单离子聚合物快离子导体

具有高锂离子迁移数和良好可加工性能的锂快离子导体对于全固态电池的发展非常重要。然而,现有的锂快离子导体主要限制于硬质陶瓷,目前尚无柔性聚合物类型的锂快离子导体被报道。在这个工作中,我们报告了一种通过三种不同有机单体的自由基聚合反应形成的三元无规共聚单离子快离子导体(SISC)。该SISC中包含丰富的锂离子传输位点和具有阴离子锚定功能的阴离子受体。此外,三种不同单体的共聚反应带来低结晶度和低玻璃化转变温度(T_g),有利于链段运动,从而获得小的锂离子传输的活化能(E_a)。电化学测试结果表明,该SISC的室温离子电导率和锂离子迁移数分别达到1.29 mS∙cm⁻¹和0.94。将SISC与锂金属负极和多种正极(包括LiFePO₄、LiCoO₂和硫化聚丙烯腈(SPAN))原位聚合,组装得到的全固态电池具有良好的电化学稳定性。其中,Li||LiFePO₄全固态电池表现出高达8C的倍率性能和良好的循环寿命(在0.5C倍率下稳定循环 > 700圈)。这项工作提供了一种新颖的聚合物基快离子导体设计理念,对于发展高性能全固态电池具有重要意义。     

Fe2O3-MWNTs Composite with Reinforced Concrete Structure as High-performance Anode Material for Lithium-ion Batteries

AFe₂O₃-MWNTs(multi-walled carbon nanotubes) composite with a reinforced concrete structure was fabricated employing a two-step method, which involves a sol-gel process followed by high-temperature in situ sintering. This Fe₂O₃-MWNTs composite, intended to be used as an anode material for lithium-ion batteries, maintained a reversible capacity as high as 896.3 mA·h/g after 100 cycles at a current density of 100 mA/g and the initial coulombic efficiency reached 75.5%. The rate capabilities of the Fe₂O₃-MWNTs composite, evaluated using the ratios of capacity at 100, 200, 500, 1000, 2000 and 100 mA/g after every 10 cycles, were determined to be 904.7, 852.1, 759.0, 653.8, 566.8 and 866.3 mA·h/g, respectively. Such a superior electrochemical performance of the Fe₂O₃-MWNTs composite is mainly attributed to the reinforced concrete construction, in which the MWNTs function as the skeleton and conductive network. Such a structure contributes to shortening the transport pathways for both Li⁺ and electrons, enhancing conductivity and accommodating volume expansion during prolonged cycling. This Fe₂O₃-MWNTs composite with the designed structure is a promising anode material for high-performance lithium-ion batteries.     

The Status of Representative Anode Materials for Lithium-Ion Batteries

Since the invention of lithium-ion batteries as a rechargeable energy storage system, it has uncommonly promoted the development of society. It has a wide variety of applications in electronic equipment, electric automobiles, hybrid vehicles, and aerospace. As an indispensable component of lithium-ion batteries, anode materials play an essential role in the electrochemical characteristics of lithium-ion batteries. In this review, we described the development from lithium-metal batteries to lithium-ion batteries in detail on the time axis as the first step; This was followed by an introduction to several commonly used anode materials, including graphite, silicon, and transition metal oxide with discussions the charge-discharge mechanism, challenges and corresponding strategies, and a collation of recent interesting work; Finally, three anode materials are summarized and prospected. Hopefully, this review can serve both the newcomers and the predecessors in the field.     

Investigation of Ba fully occupied A-site BaCo0.7Fe0.3−xNbxO3−δ perovskite stabilized by low concentration of Nb for oxygen permeation membrane

BaCo_0.7Fe_0.3−xNb_xO_3−δ (BCFN, x = 0–0.2) were prepared by the conventional solid state reaction process. The crystal structure, electrical conductivity and oxygen desorption property were studied by X-ray diffraction (XRD), different thermal analysis (DTA), four-terminal direct current conductivity and oxygen temperature programmed desorption (O₂-TPD), respectively. At x = 0.08–0.20, BCFN have a cubic perovskite structure, while it exhibits the hexagonal structure for x = 0.00 and the mixed phases of cubic perovskite with trace amount of hexagonal for x = 0.05. BCFN shows good structure stability in 5%H₂ + Ar reducing atmosphere, and it is enhanced with the increased Nb-doping content. The electrical conductivity of BCFN increases with increasing temperature and decreases with the Nb substitution content for iron. BCFN exhibits a p-type semiconductor and obeys the thermally activated small polarons hopping mechanism. The oxygen fluxes increase with the working temperature and the COG flow rate, but decrease with increasing Nb content. The flux of BCFN (x = 0.08) with 1.0 mm thickness membrane reaches 25.77 ml min⁻¹ cm⁻² at 875 °C, higher than most of the reported materials.     

Magnetic resonance study of a vanadium pentoxide gel

In this work we report results from continuous-wave (CW) and pulsed electron paramagnetic resonance (EPR) and proton nuclear magnetic resonance (NMR) studies of the vanadium pentoxide xerogel V₂O₅:nH₂O (n ≈ 1.6). The low temperature CW-EPR spectrum shows hyperfine structure due to coupling of unpaired V⁴⁺ electron with the vanadium nucleus. The analysis of the spin Hamiltonian parameters suggests that the V⁴⁺ ions are located in tetragonally distorted octahedral sites. The transition temperature from the rigid-lattice low-temperature regime to the high temperature liquid-like regime was determined from the analysis of the temperature dependence of the hyperfine splitting and the V⁴⁺ motional correlation time. The Electron Spin Echo Envelope Modulation (ESEEM) data shows the signals resulting from the interaction of ¹H nuclei with V⁴⁺ ions. The modulation effect was observed only for field values in the center of the EPR absorption spectrum corresponding to the single crystals orientated perpendicular to the magnetic field direction. At least three protons are identified in the xerogel by our magnetic resonance experiments: (I) the OH groups in the equatorial plane, (ii) the bound water molecules in the axial V=O bond and (iii) the free mobile water molecules between the oxide layers. Proton NMR lineshapes and spin-lattice relaxation times were measured in the temperature range between 150 K and 323 K. Our analysis indicates that only a fraction of the xerogel protons contribute to the measured conductivity.     

High lithium electroactivity of hierarchical porous rutile TiO2 nanorod microspheres

Here we report on the hierarchical porous rutile TiO₂ nanorod micospheres as an anode material for lithium-ion batteries. The resulting hierarchical porous rutile TiO₂ nanorod microspheres possessed much higher reversible capacity, cycling stability and rate capability than nanosized rutile TiO₂ previously reported in the literatures. These good electrochemical performances may be attributed to the facile diffusion of Li⁺ ions from outside through the porous channels into the TiO₂ nanorods in the microspheres and the high electrode–electrolyte contact area offered by hierarchical porous microspheres with a large specific surface area.     

The effect of Al substitution on the reactivity of delithiated LiNi1/3Mn1/3Co(1/3−z)AlzO2 with non-aqueous electrolyte

The high temperature reactions between 1 M LiPF₆ EC:DEC and Al-doped LiNi_1/3Mn_1/3Co_(1/3−z)Al_zO₂ charged to 4.3 V were studied by accelerating rate calorimetry (ARC) and compared with those of charged LiNi_1/3Mn_1/3Co_1/3O₂ and LiMn₂O₄. Al substitution for Co in LiNi_1/3Mn_1/3Co_1/3O₂ improves the thermal stability. Materials with z > 0.06 are less reactive with electrolyte than spinel LiMn₂O₄ at all temperatures studied. The maximum self-heating rate (SHR) attained and the specific capacity decrease as the Al content increases. There is a range of compositions near z = 0.1 that show excellent promise as materials which are both safer than and more energy dense than spinel LiMn₂O₄.     

New electrolytes using Li2O or Li2O2 oxides and tris(pentafluorophenyl) borane as boron based anion receptor for lithium batteries

A new system of electrolytes has been developed and studied for lithium-ion batteries. This new system is based on the interactions between Li₂O or Li₂O₂ and tris(pentafluorophenyl) borane (TPFPB) in carbonate based organic solvents. This opens up a completely new approach in developing non-aqueous electrolytes. In general, the solubility of Li₂O or Li₂O₂ is very low in organic solvents and the ionic conductivities of these solutions are almost undetectable. By adding certain amount of tris(pentafluorophenyl) borane (TPFPB), one type of boron based anion receptors (BBARs), the solubility of Li₂O or Li₂O₂ in carbonate based solvents was significantly enhanced. In addition, the Li⁺ transference numbers of these new electrolytes measured were as high as 0.7, which are more than 100% higher than the values for the conventional electrolytes for lithium-ion batteries. The room-temperature conductivities are around 1 × 10⁻³ S/cm. These new electrolytes are compatible with LiMn₂O₄ cathode for lithium-ion batteries.     

Synthesis and electrochemical properties of LiNi0.85 ? x Co x Mn0.15O2 as cathode materials for lithium-ion batteries

LiNi_0.85−x Co _x Mn_0.15O₂ cathode material was prepared by a rheological phase reaction method with LiNO₃, M(NO₃)₂ 6H₂O (M = Ni, Co, Mn), and citric acid as starting materials. The mixture of reactants and a proper amount of water reacted to form a rheological precursor. The rheological precursor was pretreated in autoclaves and then calcined at 750 °C under flowing oxygen. All the samples have a typical layered structure with space group R3-m and good electrochemical performances. The cobalt content has a significant effect on the electrochemical performance for the materials. LiNi_0.65Co_0.20Mn_0.15O₂ exhibits the best electrochemical properties in the five compounds. It gives an initial discharge capacity of 173.6mAhg⁻¹ (50mA g⁻¹, 3.0−4.3V), and the capacity rention after 50 cycles is 90.6%. This method is simple and effective for preparing cathode materials for lithium-ion batteries.     

介孔氧化锡的制备及其在锂离子电池中的应用

采用十六烷基三甲基溴化铵(CTAB)作模板剂, SnCl4·5H2O为无机离子源在水溶液中合成了有序介孔氧化锡材料. 通过XRD、N2-吸附脱附、TEM测试手段对合成产物进行表征, 并且测试了该材料作为锂离子电池阳极的可逆容量和循环能力. 结果表明, 合成过程中氨水的加入量对制备有序结构材料至关重要, 适量的OH-离子能将Sn(ClxBry)2-单元诱导组装到表面活性剂液晶模板上; 介孔材料用于锂离子电池阳极时循环容量保持能力良好; 首次不可逆容量高于SnO2理论损失量, 原因是介孔材料将锂离子滞留在孔中.