Electrochemical intercalation kinetics of lithium ions for spinel LiNi0.5Mn1.5O4 cathode material

The crystal structure and electrochemical intercalation kinetics of spinel LiNi_0.5Mn_1.5O₄ such as the resistance of a solid electrolyte interphase (SEI) film, charge transfer resistance (R _ct), surface layer capacitance, exchange current density (i ₀), and chemical diffusion coefficient are evaluated by Fourier transform infrared (FT-IR) and electrochemical impedance spectroscopy (EIS), respectively. FT-IR shows that LiNi_0.5Mn_1.5O₄ thus obtained has a cubic spinel structure, which can be indexed in a space group of Fd3m with a disordering distribution of Ni. EIS indicates that R _s is almost a constant at different states of charge. The thickness of SEI film increases with increasing of the cell voltage. R _ct values evidently decreases when lithium ions deintercalated from the cathode in the voltage range from OCV to 4.6 V, and R _ct value increases with increasing potential of deintercalation over 4.7 V. i ₀ varies between 0.2 and 1.6 mA cm^?2, and the solid phase diffusion coefficient of Li⁺ changed depending on the electrode potential in the range of 10^?11–10^?9 cm² s^?1.     

Combining 5 V LiNi0.5Mn1.5O4 spinel and Si nanoparticles for advanced Li-ion batteries

An advanced high-voltage Li-ion battery is reported. The electrodes are prepared from a lithium–nickel–manganese spinel as cathode and silicon nanoparticles as anode. The specific capacity as referred to the anode material is 1700 mA h g^?1, which is much higher than the reported values for most existing Li-ion batteries.     

Preparation of LiNi0.5Mn1.5O4 cathode materials by using different-sized Mn3O4 nanocrystals as precursors

Journal of Solid State Electrochemistry - High-voltage LiNi0.5Mn1.5O4 with a spinel structure is considered as important cathode materials for high-energy density Li-ion batteries (LIBs). In this...     

Enhancements of rate capability and cyclic performance of spinel LiNi0.5Mn1.5O4 by trace Ru-doping

The rate capability and cyclic performance of the LiNi_0.5Mn_1.5O₄ under high current density have been significantly improved by doping a small amount of ruthenium (Ru). Specifically, Li_1.1Ni_0.35Ru_0.05Mn_1.5O₄ and LiNi_0.4Ru_0.05Mn_1.5O₄ synthesized by solid state reaction can respectively deliver a discharge capacity of 108 and 117 mAh g^?1 at 10 C rate between 3 and 5 V. At 10 C charge/discharge rate, Li_1.1Ni_0.35Ru_0.05Mn_1.5O₄ and LiNi_0.4Ru_0.05Mn_1.5O₄ can respectively maintain 91% and 84% of their initial capacity after 500 cycles, demonstrating that Ru-doping could be a way to enhance the electrochemical performance of spinel LiNi_0.5Mn_1.5O₄.     

LiNi0.5Mn1.5O4-xFx高电压电极高温保存下的电化学行为

采用溶胶-凝胶法结合高温热处理制备了锂离子电池用5 V正极材料LiNi0.5Mn1.5O4-xFx(x=0, 0.1). 通过X射线衍射(XRD)、扫描电子显微镜(SEM)和低温氮吸附法(BET)表征了粉体材料的结构、表面形貌和比表面特性, 并以其为正极材料装配电池后, 在85 ℃下高温保存24 h, 测量了保存前后电池的一系列电化学性质变化. 结果表明, 高温保存时电池开路电压会因自放电而较快地下降. 材料的比表面积和氟掺杂显著地影响电池的电压保持能力. 比表面积愈大, 电压保持时间愈短. 氟掺杂有利于提高电池在高温条件下的电压稳定性, 并可以改善电极与电解液之间的界面性质,使充放电性能更好.     

High performance LiNi0.5Mn1.5O4 cathode materials synthesized by a combinational annealing method

High performance LiNi_0.5Mn_1.5O₄ was prepared by a combinational annealing method. All samples were characterized by X-ray diffraction, infrared, and cell measurements. With increasing the annealing time at 600 °C, LiNi_0.5Mn_1.5O₄ showed a decreased lattice parameter and an enhanced Ni-ordering. The electrochemical property of LiNi_0.5Mn_1.5O₄ was optimized by controlling the annealing time. It was found that after annealing at 600 °C for 8 h, LiNi_0.5Mn_1.5O₄ can discharge up to 138 mA h g⁻¹ with a superior cycling performance at the rate of 5/7 C. High-rate test indicated that LiNi_0.5Mn_1.5O₄ exhibited excellent electrochemical performance when charged and discharged at 1.2 C and 2.5 C, respectively. The findings reported in this work are expected to pave the way for the practical application of LiNi_0.5Mn_1.5O₄.     

锂离子电池正极材料LiNi_0.5Mn_1.5O_4表面包覆CuO的研究

本文首先通过共沉淀法和固相球磨法制备了纳米级的LiNi0.5Mn1.5O4高电压正极材料,然后通过溶胶-凝胶法制备了表面包覆CuO的CuO-LiNi0.5Mn1.5O4复合材料.通过对CuO包覆量为1%,3%和5%的复合材料的电化学性能对比,发现当包覆量为1%时,材料的性能最佳.在1 C下,材料的放电比容量高达126.1 mA h g?1,循环100次后容量保持率在99.5%.CuO包覆在纳米LiNi0.5Mn1.5O4材料表面,阻止电解液与活性颗粒的直接接触,削弱了电解液与LiNi0.5Mn1.5O4的相互作用,进而在一定程度上减缓了电解液的分解;CuO的包覆同时还缓解了电解液中HF对材料的攻击,阻止了锰的溶解和由此带来的结构改变,进而提高了材料的循环稳定性.     

熔盐法合成LiNi0.5Mn1.5O4及电化学性能

以一定比例的LiCl-LiNO_3为低熔点共混物,采用熔盐法合成了电化学性能良好的LiNi_(0.5)Mn_(1.5)O_4,XRD表征结果显示产物为单一尖晶石相,SEM表征显示出材料良好的晶形,充放电测试结果显示出材料在4.7V平台附近有较大的可逆容量,在4.1V平台附近仅有较少的可逆容量。文章讨论了影响产物晶形和性能的各种因素,建议通过退火、改变合成气氛来消除4.1V平台的产生;研究结果还显示,容量的损失主要发生在第一次放电过程中在高电位区时的电解液的氧化分解.建议通过更换适合在高电位条件下工作的电解液来克服此问题;同时,通过调整低熔点共混物的配比、气氛、反应时间等条件可以实现对产物的结晶形态和大小进行适当的控制,显示了该方法在制备LiNi_(0.5)Mn_(1.5)O_4材料中的应用前景.     

Electrochemical performance of LiNi0.5Mn1.5O4 doped with la and its compatiblity with new electrolyte system

Cathode materials LiNi_0.5Mn_1.5O₄ and LiNi_{0.5 ? x/2}La _x Mn_{1.5 ? x/2}O₄ (x = 0.04, 0.1, 0.14) were successfully prepared by the sol-gel self-combustion reaction (SCR) method. The X-ray diffraction (XRD) patterns indicated that, a few of doping La ions did not change the structure of LiNi_0.5Mn_1.5O₄ material. The scanning electronic microscopy (SEM) showed that the sample heated at 800°C for 12 h and then annealed at 600°C for 10 h exhibited excellent geometry appearance. A novel electrolyte system, 0.7 mol L^?1 lithium bis(oxalate)borate (LiBOB)-propylene carbonate (PC)/dimethyl carbonate (DMC) (1: 1, v/v), was used in the cycle performance test of the cell. The results showed that the cell with this novel electrolyte system performed better than the one with traditional electrolyte system, 1.0 mol L^?1 LiPF₆-ethylene carbonate (EC)/DMC (1: 1, v/v). And the electrochemical properties tests showed that LiNi_0.45La_0.1Mn_1.45O₄/Li cell performed better than LiNi_0.5Mn_1.5O₄/Li cell at cycle performance, median voltage, and efficiency.     

SEI layer-forming additives for LiNi0.5Mn1.5O4/graphite 5 V Li-ion batteries

This study demonstrates that proper SEI layer on graphite anode is essential in LiNi_0.5Mn_1.5O₄(LNMO)/graphite 5 V lithium-ion batteries. Succinic anhydride (SA) and 1,3-propane sultone (PS) were found to greatly extend cycle life and suppress swelling behavior of LNMO/graphite cells. The benefits of SA and PS were ascribed not only to the stable SEI layer they form on graphite but also to their stability toward the oxidation at high voltage. Using 1 M LiPF₆ EC/EMC (1/2, v/v) solutions with SA and PS, LNMO/graphite Al-laminated pouch cell with nominal capacity of 600 mA h exhibited about 80% capacity retention after 100 cycles. This is the first report on the successful LNMO/graphite 5 V LIB to our best knowledge.     

凝胶燃烧法合成5V级正极材料LiNi_(0.5)Mn_(1.5)O_4及其高倍率放电性能

采用聚乙烯吡咯烷酮(PVP)作为络合剂和燃料以凝胶燃烧法制备了具有优异高倍率放电性能的亚微米LiNi0.5Mn1.5O4材料.用热重/差热分析(TG/DTA)研究了凝胶的燃烧过程,用X射线衍射(XRD)、扫描电镜(SEM)和循环伏安(CV)研究了LiNi0.5Mn1.5O4材料的结构和形貌.结果表明材料为结晶良好的纯尖晶石相结构,由5μm左右的二次颗粒组成,颗粒大小分布均匀,一次晶粒发育良好,粒径在500nm左右.充放电测试表明材料的倍率性能和循环性能十分优异.在3.5至4.9V进行充放电测试,0.5C、1C、4C、8C和10C倍率下放电容量分别为131.9、127.6、123.4、118.4和113.7mAh·g-1.在10C大倍率放电条件下循环100、500和1000次的容量保持率分别为91.4%、80.9%和73.5%.     

磷酸钐包覆对高电压镍锰酸锂正极材料电化学性能的影响

尖晶石型镍锰酸锂(LiNi_0.5Mn_1.5O₄)因制备成本低、 放电平台高及循环寿命长等优点, 越来越多地应用于大型储能设备、 能量转换设备、 动力汽车等领域. 然而LiNi_0.5Mn_1.5O₄在高电压(5 V)充电状态下电解液易分解, 从而导致比容量降低以及循环性能衰退. 针对以上问题, 采用水热法制备磷酸钐(SmPO₄)表面包覆改性LiNi_0.5Mn_1.5O₄正极材料, 研究了SmPO₄包覆量对LiNi_0.5Mn_1.5O₄材料电化学性能的影响. 结果表明, 当SmPO₄包覆量为0.5%(质量分数)时, 改性材料(LNMO@SP-0.5)的电化学性能最优, 在0.2C和5C倍率下的放电比容量分别为129.2和90.9 mA?h/g, 而未包覆的材料Pristine LNMO的放电比容量分别仅有114.2和77.7 mA?h/g. 在常温1C倍率下循环200次后, LNMO@SP-0.5的容量保持率为93.4%, 而Pristine LNMO的容量保持率仅为86.6%. 这归因于SmPO₄包覆能够有效缓解LiNi_0.5Mn_1.5O₄材料与电解液之间的副反应, 降低电极的极化程度和电荷转移电阻, 增加了Li⁺的扩散系数.     

Improving Interfacial Electrochemistry of LiNi0.5Mn1.5O4 Cathode Coated by Mn3O4

In this work the surface of LiNi\begin{document}$_{0.5}$\end{document}Mn\begin{document}$_{1.5}$\end{document}O\begin{document}$_{4}$\end{document} (LMN) particles is modified by Mn\begin{document}$_{3}$\end{document}O\begin{document}$_{4}$\end{document} coating through a simple wet grinding method, the electronic conductivity is significantly improved from 1.53\begin{document}$\times$\end{document}10\begin{document}$^{-7}$\end{document} S/cm to 3.15\begin{document}$\times$\end{document}10\begin{document}$^{-5}$\end{document} S/cm after 2.6 wt% Mn\begin{document}$_{3}$\end{document}O\begin{document}$_{4}$\end{document} coating. The electrochemical test results indicate that Mn\begin{document}$_{3}$\end{document}O\begin{document}$_{4}$\end{document} coating dramatically enhances both rate performance and cycling capability (at 55 ℃) of LNM. Among the samples, 2.6 wt% Mn\begin{document}$_{3}$\end{document}O\begin{document}$_{4}$\end{document}-coated LNM not only exhibits excellent rate capability (a large capacity of 108 mAh/g at 10 C rate) but also shows 78% capacity retention at 55 ℃ and 1 C rate after 100 cycles.     

Spinel LiNi0.5Mn1.5O4 with ultra-thin Al2O3 coating for Li-ion batteries: investigation of improved cycling performance at elevated temperature

In this study, spinel LiNi_0.5Mn_1.5O₄ (LNMO) was successfully decorated with Al₂O₃ thin film by using atomic layer deposition (ALD) approach and evaluated as a cathode material for high-temperature applications in lithium ion batteries (LIBs). To optimize the LNMO-Al₂O₃ electrodes operated at elevated temperature (55 °C), the effects of Al₂O₃ thicknesses adjusted by controlling the ALD deposition cycle were systemically investigated. According to the series of electrochemical results, the LNMO coated with the Al₂O₃ thin layer in the thickness of ca. 2 nm was achieved by using one-cycle ALD and the LNMO-Al₂O₃ electrode exhibited superior electrochemical stability (capacity retention up to 93.7% after consecutive 150 charge/discharge cycles at 0.5 C to the pristine LNMO electrode at elevated temperature. This can be attributed to two factors: (i) the decoration of Al₂O₃ thin layer could not contribute remarkably to extra resistance for charge transfer; (ii) Al₂O₃ thin film deposition could efficiently stabilize the growth of cathode electrolyte interface (CEI) and suppress the dissolution of transition metals. Therefore, these results verify that the LNMO-Al₂O₃ electrode could be regarded as a promising cathode material for high-voltage LIBs, especially at elevated temperature operation.

     

锂离子电池用高电位正极材料LiNi0.5Mn1.5O4

由于具有工作电压高、工作范围宽、比能量大、无污染、使用寿命长等优点,锂离子电池具有广阔的应用前景。 然而,目前商业化的锂离子电池仍无法满足电动汽车对电池低成本及高能量密度的要求。研发比能量更高、价格更低廉、寿命更长的锂离子电池成为电动汽车产业发展的关键。尖晶石结构的镍锰酸锂（LiNi_0.5Mn_1.5O₄）具有三维扩散通道,有利于锂离子的传输,且结构稳定;其理论放电比容量可达147 mAh ·g^-1。 更重要的是,其电压平台高达4.7 V,具有高的能量密度与功率密度,被认为是未来锂离子电池发展中最具前途与吸引力的正极材料之一。本文介绍了LiNi_0.5Mn_1.5O₄的结构、制备方法、掺杂与包覆改性研究及其应用前景,着重介绍了材料的改性方法并指出LiNi_0.5Mn_1.5O₄目前亟需解决的问题和研究重点。     

Influence of Post-annealing in N2 on Structure and Electrochemical Characteristics of LiNi0.5Mn1.5O4

LiNi_0.5Mn_1.5O₄ prepared by a spray drying method was re-treated in N₂ at 500, 600 and 700℃, respectively. Their structural and electrochemical properties were studied by means of Fourier transform infrared(FTIR), X-ray diffraction(XRD), and charge-discharge tests. The space group of the LiNi_0.5Mn_1.5O₄ transforms from P4₃32 to Fd3 m at an annealing temperature of 700℃. The electrochemical characteristics of the treated samples are closely related to the annealing temperature. The sample treated in N₂ at 500℃ shows both an improved rate capability and cyclic performance at a high temperature compared with the as-prepared sample, while the sample treated in N₂ at 700℃ shows dramatically decrease in its reversible capacity.     

Electrochemical properties of submicro-sized layered LiNi0.5Mn0.5O2

Submicro-sized layered LiNi_0.5Mn_0.5O₂ was synthesized via an improved solid-state reaction, in which at first a precursor mixed by nickel manganese double hydroxide with lithium hydroxide solution was prepared in order to make the fully contact between these materials, and then was calcined at different temperatures. The heat treatment process and the crystal structure of materials were investigated by DTA, TGA, and XRD methods. The SEM images show that the particles of layered LiNi_0.5Mn_0.5O₂ are submicrometer in size. It was found that the layered LiNi_0.5Mn_0.5O₂ synthesized at 750 °C for 24 h in oxygen atmosphere presents the best electrochemical performance, which delivers an initial discharge capacity of 153 mAh/g in the charge/discharge potential region (vs. Li) of 2.5–4.3 V, and exhibits good cycle stability.     

Spinel LiNi0.5Mn1.5O4 and its derivatives as cathodes for high-voltage Li-ion batteries

The spinel material LiNi_0.5Mn_1.5O₄ displays a remarkable property of high charge/discharge voltage plateau at around 4.7 V. It is a promising cathode material for new-generation lithium-ion batteries with high voltage. Recently, a lot of researches related to this material have been carried out. In this review we present a summary of these researches, including the structure, the mechanism of high voltage, and the latest developments in improving its electrochemical properties like rate ability and cycle performance at elevated temperature, etc. Doping element and synthesizing nanoscale material are effective ways to improve its rate ability. The novel battery systems, like LiNi_0.5Mn_1.5O₄/Li₅Ti₄O₁₂ with good electrochemical properties, are also in progress.