發(fā)布時(shí)間：2018-03-01 21:00

  本文關(guān)鍵詞： 鋰離子電池 負(fù)極材料 Li4Ti5O12 Nb ZnCo2O4 MWCNTs　出處：《華中科技大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：當(dāng)前商業(yè)化使用的鋰離子電池負(fù)極材料主要是石墨類碳材料，然而不可逆容量大、倍率性能差等缺點(diǎn)制約了這類材料的進(jìn)一步發(fā)展。鋰離子電池負(fù)極要滿足高容量、高能量密度、高倍率性能、高循環(huán)性能的未來需求就必須開發(fā)新的材料。 Li4Ti5O12是一種充放電過程中體積效應(yīng)幾乎為零的材料，循環(huán)壽命長、高穩(wěn)定性高，是鋰離子電池負(fù)極材料研究的熱點(diǎn)。但是鈦酸鋰的電子導(dǎo)電率差，影響了它的電化學(xué)性能，需要進(jìn)行改性來改善，特別是高倍率下的電化學(xué)性能。 ZnCo2O4是一種金屬氧化物的衍生物。通過無毒性的Zn代替Co，不僅有金屬氧化物理論比容量高的特點(diǎn)，而且降低了成本和環(huán)境的污染。但是需要改性提高它的首次庫倫效率。 本文選用新型制備方法微波固相法得到了納米尺度的鋰離子電池負(fù)極材料Li4Ti5O12和ZnCo2O4，并分別進(jìn)一步進(jìn)行金屬離子Nb5+摻雜和包覆多壁碳納米管MWCNTs改性，提高了材料的電化學(xué)性能。與傳統(tǒng)固相加熱方式相比，微波輻射利用反應(yīng)物分子和微波之間的相互作用讓固相反應(yīng)進(jìn)行得更快，合成溫度相對低、反應(yīng)時(shí)間更短�，F(xiàn)代微波控制系統(tǒng)可以精確地控制反應(yīng)時(shí)間、溫度，使得微波能夠均勻快速的被反應(yīng)物或者反應(yīng)介質(zhì)吸收從而將高溫固相反應(yīng)時(shí)間縮短至十幾分鐘，是一種很好的制備納米材料的方法。Li4Ti5-xNbxO12(MW,0≤x≤0.1)的制備是采用Li2CO3、TiO2、Nb2O5為原料，利用微波固相法在750oC下保溫20min得到了分布均勻的納米尺度的鈦酸鋰材料，納米顆粒尺寸大約在200 400nm。ZnCo2O4(MW,CNTs)復(fù)合材料的制備是采用Zn(NO3)22H2O、 Co(NO3)26H2O、多壁碳納米管MWCNTs為原料，利用微波固相法在450oC保溫20min制備了ZnCo2O4(MW, CNTs)復(fù)合材料。 研究結(jié)果表明微波固相法制備的Li4Ti5-xNbxO12(MW,0≤x≤0.1)性能優(yōu)于傳統(tǒng)固相法制備的LTO (T)。特別是當(dāng)Nb摻雜量在0.03mol%時(shí)，表現(xiàn)出高容量、好的穩(wěn)定性和好的倍率性能。在1C、5C、10C以及20C充放電循環(huán)200圈后，放電比容量分別保持了174.7、157.1、141.7和130.2mAh g1。這項(xiàng)研究提供了高性能鈦酸鋰工業(yè)化生產(chǎn)的新思路。相對于傳統(tǒng)固相法制備的ZnCo2O4，ZnCo2O4(MW, CNTs)復(fù)合材料的電化學(xué)性能有了改善，，0.1C下首次庫倫效率由22%提高到了77%，20圈后放電比容量還保持了700mAh g1。
[Abstract]:The current commercial cathode materials for lithium ion batteries are mainly graphite carbon materials. However, the disadvantages of large irreversible capacity and poor rate performance restrict the further development of these materials. The future demand of high energy density, high rate performance and high cycle performance requires the development of new materials. Li4Ti5O12 is a kind of material whose volume effect is almost zero in charge and discharge process. It has long cycle life and high stability, so it is a hotspot in the research of cathode materials for lithium ion batteries. However, the electronic conductivity of lithium titanate is poor, which affects its electrochemical performance. Modification is needed to improve electrochemical performance, especially at high rates. ZnCo2O4 is a derivative of metal oxides. It not only has the characteristics of high theoretical specific capacity of metal oxides, but also reduces the cost and environmental pollution, but it needs to be modified to improve its first Coulomb efficiency. In this paper, nanoscale cathode materials Li4Ti5O12 and ZnCo _ 2O _ 4 for lithium ion batteries were prepared by microwave solid-state method. Metal ion Nb5 doped and coated multi-walled carbon nanotubes (MCNTs) were further modified respectively. The electrochemical properties of the materials are improved. Compared with the conventional solid-state heating, microwave radiation uses the interaction between reactants and microwaves to make the solid-state reaction proceed faster and the synthesis temperature is relatively low. The modern microwave control system can accurately control the reaction time and temperature, so that the microwave can be absorbed uniformly and quickly by reactants or reaction media, thus shortening the reaction time of high temperature solid phase to 10 minutes. Li4Ti5-xNbxO12MW0 鈮

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