In this paper, the use of nanostructured anode materials for rechargeable lithium-ion batteries (LIBs) is reviewed. Nanostructured materials such as nano-carbons, alloys, metal oxides, and metal sulfides/nitrides have been used as anodes for next-generation LIBs with high reversible capacity, fast power capability, good safety, and long cycle life. This is due to their relatively short mass and charge pathways, high transport rates of both lithium ions and electrons, and other extremely charming surface activities. In this review paper, the effect of the nanostructure on the electrochemical performance of these anodes is presented. Their synthesis processes, electrochemical properties, and electrode reaction mechanisms are also discussed. The major goals of this review are to give a broad overview of recent scientific researches and developments of anode materials using novel nanoscience and nanotechnology and to highlight new progresses in using these nanostructured materials to develop high-performance LIBs. Suggestions and outlooks on future research directions in this field are also given.

Recent developments in nanostructured anode materials for rechargeable lithium-ion batteries

Lead halide perovskite materials have attracted significant attention in the context of photovoltaics and other optoelectronic applications, and recently, research efforts have been directed to nanostructured lead halide perovskites. Collodial nanocrystals (NCs) of cesium lead halides (CsPbX3, X = Cl, Br, I) exhibit bright photoluminescence, with emission tunable over the entire visible spectral region. However, previous studies on CsPbX3 NCs did not address key aspects of their chemistry and photophysics such as surface chemistry and quantitative light absorption. Here, we elaborate on the synthesis of CsPbBr3 NCs and their surface chemistry. In addition, the intrinsic absorption coefficient was determined experimentally by combining elemental analysis with accurate optical absorption measurements. 1H solution nuclear magnetic resonance spectroscopy was used to characterize sample purity, elucidate the surface chemistry, and evaluate the influence of purification methods on the surface composition. We fi...

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Highly Dynamic Ligand Binding and Light Absorption Coefficient of Cesium Lead Bromide Perovskite Nanocrystals

A new chapter in the long and distinguished history of perovskites is being written with the breakthrough success of metal halide perovskites (MHPs) as solution-processed photovoltaic (PV) absorbers. The current surge in MHP research has largely arisen out of their rapid progress in PV devices; however, these materials are potentially suitable for a diverse array of optoelectronic applications. Like oxide perovskites, MHPs have ABX3 stoichiometry, where A and B are cations and X is a halide anion. Here, the underlying physical and photophysical properties of inorganic (A = inorganic) and hybrid organic–inorganic (A = organic) MHPs are reviewed with an eye toward their potential application in emerging optoelectronic technologies. Significant attention is given to the prototypical compound methylammonium lead iodide (CH3NH3PbI3) due to the preponderance of experimental and theoretical studies surrounding this material. We also discuss other salient MHP systems, including 2-dimensional compounds, where rele...

Intriguing Optoelectronic Properties of Metal Halide Perovskites

Colloidal nanocrystals of fully inorganic cesium lead halide (CsPbX3, X = Cl, Br, I, or combinations thereof) perovskites have attracted much attention for photonic and optoelectronic applications. Herein, we demonstrate a facile room-temperature (e.g., 25 °C), ligand-mediated reprecipitation strategy for systematically manipulating the shape of CsPbX3 colloidal nanocrystals, such as spherical quantum dots, nanocubes, nanorods, and nanoplatelets. The colloidal spherical quantum dots of CsPbX3 were synthesized with photoluminescence (PL) quantum yield values up to >80%, and the corresponding PL emission peaks covering the visible range from 380 to 693 nm. Besides spherical quantum dots, the shape of CsPbX3 nanocrystals could be engineered into nanocubes, one-dimensional nanorods, and two-dimensional few-unit-cell-thick nanoplatelets with well-defined morphology by choosing different organic acid and amine ligands via the reprecipitation process. The shape-dependent PL decay lifetimes have been determined t...

Ligand-Mediated Synthesis of Shape-Controlled Cesium Lead Halide Perovskite Nanocrystals via Reprecipitation Process at Room Temperature

Zero-dimensional, one-dimensional, two-dimensional and three-dimensional nanostructured materials for advanced electrochemical energy devices

Organometallic halide perovskites CH3NH3PbX3 (X = I, Br, Cl) have quickly become one of the most promising semiconductors for solar cells, with photovoltaics made of these materials reaching power conversion efficiencies of near 20%. Improving our ability to harness the full potential of organometal halide perovskites will require more controllable syntheses that permit a detailed understanding of their fundamental chemistry and photophysics. In this manuscript, we systematically synthesize CH3NH3PbX3 (X = I, Br) nanocrystals with different morphologies (dots, rods, plates or sheets) by using different solvents and capping ligands. CH3NH3PbX3 nanowires and nanorods capped with octylammonium halides show relatively higher photoluminescence (PL) quantum yields and long PL lifetimes. CH3NH3PbI3 nanowires monitored at the single particle level show shape-correlated PL emission across whole particles, with little photobleaching observed and very few off periods. This work highlights the potential of low-dimens...

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1107&context=chem_pubs

Shape Evolution and Single Particle Luminescence of Organometal Halide Perovskite Nanocrystals

In this work, we report the simple solid-state formation of porous Co3O4 with a hexagonal sheetlike structure. The synthesis is based on controlled thermal oxidative decomposition and recrystallization of precursor Co(OH)2 hexagonal nanosheets. After thermal treatment, the hexagonal sheetlike morphology can be completely preserved, despite the fact that there is a volume contraction accompanying the process: Co(OH)2-->Co3O4. Because of the intrinsic crystal contraction, a highly porous structure of the product is simultaneously created. Importantly, when evaluated as electrode materials for lithium-ion batteries, the as-prepared porous Co3O4 nanosheets exhibit superior Li-battery performance with good cycle life and high capacity (1450 mAh g(-1)) due to their porous sheetlike structure and small size. As far as we know, the performance of the Co3O4-based anode materials for lithium batteries presented here is the best up to now. Considering the improved performance and cost-effective synthesis, the as-prepared porous Co3O4 nanosheets might be suitable as anode electrodes for next-generation lithium-ion batteries.

Porous Co3O4 Nanosheets with Extraordinarily High Discharge Capacity for Lithium Batteries

Dialkyl and diaryl dichalcogenides are highly versatile and modular precursors for the synthesis of colloidal chalcogenide nanocrystals. We have used a series of commercially available dichalcogenide precursors to unveil the molecular basis for the outcome of nanocrystal preparations, more specifically, how precursor molecular structure and reactivity affect the final shape and size of II–VI semiconductor nanocrystals. Dichalcogenide precursors used were diallyl, dibenzyl, di-tert-butyl, diisopropyl, diethyl, dimethyl, and diphenyl disulfides and diethyl, dimethyl, and diphenyl diselenides. We find that the presence of two distinctively reactive C–E and E–E bonds makes the chemistry of these precursors much richer and interesting than that of other conventional precursors such as the more common phosphine chalcogenides. Computational studies (DFT) reveal that the dissociation energy of carbon–chalcogen (C–E) bonds in dichalcogenide precursors (R–E–E–R, E = S or Se) increases in the order (R): diallyl < di...

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1124&context=chem_pubs

Shape-Programmed Nanofabrication: Understanding the Reactivity of Dichalcogenide Precursors

Thick-shell CdSe/nCdS (n ≥ 10) nanocrystals were recently reported that show remarkably suppressed fluorescence intermittency or “blinking” at the single-particle level as well as slow rates of Auger decay. Unfortunately, whereas CdSe/nCdS nanocrystal synthesis is well-developed up to n ≤ 6 CdS monolayers (MLs), reproducible syntheses for n ≥ 10 MLs are less understood. Known procedures sometimes result in homogeneous CdS nucleation instead of heterogeneous, epitaxial CdS nucleation on CdSe, leading to broad and multimodal particle size distributions. Critically, obtained core/shell sizes are often below those desired. This article describes synthetic conditions specific to thick-shell growth (n ≥ 10 and n ≥ 20 MLs) on both small (sub2 nm) and large (>4.5 nm) CdSe cores. We find added secondary amine and low concentration of CdSe cores and molecular precursors give desired core/shell sizes. Amine-induced, partial etching of CdSe cores results in apparent shell-thicknesses slightly beyond those desired, es...

Yijun Guo

Papers

Shape Evolution and Single Particle Luminescence of Organometal Halide Perovskite Nanocrystals

Porous Co3O4 Nanosheets with Extraordinarily High Discharge Capacity for Lithium Batteries

Shape-Programmed Nanofabrication: Understanding the Reactivity of Dichalcogenide Precursors

Unique challenges accompany thick-shell CdSe/nCdS (n > 10) nanocrystal synthesis

Egg albumin as a nanoreactor for growing single-crystalline Fe3O4 nanotubes with high yields.