Fabrication and Electrochemical Properties of Epitaxial Samarium‐Doped Ceria Films on SrTiO3‐Buffered MgO Substrates

Thin films of samarium‐oxide‐doped (20 mol%) ceria (SDC) are grown by pulsed‐laser deposition (PLD) on (001) MgO single‐crystal substrates. SrTiO₃ (STO) prepared by PLD is used as a buffer layer on the MgO substrates to enable epitaxial growth of the fluorite‐structured SDC film; the STO layer provides a proper crystalline match between SDC and MgO, resulting in highly crystalline, epitaxial SDC films grown in the (001) orientation. Film conductivity is evaluated by electrochemical impedance spectroscopy measurements, which are performed at various temperatures (400–775 °C) in a wide range of oxygen partial pressure (pO₂) values (10^?25?1 atm) in order to separate ionic and electronic conductivity contributions. At 700 °C, SDC/STO films on (100) MgO exhibit a dominant ionic conductivity of about 7 × 10^?2 S cm^?1, down to pO₂ values of about 10^?15 atm. The absence of grain boundaries make the SDC/STO/MgO heterostructures stable to oxidation‐reduction cycles at high temperatures, in contrast to that observed for the more disordered SDC/STO films, which degraded after hydrogen exposure.     

Dynamic Current–Voltage Analysis of Oxygen Vacancy Mobility in Praseodymium‐Doped Ceria over Wide Temperature Limits

Solid‐state mixed ionic–electronic conductors (MIECs) in which ionic transport is commonly accompanied by predominant electronic conductivity underpin key technologies and require universal characterization methods for monitoring transport at the nanoscale, at both high and near ambient temperatures, the latter being especially challenging. In this study, a novel dynamic current–voltage analysis technique is utilized to decouple ionic and electronic transport properties from each other. The versatility of the method is demonstrated by enabling measurement of the oxygen vacancy mobility in Pr_0.1Ce_0.9O_2?δ thin films, across an unusually wide temperature range, from 35 to 500 °C. Despite the presence of predominant electronic conduction, the oxygen vacancy mobility in Pr_0.1Ce_0.9O_2?δ is measured, being 6.8 × 10^?6 cm² V^?1 s^?1 at 500 °C, decreasing by seven orders of magnitude down to 35 °C, and following a single thermal activation energy of 0.82 ± 0.02 eV. A comparison with previous reports on oxygen vacancy transport and with the one derived in this study from impedance spectroscopy, interpreted with the Jamnik–Maier model, further confirms the dynamic current–voltage analysis results. This method can more generally be applied to other types of MIECs, thereby enabling deeper insights into mobile ionic defect transport and accompanying thermodynamic properties.     

Imidazolium Polyesters: Structure–Property Relationships in Thermal Behavior,Ionic Conductivity,and Morphology

New bis(ω‐hydroxyalkyl)imidazolium and 1,2‐bis[N‐(ω‐hydroxyalkyl)imidazolium]ethane salts are synthesized and characterized; most of the salts are room temperature ionic liquids. These hydroxyl end‐functionalized ionic liquids are polymerized with diacid chlorides, yielding polyesters containing imidazolium cations embedded in the main chain. By X‐ray scattering, four polyesters are found to be semicrystalline at room temperature: mono‐imidazolium‐C₁₁‐sebacate‐C₆ ( 4e ), mono‐imidazolium‐C₁₁‐sebacate‐C₁₁ ( 4c ), bis(imidazolium)ethane‐C₆‐sebacate‐C₆ ( 5a ), and bis(imidazolium)ethane‐C₁₁‐sebacate‐C₁₁ ( 5c ), all with hexafluorophosphate counterions. The other imidazolium polyesters, including all those with bis(trifluoromethanesulfonyl)imide (TFSI^?) counterions, are amorphous at room temperature. Room temperature ionic conductivities of the mono‐imidazolium polyesters (4 × 10^?6 to 3 × 10^?5 S cm^?1) are higher than those of the corresponding bis‐imidazolium polyesters (4 × 10^?9 to 8 × 10^?6 S cm^?1), even though the bis‐imidazolium polyesters have higher ion concentrations. Counterions affect ionic conduction significantly; all polymers with TFSI^? counterions have higher ionic conductivities than the hexafluorophosphate analogs. Interestingly, the hexafluorophosphate polyester, 1,2‐bis(imidazolium)ethane‐C₁₁‐sebacate‐C₁₁ ( 5c ), displays almost 400‐fold higher room temperature ionic conductivity (1.6 × 10^?6 S cm^?1) than the 1,2‐bis(imidazolium)ethane‐C₆‐sebacate‐C₆ analog ( 5a , 4.3 × 10^?9 S cm^?1), attributable to the differences in the semicrystalline structure in 5c as compared to 5a . These results indicate that semicrystalline polymers may result in high ionic conductivity in a soft (low glass tranition temperature, T_g) amorphous phase and good mechanical properties of the crystalline phase.     

A Li–Al–O Solid‐State Electrolyte with High Ionic Conductivity and Good Capability to Protect Li Anode

Using a solid‐state electrolyte (SSE) to stabilize the Li metal anode is widely considered a promising route to develop next‐generation high energy density lithium batteries. Here, a new polycrystalline aluminate‐based SSE (named Li–Al–O SSE) with good capability is introduced to protect Li metal. The SSE is formed on the Li metal surface via a chemical reaction between LiOH and triethylaluminum (TEAL) with the existence of LiTFSI‐based electrolyte. It is a continuous film that consists of polycrystalline LiAlO₂, Li₃AlO₃, Al₂O₃, Li₂CO₃, LiF, and some organic compounds. Such Li–Al–O SSE possesses a room‐temperature ionic conductivity as high as 1.42 × 10^?4 S cm^?1. Meanwhile, it effectively protects the Li anode from the corrosion of H₂O, O₂, and organic solvent, and suppresses the growth of Li dendrite. With the protection of the Li–Al–O SSE, the cycle life of Li|Li symmetric cell and Li|O₂ cell is substantially elongated, indicating that the SSE exhibits an excellent protective effect under both inert and oxidizing circumstances.     

Mixed Electronic and Ionic Conduction Properties of Lithium Lanthanum Titanate

With the continued increase in Li‐metal anode rate capability, there is an equally important need to develop high‐rate cathode architectures for solid‐state batteries. A proposed method of improving charge transport in the cathode is introducing a mixed electronic and ionic conductor (MEIC) which can eliminate the need for conductive additives that occlude electrolyte–electrode interfaces and lower the net additive required in the cathode. This study takes advantage of a reduced perovskite electrolyte, Li_0.33La_0.57TiO₃ (LLTO), to act as a model MEIC. It is found that the ionic conductivity of reduced LLTO is comparable to oxidized LLTO (σ_bulk = 10^?3–10^?4 S cm^?1, σ_GB = 10^?5–10^?6 S cm^?1) and the electronic conductivity is 1 mS cm^?1. The ionic transference numbers are 0.9995 and 0.0095 in the oxidized and reduced state, respectively. Furthermore, two methods for controlling the transference numbers are evaluated. It is found that the electronic conductivity cannot easily be controlled by changing O₂ overpressures, but increasing the ionic conductivity can be achieved by increasing grain size. This work identifies a possible class of MEIC materials that may improve rate capabilities of cathodes in solid‐state architectures and motivate a deeper understanding of MEICs in the context of solid‐state batteries.     

Associating and Tuning Sodium and Oxygen Mixed‐Ion Conduction in Niobium‐Based Perovskites

Pure ionic conductors as solid‐state electrolytes are of high interest in electrochemical energy storage and conversion devices. They systematically involve only one ion as the charge carrier. The association of two mobile ionic species, one positively and the other negatively charged, in a specific network should strongly influence the total ion conduction. Nb⁵⁺‐ (4d⁰) and Ti⁴⁺‐based (3d⁰) derived‐perovskite frameworks containing Na⁺ and O^2? as mobile species are investigated as mixed ion conductors by electrochemical impedance spectroscopy. The design of Na⁺ blocking layers via sandwiched pellet sintered by spark plasma sintering at high temperatures leads to quantified transport number of both ionic charge carriers t_Na+ and t_O2?. In the 350–700 °C temperature range, ionic conductivity can be tuned from major Na⁺ contribution (t_Na+ = 88%) for NaNbO₃ to pure O^2? transport in NaNb_0.9Ti_0.1O_2.95 phase. Such a Ti‐substitution is accompanied with a ≈100‐fold increase in the oxygen conductivity, approaching the best values for pure oxygen conductors in this temperature range. Besides the demonstration of tunable mixed ion conduction with quantifiable cationic and anionic contributions in a single solid‐state structure, a strategy is established from structural analysis to develop other architectures with improved mixed ionic conductivity.     

Li6ALa2Ta2O12 (A = Sr, Ba): Novel Garnet‐Like Oxides for Fast Lithium Ion Conduction

Oxides with the nominal chemical formula Li₆ALa₂Ta₂O₁₂ (A = Sr, Ba) have been prepared via a solid‐state reaction in air using high purity La₂O₃, LiOH·H₂O, Sr(NO₃)₂, Ba(NO₃)₂, and Ta₂O₅ and are characterized by powder X‐ray diffraction (XRD) in order to identify the phase formation and AC impedance to determine the lithium ion conductivity. The powder XRD data of Li₆ALa₂Ta₂O₁₂ show that they are isostructural with the parent garnet‐like compound Li₅La₃Ta₂O₁₂. The cubic lattice parameter was found to increase with increasing ionic size of the alkaline earth ions (Li₆SrLa₂Ta₂O₁₂: 12.808(2) Å; Li₆BaLa₂Ta₂O₁₂: 12.946(3) Å). AC impedance results show that both the strontium and barium members exhibit mainly a bulk contribution with a rather small grain‐boundary contribution. The ionic conductivity increases with increasing ionic radius of the alkaline earth elements. The barium compound, Li₆BaLa₂Ta₂O₁₂, shows the highest ionic conductivity, 4.0×10^–5 S cm^–1 at 22 °C with an activation energy of 0.40 eV, which is comparable to other lithium ion conductors, especially with the presently employed solid electrolyte lithium phosphorus oxynitride (Lipon) for all‐solid‐state lithium ion batteries. DC electrical measurements using lithium‐ion‐blocking and reversible electrodes revealed that the electronic conductivity is very small, and a high electrochemical stability (> 6 V/Li) was exhibited at room temperature. Interestingly, Li₆ALa₂Ta₂O₁₂ was found to be chemically stable with molten metallic lithium.     

Extremely High Silver Ionic Conductivity in Composites of Silver Halide (AgBr,AgI) and Mesoporous Alumina

The silver ionic conductivity in heterogeneous systems of AgBr:Al₂O₃ and AgI:Al₂O₃ is highly enhanced by utilizing mesoporous Al₂O₃ as the insulating phase. The highest Ag⁺ conductivity of 3.1 × 10^–3 Ω^–1 cm^–1 (at 25 °C) has been obtained for the AgI:Al₂O₃ composite with an Al₂O₃ volume fraction of 0.3. For AgBr:Al₂O₃, the enhancement of the conductivity is satisfactorily explained in the framework of the ideal space‐charge model, while in the case of AgI:Al₂O₃ stacking disorder is also considered to contribute to the ionic conductivity.     

Polymer Light‐Emitting Electrochemical Cells: Doping Concentration,Emission‐Zone Position,and Turn‐On Time

Direct optical probing of the doping progression and simultaneous recording of the current–time behavior allows the establishment of the position of the light‐emitting p–n junction, the doping concentrations in the p‐ and n‐type regions, and the turn‐on time for a number of planar light‐emitting electrochemical cells (LECs) with a 1 mm interelectrode gap. The position of the p–n junction in such LECs with Au electrodes contacting an active material mixture of poly(2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylene vinylene) (MEH‐PPV), poly(ethylene oxide), and a XCF₃SO₃ salt (X = Li, K, Rb) is dependent on the salt selection: for X = Li the p–n junction is positioned very close to the negative electrode, while for X = K, Rb it is significantly more centered in the interelectrode gap. Its is demonstrated that this results from that the p‐type doping concentration is independent of salt selection at ca. 2 × 10²⁰ cm^–3 (ca. 0.1 dopants/MEH‐PPV repeat unit), while the n‐type doping concentration exhibits a strong dependence: for X = K it is ca. 5 × 10²⁰ cm^–3 (ca. 0.2 dopants/repeat unit), for X = Rb it is ca. 9 × 10²⁰ cm^–3 (ca. 0.4 dopants/repeat unit), and for X = Li it is ca. 3 × 10²¹ cm^–3 (ca. 1 dopants/repeat unit). Finally, it is shown that X = K, Rb devices exhibit significantly faster turn‐on times than X = Li devices, which is a consequence of a higher ionic conductivity in the former devices.     

Enhanced Ionic Conductivity in Ce0.8Sm0.2O1.9: Unique Effect of Calcium Co‐doping

In order to identify new oxide ion‐conducting materials in the ceria family of oxides, the unique effect of co‐doping is explored and a novel series of Ce_0.8Sm_0.2–xCa_xO_2–δ compositions is identified that have enhanced properties compared to the single‐doped Ce_0.8Sm_0.2O_1.9 and Ce_0.8Ca_0.2O_1.9 compositions. Moreover, the superior characteristics of the co‐doped Ce_0.8Sm_0.2–xCa_xO_2–δ powders prepared by the mixed‐fuel process aid in obtaining 98 % dense ceramics upon sintering at 1200 °C for 6 h. Though a linear increase in conductivity is observed by replacing Sm with Ca, the composition with the maximum amount of Ca and the minimum amount of Sm exhibits a significant improvement in properties compared to the rest in the series. The composition Ce_0.80Sm_0.05Ca_0.15O_2–δ exhibits a conductivity as high as 1.22 × 10^–1 S cm^–1 at 700 °C with minimum activation energy (0.56 eV) and a superior chemical stability to reduction compared to any of the hitherto known (CaSm) compositions. The absence of Ce^III, confirmed both from X‐ray photoelectron spectroscopy and X‐ray absorption spectroscopy, strongly suggests that the observed increase in conductivity is solely due to the oxide ion conductivity and not due to the partial electronic contribution arising from the presence of Ce^III and Ce^IV. To conclude, the experimental results on the Ce_0.8Sm_0.2–xCa_xO_2–δ series underscore the unique effect of calcium co‐doping in identifying a cost‐effective new composition, with a remarkably high conductivity and enhanced chemical stability to reduction, for technological applications.     

Light‐Induced Swelling‐Responsive Conductive,Adhesive, and Stretchable Wireless Film Hydrogel as Electronic Artificial Skin

Light‐induced wireless soft electronic skin hydrogels with excellent mechanical and electronic properties are important for several applications, such as soft robotics and intelligent wearable devices. Precise control of reversible stretchability and capacitive properties depending on intermolecular interaction and surface characteristics remains a challenge. Here, a thin‐film hydrogel is designed based on titanium oxide (TiO₂) polydopamine–perfluorosilica carbon dot‐conjugated chitosan–polyvinyl alcohol‐loaded tannic acid with controllable hydrophobic–hydrophilic transition in the presence of UV–vis light irradiation. The shifting of surface wettability from hydrophobic to hydrophilic by irradiation affects thin‐film water permeability and swelling ratio. This allows the penetration of water into the matrix to change its mechanical strength, electronic properties, and adhesive behavior. Specifically, the hydrogel displays mechanical strain as high as 278% in response to light stimuli and demonstrates the ability to regain its initial state determining the elasticity of the fabricated material. Moreover, the thin‐film hydrogel shows an increase in conductivity to 1.096 × 10^?3 and 1.026 × 10^?3 S cm^?1 when irradiated with UV and visible light, respectively. The hydrogel exhibits capacitive reversibility that follows finger motion which can be identified directly or remotely using wireless connection, indicative of its possible applications as an artificial electronic skin.     

The Formation of Performance Enhancing Pseudo‐Composites in the Highly Active La1–xCaxFe0.8Ni0.2O3 System for IT‐SOFC Application

The La_1–xCa_xFe_0.8Ni_0.2O_3–δ (0 ≤ x ≤ 0.9) system is investigated for potential application as a cathode material for intermediate temperature solid oxide fuel cells (IT‐SOFCs). A broad range of experimental techniques have been utilized in order to elucidate the characteristics of the entire compositional range. Low A‐site Ca content compositions (x ≤ 0.4) feature a single perovskite solid solution. Compositions with 40% Ca content (x = 0.4) exhibit the highest electrical and ionic conductivities of these single phase materials (250 and 1.9 × 10^?3 S cm^?1 at 800 °C, respectively), a level competitive with state‐of‐the‐art (La,Sr)(Fe,Co)O₃. Between 40 and 50% Ca content (0.4 > x > 0.5) a solubility limit is reached and a secondary, brownmillerite‐type phase appears for all higher Ca content compositions (0.5 ≤ x ≤ 0.9). While typically seen as detrimental to electrochemical performance in cathode materials, this phase brings with it ionic conductivity at operational temperatures. This gives rise to the effective formation of pseudo‐composite materials which feature significantly enhanced performance characteristics, while also providing the closest match in thermal expansion behavior to typical electrolyte materials. This all comes with the advantage of being produced through a simple, single‐step, low‐cost production route without the issues associated with typical composite materials. The highest performing pseudo‐composite material (x = 0.5) exhibits electronic conductivity of 300–350 S cm^?1 in the 600–800 °C temperature range while the best polarisation resistance (R_p) values of approximately 0.2 Ω cm² are found in the 0.5 ≤ x ≤ 0.7 range.     

Tough,Semiconducting Polyethylene‐poly(3‐hexylthiophene) Diblock Copolymers

Semiconducting diblock copolymers of polyethylene (PE) and regioregular poly(3‐hexylthiophene) (P3HT) are demonstrated to exhibit a rich phase behaviour, judicious use of which permitted us to fabricate field‐effect transistors that show saturated charge carrier mobilities, μ_FET, as high as 2 × 10^–2 cm² V^–1 s^–1 and ON‐OFF ratios, I_on/I_off ～ 10⁵ at contents of the insulating PE moiety as high as 90 wt %. In addition, the diblock copolymers display outstanding flexibility and toughness with elongations at break exceeding 600 % and true tensile strengths around 70 MPa, opening the path towards robust and truly flexible electronic components.     

Thiophene–Benzothiadiazole Co‐Oligomers: Synthesis,Optoelectronic Properties,Electrical Characterization,and Thin‐Film Patterning

Newly synthesized thiophene (T) and benzothiadiazole (B) co‐oligomers of different size, alternation motifs, and alkyl substitution types are reported. Combined spectroscopic data, electrochemical analysis, and theoretical calculations show that the insertion of a single electron‐deficient B unit into the aromatic backbone strongly affects the LUMO energy level. The insertion of additional B units has only a minor effect on the electronic properties. Cast films of oligomers with two alternated B rings (B–T–B inner core) display crystalline order. Bottom‐contact FETs based on films cast on bare SiO₂ show hole‐charge mobilities of 1 × 10^?3–5 × 10^?3 cm² V^?1s^?1 and I_on/I_off ratios of 10⁵–10⁶. Solution‐cast films of cyclohexyl‐substituted compounds are amorphous and do not show FET behavior. However, the lack of order observed in these films can be overcome by nanorubbing and unconventional wet lithography, which allow for fine control of structural order in thin deposits.     

Thin Films of Insoluble Poly(Oligothienylene vinylenes) Prepared by Chemical Vapor Deposition Polymerization

A series of poly(oligothienylene vinylenes) (PT_mVs, m = 2–4) with a varying number of consecutively bound thienylene rings are successfully prepared in thin films by chemical vapor deposition polymerization (CVDP) using the corresponding bis(halomethyl)thiophenes as starting materials. The chemical and electronic structures are studied spectroscopically and also by cyclic voltammetry. Top‐gate field‐effect transistors are fabricated by two consecutive CVDP cycles of PT_mV and poly(p‐xylylene) followed by the deposition of a Au gate electrode. In the case of a PT₃V active layer, a field‐effect mobility value of 0.5 × 10^–4 cm² V^–1 s^–1 is obtained.     

High‐Performance Solid Polymer Electrolytes Filled with Vertically Aligned 2D Materials

Solid state lithium metal batteries are the most promising next‐generation power sources owing to their high energy density and safety. Solid polymer electrolytes (SPE) have gained wide attention due to the excellent flexibility, manufacturability, lightweight, and low‐cost processing. However, fatal drawbacks of the SPE such as the insufficient ionic conductivity and Li⁺ transference number at room temperature restrict their practical application. Here vertically aligned 2D sheets are demonstrated as an advanced filler for SPE with enhanced ionic conductivity, Li⁺ transference number, mechanical modulus, and electrochemical stability, using vermiculite nanosheets as an example. The vertically aligned vermiculite sheets (VAVS), prepared by the temperature gradient freezing, provide aligned, continuous, run‐through polymer‐filler interfaces after infiltrating with polyethylene oxide (PEO)‐based SPE. As a result, ionic conductivity as high as 1.89 × 10^?4 S cm^?1 at 25 °C is achieved with Li⁺ transference number close to 0.5. Along with their enhanced mechanical strength, Li|Li symmetric cells using VAVS–CSPE are stable over 1300 h with a low overpotential. LiFePO₄ in all‐solid‐state lithium metal batteries with VAVS–CSPE could deliver a specific capacity of 167 mAh g^?1 at 0.1 C at 35 °C and 82% capacity retention after 200 cycles at 0.5 C.     

Constructing Electronic and Ionic Dual Conductive Polymeric Interface in the Cathode for High-Energy-Density Solid-State Batteries

Solid–solid interfaces in the composite cathode for solid-state batteries face the thorny issues of poor physical contact, chemical side reaction, temporal separation, and sluggish Li⁺/e⁻ transfer. Developing key material to achieve the composite cathode with efficient solid–solid interfaces is critical to improving the coulombic efficiency, cycling life, and energy density of solid-state batteries. Herein, electronic and ionic dual conductive polymer (DCP) is prepared for the composite cathode via intermolecular interaction on the base of lithiated polyvinyl formal-derived Li⁺ single-ion conductor (LiPVFM), lithium difluoro(oxalato)borate (LiODFB), and electronic conducting polymer. Crosslinking, coordination, and hydrogen-bonding effect enable DCP with high electrical conductivity of 68.9 S cm⁻¹, Li⁺ ionic conductivity (2.76 × 10⁻⁴ S cm⁻¹), large electrochemical window above 6 V and a high modulus of 6.8 GPa. Besides, DCP can form a coating layer on the active material powders to maintain structural integrity via buffering the internal stress during lithiation/delithiation, meanwhile, to construct long- and short-range electronic/ionic conductive channel together with a small amount of CNTs. Rigid and flexible DCP-based composite cathode enables the excellent cycling of solid-state batteries with a high loading up to 11.7 mg cm⁻² and high content of active materials close to 90 wt% without current collector.     

Enhancing Ultrafast Lithium Ion Storage of Li4Ti5O12 by Tailored TiC/C Core/Shell Skeleton Plus Nitrogen Doping

It is of great importance to reinforce electronic and ionic conductivity of Li₄Ti₅O₁₂ electrodes to achieve fast reaction kinetics and good high‐power capability. Herein, for the first time, a dual strategy of combing N‐doped Li₄Ti₅O₁₂ (N‐LTO) with highly conductive TiC/C skeleton to realize enhanced ultrafast Li ion storage is reported. Interlinked hydrothermal‐synthesized N‐LTO nanosheets are homogeneously decorated on the chemical vapor deposition (CVD) derived TiC/C nanowires forming binder‐free N‐LTO@TiC/C core–branch arrays. Positive advantages including large surface area, strong mechanical stability, and enhanced electronic/ionic conductivity are obtained in the designed integrated arrays and rooted upon synergistic TiC/C matrix and N doping. The above appealing features can effectively boost kinetic properties throughout the N‐LTO@TiC/C electrodes to realize outstanding high‐rate capability at different working temperatures (143 mAh g^?1/10 C at 25 °C and 122 mAh g^?1/50 C at 50 °C) and notable cycling stability with a capacity retention of 99.3% after 10 000 cycles at 10 C. Moreover, superior high‐rate cycling life is also demonstrated for the full cells with N‐LTO@TiC/C anode and LiFePO₄ cathode. The dual strategy may provoke wide interests in fast energy storage areas and motivate the further performance improvement of power‐type lithium ion batteries (LIBs).     

Bilayered VOPO4⋅2H2O Nanosheets with High-Concentration Oxygen Vacancies for High-Performance Aqueous Zinc-Ion Batteries

2D materials with atomically precise thickness and tunable chemical composition hold promise for potential applications in nanoenergy. Herein, a bilayer-structured VOPO₄⋅2H₂O (bilayer-VOP) nanosheet is developed with high-concentration oxygen vacancies ([Vo˙˙]) via a facile liquid-exfoliation strategy. Galvanostatic intermittent titration technique study indicates a 6 orders of magnitude higher zinc-ion coefficient in bilayer-VOP nanosheets (4.6 × 10⁻⁷ cm⁻² s⁻¹) compared to the bulk counterpart. Assistant density functional theory (DFT) simulation indicates a remarkably enhanced electron conductivity with a reduced bandgap of ≈ 0.2 eV (bulk sample: 1.5 eV) along with an ultralow diffusion barrier of ≈ 0.08 eV (bulk sample: 0.13 eV) in bilayer-VOP nanosheets, thus leading to superior diffusion kinetics and electrochemical performance. Mott–Schottky (impedance potential) measurement also demonstrates a great increase in electronic conductivity with ≈ 57-fold increased carrier concentration owing to its high concentration [Vo˙˙]. Benefited by these unique features, the rechargeable zinc-ion battery composed of bilayer-VOP nanosheets cathode exhibits a remarkable capacity of 313.6 mAh g⁻¹ (0.1 A g⁻¹), an energy density of 301.4 Wh kg⁻¹, and a prominent rate capability (168.7 mAh g⁻¹ at 10 A g⁻¹).     

Intrinsically Low Thermal Conductivity in BiSbSe3: A Promising Thermoelectric Material with Multiple Conduction Bands

Bi₂Se₃, as a Te‐free alternative of room‐temperature state‐of‐the‐art thermoelectric (TE) Bi₂Te₃, has attracted little attention due to its poor electrical transport properties and high thermal conductivity. Interestingly, BiSbSe₃, a product of alloying 50% Sb on Bi sites, shows outstanding electron and phonon transports. BiSbSe₃ possesses orthorhombic structure and exhibits multiple conduction bands, which can be activated when the carrier density is increased as high as ≈3.7 × 10²⁰ cm^?3 through heavily Br doping, resulting in simultaneously enhancing the electrical conductivities and Seebeck coefficients. Meanwhile, an extremely low thermal conductivity (≈0.6–0.4 W m^?1 K^?1 at 300–800 K) is found in BiSbSe₃. Both first‐principles calculations and elastic properties measurements show the strong anharmonicity and support the ultra‐low thermal conductivity of BiSbSe₃. Finally, a maximum dimensionless figure of merit ZT ～ 1.4 at 800 K is achieved in BiSb(Se_0.94Br_0.06)₃, which is comparable to the most n‐type Te‐free TE materials. The present results indicate that BiSbSe₃ is a new and a robust candidate for TE power generation in medium‐temperature range.