18 times that of commercial SnO2 powder (137 mAh g(-1)); a far better recovery capability of 94.3% was observed after a step-increase and sudden-recovery current. An obvious synergistic effect was found between the porous, hierarchically photonic microstructure and the presence of carbon; the synergy guarantees an effective flow of electrolyte and a short diffusion length of lithium ions, provides considerable buffering room, and prevents aggregation of SnO2 particles in the discharge/charge processes. This nature-inspired strategy points out a new direction for the fabrication of alternative anode materials.

The controlled synthesis and improved electrochemical cyclability of Mn-doped α-Fe2O3 hollow porous quadrangular prisms as lithium-ion battery anodes

The controlled synthesis of anode material Mn-doped α-Fe₂O₃ hollow porous quadrangular prisms with an enhanced electrochemical cycling stability is reported.

Coaxial Zn2GeO4@carbon nanowires directly grown on Cu foils as high-performance anodes for lithium ion batteries

Zn₂GeO₄@carbon nanowires directly grown on Cu foil using CVD method exhibit high reversible capacity and high-rate capability as LIB anode.

3D hierarchically mesoporous Cu-doped NiO nanostructures as high-performance anode materials for lithium ion batteries

We report on the rational design and synthesis of three dimensional (3D) Cu-doped NiO architectures with an adjustable chemical component, surface area, and hierarchically porous structure as anodes for lithium ion battery.