锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2研究进展

层状结构材料LiNi1/3Co1/3Mn1/3O2具有高比容量、高循环性能、低成本和环保等优点,有望取代LiCoO2成为新一代锂离子电池正极材料。在介绍LiNi1/3Co1/3Mn1/3O2的结构特点和电化学反应特性的基础上,对其主要合成方法进行了详细评述,总结了该正极材料的阴阳离子掺杂、复合离子掺杂以及表面包覆改性等技术,指出国内外目前锂离子电池材料研究中存在的问题和未来的发展方向。     

La(Mg1/2Ti1/2)O3–La2/3TiO3 microwave dielectric ceramics

Structure and microwave dielectric properties were studied in the (1−x)La(Mg_1/2Ti_1/2)O₃–xLa_2/3TiO₃ system. Ceramics with this composition in the 0⩽x⩽0.5 range were processed from powders obtained by a citrate-based chemical route. Structure of these perovskite solid solutions changed from orthorhombic for x=0.1 and 0.3 to pseudocubic for x=0.5. Microwave and radio frequency measurements revealed increase in permittivity and temperature coefficient of the resonant frequency τ_f with increasing of La_2/3TiO₃ content. Close to zero τ_f value was found near to x=0.5 composition of (1−x)La(Mg_1/2Ti_1/2)O₃–x La_2/3TiO₃.     

环氧树脂辅助制备LiNi1/3Co1/3Mn1/3O2及其储锂性能

采用环氧树脂来均匀分散Li~+,Co~(2+),Mn~(2+)和Ni~(2+),并通过环氧树脂低温固化来维持离子均匀分散,续以空气中充分煅烧制备LiNi1/3Co_(1/3)Mn_(1/3)O2材料。电化学研究显示,850℃下制得的材料具有更好的充放电性能,0.2℃倍率下的首次充放电容量分别达到186.4和135.1mAh·g~(-1)。     

MgF2包覆对正极材料LiNi1/3Co1/3Mn1/3O2性能的影响

通过浸渍法在正极材料LiNi1/3Co1/3Mn1/3O2的表面包覆MgF2,通过XRD、SEM、交流阻抗（EIS）分析、充放电测试研究了不同量MgF2包覆对LiNi1/3Co1/3Mn1/3O2正极材料的结构与电化学性能的影响。结果表明,MgF2以非晶态形式包覆于LiNi1/3Co1/3Mn1/3O2材料颗粒的表面,当包覆量为3%（物质的量分数,下同）时,三元正极材料具有优良的电化学性能,在3.0~4.6 V充放电范围内0.1C充放电倍率下,首次放电比容量为196.3 mA·h/g,1C循环50次后容量保持率为95.7%,55 ℃高温下1C循环50次后容量保持率为93.3%。     

正极材料LiCo1/3Ni1/3Mn1/3O2的制备与电化学性能

采用固相法和沉淀法合成了锂离子电池正极材料LiCo1／3Ni1／3Mn1／3O2探讨了合成温度、不同合成方法对材料的电化学性能的影响。利用充放电测试、循环伏安测试方法对合成的LiCo1／3Ni1／3Mn1／3O2进行了表征。结果表明,固相法900℃煅烧合成的材料电化学性能较好,沉淀法合成的材料电化学性能最好,以10．0mA／g的电流充放电,首次放电比容量为576．0C／g,循环50次后放电比容量仍保持501．5C／g。以100．0mA／g的大电流放电,放电比容量达到430．2C／g。     

正极材料LiCo1/3Ni1/3Mn1/3O2共沉淀合成法的研究

讨论了焙烧温度对LiCo1/3Ni1/3Mn1/3O2的共沉淀法合成过程的影响,结合XRD、SEM、振实密度分析和充放电测试等手段获得了共沉淀法制备LiCo1/3Ni1/3Mn1/3O2的最佳合成温度。获得了共沉淀法制备LiCo1/3Ni1/3Mn1/3O2的最佳焙烧温度为900℃,在上述最佳焙烧温度条件下合成的正极材料具有优异的电化学性能。     

棒状结构的LiNi1/3Co1/3Mn1/3O2的合成及研究

用VGCF为模板,用共沉淀方法辅助合成了棒状结构的LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2。通过X-射线衍射仪(XRD)、X射线能谱仪(EDX)、扫描电子显微镜(SEM)对其结构进行了表征,并研究了其电化学性能。结果表明:该材料为棒状且表面多孔,并表现出了良好的电化学性能。在0. 2 C(1 C=170 m A/g)的电流密度下,其容量为160 m Ah/g以上,在1 C下经过250个循环后容量仍然有115. 2 m Ah/g,对于制备其他棒状结构的锂离子正极材料提供了一定的借鉴。     

Al2O3包覆LiNi1/3Co1/3Mn1/3O2锂离子电池正极材料

综述了Al2O3包覆LiNi(1/3)Co(1/3)Mn(1/3)O2锂离子电池正极材料的研究现状与进展,并评述了其制备方法和包覆改性;讨论了包覆改善该正极材料性能的机理;提出了这种正极材料的研发过程中的一些问题并对其未来的发展前景作了展望。     

Ba1-3x/2Lax(Mg1/3Ta2/3)O3陶瓷的微波介电性能

采用固相合成法制备了Ba1-3x/2Lax(Mg1/3Ta2/3陶瓷,研究了La掺杂对钽镁酸钡的结构和微波介电性能的影响.结果表明:A位取代能改进其烧结性能.在x≤0.02时,烧结样品为单相的钙钛矿结构,B位离子1:2有序;当x>0.02时出现第二相Ba0.5TaO3.B位离子有序度随着x的增大先增加后减小,在x=0.04时出现最大值.x≤0.02时介电常数变化较小,而后其值逐渐增大.品质因数与谐振频率的乘积(Q×f)值随着x的增大先增大后减小,在x=0.02时取得最大值;谐振频率温度系数(τf)值随着x增大而增大.     

Bi1/2Na1/2TiO3–BaTiO3 based thick-film capacitors for high-temperature applications

Thick films with compositions (1 − x)(0.94Bi_1/2Na_1/2TiO₃–0.06BaTiO₃)–x(K_0.5Na_0.5NbO₃) (x = 0, 0.03, 0.09 and 0.18) have been prepared and their structural and electrical properties have been investigated. Dielectric properties show that these films are well suited for high-temperature applications due to their low variance in permittivity (<15%) over large temperature ranges. The thick film with x = 0.18 offers an operational temperature range from room temperature to 350 °C. Films with x = 0.03 and 0.09 also possess a stabile permittivity up to 400 °C. The improvement in the thermal stability of the permittivity is attributed to the addition of K_0.5Na_0.5NbO₃ which leads to breaking of the long-range order in the materials. However, the polarizability of the materials was found to decrease possibly due to the clamping effect of the substrate. The characteristics of each film are discussed based on dielectric and electrical properties.     

The effect of Fe-acceptor doping on the electrical properties of Na1/2Bi1/2TiO3 and 0.94 (Na1/2Bi1/2)TiO3–0.06 BaTiO3

Na_1/2Bi_1/2TiO₃ (NBT) based ceramics are amongst the most promising lead-free ferroelectric materials. It was expected that the defect chemistry and the effect of doping of NBT would be similar to that observed for lead based materials, however, acceptor doping does not lead to ferroelectric hardening. Instead, high oxygen ionic conductivity is induced. Nevertheless, for solid solutions with BaTiO₃ (BT), which are more relevant with respect to ferroelectric applications, such a drastic change of electrical properties has not been observed so far. To rationalize the difference in defect chemistry between NBT and its solid solution 94(Na_1/2Bi_1/2TiO₃)–0.06 BaTiO₃ (NBT–6BT) compositions with different concentrations of Fe-dopant were investigated. The study illustrates that the materials exhibit very similar behavior to NBT, and extraordinarily high oxygen ionic conductivity could also be induced in NBT–6BT. The key difference between NBT–6BT and NBT is the range of the dependence of ionic conductivity with dopant concentration. Previous studies of NBT–6BT have not reached sufficiently high dopant concentrations to observe high conductivity. In consequence, the same defect chemical model can be applied to both NBT and its solid solutions. This will help to rationalize the effect of doping on ferroelectric properties of NBT-ceramics and defect chemistry related degradation and fatigue.     

Dielectric and piezoelectric properties of Pb(Sc1/2Nb1/2)O3–Pb(Ni1/3Nb2/3)O3–PbTiO3 ternary ceramic materials

The dielectric and electrical properties of xPb(Sc_1/2Nb_1/2)O₃–yPb(Ni_1/3Nb_2/3)O₃–zPbTiO₃ (PSNNT 100x/100y/100z) ternary ceramic materials near the morphotropic phase boundary (MPB) were investigated. The MPB follows on almost linear region between PSNNT 58/00/42 and PSNNT 00/68/32 of the binary systems. The maximum electromechanical coupling factor kp=70·7% was found at PSNNT 36/26/38, where ε₃₃^T/ε₀=3019 and Tc=210°C were obtained. These values are similar to those of the Pb(Sc_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ system and better than those of PZT.     

合成方法对LiCo1/3Ni1/3Mn1/3O2材料结构与性能的影响

本文用高温固相法和共沉淀法合成了层状结构的LiCo1/3Ni1/3Mn1/3O2材料.用X射线衍射仪(XRD)、环境扫描电子显微镜(ESEM)、电化学工作站、充放电仪等设备测试了该材料的结构和电化学性能.结果表明共沉淀法合成的材料层状结构更明显,颗粒的粒度小,材料的可逆性好.放电比容量和循环性能均优于高温固相法合成的材料.     

不同铝源对LiNi1/3Co1/3Mn1/3O2材料的包覆改性研究

分别以纳米氧化铝、氢氧化铝及异丙醇铝为原料,采用液相浸渍法对LiNi1/3Co1/3Mn1/3O2材料进行氧化铝包覆,考察不同包覆源在LiNi1/3Co1/3Mn1/3O2材料表面进行氧化铝包覆后对材料电化学性能的影响。SEM及XRD结果显示,产物为层状α-NaFeO2结构,氧化铝均匀包覆在LiNi1/3Co1/3Mn1/3O2材料表面。充放电性能测试结果表明,在3种铝源中,以异丙醇铝为包覆源的材料性能最佳：在3.0~4.6 V的电压下,0.1 C倍率下首次放电比容量为196.1 mA·h/g, 1 C下循环50周后容量保持率为95.6%。     

(1-y)Ca1-xLa2x/3TiO3-yCa(Mg1/3Nb2/3)O3复合体系的微波介电性能

采用固相合成法制备了(1-y)Ca1-xLa2x/3TiO3-yCa(Mg1/3Nb2/3)O3系列微波介质陶瓷材料.研究了复合系统的微波介电性能和微观结构.研究结果表明在y=0.4～0.6范围内,体系形成了单一的钙钛矿结构.当复合体系组成为0.5Ca0.6La0.267TiO3-0.5Ca(Mg1/3·Nb2/3)O3时,在1 400℃下烧结保温4 h所制备的材料表现出良好的微波介电性能εr=55,Q×f=45 000 GHz(7.6 GHz下),τf=0.04×10-6/℃.     

(1-y)Ca1-xLa2x/3TiO3-yCa(Mg1/3Nb2/3)O3复合微波介质陶瓷的研究

采用固相合成法制备了 ( 1-y)Ca1 -xLa2x/ 3 TiO3 -yCa(Mg1 / 3 Nb2 / 3 )O3 系列微波介质陶瓷材料 ,研究了复合系统的微波介电性能、烧结性能和微观结构。研究结果表明 :在y =0 .4～ 0 .6范围内 ,体系形成了单一的钙钛矿结构 ;当复合体系组成 0 .5Ca0 .6La0 .2 67TiO3 -0 .5Ca(Mg1 / 3 Nb2 / 3 )O3 时 ,在 14 0 0℃下烧结保温 4小时所得到材料的微波介电性能最佳 ;εf=5 5 ,Q×f =45 0 0 0GHz( 7.6GHz下 ) ,τf=0 .0 4ppm/℃。     

添加剂对Ba(Zn1/3Nb2/3)O3-Sr(Zn1/3Nb2/3)O3陶瓷介电性能的影响

研究了MnCO3,BaZrO3对0.35Ba(Zn1/3Nb2/3)O3(BZN)-0.65Sr(Zn1/3Nb2/3)O3(SZN)陶瓷介电性能的影响.研究表明:添加MnCO3,BaZrO3时,对陶瓷的烧结均起促进作用,增大介电常数.加入1%(质量分数)的MnCO3可使陶瓷具有较小的介质损耗,同时MnCO3对陶瓷的介电常数温度系数具有正向调整作用.加入BaZrO3后通过生成液相而减少了第二相Ba5Nb4O15,BaNb2O6的生成.所制备的(0.35BZN0.65SZN)+0.1%MnCO3陶瓷的εr≈43.6,αe≈-8×10-6/K,tanδ＝0.6×10-4,且烧结温度低于1 300℃.     

Depolarization temperature and piezoelectric properties of (Bi1/2Na1/2)TiO3–(Bi1/2Li1/2)TiO3–(Bi1/2K1/2)TiO3 lead-free piezoelectric ceramics

The phase transition temperature and piezoelectric properties of x(Bi_1/2Na_1/2)TiO₃–y(Bi_1/2Li_1/2)TiO₃–z(Bi_1/2K_1/2)TiO₃ [x + y + z = 1] (abbreviated as BNLKT100y–100z) ceramics were investigated. BNLKT100y–100z ceramics were prepared by conventional ceramic fabrication. The depolarization temperature T_d was determined by the temperature dependence of the dielectric and piezoelectric properties. This study focuses on the effect of Li¹⁺ and K¹⁺ ions on T_d and the piezoelectric properties of BNT ceramics. BNLKT100y–100z (y = 0–0.08) has a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases at z = 0.18–0.20, and high piezoelectric properties were obtained at the MPB composition. The piezoelectric constant d₃₃ increased with increasing y; however, T_d decreased above y = 0.06. The d₃₃ and T_d values of BNLKT4-20 and BNLKT8-20 were 176 pC/N and 171 °C, and 190 pC/N and 115 °C, respectively.