•The recent research progress on mesocrystal based high performance electrodes for lithium-ion batteries is reviewed.•Mesocrystal assemblies possess the structural and chemical stability of ...microsized electrodes and the improved electrochemical properties associated with nanosized electrodes.•Improved understanding of mesocrystal formation mechanisms can significantly improve the development and synthesis of such electrodes.
Lithium-ion batteries are a well-established technology that has seen gains in performance based on materials chemistry over the past two decades. Although there are many material selections available when assembling such a device, the fundamental design and structure remains the same – two electrodes of different potential separated by an intermediary electrolyte. Despite recent advancements with electrode materials, considerable improvements in energy density and stability are still necessary in order to achieve energy storage parity. The design of structurally oriented nanoparticles can circumvent the thermodynamic instability, undesired side reactions, high processing costs, and potential nano-toxicity effects associated with nanoparticle synthesis, processing, and use. A great deal of recent efforts have focused on the formation and understanding of ordered nanoparticle superstructures with a vast range of architectures; in particular, crystallographically oriented nanoparticle superstructures, or mesocrystals. Mesocrystals can be delineated by their high degree of crystallinity, porosity, and nanoparticle subunit alignment along a crystallographic register. Given their unique combination of nanoparticle properties and order over a microscopic size regime, mesocrystals have strong potential as active materials for lithium-ion battery electrodes. Such assemblies would possess the structural and chemical stability of microsized electrodes while exploiting the beneficial properties associated with nanosized electrodes and their large reactive surface area.
Aqueous zinc ion batteries (ZIBs) are truly promising contenders for the future large-scale electrical energy storage applications due to their cost-effectiveness, environmental friendliness, ...intrinsic safety, and competitive gravimetric energy density. In light of this, massive research efforts have been devoted to the design and development of high-performance aqueous ZIBs; however, there are still obstacles to overcome before realizing their full potentials. Here, the current advances, existing limitations, along with the possible solutions in the pursuit of cathode materials with high voltage, fast kinetics, and long cycling stability are comprehensively covered and evaluated, together with an analysis of their structures, electrochemical performance, and zinc ion storage mechanisms. Key issues and research directions related to the design of highly reversible zinc anodes, the exploration of electrolytes satisfying both low cost and good performance, as well as the selection of compatible current collectors are also discussed, to guide the future design of aqueous ZIBs with a combination of high gravimetric energy density, good reversibility, and a long cycle life.
.
Display omitted
▶ Nanoparticles forming photoelectrode film offer large surface for dye adsorption. ▶ One-dimensional nanostructures provide direct pathways for electron transport. ▶ Aggregates of ...nanoparticles produce both large surface area and light scattering. ▶ Use of aggregates allow for photoelectrode film thinner than conventional ones. ▶ Thinner photoelectrode film means shorter electron transport and less recombination.
Nanotechnology opens a door to tailing materials and creating various nanostructures for use in dye-sensitized solar cells. This review classifies the nanostructures into (1) nanoparticles, which offer large surface area to photoelectrode film for dye-adsorption, (2) core–shell structures, which are derived from the nanoparticles however with a consideration to reduce charge recombination by forming a coating layer, (3) one-dimensional nanostructures such as nanowires and nanotubes, which provide direct pathways for electron transport much faster than in the nanoparticle films, and (4) three-dimensional nanostructures such as nanotetrapods, branched nanowires or nanotubes, and oxide aggregates, which not only emphasize providing large surface area but also aim at attaining more effective light harvesting and charge transport or collection. The review ends with an outlook proposing that the oxide aggregates are a potentially promising structure which may possibly achieve higher efficiency than the record by reason that the bifunction of aggregates in providing large surface area and generating light scattering allows for photoelectrode film thinner than usual and thus decreases the charge recombination of DSCs.
Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. This Review ...describes some recent developments in the synthesis and characterization of nanostructured cathode materials, including lithium transition metal oxides, vanadium oxides, manganese oxides, lithium phosphates, and various nanostructured composites. The major goal of this Review is to highlight some new progress in using these nanostructured materials as cathodes to develop lithium batteries with high energy density, high rate capability, and excellent cycling stability resulting from their huge surface area, short distance for mass and charge transport, and freedom for volume change in nanostructured materials.
This Review describes some recent developments in the synthesis and characterizations of nanostructured cathode materials for Li‐ion rechargeable batteries with high energy density, high rate capability and excellent cycling stability. The nanostructured cathode materials provide high surface area, short distance for mass and charge transport, and freedom for volume change.
Presently, sustainable energy as well as efficient and economical energy conversion and storage technologies has become important work in light of the rising environmental issues and dependence on ...portable and uninterrupted power sources. Increasingly more researchers are focusing on harvesting and converting solar energy, mechanical vibration, waste heat, and wind to electricity. Electrical energy storage technologies play a significant role in the demand for green and sustainable energy. Rechargeable batteries or secondary batteries, such as Li-ion batteries, Na-ion batteries, and Mg-ion batteries, reversibly convert between electrical and chemical energy via redox reactions, thus storing the energy as chemical potential in their electrodes. The energy density of a rechargeable battery is determined collectively by the specific capacity of electrodes and the working voltage of the cell, which is the differential potential between the cathode and the anode. Over the past decades, a significant number of studies have focused on enhancing this specific capacity; however, studies to understand and manipulate the electrochemical potential of the electrode materials are limited. In this review, the material characteristics that determine and influence the electrochemical potentials of electrodes are discussed. In particular, the cathode materials that convert electricity and chemical potential through electrochemical intercalation reactions are investigated. In addition, we summarize the selection criteria for elements or compounds and the effect of the local atomic environment on the discharge potential, including the effects of site energy, defects, crystallinity, and microstructure, using LiMn2O4, V2O5, Mo6S8, LiFePO4, and LiCoO2 as model samples for discussion.
The composition, crystallinity, morphology, and trap‐state density of halide perovskite thin films critically depend on the nature of the precursor solution. A fundamental understanding of the ...liquid‐to‐solid transformation mechanism is thus essential to the fabrication of high‐quality thin films of halide perovskite crystals for applications such as high‐performance photovoltaics and is the topic of this Review. The roles of additives on the evolution of coordination complex species in the precursor solutions and the resulting effect on perovskite crystallization are presented. The influence of colloid characteristics, DMF/DMSO‐free solutions and the degradation of precursor solutions on the formation of perovskite crystals are also discussed. Finally, the general formation mechanism of perovskite thin films from precursor solutions is summarized and some questions for further research are provided.
The nature of precursor solutions not only impacts the nucleation rate and crystallization kinetics of perovskite crystals, but also influences the physical properties of perovskite thin films. This Review presents the comprehensive understanding on the nature of perovskite precursor solutions and the formation mechanism of perovskite thin films from these precursor solutions.
Nanostructured metal oxide semiconductors (MOS), such as TiO2 and ZnO, have been regarded as an attractive material for the quantum dots sensitized solar cells (QDSCs), owing to their large specific ...surface area for loading a large amount of quantum dots (QDs) and strong scattering effect for capturing a sufficient fraction of photons. However, the large surface area of such nanostructures also provides easy pathways for charge recombination, and surface defects and connections between adjacent nanoparticles may retard effective charge injection and charge transport, leading to a loss of power conversion efficiency. Introduction of the surface modification for MOS or QDs has been thought an effective approach to improve the performance of QDSC. In this paper, the recent advances in the control of nanostructures and interfaces in QDSCs and prospects for the further development with higher power conversion efficiency (PCE) have been discussed.
•Design and fabrication of hierarchical nanostructured metal oxide semiconductors.•Engineering interface chemistry can reduce the surface charge recombination.•Recent work in excitonic solar cells ...was summarized.
Excitonic solar cells (ESCs) including dye-sensitized solar cells (DSCs), quantum dot-sensitized solar cells (QDSCs), perovskites solar cells (PSCs) and inverted organic photovoltaics (OPVs), are built upon metal oxide semiconductors (MOSs), which have attracted considerable attention recently and showed a promising development for the next generation solar cells. The development of nanotechnology has created various MOS nanostructures to open up new perspectives for their exploitation, significantly improving the performances of ESCs. One of the outstanding advantages is that the nanostructured mesoporous MOSs offer large specific surface area for loading a large amount of active materials (dyes, quantum dots or perovskites) so as to capture a sufficient fraction of photons as well as to facilitate efficient charge transfer. This review focuses on the recent work on the design, fabrication and surface modification of nanostructured MOSs to improve the performance of ESCs. The key issues for the improvement of efficiency, such as enhancing light harvesting and reducing surface charge recombination, are discussed in this paper.
A Perovskite is any material with the same type of crystal struc- ture of CaTiO3, a mineral discovered in 1839 1 , with the chemical formula of ABX3, where A and B are two cations and X is an anion. ...Inorganic metal trihalide perovskites, CsPbX3 （X = CI, Br, and I）, were synthesized almost 60 years later by reacting PbX2 and CsX salts in aqueous solutions 2. In the ideal cubic-symmetry struc- ture, the A ions in 12-fold cuboctahedral coordination are much larger than the B ions in 6-fold octahedral coordination. Because perovskite does not possess a close packed anion sub-lattice with flexible bond angles, many types of distortions from the ideal structure can occur including the tilt and distortion of octahedra and displacement of cations out of the centers of their coordination polyhedra, leading to lower symmetries： tetragonal, orthorhombic, rhombohedral and monoclinic. Layered perovskites, also known as two-dimensional perovskites, are formed when thin sheets intrude and separate ABX3 structure. Complexity of both chemical compo- sition and crystal structure often renders great challenges in the synthesis and formation of single crystalline stoichiometric per- ovskite phase without co-existence of undesirable parasitic phases.
PDF
