Interface control for high-performance all-solid-state Li thin-film batteries

We fabricated and evaluated four types of Li batteries, in this case a LTO/liquid electrolyte/Li battery, a LTO/LiPON/Li all-solid-state battery, and LTO/LiPON + liquid electrolyte/Li batteries with and without a separator to investigate and clarify the effects of each interface. Through the present research, it was found that a conventional polymer-based separator increases the impedance in the middle frequency region, resulting in an increase in the total cell resistance. After replacing the polymer-based separator with a thin-film solid electrolyte, the cycleability and capacity of the cell were comparable to those of a conventional Li-ion battery with a polymer separator. The all-solid-state Li thin-film battery without a liquid electrolyte exhibits the lowest capacity due to the large interfacial resistance between the Li metal and the LiPON solid electrolyte. However, we found that the insertion of an Al₂O₃ interlayer between the Li and LiPON improves the capacity.     

Low Temperature Water–Gas Shift: Alkali Doping to Facilitate Formate C–H Bond Cleaving over Pt/Ceria Catalysts—An Optimization Problem

Doping Pt/ceria catalysts with alkali metals was found to lead to an important weakening of the formate C–H bond, as demonstrated by a shift to lower wavenumbers of the ν(CH) vibrational mode. However, with high alkalinity (∼2.5%Na or equimolar amounts of K, Rb, or Cs), a tradeoff was observed such that while the formate became more reactive, the stability of the carbonate species, which arises from the formate decomposition, was found to increase. This was observed by TPD-MS measurements of the adsorbed CO₂ probe molecule. Increasing the amount of alkali to levels that were too high also led to lower catalyst BET surface area, the blocking of the Pt surface sites as observed in infrared measurements, and also a shift to higher temperature of the surface shell reduction step of ceria during TPR. When the alkalinity was too high, the CO conversion rate during water–gas shift decreased in comparison with the undoped Pt/ceria catalyst. However, at lower levels of alkali, the abovementioned inhibiting factors on the water–gas shift rate were alleviated such that the weakening of the formate C–H bond could be utilized to improve the overall turnover efficiency during the water–gas shift cycle. This was demonstrated at 0.5%Na (or equimolar equivalent levels of K) doping levels. Not only was the formate turnover rate found to increase significantly during both transient and steady state DRIFTS tests, but this effect was accompanied by a notable increase in the CO conversion rate during low temperature water–gas shift.     

New insight into the modification of Li-rich cathode material by stannum treatment

In this work, Sn is used to dope the Li-rich cathode material to improve the electrochemical performance of Li ion battery. After Sn treatment, the lattice parameters a, c and lattice volume V become larger. Compared with the pristine sample, the Sn-contained samples show longer plateaux at about 4.5 V in the first charging process, which means that Sn can activate the Li₂MnO₃ component. Meanwhile, with appropriate content of Sn doping, the sample exhibits enhanced rate capability and cycling stability. Especially, the sample S10 shows the best electrochemical performance, with a capacity retention of 88.66% after 100 cycles at 1 C (1 C=250 mA g⁻¹). The mechanisms of Sn doping have also been investigated. The increased activation of Li₂MnO₃ is due to the improved conductivity of Li₂MnO₃ phase by Sn doping, and the enhanced electrochemical performance is mainly ascribed to the increased ability of Li ion diffusing into bulk phase and the improved structure stability during the prolonged charge-discharge cycles. It is suggested that Sn doping is an effective way to improve the electrochemical performance of Li-rich cathode material.     

Li NMR spectroscopy and ion conduction mechanism of composite gel polymer electrolyte: A comparative study with variation of salt and plasticizer with filler

Microporous composite gel polymer electrolyte (CGPE) has been prepared by incorporating the home-made silica aerogel (SAG) particles into the poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) copolymer/LiClO₄ matrix. The ionic transport behavior of the electrolyte is studied with various experimental techniques such as AC impedance, X-ray diffraction (XRD), infrared (IR) spectra, nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA), etc. The results reveal that the SAG particles are well dispersed in the electrolytes and incorporate with the other components of the CGPEs. The solid-state ⁷Li NMR study has confirmed the interactions of lithium ion with SAG, polymer and plasticizers, causing to form the microporous structure and reduce the glass transition temperature and crystallinity, resulting in an increase in ionic conductivity of the CGPE. The best ionic conductivity (1.04 × 10⁻² S/cm at room temperature) is obtained from the composite polymer electrolyte containing 4 wt% of SAG, which is approximately four times higher than the ionic conductivity of the electrolyte without the filler.     

负极材料Li_4Ti_5O_(12)合成中优化原料组成的研究

以不同的钛源(锐钛矿型TiO2、金红石型TiO2和无定形TiO2)和不同的锂源(Li2CO3和LiOH.H2O),采用高温固相合成法合成Li4Ti5O12,并对Li4Ti5O12的合成工艺进行了优化。经试验发现,在900℃下以锐钛矿型TiO2和Li2CO3为原料合成的Li4Ti5O12具有良好的电化学性能,Li4Ti5O12材料在Li+嵌入和脱出的过程中,其晶型不发生变化。     

Ca（0.2）（Li（1/2）Sm（1/2））（0.8）TiO3微波介质陶瓷低温烧结研究

以Ca0.2(Li1/2Sm1/2)0.8TiO3(CLST-0.8)为基料,添加质量分数10%的CaO-B2O3-SiO2(CBS)复合氧化物、4%的Li2O-B2O3-SiO2-CaO-Al2O3(LBSCA)玻璃料和0～2%的CuO氧化物为复合烧结助剂,研究了CuO含量的变化对CLST-0.8陶瓷的低温烧结行为及微波介电性能的影响.随着CuO添加量的增加,陶瓷体积密度、介电常数εr、无载品质因数与谐振频率乘积Qf值,都呈先增加后降低,谐振频率温度系数τf则呈先降低后升高的趋势.添加10%CBS、4.0%LBSCA和1.0%CuO的CLST-0.8微波介质陶瓷,可在900℃下保温5h烧结,并具有较佳的微波介电性能:εr=58.36,Qf=2011GHz, τf=3.44 ppm/℃.     

共沉淀法合成磷酸亚铁锂正极材料及性能研究

采用共沉淀法合成了橄榄石型磷酸亚铁锂正极材料。利用X射线衍射，扫描电子显微镜，振实密度测定以及电化学测试等方法对该材料进行了结构表征和性能测试。结果表明：在较宽的温度范围内，都能形成单一的橄榄石型晶体结构，并具有较高的振实密度。其中，在650℃下合成的产物结构完整，表面形貌较好，粒径分布均匀，振实密度高达1．67g／cm^3。在室温及0．05C倍率下，该材料的首次放电容量为133．6mA·h／g，循环20次后，未见明显衰减。     

锂离子电池正极材料镍酸锂研究进展

镍酸锂具有比容量高、污染小、价格适中、与电解液匹配好等优点，被认为是一种较有发展前景的锂离子电池正极材料。但它合成困难，循环稳定性差。近几年来一些研究人员从合成方法、掺杂改性等方面对镍酸锂做了大量的研究工作。介绍了作为锂离子电池正极材料的镍酸锂的结构特征、电化学性能及现阶段存在的问题；综述了近几年来国内外的电化学研究者对锂离子电池正极材料镍酸锂的合成及稀土掺杂方面的研究进展和稀土掺杂对镍酸锂的结构和电化学性能的影响；并对镍酸锂未来的发展方向做了展望。     

异形玉叶金花果实不同提取部位抗氧化活性研究

以乙醇为溶剂提取异形玉叶金花果实,经减压浓缩后,依次用乙酸乙酯和正丁醇进行萃取。用DPPH自由鼙的清除能力来评价两个部位的抗氧化活性。结果表明,己酸乙酯部位浓度为283．20μg/mL时自由基清除率大于50％,IC50=304．85μg／mL,正丁醇部位浓度为17760μg／mL．时自由基清除率大于50％,IC50-224．07μg／mL。正丁醇部位抗氧化能力比乙酸乙酯部位更好。     

GH864合金蠕变/疲劳裂纹扩展速率及a-N曲线分析

研究了GH864合金不同保载时间下650℃蠕变/疲劳裂纹扩展行为,分析了裂纹扩展过程中蠕变和氧化的作用,以及a-N曲线的转折点含义。结果表明:保载5s时GH864合金以穿晶断裂为主,疲劳作用占主导;保载90s时GH864合金以沿晶断裂为主,蠕变作用占主导。利用Saxena模型可较好地表征本实验条件下650℃蠕变/疲劳交互作用的裂纹扩展速率曲线,可估算较高应力强度因子和较低应力强度因子的裂纹扩展速率。另外,用Saxena模型可求出蠕变和疲劳的表达式,对比分析高温蠕变/疲劳交互作用的裂纹扩展过程中蠕变和疲劳的作用及所占的比例。最后针对a-Ni/Nf、da/dN-a曲线及da/dN-N曲线变换中出现的拐点,结合断口形貌分析了转折点对应的含义。高温合金及其它材料的裂纹扩展速率曲线也适用于以上曲线分析方法。