Surface modification of LiMn2O4 cathode with LaCoO3 by a molten salt method for lithium ion batteries

Spinel LiMn₂O₄ is a promising cathode due to its advantages of low-cost, nontoxicity and thermal stability. However, the dissolution of manganese and the phase transformation induce the rapid capacity fade. Surface coating is an effective method to improve its electrochemical performance. In this work, spinel LiMn₂O₄ modified with perovskite LaCoO₃ was prepared using a novel molten salt method. The resulted samples were characterized by X-ray diffraction (XRD), transmission/scanning electron microscopy (TEM/SEM), Fourier transformation infrared (FT-IR), Raman, and X-ray photoelectronic spectroscopy. The content of Mn³⁺ increased with the LaCoO₃ coating accompanied by the increased concentration of oxygen vacancy. LiMn₂O₄ modified with 2% LaCoO₃ shows a higher capacity and cycling stability than others at 0.2 C, while the cathode with 4% LaCoO₃ shows the best rate performance at a larger current at 2 and 5 C. This enhanced performance can be attributed to improved interfacial conductivity between the cathode and electrolyte and the protective effects of coating.     

Li2ZnTi3O8@α-Fe2O3 composite anode material for Li-ion batteries

Li₂ZnTi₃O₈@α-Fe₂O₃ composites have been successfully prepared by a facile hydrothermal process. Li₂ZnTi₃O₈/α-Fe₂O₃ composites show similar irregular spherical morphologies like Li₂ZnTi₃O₈ and relatively smaller particle sizes than pristine Li₂ZnTi₃O₈. Among all Li₂ZnTi₃O₈/α-Fe₂O₃ composites, Li₂ZnTi₃O₈/α-Fe₂O₃ composite (5 wt%) exhibits the best electrochemical properties. Li₂ZnTi₃O₈/α-Fe₂O₃ composite (5 wt%) delivers a reversible charge capacity of 184.8 mAh g^?1 even at 1000 mA g^?1 after 500 cycles, while pristine Li₂ZnTi₃O₈ only delivers a reversible charge capacity of 110.7 mAh g^?1. The strong covalent bonds between Li₂ZnTi₃O₈ and α-Fe₂O₃ will be formed, which is beneficial for the reduction of interfacial energy and thus helpful for the stabilization of the composite. Because of the special synergistic effect of the multi-phase interface, Li₂ZnTi₃O₈/α-Fe₂O₃ composites not only possess the advantages of single components but also show novel and attractive performances, such as the enhanced ionic conductivity, reduced interfacial charge transfer impedance, improved migration rate of lithium ions, and the enhancement of the rate performance and reversible capacity. The as-prepared Li₂ZnTi₃O₈/α-Fe₂O₃ composites reveal important potentials as anode materials for next-generation rechargeable Li-ion batteries, and this work also offers an effective strategy to design high performance lithium storage materials for advanced lithium-ion batteries.     

A single-source molten salt synthesis of rod-shaped Na2Ti6O13 crystals

As one of the most potential negative electrode materials, Na₂Ti₆O₁₃ is expected to play an important role in the area of high-performance battery. In this work, we have developed an easy, efficient and controllable method to prepare rod-shaped Na₂Ti₆O₁₃ crystals. This approach utilized a single-source molten salt strategy and only needed to sinter a special precursor synthesized from an aqueous solution containing H₃BO₃ and (NH₄)₂TiF₆ in presence of sodium salts. The component and shape of precursor crystals can be tuned by adjusting the reagent concentration and reaction temperature. By sintering precursor crystals in air at 900 °C for 30 min, Na₂Ti₆O₁₃ with high crystallinity and purity can be obtained. X-ray diffraction and scanning electron micrographs results of different sintering times show that the sintering process can be divided into two steps. Firstly, the precursor crystals are converted to TiO₂ (anatase) nano-particles and amorphous sodium salts. Subsequently, molten salt reaction occurs between amorphous sodium salts and TiO₂ and forms rod-shaped Na₂Ti₆O₁₃ crystals.     

One-step synthesis of recoverable CuCo2S4 anode material for high-performance Li-ion batteries

A facile one-step hydrothermal method has been adopted to directly synthesize the CuCo₂S₄ material on the surface of Ni foam. Due to the relatively large specific surface area and wide pore size distribution, the CuCo₂S₄ material not only effectively increases the reactive area, but also accommodates more side reaction products to avoid the difficulty of mass transfer. When evaluated as anode for Li-ion batteries, the CuCo₂S₄ material exhibits excellent electrochemical performance including high discharge capacity, outstanding cyclic stability and good rate performance. At the current density of 200 mA·g⁻¹, the CuCo₂S₄ material shows an extremely high initial discharge capacity of 2510 mAh·g⁻¹, and the cycle numbers of the material even reach 83 times when the discharge capacity is reduced to 500 mAh·g⁻¹. Furthermore, the discharge capacity can reach 269 mAh·g⁻¹ at a current of 2000 mA·g⁻¹. More importantly, when the current density comes back to 200 mA·g⁻¹, the discharge capacity could be recovered to 1436 mAh·g⁻¹, suggesting an excellent capacity recovery characteristics.     

Facile synthesis of spinel LiNi0.5Mn1.5O4 as 5.0 V-class high-voltage cathode materials for Li-ion batteries

LiNi_0.5Mn_1.5O₄ and LiMn₂O₄ with novel spinel morphology were synthesized by a hydrothermal and post-calcination process. The synthesized LiMn₂O₄ particles (5-10 μm) are uniform hexahedron, while the LiNi_0.5Mn_1.5O₄ has spindle-like morphology with the long axis 10-15 μm, short axis 5-8 μm. Both LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ show high capacity when used as cathode materials for Li-ion batteries. In the voltage range of 2.5-5.5 V at room temperature, the LiNi_0.5Mn_1.5O₄ has a high discharge capacity of 135.04 mA·h·g^-1 at 20 mA·g^-1, which is close to 147 mA·h·g^-1 (theoretical capacity of LiNi_0.5Mn_1.5O₄). The discharge capacity of LiMn₂O₄ is 131.08 mA·h·g^-1 at 20 mA·g^-1. Moreover, the LiNi_0.5Mn_1.5O₄ shows a higher capacity retention (76%) compared to that of LiMn₂O₄ (61%) after 50 cycles. The morphology and structure of LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ are well kept even after cycling as demonstrated by SEM and XRD on cycled LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ electrodes.     

硬币状氧化镍的制备及其电化学性能研究

通过均匀沉淀法,以氨水作为络合剂,制备了β-氢氧化镍,经450℃煅烧处理得到纳米氧化镍,通过充放电测试和循环伏安测试研究了该产物作为锂离子电池负极材料的电化学性能.XRD、IR表明,反应产物为纯相,SEM和TEM表明,产物形貌为硬币状的特殊形貌.在放电电位区间0.01～3.0 V vs Li/Li＋,0.2C倍率下充放电,初始容量1 050 mAh/g,第2次容量损失35.8％,50次循环后,质量比容量为355 mAh/g,硬币状纳米氧化镍其特殊的形貌具有较大的比表面积,增加了电化学活性点,降低了界面反应的极化,从而提高了NiO电极的电化学性能.     

锂离子电池正极材料LiMn_2O_4的合成与性能改进

用传统的高温固相法合成了尖晶石型LiMn_(195)La_(0.05O4)锂离子电池正极材料.通过充-放电测试,其最高容量为117.1mAh/g,经过50次循环后容量为108.4 mAh/g,平均每次循环的容量衰减率为0.15%.利用X射线衍射仪(XRD)和电子扫描电镜(SEM)对材料进行表征.XRD测试结果表明,样品为尖晶石结构;SEM结果表明,样品颗粒形状理想,粒径分布均匀.     

Effect of Fe-doping followed by C+SiO2 hybrid layer coating on Li3V2(PO4)3 cathode material for lithium-ion batteries

A novel Li₃V₂(PO₄)₃ composite modified with Fe-doping followed by C+SiO₂ hybrid layer coating (LVFP/C-Si) is successfully synthesized via an ultrasonic-assisted solid-state method, and characterized by XRD, XPS, TEM, galvanostatic charge/discharge measurements, CV and EIS. This LVFP/C-Si electrode shows a significantly improved electrochemical performance. It presents an initial discharge capacity as high as 170.8 mA h g⁻¹ at 1 C, and even delivers an excellent initial capacity of 153.6 mA h g⁻¹ with capacity retention of 82.3% after 100 cycles at 5 C. The results demonstrate that this novel modification with doping followed by hybrid layer coating is an ideal design to obtain both high capacity and long cycle performance for Li₃V₂(PO₄)₃ and other polyanion cathode materials in lithium ion batteries.     

On the sol-gel synthesis mechanism of nanostructured Li3.95La0.05Ti4.95Ag0.05O12 with enhanced electrochemical performance for lithium ion battery

A modified sol-gel process using ethylene diamine tetraacetic acid and citric acid as bi-components chelating agent was used to prepare Li_3.95La_0.05Ti_4.95Ag_0.05O₁₂ (LLTAO). The reactions between raw materials and the possible route of hydrolysis-sintering processes were detailed analyzed and studied. The phases forming mechanism and structure of the colloidal particles, gel and the precursor were also discussed. Interface reaction between chelating agents and precipitate contributes a lot to the products. XRD, SEM, FT-IR, TEM and TG-DSC were used to characterize the intermediates and final powders. The intermediate product of Li and Ti is in nanometer scale, uniformly distributed in precursor. The La³⁺ and Ag⁺ co-doping could greatly improve the electrochemical performance of LTO, which reached the capacity of 179, 168, 163, 151, 133, 109 and 76 mA h g⁻¹ at 0.5C, 1C, 2C, 5C, 10C, 20C and 40C discharge rate, respectively. The electrochemical performance of lithium intercalation/extraction was characterized by electrochemical impedance spectroscopy at room temperature.     

A novel method for preparation of macroposous lithium nickel manganese oxygen as cathode material for lithium ion batteries

A simple one-step route using gas template method is applied to synthesize macroporous LiNi_0.5Mn_0.5O₂ which is characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Telle (BET) surface area, charge–discharge tests and electrochemical impedance spectroscopy (EIS) measurements. The as-synthesized material shows pure crystalline phase of LiNi_0.5Mn_0.5O₂, while the microstructure is comprised of macrospores ranging from 0.2 to 0.5 μm. The first discharge capacity is of 174 mAh g⁻¹ at 0.1 C rate, which is much higher than that of the material synthesized by the conventional solid state reaction method. Furthermore, the macroporous LiNi_0.5Mn_0.5O₂ material shows remarkable rate capacity and cycle stability, which may be attributed to the shorter lithium ion diffusion distance and better electrolyte penetration.     

Molten salt synthesis of LiNi0.5Mn1.5O4 spinel for 5 V class cathode material of Li-ion secondary battery

Well-ordered high crystalline LiNi_0.5Mn_1.5O₄ spinel has been readily synthesized by a molten salt method using a mixture of LiCl and LiOH salts. Synthetic variables on the synthesis of LiNi_0.5Mn_1.5O₄, such as synthetic atmosphere, LiCl salt amount, synthetic temperature, and synthetic time, were intensively investigated. X-ray diffraction (XRD) patterns and scanning electron microscopic (SEM) images showed that LiNi_0.5Mn_1.5O₄ synthesized at 900 and 950 °C have cubic spinel structure () with clear octahedral dimension. LiNi_0.5Mn_1.5O₄ spinel phase began to decompose at around 1000 °C accompanied with structural and morphological degradation. LiNi_0.5Mn_1.5O₄ powders synthesized at 900 °C for 3 h delivered an initial discharge capacity of 139 mAh/g with excellent capacity retention rate more than 99% after 50 cycles.     

锂离子电池正极材料镍酸锂研究进展

镍酸锂具有比容量高、污染小、价格适中、与电解液匹配好等优点，被认为是一种较有发展前景的锂离子电池正极材料。但它合成困难，循环稳定性差。近几年来一些研究人员从合成方法、掺杂改性等方面对镍酸锂做了大量的研究工作。介绍了作为锂离子电池正极材料的镍酸锂的结构特征、电化学性能及现阶段存在的问题；综述了近几年来国内外的电化学研究者对锂离子电池正极材料镍酸锂的合成及稀土掺杂方面的研究进展和稀土掺杂对镍酸锂的结构和电化学性能的影响；并对镍酸锂未来的发展方向做了展望。     

用于锂离子电池负极SnO2MCMB复合材料的研究

以中间相碳微球(MCMB)为核心,用直接沉淀法制备了一种氧化锡颗粒修饰的新型复合碳材料.用X射线衍射和扫描电镜对材料的结构及形貌进行了表征.通过恒流充放电、交流阻抗、循环伏安等测试手段对该材料的嵌脱锂特性进行了研究,循环20周后其比容量仍然保持在360 mAh/g以上.此种复合物可以作为一种锂离子电池新型负极材料.     

Effect of LiF dosage on morphology of ZrO2 prepared by the molten salt method

Zirconia nanorods and polyhedral particles were prepared using the molten-salt method. The effects of the LiF dosage on the ZrO₂ crystal morphology were studied using XRD combined with Rietveld refinement, FE-SEM combined with EDS, FTIR, Raman spectroscopy, and high-temperature microscopy. The results show that the ZrO₂ obtained with LiF is in the monoclinic phase. ZrO₂ nanorods were synthesized at low LiF dosages. Polyhedral ZrO₂ particles were synthesized, and the ZrO₂ crystal planes (100) and (200) were exposed to a high LiF dosage. LiF promoted the dissolution of ZrO₂ and was adsorbed onto the ZrO₂ crystal surface. This work provides a new strategy for controlling morphology and crystal surface exposure.     

Hydrothermal synthesis of spherical Li4Ti5O12 material for a novel durable Li4Ti5O12/LiMn2O4 full lithium ion battery

Pure spherical Li₄Ti₅O₁₂ spinel material is quickly synthesized via an efficient hydrothermal procedure. The obtained Li₄Ti₅O₁₂ particle size is about 0.5 µm. The Li₄Ti₅O₁₂ has an initial discharge capacity of 162.2 mA h g⁻¹ and capacity retention of 97.5% after 100 cycles at a rate of 0.2 C. Then, a 2.5 V and long-lasting Li-ion cell with a LiMn₂O₄ cathode and a Li₄Ti₅O₁₂ anode is developed. Electrochemical measurements of the cell indicate that the Li₄Ti₅O₁₂/LiMn₂O₄ full cell, with a weight ratio of 1.5 between cathode and anode, exhibits excellent electrochemical performance, delivering a reversible capacity of 130 mA h g⁻¹ at room temperature. The full cell also exhibits outstanding electrochemical performances at high temperature, as it has an initial discharge capacity of 109.6 mA h g⁻¹, along with a capacity retention rate of 88.9% after 100 cycles at 55 °C.     

锂离子电池正极材料Li2FeSiO4的研究进展

综述了合成Li2FeSiO4的方法,着重介绍了固相、溶胶-凝胶、水热、微波等几种主要的合成方法,并针对Li2FeSiO4电导率低的缺点,详细阐述了Li2FeSiO4电化学性能的改善方法,包括材料纳米化、孔状材料的制备、碳包覆和离子掺杂等。探讨了当前存在的问题及未来的研究方向。     

Structural,microstructural and electrochemical studies on LiMn2-x(GdAl)xO4 with spinel structure as cathode material for Li-ion batteries

Gd and Al co-doped LiMn_2-x(GdAl)_xO₄ (x?=?0, 0.01, 0.02, 0.03, 0.04 and 0.05) materials with spinel structure were synthesized by sol–gel method. Powder X-ray diffraction results confirm the formation of cubic spinel structure and average particle sizes are found to be between 80 and 110?nm from FE-SEM and TEM analysis. Decrease in peak potential difference as a function of doping in Cyclic Voltammetry results establishes enhancement in Li⁺ intercalation and de-intercalation. Electrochemical Impedance Spectroscopy (EIS) results showed that accumulation of charges on electrode has improved with doping over pristine samples. At a doping of x?=?0.02 charge transfer resistance values were found to be least. First cycle charge–discharge profiles for LiMn_1.96(GdAl)_0.02O₄ shows 139.2?mAh/g discharge capacity over other doped derivatives and pure LiMn₂O₄ (119.6?mAh/g) in aqueous Li₂SO₄ electrolyte. Doping of x?=?0.02 exhibit good cycling performance with only a total 4% capacity loss after 30 cycles.     

Study on the performance characteristics of Li–V–O nanocomposite as cathode material for Li-ion batteries

The Li–V–O composite (n_Li:n_V = 1:3.5) was synthesized by a hydrothermal method and post-treated at 300 °C. XRD analysis confirms that the composite is a binary LiV₃O₈–V₂O₅ composite system with the formula of 0.8LiV₃O₈·0.2V₂O₅. The composite consists of small laminar nanocrystallites with numerous cavities between the stacked laminar nanocrystallites, which can provide good channels for Li⁺ transfer during charge–discharge cycling. The initial discharge capacities of LiV₃O₈ and 0.8LiV₃O₈·0.2V₂O₅ samples were 276 and 365 mAh/g after 20 cycles, the discharge capacities of the two samples were 197.6 and 304 mAh/g, respectively. Smaller capacity loss indicates that the capacity retention of the composite is superior to that of bare LiV₃O₈ cathode.     

Research on saggars of lightweight design used to prepare cathode materials for Li-ion batteries

The focus of lightweight refractory is equivalent volume replacement that uses lower-density raw materials to replace the original high-density raw materials. In this study, we employ porous mullite microspheres (PMM) to replace mullite particles to realize the weight-lighting of mullite–cordierite saggars used to prepare cathode materials for Li-ion batteries.To confirm that lightweight saggars satisfy the quality standards of production, we conducted various tests, including mechanical properties, thermal shock stability and corrosion resistance. Compared with samples with mullite particles, samples with PMM have a comparatively stable material structure and excellent performance. Furthermore, PMM reduce mullite consumption and enhance their resistance to prevent stress shedding in the corrosion process.     

水热法制备正交结构层状LiMnO2正极材料的研究进展

层状LiMnO2正极材料的理论容量几乎为尖晶石型锰酸锂（LiMn2O4）的2倍,研究和应用前景广阔.作者较详细的介绍了近年来国内外有关水热法制备层状LiMnO2正极材料的研究工作,评述了由不同锰源制备层状LiMnO2正极材料所存在的优缺点,对今后水热法制备层状LiMnO2正极材料的研究及发展前景进行了展望.