【摘要】：碳納米管作為鋰離子電池負(fù)極材料,性能與其形貌結(jié)構(gòu)有著密切的關(guān)系。本文利用CVD工藝合成了具有不同形貌結(jié)構(gòu)的兩種碳管膜并測試其鋰電性能。缺陷較多的碳管膜(CNT-2)的比表面積為163.6 cm~2 g~(-1),大于結(jié)晶性良好的CNT~(-1)碳管膜(122.7 cm~2 g~(-1))的比表面積,在3000 m Ah g~(-1)高電流密度下穩(wěn)定循環(huán)500次后,CNT-2的可逆容量仍保持在108 m Ah g~(-1),而CNT~(-1)的可逆容量則只有61m Ah g~(-1)。上述結(jié)果表明CNT-2的缺陷結(jié)構(gòu)有利于鋰離子的傳輸,更適合用于高功率電池。本文重點(diǎn)研究了Ti O_2改性對CNTs鋰電性能的影響。通過在碳納米管前驅(qū)體溶液中引入鈦酸四丁酯作為鈦源,制備CNTs/Ti O_2復(fù)合膜。實(shí)驗(yàn)發(fā)現(xiàn)當(dāng)鈦酸四丁酯的含量為19 wt.%時(shí),獲得的19.0 wt.%-CNTs/Ti O_2復(fù)合膜具有優(yōu)異的電化學(xué)性能,其結(jié)構(gòu)特點(diǎn)是Ti O_2納米顆粒鑲嵌在CNTs表面,Ti O_2主要以金紅石相存在,質(zhì)量分?jǐn)?shù)為17.6 wt.%。在30 m A g~(-1)電流密度下,19.0 wt.%-CNTs/Ti O_2首次充放電的庫侖效率為60.3%,可逆容量達(dá)到500 m Ah g~(-1),遠(yuǎn)高于CNTs(30.3%,350 m Ah g~(-1)),并且在3000 m A g~(-1)電流密度下循環(huán)500次后,19.0 wt.%-CNTs/Ti O_2容量穩(wěn)定在134 m Ah g~(-1),而CNTs為90 m Ah g~(-1)。本文還在Li Fe PO_4前驅(qū)體中引入乙酸鎳作為催化劑,以乙炔氣為碳源,利用氣相沉積法,在700℃合成Li Fe PO_4的同時(shí)在其表面生長CNTs,原位制備Li Fe PO_4/CNTs復(fù)合材料。研究證明:當(dāng)乙炔流量為12ml/min,乙酸鎳為4 wt.%時(shí),制備的Li Fe PO_4/CNTs復(fù)合材料具有較好的充放電效率。
[Abstract]:The properties of carbon nanotubes (CNTs) as anode materials for lithium ion batteries are closely related to their morphology and structure. In this paper, two kinds of carbon tube films with different morphologies were synthesized by CVD process and their lithium electrical properties were tested. The specific surface area of the carbon tube film (CNT-2) with more defects is 163.6 cm~2 g ~ (-1), which is larger than that of the CNT~ (-1) carbon tube film (122.7 cm~2 g ~ (-1) with good crystallinity. At a high current density of 3000 m Ah g ~ (-1), the reversible capacity of CNT-2 remains at 108m Ah g ~ (-1) after 500 stable cycles, while the reversible capacity of CNT~ (-1) is only 61m Ah g ~ (-1). The results show that the defect structure of CNT-2 is favorable for lithium ion transport and is more suitable for high power battery. The effect of modification of Ti O _ 2 on the electrical properties of CNTs lithium was studied in this paper. CNTs/Ti O _ 2 composite membrane was prepared by introducing tetrabutyl titanate into carbon nanotube precursor solution as titanium source. It was found that the obtained 19.0 wt.%-CNTs/Ti O _ 2 composite film had excellent electrochemical performance when the content of tetrabutyl titanate was 19 wt.%. The structure of the composite film was characterized by the fact that Ti O _ 2 nanoparticles were embedded on the surface of CNTs in rutile phase, with a mass fraction of 17.6 wt.%.. The Coulomb efficiency of the first charge and discharge is 60.3 at 30mAg-1 current density, and the reversible capacity is 500m Ah g-1, which is much higher than that of CNTs (30.3 / 350m Ah g-1), and the capacity of 19.0 wt.%-CNTs/Ti O2 is stabilized at 134mAh after 500 cycles at the current density of 3000 mAg-1. G ~ (-1) and CNTs were 90 m Ah g ~ (-1). In this paper, nickel acetate as catalyst and acetylene gas as carbon source were introduced into Li Fe PO_4 precursor, Li Fe PO_4 was synthesized at 700 鈩，

本文編號：2242637