Nd3+-doped Li3V2(PO4)3 cathode material with high rate capability for Li-ion batteries

A series of Nd3+-doped Li3NdxV2àx(PO4)3(x = 0.00, 0.02, 0.05, 0.08 or 0.1) composites are synthesized by the rheological phase reaction method. The XRD results indicate that Nd3+ions have been successfully merged into a lattice structure. Doped samples show good electrochemical performance in high discharge rate and long cycle. In the potential range of 3.0–4.3 V, Li3Nd0.08V1.92(PO4)3exhibits an initial discharge capacity of 115.8 m Ah/g at 0.2 C and retain 80.86% of capacity retention at 2 C in the 51 st cycle.In addition, Li3Nd0.05V1.95(PO4)3holds at 100.4 m Ah/g after 80 cycles at 0.2 C with a capacity retention of92.4%. Finally, the CV test proves that the potential polarization of Li3Nd0.08V1.92(PO4)3decreased compared with the un-doped one.     

富锂层状正极材料Li2MnO3的表面改性及其电化学性能研究

Li₂MnO₃正极材料具有较高的理论容量（459 mAh·g ^-1）,不仅安全无毒还能够大大降低电池的制造成本,从而受到越来越多的关注. 然而,较低的首圈库仑效率和较差的循环性能妨碍了其在锂电池中的实际应用. 在此,作者研究了MgF₂涂层对Li₂MnO₃正极材料的电化学性能. 结果表明,MgF₂涂层诱导部分层状Li₂MnO₃向尖晶石相转化,从而降低了首圈不可逆容量,提高库仑效率. 重量比为0.5%、1.0%和2.0%的MgF₂涂层电极的初始库仑效率分别为70.1%、77.5%和84.9%,而原始电极仅为57.7%. 充放电曲线表明,1.0wt.%MgF₂涂层改性的Li₂MnO₃具有最高的充放电容量和最佳的循环稳定性. 40个循环后1.0wt.%MgF₂涂层样品的容量保持率为81%,远高于原始样品的容量保持率（53.6%）. 电化学阻抗谱结果表明MgF₂涂层减少了不利成分的快速沉积,并改善了电极的循环稳定性.     

固相烧结法制备锂离子电池正极材料Li2FeP2O7及其电化学性能研究

介绍了一种先冷冻干燥后固相烧结制备正极材料Li₂FeP₂O₇的方法. 利用X射线衍射(XRD)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)和傅里叶变换红外光谱(FTIR)对材料的组成和形态进行表征, 并通过循环伏安曲线(CV)和电化学阻抗谱(EIS)研究了Li₂FeP₂O₇材料的电化学性能. 研究发现, 合成Li₂FeP₂O₇的最佳温度为590 ℃, 此温度下反应较完全且产物杂质较少, 1.6C倍率下的放电比容量达到55 mA·h·g^?1, 明显高于其它温度下合成样品的放电比容量. 该温度下合成的Li₂FeP₂O₇还具有低阻抗和较大的交换电流密度, 说明这种合成方式有利于提高锂离子在Li₂FeP₂O₇中的扩散.     

CoAl2O4包覆LiNi1/3Co1/3Mn1/3O2的电化学性能

通过共沉淀法制得类球形锂离子电池正极材料LiNi_1/3Co_1/3Mn_1/3O₂,并用非水相共沉法对其进行CoAl₂O₄包覆得到LNCMO(x). 采用X射线衍射（XRD）、扫描电子显微术（SEM）和透射电子显微术（TEM）测试材料的结构和观察材料形貌. 结果表明,CoAl₂O₄在材料表面形成8 nm均匀包覆层,未改变主体材料的结构. 电化学性能测试表明,1%（by mass）CoAl₂O₄包覆量的LiNi1/3Co1/3Mn1/3O2材料（LNCMO(1)）高充电电压（3.0 ~ 4.6 V,150 mA·g^-1）100周期循环放电容量保持率为93.7%（无包覆LNCMO(0)保持率为74.4%）;55 °C高温100周期循环容量保持率为77%（无包覆LNCMO(0)保持率17%）. XRD和电感耦合等离子体原子发射光谱（ICP-AES）测试表明,CoAl₂O₄包覆的LNCMO(x)材料可有效地减缓材料中Mn离子在电解液的溶解,提高材料结构稳定性和热稳定性.     

纳米MgO掺杂改善LiNi1/3Co1/3Mn1/3O2正极材料

将氢氧化物共沉淀法制备的(Ni_1/3Co_1/3Mn_1/3)（OH）₂在500℃热处理5 h得到具有尖晶石结构、纳米尺寸的氧化物M₃O₄(M=Ni_1/3Co_1/3Mn_1/3).将其与LiOH及不同量的纳米MgO混合均匀,并在850℃热处理24 h制备了Li(Ni_1/3Co_1/3Mn_1/3)_1/xMg_xO₂（x=0,0.01,0.02,0.03,0.04,0.05）正极村料.随着Mg掺杂量的增大,正极材料的晶胞参数增大;少量的Mg掺杂增大了锂离子的扩散系数,而过度掺杂却使锂离子扩散系数有所降低,其中Li(Ni_1/3Co_1/3Mn_1/3)_0.98Mg_0.02O₂的锂离子扩散系数最大,其脱出和嵌入扩散系数分别为D_Li-dein=29.20×10^-11cm²·S^-1和D_Li-in=4.760×10^-11cm²·s^-1;其以3C倍率充放电的平均放电比容量为139.3 mAh·g^-1,比未掺杂的原粉约高9.5 mAh·g^-1;另外其循环性能也得到了大幅度改善.     

Li3V2(PO4)3/C正极材料在不同电压区间的电化学行为及容量衰减原因

采用溶胶-凝胶法制备锂离子电池正极材料Li₃V₂(PO₄)₃/C. 通过恒电流充放电测试、循环伏安(CV)、电化学阻抗谱(EIS)等方法, 研究了Li₃V₂(PO₄)₃/C 在不同电压区间的电化学行为(3.0-4.5 V和3.0-4.8 V). 结果表明, 3.0-4.8 V电压区间的循环性能和倍率性能均不及3.0-4.5 V电压区间的. 3.0-4.5 V区间0.1C (1C=150mA·g^-1)倍率首次放电比容量为127.0 mAh·g^-1, 循环50次后容量保持率为99.5%, 而3.0-4.8 V区间的分别为168.2 mAh·g^-1和78.5%. 经过高倍率测试后再回到0.1C倍率充放电, 3.0-4.5 V和3.0-4.8 V的放电比容量分别为初始0.1C倍率的99.0%和80.7%. 经过3.0-4.8 V电压区间测试后, 少部分第三个锂离子能够在低于4.5V的电压脱出, 使3.0-4.5 V电压区间的放电比容量提升了7.4%. CV结果表明3.0-4.8 V区间的容量损失主要表现为第一个锂离子的不可逆损失. 极片的X射线衍射(XRD)和X射线光电子能谱(XPS)分析测试结果表明经过3.0-4.8 V测试后, Li₃V₂(PO₄)₃的结构发生了轻微的改变. 电感耦合等离子体(ICP)测试结果表明循环后的电解液中含有少量的V. 结构变形和V溶解可能是Li₃V₂(PO₄)₃在3.0-4.8 V区间容量衰减的主要原因.     

Electrochemical performance of a nano SnO2-modified LiNi1/3Co1/3Mn1/3O2 cathode material

The nano SnO₂-modified LiNi_1/3Co_1/3Mn_1/3O₂ was successfully prepared by a carrier transfer method. The pristine and modified samples were characterized with various techniques such as XRD, SEM, XPS and EDS. The results showed that the SnO₂ particles did not enter the crystal structure of LiNi1/3Co1/ 3Mn1/3O₂, many nano SnO₂ particles were uniformly covered on the surface of LiNi_1/3Co_1/3Mn_1/3O₂ and the modified thin layer could inhibit the dissolution of transition metal oxides. The electrochemical tests indicated that the existence of nano SnO₂ could improve the discharge capacity and rate capability owing to the decreased interfacial polarization. The cycling stability was remarkably improved at room temperature and 55 ℃. The XRD patterns of the fresh NCM electrode and after 50 cycles proved that the structural change of NCM was not so effective on the capacity fade.     

纳米Al2O3包覆富锂锰基正极材料Li1.2Ni0.13Co0.13Mn0.54O2的性能研究

采用纳米三氧化二铝(Al₂O₃)对富锂锰基正极材料Li_1.2Ni_0.13Co_0.13Mn_0.54O₂进行表面均匀包覆, 并考察了最优纳米Al₂O₃包覆量下材料的电化学性能. 扫描电子显微镜(SEM)和透射电子显微镜(TEM)显示了纳米Al₂O₃对富锂锰基正极材料表面均匀包覆, X射线衍射分析(XRD)结果表明包覆后富锂材料依然具有良好的层状结构. 恒流充/放电循环测试发现, 包覆后的Li_1.2Ni_0.13Co_0.13Mn_0.54O₂材料的首次放电比容量为249.7 mA·h/g, 循环100次后的容量保持率为89.5%, 与未包覆的Li_1.2Ni_0.13Co_0.13Mn_0.54O₂材料相比, 容量保持率提升约13%. 循环伏安(CV)和电化学阻抗(EIS)测试结果表明, 纳米Al₂O₃包覆可有效抑制材料极化, 降低界面阻抗和电荷转移阻抗, 进而提升富锂锰基正极材料的电化学性能.     

Lotus-stalk Bi4Ge3O12 as binder-free anode for lithium and sodium ion batteries

The synthesized lotus-stalk Bi₄Ge₃O₁₂ utilized as binder-free anode for LIBs demonstrates excellent cycling performance. The synthesized lotus-stalk Bi₄Ge₃O₁₂ is composed of nanosheets, which is contribute to outstanding lithium storage performance.     

高倍率性能锂离子电池Li[Ni1/3Co1/3Mn1/3]O2正极材料的制备及其电化学性能

采用改进的碳酸盐共沉淀与高温固相法相结合的方法制备出了高倍率性能的锂离子电池正极材料Li[Ni_1/3Co_1/3Mn_1/3]O₂, 通过X射线衍射(XRD)、扫描电镜(SEM)、循环伏安扫描(CV)、电化学阻抗谱(EIS)和电化学性能测试等手段对材料进行表征. 结果表明, 该方法制备的材料具有良好的α-NaFeO₂型层状结构(R3m(166)), 一次粒径平均大小为157 nm, 二次颗粒成球形. 同传统碳酸盐制备得到的材料相比, 该材料具备良好的倍率性能和循环性能, 在2.7-4.3 V 电压范围内, 0.1C (1.0C=180 mA·g^-1)倍率下, 首次放电比容量为156.4mAh·g^-1, 库仑效率为81.9%. 在较高倍率下, 即0.5C、5.0C和20C时, 其放电比容量分别为136.9、111.3、81.3mAh·g^-1. 在1C倍率下100次循环容量保持率为92.9%, 高于传统共沉淀法得到的材料(87.0%).     

Ag/C包覆对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响

运用共沉淀和元素化学沉积相结合的方法,制备出了具有Ag/C包覆层的层状富锂固溶体材料Li[Li0.2Mn0.54Ni0.13Co0.13]O2.通过X射线衍射(XRD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、恒流充放电、循环伏安(CV),电化学阻抗谱(EIS)和X射线能量散射谱(EDS)方法,研究了Ag/C包覆层对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响.结果表明,Ag/C包覆层的厚度约为25 nm,Ag/C包覆在保持了固溶体材料α-NaFeO2六方层状晶体结构的前提下,显著地改善了Li[Li0.2Mn0.54Ni0.13Co0.13]O2的电化学性能.在2.0-4.8 V(vs Li/Li+)的电压范围内,首次放电(0.05C)容量由242.6 mAh·g-1提高到272.4 mAh·g-1,库仑效率由67.6%升高到77.4%;在0.2C倍率下,30次循环后,Ag/C包覆的电极材料容量为222.6 mAh·g-1,比未包覆电极材料的容量高出14.45%;包覆后的电极材料在1C下的容量仍为0.05C下的81.3%.循环伏安及电化学交流阻抗谱研究表明,Ag/C包覆层抑制了材料在充放电过程中氧的损失,有效降低了Li[Li0.2Mn0.54Ni0.13Co0.13]O2颗粒的界面膜电阻与电化学反应电阻.     

Li3Fe2(PO4)3/C正极材料的电化学性能及其反应机理研究

采用溶胶凝胶及高能球磨制得Li₃Fe₂(PO₄)₃/C材料,利用多种物理及其电化学技术观察材料形貌,表征材料结构及电化学性能,用电化学原位XAFS等初步研究Li₃Fe₂(PO₄)₃/C超理论容量电化学反应机理. 结果显示,Li₃Fe₂(PO₄)₃/C的结构为单斜晶系,空间群P21/n. 2.0 ~ 4.0 V电位区间,10 mAh·g^-1电流密度,Li₃Fe₂(PO₄)₃/C电极的首周期放电比容量为129 mAh·g^-1,达到其理论容量. 若电位区间拓宽至2.0 ~ 4.95 V,其首周期放电比容量高达165 mAh·g^-1,超出理论的“额外”容量30%. 电化学原位XAFS测试未观察到明显的Fe³⁺/Fe⁴⁺氧化还原对参与电化学反应,初步推测“额外”容量可能来自于该复合材料的高浓度表面缺陷.     

Solid state synthesis of lithiated manganese oxides from mechanically activated Li2CO3–Mn3O4 mixtures

The solid state formation of lithium manganese oxides has been studied from the thermal decomposition of mixtures Li₂CO₃–Mn₃O₄ with X_Li (lithium cationic fraction)=0.33 (LiMn₂O₄), 0.50 (LiMnO₂) and 0.66 (Li₂MnO₃). The analysis of the reactivity has been performed mainly by thermoanalytical (TG/DSC) and diffractometric (XRPD) techniques either on physical mixtures and on mixtures subjected to mechanical activation by high energy milling. At X_Li=0.33, the cubic lithium manganese spinel oxide (LiMn₂O₄) forms in air. TG measurements showed that the reaction starts at a considerably lower temperature in the activated mixture. By variable temperature X-ray diffraction it has been assessed that, upon mechanical activation, LiMn₂O₄ forms directly and its formation is completed within 700 °C whereas, starting from a physical mixture, the formation goes through Mn₂O₃ and is complete only at 800 °C. At T>820 °C LiMn₂O₄ reversibly decomposes to LiMnO₂ and Mn₃O₄ with an enthalpy of 30.05 kJ mol⁻¹ of LiMn₂O₄. At X_Li=0.50, by annealing under nitrogen flow for 6 h at 650 °C the activated mixture, the orthorhombic LiMnO₂ is formed. Such a formation goes through a mixture of LiMnO₂ and LiMn₂O₄. The enthalpy of LiMnO₂ solid state formation from the activated mixture has been determined to be 57.4 kJ mol⁻¹ of LiMnO₂. At X_Li=0.66 in air the mechanical activation considerably lowers the temperature within the monoclinic phase Li₂MnO₃ forms. Besides the reaction enthalpy could be determined as 40.13 kJ mol⁻¹ of Li₂MnO₃. The reaction, when performed under nitrogen flow, goes through the formation of LiMnO₂. Such a first stage of the reaction is affected by the temperature of reaction rather than by mechanical activation. The activation greatly enhances the second stage of the reaction leading from LiMnO₂ to Li₂MnO₃.     

Improved electrochemical properties in the Li3Fe2(PO4)3 by titanium and vanadium doping

Ti⁴⁺ ions were introduced to the VO₄^3- substituted Li₃Fe₂(PO₄)₃ by sol-gel method. Simultaneous substitution of Ti⁴⁺ for Fe³⁺ and VO₄^3- for PO₄^3- in the Li₃Fe₂(PO₄)₃ resulted in a net improvement in the rate capability and cycling performance, as compared with the single Ti⁴⁺ or VO₄^3- substituted compound.     

锂离子电池负极材料Li3V2(BO3)3/C 复合材料的合成及电化学性能研究

本文以草酸锂、五氧化二钒、硼酸为原料,二水合草酸为碳原和还原剂,无水乙醇为分散剂,采用球磨法合成了Li₃V₂(BO₃)₃/C（LVB/C）复合材料前驱体,后经高温热处理得到LVB/C复合材料. 采用TG-DTA技术对前驱体进行了热分析,通过XRD、SEM、EDS等技术研究了烧结条件对 LVB/C 材料的晶体结构、微观形貌、含碳量的影响. 通过恒流充放电测试、循环性能测试、循环伏安测试和电化学阻抗测试等技术研究了烧结条件对 LVB/C 材料电化学性能的影响. 电化学测试结果表明,800 ℃下烧结10 h得到的样品电化学性能最佳,在50mA•g^-1电流密度下,首次充放电比容量分别为427.6mAh•g^-1和669.1 mAh•g^-1,循环10次后,容量保持率分别为55.4 %和35.2 %.     

MOF derived Co3O4/N-doped carbon nanotubes hybrids as efficient catalysts for sensitive detection of H2O2 and glucose

Developing enzyme-free sensors with high sensitivity and selectivity for H2O2 and glucose is highly desirable for biological science.Especially,it is attractive to exploit noble-metal-free nanomaterials with large surface area and good conductivity as highly active and selective catalysts for molecular detection in enzyme-free sensors.Herein,we successfully fabricate hollow frameworks of Co3O4/N-doped carbon nanotubes(Co3O4/NCNTs)hybrids by the pyrolysis of metal-organic frameworks followed by calcination in the air.The as-prepared novel hollow Co3O4/NCNTs hybrids exhibit excellent electrochemical performance for H2O2 reduction in neutral solutions and glucose oxidation in alkaline solutions.As sensor electrode,the Co3O4/NCNTs show excellent non-enzymatic sensing ability towards H2O2 response with a sensitivity of 87.40μA(mmol/L)^-1 cm^-2,a linear range of 5.00μmol/L-11.00 mmol/L,and a detection limitation of 1μmol/L in H2O2 detection,and a good glucose detection performance with 5μmol/L.These excellent electrochemical performances endow the hollow Co3O4/NCNTs as promising alternative to enzymes in the biological applications.     

Preparation and Electrochemical Properties of xLi2MnO3·(1-x)LiMn2O4 Composites

Li₂MnO₃-doped spinel LiMn₂O₄ composites were synthesized by sol-gel method to improve the electrochemical performance of LiMn₂O₄. The microstructures, morphologies and electrochemical performance of the obtained xLi₂MnO₃·(1-x)LiMn₂O₄ composites were characterized by X-ray diffraction(XRD), scan electron microscopy(SEM) and a galvanostatic charge-discharge process. It was found that both Li₂MnO₃ and LiMn₂O₄ components exist in xLi₂MnO₃·(1-x)LiMn₂O₄(02MnO₃·0.7LiMn₂O₄ composite shows the optimized electrochemical performance, including discharge capacity and cycle stability. It was demonstrated that Li₂MnO₃-doped spinel LiMn₂O₄ cathode material can work at wide potential window with quite good capacity retention and considerably larger reversible capacity compared to single-phase LiMn₂O₄ component.     

复合导电添加剂对全固态锂硫电池性能影响的研究

使用硫化物固体电解质的全固态锂硫电池由于多硫化物不溶于硫化物固体电解质及硫化物电解质不可燃的特性,得以完全避免穿梭效应并显著提高了电池的安全性能而被认为是极具潜力的下一代储能电池。如何建立并平衡复合正极中离子/电子导电网络且维持复合正极中较高活性物质含量对于全固态锂硫电池至关重要。本文以单质硫为活性物质研究了复合导电添加剂对全固态锂硫电池性能的影响,发现以乙炔黑（AB）为导电碳材料明显优于Super P和Ketjen Black;优化复合正极的组成,发现硫：乙炔黑：固体电解质的质量比为40:20:40时,全固态锂硫电池在室温和60℃下均具有良好的电化学性能。     

Synthesis of carbon-coated Li4Ti5O12 and its electrochemical performance as anode material for lithium-ion battery

Carbon-coated Li_4Ti_5O_(12) sample was synthesized by a sol-gel method. The Li_4Ti_5O_(12) powders were obtained by calcinations of the gels at 750, 800, 850,900 ℃ at N_2 atmosphere. The structure, morphology and electrochemical properties of the materials were characterized by SEM, XRD and charge and discharge. The final product sintered at 850 ℃ demonstrates excellent performance with a specific capacity of 163.5 mAh/g after 100 cycles at 1C. Furthermore, the discharge specific capacity of the sample can retain 80 mAh/g at 10C.     

流变相法制备海藻酸基碳包覆Li3V2(PO4)3材料的电化学性能

Li₃V₂(PO₄)₃/C (LVP/C) cathode materials were successfully prepared by a rheological phase method using alginic acid as the carbon source. The X-ray diffraction (XRD) patterns demonstrate that all the samples contain pure LVP with the same monoclinic structure. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that LVP/C materials have a uniform particle size. The LVP/C sample with 10% (w) alginic acid shows the best cycling stability. It delivers a discharge capacity of 117.5 mAh·g^-1 (3.0-4.3 V), which can be maintained at 116.5 mAh·g^-1 after 50 cycles at a rate of 0.1C. Its capacity retentions of 99.1% (3.0-4.3 V) and 76.8% (3.0-4.8 V) after 50 cycles are prominently higher than those of pristine Li₃V₂(PO₄)₃, which are 89.7% (3.0-4.3 V) and 62.39% (3.0-4.8 V). These outstanding electrochemical performances are mainly attributed to the alginic acid-based carbon coating, which can increase the electronic conductivity of materials and buffer the mechanical damage of the active materials during the Li ion insertion/extraction process, thus improving the electrochemical performance of the LVP/C samples.