High lithium conductivities in weakly-ionophilic low-dimensional block copolymer electrolytes

The structure of amphiphilic low-dimensional copolymer electrolytes I of similar overall composition but prepared by different synthetic procedures X and Y are described. I are copolymers of poly[2,5,8,11,14-pentaoxapentadecamethylene(5-alkyloxy-1,3-phenylene)] (CmO5) and poly[2,-oxatrimethylene(5-alkyloxy-1,3-phenylene)] (CmO1) where the alkyl side chains having m carbons are hexadecyl or mixed dodecyl/octadecyl (50/50). ¹H NMR shows that the copolymers have 50% (m = 16) or only 18 and 13% of CmO5 units and DSC indicates that the copolymers have ‘block’ sequencing of CmO1 and CmO5 segments. Molecular dynamics modelling indicates that in CmO5 Li⁺ and BF₄⁻ ions are separated by Li⁺ encapsulation in tetraethoxy segments but in ionophobic CmO1 units the salt is mostly present as neutral aggregates decoupled from the polymer. Conductivities of these microphase-separated mixtures with salt-bridge amphiphilic polyethers II and III of each system are similar. They have low temperature dependence over the range 20 °C to 110 °C at ∼10⁻³ S cm⁻¹. ⁷Li NMR linewidth measurements confirm high lithium mobilities at −20 °C. A conduction mechanism is proposed whereby Li⁺ hopping takes place along rows of decoupled aggregates (dimers/quadrupoles) within an essentially block copolymer structure. Subambient measurements to −10 °C gave a conductivity of 4 × 10⁻⁵ S cm⁻¹.     

氢分子在Li(100)面的吸附旋转势能面研究

利用推广的LEPS势分析H_2在Li(100)面的吸附、迁移、旋转等行为.给出的这种作用是短程相互作用,它因吸附位、吸附方式不同而不同,使H_2分别呈稳定分子吸附态、亚稳分子吸附态.这些吸附态通过H_2沿表面迁移而相互转换;通过H_2绕质心的转动而进行立式与卧式吸附方式之间的转变.并指出亚稳分子吸附态具有变型小、属弱化学吸附,迁移性强,不易解离成原子等特性.     

水体系自组装法制备钛酸锂纳米负极材料研究

以偏钛酸粉末作为钛源,制备钛酸锂(Li4Ti5O12)纳米材料,Li4Ti5O12由含锂过氧化钛配合物分解自组装后经煅烧结晶而得。采用X射线衍射、扫描电子显微镜、氮气吸附-脱附和恒流充放电测试对材料结构、形貌和电化学性能进行表征。结果表明:水体系下,锂钛摩尔比为4∶5、于600℃煅烧5h得到的Li4Ti5O12纳米球颗粒粒径在500nm左右,且具有丰富的孔隙,比表面积达到22.947m2/g;在电流密度4000mA/g条件下,比容量为157mAh/g,电流密度500mA/g下循环400次放电容量保持率为95.2%。表明水体系自组装形成的Li4Ti5O12纳米负极材料可以缩短锂离子迁移距离,其多孔性可以增大电解液与电极活性材料的接触面积,使离子电子传输速率同时得到提高,从而获得优异的电化学性能。     

GH3625合金管材冷变形行为及热处理工艺研究

通过室温压缩试验、数学模型拟合、光学显微镜和洛氏硬度计等手段,并建立GH3625合金管材冷变形本构方程,研究了冷变形及热处理对GH3625合金管材组织和性能的影响。研究表明,GH3625合金管材加工硬化规律基本符合Hollomon方程,其中冷变形量是影响加工硬化的主要因素;随着冷变形量的增大,晶粒的变形程度增大,晶粒的变形均匀性逐渐改善,平均晶粒尺寸减小;合金的平均晶粒尺寸随热处理温度的升高呈现出先减小后增大的趋势,在1 100~1 250℃范围内晶粒长大激活能为180.46kJ/mol;硬度随热处理温度的升高而降低,且在晶粒长大过程中合金的硬度值与平均晶粒尺寸满足Hall-Patch关系式。     

直接时效热连轧GH4169合金的力学性能与变形特征

通过对热连轧GH4169合金进行直接时效处理、组织形貌观察和力学性能测试,研究了直接时效热连轧合金的力学性能和变形特征.结果表明,直接时效热连轧GH4169合金组织由细小晶粒组成,具有明显的形变孪晶特征,且有细小#$和#%相在合金中弥散析出,可提高合金强度.在实验温度范围内,合金的抗拉和屈服强度随着温度的升高而逐渐下降;在拉伸过程中,直接时效热连轧GH4169合金的变形特征是孪晶变形和位错的双取向滑移;在拉伸后期,大量微孔沿晶界或晶内形成并聚合形成裂纹,致使合金发生韧性断裂.     

Li4Ti5O12合成及电化学性质研究

报道一种合成Li4Ti5O12的新颖方法。XRD结果表明该方法合成的Li4Ti5O12化合物为尖晶石结构。用扫描透射显微镜对该化合物的粒径和形貌进行了分析．并对Li4Ti5O12的电化学性能进行测试。结果表明，通过该法合成的尖晶石材料在3．2-0．8V电压范围，采用一定电流密度下进行充放电，具有较高的放电容量（235mAh／g）和较好的循环性能。该法合成的具有良好电化学性能的Li4Ti5O12,使得其成为很有潜力的锂离子电池负极材料。     

高性能锂电池材料Li4Ti5O12/C的制备与性能

分别以蔗糖、可溶性淀粉作为碳源,采用固相法在N2气氛中制备尖晶石结构的Li4Ti5O12/C复合正极材料,通过X射线衍射（XRD）,扫描电子显微镜（SEM）分析和电化学性能测试表征了Li4Ti5O12/C的晶体结构、表面形貌和电化学性能,结果表明,碳源的加入抑制了晶粒的生长,增大了材料的比表面积,增强了材料的电化学性能,其中,碳源为可溶性淀粉时,样品在0．1C下首次放电比容量达到了164．9mAhg^-1,在2．OCT首次放电比容量可达到125．4mAhg^-1,且循环性能良好。     

一种提锂杂化膜的制备及其提锂性能研究

将提锂吸附剂前驱体尖晶石型锰氧化物（Spinel-type manganese oxide,SMO）Li_1.6-Mn_1.6O₄与聚氯乙烯（PVC）杂化,采用溶剂-非溶剂交换法成功制备了用于海水提锂的平板膜.该杂化膜用酸处理抽出其中的锂得到具有提锂性能的膜,对膜进行了一系列提锂性能测试.实验结果表明,酸洗处理后的膜对富锂溶液中锂的吸附约6 h达平衡,最大吸附量为29 mg/g,之后采用0.5 mol/L HCl溶液脱锂约1 h锂的脱出基本达到平衡,Li⁺的脱附率在95%左右,锰的溶损率在3.5%左右.该膜在含有Li⁺、Na⁺、K⁺、Mg²⁺、Ca²⁺离子的竞争吸附过程中对Li⁺表现出很好的选择性,同时重复实验也表明,这种提锂杂化膜具有很好的稳定性.     

水热法制备花状纳米片簇Li4Ti5O12及其储锂性能

以氢氧化锂和钛酸四丁酯为原料,采用水热法制备出花状纳米片簇Li4Ti5O12粉体,研究了不同原料配比对产物晶体结构的影响。采用XRD、SEM对Li4Ti5O12的晶体结构和形貌进行了分析,结果表明所得产物是由Li4Ti5O12纳米片层组成的花状微球,所得晶体为尖晶石型结构。恒电流充放电实验表明,Li4Ti5O12在充放电倍率为0.1、1和2C下首次放电比容量分别为160、141和128mAh/g。     

Processing and properties of Al–Li–SiCp composites

Al–Li–SiC_p composites were fabricated by a modified version of the conventional stir casting technique. Composites containing 8, 12 and 18 vol% SiC particles (40 mm) were fabricated. Hardness, tensile and compressive strengths of the unreinforced alloy and composites were determined. Ageing kinetics and effect of ageing on properties were also investigated. Additions of SiC particles increase the hardness, 0.2% proof stress, ultimate tensile strength and elastic modulus of Al–Li–8%SiC and Al–Li–12%SiC composites. In case of the composite reinforced with 18% SiC particles, although the elastic modulus increases the 0.2% proof stress and compressive strength were only marginally higher than the unreinforced alloy and lower than those of Al–Li–8%SiC and Al–Li–12%SiC composites. Clustering of SiC particles appears to be responsible for reduced the strength of Al–Li–18%SiC composite. The fracture surface of unreinforced 8090 Al-Li alloy (8090Al) shows a dimpled structure, indicating ductile mode of failure. Fracture in composites occurs by a mixed mode, giving rise to a bimodal distribution of dimples in the fracture surface. Cleavage of SiC particles was also observed in the fracture surface of composites. Composites show higher peak hardness and lower peak ageing time compared with unreinforced 8090Al alloy. Macroand microhardness increase significantly after peak ageing. Ageing also results in considerable improvement in strength of the unreinforced 8090Al alloy and its composites. This is attributed to formation of δ^' (Al₃Li) and S^' (Al₂CuMg) precipitates during ageing. Per cent elongation, however, decreases due to age hardening. Al–Li–12%SiC, which shows marginally lower UTS and compressive strength than the Al–Li–8%SiC composite in extruded condition, exhibits higher strength than Al–Li–8%SiC in peak-aged condition.