Performance enforcement of gel polymer electrolyte for lithium ion battery with co-doping silicon dioxide and zirconium dioxide nanoparticles

In this work, we report a new method to enforce the comprehensive performances of gel polymer electrolyte (GPE) for lithium ion battery. Poly(methyl methacrylate-acrylonitrile-vinyl acetate) [P(MMA-AN-VAc)] is synthesized as polymer matrix. The physical and electrochemical performances of the matrix and the corresponding GPEs, doped with nano-SiO₂ and nano-ZrO₂ particles individually or simultaneously, are investigated by scanning electron microscopy, thermogravimetry, electrochemical impedance spectroscopy, and charge/discharge test. It is found that the membrane co-doped with 5 wt.% nano-SiO₂?+?5 wt.% nano-ZrO₂ and the corresponding GPE combine the advantages of those doped individually with 10 wt.% nano-SiO₂ or 10 wt.% nano-ZrO₂. Accordingly, the comprehensive performances of the membrane and the corresponding GPE, in terms of thermal stability, ionic conductivity, and electrochemical stability on the anode and cathode of lithium ion battery, is enforced by co-doping 5 wt.% nano-SiO₂ and 5 wt.% nano-ZrO₂.     

Improved electrochemical performance of LiNi0.5Mn1.5O4 as cathode of lithium ion battery by Co and Cr co-doping

Three samples, LiNi_0.5Mn_1.5O₄, LiNi_0.4Mn_1.4Co_0.2O₄, and LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄, were prepared by sol–gel method and characterized by powder X-ray diffraction, Fourier transformed infrared spectroscope, scanning electron microscopy, Brunauer–Emmett–Teller surface area, four-probe resistance, cyclic voltammetry, electrochemical impedance spectroscopy, and charge–discharge test. It is found that the co-doped sample LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄ exhibits an improved performance compared with the Co-doped sample LiNi_0.4Mn_1.4Co_0.2O₄ and the undoped sample LiNi_0.5Mn_1.5O₄, especially at elevated temperature. At 25 °C, the discharge capacity of LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄ is 130 mAh g^?1 at 0.1 C and 103 mAh g^?1 at 10 C. At an elevated temperature (55 °C), its 1 C discharge capacity is 136 mAh g^?1 and maintains 95.6 % of its initial capacity after 100 cycles. Compared with the reported results of LiNi_0.4Mn_1.4Co_0.2O₄ and LiNi_0.475Mn_1.475Co_0.05O₄, the co-doped sample LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄, with least content of Co, 0.05, possesses not only the high C-rate capacity but also the structural stability. The mechanism on the electrochemical performance improvement of LiNi_0.5Mn_1.5O₄ by the co-doping was discussed.     

Preparation of Fluorescent Polystyrene via ATRP with Dimethylamino Chalcones as Initiator

4‐(3‐(4‐(Dimethylamino)phenyl)acryloyl)phenyl‐2‐bromo‐2‐methylpropanoate (APPBr) was used for the heterogeneous atom transfer radical polymerization (ATRP) of styrene (St) with copper(I) bromide/N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (PMDETA) catalytic system. The functional end group was characterized via UV‐Vis and ¹H NMR spectra. The polymerization showed a first‐order kinetic characteristic and each of the obtained polymers had well‐controlled molecular weight and relatively low polydispersity index (PDI). Furthermore, the obtained end‐functionalized polystyrene (PS) in solution showed strong green‐light emission which is further affected by mixing different metal cations. In particular, the fluorescent intensity of the polymer was decreased in the presence of Ag⁺, Cu²⁺ and Fe³⁺.     

不同波长的光对生物柴油氧化安定性的影响

为了研究光对生物柴油氧化安定性的影响,以小桐子生物柴油为研究对象,在20 ℃下用不同波长的光照射处理48 h,并对处理后的样品进行氧化安定性分析。 结果表明,不同波长的光对生物柴油氧化的促进作用是不同的,以紫光为代表的短波长光对小桐子油生物柴油氧化的促进作用最强,其诱导期由5.12 h降至2.65 h,减少48%;波长较长的红光对生物柴油氧化的促进作用最弱,其诱导期降至4.61 h,减少10%。 对不同波长的光处理的生物柴油进行酸值滴定、成分分析和紫外表征,结果表明,随着光波长的减小,生物柴油的酸值从0.2577 mg/g 增加到0.3438 mg/g;含有两个碳碳双键的亚油酸甲酯的相对含量降低;共轭双键的吸收峰增大。 说明光波长越短,对生物柴油氧化的促进作用越强。     

Robust control of reaction wheel bicycle robot via adaptive integral terminal sliding mode

Nonlinear Dynamics - In this paper, the modelling of a reaction wheel bicycle robot (RWBR) is identified from a second-order mathematical model which is similar to an inverted pendulum, and an...     

Polyethylene-supported poly(methyl methacrylate<Emphasis Type="Italic">-co-</Emphasis>butyl acrylate)-based novel gel polymer electrolyte for lithium ion battery

A new copolymer, poly(methyl methacrylate-co-butyl acrylate) (P(MMA-co-BA)), was synthesized by emulsion polymerization with different mass ratio of methyl methacrylate (MMA) and butyl acrylate (BA). The membranes were prepared by phase inversion and corresponding gel polymer electrolytes (GPEs) were obtained by immersing the membrane into a liquid electrolyte. In this design, the hard monomer MMA provided the copolymer with good electrolyte uptake, while the soft monomer BA provided the GPE with strong adhesion between the anode and cathode of lithium ion battery. The properties of the resulting product were investigated by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectra, scanning electron spectroscopy, linear sweep voltammetry, thermogravimetric analysis, cyclic voltammetry, electrochemical impedance spectroscopy and charge/discharge test. The results show that the obtained GPE based on P(MMA-co-BA) with the mass ratios of MMA and BA = 6:1 exhibits good conductivity (as high as 1.2 × 10^?3 S cm^?1) at room temperature and high electrochemical stability (up to 4.9 V vs. Li/Li⁺). With the application of the polyethylene (PE)-supported GPE in Li/Li(Li_0.13Ni_0.30Mn_0.57)O₂ battery, the battery presents good cyclic stability (maintaining 95.4 % of its initial discharge capacity after 50 cycles) at room temperature.     

超快扫描量热技术表征高分子结晶动力学

高分子结晶行为是高分子材料加工过程研究的热点,因为高分子组分和加工工艺控制着高分子结晶及其产物性能。差示扫描量热仪(DSC)是研究高分子结晶动力学常规手段。但是,普通DSC所能达到的最快降温速率一般无法抑制较快的样品结晶,结晶行为将在等温结晶动力学测试之前发生,因此可进行等温结晶的研究温度范围局限于较低结晶过冷度的高温区域。近年来,具有超快速升降温扫描速率和精准控温的快速扫描芯片量热仪(FSC,其商业化版本Flash DSC 1)得到了广泛应用。FSC可以抑制高分子样品在升降温过程中的结晶成核,避免对之后的结晶动力学测试产生影响。因此FSC技术将高分子结晶动力学的研究温度区间延伸至具有较大过冷度的低温区,加深了我们对高分子结晶成核机理以及高分子工业加工过程的理解。本文首先介绍了由初级成核方程描述的高分子结晶动力学原理,初级成核自由能位垒(?G~*)和扩散活化能位垒(?U)分别控制了高低温区的结晶动力学。我们还总结了FSC技术的发展,包括氮化硅薄膜芯片技术、快速扫描量热仪、商业化Flash DSC 1在不同高分子结晶熔融行为研究中的应用。然后介绍表征高分子等温结晶动力学的方法,其中包括样品制备、质量估算、消除热历史、临界扫描速率的确定等,并举例介绍FSC在高分子结晶动力学研究中的应用,涵盖高分子总结晶动力学、结晶成核动力学、高分子焓松弛对结晶成核的影响、FSC联用技术等方面。应用举例中对应形貌和结晶信息,分析了通过FSC测试得到的结晶成核动力学特点。另外通过比较不同结构特点的高分子,总结了我们对结晶动力学行为的基本理解。总之,FSC技术是一种能够提供相转变动力学和热力学信息的高效工具,特别是应用于分析只能在快速扫描中得到的样品结构变化信息。同时我们希望本文能够帮助读者考虑超快扫描量热技术在其他材料研究上的应用,包括合金、药物、生物大分子等。     

2014年毛细管电泳技术年度回顾

本文为2014年毛细管电泳(CE)技术的年度回顾.介绍了2014年涉及CE技术的国际会议5个,国内会议2个,总结了各会议的研究报道情况;归纳了在ISI Web of Science中检索到的2014年度发表的与CE技术相关的论文,并对以上论文在生物医药研究、检测器使用以及重要分析化学杂志发表的情况进行了分类说明.最后,回顾和比较了2012-2014年的CE进展.     

雌雄木蜂对活血丹盗蜜的行为差异及原因

通过近三年的野外观察和实验揭示了活血丹的盗蜜者为中华木蜂．但其雌雄个体具有不同的访花特性和影响．雄蜂的体形稍小，访花频率是雌蜂的4倍，单花访问时间较雌蜂短（2．18s／7．48s），但在一个居群的单次访花数印是雌蜂的5倍（42．48／8．81），对被盗蜜花的损伤也较雌蜂低；在开放条件下，被雌雄小蜂访问过的花的座果率有明显差异（34．72％／73．59％）．结果表明，体形大小的差异可能是活血丹的花冠管长度、硬度及单花产蜜量仪能适成雄蜂的盗蜜，小适心雌蜂盗蜜的主要原因，对食物资源的合理利用可能导致了中华木蜂雌雄个体在对活血丹的取食行为上发生了分化，并对其花部进化施加了不同的选择压力．