Regulation of Interface Ion Transport by Electron Ionic Conductor Construction toward High-Voltage and High-Rate LiNi0.5Co0.2Mn0.3O2 Cathodes in Lithium Ion Battery.

Simultaneously achieving high-energy-density and high-power-density is a crucial yet challenging objective in the pursuit of commercialized power batteries. In this study, atomic layer deposition (ALD) is employed combined with a coordinated thermal treatment strategy to construct a densely packed, electron-ion dual conductor (EIC) protective coating on the surface of commercial LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode material, further enhanced by gradient Al doping (Al@EIC-NCM523). The ultra-thin EIC effectively suppresses side reactions, thereby enhancing the stability of the cathode-electrolyte interphase (CEI) at high-voltages. The EIC's dual conduction capability provides a potent driving force for Li+ transport at the interface, promoting the formation of rapid ion deintercalation pathways within the Al@EIC-NCM523 bulk phase. Moreover, the strategic gradient doping of Al serves to anchor the atomic spacing of Ni and O within the structure of Al@EIC-NCM523, curbing irreversible phase transitions at high-voltages and preserving the integrity of its layered structure. Remarkably, Al@EIC-NCM523 displays an unprecedented rate capability (114.7 mAh g-1 at 20 C), and a sustained cycling performance (capacity retention of 74.72% after 800 cycles at 10 C) at 4.6 V. These findings demonstrate that the proposed EIC and doping strategy holds a significant promise for developing high-energy-density and high-power-density lithium-ion batteries (LIBs).

Scalable Precise Nanofilm Coating and Gradient Al Doping Enable Stable Battery Cycling of LiCoO2 at 4.7 V.

The quest for smart electronics with higher energy densities has intensified the development of high-voltage LiCoO2 (LCO). Despite their potential, LCO materials operating at 4.7 V faces critical challenges, including interface degradation and structural collapse. Herein, we propose a collective surface architecture through precise nanofilm coating and doping that combines an ultra-thin LiAlO2 coating layer and gradient doping of Al. This architecture not only mitigates side reactions, but also improves the Li+ migration kinetics on the LCO surface. Meanwhile, gradient doping of Al inhibited the severe lattice distortion caused by the irreversible phase transition of O3-H1-3-O1, thereby enhanced the electrochemical stability of LCO during 4.7 V cycling. DFT calculations further revealed that our approach significantly boosts the electronic conductivity. As a result, the modified LCO exhibited an outstanding reversible capacity of 230 mAh g-1 at 4.7 V, which is approximately 28% higher than the conventional capacity at 4.5 V. To demonstrate their practical application, our cathode structure shows improved stability in full pouch cell configuration under high operating voltage. LCO exhibited an excellent cycling stability, retaining 82.33% after 1000 cycles at 4.5 V. This multifunctional surface modification strategy offers a viable pathway for the practical application of LCO materials.

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.

Low-Overpotential Rechargeable Na-CO2 Batteries Enabled by an Oxygen-Vacancy-Rich Cobalt Oxide Catalyst.

Rechargeable sodium-carbon dioxide (Na-CO2) batteries have been proposed as a promising CO2 utilization technique, which could realize CO2 reduction and generate electricity at the same time. They suffer, however, from several daunting problems, including sluggish CO2 reduction and evolution kinetics, large polarization, and poor cycling stability. In this study, a rambutan-like Co3O4 hollow sphere catalyst with abundant oxygen vacancies was synthesized and employed as an air cathode for Na-CO2 batteries. Density functional theory calculations reveal that the abundant oxygen vacancies on Co3O4 possess superior CO2 binding capability, accelerating CO2 electroreduction, and thereby improving the discharge capacity. In addition, the oxygen vacancies also contribute to decrease the CO2 decomposition free energy barrier, which is beneficial for reducing the overpotential further and improving round-trip efficiency. Benefiting from the excellent catalytic ability of rambutan-like Co3O4 hollow spheres with abundant oxygen vacancies, the fabricated Na-CO2 batteries exhibit extraordinary electrochemical performance with a large discharge capacity of 8371.3 mA h g-1, a small overpotential of 1.53 V at a current density of 50 mA g-1, and good cycling stability over 85 cycles. These results provide new insights into the rational design of air cathode catalysts to accelerate practical applications of rechargeable Na-CO2 batteries and potentially Na-air batteries.

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.

Efficient Polytelluride Anchoring for Ultralong-Life Potassium Storage: Combined Physical Barrier and Chemisorption in Nanogrid-in-Nanofiber.

Metal tellurides (MTes) are highly attractive as promising anodes for high-performance potassium-ion batteries. The capacity attenuation of most reported MTe anodes is attributed to their poor electrical conductivity and large volume variation. The evolution mechanisms, dissolution properties, and corresponding manipulation strategies of intermediates (K-polytellurides, K-pTex) are rarely mentioned. Herein, we propose a novel structural engineering strategy to confine ultrafine CoTe2 nanodots in hierarchical nanogrid-in-nanofiber carbon substrates (CoTe2@NC@NSPCNFs) for smooth immobilization of K-pTex and highly reversible conversion of CoTe2 by manipulating the intense electrochemical reaction process. Various in situ/ex situ techniques and density functional theory calculations have been performed to clarify the formation, transformation, and dissolution of K-pTex (K5Te3 and K2Te), as well as verifying the robust physical barrier and the strong chemisorption of K5Te3 and K2Te on S, N co-doped dual-type carbon substrates. Additionally, the hierarchical nanogrid-in-nanofiber nanostructure increases the chemical anchoring sites for K-pTex, provides sufficient volume buffer space, and constructs highly interconnected conductive microcircuits, further propelling the battery reaction to new heights (3500 cycles at 2.0 A g-1). Furthermore, the full cells further demonstrate the potential for practical applications. This work provides new insights into manipulating K-pTex in the design of ultralong-cycling MTe anodes for advanced PIBs.

An Intrinsic Stable Layered Oxide Cathode for Practical Sodium-Ion Battery: Solid Solution Reaction, Near-Zero-Strain and Marvelous Water Stability.

Non-aqueous solvents, in particular N,N-dimethylaniline (NMP), are widely applied for electrode fabrication since most sodium layered oxide cathode materials are readily damaged by water molecules. However, the expensive price and poisonousness of NMP unquestionably increase the cost of preparation and post-processing. Therefore, developing an intrinsically stable cathode material that can implement the water-soluble binder to fabricate an electrode is urgent. Herein, a stable nanosheet-like Mn-based cathode material is synthesized as a prototype to verify its practical applicability in sodium-ion batteries (SIBs). The as-prepared material displays excellent electrochemical performance and remarkable water stability, and it still maintains a satisfactory performance of 79.6% capacity retention after 500 cycles even after water treatment. The in situ X-ray diffraction (XRD) demonstrates that the synthesized material shows an absolute solid-solution reaction mechanism and near-zero-strain. Moreover, the electrochemical performance of the electrode fabricated with a water-soluble binder shows excellent long-cycling stability (67.9% capacity retention after 500 cycles). This work may offer new insights into the rational design of marvelous water stability cathode materials for practical SIBs.

Lattice Distortion and H-passivation in Pure Carbon Electrocatalysts for Efficient and Stable Two-electron Oxygen Reduction to H2 O2.

The exploration of inexpensive and efficient catalysts for oxygen reduction reaction (ORR) is crucial for chemical and energy industries. Carbon materials have been proved promising with different catalysts enabling 2 and 4e- ORR. Nevertheless, their ORR activity and selectivity is still complex and under debate in many cases. Many structures of these active carbon materials are also chemically unstable for practical implementations. Unlike the well-discussed structures, this work presents a strategy to promote efficient and stable 2e- ORR of carbon materials through the synergistic effect of lattice distortion and H-passivation (on the distorted structure). We show how these structures can be formed on carbon cloth, and how the reproducible chemical adsorption can be realized on these structures for efficient and stable H2 O2 production. The work here gives not only new understandings on the 2e- ORR catalysis, but also the robust catalyst which can be directly used in industry.

Valence Oscillation of Ru Active Sites for Efficient and Robust Acidic Water Oxidation.

The continuous oxidation and leachability of active sites in Ru-based catalysts hinder practical application in proton-exchange membrane water electrolyzers (PEMWE). Herein, robust inter-doped tungsten-ruthenium oxide heterostructures [(Ru-W)Ox ] fabricated by sequential rapid oxidation and metal thermomigration processes are proposed to enhance the activity and stability of acidic oxygen evolution reaction (OER). The introduction of high-valent W species induces the valence oscillation of the Ru sites during OER, facilitating the cyclic transition of the active metal oxidation states and maintaining the continuous operation of the active sites. The preferential oxidation of W species and electronic gain of Ru sites in the inter-doped heterostructure significantly stabilize RuOx on WOx substrates beyond the Pourbaix stability limit of bare RuO2 . Furthermore, the asymmetric Ru-O-W active units are generated around the heterostructure interface to adsorb the oxygen intermediates synergistically, enhancing the intrinsic OER activity. Consequently, the inter-doped (Ru-W)Ox heterostructures not only demonstrate an overpotential of 170 mV at 10 mA cm-2 and excellent stability of 300 h in acidic electrolytes but also exhibit the potential for practical applications, as evidenced by the stable operation at 0.5 A cm-2 for 300 h in PEMWE.

Stabilizing Low-Valence Single Atoms by Constructing Metalloid Tungsten Carbide Supports for Efficient Hydrogen Oxidation and Evolution.

Designing novel single-atom catalysts (SACs) supports to modulate the electronic structure is crucial to optimize the catalytic activity, but rather challenging. Herein, a general strategy is proposed to utilize the metalloid properties of supports to trap and stabilize single-atoms with low-valence states. A series of single-atoms supported on the surface of tungsten carbide (M-WCx , M=Ru, Ir, Pd) are rationally developed through a facile pyrolysis method. Benefiting from the metalloid properties of WCx , the single-atoms exhibit weak coordination with surface W and C atoms, resulting in the formation of low-valence active centers similar to metals. The unique metal-metal interaction effectively stabilizes the low-valence single atoms on the WCx surface and improves the electronic orbital energy level distribution of the active sites. As expected, the representative Ru-WCx exhibits superior mass activities of 7.84 and 62.52 A mgRu -1 for the hydrogen oxidation and evolution reactions (HOR/HER), respectively. In-depth mechanistic analysis demonstrates that an ideal dual-sites cooperative mechanism achieves a suitable adsorption balance of Had and OHad , resulting in an energetically favorable Volmer step. This work offers new guidance for the precise construction of highly active SACs.

Sodium Layered/Tunnel Intergrowth Oxide Cathodes: Formation Process, Interlocking Chemistry, and Electrochemical Performance.

Manganese-based layered oxides are prospective cathode materials for sodium-ion batteries (SIBs) due to their low cost and high theoretical capacities. The biphasic intergrowth structure of layered cathode materials is essential for improving the sodium storage performance, which is attributed to the synergistic effect between the two phases. However, the in-depth formation mechanism of biphasic intergrowth materials remains unclear. Herein, the layered/tunnel intergrowth Na0.6MnO2 (LT-NaMO) as a model material was successfully prepared, and their formation processes and electrochemical performance were systematically investigated. In situ high-temperature X-ray diffraction displays the detailed evolution process and excellent thermal stability of the layered/tunnel intergrowth structure. Furthermore, severe structural strain and large lattice volume changes are significantly mitigated by the interlocking effect between the phase interfaces, which further enhances the structural stability of the cathode materials during the charging/discharging process. Consequently, the LT-NaMO cathode displays fast Na+ transport kinetics with a remarkable capacity retention of ∼70.5% over 300 cycles at 5C, and its assembled full cell with hard carbon also exhibits high energy density. These findings highlight the superior electrochemical performance of intergrowth materials due to interlocking effects between layered and tunnel structures and also provide unique insights into the construction of intergrowth cathode materials for SIBs.

Defect-Healing Induced Monoclinic Iron-Based Prussian Blue Analogs as High-Performance Cathode Materials for Sodium-Ion Batteries.

Prussian blue analogs (PBAs) have attracted wide interest as a class of ideal cathodes for rechargeable sodium-ion batteries due to their low cost, high theoretical capacity, and facile synthesis. Herein, a series of highly crystalline Fe-based PBAs (FeHCF) cubes, where HCF stands for the hexacyanoferrate, is synthesized via a one-step pyrophosphate-assisted co-precipitation method. By applying this proposed facile crystallization-controlled method to slow down the crystallization process and suppress the defect content of the crystal framework of the PBAs, the as-prepared materials demonstrate high crystallization and a sodium-rich induced rhombohedral phase. As a result, the as prepared FeHCF can deliver a high specific capacity of up to 152.0 mA h g-1 (achieving ≈90% of its theoretical value) and an excellent rate capability with a high-capacity retention ratio of 88% at 10 C, which makes it one of the most competitive candidates among the cathodes reported regarding both capacity and rate performance. A highly reversible three-phase-transition sodium-ion storage mechanism has been revealed via multiple in situ techniques. Furthermore, the full cells fabricated with as-prepared cathode and commercial hard carbon anode exhibit excellent compatibility which shows great prospects for application in the large-scale energy storage systems.

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.

A Disordered Rubik's Cube-Inspired Framework for Sodium-Ion Batteries with Ultralong Cycle Lifespan.

Sodium-ion batteries (SIBs) with fast-charge capability and long lifespan could be applied in various sustainable energy storage systems, from personal devices to grid storage. Inspired by the disordered Rubik's cube, here, we report that the high-entropy (HE) concept can lead to a very substantial improvement in the sodium storage properties of hexacyanoferrate (HCF). An example of HE-HCF has been synthesized as a proof of concept, which has achieved impressive cycling stability over 50 000 cycles and an outstanding fast-charging capability up to 75 C. Remarkable air stability and all-climate performance are observed. Its quasi-zero-strain reaction mechanism and high sodium diffusion coefficient have been measured and analyzed by multiple in situ techniques and density functional theory calculations. This strategy provides new insights into the development of advanced electrodes and provides the opportunity to tune electrochemical performance by tailoring the atomic composition.

A strategy for anode modification for future zinc-based battery application.

In the past several years, rechargeable zinc batteries, featuring the merits of low cost, environmental friendliness, easy manufacturing, and enhanced safety, have, attracted much attention. Zinc (Zn) anodes for zinc metal batteries play an important role. In this review, the fundamental understanding of these batteries and modification strategies to deal with the problematic issues for Zn anodes, including dendrite growth, corrosion, and the hydrogen evolution phenomenon will be summarized. The practical application of Zn anodes can still lead to Zn dendrites, various side reactions, and serious safety risks. Therefore, metal-free anodes for "rocking chair" zinc ion batteries to replace Zn anodes are systemically reviewed. The performance and the zinc storage mechanism of metal-free anodes will be discussed. Subsequently, a "rocking chair" zinc ion battery prototype selected as a recent example is assessed to explore the merits and demerits of Zn anodes and metal-free anodes. To conclude, a perspective on the future of zinc metal batteries and "rocking chair" zinc ion batteries is presented. It is hoped that this review may provide for further improvement of commercial rechargeable zinc batteries.

Na1.51 Fe[Fe(CN)6 ]0.87 ·1.83H2 O Hollow Nanospheres via Non-Aqueous Ball-Milling Route to Achieve High Initial Coulombic Efficiency and High Rate Capability in Sodium-Ion Batteries.

Prussian blue analogues (PBAs) have attracted extensive attention as cathode materials in sodium-ion batteries (SIBs) due to their low cost, high theoretical capacity, and facile synthesis process. However, it is of great challenge to control the crystal vacancies and interstitial water formed during the aqueous co-precipitation method, which are also the key factors in determining the electrochemical performance. Herein, an antioxidant and chelating agent co-assisted non-aqueous ball-milling method to generate highly-crystallized Na2- x Fe[Fe(CN)6 ]y with hollow structure is proposed by suppressing the speed and space of crystal growth. The as-prepared Na2- x Fe[Fe(CN)6 ]y hollow nanospheres show low vacancies and interstitial water content, leading to a high sodium content. As a result, the Na-rich Na1.51 Fe[Fe(CN)6 ]0.87 ·1.83H2 O hollow nanospheres exhibit a high initial Coulombic efficiency, excellent cycling stability, and rate performance via a highly reversible two-phase transition reaction confirmed by in situ X-ray diffraction. It delivers a specific capacity of 124.2 mAh g-1 at 17 mA g-1 , presenting ultra-high rate capability (84.1 mAh g-1 at 3400 mA g-1 ) and cycling stability (65.3% capacity retention after 1000 cycles at 170 mA g-1 ). Furthermore, the as-reported non-aqueous ball-milling method could be regarded as a promising method for the scalable production of PBAs as cathode materials for high-performance SIBs.

Organic Small Molecules with Electrochemical-Active Phenolic Enolate Groups for Ready-to-Charge Organic Sodium-Ion Batteries.

Organic materials have attracted much attention in sodium ion batteries (SIBs) because of their advantages such as being environmentally benign and having high designability. Capacities and cycle life of organic materials are the most important parameters in most research which has been paid much effort to obtain an impressive electrochemical performance on the material level, and the sodium-detachable ability of these materials to directly match with the sodium-free anode is neglected. In this work, one organic sodium salt (C6 H2 Na2 O6 ) exhibits the unique ability (charging first in half cell) unlike other reported organic cathode materials (normally discharging first) for SIBs. The redox mechanism and structure change are investigated by in situ and ex situ tests to give a better understanding for C6 H2 Na2 O6 . Satisfying electrochemical performance (74% capacity retention after 600 cycles at 0.05 A g-1 and 63% capacity retention at 5 A g-1 when compared with capacity at 0.05 A g-1 ) is achieved by the C6 H2 Na2 O6 electrode. In addition, matched with hard carbon, full cells are assembled successfully like other transition metal containing cathode materials because C6 H2 Na2 O6 electrode can deliver its sodium ions to a sodium-free anode directly without any presodiation.

Ball Milling Solid-State Synthesis of Highly Crystalline Prussian Blue Analogue Na2-x MnFe(CN)6 Cathodes for All-Climate Sodium-Ion Batteries.

With a series of merits, Prussian blue analogs (PBAs) have been considered as superior cathode materials for sodium-ion batteries (SIBs). Their commercialization, however, still suffers from inferior stability, considerable [Fe(CN)6 ] defects and interstitial water in the framework, which are related to the rapid crystal growth. Herein, a "water-in-salt" nanoreactor is proposed to synthesize highly crystallized PBAs with decreased defects and water, which show both superior specific capacity and rate capability in SIBs. The air-stability, all-climate, and full-cell properties of our PBA have also been evaluated, and it exhibits enhanced electrochemical performance and higher volume yield than its counterpart synthesized via the water-based co-precipitation method. Furthermore, their highly reversible sodium-ion storage behavior has been measured and identified via multiple in situ techniques. This work could pave the way for the PBA-based SIBs in grid-scale energy-storage systems.

Ice-Assisted Synthesis of Highly Crystallized Prussian Blue Analogues for All-Climate and Long-Calendar-Life Sodium Ion Batteries.

For practical sodium-ion batteries, both high electrochemical performance and cost efficiency of the electrode materials are considered as two key parameters. Prussian blue analogues (PBAs) are broadly recognized as promising cathode materials due to their low cost, high theoretical capacity, and cycling stability, although they suffer from low-crystallinity-induced performance deterioration. Herein, a facile "ice-assisted" strategy is presented to prepare highly crystallized PBAs without any additives. By suppressing structure defects, the cathode exhibits a high capacity of 123 mAh g-1 with initial Coulombic efficiency of 87.2%, a long cycling lifespan of 3000 cycles, and significantly enhanced high/low temperature performance and calendar life. Remarkably, the low structure distortion and high sodium diffusion coefficient have been identified via in situ synchrotron powder diffraction and first-principles calculations, while its thermal stability has been analyzed by in situ heated X-ray powder diffraction. We believe the results could pave the way to the low-cost and large-scale application of PBAs in all-climate sodium-ion batteries.

Prussian Blue Analogues for Sodium-Ion Batteries: Past, Present, and Future.

Prussian blue analogues (PBAs) have attracted wide attention for their application in the energy storage and conversion field due to their low cost, facile synthesis, and appreciable electrochemical performance. At the present stage, most research on PBAs is focused on their material-level optimization, whereas their properties in practical battery systems are seldom considered. This review aims to first provide an overview of the history and parameters of PBA materials and analyze the fundamental principles toward rational design of PBAs, and then evaluate the prospects and challenges for PBAs for practical sodium-ion batteries, hoping to bridge the gap between laboratory research and commercial reality.