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Zero-dimensional carbon dots have emerged as important nanofillers for the separation membrane due to their small specific size and rich surface functional groups. This study proposed a strategy based on hydrophobic carbon dots (HCDs) to regulate water channels for an efficient forward osmosis (FO) membrane. Thin-film composite (TFC) membranes with superior FO performance are fabricated by introducing HCDs as the nanofiller in the polyacrylonitrile support layer. The introduction of HCDs promotes the formation of the support layer with coherent finger-like hierarchical channels and micro-convex structure and an integrated polyamide active layer. Compared to the original membrane, TFC-FO membrane with 10 wt% HCDs exhibits high water flux (15.47 L m−2 h−1) and low reverse salt flux (2.9 g m−2 h−1) using 1 mol/L NaCl as the draw solution. This improved FO performance is attributed to the lower structural parameters of HCDs-induced water channels and alleviated internal concentration polarization. Thus, this paper provides a feasible strategy to design the membrane structure and boost FO performance.

Despite the intriguing merits of lithium-sulfur (Li-S) systems, they still suffer from the notorious “shuttling-effect” of polysulfides. Herein, carbon materials with rational tailoring of morphology and pores were designed for strong loading/adsorption with the controlling of energy-storage ability. Through rational tailoring, it is strongly verified that such engineering of evolutions result in variational of sulfur immobilization in the obtained carbon. As expected, the targeted sample delivers a stable capacity of 925 mAh g−1 after 100 loops. Supporting by the “cutting-off” manners, it is disclosed that mesopores in carbon possess more fascinated traits than micro/macropores in improving the utilization of sulfur and restraining Li2Sx (4 ≤ x ≤ 8). Moreover, the long-chain polysulfide could be further consolidated by auto-doping oxygen groups. Supported by in-depth kinetic analysis, it is confirmed that the kinetics of ion/e- transfer during charging and discharging could be accelerated by mesopores, especially in stages of the formation of solid S8 and Li2S, further improving the capacity of ion-storage in Li-S battery. Given this, the elaborate study provide significant insights into the effect of pore structure on kinetic performance about Li-storage behaviors in Li-S battery, and give guidance for improving sulfur immobilization.

High-performance lithium ion capacitors (LICs) have been seriously hindered by the very low capacity and unclear capacitive mechanism of carbon cathode. Herein, after the combination of experimental results and theoretical calculations, it is found that the critical pore size of 0.8 nm for PF6− ion adsorption decreases strong interactive repulsion of electrons and largely reduces adsorption energy barrier, which greatly improves the charge accommodation capacity in electrical double-layer behavior. Most importantly, the chemical-bond evolution process of C=O group has been firstly revealed by X-ray photoelectron spectroscopy (XPS), indicating that the introduction of C=O group can provide abundant redox active sites for PF6− ion adsorption accompanied with enhanced pseudocapacitive capacity. Attributed to the synergistic effect of dual capacitive mechanism, porous carbon sheet (PCS) cathode shows a reversible specific capacity of 53.6 mAh g−1 even at a high current density of 50 A g−1. Significantly, the quasi-solid-state LIC manifests state-of-the-art electrochemical performances with an integrated maximum energy density of 163 Wh kg−1 and an outstanding power density of 15,000 W kg−1. This elaborate work promotes better fundamental understanding about capacitive mechanism of PF6− ion and offers a rational dual-capacitive strategy for the design of advanced carbon cathodes.

Carbon dots are a new class of carbon materials with ultrasmall size and unique physicochemical property. They have been widely studied since their discovery and have been gradually applied in various fields due to their quantum size, abundant surface functional groups, great biocompatibility, non-toxicity and photoluminescence characteristics. Recently, applications of carbon dots in the new generation batteries have also shown great potential. This review systematically summarized the research status of carbon dots in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), potassium ion batteries (PIBs), lithium-sulfur batteries (LSBs), etc., and discussed the applications of carbon dots in electrode materials, separator and electrolyte of advanced batteries in detail. Moreover, we also analyzed the challenges and development directions of carbon dots in batteries. This review aims to provide guidance and reference for the design and manufacture of the next generation of high-performance batteries.

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.

Ameliorating the interfacial issues of the zinc anode, particularly dendrite growth and electrode corrosion, is imperative for rechargeable zinc metal batteries. Herein, an electrochemical-inert li...

Rechargeable aqueous zinc-ion batteries (ZIBs) are attractive candidates for next-generation batteries. However, the challenge of uneven zinc electroplating/electrostripping on bare Zn anodes has severely restrained the practical application of ZIBs. To address this problem, a straightforward strategy of sliver particle-coated zinc plate (designated as Zn@Ag) via the metallic replacement reaction as the zinc metal anode has been employed to facilitate uniform and stable Zn-plating/stripping. The newly formed AgZn3 alloy from silver particles at the first zinc-plating cycle with good zinc affinity can effectively lower the energy barrier of zinc nucleation and promote uniform electric field distribution for the flow of Zn ions, resulting in stable zinc deposition. Benefiting from the in situ formed alloy phase, the Zn@Ag anode achieves stable cycling for over 1700 h with a very low polarization voltage of about 21 mV at 0.25 mA cm−2 and 0.25 mA h cm−2, while the bare Zn anode just exhibits less than 150 cycles with large voltage fluctuation and polarization under same conditions. As a consequence, greatly improved performance of the Zn@Ag//CNT/MnO2 full-cell with twice the capacity (177 mA h g−1) than that of bare Zn//CNT/MnO2 full-cell (71 mA h g−1) after 400 cycles at 0.6 A g−1 can be realized. This work provides a facile and effective approach to regulate Zn deposition for the achievement of long-life rechargeable ZIBs.

A dynamic hydrophobic molecular membrane (DHM) of quaternary phosphonium salts has been in situ constructed on an electrified anode. The DHM can act as a resistor to regulate the distribution and reduction rates of zinc species, thus refining grains and facilitating the formation of dendrite-free zinc anodes to improve battery cycle stability.

As a promising cathode material for high performance lithium ion batteries, olivine LiMnxFe1−xPO4 (LMFP) combines the high safety of LiFePO4 and the high energy density of LiMnPO4. However, there are still obstacles to overcome for achieving higher rate performance, especially its inherent low electronic conductivity and Li+ diffusion coefficient. Here, the restricting factors for realizing high rate performance LMFP cathode materials are reviewed systematically. The bulk properties that affect the internal ion transport and electronic conduction are thoroughly expounded, particularly the phase transition mechanism, lattice distortion, point defects, element doping, Fe/Mn ratio and particle morphology. Moreover, the effect of utilizing a carbon-based/non-carbon material coating for improving the interface structure on rate performance is discussed comprehensively. A particular emphasis is placed on the design of LMFP-based batteries with high rate capability as well from the aspect of cell preparation technology, including the electrolyte selection and electrode design. Finally, on the basis of state-of-the-art understanding of bulk properties, the interface structure and cell preparation engineering, several technical challenges and research trends in improving the rate performance of LMFP cathode materials are proposed.

Sodium super ionic conductor (NASICON) based electrode and electrolyte compounds offer new prospect to achieve higher energy/power densities, improved safety, and longer cycle life in sodium ion batteries (SIBs). For many years NASICON compounds have not been regarded as a possible electrode material for SIBs, mainly because, the research was focusing on the electrolyte aspect. However, in recent years NASICON type materials have attracted a great deal of attention as an electrode as well due to their excellent properties, which include high ionic mobility, better safety and improved structural stability. This review for the first time features and consolidates the ion diffusion mechanisms and crystal structures of different explored NASICON materials. It also provides insight into the present challenges to commercialize these materials for developing functional SIBs. We believe that the thorough understanding of the ion diffusion mechanisms and crystal structures of NASICON based materials is necessary to design new electrodes and will be useful to improve the electrochemical performances of SIBs. The advantages/disadvantages of each category of materials are also discussed. Apart from the widely investigated NASICON type cathode and anode materials, the rarely explored electrolyte material is also included for the complete review of this potential material. We believe that our detailed analysis on crystal structure and ion diffusion mechanism presented in this review will provide insights into important progress that are made in NASICON materials and could open up new opportunities for devising battery formulations that would continue to evolve and will also appeal to broad research audience.

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 sp2 graphitic 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.

Lithium metal anode is usually described as the “Holy Grail” electrode and stimulates widely interest of researchers due to an ultrahigh theoretical specific capacity and lowest electrochemical potential. Lithium metal anode can match well with the growing demand for high energy density when coupled with suitable cathode. However, the defects related to lithium metal anode, especially Li dendrite growth, stunt tremendously the practical application of metallic Li−based batteries. To deal with the aforementioned issue, a series of strategies have been proposed successively. Thereinto, it is worth noting that electrolyte additives, served as “vitamin” in the batteries, are in urgent demand for its convenience and cost-effectiveness. To understand the beneficial role of electrolyte additives for stable Li anode in depth, firstly, we introduced several main mechanism of Li dendrite growth. Moreover, the effects of electrolyte additives for Li metal anode was expounded. Furthermore, we reviewed recent progress of electrolyte additives in protecting Li anode. Finally, we summarized the existing challenges of additives and proposed some prospects combined with the practice.

Interfacial chemical bonds have captured surging attentions as the effective improving manners for electrochemical ions-storage and energy-conversion systems, including alkali-ions batteries, photocatalysis (PC), electrocatalysis (EC) and photo-electrocatalysis (PEC). Compared to the traditional modified manners for carbon-metal composites, introducing bonds would render the great evolution of their electrochemical properties, mainly resulting from the increased active sites, quick electrons transfer and so on. In this review, the recent process of bonds was detailed summarized in relative areas. Meanwhile, the bonds could be divided into M − C and M-X-C (M presents metal elements; C is about carbon materials; X = O, S, N etc.), and their relative physical-chemical traits with validation means have been concluded. Moreover, despite the merits above, for battery systems, the bonds were deemed as the roles of enhancing structural stability and interfacial ions-storage capability. Alternatively, for PC and PEC systems, chemical bonds could speed up the interfacial charge transfer and hinder the recombination of photo-generated electrons and holes, whilst for EC system, they would serve as highly active electrocatalytic center, providing more stable interfacial structure. Finally, the review was anticipated to offer systematic and in-depth comprehension for interfacial bonds, whilst guiding the further exploring of the interface about advanced composites.

From the perspective of resource reserves, environmental effects, and production costs, direct utilization of natural ores as electrode materials for rechargeable batteries after mineral processing is of more practical significance than chemosynthetic materials. While the corresponding investigation is relatively insufficient, herein phenolic resin (PR)-coated natural pyrite composite (FeS₂@PR) is successfully fabricated using natural pyrite and oligomeric phenolic resin as starting materials. Subsequent oligomer polymerization and calcination process convert FeS₂@C into sulfur-doped carbon-coated Fe₇S₈ (FS@C). Benefiting from the good electric and ionic conductivity of Fe₇S₈, abundant sulfur active sites, and porosity on carbon shell and effective carbon buffering, FS@C exhibits impressive electrochemical performance as anodes for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). It delivers high reversible capacities of 1319 and 796 mAh g–¹ after 100 cycles at 0.1 A g–¹ for LIBs and SIBs, respectively. Even at a high current density of 2.0 A g–¹, considerable capacities of 771 mAh g–¹ after 1000 cycles and 545 mAh g–¹ after 400 cycles are retained for LIBs and SIBs. This work provides a promising prospect toward scalable production of high-capacity iron sulfide anode for lithium-ion and sodium-ion batteries.

Two-dimensional (2D) molybdenum disulfide (MoS2) holds significant promise as an energy storage material, whereas the exfoliation of MoS2 into few-layer from natural molybdenites remains a challenge. An efficient electrochemical strategy was proposed for the preparation of few-layer MoS2 through cationic intercalation. Few-layer MoS2 without the impurity phases was obtained with high yield through Raman mapping analysis, and the intermediate (TBA+) x MoS2 x − was captured by in-situ Raman. Note that the charge transport kinetics of the exfoliated few-layer MoS2 was further enhanced by the introduction of graphene, which could efficiently enhance the Na+ diffusion mobility, alleviate the volume change of MoS2 and stabilize the reaction products. Commendably, the exfoliated MoS2/graphene hybrid shows a reversible specific capacity of 642.8 mA h g−1 at0.1 A g−1, superior rate performance (447.8 and 361.9 mA h g−1 at 1 and 5 A g−1, respectively) and remarkable long-cycle stability with 328.7 mA h g−1 at 1 A g−1 after 1000 cycles for sodium-ion batteries (SIBs). Therefore, this efficient electrochemical exfoliation method can be driven to prepare other few-layer 2D materials for SIBs.

As new-generation electrochemical energy-storage systems, lithium-ion capacitors (LICs) have combined the advantages of both lithium-ion batteries and supercapacitors, manifesting the merits of high-energy density under power density. Triggered by outstanding physicochemical characteristics and two different charge-storage mechanisms (including the Li+ insertion and electric double-layer capacitor characteristics), carbon materials have been intensively studied for fabricating high-performance LICs. However, the construction of high-performance LICs have been greatly limited by the unbalanced capacity and kinetic imbalance between the sluggish ion diffusion process of anode and fast electrostatic accumulation behavior of cathode. Thus, aimed at improving two different electrochemical storage performances, rational design of carbon materials has been summarized in this short review, which provide the directional guidance for engineering optimized carbon electrodes and become a breakthrough for improving energy/power densities of LICs. Furthermore, the prospects and unresolved scientific issues of LICs are also proposed.

In the development of rechargeable Li metal batteries, current collectors with high porosity, rational pore structure and lithiophilic skeleton are essentially needed to suppress Li dendrite and accommodate the volume variation. Herein, 3D hierarchical porous collector activated from chemical dealloying of brass mesh is elaborately decorated with highly lithiophilic Sn layer via electroless plating method for dendrite-free Li metal anode. During Li plating process, the nucleation overpotential is remarkably reduced with the in-situ electrochemically generated Li–Sn alloy, realizing uniform Li nucleation/growth. Meanwhile, unique hierarchical porous structure with a high porosity of 60.2% ensures well dispersed current density for homogeneous Li deposition and accommodation. As expected, a high coulombic efficiency above 98% for 240 cycles at 1 ​mA ​cm−2 and a prolonged lifespan of symmetrical cells for 800 ​h ​at 1 ​mA ​cm−2 with lower polarization are achieved, which further renders the LiFePO4 based full cells with improved capacity retention up to 92.9% after 200 cycles at 0.5C. This work proposes a highly effective strategy to realize dendrite-free Li metal anode.

Cathodes with high cycling stability and rate capability are required for ambient temperature sodium ion batteries in renewable energy storage application. Na3V2(PO4)3 is 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)3 is seriously hindered by its intrinsically poor electronic conductivity. Herein, solvent evaporation method is presented to obtain the nitrogen-doped carbon coated Na3V2(PO4)3 cathode 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)3 without 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.

2D carbon materials show extraordinarily promising prospects in energy storage systems. To improve the performance of lithium-ion capacitors (LICs), it is urgently necessary for addressing the sluggish kinetics behavior of battery-type carbon negative electrode. Herein, novel 2D defective high-graphitic carbon nanosheets (GNS), which is derived from in-situ catalytic graphitization of 1D nanorods precursor, are presented and employed as negative electrode materials in LICs. The effects of defects contained in the as-prepared samples are further explored by the First-principle calculations, revealing that carbonylation and N-doping (particularly pyridine N) manifest synergistic effect on improving the electronic conductivity and regulating the microstructure. The high reversible capacity accompanied with large plateau capacity and superior rate capability in the half-cell test implies that GNS can be a promised candidate as negative electrode for LICs. Excitingly, the fabricated LICs exhibit high energy density of 112 Wh kg−1 and excellent power density of 19,600 W kg−1, together with outstanding energy density retention of 96.5% after 5000 cycles at 5 A g−1. The defects-controlled in-situ catalytic strategy for preparing GNS may provide a brand-new way for materials design for energy storage.

Antimony sulfide as an energy storage material with remarkable theoretical capacity has captured the attention of several researchers, but it has disadvantages such as volume expansion, polysulfide dissolution, and sluggish kinetics. By utilizing the oxygen functional groups in phenolic resin, engineering the nature mineral Sb2S3 with hierarchical interfaces (Sb, S-doped carbon) can be undertaken, effectively facilitating the diffusion of ions and accommodating volume changes. Importantly, the double-controlling synergistic effects of the Sb shell and S-doped carbon would prolong the diffusion pathway of polysulfides, considerably enhancing the sodium-ion storage capability. As a result, a capacity retention rate of 97.1% at 0.1 A g−1 could be obtained after 200 cycles. At 0.5, 1.0, and 2.0 A g−1 after 150 cycles, capacities of 422.6, 367, and 311.1 mA h g−1, respectively, could be retained. A detailed investigation regarding capacity confirmed that the introduced hierarchical interfaces could significantly promote the faster transfer of electrons and trapping of polysulfides accompanied with improved reversible conversion reactions. The quantitative analyses of capacitive contribution and EIS data revealed that the core–shell structure and S-doped carbon could fundamentally boost the pseudocapacitive behaviors with improved transfer of electrons/ions. This rational design is expected to brighten the prospects for designing metal sulfides for use as advanced anodes in sodium-ion batteries.

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.

Dual-functional porous copper films were prepared by dynamic hydrogen bubble template (DHBT) technique to achieve in situ SERS monitoring of electrocatalytic reaction. The morphology and SERS activity of porous copper films were effectively modulated by electrolyte additive, current density, and deposition time. The interfacial evolution behaviors of porous copper films were monitored by in situ synchrotron radiation X-ray imaging. The three-dimensional porous copper films in the presence of CTAB additive present a thinner leaf-like dendritic structure and excellent SERS activity. Although the diverse morphologies of porous copper films are obtained with inorganic additives including (NH4)2SO4, Na2SO4, or NaCl, they are deleterious to the SERS activity due to the microstructural changes of copper films, even significantly lower than that of the additive-free condition. The obtained porous copper films exhibit high sensitivity (10−9 mol/L) and good reproducibility for efficient SERS detection. Furthermore, the electrocatalytic reduction process of 4-nitrophenol on the porous copper films was successfully in situ monitored based on their excellent SERS activity.

Transition-metal selenides have captured sustainable research attention in energy storage and conversion field as promising anodes for sodium-ion batteries. However, for the majority of transition metal selenides, the potential windows have to compress to 0.5-3.0 V for the maintenance of cycling and rate capability, which largely sacrifices the capacity under low voltage and impair energy density for sodium full batteries. Herein, through introducing diverse metal ions, transition-metal selenides consisted of different composition doping (CoM-Se2@NC, M = Ni, Cu, Zn) are prepared with more stable structures and higher conductivity, which exhibit superior cycling and rate properties than those of CoSe2@NC even at a wider voltage range for sodium ion batteries. In particular, Zn2+ doping demonstrates the most prominent sodium storage performance among series materials, delivering a high capacity of 474 mAh g-1 after 80 cycles at 500 mA g-1 and rate capacities of 511.4, 382.7, 372.1, 339.2, 306.8, and 291.4 mAh g-1 at current densities of 0.1, 0.5, 1.0, 1.4, 1.8, and 2.0 A g-1, respectively. The composition adjusting strategy based on metal ions doping can optimize electrochemical performances of metal selenides, offer an avenue to expand stable voltage windows, and provide a feasible approach for the construction of high specific energy sodium-ion batteries.

Considering serious pollution from the traditional chemical synthesis process, the resource-rich, clean electrode materials are greatly desired. Conventional electrochemical performance improvement methods, such as quantum dot or coating, are complicated and costly. In this study, CuFeS2 with an enhanced cycle performance is prepared from natural ore chalcopyrite through simple flotation and acid leaching. We obtain micro-sized CuFeS2 with high yield and purity. Electrochemical measurement shows that the natural chalcopyrite with an EDD-S electrolyte displays a high initial charge capacity (992 mAh·g−1 at the initial discharge current density of 0.2 C), an excellent rate performance, and good cycle property. The discharge capacities are approximately 870, 850, 830, 800, 750, and 680 mAh·g−1 at current densities of 0.1, 0.2, 0.3, 0.5, 1, and 2 C, respectively. When the current density is reduced back to 0.1 C, the reversible capacity can recover to 860 mAh·g−1, the cyclability is impressive (initial capacity of 700 mAh·g−1 and 660 mAh·g−1 maintained for 1000 cycles at a high current density of 2 C, corresponding to an excellent capacity retention of 94% after 1000 cycles).

Potassium-ion battery (PIB) is a promising candidate in grid energy storage field because of the abundant potassium resource and its low cost. More efforts should be made to research anode material with long cycling performance due to the fading potassium capacity of graphite. Honeycomb hard carbon (HHC) with uniform pore structure and weakly ordered turbostratic domains was successfully prepared from carbon quantum dots (CQDs) through the calcination with the assistance of SiO2 nanospheres. As anode material for PIBs, HHC delivered a high specific capacity of 195.3 mA h g−1 and 67.43% capacity retention after 150 cycles at a current density of 0.1 A g−1. The electrochemical behaviors of HHC electrode were investigated in detail by electrochemical impedance spectroscopy (EIS) at various voltages and calculation of capacitive contribution, exhibiting favorable potassium storage property.

The excellent energy storage performance of covalent sulfur-carbon material has gradually attracted great interest. However, in the electrochemical sodium storage process, the bond evolution mechanism remains an elusive topic. Herein, we develop a one-step annealing strategy to achieve a high covalent sulfur-carbon bridged hybrid (HCSC) utilizing phenylphosphinic acid as the carbon-source/catalyst and sodium sulfate as the sulfur-precursor/salt template, in which the sulfur mainly exists in the forms of C–S–C and C–S–S–C. Notably, most of the bridge bonds are electrochemically cleaved when the cycling voltage is lower than 0.6 V versus Na/Na+, leading to the appearance of two visible redox peaks in the following cyclic voltammogram (CV) tests. The in-situ and ex-situ characterizations demonstrate that S2− is formed in the reduction process and the carbon skeleton is concomitantly and irreversibly isomerized. Thus, the cleaved sulfur and isomerized carbon could jointly contribute to the sodium storage in 0.01–3.0 V. In a Na-S battery system, the activated HCSC in cut off voltage window of 0.6–2.8 V achieves a high reversible capacity (770 mA h g−1 at 300 mA g−1). This insight reveals the charge storage mechanism of sulfur-carbon bridged hybrid and provides an improved enlightenment on the interfacial chemistry of electrode materials.

Recycling of spent lithium-ion batteries has received widespread concern on account of the high content of hazardous and valuable metals contained therein. In this research, ammonia leaching proces...

Structural fabrication and modification are the effective approaches to regulate the electrochemical performances of anatase TiO2. Herein, the template-annealing-etching processes are carried out to synthesize inverse opal TiO2 with N-doped carbon layer and oxygen vacancies surface as an anode material for advanced lithium ion batteries and sodium ion batteries. These structural features not only shorten the diffusion paths and enhance the electronic conductivity, but also induce the dominant pseudocapacitive contribution. As a result, the as-prepared electrode exhibits the excellent Li+/Na+ storage performances, including a high capacity retention (462 mAh g−1 after 300 cycles at 0.5 A g−1) and a fast cycling capability (180 mAh g−1 after 3500 cycles under 10 A g−1) for lithium storage; a reversible capacity of 140 mAh g−1 after 400 cycles under 1 A g−1 for sodium storage. Revealed by cyclic voltammetry, the pseudocapacitive contribution is as high as 74.49% and 73.38% at 1 mV s−1 for lithium ion batteries and sodium ion batteries, respectively. This work may promise a general approach to synthesize metal oxides anode materials for advanced energy storage devices.

As an anode for lithium-ion batteries, metallic bismuth (Bi) can provide a superb volumetric capacity of 3800 mA h cm–3, showing perspective value for application. It is a pity that the severe volu...

Among a succession of promising electrode materials of post-transition metal oxides, Sb2O3 has drawn growing attention on energy storage field owing to its high theoretical capacity and abundant resources. Nevertheless, the inherent flaw of serious volume variation during the process of ion insertion/desertion greatly hinders the application of Sb2O3 in energy storage system. Therefore, an octahedral Sb2O3 is prepared via facile and low cost approach as anode materials for lithium-ion batteries and sodium-ion batteries. Such obtained octahedral Sb2O3 composite exhibits high specific charge capacity of 640.8 mA h g−1 at a current density of 0.2 A g−1 after 50 cycles in lithium-ion batteries. Due to the excellent electrochemical properties for lithium ions storage, the obtained octahedral Sb2O3 is further studied on sodium ions storage. And the electrode delivers a specific charge capacity of 435.6 mA h g−1 at a current density of 0.1 A g−1 after 50 cycles. Briefly, this work could open up a new method to use Sb2O3 as rechargeable anode materials in scalable application and offer a reference for the development of antimony compounds in energy storage domain.

Compared to chemosynthetic CuFeS2, natural chalcopyrite (CuFeS2) can be regarded as a promising anode material for exploring ultrafast and stable Li-ion batteries benefiting from it being firsthand, eco-friendly, and resource-rich. Considering the nonuniform size distribution in it and the fact that homogeneous grain distributions can effectively restrain the aggregation of active materials, the engineering of size is deemed an effective strategy to achieve excellent Li-storage performances. Herein, varisized natural CuFeS2 are obtained by facial mineral processing technology and outstanding Li-storage performances are exhibited. Along with the decreasing of size, the contribution of pseudocapacitive as well as the ion transfer rates are significantly boosted. As expected, even at 1 A g-1, a remarkable capacity of 1009.7 mA h g-1 is displayed by the sample with the smallest size and most uniform distributions even after 500 cycles. Furthermore, supported by the detailed analysis of in situ X-ray diffraction and kinetic features, a hybrid of multiple lithium-metal sulfur systems and the major origin of the enhanced capacity upon long cycles are confirmed. Remarkably, this work is expected to increase the far-ranging applications of natural chalcopyrite as a firsthand anode material for lithium-ion batteries (LIBs) and inform the readers about the effects of particle size on Li-storage performances.

The production of polysulfides during discharging and their solubility in electrolytes are issues encountered in lithium–sulfur batteries. In this study, a novel chalcopyrite material with fixed sulfur was developed based on its chemical affinity for lithium–sulfur batteries. Pure micro-sized chalcopyrite (CuFeS2) was prepared from its natural ore by simple flotation. Sulfur in the prepared chalcopyrite can be fixed in the electrode during charging–discharging because copper and iron are sulfur-friendly elements in nature. The fixing of sulfur leads to a high initial charge capacity (1300 mA h g−1 at the initial discharge current density of 100 mA g−1), excellent rate performance, and good cycling properties. The discharge capacities are approximately 1200, 1050, 970, 930, and 875 mA h g−1 at current densities of 100, 200, 300, 500, and 1000 mA g−1, respectively. When the current density is reduced to 100 mA g−1, the reversible capacity can recover to 1000 mA h g−1, and the cyclability becomes impressive (initial capacity of 1130 mA h g−1, and 767 mA h g−1 is maintained for 100 cycles at a high current density of 1000 mA g−1). Given the abundance of chalcopyrite in nature and the simplicity and low cost of flotation extraction, chalcopyrite exhibits potential to be applied to lithium–sulfur batteries.

Sodium-ion capacitors (SICs), as new-generation electrochemical energy-storage systems, have combined the advantages of high energy and power densities, meeting the urgent demand for versatile electronic equipment and grid energy-storage stations. Nevertheless, the electrochemical performance of SICs is seriously restricted by the kinetic mismatch between the battery-type anode and capacitor-type cathode. In this work, N-doped 3D carbon (NHPC) delivered a high reversible specific capacity of 197 mA h g−1 at 2 A g−1, and the mechanism of its electrochemistry mainly involved strong pseudocapacitive storage that promoted quick physical adsorption/desorption. Moreover, further activation of NHPC yielded nitrogen-doped hierarchical porous activated carbon (NHPAC), which displayed a large specific surface area of 1478 m2 g−1 with abundant meso/macropores, and brought about fast adsorption/desorption of anions on its surface. The full-carbon SIC device benefitted from the similar material systems used for its anode and cathode, and hence achieved a high energy density of 115 W h kg−1 at 200 W kg−1 as well as long-term cyclability in the potential range of 0–4.0 V. This rational strategy of kinetic matching might open up a potential avenue for the development of additional advanced SICs.

Antimony sulfide (Sb2S3) has drawn widespread attention as an ideal candidate anode material for sodium-ion batteries (SIBs) due to its high specific capacity of 946 mA h g−1 in conversion and alloy reactions. Nevertheless, volume expansion, a common flaw for conversion-alloy type materials during the sodiation and desodiation processes, is bad for the structure of materials and thus obstructs the application of antimony sulfide in energy storage. A common approach to solve this problem is by introducing carbon or other matrices as buffer material. However, the common preparation of Sb2S3 could result in environmental pollution and excessive energy consumption in most cases. To incorporate green chemistry, natural stibnite ore (Sb2S3) after modification via carbon sheets was applied as a first-hand material in SIBs through a facile and efficient strategy. The unique composites exhibited an outstanding electrochemical performance with a higher reversible capacity, a better rate capability, as well as an excellent cycling stability compared to that of the natural stibnite ore. In short, the study is expected to offer a new approach to improve Sb2S3 composites as an anode in SIBs and a reference for the development of natural ore as a first-hand material in energy storage.

Spinel Li4Ti5O12 (LTO) shows great security and structural stability as a promising anode material for lithium-ion batteries (LIBs), but its application is restricted by its low conductivity and diffusion coefficient. Thus, LTO quantum dots (QDs) anchored on 3D carbon frameworks (CFs) from carbon dots are constructed to overcome these issues; LTO with a quantum size is designed to largely reduce the diffusion distance of Li+ and 3D CFs are introduced to enhance the electronic conductivity. As expected, the composite attains a high discharge capacity of 191 mA h g−1 at 0.2C and 115.4 mA h g−1 at a high rate of 40C; even when the current density is reduced back to 0.5C from 40C, the reversible capacity of 169.1 mA h g−1 can still be restored and the capacity retention is 92.96%, which is much better than that of bare LTO particles. This work will provide a feasible idea for improving the performance of anode materials for LIBs.

Two-dimensional transition metal dichalcogenides are promising candidates for lithium-ion and sodium-ion batteries. It is becoming more meaningful to explore the effective preparation method of these materials and study their surface, interfacial, and chemical characteristics for energy storage. Herein, low crystalline MoS2 nanoflakes embedded on N-doped CNT (MoS2/N-CNT) have been designed utilizing Mo metal as the raw material through alternating current and hydrothermal technique. Through this approach, a strong interaction has been formed between the few layers of MoS2 nanoflakes and N-CNT via chemical bonds (C–O–Mo, C–S–Mo, and C–O–S), which can shorten the ion diffusion and electronic transmission paths and even maintain the structural integrity. Meanwhile, the expanded interlayers, doped N, and the many defects in MoS2/N-CNT further make it favorable for effective energy storage. Therefore, MoS2/N-CNT presents high specific capacity, ultra-long cycling stability (1003 mA h g−1 after 800 cycles at 2 A g−1), and excellent rate capacity for lithium-ion batteries. The electrode also shows similar sodium storage performance (the capacity is 4.97 times higher than that of pure MoS2 at 10 A g−1). These results provide a novel strategy to enhance the synergistic effect of layered transition metal dichalcogenide/carbon composites with unique structural properties, which is beneficial for lithium and sodium storage.

Rational design and facile preparation of non-noble trifunctional electrocatalysts with high performance, low cost and strong durability for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are highly demanded, but remain as a big challenge. Herein, we report a spontaneous gas-foaming method to prepare nitrogen doped ultrathin carbon nanosheets (NCNs) by simply pyrolysing a mixture of citric acid and NH4Cl. Under the optimized pyrolysis temperature (carbonized at 1000 °C) and mass ratio of precursors (1 : 1), the synthesized NCN-1000-5 sample possesses an ultrathin sheet structure, an ultrahigh specific surface area (1793 m2 g−1), and rich edge defects, and exhibits low overpotential and robust stability for the ORR, OER and HER. By means of density functional theory (DFT) computations, we revealed that the intrinsic active sites for the ORR, OER and HER are the carbon atoms located at the armchair edge and adjacent to the graphitic N dopants. When practically used as a catalyst in rechargeable Zn–air batteries, a high energy density (806 W h kg−1), a low charge/discharge voltage gap (0.77 V) and an ultralong cycle life (over 330 h) were obtained at 10 mA cm−2 for NCN-1000-5. This work not only presents a versatile strategy to develop advanced carbon materials with ultrahigh specific surface area and abundant edge defects, but also provides useful guidance for designing and developing multifunctional metal-free catalysts for various energy-related electrocatalytic reactions.

Numerous interests have been captured for bimetallic NiCo2S4 ascribed to its excellent electrical conductivity, whilst its sluggish sodium-ion kinetics at high-rate limits the advancement of reversible sodium storage. Herein, NiCo2S4 nanodots (~ 9 nm) uniformly incorporated with N-doped carbon are prepared (NiCo2S4@NC) through bottom-up strategy from 0D to stable structure. Considering that the suitable ether-based electrolyte (NaCF3SO3/DEGDME) may well promote faster sodium-ion transportation due to flexible one-dimensional chain structure and favorable solvent-salt interaction, and the optimal voltage region (0.4–3.0 V) could effectively successfully sidestep the side reaction and maintain reversible phase transformation. Such multi-factors tuned NiCo2S4@NC offers remarkable electrochemical performance as anode for SIBs. It delivers a stable capacity of 570.1 mAh g−1 after 200 cycles at 0.2 A g−1, and still retains 395.6 mAh g−1 at 6.0 A g−1 after 5,000 loops. Significantly, the mechanism and dynamics explorations by cyclic voltammetry (CV) profoundly reveal the dominant surface-capacitive behaviors of NiCo2S4@NC. A suite of in-situ electrochemical impedance spectroscopy (EIS) analyses further explore the regular dual-interface resistances of NiCo2S4@NC during the sodiation/desodiation process, corresponding to the reversible phase evolution and stable carbon matrix. This systematic study establishes a firm foundation for the later research of TMDs as excellent energy-storage anode materials for SIBs.

Compared to other energy storage types, capacitive energy-storage serves increasingly significant roles in shortening reversible cycling times and enlarging high power than traditional batteries. It still suffers from the low pseudo-capacitive level and short of electrodes, along with low energy density. Considering the great theoretical capacity, here 1D chain-like Co3O4 is prepared though the thermal oxidation of the self-assembled rod-like Co-precursor. Followed by in-situ polymerization of pyrrole monomer, the Co3O4 were encapsulated in the transparent PPy shell. Particle size-tuning, 1D architecture-altering, conducting PPy introduction could effectively broaden the energy distribution of ions, increase the speed of ions directional transferring and improve the conductivity with protecting electrode materials. As Li-storage anodes, Co3O4/PPy delivers a stable capacity of 816.6 mAh g−1 at 1.0 A g−1 after 300 cycles. 801.3 mAh g−1 at 5.0 A g−1. The capacity of full-cell still delivers 526 mAh g−1 at 3.0 A g−1 after 50 loops. Supported by detailed kinetic analysis of CV curves, it is confirmed, (1) the nature of Co3O4 approaches to capacitor-like behavior; (2) its electrochemical properties are dominated by capacitive contributions with increased current density as well as cycling. This work provides an in-depth sight on Co3O4, and further improving its pseudo-capacitive behaviors.

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-1 during the 1st cycle and 317.7 mA h g-1 during 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.

Rechargeable aqueous Zn-ion batteries are promising candidates for large-scale energy storage systems. However, there are many unresolved problems in commercial Zn foils such as dendrite growth and structural collapse. Herein, Cu mesh modified with CuO nanowires is constructed to simultaneously coordinate the ion distribution and electric field during Zn nucleation and growth. Owing to the improved uniformity of Zn plating and the confined Zn growth in the 3D framework, the prepared Zn anodes can be operated steadily in symmetrical cells for 340 h with a low voltage hysteresis (20 mV). This work can provide a new strategy to design the dendrite-free Zn anodes for practical application.

The electrodeposition of zinc with thiourea derivatives as additives was investigated. The dynamic deposition and dissolution processes of zinc deposits were monitored in situ with synchrotron radiation X-ray imaging to reveal the inhibition role of additives on zinc dendrites. The real-time images show a large amount of zinc dendrites grow directly on the substrate surface in blank electrolyte. The microstructure of zinc deposits is sensitive to the molecular structure of additives. After adding thiourea derivatives, both the nucleation overpotential and the degree of polarization increase in the order of additive-free

Utilizing copper coordination compound as Cu, S, N and C sources, nano-sized Cu9S5 coated with N, S co-doped carbon (NSC) has been prepared via one-step calcination. The uniform nanosize Cu9S5 were well coated by NSC with the thickness of about 4 nm. The Cu9S5/NSC composite as a new anode for sodium-ion battery shows high reversible charge specific capacity of 412.0 mAh g−1 at 100 mA g−1 and good capacity retention after 200 cycles, which is attributed to the encapsulated structure and strong binding interaction between Cu9S5 and NSC (bridge bonds of C-S-Cu and C-O-Cu).

The ultrathin TiO2 nanosheets doped by nitrogen tightly attaching on carbon nanotubes are designed and evaluated as anode for sodium ion batteries. The TiO2 nanosheets attaching on carbon nanotubes composite shows a high specific capacity of 248.5 mAh g−1 at the rate of 0.5 C, and it can still deliver a specific capacity of 100.9 mAh g−1 at a high rate of 20 C, which verifies an outstanding sodium storage capacity and an excellent rate capability. More encouragingly, at a rate of 10 C, the specific capacity can be still kept at 154.2 mAh g−1 after 3500 cycles, displaying a remarkable long-term cyclic stability. Note that the corresponding kinetics analysis suggests that the pseudocapacitive behaviour is responsible for the updating sodium storage performances of TiO2 nanosheets composite. Additionally, the cooperation effects of carbon nanotubes preservation and nitrogen modification can provide fast electronic pathways, and the TiO2 nanosheets can promote sodium ions transport and increase the active sites for sodium storage. The merits of multiple functional and tailor-designed strategies make contributions to develop high-performance TiO2 anodes in sodium ion batteries.

By reason of rich sodium resources, sodium-ion batteries have excited enormous consideration for adhibition in the developing energy-storage stations. And not surprisingly, the exploration of cost-effective anode materials for SIBs have been a conspicuous topic. Herein, iron trioxide embedded in the nitrogen-doped carbon matrix with strong oxygen-bridge bonds is synthesized by using the iron based metal organic framework as template. The obtained composite delivers excellent electrochemical properties, such as specific capacity of 473.7 mAh g−1 at the current density of 100 mA g−1 after 100 cycles. Besides, the reversible capacity still remains at 155.3 mAh g−1 at the high density of 4000 mA g−1. This remarkable sodium-ion storage capability could be attributed to the incorporation of nitrogen atoms into carbon matrix and the strong chemical bonds between iron trioxide and carbon matrix, which can restrain electrode pulverization and also retain an interparticle connection even after long cycling that could offer a good electronic conductive pathway. This engineer strategy for preparing iron trioxide possess strong interfacial interaction with nitrogen-doped carbon matrix can be applied to other metal phosphides and metal oxide materials.

Tuning hierarchical pore structure of carbon materials is an effective way to achieve high energy density under high power density of carbon-based supercapacitors. However, at present, most of methods for regulating pores of carbon materials are too complicated to be achieved. In this work, a durian shell derived porous carbon (DSPC) with abundant porous is prepared through chemical activation as a defect strategy. Hierarchical porous structure can largely enhance the transfer rate of electron/ion. Furthermore, DSPC with multiple porous structure exhibits excellent properties when utilized as electrode materials for electric double layer capacitors (EDLCs), delivering a specific capacitance of 321 F g-1 at 0.5 A g-1 in aqueous electrolyte. Remarkably, a high energy density of 27.7 Wh kg−1 is obtained at 675 W kg−1 in an organic two-electrode device. And large capacity can be remained even at high charge/discharge rate. Significantly, hierarchical porous structure allows efficient ion diffusion and charge transfer, resulting in a prominent cycling stability. This work is looking forward to providing a promising strategy to prepare hierarchical porous carbon-based materials for supercapacitors with ultrafast electron/io¬¬¬n transport.

The Li-ion desertion process of a single LiFePO4 particle with a diameter of 400 nm in aqueous media at high potential is investigated by stochastic collision of the particle at a microelectrode. No extra additive, such as polymeric binder or conductive carbon, is involved in this stochastic measurement. The ion diffusion inside the particle is proved to be the rate-determining step that limits the discharge rate of batteries using LiFePO4 in an aqueous environment. This result offers guidance for exploring the most effective enhancement of Li-ion batteries. Moreover, this general method can be applied to study the electrochemical behavior of other electrode materials as an alternative and complementary route.

Sodium-ion batteries (SIBs) are regarded as a promising candidate for large-scale energy storage applications, however, its sluggish sodiation kinetics limit high power capabilities. First-principles density functional theory (DFT) calculations demonstrates that the replacement of large anions, within a Co3X4 (X = O, S, Se) complex, can facilitate electron transfer through the reduction of the energy band gap (Eg) and the regulation of structural, electronic and bonding properties of Co-X, suggesting that the substituted Co3X4 in the following order O Na2S > Na2Se) with the increased active sites, which are paramount for electrochemical properties. The work in this article sheds light on the in-depth understanding of the improved sodium-storage behavior with the advancing VI group anions and provides an effective strategy for the design of high-rate electrode materials for SIBs.