Protective Interlayer Research Articles

A Cu-Zn bimetallic organic framework as protective interlayer for dendrite-free Zn deposition in zinc-based flow batteries

Zinc-based flow batteries hold great promise for grid-scale energy storage. However, the formation of zinc dendrites challenges their lifespan and safety. In this work, we devise a bimetallic organic framework material on carbon cloth (CuZn@MOF-CC) using a one-step dip coating method to address the dendrite issue. The prepared CuZn@MOF-CC promotes the creation of zincophilic sites on the electrode surface, facilitating smooth and uniform zinc deposition. Electrochemical csharacterizations and density functional theory (DFT) calculations reveal much stronger electronic interactions between CuZn@MOF and the zinc atoms compared to the commonly used anode material through an obvious electron interaction between the Zn atom and the Cu sites linked in the CuZn@MOF chain. By mitigating the zinc dendrite problem, this approach effectively improves the coulombic efficiency, cycle life, and safety of zinc-based flow batteries. The battery incorporating the prepared material demonstrates impressive stability, exceeding 450 cycles without dendrites at a high current density of 320 mA cm−2, paving the way for efficient and reliable energy storage solutions and a sustainable future.

Dual-Component Interlayer Enables Uniform Lithium Deposition and Dendrite Suppression for Solid-State Batteries.

β-Lithium thiophosphate (LPS) exhibits high Li+ conductivity and has been identified as a promising ceramic electrolyte for safe and high-energy-density all-solid-state batteries. Integrating LPS into solid-state lithium (Li) batteries would enable the use of a Li electrode with the highest deliverable capacity. However, LPS-based batteries operate at a limited current density before short-circuiting, posing a major challenge for the development of application-relevant batteries. In this work, we designed a dual-component interfacial protective layer called LiSn-LiN that forms in situ between the Li electrode and LPS electrolyte. The LiSn component, Li22Sn5, exhibits enhanced Li diffusivity compared with the metallic lithium and facilitates a more uniform lithium deposition across the electrode surface, thus eliminating Li dendrite formation. Meanwhile, the LiN component, Li3N, shows enhanced mechanical stiffness compared with LPS and functions to suppress dendrite penetration. This chemically robust LiSn-LiN interlayer provides a more than doubled deliverable critical current density compared to systems without interfacial protection. Through combined XPS and XAFS analyses, we determined the local structure and the formation kinetics of the key functional Li22Sn5 phase formed via the electrochemical reduction of a Sn3N4 precursor. This work demonstrates an example of the structural-specific design of a protective interlayer with a desired function - dendrite suppression. The structure of a functional protective layer for a given solid-state battery should be tailored based on the given battery configuration and its unique interfacial chemistry.

NaBix/NaVyOz Hybrid Interfacial Layer Enables Stable and Dendrite-Free Sodium Anodes.

The challenges of sodium metal anodes, including formation of an unstable solid-electrolyte interphase (SEI) and uncontrolled growth of sodium dendrites during charge-discharge cycles, impact the stability and safety of sodium metal batteries. Motivated by the promising commercialization potential of sodium metal batteries, it becomes imperative to systematically explore innovative protective interlayers specifically tailored for sodium metal anodes. In this work, a NaBix/NaVyOz hybrid and porous interfacial layer on sodium anode is successfully fabricated via pretreating sodium with bismuth vanadate. The hybrid interlayer effectively combines the advantages of sodium vanadates and alloys, raising a synergistic effect in facilitating sodium deposition kinetics and inhibiting the growth of sodium dendrites. As a result, the modified sodium electrodes (BVO-Na) can stably cycle for 2000h at 0.5mAcm-2 with a fixed capacity of 1mAhcm-2, and the BVO-Na||Na3V2(PO4)3 full cell sustains a high capacity of 94 mAh g-1 after 600 cycles at 5C. This work demonstrates that constructing an artificial hybrid interlayer is a practical solution to obtain high performance anodes in sodium metal batteries.

Electric‐Responded 2D Black Phosphorus Nanosheets Induce Uniform Zn2+ Deposition for Efficient Aqueous Zinc‐Metal Batteries

AbstractAqueous zinc‐metal batteries (AZMBs) have demonstrated inspiring potential for large‐scale energy storage applications. However, their further utilization is impeded by issues such as severe side reactions and the uncontrolled penetrating dendrites growth. In this study, an innovative approach to modify the aqueous electrolyte with 2D black phosphorus nanosheets (denoted as 2D BP nanosheets) is proposed. The 2D BP nanosheets under the electric field acted as a unique electron directional migration character, can dynamically homogenize the electric field, facilitate homogeneous Zn2+ conduction. The nanosheets covering on the protuberances can also induce stable and homogeneous Zn2+ deposition, thereby effectively inhibit the formation of penetrating dendrites. More importantly, this special protective interlayer can further prevent the direct contact between reactive Zn‐metal and activated water molecules, thereby inhibiting the occurrence of undesirable side‐reactions. The incorporation of BP nanosheets induced significant improvement in electrochemical stability and reversibility for AZMBs. As a result, Zn//Zn symmetric batteries based on 2D BP nanosheets added electrolyte exhibited steady cycling for over 2800 h at 1 mA cm−2 1 mAh cm−2. Zn//NVO full‐cell preserved 78.85% capacity even after ultra‐long 1000 cycles. The successful application of 2D BP nanosheets introduce a novel method to accelerate the practical application of AZMBS.

Sacrifice Few to Save Many: Fire Protective Interlayers in Carbon-Fiber-Reinforced Laminates

Sacrifice Few to Save Many: Fire Protective Interlayers in Carbon-Fiber-Reinforced Laminates

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

PEO-Based Polymer Membranes As Lithium Protective Interlayers to Improve the Interfacial Compatibility with Sulfide Solid Electrolytes

While the last century was unquestionably dominated by energy generation from fossil fuels, the 21st century seems devoted to the energy transition towards more sustainable sources. Because of their high energy density, efficiency and flexibility, Li-ion batteries (LIBs) are currently dominating the electrochemical energy storage market share. However, driven by the continuous technological progresses resulting in more powerful portable devices as well as the rapid growth of EVs, the rapidly increasing market is demanding for batteries with higher energy densities and longer lifespan. The integration of a high specific capacity and low redox potential material like lithium metal in lithium metal batteries (LMBs) may help to achieve these goals. Nevertheless, its integration in commercial systems requires to address key issues such as users’ safety and environmental risks related to the thermal runaway phenomenon. All-solid-state lithium batteries (ASSLBs) are considered one of the most promising alternatives to state-of-the-art lithium-ion batteries because of their improved safety. Among the several solid electrolytes (SE) proposed, the sulfide-based ones, e.g., Li6PS5Cl (LPSCl), are considered promising candidate materials because of their comparatively high ionic conductivity.[1] Despite these advantages they suffer of some interfacial challenges on both the cathode and the anode side.[2] In this regard, we focused on the SE/lithium interface investigating the use of Li+ ion conductive polymer interlayers with the aim of (i) separate the two interphases suppressing the side reactions and (ii) improve the physical contact between the interphases, to eventually achieve homogeneous lithium stripping-plating improving the compatibility of the sulfide solid electrolyte with lithium metal.Polyethylene oxide (PEO) is a well-known polymer used in electrochemical applications thanks to its ability of conducting lithium ions. Using it as polymer matrix, several PEO-based polymer interlayers were prepared differing in the salt composition. Starting from a PEO/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) membrane (EO:Li = 10:1), a partially substitution (10 and 20 %wt.) of this last were made with lithium bis(fluorosulfonyl)imide (LiFSI) and lithium tricyanomethanide (LiTCM).[3] The polymer interlayers were prepared by a UV-induced (co)polymerization to interlink the polymer matrix with the tetraglyme plasticizer.[4] The as-obtained sticky membranes were physical-chemically characterized and their interfacial behavior electrochemical investigated.

Efficient and Stable Tin–Lead Perovskite Photoconversion Devices Using Dual‐Functional Cathode Interlayer

AbstractTin–lead halide perovskites (TLHPs) are promising photoactive materials for photovoltaics (PVs) due to reduced toxicity and broad light absorption. However, their inherent ionic vacancies facilitate inward metal diffusion, accelerating device degradation. Here, efficient, stable TLHP‐based PV and photoelectrochemical (PEC) devices are reported containing a chemically protective cathode interlayer—amine‐functionalized perylene diimide (PDINN). Solution‐processed PDINN effectively extract electrons and suppress inward‐metal diffusion by forming tridentate metal complexes with its nucleophilic sites. The PV device achieved an efficiency of 23.21% (>81% retention after 750 h at 60 °C and >90% retention after 3100 h at 23 ± 4 °C), and the first demonstration of TLHP‐based PEC devices exhibit a record‐high bias‐free solar hydrogen production rate (33.0 mA cm−2; ≈3.42 × 10−6 kg s−1 m−2) when coupled with biomass oxidation, which is ≈1.7‐fold higher than the ultimate target set by the U.S. Department of Energy for one‐sun hydrogen production. These findings demonstrate the potential of TLHPs for efficient, stable photoconversion by the molecular design of the cathode interlayer.

Protective NaSICON Interlayer between a Sodium-Tin Alloy Anode and Sulfide-Based Solid Electrolytes for All-Solid-State Sodium Batteries.

This paper presents a suitable combination of different sodium solid electrolytes to surpass the challenge of highly reactive cell components in sodium batteries. The focus is laid on the introduction of ceramic Na3.4Zr2Si2.4P0.6O12 serving as a protective layer for sulfide-based separator electrolytes to avoid the high reactivity with the sodium metal anode. The chemical instability of the anode|sulfide solid electrolyte interface is demonstrated by impedance spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The Na3.4Zr2Si2.4P0.6O12 disk shows chemical stability with the sodium metal anode as well as the sulfide solid electrolyte. Impedance analysis suggests an electrochemically stable interface. Electron microscopy points to a reaction at the Na3.4Zr2Si2.4P0.6O12 surface toward the sulfide solid electrolyte, which does not seem to affect the performance negatively. The results presented prove the chemical stabilization of the anode-separator interface using a Na3.4Zr2Si2.4P0.6O12 interlayer, which is an important step toward a sodium all-solid-state battery. Due to the applied pressure that is mandatory for battery cells with sulfide-based cathode composite, the use of a brittle ceramic in such cells remains challenging.

Self-healing and robust polymer-based protective interlayer containing boronic esters for stabilizing lithium metal anode

Lithium (Li) metal batteries have attracted wide research interests due to the ultrahigh theoretical capacity of Li anode. However, lithium metal anodes suffer from the inhomogeneous Li deposition, resulting in capacity fade and unacceptable safety hazards. More importantly, the huge volume change of the mechanically fragile solid electrolyte interphase (SEI) further induces the dendrite growth during repeated Li plating. Therefore, it is critical to protect Li metal anodes and inhibit the growth of Li dendrites for stabilizing the Li plating process. Herein, we fabricated a novel polymer-based protective interlayer (LBP) with a stable cross-linked network containing abundant boron moieties via the thiol-ene click reaction. The polymer-based protective interlayer obtains self-healing properties through the boronic ester transesterification and enhances the safety of lithium batteries. Besides, the dense layer with a cross-linked network effectively retards the air corrosion when the Li metal was exposed to the air environment. Furthermore, the vacant p orbital in the boron atoms of boronic ester can trap anions of Li salt and regulate a homogeneous Li deposition, enhancing the interface stability of Li metal. Consequently, the Li|Li symmetric cell with LBP protective interlayer shows stable stripping/plating voltage over 3500 h at 1.0 mA cm−2. The LBP-Li|LFP cell maintains a high capacity of 142.2 mAh/g after 300 cycles, demonstrating the cell with LBP-Li exhibits excellent cycling stability. The design of this advanced protective interlayer with multiple capabilities is potential to shed a light for high-performance lithium metal batteries.

Modeling and validation of forming by vaporizing foil actuators

Sheet metal forming by means of vaporizing actuators attempts to utilize the explosion-like expansion of a cheap and simple aluminum foil, which occurs when a high capacitor discharge current heats it up to the gas phase within a very short time. Until now, mainly basic experimental investigations of this flexible, relatively young manufacturing process exist. In this work, the modeling of the complete forming process, i.e. including the expanding actuator, is conducted for the first time. A crucial parameter is the energy deposition until the so-called burst point, eventually representing an initial equation of state condition for the actuator in the forming simulation. The actuator is modeled using Smoothed Particle Hydrodynamics (SPH), while deformable solid bodies interacting with it are modeled by the Finite Element Method (FEM). The dynamic character of the process especially necessitates the incorporation of the strain rate-dependent constitutive behavior of the solids, which are a steel sheet and a protective polyurethane interlayer. Free forming histories of circular DC01 blanks are recorded with a Photon Doppler Velocimetry (PDV) system. The resulting curves validate the adopted modeling approach for three different, experimentally measured electrical energy depositions. Further aspects of the established numerical model are addressed: It is found, i.a., that the impulse of the bursting actuator is transferred to the blank through the elastomeric interlayer principally without changing the amplitude and effective area. The maximum free kinetic particle energy, however, restricts the possible energy available for deforming solids, and therefore expresses an upper bound for the process efficiency.

Carbonized bacterial cellulose as free-standing cathode host and protective interlayer for high-performance potassium-sulfur batteries with enhanced kinetics and stable operation

Due to the limited capacity of Lithium (Li)-ion batteries and the scarce reserves of Li, potassium-sulfur battery (KSB) seems to be the most appealing candidate for next-generation advanced energy storage systems owing to the abundance of sulfur as well as potassium in addition to the high capacity offered by sulfur cathodes. However, the development of KSB is in the nascent stage, primarily because of the highly unstable and reactive potassium anode, which needs special consideration for its protection. To overcome this, for the first time to the best of our knowledge, we introduce the free-standing carbonized bacterial cellulose (CBC) not only as an anode-protective interlayer but also as a cathode host. Further, the K2S6 catholyte is used as an active material, enabling the even distribution of active sulfur and high sulfur loading. Benefitting from the superior physicochemical properties of CBC and the introduction of it as a protective interlayer, the KSB, as developed, can be cycled for continuous 500 cycles even at high current rates such as 2 and 5C, respectively. The cell with CBC as a cathode host and an interlayer retained 73% and 62% of initial capacity after 300 and 500 cycles at 1 and 2C, respectively. Potassium striping and plating test show that the CBC interlayer effectively enables uniform nucleation and growth, reducing dendrite formation. The first-principles calculations are also performed to substantiate these advancements in electrochemical performances. This study may pave the way for the practical realization of KSB with stable operation and long cycle life.

Organic Eutectic Mixture Incorporated with Graphene Oxide Sheets as Lithiophilic Artificial Protective Layer for Dendrite‐Free Lithium Metal Batteries

AbstractFor wide and safe applications of Li metal batteries, the suppression of Li dendrite growth during cycling is the most crucial yet challenging topic. In this work, an artificial protective interlayer of GO‐BQ@LiTFSI (GBL) is designed to overcome this issue. The GBL interlayer is prepared by incorporating graphene‐oxide sheets with a liquid organic eutectic mixture of 1,4‐benzoquinone and bis (trifluoromethane) sulfonamide lithium salt. With the exceptional merits of these functional materials, the incorporation endows the GBL interlayer with rich lithiophilic active sites, good ionic conductivity, superior thermal stability and compatibility with the electrolyte, and the precursor supply stations for the formation of a compact and LiF‐rich solid‐electrolyte interface (SEI). Consequently, the GBL effectively promotes the uniform nucleation of Li at low over‐potentials and regulates the Li‐ion flux, leading to the formation of planar Li metal. After utilizing the GBL interlayer in the Li||Li symmetric cells, high electrochemical stability for 600 h is achieved at a current density of 3 mA cm−2 and a capacity of 3 mAh cm−2. Remarkably, this modification enables Li||LiFePO4 full cells with 1600 cycles at 1C and a high‐capacity retention of 95.23% with a cathode mass loading of ≈6 mg cm−2.

Single-Ion Conducting Polymeric Protective Interlayer for Stable Solid Lithium-Metal Batteries

With many reported attempts on fabricating single-ion conducting polymer electrolytes, they still suffer from low ionic conductivity, narrow voltage window, and high cost. Herein, we report an unprecedented approach on improving the cationic transport number (tLi+) of the polymer electrolyte, i.e., single-ion conducting polymeric protective interlayer (SIPPI), which is designed between the conventional polymer electrolyte (PVEC) and Li-metal electrode. Satisfied ionic conductivity (1 mS cm-1, 30 °C), high tLi+ (0.79), and wide-area voltage stability are realized by coupling the SIPPI with the PVEC electrolyte. Benefiting from this unique design, the Li symmetrical cell with the SIPPI shows stable cycling over 6000 h at 3 mA cm-2, and the full cell with the SIPPI exhibits stable cycling performance with a capacity retention of 86% over 1000 cycles at 1 C and 25 °C. This incorporated SIPPI on the Li anode presents an alternative strategy for enabling high-energy density, long cycling lifetime, and safe and cost-effective solid-state batteries.

Degradation Prevention of Latp Towards Li Metal and Interface Improvement By Layer-By-Layer Polymer Assembly Technique

Degradation of Li1.3Al0.3Ti1.7(PO4)3 (LATP), NASICON-types solid electrolyte (Figure 1) towards Li metal creates a dramatic issue, as materials itself is very promising due to its stability towards air and moisture and facile fabrication methods.Figure 1. Illustration of Li1.3Al0.3Ti1.7(PO4)3 degradation towards Li metalSolid electrolytes containing titanium, germanium suffer from reduction while contacting with Li metal. Reduction of Ti4+ to Ti3+ in LATP leads to a formation of mixed conductive interphase, a secondary phase that hinders lithium ion conduction between the solid electrolyte and electrode. In the majority cases, this problem can be solved by applying artificial interlayer that prevents the direct contact of these components. In addition, the protective interlayer also helps to reduce interfacial impedance that present between electrolyte and electrodes. In our research, we resolved it by applying thin composite gel polymer electrolyte (GPE) as interlayer using layer by layer (LbL) technique. Despite preventing the side reaction, the simultaneous coating on both sides of LATP pellets improved interfacial contact between cathode and electrolyte, anode and electrolyte. The effect of this modification was characterized by physical, chemical and electrochemical analyses. Acknowledgement This research was supported by the research grants #021220CRP0122 “Development of highly sensitive MOS based nano-film gas sensors” from Nazarbayev University. Figure 1

PEO-based Interlayers for LAGP-type Solid-State Lithium-Metal Batteries

Solid-state electrolytes (SSEs) are expected to play a decisive role for the realization of safer rechargeable batteries and may, additionally, allow for the employment of lithium-metal anodes, thus, paving the way for significantly higher energy densities. 1, 2 There are essentially two main groups of SSEs: (i) polymer and (ii) inorganic solids. The latter can be divided, e.g., into sulfide and oxide based electrolytes. 3 Among the oxides, the so-called NASICON-type electrolytes such as LAGP (lithium aluminum germanium phosphate) are considered as attractive low-cost alternative compared to sulfides. 4 Nonetheless, the incompatibility of LAGP with lithium metal accompanied by the formation of highly resistive interfacial reaction products, detrimentally affecting cycle life and rate capability, remain a great challenge. 5 To overcome this issue, the introduction of polyether (e.g., polyethylene oxide, PEO) as protective interlayer between the lithium-metal anode and the LAGP SSE was proposed. 6, 7, 8 The successful use of such interlayers, however, requires a fast and efficient charge transfer across this interlayer. Herein, we present a comprehensive investigation of PEO-based interlayers comprising varying amounts of ionic liquid-based electrolytes, which consist ofN-butyl-N-methyl pyrrolidinium-based and lithium cations as well as bis(fluorosulfonyl)imide (FSI-) and bis(trifluoromethanesulfonyl)imide (TFSI-) anions. Optimized compositions and the incorporation of selected additives further enhances the charge transfer across this interlayer and the two interfaces with the LAGP electrolyte and lithium metal, enabling long-term stable cycle life and good rate capability of the resulting lithium-metal battery cells.

Effect of tantalum interlayer on hydroxyapatite biointerface for orthopedic applications

Various attempts have been made during recent decades to improve the functionality, biocompatibility and osseointegration of metallic implants. With technological advancement, modifying superficial properties of orthopedic implants has undergone great evolution. Current efforts of scientists and the orthopedic industry have focused on modifying surface properties to achieve a specific biointerface that can reduce patient's healing time and prevent aseptic loosening. This study investigates the contribution of a protective tantalum interlayer deposited on titanium substrates on the growth of hydroxyapatite (HAp) crystals with hydrothermal synthesis method. We investigated the morphology and structure of the produced coatings, as well as in vitro bioactivity in simulated body fluid and biocompatibility in osteoblast-like cell culture. The hydrothermal method allows to synthesize coating with micro-sized HAp crystallites that exhibit rod-like hexagonal shape. The diameter of HAp crystallites may be controlled and driven by nature of the interlayer (tantalum, tantalum oxide or titanium oxide) previously formed on the titanium substrate. Coatings with smaller diameters of HAp crystals (between 0,3 μm and 0,6 μm) synthesized on tantalum-based films were found to be more favorable for cell viability and attachment. High bioactivity and positive effect on the osteoblast-like cells of the HAp biointerface with a tantalum intermediate layer was observed.

All-Solid-State Lithium Metal Batteries Enabled By Solid Electrolytes with Low-Temperature Processability

All-Solid-State lithium metal batteries are highly sought-after to improve the safety of high energy density batteries for electric vehicles, aircraft, and seacraft. Despite the proliferation of high-conductivity solid electrolytes, it remains a significant challenge to create conformal interfaces between them and the active materials in the battery. Furthermore, the poor electrochemical stability of known solid electrolytes often necessitates the co-design of protective coatings and interlayers, which increase cell resistance. Here, I will discuss a novel materials platform for advanced solid electrolytes that are readily processed at <150C, creating molecularly coherent interfaces with both lithium metal as well as a diverse selection of high-voltage storage materials and conductive carbons integrated in the cathode. I will describe how the composition may be tailored to achieve conductivity up to 10 mS/cm at ambient temperature. In stride, I will present electroanalytical and surface analytical characterization to define pathways for promoting or inhibiting the formation of interphases at the anode and cathode. Through control over interphases, we realize highly stable all-solid-state cells with >500 cycles with less than 80% capacity fade at current densities up to 1 mA/cm2 at an cell temperatures <45 C and stack pressures less than 0.5 MPa.

Short-beam shear fatigue life assessment of thermally cycled carbon–aluminium laminates with protective glass interlayers

Fibre metal laminates (FMLs) are attractive construction materials, especially for use in aerospace and transport facilities. Throughout their service life, thin-walled structures made of FMLs are exposed to static and dynamic loads, as well as corrosion and the unfavourable influence of environmental conditions. The paper presents an experimental analysis of the combined mechanical and environmental long-term behaviour of carbon-based fibre metal laminates and their variants with protective glass layers. The Al alloy/CFRP and Al alloy/GFRP/CFRP laminates in a 3/2 configuration were used. The tested laminates were subjected to 1500 thermal cycles with a temperature range of 130 °C. The static and fatigue interlaminar shear strengths were tested before and after thermal conditioning. It was shown that the stable stiffness reduction in the tested laminates was observed with increasing fatigue cycles, due to the progressive fatigue damage accumulation. The thermally cycled laminates feature slightly smoother stiffness loss, while a more rapid decrease was observed in thermally untreated laminates. Moreover, the fatigue life of the tested laminates subjected to thermal cycling revealed nine times fewer fatigue cycles of laminates with glass protectors after thermal cycles in comparison to the laminates not subjected to thermal cycling.

Mixed Ionic-Electronic Conductivity, Redox Behavior and Thermochemical Expansion of Mn-Substituted 5YSZ as an Interlayer Material for Reversible Solid Oxide Cells.

Manganese-substituted 5 mol.% yttria-stabilized zirconia (5YSZ) was explored as a prospective material for protective interlayers between electrolyte and oxygen electrodes in reversible solid oxide fuel/electrolysis cells. [(ZrO2)0.95(Y2O3)0.05]1−x[MnOy]x (x = 0.05, 0.10 and 0.15) ceramics with cubic fluorite structure were sintered in air at 1600 °C. The characterization included X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetry and dilatometry in controlled atmospheres, electrical conductivity measurements, and determination of oxygen-ion transference numbers by the electromotive force (EMF) technique. Mn-substituted 5YSZ solid solutions exhibit variable oxygen nonstoichiometry with manganese cations in a mixed 2+/3+ oxidation state under oxidizing conditions. Substitution by manganese gradually increases the extent of oxygen content variation on thermal/redox cycling, chemical contribution to thermal expansion and dimensional changes on reduction. It also deteriorates oxygen-ionic conductivity and improves p-type electronic conductivity under oxidizing conditions, leading to a gradual transformation from predominantly ionic to prevailing electronic transport with increasing x. Mn2+/3+→Mn2+ transformation under reducing atmospheres is accompanied by the suppression of electronic transport and an increase in ionic conductivity. All Mn-substituted 5YSZ ceramics are solid electrolytes under reducing conditions. Prolonged treatments in reducing atmospheres, however, promote microstructural changes at the surface of bulk ceramics and Mn exsolution. Mn-substituted 5YSZ with 0.05 ≤ x < 0.10 is considered the most suitable for the interlayer application, due to the best combination of relevant factors, including oxygen content variations, levels of ionic/electronic conductivity and thermochemical expansion.