锂离子电池LiNi0.6Co0.2Mn0.2O2正极材料的硼元素掺杂改性调控

采用草酸盐共沉淀法结合后续热处理技术制备硼掺杂LiNi0.6Co0.2Mn0.2O2正极材料.研究了不同硼源(B2O3,H3BO3和LiBO2)掺杂对材料形貌、结构和电化学性能的影响.通过X射线衍射仪和Rietveld精修分析证明了硼(B)元素掺杂到材料晶格中.电化学性能研究表明:B2O3掺杂效果最佳,具有优异的倍率性...     

WO3 membrane-encapsulated layered LiNi0.6Co0.2Mn0.2O2 cathode material for advanced Li-ion batteries

Despite Nickel-rich materials have all the advantages of high capacity, long cycle life and low cost, there is still a disadvantage that the capacity decreases rapidly as the number of cycles increases. In order to solve this problem, WO₃ was uniformly coated on the surface of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials by wet coating, and its cycling performance was greatly improved with the higher capacity. The coated materials were analyzed by X-ray diffraction(XRD), Scanning electron microscope (SEM), high resolution Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy(XPS). The results showed that the coating thickness was around 3.15?nm, and some tungsten ions were doped into the lattice of the near surface area of the LiNi_0.6Co_0.2Mn_0.2O₂ material. In addition, the results of charge-discharge test showed that 1?wt%WO₃ coating LiNi_0.6Co_0.2Mn_0.2O₂ had the best performance, and delivered a discharge capacity of 140 mAh g^?1 (the capacity retention rate is 84.8%) in the potential interval of 2.8–4.3?V at 1?C (1?C?=?165?mA?g^?1) after 200 cycles, while the bare cathode material only delivered a discharge capacity of 120 mAhg^?1 (the capacity retention rate is 75%). The phenomenon indicates that the WO₃ coating plays a role in inhibiting the harmful side reactions between the cathode material and the electrolyte, improving the electrochemical and structure stability of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials.     

Enhanced electrochemical performance of ZrO2 modified LiNi0.6Co0.2Mn0.2O2 cathode material for lithium ion batteries

LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode has been modified by incorporating ZrO₂ nanoparticles to improve its electrochemical performance. Compared to the pristine electrode, the cycling stability and rate capability of 0.5 wt% ZrO₂ modified-NCM622 have been improved significantly. The 0.5 wt% ZrO₂ modified-NCM622 cathode shows a capacity retention of 83.8% after 100 cycles at 0.1 C between 2.8 and 4.3 V, while that of the pristine NCM622 electrode is only 75.6%. When the current rate is set as 5C, the capacity retention of the 0.5 wt% ZrO₂-modified NCM622 is 10% higher than that of the pristine NCM622. Also, the rate capability of 0.5 wt% ZrO₂-modified NCM622 is better than that of the pristine NCM622 at various C-rates in a voltage range of 2.8–4.3 V. The enhanced electrochemical performances of the ZrO₂-modified NCM622 cathodes can be attributed to their high Li-ion conductivity and structural stability.     

高密度LiNi_(0.8)Co_(0.2)O_2的合成

以二次干燥化学共沉淀法制得高密度前驱体Ni0.8Co0.2(OH)2,再与LiNO3混合,经600℃恒温6 h,800℃恒温24 h两个恒温阶段烧结,得到高密度LiNi0.8Co0.2O2,探讨了锂源、镍源、Li/(Ni+Co)摩尔比、合成温度等因素对产品的影响,优化了LiNi0.8Co0.2O2的合成工艺。所得非球形LiNi0.8Co0.2O2粉末振实密度高达3.15 g/cm3,大幅度地提高正极材料的体积比能量。X射线衍射分析表明,合成的LiNi0.8Co0.2O2具有规整的层状NaFeO2结构,充放电测试表明,材料具有良好的电化学性能。     

前驱体对三元正极材料LiNi0.5Co0.2Mn0.3O2性能影响的研究

以碳酸锂为锂源,将三种不同厂家的镍钴锰氢氧化物前驱体通过固相烧结法制备锂离子电池三元材料LiNi0.5Co0.2Mn0.3O2(简称NCM),并用纳米氧化铝溶液对其进行了包覆.采用X射线衍射仪、扫描电子显微镜、恒电流充放电测试仪等对材料的物理和电化学性能进行分析测试.结果表明:在前驱体元素组成基本一致的情况下,包覆前后三种前驱体制备的正极材料半电池首次容量由166.7 mAh/g、166.0 mAh/g和166.1 mAh/g改变为169.8 mAh/g、167.4 mAh/g和165.9 mAh/g,而100周循环保持率由92.6％、92.3％和93.2％上升到96.2％、96.0％和96.3％.这种改善应源于包覆过程中形成的快离子导体抑制了循环过程中电池直流内阻(DCIR)的增加.但对于不同前驱体制备的正极材料,包覆后电子传导能力以及界面相容性会有所不同.     

Nano-Y2O3-coated LiNi0.5Co0.2Mn0.3O2 cathodes with enhanced electrochemical stability under high cut-off voltage and high temperature

LiNi_0.5Co_0.2Mn_0.3O₂ (523) coated with ~ 20 nm thick Y₂O₃ nano-membrane is prepared via a sol-type chemical precipitation process based on electrostatic attraction between the materials. The nano-Y₂O₃-coated 523 cathode can deliver 160.3 mA h g⁻¹ (87.8% of its initial discharge capacity) after 50 cycles at 1 C (180 mA g⁻¹) between 3.0 and 4.6 V by coin cell testing, while the pristine 523 keeps only 146.2 mA h g⁻¹ with 78.6% capacity retention left. The capacity retention rate increases from 50% to 86.7% after 150 cycles at 1 C in 3.0–4.35 V by soft package testing under 45 °C. Through this novel Y₂O₃ coating operation, both the charge transfer resistance and the electrode polarization of the 523 electrode have been suppressed, and its structure stability is also improved.     

掺混工艺对LiNi0.5Co0.2Mn0.3O2 正极材料性能的影响

以碳酸锂及镍钴锰氢氧化物前驱体为原料,通过固相烧结法制备成D50为7.7、19.92 μm的两种规格的锂离子电池三元材料NCM-S和NCM-B。按NCM-B质量占比为20%~90%,将上述两种材料掺混获得系列化的样品。采用激光粒度分析仪、振实密度仪、扫描电子显微镜、充放电测试仪对材料的物理及电化学性能进行分析测试。结果表明：与大颗粒样品NCM-B相比,NCM-80%样品振实密度由2.90 g/cm3提高至2.96 g/cm3,放电比容量由 176.3 mA·h/g提升到178.6 mA·h/g,100周循环容量保持率由91.9%提升至92.7%。以上结果可以归因于小颗粒在紧密堆积的大颗粒中的填隙作用,改善了活性材料的导电网络,提高了电池的能量密度。     

基于分级共沉淀法制备锂离子电池LiNi0.5Co0.2Mn0.3O2正极材料

通过分级共沉淀（分级进料）方法,结合高温热处理合成了金属元素（Ni,Mn）浓度从中心到表面呈梯度分布（中心富Ni,表面富Mn）的球形三元正极材料LiNi_0.5Co_0.2Mn_0.3O₂。利用X射线衍射（XRD）、场发射扫描电镜（FESEM）、能谱仪（EDS）和电感耦合等离子质谱仪（ICP-MS）等表征了所制备材料的成分、形貌和元素分布。通过恒流充放电和循环伏安、交流阻抗等方法对材料的电化学性能进行测试。结果表明,与传统的一级共沉淀方法相比,分级共沉淀所制备材料展现出更高的倍率性能（20 C放电比容量为104.1 mAh·g^-1）、循环保持率（0.5 C循环200次容量保持率为95.8%）和快速充放电性能（20 C/20 C放电比容量为85.4 mAh·g^-1）。这种分级进料制备技术可以有效提高共沉淀法制备锂离子电池三元正极材料的电化学性能。     

Direct regeneration of LiNi0.5Co0.2Mn0.3O2 cathode material from spent lithium-ion batteries

At present, metal ions from spent lithium-ion batteries are mostly recovered by the acid leaching procedure, which unavoidably introduces potential pollutants to the environment. Therefore, it is necessary to develop more direct and effective green recycling methods. In this research, a method for the direct regeneration of anode materials is reported, which includes the particles size reduction of recovered raw materials by jet milling and ball milling, followed by calcination at high temperature after lithium supplementation. The regenerated LiNi_0.5Co_0.2Mn_0.3O₂ single-crystal cathode material possessed a relatively ideal layered structure and a complete surface morphology when the lithium content was n(Ni + Co + Mn):n(Li) = 1:1.10 at a sintering temperature of 920 ℃, and a sintering time of 12 h. The first discharge specific capacity was 154.87 mA·h·g^-1 between 2.75 V and 4.2 V, with a capacity retention rate of 90% after 100 cycles.     

Improved electrochemical performance of layered LiNi0.4Co0.2Mn0.4O2 via Li2ZrO3 coating

A Li₂ZrO₃ coating technique was successfully applied to layered lithium transition metal mixed oxide LiNi_0.4Co_0.2Mn_0.4O₂ to enhance its electrochemical performance using Zr(NO₃)₄·5H₂O and CH₃COOLi·2H₂O as coating reagents. The existence of Li₂ZrO₃ coating layer was identified by X-ray diffraction (XRD), Environmental scanning electron microscopy (ESEM), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The Li₂ZrO₃ shell decreased the exposed area of electrode core to electrolyte, and thus suppressed the dissolution of transition metal and side reaction between them. In addition, coating with Li₂ZrO₃ improved the ion transportation characteristics. As a result, an enhanced electrochemical performance in terms of discharge capacity, rate performance, and capacity retention were obtained, especially at higher temperature of 50 °C. Analysis of electrochemical impedance spectra (EIS) showed that the coated material exhibited lower charge transfer resistance (R_ct) with less variation during cycling, which indicated the electrode/electrolyte interface of coated material was more favorable and stable for electrochemical reaction.     

烧结温度对LiNi0.5Co0.3Mn0.2O2物理及其电化学性能的影响

以共沉淀法制备出的球形Ni0.5Co0.3Mn0.2(OH)2为前驱体,以碳酸锂为锂源,通过高温固相法合成了球形LiNi0.5Co0.3Mn0.2O2正极材料。通过热重分析(TGA/DSC)、X射线衍射(XRD)、扫描电子显微镜(SEM)、粒度分布、以及电化学性能的测试考查了不同烧结温度对LiNi0.5Co0.3Mn0.2O2的物理性能及电化学性能的影响。结果表明,900℃下烧结得到的LiNi0.5Co0.3Mn0.2O2晶体结构完整、球形形貌规则、粒度分布均匀,并表现出了优异的电化学性能,0.2 C首次放电容量达到了166.7 mA.h/g;1 C首次放电容量为151.6 mA.h/g,20次循环后,容量保持率高达97.9%。     

陈化温度对LiNi0.5Co0.2Mn0.3O2型正极 材料电化学性能的影响

以简单的球磨-干燥-煅烧法,制备了具有稳定α-NaFeO2型层状结构（R-3m空间群）的LiNi0.5Co0.2Mn0.3O2 型的三元正极材料。通过X射线衍射分析、傅里叶红外光谱、扫描电子显微镜、充放电循环、循环伏安、交流阻抗谱等手段测试了样品的理化性能。研究表明：球磨浆料的陈化温度对样品性能有明显的影响。在0.1C、1C、2C、3C、5C、6C、8C和10C倍率电流和连续充放电下,经过50 ℃陈化浆料制备的亚微米样品的放电容量分别为172.3、161.4、151.5、145.2、136.9、133.2、126.3、121.4 mA·h/g,表现出较好的大倍率电流放电性能。随着循环次数的增加,该样品的锂离子扩散系数和电荷传递阻抗均发生变化。该样品的未循环、充放电循环1次及循环40次样品的锂离子扩散速率分别为1.45×10-16、6.60×10-16、7.92×10-15 cm/s。     

Realization of a high voltage Ni rich layer LiNi0.5Co0.2Mn0.3O2 single crystalline cathode for LIBs by surface modification

Single crystalline ternary cathode material LiNi_0.5Co_0.2Mn_0.3O₂(NCM523) can operate at extremely high voltages and could offer exceptional energy density. The single crystal morphology is less easy to form the cracks and could express better structure stability compared to the polycrystalline counterpart. However, irreversible parasitic side reactions in the interface during cycling may lead to rapid electrochemical degradations. Herein, a simple chemical wet method that modifies the single-crystal NCM523 particles with Al₂O₃ coating is proposed. The coating layer can effectively suppress the phase transformation and irreversible phase transition on the NCM surface during cycling. Furthermore, the cladding layer can prevent the erosion of by-products such as HF. As a result, the Al₂O₃ modified NCM523 delivers a high specific capacity of 192.5mAh g^?1, excellent cycling stability and rate capability. The capacity retention was 91.7% after 50 cycles even at ultra-high cut-off voltage of 4.7 V. This surface engineering strategy paves the way to promote the development of small size single crystal NCM523 materials for next generation LIBs.     

A green and economical route to the precursor for the synthesis of single crystal LiNi0.5Co0.2Mn0.3O2

Single crystal LiNi_1-x-yCo_xMn_yO₂(NCM) cathode materials are typically synthesized using spherical polycrystalline hydroxides which are often prepared via coprecipitation reactions. However, the spherical morphology of polycrystalline hydroxides is not essential for the precursor in the synthesis of single crystal NCM, and also the coprecipitation process is not environmentally friendly and cost-effective enough. Herein a new process based on room-temperature solid-state metathesis reactions is developed to prepare the precursor for the synthesis of single crystal LiNi_0.5Co_0.2Mn_0.3O₂(NCM523). The whole process is free of any undesirable chemicals, and the resulting nanosize precursor can facilitate the synthesis of micron-level single crystal NCM523 at relatively lower sintering temperatures with less lithium excess. Moreover, the obtained single crystal NCM523 can exhibit comparable reversible capacities as compared with that synthesized from the coprecipitated spherical polycrystalline hydroxides. This work demonstrates a green and economical route to the precursor for the synthesis of single crystal NCM.     

ZrO_2包覆富锂正极材料Li[Li_(0.2)Ni_(0.2)Mn_(0.6)]O_2

采用共沉淀-高温固相法制备了富锂正极材料Li[Li0.2Ni0.2Mn0.6]O2,并使用Zr(OC3H7)4进行了Zr O2包覆改性。通过X射线粉末衍射(XRD)、透射电子显微镜(TEM)和电化学测试手段讨论了Zr O2包覆对材料的结构、形貌和电化学性能的影响。Zr O2能均匀覆盖在Li[Li0.2Ni0.2Mn0.6]O2颗粒表面,包覆后材料的电化学性能有一定的改善。包覆质量分数0.5%的Zr O2样品表现了提高的循环和倍率性能。首次放电容量(0.1 C,2.0~4.8 V)高达250.8 m Ah·g-1,循环45周(0.2C)容量保持为201.6 m Ah·g-1,2.0 C倍率放电容量可达123.2 m Ah·g-1。     

锂离子电池正极材料LiNi0.8Co0.2O2的研究

低成本、高比容量的LiNi0.8Co0.2O2是取代已商品化锂电池正极材料LiCoO2的候选材料。用工业原料,通过共沉淀法(pH=11 2±0 05)合成了β Ni0.8Co0.2(OH)2,将其和LiOH·H2O混合,在空气中先后于650℃和750℃烧结8h和20h,制得具有良好层状结构的LiNi0.8Co0.2O2。用合成的材料制备电池,在0 2C、3 0～4 1V进行充放电实验,其放电平台在3 8V以上,首次放电容量超过170mA·h/g,10次循环后,放电容量还能保持在164mA·h/g左右,且库仑效率达到96%以上。     

活性炭对三元电池电容电化学性能的影响

文章以电池电容软包单体为研究对象,采用恒流充放电测试,研究了正极活性物质中不同活性炭掺入量(0,20%,30%)对NCM三元体系电池电容容量、充放电性能、倍率性能和循环寿命等电化学性能的影响。结果表明:随着正极活性物质中活性炭掺入量的增加,软包单体样品的容量降低,倍率性能提高,循环性能趋于稳定;但当掺入活性炭超过一定量时,不利于器件整体容量的发挥,循环性能会变差,并不能使器件同时发挥出电容和电池的优点,反倒都会进行破坏。为使电池和电容两方面特性兼容发挥,活性物质中活性炭的掺入量应低于活性物质总质量的30%。     

一步固相法合成Li1.2Ni0.13Co0.13Mn0.54O2正极材料的工艺优化

以球形前驱体Ni0.13Co0.13Mn0.54(OH)0.8以及Li2CO3为原料,用正交实验方法优化一步固相法制备Li1.2Ni0.133Co0.133Mn0.534O2正极材料的合成工艺,考察焙烧温度、焙烧时间以及锂盐过量分数等因素对材料电化学性能的影响,得到最佳工艺组合:焙烧温度850℃;焙烧时间18 h;锂盐过量分数2%。按最佳工艺合成的样品0.2 C、1 C首次放电容量分别为262.6 mAh/g和234.6mAh/g,且表现出良好的循环稳定性。     

低共熔混合锂盐合成LiNi_(0.8)Co_(0.2)O_2的研究

在空气气氛中,采用低共熔混合物L iNO3-L iOH为锂盐,制备出了锂离子电池正极材料L iN i0.8Co0.2O2。XRD分析表明:此工艺制得的正极材料具有完整的层状结构。电性能测试表明:在0.5 mA/cm2的充放电电流密度和2.7~4.2 V的电压范围内,L iN i0.8Co0.2O2首次放电比容量为145.2 mA.h/g,充放电库仑效率为83.8%;循环20次后,放电比容量为124.8 mA.h/g。该方法能制备出电化学性能良好的L iN i0.8Co0.2O2正极材料。