新型共混的PEO/TPU/PVDF-HFP基聚合物电解质的制备及性能

通过相转化法制备基于聚氧化乙烯（PEO）/热塑性聚氨酯（TPU）/聚偏氟乙烯-六氟丙烯（PVDF-HFP）三种高聚物共混形成的电解质隔膜, 浸泡在1 mol/L六氟磷酸锂（LiPF6）的碳酸乙烯酯（EC）: 碳酸二甲酯（DMC）: 碳酸甲乙酯（EMC）=1:1:1的电解液中形成一种新型的凝胶态聚合物电解质（GPE）。采用SEM、FTIR、XRD、TG、DSC、拉伸性能和电化学性能进行了表征。结果表明，聚合物配比为3:1:4的隔膜具备均匀的多孔形貌，结晶峰面积最低，拉伸强度达到了15 MPa，离子电导率为7.9?10^(-3) S?cm，综合性能最佳。将聚合物配比为3:1:4的隔膜装配成CR2032纽扣电池进行电池循环性能测试，结果表明，在0.2 C下电池的充放电比容量分别达到了164 mAh/g和161 mWh/g，在150次循环后，放电比容量仍能保持在152 mAh/g 左右，库仑效率保持97%以上，是一种优异的电池材料。     

黏结剂对SnO_2/石墨烯负极材料电化学行为的影响

针对SnO2用作锂离子电池负极材料所存在的体积膨胀率高及导电性差的不足,考察了羧甲基纤维素钠(CMC)/丁苯橡胶(SBR)和聚偏氟乙烯(PVDF)黏结剂对SnO2、SnO2/石墨烯负极材料电化学性能的影响。结果表明:1)200 mA/g下经过30次充放电循环后,当以CMC/SBR作复合黏结剂时,SnO2的首次放电容量和容量保持率分别为581.3 mA·h/g和37.6%,明显高于PVDF作黏结剂时的电化学性能(135.3 mA·h/g、10.6%);2)200 mA/g下经过100次循环后,当以CMC/SBR作复合黏结剂时,SnO2/石墨烯复合负极材料的首次放电容量、容量保持率分别为702.3 mA·h/g和43.8%,也高于PVDF作黏结剂时的电化学性能(552 mA·h/g和32.8%)。     

PVDF-HFP接枝PEG聚合物电解质的制备和性能研究

以聚偏二氟乙烯-六氟丙烯(PVDF-14VP)接枝聚乙二醇(PEG)为基质,用萃取法制备了均相结构的微孔型聚合物电解质.对此共聚物电解质和纯PVDF-HFP电解质进行比较表征,并以接枝共聚物电解质组装扣式电池进行了性能检测.结果表明,PVDF-HFP接枝PEG后可提高吸液率、保液能力和电导率.20℃时PVDF-HFP和PVDF-HFP-g-PEG的电导率分别为2.60×10-3S/cm和3.28×10-3S/cm.0.2 C充放电时,电池首次放电比容量为119.3 mAh/g.50次充放电循环过程中,充放电效率为99%.初始放电比容鼍为120.7 mAh/g,终止放电容量为115.9 mAh/g.0.5、1、2 C的放电比容量分别为0.2 C放电容量的96.2%、94.5%和81.3%.     

蚕丝/聚氧化乙烯复合固态聚合物电解质

以天然蚕丝为骨架支撑材料,将聚氧化乙烯(PEO)和锂盐溶液浇铸在蚕丝上干燥成膜,制备得到蚕丝/PEO复合固态聚合物电解质(Silk-PEO-SPE)。通过FTIR、电子拉力机、同步热分析仪、电化学窗口测试、电导率测试对固态聚合物电解质进行了结构和性能表征,并以磷酸铁锂为正极,金属锂为负极组装全固态电池,测试了电池的充放电性能。结果表明,与传统PEO固态聚合物电解质相比,复合固态聚合物具有较好的机械强度(达到10 MPa)和优异的电化学窗口(达到4.6 V),以该电解质组装的全固态锂电池在60℃、1 C电流密度下放电比容量达到113 mA·h/g,循环100次容量保持率达到97%,显示出较优异的循环稳定性。     

一种能够抑制锂枝晶的锂金属电池电解液润湿性添加剂

将氟代有机溶剂2,2,3,3-四氟丙基甲基丙烯酸酯(TFPMA)作为双功能添加剂引入碳酸酯电解液体系,考察了TFPMA质量分数对增大润湿性的影响.采用交流阻抗、恒流充放电等测试了添加TFPMA后的锂金属电池性能.采用SEM和XPS表征了循环后的锂金属电极表面.结果表明,1.0％(质量分数,下同)TFPMA的添加使电解液与隔膜间的接触角从54°降至44°,内阻从6.15Ω降至1.94Ω,Li-LiFePO4电池在5 C电流密度下的比容量从66 mA·h/g提升至80 mA·h/g,1 C电流密度下的恒电流循环在100圈时还保持99％以上的库仑效率.TFPMA还促进了Li+的均匀沉积和优良固体电解质界面膜的形成,抑制了锂枝晶,电解液添加了1.0％TFPMA后,Li-Cu电池可以循环100圈以上,而库仑效率没有发生较大下降.循环后电极的SEM图表明,添加了1.0％TFPMA电解液的锂金属负极表面沉积更加平整,有较少的锂枝晶生成.     

纳米二氧化硅对PVDF/CA锂离子电池共混膜性能影响的研究

以聚偏氟乙烯(PVDF)与醋酸纤维素(CA)的共混物为基本材料,加入纳米SiO2对其进行共混改性,制备了有机/无机复合锂离子电池隔膜,研究了纳米SiO2添加量对复合膜物理性能与电化学性能的影响。通过万能试验机、接触角仪、扫描电子显微镜(SEM)、热重分析仪(TG)、交流阻抗与电池充放电测试,对复合隔膜及其组装的电池进行表征,结果表明,在PVDF/CA共混基体中加入纳米SiO2可有效提高隔膜的相关性能,其中添加9%纳米SiO 2的复合膜(PCS9)综合性能较优,即吸液率124.97%,离子电导率1.01 mS/cm,拉伸强度27.35 MPa,组装的锂离子半电池在0.2 C/0.2 C下循环充放电50圈后,放电比容量保持良好稳定,达到145.7 mA·h/g左右。     

新能源汽车固态电池中的锂枝晶抑制研究

相比于商业化的锂离子电池,固态电池具有更高的能量密度和更好的安全性。然而,固体电解质依旧面临锂枝晶生长的问题。以目前已大规模工业化的聚氧化乙烯（PEO）基电解质作为研究对象,通过将PEO与高杨氏模量的石榴石型电解质复合,抑制了锂枝晶在PEO基复合电解质中的生长,不仅使电解质膜的离子电导率从9.8×10^-6 S/cm增加到了3.8×10^-4 S/cm,还使锂/锂对称电池的临界电流密度从0.4 mA/cm²提高到1.6 mA/cm²。与此同时,组装的基于金属锂负极与传统石墨负极的软包电池可分别获得334.5 W·h/kg与218.2 W·h/kg的能量密度。其中,钴酸锂/复合电解质/石墨软包全电池循环1 000次后的容量保持率可达92.3%,能够满足新能源汽车的需求。     

寡层Ti3C2Tx改性锂硫电池隔膜的研究

利用氟化锂和盐酸对前驱体Ti₃AlC₂进行刻蚀,成功得到寡层Ti₃C₂T_x纳米片,通过真空抽滤将其负载至商用锂硫电池PE隔膜上,得到修饰层厚度约为710 nm的层状选择性透过Ti₃C₂T_x材料修饰PE隔膜。通过层间距筛分多硫化物和锂离子,该复合隔膜能够有效阻挡多硫化物的穿过,但不影响锂离子的传输。实验结果表明,选择性透过隔膜的锂硫电池具有优异的循环性能,在1 C倍率下,其初始比容量为750.3 mA·h/g,循环200圈后比容量仍然有481.3 mA·h/g,容量保持率高达64.15%。     

对甲基苯磺酸钠掺杂聚吡咯/二氧化钛纳米管阵列全电池的电化学储锂性能

采用电化学方法制备了对甲基苯磺酸钠掺杂的聚吡咯(TsONa/PPy)锂离子电池正极材料和二氧化钛纳米管阵列(TiO_2NT)负极材料。利用扫描电子显微镜和X射线能量色散光谱仪研究了样品的微观结构及形貌,并进一步组装成全电池,利用恒流充–放电和循环伏安(CV)技术测试了其电化学性能。结果表明:对甲基苯磺酸钠掺杂的聚吡咯正极材料是由直径为3μm左右的微球组成,二氧化钛负极材料则呈现三维有序纳米管阵列形貌,两种电极材料的表面皆凸凹不平;由二者组成的全电池首次放电比容量约为105 mA·h/g,经过50次循环后,可逆放电比容量仍保持在65 mA·h/g,表现了良好的循环稳定性,此外还表现了良好的倍率性能。     

MnO2@ACFF中间层强化高载量硫电极性能稳定性作用

为提高碳材料对聚硫化物的吸附能力,将MnO₂原位化学沉积于活性碳纤维炭毡(ACFF)的碳纤维表面,得到了聚硫化物吸附强化的多孔导电材料(MnO₂@ACFF)。将其作为中间层设置于隔膜和硫电极之间,有效控制了高载量硫电极的聚硫离子穿梭,提高了活性物质利用率和库伦效率,降低了电极极化和电化学反应阻抗,提高了电极循环稳定性,避免了锂硫电池的突然失效。在2 mA/cm²的电流密度下,载硫量为15 mg/cm²的硫电极经过350次充放电循环仍保有430 mA·h/g的比容量。提高硫电极载硫量虽然使电极的循环稳定性下降,但载量为20 mg/cm²和30 mg/cm²的硫电极0.1 C下经过100次循环,仍分别保有736 mA·h/g和446 mA·h/g的比容量,比容量保持率为65%,而且面积比容量和面积比能量也能分别保持64%和42%,高于当前锂离子电池的面积比容量和面积比能量。     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.