Exceptional Visible‐Light‐Driven Cocatalyst‐Free Photocatalytic Activity of g‐C3N4 by Well Designed Nanocomposites with Plasmonic Au and SnO2

In this work, plasmonic Au/SnO₂/g‐C₃N₄ (Au/SO/CN) nanocomposites have been successfully synthesized and applied in the H₂ evolution as photocatalysts, which exhibit superior photocatalytic activities and favorable stability without any cocatalyst under visible‐light irradiation. The amount‐optimized 2Au/6SO/CN nanocomposite capable of producing approximately 770 μmol g^?1 h^?1 H₂ gas under λ > 400 nm light illumination far surpasses the H₂ gas output of SO/CN (130 μmol g^?1), Au/CN (112 μmol g^?1 h^?1), and CN (11 μmol g^?1 h^?1) as a contrast. In addition, the photocatalytic activity of 2Au/6SO/CN maintains unchanged for 5 runs in 5 h. The enhanced photoactivity for H₂ evolution is attributed to the prominently promoted photogenerated charge separation via the excited electron transfer from plasmonic Au (≈520 nm) and CN (470 nm > λ > 400 nm) to SO, as indicated by the surface photovoltage spectra, photoelectrochemical I–V curves, electrochemical impedance spectra, examination of formed hydroxyl radicals, and photocurrent action spectra. Moreover, the Kelvin probe test indicates that the newly aligned conduction band of SO in the fabricated 2Au/6SO/CN is indispensable to assist developing a proper energy platform for the photocatalytic H₂ evolution. This work distinctly provides a feasible strategy to synthesize highly efficient plasmonic‐assisted CN‐based photocatalysts utilized for solar fuel production.     

Poly(1,4‐di(2‐thienyl))benzene Facilitating Complete Light‐Driven Water Splitting under Visible Light at High pH

The recent discovery that metal‐free polyterthiophene (PTTh) prepared by iodine‐vapor‐assisted polymerization (IVP) can catalyze the hydrogen evolution reaction (HER) when illuminated, and this light‐enhanced electrolysis expresses a non‐Nernstian relation with pH, provides the foundation for further improvement of the photovoltage of the reaction by engineering the band structure of the light‐absorbing polymer. Deviating from an all‐thiophene backbone, using poly(1,4‐di(2‐thienyl))benzene (PDTB) lowers the highest occupied molecular orbital level by ≈0.3 eV compared with polythiophene, and PDTB simultaneously maintains the photoelectrocatalytic properties without an all‐thiophene backbone, resulting in very high conversion rate of 600 mmol(H₂) h^?1 g^?1 at 0 V versus the reversible hydrogen electrode (RHE) at pH 11. PDTB shows the same non‐Nernstian behavior as PTTh with increasing onset potential (versus RHE) at higher pH, and the open circuit potential on PDTB under visible light reaches 1.4 V versus RHE at pH 12. The PDTB photocathode thus produces a photovoltage above the theoretical potential for the complete water‐splitting (1.229 V) and is indeed able to produce hydrogen in a one‐photon‐per‐electron light‐driven water splitting setup with MnO_x as the anode at a rate of 6.4 mmol h^?1 g_PDTB^?1.     

Ultrafast All‐Solid‐State Coaxial Asymmetric Fiber Supercapacitors with a High Volumetric Energy Density

Fiber‐supercapacitors (FSCs) are promising energy storage devices that can complement or even replace microbatteries in miniaturized portable and wearable electronics. Currently, a major challenge for FSCs is achieving ultrahigh volumetric energy and power densities simultaneously, especially when the charge/discharge rates exceed 1 V s^?1. Herein, an Au‐nanoparticle‐doped‐MnO_x@CoNi‐alloy@carbon‐nanotube (Au–MnO_x@CoNi@CNT) core/shell nanocomposite fiber electrode is designed, aiming to boost its charge/discharge rate by taking advantage of the superconductive CoNi alloy network and the greatly enhanced conductivity of the Au doped MnO_x active materials. An all‐solid‐state coaxial asymmetric FSC (CAFSC) prototype device made by wrapping this fiber with a holey graphene paper (HGP) exhibits excellent performance at rates up to 10 V s^?1, which is the highest charge rate demonstrated so far for FSCs based on pseudocapacitive materials. Furthermore, our fully packaged CAFSC delivers a volumetric energy density of ≈15.1 mW h cm^?3, while simultaneously maintaining a high power density of 7.28 W cm^?3 as well as a long cycle life (90% retention after 10 000 cycles). This value is the highest among all reported FSCs, even better than that of a typical 4 V/500 µA h thin‐film lithium battery.     

All‐Printed MnHCF‐MnOx‐Based High‐Performance Flexible Supercapacitors

Here, a simple active materials synthesis method is presented that boosts electrode performance and utilizes a facile screen‐printing technique to prepare scalable patterned flexible supercapacitors based on manganese hexacyanoferrate‐manganese oxide and electrochemically reduced graphene oxide electrode materials (MnHCF‐MnO_x/ErGO). A very simple in situ self‐reaction method is developed to introduce MnO_x pseudocapacitor material into the MnHCF system by using NH₄F. This MnHCF‐MnO_x electrode materials can deliver excellent capacitance of 467 F g^?1 at a current density of 1 A g^?1, which is a 2.4 times capacitance increase compared to MnHCF. In addition a printed, patterned, flexible MnHCF‐MnO_x/ErGO supercapacitor is fabricated, showing a remarkable areal capacitance of 16.8 mF cm^?2 and considerable energy and power density of 0.5 mWh cm^?2 and 0.0023 mW cm^?2, respectively. Furthermore, the printed patterned flexible supercapacitors also exhibit exceptional flexibility, and the capacitance remains stable, even while bending to various angles (60°, 90°, and 180°) and for 100 cycles. The flexible supercapacitor arrays integrated by multiple prepared single supercapacitors can power various LEDs even in the bent states. This approach offers promising opportunities for the development of printable energy storage materials and devices with high energy density, large scalability, and excellent flexibility.     

Mn‐Rich P′2‐Na0.67[Ni0.1Fe0.1Mn0.8]O2 as High‐Energy‐Density and Long‐Life Cathode Material for Sodium‐Ion Batteries

Herein, P′2‐type Na_0.67[Ni_0.1Fe_0.1Mn_0.8]O₂ is introduced as a promising new cathode material for sodium‐ion batteries (SIBs) that exhibits remarkable structural stability during repetitive Na⁺ de/intercalation. The O? Ni? O? Mn? O? Fe? O bond in the octahedra of transition‐metal layers is used to suppress the elongation of the Mn? O bond and to improve the electrochemical activity, leading to the highly reversible Na storage mechanism. A high discharge capacity of ≈220 mAh g^?1 (≈605 Wh kg^?1) is delivered at 0.05 C (13 mAg^?1) with a high reversible capacity of ≈140 mAh g^?1 at 3 C and excellent capacity retention of 80% over 200 cycles. This performance is associated with the reversible P′2–OP4 phase transition and small volume change upon charge and discharge (≈3%). The nature of the sodium storage mechanism in a full cell paired with a hard carbon anode reveals an unexpectedly high energy density of ≈542 Wh kg^?1 at 0.2 C and good capacity retention of ≈81% for 500 cycles at 1 C (260 mAg^?1).     

Lithium‐Pretreated Hard Carbon as High‐Performance Sodium‐Ion Battery Anodes

Hard carbon (HC) is the state‐of‐the‐art anode material for sodium‐ion batteries (SIBs). However, its performance has been plagued by the limited initial Coulombic efficiency (ICE) and mediocre rate performance. Here, experimental and theoretical studies are combined to demonstrate the application of lithium‐pretreated HC (LPHC) as high‐performance anode materials for SIBs by manipulating the solid electrolyte interphase in tetraglyme (TEGDME)‐based electrolyte. The LPHC in TEGDME can 1) deliver > 92% ICE and ≈220 mAh g^?1 specific capacity, twice of the capacity (≈100 mAh g^?1) in carbonate electrolyte; 2) achieve > 85% capacity retention over 1000 cycles at 1000 mA g^?1 current density (4 C rate, 1 C = 250 mA g^?1) with a specific capacity of ≈150 mAh g^?1, ≈15 times of the capacity (10 mAh g^?1) in carbonate. The full cell of Na₃V₂(PO₄)₃‐LPHC in TEGDME demonstrated close to theoretical specific capacity of ≈98 mAh g^?1 based on Na₃V₂(PO₄)₃ cathode, ≈2.5 times of the value (≈40 mAh g^?1) with nontreated HC. This work provides new perception on the anode development for SIBs.     

Direct Growth of Flower‐Like δ‐MnO2 on Three‐Dimensional Graphene for High‐Performance Rechargeable Li‐O2 Batteries

A challenge still remains to develop high‐performance and cost‐effective air electrode for Li‐O₂ batteries with high capacity, enhanced rate capability and long cycle life (100 times or above) despite recent advances in this field. In this work, a new design of binder‐free air electrode composed of three‐dimensional (3D) graphene (G) and flower‐like δ‐MnO₂ (3D‐G‐MnO₂) has been proposed. In this design, graphene and δ‐MnO₂ grow directly on the skeleton of Ni foam that inherits the interconnected 3D scaffold of Ni foam. Li‐O₂ batteries with 3D‐G‐MnO₂ electrode can yield a high discharge capacity of 3660 mAh g^?1 at 0.083 mA cm^?2. The battery can sustain 132 cycles at a capacity of 492 mAh g^?1 (1000 mAh g_carbon ^?1) with low overpotentials under a high current density of 0.333 mA cm^?2. A high average energy density of 1350 Wh Kg^?1 is maintained over 110 cycles at this high current density. The excellent catalytic activity of 3D‐G‐MnO₂ makes it an attractive air electrode for high‐performance Li‐O₂ batteries.     

Nanostructured Ternary Electrodes for Energy‐Storage Applications

A three‐component, flexible electrode is developed for supercapacitors over graphitized carbon fabric, utilizing γ‐MnO₂ nanoflowers anchored onto carbon nanotubes (γ‐MnO₂/CNT) as spacers for graphene nanosheets (GNs). The three‐component, composite electrode doubles the specific capacitance with respect to GN‐only electrodes, giving the highest‐reported specific capacitance (308 F g^?1) for symmetric supercapacitors containing MnO₂ and GNs using a two‐electrode configuration, at a scan rate of 20 mV s^?1. A maximum energy density of 43 W h kg^?1 is obtained for our symmetric supercapacitors at a constant discharge‐current density of 2.5 A g^?1 using GN–(γ‐MnO₂/CNT)‐nanocomposite electrodes. The fabricated supercapacitor device exhibits an excellent cycle life by retaining ≈90% of the initial specific capacitance after 5000 cycles.     

High‐Temperature Treatment of Li‐Rich Cathode Materials with Ammonia: Improved Capacity and Mean Voltage Stability during Cycling

Li‐rich electrode materials of the family x Li₂MnO₃·(1?x )LiNi_a Co_b Mn_c O₂ (a + b + c = 1) suffer a voltage fade upon cycling that limits their utilization in commercial batteries despite their extremely high discharge capacity, ≈250 mA h g^?1. Li‐rich, 0.35Li₂MnO₃·0.65LiNi_0.35Mn_0.45Co_0.20O₂, is exposed to NH₃ at 400 °C, producing materials with improved characteristics: enhanced electrode capacity and a limited average voltage fade during 100 cycles in half cells versus Li. Three main changes caused by NH₃ treatment are established. First, a general bulk reduction of Co and Mn is observed via X‐ray photoelectron spectroscopy and X‐ray absorption near edge structure. Next, a structural rearrangement lowers the coordination number of Co? O and Mn? O bonds, as well as formation of a surface spinel‐like structure. Additionally, Li⁺ removal from the bulk causes the formation of surface LiOH, Li₂CO₃, and Li₂O. These structural and surface changes can enhance the voltage and capacity stability of the Li‐rich material electrodes after moderate NH₃ treatment times of 1–2 h.     

A Dual‐Insertion Type Sodium‐Ion Full Cell Based on High‐Quality Ternary‐Metal Prussian Blue Analogs

Prussian blue analogs (PBAs) are especially investigated as superior cathodes for sodium‐ion batteries (SIBs) due to high theoretical capacity (≈170 mA h g^?1) with 2‐Na storage and low cost. However, PBAs suffer poor cyclability due to irreversible phase transition in deep charge/discharge states. PBAs also suffer low crystallinity, with considerable [Fe(CN)₆] vacancies, and coordinated water in crystal frameworks. Presently, a new chelating agent/surfactant coassisted crystallization method is developed to prepare high‐quality (HQ) ternary‐metal Ni_xCo_1?x[Fe(CN)₆] PBAs. By introducing inactive metal Ni to suppress capacity fading caused by excessive lattice distortion, these PBAs have tunable limits on depth of charge/discharge. HQ‐Ni_xCo_1?x[Fe(CN)₆] (x = 0.3) demonstrates the best reversible Na‐storage behavior with a specific capacity of ≈145 mA h g^?1 and a remarkably improved cycle performance, with ≈90% capacity retention over 600 cycles at 5 C. Furthermore, a dual‐insertion full cell on the cathode and NaTi₂(PO₄)₃ anode delivers reversible capacity of ≈110 mA h g^?1 at a current rate of 1.0 C without capacity fading over 300 cycles, showing promise as a high‐performance SIB for large‐scale energy‐storage systems. The ultrastable cyclability achieved in the lab and explained herein is far beyond that of any previously reported PBA‐based full cells.     

High‐Performance Reversible Aqueous Zn‐Ion Battery Based on Porous MnOx Nanorods Coated by MOF‐Derived N‐Doped Carbon

Rechargeable aqueous zinc‐ion batteries (ZIBs) have been emerging as potential large‐scale energy storage devices due to their high energy density, low cost, high safety, and environmental friendliness. However, the commonly used cathode materials in ZIBs exhibit poor electrochemical performance, such as significant capacity fading during long‐term cycling and poor performance at high current rates, which significantly hinder the further development of ZIBs. Herein, a new and highly reversible Mn‐based cathode material with porous framework and N‐doping (MnO_x@N‐C) is prepared through a metal–organic framework template strategy. Benefiting from the unique porous structure, conductive carbon network, and the synergetic effect of Zn²⁺ and Mn²⁺ in electrolyte, the MnO_x@N‐C shows excellent cycling stability, good rate performance, and high reversibility for aqueous ZIBs. Specifically, it exhibits high capacity of 305 mAh g^?1 after 600 cycles at 500 mA g^?1 and maintains achievable capacity of 100 mAh g^?1 at a quite high rate of 2000 mA g^?1 with long‐term cycling of up to 1600 cycles, which are superior to most reported ZIB cathode materials. Furthermore, insight into the Zn‐storage mechanism in MnO_x@N‐C is systematically studied and discussed via multiple analytical methods. This study opens new opportunities for designing low‐cost and high‐performance rechargeable aqueous ZIBs.     

Insight of a Phase Compatible Surface Coating for Long‐Durable Li‐Rich Layered Oxide Cathode

Li‐rich layered oxides (LLOs) can deliver almost double the capacity of conventional electrode materials such as LiCoO₂ and LiMn₂O₄; however, voltage fade and capacity degradation are major obstacles to the practical implementation of LLOs in high‐energy lithium‐ion batteries. Herein, hexagonal La_0.8Sr_0.2MnO_3?y (LSM) is used as a protective and phase‐compatible surface layer to stabilize the Li‐rich layered Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ (LM) cathode material. The LSM is Mn? O? M bonded at the LSM/LM interface and functions by preventing the migration of metal ions in the LM associated with capacity degradation as well as enhancing the electrical transfer and ionic conductivity at the interface. The LSM‐coated LM delivers an enhanced reversible capacity of 202 mAh g^?1 at 1 C (260 mA g^?1) with excellent cycling stability and rate capability (94% capacity retention after 200 cycles and 144 mAh g^?1 at 5 C). This work demonstrates that interfacial bonding between coating and bulk material is a successful strategy for the modification of LLO electrodes for the next‐generation of high‐energy Li‐ion batteries.     

High‐Performance Fiber‐Shaped All‐Solid‐State Asymmetric Supercapacitors Based on Ultrathin MnO2 Nanosheet/Carbon Fiber Cathodes for Wearable Electronics

Flexible fiber‐shaped supercapacitors have shown great potential in portable and wearable electronics. However, small specific capacitance and low operating voltage limit the practical application of fiber‐shaped supercapacitors in high energy density devices. Herein, direct growth of ultrathin MnO₂ nanosheet arrays on conductive carbon fibers with robust adhesion is exhibited, which exhibit a high specific capacitance of 634.5 F g^?1 at a current density of 2.5 A g^?1 and possess superior cycle stability. When MnO₂ nanosheet arrays on carbon fibers and graphene on carbon fibers are used as a positive electrode and a negative electrode, respectively, in an all‐solid‐state asymmetric supercapacitor (ASC), the ASC displays a high specific capacitance of 87.1 F g^?1 and an exceptional energy density of 27.2 Wh kg^?1. In addition, its capacitance retention reaches 95.2% over 3000 cycles, representing the excellent cyclic ability. The flexibility and mechanical stability of these ASCs are highlighted by the negligible degradation of their electrochemical performance even under severely bending states. Impressively, as‐prepared fiber‐shaped ASCs could successfully power a photodetector based on CdS nanowires without applying any external bias voltage. The excellent performance of all‐solid‐state ASCs opens up new opportunity for development of wearable and self‐powered nanodevices in near future.     

Anatase TiO2 Confined in Carbon Nanopores for High‐Energy Li‐Ion Hybrid Supercapacitors Operating at High Rates and Subzero Temperatures

Li‐ion hybrid supercapacitors (Li‐HSCs) hold great promise in future electrical energy storage due to their relatively high power and energy density. However, a major challenge lies in the slow kinetics of Li‐ion intercalation/extraction within metal‐oxide electrodes. Here, it is shown that ultrafast charge storage is realized by confining anatase TiO₂ nanoparticles in carbon nanopores to enable a high‐rate anode for Li‐HSCs. The porous carbon with interconnected pore walls and open channels not only works as a conductive host to protect TiO₂ from structural degradation but also provides fast pathways for ion/electron transport. As a result, the assembled cells exhibit remarkable rate capabilities with a specific capacity of ≈140 mAh g^?1 at a slow charge and ≈60 mAh g^?1 at a 3.5 s fast charge. While the charge/discharge process can be completed as fast as that of state‐of‐the‐art electrical double‐layer capacitors (EDLCs), the produced nanocomposites show three to seven times higher volumetric capacitance than activated carbons used in commercial EDLCs with acetonitrile‐based electrolytes. Equally important for some applications in cold climates or the space, the Li‐HSCs can operate at subzero temperatures as low as ?40 °C, which is likely only limited by thermal properties of the acetonitrile (melting point of ?45 °C).     

Porosity‐Controlled TiNb2O7 Microspheres with Partial Nitridation as A Practical Negative Electrode for High‐Power Lithium‐Ion Batteries

Titanium niobium oxide (TiNb₂O₇) has been recognized as a promising anode material for lithium‐ion batteries (LIBs) in view of its potential to operate at high rates with improved safety and high theoretical capacity of 387 mAh g^?1. However, it suffers from poor Li⁺ ion diffusivity and low electronic conductivity originated from its wide band gap energy (E_g > 2 eV). Here, porous TiNb₂O₇ microspheres (PTNO MSs) are prepared via a facile solvothermal reaction. PTNO MSs have a particle size of ≈1.2 μm and controllable pore sizes in the range of 5–35 nm. Ammonia gas nitridation treatment is conducted on PTNO MSs to introduce conducting Ti_1?xNb_xN layer on the surface and form nitridated PTNO (NPTNO) MSs. The porous structure and conducting Ti_1?xNb_xN layer enhance the transport kinetics associated with Li⁺ ions and electrons, which leads to significant improvement in electrochemical performance. As a result, the NPTNO electrode shows a high discharge capacity of ≈265 mAh g^?1, remarkable rate capability (≈143 mAh g^?1 at 100 C) and durable long‐term cyclability (≈91% capacity retention over 1000 cycles at 5 C). These results demonstrate the great potential of TiNb₂O₇ as a practical high‐rate anode material for LIBs.     

Optimization of Carbon‐ and Binder‐Free Au Nanoparticle‐Coated Ni Nanowire Electrodes for Lithium‐Oxygen Batteries

A Au nanoparticle‐coated Ni nanowire substrate without binder or carbon is used as the electrode (denoted as the Au/Ni electrode) for Li‐oxygen (Li‐O₂) batteries. A minimal amount of Au nanoparticles with sizes of <30 nm on a Ni nanowire substrate are coated using a simple electrodeposition method to the extent that maximum capacity can be utilized. This optimized, one body, Au/Ni electrode shows high capacities of 921 mAh g^?1_Au, 591 mAh g^?1_Au, and 359 mAh g^?1_Au, which are obtained at currents of 300 mAg^?1_Au, 500 mAg^?1_Au, and 1000 mAg^?1_Au respectively. More importantly, the Au/Ni electrode exhibits excellent cycle stability over 200 cycles.     

Mesoporous TiO2‐Sn/C Core‐Shell Nanowire Arrays as High‐Performance 3D Anodes for Li‐Ion Batteries

Three‐dimensional mesoporous TiO₂‐Sn/C core‐shell nanowire arrays are prepared on Ti foil as anodes for lithium‐ion batteries. Sn formed by a reduction of SnO₂ is encapsulated into TiO₂ nanowires and the carbon layer is coated onto it. For additive‐free, self‐supported anodes in Li‐ion batteries, this unique core‐shell composite structure can effectively buffer the volume change, suppress cracking, and improve the conductivity of the electrode during the discharge‐charge process, thus resulting in superior rate capability and excellent long‐term cycling stability. Specifically, the TiO₂‐Sn/C nanowire arrays display rechargeable discharge capacities of 769, 663, 365, 193, and 90 mA h g^?1 at 0.1C, 0.5C, 2C 10C, and 30C, respectively (1C = 335 mA g^?1). Furthermore, the TiO₂‐Sn/C nanowire arrays exhibit a capacity retention rate of 84.8% with a discharge capacity of over 160 mA h g^?1, even after 100 cycles at a high current rate of 10C.     

Controlled Oxygen Redox for Excellent Power Capability in Layered Sodium‐Based Compounds

A high‐rate of oxygen redox assisted by cobalt in layered sodium‐based compounds is achieved. The rationally designed Na_0.6[Mg_0.2Mn_0.6Co_0.2]O₂ exhibits outstanding electrode performance, delivering a discharge capacity of 214 mAh g^?1 (26 mA g^?1) with capacity retention of 87% after 100 cycles. High rate performance is also achieved at 7C (1.82 A g^?1) with a capacity of 107 mAh g^?1. Surprisingly, the Na_0.6[Mg_0.2Mn_0.6Co_0.2]O₂ compound is able to deliver capacity for 1000 cycles at 5C (at 1.3 A g^?1), retaining 72% of its initial capacity of 108 mAh g^?1. X‐ray absorption spectroscopy analysis of the O K‐edge indicates the oxygen‐redox species (O^2?/1?) is active during cycling. First‐principles calculations show that the addition of Co reduces the bandgap energy from ≈2.65 to ≈0.61 eV and that overlapping of the Co 3d and O 2p orbitals facilitates facile electron transfer, enabling the long‐term reversibility of the oxygen redox, even at high rates. To the best of the authors' knowledge, this is the first report on high‐rate oxygen redox in sodium‐based cathode materials, and it is believed that the findings will open a new pathway for the use of oxygen‐redox‐based materials for sodium‐ion batteries.     

Li+ Pre‐Insertion Leads to Formation of Solid Electrolyte Interface on TiO2 Nanotubes That Enables High‐Performance Anodes for Sodium Ion Batteries

Recently, sodium ion batteries (SIBs) have been widely investigated as one of the most promising candidates for replacing lithium ion batteries (LIBs). For SIBs or LIBs, designing a stable and uniform solid electrolyte interphase (SEI) at the electrode–electrolyte interface is the key factor to provide high capacity, long‐term cycling, and high‐rate performance. In this paper, it is described how a remarkably enhanced SEI layer can be obtained on TiO₂ nanotube (TiO₂ NTs) arrays that allows for a strongly improved performance of sodium battery systems. Key is that a Li⁺ pre‐insertion in TiO₂ NTs can condition the SEI for Na⁺ replacement. SIBs constructed with Li‐pre‐inserted NTs deliver an exceptional Na⁺ cycling stability (e.g., 99.9 ± 0.1% capacity retention during 250 cycles at a current rate of 50 mA g^?1) and an excellent rate capability (e.g., 132 mA h g^?1 at a current rate of 1 A g^?1). The key factor in this outstanding performance is that Li‐pre‐insertion into TiO₂ NTs leads not only to an enhanced electronic conductivity in the tubes, but also expands the anatase lattice for facilitated subsequent Na⁺ cycling.     

Integrating Band Structure Engineering with All‐Scale Hierarchical Structuring for High Thermoelectric Performance in PbTe System

PbTe_1?x Se_x ‐2%Na‐y%SrTe system is investigated and a high maximum ZT of 2.3 at 923 K for PbTe_0.85Se_0.15‐2%Na‐4%SrTe is reported. This is achieved by performing electronic band structures modifications as well as all‐scale hierarchical structuring and combining the two effects. It is found that high ZTs in PbTe_0.85Se_0.15‐2%Na‐4%SrTe are possible at all temperature from 300 to 873 K with an average ZT_ave of 1.23. The high performance in PbTe_1?x Se_x ‐2%Na‐y%SrTe can be achieved by either choosing PbTe‐2Na‐4SrTe or PbTe_0.85Se_0.15‐2Na as a matrix. At room temperature the carrier mobility shows negligible variations as SrTe fraction is increased, however the lattice thermal conductivity is significantly reduced from ≈1.1 to ≈0.82 W m^?1 K^?1 when 5.0% SrTe is added, correspondingly, the lattice thermal conductivity at 923 K decreases from ≈0.59 to ≈0.43 W m?¹ K^?1. The power factor maxima of PbTe_1?x Se_x ‐2Na‐4SrTe shift systematically to higher temperature with rising Se fractions due to bands divergence. The maximum power factors reach ≈27, ≈30, ≈31 μW cm^?1 K^?2 for the x = 0, 0.05, and 0.15 samples peak at 473, 573, and 623 K, respectively. The results indicate that ZT can be increased by synergistic integration of band structure engineering and all‐scale hierarchical architectures.