Space Charge Layer Research Articles

Modelling Interfaces for Solid Electrolytes

All-solid-state batteries (ASSBs) are candidates for the next-generation of battery electric vehicles. They potentially enable the use of lithium metal as an anode material thereby highly improving the energy density of the battery. Among the most promising candidates for solid electrolytes are polycrystalline materials such as LLZO, due to their high ionic conductivity and chemical stability. Lithium dendrites form above a critical current density (CDC) of as low as 0.6 mA/cm² [1], however. While some explanations where suggested, the underlying mechanisms are not yet understood. In a recent paper a more viable CDC of 5 mA/cm² was reported, which was achieved by protonating the interfaces and grain boundaries [2], this shows that understanding both external and internal interfaces is crucial for the successful development of ASSBs.One often used tool in battery analysis is Electrochemical Impedance Spectroscopy (EIS). We developed a continuum scale model [3] in order to compare experimental impedance data with simulated impedances for a range of possible interface configurations. Space charge layers and their effects are resolved in the model and material properties are informed by atomistic simulations.In our contribution we simulate impedances at ASSB internal and external interfaces. The comparison to experiment helps us validate the model while better understanding the effect that different interface configurations have on resistance and capacitance. The gained understanding can inform the development and manufacturing of future ASSBs. Acknowledgements This work contributes to the research performed at CELEST (Center for Electrochemical Energy Storage Ulm-Karlsruhe). The authors thank the German Ministry of Education and Research (BMBF) for funding of the project CatSE II under grant number 03XP0223E. Han, F., Westover, A. S. et al. Nature Energy 2019, 4(3), 187-196. DOI: 1038/s41560-018-0312-zKim, S., Kim, J. S. et al. Nature Commun 2022, 13(1), 1-12. DOI: 10.1038/s41467-022-29531-xBecker-Steinberger, K., Schardt, S. et al. arXiv 2021 DOI: 10.48550/arXiv.2101.10294

Stabilizing of Lithium-Solid-Electrolyte Interfaces by Atomic Layer Deposition Prepared Nano-Interlayers for a Model All-Solid-State Battery

To understand the electrochemistry of all-solid-state batteries (ASSBs), the use of electrochemical equivalent circuits with a physical meaning is essential. A model battery is needed whose characterization is independent of the influence of the complex battery assembly.Therefore, LICGC©, a model solid electrolyte is chosen that shows stability in air, but on the other hand is also well-known for its instability against metallic lithium upon direct contact. As a first step towards a model ASSB, the interface between lithium and the solid electrolyte (SE) is stabilized with thin (5 nm and 10 nm) coatings of titanium oxide (TO). Impedance data shows that symmetric cells with the TO coatings are protected from rapid SE surface degradation due to reducing lithium. Titanium oxide nano-interlayers can hence serve as a protective interlayer on the anode side of a model ASSB. Additionally, the formation of space charge layers (SCLs), which have been already documented for LICGC alone, appear once again at the interface between metal oxide interlayer and the solid electrolyte. The observed SCL thickness can reach up to ∼ 5 µm (cf. figure). Figure 1

"Soggy-Sand" Chemistry for High-Voltage Aqueous Zinc-Ion Batteries.

The narrow electrochemical stability window, deleterious side reactions, and zinc dendrites prevent the use of aqueous zinc-ion batteries. Here, aqueous "soggy-sand" electrolytes (synergistic electrolyte-insulator dispersions) are developed for achieving high-voltage Zn-ion batteries. How these electrolytes bring a unique combination of benefits, synergizing the advantages of solid and liquid electrolytes is revealed. The oxide additions adsorb water molecules and trap anions, causing a network of space charge layers with increased Zn2+ transference number and reduced interfacial resistance. They beneficially modify the hydrogen bond network and solvation structures, thereby influencing the mechanical and electrochemical properties, and causing the Mn2+ in the solution to be oxidized. As a result, the best performing Al2 O3 -based "soggy-sand" electrolyte exhibits a long lifeof 2500 h in Zn||Zn cells. Furthermore, it increases the charging cut-off voltage for Zn/MnO2 cells to 2V, achieving higher specific capacities. Even with amass loading of 10 mgMnO2 cm-2 , it yields a promising specific capacity of 189 mAh g-1 at 1 A g-1 after 500 cycles. The concept of "soggy-sand" chemistry provides a new approach to design powerful and universal electrolytes for aqueous batteries.

Exploring the role of Ti3C2TxMXene in photoelectrochemical water splitting over solution-processed BiVO4 photoanode

Transition metal carbides, nitrides, or carbonitrides known as MXenes commonly improve the efficiency of photo(electro)catalysts, but their role is still not fully explored. Herein, we developed a novel and facile solution-processing method to fabricate BiVO4 and Ti3C2Tx-modified BiVO4 (Ti3C2Tx/BiVO4) photoanodes to explore the role of Ti3C2Tx MXene in photoelectrochemical water splitting. The charge transfer and recombination kinetics were studied by transient open-circuit potential, transient photocurrent, photoelectrochemical impedance spectroscopy, and intensity-modulated photocurrent spectroscopy. It was demonstrated that Ti3C2Tx forms a Schottky-like junction at the BiVO4/Ti3C2Tx interface and that it acts as a hole transport/storage layer. The Ti3C2Tx layer creates a built-in electric field at the surface that increases the band bending and space charge layer width, eventually enhancing the charge separation efficiency. Modification of Ti3C2Tx/BiVO4 with a water oxidation catalyst such as cobalt phosphate (Co-Pi) was essential to deliver the maximum photocurrent. For instance, the Co-Pi/Ti3C2Tx/BiVO4 photoanode delivered 4.72 mA/cm−2 at 1.23 VRHE, which is 2- and 11-fold higher than those of Ti3C2Tx/BiVO4 and pristine BiVO4 photoanodes, respectively. This study provides a practical protocol for fabricating Ti3C2Tx/BiVO4 and reveals the role of MXene in photoelectrochemical water splitting.

Interfacial engineering of LiCoO2/Li10GeP2S12 with electron-ion mixed conductor Li7.5La3Zr1.5Co0.5O12 for high stable all-solid-state batteries

The space charge layer and interfacial side reactions between cathode and solid electrolyte seriously limit the electrochemical performances of sulfide electrolyte-based all-solid-state lithium batteries (ASSLIBs). In addition, the periodic strain of the cathode material during the charging-discharging process causes the cathode particles cracking and detachment from the electrolyte. Surface coating is an effective approach to improve electrochemical performances, and the coating material should have high ion and electron conductivity to ensure ion and electron conduction. Ionic-electronic mixed conductor Li7.5La3Zr1.5Co0.5O12 (LLZCO) is chosen as the coating material, and coated on the surface of LiCoO2 (LCO) by co-precipitation method. The pristine and coated LCO are assembled into LCO|Li10GeP2S12|InLi ASSLIBs. The buffering layer can reduce the space charge layer and maintain the stability of the cathode particles. The initial discharge specific capacity of the coated sample is 121.0 mAh g−1 (1.9–3.6 V, 0.2C, RT), with a capacity retention rate of 96.0 % after 100 cycles.

Understanding Interfaces at the Positive and Negative Electrodes on Sulfide-Based Solid-State Batteries.

Despite the high ionic conductivity and attractive mechanical properties of sulfide-based solid-state batteries, this chemistry still faces key challenges to encompass fast rate and long cycling performance, mainly arising from dynamic and complex solid-solid interfaces. This work provides a comprehensive assessment of the cell performance-determining factors ascribed to the multiple sources of impedance from the individual processes taking place at the composite cathode with high-voltage LiNi0.6Mn0.2Co0.2O2, the sulfide argyrodite Li6PS5Cl separator, and the Li metal anode. From a multiconfigurational approach and an advanced deconvolution of electrochemical impedance signals into distribution of relaxation times, we disentangle intricate underlying interfacial processes taking place at the battery components that play a major role on the overall performance. For the Li metal solid-state batteries, the cycling performance is highly sensitive to the chemomechanical properties of the cathode active material, formation of the SEI, and processes ascribed to Li diffusion in the cathode composite and in the space-charge layer. The outcomes of this work aim to facilitate the design of sulfide solid-state batteries and provide methodological inputs for battery aging assessment.

Unraveling the Mechanism of Very Initial Dendritic Growth Under Lithium Ion Transport Control in Lithium Metal Anodes.

Lithium metal deposition is strongly affected by the intrinsic properties of the solid-electrolyte interphase (SEI) and working electrolyte, but a relevant understanding is far from complete. Here, by employing multiple electrochemical techniques and the design of SEI and electrolyte, we elucidate the electrochemistry of Li deposition under mass transport control. It is discovered that SEIs with a lower Li ion transference number and/or conductivity induce a distinctive current transition even under moderate potentiostatic polarization, which is associated with the control regime transition of Li ion transport from the SEI to the electrolyte. Furthermore, our findings help reveal the creation of a space-charge layer at the electrode/SEI interface due to the involvement of the diffusion process of Li ions through the SEI, which promotes the formation of dendrite embryos that develop and eventually trigger SEI breakage and the control regime transition of Li ion transport. Our insight into the very initial dendritic growth mechanism offers a bridge toward design and control for superior SEIs.

A 250 nm high-performance AlGaN-based metal–semiconductor–metal deep ultraviolet detector

The present work reports a Al0.67Ga0.33N Metal–Semiconductor–Metal (MSM) detector with a high quantum efficiency (QE) by metal organic chemical vapor deposition (MOCVD) and Standard photolithography. As previously reported, the electrode spacing between the metal fingers of MSM detectors, annealing temperature, and electrode material affect the performance of detectors. Our work demonstrates a high QE detector by optimizing the electrode and annealing temperature. At 14 V bias, the ultraviolet-to-visible rejection ratio is measured as high as 1000. It is also found that the responsivity increases with the bias voltage. Due to the influence of the image force and tunnel effect, the QE exceeds 100 % and the responsivity reaches 4.24 A/W near 250 nm. The specific detectivity (D*) also reaches 1.32 × 1011 Jones. Compared with the literature, this is the highest QE of MSM devices with Ti electrodes on the AlGaN layer at this wavelength. This gain mechanism should be related to trapping photo carriers at the semiconductor/metal interface, image-force lowering of Schottky barrier height, and the expansion of the space charge layer (SCR).

Cathode sheath parameters and their influences on arc root behavior after liquid metal bridge rupture in atmospheric air

The cathode sheath (CS) formation of the direct current air circuit breaker is simulated by a fluid model, and the influence of metal vapor concentration between the contacts after liquid metal bridge rupture is considered. The CS conductivity increases with the increasing concentration of copper vapor. The copper vapor concentration increases from 5% to 95%, and the thickness of the positive space charge layer and ionization layer increases from 22.3 and 49.1 μm to 51.8 and 81.7 μm, respectively. Increasing the CS conductivity is beneficial for the motion of arc roots in a certain range.

Li, Na, K, Mg, Zn, Al, and Ca Anode Interface Chemistries Developed by Solid-State Electrolytes.

Solid-state batteries (SSBs) have received significant attention due to their high energy density, reversible cycle life, and safe operations relative to commercial Li-ion batteries using flammable liquid electrolytes. This review presents the fundamentals, structures, thermodynamics, chemistries, and electrochemical kinetics of desirable solid electrolyte interphase (SEI) required to meet the practical requirements of reversible anodes. Theoretical and experimental insights for metal nucleation, deposition, and stripping for the reversible cycling of metal anodes are provided. Ion transport mechanisms and state-of-the-art solid-state electrolytes (SEs) are discussed for realizing high-performance cells. The interface challenges and strategies are also concerned with the integration of SEs, anodes, and cathodes for large-scale SSBs in terms of physical/chemical contacts, space-charge layer, interdiffusion, lattice-mismatch, dendritic growth, chemical reactivity of SEI, current collectors, and thermal instability. The recent innovations for anode interface chemistries developed by SEs are highlighted with monovalent (lithium (Li+ ), sodium (Na+ ), potassium (K+ )) and multivalent (magnesium (Mg2+ ), zinc (Zn2+ ), aluminum (Al3+ ), calcium (Ca2+ )) cation carriers (i.e.,lithium-metal, lithium-sulfur, sodium-metal, potassium-ion, magnesium-ion, zinc-metal, aluminum-ion, and calcium-ion batteries) compared to those of liquid counterparts.

Nano-Bio Interface Engineering Using Cyclovoltammetry and Design of Nanostructured Lanthanide Oxysulfide Thin Films

Nanoparticles (NPs) in which magnetic and optical properties coexist have been intensively explored for diverse biomedical applications including diagnostic, in vivo imaging and therapy. Gadolinium oxysulfide (Gd2O2S) NPs are promising candidates for biotechnologies as they have been used as MRI contrast agent or X-ray absorbing materials. When doped with cerium, they gain an additional functionality as visible light absorber due to the decrease in the material bandgap from 4.7 eV non-doped to 2.5 eV with 5% of Ce. Further biomedical applications may be envisioned thanks to the combined antioxidant properties of cerium and the magnetic properties of gadolinium.Understanding the molecular-level interactions between organisms and nanoparticles to guide and enable the design of novel materials that are less toxic remains a challenge. In order to understand these interactions at the nanoscale, we studied the change in the physico-chemical properties of (Gd,Ce) oxysulfide NPs when they are immersed in a biological medium. In biological medium, pristine nanomaterials transform and acquire a corona of biomolecules, such as proteins, which can modify their identity. This is known as the nano-bio interface. A better understanding of how nanoparticles interaction with a biological system affect their properties is critical to the future development of multifunctional NPs.Our recent work provides us with a privileged access to composition-controlled nanoplates with a narrow size distribution for a large range of Ln. In particular, we mastered the preparation of mixed-lanthanide nanoplates with tunable band gap and magnetic properties while providing an in-depth understanding of their structural and surface features. The challenge addressed here is to prepare and characterize ligand-free nanostructured thin films made from the NPs suspension. Compared to studies realized in solution, thin films allow to reach the surface of the nanoparticles without any interaction from the ligands. Moreover, it allows spectroscopic and electrochemical methods to be used for the monitoring of the NPs intrinsic properties.The design and development of nanostructured thin films started with the colloidal synthesis of (Gd,Ce) oxysulfide NPs which provides a phase-pure powder. The nanoparticles were then dispersed into an optimized mix of solvents in order to get a stable colloidal suspension. Dip coating is an easy method to deposit matter on a substrate while having a fine control of the thickness and homogeneity. This process was optimized to obtain homogenous films with a withdrawal speed of 2 mm/s under low relative humidity. Thin films of optical quality with a thickness from 40 nm to 150 nm were obtained using single-layer and multilayer deposition on various substrates including silicon, FTO and kapton (Figure A). In situ UV and IR Spectroscopic Ellipsometry were used to monitor the variations of thickness and optical constants, together with the chemical species present at the surface, upon heating the films in different conditions. This study allowed to finely tune the thermal treatment in order to get rid of the stabilizing ligands while preserving the integrity of the nanoplates, as confirmed by Transmission Electron Microscopy (Figure B shows the scraped film). As a result, we have access to the bare surface of the NPs, which was hardly possible in solution. The change in the band gap of the material was monitored through UV-Variable Angle Spectroscopic Ellipsometry. This non-invasive technique is the gold-standard for the characterization of optical quality thin films and gives refractive index of the material (Figure C shows the Tauc plot with the linear fit giving the band gap of the material).The film can be immersed into a biological medium where proteins are expected to bind to the surface of the NP and significantly change their reactivity and mobility. Cyclovoltammetry helped us to probe the access to the NPs and monitor the position of the conduction band. We used redox probes of different standard potentials as electrolytes (Figure D). Electron exchange with the semiconductor electrode is supposed to occur through the conduction band as the valence band is too far in energy. For a redox couple with a standard potential negative to the conduction band edge, when the applied potential equals E0 redox, the semiconductor is accumulating electrons at its surface in a so-called space charge layer. Under these conditions, whether a positive or negative bias is applied (compared to E0 redox), the SC is maintained in an accumulation mode. This was very helpful to check whereas the electronical properties of the material changed upon exposition to biological medium. This could lead to a better understanding and prediction of the chemical interactions at the interface with biomolecular systems. Figure 1

Atomic-Scale Engineering of Grain Boundary Chemistry and Potential for Li-Garnet Solid-State Electrolytes

With increasing demands to replace flammable liquid electrolytes, solid-state electrolytes have sparked interests both in academic and industrial sectors. In particular, Li-garnet LLZO (Li7La3Zr2O12) exhibits outstanding electrical, chemical, and mechanical properties. Despite the promise, LLZO suffers from the formation of lithium (Li) dendrites at high current operations, thereby limiting the safety and performance of garnet-based solid-state batteries. Li metal nucleation and growth reportedly initiate and grow along the locality of grain boundaries (GBs) in such polycrystalline electrolytes, due either to low ionic or high electronic conductivity of the boundaries. However, limited understanding yet exists on the origins of the local GB conductivity mismatch. The mechanistic understanding should be an important prerequisite to develop engineering strategies of the failing GB interfaces. In this work, we first apply grain boundary core-space charge layer model to understand the basis of Li metal nucleation at GBs. Grain boundary core of LLZO is modeled to have excess negative charge potential, leading to the subsequent Li ionic carrier depletion and electronic carrier accumulation in the adjacent space charge layers. The carrier concentration variations then drive the local electronic conductivity surge and detrimental Li metal nucleation at the GBs. Both electrochemical and microscopic characterization techniques are employed to investigate the atomic-level composition and space charge potential at the GBs. This understanding offers us new strategies for controlling Li nucleation. First, sintering atmosphere is selectively chosen to reduce the potential barrier by suppressing intrinsic defect accumulation at the GB core. Second, an aliovalent dopant, with net-positive charge, is introduced to segregate to GB and mitigate the negative core potential. Both approaches are shown effective in lowering the electronic conductivity and to impede Li metal penetration. We successfully achieve critical current densities (CCD) of ~ 1 mA cm-2,a two-fold increase over prior reports. Our theoretical understanding and the engineering approaches will aid in interpreting the failure origin of the garnet electrolytes, and provide a blueprint on how to engineer GBs for improved safety and performance of all-solid-state Li metal batteries.

(Invited) Towards a Mechanistic Understanding of the Oxygen Evolution Reaction on Hematite: Operando Characterization of Band Bending and Interfacial Chemical Speciation Using Sum Frequency Generation Spectroscopy

Hematite is an attractive photoanode for the oxygen evolution reaction (OER) due to its cheap price, relatively small band gap, stability in alkaline solution and a valence band energy suitable for OER catalysis. However, insight into the OER mechanism, and thus the capability to rationally modify this material to optimize performance, is limited by the challenge in relating band bending, surface state population and chemical reactivity operando. Conventionally these issues are addressed by some combination of electrochemical impedance spectroscopy (EIS), photocurrent/voltage kinetics, and linear optical spectroscopies in the visible. While important, all of these approaches suffer from significant limitations: e.g. EIS and related techniques integrate over all charge transfer processes in the device while only those at the hematite/water interface are of interest (and thus require a challenging to validate model to quantify) and UV/Vis absorption measurements (whether steady-state or time resolved) are bulk-sensitive and probe spectrally broad features that are challenging to relate to surface structure.Sum Frequency Generation (SFG) spectroscopy is interface-specific by its symmetry selection rules, can straightforwardly probe interfacial chemical speciation if one of the two incident fields is in the infrared, and is sensitive to the amplitude of interfacial electric fields. These attributes make the technique particularly suitable for characterization of interfacial chemical speciation, double layer and space charge layer structure at the working electrode/electrolyte interface within thin-film spectroelectrochemical cells. Here I describe our recent efforts to characterize chemical speciation and interfacial field at a hematite/electrolyte interface, in the presence and absence of external illumination, as one moves from the Hematite flat band potential through the onset of the OER. Using vibrationally resonant SFG spectroscopy, at infrared wavelengths > 10 micron, we quantify the population of surface holes, i.e. Fe(IV)=0 groups, as the OER turns on. Concurrently we quantify the development of the space charge potential using non-resonant SFG. Recent work has argued, largely from current or optical transients in the visible under chopped illumination, that the OER on Hematite proceeds by a multi-hole mechanism. Because our approach allows for the simultaneous quantification of interfacial field and chemical speciation we directly address this mechanism and the circumstances under which it is expected to apply. More generally, the role of interfacial field in oxidation catalysis has been an object of much current interest. The approach described here – in which interfacial speciation and field can be quantified operando – offers an ability to explore this relationship not possible via any other combination of experimental approaches.

Reversible Redox Probes to Determine the Band Edge Locations for Nano-TiO2

Semiconductor (photo-)electrocatalysts show immense promise in answering the difficulties faced in CO2 electrolysis in relation to the reduction product selectivity. We thus see materials like ZnO[1], Cu2-xSe[2], MoS2 [3], TiO2 [4] and their numerous composites being frequently investigated for their catalytic properties in CO2 (photo-)electroreduction. These catalysts are fabricated via varying techniques and can assume very different thicknesses and morphologies. Although the nano-semiconductors may behave differently, often only the bulk properties are considered when proposing possible reaction pathways. Determining band edge locations of semiconductors in solutions is one such case, where Mott-Schottky (MS) measurements are a widely accepted strategy. The measurement of the potential dependence of the capacitance of the semiconductor space-charge layer under depletion indeed forms an elegant method to determine the flat-band potential and hence the band edge positions for bulk semiconductors in solution. However, the MS method cannot be used for nano-structured semiconductor electrodes in the form of thin films, nanorods or nanoparticles coated on conducting substrates, as their nano-dimensions are typically much smaller than that of a semiconductor depletion layer.In this work, we explored an alternate strategy to determine band edge positions of nano-semiconductors using reversible redox probes. A model thin film system comprised of 30nm anatase TiO2 is used to demonstrate the feasibility of the strategy in aqueous electrolyte solutions. Fe, Ru and Cr based reversible redox species were used as electrochemical probes in cyclic voltammetry experiments with varying solution pH. Based on the presence/absence of the reversible behavior of these probes, we can deduce the TiO2 band edge locations. The procedure also allows us to draw parallels between semiconductor-metal and semiconductor-solution interfaces to gain new insights into the CO2 reduction mechanism on such semiconductor electrodes. Figure 1

Lithium Dendrite Growth, Healing Strategies and Microstructural Imparity in Solid Electrolyte of All Solid-State Batteries

The major challenges for the development of all solid-state batteries (ASSBs) are stable solid electrolytes and robust interfacial design that enables to charge and discharge ASSBs faster for a practical application at ambient conditions. However, ASSBs have several interfaces such as anode | solid electrolyte (SE), cathode | SE, catholyte | active material, etc. These interface properties vary depending on the contact condition, energy states, type defects and chemical/electrochemical stability. The life and performance of ASSB relies largely on these interfaces since Li-depleted space-charge layer generation, and spatial variation in interfacial adhesion originates at the interfaces and results inhomogeneous current distribution which ultimately leads to dendrite formation and battery failure. Our group has developed an electrochemical approach to healing the dendrite from the solid electrolyte [1] that would revive the battery from the failure state. This presentation will focus on the deliberately dendrite growth inside into the sintered dense Li6.25Al0.25La3Zr2O12 (LALZO) plate, removal strategy of the growth dendrite from the LALZO by developed electrochemical technique and characterize its microstructural imparity after dendrite healing. Noting that after the dendrite healing the microstructure of solid electrolyte LALZO is assumed to be different from the original state. Here we performed the neutron tomography of the LALZO solid electrolyte to understand the microstructural integrity after the healing of dendrite from the LALZO solid electrolyte. The obtained results and developed process provide the pathway to revive the battery not only in cell level but also a module or a system level. Figure 1

Ferroelectric Polarization in BaTiO3 Nanocrystals Controls Photoelectrochemical Water Oxidation and Photocatalytic Hydrogen Evolution.

Ferroelectric (FE) semiconductors such as BaTiO3 support a remnant polarization after the application of an electric field that can promote the separation of photogenerated charge carriers. Here, we demonstrate FE-enhanced photocatalytic hydrogen evolution and photoelectrochemical water oxidation with barium titanate nanocrystals for the first time. Nanocrystals of the ferroelectric tetragonal structure type were obtained by a hydrothermal synthesis from TiO2 and barium hydroxide in 63% yield. BaTiO3 nanocrystal films on tantalum substrates exhibit water oxidation photocurrents of 0.141 mA cm-2 at 1.23 V RHE under UV light (60 mW cm-2) illumination. Electric polarization at 52.8 kV cm-1 normal to the film plane increases the photocurrent by a factor of 2 or decreases it by a factor of 3.5, depending on the field polarity. It also shifts the onset potential by -0.15 or +0.09 V and it modifies the surface photovoltage signal. Lastly, exposure to an electric field increases the H2 evolution rate of Pt/BaTiO3 by a factor of ∼1.5, and it raises the selectivity of photodeposition of silver onto the (001) facets of the nanocrystal. All FE enhancements can be removed by heating samples above the Curie temperature of BaTiO3. These findings can be explained by FE dipole-induced changes to the potential drop across the space charge layer of the material. The ability to use the ferroelectric effect to enhance hydrogen evolution and water oxidation is of potential interest for the development of improved solar energy for fuel conversion systems.

Benchmarking the yttrium content in the low temperature/low humidity electrical properties of yttrium-doped barium cerate

Yttrium-doped barium cerate (BCY) is one of the best proton-conducting ceramics to be used in fuel cells/electrolyzers at intermediate temperatures, due to its high hydration enthalpy and high conductivity. Nonetheless, it has commonly been discarded for these applications due to its instability in the presence of carbonaceous and humidified atmospheres. A recent work has addressed this issue, by suggesting the use of this material in very low water vapor partial pressures (pH2O ∼ 10−4 atm) [Electrochimica Acta 334 (2020) 135625] and at low temperatures (T ≤ 400 °C). Under these conditions, BCY can still offer pure protonic conductivity while also offering suitable stability. In the current work, we provide a comprehensive analysis of the effects of the acceptor dopant concentration (Y2O3) in the structural, microstructural, and electrical properties in a wide compositional series of BaCe1-xYxO3-δ (x = 0.05, 0.10, 0.20 and 0.30) at low levels of humidity in the low temperature range (100–400 °C). The results show that BaCe0.9Y0.1O3-δ (BCY10) offers the highest bulk conductivity in these conditions, while further increase in dopant concentration leads to impairment due to “proton trapping” effects. In contrast, the specific grain boundary conductivity increases with increasing dopant concentration due to a reduction of Schottky barrier height at the space-charge layer. We demonstrate that, by operating at very low temperatures (e.g., below 400 °C), the peak performing, BCY10 material can still operate at very low levels of water vapor partial pressure (pH2O ∼ 10−4 atm), where its stability can be maintained. This work paves the way for the optimization of this material, with a focus on utilizing low humidity levels and low temperatures, where it can offer a competitive advantage over that of the majority of other proton-conducting perovskites for potential applications operating under these conditions.

Solid Electrolyte: Strategies to Address the Safety of All Solid‐State Batteries

Lithium metal batteries (LMBs) are in the spotlight as a next‐generation battery due to their high theoretical capacity. However, LMBs still suffer from inferior cycle stability owing to dendritic lithium (Li) growth during Li plating and stripping, leading to battery explosion. To solve this problem, solid electrolytes have emerged as a promising candidate by suppressing the dendritic Li growth. Despite numerous efforts, however, many challenges, such as low ionic conductivity, air stability, space charge layer, and contact loss issues, have been encountered. This review aims to provide the current challenges and new insights of solid electrolytes and then explore optimal solutions for next‐generation solid electrolytes.

Creep and Superplasticity of Gadolinium‐Doped Ceria Ceramics under AC Electric Current

Shaping of dense ceramics is difficult due to their inherent brittleness. Nanograined ceramics like tetragonal zirconia (TZP) can be superplastically deformed and shaped at high temperatures owing to grain boundary sliding (GBS). Herein, the enhanced plasticity of gadolinium‐doped ceria (GDC) ceramics under mild and strong AC electric current in terms of steady state creep rate under both compressive and tensile loading is demonstrated. A current density of 25 and 200 mA mm−2 is used for the creep deformation. The creep rate increases by up to two orders of magnitude under electric current. The stress exponent remains unchanged for creep experiments at 1200 °C with and without electric current, suggesting a GBS mechanism of plastic deformation in both cases. The field‐enhanced creep rate is attributed to the interaction of space–charge layer and the electric field resulting in enhanced GBS. A higher current density results in enhanced ductility of GDC even when the Joule heating effect is compensated by reducing the furnace temperature.

"Win-Win" Modification of LiCoO2 Enables Stable and Long-Life Cycling of Sulfide-Based All Solid-State Batteries.

Interfacial side reactions and space charge layers between the oxide cathode material and the sulfide solid-state electrolytes (SSEs), along with the structural degradation of the active material, significantly compromise the electrochemical performance of all-solid-state batteries (ASSLBs). Surface coating and bulk doping of the cathodes are considered the most effective approaches to mitigate the interface issues between the cathode and SSEs and enhance the structural integrity of composite cathodes. Here, a one-step low-cost means is ingeniously designed to modify LiCoO2 (LCO) with heterogeneous Li2 TiO3 /Li(TiMg)1/2 O2 surface coating and bulk gradient Mg doping. When applied in Li10 GeP2 S12 -based ASSLBs, the Li2 TiO3 and Li(TiMg)1/2 O2 coating layers effectively suppress interfacial side reactions and weaken space charge layer effect. Furthermore, gradient Mg doping stabilizes the bulk structure to mitigate the formation of spinel-like phases during local overcharging caused by solid-solid contact. The modified LCO cathodes exhibit excellent cycle performance with a capacity retention of 80 % after 870 cycles. This dual-functional strategy provides the possibility for large-scale commercial implementation of cathodes modification in sulfide based ASSLBs in the future.