Achieving a Deeply Desodiated Stabilized Cathode Material by the High Entropy Strategy for Sodium-ion Batteries.

Manganese-based layered oxides are currently of significant interest as cathode materials for sodium-ion batteries due to their low toxicity and high specific capacity. However, the practical applications are impeded by sluggish intrinsic Na+ migration and poor structure stability as a result of Jahn-Teller distortion and complicated phase transition. In this study, a high-entropy strategy is proposed to enhance the high-voltage capacity and cycling stability. The designed P2-Na0.67Mn0.6Cu0.08Ni0.09Fe0.18Ti0.05O2 achieves a deeply desodiation and delivers charging capacity of 158.1 mA h g-1 corresponding to 0.61 Na with a high initial Coulombic efficiency of 98.2%. The charge compensation is attributed to the cationic and anionic redox reactions conjunctively. Moreover, the crystal structure is effectively stabilized, leading to a slight variation of lattice parameters. This research carries implications for the expedited development of low-cost, high-energy-density cathode materials for sodium-ion batteries.

Interfacial Spinel Local Interlocking Strategy Toward Structural Integrity in P3 Oxide Cathodes.

P3-layered transition oxide cathodes have garnered considerable attention owing to their high initial capacity, rapid Na+ kinetics, and less energy consumption during the synthesis process. Despite these merits, their practical application is hindered by the substantial capacity degradation resulting from unfavorable structural transformations, Mn dissolution and migration. In this study, we systematically investigated the failure mechanisms of P3 cathodes, encompassing Mn dissolution, migration, and the irreversible P3-O3' phase transition, culminating in severe structural collapse. To address these challenges, we proposed an interfacial spinel local interlocking strategy utilizing P3/spinel intergrowth oxide as a proof-of-concept material. As a result, P3/spinel intergrowth oxide cathodes demonstrated enhanced cycling performance. The effectiveness of suppressing Mn migration and maintaining local structure of interfacial spinel local interlocking strategy was validated through depth-etching X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and in situ synchrotron-based X-ray diffraction. This interfacial spinel local interlocking engineering strategy presents a promising avenue for the development of advanced cathode materials for sodium-ion batteries.

2D Ferromagnetic M3 GeTe2 (M = Ni/Fe) for Boosting Intermediates Adsorption toward Faster Water Oxidation.

In this work, 2D ferromagnetic M3 GeTe2 (MGT, M = Ni/Fe) nanosheets with rich atomic Te vacancies (2D-MGTv ) are demonstrated as efficient OER electrocatalyst via a general mechanical exfoliation strategy. X-ray absorption spectra (XAS) and scanning transmission electron microscope (STEM) results validate the dominant presence of metal-O moieties and rich Te vacancies, respectively. The formed Te vacancies are active for the adsorption of OH* and O* species while the metal-O moieties promote the O* and OOH* adsorption, contributing synergistically to the faster oxygen evolution kinetics. Consequently, 2D-Ni3 GeTe2v exhibits superior OER activity with only 370 mV overpotential to reach the current density of 100 mA cm-2 and turnover frequency (TOF) value of 101.6 s-1 at the overpotential of 200 mV in alkaline media. Furthermore, a 2D-Ni3 GeTe2v -based anion-exchange membrane (AEM) water electrolysis cell (1 cm2 ) delivers a current density of 1.02 and 1.32 A cm-2 at the voltage of 3 V feeding with 0.1 and 1 m KOH solution, respectively. The demonstrated metal-O coordination with abundant atomic vacancies for ferromagnetic M3 GeTe2 and the easily extended preparation strategy would enlighten the rational design and fabrication of other ferromagnetic materials for wider electrocatalytic applications.

Linearly Interlinked Fe-Nx-Fe Single Atoms Catalyze High-Rate Sodium-Sulfur Batteries.

Linearly interlinked single atoms offer unprecedented physiochemical properties, but their synthesis for practical applications still poses significant challenges. Herein, linearly interlinked iron single-atom catalysts that are loaded onto interconnected carbon channels as cathodic sulfur hosts for room-temperature sodium-sulfur batteries are presented. The interlinked iron single-atom exhibits unique metallic iron bonds that facilitate the transfer of electrons to the sulfur cathode, thereby accelerating the reaction kinetics. Additionally, the columnated and interlinked carbon channels ensure rapid Na+ diffusion kinetics to support high-rate battery reactions. By combining the iron atomic chains and the topological carbon channels, the resulting sulfur cathodes demonstrate effective high-rate conversion performance while maintaining excellent stability. Remarkably, even after 5000 cycles at a current density of 10 A g-1, the Na-S battery retains a capacity of 325 mAh g-1. This work can open a new avenue in the design of catalysts and carbon ionic channels, paving the way to achieve sustainable and high-performance energy devices.

Multifunctional Separator Enables High-Performance Sodium Metal Batteries in Carbonate-Based Electrolytes.

Sodium metal has become one of the most promising anodes for next-generation cheap and high-energy-density metal batteries; however, challenges caused by the uncontrollable sodium dendrite growth and fragile solid electrolyte interphase (SEI) restrict their large-scale practical applications in low-cost and wide-voltage-window carbonate electrolytes. Herein, a novel multifunctional separator with lightweight and high thinness is proposed, assembled by the cobalt-based metal-organic framework nanowires (Co-NWS), to replace the widely applied thick and heavy glass fiber separator. Benefitting from its abundant sodiophilic functional groups and densely stacked nanowires, Co-NWS not only exhibits outstanding electrolyte wettability and effectively induces uniform Na+ ion flux as a strong ion redistributor but also favors constructing the robust N,F-rich SEI layer. Satisfactorily, with 10 µL carbonate electrolyte, a Na|Co-NWS|Cu half-cell delivers stable cycling (over 260 cycles) with a high average Coulombic efficiency of 98%, and the symmetric cell shows a long cycle life of more than 500 h. Remarkably, the full cell shows a long-term life span (over 1500 cycles with 92% capacity retention) at high current density in the carbonate electrolyte. This work opens up a strategy for developing dendrite-free, low-cost, and long-life-span sodium metal batteries in carbonate-based electrolytes.

Liquid-Like Li-Ion Conduction in Oxides Enabling Anomalously Stable Charge Transport across the Li/Electrolyte Interface in All-Solid-State Batteries.

The softness of sulfur sublattice and rotational PS4 tetrahedra in thiophosphates result in liquid-like ionic conduction, leading to enhanced ionic conductivities and stable electrode/thiophosphate interfacial ionic transport. However, the existence of liquid-like ionic conduction in rigid oxides remains unclear, and modifications are deemed necessary to achieve stable Li/oxide solid electrolyte interfacial charge transport. In this study, by combining the neutron diffraction survey, geometrical analysis, bond valence site energy analysis, and ab initio molecular dynamics simulation, 1D liquid-like Li-ion conduction is discovered in LiTa2 PO8 and its derivatives, wherein Li-ion migration channels are connected by four- or five-fold oxygen-coordinated interstitial sites. This conduction features a low activation energy (0.2 eV) and short mean residence time (<1 ps) of Li ions on the interstitial sites, originating from the Li-O polyhedral distortion and Li-ion correlation, which are controlled by doping strategies. The liquid-like conduction enables a high ionic conductivity (1.2 mS cm-1 at 30 °C), and a 700 h anomalously stable cycling under 0.2 mA cm-2 for Li/LiTa2 PO8 /Li cells without interfacial modifications. These findings provide principles for the future discovery and design of improved solid electrolytes that do not require modifications to the Li/solid electrolyte interface to achieve stable ionic transport.

Solvent control of water O-H bonds for highly reversible zinc ion batteries.

Aqueous Zn-ion batteries have attracted increasing research interest; however, the development of these batteries has been hindered by several challenges, including dendrite growth, Zn corrosion, cathode material degradation, limited temperature adaptability and electrochemical stability window, which are associated with water activity and the solvation structure of electrolytes. Here we report that water activity is suppressed by increasing the electron density of the water protons through interactions with highly polar dimethylacetamide and trimethyl phosphate molecules. Meanwhile, the Zn corrosion in the hybrid electrolyte is mitigated, and the electrochemical stability window and the operating temperature of the electrolyte are extended. The dimethylacetamide alters the surface energy of Zn, guiding the (002) plane dominated deposition of Zn. Molecular dynamics simulation evidences Zn2+ ions are solvated with fewer water molecules, resulting in lower lattice strain in the NaV3O8·1.5H2O cathode during the insertion of hydrated Zn2+ ions, boosting the lifespan of Zn|| NaV3O8·1.5H2O cell to 3000 cycles.

Prussian Blue Analogues with Optimized Crystal Plane Orientation and Low Crystal Defects toward 450†Wh kg-1 Alkali-Ion Batteries.

Prussian blue analogues (PBAs) have been regarded as promising cathode materials for alkali-ion batteries owing to their high theoretical energy density and low cost. However, the high water and vacancy content of PBAs lower their energy density and bring safety issues, impeding their large-scale application. Herein, a facile "potassium-ions assisted" strategy is proposed to synthesize highly crystallized PBAs. By manipulating the dominant crystal plane and suppressing vacancies, the as-prepared PBAs exhibit increased redox potential resulting in high energy density up to ≈450 Wh kg-1 , which is at the same level of the well-known LiFePO4 cathodes for lithium-ion batteries. Remarkably, unconventional highly-reversible phase evolution and redox-active pairs were identified by multiple in situ techniques for the first time. The preferred guest-ion storage sites and migration mechanism were systematically analysed through theoretical calculations. We believe these results could inspire the design of safe with high energy density.

Regulating the reduction reaction pathways via manipulating the solvation shell and donor number of the solvent in Li-CO2 chemistry.

Transforming CO2 into valuable chemicals is an inevitable trend in our current society. Among the viable end-uses of CO2, fixing CO2 as carbon or carbonates via Li-CO2 chemistry could be an efficient approach, and promising achievements have been obtained in catalyst design in the past. Even so, the critical role of anions/solvents in the formation of a robust solid electrolyte interphase (SEI) layer on cathodes and the solvation structure have never been investigated. Herein, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in two common solvents with various donor numbers (DN) have been introduced as ideal examples. The results indicate that the cells in dimethyl sulfoxide (DMSO)-based electrolytes with high DN possess a low proportion of solvent-separated ion pairs and contact ion pairs in electrolyte configuration, which are responsible for fast ion diffusion, high ionic conductivity, and small polarization. The 3 M DMSO cell delivered the lowest polarization of 1.3 V compared to all the tetraethylene glycol dimethyl ether (TEGDME)-based cells (about 1.7 V). In addition, the coordination of the O in the TFSI- anion to the central solvated Li+ ion was located at around 2 Å in the concentrated DMSO-based electrolytes, indicating that TFSI- anions could access the primary solvation sheath to form an LiF-rich SEI layer. This deeper understanding of the electrolyte solvent property for SEI formation and buried interface side reactions provides beneficial clues for future Li-CO2 battery development and electrolyte design.

Revealing the Origin of Transition-Metal Migration in Layered Sodium-Ion Battery Cathodes: Random Na Extraction and Na-Free Layer Formation.

Cation migration often occurs in layered oxide cathodes of lithium-ion batteries due to the similar ion radius of Li and transition metals (TMs). Although Na and TM show a big difference of ion radius, TMs in layered cathodes of sodium-ion batteries (SIBs) can still migrate to Na layer, leading to serious electrochemical degeneration. To elucidate the origin of TM migration in layered SIB cathodes, we choose NaCrO2 , a typical layered cathode suffering from serious TM migration, as a model material and find that the TM migration is derived from the random desodiation and subsequent formation of Na-free layer at high charge potential. A Ru/Ti co-doping strategy is developed to address the issue, where the doped active Ru is first oxidized to create a selective desodiation and the doped inactive Ti can function as a pillar to avoid complete desodiation in Ru-contained TM layers, leading to the suppression of the Na-free layer formation and subsequent enhanced electrochemical performance.

Stabilizing Cobalt-free Li-rich Layered Oxide Cathodes through Oxygen Lattice Regulation by Two-phase Ru Doping.

The application of Li-rich layered oxides is hindered by their dramatic capacity and voltage decay on cycling. This work comprehensively studies the mechanistic behaviour of cobalt-free Li1.2 Ni0.2 Mn0.6 O2 and demonstrates the positive impact of two-phase Ru doping. A mechanistic transition from the monoclinic to the hexagonal behaviour is found for the structural evolution of Li1.2 Ni0.2 Mn0.6 O2, and the improvement mechanism of Ru doping is understood using the combination of in operando and post-mortem synchrotron analyses. The two-phase Ru doping improves the structural reversibility in the first cycle and restrains structural degradation during cycling by stabilizing oxygen (O2- ) redox and reducing Mn reduction, thus enabling high structural stability, an extraordinarily stable voltage (decay rate <0.45 mV per cycle), and a high capacity-retention rate during long-term cycling. The understanding of the structure-function relationship of Li1.2 Ni0.2 Mn0.6 O2 sheds light on the selective doping strategy and rational materials design for better-performance Li-rich layered oxides.

Introducing 4s-2p Orbital Hybridization to Stabilize Spinel Oxide Cathodes for Lithium-Ion Batteries.

Oxides composed of an oxygen framework and interstitial cations are promising cathode materials for lithium-ion batteries. However, the instability of the oxygen framework under harsh operating conditions results in fast battery capacity decay, due to the weak orbital interactions between cations and oxygen (mainly 3d-2p interaction). Here, a robust and endurable oxygen framework is created by introducing strong 4s-2p orbital hybridization into the structure using LiNi0.5 Mn1.5 O4 oxide as an example. The modified oxide delivers extraordinarily stable battery performance, achieving 71.4 % capacity retention after 2000 cycles at 1 C. This work shows that an orbital-level understanding can be leveraged to engineer high structural stability of the anion oxygen framework of oxides. Moreover, the similarity of the oxygen lattice between oxide electrodes makes this approach extendable to other electrodes, with orbital-focused engineering a new avenue for the fundamental modification of battery materials.

In Operando Neutron Scattering Multiple-Scale Studies of Lithium-Ion Batteries.

Real-time observation of the electrochemical mechanistic behavior at various scales offers new insightful information to improve the performance of lithium-ion batteries (LIBs). As complementary to the X-ray-based techniques and electron microscopy-based methodologies, neutron scattering provides additional and unique advantages in materials research, owing to the different interactions with atomic nuclei. The non-Z-dependent elemental contrast, in addition to the high penetration ability and weak interaction with matters, makes neutron scattering an advanced probing tool for the in operando mechanistic studies of LIBs. The neutron-based techniques, such as neutron powder diffraction, small-angle neutron scattering, neutron reflectometry, and neutron imaging, have their distinct functionalities and characteristics regimes. These result in their scopes of application distributed in different battery components and covering the full spectrum of all aspects of LIBs. The review surveys the state-of-the-art developments of real-time investigation of the dynamic evolutions of electrochemically active compounds at various scales using neutron techniques. The atomic-scale, the mesoscopic-scale, and at the macroscopic-scale within LIBs during electrochemical functioning provide insightful information to battery researchers. The authors envision that this review will popularize the applications of neutron-based techniques in LIB studies and furnish important inspirations to battery researchers for the rational design of the new generation of LIBs.

Chromium Ion Pair Luminescence: A Strategy in Broadband Near-Infrared Light-Emitting Diode Design.

Portable near-infrared (NIR) light sources are in high demand for applications in spectroscopy, night vision, bioimaging, and many others. Typical phosphor designs feature isolated Cr3+ ion centers, and it is challenging to design broadband NIR phosphors based on Cr3+-Cr3+ pairs. Here, we explore the solid-solution series SrAl11.88-xGaxO19:0.12Cr3+ (x = 0, 2, 4, 6, 8, 10, and 12) as phosphors featuring Cr3+-Cr3+ pairs and evaluate structure-property relations within the series. We establish the incorporation of Ga within the magentoplumbite-type structure at five distinct crystallographic sites and evaluate the effect of this incorporation on the Cr3+-Cr3+ ion pair proximity. Electron paramagnetic measurements reveal the presence of both isolated Cr3+ and Cr3+-Cr3+ pairs, resulting in NIR luminescence at approximately 650-1050 nm. Unexpectedly, the origin of broadband NIR luminescence with a peak within the range 740-820 nm is related to the Cr3+-Cr3+ ion pair. We demonstrate the application of the SrAl5.88Ga6O19:0.12Cr3+ phosphor, which possesses an internal quantum efficiency of ∼85%, a radiant flux of ∼95 mW, and zero thermal quenching up to 500 K. This work provides a further understanding of spectral shifts in phosphor solid solutions and in particular the application of the magentoplumbites as promising next-generation NIR phosphor host systems.

Crystallographic-Site-Specific Structural Engineering Enables Extraordinary Electrochemical Performance of High-Voltage LiNi0.5 Mn1.5 O4 Spinel Cathodes for Lithium-Ion Batteries.

The development of reliable and safe high-energy-density lithium-ion batteries is hindered by the structural instability of cathode materials during cycling, arising as a result of detrimental phase transformations occurring at high operating voltages alongside the loss of active materials induced by transition metal dissolution. Originating from the fundamental structure/function relation of battery materials, the authors purposefully perform crystallographic-site-specific structural engineering on electrode material structure, using the high-voltage LiNi0.5 Mn1.5 O4 (LNMO) cathode as a representative, which directly addresses the root source of structural instability of the Fd 3 ¯ m structure. By employing Sb as a dopant to modify the specific issue-involved 16c and 16d sites simultaneously, the authors successfully transform the detrimental two-phase reaction occurring at high-voltage into a preferential solid-solution reaction and significantly suppress the loss of Mn from the LNMO structure. The modified LNMO material delivers an impressive 99% of its theoretical specific capacity at 1 C, and maintains 87.6% and 72.4% of initial capacity after 1500 and 3000 cycles, respectively. The issue-tracing site-specific structural tailoring demonstrated for this material will facilitate the rapid development of high-energy-density materials for lithium-ion batteries.

Constructing nitrided interfaces for stabilizing Li metal electrodes in liquid electrolytes.

Traditional Li ion batteries based on intercalation-type anodes have been approaching their theoretical limitations in energy density. Replacing the traditional anode with metallic Li has been regarded as the ultimate strategy to develop next-generation high-energy-density Li batteries. Unfortunately, the practical application of Li metal batteries has been hindered by Li dendrite growth, unstable Li/electrolyte interfaces, and Li pulverization during battery cycling. Interfacial modification can effectively solve these challenges and nitrided interfaces stand out among other functional layers because of their impressive effects on regulating Li+ flux distribution, facilitating Li+ diffusion through the solid-electrolyte interphase, and passivating the active surface of Li metal electrodes. Although various designs for nitrided interfaces have been put forward in the last few years, there is no paper that specialized in reviewing these advances and discussing prospects. In consideration of this, we make a systematic summary and give our comments based on our understanding. In addition, a comprehensive perspective on the future development of nitrided interfaces and rational Li/electrolyte interface design for Li metal electrodes is included.

Electron-Injection-Engineering Induced Phase Transition toward Stabilized 1T-MoS2 with Extraordinary Sodium Storage Performance.

Phase transition engineering, with the ability to alter the electronic structure and physicochemical properties of materials, has been widely used to achieve the thermodynamically unstable metallic phase MoS2 (1T-MoS2), although the complex operating conditions and low yield of previous strategies make the large-scale fabrication of 1T-MoS2 a big challenge. Herein, we report a facile electron injection strategy for phase transition engineering and fabricate a composite of conductive TiO chemically bonded to 1T-MoS2 nanoflowers (TiO-1T-MoS2 NFs) on a large scale. The underlying mechanism analysis reveals that electron-injection-engineering triggers a reorganization of the Mo 4d orbitals and results in a 100% phase transition of MoS2 from 2H to 1T. In the TiO-1T-MoS2 NFs composite, the 1T-MoS2 demonstrates a higher electronic conductivity, a lower Na+ diffusion barrier, and a more restricted S release than 2H-MoS2. In addition, conductive TiO bonding successfully resolves the stability challenge of the 1T phase. These merits endow TiO-1T-MoS2 NFs electrodes with an excellent rate capability (650/288 mAh g-1 at 50/20 000 mA g-1, respectively) and an outstanding cyclability (501 mAh g-1 at 1000 mA g-1 after 700 cycles) in sodium ion batteries. Such an improvement signifies that this facile and scalable phase-transition engineering combined with a deep mechanism analysis offers an important reference for designing advanced materials for various applications.

Lithium Metal Electrode with Increased Air Stability and Robust Solid Electrolyte Interphase Realized by Silane Coupling Agent Modification.

The quality of the solid electrolyte interphase (SEI) layer is the decisive factor for the electrochemical performance of Li-metal-based batteries. Due to the absence of effective bonding, a natural SEI layer may exfoliate from the Li anode during interfacial fluctuations. Here, a silane coupling agent is introduced to serve as an adhesion promoter to bridge these two dissimilar materials via both chemical bonding and physical intertwining effects. Its inorganic reactive groups can combine with the Li substrate by forming LiOSi bonds, while organic functional groups can take part in the formation of the SEI layer and thereby bond with SEI components. Li metal electrodes with silane coupling agent modification exhibit excellent electrochemical performance, even under extreme testing conditions. This modification layer with dense structure could also protect the Li metal from corrosion by air, evidenced by the comparable electrochemical activity of the modified Li metal electrodes even after being exposed in air for 2 h. This design provides a promising pathway for the development of Li metal electrodes that will be stable both in electrolyte and in air.

Manipulating the Solvation Structure of Nonflammable Electrolyte and Interface to Enable Unprecedented Stability of Graphite Anodes beyond 2 Years for Safe Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) are attractive for low-cost and large-scale energy storage applications, in which graphite is one of the most promising anodes. However, the large size and the high activity of K+ ions and the highly catalytic surface of graphite largely prevent the development of safe and compatible electrolytes. Here, a nonflammable, moderate-concentration electrolyte is reported that is highly compatible with graphite anodes and that consists of fire-retardant trimethyl phosphate (TMP) and potassium bis(fluorosulfonyl)imide (KFSI) in a salt/solvent molar ratio of 3:8. It shows unprecedented stability, as evidenced by its 74% capacity retention over 24 months of cycling (over 2000 cycles) at the 0.2 C current rate. Electrolyte structure and surface analyses show that this excellent cycling stability is due to the nearly 100% solvation of TMP molecules with K+ cations and the formation of FSI- -derived F-rich solid electrolyte interphase (SEI), which effectively suppresses the decomposition of the solvent molecules toward the graphite anode. Furthermore, excellent performance on high-mass loaded graphite electrodes and in a full cell with perylenetetracarboxylic dianhydride cathode is demonstrated. This study highlights the importance of the compatibility of both electrolyte and the interface, and offers new opportunities to design the electrolyte-SEI nexus for safe and practical PIBs.

Multi-Site Cation Control of Ultra-Broadband Near-Infrared Phosphors for Application in Light-Emitting Diodes.

Near-infrared (NIR) phosphors are fascinating materials that have numerous applications in diverse fields. In this study, a series of La3Ga5GeO14:Cr3+ phosphors, which was incorporated with Sn4+, Ba2+, and Sc3+, was successfully synthesized using solid-state reaction to explore every cationic site comprehensively. The crystal structures were well resolved by combining synchrotron X-ray diffraction and neutron powder diffraction through joint Rietveld refinements. The trapping of free electrons induced by charge unbalances and lattice vacancies changes the magnetic properties, which was well explained by a Dyson curve in electron paramagnetic resonance. Temperature and pressure-dependent photoluminescence spectra reveal various luminescent properties between strong and weak fields in different dopant centers. The phosphor-converted NIR light-emitting diode (pc-NIR LED) package demonstrates a superior broadband emission that covers the near-infrared (NIR) region of 650-1050 nm. This study can provide researchers with new insight into the control mechanism of multiple-cation-site phosphors and reveal a potential phosphor candidate for practical NIR LED application.