In a novel attempt to exploit corn starch as gelling agent (in sol–gel method) and combustible fuel (in solution-assisted combustion method), high-capacity LiMn0.4Ni0.4Co0.2O2 and LiMn1/3Ni1/3Co1/3O2 cathode materials have been prepared and a comparison of electrochemical performance of the same has been made. Among the two compounds chosen for the study, LiMn1/3Ni1/3Co1/3O2 exhibits better physical and electrochemical properties. Particularly, LiMn1/3Ni1/3Co1/3O2 cathode synthesized using corn starch-assisted combustion method exhibits an appreciable capacity of 176 mAh g?1, excellent capacity retention of 93 % up to 100 cycles and susceptible to rate capability test up to 1 C rate, thus qualifying the same for high-capacity and high-rate lithium battery applications. The study demonstrates the possibility of exploiting corn starch as gelling agent and as a combustible fuel in synthesizing lithium intercalating oxide compounds with improved electrochemical behaviour. 相似文献
P2‐type Na2/3Ni1/3Mn2/3O2 was synthesized by a controlled co‐precipitation method followed by a high‐temperature solid‐state reaction and was used as a cathode material for a sodium‐ion battery (SIB). The electrochemical behavior of this layered material was studied and an initial discharge capacity of 151.8 mA h g?1 was achieved in the voltage range of 1.5–3.75 V versus Na+/Na. The retained discharge capacity was found to be 123.5 mA h g?1 after charging/discharging 50 cycles, approximately 81.4 % of the initial discharge capacity. In situ X‐ray diffraction analysis was used to investigate the sodium insertion and extraction mechanism and clearly revealed the reversible structural changes of the P2‐Na2/3Ni1/3Mn2/3O2 and no emergence of the O2‐Ni1/3Mn2/3O2 phase during the cycling test, which is important for designing stable and high‐performance SIB cathode materials. 相似文献
采用碳酸盐共沉淀法通过调节NH_3·H_2O用量来实现可控制备超高倍率纳米结构LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料。NH_3·H_2O用量会对颗粒的形貌、粒径、晶体结构以及材料电化学性能产生较大的影响。X射线衍射(XRD)分析和扫描电镜(SEM)结果表明,随着NH_3·H_2O用量的降低,一次颗粒形貌由纳米片状逐渐过渡到纳米球状,且nNH_3·H_2O∶(nNi+nCo+nMn)=1∶2样品晶体层状结构最完善、Li~+/Ni~(2+)阳离子混排程度最低。电化学性能测试结果也证实了nNH_3·H_2O∶(nNi+nCo+nMn)=1∶2样品具有最优异的循环稳定性和超高倍率性能。具体而言,在2.7~4.3 V,1C下循环300次后的放电比容量为119 m Ah·g~(-1),容量保持率为81%,中值电压基本无衰减(保持率为97%)。在100C(18 Ah·g~(-1))的超高倍率下,放电比容量还能达到56 m Ah·g~(-1),具有应用于高功率型锂离子电池的前景。此NH_3·H_2O比例值对于共沉淀法制备其他高倍率、高容量的正/负极氧化物材料具有一定的工艺参考价值。 相似文献
LiNi1/3Co1/3Mn1/3O2 cathode materials for the application of lithium ion batteries were synthesized by carbonate co-precipitation routine using
different ammonium salt as a complexant. The structures and morphologies of the precursor [Ni1/3Co1/3Mn1/3]CO3 and LiNi1/3Co1/3Mn1/3O2 were investigated through X-ray diffraction, scanning electron microscope, and transmission electron microscopy. The electrochemical
properties of LiNi1/3Co1/3Mn1/3O2 were examined using charge/discharge cycling and cyclic voltammogram tests. The results revealed that the microscopic structures,
particle size distribution, and the morphology properties of the precursor and electrochemical performance of LiNi1/3Co1/3Mn1/3O2 were primarily dependent on the complexant. Among all as-prepared LiNi1/3Co1/3Mn1/3O2 cathode materials, the sample prepared from Na2CO3–NH4HCO3 routine using NH4HCO3 as the complexant showed the smallest irreversible capacity of 19.5 mAh g−1 and highest discharge capacity of 178.4 mAh g−1 at the first cycle as well as stable cycling performance (98.7% of the initial capacity was retained after 50 cycles) at
0.1 C (20 mA g−1) in the voltage range of 2.5–4.4 V vs. Li+/Li. Moreover, it delivered high discharge capacity of over 135 mAh g−1 at 5 C (1,000 mA g−1). 相似文献
Li(Mn1/3Ni1/3Co1/3)O2 cathode materials were fabricated by a hydroxide precursor method. Al2O3 was coated on the surface of the Li(Mn1/3Ni1/3Co1/3)O2 through a simple and effective one-step electrostatic self-assembly method. In the coating process, a NHCO3-H2CO3 buffer was formed spontaneously when CO2 was introduced into the NaAlO2 solution. Compared with bare Li(Mn1/3M1/3Co1/3)O2, the surface-modified samples exhibited better cycling performance, rate capability and rate capability retention. The Al2O3-coated Li(Mn1/3Ni1/3Co1/3)O2 electrodes delivered a discharge capacity of about 115 mAh·g?1 at 2 A·g?1, but only 84 mAh·g?1 for the bare one. The capacity retention of the Al2O3-coated Li(Mn1/3Ni1/3Co1/3)O2 was 90.7% after 50 cycles, about 30% higher than that of the pristine one. 相似文献
Spherical LiNi1/3Co1/3Mn1/3O2 powders have been synthesized from co-precipitated spherical metal hydroxide. The electrochemical performances of the LiNi1/3Co1/3Mn1/3O2 electrodes in 1 M LiNO3, 5 M LiNO3, and saturated LiNO3 aqueous electrolytes have been studied using cyclic voltammetry and ac impedance tests in this work. The results show that
LiNi1/3Co1/3Mn1/3O2 electrode in saturated LiNO3 electrolyte exhibits the best electrochemical performance. An aqueous rechargeable lithium battery containing LiNi1/3Co1/3Mn1/3O2 cathode, LiV2.9Ni0.050Mn0.050O8 anode, and saturated LiNO3 electrolyte is fabricated. The battery delivers an initial capacity of 98.2 mAh g−1 and keeps a capacity of 63.9 mAh g−1 after 50 cycles at a rate of 0.5 C (278 mA g−1 was assumed to be 1 C rate). 相似文献
Li(Ni1/3Co1/3Mn1/3)O2 microspheres with a tap density of 2.41 g cm−3 have been synthesized for applications in high power and high energy systems, using a simple rheological phase reaction route. Cyclic voltammograms (CV) showed no shift of anodic and cathodic peaks centred at 3.81, 3.69 V for the Ni2+/Ni4+ couple after first cycle. The results of power pulse area specific impedance (ASI) and differential scanning calorimetry (DSC) tests showed lower power impedance and increased thermal stability of the electrode at high rate. These merits mentioned above provided significant improved capacity and rate performance for Li(Ni1/3Co1/3Mn1/3)O2 microspheres, which 159, 147 mAh g−1 discharge capacity was delivered after 100 cycles between 2.5–4.6 V vs. Li at a different discharge rate of 2.5 C (500 mA g−1), 5 C and a constant 0.5 C charge rate, respectively. 相似文献
Porous structure Li[Ni1/3Co1/3Mn1/3]O2 has been synthesized via a facile carbonate co‐precipitation method using Li2CO3 as template and lithium‐source. The physical and electrochemical properties of the materials were examined by many characterizations including TGA, XRD, SEM, EDS, TEM, BET, CV, EIS and galvanostatic charge‐discharge cycling. The results indicate that the as‐synthesized materials by this novel method own a well‐ordered layered structure α‐NaFeO2 [space group: R‐3m(166)], porous morphology, and an average primary particle size of about 150 nm. The porous material exhibits larger specific surface area and delivers a high initial capacity of 169.9 mAh·g?1 at 0.1 C (1 C=180 mA·g?1) between 2.7 and 4.3 V, and 126.4, 115.7 mAh·g?1 are still respectively reached at high rate of 10 C and 20 C. After 100 charge‐discharge cycles at 1 C, the capacity retention is 93.3%, indicating the excellent cycling stability. 相似文献
Li‐rich layered oxide Li1.18Ni0.15Co0.15Mn0.52O2 (LNCM) is, for the first time, examined as the positive electrode for hybrid sodium‐ion battery and its Na+ storage properties are comprehensively studied in terms of galvanostatic charge–discharge curves, cyclic voltammetry and rate capability. LNCM in the proposed sodium‐ion battery demonstrates good rate capability whose discharge capacity reaches about 90 mA h g?1 at 10 C rate and excellent cycle stability with specific capacity of about 105 mA h g?1 for 200 cycles at 5 C rate. Moreover, ex situ ICP‐OES suggests interesting mixed‐ions migration processes: In the initial two cycles, only Li+ can intercalate into the LNCM cathode, whereas both Li+ and Na+ work together as the electrochemical cycles increase. Also the structural evolution of LNCM is examined in terms of ex situ XRD pattern at the end of various charge–discharge scans. The strong insight obtained from this study could be beneficial to the design of new layered cathode materials for future rechargeable sodium‐ion batteries. 相似文献
The discovery of the icosahedral phase (i‐phase) in rapidly quenched Ti1.6V0.4Ni1?xCox(x=0.02–0.1) alloys is described herein. The i‐phase occurs in a similar amount relative to the coexisting β‐Ti phase. The electron diffraction patterns show the distinct spot anisotropy, indicating that the i‐phase is metastable. The electrochemical hydrogen storage performances of these five alloy electrodes are also reported herein. The hydrogen desorption of nonelectrochemical recombination in the cyclic voltammetric (CV) response exhibits the demand for electrocatalytic activity improvement. A discharge capacity of 261.5 mA h g?1 was measured in a Ti1.6V0.4Ni0.96Co0.04 alloy electrode at 30 mA g?1 and 303 K and it is shown that an appropriate amount of Co element addition would enhance the cycling stability at the expense of high‐rate discharging ability.相似文献
A porous, hollow, microspherical composite of Li2MnO3 and LiMn1/3Co1/3Ni1/3O2 (composition: Li1.2Mn0.53Ni0.13Co0.13O2) was prepared using hollow MnO2 as the sacrificial template. The resulting composite was found to be mesoporous; its pores were about 20 nm in diameter. It also delivered a reversible discharge capacity value of 220 mAh g?1 at a specific current of 25 mA g?1 with excellent cycling stability and a high rate capability. A discharge capacity of 100 mAh g?1 was obtained for this composite at a specific current of 1000 mA g?1. The high rate capability of this hollow microspherical composite can be attributed to its porous nature.
Spherical Li[Ni0.5Mn0.3Co0.2]O2 was prepared by both the continuous hydroxide co-precipitation method and continuous carbonate co-precipitation method under different calcined temperatures. The physical properties and electrochemical behaviors of Li[Ni0.5Mn0.3Co0.2]O2 prepared by two methods were characterized by X-ray diffraction, scanning electron microscope, and electrochemical measurements. It has been found that different preparation methods will result in the differences in the morphology (shape, particle size, and tap density), structure stability, and the electrochemical characteristics (shape of initial charge/discharge curve, cycle stability, and rate capability) of the final product Li[Ni0.5Mn0.3Co0.2]O2. The physical and electrochemical properties of the spherical Li[Ni0.5Mn0.3Co0.2]O2 prepared by continuous hydroxide co-precipitation is apparently superior to the one prepared by continuous carbonate co-precipitation method. The optimal sample prepared by continuous hydroxide co-precipitation at 820 °C exhibits a hexagonally ordered layer structure, high special discharge capacity, good capacity retention, and excellent rate capability. It delivers high initial discharge capacity of 175.2 mAh g?1 at 0.2 C rate between 3.0 and 4.3 V, and the capacity retention of 98.8 % can be maintained after 50 cycles. While the voltage range is broadened up to 2.5 and 4.6 V vs. Li+/Li, the special discharge capacities at 0.2 C, 0.5 C, 1 C, 2 C, 5 C, and 10 C rates are as high as 214.3, 205.0, 198.3, 183.3, 160.1 and 135.2 mAh g?1, respectively. 相似文献
In this study, we report the first preparation of phase‐pure Co9S8 yolk–shell microspheres in a facile two‐step process and their improved electrochemical properties. Yolk–shell Co3O4 precursor microspheres are initially obtained by spray pyrolysis and are subsequently transformed into Co9S8 yolk–shell microspheres by simple sulfidation in the presence of thiourea as a sulfur source at 350 °C under a reducing atmosphere. For comparison, filled Co9S8 microspheres were also prepared using the same procedure but in the absence of sucrose during the spray pyrolysis. The prepared yolk–shell Co9S8 microspheres exhibited a Brunauer–Emmett–Teller (BET) specific surface area of 18 m2 g?1 with a mean pore size of 16 nm. The yolk–shell Co9S8 microspheres have initial discharge and charge capacities of 1008 and 767 mA h g?1 at a current density of 1000 mA g?1, respectively, while the filled Co9S8 microspheres have initial discharge and charge capacities of 838 and 638 mA h g?1, respectively. After 100 cycles, the discharge capacities of the yolk–shell and filled microspheres are 634 and 434 mA h g?1, respectively, and the corresponding capacity retentions after the first cycle are 82 % and 66 %. 相似文献
Quasi-spherical (Ni0.5Co0.2Mn0.3)(OH)2 precursor is prepared via a continuous hydroxide co-precipitation method using sodium lactate as the green chelating agent. A layered structure Li(Ni0.5Co0.2Mn0.3)O2 is synthesized by calcining the mixture of as-prepared precursor and Li2CO3 in air. X-ray photoelectron spectroscopy (XPS) indicates that Ni, Co, and Mn exist in the oxidation states of +2/+3, +3 and +4, respectively. The influence of calcination temperature on the structural, morphological, electrochemical properties of Li(Ni0.5Co0.2Mn0.3)O2 oxides are investigated in detail. As a result, the sample calcined at 850 °C shows excellent electrochemical performance, which could be ascribed to its good crystal structure, low cation disorder, appropriate crystallinity. This sample delivers an initial discharge capacity of 192.6 mA h g?1 with a coulombic efficiency of 89.5 % at a current density of 20 mA g?1, and exhibits good rate capability and stable cyclability. Finally, the electrochemical performance of the sodium lactate-derived sample is briefly compared with those of the oxalic acid-derived and ammonia-derived oxide. 相似文献