Impact of CO2 activation on the structure, composition, and performance of Sb/C nanohybrid lithium/sodium-ion battery anodes

Antimony (Sb) has been regarded as one of the most promising anode materials for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) and attracted much attention in recent years. Alleviating the volumetric effect of Sb during charge and discharge processes is the key point to promote Sb-based anodes to practical applications. Carbon dioxide (CO2) activation is applied to improve the rate performance of the Sb/C nanohybrid anodes caused by the limited diffusion of Li/Na ions in excessive carbon components. Based on the reaction between CO2 and carbon, CO2 activation can not only reduce the excess carbon content of the Sb/C nanohybrid but also create abundant mesopores inside the carbon matrix, leading to enhanced rate performance. Additionally, CO2 activation is also a fast and facile method, which is perfectly suitable for the fabrication system we proposed. As a result, after CO2 activation, the average capacity of the Sb/C nanohybrid LIB anode is increased by about 18 times (from 9 mA h g−1 to 160 mA h g−1) at a current density of 3300 mA g−1. Moreover, the application of the CO2-activated Sb/C nanohybrid as a SIB anode is also demonstrated, showing good electrochemical performance

A Chronicle Review of Nonsilicon (Sn, Sb, Ge)-Based Lithium/Sodium-Ion Battery Alloying Anodes

Since the commercialization of lithium-ion batteries (LIBs) in the early 1990s, tin (Sn), antimony (Sb), and germanium (Ge)-based anodes have attracted considerable research interest as promising candidates for next-generation LIBs due to their high theoretical capacities, suitable operating voltages, and natural abundance. Additionally, the awareness of limited global lithium sources promoted the renaissance of sodium-ion batteries (SIBs) in recent years. Sn, Sb, and Ge can electrochemically alloy with sodium and are regarded as promising anode candidates for high-performance SIBs. However, these alloying/dealloying anodes suffer severe volume expansion during lithiation or sodiation processes, which is one of the biggest obstacles toward practical applications. In order to solve this problem, several strategies are developed including reducing the absolute size of particles, creating interior void space, and introducing buffer media. After more than two decades' efforts, the electrochemical performance of Sn, Sb, and Ge-based anodes is significantly improved. Considerable studies about Sn, Sb, and Ge-based anodes are summarized in a chronicle perspective and the brief development histories of the three anodes are outlined. With this unique review, light will be shed on the future trends of the studies on the Sn, Sb, and Ge-based anodes for advanced rechargeable batteries

In Situ Incorporation of Super-Small Metallic High Capacity Nanoparticles and Mesoporous Structures for High-Performance TiO2/SnO2/Sn/Carbon Nanohybrid Lithium-Ion Battery Anodes

TiO2 is a promising lithium-ion battery anode due to its good operation safety enabled by its voltage profile. However, the intrinsically low electronic/ionic conductivity and moderate reversible capacity compromise its potential for practical applications. It is proposed in this work to incorporate super-small sized metallic high capacity tin-based nanoparticles into TiO2/carbon nanohybrids, coupled with in situ generation of mesoporous structures. Difunctional methacrylate resin monomers are used as the solvent and carbon source, followed by carbonization and hydrofluoric (HF) etching treatment. The precursors of TiO2, tin-based component, and SiOx porogen agent are homogeneously integrated into the cross-linking network at a molecular level. High reversible capacities, excellent rate capability, and good capacity retention are achieved simultaneously due to synergistic effects from the tin-based component bearing high capacity and good electron conductivity, and mechanical buffer medium of the mesoporous structures. Reversible capacities of 452 mAh g(-1) are achieved after 400 cycles at 200 mA g(-1). High rate capacity of 131 mAh g(-1) is maintained at 5 A g(-1). The overall capacities are increased by more than 2 times compared with the capacities of the tin-free TiO2/C and pristine TiO2/SnO2/Sn/SiOx/C nanohybrids

Synergistic effects from super-small sized TiO2 and SiOx nanoparticles within TiO2/SiOx/carbon nanohybrid lithium-ion battery anode

Synergistic effects from super-small sized TiO2 and SiOx nanoparticles within TiO2/SiOx/carbon nanohybrid lithium-ion battery anod

Tailored fabrication of quasi-isoporous and double layered αα-Fe2_2O3_3 thin films and their application in photovoltaic devices

A series of $\alpha-Fe_2O_3$ thin films with distinct morphologies are prepared via a facile polystyrene-block-polyethylene oxide templated sol–gel method. By tailoring the poor solvent contents and FeCl$_3$-to-polymer weight ratio in the sol–gel solutions, quasi-isoporous $\alpha-Fe_2O_3$ thin films with different substructures and thicknesses are obtained. Via a thermal annealing post-treatment, double layered structures are induced by a synergistic dewetting and Oswald ripening effect. Special focus is set on the $\alpha-Fe_2O_3$ thin films prepared with no annealing/annealing-medium $FeCl_3$ concentration, as they possess uniform periodic structures, which is suitable to be used as hole blocking modification layer of perovskite solar cells (PSCs). An improved power conversion efficiency (PCE) is obtained when the double layered $\alpha-Fe_2O_3$ thin film is applied as the hole blocking modification layer for PSCs. The improved PCE primarily originates from the increased $V_{OC}$, which probably benefits from the synergistic effect of the suppressed charge carrier recombination at the interfaces, the enhanced light transmittance as well as the superior electron extraction capacity

Tailoring the Optical Properties of Sputter-Deposited Gold Nanostructures on Nanostructured Titanium Dioxide Templates Based on In Situ Grazing-Incidence Small-Angle X-ray Scattering Determined Growth Laws

Gold/titanium dioxide (Au/TiO$_2$) nanohybrid materials have been widely applied in various fields because of their outstanding optical and photocatalytic performance. By state-of-the-art polymer templating, it is possible to make uniform nanostructured TiO$_2$ layers with potentially large-scale processing methods. We use customized polymer templating to achieve TiO$_2$ nanostructures with different morphologies. Au/TiO$_2$ hybrid thin films are fabricated by sputter deposition. An in-depth understanding of the Au morphology on the TiO$_2$ templates is achieved with in situ grazing-incidence small-angle X-ray scattering (GISAXS) during the sputter deposition. The resulting Au nanostructure is largely influenced by the TiO$_2$ template morphology. Based on the detailed understanding of the Au growth process, characteristic distances can be selected to achieve tailored Au nanostructures at different Au loadings. For selected sputter-deposited Au/TiO$_2$ hybrid thin films, the optical response with a tailored localized surface plasmon resonance is demonstrated

Template-Induced Growth of Sputter-Deposited Gold Nanoparticles on Ordered Porous TiO2_2 Thin Films for Surface-Enhanced Raman Scattering Sensors

Ordered porous gold/titanium dioxide (Au/TiO$_2$) hybrid nanostructured films are specifically interesting in large-scale applications using localized surface plasmon resonances (LSPRs) and surface-enhanced Raman scattering (SERS). Deposition of Au nanoparticles via sputter deposition is one of the promising technologies to establish optically active sites at low cost in combination with nanostructured TiO$_2$ films. In this work, we investigate the optical response of sputter-deposited Au/TiO$_2$ nanohybrid thin films with a focus on the plasmonic response and application as molecular sensors. The LSPR peak red shifts with an increasing thickness of deposited Au. The Raman intensity of deposited molecules, probed with rhodamine 6G (R6G), depends on the deposited gold thickness. It has its maximum at an effective Au thickness of 3.4 nm. To elucidate the origin of this behavior, we apply in situ grazing-incidence small-angle X-ray scattering (GISAXS) to investigate the growth kinetics of Au on a TiO$_2$ template during sputter deposition. On the basis of time-resolved GISAXS, the growth characteristics of sputter-deposited Au on a TiO$_2$ template with a final effective Au layer thickness around the percolation threshold is described with the well-known four-stage model of nucleation and cluster formation, diffusion-mediated growth, adsorption-mediated growth, and grain growth. The maximum in SERS intensity is corroborated by the existence and optimal size of hot spots in the narrow space occurring between the sputter-deposited Au clusters, on staying below the percolation threshold. On the basis of the growth laws extracted, we give a guideline for tailoring the ordered porous Au/TiO$_2$ nanohybrid thin films for SERS sensor applications

Scalable in Situ Synthesis of Li4Ti5O12/Carbon Nanohybrid with Supersmall Li4Ti5O12 Nanoparticles Homogeneously Embedded in Carbon Matrix

Li4Ti5O12 (LTO) is regarded as a promising lithium-ion battery anode due to its stable cyclic performance and reliable operation safety. The moderate rate performance originated from the poor intrinsic electron and lithium-ion conductivities of the LTO has significantly limited its wide applications. A facile scalable synthesis of hierarchical Li4Ti5O12/C nanohybrids with supersmall LTO nanoparticles (ca. 17 nm in diameter) homogeneously embedded in the continuous submicrometer-sized carbon matrix is developed. Difunctional methacrylate monomers are used as solvent and carbon source to generate TiO2/C nanohybrid, which is in situ converted to LTO/C via a solid-state reaction procedure. The structure, morphology, crystallinity, composition, tap density, and electrochemical performance of the LTO/C nanohybrid are systematically investigated. Comparing to the control sample of the commercial LTO composited with carbon, the reversible specific capacity after 1000 cycles at 175 mA g(-1) and rate performance at high current densities (875, 1750, and 3500 mA g(-1)) of the Li4Ti5O12/C nanohybrid have been significantly improved. The enhanced electrochemical performance is due to the unique structure feature, where the supersmall LTO nanoparticles are homogeneously embedded in the continuous carbon matrix. Good tap density is also achieved with the LTO/C nanohybrid due to its hierarchical micro-/nanohybrid structure, which is even higher than that of the commercial LTO powder

The Influence of CsBr on Crystal Orientation and Optoelectronic Properties of MAPbI3_3 -Based Solar Cells

Crystal orientations are closely related to the behavior of photogenerated charge carriers and are vital for controlling the optoelectronic properties of perovskite solar cells. Herein, we propose a facile approach to reveal the effect of lattice plane orientation distribution on the charge carrier kinetics via constructing CsBr-doped mixed cation perovskite phases. With grazing-incidence wide-angle X-ray scattering measurements, we investigate the crystallographic properties of mixed perovskite films at the microscopic scale and reveal the effect of the extrinsic CsBr doping on the stacking behavior of the lattice planes. Combined with transient photocurrent, transient photovoltage, and space-charge-limited current measurements, the transport dynamics and recombination of the photogenerated charge carriers are characterized. It is demonstrated that CsBr compositional engineering can significantly affect the perovskite crystal structure in terms of the orientation distribution of crystal planes and passivation of trap-state densities, as well as simultaneously facilitate the photogenerated charge carrier transport across the absorber and its interfaces. This strategy provides unique insight into the underlying relationship between the stacking pattern of crystal planes, photogenerated charge carrier transport, and optoelectronic properties of solar cells

Si/Ag/C Nanohybrids with in Situ Incorporation of Super-Small Silver Nanoparticles: Tiny Amount, Huge Impact

Silicon (Si) has been regarded as one of the most promising anodes for next-generation lithium-ion batteries (LIBs) due to its exceptional capacity, appropriate voltage profile, and reliable operation safety. However, poor cyclic stability and moderate rate performance have been critical drawbacks to hamper the practical application of Si-based anodes. It has been one of the central issues to develop new strategies to improve the cyclic and rate performance of the Si-based lithium-ion battery anodes. In this work, super-small metal nanoparticles (2.9 nm in diameter) are in situ synthesized and homogeneously embedded in the in situ formed nitrogen-doped carbon matrix, as demonstrated by the Si/Ag/C nanohybrid, where epoxy resin monomers are used as solvent and carbon source. With tiny amount of silver (2.59% by mass), the Si/Ag/C nanohybrid exhibits superior rate performance compared to the bare Si/C sample. Systematic structure characterization and electrochemical performance tests of the Si/Ag/C nanohybrids have been performed. The mechanism for the enhanced rate performance is investigated and elaborated. The temperature-dependent I-V behavior of the Si/Ag/C nanohybrids with tuned silver contents is measured. Based on the model, it is found that the super-small silver nanoparticles mainly increase charge carrier mobility instead of the charge carrier density in the Si/Ag/C nanohybrids. The evaluation of the total electron transportation length provided by the silver nanoparticles within the electrode also suggests significantly enhanced charge carrier mobility. The existence of tremendous amounts of super-small silver nanoparticles with excellent mechanical properties also contributes to the slightly improved cyclic stability compared to that of simple Si/C anodes