High-Entropy Engineering of Cubic SiP with Metallic Conductivity for Fast and Durable Li-Ion Batteries.

A cost-effective, scalable ball milling process is employed to synthesize the InGeSiP3 compound with a cubic ZnS structure, aiming to address the sluggish reaction kinetics of Si-based anodes for Lithium-ion batteries. Experimental measurements and first-principles calculations confirm that the synthesized InGeSiP3 exhibits significantly higher electronic conductivity, larger Li-ion diffusivity, and greater tolerance to volume change than its parent phases InGe (or Si)P2 or In (or Ge, or Si)P. These improvements stem from its elevated configurational entropy. Multiple characterizations validate that InGeSiP3 undergoes a reversible Li-storage mechanism that involves intercalation, followed by conversion and alloy reactions, resulting in a reversible capacity of 1733 mA h g-1 with an initial Coulombic efficiency of 90%. Moreover, the InGeSiP3-based electrodes exhibit exceptional cycling stability, retaining an 1121 mA h g-1 capacity with a retention rate of ≈87% after 1500 cycles at 2000 mA g-1 and remarkable high-rate capability, achieving 882 mA h g-1 at 10 000 mA g-1. Inspired by the distinctive characteristic of high entropy, the synthesis is extended to high entropy GaCu (or Zn)InGeSiP5, CuZnInGeSiP5, GaCuZnInGeSiP6, InGeSiP2S (or Se), and InGeSiPSSe. This endeavor overcomes the immiscibility of different metals and non-metals, paving the way for the electrochemical energy storage application of high-entropy silicon-phosphides.

Atomic reconstruction for realizing stable solar-driven reversible hydrogen storage of magnesium hydride.

Reversible solid-state hydrogen storage of magnesium hydride, traditionally driven by external heating, is constrained by massive energy input and low systematic energy density. Herein, a single phase of Mg2Ni(Cu) alloy is designed via atomic reconstruction to achieve the ideal integration of photothermal and catalytic effects for stable solar-driven hydrogen storage of MgH2. With the intra/inter-band transitions of Mg2Ni(Cu) and its hydrogenated state, over 85% absorption in the entire spectrum is achieved, resulting in the temperature up to 261.8 °C under 2.6 W cm-2. Moreover, the hydrogen storage reaction of Mg2Ni(Cu) is thermodynamically and kinetically favored, and the imbalanced distribution of the light-induced hot electrons within CuNi and Mg2Ni(Cu) facilitates the weakening of Mg-H bonds of MgH2, enhancing the "hydrogen pump" effect of Mg2Ni(Cu)/Mg2Ni(Cu)H4. The reversible generation of Mg2Ni(Cu) upon repeated dehydrogenation process enables the continuous integration of photothermal and catalytic roles stably, ensuring the direct action of localized heat on the catalytic sites without any heat loss, thereby achieving a 6.1 wt.% H2 reversible capacity with 95% retention under 3.5 W cm-2.

Phase transitions associated with magnetic-field induced topological orbital momenta in a non-collinear antiferromagnet.

Resistivity measurements are widely exploited to uncover electronic excitations and phase transitions in metallic solids. While single crystals are preferably studied to explore crystalline anisotropies, these usually cancel out in polycrystalline materials. Here we show that in polycrystalline Mn3Zn0.5Ge0.5N with non-collinear antiferromagnetic order, changes in the diagonal and, rather unexpected, off-diagonal components of the resistivity tensor occur at low temperatures indicating subtle transitions between magnetic phases of different symmetry. This is supported by neutron scattering and explained within a phenomenological model which suggests that the phase transitions in magnetic field are associated with field induced topological orbital momenta. The fact that we observe transitions between spin phases in a polycrystal, where effects of crystalline anisotropy are cancelled suggests that they are only controlled by exchange interactions. The observation of an off-diagonal resistivity extends the possibilities for realising antiferromagnetic spintronics with polycrystalline materials.

Suppressing Surface Ligand-to-Metal Charge Transfer toward Stable High-Voltage LiCoO2.

Increasing the charging cutoff voltage is a viable approach to push the energy density limits of LiCoO2 and meet the requirements of the rapid development of 3C electronics. However, an irreversible oxygen redox is readily triggered by the high charging voltage, which severely restricts practical applications of high-voltage LiCoO2. In this study, we propose a modification strategy via suppressing surface ligand-to-metal charge transfer to inhibit the oxygen redox-induced structure instability. A d0 electronic structure Zr4+ is selected as the charge transfer insulator and successfully doped into the surface lattice of LiCoO2. Using a combination of theoretical calculations, ex situ X-ray absorption spectra, and in situ differential electrochemical mass spectrometry analysis, our results show that the modified LiCoO2 exhibits suppressed oxygen redox activity and stable redox electrochemistry. As a result, it demonstrates a robust long-cycle lattice structure with a practically eliminated voltage decay (0.17 mV/cycle) and an excellent capacity retention of 89.4% after 100 cycles at 4.6 V. More broadly, this work provides a new perspective on suppressing the oxygen redox activity through modulating surface ligand-to-metal charge transfer for achieving a stable high-voltage ion storage structure.

Thermally Induced Oxygen Vacancies and High Oxide Ion Conduction in K2ZnV2O7 with a Melilite-Related Structure.

Donor-doped melilite materials with interstitial oxygen defects in the structure are good oxide ion conductors with negligible electronic conduction and show great potential in the ceramic electrolyte of intermediate-temperature solid oxide fuel cells (IT-SOFC). However, the parent melilite-structured materials with stoichiometric oxygen are usually insulators. Herein, we reported high and pure oxide ion conduction in the parent K2ZnV2O7 material with a melilite-related structure, e.g., ∼1.14 × 10-3 S/cm at 600 °C, which is comparable to that of the state-of-the-art yttrial-stabilized ZrO2 applied in practical fuel cells. Neutron diffraction data revealed the interesting thermally induced formation of oxygen vacancies at elevated temperatures, which triggered the transformation of the material from electronically conducting to purely and highly oxide ion-conducting. The VO4 tetrahedron with non-bridging terminal oxygen in K2ZnV2O7 was proved to be the key structural factor for transporting oxygen vacancies. The molecular dynamic simulation based on the interatomic potential approach revealed that long-range oxide ion diffusion was achieved by breaking and re-forming the 5-fold MO4 (M = Zn and V) tetrahedral rings. These findings enriched our knowledge of melilite and melilite-related materials, and creating oxygen vacancies in a melilite-related material may be a new strategy for developing novel oxide ion conductors.

Tailoring Ion Ordering in Perovskite Oxide for High-Temperature Oxygen Evolution Reaction.

Perovskites exhibit excellent high-temperature oxygen evolution reaction (OER) activities as the anodes of solid oxide electrolysis cells (SOECs). However, the relationship between ion ordering and OER performances is rarely investigated. Herein, a series of PrBaCo2-x Fex O5+δ perovskites with tailored ion orderings are constructed. Physicochemical characterizations and density functional theory calculations confirm that the oxygen bulk migration and surface transport capacities as well as the OER activities are promoted by the A-site cation ordering, but weakened by the oxygen vacancy ordering. Hence, SOEC with the A-site-ordered and oxygen-vacancy-disordered PrBaCo2 O5+δ anode exhibits the highest performance of 3.40 A cm-2 at 800 °C and 2.0 V. This work sheds light on the critical role of ion orderings in the high-temperature OER performance and paves a new way for screening novel anode materials of SOECs.

Mixed electronic and oxide ionic conduction and migration mechanisms in digermanate La2-xCaxGe2O7-x/2.

Mixed electronic and oxide ionic conduction was enabled in digermanate-type La2-xCaxGe2O7-x/2 containing Ge3O10 chains and isolated GeO4 units by substitution of La3+ with Ca2+. The structure and solid solution limit of Ca doped La2Ge2O7 were studied by systematic experiments, including rotation electron diffraction (RED), X-ray diffraction (XRD) and neutron powder diffraction (NPD) experiments, etc. The preferred occupation of Ca2+ and oxygen vacancies was investigated by Rietveld analysis of the NPD data. The obtained conducting material La1.925Ca0.075Ge2O6.963 exhibits superior thermal stability and an order of magnitude improvement in conductivity compared to the parent La2Ge2O7 (∼9 × 10-5 S cm-1 at 1000 °C). BVEL calculations reveal that the oxygen vacancies were stabilized and transported within the framework of La2Ge2O7 by sharing oxygen and oxygen exchange between the adjacent Ge3O10 chains and GeO4 units, exhibiting a three-dimensional oxide ion transport nature.

Magnetic clusters and ferromagnetic spin glass in the novel hexagonal perovskite 12R-Ba4SbMn3O12.

A 12-layer hexagonal perovskite Ba4SbMn3O12 (space group: R3̄m; a = 5.72733(3) Å, and c = 28.1770(3) Å) has been synthesized by high-temperature solid-state reactions and studied using powder X-ray and neutron diffraction and magnetization measurements. This 12R polytype structure contains one corner-sharing (Sb, Mn)O6 octahedron and a trimer of face-sharing MnO6 octahedra per formula unit. Ba4SbMn3O12 displays a paramagnetic state of the Mn3 magnetic cluster at 100-200 K, which partially disassociates into individual Mn ions at 250-300 K. The ferromagnetic interaction between these Mn3 clusters is mainly mediated by Mn3+ at the M1 site, leading to dynamic ferromagnetic clusters below T D = ∼70 K and ferromagnetic spin freezing transition at T g = ∼11.5 K. The stability of Mn3 magnetic clusters in the 12R polytypes is related to the intracluster Mn-Mn distance.

Realizing High Capacity and Zero Strain in Layered Oxide Cathodes via Lithium Dual-Site Substitution for Sodium-Ion Batteries.

Sodium-ion batteries have garnered unprecedented attention as an electrochemical energy storage technology, but it remains challenging to design high-energy-density cathode materials with low structural strain during the dynamic (de)sodiation processes. Herein, we report a P2-layered lithium dual-site-substituted Na0.7Li0.03[Mg0.15Li0.07Mn0.75]O2 (NMLMO) cathode material, in which Li ions occupy both transition-metal (TM) and alkali-metal (AM) sites. The combination of theoretical calculations and experimental characterizations reveals that LiTM creates Na-O-Li electronic configurations to boost the capacity derived from the oxygen anionic redox, while LiAM serves as LiO6 prismatic pillars to stabilize the layered structure through suppressing the detrimental phase transitions. As a result, NMLMO delivers a high specific capacity of 266 mAh g-1 and simultaneously exhibits the nearly zero-strain characteristic within a wide voltage range of 1.5-4.6 V. Our findings highlight the effective way of dual-site substitution to break the capacity-stability trade-off in cathode materials for advanced rechargeable batteries.

The evolution of anionic nanoclusters at the electrode interface in water-in-salt electrolytes.

Water-in-salt electrolytes (WiSEs) have attracted extensive attention as promising alternatives to organic electrolytes. The limited electrochemical stability windows (ESWs) of aqueous electrolytes are significantly widened by WiSEs. However, the actual ESWs are lower than predicted as the interphase with WiSEs is not as stable as the solid electrolyte interphase (SEI) in conventional lithium-ion batteries. Therefore, identifying the interface state in WiSEs is vital to understanding their electrochemical behavior. Here, the structure of the lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) electrolyte near the interface of the carbon electrode (Ketjen black) was evaluated by experimental methods (neutron diffraction, Raman, and nuclear magnetic resonance spectroscopy) and molecular dynamics (MD) simulations. The results reveal that the introduction of carbon electrodes increases the size of the anionic nanoclusters and enhances the microphase separation at the interface. The MD simulations show that cation-π interactions are responsible for the evolution of anionic nanoclusters at the electrode interface. Moreover, lower charge transfer resistance is achieved at carbon-based electrodes due to the specific interface state. Our findings provide a strategy for introducing cation-π interactions between electrodes and electrolytes to improve the electrochemical performance.

Thermal batteries based on inverse barocaloric effects.

To harvest and reuse low-temperature waste heat, we propose and realize an emergent concept-barocaloric thermal batteries based on the large inverse barocaloric effect of ammonium thiocyanate (NH4SCN). Thermal charging is initialized upon pressurization through an order-to-disorder phase transition, and the discharging of 43 J g-1 takes place at depressurization, which is 11 times more than the input mechanical energy. The thermodynamic equilibrium nature of the pressure-restrained heat-carrying phase guarantees stable long-duration storage. The barocaloric thermal batteries reinforced by their solid microscopic mechanism are expected to substantially advance the ability to take advantage of waste heat.

Giant Exchange-Bias-Like Effect at Low Cooling Fields Induced by Pinned Magnetic Domains in Y2 NiIrO6 Double Perovskite.

Exchange bias (EB) is highly desirable for widespread technologies. Generally, conventional exchange-bias heterojunctions require excessively large cooling fields for sufficient bias fields, which are generated by pinned spins at the interface of ferromagnetic and antiferromagnetic layers. It is crucial for applicability to obtain considerable exchange-bias fields with minimum cooling fields. Here, an exchange-bias-like effect is reported in a double perovskite, Y2 NiIrO6 , which shows long-range ferrimagnetic ordering below 192 K. It displays a giant bias-like field of 1.1 T with a cooling field of only 15 Oe at 5 K. This robust phenomenon appears below 170 K. This fascinating bias-like effect is the secondary effect of the vertical shifts of the magnetic loops, which is attributed to the pinned magnetic domains due to the combination of strong spin-orbit coupling on Ir, and antiferromagnetically coupled Ni- and Ir-sublattices. The pinned moments in Y2 NiIrO6 are present throughout the full volume, not just at the interface as in conventional bilayer systems.

Regulating the Potential of Anion Redox to Reduce the Voltage Hysteresis of Li-Rich Cathode Materials.

Layered Li-rich oxides (LROs) that exhibit anionic and cationic redox are extensively studied due to their high energy storage capacities. However, voltage hysteresis, which reduces the energy conversion efficiency of the battery, is a critical limitation in the commercial application of LROs. Herein, using two Li2RuO3 (LRO) model materials with C2/c and P21/m symmetries, we explored the relationship between voltage hysteresis and the electronic structure of Li2RuO3 by neutron diffraction, in situ X-ray powder diffraction, X-ray absorption spectroscopy, macro magnetic study, and electron paramagnetic resonance (EPR) spectroscopy. The charge-transfer band gap of the LRO cathode material with isolated eg electron filling decreases, reducing the oxidation potential of anion redox and thus displaying a reduced voltage hysteresis. We further synthesized Mn-based Li-rich cathode materials with practical significance and different electron spin states. Low-spin Li1.15Ni0.377Mn0.473O2 with isolated eg electron filling exhibited a reduced voltage hysteresis and high energy conversion efficiency. We rationalized this finding via density functional theory calculations. This discovery should provide critical guidance in designing and preparing high-energy layered Li-rich cathode materials for use in next-generation high-energy-density Li-ion batteries based on anion redox activity.

A colossal barocaloric effect induced by the creation of a high-pressure phase.

As a promising environment-friendly alternative to current vapor-compression refrigeration, solid-state refrigeration based on the barocaloric effect has been attracting worldwide attention. Generally, both phases in which a barocaloric effect occurs are present at ambient pressure. Here, instead, we demonstrate that KPF6 exhibits a colossal barocaloric effect due to the creation of a high-pressure rhombohedral phase. The phase diagram is constructed based on pressure-dependent calorimetric, Raman scattering, and neutron diffraction measurements. The present study is expected to provide an alternative routine to colossal barocaloric effects through the creation of a high-pressure phase.

RuO2 electronic structure and lattice strain dual engineering for enhanced acidic oxygen evolution reaction performance.

Developing highly active and durable electrocatalysts for acidic oxygen evolution reaction remains a great challenge due to the sluggish kinetics of the four-electron transfer reaction and severe catalyst dissolution. Here we report an electrochemical lithium intercalation method to improve both the activity and stability of RuO2 for acidic oxygen evolution reaction. The lithium intercalates into the lattice interstices of RuO2, donates electrons and distorts the local structure. Therefore, the Ru valence state is lowered with formation of stable Li-O-Ru local structure, and the Ru-O covalency is weakened, which suppresses the dissolution of Ru, resulting in greatly enhanced durability. Meanwhile, the inherent lattice strain results in the surface structural distortion of LixRuO2 and activates the dangling O atom near the Ru active site as a proton acceptor, which stabilizes the OOH* and dramatically enhances the activity. This work provides an effective strategy to develop highly efficient catalyst towards water splitting.

Neutron powder-diffraction study of phase transitions in strontium-doped bismuth ferrite: 1. Variation with chemical composition.

We report results from a study of the crystal and magnetic structures of strontium-doped BiFeO3using neutron powder diffraction and the Rietveld method. Measurements were obtained over a wide range of temperatures from 300-800 K for compositions between 10%-16% replacement of bismuth by strontium. The results show a clear variation of the two main structural deformations-symmetry-breaking rotations of the FeO6octahedra and polar ionic displacements that give ferroelectricity-with chemical composition, but relatively little variation with temperature. On the other hand, the antiferromagnetic order shows a variation with temperature and a second-order phase transition consistent with the classical Heisenberg model. There is, however, very little variation in the behaviour of the antiferromagnetism with chemical composition, and hence with the degree of the structural symmetry-breaking distortions. We therefore conclude that there is no significant coupling between antiferromagnetism and ferroelectricity in Sr-doped BiFeO3and, by extension, in pure BiFeO3.

Defect engineering on V2O3 cathode for long-cycling aqueous zinc metal batteries.

Defect engineering is a strategy that is attracting widespread attention for the possibility of modifying battery active materials in order to improve the cycling stability of the electrodes. However, accurate investigation and quantification of the effect of the defects on the electrochemical energy storage performance of the cell are not trivial tasks. Herein, we report the quantification of vanadium-defective clusters (i.e., up to 5.7%) in the V2O3 lattice via neutron and X-ray powder diffraction measurements, positron annihilation lifetime spectroscopy, and synchrotron-based X-ray analysis. When the vanadium-defective V2O3 is employed as cathode active material in an aqueous Zn coin cell configuration, capacity retention of about 81% after 30,000 cycles at 5 A g-1 is achieved. Density functional theory calculations indicate that the vanadium-defective clusters can provide favorable sites for reversible Zn-ion storage. Moreover, the vanadium-defective clusters allow the storage of Zn ions in V2O3, which reduces the electrostatic interaction between the host material and the multivalent ions.

New insights into Li distribution in the superionic argyrodite Li6PS5Cl.

By using temperature-dependent neutron powder diffraction combined with maximum entropy method analysis, a previously unreported Li lattice site was discovered in the argyrodite Li6PS5Cl solid-state electrolyte. This new finding enables a more complete description of the Li diffusion model in argyrodites, providing structural guidance for designing novel high-conductivity solid-state electrolytes.

Topological Transformation of Mg-Containing Layered Double Hydroxide Nanosheets for Efficient Photodriven CH4 Coupling.

Direct conversion of methane (CH4 ) to fuels and other high value-added chemicals is an attractive technology in the chemical industry; however, practical challenges to sustainable processes remain. Herein, we report the preparation of a heterostructured Co-doped MgO-based catalyst through topological transformation of a MgCo-layered double hydroxide (LDH) calcination from 200 to 1100 °C. Remarkably, the catalyst can activate CH4 coupling to produce C2 H6 with a selectivity of 41.60 % within 3 h under full-spectrum irradiation through calcination of LDH at 800 °C. Characterization studies and catalytic results suggest that the highly dispersed active sites and large interfaces amongst the Co-doped MgO-based catalysts enable surface activation of CH4 to methyl (CH3 *), in turn promoting coupling of CH3 * to C2 H6 . This study introduces a promising pathway for photodriven CH4 coupling to give high value-added chemicals by using layered double hydroxides as a precursor.

A cost-effective and humidity-tolerant chloride solid electrolyte for lithium batteries.

Li-ion-conducting chloride solid electrolytes receive considerable attention due to their physicochemical characteristics such as high ionic conductivity, deformability and oxidative stability. However, the raw materials are expensive, and large-scale use of this class of inorganic superionic conductors seems unlikely. Here, a cost-effective chloride solid electrolyte, Li2ZrCl6, is reported. Its raw materials are several orders of magnitude cheaper than those for the state-of-the-art chloride solid electrolytes, but high ionic conductivity (0.81 mS cm-1 at room temperature), deformability, and compatibility with 4V-class cathodes are still simultaneously achieved in Li2ZrCl6. Moreover, Li2ZrCl6 demonstrates a humidity tolerance with no sign of moisture uptake or conductivity degradation after exposure to an atmosphere with 5% relative humidity. By combining Li2ZrCl6 with the Li-In anode and the single-crystal LiNi0.8Mn0.1Co0.1O2 cathode, we report a room-temperature all-solid-state cell with a stable specific capacity of about 150 mAh g-1 for 200 cycles at 200 mA g-1.