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.     

表面活性剂对氧化铝修饰富锂锰基正极材料的影响

采用氧化铝修饰改性富锂锰基正极材料,探讨了表面活性剂在修饰改性中的作用。利用扫描电子显微镜、X射线衍射仪、透射电子显微镜和电化学性能测试等方法对材料结构和电化学性能进行分析。实验结果表明,十二烷基三甲基溴化铵(DTAB)能使Al_2O_3纳米颗粒均匀包覆在富锂锰基正极材料表面,有效增强了复合材料结构的稳定性。在600 mA·g~(-1)电流密度下,该复合材料的初始放电容量为186mAh·g~(-1)。经过500次循环后,其可逆放电比容量仍高于132 mAh·g~(-1),初始容量保持率高达71%。此外,电压衰退也被有效抑制,复合材料表现出优异的综合电化学性能。     

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.     

锂离子电池用Cr2O3/TiO2复合材料的电化学性能

采用高温固相反应法合成了Cr₂O₃/TiO₂复合材料, 运用X射线衍射(XRD)、扫描电子显微镜(SEM)、充放电测试、循环伏安(CV)、电化学阻抗谱(EIS)等对其结构、形貌和电化学性能进行了表征. 研究结果表明: TiO₂掺杂能够显著改善Cr₂O₃的充放电循环性能, Cr₂O₃/TiO₂复合材料在充放电循环22周后仍有454 mAh·g^-1的可逆循环容量, 容量保持率达到了73.6%, 主要归因于TiO₂掺杂能够显著提高Cr₂O₃的电导率. Cr₂O₃/TiO₂复合材料首次放电过程中由于电极体积膨胀导致的固体电解质相界面(SEI)膜迅速增厚和活性材料电导率的降低可能是其首次充放电过程中存在较大不可逆容量和循环容量衰减的重要原因.     

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.     

二维纳米片组成的花状铁醇盐及其微纳结构三氧化二铁衍生物的储锂性能

Fe₂O₃作为锂电池负极材料具有诸多优点,但其较低的本征电导率和充放电循环过程中材料粉化使得其电化学储锂性能有待改善。 本文以具有花状微纳结构的铁醇盐为反应中间体,在空气气氛下烧结制备出具有花状微纳结构的铁基负极材料Fe₂O₃。 纳米花状的铁醇盐可以在低烧结温度下转化为目标产物,从而使得产物能够保持中间体的形貌。 300 ℃热处理条件下,所得样品在电流密度为200 mA/g时首次放电比容量为1360 mA·h/g,循环100次后的容量仍然达到515.6 mA·h/g;相比之下,450和800 ℃热处理所得样品100次循环后,比容量分别为247.6和206.7 mA·h/g。 微纳结构在增加材料的活性的同时,也能够抑制材料的粉化现象,因而所制得的材料表现出较大的比容量和良好的循环性能,为解决Fe₂O₃负极材料循环性能差的问题提供了思路。     

Microwave assisted hydrothermal synthesis of tin niobates nanosheets with high cycle stability as lithium-ion battery anodes

SnNb₂O₆ and Sn₂Nb₂O₇ nanosheets were synthetized via microwave assisted hydrothermal method, and innovatively employed as anode materials for lithium-ion battery. Compared with Sn₂Nb₂O₇ and the previously reported pure Sn-based anode materials, the SnNb₂O₆ electrode exhibited outstanding cycling performance.     

Enhanced electrochemical performance and mechanism study of AgLi1/3Sn2/3O2 for lithium storage

AgLi_1/3Sn_2/3O₂ with delafossite structure is prepared by treating Li₂SnO₃ with molten AgNO₃ and it exhibits improved electrochemical performance compared to Li₂SnO₃.     

Synthesis of iron oxide cubes/reduced graphene oxide composite and its enhanced lithium storage performance

Fe₃O₄ is considered as a promising electrode material for lithium-ion batteries(LIBs) due to its low cost and high theoretical capacity(928 mAh/g).Nevertheless,the huge volume expansion and poor conductivity seriously hamper its practical applications.In this study,we use a facile hydrothermal reaction together with a post heat treatment to construct the three-dimensional heterostructured composite(Fe₃O₄/rGO) inwhich reduced graphene oxide sheets wraped the Fe₃O₄ submicron cubes as the conductive network.The electric conduction and electrode kinetics of lithium ion insertion/extraction reaction of the composite is enhanced due to the assist of conductive rGO,and thus the Listorage performance is obviously improved.The composite exhibits a reversible charge capacity of772.1 mAh/g at the current density of 0.1 A/g,and the capacity retention reaches 70.3% after400 cycles at0.5 A/g,demonstrating obviously higher specific capacity and rate capability over the Fe₃O₄ submicron cubes without rGO,and much superior cycling stability to the parent Fe_2 O_3 submicron cubes without rGO.On the other hand,as a synergic conductive carbon support,the flexible rGO plays an important role in buffering the large volume change during the repeated discharge/charge cycling.     

V2O3空心球的制备及在锂硫电池中的应用

在NH₃辅助下将制备的V₂O₅空心球高温还原为V₂O₃空心球, 并利用透射电子显微镜、 扫描电子显微镜、 X射线衍射和X射线光电子能谱等手段对材料的形貌与结构进行表征. 将V₂O₃空心球与硫机械混合后, 不经过熔融复合直接作为锂硫电池的正极材料. 电化学测试结果显示, 在0.2C倍率下, 电池首次放电比容量达到1375 mA·h/g, 循环100次后放电比容量可以维持在815 mA·h/g; 在1C高倍率下, 电池首次放电比容量为710 mA·h/g, 经过500次循环后, 放电比容量仍能达到530 mA·h/g, 表明V₂O₃空心球的加入能够有效提高锂硫电池的循环性能.     

磷酸钒锂/石墨烯复合正极材料的制备及表征

通过三聚氰胺甲醛树脂(MR)中的羟基与石墨烯氧化物(GO)中的羧基发生的沉淀反应来制备功能化的氧化石墨烯前驱体,然后利用溶胶-凝胶及高温热处理方法制备磷酸钒锂/石墨烯复合材料,利用此材料制备了电池电极,并对电极材料进行了结构和电化学表征。结果表明,所得磷酸钒锂为单斜晶系结构,石墨烯堆叠程度显著降低,也有效避免了磷酸钒锂颗粒的团聚,提高了材料的电化学性能。电池的充放电曲线极化较小,在3.0~4.3 V的区间内20 C倍率仍有86 mA·h/g的可逆容量。0.1 C循环100次后容量为119.7 mA·h/g,容量保持率94%。在3.0~4.8 V的高电压区间,10 C倍率下可逆容量80 mA·h/g,0.1 C循环100次后仍有145.6 mA·h/g的可逆容量。优异的循环和倍率性能以及较低的碳含量符合锂离子正极材料实用的要求。     

Nitrogen-doped Carbon Coated Na3V2(PO4)3 with Superior Sodium Storage Capability

Cathodes with high cycling stability and rate capability are required for ambient temperature sodium ion batteries in renewable energy storage application. Na₃V₂(PO₄)₃ is an attractive cathode material with excellent electrochemical stability and fast ion diffusion coefficient within the 3D NASICON structure. Nevertheless, the practical application of Na₃V₂(PO₄)₃ is seriously hindered by its intrinsically poor electronic conductivity. Herein, solvent evaporation method is presented to obtain the nitrogen-doped carbon coated Na₃V₂(PO₄)₃ cathode material, delivering enhanced electrochemical performances. N-Doped carbon layer coating serves as a highly conducting pathway, and creates numerous extrinsic defects and active sites, which can facilitate the storage and diffusion of Na⁺. Moreover, the N-doped carbon layer can provide a stable framework to accommodate the agglomeration of the electrode upon electrode cycling. N-Doped carbon coated Na₃V₂(PO₄)₃(NC-NVP) exhibits excellent long cycling life and superior rate performances than bare Na₃V₂(PO₄)₃ without carbon coating. NC-NVP delivers a stable capacity of 95.9 mA·h/g after 500 cycles at 1 C rate, which corresponds to high capacity retention(94.6%) with respect to the initial capacity(101.4 mA·h/g). Over 91.3% of the initial capacity is retained after 500 cycles at 5 C, and the capacity can reach 85 mA·h/g at 30 C rate.     

Synthesis of spherical LiNi0.8Co0.15Al0.05O2 cathode materials for lithium-ion batteries by a co-oxidation-controlled crystallization method

Spherical Ni_0.8Co_0.15Al_0.05OOH precursor,prepared by a co-oxidation-controlled crystallization method,was used to synthesize LiNi_0.8Co_0.15Al_0.05O₂.The obtained LiNi_0.8Co_0.15Al_0.05O₂ materials showed excellent electrochemical performance,with an initial discharge capacity of 193.5 mAh/g and capacity retention of 95.1%after 50 cycles when cycled at 0.2℃rate between 2.8 and 4.3 V.     

Synthesis and electrochemical performance of LiNi0.6Co0.2Mn0.2O2 as a concentration-gradient cathode material for lithium batteries

A well-ordered and spherical LiNi0.6Co0.2Mn0.2O2 cathode material was successfully synthesized from Ni and Mn concentration-gradient precursors via co-precipitation. The crystal structure, morphology and electrochemical properties of LiNi0.6Co0.2Mn0.2O2 were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and charge-discharge tests. The material delivered an initial discharge capacity of 174.3 mAh/g at 180 mA/g （1 C rate） between 2.8 and 4.3 V and more than 93.1% of that was retained after 100 cycles. In addition, it also exhibited excellent rate capability, high cut-off voltage and temperature performance.     

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.     

Fe_3O_4/RGO复合材料的制备及其电化学性能研究

以改进Hummers法合成的氧化石墨烯(GO)为前驱体,通过水热法结合烧结工艺制备了四氧化三铁/还原氧化石墨烯(Fe_3O_4/RGO)复合材料。利用X射线衍射(XRD)、拉曼光谱(Raman)、扫描电镜(SEM)、透射电镜(TEM)等手段对复合材料的理化性能进行表征;通过充放电测试、循环伏安(CV)和电化学阻抗谱(EIS)等技术,综合考察了材料的储锂性能及电化学性能增强机制。结果表明,在200和600 m A/g电流密度下,Fe_3O_4/RGO复合负极循环60次后的放电比容量分别保持在709和479 mAh/g,表现出良好的倍率性能;相较于纯Fe_3O_4负极,复合负极呈现出更优异的锂电性能,其电化学性能的改善得益于RGO能增强材料的电导性和结构稳定性。     

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 %.     

原位相分离合成V_2O_5/Fe_2V_4O_(13)纳米复合材料及其储钠性能

钠具有资源丰富、成本低廉等优势,因此钠离子电池被认为是未来替代锂离子电池的最佳候选者之一。然而,寻找合适的电极材料是当前制备高性能钠离子电池面临的难题之一。在众多候选材料中,钒酸盐材料通过引入阳离子增加钒的配位数,使得材料结构的稳定性得到提高,从而改善了钠离子电池的电化学性能。本文研究了一种原位相分离法合成V_2O_5/Fe_2V_4O_(13)纳米复合材料。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)等对电极材料形貌、组成和结构进行了表征。实验结果显示,V_2O_5/Fe_2V_4O_(13)纳米复合材料相对于V2O5纳米线材料,结构更加稳定,在0.1 A·g~(-1)电流密度下,初始放电容量由295.4 m Ah·g~(-1)提升到342 m Ah·g~(-1),循环100圈容量保持率由26.6%提高到65.8%,获得了更加优异的倍率性能(在1.0 A·g~(-1)电流密度下,容量由44 m Ah·g~(-1)提高到160 m Ah·g~(-1))。因此,V_2O_5/Fe_2V_4O_(13)纳米复合材料的研究为开拓新型高性能钠离子电池负极材料拓宽了思路。     

三元掺杂改性锂离子电池正极材料Li3V2(PO4)3

以柠檬酸为螯合剂和还原剂, NH₄VO₃为钒源,通过溶胶-凝胶法制备了锂离子电池正极材料Li₃V₂(PO₄)₃及其三元掺杂体系Li_2.85Na_0.15V_1.9Al_0.1(PO₄)_2.9F_0.1.分别采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、能量损失谱(EELS)、拉曼(Raman)光谱、扫描电子显微镜(SEM)、X射线能谱(EDS)、恒流充放电、循环伏安(CV)和交流阻抗谱(EIS)等技术对材料的微观结构、颗粒形貌和电化学性能进行分析.结果表明:在残余碳包覆的基础上, Na、Al、F三元掺杂有利于稳定Li₃V₂(PO₄)₃的晶体结构,进一步减少颗粒团聚和提升材料导电特性,促进第三个锂离子的脱出和嵌入,从而显著改善Li₃V₂(PO₄)₃的实用电化学性能.未经掺杂的Li₃V₂(PO₄)₃原粉在1/9C、1C和6C倍率下的可逆比容量分别为141、119和98 mAh·g^-1,而三元掺杂改性材料在1/9C、1C、8C和14C倍率下的比容量分别为172、139、119和115 mAh·g^-1.在1C倍率下循环300圈后,掺杂体系的比容量依然高达118 mAh·g^-1,比原粉高出32.6%.值得注意的是,这种三元掺杂还使Li₃V₂(PO₄)₃的多平台放电曲线近似转变为一条斜线,显示出可能不同的储锂机制.     

Controlling the morphology,size and phase of Nb2O5 crystals for high electrochemical performance

Herein, the nano-sized niobium pentoxide (Nb₂O₅) with different morphologies and phase structures are synthesized through a very simple thermal treatment method, including the pseudohexagonal Nb₂O₅ nanosheets and pseudohexagonal Nb₂O₅ nanoparticles, orthorhombic Nb₂O₅ nanoparticles. The synthesized pseudohexagonal Nb₂O₅ nanosheets and orthorhombic Nb₂O₅ nanoparticles exhibit better cycling and rate performance than the pseudohexagonal Nb₂O₅ nanoparticles due to the different morphologies and phase structures.