Due to high theoretical specific capacity and low cost, Fe₂O₃ has become an attractive research field in anode materials for lithium-ion batteries (LIBs). In this study, by using PVP/FeCl₃ solutions with different concentrations as precursors, Fe₂O₃ nanofibers with different diameters were prepared by electrospinning technology and anneal treatment. In addition, Fe₂O₃ nanoparticles were prepared by hydrothermal synthesis method. The crystalline structure, morphology and electrochemical performances of the composites were investigated by X-ray diffraction, thermogravimetric analysis, infrared spectrum, scanning electron microscope, transmission electron microscope, and charge-discharge tests. Results showed that Fe₂O₃ nanofibers has better electrochemical performance than Fe₂O₃ nanoparticles. Fe₂O₃ nanofibers with diameter of 160 nm exhibited the highest rate and cycle performance as anode material in LIBs. It was found that the Fe₂O₃ electrode could deliver a discharge capacity of 827.3 mAh/g at 0.1 A/g current density and 439.1 mAh/g at 2 A/g after 70 cycles.

Porous semi-hollow/solid ZnMn₂O₄ microspheres were controllably synthesized via template and solvothermal methods respectively. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). It is found that the solvent ratio exerts a crucial effect on the morphology and microstructure of solid ZnMn₂O₄ microspheres. The porous solid ZnMn₂O₄ microspheres could be obtained when the volume ratio of ethylene glycol to deionized water was 3 : 1. The semi-hollow ZnMn₂O₄ microspheres with a double-layer ZnMn₂O₄ shell and a small C core could be synthesized via a template-solvothermal method and post-calcination process. The electrochemical properties of as-prepared semi-hollow/solid ZnMn₂O₄ microspheres as anode materials of lithium-ion batteries were investigated. Semi-hollow ZnMn₂O₄ microspheres exhibit higher initial discharge capacity, better rate capacity and cycling performance than solid ZnMn₂O₄ microspheres.

Using SBA-15 of SiO₂ template as precursor, a bundle-shaped ordered mesoporous nanoarchitecture Si/C composite (OMP-Si/C) was successfully assembled 2D-directionally by a magnesiothermic reduction reaction (MRR) route and the ensuing carbon-coating modification processing, and the MRR process of the SBA-15 was investigated in depth, the electrochemical performance of as-prepared OMP-Si/C composites was tested. Analysis based on XRD data reveals the presence of a reaction path of Mg₂Si intermediate phase in MRR process, on which a T-t (reaction temperature-reaction time) phase transition diagram is proposed. DSC/TG analysis shows that Mg particles may melt below its melting point (648℃) upon reaction, and in liquid-solid reaction pattern react with SiO₂ via melting-reaction teamwork. Observed from FE-SEM, SBA-15 column units are validated to assemble into a lotus-root-chain-bundle shaped nanoarchitecture of ordered mesoporous silicon, which can effectively offset the drastic volume change of Si material inherent in the charge/discharge process, and exhibit excellent cycling stability and rate capability. Based on the micro-fluid field assembling mechanism, the two-dimensional directional assembly process can be reasonably interpreted.

The thermodynamic data of various species in Li-Ni-Co-Mn-H₂O system is obtained by thermodynamics calculation, and E-pH diagrams for Li-Ni-Co-Mn-H₂O system with activity 1.00 at 25℃ and 200℃ were constructed. From E-pH diagrams, it shows that there is no predominant region of the LiNi_xCo_yMn_1-x-yO₂ composite oxide in pH range of 3~13 at 25℃. However, the stability region of various species expands towards the low pH and low potential zones as the temperature increases. When pH is between 9.7~13.0 at 200℃, synthesis of LiNi_xCo_yMn_1-x-yO₂ via aqueous process is thermodynamically possible, and high temperature is favorable. Experimental results showed that the composite precursor (LNCM) with α-NaFeO₂ structure was successfully prepared in aqueous solution by using (Ni_0.5Co_0.2Mn_0.3)(OH)₂ as precursor and LiOH·H₂O as raw material. LiNi_0.5Co_0.2Mn_0.3O₂ cathode materials were then obtained by post heat treatment and following tests exhibited excellent cycling performance. These experimental results are in consistent with the information given in E-pH diagram of the Li-Ni-Co-Mn-H₂O system, and the as-prepared LiNi_0.5Co_0.2Mn_0.3O₂ cathode materials show excellent cycling performance.

Solid state lithium batteries based on garnet-type solid electrolytes face the problem of contact between the solid electrolytes and the solid cathodes, which deteriorates the cycle performance. Aiming to overcome such problem, the solid state batteries with the LiNi_1/3Co_1/3Mn_1/3O₂-based cathodes, the Li_6.4La₃Zr_1.4Ta_0.6O₁₂ ceramic electrolytes, and the lithium metal anodes were studied. For constructing the LiNi_1/3Co_1/3Mn_1/3O₂-based composite cathodes, three-kind carbons were used as electronic conducting additives. It is found that the batteries with cathodes containing vapor grown carbon fibers (VGCFs) show better cycle performance than those with granular Ketjen Black as well as Super P carbons. Analysis indicates that the VGCFs result in less side reaction at high charge potential than do other two electronic additives, leading to reduced carbonates that cause the increase of the internal cell resistance. These results suggest that stability of electronic additives has important influence on cycle performance of solid state lithium batteries.

With the increasing demand for light, small, high power rechargeable lithium ion batteries in the application of mobile phones, laptop computers, electric vehicles, hybrid electric vehicles, electrochemical energy storage, and smart grids, the development of anode materials with high safety, environmental benignity, high power density, and long cycle life is in progress in recent years. The spinel lithium titanium oxide (Li₄Ti₅O₁₂) anode has become more attractive as alternative anode because of its high safety, abundant titanium dioxide raw materials, stable charge/discharge voltage plateau of 1.5 V (vs. Li/Li⁺), and excellent cycling performance due to its zero-strain volume during charge/discharge process. However, the commercial use of Li₄Ti₅O₁₂ anode material has been hindered by the low intrinsic electronic conductivity. This review focuses on recent studies of the electronic structure and performance, synthesis methods and strategies for improvement in the lithium storage capacity, charge/discharge characteristics, then on its near future development.

Recent years, alloy attracted significant research interest as anode materials for room temperature sodium-ion batteries, due to its high specific capacity and low cost. Among them, the study of Si-based alloy anodes are very limited, owing to the low electrochemical reactivity of Si with Na ions. In this study, Sb-Si nanocomposite thin films were successfully prepared by pulsed laser deposition. Their electrochemical performance and reaction mechanism were studied as new anode materials for sodium ion batteries. They exhibited a reversible specific capacity of about 0.011 mAh/cm² (corresponding to 270 mAh/g) over 100 cycles at a rate of 10 μA/cm², which is much higher than those for pure Si or Sb thin films prepared under the same condition. The investigation of electrochemical reaction mechanism reveals that Na₃Sb and NaSi nanocrystallines are formed after discharge, due to the alloying reaction between the Sb-Si films and Na. During the recharge process, Na₃Sb and NaSi phases both decompose and form Sb and Si nanocrystallines again, respectively. It is proposed that heterogeneous grain boundaries existing in the Sb-Si nanocomposite thin films are benefical to Na-ion transportation, thus enhance the electrochemical performance of the nanocomposite thin film electrode.

With the development of electric vehicles, portable applications and energy storage systems, high-performance lithium-ion batteries are urgently demanded, and the corresponding research becomes much more important. Electrolyte is one of the indispensable components for lithium-ion battery, resulting in a significant impact on the rate performance, temperature range, cycling performance, safety issue and so on. Lithium salt as the key component, is an important factor dominating the performance of the electrolyte. Various lithium salts and their solvation structures in the electrolyte evidently affect the quality of SEI layer derived from electrolytes and lithium ion migration behavior, leading to completely different electrochemical properties. The characteristics of different novel lithium salts are introduced in detail. Furthermore, the fact that a single lithium salt can’t meet all the required performance propels to design the high performance electrolyte with multi-salts. This electrolyte shows a series of advantages in expanding the working temperature range, suppressing the metal ion dissolution and improving the rate performance. Simultaneously, based on tuning the solvation structure of Li⁺ by increasing the concentration, a novel concentrated electrolyte is introduced, displaying the advantages such as the suppressed graphite peeling, the expanded electrochemical window, the suppressed Al corrosion, the improved metallic lithium plating/stripping and so on. Furthermore, detail discussion focuses on the mechanisms for the enhanced performance of the two excellent electrolytes. Finally, development tendency and application prospect of lithium-salt based electrolytes, especially these two novel electrolytes are discussed.

Zinc-air battery has great advantages such as high energy density, low cost and environmentally friendliness. Air electrode plays an important role in electrochemical performance of a zinc-air battery. In this paper, we report our study of a novel air electrode on which a porous perovskite ceramic La_0.7Sr_0.3CoO_3-δ(LSC) with Ag nanoparticles directly grown. The porous LSC is used as substrate while Ag as catalyst. The porous structure of substrate attributes to the amount and dispersion of Ag nanoparticles which affect the electrochemical performance of air electrode. Therefore, the property of the Ag-LSC electrode is optimized by adjusting the mass content of pore-former (starch). Experimental results show that the Ag-LSC electrode, with a porosity of ~32% and a Ag load of ~30 mg/cm², exhibits the best performance in all tested samples, and a zinc-air battery assembled with such air electrode gives the maximum power density of 141 mW/cm. What’s more, in order to ensure the gas diffusion channels, the hydrophilicity and hydrophobicity of the cathode is modified with PTFE to prevent flooding. After all that, the life-time of the zinc-air battery, with optimization by coating a PTFE layer as hydrophobic agent on the surface of the selected Ag-LSC electrode, prolongs significantly.

Li-O₂ batteries are regarded as a promising energy storage system for their extremely high energy density. MnO₂-based materials are recognized as efficient and low-cost catalyst for a Li-O₂ battery positive electrode material. In this work, α-MnO₂ nanowires were successfully synthesized by a hydrothermal method and their electrocatalytic performance were investigated in Li-O₂ batteries. X-ray diffraction and field emission scanning electron microscope confirms the formation of α-MnO₂. The Li-O₂ battery which consists of α-MnO₂ nanowires shows a high discharge capacity up to 12000 mAh•g^-1 at a restrict voltage of 2.0 V with the current density of 100 mA•g^-1. When restricting the discharge capacity at 500 mAh•g^-1, it can operate over 40 cycles and exhibit good cycle stability. These results indicate that the α-MnO₂ nanowires can be used as positive electrode catalysts for Li-O₂ batteries.

Rechargeable lithium-oxygen (Li-O₂) batteries have recently attracted great attention due to their superior energy storage density. However, its practical application is seriously limited by some problems such as high charging and discharging overpotential. Metal palladium as a catalyst can simultaneously reduce the charging and discharging overpotential in Li-O₂ batteries by enhancing catalytic activity of air electrode, but its catalytical mechanism is insufficient. Here, using first-principles calculations, a three-phase interface model which consists of Pd/O₂/Li₂O₂ is constructed to explore the mechanism of charge and discharge reaction. The result indicates that the Pd/O substrate enhances its adsorption of LiO₂ by promoting charge transfer between substrate and Li₂O₂, thereby accelerating discharge product formed on the electrode surface, and effectively reducing the charging overpotential by 0.43 V.

Fe, N doped 2D porous carbon catalyst was synthesized by pyrolysizing the precursor, ZIF-8, on graphene. Meanwhile, Fe-2,2-bipy were coordinated on ZIF-8. The catalyst was analyzed by SEM, XRD, and XPS for morphology, structure and component. The ORR and OER performance of the Fe, N doped 2D porous carbon catalyst were characterized by RDE, CV curves and LSV curves. It was found that the Fe, N doped 2 D porous carbon catalyst shows uniform 2D structure and that the content of Fe element is 1.32%. The catalyst shows 0.83 V half-wave potentials for oxygen reduction reaction (ORR) in 0.1 mol/L KOH solution and 420 mV over-potential for oxygen evolution reaction (OER) at 10 mA/cm² in 1 mol/L KOH solution. Then, a zinc-air battery was assembled using as-synthesized catalyst. The power density of zinc-air battery is up to 245 mV/cm². Furthermore, it shows superior cycling stability.

Prussian blue (PB) is a kind of metal-organic framework complex that displays wide application prospect as cathode material for aqueous sodium-ion batteries. In this study, PB composites were prepared by a single source method. Furthermore, effects of reaction temperature, time and concentration of hydrochloric acid on PB morphology and electrochemical performance were systematically investigated. The results showed that crystallinity and electrochemical stability of PB were improved by increasing reaction temperature. The aqueous sodium-ion battery with PB synthesized at 80 ℃ as cathode material displayed a capacity retention of 93.9% after 100 cycles. The particle size of PB grew with the extension of reaction time until 6 h. It’s exhibited that the extended reaction time was beneficial to the cycle performance of device fabricated with PB prepared for 10 h, delivering 90% capacity retention after 100 cycles. Increment of the hydrochloric concentration acid changed the surface morphology, and thus improved electrochemical performance of PB. When the concentration of hydrochloric acid reached 0.20 mol/L, a capacity of 67.5 mAh/g could be maintainted after 100 discharge-charge. This work may provide theoretical and experimental gaidence for preparing high performance PB-based aqueous sodium-ion batteries.

This work reported a facile strategy for preparing S/Co-NC composite sulfur cathode materials with different Co loadings derived from ZIF-67, which were applied as cathode materials for Li-S batteries. SEM and TEM were used to observe the morphology and pore structure of Co-NC composite. XRD analysis was employed to investigate the crystalline state of cobalt embedded in porous carbon materials. N₂ adsorption-desorption techniques was used to characterize the BET surface area and pore volume of Co-NC samples. Experimental results showed that the Co-NC with Co content of 15.93wt% exhibited the superior electrochemical performance. The cathode equipped with optimized composite showed a high capacity retention rate of 94.84% between 50 ^th to 200 ^th cycles at 0.2C current density, and even at high current density (5.0C), a high discharge capacity of 718.8 mAh?g ^-1 could still be obtained.

Low energy/power density and inferior cycling stability are bottlenecks to restrict the applications of sodium-ion batteries. Recently, coating the surface of cathode material by metal oxides containing oxygen vacancies, was regarded as an effective strategy to improve electrical conductivity and power/energy density. In this study, Na₃V₂(PO₄)₂F₃@V₂O_5-x nanosheets were synthesized via hydrothermal strategy followed by heat treatment. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis were applied to investigate the structure of Na₃V₂(PO₄)₂F₃@V₂O_5-x. As a cathode of sodium- ion batteries, Na₃V₂(PO₄)₂F₃@V₂O_5-x delivers excellent cycling stability and rate capability. It exhibits an initial discharge capacity of 123 mAh?g ^-1 at 0.2C, and a discharge capacity of 109 mAh?g ^-1 after 140 cycles. At 1C, its initial reversible capacity is 72 mAh?g ^-1, which remains 84% after 500 cycles. The outstanding electrochemical property could be ascribed to its enhanced sodium-diffusion and improved electronic conductivity induced by disordered surface coating. Furthermore, it encourages more investigations into practical sodium-ion battery applications.

High-quality Fe₄[Fe(CN)₆]₃ (HQ-FeHCF) nanocubes were synthesized by a simple hydrothermal method. Its structure, morphology and water content are characterized. Fe₄[Fe(CN)₆]₃ exhibits regular cubic shape with a uniform size of ca. 500 nm, which belongs to the face-centered cubic phase. Fe₄[Fe(CN)₆]₃ shows discharge capacities of 124, 118, 105, 94, 83, 74 and 64 mAh·g ^-1 at 1C, 2C, 5C, 10C, 20C, 30C and 40C rate, respectively, in the aqueous ternary electrolyte of NaClO₄-H₂O-Polyethylene glycol. Its capacity retention remains 100% after 500 charge/discharge cycles at the rate of 5C. The full battery with Fe₄[Fe(CN)₆]₃ as cathode and NaTi₂(PO₄)₃ as anode was fabricated, which delivers a specific energy density of 126 Wh·kg ^-1 (based on the active electrode materials) with a voltage output of 1.9 V. Furthermore, 92% of its initial discharge capacity retains after 140 charge/discharge cycles at a rate of 5C, and its Coulomb efficiency is close to 100%.

All-solid-state lithium battery (ASSLB) with inorganic solid state electrolytes is one of promising candidates for electric vehicles and large-scale smart grids for storage of alternative energy resources due to their benefits in safety, energy density, operable temperature range, and longer cycle life. As the key component in ASSLB, inorganic lithium-ion-based solid-state electrolytes (SSEs), especially the garnet-type solid electrolytes that own ionic conductivities in the order of 10 ^-3 S·cm ^-1 at room temperature and are relative safe vs. Li metal, have obvious advantages in ASSLB. However, interfacial instability and their poor solid-solid contact between garnet and cathode result in high interfacial resistance, low efficiency, and poor cycle performance. Based on these understandings and analyses of interface characteristics and issues, this work presents a brief review on modification of interface, covering composite cathode, composite electrolyte, interface engineering, and interface layer．Some approaches of improving interface wettability and future research directions of ASSLB are given as well, which endeavor to realize the practical applications of ASSLB.

Mn ²⁺ intercalation strategy to optimize the sodium storage performance of V₂C MXene was studied. The intercalated Mn ²⁺ not only enlarged the interlayer spacing of V₂C MXene but also formed a V-O-Mn covalent bond, which was beneficial to stabilize the structure of V₂C and inhibit the structural collapse caused by volume change during Na ⁺ decalation or intercalation. As a result, the intercalated V₂C MXene (V₂C@Mn) electrode showed a high specific capacity of 425 mAh·g ^-1 at the current density of 0.05 A·g ^-1, and 70% retention after 1200 cycles. This result clearly suggests that cations intercalated MXene has a great prospect in Na ⁺ storage.

Manganese-based oxides are promising cathode materials for zinc-ion batteries. However, these materials often suffer from rapid capacity fade due to structure collapse during charge and discharge processes. Here, we report that core-shell structured Mn₃O₄@ZnO nanosheet arrays are synthesized on the carbon cloth, combining microwave hydrothermal process with atomic layer deposition. With an optimized thickness of ZnO coating layer, the capacity retention of the as-formed Mn₃O₄@ZnO nanosheet arrays exhibits 60.3% over 100 discharge-charge cycles at a current density of 100 mA·g ^-1. It is demonstrated that the introduction of ZnO layers is beneficial to maintain the microstructure and improve the structural stability of the Mn₃O₄ electrode material during the discharge-charge process, benefiting from avoiding direct contact with the electrolyte. The design of the well-defined core-shell structure provides an effective way to develop high-performance manganese-based oxide cathode materials for zinc-ion batteries.