Amorphous nickel borate nanosheets as cathode material with high capacity and better cycling performance for zinc ion battery

Zinc-ion batteries are under current research focus because of their uniqueness in low cost and high safety. However, the pursuing of high-performance cathode materials of aqueous Zinc ion batteries (AZBs) with low cost, high energy density and long cycle life has become the key problem to be solved. Herein we synthesized a series of amorphous nickel borate (AM-NiBO) nanosheets by varying corrosion time with in-situ electrochemical corrosion method. The AM-NiBO-T13 as electrode material possesses a high areal capacity of 0.65 mAh/cm² with the capacity retention of 95.1% after 2000 cycles. In addition, the assembled AM-NiBO-T13//Zn provides high energy density (0.77 mWh/cm² at 1.76 mW/cm²). The high areal capacity and better cycling performance can be owing to the amorphous nanosheets structure and the stable coordination characteristics of boron and oxygen in borate materials. It shows that amorphous nickel borate nanosheets have great prospects in the field of energy storage.     

Amorphous Selenium and Crystalline Selenium Nanorods Graphene Composites as Cathode Materials for All-Solid-State Lithium Selenium Batteries

Selenium (Se) is an element in the same main group as sulfur and is characterized by high electrical conductivity and large capacity (675 mAh g⁻¹). Herein, a novel ultra-high dispersion amorphous selenium graphene composite (a-Se/rGO) was synthesized and a selenium nanorods graphene composite (b-Se/rGO) was prepared by hydrothermal method as the cathode material for all solid-state lithium−selenium (Li−Se) batteries, hoping to improve the efficiency and utilization rate of active substances in all solid-state batteries. The all-solid-state batteries were assembled using a heated thawing electrolyte (2LiIHPN−LiI; HPN=3-hydroxypropionitrile). The utilization rate of a-Se/rGO was 103 % and the capacity was 697 mAh g⁻¹, which remained at 281 mAh g⁻¹ (41.6 % of the 675 mAh g⁻¹) after 30 cycles under 0.5 C. Notably, a-Se/rGO showed excellent performance concerning its utilization rate, with a capacity of up to 610 mAh g⁻¹ at 2 C, due to the high availability of amorphous Se and the special properties of the electrolytes. However, in the charge and discharge cycles, the second discharge capacity of a-Se/rGO was more significantly attenuated than that of the first discharge due to the formation of larger crystals of selenium during the charging process. The battery assembled using b-Se/rGO maintained a capacity of 270.58 mAh g⁻¹ after 30 cycles (the retention rate of discharge capacity was 66.13 % compared with that in the first cycle). Through TEM and other relevant tests, it is speculated that amorphous selenium is conducive to capacity release, which, however, is affected by the formation of crystalline selenium after the first charge process.     

Rational Design of Cellulose Nanofibrils Separator for Sodium-Ion Batteries

Cellulose nanofibrils (CNF) with high thermal stability and excellent electrolyte wettability attracted tremendous attention as a promising separator for the emerging sodium-ion batteries. The pore structure of the separator plays a vital role in electrochemical performance. CNF separators are assembled using the bottom-up approach in this study, and the pore structure is carefully controlled through film-forming techniques. The acid-treated separators prepared from the solvent exchange and freeze-drying demonstrated an optimal pore structure with a high electrolyte uptake rate (978.8%) and Na⁺ transference number (0.88). Consequently, the obtained separator showed a reversible specific capacity of 320 mAh/g and enhanced cycling performance at high rates compared to the commercial glass fiber separator (290 mAh/g). The results highlight that CNF separators with an optimized pore structure are advisable for sodium-ion batteries.     

Preparation and characterization of high-rate and long-cycle LiFePO4/C nanocomposite as cathode material for lithium-ion battery

Olivine LiFePO₄/C nanocomposite cathode materials with small-sized particles and a unique electrochemical performance were successfully prepared by a simple solid-state reaction using oxalic acid and citric acid as the chelating reagent and carbon source. The structure and electrochemical properties of the samples were investigated. The results show that LiFePO₄/C nanocomposite with oxalic acid (oxalic acid: Fe²⁺= 0.75:1) and a small quantity of citric acid are single phase and deliver initial discharge capacity of 122.1 mAh/g at 1 C with little capacity loss up to 500 cycles at room temperature. The rate capability and cyclability are also outstanding at elevated temperature. When charged/discharged at 60 °C, this materials present excellent initial discharge capacity of 148.8 mAh/g at 1 C, 128.6 mAh/g at 5 C, and 115.0 mAh/g at 10 C, respectively. The extraordinarily high performance of LiFePO₄/C cathode materials can be exploited suitably for practical lithium-ion batteries.     

Na2FePO4F/Biocarbon Nanocomposite Hollow Microspheres Derived from Biological Cell Template as High-Performance Cathode Material for Sodium-Ion Batteries

We have successfully synthesized Na₂FePO₄F/biocarbon nanocomposite hollow microspheres from Fe^III precursor as cathodes for sodium-ion batteries through self-assembly of yeast cell biotemplate and sol-gel technology. The carbon coating on the nanoparticle surface with a mesoporous structure enhances electron diffusion into Na₂FePO₄F crystal particles. The improved electrochemical performance of Na₂FePO₄F/biocarbon nanocomposites is attributed to the larger electrode−electrolyte contact area and more active sites for Na⁺ on the surface of hollow microspheres compared with those of Na₂FePO₄F/C. The Na₂FePO₄F/biocarbon nanocomposite exhibits a high initial discharge capacity of 114.3 mAh g⁻¹ at 0.1 C, long-cycle stability with a capacity retention of 74.3 % after 500 cycles at 5 C, and excellent rate capability (70.2 mAh g⁻¹ at 5 C) compared with Na₂FePO₄F/C. This novel nanocomposite hollow microsphere structure is suitable for improving the property of other cathode materials for high-power batteries.     

A Long‐Cycling Aqueous Zinc‐Ion Pouch Cell: NASICON‐Type Material and Surface Modification

Aqueous zinc‐ion batteries (ZIBs) have become the highest potential energy storage system for large‐scale applications owing to the high specific capacity, good safety and low cost. In this work, a NASICON‐type Na₃V₂(PO₄)₃ cathode modified by a uniform carbon layer (NVP/C) has been synthesized via a facile solid‐state method and exhibited significantly improved electrochemical performance when working in an aqueous ZIB. Specifically, the NVP/C cathode shows an excellent rate capacity (e. g., 48 mAh g^?1 at 1.0 A g^?1). Good cycle stability is also achieved (e. g., showing a capacity retention of 88% after 2000 cycles at 1.0 A g^?1). Furthermore, the Zn²⁺ (de)intercalation mechanism in the NVP cathode has been determined by various ex‐situ techniques. In addition, a Zn||NVP/C pouch cell has been assembled, delivering a high capacity of 89 mAhg^?1 at 0.2 A g^?1 and exhibiting a superior long cycling stability.     

A Multi-Wall Sn/SnO2@Carbon Hollow Nanofiber Anode Material for High-Rate and Long-Life Lithium-Ion Batteries

Multi-wall Sn/SnO₂@carbon hollow nanofibers evolved from SnO₂ nanofibers are designed and programable synthesized by electrospinning, polypyrrole coating, and annealing reduction. The synthesized hollow nanofibers have a special wire-in-double-wall-tube structure with larger specific surface area and abundant inner spaces, which can provide effective contacting area of electrolyte with electrode materials and more active sites for redox reaction. It shows excellent cycling stability by virtue of effectively alleviating pulverization of tin-based electrode materials caused by volume expansion. Even after 2000 cycles, the wire-in-double-wall-tube Sn/SnO₂@carbon nanofibers exhibit a high specific capacity of 986.3 mAh g⁻¹ (1 A g⁻¹) and still maintains 508.2 mAh g⁻¹ at high current density of 5 A g⁻¹. This outstanding electrochemical performance suggests the multi-wall Sn/SnO₂@ carbon hollow nanofibers are great promising for high performance energy storage systems.     

Nitrogen‐Doped Hollow Amorphous Carbon Spheres@Graphitic Shells Derived from Pitch: New Structure Leads to Robust Lithium Storage

Nitrogen‐doped mesoporous hollow carbon spheres (NHCS) consisting of hybridized amorphous and graphitic carbon were synthesized by chemical vapor deposition with pitch as raw material. Treatment with HNO₃ vapor was performed to incorporate oxygen‐containing groups on NHCS, and the resulting NHCS‐O showed excellent rate capacity, high reversible capacity, and excellent cycling stability when tested as the anode material in lithium‐ion batteries. The NHCS‐O electrode maintained a reversible specific capacity of 616 mAh g^?1 after 250 cycles at a current rate of 500 mA g^?1, which is an increase of 113 % compared to the pristine hollow carbon spheres. In addition, the NHCS‐O electrode exhibited a reversible capacity of 503 mAh g^?1 at a high current density of 1.5 A g^?1. The superior electrochemical performance of NHCS‐O can be attributed to the hybrid structure, high N and O contents, and rich surface defects.     

Ultrahigh rate binder-free Na_3V_2(PO_4)_3/carbon cathode for sodium-ion battery

Sodium ion batteries(SIBs)are very promising for large-scale energy storage in virtue of its high energy density,abundant sodium resources and low environmental impact,etc.However,it is still a big challenge to develop high-performance and durable cathode materials for SIBs.Among different candidate materials,Na_3V_2(PO_4)_3has attracted great attentions due to its high theoretical capacity(117 mAh/g),stable framework structure and excellent ionic conductivity.However,Na_3V_2(PO_4)_3delivers inferior rate capability and cycling stability due to its poor electronic conductivity.In this work,free-standing Na_3V_2(PO_4)_3/carbon nanofiber membranes are synthesized by an electrospinning-sintering route.The sample could deliver excellent cycling capability with specific capacity of 112 mAh/g at 1 C after 250cycles and ultrahigh rate capability with 76.9 mAh/g even at 100 C,which is superior to many state-ofthe-art SIB cathode materials.This can be attributed to the hierarchically distributed Na_3V_2(PO_4)_3crystals in carbon nanofiber network,which possesses outstanding electronic/ionic conductivity and thus leads to an ultrahigh rate capability.     

High-performance nitrogen and sulfur co-doped nanotube-like carbon anodes for sodium ion hybrid capacitors

Sodium ion hybrid capacitors are of great concern in large-scale and cost-effective electrical energy storage owing to their high energy and power densities, as well as natural abundance and wide distribution of sodium. However, it is difficult to find a well-pleasing anode material that matches the high-performance cathode materials to achieve good energy and power output for sodium ion hybrid capacitors. In this paper, nitrogen and sulfur co-doped nanotube-like carbon prepared by a simple carbonization process of high sulfur-loaded polyaniline nanotubes is introduced as the anode. The assembled sodium ion half cell based on the optimal nanotube-like carbon delivers a high reversible capacity of ∼304.8 mAh/g at 0.2 A/g and an excellent rate performance of ∼124.8 mAh/g at 10 A/g in a voltage window of 0.01–2.5 V (versus sodium/sodium ion). For the hybrid capacitors assembled using the optimal nanotube-like carbon as the anode and high-capacity activated carbon as the cathode, high energy densities of ∼100.2 Wh/kg at 250 W/kg and ∼50.69 Wh/kg at 12,500 W/kg are achieved.     

Reduced graphene oxide wrapped hollow molybdenum trioxide nanorod for high performance lithium-ion batteries

Reduced graphene oxide wrapped hollow molybdenum trioxide nanorods have been fabricated as a high performance anode material for lithium batteries.     

锂离子电池正极材料Na3V2（PO4）2F3的原位XRD及固体核磁共振研究

采用溶胶凝胶法制备Na3V2（PO4）2F3/C复合材料,该材料具有优异的电化学循环性能和倍率性能.利用电化学原位同步辐射X射线衍射（XRD）及魔角旋转固体核磁共振（MASSS-NMR）技术研究了Na3V2（PO4）2F3材料充放电过程中结构变化过程及Li/Na嵌入-脱出反应.研究结果表明,Na3V2（PO4）2F3的电极反应按嵌入-脱出反应机理进行,充放电过程中材料具有优异的结构稳定性.我们还发现Na3V2（PO4）2F3与电解液接触后与电解液中的Li＋发生部分交换反应形成LixNa3-xV2（PO4）2F3.在首次充电时,Li＋和结构中Na1位置的Na＋共同从晶格中脱出;而首次放电过程中,Na＋和Li＋共同嵌入到晶格中;充放电过程中发生的是Li＋和Na＋的共嵌入-脱出反应.     

A Multi‐Wall Sn/SnO2@Carbon Hollow Nanofiber Anode Material for High‐Rate and Long‐Life Lithium‐Ion Batteries

Multi‐wall Sn/SnO₂@carbon hollow nanofibers evolved from SnO₂ nanofibers are designed and programable synthesized by electrospinning, polypyrrole coating, and annealing reduction. The synthesized hollow nanofibers have a special wire‐in‐double‐wall‐tube structure with larger specific surface area and abundant inner spaces, which can provide effective contacting area of electrolyte with electrode materials and more active sites for redox reaction. It shows excellent cycling stability by virtue of effectively alleviating pulverization of tin‐based electrode materials caused by volume expansion. Even after 2000 cycles, the wire‐in‐double‐wall‐tube Sn/SnO₂@carbon nanofibers exhibit a high specific capacity of 986.3 mAh g^?1 (1 A g^?1) and still maintains 508.2 mAh g^?1 at high current density of 5 A g^?1. This outstanding electrochemical performance suggests the multi‐wall Sn/SnO₂@ carbon hollow nanofibers are great promising for high performance energy storage systems.     

SnO2 hollow nanospheres assembled by single layer nanocrystals as anode material for high performance Li ion batteries

SnO₂ hollow nanospheres were successfully synthesized via a facile one-step solvothermal method.Characterizations show that the as-prepared SnO₂ spheres are of hollow structure with a diameter at around 50 nm,and especially,the shell of the spheres is assembled by single layer SnO₂ nanocrystals.The surface area of the material reaches up to 202.5 m²/g.As an anode material for Li ion batteries,the sample exhibited improved electrochemical performance compared with commercial SnO₂ particles.After cycled at high current rate of 0.5 C,1 C and 0.5 C for 20 cycles,respectively,the electrode can maintain a capacity of 509 mAh/g.The suitable shell thickness/diameter ratio endows the good structural stability of the material during cycling,which promises the excellent cycling performance of the electrode.The large surface area and the ultra thin shell ensure the high rate performance of the material.     

Pre-potassiated hydrated vanadium oxide as cathode for quasi-solid-state zinc-ion battery

Zinc-ion batteries（ZIBs）, in particular quasi-solid-state ZIBs, occupy a crucial position in the field of energy storage devices owing to the superiorities of abundant zinc reserve, low cost, high safety and high theoretical capacity of zinc anode. However, as divalent Zn²⁺ions experience strong electrostatic interactions when intercalating into the cathode materials, which poses challenges to the structural stability and higher demand in Zn²⁺ions diffusion kinetics of the ...     

Surfactant-Mediated and Morphology-Controlled Nanostructured LiFePO4/Carbon Composite as a Promising Cathode Material for Li-Ion Batteries

The synthesis of morphology-controlled carbon-coated nanostructured LiFePO₄ (LFP/Carbon) cathode materials by surfactant-assisted hydrothermal method using block copolymers is reported. The resulting nanocrystalline high surface area materials were coated with carbon and designated as LFP/C123 and LFP/C311. All the materials were systematically characterized by various analytical, spectroscopic and imaging techniques. The reverse structure of the surfactant Pluronic® 31R1 (PPO-PEO-PPO) in comparison to Pluronic® P123 (PEO-PPO-PEO) played a vital role in controlling the particle size and morphology which in turn ameliorate the electrochemical performance in terms of reversible specific capacity (163 mAh g⁻¹ and 140 mAh g⁻¹ at 0.1 C for LFP/C311 and LFP/C123, respectively). In addition, LFP/C311 demonstrated excellent electrochemical performance including lower charge transfer resistance (146.3 Ω) and excellent cycling stability (95 % capacity retention at 1 C after 100 cycles) and high rate capability (163.2 mAh g⁻¹ at 0.1 C; 147.1 mAh g⁻¹ at 1 C). The better performance of the former is attributed to LFP nanoparticles (<50 nm) with a specific spindle-shaped morphology. Further, we have also evaluated the electrode performance with the use of both PVDF and CMC binders employed for the electrode fabrication.     

Cascading V2O3/N-doped carbon hybrid nanosheets as high-performance cathode materials for aqueous zinc-ion batteries

In recent years, especially when there is increasing concern about the safety issue of lithium-ion batteries（LIBs）, aqueous Zn-ion batteries（ZIBs） have been getting a lot of attention because of their costeffectiveness, materials abundance, high safety, and ecological friendliness. Their working voltage and specific capacity are mainly determined by their cathode materials. Vanadium oxides are promising cathode materials for aqueous ZIBs owing to their low cost, abundant resources, and multivale...     

Amorphous Zr(OH)_4 coated LiNi_(0.915)Co_(0.075)Al_(0.01)O_2 cathode material with enhanced electrochemical performance for lithium ion batteries

LiNi_(0.915)Co_(0.075)Al_(0.01)O_2(NCA) with Zr(OH)_4 coating is demonstrated as high performance cathode material for lithium ion batteries(LIBs). The coated materials are synthesized via a simple dry coating method of NCA with Zr(OH)_4 powders, and then characterized with scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). Experimental results show that amorphous Zr(OH)_4 powders have been successfully coated on the surface of spherical NCA particles, exhibiting improved electrochemical performance. 0.50 wt% Zr(OH)_4 coated NCA delivers a capacity of 197.6 mAh/g at the first cycle and 154.3 mAh/g after 100 cycles with a capacity retention of 78.1% at 1 C rate. In comparison, the pure NCA shows a capacity of 194.6 mAh/g at the first cycle and 142.5 mAh/g after 100 cycles with a capacity retention of 73.2% at 1 C rate. Electrochemical impedance spectroscopy(EIS) results show that the coated material exhibits a lower resistance, indicating that the coating layer can efficiently suppress transition metals dissolution and decrease the side reactions at the surface between the electrode and electrolyte. Therefore, surface coating with amorphous Zr(OH)_4 is a simple and useful method to enhance the electrochemical performance of NCA-based materials for the cathode of LIBs.     

An Amorphous Molybdenum Polysulfide Cathode for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMBs) attract research interest owing to the low cost and high reliability, but the design of cathode materials is the major difficulty of their development. The bivalent magnesium cation suffers from a strong interaction with the anion and is difficult to intercalate into traditional magnesium intercalation cathodes. Herein, an amorphous molybdenum polysulfide (a-MoS_x) is synthesized via a simple one-step solvothermal reaction and used as the cathode material for RMBs. The a-MoS_x cathode provides a high capacity (185 mAh g⁻¹) and a good rate performance (50 mAh g⁻¹ at 1000 mA g⁻¹), which are much superior compared with crystalline MoS₂ and demonstrate the privilege of amorphous RMB cathodes. A mechanism study demonstrates both of molybdenum and sulfur undergo redox reactions and contribute to the capacity. Further optimizations indicate low-temperature synthesis would favor the magnesium storage performance of a-MoS_x.     

Hierarchical porous carbon/selenium composites derived from abandoned paper cup as Li-Se battery cathodes

Paper cup composed of crude cellulose is a common waste in daily life. In this paper, hierarchical porous carbons have been successfully prepared by an initial hydrothermal treatment and subsequent activation route from abandoned paper cup, and then paper cup derived carbons are used as scaffolds to fabricate serial carbon/Se composites. The optimal composite presents unique 3D porous structure, with amorphous selenium uniformly confined into the micropores of carbon. As the cathode materials of Li-Se battery, this composite reveals an initial reversible discharge capacity of 517.2 mAh g⁻¹ at 0.2C, and a capacity value of 431.9 mAh g⁻¹ can be retained after 60 cycles. Even at a high rate of 4C, a capacity value of 295.8 mAh g⁻¹ can be obtained. By comparison, the improved electrochemical performance of the optimal composite should be attributed to reasonable porous structure and effective encapsulation of amorphous selenium.