Fatigue‐Free and Bending‐Endurable Flexible Mn‐Doped Na0.5Bi0.5TiO3‐BaTiO3‐BiFeO3 Film Capacitor with an Ultrahigh Energy Storage Performance

As the rapid development of intelligent systems moves toward flexible electronics, capacitors with extraordinary flexibility and an outstanding energy storage performance will open up broad prospects for powering portable/wearable electronics and pulsed power applications. This work presents a simple one‐step process to fabricate a flexible Mn‐doped 0.97(0.93Na_0.5Bi_0.5TiO₃‐0.07BaTiO₃)‐0.03BiFeO₃ (Mn:NBT‐BT‐BFO) inorganic thin film capacitor with the assistance of a 2D fluorophlogopite mica substrate. The film element, which has a high breakdown strength, great relaxor dispersion, and the coexistence of ferroelectric and antiferroelectric phases, has a high recoverable energy storage density (W_rec ≈81.9 J cm^?3), high efficiency (η ≈64.4%), superior frequency stability (500 Hz–20 kHz), excellent antifatigue property (1 × 10⁹ cycles), and a broad operating temperature window (25–200 °C). The all‐inorganic Mn:NBT‐BT‐BFO/Pt/mica capacitor has a prominent mechanical‐bending resistance without obvious deterioration in its corresponding energy storage capability when it is subjected to a bending radius of 2 mm or repeated bending for 10³ cycles. This work is the first demonstration of an all‐inorganic flexible film capacitor and sheds light on dielectric energy storage devices for portable/wearable applications.     

Heterojunction‐Depleted Lead‐Free Perovskite Solar Cells with Coarse‐Grained B‐γ‐CsSnI3 Thin Films

Perovskite solar cells (PSCs) have been emerging as a breakthrough photovoltaic technology, holding unprecedented promise for low‐cost, high‐efficiency renewable electricity generation. However, potential toxicity associated with the state‐of‐the‐art lead‐containing PSCs has become a major concern. The past research in the development of lead‐free PSCs has met with mixed success. Herein, the promise of coarse‐grained B‐γ‐CsSnI₃ perovskite thin films as light absorber for efficient lead‐free PSCs is demonstrated. Thermally‐driven solid‐state coarsening of B‐γ‐CsSnI₃ perovskite grains employed here is accompanied by an increase of tin‐vacancy concentration in their crystal structure, as supported by first‐principles calculations. The optimal device architecture for the efficient photovoltaic operation of these B‐γ‐CsSnI₃ thin films is identified through exploration of several device architectures. Via modulation of the B‐γ‐CsSnI₃ grain coarsening, together with the use of the optimal PSC architecture, planar heterojunction‐depleted B‐γ‐CsSnI₃ PSCs with power conversion efficiency up to 3.31% are achieved without the use of any additives. The demonstrated strategies provide guidelines and prospects for developing future high‐performance lead‐free PVs.     

Thermally Durable Lithium‐Ion Capacitors with High Energy Density from All Hydroxyapatite Nanowire‐Enabled Fire‐Resistant Electrodes and Separators

The reliability and durability of lithium‐ion capacitors (LICs) are severely hindered by the kinetic imbalance between capacitive and Faradaic electrodes. Efficient charge storage in LICs is still a huge challenge, particularly for thick electrodes with high mass loading, fast charge delivery, and harsh working conditions. Here, a unique thermally durable, stable LIC with high energy density from all‐inorganic hydroxyapatite nanowire (HAP NW)‐enabled electrodes and separators is reported. Namely, the LIC device is designed and constructed with the electron/ion dual highly conductive and fire‐resistant composite Li₄Ti₅O₁₂‐based anode and activated carbon‐based cathode, together with a thermal‐tolerant HAP NW separator. Despite the thick‐electrode configuration, the as‐fabricated all HAP NW‐enabled LIC exhibits much enhanced electrochemical kinetics and performance, especially at high current rates and temperatures. Long cycling lifetime and state‐of‐the‐art areal energy density (1.58 mWh cm^?2) at a high mass loading of 30 mg cm^?2 are achieved. Benefiting from the excellent fire resistance of HAP NWs, such an unusual LIC exhibits high thermal durability and can work over a wide range of temperatures from room temperature to 150 °C. Taking full advantage of synergistic configuration design, this work sets the stage for designing advanced LICs beyond the research of active materials.     

Fatigue‐Free Aurivillius Phase Ferroelectric Thin Films with Ultrahigh Energy Storage Performance

Dielectric capacitors have become a key enabling technology for electronics and electrical systems. Although great strides have been made in the development of ferroelectric ceramic and thin films for capacitors, much less attention has been given to preventing polarization fatigue, while improving the energy density, of ferroelectrics. Here superior capacitive properties and outstanding stability are reported over 10⁷ charge/discharge cycles and a wide temperature range of ?60 to 200 °C of ferroelectric Aurivillius phase Bi_3.25La_0.75Ti₃O₁₂‐BiFeO₃ (BLT‐BFO), which represents one of the best capacitive performances recorded for the ferroelectric materials. The modification of BLT thin films with BFO overcomes the constraints of ferroelectric Aurivillius compounds and presents an unprecedented combination of the ideal features including improved polarization, reduced ferroelectric hysteresis, and lowered leakage current for high‐energy‐density capacitors. Given the lead‐free and fatigue‐free nature of this Aurivillius phase ferroelectric, this work unveils a new approach towards high‐performance eco‐friendly ferroelectric materials for electrical energy storage applications.     

Spontaneous Growth of 3D Framework Carbon from Sodium Citrate for High Energy‐ and Power‐Density and Long‐Life Sodium‐Ion Hybrid Capacitors

Carbon sheets with 3D architectures, large graphitic interlayer spacing, and high electrical conductivity are highly expected to be an ideal anode material for sodium‐ion hybrid capacitors (SIHCs). Pursuing a simple synthesis methodology and advancing it from the laboratory to industry is of great importance. In this study, a new approach is presented to prepare 3D framework carbon (3DFC) with the above integrated advantages by a direct calcination of sodium citrate without aid of any additional carbon source, template, or catalyst. The first‐principle calculations verify that the large interlayer spacing and the curvature structure of 3DFC facilitate the sodium ion insertion/extraction. As a consequence, the optimal 3DFC sample exhibits high reversible capacity as well as excellent rate and cycling performance. On this basis, a dual‐carbon SIHC is fabricated by employing 3DFC as battery‐type anode and 3DFC‐derived nanoporous carbon as capacitor‐type cathode. It is able to deliver high energy‐ and power‐density feature as well as outstanding long‐term cycling stability in the potential range of 0–4.0 V. This study may open an avenue for developing high‐performance carbon electrode materials and pushes the practical applications of SIHCs a decisive step forward.     

Superior Multifunctional Activity of Nanoporous Carbons with Widely Tunable Porosity: Enhanced Storage Capacities for Carbon‐Dioxide,Hydrogen, Water,and Electric Charge

Nanoporous carbons (NPCs) with engineered specific pore sizes and sufficiently high porosities (both specific surface area and pore volume) are necessary for storing energy in the form of electric charges and molecules. Herein, NPCs, derived from biomass pine‐cones, coffee‐grounds, graphene‐oxide and metal‐organic frameworks, with systematically increased pore width (<1.0 nm to a few nm), micropore volume (0.2–0.9 cm³ g^?1) and specific surface area (800–2800 m² g^?1) are presented. Superior CO₂, H_2, and H₂O uptakes of 35.0 wt% (≈7.9 mmol g^?1 at 273 K), 3.0 wt% (at 77 K) and 85.0 wt% (at 298 K), respectively at 1 bar, are achieved. At controlled microporosity, supercapacitors deliver impressive performance with a capacity of 320 and 230 F g^?1 at 500 mA g^?1, in aqueous and organic electrolytes, respectively. Excellent areal capacitance and energy density (>50 Wh kg^?1 at high power density, 1000 W kg^?1) are achieved to form the highest reported values among the range of carbons in the literature. The noteworthy energy storage performance of the NPCs for all five cases (CO₂, H₂, H₂O, and capacitance in aqueous and organic electrolytes) is highlighted by direct comparison to numerous existing porous solids. A further analysis on the specific pore type governed physisorption capacities is presented.     

Reaching the Energy Density Limit of Layered O3‐NaNi0.5Mn0.5O2 Electrodes via Dual Cu and Ti Substitution

Although being less competitive energy density‐wise, Na‐ion batteries are serious alternatives to Li‐ion ones for applications where cost and sustainability dominate. O3‐type sodium layered oxides could partially overcome the energy limitation, but their practical use is plagued by a reaction process that enlists numerous phase changes and volume variations while additionally being moisture sensitive. Here, it is shown that the double substitution of Ti for Mn and Cu for Ni in O3‐NaNi_0.5?yCu_yMn_{0.5? z}Ti_zO₂ can alleviate most of these issues. Among this series, electrodes with specific compositions are identified that can reversibly release and uptake ≈0.9 sodium per formula unit via a smooth voltage‐composition profile enlisting minor lattice volume changes upon cycling as opposed to ΔV/V≈23% in the parent NaNi_0.5Mn_0.5O₂ while showing a greater resistance against moisture. The positive attributes of substitution are rationalized by structure considerations supported by density functional theory (DFT) calculations. Electrodes with sustained capacities of ≈180 mAh g^?1 are successfully implemented into 18 650 Na‐ion cells having greater performances, energy density‐wise (≈250 Wh L^?1), than today's Na₃V₂(PO₄)₂F₃/HC Na‐ion technology which excels in rate capabilities. These results constitute a step forward in increasing the practicality of Na‐ion technology with additional opportunities for applications in which energy density prevails over rate capability.     

Simultaneous Achieving of High Faradaic Efficiency and CO Partial Current Density for CO2 Reduction via Robust,Noble‐Metal‐Free Zn Nanosheets with Favorable Adsorption Energy

Electrocatalytic CO₂ reduction to fuels is considered a promising strategy for the sustainable carbon cycle. However, the improvement of the catalytic performance of CO₂ electrocatalysts still poses many challenges, especially achieving the large partial current density of product and high faradaic efficiency simultaneously, which are essential for future applications of the electrochemical CO₂ reduction reaction. In response, herein, an in situ porous Zn catalyst is prepared and exhibits high faradaic efficiency and large CO partial current density at the same time, benefiting from the porous architecture with increased exposure and accessibility of active sites. Furthermore, density functional theory calculations demonstrate that the high faradaic efficiency is attributed to the favorable adsorption energy of the key intermediate, which promotes CO₂ electroreduction to CO.