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

Rechargeable batteries currently hold the largest share of the electrochemical energy storage market, and they play a major role in the sustainable energy transition and industrial decarbonization to respond to global climate change. Due to the increased popularity of consumer electronics and electric vehicles, lithium-ion batteries have quickly become the most successful rechargeable batteries in the past three decades, yet growing demands in diversified application scenarios call for new types of rechargeable batteries. Tremendous efforts are made to developing the next-generation post-Li-ion rechargeable batteries, which include, but are not limited to solid-state batteries, lithium–sulfur batteries, sodium-/potassium-ion batteries, organic batteries, magnesium-/zinc-ion batteries, aqueous batteries and flow batteries. Despite the great achievements, challenges persist in precise understandings about the electrochemical reaction and charge transfer process, and optimal design of key materials and interfaces in a battery. This roadmap tends to provide an overview about the current research progress, key challenges and future prospects of various types of rechargeable batteries. New computational methods for materials development, and characterization techniques will also be discussed as they play an important role in battery research.

P2-type layered oxide, Na2/3Ni1/3Mn2/3O2, has drawn particular interest as a promising cathode material for sodium-ion batteries (SIBs) due to its fast sodium-ion transport channels with low migration potential. However, some catastrophic flaws, such as air instability, complicated multiphase evolution, and irreversible anionic redox, limit its electrochemical performance and hinder its application. Here, an air-stable single-crystal P2-type Na2/3Ni1/3Mn1/3Ti1/3O2is proposed based on the multifunctional structural modulation of Ti substitution that could alleviate the issues for practical SIBs. As a result, the cathode with high energy density shows excellent air stability and highly reversible phase transitions (P2-OP4), and delivers faster kinetics and stable anion redox chemistry. Meanwhile, a thorough investigation of the relationship between structure, function, and properties is demonstrated, emphasizing formation processes, electrochemical behavior, structural evolution, and air stability. Overall, this study provides the direction of multifunctional structural modulation for the development of high-performance sodium-based layered cathode materials for practical applications.

Na4Fe3(PO4)2(P2O7) (NFPP) with the advantages of low cost and stable crystal structure has been considered a highly promising cathode candidate for sodium-ion batteries. However, limited by its undesirable intrinsic conductivity, it still suffers from unsatisfactory electrochemical performance. Herein, we synthesized NFPP/C composites with porous structure (p-NFPP) by a facile self-assembly strategy. Its well-developed pore structure can effectively reduce the ion diffusion path, accelerate electrolyte infiltration and accommodate volume expansion during the charge/discharge process. In addition, in-situX-ray diffraction revealed the superior structural stability of p-NFPP. They enable a high reversible capacity (104.8 mAh g−1), and good rate performance (75.0 mAh g−1at 10 A g−1), and excellent cycling stability (a reversible capacity of 85.1 mAh g−1after 2000 cycles). More importantly, the p-NFPP realizes a stable operation in a wide temperature range of 55°C to −10°C. This work highlights morphology engineering as a powerful strategy to boost the all-climate sodium storage performance of electrode materials.

Because of the low price and abundant reserves of sodium compared with lithium, the research of sodium-ion batteries (SIBs) in the field of large-scale energy storage has returned to the research spotlight. Layered oxides distinguish themselves from the mains cathode materials of SIBs owing to their advantages such as high specific capacity, simple synthesis route, and environmental benignity. However, the commercial development of the layered oxides is limited by sluggish kinetics, complex phase transition and poor air stability. Based on the research ideas from macro- to micro-scale, this review systematically summarizes the current optimization strategies of sodium-ion layered oxide cathodes (SLOC) from different dimensions: microstructure design, local chemistry regulation and structural unit construction. In the dimension of microstructure design, the various structures such as the microspheres, nanoplates, nanowires and exposed active facets are prepared to improve the slow kinetics and electrochemical performance. Besides, from the view of local chemistry regulation by chemical element substitution, the intrinsic electron/ion properties of SLOC have been enhanced to strengthen the structural stability. Furthermore, the optimization idea of endeavors to regulate the physical and chemical properties of cathode materials essentially is put forward from the dimension of structural unit construction. The opinions and strategies proposed in this review will provide some inspirations for the design of new SLOC in the future.

Electroactive acid anhydride with multicarbonyl is highly promising for electrochemical energy storage because of its high specific capacity and environmental benignity. Its low electrical conductivity and high dissolution in organic electrolyte, however, result in poor cycling and rate capabilities. Here, we report a naphthalene polyimide derivative (NPI) synthesized by using anhydride under condensation polymerization conditions, along with its composite with graphene (NPI-G) fabricated via in situ polymerization. The composite delivers a high reversible capacity and outstanding cycling stability and rate capability as a cathode for sodium-ion batteries (SIBs) owing to the formation of a polymer, the improvement in the electrical conductivity brought about by the highly dispersed graphene sheets, and the enhancement of structural stability resulting from the π–π stacking interaction between the phenyl groups of NPI and the six-member carbon rings of graphene. This investigation sheds light on the development, design, and screening of next-generation organic electrode materials with high performance for SIBs.

Silicon (Si) is one of the most promising anode materials for the next generation of lithium-ion battery (LIB) due to its high specific capacity, low lithiation potential, and natural abundance. However, the huge variation in volume during the storage of lithium, along with the low conductivity of element, are the main factors hindering its commercial application. Designing micro–nano structures as well as composites of heterogeneous materials have proven to be effective strategies to overcome these issues. Electrospinning technology is an affordable and scalable method for easily constructing a unique hierarchical micro–nano structure while realizing composites of heterogeneous materials. So far, many efforts have been made to solve the problems of Si-based anodes with general electrospinning. This review considers the technical fundamental and design strategies for electrospun Si-based nanofibers, including preparation processes, structural engineering, and lithium storage performance. The structure–performance relationship of various materials and the effects of compositing with heterogeneous materials are explored in detail. Finally, the remaining challenges are discussed, along with directions for future research. This review will provide inspiration for researchers in the design and manufacture of electrospun Si-based nanofibers for LIBs.

Herein, a chemically bonded CuP2/C composite was prepared by a facile high-energy ball-milling method. The CuP2/C composite anode exhibits high reversible capacity, excellent rate performance, and superior cycling stability for potassium-ion batteries.

•The spinel-like structure could play an important role in boosting electron transport to coordinate with the timely Na+ insertion/extraction and function as a stabilizer for the host cathode structures.•This review summarizes the recent advances of spinel engineering on layered oxide cathodes, especially focusing on the concepts of post-spinel structure, layered oxide integrated spinel-like structure, and spinel transition.•The concept of spinel engineering will drive the development of new materials and chemistries in Na-based electrode materials, which can be useful to guide rational structural engineering and design for SIBs.

Developing hard carbon with a high initial Coulombic efficiency (ICE) and very good cycling stability is of great importance for practical sodium-ion batteries (SIBs). Defects and oxygen-containing groups grown along either the carbon edges or the layers, however, are inevitable in hard carbon and can cause a tremendous density of irreversible Na+sites, decreasing the efficiency and therefore causing failure of the battery. Thus, eliminating these unexpected defect structures is significant for enhancing the battery performance. Herein, we develop a strategy of applying a soft-carbon coating onto free-standing hard-carbon electrodes, which greatly hinders the formation of defects and oxygen-containing groups on hard carbon. The electrochemical results show that the soft-carbon-coated, free-standing hard-carbon electrodes can achieve an ultrahigh ICE of 94.1% and long cycling performance (99% capacity retention after 100 cycles at a current density of 20 mA g–1), demonstrating their great potential in practical sodium storage systems. The sodium storage mechanism was also investigated by operando Raman spectroscopy. Our sodium storage mechanism extends the “adsorption–intercalation–pore filling–deposition” model. We propose that the pore filling in the plateau area might be divided into two parts: (1) sodium could fill in the pores near the inner wall of the carbon layer; (2) when the sodium in the inner wall pores is close to saturation, the sodium could be further deposited onto the existing sodium.

With the growing demand for energy storage, layered oxide cathodes (NaxTMO2) for sodium-ion batteries (SIBs) have become the spotlight for researchers. However, irreversible multiphase transformation and structural degradation, as well as lattice oxygen loss, hindered their commercialization. Electronic structure modulation based on the orbital hybridization concept is an important way to solve key scientific problems. Herein, due to its unique electronic structure, Sn is chosen as the proof of the conceptual element, and its effect on layered oxide cathode is summarized in three aspects: reversible phase transformation, abnormal structural regulation, and stable anionic redox. Firstly, the large size of Sn4+suppresses the sliding of the transition metal oxide (TMO2) layer and Na+/vacancy ordering as well as enhances the delocalization of electrons. Secondly, Sn with a similar ionic radius to other TM ions in the structure promotes the stacking of the O3 phase. What’s more, the distinctive electronic structure of Sn4+will enhance the operating voltage. Thirdly, a strong Sn-O bond stabilizes the lattice oxygen, promotes stable anion redox, and improves the energy density of the battery. Therefore, electronic structure modulation can provide technical direction for the development and industrialization of high-performance SIBs.

Manganese-based layered oxides show promise as cathode materials for sodium-ion batteries (SIBs). However, several challenges including sluggish Na+kinetics, complex phase transitions, and poor air stability hinder their practical application. Herein, we proposed a dual-function strategy that not only precisely manipulates dynamic structural evolution from layered to tunnel structure, but also effectively suppresses Na+/vacancy and charge ordering by inhibiting electron delocalization. A series of Ti-substituted Na2/3Mn1-xTixO2(x=0, 1/9, 2/9, 1/3) as proof of concept materials were designed to demonstrate the dual-function strategy. As a result, the optimized Na2/3Mn8/9Ti1/9O2cathode material delivers a high specific capacity of 202.9 mAh g−1at 0.1C within 1.5−4.3V, equivalent to 536.6Whkg−1of energy density, and exhibits 71.0% of capacity retention after 300 cycles at 1C. Meanwhile, a highly reversible P2/Tunnel-OP4/Tunnel phase transition process and interlocking effect between the layered and tunnel structure as well as prominent moisture stability even after soak water treatment are further confirmed by in-situcharge and discharge XRD and other advanced characterization techniques. It is worth noting that the electrode assembled with water-solution binder still displays a high capacity retention of 85.4% after 400 cycles at 1C. Our dual-function strategy provides valuable guidance for developing high-energy density and water-stable practical SIB cathode materials.

A core–shell–shell heterostructure of Si nanoparticles as the core with mesoporous carbon and crystalline TiO2as the double shells (Si@C@TiO2) is utilized as an anode material for lithium-ion batteries, which could successfully tackle the vital setbacks of Si anode materials, in terms of intrinsic low conductivity, unstable solid–electrolyte interphase (SEI) films, and serious volume variations. Combined with the high theoretical capacity of the Si core (4200 mA h g–1), the double shells can perfectly avoid direct contact of Si with electrolyte, leading to stable SEI films and enhanced Coulombic efficiency. On the other hand, the carbon inner shell is effective at improving the overall conductivity of the Si-based electrode; the TiO2outer shell is expected to serve as a rigid layer to achieve high structural stability and integrity of the core–shell–shell structure. As a result, the elaborate Si@C@TiO2core–shell–shell nanoparticles are proven to show excellent Li storage properties. It delivers high reversible capacity of 1726 mA h g–1over 100 cycles, with outstanding cyclability of 1010 mA h g–1even after 710 cycles.

Red phosphorus/graphite (P/G) and red phosphorus/carbon nanotube (P/CNT) composites were prepared by ball milling red phosphorus with CNTs and graphite, respectively. The electrochemical results show superior electrochemical performances of the P/G and P/CNT composites compared with that of the reference sample milled with Super-P carbon. After 70 cycles, the P/G and P/CNT composites remained 771.6 and 431.7 mA h g−1, with 68 % and 50 % capacity retention, respectively. With increasing the milling time (20 h), CNTs were cut into short pieces and then broken into carbon rings and sheets which were well mixed with red phosphorus. The morphology of the P/CNT composite can buffer the large volume changes from alloying and de-alloying during cycling, resulting in the enhanced cycling stability. [ABSTRACT FROM AUTHOR]

Electrode materials with high conductivity, strong chemisorption, and catalysis toward polysulfides are recognized as key factors for metal-sulfur batteries. Nevertheless, the construction of such functional material is a challenge for room-temperature sodium-sulfur (RT-Na/S) batteries. Herein, a multiregion Janus-featured CoP-Co structure obtained viasequential carbonization–oxidation–phosphidation of heteroseed zeolitic imidazolate frameworks is introduced. The structural virtues include a heterostructure existing in a CoP-Co structure and a conductive network of N-doped porous carbon nanotube hollow cages (NCNHCs), endowing it with superior conductivity in both the short- and long-range and strong polarity toward polysulfides. Thus, the S@CoP-Co/NCNHC cathode exhibits superior electrochemical performance (448 mAh g–1remained for 700 times cycling under 1 A g–1) and an optimized redox mechanism in polysulfides conversion. Density functional theory calculations present that the CoP-Co structure optimizes bond structure and bandwidth, whereas the pure CoP is lower than the corresponding Fermi level, which could essentially benefit the adsorptive capability and charge transfer from the CoP-Co surface to Na2Sxand therefore improve its affinity to polysulfides.

The precise control of the morphology of inorganic materials during their synthesis is important yet challenging. Here we report that the morphology of a wide range of inorganic materials, grown by rapid precipitation from a metal cation solution, can be tuned during their crystallization from one- to three-dimensional (1D to 3D) structures without the need for capping agents or templates. This control is achieved by adjusting the balance between the electrolytic dissociation (α) of the reactants and the supersaturation (S) of the solutions. Low-α,weak electrolytes promoted the growth of anisotropic (1D and 2D) samples, with 1D materials favoured in particular at low S. In contrast, isotropic 3D polyhedral structures could only be prepared in the presence of strong electrolyte reactants (α≈ 1) with low S. Using this strategy, a wide range of materials were prepared, including metal oxides, hydroxides, carbonates, molybdates, oxalates, phosphates, fluorides and iodate with a variety of morphologies. Precipitation enables the straightforward production of a variety of inorganic materials, but the rapid reaction rates involved typically make controlling their morphologies difficult. Now, the growth of either one-, two- or three-dimensional materials has been promoted by tuning of the reactants’ electrolytic dissociation and solution supersaturation, without the need for capping agents and templates.

Searching for efficient electrocatalyst to breakthrough sluggish CO2reduction and evolution reactions is still a challenge for development of Li-CO2batteries. Recently, Xing et al. report a RuRh alloy nanosheet-based battery, achieving the lowest voltage gap during the charge and discharge process.

Dual ion batteries based on Na+and PF6–received considerable attention due to their high operating voltage and the abundant Na resources. Here, cheap and easily obtained graphite that served as a cathode material for dual ion battery delivered a very high average discharge platform (4.52 V vs Na+/Na) by using sodium hexafluorophosphate in propylene carbonate as electrolyte. Moreover, the all-carbon dual ion batteries with graphite as cathode and hard carbon as anode exhibited an ultrahigh discharge voltage of 4.3 V, and a reversible capacity of 62 mAh·g–1at 40 mA·g–1. Phase changes have been investigated in detail through in situ X-ray diffraction and in situ Raman characterizations. The stable structure provides long life cycling performance, and the pseudocapacitance behavior also demonstrates its benefits to the rate capability. Thus, dual ion batteries based on sodium chemistry are very promising to find their applications in future.

Carbon-encapsulated Sn@N-doped carbon tubes with submicron diameters were obtained via the simple reduction of C@SnO2@N-doped carbon composites that were fabricated by a hydrothermal approach. Sn nanoparticles encapsulated in carbon layers were distributed uniformly on the surfaces of the N-doped carbon nanotubes. The electrochemical performances of the composites were systematically investigated as anode materials in sodium-ion batteries (SIBs). The composite electrode could attain a good reversible capacity of 398.4 mAh g–1when discharging at 100 mA g–1, with capacity retention of 67.3% and very high Coulombic efficiency of 99.7% over 150 cycles. This good cycling performance, when compared to only 17.5 mAh g–1delivered by bare Sn particles prepared via the same method without the presence of N-doped carbon, could be mainly ascribed to the uniform distribution of the precursor SnO2on the substrate of N-doped carbon tubes with three-dimensional structure, which provides more reaction sites to reduce the diffusion distance of Na+, further facilitating Na+-ion diffusion and relieves the huge volume expansion during charging/discharging. These outcomes imply that such a Sn/C composite would provide more options as an anode candidate for SIBs.

Room-temperature sodium–sulfur batteries are competitive candidates for large-scale stationary energy storage because of their low price and high theoretical capacity. Herein, pure S nanosheet cathodes can be grown in situ on three-dimensional Cu foam substrate with the condensation between binary polymeric binders, serving as a model system to investigate the formation and electrochemical mechanism of unique S nanosheets on the Cu current collectors. On the basis of the confirmed conversion reactions to Na2S, The constructed cathode exhibits ultrahigh initial discharge/charge capacity of 3189/1403 mAh g–1. These results suggest that there is great potential to optimize S cathode by exploiting low-cost Cu substrates instead of conventional Al current collectors.

The exploration of highly efficient catalysts for the oxygen reduction reaction to improve sluggish kinetics still remains a great challenge for advanced energy conversion and storage in metal/air batteries. In this work, ultrafine Mn3O4nanowires/three-dimensional graphene/single-walled carbon nanotube catalysts with an electron transfer number of 3.95 (at 0.60 V vs Ag/AgCl) and kinetic current density of 21.7–28.8 mA cm–2were developed via a microwave-irradiation-assisted hexadecyl trimethylammonium bromide (CTAB) surfactant procedure to greatly enhance the overall catalytic performance in Mg/air batteries. To match the electrochemical activity of the cathode catalysts, a large-scale Mg anode prepared with micropersimmon-like particles via a mechanical disintegrator and Mg(NO3)2–NaNO2-based electrolyte containing 1.0 wt % trihexyl(tetradecyl)phosphonium chloride ionic liquid were applied. Combining the ultrafine Mn3O4nanowires/three-dimensional graphene/single-walled carbon nanotube as an efficient electrocatalyst for the oxygen reduction reaction and an Mg micro-/nanoscale anode in the novel electrolyte, the advanced Mg/air batteries demonstrated a high cell open circuit voltage (1.49 V), a high plateau voltage (1.34 V), and a long discharge time (4177 min) at 0.2 mA cm–1, showing a high energy density. Therefore, it is believed that this device configuration has great potential for application in new energy storage technologies.

High voltage (5-V class) spinel LiCr0.2Ni0.4Mn1.4O4is one of the most promising cathode materials to meet the energy requirements of lithium-ion batteries for electric vehicles and hybrid electric vehicles. For the mass production of this material (1 kg or higher), different synthesis routes will lead to different electrochemical performances, even with similar morphology and similar crystal structure obtained from laboratory X-ray diffraction, and the reason for this issue is still not clear. Herein, we have investigated the reasons for the different electrochemical performances resulting from three common synthesis routes (spray pyrolysis, coprecipitation, and sol–gel). Taking advantage of the high-resolution X-ray beam in synchrotron X-ray diffraction, we find that varying phase composition and the generated impurities, rather than the particle distribution, are likely to be the main reasons for the detected electrochemical variations. A higher amount of impurities will result in greater charge transfer resistance, inferior cycling stability, and more oxygen/lithium vacancies. Therefore, it is very important to obtain a deeper understanding with the help of higher-resolution X-rays and to provide better guidance for mass production of this cathode material for practical applications.

Molybdenum disulfide is popular for rechargeable batteries, especially in Li-ion batteries, because of its layered structure and relatively high specific capacity. In this paper, we report MoS2–C nanocomposites that are synthesized by a hydrothermal process, and their use as anode material for Li-ion batteries. Ascorbic acid is used as the carbon source, and the carbon contents can be tuned from 2.5 wt % to 16.2 wt %. With increasing of carbon content, the morphology of MoS2–C nanocomposites changes from nanoflowers to nanospheres, and the particle size is decreased from 200 to 60 nm. This change is caused by the chemical complex interaction of ascorbic acid. The MoS2–C nanocomposite with 8.4 wt % C features a high capacity of 970 mAh g–1and sustains a capacity retention ratio of nearly 100% after 100 cycles. When the current increases to 1000 mA g–1, the capacity still reaches 730 mAh g–1. The above manifests that the carbon coating layer does not only accelerate the charge transfer kinetics to supply quick discharging and charging, but also hold the integrity of the electrode materials as evidenced by the long cycling stability. Therefore, MoS2-based nanocomposites could be used as commercial anode materials in Li-ion batteries.

Three-dimensional (3D) metal oxide superstructures have demonstrated great potentials for structure-dependent energy storage and conversion applications. Here, we reported a facile hydrothermal method for direct growth of highly ordered single crystalline nanowire array assembled 3D orthorhombic Nb3O7(OH) superstructures and their subsequent thermal transformation into monoclinic Nb2O5with well preserved 3D nanowire superstructures. The performance of resultant 3D Nb3O7(OH) and Nb2O5superstructures differed remarkably when used for energy conversion and storage applications. The thermally converted Nb2O5superstructures as anode material of lithium-ion batteries (LiBs) showed higher capacity and excellent cycling stability compared to the Nb3O7(OH) superstructures, while directly hydrothermal grown Nb3O7(OH) nanowire superstructure film on FTO substrate as photoanode of dye-sensitized solar cells (DSSCs) without the need for further calcination exhibited an overall light conversion efficiency of 6.38%, higher than that (5.87%) of DSSCs made from the thermally converted Nb2O5film. The high energy application performance of the niobium-based nanowire superstructures with different chemical compositions can be attributed to their large surface area, superior electron transport property, and high light utilization efficiency resulting from a 3D superstructure, high crystallinity, and large sizes. The formation process of 3D nanowire superstructures before and after thermal treatment was investigated and discussed based on our theoretical and experimental results.

Silicon as an electrode suffers from short cycling life, as well as unsatisfactory rate-capability caused by the large volume expansion (~400%) and the consequent structural degradation during lithiation/delithiation processes. Here, we have engineered unique void-containing mesoporous carbon-encapsulated commercial silicon nanoparticles (NPs) in yolk-shell structures. In this design, the silicon NPs yolk are wrapped into open and accessible mesoporous carbon shells, the void space between yolk and shell provides enough room for Si expansion, meanwhile, the porosity of carbon shell enables fast transport of Li+ions between electrolyte and silicon. Our ex-situcharacterization clearly reveals for the first time that a favorable homogeneous and compact solid electrolyte interphase (SEI) film is formed along the mesoporous carbon shells. As a result, such yolk-shell Si@mesoporous-carbon nanoparticles with a large void exhibits long cycling stability (78.6% capacity retention as long as 400 cycles), and superior rate-capability (62.3% capacity retention at a very high current density of 8.4Ag−1).

Improving the electrochemical kinetics and the intrinsic poor conductivity of transition metal dichalcogenide (TMD) electrodes is meaningful for developing next-generation energy storage systems. As one of the most promising TMD anode materials, ReS2shows attractive performance in potassium-ion batteries (PIBs). To overcome the poor kinetic ion diffusion and limited cycling stability of the ReS2-based electrode, herein, the interlayer distance expanding strategy was employed, and reduced graphene oxide (rGO) was introduced into ReS2. Few-layered ReS2nanosheets were grown on the surface of the rGO with expanded interlayer distance. The prepared ReS2nanosheets show an expanded distance (∼0.77 nm). The synthesized EI-ReS2@rGO composites were used in PIBs as anode materials. The K-ion storage mechanism of the ReS2-based anode was investigated by in situ X-ray diffraction (XRD) technology, which shows the intercalation and conversion types. The EI-ReS2@rGO nanocomposites show high specific capacities of 432.5, 316.5, and 241 mAh g–1under 0.05, 0.2, and 1.0 A g–1current densities and exhibit excellent reversibility at 1.0 A g–1. Overall, this strategy, which finely tunes the local chemistry and orbital hybridization for high-performance PIBs, will open up a new field for other materials.

Li4Ti5O12microspheres composed of nanoflakes were synthesized within 1 h by a combination of a microwave-assisted hydrothermal method and a microwave postannealing process. The Li4Ti5O12microspheres were characterized by X-ray diffraction, Brunauer–Emmett–Teller N2adsorption, scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. Sodium carboxymethyl cellulose (CMC) was also investigated as a low-cost green binder. The electrochemical tests, including constant current charge–discharge, cyclic voltammetry, and electrochemical impedance spectroscopy, demonstrated that the electrode using CMC as binder had better high-rate capability than the one with polyvinylidene fluoride (PVDF) binder. The electrode using CMC and PVDF as binder had the same lithium diffusion coefficient. The electrode using CMC as binder showed much lower charge transfer resistance, lower apparent activation energy, and lower apparent diffusion activation energy than for the electrode using PVDF as the binder. Apparent activation energies of Li4Ti5O12microsphere electrodes using CMC and PVDF as binder were calculated to be 26.8 and 33.6 kJ mol–1, respectively.

Flexible silicon/single-walled carbon nanotube (Si/SWCNT) composite paper was prepared using the pulsed laser deposition (PLD) method to deposit Si onto SWCNT paper. In the composite, Si mainly shows nanoworm-like morphology. Increasing deposition time results in an increased amount of Si microspheres. Electrochemical measurements show that the capacity of the composite paper is improved by the presence of Si. The Si/SWCNT composite with only 2.2% Si shows a capacity of 163 mA h g−1at a current density of 25 mA g−1up to 50 cycles, which is more than 60% improvement of the capacity of pristine CNT paper. The Si contribution in the 2.2%-Si/SWCNT sample is calculated to be higher than 3000 mA h g−1.

A ‘solid–liquid’ conversion for increasing the sulfur content from ~ 50 to 72% for RT Na–S batteries is developed.The redox mechanisms of two types of sulfur: sulfur on the surface of a cathode host (155S) and sulfur in the pores of the host (300S) in ether and carbonate ester electrolytes are studied.The function of NaNO3additive on modifying Na anode and confining the shuttle effect of dissolving polysulfides during ‘solid–liquid’ conversion is visualized.

Li-CO2batteries are one type of promising energy storage and conversion devices to capture and utilize the greenhouse gas CO2, mitigating global temperature rise and climate change. Catalysts that could effectively decompose the discharge product, Li2CO3, are essential for high-performance Li-CO2batteries. Benefiting from the interconnected porous structure, favorable oxygen vacancy, and the synergistic effects between the carbon nanotube (CNT) and layered birnessite δ-MnO2, our Li-CO2cathodes with the as-prepared CNT@δ-MnO2catalyst can efficiently afford a large reaction surface area and abundant active sites, provide sufficient electron/Li+transport pathways, and facilitate electrolyte infiltration and CO2diffusion, demonstrating low overpotential and superior cycling stability, which have been proven by both experimental characterization and theoretical computation. It is expected that this work can provide guidance for the design and synthesis of high-performance electrochemical catalysts for Li-CO2batteries.

Self-oriented Ca3Co4O9nanoflake thin film has been prepared by a simple sol–gel method as the anode for thin-film lithium-ion batteries. The X-ray diffraction and transmission electron microscopy results show that the prepared Ca3Co4O9/Ptfilm is c-axis self-oriented and composed of nanoflakes approximately 2μmin diameter and 200–300 nm thick. The reversible lithium storage capacity of the Ca3Co4O9thin-film electrode at 1 C is around 800mAhg−1, and it retains more than 70% capacity after 50 cycles, suggesting that the Ca3Co4O9thin film can be used as the anode for lithium-ion batteries.

Flexible porous Co(OH)2nanoflake films were prepared by galvanostatic electrodeposition on lightweight and inexpensive stainless steel mesh. The as-prepared porous Co(OH)2nanoflake films were characterized by X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. Electrochemical tests including cyclic voltammetry, constant current charge–discharge, and electrochemical impedance spectroscopy were also used to investigate the electrochemical performance. The results show that the highest capacitance is 609.4Fg−1, the specific capacitance decreases by less than 5% as the mass loading of Co(OH)2increases by more than 340%, and the specific capacitance only decreases by less than 15% when the current densities increase up to 10 times, indicating the good high-rate performance. The electrochemically active specific surface area of the annealed porous Co(OH)2nanoflake films remained virtually unchanged after 3000cycles, showing the stability of the microstructure.