Amorphous materials distinguish themselves from crystalline materials by lacking long-range order while retaining structural order at the local scale (2-5 Å). However, the complexity in topological and chemical order prevents current characterization tools from fully unveiling the structure in disordered materials. Consequently, the nature of medium-range order in amorphous materials has remained elusive. The Zachariasen and crystal competing models have been proposed to describe disordered phases and have both been verified through synthesis and characterization. The main difference between them is thought to be whether the amorphous phase shows medium-range order. Here we demonstrate a form of organized inorganic matter that is amorphous in two dimensions, while exhibiting long-range order and a high degree of crystallinity in the third. The structure consists of periodically stacked 2-dimensional amorphous Nb-W-O monolayers without long-range in-plane order. The unique periodic and therefore crystalline stacking along one principal axis enables direct imaging and revealed that the amorphous Nb-W-O monolayers formed in agreement with the Zachariasen model for 2 dimensions. Our findings show that the gap between crystalline and amorphous materials does not only depend on medium-range order but can also apply to principal dimensions within the same solid.

Advanced optical functionalities are typically achieved using interference multilayer coatings composed of alternating materials with contrasting refractive indices. Here, we propose a mono-material concept in which the required refractive-index contrast is generated within a single material through a multilayer stack of porous and dense microstructured titanium dioxide (TiO2). A key challenge in such architectures is the deposition of dense layers on porous ones without intermixing or excessive roughness. To address this, titanate 2D nanosheets are introduced as an interfacial layer. To demonstrate this concept, a visible near-infrared optical filter was designed using optical simulations and experimentally realized. The desired refractive-index contrast was achieved by tuning the porosity of consecutive amorphous TiO2 layers, with similar to 1 nm crystalline Ti0.87O2 titanate nanosheet interlayers enabling sequential stacking of dense and porous TiO2. This approach enabled the fabrication of a six-layer mono-material optical filter and establishes a sustainable strategy for designing versatile mono-material optical coatings.

Abstract Garnet Li 7 La 3 Zr 2 O 12 electrolyte is considered a key enabler of solid-state batteries with Li metal electrodes, but the grain boundaries impair its performance. To date, the understanding of grain boundary structures and its impact on performance remains elusive. Here, we show that element segregation at Li 7 La 3 Zr 2 O 12 grain boundaries critically governs Li transport and nucleation. During conventional sintering, Al, Ta, and La segregate at grain boundaries, locally depleting Li and creating space-charge layers that lower total ionic conductivity. Simultaneously, this segregation leads to higher electronic conductivity along grain boundaries, which promotes Li nucleation at grain boundary edges with increased risk of dendrite formation. The underlying mechanism of segregation is governed by both thermodynamic driving forces and diffusion kinetics. Building on this understanding, we develop a strategy to achieve segregation-free grain boundaries through a rapid sintering protocol that utilizes the onset of solid-state softening. This approach yields transparent, polycrystalline Li 7 La 3 Zr 2 O 12 with negligible grain boundary impedance and enhanced dendrite tolerance. By elucidating the structural origins and electrochemical consequences of grain boundary segregation, this work provides a guidance for the rational optimization of solid electrolytes.

Sodium acetate trihydrate (SAT) is a well-known salt hydrate phase change material (PCM) with large energy density and a high degree of supercooling, making it suitable for long-term thermal storage. However, effectively discharging heat from the supercooled SAT remains a challenge. This study delves into optimizing the electrical nucleation process in an SAT-based PCM, beginning with the validation of electrode pre-treatment and concluding with initiation under various conditions. The research identifies the optimal voltage and electrode spacing for nucleation. The crucial role of diffusion field interactions from growing crystals at different sites is highlighted, noting that their convergence creates a complex concentration gradient profile that hampers crystallization efficiency. Additionally, an increase in electrode pairs correlates with a more uniform heat distribution. Findings revealed that through material modification and nucleation strategy optimization, the theoretical crystallization time for SAT-based PCMs can vary significantly, ranging from 44 to 252 s. This variability, offering up to a 472.73 % extension in discharge time, underscores the PCM's adaptability for customized applications, especially in fields requiring variable discharge rates, such as residential heating and electronic thermal management.

With the widespread application of flexible pressure sensors in various fields, the demand for developing high‐performance flexible pressure sensors is increasing. Two‐dimensional oxide pressure sensors (2DOPSs) hold immense potential due to their ultra‐high sensitivity. However, further improving the overall performance of the device remains a challenge for 2DOPSs, especially to widen the pressure sensing range of the sensor. In this article, the effect of substrate and electrode materials on the performance of the Ca 2 Nb 3 O 10 nanosheet pressure sensors is investigated. It is found that the lower the Rockwell hardness of the electrodes of the device, the easier the substrate material deforms under pressure, and the lower the device pressure threshold, the higher the sensitivity. The optimization of the substrates and electrodes yields Ca 2 Nb 3 O 10 nanosheet pressure sensors with sensitivity up to 10 5 kPa −1 in a large detection range, fast response time (83/165 ms) and good stability. This work provides guideline for further development of 2DOPSs.

Sodium-ion batteries (SIBs) are an alternative to lithium-ion batteries (LIBs) due to the low cost. However, the large ionic radius of Na-ion hinders their efficient diffusion within the hosts of SIBs. Interlayer expansion of intercalation hosts is a option to increase the mobility of sodium ions. In this paper, tetraalkylammonium ions of different chain lengths were inserted into the lepidocrocite-type titanate to obtain interlayer modulation for investigation of their potential as anodes in SIBs. Surprisingly, the biggest interlayer spacing produced by the longer chain length of tetrabutylammonium ions does not give the best performance. The tetraethylammonium intercalated layered titanate surpasses others with a specific capacity of 175 mAh g-1 at 0.1 A g-1. The phenomena could be explained by variation of the charge transfer resistance and and diffusion coefficient induced by changing guest ion species. This work provides a useful guide for developing high-efficiency layered electrode materials for SIBs.

In thermochemical heat storage, higher adsorbent porosity improves reaction kinetics by facilitating mass transfer but compromises mechanical stability. This study addresses this challenge by incorporating 5–20 wt% sepiolite to reinforce porous potassium carbonate (K2CO3) granules while preserving reaction efficiency. Specifically, KS20 granules, containing 20 wt% sepiolite, exhibited a substantial increase in maximum compressive load from 26.8 N to 48.4 N, strengthening cohesion within the K2CO3 granules. At the material level, KS20 granules demonstrated a volumetric energy density of 0.9 GJ/m3. The partial substitution of K2CO3 with sepiolite had minimal impact on the total hydration energy density, as sepiolite actively contributed to adsorption through physisorption. In addition, its mesoporous structure retains moisture internally, preventing agglomeration. KS20 granules exhibited excellent cyclability, with stable structural integrity and resistance to agglomeration, ensuring minimal material loss and performance degradation over multiple cycles. Moreover, they maintain their effectiveness under varying environmental conditions, reducing the risk of unwanted reactions or physical breakdown during storage and transportation.

Amine-based hydrogel sorbents are an emerging material for efficient CO2 capture. However, the influence of the sorbent properties on their CO2 absorption dynamics still remains unknown, blocking their optimization for specific applications. Therefore, in this study, we present a particle-scale model describing the spatio-temporal CO2 absorption in tailor-made particle sorbents comprising a hydrogel core (crosslinked polyethylenimine) and a coating layer (silica nanoparticles). Incorporating both physical diffusion of CO2 and amine-CO2 reactions within the particle, the model also addresses the effect of water on both physical diffusion and the reaction. The model is fitted to experimentally measured CO2 absorption profiles of the particles over time at different temperatures. Subsequently, we validate the model against measurements of the CO2 absorption profiles for control parameters that were excluded from the fitting (water content and particle geometry), confirming that the physical mechanisms are correctly captured. Finally, we model the spatiotemporal evolution of the CO2 absorption and the free amine concentration inside the particle. By altering the shell diffusion coefficient and particle size in the model, we show that: (1) the silica shell hardly hinders the absorption process, and (2) decreasing the particle size strongly accelerates the absorption, albeit with sub-quadratic scaling due to the coupling of diffusion and reaction. Our work provides deeper insight into the CO2 absorption mechanisms of hydrogel sorbents, enabling rational design and optimization of such materials.

Quasi-two-dimensional (quasi-2D) lead halide perovskites with alternating cations in the interlayer (ACI) space represent a promising type of material for optoelectronics. Similar to the Ruddlesden-Popper and Dion-Jacobson types of perovskites, domains with different thicknesses (n) and bandgaps are formed within a single film. This work focuses on ⟨n⟩ = 5 ACI perovskites based on guanidinium (GA+) and methylammonium (MA+) cations and investigates the influence of the GA:MA ratio in the interlayer space on the photophysical processes after photoexcitation. Using a combination of time-resolved photoluminescence (TRPL) and femtosecond transient absorption (TA) spectroscopy, hot carrier cooling, the occurrence and directionality of energy or charge transfer between the different domains, and the exciton and charge carrier dynamics are studied and modeled using target analysis. After the thermalization of hot carriers and excitons, exciton transfer from low-n to high-low-n domains occurs within 10 ps, after which they dissociate into free charges. From there, charge transfer into the intermediate-n domains occurs in about 22-54 ps. In the layers with excess GA, this process possibly occurs in an undesirable competition with self-trapped exciton (STE) formation. From the intermediate-n domains, charges are transferred into the high-n domains in 95-159 ps, which process occurs the fastest in the GA-MA layer. Finally, charge carriers decay intrinsically on the nanosecond scale with the longest lifetimes for the GA-MA and GA-2MA systems, which is beneficial for PV applications.

Mixed-phase copper niobate anodes for lithium-ion batteries consisting of various phases work synergistically to deliver high electrochemical capacities at exceptional cycling rates.

Flexible pressure sensors present enormous potential for applications in health monitoring, human-machine interfacing, and electronic skins (e-skin). However, at the cost of flexibility, the design of flexible pressure sensors has been facing the trade off between high sensitivity and wide sensing range. Herein, we propose a sandwiched structure composed of monolayer films of calcium niobate nanosheets to endow the device with both ultrahigh sensitivity and a wide sensing range. Tunable contact between the two electrodes of the pressure sensor through the gaps in the insulative monolayer film and precise thickness modulation of the monolayer films at the nanoscale result in an ultrahigh sensitivity and wide sensing range of the sensors. By virtue of these two traits, the pressure sensor distinguishes itself with unprecedented performances of ultrahigh sensitivity (6.43 x 10(4) kPa(-1)), a wide sensing range (1.94-60.00 kPa), a fast response time (<165 ms), and reliable repeatability. In addition, the sensor has a sensing mechanism transition from capacitive mode to piezoresistive mode from low pressure to high pressure. The sensors demonstrates the ability for motion detection of the human body. This work sheds light on the development of highly sensitive flexible pressure sensors.

Titanium dioxide (TiO 2 ) has long been receiving attention as a promising material for enhancing the performance of photovoltaic devices due to its tunable optoelectronic properties. This paper reviews the utilization of TiO 2 in recent photovoltaic applications, focusing primarily on its role as an optical material. The fundamental properties of TiO 2 are reviewed, such as its wide bandgap and unique property of tunable refractive index. Furthermore, various strategies are discussed to harness the fundamental properties of TiO 2 to improve light absorption and charge carrier generation within various photovoltaic devices. Overall, the pivotal role of TiO 2 as an Earth-abundant and non-critical optical material is highlighted for future advances in the power conversion efficiency and viability of photovoltaic technologies, paving the way for future research and developments aimed at achieving sustainable and cost-effective solar energy conversion.

Quasi-2D lead-halide perovskites consist of conducting inorganic layers with tunable thickness (n) separated by large organic spacer cations. Typically, domains with different n and bandgaps are formed within a single film. Here, the crystallization of the films is tuned by mixing Dion-Jacobson (DJ) with Ruddlesden-Popper (RP) spacer cations. Compared to the quasi-2D perovskite film based on solely the DJ type spacer 1,4-phenylenedimethylammonium (PDMA), a film with less defects and more vertically aligned crystallization is achieved by addition of the RP type spacer propylammonium (PA). As the film structure plays an important role in the photophysics, time-resolved photoluminescence (TRPL) and femtosecond transient absorption (TA) are used to investigate the impact of mixing these spacer cations on the dynamics of hot carrier cooling, the occurrence and directionality of energy or electron transfer between the different domains, and the exciton and charge carrier dynamics. Exciton transfer from low-n to high-n domains occurs at a favorable faster rate for the PDMA-based film (0.0640 ps-1) compared to the PA-based film (0.0365 ps-1), while the mixed spacer film demonstrates intermediate behavior (0.0473 ps-1). This study facilitates the design of advanced materials with optimized photophysical characteristics for a next generation of optoelectronic devices. This study investigates the impact of combining Ruddlesden-Popper and Dion-Jacobson spacers on the photophysics of quasi-2D lead-halide perovskite films. Time-resolved photoluminescence and femtosecond transient absorption are used to study the influence of spacer mixing on the hot carrier cooling dynamics, the occurrence and directionality of energy or electron transfer between different domains, and the behavior of excitons and charge carriers. image

Quasi-2D perovskites have attracted attention as potential solar energy absorber materials due to their balanced efficiency and stability and their unique quantum-well structures. In order to facilitate directional excitons and charge carrier transport and preferential energy transfer landscape in photovoltaic thin films, the phase distribution formed by different types of microstructural domains should be regulated. In this work, the Dion-Jacobson-type spacer 1,4-phenylenedimethanammonium (PDMA) was used, and different strategies were pursued to control the phase distribution in formamidinium-based (FA) quasi-2D perovskites based on the composition of (PDMA)FA4Pb5I16. In general, doping with FACl modulated the crystallization kinetics, forming 2D low-n crystals on the top surface or a reversed-gradient phase distribution, depending on whether excess or substitutional doping was employed. Alternatively, mixing with a Ruddlesden-Popper spacer helped bridging to adjacent octahedra in pure PDMA-based perovskites and improved crystallization, while regulating the quantum-well structures to give a normal-gradient phase distribution, where 2D domains resided on the bottom side. By combining FACl doping and spacer mixing, the film showed both a reversed-gradient phase distribution and larger vertically aligned grains. This work contributes to the knowledge of how to manipulate and regulate the phase distribution in FA-based quasi-2D perovskites and further paves the way for fabricating corresponding devices with high efficiency and stability. Mixing a Dion-Jacobson spacer and a Ruddlesden-Popper spacer regulates quasi-2D perovskite thin films for a normal-gradient phase distribution, while FACl additive doping regulates the films to give a reversed-gradient phase distribution.

The diammonium precursor 1,4-phenylenedimethanammonium (PDMA) was used as a large organic spacer for the preparation of Dion-Jacobson-type quasi-2D perovskites (PDMA)(MA)n-1PbnI3n+1 (MA = methylammonium). Films with composition ⟨n⟩ = 5 comprised randomly orientated grains and multiple microstructural domains with locally differing n values. However, by mixing the Dion-Jacobson-type spacer PDMA and the Ruddlesden-Popper-type spacer propylammonium (PA), the crystal orientation in both the vertical and the horizonal directions became regulated. High crystallinity owing to well-matched interlayer distances was observed. Combining this spacer-engineering approach with the addition of methylammonium chloride (MACl) led to full vertical alignment of the crystal orientation. Moreover, the microstructural domains at the substrate interface changed from low-n (n = 1, 2, 3) to high-n (n = 4, 5), which may be beneficial for hole extraction at the interface between perovskite and hole transport layer due to a more finely tuned band alignment. Our work sheds light on manipulating the crystallization behavior of quasi-2D perovskite and further paves the way for highly stable and efficient perovskite devices.

The escalating atmospheric CO2 levels, which has been driving global warming, highlights the necessity to develop efficient CO2 capture technology, such as solid-based sorbents. Understanding the CO2 adsorption mechanism in these sorbents is important for their optimization, which, however, current semi-empirical models are not able to comprehensively demonstrate. In this paper, a diffusion-reaction model is proposed to elucidate the CO2 adsorption of a core-shell structured hydrogel sorbent. As the sorbent comprises a polyethylenimine hydrogel particle encapsulated by a silica shell, the model is developed by considering both physical diffusion and CO2-amine chemical reactions. As a result, the model describes the CO2 adsorption capacities of experimentally fabricated particles across diverse adsorption temperatures. Moreover, it unveils the CO2 adsorption process within the particle by displaying the evolution of amine-CO2 reaction rates, CO2 distribution, and amine consumption profiles. Notably, the model shows that the hydrogel core contributes to the primary diffusion resistance, a contrast to the less resistant silica shell. Overall, our diffusion-reaction model illuminates a fresh perspective on interpreting the CO2 adsorption mechanism of amine-based solid sorbents, from which insights can be gained for optimizing sorbent production in pursuit of carbon capture applications.

Flexible pressure sensors with high sensitivity have gained considerable attention in the electronic skin, human motion control, and health monitoring fields. Porous structures strongly enhance the compressibility and sensitivity in piezoresistive sensors compared with bulk materials. However, traditional foam fabrication methods lead to poor adhesion between nanofillers and polymer matrix, instability, complexity, and low reproducibility. We report a single-step 3D printing process for silver nanoparticle-embedded foams, creating pressure sensors with controlled conductivity, shape, and stiffness. Our silver nanoparticle-embedded foam-based sensors achieve high sensitivity with a wide working range and minimal hysteresis. Additionally, these sensors demonstrated robust durability, maintaining consistent resistance signals across 250 cyclic tests, and are integrated into a pressure patch and smart shoe sole for human motion monitoring.

All-solid-state batteries based on the active cathode material LiCoO2 (LCO), a garnet-type Li7La3Zr2O12 (LLZO) electrolyte and a Li-metal anode are attracting a lot of attention as a robust and safe alternative to conventional lithium-ion batteries. The challenges in the practical realization of such cells are related to high-temperature sintering, which compacts the ceramic powder but also leads to undesirable material interactions such as cation interdiffusion and secondary phase formation. Even if high initial capacities can be achieved, the all-inorganic cells suffer from a strong capacity drop due to various degradation phenomena during processing and operation, which are not yet fully understood. In this study, the thermodynamic and kinetic aspects of co-sintering as well as the structural evolution of materials and interfaces during processing and operation of co-sintered LCO-LLZO cathodes are investigated in detail. A thermodynamic model for the interdiffusion of cations is derived and the effects of the diffusion of Al- and Co-ions, which occurs during the processing and cycling of the cells, are investigated. In LLZO, the diffusion of 0.13 Co per formula unit (pfu) has a negligible effect on ionic and electronic conductivity and electrochemical stability. In contrast, the substitution of 0.01 pfu Al and the induced disorder in the layer structure of LCO increases the polarization during cycling. All-inorganic cells fabricated with optimized sintering parameters to minimize interdiffusion between LCO and LLZO show good initial performance but similar degradation during cycling, as the used processing parameters result in a more porous microstructure leading to the development of cracks along the LLZO/LCO interface. The results obtained highlight the inherent instabilities of all-ceramic cathodes with unprotected LCO/LLZO interfaces, which require precise tuning of materials and processing parameters to achieve both high mechanical stability and low interdiffusion.

The caking phenomenon poses a significant challenge in thermochemical heat storage systems, which arises from the agglomeration of powdered salt hydrates. This impedes the flow of gas molecules through the reactor bed and negatively impacts the reactions kinetics, leading to decreased overall efficiency of heat storage. To tackle this challenge, an innovative approach is proposed, involving the synthesis of porous potassium carbonate (K2CO3) granules using potassium bicarbonate (KHCO3) as a pore former in varying ratios of 10, 20, 40, and 50 wt%. It is essential to note that the maximum amount of KHCO3 for effective granulation is around 50 wt% of the total batch, as exceeding this limit prevents granule formation. This method results in the formation of porous K2CO3 granules that are 100% pure and free from any additives that could impact the energy density. In terms of diffusion kinetics, the granules with 40 wt% (K40) and 50 wt% (K50) of KHCO3 demonstrated significant improvements in effective diffusion coefficients in comparison with the K2CO3 granule without pore former. Regarding cyclic performance, K2CO3 granule without pore former showed slow kinetics and incomplete hydration even after 10 cycles. In contrast, the K40 and K50 granules demonstrated significantly faster hydration kinetics, with K40 achieving complete hydration by the 4th cycle and K50 reaching the highest water loading capacity of 1.5 mol H2O/mol K2CO3 from the first cycle. The K50 granule, with a hydrated state density of 1.74 g/cm3, achieved a volumetric energy density of 0.96 GJ/m3. Compared to other developed granules, K50 exhibited superior hydration kinetics, positioning it as a promising candidate for thermochemical heat storage applications. This study highlights the potential of modifying pore morphology to improve the efficiency of thermochemical heat storage and demonstrates that the wet granulation technique can be effectively utilized for the mass production of salt hydrate granules.