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Al impurity is among the most likely components to enter the spent lithium-ion battery (LIB) cathode powder due to the strong adhesion between the cathode material and the Al current collector. However, high-value metal elements tend to be lost during the deep removal of Al impurities to obtain high-purity metal salt products in the conventional hydrometallurgical process. In this work, the harmful Al impurity is designed as a beneficial ingredient to upcycle high-voltage LiCoO2by incorporating robust Al–O covalent bonds into the bulk of the cathode assisted with Ti modification. Benefiting from the strong Al–O and Ti–O bonds in the bulk, the irreversible phase transitions of the upcycled R-LCO-AT have been significantly suppressed at high voltages, as revealed by in situ XRD. Moreover, a Li+-conductive Li2TiO3protective layer is constructed on the surface of R-LCO-AT by pinning slow-diffusion Ti on the grain boundaries, resulting in improved Li+diffusion kinetics and restrained interface side reactions. Consequently, the cycle stability and rate performance of R-LCO-AT were significantly enhanced at a high cutoff voltage of 4.6 V, with a discharge capacity of 189.5 mAhg–1at 1 C and capacity retention of 92.9% over 100 cycles at 4.6 V. This study utilizes the detrimental impurity element to upcycle high-voltage LCO cathodes through an elaborate bulk/surface structural design, offering a strategy for the high-value utilization of spent LIBs.

On the basis of the sustainable concept, organic compounds and carbon materials both mainly composed of light C element have been regarded as powerful candidates for advanced electrochemical energy storage (EES) systems, due to theie merits of low cost, eco-friendliness, renewability, and structural versatility. It is investigated that the carbonyl functionality as the most common constituent part serves a crucial role, which manifests respective different mechanisms in the various aspects of EES systems. Notably, a systematical review about the concept and progress for carbonyl chemistry is beneficial for ensuring in-depth comprehending of carbonyl functionality. Hence, a comprehensive review about carbonyl chemistry has been summarized based on state-of-the-art developments. Moreover, the working principles and fundamental properties of the carbonyl unit have been discussed, which has been generalized in three aspects, including redox activity, the interaction effect, and compensation characteristic. Meanwhile, the pivotal characterization technologies have also been illustrated for purposefully studying the related structure, redox mechanism, and electrochemical performance to profitably understand the carbonyl chemistry. Finally, the current challenges and promising directions are concluded, aiming to afford significant guidance for the optimal utilization of carbonyl moiety and propel practicality in EES systems.

Layered sodium transition-metal (TM) oxides generally suffer from severe capacity decay and poor rate performance during cycling, especially at a high state of charge (SoC). Herein, an insight into failure mechanisms within high-voltage layered cathodes is unveiled, while a two-in-one tactic of charge localization and coherent structures is devised to improve structural integrity and Na+transport kinetics, elucidated by density functional theory calculations. Elevated Jahn–Teller [Mn3+O6] concentration on the particle surface during sodiation, coupled with intense interlayer repulsion and adverse oxygen instability, leads to irreversible damage to the near-surface structure, as demonstrated by X-ray absorption spectroscopy and in situ characterization techniques. It is further validated that the structural skeleton is substantially strengthened through the electronic structure modulation surrounding oxygen. Furthermore, optimized Na+diffusion is effectively attainable via regulating intergrown structures, successfully achieved by the Zn2+inducer. Greatly, good redox reversibility with an initial Coulombic efficiency of 92.6%, impressive rate capability (86.5 mAh g–1with 70.4% retention at 10C), and enhanced cycling stability (71.6% retention after 300 cycles at 5C) are exhibited in the P2/O3 biphasic cathode. It is believed that a profound comprehension of layered oxides will herald fresh perspectives to develop high-voltage cathode materials for sodium-ion batteries.

The expedited synthesis of advanced bifunctional catalysts from waste resources is promising for improving the application of Zn–air batteries (ZAB). In this study, a self-vulcanization strategy was developed to directly transform industrial organic cobalt dimethyldithiocarbamate (CDC) residue into bifunctional oxygen electrocatalysts with an N,S-codoped carbon skeleton and a Co1–xS/Co9S8heterogeneous interface. The catalytic activity of the CDC-derived catalysts depended on the self-vulcanization temperature. CDC-800 exhibited bifunctional catalytic activity for oxygen evolution (η = 371 mV at 10 mA cm–2) and oxygen reduction (E1/2= 0.76 V) reactions. The assembled rechargeable ZAB with a CDC-800 air cathode exhibited an excellent peak power density (75.2 mW cm–2), specific capacity (873 mA h gZn–1), and cycle stability (over 670 h), respectively. This superior catalytic performance mainly resulted from the self-vulcanized Co1–xS/Co9S8heterogeneous interface. Therefore, direct self-vulcanization of organic cobalt residues can contribute to the reduction of the pollution caused by hazardous wastes and sustainable preparation of high-performance bifunctional catalysts.

Lithium metal batteries (LMBs) offer significant advantages in energy density and output voltage, but they are severely limited by uncontrollable Li dendrite formation resulting from uneven Li+behaviors and high reactivity with potential co-solvent plating. Herein, to uniformly enhance the Li behaviors in desolvation and diffusion, the local Li+solvation shell structure is optimized by constructing an anion-braking separator, hence dynamically reducing the self-amplifying behavior of dendrites. As a prototypal, two-dimensional lithiated-montmorillonite (LiMMT) is blade-coated on the commercial separator, where abundant −OH groups as Lewis acidic sites and electron acceptors could selectively adsorb corresponding FSI–anions, regulating the solvation shell structure and restricting their migration. Meanwhile, the weakened anion mobility delays the time of breaking electrical neutrality, and the Li nucleation density is quantified through the respective experimental, theoretical and spectroscopical results, providing a comprehensive understanding of modifying anion and cation behaviors on dendritic growth suppression. As anticipated, a long Li plating/stripping lifespan up to 1800 h and a significantly increased average Coulombic efficiency of 98.8% are achieved under 3.0 mAh cm–2. The fabricated high-loading Li-LFP or Li-NCM523 full-cells display the cycle durability with enhanced capacity retention of nearly 100%, providing the instructive guide towards realizing dendrite-free LMBs.

Cathodes with high cycling stability and rate capability are required for ambient temperature sodium ion batteries in renewable energy storage application. Na3V2(PO4)3is an attractive cathode material with excellent electrochemical stability and fast ion diffusion coefficient within the 3D NASICON structure. Nevertheless, the practical application of Na3V2(PO4)3is seriously hindered by its intrinsically poor electronic conductivity. Herein, solvent evaporation method is presented to obtain the nitrogen-doped carbon coated Na3V2(PO4)3cathode material, delivering enhanced electrochemical performances. N-Doped carbon layer coating serves as a highly conducting pathway, and creates numerous extrinsic defects and active sites, which can facilitate the storage and diffusion of Na+. Moreover, the N-doped carbon layer can provide a stable framework to accommodate the agglomeration of the electrode upon electrode cycling. N-Doped carbon coated Na3V2(PO4)3(NC-NVP) exhibits excellent long cycling life and superior rate performances than bare Na3V2(PO4)3without carbon coating. NC-NVP delivers a stable capacity of 95.9 mA·h/g after 500 cycles at 1 C rate, which corresponds to high capacity retention(94.6%) with respect to the initial capacity(101.4 mA·h/g). Over 91.3% of the initial capacity is retained after 500 cycles at 5 C, and the capacity can reach 85 mA·h/g at 30 C rate.

The 3-D visual positioning of aviation engine rotor bolts is of great significance for automatic connection status detection. However, the internal aviation engine rotor space is narrow, and the shooting angle is limited. Existing vision-based positioning methods based on vertical shooting are insufficient to meet aviation bolt positioning requirements. In this article, a robust bolt visual positioning method at arbitrary shooting angles is proposed. First, a deep learning-based object detection method is employed to extract bolts from both the color image and depth image. Then, an arc-support line segments (ASLSs) method based on generative adversarial network (GAN) preprocessing (ASLS-G) is used to detect multiple elliptical targets from the low-pixel color region of the bolt (CROB). By fusing color image and depth image information, an adaptive threshold slice vector (ATSV) algorithm is proposed to screen out the elliptical targets corresponding to the bottom of the bolts. Finally, a symmetrical depth mean (SDM) algorithm is proposed to obtain the depth value of the bolts and calculate their 3-D coordinates. The experimental results show that the mean absolute error of the bolt coordinate values in each direction in the bolt coordinate system is less than 0.8968 mm, and the standard deviation does not exceed 0.1636 mm, which verifies the effectiveness of the proposed method. Measurement experiments were conducted on the distance between bolts and the bolt distribution radius for a real aviation engine rotor, demonstrating that the proposed method can be applied to a broader range of real-world scenarios.

The diversification of metal elements with similar physicochemical characteristics in lithium-ion batteries (LIBs) results in great challenges in the recycling of spent LIBs. Aiming at eco-friendly, efficient, and industrial-applicable recycling, we propose a novel carbothermic reduction strategy for selective extraction of lithium and sustainable recovery of high-value metals from spent LiNixCoyMn1–x–yO2(NCM) cathode. The reduction mechanism and phase structure evolution of spent NCM revealed that the spent NCM microspheres are converted into multicomponent particles of water-soluble lithium salts (Li2CO3and Li2O) and water-insoluble M or MO (M = Ni, Co, Mn) after carbothermic reduction. Depending on the different properties of the reduced products, two different recycling routes were proposed based on disparate roasting temperatures. In the low-temperature route, 96.6% of Li can be selectively leached out by using water as the only leaching reagent after roasting at 550 °C for 1 h. For the high-temperature route, 98.1% of Li is selectively extracted by water leaching; after that, wet-magnetic separation was employed to collect transition metals depending on the magnetic differences of the product. In particular, the whole process is simple and eco-friendly and has no other chemical consumption. This work provides two efficient and environmentally friendly ways of recycling spent LIBs based on selective lithium extraction.

Sodium layered oxides always suffer from sluggish kinetics and deleterious phase transformations at deep-desodiation state (i.e., >4.0 V) in O3 structure, incurring inferior rate capability and grievous capacity degradation. To tackle these handicaps, here, a configurational entropy tuning protocol through manipulating the stoichiometric ratios of inactive cations is proposed to elaborately design Na-deficient, O3-type NaxTmO2cathodes. It is found that the electrons surrounding the oxygen of the TmO6octahedron are rearranged by the introduction of MnO6and TiO6octahedra in Na-deficient O3-type Na0.83Li0.1Ni0.25Co0.2Mn0.15Ti0.15Sn0.15O2−δ(MTS15) with expanded O–Na–O slab spacing, giving enhanced Na+diffusion kinetics and structural stability, as disclosed by theoretical calculations and electrochemical measurements. Concomitantly, the entropy effect contributes to the improved reversibility of Co redox and phase-transition behaviors between O3 and P3, as clearly revealed by ex situsynchrotron X-ray absorption spectra and in situX-ray diffraction. Notably, the prepared entropy-tuned MTS15 cathode exhibits impressive rate capability (76.7% capacity retention at 10 C), cycling stability (87.2% capacity retention after 200 cycles) with a reversible capacity of 109.4 mAh g–1, good full-cell performance (84.3% capacity retention after 100 cycles), and exceptional air stability. This work provides an idea for how to design high-entropy sodium layered oxides for high-power density storage systems.

Na4Fe3(PO4)2(P2O7) (NFPP) is an attractive candidate for Na+batteries (SIBs) and Li+batteries (LIBs). However, the real implementation of NFPP has been critically restrained by the inferior intrinsic electronic conductivity. Herein, in situcarbon-coated mesoporous NFPP, obtained via freeze drying and heat treatment, demonstrates highly reversible insertion/extraction of Na+/Li+. Mechanically, the electronic transmission and structural stabilities of NFPP are significantly enhanced by the graphitized carbon coating layer. Chemically, the porous nanosized structure shortens Na+/Li+diffusion paths and increases the contact area between the electrolyte and NFPP, ultimately rendering fast ion diffusion. Greatly, long-lasting cyclability (88.5% capacity retention for over 5000 cycles), decent thermal stability at 60 °C, and impressive electrochemical performances are demonstrated in LIBs. The insertion/extraction mechanisms of NFPP in both SIBs and LIBs are systematically investigated, confirming its small volume expansion and high reversibility. The superior electrochemical performances and the insertion/extraction mechanism investigation confirm the feasibility of utilizing NFPP as a cathode material for Na+/Li+batteries.

Lithium metal, the most promising anode material, is receiving increasing interest owing to its high theoretical capacity (3860 mA h g–1) and low negative potential (−3.04 V vs. standard hydrogen electrode). However, the uneven Li dissolution/deposition behavior causes a degraded cycle stability and safety issues, thus seriously restricting the application of Li-metal batteries (LMBs). Separator modification is one of the most versatile and feasible approaches to overcome this problem. In this study, polypropylene (PP) separators are prepared and coated with an inert hexagonal boron nitride (h-BN) layer, which can provide sufficient ion transport channels and physical protection. The h-BN@PP separator exhibits a remarkable effect on the regulation of the diffusion and nucleation of Li+to realize a homogeneous Li microstructure, thereby reducing the voltage polarization and improving the cycle performance of the battery. All LMBs equipped with the modified separators exhibit excellent cycling stabilities. The Li|Li symmetric cell exhibits a stable cycling for over 2300 h with a polarization voltage of 13 mV. In conclusion, the modified h-BN@PP separator has significant potential for stabilizing various Li metal anodes, which strongly promotes the applications of advanced LMBs.

Given the inherent features of open tunnel-like structures, moderate lithiation potential (1.0–3.0 V vs Li/Li+), and reversible redox couples (Nb5+/Nb4+and Nb4+/Nb3+redox couples), niobium-based oxides with Wadsley–Roth crystallographic shear structure are promising anode materials. However, their practical rate capability and cycling stability are still hindered by low intrinsic electronic conductivity and structural stability. Herein, ultrathin carbon-confined Nb12O29materials with rich oxygen vacancies (Nb12O29–x@C) were designed and synthesized to address above-mentioned challenges. Computational simulations combined with experiments reveal that the oxygen vacancies can regulate the electronic structure to increase intrinsic electronic conductivity and reduce the Li+diffusion barrier. Meanwhile, the carbon coating can enhance structural stability and further improve the electronic conductivity of the Nb12O29material. As a result, the as-prepared Nb12O29–x@C exhibits high reversible capacity (226 mAh g–1at 0.1 A g–1), excellent high-rate performance (83 mAh g–1at 5.0 A g–1), and durable cycling life (98.1% capacity retention at 1.0 A g–1after 3000 cycles). The lithium storage mechanism and structural stability of Nb12O29–x@C were also revealed by in situX-ray diffraction (XRD), ex situX-ray photoelectron spectroscopy (XPS), and ex situRaman spectroscopy. When applied as the anode of lithium-ion capacitors (LICs), the as-built LIC achieves high energy density (72.4 Wh kg–1) within the voltage window of 0.01–3.5 V, demonstrating the practical application potential of the Nb12O29–x@C materials.

P2-Na0.66MnO2cathode shows large capacities, but it suffers from rapid capacity fade due to the instability of the interlayer structure. Cu-substitution can effectively suppress the expansion/contraction of MnO6octahedron, thus acting as a buffer.

Fast zinc ion diffusion alloy layer delivers fast 3D diffusion and uniform distribution of zinc ions across the lateral plane to realize the highly reversible Zn plating/stripping process.

The Eu-LMO cathode structural stability and performance are significantly enhanced, attributed to the effective suppression of Jahn-Teller distortion.

Solid polymer electrolyte (SPE) has been considered as promising candidate electrolyte for solid-state lithium metal battery. However, the low ion conductivity and poor interface stability seriously hinder the development of SPE. Introducing the functional filler is a commonly used and effective approach to solving these issues. The poor compatibility and ambiguous mechanism of action are currently the main challenges. In this study, we design and synthesize carbon dots (NSFCDs) with quaternary functional groups, which are introduced into the SPE in the polymerization process of hybrid polymer electrolyte (HPE). The detailed effect law of polyfunctional groups on the polymer chain structure, interface structure of electrolyte/electrode and ion migration is systematically revealed. The dense polymer network endows HPE with enhanced mechanical properties. Through the regulation of polymer segments, the coordination environment of lithium ions is altered, promoting ion transport. The solid electrolyte interface (SEI) induced by NSFCDs and lithium salt anions effectively improves the morphology of lithium ion deposition and alleviates volume strain. As a result, the HPE based on polyethylene oxide (PEO) constructed by free radical polymerization of NSFCDs and polyethylene glycol diacrylate (PEGDA) exhibits excellent comprehensive performance, the assembled Li symmetric battery can cycle stably for 4000 h.

As a new type cathode material for aqueous zinc-ion batteries (ZIBs), manganese-based sulfides have gradually received researchers’ concern in recent years due to their lower electronegativity, higher electronic conductivity and better electrochemical activity compared with the corresponding manganese-based oxides. However, the revelation of energy storage mechanism for manganese-based sulfides is full of great challenges, which largely restricts their application. Herein, inspired by density functional theory calculations, we design and synthesize the γ-MnS and α-MnS hollow microspheres with different crystallographic types for the first time, delivering significantly different energy storage mechanisms of the two MnS electrodes. Impressively, the γ-MnS electrode can stably exist and store energy during the whole charging/discharging processes, while the α-MnS electrode first undergoes irreversible in situ oxidation to generate ZnMnO3/MnOxduring the initial charging process, and then the reversible H+/Zn2+co-insertion/extraction energy storage behavior occurs during the subsequent discharging/charging processes. This unique phase transition mechanism caused by in situ electrochemical oxidation enables the α-MnS electrode to achieve enhanced ion diffusion kinetics, thereby improving the rate capability and cyclic stability. This work not only enriches the energy storage mechanism of manganese-based sulfide cathodes, but also offers research ideas for the design and development of advanced manganese-based cathodes.

Ion electrokinetic regulation in electrolyte is of great significance to alleviating polysulfide shuttling and dendritic growth in lithium-sulfur (Li-S) batteries. Inspired by the tunable solute-polymer interactions of ion exchange membrane, herein we implant an ion-selective “skin” constructed by isocyanoethyl methacrylate grafted polyethylenimine (PEI-IEM) in electrolyte via in situgelation. This tailored skin endows the PEI-IEM-based gel polymer electrolyte (GPE) with a hyper-branched network with abundant polar groups, thus upgrading the electrolyte flame resistance, realizing obstruction on polysulfide migration, and facilitating Li+transport against uneven deposition. Consequently, the PEI-IEM-based GPE empowers enhanced S electrochemical reversibility and high security, as evidenced by a 10 Ah Li-S pouch cell with a low electrolyte/S ratio of 2.6 and 1.4× excess Li anode that delivers an energy density of 412.7 Wh kg−1. This proof-of-concept study provides new insights for tailoring the ionic behaviors of electrolyte to achieve high-energy and safe Li-S batteries.

Aqueous Zn metal batteries suffer from rapid cycling deterioration due to the severe water corrosion and dendrite growth on Zn anodes. Herein, a highly antiwater Znx-diethylenetriaminepenta(methylene-phosphonic acid) interface layer with good zinc affinity and special nanoscaled 3D granular structure is designed on Zn metal to address these problems. Experimental results combined with theoretical analysis and COMSOL simulations reveal that the hydrophobic groups in such Zn-based organic complex are the decisive factor in preventing H2O from damaging Zn anode surface. The massive Zn2+attractive sites formed by interaction of methylene-phosphonic acid groups and Zn cause ion channel for fast zinc-ion adsorption and migration. And the developed nano granular architecture on the surface induces redistributed Zn2+ion flux to realize homogenization with smooth and compact surface deposition. Under the synergism, such modified anodes exhibit long cycling lifespan over 1300 h with a relatively low polarization voltage at 5 mA cm–2. Also, the assembled full cells (including Zn//V2O5and Zn//MnO2cell) based on this anode are also demonstrated. The work provides a simple, low cost, and efficient pathway by combining the two concepts of structural design and constructing protective layers on the surface to prepare high-performance Zn anodes toward prospering aqueous zinc–metal batteries.

This review summarizes the up-to-date developments of composite electrolyte from three approaches: ion transport path, ionic conductivity, interfacial issues.

The low-cost and efficient bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critical for advanced rechargeable Zn–air batteries (ZABs). Herein, we designed and fabricated a bifunctional m-Fe2.04Ni0.66@GCFs catalyst using a sustainable physical upcycling strategy involving spent artificial diamond accelerants. Experiments and theoretical calculations verified that dual-metal active-site synergy between *Fe2.04Ni0.66@GC and Fe2.04*Ni0.66@GC enhances the rapid adsorption/desorption of *OOH/*OH species, thereby improving ORR/OER performance. In situ Raman technique confirmed that ORR/OER activities are dependent on the FeOOH, Fe(OH)2, and β-NiOOH intermediates formed during the reaction. Impressively, the m-Fe2.04Ni0.66@GCFs catalyst exhibited outstanding ORR/OER activities with a small potential difference of only 0.73 V in alkaline media. The assembled rechargeable ZAB exhibited high peak power density (115.2 mW cm−2), large specific capacity (786.9 mA h g−1), and long-term charge-discharge cycling stability of more than 1200 cycles. These results not only contribute to the design of efficient bifunctional catalysts, but also provide a new approach to the high-value utilisation of waste catalyst resources.

The implementation of Ni-rich cathodes with high energy density has been critically restrained by stress corrosion. Herein, crack-free LiNbO3-coated LiNi0.88Co0.10Mn0.02O2, as theoretically predicted, demonstrates highly reversible lithiation/delithiation. Mechanically, the phase transition (H1 → H2 → H3) is significantly alleviated by the excogitation of the interfacial force invoked by the LiNbO3coating layer, as verified by X-ray absorption spectroscopy and extended X-ray absorption near-edge structure spectroscopy. Meanwhile, the stabilities of the crystal structure are remarkably strengthened by the strong Nb–O bond activated by Nb5+doping that is confirmed by Rietveld refinement of X-ray diffraction and differential capacitance curves. Chemically, the interface shielding effect is conducive to protecting the electrode against electrolyte corrosion along with subsequent transition-metal dissolution, ultimately rendering a faster/highly convertible lithium-ion diffusion. Greatly, the excellent electrochemical properties (74% capacity retention after 300 cycles at 2 C within 2.5–4.3 V) and structural stability (the morphology remains intact after 500 cycles at 5 C within 2.5–4.3 V) are successfully achieved. Given this, this elaborate work might inaugurate a potential avenue for rationally tuning the structure/interface evolution toward Ni-rich materials.

Sodium-ion batteries (SIBs) have gained more scientists’ interest, owing to some facts such as the natural abundance of Na, the similarities of physicochemical characteristics between Li and Na. The irreversible Na+ions consumption during the first cycle of charge/discharge process (due to the formation of the solid electrolyte interface (SEI) on the electrode surface and other irreversible reactions) is the factor that determines high performance SIBs and largely reduces the capacity of the full cell SIBs. Thus, the initial coulombic efficiency (ICE) of SIBs for both anode and cathode materials, is a key parameter for high performance SIBs, and the point is to increase the transport rate of the Na+ions. Therefore, developing SIBs with high ICE and rate performance becomes vital to boost the commercialization of SIBs. Here we provide a review on the methods to improve the ICE and the rate performance, by summarizing some methods of improving the ICE and rate performance of the anode and cathode materials for SIBs, and end by a conclusion with some perspectives and recommendations.

Hydrophobic carbon dots (HCDs) were introduced into the polyacrylonitrile support layer as the nanofiller to regulate water channels for an efficient forward osmosis (FO) membrane.

Nanoengineering of metal anode materials shows great potential for energy storage with high capacity. Zero-dimensional nanoparticles are conducive to acquire remarkable electrochemical properties in sodium-ion batteries (SIBs) because of their enlarged surface active sites. However, it is still difficult to fulfill the requirements of practical applications in batteries owing to the deficiency of efficient and scalable preparation approaches of high-performance metal electrode materials. Herein, an electrochemical cathodic corrosion method is proposed for the tunable preparation of nanostructured antimony (Sb) by the introduction of a surfactant, which can efficiently avoid the agglomeration of Sb atom clusters generated from the Zintl compound and further stacking into bulk during the electrochemical process. Subsequently, graphene as the support and conductive matrix is uniformly interspersed by generating Sb nanoparticles (Sb/Gr). Moreover, the reversible crystalline-phase evolution of Sb ⇋ NaSb ⇋Na3Sb for Sb/Gr was studied by in situ X-ray diffraction (XRD). Benefiting from the interconnection of the conductive network, Sb/Gr anodes deliver a high capacity of 635.34 mAh g–1, a retained capacity of 507.2 mAh g–1after 150 cycles at 0.1 C (1 C = 660 mAh g–1), and excellent rate performance with the capacities of 473.41 and 405.09 mAh g–1at 2 and 5 C, respectively. The superior cycle stability with a capacity of 346.26 mAh g–1is achieved after 500 cycles at 2 C. This electrochemical approach offers a new route toward developing metal anodes with designed nanostructures for high-performance SIBs.

The practical application of lithium-ion batteries suffers from low energy density and the struggle to satisfy the ever-growing requirements of the energy-storage Internet. Therefore, developing next-generation electrode materials with high energy density is of the utmost significance. There are high expectations with respect to the development of lattice oxygen redox (LOR)—a promising strategy for developing cathode materials as it renders nearly a doubling of the specific capacity. However, challenges have been put forward toward the deep-seated origins of the LOR reaction and if its whole potential could be effectively realized in practical application. In the following Review, the intrinsic science that induces the LOR activity and crystal structure evolution are extensively discussed. Moreover, a variety of characterization techniques for investigating these behaviors are presented. Furthermore, we have highlighted the practical restrictions and outlined the probable approaches of Li-based layered oxide cathodes for improving such materials to meet the practical applications.

Carbon dot is a type of carbon material with an ultrasmall size of less than 10 nm for all three dimensions, which has attracted more and more attention due to its useful merits. Unfortunately, the complicated synthesis method and low yield largely limit its wide large-scale application. Herein, an inexpensive and high-efficiency aldol condensation method under ambient temperature and pressure was proposed for the large-scale synthesis of CDs, which can obtain products with 1.083 kg in 2 h and realize the functionalization of carbon dots doped with nitrogen (NCDs) and sulfur/nitrogen doubly (NSCDs), and then the mechanism and structure of CDs formation were explained. Moreover, utilizing the feature of controllable assembly of carbon dots, and combined with theoretical calculations, we have designed functionalized 1D carbon fibers (CF) to construct high-performance potassium storage anode materials through the assembly of carbon dots induced by a Zn compound. Benefitting from the microstructure and surface functional groups derived from CDs, the N-doped CF (NCF700) exhibits superior electrochemical energy storage performance for potassium ion batteries (PIBs). This study provides a low-cost and high-yield method to produce CDs and promotes the practical application of CDs in electrochemical energy storage.

Conventional polycrystalline LiMn2O4(PC-LMO) suffers from poor Li+diffusion rates and structural instability, negatively affecting its electrochemical performance. Here, we design a single-crystal LMO cathode material using BaO flux (SC-LMOB) to address these issues. The BaO flux enables the fabrication of brick-like single-crystal particles, enhancing Li+diffusion by shortening the diffusion path and increasing the unit cell volume. This process also reduces the specific surface area and stabilizes the crystal structure, effectively mitigating Mn dissolution and polarization. As a result, SC-LMOB exhibits ultra-high rate performance and superior structural stability, retaining 88.8% of its capacity at a 20 C discharge rate and achieving capacity retentions of 85.3% and 86.0% after 500 and 300 cycles at 1 C at room and elevated temperatures, respectively. This structural design offers a low-cost, scalable approach for fabricating single-crystal cathode materials with excellent performance.

Hard carbon (HC) is a promising anode material for sodium-ion batteries. However, the intrinsic relationship between the closed pores/surface groups and sodium storage performance has been unclear, leading to difficulties in targeted regulation. In this study, renewable tannin extracts were used as raw materials to prepare HC anodes with abundant tunable closed pores and carbonyl groups through a pyrolytic modulation strategy. Combining ex situ characterizations reveals that closed pores and carbonyl groups are regulated by the pyrolytic process. Further, it is demonstrated that the plateau region is mainly contributed by the closed pores; highly stable fluorine-rich solid electrolyte interphase compositions are produced through carbonyl-induced interfacial catalysis. The optimized HC anode displays good cycling stability, exhibiting a high reversible capacity (360.96 mAh g−1) at 30 mA g−1and capacity retention of up to 94% after 500 cycles at 1 A g−1. Moreover, the full battery assembled with Na3V2(PO4)3/C demonstrates a stable cycling performance. These findings provide a fresh knowledge of the structural design of high-performance HC anode materials and the mechanism of sodium storage in HC.

High specific capacity and long cycling life of anode materials still remain major challenges in the development of sodium-ion batteries (SIBs). Nowadays, transition metal phosphides have been reckoned as promising anodes in view of their high theoretical specific capacities, low potential for sodium storage, and superior conductivity. Herein, molybdenum phosphide (MoP) nanorods wrapped with thin carbon layer have been prepared and applied as an anode for SIBs. By utilizing in situ X-ray diffraction technology, a conversion-type mechanism of MoP anode has been disclosed. This kind of MoP electrode exhibits extraordinary electrochemical properties, including excellent cycling performance with a discharge capacity of 398.4 mA h g–1at a current density of 100 mA g–1after 800 cycles, and remarkable rate capabilities, which remain 104.5 mA g–1at 1600 mA h g–1even after 10 000 loops. The distinguished performances stem from synergetic merits of the morphology, structure, and mechanism of MoP. It is expected that MoP will be a promising anode material for SIBs and this work would provide theoretical basis for the scalable research and applications of MoP-based anode materials for SIBs.

Considering serious pollution from the traditional chemical synthesis process, the resource-rich, clean, and first-hand electrode materials are greatly desired. Natural ore molybdenite (MoS2), as the low-cost, high-yield, and environmental-friendly natural source, is investigated as a first-hand anode material for lithium-ion batteries (LIBs). Compared with chemosynthetic pure MoS2, natural molybdenite provides an ordered ion diffusion channel more effectively owing to its excellent characteristics, containing well-crystalline, large lattice distance, and trance dopants. Even at a large current density of 2.0 A g–1, a natural molybdenite electrode employing a carboxymethyl cellulose binder displays an initial charge capacity of 1199 mA h g–1with a capacity retention of 72% after 1000 cycles, much higher than those of the electrodes utilizing a poly(vinylidene fluoride) binder. These types of binders play a crucial role in stabilizing a microstructure demonstrated by ex situ scanning electron microscopy and in affecting pseudocapacitive contributions quantitatively determined by a series of kinetic exploration. Briefly, this work might open up a new avenue toward the use of natural molybdenite as a first-hand LIB anode in scalable applications and deepen our understanding on the fundamental effect of binders in the metal–sulfide.

The carbon coating strategy has emerged as an indispensable approach to improve the conductivity of polyanionic cathodes. However, owing to the complex reaction process between precursors of carbon and cathode, establishing a unified screening principle for carbonaceous precursors remains a technical challenge. Herein, we reveal that carbonaceous precursor pyrolysis chemistry undeniably influences the formation process and performance of Na3V2(PO4)3(NVP) cathodes from in situ insights. By investigating three types of carbonaceous precursors, it is found that O/H-containing functional groups can provide more bonding sites for cathode precursors and generate a reducing atmosphere by pyrolysis, which is beneficial to the formation of polyanionic materials and a uniform carbon coating layer. Conversely, excessive pyrolysis of functional groups leads to a significant amount of gas, which is detrimental to the compactness of the carbon layer. Furthermore, the substantial presence of residual heteroatoms diminishes graphitization. In this case, it is demonstrated that carbon dots (CDs) precursors with suitable functional groups can comprehensively enhance the Na+migration rate, reversibility, and interface stability of the cathode material. As a result, the NVP/CDs cathode displays outstanding capacity retention, maintaining 92% after 10,000 cycles at a high rate of 50 C. Altogether, these findings provide a valuable benchmark for carbon source selection for polyanionic cathodes.

P2-Na2/3Ni1/3Mn2/3O2has shown great potential as cathode material for sodium-ion batteries with its high theoretical capacity and energy density. However, severe structural changes are induced by charging P2-Na2/3Ni1/3Mn2/3O2above 4.2V, resulting in rapid capacity decay and poor kinetic capability. In this study, we propose a Zn/Ti synergistic modification strategy to stabilize the P2-type cathode under high voltage. It is found that the P2-O2 phase transition with large volume change is replaced by a milder P2-Z phase transition with the noteworthy improvement in structural stability and Na+diffusion kinetics, due to the disordered Na+/vacancy and the suppressed of the sliding of transition metal layers, as disclosed by density functional theory calculations and in-situX-ray diffraction. Concurrently, The phenomenon of Ni and O reductive coupling is inhibited by regulating local O coordination owing to the incorporation of a strong Ti−O covalence bond, leading to the more reversible charge compensation mechanism and the inhibited lattice O evolution, as clearly revealed by ex-situX-ray absorption spectroscopy and Differential Electrochemical Mass Spectrometry. Consequently, we obtained a stable P2-Na0.67Zn0.05Ni0.28Mn0.52Ti0.15O2cathode, achieving an average discharge voltage of 3.62V at 0.1C and a capacity retention of 80% after 500 cycles at 2C. This research provides valuable insights into the enhancement of sodium-ion battery cathode materials by utilizing different functional ions in synergy.

The exploration of advanced materials through rational structure/phase design is the key to develop high-performance lithium-ion capacitors (LICs). However, high complexity of material preparation and difficulty in quantity production largely hinder the further development. Herein, Cu5FeS4-x/C (CFS@C) heterojunction with rich sulfur vacancies has successfully achieved from natural bornite, presenting low cost-effective and bulk-production prospect. Density functional theory calculations (DFT) indicate that rich vacancies in bulk phase can decrease band gap of bornite and thus improve its intrinsic electron conductivity, as well as the heterojunction spontaneously evokes a built-in electric field between its interfacial region, largely reducing the migration barrier from 1.27 eV to 0.75 eV. Benefited from these merits, the CFS@C electrodes deliver outperformed lithium storage performance, e.g., high reversible capacity (822.4 mAh/g at 0.1 A/g), excellent cycling stability (up to 820 cycles at 2 A/g and 540 cycles at 5 A/g with respective capacity retention of over or nearly 100%). With CFS@C as anode and porous carbon nanosheets (PCS) as cathode, the assembled CFS@C//PCS LIC full cells exhibit high energy/power density characteristics of 139.2 Wh/kg at 2500 W/kg. This work is expected to offer significant insights into structure modifications/devising toward natural minerals for advanced energy-storage systems.

With the low cost, excellent safety and high theoretical specific capacity, aqueous zinc-ion batteries (AZIBs) are considered as a potential rival for lithium-ion batteries to promote the sustainable development of large-scale energy storage technologies. However, the notorious Zn dendrites and low Coulombic efficiency (CE) limit further development of AZIBs, due to the unstable electrochemical deposition/stripping behavior of Zn anode in aqueous zinc ion electrolytes. In this review, critical issues and advances are summarized in electrolyte engineering strategies. These strategies are focused on active water molecules during electrochemical process, including high-concentration electrolytes, ionic liquids, gel-polymer electrolytes and functional additives. With suppressed active water molecules, the solvation and de-solvation behavior of Zn2+can be regulated, thereby modulating the electrochemical performance of Zn anode. Finally, the inherent problems of these strategies are discussed, and some promising directions are provided on electrolytes engineering for high performance Zn anode in AZIBs.

The development of fast-charging and wide-temperature sodium-ion batteries (SIBs) is of great significance to all-climate energy storage. However, the gigantic challenge lies in achieving super dynamic performance and stability of cathode materials. Herein, the defect configuration entropy (DCE) is conceptualized in Na3V2(PO4)3/carbon composite (NVP/C) cathode by manipulating heteroatoms and vacancies in the surface carbon layer. It is found that the bonding energy between the carbon layer and NVP interface increases with the DCE. Accompanying, the Na+migration energy barrier is reduced and the electronic conductivity is enhanced, which are pivotal factors underpinning the low-temperature performance. Furthermore, the increase of DCE engenders the formation of a NaF-rich cathode-electrolyte interface, furnishing support for high-temperature stability. As a result, the DCE-strengthened NVP/carbon composite cathode exhibits a high capacity of ~88 mAh g-1at an ultrahigh rate of 200C (13s per charge process). Moreover, the superior electrochemical performance in the wide temperature range of -30-60 °C is achieved with 0.101% capacity decay per cycle at -20 ℃, and 0.0047% capacity decay per cycle at 60 ℃.

The development of electric vehicle and plug-in hybrid electric vehicles (EV and PHEV) has increased the demand for fast charging battery technology. The sodium-ion battery has the potential application in the field of low-speed electric vehicle, which puts forward the requirement for the development and application of fast charging technology. However, the slow dynamics of traditional anode materials for sodium-ion batteries limit their application in fast charging conditions. The development of anode materials with fast sodium-ion diffusion ability is the key to achieve fast charging sodium-ion batteries. In this paper, the research status of anode materials for fast charging sodium-ion batteries is reviewed, including the influencing factors for fast charging performance, the structural features and sodium storage mechanisms of different kinds of anode materials, and the strategies to increase the rate performance of anode materials. Finally, the challenges faced by anode materials for fast charging sodium-ion batteries are discussed and the prospect of their future development is put forward.

Sodium-ion batteries (SIBs) have significant potential for applications in portable electric vehicles and intermittent renewable energy storage due to their relatively low cost. Currently, hard carbon (HC) materials are considered commercially viable anode materials for SIBs due to their advantages, including larger capacity, low cost, low operating voltage, and inimitable microstructure. Among these materials, renewable biomass-derived hard carbon anodes are commonly used in SIBs. However, the reports about biomass hard carbon from basic research to industrial applications are very rare. In this paper, we focus on the research progress of biomass-derived hard carbon materials from the following perspectives: (1) sodium storage mechanisms in hard carbon; (2) optimization strategies for hard carbon materials encompassing design, synthesis, heteroatom doping, material compounding, electrolyte modulation, and presodiation; (3) classification of different biomass-derived hard carbon materials based on precursor source, a comparison of their properties, and a discussion on the effects of different biomass sources on hard carbon material properties; (4) challenges and strategies for practical of biomass-derived hard carbon anode in SIBs; and (5) an overview of the current industrialization of biomass-derived hard carbon anodes. Finally, we present the challenges, strategies, and prospects for the future development of biomass-derived hard carbon materials.

A thermodynamically directed Ta/Ti dual-modification has been proposed to successfully engineer a multifunctional Ni-rich LiNi0.834Co0.11Mn0.056O2cathode incorporating a LiTaO3grain boundary coating alongside simultaneous Ti-doping, which is determined by the variation tendency of the structure/interface formation energy when introducing foreign elements. Notably, the dual-modification strategy significantly improves the structural/interfacial stability and Li+diffusion kinetics of Ni-rich cathode.

Stabilizing zinc anode is a systematic project for aqueous zinc ion batteries (ZIBs), which needs to solve many problems such as dendrite growth, corrosion, hydrogen evolution, and other side reactions. It is urgent to develop a protective layer for zinc anode to solve these problems at one time. Based on the results of calculation, a hydrophobic multifunctional fluorinated carbon dots (F-CDs) protective layer with three kinds of zincophilic groups (-CO, -CHO and -F) was constructed on the Zn anode surface. As expected, these zincophilic groups on the F-CDs layer functioned as zincophilic sites to achieve uniform Zn deposition. Especially, the -F group could in-situ promote the formation of ZnF2under the F-CDs layer and the ZnF2layer is usually considered as a solid Zn2+conductor layer to further even Zn deposition. Additionally, the experimental results also demonstrated that the F-CDs layer coupled with in-situ generated ZnF2interlayer can not only tackle above issues in an integrated way, but also induce the deposition of Zn on the preferred (002) plane. Therefore, the Zn@F-CDs anode exhibits an ultra-long cycling life over 3500 h at 1 mA cm–2, together with an excellent average coulombic efficiency (99.32% for over 1100 h) in half cells.

Titanium oxides have been considered promising anode materials for lithium-ion batteries (LIBs). However, the poor conductivity and low specific capacity of bulk titanium oxides limit their application. In this study, a carbon dot-modified TiO2@SiO2aerogel was successfully fabricated through a facile ambient pressure drying strategy and used as an anode material of LIBs. Benefiting from the crosslinking of carbon dots and the surface modification of SiO2, the as-prepared hierarchical aerogel exhibited a high initial discharge capacity of 974 mAh g−1and maintained a capacity of 299 mAh g−1after 100 cycles at 0.1 A g−1. It also retained a discharge capacity of 111 mAh g−1with a CE of 99.9% at 3 A g−1. The carbon dot-modified cross-linking skeleton contributes to the structural integrity of the TiO2@SiO2aerogel during repeated insertion/extraction of lithium ions, guaranteeing outstanding cycling and high-rate performance. This ambient pressure drying strategy provides a facile and feasible way to produce high-performance aerogel anode materials for lithium-ion storage.

Oxygen-respirable sponge was constructed by carbon dots-assisted synthesis strategy.The hydrophilicity and aerophilicity of Co@C–O–Cs active sites boost oxygen diffusion and the bifunctional oxygen reduction reaction and oxygen evolution reaction activities.Co@C–O–Cs-based Zn-air battery (ZAB) displays excellent specific capacity and stability, and the all-solid-state Co@C–O–Cs-based ZAB exhibits excellent flexibility.

The robust organic/inorganic hybrid interlayer derived from in situ formed tribofilms were fabricated by using a scalable rolling method.The interlayer facilitates dendrite-free lithium metal anodes by building local de-solvation environments near the interface and inhibiting both dendrite growth and electrolytes corrosion.The symmetrical cell exhibits a remarkable lifespan of 5,600 h (1.0 mA cm-2and 1.0 mAh cm-2) and 1,350 cycles even at a harsh condition (18.0 mA cm-2and 3.0 mAh cm-2).

Carbon-based materials have attracted much interest as one of the promising anodes for sodium-ion batteries. However, low utilization of electrolyte and slow ion-transfer rate during electrochemical process hinder the further application of traditional bulk carbon. In order to enhance the diffusion kinetics and maintain the reversibility, hierarchical hollow carbon microbox was successfully prepared through a tunable bottom-up self-template routine for sodium-ion batteries. During annealing process, the morphology construction and activation happened synchronously. Based on that, a range of cross-linked porous nanosheet and hollow microbox were attained by manipulating reactant condition. The generation of texture and physical property are analyzed and are established linkages related to the electrochemical behavior. As results depicted in kinetic exploration and simulation based on cyclic voltammetry, the surface-controlled electrochemical behavior gradually turns to be the diffusion-controlled behavior as the hollow microbox evolves to porous nanosheet. The probable reason is that the rational microstructure/texture design leads to the accelerated diffusion kinetic procedure and the reduced concentration difference polarization. Sodium storage mechanism was deduced as reversible binding of Na-ions with local defects, including vacancies on sp2graphitic layers, at the edges of flakes and other structural defects instead of intercalation. Bestowed by the morphology design, the broad pore width distribution, abundant defects/active sites and surface functionality, hollow microbox electrode delivers great electrochemical performances. This work is expected to propose a novel and effective strategy to prepare tunable hierarchical hollow carbon microbox and induce the fast kinetic of carbon anode material.

Owing to the slight volume expansion after potassiation, hard carbon is regarded as a promising anode material for potassium-ion batteries (PIBs). Heteroatom doping (such as sulfur or nitrogen) is a common method to modify hard carbon for high K-storage capacity and long cycling performance. High sulfur-doped hard carbon with a sulfur content of 25.8 wt % is prepared by calcining glucose in molten salt (K2SO4@LiCl/KCl). It exhibits high specific capacities of 361.4 mA h g–1during the 1st cycle and 317.7 mA h g–1during the 100th cycle at 0.05 A g–1. The high capacity arises from the K–S reaction behavior, which is demonstrated by the cyclic voltammetry test and galvanostatic intermittent titration technique. This work is an effective application of the molten salt method for PIBs, furnishing an understanding to K-storage behaviors of hard carbon- with high sulfur content.

Transition metal phosphides (TMPs) have gained increased attention in energy storage due to their potential applications for optimizing electrochemical performances. However, their preparation routes usually require highly toxic and flammable phosphorus sources with strict reaction conditions. The existence of multiple energetically favorable stoichiometries also makes it a challenge to achieve phase control of metal phosphides. In this work, we have successfully realized the phase-controllable framework of cobalt phosphide from Co2P to CoP by employing a semi-interpenetrating network (semi-IPN) hydrogel as a precursor. Interestingly, the semi-IPN hydrogel could serve as a self-assembly/sacrificing template to accomplish 3D space confinement, where poly(vinylphosphonic acid) (PVPA) was identified as a prominent phosphorus source due to its strong metal complexation ability and high thermal stability. Furthermore, this route is successfully extended to the synthesis of other TMPs, including Fe2P, Ni2P, and Cu3P. The specific structure of cobalt phosphides gives rise to superior lithium storage performance, showing superior cycling stability (495.2 mAh g–1after 1000 cycles at 2.0 A g–1). This approach envisions a new outlook on exploitation of essential functional hydrogels for the creation of inorganic materials toward sustainable energy development.

Discovering cathode materials composed of earth-abundant elements has become the current priority for developing sodium-ion batteries (SIBs) to meet the ever-increasing demand of large-scale energy storage. Herein, for the first time, layered NaxMO2(M = Cu, Fe, Mn) cathodes are successfully prepared by directly using concentrated chalcopyrite ores as precursors. Greatly, impurity elements like Si and Ca are found to be crucial to tailoring the phase structure of as-obtained layered oxides as a P2 or O3 type, which removes the traditional concern that the impurities may restrict the utilization of natural ores. More interestingly, a certain amount of the Ca elements remaining in the Na sites through a self-doping process endows the P2-type products with enhanced structural stability. In half-cells, P2-type NaxMO2with self-doped Ca elements shows superior rate capability and cycling stability (56 mAh g–1at 5 C and 90% capacity retention after 100 cycles at 1 C). In contrast, less impurity elements are favorable for O3-type oxides to achieve a high capacity of 107 mAh g–1at 0.1 C and 84% capacity retention after 200 cycles at 2 C. This new strategy would efficiently shorten the process for preparing electrode materials and open a feasible route to construct cheap and durable SIBs.

The sluggish kinetics and large overpotential of the oxygen reduction reaction (ORR) severely limit the widespread production and application of metal–air batteries. Herein, a conductive three-dimensional (3D) porous spiral-like polyhedron structure composed of nitrogen-doped carbon nanosheets (L/D-SPNC) was utilized as catalysts with combination of 3D hierarchical porous properties and distinguishing intrinsic properties of two-dimensional (2D) nanosheets for ORR. The chiral template, l/d-tartaric acid, induces the self-assembly of the supramolecule and the formation of an orderly array of carbon with spiral-like surface feature on a molecular scale. The resulting L/D-SPNC exhibits a small wall thickness (2.5 nm), large specific surface area (2034.2 m2/g), and high conductivity (155.76 S/m), which indicates that the properties of 2D nanosheets building blocks are kept in 3D mode. As catalysts for ORR, the optimized L-SPNC-950-1 exhibits a more positive onset potential of 1.03 V compared with those of Pt/C (1.00 V) and a half-wave potential of 0.87 V is also comparable to those of Pt/C (0.87 V). Al–air battery discharge data demonstrate that the spiral-like structure facilitates the diffusion of the electrolyte and oxygen on a three-phase interface, causing weak polarization. Density functional theory (DFT) calculations prove that the twisted surface aggravates the differential charge distribution between C–C/C–N bonds.

Well-tailored sulfur-doped anatase titanium dioxide nanoparticles anchored on a large-area carbon sheet are designed, where the in situ sulfur-doped titanium dioxide directly comes from titanium oxysulfate and the large-area carbon sheet is derived from glucose. When applied as an anode material for sodium-ion batteries, it exhibits an excellent electrochemical performance including a high capacity [256.4 mA h g–1at 2 C (1 C = 335 mA h g–1) after 500 cycles] and a remarkable rate of cycling stability (100.5 mA h g–1at 30 C after 500 cycles). These outstanding sodium storage behaviors are ascribed to the nanosized particles (about 8–12 nm), good electronic conductivity promoted by the incorporation of carbon sheet and sulfur, as well as the unique chemical bond based on the electrostatic interaction.