本文關(guān)鍵詞：鋅鋁水滑石納米復(fù)合材料的制備及其在鋅鎳電池中的應(yīng)用研究　出處：《中南大學(xué)》2014年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 鋅鎳電池 鋅鋁水滑石 電化學(xué)活性 納米復(fù)合物 碳納米管 納米銀顆粒 石墨烯

【摘要】：摘要：鋅鎳電池是一種高能量密度的堿性蓄電池,其電池性能遠(yuǎn)遠(yuǎn)高于鎘鎳和鎳氫電池,加上這種電池原材料豐富,電解液和活性物質(zhì)無毒,電池體系綠色無污染,越來越受到各國研究機(jī)構(gòu)的重視。然而鎳鋅二次電池中常規(guī)負(fù)極材料的放電產(chǎn)物易溶于堿性電解液,從而會導(dǎo)致電池循環(huán)壽命降低oZnAl-LDH材料由于其新穎的二維納米結(jié)構(gòu),在堿性電解液中具有很好的穩(wěn)定性和電化學(xué)活性等優(yōu)點(diǎn),被認(rèn)為最有潛力成為下一代鋅鎳電池的新型負(fù)極材料。然而,單相的ZnAl-LDH材料本身的導(dǎo)電性較差限制了其電化學(xué)性能的進(jìn)一步提升。因此,將ZnAl-LDH材料與導(dǎo)電性較好的碳、金屬等復(fù)合,通過發(fā)揮兩種材料各自的優(yōu)勢,改善復(fù)合材料的導(dǎo)電性和機(jī)械強(qiáng)度,從而極大地提高復(fù)合材料的電化學(xué)性能。本文圍繞新型ZnAl-LDH納米復(fù)合材料的制備和相關(guān)電化學(xué)性能展開研究,主要內(nèi)容如下： (1)通過離心分離的方法將ZnAl-LDH固體沉淀和鹽溶液分離,再重新分散在超純水中,使ZnAl-LDH在超純水環(huán)境中水熱生長結(jié)晶,水熱反應(yīng)24小時(shí)后得到了晶形規(guī)則、大小均一的二維納米片材料。相比于常規(guī)的水熱法和共沉淀法,本方法合成的水滑石結(jié)構(gòu)更加規(guī)則,分布更加均勻,沒有出現(xiàn)團(tuán)聚現(xiàn)象,ZnAl-LDH樣品呈規(guī)則的六邊形晶體結(jié)構(gòu),質(zhì)量和純度較高,非常適合應(yīng)用到鋅鎳電池負(fù)極材料中。 (2)利用正負(fù)電荷之間的靜電力作用,將表面修飾后的碳納米管和ZnAl-LDH兩種納米材料結(jié)合在一起,生成三維ZnAl-LDH/CNTs復(fù)合物。對復(fù)合物的結(jié)構(gòu)進(jìn)行表征后發(fā)現(xiàn),CNTs均勻分布在ZnAl-LDH納米片表面,形成一種導(dǎo)電網(wǎng)狀結(jié)構(gòu)。將其作為負(fù)極活性物質(zhì)應(yīng)用到鋅鎳電池中,通過恒流充放電曲線研究、CV曲線測試、電池循環(huán)性能實(shí)驗(yàn),證明電池的循環(huán)穩(wěn)定性、充放電性能以及電極的放電比容量均有顯著提升。 (3)運(yùn)用銀鏡反應(yīng)技術(shù),在ZnAl-LDH納米片表面進(jìn)行納米銀修飾,首次制備出銀包覆ZnAl-LDH納米片材料。通過電池的恒流充放電實(shí)驗(yàn),發(fā)現(xiàn)這種銀包覆ZnAl-LDH納米片材料具有更高的放電容量、更為優(yōu)異的充放電性能和循環(huán)穩(wěn)定性。進(jìn)一步采用交流阻抗技術(shù)對其進(jìn)行研究,發(fā)現(xiàn)這種銀包覆ZnAl-LDH納米片的電荷轉(zhuǎn)移電阻相比于沒有包覆之前有明顯的下降,證明了銀包覆技術(shù)可以顯著改善電極的導(dǎo)電性,降低電極的電荷轉(zhuǎn)移電阻,使活性物質(zhì)的電化學(xué)性能顯著提升。 (4)合成不同銀含量的Ag/ZnAl-LDH復(fù)合物,研究復(fù)合物中銀的含量對其電化學(xué)性能的影響。通過各種結(jié)構(gòu)表征手段,證明了導(dǎo)電相銀包覆在ZnAl-LDH納米片表面,不同銀含量的復(fù)合物樣品中銀包覆層的分布和存在狀態(tài)不同,當(dāng)銀的含量達(dá)到7.49wt.%(AL15)時(shí),形成一層均勻的銀包覆層。綜合考慮電池的循環(huán)穩(wěn)定性和放電容量,AL15樣品的性能最佳,在循環(huán)300次以后,AL15的放電容量沒有出現(xiàn)明顯衰減,在整個(gè)300次充放電循環(huán)中放電容量始終穩(wěn)定在-400mAh g-。 (5)采用溶液直接還原法,在不用任何還原劑的情況下,將硝酸銀溶液中的銀離子直接還原成納米銀顆粒,沉積在ZnAl-LDH納米片表面。電化學(xué)性能測試表明Ag-LDH復(fù)合物樣品相比于純的ZnAl-LDH,其電化學(xué)性能得到了顯著改善。電化學(xué)交流阻抗譜分析結(jié)果表明,Ag-LDH復(fù)合物的電荷轉(zhuǎn)移電阻明顯降低。這證明了高導(dǎo)電的納米銀顆粒沉積在ZnAl-LDH納米片表面,可以通過降低電荷轉(zhuǎn)移電阻的方式,提高電極材料的電荷傳輸速率和電子導(dǎo)電性,改善電極材料的電化學(xué)性能。(6)采用自組裝的方法將GO和ZnAl-LDH組裝在一起,然后通過水熱還原法,將GO還原成石墨烯,得到graphene/ZnAl-LDH復(fù)合物。對graphene/ZnAl-LDH復(fù)合物樣品的結(jié)構(gòu)進(jìn)行表征,證明了超薄的石墨烯將ZnAl-LDH納米片包裹在中心,形成新穎的膠囊狀結(jié)構(gòu)。由于外層的graphene具有非常好的電子傳導(dǎo)特性,可以大大加快電子在活性物質(zhì)之間以及活性物質(zhì)與集流體之間的傳導(dǎo)過程。由于膠囊狀graphene/ZnAl-LDH復(fù)合物具有以上優(yōu)點(diǎn),在電池的循環(huán)性能和放電容量方面均有大幅提升。在1C條件下電池恒流充放電循環(huán)1000次以后,電池容量僅衰減3%,穩(wěn)定在～405mAh g-1,這種優(yōu)異的循環(huán)特性,非常適合作為鋅鎳電池負(fù)極活性材料。
[Abstract]:Abstract: zinc nickel battery is an alkaline battery with high energy density, the battery performance is far higher than that of nickel cadmium and nickel metal hydride batteries, the battery with abundant raw materials, electrolyte and the active material of non-toxic, pollution-free battery system, more and more attention the world research institutions. However, the conventional nickel zinc anode material discharge products two the battery in soluble in alkaline electrolyte, which will cause the battery cycle life to reduce oZnAl-LDH materials due to their novel two-dimensional nanostructures, has good stability and electrochemical activity and in alkaline electrolyte, is considered the most has the potential to become a novel anode material of Zn Ni battery for the next generation. However, further enhance the conductivity poor single-phase ZnAl-LDH material itself limit its electrochemical performance. Therefore, the ZnAl-LDH material with good electrical conductivity of carbon, metal complex, through the play two The advantages of different materials improve the electrical conductivity and mechanical strength of composites, which greatly improve the electrochemical performance of composites. In this paper, the preparation and electrochemical properties of new ZnAl-LDH nanocomposites are studied.
(1) ZnAl-LDH solid and salt solution separated by centrifugal separation method, re dispersed in ultra pure water, the growth of ZnAl-LDH crystal in hydrothermal ultrapure water environment, hydrothermal reaction after 24 hours the regular crystal shape, two-dimensional nano sheet material with uniform size. Compared to the conventional hydrothermal method and co precipitation method, hydrotalcite structure synthesized by this method is more regular, more uniform distribution, no agglomeration, ZnAl-LDH samples with hexagonal crystal structure rules, quality and high purity, very suitable for application to the zinc nickel battery anode material.
(2) the use of electrostatic interaction between positive and negative electric charges, the surface modification of carbon nanotubes and ZnAl-LDH two nano materials together, 3D ZnAl-LDH/CNTs complexes. The complexes were characterized and found that CNTs distributed evenly on the surface of nano ZnAl-LDH, the formation of a conductive mesh as the structure. The anode active material applied to nickel zinc batteries, by galvanostatic charge discharge curve, CV curve test, cell cycle performance test, cycle stability proof battery, charge and discharge performance and electrode discharge capacity were significantly improved.
(3) the use of silver mirror reaction technology of silver nanoparticles on the surface of ZnAl-LDH nano film, first prepared silver coated ZnAl-LDH nano materials. By galvanostatic charge discharge test battery, found that the silver coated nano ZnAl-LDH materials have higher discharge capacity, more charge discharge performance and cycle stability excellent further. AC impedance technique is used to study, found that compared to uncoated before significantly decreased the silver coated ZnAl-LDH nano sheet charge transfer resistance, proved that the conductivity silver coating technology can significantly improve the electrode, electrode low charge transfer resistance, the electrochemical performance of active material was significantly improved.
(4) Ag/ZnAl-LDH complexes synthesized with different silver content, content of silver complexes influence on its electrochemical properties. Through various structural characterization, proved that the conductive coating on the surface of ZnAl-LDH nano silver, silver with different silver content composite coating sample distribution and existence, when the content of silver reach 7.49wt.% (AL15), to form a uniform layer of silver coating layer. Considering the cell cycle stability and discharge capacity of AL15, the best performance in the sample, after 300 cycles, the discharge capacity of AL15 without significant attenuation, the 300 charge discharge cycles in discharge capacity has stabilized at -400mAh g-.
(5) using the method of direct reduction in the solution without any reducing agent under the condition of silver ions in silver nitrate solution of the direct reduction of silver nanoparticles, nanosheets deposited on ZnAl-LDH surface. The electrochemical performance tests show that the Ag-LDH composite samples compared to the pure ZnAl-LDH, the electrical properties are significantly improved. Electrochemical AC impedance analysis results show that the charge transfer resistance of Ag-LDH composite decreased obviously. This proved that nano silver particles deposited in high conductive nano ZnAl-LDH surface, and can reduce the charge transfer resistance, charge rate and provided transmission of high electronic conductivity of the electrode material, improve the electrochemical performance of electrode materials (6.) by a self-assembly method GO and ZnAl-LDH are assembled together, and then through the hydrothermal reduction method, GO reduced to graphene, graphene/ZnAl-LDH complexes of graphene/ZnAl-LDH complex. The structure of complexes were characterized and proved that graphene thin ZnAl-LDH nano film wrapped in the center, forming a capsule like structure of the novel. Because the outer graphene has very good electronic transmission characteristics, can greatly accelerate the process of electronic conduction between the active substance and active substances and collector. Because the capsule shaped graphene/ZnAl-LDH composite has more advantages, greatly enhance the cell cycle performance and discharge capacity were. Under the condition of 1C battery constant current 1000 charge discharge cycles, battery capacity decay is only 3%, stable in g-1 ~ 405mAh, the excellent cycle characteristics, very suitable as anode active material of nickel zinc battery.

【學(xué)位授予單位】：中南大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TB332;TM912.2

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