多元过渡金属氧化物钠离子电池电极材料的合成及性能研究

发布时间：2018-01-13 07:05

本文关键词：多元过渡金属氧化物钠离子电池电极材料的合成及性能研究　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：钠离子电池(SIBs)因其原料储量丰富、成本低廉等独特的优势,将会在大规模储能领域发挥巨大的作用。但钠离子半径较大,因此寻找理想的电极材料是钠离子电池发展的关键。P2型层状过渡金属氧化物因其结构稳定、离子迁移率高、理论比容量高等特点成为SIBs电极材料的研究热点。过渡金属元素的多种价态间不同的氧化还原电位使其具有多个工作电压,因此既可以作为钠离子电池正极材料也可以作为负极材料。本研究通过多种不同的合成方法来制备多元过渡金属氧化物电极材料,以期获得多种形貌,颗粒尺寸均一的产物,然后对电极材料进行表面处理,改善其电化学性能,并取得以下主要成果:(1)分别通过固相法和溶胶—凝胶法合成Na_(2/3)Ni_(1/6)Ti_(2/3)Co_(1/6)O_2(NNTC),探讨了两种制备方法的工艺参数,并将产物进行对比。通过固相法,以Na2CO3、NiO、TiO2、CoO为原料,在氩气保护下950℃煅烧12h制得直径约5μm,厚度约1-2μm的片状纯相NNTC;在溶胶—凝胶法中以钛酸丁酯、C4H6O4Ni·4H2O、C4H6O4Co·4H2O和Na2CO3为原料合成前躯体,然后在氩气保护下900℃煅烧12h合成出0.5-1μm颗粒状纯相NNTC。(2)为改善NNTC的导电性,以葡萄糖为原料对NNTC颗粒进行碳包覆,探讨了葡萄糖加入量对电池容量的影响。结果表明,当葡萄糖加入量为10 wt%时,NNTC/C复合材料具有最优异的电化学性能。NNTC/C在0.2-2.5V电压区间内,0.2C倍率下进行充放电测试,首次充/放电比容量为122/110 mA h g-1,在循环500次后,容量保持率依然能达到82%,表现出非常优异的电化学性能。XPS测试表明,在0.2-2.5V电压区间内进行充放电测试,随着钠离子的嵌入和脱出,电极材料中只有Ti4+/Ti3+氧化还原电对发生电位变化。非原位XRD的测试结果表明,在钠离子的迁移过程中,没有新物相的产生,仅会引起NNTC晶体1.5%的晶胞体积变化率,循环过程高度可逆。(3)分别通过固相法和共沉淀法合成Na_(2/3)Ni_(1/3)Mn_(2/3)O_2(NNM),探讨了两种制备方法的工艺参数,并将产物进行对比。通过固相法,以NaCO3、NiO、MnO2为原料,在空气中900℃煅烧12h可以制得直径为1-2μm,厚度约0.5-1μm圆片状NNM纯相;共沉淀法合成NNM过程中,以MnSO4·H2O和NiSO4·6H2O为溶质,NH4HCO3为沉淀剂,加入少量乙醇后室温下反应3h生成球形的MnCO3、NiCO3的共沉淀物,与NaCO3混合后在盐浴中空气气氛下900℃煅烧12h得到无规则形状,尺寸大小不一的NNM样品。(4)通过熔盐法,以葡萄糖为碳源在LiCl/KCl(2:3)混合盐体系中,氩气保护下400℃反应12h进行碳负载,合成了三维网状碳负载NNM的复合材料(NNM@C),改善了NNM的导电性。NNM@C电极材料碳含量约为9%时具有最优异的电化学性能,NNM@C和NNM以0.2C倍率在2-3.9V电压范围内充放电,放电比容量分别为93.18 mA h g-1和94.85 mA h g-1;在100次循环后,容量保持率分别为87%和49%,循环伏安和交流阻抗测试结果表明三维网状碳负载后的NNM@C导电性增强,电池内阻明显降低,纯相NNM进行碳负载后电化学性能明显提高。
[Abstract]:Sodium ion battery (SIBs) because of its abundant raw materials, low cost and other unique advantages, will be able to play a great role in the field of mass storage. But the sodium ion radius, so the electrode materials is to find an ideal development of sodium ion battery key type.P2 layered transition metal oxide because of its stable structure, high ion mobility the theory of high specific capacity, has become a research hotspot of SIBs electrode materials. Various valence states of transition metal elements between the different redox potential which has a plurality of working voltage, therefore can be used as cathode materials of sodium ion battery can also be used as anode material. The synthetic method by different preparation of multi-element transition metal oxide electrode materials, in order to obtain a variety of morphology, uniform particle size of the product, and then the electrode material for surface treatment, improve its electrochemical performance, and get to The main results: (1) respectively by solid phase method and sol gel method for synthesis of Na_ (2/3) Ni_ (1/6) Ti_ (2/3) Co_ (1/6) O_2 (NNTC), discusses the process parameters of two kinds of preparation methods, and the products were compared. The solid phase method, Na2CO3, NiO. TiO2, CoO as raw materials, preparation of diameter of about 5 m under the protection of argon 950 8C 12h, thickness of about 1-2 m sheet in pure phase NNTC; sol-gel method with tetrabutyl titanate, C4H6O4Ni, 4H2O, C4H6O4Co, 4H2O and Na2CO3 as the raw material for the synthesis of the precursor, and then under the protection of argon 900 calcined 12h synthesis of 0.5-1 m particulate phase pure NNTC. (2) to improve the conductivity of NNTC, using glucose as raw material of carbon coated NNTC particles, discusses the effect of glucose addition on battery capacity. The results showed that when glucose was added 10 wt%, NNTC/C composite has the best. The electrochemical properties of.NNTC/C in 0.2-2.5V voltage area In charge and discharge test 0.2C rate, the initial charge / discharge capacity of 122/110 mA h in g-1, after 500 cycles, the capacity retention rate can still reach 82%, showed excellent electrochemical performance of.XPS test showed that the charge discharge test in 0.2-2.5V voltage range, with sodium ions and embedding extrusion, electrode material only Ti4+/Ti3+ redox potential changes to occur. The test results show that in situ XRD, the migration process of sodium ions, no new phase, only can cause the cell volume change of NNTC crystal rate of 1.5%, circulation process is highly reversible. (3) respectively by solid phase method and co precipitation method synthesis of Na_ (2/3) Ni_ (1/3) Mn_ (2/3) O_2 (NNM), discusses the process parameters of two kinds of preparation methods, and the products were compared. By solid-state method, using NaCO3, NiO, MnO2 as raw materials, calcined in air for 900 12h can be prepared with diameter 1 -2 m, a thickness of about 0.5-1 mu m flake NNM pure phase; co precipitation synthesis process of NNM, MnSO4, H2O and NiSO4 to 6H2O for the solute, NH4HCO3 as precipitant, adding a small amount of ethanol at room temperature after the reaction of 3H formation of spherical MnCO3 precipitates NiCO3, irregular shape after mixing with NaCO3 in the bath atmosphere 900 8C 12h, the size of a NNM sample. (4) by molten salt method, using glucose as carbon source in LiCl/KCl (2:3) mixed salt system, reacting at 400 DEG C 12h under argon carbon load, composite three-dimensional carbon supported NNM were synthesized. (NNM@C), to improve the conductivity of electrode materials of.NNM@C NNM carbon content is about 9% with the most excellent electrochemical performance, NNM@C and NNM with the rate of 0.2C in the voltage range of 2-3.9V charge and discharge, discharge were 93.18 mA and 94.85 h g-1 mA h g-1 capacity; after 100 cycles, the capacity retention rate respectively. For 87% and 49%, cyclic voltammetry and AC impedance test results showed that the conductivity of NNM@C increased after three dimensional net carbon loading, and the internal resistance of the battery decreased significantly. The pure phase NNM had a significant improvement in electrochemical performance after carbon loading.

【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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