The unsatisfactory rate capability and poor cycling stability at high rate of sodium-ion batteries(SIBs) have impeded their practical applications. Herein, a Na3V2(PO4)3/Na3V3(PO4)4 multiphase cathode materials for high-rate and long cycling SIBs was successfully synthesized by regulation the stoichiometric ratio of raw materials. The combined experiment and simulation results show that the multiphase materials consisted of NASICON structural phase Na3V2(PO4)3 and layered structure phase Na3V3(PO4)4, possess abundant phase boundaries. Electrochemical experiments demonstrate that the multiphase materials maintain a remarkable reversible capacity of 69.0 mA h g-1 even at an ultrahigh current density of 100 C with a high capacity retention of 81.25 % even after 10,000 cycles. Na3V2(PO4)3/Na3V3(PO4)4 electrode exhibits a higher working voltage, superior rate capability and better cycling stability than Na3V2(PO4)3 electrode, which indicates that the introduction of second phase can be an effective strategy for the development of novel cathode materials for SIBs. 相似文献
Organic-based electrode materials for lithium-ion batteries (LIBs) are promising due to their high theoretical capacity, structure versatility and environmental benignity. However, the poor intrinsic electric conductivity of most polymers results in slow reaction kinetics and hinders their application as electrode materials for LIBs. A binder-free self-supporting organic electrode with excellent redox kinetics is herein demonstrated via in situ polymerization of a uniform thin polyimide (PI) layer on a porous and highly conductive carbonized nanofiber (CNF) framework. The PI active material in the porous PI@CNF film has large physical contact area with both the CNF and the electrolyte thus obtains superior electronic and ionic conduction. As a result, the PI@CNF cathode exhibits a discharge capacity of 170 mAh·g−1 at 1 C (175 mA·g−1), remarkable rate-performance (70.5% of 0.5 C capacity can be obtained at a 100 C discharge rate), and superior cycling stability with 81.3% capacity retention after 1,000 cycles at 1 C. Last but not least, a four-electron transfer redox process of the PI polymer was realized for the first time thanks to the excellent redox kinetics of the PI@CNF electrode, showing a discharge capacity exceeding 300 mAh·g−1 at a current of 175 mA·g−1.
NaFeTiO4 nanorods of high yields (with diameters in the range of 30-50 nm and lengths of up to 1-5 μm) were synthesized by a facile sol-gel method and were utilized as an anode material for sodium-ion batteries for the first time.The obtained NaFeTiO4 nanorods exhibit a high initial discharge capacity of 294 mA·h·g-1 at 0.2 C (1 C =177 mA·g-1),and remain at 115 mA·h·g-1 after 50 cycles.Furthermore,multi-walled carbon nanotubes (MWCNTs) were mechanically milled with the pristine material to obtain NaFeTiO4/MWCNTs.The NaFeTiO4/MWCNTs electrode exhibits a significantly improved electrochemical performance with a stable discharge capacity of 150 mA·h·g-1 at 0.2 C after 50 cycles,and remains at 125 mA·h·g-1 at 0.5 C after 420 cycles.The NaFeTiO4/MWCNTs//Na3V2(PO4)3/C full cell was assembled for the first time;it displays a discharge capacity of 70 mA·h·g-1 after 50 cycles at 0.05 C,indicating its excellent performances.X-ray photoelectron spectroscopy,ex situ X-ray diffraction,and Raman measurements were performed to investigate the initial electrochemical mechanisms of the obtained NaFeTiO4/MWCNTs. 相似文献
The synthesis of a composite of cobalt phosphide nanowires and reduced graphene oxide (denoted CoP/RGO) via a facile hydrothermal method combined with a subsequent annealing step is reported. The resulting composite presents large specific surface area and enhanced conductivity, which can effectively facilitate charge transport and accommodates variations in volume during the lithiation/de-lithiation processes. As a result, the CoP/RGO nanocomposite manifests a high reversible specific capacity of 960 mA·h·g–1 over 200 cycles at a current density of 0.2 A·g–1 (297 mA·h·g–1 over 10,000 cycles at a current density of 20 A·g–1) and excellent rate capability (424 mA·h·g–1 at a current density of 10 A·g–1).
Bi is a promising candidate for energy storage materials because of its high volumetric capacity,stability in moisture/air,and facile preparation.In this study,the electrochemical performance of nanosized-Bi-embedded one-dimensional (1D) carbon nanofibers (Bi/C nanofibers) as anodes for Li-ion batteries (LIBs) and Na-ion batteries (NIBs) was systematically investigated.The Bi/C nanofibers were prepared using a single-nozzle electrospinning method with a specified Bi source followed by carbothermal reduction.Abundant Bi nanoparticles with diameters of approximately 20 nm were homogeneously dispersed and embedded in the 1D carbon nanofibers,as confirmed by structural and morphological characterization.Electrochemical measurements indicate that the Bi/C nanofiber anodes could deliver a long cycle life for LIBs and a preferable rate performance for NIBs.The superior electrochemical performances of the Bi/C nanofiber anodes are attributed to the 1D carbon nanofiber structure and uniform distribution of Bi nanoparticles embedded in the carbon matrix.This unique embedded structure provides a favorable electron carrier and buffering matrix for the effective release of mechanical stress caused by volume change and prevents the aggregation of Bi nanoparticles. 相似文献
Lithium-ion batteries (LIBs) are currently recognized as one of the most popular power sources available. To construct advanced LIBs exhibiting long-term endurance, great attention has been paid to enhancing their poor cycle stabilities. As the performance of LIBs is dependent on the electrode materials employed, the most promising approach to improve their life span is the design of novel electrode materials. We herein describe the rational design of a three-dimensional (3D) porous MnO/C-N nanoarchitecture as an anode material for long cycle life LIBs based on their preparation from inexpensive, renewable, and abundant rapeseed pollen (R-pollen) via a facile immersion-annealing route. Remarkably, the as-prepared MnO/C-N with its optimized 3D nanostructure exhibited a high specific capacity (756.5 mAh·g?1 at a rate of 100 mA·g?1), long life span (specific discharge capacity of 513.0 mAh·g?1, ~95.16% of the initial reversible capacity, after 400 cycles at 300 mA·g?1), and good rate capability. This material therefore represents a promising alternative candidate for the high-performance anode of next-generation LIBs.
Tricobalt tetroxide (Co3O4) is one of the promising anodes for lithium-ion batteries (LIBs) due to its high theoretical capacity. However, the poor electrical conductivity and the rapid capacity decay hamper its practical application. In this work, we design and fabricate a hierarchical Co3O4 nanorods/N-doped graphene (Co3O4/NG) material by a facile hydrothermal method. The nitrogen-doped graphene layers could buffer the volume change of Co3O4 nanorods during the delithium/lithium process, increase the electrical conductivity, and profit the diffusion of ions. As an anode, the Co3O4/NG material reveals high specific capacities of 1873.8 mA·h·g−1 after 120 cycles at 0.1 A·g−1 as well as 1299.5 mA·h·g−1 after 400 cycles at 0.5 A·g−1. Such superior electrochemical performances indicate that this work may provide an effective method for the design and synthesis of other metal oxide/N-doped graphene electrode materials. 相似文献
A hierarchically 3D structured milled lamellar MoS2/nano-silicon@carbon hybrid with medium capacity and long-term lifespan is designed by a green and scalable approach using ball milling process and spray-drying/pyrolysis routes. The microspheres consist of low-content nano-silicon (20 wt%), milled lamellar MoS2 sheets and porous carbon skeletons. A mixture of silicon nanoparticles and MoS2 flakes serves as an inner core, while porous carbon pyrolyzed from petroleum pitch acts as a protective shell. The particular architecture affords robust mechanical support, abundant buffering space and enhanced electrical conductivity, thus effectively accommodating drastic volume variation during repetitive Li+ intercalation/extraction. The Si/MoS2@C hybrid delivers a high initial discharge specific capacity of 1257.8 mA h g−1 and exhibits a reversible capacity of 767.52 mA h g−1 at a current density 100 mA g-1 after 250 cycles. Most impressively, the electrode depicts a superior long-cycling durability with a discharge capacity of 537.6 mA h g−1 even after 1200 cycles at a current density of 500 mA g-1. Meanwhile, the hybrid also shows excellent rate performance such as 388.1 mA h g−1 even at a large current density of 3000 mA g-1. 相似文献
The requirement for silicon-based anode material is growing and has received attentions. Silicon is a promising anode material for lithium-ion batteries due to the high theoretical capacity. However, the high volumetric variability of silicon has led to severe chalking and rapid capacity degradation. To ameliorate these problems, a carbon-covered silicon material with a 3D conductive network structure was prepared employing glucose and phytic acid as carbon sources. When acted as the anode for Lithium-ion batteries, the prepared composite material delivered 1612 mAh/g in the first cycle and approximately 600 mAh/g at 0.1 A/g after 200 cycles. In addition, even at 5 A/g, a high capacity of 503 mAh/g was reached, and when recovered to 0.1 A/g, the capacity of 878 mAh/g was maintained. 相似文献
The geometric size and distribution of magnetic nanoparticles are critical to the morphology of graphene (GN) nanocomposites, and thus they can affect the capacity and cycling performance when these composites are used as anode materials in lithium-ion batteries (LiBs). In this work, Fe3O4 nanorods were deposited onto fully extended nitrogen-doped GN sheets from a binary precursor in two steps, a hydrothermal process and an annealing process. This route effectively tuned the Fe3O4 nanorod size distribution and prevented their aggregation. The transformation of the binary precursor was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). XPS analysis indicated the presence of N-doped GN sheets, and that the magnetic nanocrystals were anchored and uniformly distributed on the surface of the flattened N-doped GN sheets. As a high performance anode material, the structure was beneficial for electron transport and exchange, resulting in a large reversible capacity of 929 mA·h·g–1, high-rate capability, improved cycling stability, and higher electrical conductivity. Not only does the result provide a strategy for extending GN composites for use as LiB anode materials, but it also offers a route for the preparation of other oxide nanorods from binary precursors.
The oxygen vacancies and micro-nano structure can optimize the electron/Li+migration kinetics in anode materials for lithium batteries(LIBs).Here,porous micro-nano structured VNb9O25 composites with rich oxygen vacancies were reasonably prepared via a facile solvothermal method combined with annealing treatment at 800℃for 30 h(VNb9 O25-30 h).This micro-nano structure can enhance the contact of active material/electrolyte,and shorten the Li+diffusion distance.The introduction of oxygen vacancies can further boosts the intrinsic conductivity of VNb9O25-30 h for achieving excellent LIB performance.The as-prepared VNb9O25-30 h anode showed advanced rate capability with reversible capacity of 122.2 mA h g-1 at 4 A g-1,and delivered excellent capacity retention of～100％after 2000 cycles.Meanwhile,VNb9O25-30 h provides unexpected long-cycle life(i.e.,reversible capacity of 165.7 mA h g-1 at 1 A g-1 with a high capacity retention of 85.6％even after 8000 cycles).Additionally,coupled with the LiFePO4 cathode,the LiFePO4//VNb9O25-30 h full cell delivers superior LIB properties with high reversible capacities of 91.6 mA h g-1 at 5C for 1000 cycles.Thus,such reasonable construction method can assist in other high-performance niobium-based oxides in LIBs. 相似文献
