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1.
采用固相燃烧法快速合成了LiNi0.08FexMn1.92-xO4(x≤0.08)正极材料,并探究了正极材料样品的结构、形貌、电化学性能及动力学性能。结果表明,Ni-Fe共掺没有改变LiMn2O4的立方尖晶石结构,促进了其晶体发育和{111}、{110}、{100}晶面的择优生长,部分颗粒形成了以高暴露{111}晶面为主和少量{110}、{100}晶面的截断八面体形貌。LiNi0.08Fe0.05Mn1.87O4样品在较低倍率(≤5 C)时,其倍率性能和长循环寿命得到显著提高,在25℃下,1 C的首次放电比容量为106.1 mAh/g, 1 000次循环后容量保持率为82.0%;5 C的首次放电比容量为100.1 mAh/g, 2 000次循环后容量保持率为72.8%。LiNi0.08Fe0.05Mn1.87 相似文献
2.
本文实验以Mn3O4为锰源和Li2CO3为锂源,对不同温度制备的尖晶石型LiMn2O4的结构和电化学性能进行了分析研究。XRD分析测试表明在不同温度段制得的尖晶石LiMn2O4均为纯相;SEM分析测试表明不同温度制得的尖晶石LiMn2O4晶粒大小均匀,随着煅烧温度上升LiMn2O4晶粒逐渐长大。尖晶石LiMn2O4的电化学性能测试结果表明,在650~750℃范围煅烧的尖晶石LiMn2O4要优于750℃以上煅烧的样品。 相似文献
3.
尖晶石型Li Mn2O4正极材料由于Jahn–Teller效应和Mn溶解,在充放电过程中容量衰减严重,循环稳定性差。联合元素掺杂和单晶形貌调控策略,采用固相燃烧法制备了具有{111}、{100}和{110}晶面的去顶角八面体单晶LiFe0.12Mn1.88O4正极材料。研究结果表明,Fe掺杂没有改变尖晶石型Li Mn2O4的晶体结构,有效抑制了Jahn–Teller效应,促进了材料的结晶性及{400}和{440}衍射峰晶面的择优生长,表现出良好的倍率性能和容量保持率。在25℃,1 C和5 C倍率下LiFe0.12Mn1.88O4的首次放电比容量分别为105.2 mA·h/g和92.4 mA·h/g,1 000次循环后容量保持率分别为71.1%和75.2%;在高倍率10 C下,经1 000次循环后,其容量保持率可达到88.4%。在55℃和1 C条件下,首次放电比容量为10... 相似文献
4.
利用微波辅助双模板法、软模板法制备了一系列的CeO2/g-C3N4复合催化材料,通过XRD、N2吸附-脱附、XPS、SEM和TEM等方式对材料进行表征,并对其湿式催化性能进行研究。结果表明,双模板法制备的D-CeO2/g-C3N4复合材料表现出立方相CeO2和层叠g-C3N4的特征,比表面积和孔径较大,属于介孔结构,表面存在Ce3+和Ce4+,有利于氧空位的形成。加入1 g嵌段共聚物 F127,使用无水乙醇溶液为溶剂,调节混合液呈碱性,微波辐射反应120 min后得到的D-CeO2/g-C3N4(7.5)样品,结构完整均匀,具有最佳形貌特征。控制反应温度75 ℃,D-CeO2/g-C3N4(7.5)投加0.7 g,H2O2投加 0.5 mL,初始pH值为5时,100 mg/L的苯酚溶液COD去除率可达80%以上。 D-CeO2/g-C3N4(7.5) 复合催化材料使用五次以后仍可达60%以上的催化降解效果。 相似文献
5.
LiMn2O4作为锂离子电池正极材料得到了广泛的研究,文章对LiMn2O4及其衍生物作为正极材料的研究进行归纳和总结。 相似文献
6.
以十水合碳酸钠(SCD)、十二水合磷酸氢二钠(DHPD)为相变主体,制备了低过冷度,无相分离的共晶水合盐(EHS),以九水合硅酸钠为成核剂。进一步使用气相SiO2为支撑材料,采用浸渍法制备了相变前后形状稳定的 EHS/SiO2定形相变储能材料(SSPCM)。所得SSPCM的相变温度为 24.08 ℃,焓值为 146.6 J/g,过冷度为 0.55 ℃,热导率为 0.5454 W/m?K。同保温泡沫相比,其可将模拟房内部中心温度的升温时间延长 3.26 倍,降温时间延长 1.39 倍,具有优异的“热缓冲”性能,在建筑节能领域具有广阔的应用前景。 相似文献
7.
为了提高微生物燃料电池(MFC)对沼液中有机质的降解和产电效率,将纳米Fe3O4与MFC结合,对比研究了纳米Fe3O4以Fe3O4@生物炭和Fe3O4@碳毡两种不同介入方式对MFC性能的影响。结果表明,两种方式均可成功启动MFC,且产电效率远高于无纳米Fe3O4介入的空白实验,最高电压分别为699和707 mV,最高电压均持续时间长达10 d。Fe3O4@碳毡与Fe3O4@生物炭介入下MFC最大功率密度分别为700和578 mW/m2,相较于未使用纳米Fe3O4的MFC提高了43%和31%。将Fe3O4@碳毡作为阳极电极得到的化学需氧量(COD)降解率最高,为51.76%;直接投加Fe3O4@生物炭对NH4+-N的降解影响最大,投加Fe3O4@生物炭后NH4+-N含量由(6800.14±57.86) mg/L降至(689.14±37.29) mg/L,NH4+-N降解率达到89.87%。纳米Fe3O4参与的MFC微生物群落结构合理,两种介入方式均刺激了主要水解细菌梭菌纲(Clostridia)的生长富集。随着纳米Fe3O4的位置变化,Clostridia的相对丰度在以Fe3O4@生物炭和Fe3O4@碳毡介入的MFC中分别达到61.11%、50.98%。二者的电活化细菌中β-变形菌纲(Betaproteobacteria)含量最高,并且在反应后碳毡上发现了反硝化细菌芽孢八叠球菌属(Sporosarcina)。 相似文献
8.
利用水热法将MnFe2O4负载在生物质气化炭渣(CR)得到负载型复合催化剂MnFe2O4-CR,通过SEM、XRD、XPS、BET和VSM等技术对复合催化剂进行表征,并将其用于活化过一硫酸盐(PMS)降解盐酸四环素(TC)。考察了不同反应体系、催化剂的不同复合比例、PMS用量、催化剂用量、温度、pH、阴离子(HCO3–、H2PO4–、Cl–、NO3–)和腐植酸(HA)对MnFe2O4-CR/PMS体系降解TC的影响,并探究了MnFe2O4-CR的稳定性和循环使用性,探讨了MnFe2O4-CR/PMS体系中TC可能的降解机理。结果表明,MnFe2O4与炭渣的质量比为1∶2时制备的MnFe2O4-CR催化效果良好,在30 ℃,30 mg MnFe2O4-CR催化40 mg PMS,在90 min内对100 mL质量浓度为50 mg/L自然pH的TC溶液中TC的降解率达到91.32%;MnFe2O4-CR可利用其磁性回收,经过5次循环利用,催化PMS降解TC的降解率仍能达到82.90%。表明MnFe2O4-CR具有良好的稳定性和重复使用性。自由基淬灭实验表明,MnFe2O4-CR/PMS体系中,SO4??、?OH 、1O2 和O2??是降解TC的主要活性氧物种,并提出了相应的催化降解机理。 相似文献
9.
以LiNO3、Ni(NO3)2·6H2O、Mn(NO3)2为主要原料,尿素作燃料,采用低温燃烧法合成了亚微米级、电化学性能良好、单晶形貌的5 V锂离子电池正极材料LiNi0.5Mn1.5O4。考察了不同回火温度对所合成产物的结构、形貌和电化学性能的影响,并通过X射线衍射、扫描电镜和充放电实验对不同回火温度下合成的产物进行了表征。实验结果表明,在不同回火温度得到的样品均具有尖晶石结构。但是在回火温度为800℃和900℃下合成的样品产生了较多的杂质相,随着回火温度的升高,合成产物的结晶度逐渐提高,粒径逐渐增大。在回火温度为850℃得到的样品成清晰的八面体外形,结晶良好,粒径适中,在3.5~4.9 V内0.1 C倍率下首次放电容量最高,30次循环后其容量保持率最好,其电化学性能最好。 相似文献
10.
采用喷雾干燥法、共沉淀法、固相法3种方法制备化学计量式为Li1.2Ni0.17Co0.07Mn0.56O2的锂离子电池富锂正极材料。电化学测试表明,喷雾干燥法制备的材料电化学性能最好,0.1 C充放电首圈脱锂和嵌锂容量分别为283.9 mA/(h?g)和231.7 mA/(h?g)。与共沉淀法和固相法相比较,喷雾干燥法制备的材料1 C倍率充放电时表现出良好的循环稳定性,50次循环后容量没有衰减,仍为153.4 mA/(h?g),共沉淀法和固相法制备的材料50次循环放电容量分别为133.5 mA/(h?g)和123.6 mA/(h?g)。ICP分析结果指出,喷雾干燥法制备的电极材料元素比例最符合初始的Li1.2Ni0.17Co0.07Mn0.56O2设计配比。而且喷雾干燥法制备的材料颗粒更为细小均匀,有利于提高材料的电化学性能。 相似文献
11.
Fei CaoJai Prakash 《Electrochimica acta》2002,47(10):1607-1613
Novel Electrostatic Spray Deposition (ESD) technique was used to fabricate LiMn2O4 spinel thin-films. Cyclic voltammograms of both the ESD and porous laminate films show the double peaks in the 4.0 V range characteristic of the LiMn2O4 spinel materials. The porous laminates exhibit two semicircles in the impedance spectra while the ESD films show only one single semicircle. The diffusion time constant in the laminate films was typically one order of magnitude larger than that in the ESD thin-films. The apparent lithium-ion chemical diffusion coefficient in LiMn2O4 was found to be of the order of 10−9 cm2/s for both the porous laminate film and the ESD films despite the difference in the diffusion time constants. 相似文献
12.
Micro-spherical particle of MnCO3 has been successfully synthesized in CTAB-C8H18-C4H9OH-H2O micro-emulsion system. Mn2O3 decomposed from the MnCO3 is mixed with Li2CO3 and sintered at 800 °C for 12 h, and the pure spinel LiMn2O4 in sub-micrometer size is obtained. The LiMn2O4 has initial discharge specific capacity of 124 mAh g−1 at discharge current of 120 mA g−1 between 3 and 4.2 V, and retains 118 mAh g−1 after 110 cycles. High-rate capability test shows that even at a current density of 16 C, capacity about 103 mAh g−1 is delivered, whose power is 57 times of that at 0.2 C. The capacity loss rate at 55 °C is 0.27% per cycle. 相似文献
13.
Pure-phase and well-crystallized spinel LiMn2O4 powders as cathode materials for lithium-ion batteries were successfully synthesized by a new simple microwave-assisted rheological phase method, which was a timesaving and efficient method. The physical properties of the as-synthesized samples compared with the pristine LiMn2O4 obtained from the rheological phase method were investigated by thermogravimetry analysis (TGA), X-ray diffraction (XRD) and scanning electronic microscope (SEM). The as-prepared powders were used as positive materials for lithium-ion battery, whose charge/discharge properties and cycle performance were examined in detail. The powders resulting from the microwave-assisted rheological phase method were pure, spinel structure LiMn2O4 particles of regular shapes with distribution uniformly, and exhibited promising electrochemical properties for battery. Furthermore, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the reactions of Li-ion insertion into and extraction from LiMn2O4 electrode. 相似文献
14.
Spherical LiMn2O4 particles were successfully synthesized by dynamically sintering spherical precursor powders, which were prepared by a slurry spray-drying method. The effect of the sintering process on the morphology of LiMn2O4 was studied. It was found that a one-step static sintering process combined with a spray-drying method could not be adopted to prepare spherical products. A two-step sintering procedure consisting of completely decomposing sprayed precursors at low temperature and further sintering at elevated temperature facilitated spherical particle formation. The dynamic sintering program enhanced the effect of the two-step sintering process in the formation of spherical LiMn2O4 powders. The LiMn2O4 powders prepared by the dynamic sintering process, after initially decomposing the spherical spray-dried precursor at 180 °C for 5 h and then sintering it at 700 °C for 8 h, were spherical and pure spinel. The as-prepared spherical material had a high tap density (ca. 1.6 g/cm3). Its specific capacity was about 117 mAh/g between 3.0 and 4.2 V at a rate of 0.2 C. The retention of capacity for this product was about 95% over 50 cycles. The rate capability test indicated that the retention of the discharge capacity at 4C rate was still 95.5% of its 0.2 rate capacity. All the results showed that the spherical LiMn2O4 product made by the dynamic sintering process had a good performance for lithium ion batteries. This novel method combining a dynamic sintering system and a spray-drying process is an effective synthesis method for the spherical cathode material in lithium ion batteries. 相似文献
15.
Spherical spinel LiMn2O4 particles were successfully synthesized from a mixture of manganese compounds containing commercial manganese carbonate by sintering of the spray-dried precursor. Different preparation routes were investigated to improve the tap density and to enhance the electrochemical performance of LiMn2O4. The structure and morphology of the LiMn2O4 particles were confirmed by X-ray diffraction (XRD) and scanning electron microscopy. The results showed that hollow spherical LiMn2O4 particles could be obtained when only commercial MnCO3 was used as the manganese source. These particles had a low tap density (ca.0.8 g/cm3). Perfect micron-sized spherical LiMn2O4 particles with good electrochemical performance were obtained by spray-drying a slurry composed of MnCO3, Mn(CH3CHOO)2 and LiOH, followed by a dynamic sintering process and a stationary sintering process. The as-prepared spherical LiMn2O4 particles comprised hundreds of nanosize crystal grains and had a high tap density(ca. 1.4 g/cm3). The galvanostatic charge-discharge measurements indicated that the spherical LiMn2O4 particles had an initial capacity of 121 mAh/g between 3.0 and 4.2 V at 0.2 C rate and still delivered a reversible capacity of 112 mAh/g at 2 C rate. The retention of capacity after 50 cycles was still 96% of its initial capacity at 0.2 C. All the results showed that the as-prepared spherical LiMn2O4 particles had an excellent electrochemical performances. The methods we used for preparing spherical LiMn2O4 are energy-saving and suitable for industrial application. 相似文献
16.
Ali Eftekhari 《Electrochimica acta》2003,48(19):2831-2839
Fractal dimension of a LiMn2O4 electrode prepared by sol-gel method was determined using electrochemical techniques based on the phenomenon of “diffusion towards electrode surface”. A simple discussion was made on the methodology to understand what is really estimated as the fractal dimension. It was demonstrated that the value of fractal dimension determined based on electrochemical methods is strongly dependent on the electrochemical system situation. This is generally true for all real electrodes involving insertion/extraction processes. This comes from the fact that surface morphology of the electrode is subject of significant changes during the electrochemical experiment. 相似文献
17.
Single crystalline cubic spinel LiMn2O4 nanowires were synthesized by hydrothermal method and the precursor calcinations. The phase structures and morphologies were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). Galvanostatic charging/discharging cycles of as-prepared LiMn2O4 nanowires were performed in an aqueous LiNO3 solution. The initial discharge capacity of LiMn2O4 nanowires was 110 mAh g−1, and the discharge capacity was still above 100 mAh g−1 after 56 cycles at 10C-rate, and then 72 mAh g−1 was registered after 130 cycles. This is the first report of a successful use of single crystalline spinel LiMn2O4 nanowire as cathode material for the aqueous rechargeable lithium battery (ARLB). 相似文献
18.
The cycling performance of LiMn2O4 at room and elevated temperatures is improved by FePO4 modification through chemical deposition method. The pristine and FePO4-coated LiMn2O4 materials are characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. Their cycling performances are thoroughly investigated and compared. The 3 wt.% FePO4-coated LiMn2O4 exhibits capacity losses of only 32% and 34% at room temperature and 55 °C, respectively, after 80 cycles, much better than those of the pristine material, 55% and 72%. The cyclic voltammograms at 55 °C reveal that the improvement in the cycling performance of FePO4-coated LiMn2O4 electrodes can be attributed to the stabilization of spinel structures. The separation of FePO4 between active materials and electrolyte and its interaction with SEI (solid electrolyte interphase) film are believed to account for the improved performances. 相似文献
19.
Sub-micro spinel-structured LiMn1.5Ni0.5O4 material was prepared by a spray-drying method. The electrochemical properties of LiMn1.5Ni0.5O4 were investigated using Li ion model cells, Li/LiPF6 (EC + DMC)/LiMn1.5Ni0.5O4. It was found that the first reversible capacity was about 132 mAh g−1 in the voltage range of 3.60-4.95 V. Ex situ X-ray diffraction (XRD) analysis had been used to characterize the first charge/discharge process of the LiMn1.5Ni0.5O4 electrode. The result suggested that the material configuration maintained invariability. At room temperature, on cycling in high-voltage range (4.50-4.95 V) and low-voltage range (3.60-4.50 V), the discharge capacity of the material was about 100 and 25 mAh g−1, respectively, and the spinel LiMn1.5Ni0.5O4 exhibited good cycle ability in both voltage ranges. However, at high temperature, the material showed different electrochemical characteristics. Excellent electrochemical performance and low material cost make this spinel compound an attractive cathode for advanced lithium ion batteries. 相似文献
20.
Synthesis of highly crystalline spinel LiMn2O4 by a soft chemical route and its electrochemical performance 总被引:1,自引:0,他引:1
Highly crystalline spinel LiMn2O4 was successfully synthesized by annealing lithiated MnO2 at a relative low temperature of 600 °C, in which the lithiated MnO2 was prepared by chemical lithiation of the electrolytic manganese dioxide (EMD) and LiI. The LiI/MnO2 ratio and the annealing temperature were optimized to obtain the pure phase LiMn2O4. With the LiI/MnO2 molar ratio of 0.75, and annealing temperature of 600 °C, the resulting compounds showed a high initial discharge capacity of 127 mAh g−1 at a current rate of 40 mAh g−1. Moreover, it exhibited excellent cycling and high rate capability, maintaining 90% of its initial capacity after 100 charge-discharge cycles, at a discharge rate of 5 C, it kept more than 85% of the reversible capacity compared with that of 0.1 C. 相似文献