Hierarchical hollow microcuboid LiNi0.5Mn1.5O4 as cathode material with excellent rate and cycling performance for lithium-ion batteries

Journal of Solid State Electrochemistry - The rational design of the structure is the key to engineering spinel LiNi0.5Mn1.5O4 cathode material to enhance Li+/electron transport and relieve the...     

Macroporous Co3O4 platelets with excellent rate capability as anodes for lithium ion batteries

This paper reports the microwave-assisted synthesis of Co₃O₄ nanomaterials with different morphologies including nanoparticles, rod-like nanoclusters and macroporous platelets. The new macroporous platelet-like Co₃O₄ morphology was found to be the best suitable for reversible lithium storage properties. It displayed superior cycling performances than nanoparticles and rod-like nanoclusters. More interestingly, excellent high rate capabilities (811 mAh g^?1 at 1780 mA g^?1 and 746 mAh g^?1 at 4450 mA g^?1) were observed for macroporous Co₃O₄ platelet. The good electrochemical performance could be attributed to the unique macroporous platelet structure of Co₃O₄ materials.     

Novel method to enhance the cycling performance of spinel LiMn2O4

In this study, a novel method was presented to improve the cycle performance of the spinel LiMn₂O₄ This method is quite different from the traditional way of coating LiMn₂O₄ particle itself with inorganic and organic compounds. First we covered the current collector with the mixture of LiMn₂O₄ particle, conductive agents and binders, and then deposited an aluminum film onto it by means of vacuum evaporation. The pure electrode and the modified electrode were investigated using a combination of scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and charge–discharge tests. The enhancement of the capacity retention of modified electrode is significant, maintaining 93.5% of the maximum capacity after 200 cycles at charge–discharge rate of C/2, while pure electrode only 63.7%. It was found that the improvement of cycling performance is greatly ascribed to the good electrical conductivity of aluminum film deposited on the surface of spinel LiMn₂O₄.     

Na-doped layered LiNi0.8Co0.1Mn0.1O2 with improved rate capability and cycling stability

Journal of Solid State Electrochemistry - We have prepared LiNi0.8Co0.1Mn0.1O2 (LNMCO) doped with Na+ and studied its properties using X-ray diffraction (XRD), energy dispersive X-ray analysis...     

Excellent cycling stability of spherical spinel LiMn2O4 by Y2O3 coating for lithium-ion batteries

The Y₂O₃ nano-film is coated on the surface of the spherical spinel LiMn₂O₄ by precipitation method and subsequent heat treatment at 550 °C for 5 h in air. The structure and performance of the bare LiMn₂O₄ and Y₂O₃-coated LiMn₂O₄ are characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive analysis X-ray spectroscopy, galvanostatic charge–discharge, cyclic voltammetry, and impedance spectroscopy. It has been found that the addition of Y₂O₃ does not change the bulk structure of LiMn₂O₄, and the thickness of the Y₂O₃ coating layer is approximate to 3.0 nm. The 1 wt% Y₂O₃-coated LiMn₂O₄ electrode reveals excellent cycling performance with 80.3 % capacity retention after 500 cycles at 1 C at 25 °C. When cycling at elevated temperature 55 °C, the as-prepared sample still shows 76.7 % capacity retention after 500 cycles. These remarkable improvements indicate that thin Y₂O₃ coating on the surface of LiMn₂O₄ is an effective way to improve the electrochemistry performance. Besides, the suppression of Mn dissolution into the electrolyte via the Y₂O₃ coating layer can be accounted for the improved performances.     

锂离子电池正极材料尖晶石LiMn2O4的研究现状

从制备方法,循环性能,比容量,高温性能等方面对近年来有关LiMn2O4尖晶石的研究作一综述;讨论合成方法,反应条件,尖晶石的晶体结构及改性对正极材料性能的影响,并预示该类正极材料今后的研究方向。     

Aqueous rechargeable lithium battery (ARLB) based on LiV3O8 and LiMn2O4 with good cycling performance

Crystalline LiV₃O₈ and LiMn₂O₄ were prepared by conventional solid-state reaction and characterized by X-ray diffraction analysis. Cyclic voltammetry technique was employed to evaluate the electrochemical behaviors of LiV₃O₈ and LiMn₂O₄ in 2 mol/l Li₂SO₄ aqueous solution, and the results show that both LiV₃O₈ and LiMn₂O₄ are very stable in this aqueous electrolyte and can be used as the negative and positive electrode material without evident hydrogen or oxygen evolution. An aqueous rechargeable lithium battery (ARLB) was fabricated by using the above two intercalation compounds as the negative and positive electrodes. This battery exhibits good cycling behavior and the average discharge voltage is about 1.04 V.     

Preparation of spherical spinel LiMn2O4 cathode material for lithium ion batteries

A novel process is proposed for synthesis of spinel LiMn₂O₄ with spherical particles from the inexpensive materials MnSO₄, NH₄HCO₃, and NH₃H₂O. The successful preparation started with carefully controlled crystallization of MnCO₃, leading to particles of spherical shape and high tap density. Thermal decomposition of MnCO₃ was investigated by both DTA and TG analysis and XRD analysis of products. A precursor of product, spherical Mn₂O₃, was then obtained by heating MnCO₃. A mixture of Mn₂O₃ and Li₂CO₃ was then sintered to produce LiMn₂O₄ with retention of spherical particle shape. It was found that if lithium was in stoichiometric excess of 5% in the calcination of spinel LiMn₂O₄, the product had the largest initial specific capacity. In this way spherical particles of spinel LiMn₂O₄ were of excellent fluidity and dispersivity, and had a tap density as high as 1.9 g cm^–3 and an initial discharge capacity reaching 125 mAh g^–1. When surface-doped with cobalt in a 0.01 Co/Mn mole ratio, although the initial discharge capacity decreased to 118 mAh g^–1, the 100th cycle capacity retention reached 92.4% at 25°C. Even at 55°C the initial discharge capacity reached 113 mAh g^–1 and the 50th cycle capacity retention was in excess of 83.8%.     

A graphene-amorphous FePO4 hollow nanosphere hybrid as a cathode material for lithium ion batteries

Amorphous FePO(4) hollow nanospheres were directly grown on graphene for use as a cathode material in lithium ion batteries. This hybrid exhibits high rate capability and good cycle stability because of efficient Li(+) ion diffusion through the thin wall of the hollow nanospheres and fast electron transport through the graphene.     

Nanofibers of LiMn2O4 by electrospinning

Through sol-gel processing and electrospinning technique, extrathin fibers of poly(vinyl alcohol) (PVA)/lithium chloride/manganese acetate composite fibers were prepared. After calcination of the above precursor fibers at 600 degrees C, the spinel lithium manganese oxide (LiMn2O4) nanofibers, with a diameter of 100-200 nm, were successfully obtained. The fibers were investigated by TG-DTA, XRD, FT-IR, and SEM, respectively. The results showed that the crystalline phase and morphology of the fibers were largely influenced by the calcination temperature.     

Spinel-to-CaFe2O4-type structural transformation in LiMn2O4 under high pressure

A new form of LiMn2O4 is reported. The structure is the CaFe2O4-type and 6% denser than the spinel. The structure transformation was achieved by heating at 6 GPa. Analysis of the neutron diffraction pattern confirmed an average of the structure; the unit cell was orthorhombic at a = 8.8336(5) angstroms, b = 2.83387(18) angstroms, and c = 10.6535(7) angstroms (Pnma). Electron diffraction patterns indicated an order of superstructure 3a x b x c, which might be initiated by Li vacancies. The exact composition is estimated at Li(0.92)Mn2O4 from the structure analysis and quantity of intercalated Li. The polycrystalline CaFe2O4-type compound showed semiconducting-like characters over the studied range above 5 K. The activation energy was reduced to approximately 0.27 eV from approximately 0.40 eV at the spinel form, suggesting a possible enhancement of hopping mobility. Magnetic and specific-heat data indicated a magnetically glassy transition at approximately 10 K. As the CaFe2O4-type transition was observed for the mineral MgAl2O4, hence the new form of the lithium manganese oxide would provide valuable opportunities to study not only the magnetism of strongly correlated electrons but also the thermodynamics of the phase transition in the mantle.     

Facile synthesis of porous LiMn2O4 micro-/nano-hollow spheres with extremely excellent cycle stability as cathode of lithium-ion batteries

Journal of Solid State Electrochemistry - In present work, the porous LiMn2O4 micro-/nano-hollow spheres are directly prepared from the globe precursor MnCO3 obtained via a facile precipitation...     

尖晶石型LiMn2O4电池材料的元素掺杂

尖晶石型LiMn2O4正极材料因资源丰富、无毒、安全及制备简单、技术较成熟等优点而成为最具竞争力的新一代商用锂离子二次电池的正极材料之一.由于LiMn2O4的循环稳定性、高温(＞55℃)稳定性和大电流放电等因素限制了推广应用.本文从材料的结构组成对锂离子嵌脱过程的作用机理,论述了元素掺杂对尖晶石型LiMn2O4正极材料电化学特性的影响,指出了元素掺杂本体改性锰酸锂正极材料的方法和特点.     

A Raman Study of Spinel LiMn2O4

A Raman study was carried out for LiMnzO4, which was synthesized via the mixture of Mn3O4 and LiNO3 sintered at different temperatures. It is shown that there are two kinds of Raman spectra for LiMn2O4 at different sintering temperatures, while the X-ray diffraction patterns of LiMnzO4 sintered at different temperatures are the same. Five Raman bands observed for the materials sintered below 500 ℃ are consistent with the theoretical prediction for spinel structure based on the group theory. Only two Raman bands were observed for the materials sintered at temperatures higher than 500 ℃. The best preparation condition for obtaining a good spinel LiMn2O4 is suggested based on the Raman study.     

长寿命、高倍率(Li4Ti5O12-AC)/( LiMn2O4-AC)电池电容的制备及性能研究

以商业微米级锰酸锂(LiMn2O4)为正极,钛酸锂(Li4Ti5O12)为负极,分别与商业活性炭(AC)复合,组装成软包装电池电容样品并进行电化学测试。测试结果表明：当样品正负极均复合AC时,其电化学性能要优于只有正极复合AC和未复合AC的样品。其中,正负极活性炭复合比例为5 wt.%,负极与正极的理论容量比(N/P)为1.01时,电池电容样品拥有良好的倍率性能,且其在0.5 C时的放电比容量为56.4 mAh/g,5 C时的容量保持率为0.5 C的72.2%。此外,与未复合AC的样品相比,单体在5 C倍率下经2000次循环后的容量保持率仍有77.5%,远高于前者的30.4%。     

熔融浸渍法制备锂离子电池正极材料LiMn2O4的研究

采用LiNO3和MnO2为原料,在650℃下制备了尖晶石型的LiMn2O4.通过X射线衍射、扫描电子显微镜、热重分析和电化学性能测试,发现该化合物具有很高的放电比容量和较好的循环性能,首次放电比容量可达到122 mA·h/g.并对循环性能衰减的各种因素进行了讨论.     

Effects of AgNPs-coating on the electrochemical performance of LiMn2O4 cathode material for lithium-ion batteries

Journal of Solid State Electrochemistry - The Jahn–Teller effect and severe side reactions with liquid electrolyte have been considered as the main obstacles to the further application of...     

尖晶石LiMn2O4的合成工艺与评价

本文采用不同的起始原料,分别用Pechini法、熔融盐浸渍法和沉淀转化法制备用于锂离子电池正极材料的尖晶石锰酸锂LiMnO4,结合化学分析和X射线衍射分析对产物进行表征.实验结果表明,三种工艺均能制备单相尖晶石,晶格参数与纯LiMn2O4一致:Pechini法制得的产物晶粒度和颗粒尺寸最小,分别为～17nm和～1.5μm.由于三种工艺分别制备了高活性的前驱物,反应组分混合均匀,使固相合成反应能在800℃下6～8小时完成.同时,热处理制度的研究表明,提高煅烧温度可能引起锰的还原,而延长煅烧时间会促进锰的氧化,有助于获得不缺氧的尖晶石.在实验的三种工艺路线中,沉淀转化法是最有希望工业化的.