Polyether-b-Amide Based Solid Electrolytes with Well-Adhered Interface and Fast Kinetics for Ultralow Temperature Solid-State Lithium Metal Batteries

Solid-state lithium metal batteries (SSLMBs) are highly desirable for energy storage because of the urgent need for higher energy density and safer batteries. However, it remains a critical challenge for stable cycling of SSLMBs at low temperature. Here, a highly viscoelastic polyether-b-amide (PEO-b-PA) based composite solid-state electrolyte is proposed through a one-pot melt processing without solvent to address this key process. By adjusting the molar ratio of PEO-b-PA to lithium bis(trifluoromethanesulphonyl)imide (ethylene oxide:Li = 6:1) and adding 20 wt.% succinonitrile, fast Li⁺ transport channel is conducted within the homogeneous polymer electrolyte, which enables its application at ultra-low temperature (−20 to 25 °C). The composite solid-state electrolyte utilizes dynamic hydrogen-bonding domains and ion-conducting domains to achieve a low interfacial charge transfer resistance (<600 Ω) at −20 °C and high ionic conductivity (25 °C, 3.7 × 10⁻⁴ S cm⁻¹). As a result, the LiFePO₄|Li battery based on composite electrolyte exhibits outstanding electrochemical performance with 81.5% capacity retention after 1200 cycles at −20 °C and high discharge specific capacities of 141.1 mAh g⁻¹ with high loading (16.1 mg cm⁻²) at 25 °C. Moreover, the solid-state SNCM811|Li cell achieves excellent safety performance under nail penetration test, showing great promise for practical application.     

Absolutely-Zero-Expansion Behavior Enables Ultra-Long Life for Stationary Energy Storage

Ultra-long-life (at least 10 000 cycles) lithium-ion batteries are very effective for stationary energy-storage applications. However, even “zero-strain” materials with small unit-cell-volume changes of <1% cannot last for ultra-long cycles due to gradually accumulated intracrystal strain/stress. Here, Li[Li_0.2Cr_0.4Ti_1.4]O₄ is explored as the first absolutely-zero-expansion material with unit-cell-volume variations of zero during Li⁺ storage. Its absolutely-zero-expansion mechanism is intensively studied, revealing that 16c-octahedron shrinkage fully offsets 16d-octahedron expansion through reversible O²⁻ movement. It delivers better cycling stability than, as far as  we  know, all electrochemical energy-storage materials previously reported. Its capacity retention at 10 C and 1.0 mg cm⁻² after 17 000 cycles reaches 91.5%. When the active-material loading significantly increases to 6.4 mg cm⁻², its capacity retention at 5 C after 500 cycles reaches 95.7%. At an elevated temperature of 45 °C, it not only keeps excellent cycling stability but also exhibits significantly enhanced rate capability. Therefore, Li[Li_0.2Cr_0.4Ti_1.4]O₄ is especially suitable for stationary energy storage.     

Hierarchically Macro–Microporous Covalent Organic Frameworks for Efficient Proton Conduction

Assembling molecular proton carriers into crosslinked networks is widely used to fabricate proton conductors, but they often suffer losses in conduction efficiency and stability accompanied by unclear causes. Covalent organic frameworks (COFs), with well-defined crystal frameworks and excellent stability, offer a platform for exploring the proton transfer process. Herein, a strategy to construct proton conductors that induce conductivity and stability by introducing bottom-up hierarchical structure, mass transport interfaces, and host–guest interactions into the COFs is proposed. The proton-transport platforms are designed to possess hierarchically macro–microporous structure for proton storage and mass transport. The protic ionic liquids, with low proton dissociation energies investigated by DFT calculation, are installed at open channel walls for faster proton motion. As expected, the resultant proton conductors based on a covalent organic framework (PIL_0.5@m-TpPa-SO₃H) with hierarchical pores increase conductivity by approximately three orders of magnitude, achieving the value of 1.02 × 10⁻¹ S cm⁻¹ (90 °C, 100% RH), and maintain excellent stability. In addition, molecular dynamics simulations reveal the mechanism of “hydrogen-bond network” for proton conduction. This work offers a fresh perspective on COF-based material manufacturing for high-performance proton conductors via a protocol of macro-micropores.     

Room-Temperature Symmetric Giant Positive and Negative Electrocaloric Effect in PbMg0.5W0.5O3 Antiferroelectric Ceramic

As an emerging solid-state refrigeration technology with zero-emission and high energy conversion efficiency, there is a compelling need for ferroelectric materials with giant electrocaloric effects (ECEs) at room temperature suitable for refrigeration applications. The complex perovskite antiferroelectric (AFE), PbMg_0.5W_0.5O₃, containing non-equivalent B-site ions with a symmetric giant positive and negative ECE near room temperature is presented. At the Curie temperature of 36 °C, the first-order AFE–paraelectric phase transition gives rise to a large enthalpy change of 3.92 J g⁻¹, more than four times that of BaTiO₃. This leads to a significant ECE under the influence of an electric field. The direct electrocaloric characterization shows that the adiabatic temperature change, ΔT, exhibits symmetric peaks with a giant positive maximum of 1.79 K (ΔS = 1.68 J kg⁻¹ K⁻¹) at 36 °C and a negative maximum of −2.02 K (ΔS = −1.93 J kg⁻¹ K⁻¹) at 34 °C. The ultrahigh magnitude of ΔT near room temperature makes PbMg_0.5W_0.5O₃ a superior electrocaloric material far beyond traditional PbZrO₃-based AFEs. The coexistence of symmetric giant positive and negative ΔT to further improve cooling efficiency is expected. In addition, the good reversibility and negligible leakage current should pave the way for practical applications.     

Controlled Nitrogen Doping in Crumpled Graphene for Improved Alkali Metal-Ion Storage under Low-Temperature Conditions

The significant performance decay in conventional graphite anodes under low-temperature conditions is attributed to the slow diffusion of alkali metal ions, requiring new strategies to enhance the charge storage kinetics at low temperatures. Here, nitrogen (N)-doped defective crumpled graphene (NCG) is employed as a promising anode to enable stable low-temperature operation of alkali metal-ion storage by exploiting the surface-controlled charge storage mechanisms. At a low temperature of −40 °C, the NCG anodes maintain high capacities of ≈172 mAh g⁻¹ for lithium (Li)-ion, ≈107 mAh g⁻¹ for sodium (Na)-ion, and ≈118 mAh g⁻¹ for potassium (K)-ion at 0.01 A g⁻¹ with outstanding rate-capability and cycling stability. A combination of density functional theory (DFT) and electrochemical analysis further reveals the role of the N-functional groups and defect sites in improving the utilization of the surface-controlled charge storage mechanisms. In addition, the full cell with the NCG anode and a LiFePO₄ cathode shows a high capacity of ≈73 mAh g⁻¹ at 0.5 °C even at −40 °C. The results highlight the importance of utilizing the surface-controlled charge storage mechanisms with controlled defect structures and functional groups on the carbon surface to improve the charge storage performance of alkali metal-ion under low-temperature conditions.     

Interlayer Injection of Low-Valence Zn Atoms to Activate MXene-Based Micro-Redox Capacitors With Battery-Type Voltage Plateaus

Insufficient and unstable energy output is the bottleneck issue radically restricting the application of micro-supercapacitors (MSCs). Herein, an interlayer atom injection strategy that can anchor low-valence Zn atoms (Zn^δ+, 0 < δ <2) on O-terminals of Ti₃C₂T_x (MXene) flakes within the MXene/silver-nanowires hybrid cathode of symmetric MSCs is first presented. Combining the polyacrylamide/ZnCl₂ hydrogel electrolyte rich in Cl⁻ and Zn²⁺ ions, the matched Zn^δ+/Zn²⁺ (−0.76 V vs SHE) and Ag/AgCl (0.23 V vs SHE), redox couples between the symmetrical electrodes are activated to offer faradaic charge storage beside ions-intercalation involved pseudocapacitance. Thus, a battery-type voltage plateau (≈0.9 V) appears in the discharge curve of a fabricated pseudo-symmetric micro-redox capacitor, simultaneously achieving energy density enhancement (117 µWh cm⁻² at 0.5 mA cm⁻²) and substantially improved power output stability (46% of the energy from the plateau region) relative to that before activation (98 µWh cm⁻² without voltage platform). The work provides a fire-new strategy to overcome the performance bottlenecks confronting conventional MSCs.     

Giant Polarization in Quasi-Adiabatic Ferroelectric Na+ Electrolyte for Solid-State Energy Harvesting and Storage

The advent of new solid-state energy storage devices to tackle the electrical revolution requires the usage of nonlinear behavior leading to emergent phenomena. The ferroelectric analyzed herein belongs to a family of electrolytes that allow energy harvesting and storage as part of its self-charging features when thermally activated. The Na_2.99Ba_0.005ClO electrolyte shows quasi-adiabatic behavior with a continuous increase in polarization upon cycling, displaying almost no hysteresis. The maximum polarization obtained at a weak electric field is giant and similar to the remanent polarization. It depends on the temperature with a pyroelectric coefficient of 5.37 C m⁻² °C⁻¹ from −5 to 46 °C. The emergence occurs via negative resistance and capacitance. The glass transition is found to have its origins in the sharp depolarization at 46 – 48 °C. Above –10 °C, at ≈ –5 °C, another thermal anomaly may rely on the topologic characteristics of the A_3–2xBa_xClO (A = Li, Na, K) glass electrolytes enabling positive feedback of the current of electrons throughout the surface of the inner cell. The phenomena may pave the way toward a better understanding of dipolar nanodomain fragile glasses with exceptional ferroelectric characteristics to architect energy harvesting and storage devices based on multivalent thermally activated Na⁺-ion-ion electrolytes.     

Effects of Growth Temperature on Indium Incorporation in InAlN Alloys Grown by GSMBE on Si(111)

In _x Al_1−x N alloys with low indium content (0.025 < x < 0.080) were grown on Si(111) substrates, with an AlN buffer layer, using gas source molecular beam epitaxy with ammonia under nitrogen-rich conditions. Composition was varied by changing the growth temperature from 580°C to 660°C. Growth temperature in excess of 580°C was found to be necessary to obtain compositional uniformity. As temperature was varied from 590°C to 660°C, both the growth rate and indium incorporation decreased substantially. Rising In content observed near the surface of each sample was attributed to native indium oxide formation.     

Effects of Ca and Mn Additions on the Microstructure and Dielectric Properties of (Bi<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>)TiO<Subscript>3</Subscript> Ceramics

Dielectric ceramics based on the solid solution (1 − x)Bi_0.5Na_0.5TiO₃ (BNT)-xCaTiO₃ (CT) were synthesized by the conventional solid-state route. BNT with various contents of CT formed a complete solid solution and exhibited a rhombohedral structure. CT in this solid solution with BNT was observed to decrease the dielectric constant at higher temperatures and raise the dielectric constant at lower temperatures. On the other hand, decreased ferroelectricity was observed with increasing CT concentration, resulting in a downward shift of the depolarization temperature and a decrease of the dissipation factor. With the addition of Mn²⁺ to 0.86BNT-0.14CT, the temperature characteristics of capacitance were improved (−55°C to 250°C, ΔC/C _25°C ≤ ±15%). By doping with 1.5 wt.% Mn²⁺, the dielectric constant at room temperature reached over 900, with a dielectric loss of less than 1%.     

Inkjet Printing of Perovskites for Breaking Performance–Temperature Tradeoffs in Fabric-Based Thermistors

A novel low-temperature route is developed for inkjet printing of the perovskite Cs₂SnI₆, to create wearable negative-temperature-coefficient thermistors with unprecedented performance on thermally sensitive fabrics. A low processing temperature of 120 °C is achieved by creating a stable and printable ink using binary metal iodide salts, which is thermally transformed into dense Cs₂SnI₆ crystals after printing. The optimally printed Cs₂SnI₆ shows a temperature measurement range up to 120 °C, high sensitivity (4400 K), and temperature coefficient of resistivity (0.05 °C⁻¹), and stability under ambient environmental conditions and bending. The approach breaks a critical tradeoff that has hindered wearable fabric-based thermistors by enabling damage-free fabrication of devices with commercially comparable performance, evincing significant applications in multifunctional textiles and beyond.     

Surface-induced highly oriented perylo[1,12-b,c,d]selenophene thin films for high performance organic field-effect transistors

Epitaxial crystallization of perylo[1,12-b,c,d]selenophene (PESE) on highly oriented polyethylene (PE) substrate through vapor phase deposition has been achieved. Oriented PESE crystals with different crystalline morphologies can be fabricated by changing the temperature of PE substrate during vacuum evaporation. When the PE substrate temperature is lower than 70 °C, sparsely dispersed PESE lathlike crystals are produced with their long axis preferentially aligned perpendicular to the chain direction of PE crystals. While the close films of PESE with lathlike crystals aligned with long axis parallel to the chain direction of PE film were obtained above 90 °C. Transistors based on expitaxially crystallized PESE films have been fabricated and the transistor properties were also studied. It is found that transistors show different electrical characteristics depending on the preparation conditions of expitaxially crystallized PESE films. The transistors based on the PESE/PE-SiO₂/Si with PESE deposited on oriented PE film at low temperature, i.e., <70 °C, display a similar poor properties with the PESE/OTS-SiO₂/Si type transistors. However, when the deposition temperature was elevated to 90 °C, the transistors exhibit a maximum field-effect mobility of 4.4 × 10⁻² cm² V⁻¹ s⁻¹ and maximum on/off ratio of 2.0 × 10⁵, which are about 2 orders of magnitudes higher than the PESE/OTS-SiO₂/Si based transistors.     

Thermal annealing effect on light emission profile of polyfluorenes containing double bond subunit

We presented comprehensive photoluminescence (PL) and electroluminescence (EL) studies of polyfluorene based electroactive polymer (SF4) containing double bond side chain to investigate its characteristics as a function of temperature. Annealing treatment was conducted for thin films on glass substrates and also for the organic light emitting diodes (OLEDs) at different temperatures. While polymer thin film coated on to glass substrate annealed at < 150 °C exhibited green color emission, OLEDs that annealed at >150 °C shifted white color emission. It was implying that the emission was taking place interchain interaction. Phase modulation at higher annealing temperatures was occurred on the thin film as shown AFM images. Further, annealed polymer film with 120 °C exhibited the best performance in OLED device with luminance 5241 cd m⁻², a maximum efficiency 1.54 cd A⁻¹ and external quantum efficiency 0.54% compared to other polymer films annealed with different temperatures.     

High-Temperature Capacitor Materials Based on Modified BaTiO<Subscript>3</Subscript>

High-temperature capacitor materials sintered at 1120°C were prepared in a BaTiO₃ (BT)-Na_0.5Bi_0.5TiO₃ (NBT)-Nb₂O₅-ZnO-CaZrO₃ system. The Curie temperature of BaTiO₃ was increased by NBT doping, and a secondary phase occurred when adding ≥5 mol% NBT. The effects of Nb₂O₅, ZnO, and CaZrO₃ on the dielectric properties and the microstructure of BT ceramics doped with 1 mol% NBT were analyzed. The overall dielectric constant decreased when the Nb₂O₅ content increased, and increased when the ZnO content increased. The dielectric constant peak at the Curie temperature was effectively depressed, and a broad secondary dielectric constant peak appeared at 60°C when the ZnO concentration was ≥4.5 mol%. Significant grain growth was observed by scanning electron microscope (SEM) analysis as the amount of ZnO increased. The high-temperature capacitor specification (−55°C to +175°C, ΔC/C _25°C less than ±15%) is met when 7 mol% to 8 mol% CaZrO₃ is added.     

Enhancing Oxygen Reduction Activity and Cr Tolerance of Solid Oxide Fuel Cell Cathodes by a Multiphase Catalyst Coating

Intermediate temperature solid oxide fuel cells (IT-SOFCs) are cost-effective and efficient energy conversion systems. The sluggish oxygen reduction reaction (ORR) and the degradation of cathodes are critical challenges to the commercialization of IT-SOFCs. Here, a highly efficient multiphase (MP) catalyst coating, consisting of Ba_1−xCo_0.7Fe_0.2Nb_0.1O_3−δ (BCFN) and BaCO₃, to enhance the ORR activity and durability of the state-of-the-art lanthanum strontium cobalt ferrite (La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ, LSCF) cathode is reported. The conformal MP catalyst-coated LSCF cathode shows a polarization resistance (R_p) of 0.048 Ω cm² at 650 °C, about one order of magnitude smaller than that of the bare LSCF. In an accelerated Cr-poisoning test, the degradation rate of the catalyst-coated LSCF electrode is 10⁻³ Ω cm² h⁻¹ (0.59% h⁻¹) over 200 h, only one fifth of the degradation rate of the bare LSCF electrode at 750 °C. In addition, anode-supported single cells with the MP catalyst-coated LSCF cathode show a dramatically enhanced peak power density (1.4 W cm⁻² vs 0.67 W cm⁻² at 750 °C) and increased durability against Cr and H₂O. Both experimental results and density functional theory-based calculations indicate that the BCFN phase improves the ORR activity while the BaCO₃ phase enhances the stability of the LSCF cathode.     

A Complexing Agent to Enable a Wide-Temperature Range Bromine-Based Flow Battery for Stationary Energy Storage

Bromine-based flow batteries (Br-FBs) are considered one of the most promising energy storage systems due to their features of high energy density and low cost. However, they generally suffer from uncontrolled diffusion of corrosive bromine particularly at high temperatures. That is because the interaction between polybromide anions and the commonly used complexing agent (N–methyl–N–ethyl–pyrrolidinium bromide [MEP]) decreases with increasing temperatures, which causes serious self-discharge and capacity fade. Herein, a novel bromine complexing agent, 1–ethyl–2–methyl–pyridinium bromide (BCA), is introduced in Br-FBs to solve the above problems. It is proven that BCA can combine with polybromide anions very well even at a high temperature of 60 °C. Moreover, the BCA contributes to decreasing the electrochemical polarization of Br⁻/Br₂ couple, which in turn improves their power density. As a result, a zinc–bromine flow battery with BCA as the complexing agent can achieve a high energy efficiency of 84% at 40 mA cm⁻², even at high temperature of 60 °C and it can stably run for more than 400 cycles without obvious performance decay. This paper provides an effective complexing agent to enable a wide temperature range Br-FB.     

Beam-Mode Piezoelectric Properties of Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals for Medical Linear Array Applications

In this work, the dielectric and beam-mode piezoelectric properties of ternary 0.35Pb(In_1/2Nb_1/2)O₃-0.35Pb(Mg_1/3Nb_2/3)O₃-0.30PbTiO₃ (PIMNT35/35/30) piezoelectric single crystals were investigated. The Curie temperature (T _C) and rhombohedral-to-tetragonal phase-transition temperature (T _rt) are 187°C and 127°C, about 30°C higher than those of PMNT crystals. The beam-mode coupling coefficient k ₃₃ ^w was found to be 90.3%. Furthermore, 3.5-MHz linear arrays based on PIMNT35/35/30 crystals and Pb(Zr_1−x Ti _x )O₃ ceramic (PZT-5H) were simulated using PiezoCAD software. The results indicate that the sensitivity and −6 dB bandwidth of a PIMNT35/35/30 transducer would be approximately 4 dB and 20% higher, respectively, compared with a traditional PZT transducer.     

Preparation and Characterization of Ultralow-Dielectric-Constant Porous SiCOH Thin Films Using 1,2-Bis(triethoxysilyl)ethane,Triethoxymethylsilane, and a Copolymer Template

Ultralow-dielectric-constant (k) porous SiCOH films have been prepared using 1,2-bis(triethoxysilyl)ethane, triethoxymethylsilane, and a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymer template by means of spin-coating. The resulting films were characterized by cross-section scanning electron microscopy, small-angle x-ray diffraction, atomic force microscopy, Fourier-transform infrared spectroscopy, nanomechanical testing, and electrical measurements. Thermal treatment at 350°C for 2 h resulted in the formation of ultralow-k films with k of ∼2.0, leakage current density of 3 × 10⁻⁸ A/cm² at 1 MV/cm, reduced modulus (E _r) of ∼4.05 GPa, and hardness (H) of ∼0.32 GPa. After annealing between 400°C and 500°C for 30 min, the resulting films showed fluctuant k values of 1.85 to 2.22 and leakage current densities of 3.7 × 10⁻⁷ A/cm² to 3 × 10⁻⁸ A/cm² at 0.8 MV/cm, likely due to the change of the film microstructure. Compared with 350°C annealing, higher-temperature annealing can improve the mechanical strength of the ultralow-k film, i.e., E _r ≈ 5 GPa and H ≈ 0.56 GPa after 500°C annealing.     

Stabilization of the Polar Structure and Giant Second-Order Nonlinear Response of Single Crystal γ-NaAs0.95Sb0.05Se2

The dearth of suitable materials significantly restricts the practical development of infrared (IR) laser systems with highly efficient and broadband tuning. Recently, γ-NaAsSe₂ is reported, and it exhibits a large nonlinear second-harmonic generation (SHG) coefficient of 590 pm V⁻¹ at 2 µm. However, the crystal growth of γ-NaAsSe₂ is challenging because it undergoes a phase transition to centrosymmetric δ-NaAsSe₂. Herein, the stabilization of non-centrosymmetric γ-NaAsSe₂ by doping the As site with Sb, which results in γ-NaAs_0.95Sb_0.05Se₂ is reported. The congruent melting behavior is confirmed by differential thermal analysis with a melting temperature of 450 °C and crystallization temperature of 415 °C. Single crystals with dimensions of 3 mm × 2 mm are successfully obtained via zone refining and the Bridgman method. The purification of the material plays a significant role in crystal growth and results in a bandgap of 1.78 eV and thermal conductivity of 0.79 Wm⁻¹ K⁻¹. The single-crystal SHG coefficient of γ-NaAs_0.95Sb_0.05Se₂ exhibits an enormous value of |d₁₁| = 648 ± 74 pm V⁻¹, which is comparable to that of γ-NaAsSe₂ and ≈20× larger than that of AgGaSe₂. The bandgap of γ-NaAs_0.95Sb_0.05Se₂ (1.78 eV) is similar to that of AgGaSe₂, thus rendering it highly attractive as a high-performing nonlinear optical material.     

Colossal Barocaloric Effect by Large Latent Heat Produced by First-Order Intersite-Charge-Transfer Transition

Materials which show novel thermal properties can be used to make highly efficient and environmentally friendly energy systems for thermal energy storage and refrigeration through caloric effects. An A-site-ordered quadruple perovskite-structure oxide, NdCu₃Fe₄O₁₂, is found to release significant latent heat, 25.5 kJ kg⁻¹ (157 J cc⁻¹), at the intersite-charge-transfer transition temperature near room temperature. The transition is first-order and accompanied by an unusual magnetic ordering and a large negative-thermal-expansion-like volume change, and thus, it causes a large entropy change (84.2 J K⁻¹ kg⁻¹). The observed entropy change is comparable to the largest changes reported in inorganic solid materials, and more importantly, it is utilized through a colossal barocaloric effect. The adiabatic temperature change by applying 5.1 kbar pressure is estimated to reach 13.7 K, which means efficient refrigeration can be realized through this effect.     

3D HfO2 Thin Film MEMS Capacitor with Superior Energy Storage Properties

Capacitors are ubiquitous and crucial components in modern technologies. Future microelectronic devices require novel dielectric capacitors with higher energy storage density, higher efficiency, better frequency and temperature stabilities, and compatibility with integrated circuit (IC) processes. Here, in order to overcome these challenges, a novel 3D HfO₂ thin film capacitor is designed and fabricated by an integrated microelectromechanical system (MEMS) process. The energy storage density (ESD) of the capacitor reaches 28.94 J cm⁻³, and the energy storage efficiency of the capacitor is up to 91.3% under an applied electric field of 3.5 MV cm⁻¹. The ESD can be further improved by reducing the minimum period structure size of the 3D capacitor. Moreover, the 3D capacitor exhibits excellent temperature stability (up to 150 °C) and charge-discharge endurance (10⁷ cycles). The results indicate that the 3D HfO₂ thin film MEMS capacitor has enormous potential in energy storage applications in harsh environments, such as pulsed discharge and power conditioning electronics.