Driving range and fast charge capability of electric vehicles are heavily dependent on the 3D microstructure of lithium-ion batteries (LiBs) and substantial fundamental research is required to ...optimise electrode design for specific operating conditions. Here we have developed a full microstructure-resolved 3D model using a novel X-ray nano-computed tomography (CT) dual-scan superimposition technique that captures features of the carbon-binder domain. This elucidates how LiB performance is markedly affected by microstructural heterogeneities, particularly under high rate conditions. The elongated shape and wide size distribution of the active particles not only affect the lithium-ion transport but also lead to a heterogeneous current distribution and non-uniform lithiation between particles and along the through-thickness direction. Building on these insights, we propose and compare potential graded-microstructure designs for next-generation battery electrodes. To guide manufacturing of electrode architectures, in-situ X-ray CT is shown to reliably reveal the porosity and tortuosity changes with incremental calendering steps.
Palladium-based alloy materials as cathodes for the reduction of oxygen are regarded as potential substitutes for platinum-based catalysts in fuel cells. In this work, we present a scientometric ...analysis and critically review the use of Pd alloys for the oxygen reduction reaction (ORR). Through scientometric analysis, publication information, research fronts and hotspots are identified. For the critical review, reaction mechanisms in different media are discussed, with the aid of volcano plots to show the general principles for catalyst modifications to maximise the ORR. Influencing factors, including alloying, structure, strain and ligands, particle size, crystal facets and dealloying are considered with a view to informing the theoretical feasibility to enhance the ORR activity. In addition, Pd-based alloys synthesized by different methods are presented and compared in terms of ORR activities. Future research directions are discussed and possible approaches to mass production for industrialization are also proposed.
This review provides an overview on Pd-based electrocatalysts for the oxygen reduction reaction (ORR) through the scientometric analysis and critical review methods. The main focus is on activity regulation and synthetic methods.
Owing to the development of aqueous rechargeable zinc‐ion batteries (ZIBs), flexible ZIBs are deemed as potential candidates to power wearable electronics. ZIBs with solid‐state polymer electrolytes ...can not only maintain additional load‐bearing properties, but exhibit enhanced electrochemical properties by preventing dendrite formation and inhibiting cathode dissolution. Substantial efforts have been applied to polymer electrolytes by developing solid polymer electrolytes, hydrogel polymer electrolytes, and hybrid polymer electrolytes; however, the research of polymer electrolytes for ZIBs is still immature. Herein, the recent progress in polymer electrolytes is summarized by category for flexible ZIBs, especially hydrogel electrolytes, including their synthesis and characterization. Aiming to provide an insight from lab research to commercialization, the relevant challenges, device configurations, and life cycle analysis are consolidated. As flexible batteries, the majority of polymer electrolytes exploited so far only emphasizes the electrochemical performance but the mechanical behavior and interactions with the electrode materials have hardly been considered. Hence, strategies of combining softness and strength and the integration with electrodes are discussed for flexible ZIBs. A ranking index, combining both electrochemical and mechanical properties, is introduced. Future research directions are also covered to guide research toward the commercialization of flexible ZIBs.
An insight from lab research to commercialization for flexible zinc‐ion batteries is provided by comprehensively reviewing the development of polymer electrolytes, relevant challenges and strategies, and device configurations. Aiming to quantify the feasibility for commercialization, a ranking index is proposed combining both electrochemical and mechanical properties. Future research directions are also covered to guide research toward commercialization.
Electrocatalytic organic compound oxidation reactions (OCORs) have been intensively studied for energy and environmentally benign applications. However, relatively little effort has been devoted to ...developing a fundamental understanding of OCORs, including the detailed competition with side reactions and activity limitations, thus inhibiting the rational design of high-performance electrocatalysts. Herein, by taking the NiWO
4
-catalysed urea oxidation reaction (UOR) in aqueous media as an example, the competition between the OCOR and the oxygen evolution reaction (OER) within a wide potential range is examined. It is shown that the root of the competition can be ascribed to insufficient surface concentration of dynamic Ni
3+
, an active site shared by both the UOR and OER. A similar phenomenon is observed in other OCOR electrocatalysts and systems. To address the issue, a "controllable reconstruction of pseudo-crystalline bimetal oxides" design strategy is proposed to maximise the dynamic Ni
3+
population and manipulate the competition between the UOR and the OER. The optimised electrocatalyst delivers best-in-class performance and an ∼10-fold increase in current density at 1.6 V
versus
the reversible hydrogen electrode for alkaline urea electrolysis compared to those of the pristine materials.
A detrimental competition between the urea oxidation reaction (UOR) and oxygen evolution reaction is identified. Strategies are proposed to alleviate such competition and boost the performance of the UOR and other organic compound oxidation reactions.
The performance of lithium ion electrodes is hindered by unfavorable chemical heterogeneities that pre-exist or develop during operation. Time-resolved spatial descriptions are needed to understand ...the link between such heterogeneities and a cell's performance. Here, operando high-resolution X-ray diffraction-computed tomography is used to spatially and temporally quantify crystallographic heterogeneities within and between particles throughout both fresh and degraded Li
Mn
O
electrodes. This imaging technique facilitates identification of stoichiometric differences between particles and stoichiometric gradients and phase heterogeneities within particles. Through radial quantification of phase fractions, the response of distinct particles to lithiation is found to vary; most particles contain localized regions that transition to rock salt LiMnO
within the first cycle. Other particles contain monoclinic Li
MnO
near the surface and almost pure spinel Li
Mn
O
near the core. Following 150 cycles, concentrations of LiMnO
and Li
MnO
significantly increase and widely vary between particles.
With the rapid growth in energy consumption, renewable energy is a promising solution. However, renewable energy (e.g., wind, solar, and tidal) is discontinuous and irregular by nature, which poses ...new challenges to the new generation of large‐scale energy storage devices. Rechargeable batteries using aqueous electrolyte and multivalent ion charge are considered more suitable candidates compared to lithium‐ion and lead‐acid batteries, owing to their low cost, ease of manufacture, good safety, and environmentally benign characteristics. However, some substantial challenges hinder the development of aqueous rechargeable multivalent ion batteries (AMVIBs), including the narrow stable electrochemical window of water (≈1.23 V), sluggish ion diffusion kinetics, and stability issues of electrode materials. To address these challenges, a range of encouraging strategies has been developed in recent years, in the aspects of electrolyte optimization, material structure engineering and theoretical investigations. To inspire new research directions, this review focuses on the latest advances in cathode materials for aqueous batteries based on the multivalent ions (Zn2+, Mg2+, Ca2+, Al3+), their common challenges, and promising strategies for improvement. In addition, further suggestions for development directions and a comparison of the different AMVIBs are covered.
Aqueous rechargeable multivalent ion batteries are considered suitable candidates for grid‐scale energy storage, due to their low cost, ease of manufacture, safe, and environmentally benign properties. This article reviews the latest advances in cathode materials for aqueous batteries based on the multivalent ions (Zn2+, Mg2+, Ca2+, Al3+) charge carriers, their challenges, and promising strategies for further improvement.
A facile and controllable low-temperature (450 ° C) route is reported to produce ultra-small Co 3 O 4 /Co nanoparticles in nitrogen-doped hyperporous graphenic networks (Co 3 O 4 /Co@N-G-450). ...Firstly, a monolayer of ZIF-67 nanocrystals is directly grown in thermal-shock exfoliated graphene networks (EGO) of suitable porosity and pore-widths. Later, the ZIF-67 is etched by targeting the small concentrations of residual oxygen functionalities on EGO (≈13 atom%) under a nitrogen atmosphere at 450 °C. Therefore, the partial gasification of ZIF-67 followed by oxidation of the resultant open cobalt metal centres produces a highly active nanophase of Co 3 O 4 /Co@N-G in a mass yield of >65 wt%. The as-synthesised Co 3 O 4 /Co@N-G-450 catalyst, without any further acid washing or oxidation process, exhibits an outstanding ORR performance with a high onset (0.962 V vs. RHE) and half-wave (0.808 V vs. RHE) potential as well as limiting current density (5.2 mA cm −2 ) in 0.1 M KOH solution. These merits are comparable to those of commercial Pt/C and many ZIF-derived catalysts, synthesised under extended and complex chemical treatment. Moreover, the catalyst also exhibits fast reaction kinetics with a dominant 4-electron reaction pathway and high durability.
Characterization of the guest-host interactions and the heterogeneity of porous materials is essential across the physical and biological sciences, for example for gas sorption and separation, ...pollutant removal from wastewater, biological systems (protein-ligand binding) and molecular recognition materials such as molecularly imprinted polymers. Information about the guest-host interactions can be obtained from calorimetric experiments. Alternatively, more detailed information can be obtained by properly analysing the experimentally acquired adsorption equilibrium data. Adsorption equilibrium is usually interpreted using theoretical adsorption isotherms that correlate with the equilibrium concentration of the adsorbate in the solid phase and in the bulk fluid at a constant temperature. Such theoretical isotherms or expressions can accurately predict the adsorbent efficiency (at equilibrium) as a function of process variables such as the initial adsorbate concentration, adsorbent mass, reactor volume and temperature. Detailed analysis of the adsorption isotherms permits the calculation of the number density of the adsorbent sites, their binding energy for the guest molecules and information about the distribution of adsorption site binding energies. These analyses are discussed in this review. A critical evaluation of the analytical and numerical methods that can characterize the heterogeneity and guest-host interactions involved in terms of discrete or continuous binding site affinity distribution was performed. Critical discussion of the limitations and the advantages of these models is provided. An overview of the experimental techniques that rely on calorimetric and chromatographic principles to experimentally measure the binding energy and characteristic properties of adsorbent surfaces is also included. Finally, the potential use of site energy distribution functions and their potential to provide new information about the binding energy of adsorbents for a specific guest molecule application is discussed.
Heterogeneity of porous structures is an important material property involved during the design of adsorbents, catalysts and molecular recognition materials. This review discusses the mathematical methods that can characterize adsorption site energies and surface heterogeneity from the adsorption isotherms.
The temporally and spatially resolved tracking of lithium intercalation and electrode degradation processes are crucial for detecting and understanding performance losses during the operation of ...lithium-batteries. Here, high-throughput X-ray computed tomography has enabled the identification of mechanical degradation processes in a commercial Li/MnO
primary battery and the indirect tracking of lithium diffusion; furthermore, complementary neutron computed tomography has identified the direct lithium diffusion process and the electrode wetting by the electrolyte. Virtual electrode unrolling techniques provide a deeper view inside the electrode layers and are used to detect minor fluctuations which are difficult to observe using conventional three dimensional rendering tools. Moreover, the 'unrolling' provides a platform for correlating multi-modal image data which is expected to find wider application in battery science and engineering to study diverse effects e.g. electrode degradation or lithium diffusion blocking during battery cycling.
Catastrophic failure of lithium-ion batteries occurs across multiple length scales and over very short time periods. A combination of high-speed operando tomography, thermal imaging and ...electrochemical measurements is used to probe the degradation mechanisms leading up to overcharge-induced thermal runaway of a LiCoO
pouch cell, through its interrelated dynamic structural, thermal and electrical responses. Failure mechanisms across multiple length scales are explored using a post-mortem multi-scale tomography approach, revealing significant morphological and phase changes in the LiCoO
electrode microstructure and location dependent degradation. This combined operando and multi-scale X-ray computed tomography (CT) technique is demonstrated as a comprehensive approach to understanding battery degradation and failure.
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