核壳结构MoOx/C微球的制备及储锂性能

采用水热法合成了MoO_3/酚醛树脂前驱体,然后在空气中进行煅烧处理,成功制备了一种新型核壳MoOx/C微球。对材料的晶体结构、形貌和元素价态进行分析表明,该材料的主要成分是单斜相MoO_2、正交晶系MoO_3和碳。树脂在空气中的煅烧碳化将MoO_3/酚醛树脂前驱体中的六方晶系的MoO_3还原为单斜相MoO_2。其中少量的MoO_2会在空气中重新被氧化成正交晶系的MoO_3,形成了MoO_2/MoO_3异质结构。在这一系列反应的综合作用下,形成这种表面有裂纹的核壳MoOx/C微球复合材料。将该材料用作锂离子电池负极材料,表现出了循环稳定性高、倍率性能好等优异的电化学性能。在100 mA·g-1的电流密度下充放电循环100次之后,可逆容量达640.6 mAh·g-1。     

In-situ Grown SnO2 Nanospheres on Reduced GO Nanosheets as Advanced Anodes for Lithium-ion Batteries

Nanostructured tin dioxide (SnO₂) has emerged as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity (1494 mA h g⁻¹) and excellent stability. Unfortunately, the rapid capacity fading and poor electrical conductivity of bulk SnO₂ material restrict its practical application. Here, SnO₂ nanospheres/reduced graphene oxide nanosheets (SRG) are fabricated through in-situ growth of carbon-coated SnO₂ using template-based approach. The nanosheet structure with the external layer of about several nanometers thickness can not only accommodate the volume change of Sn lattice during cycling but also enhance the electrical conductivity effectively. Benefited from such design, the SRG composites could deliver an initial discharge capacity of 1212.3 mA h g⁻¹ at 0.1 A g⁻¹, outstanding cycling performance of 1335.6 mA h g⁻¹ after 500 cycles at 1 A g⁻¹, and superior rate capability of 502.1 mA h g⁻¹ at 5 A g⁻¹ after 10 cycles. Finally, it is believed that this method could provide a versatile and effective process to prepare other metal-oxide/reduced graphene oxide (rGO) 2D nanocomposites.     

考虑介质膨胀速率的锂离子电池管状电极中扩散诱导应力及轴向支反力分析

硅作为锂离子电池阴极材料相对于传统负极材料具有高比容量,价格低廉等优势.本文针对充电过程中锂离子电池中电极建立力学模型和扩散模型,并在扩散模型引入考虑介质膨胀速率的影响.以硅空心柱形电极为例,分析了恒流充电下介质膨胀速率对电极中扩散诱导应力分布的影响,并研究了不同内外半径比、充电速率、材料参数以及锂化诱导软化系数(lithiation induced softening factor,LISF)对轴向的支反力达到临界欧拉屈曲力所需时间的影响.结果表明,随着电极中锂浓度上升,介质膨胀速率对应力分布的影响增大,对轴向的支反力影响较小.弹性模量和应力成正比,但其与轴向的支反力达到临界欧拉屈曲力所需时间无关;扩散系数与所需时间成反比;偏摩尔体积增大时,达到临界屈曲力所需时间减少;随着LISF绝对值增大,完全锂化时轴向力降低.     

X‐ray Raman spectroscopy of lithium‐ion battery electrolyte solutions in a flow cell

The effects of varying LiPF₆ salt concentration and the presence of lithium bis(oxalate)borate additive on the electronic structure of commonly used lithium‐ion battery electrolyte solvents (ethylene carbonate–dimethyl carbonate and propylene carbonate) have been investigated. X‐ray Raman scattering spectroscopy (a non‐resonant inelastic X‐ray scattering method) was utilized together with a closed‐circle flow cell. Carbon and oxygen K‐edges provide characteristic information on the electronic structure of the electrolyte solutions, which are sensitive to local chemistry. Higher Li⁺ ion concentration in the solvent manifests itself as a blue‐shift of both the π* feature in the carbon edge and the carbonyl π* feature in the oxygen edge. While these oxygen K‐edge results agree with previous soft X‐ray absorption studies on LiBF₄ salt concentration in propylene carbonate, carbon K‐edge spectra reveal a shift in energy, which can be explained with differing ionic conductivities of the electrolyte solutions.     

Effects of Annealing Temperature on Microstructure and Electrochemical Properties of Perovskite-type Oxide LaFeO3 as Negative Electrode for Metal Hydride/Nickel(MH/Ni) Batteries

We reported the effects of annealing temperatures on microstructure and electrochemical properties of perovskite-type oxide LaFeO₃ prepared by stearic acid combustion method. X-Ray diffraction(XRD) patterns show that the annealed LaFeO₃ powder has orthorhombic structure. Scanning electron microscopy(SEM) and transmission electron microscopy(TEM) images show the presence of homogeneously dispersed, less aggregated, and small crystals(30-40 nm) at annealing temperatures of 500 and 600℃. However, as the annealing temperature was increased to 700 and 800℃, the crystals began to combine with each other and grew into further larger crystals(90-100 nm). The electrochemical performance of the annealed oxides was measured at 60℃ using chronopotentiometry, poten-tiodynamic polarization, and cyclic voltammetry. As the annealing temperature increased, the discharge capacity and anti-corrosion ability of the oxide electrode first increased and then decreased, reaching the optimum values at 600℃, with a maximum discharge capacity of 563 mA·h/g. The better electrochemical performance of LaFeO₃ annealed at 600℃ could be ascribed to their smaller and more homogeneous crystals.     

水系钠离子电池电极材料研究进展

随着太阳能、风能等可再生能源发电并网普及应用和智能电网建设,储能技术成为能源优化利用的核心技术之一。水系钠离子电池具有资源丰富、价格低廉等优势,作为未来电网储能的重要选择而成为近年来电化学储能技术前沿的研究热点。由于受到水的热力学电化学窗口限制及嵌钠反应的特殊性(例如溶液的pH值、氧的溶解等),以及容量、电化学电位、适应性及催化效应等,电极材料选择面临挑战,进而影响水系钠离子电池的应用。因此,电极材料成为水系钠离子电池的研究重点。本文简要概括了水系钠离子电池的特点,并对氧化物、聚阴离子化合物、普鲁士蓝类似物和有机物等电极材料体系的最新研究进展进行了总结,并概括了将来的发展方向,为推动水系钠离子电池的发展和能源优化研究奠定了基础。     

锂硫电池用石墨烯基材料的研究进展

锂硫电池因其理论能量密度高、资源丰富和环境友好等优势,被认为是最有发展前景的下一代电化学储能系统之一。然而,硫的绝缘性、充放电中间产物多硫化物的溶解和扩散、硫的体积膨胀以及锂负极安全性等问题,严重制约着锂硫电池的商业应用。石墨烯因其具有高导电、高柔性等诸多优异特性而被广泛研究,将其用于锂硫电池的正极载体、隔膜涂层和集流体中,以期实现高比能、高稳定性的锂硫电池。本文综述了石墨烯基材料,包括石墨烯、功能化石墨烯、掺杂石墨烯和石墨烯复合物,在锂硫电池中应用的研究进展,并展望了锂硫电池用石墨烯基材料的未来发展方向。     

有机氧化还原液流电池的研究进展

氧化还原液流电池（简称液流电池）是一种正在积极研制开发的新型大容量电化学储能装置,其活性物质是流动的电解质溶液,最显著的特点是规模化蓄电. 在广泛利用可再生能源的呼声高涨形势下,可以预见液流电池将迎来一个快速发展的时期. 氧化还原活性物质是液流电池能源转化的载体,也是液流电池中最核心的部分.传统液流电池利用无机材料作为活性物质,然而,无机材料成本高、毒性、资源有限、形成枝晶和电化学活性低等缺点限制了液流电池的大规模应用. 有机活性物质由于具有成本低、“绿色”、资源丰富、分子能级易于调节和电化学反应快等优点,引起了国内外的广泛关注. 近年来,有机液流电池的性能得到快速提升,一系列有机活性物质相继被开发出来. 本文梳理了近年来有机液流电池的研究进展. 首先简要介绍了液流电池的应用领域和技术特点;然后根据电解液种类的不同,详细讨论了有机活性物质在水系和非水系液流电池的应用情况;最后展望了有机液流电池走向实际应用所面临的挑战和潜在研究方向.     

氟化石墨材料的改性及其电化学性能研究

本文以商用氟化石墨为原料,通过水合肼还原的方法对氟化石墨（CF_x）进行改性处理,系统研究了不同水合肼用量对材料电化学性能的影响. 采用XRD、SEM、EDS、XPS、交流阻抗（EIS）和恒流放电测试技术,对改性氟化石墨材料的物相及电化学性能进行了分析研究. 结果表明,采用改性氟化石墨材料制备的锂/氟化碳（Li/CF_x）电池的电压滞后现象得到明显改善,且不同水合肼用量对材料的电化学性能有重要影响. H-CF_x-2（CF_x：C₂H₆O：N₂H₄·H₂O 的比例为1：2：1）材料的综合性能最佳,在0.1C 倍率下,材料的克比容量达到794.5 mAh·g^-1,平台电压为2.53V,电压滞后现象的低波电压为2.37 V.     

Silyl-group functionalized organic additive for high voltage Ni-rich cathode material

To allow stable cycling of layered nickel-rich cathode material at high voltage, silyl-functionalized dimethoxydimethylsilane is proposed as a multi-functional additive. In contrast to typical functional additive, dimethoxydimethylsilane does not make artificial cathode-electrolyte interfaces by electrochemical oxidation because it is quite stable under anodic polarization. We find that dimethoxydimethylsilane mainly focuses on scavenging nucleophilic fluoride species that can be produced by electrolyte decomposition during cycling, leading to improving interfacial stability of both nickel-rich cathode and graphite anode. As a result, the cell cycled with dimethoxydimethylsilane-controlled electrolyte exhibits 65.7% of retention after 100 cycle, which is identified by systematic spectroscopic analyses for the cycled cell.