Properties of Flame Sprayed Ce0.8Gd0.2O1.9‐δ Electrolyte Thin Films

Thin films of Ce_0.8Gd_0.2O_1.9‐δ (CGO) are deposited by flame spray deposition with a deposition rate of about 30 nm min^?1. The films (deposited at 200 °C) are dense, smooth, and particle‐free and show a biphasic amorphous/nanocrystalline microstructure. Isothermal grain growth and microstrain are determined as a function of dwell time and temperature and correlated to the electrical conductivity. CGO films annealed for 10 h at 600 °C present the best electrical conductivity of 0.46 S m^?1 measured at 550 °C. Reasons for the superior performance of films annealed at low temperature over higher‐temperature‐treated samples are discussed and include grain‐size evolution, microstrain relaxation, and chemical decomposition. Nanoindentation measurements are conducted on the CGO thin films as a function of annealing temperature to determine the hardness and elastic modulus of the films for potential application as free‐standing electrolyte membranes in low‐temperature micro‐SOFCs (solid oxide fuel cells).     

Micro Solid Oxide Fuel Cells on Glass Ceramic Substrates

Miniaturized solid oxide fuel cells are fabricated on a photostructurable glass ceramic substrate (Foturan) by thin film and micromachining techniques. The anode is a sputtered platinum film and the cathode is made of a spray pyrolysis (SP)‐deposited lanthanum strontium cobalt iron oxide (LSCF), a sputtered platinum film and platinum paste. A single‐layer of yttria‐stabilized zirconia (YSZ) made by pulsed laser deposition (PLD) and a bilayer of PLD–YSZ and SP–YSZ are used as electrolytes. The total thickness of all layers is less than 1 µm and the cell is a free‐standing membrane with a diameter up to 200 µm. The electrolyte resistance and the sum of polarization resistances of the anode and cathode are measured between 400 and 600 °C by impedance spectroscopy and direct current (DC) techniques. The contribution of the electrolyte resistance to the total cell resistance is negligible for all cells. The area‐specific polarization resistance of the electrodes decreases for different cathode materials in the order of Pt paste > sputtered Pt > LSCF. The open circuit voltages (OCVs) of the single‐layer electrolyte cells ranges from 0.91 to 0.56 V at 550 °C. No electronic leakage in the PLD–YSZ electrolyte is found by in‐plane and cross‐plane electrical conductivity measurements and the low OCV is attributed to gas leakage through pinholes in the columnar microstructure of the electrolyte. By using a bilayer electrolyte of PLD–YSZ and SP–YSZ, an OCV of 1.06 V is obtained and the maximum power density reaches 152 mW cm⁻² at 550 °C.     

An Electrolyte‐Free Fuel Cell Constructed from One Homogenous Layer with Mixed Conductivity

Rather than using three layers, including an electrolyte, a working fuel cell is created that employs only one homogenous layer with mixed conductivity. The layer is a composite made from a mixture of metal oxide, Li_0.15Ni_0.45Zn_0.4 oxide, and an ionic conductor; ion‐doped ceria. The single‐component layer has a total conductivity of 0.1–1 S cm^?1 and exhibits both ionic and semiconducting properties. This homogenous one‐layer device has a power output of more than 600 mW cm^?2 at 550 °C operating with H₂ and air. Overall conversion is completed in a similar way to a traditional fuel cell, even though the device does not include the electrolyte layer critical for traditional fuel‐cell technologies using the three‐component anode–electrolyte–cathode structure.     

A High Power Density Intermediate‐Temperature Solid Oxide Fuel Cell with Thin (La0.9Sr0.1)0.98(Ga0.8Mg0.2)O3‐δ Electrolyte and Nano‐Scale Anode

Solid oxide fuel cells (SOFCs) with thin (La_0.9Sr_0.1)_0.98Ga_0.8Mg_0.2O_3‐δ (LSGM) electrolytes are primary candidates for achieving high (> 1 W cm^‐2) power density at intermediate (< 650 °C) temperatures. Although high power density LSGM‐electrolyte SOFCs have been reported, it is still necessary to develop a fabrication process suitable for large‐scale manufacturing and to minimize the amount of LSGM used. Here we show that SOFCs made with a novel processing method and a Sr_0.8La_0.2TiO_{3‐ α} (SLT) oxide support can achieve high power density at intermediate temperature. The SLT support is advantageous, especially compared to LSGM supports, because of its low materials cost, electronic conductivity, and good mechanical strength. The novel process is to first co‐fire the ceramic layers – porous SLT support, porous LSGM layer, and dense LSGM layer – followed by infiltration of nano‐scale Ni into the porous layers. Low polarization resistance of 0.188 Ωcm² was achieved at 650 °C for a cell with an optimized anode functional layer (AFL) and an (La,Sr)(Fe,Co)O₃ cathode. Maximum power density reached 1.12 W cm^?2 at 650 °C, limited primarily by cathode polarization and ohmic resistances, so there is considerable potential to further improve the power density.     

High‐Performance Micro‐Solid Oxide Fuel Cells Fabricated on Nanoporous Anodic Aluminum Oxide Templates

Micro‐solid oxide fuel cells (μ‐SOFCs) are fabricated on nanoporous anodic aluminum oxide (AAO) templates with a cell structure composed of a 600‐nm‐thick AAO free‐standing membrane embedded on a Si substrate, sputter‐deposited Pt electrodes (cathode and anode) and an yttria‐stabilized zirconia (YSZ) electrolyte deposited by pulsed laser deposition (PLD). Initially, the open circuit voltages (OCVs) of the AAO‐supported μ‐SOFCs are in the range of 0.05 V to 0.78 V, which is much lower than the ideal value, depending on the average pore size of the AAO template and the thickness of the YSZ electrolyte. Transmission electron microscopy (TEM) analysis reveals the formation of pinholes in the electrolyte layer that originate from the porous nature of the underlying AAO membrane. In order to clog these pinholes, a 20‐nm thick Al₂O₃ layer is deposited by atomic layer deposition (ALD) on top of the 300‐nm thick YSZ layer and another 600‐nm thick YSZ layer is deposited after removing the top intermittent Al₂O₃ layer. Fuel cell devices fabricated in this way manifest OCVs of 1.02 V, and a maximum power density of 350 mW cm^?2 at 500 °C.     

Carbonized Polyacrylonitrile‐Stabilized SeSx Cathodes for Long Cycle Life and High Power Density Lithium Ion Batteries

A facile synthesis of selenium sulfide (SeS_x)/carbonized polyacrylonitrile (CPAN) composites is achieved by annealing the mixture of SeS₂ and polyacrylonitrile (PAN) at 600 °C under vacuum. The SeS_x molecules are confined by N‐containing carbon (ring) structures in the carbonized PAN to mitigate the dissolution of polysulfide and polyselenide intermediates in carbonate‐based electrolyte. In addition, formation of solid electrolyte interphase (SEI) on the surface of SeS_x/CPAN electrode in the first cycle further prevents polysulfide and polyselenide intermediates from dissolution. The synergic restriction of SeS_x by both CPAN matrix and SEI layer allows SeS_x/CPAN composites to be charged and discharged in a low‐cost carbonate‐based electrolyte (LiPF₆ in EC/DEC) with long cycling stability and high rate capability. At a current density of 600 mA g^?1, it maintains a reversible capacity of 780 mAh g^?1 for 1200 cycles. Moreover, it retains 50% of the capacity at 60 mA g^?1 even when the current density increases to 6 A g^?1. The superior electrochemical performance of SeS_x/CPAN composite demonstrates that it is a promising cathode material for long cycle life and high power density lithium ion batteries. This is the first report on long cycling stability and high rate capability of selenium sulfide‐based cathode material.     

All‐Solution‐Processed Indium‐Free Transparent Composite Electrodes based on Ag Nanowire and Metal Oxide for Thin‐Film Solar Cells

Fully solution‐processed Al‐doped ZnO/silver nanowire (AgNW)/Al‐doped ZnO/ZnO multi‐stacked composite electrodes are introduced as a transparent, conductive window layer for thin‐film solar cells. Unlike conventional sol–gel synthetic pathways, a newly developed combustion reaction‐based sol–gel chemical approach allows dense and uniform composite electrodes at temperatures as low as 200 °C. The resulting composite layer exhibits high transmittance (93.4% at 550 nm) and low sheet resistance (11.3 Ω sq^‐1), which are far superior to those of other solution‐processed transparent electrodes and are comparable to their sputtered counterparts. Conductive atomic force microscopy reveals that the multi‐stacked metal‐oxide layers embedded with the AgNWs enhance the photocarrier collection efficiency by broadening the lateral conduction range. This as‐developed composite electrode is successfully applied in Cu(In_1‐x,Ga_x)S₂ (CIGS) thin‐film solar cells and exhibits a power conversion efficiency of 11.03%. The fully solution‐processed indium‐free composite films demonstrate not only good performance as transparent electrodes but also the potential for applications in various optoelectronic and photovoltaic devices as a cost‐effective and sustainable alternative electrode.     

Short communication: Effects of heat treatments and CdCl2, pretreatments on the stoichiometries of solution-grown CdS thin films

Solution grorwth of CdS on SnO₂-coated glass with subsequent heat treatments is known to produce stoichiometric CdS thin films with characteristic thicknesses of about 1000 Å. We show that heating solution-grown CdS thin films in a nitrogen atmosphere to ⩾ 450° C results in sulphur loss. Heating to 550°C leads to a 50% loss of sulphur, leaving the entire 1000-A CdS thin film with a concentration of about 75 at.% Cd and 25 at.% S. However, dipping the CdS thin films in a CdCl₂ solution prior to heating coats the CdS, leaving a CdCl₂ layer that acts as a protective coating and prohibits the loss of sulphur. Cadmium sulphide thin films dipped in a CdCl₂ solution and then heated to 550°C are stoichiometric.     

La0.5Sr0.5CoO3的化学溶液淀积法制备与表征及其应用

采用化学溶液淀积法制备了具有纯钙钛矿结构和良好导电性能的La_(0.5)Sr_(0.5)CoO_3(LSCO)薄膜。LSCO的电阻率随着退火温度的升高、退火时间的增长和厚度增加而减小。650°C退火可以得到7mΩ·cm的电阻率。分别在LSCO和Pt衬底上制备了Bi_4Ti_3O_(12)(BTO)薄膜,分析结果表明,使用LSCO衬底对BTO的析晶有影响,击穿电压、铁电特性均有较大改善。     

High‐Performance All‐Solid‐State Cells Fabricated With Silicon Electrodes

All solid‐state thin‐film lithium microbatteries are a promising component able to fulfill most of the specific requirements to power autonomous microsystems. Nevertheless, metallic lithium, which is commonly used as the negative electrode in microbatteries, has a very low melting temperature (T_m = 181 °C) that appears to be incompatible with the solder‐reflow operation (maximum temperature T_max ≈ 260 °C) usually used to connect electronic components. Silicon is a promising candidate to replace lithium in solder‐reflowable lithium‐ion cells due to its high volumetric capacity (834 μAh cm^?2 μm^?1 for Li₁₅Si₄) and its ability to reversibly insert lithium at a low potential. Nevertheless, it suffers from a large volumetric expansion during lithium insertion (280%), which is partly responsible for a rapid capacity fading when cycled in liquid electrolyte. In this study, all‐solid‐state Li/LiPONB/Si cells are prepared using physical vapor deposition (PVD) techniques. The cycle life and the coulombic efficiency are found to be excellent in these solid‐state cells with almost no loss during 1500 cycles. Despite the large volume expansion due to lithium insertion confirmed by scanning electron microscopy, no evidence of cracks is found in the film or at the electrode/electrolyte interface, even after 1500 cycles.     

Enabling High-Performance NASICON-Based Solid-State Lithium Metal Batteries Towards Practical Conditions

Solid-state lithium metal batteries (SSLMBs) are promising next-generation high-energy rechargeable batteries. However, the practical energy densities of the reported SSLMBs have been significantly overstated due to the use of thick solid-state electrolytes, thick lithium (Li) anodes, and thin cathodes. Here, a high-performance NASICON-based SSLMB using a thin (60 µm) Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) electrolyte, ultrathin (36 µm) Li metal, and high-loading (8 mg cm⁻²) LiFePO₄ (LFP) cathode is reported. The thin and dense LAGP electrolyte prepared by hot-pressing exhibits a high Li ionic conductivity of 1 × 10⁻³ S cm⁻¹ at 80 °C. The assembled SSLMB can thus deliver an increased areal capacity of ≈1 mAh cm⁻² at C/5 with a high capacity retention of ≈96% after 50 cycles under 80 °C. Furthermore, it is revealed by synchrotron X-ray absorption spectroscopy and in situ high-energy X-ray diffraction that the side reactions between LAGP electrolyte and LFP cathode are significantly suppressed, while rational surface protection is required for Ni-rich layered cathodes. This study provides valuable insights and guidelines for the development of high-energy SSLMBs towards practical conditions.     

High efficiency low temperature grown Cu(In,Ga)Se2 thin film solar cells on flexible substrates using NaF precursor layers

We report a total‐area efficiency of 15.9% for flexible Cu(In,Ga)Se₂ thin film solar cells on polyimide foil (cell area 0.95 cm²). The absorber layer was grown by a multi‐stage deposition process at a maximum nominal process temperature of 420°C. The Na was added via evaporation of a NaF layer prior to the absorber deposition leading to an enhanced V_oc and FF. Growth conditions and device characterization are described. Copyright © 2011 John Wiley & Sons, Ltd.     

Growth-Temperature-Controlled Optical Properties of Textured MgxZn1?xO Thin Films

Pulsed laser deposition was used to grow magnesium zinc oxide thin films on amorphous fused silica substrates at several temperatures between room temperature and 750°C. In this study, the effect of growth temperature on the optical properties of textured Mg _x Zn_1−x O thin films was examined. The optical properties of the films were measured using absorption and photoluminescence spectrometry. Absorption spectra revealed that the bandgap values of textured Mg _x Zn_1−x O thin films were enhanced in films grown at higher temperatures. The absorption spectra near the absorption edge were fitted using the Urbach equation in order to investigate the effects of growth temperature on exponential band tail and bandgap. The photoluminescence spectra were measured for magnesium zinc oxide thin films deposited at 250°C, 350°C, 450°C, 550°C, and 650°C. The film grown at 350°C provided the highest excitonic peak intensity. On the other hand, the film grown at 250°C exhibited the lowest excitonic peak intensity. The excitonic peak intensity was considerably reduced in magnesium zinc oxide thin films grown at temperatures greater than 350°C. The ability to perform substrate-temperature-dependent bandgap engineering of Mg _x Zn_1−x O will enable use of this material in next-generation optical and optoelectronic devices.     

Novel Diffusion‐Barrier Materials Against Oxygen for High‐Density Dynamic Random Access Memory Capacitors

A new design concept for diffusion barriers in high‐density memory capacitors is suggested, and both RuTiN (RTN) and RuTiO (RTO) films are proposed as sacrificial oxygen diffusion barriers. The newly developed RTN and RTO barriers show a much lower sheet resistance than various other barriers, including binary and ternary nitrides (reported by others), up to 800 °C, without a large increase in the resistance. For both the Pt/RTN/TiSi_x/n⁺⁺poly‐plug/n⁺ channel layer/Si and the Pt/RTO/RTN/TiSi_x/n⁺⁺poly‐plug/n⁺ channel layer/Si contact structures, contact resistance—the most important electrical parameter for the diffusion barrier in the bottom electrode structure of capacitors—was found to be as low as 5 kohm, even after annealing up to 750 °C. When the RTN film was inserted as a glue layer between the bottom Pt electrode layer and the TiN barrier film in the chemical vapor deposited (Ba,Sr)TiO₃ (CVD–BST) simple stack‐type structure, the RTN glue layer was observed to be thermally stable to temperatures 150 °C higher than that to which the TiN glue layer is stable. Moreover, the capacitance of the physical vapor deposited (PVD)–BST simple stack‐type structure adopted TiN glue layer initially degraded after annealing at 500 °C, and, thereafter, completely failed. In the case of the RTN and RTO/RTN glue layers, however, the capacitance continuously increased up to 550 °C. Thus, the new RTN and RTO films, which act as diffusion barriers to oxygen, are very promising materials for achieving high‐density capacitors.     

A New Family of Proton‐Conducting Electrolytes for Reversible Solid Oxide Cells: BaHfxCe0.8−xY0.1Yb0.1O3−δ

Reversible solid oxide cells based on ceramic proton conductors have potential to be the most efficient system for large‐scale energy storage. The performance and long‐term durability of these systems, however, are often limited by the ionic conductivity or stability of the proton‐conducting electrolyte. Here new family of solid oxide electrolytes, BaHf_xCe_0.8?xY_0.1Yb_0.1O_3?δ (BHCYYb), which demonstrate a superior ionic conductivity to stability trade‐off than the state‐of‐the‐art proton conductors, BaZr_xCe_0.8?xY_0.1Yb_0.1O_3?δ (BZCYYb), at similar Zr/Hf concentrations, as confirmed by thermogravimetric analysis, Raman, and X‐ray diffraction analysis of samples over 500 h of testing are reported. The increase in performance is revealed through thermodynamic arguments and first‐principle calculations. In addition, lab scale full cells are fabricated, demonstrating high peak power densities of 1.1, 1.4, and 1.6 W cm^?2 at 600, 650, and 700 °C, respectively. Round‐trip efficiencies for steam electrolysis at 1 A cm^?2 are 78%, 72%, and 62% at 700, 650, and 600 °C, respectively. Finally, CO₂? H₂O electrolysis is carried out for over 700 h with no degradation.     

Scalable Oxygen‐Ion Transport Kinetics in Metal‐Oxide Films: Impact of Thermally Induced Lattice Compaction in Acceptor Doped Ceria Films

In this paper, we focus on the effect of processing‐dependent lattice strain on oxygen ion conductivity in ceria based solid electrolyte thin films. This is of importance for technological applications, such as micro‐SOFCs, microbatteries, and resistive RAM memories. The oxygen ion conductivity can be significantly modified by control of lattice strain, to an extent comparable to the effect of doping bulk ceria with cations of different diameters. The interplay of dopant radii, lattice strain, microstrain, anion‐cation near order and oxygen ion transport is analyzed experimentally and interpreted with computational results. Key findings include that films annealed at 600 °C exhibit lattice parameters close to those of their bulk counterparts. With increasing anneal temperature, however, the films exhibited substantial compaction with lattice parameters decreasing by as much as nearly 2% (viz, Δd_{600–1100 °C}: –1.7% (Sc⁺³) > –1.5% (Gd⁺³) > –1.2% (La⁺³)) for the annealing temperature range of 600–1100 °C. Remarkably 2/3^rd of the lattice parameter change obtained in bulk ceria upon changing the acceptor diameter from the smaller Sc to larger La, can be reproduced by post annealing a film with fixed dopant diameter. While the impact of lattice compaction on defect association/ordering cannot be entirely excluded, DFT computation revealed that the main effect appears to result in an increase in migration energy and consequent drop in ionic conductivity. As a consequence, it is clear that annealing procedures should be held to a minimum to maintain the optimum level of oxygen ion conductivity for energy‐related applications. Results reveal also the importance to understand the role of electro‐chemo‐mechanical coupling that is active in thin film materials.     

Ex‐Solved Ag Nanocatalysts on a Sr‐Free Parent Scaffold Authorize a Highly Efficient Route of Oxygen Reduction

The electrocatalytic value of nanoparticles has attracted substantial attention in relation to energy conversion devices, including solid oxide fuel cells. Among various forms of analogs, ex‐solved metal nanoparticles originating from their parent oxides display strong particle‐substrate interactions and thus have the benefits of extended durability and of course enhanced catalytic activity. Inspired by recent advances, here, novel air‐electrode materials based on BaCoO_3–δ perovskites decorated with socketed Ag nanoparticles are presented. Doping with niobium (Nb⁵⁺) and tantalum (Ta⁵⁺) can significantly promote the stability of the cubic perovskite phase. The developed oxides exhibit promising performance outcomes in the highly prized low‐to‐intermediate temperature regimes (450–650 °C). Moreover, the exclusion of Ag particles further activates the parent scaffold, thereby conveying record‐level area‐specific resistance (e.g., ≈0.02 Ω cm² at 650 °C). Coupled with the unique nanoarchitecture, the newly designed cathode showcases in this study hold great promise for future air‐electrodes in fuel cells.     

The Remarkable Thermal Stability of Amorphous In‐Zn‐O Transparent Conductors

Transparent conducting oxides (TCOs) are increasingly critical components in photovoltaic cells, low‐e windows, flat panel displays, electrochromic devices, and flexible electronics. The conventional TCOs, such as Sn‐doped In₂O₃, are crystalline single phase materials. Here, we report on In‐Zn‐O (IZO), a compositionally tunable amorphous TCO with some significantly improved properties. Compositionally graded thin film samples were deposited by co‐sputtering from separate In₂O₃ and ZnO targets onto glass substrates at 100 °C. For the metals composition range of 55–84 cation% indium, the as‐deposited IZO thin films are amorphous, smooth (R_RMS < 0.4 nm), conductive (σ ∼ 3000 Ω⁻¹ · cm⁻¹), and transparent in the visible (T_Vis > 90%). Furthermore, the amorphous IZO thin films demonstrate remarkable functional and structural stability with respect to heating up to 600 °C in either air or argon. Hence, though not completely understood at present, these amorphous materials constitute a new class of fundamentally interesting and technologically important high performance transparent conductors.     

Solvation Engineering Enables High-Voltage Lithium Ion and Metal Batteries Operating Under −50 and 80 °C

Extreme temperatures (<-20 °C or >50 °C) would seriously impair the performance of lithium batteries through deteriorating bulk ion transport and electrode interfaces. Here, a rational design of weak solvent and anti-solvent combination is presented for wide-temperature electrolytes. The weak solvent provides accelerated desolvation kinetics of Li⁺ around the anode region, while the anti-solvent not only functions as an antifreeze agent for smooth ion migration at low temperatures but also interacts with the weak solvent to boost the formation of ionic aggregates. The weak and anti-solvent electrolyte (WAE) exerts excellent compatibility with both lithium metal and graphite. Under −40 °C, Li anode delivers 98.5% Coulombic efficiency and graphite outputs capacity over 230 mAh g^-1. Lithium-ion/metal batteries by pairing graphite anode with LiCoO₂ cathode with a negative to positive capacity ratio of 0.75 can realize steady operation at −50 °C with an average coulombic efficiency of 99.9%. Lithium metal batteries with 4.2 mAh cm^-2 high LiCoO₂ cathode loading and 50 µm thin lithium anode deliver 73.8% capacity output at −40 °C. Besides, the cells are stable up to 80 °C with an average coulombic efficiency of 99.7%. This research demonstrates a relatively loose Li⁺ solvation environment in WAE systems and provides wide-temperature electrolyte for high-performance lithium ion and metal batteries.     

Li‐CO2 Batteries Efficiently Working at Ultra‐Low Temperatures

Lithium‐carbon dioxide (Li‐CO₂) batteries are considered promising energy‐storage systems in extreme environments with ultra‐high CO₂ concentrations, such as Mars with 96% CO₂ in the atmosphere, due to their potentially high specific energy densities. However, besides having ultra‐high CO₂ concentration, another vital but seemingly overlooked fact lies in that Mars is an extremely cold planet with an average temperature of approximately ?60 °C. The existing Li‐CO₂ batteries could work at room temperature or higher, but they will face severe performance degradation or even a complete failure once the ambient temperature falls below 0 °C. Herein, ultra‐low‐temperature Li‐CO₂ batteries are demonstrated by designing 1,3‐dioxolane‐based electrolyte and iridium‐based cathode, which show both a high deep discharge capacity of 8976 mAh g^?1 and a long lifespan of 150 cycles (1500 h) with a fixed 500 mAh g^?1 capacity per cycle at ?60 °C. The easy‐to‐decompose discharge products in small size on the cathode and the suppressed parasitic reactions both in the electrolyte and on the Li anode at low temperatures together contribute to the above high electrochemical performances.