本文選題：鋰離子電池 + 負(fù)極材料�。� 參考：《天津工業(yè)大學(xué)》2017年碩士論文

【摘要】：由于氧化鈷和三氧化二鐵具有高的理論比容量、豐富的來源和環(huán)境友好等特點(diǎn)已成為鋰離子電池負(fù)極材料研究的熱點(diǎn)。但是由于它們的導(dǎo)電性差,首次庫倫效率低,循環(huán)性能差等缺點(diǎn),限制了其廣泛的應(yīng)用。因此,在保持高容量的條件下,提高氧化鈷和三氧化二鐵材料的導(dǎo)電性,抑制其在充放電過程中出現(xiàn)的體積膨脹、顆粒團(tuán)聚以及活性材料粉化等問題是解決上述缺陷的有效途徑。本文以EDTA-2Na為碳源和氮源,合成出具有良好的循環(huán)性能和倍率性能的鋰離子電池負(fù)極材料。具體的研究內(nèi)容如下:采用EDTA-Fe為前驅(qū)體制備出碳包囊納米尺度γ-Fe2O3納米粒子(Fe2O3@NC)。研究結(jié)果表明,尺寸大小約23nm的γ-Fe2O3晶粒均勻分散在碳基質(zhì)中。電化學(xué)測試結(jié)果顯示,該復(fù)合電極材料在100 mA/g的電流密度下,經(jīng)過50次循環(huán),庫侖效率高達(dá)98%,可逆比容量保持為487 mAh/g,容量保持率為71%;在1600 mA/g的電流密度下,可逆比容量保持有100 mAh/g,當(dāng)電流密度恢復(fù)至50 mA/g時(shí),放電比容量仍然可以快速恢復(fù)至585 mAh/g。Fe2O3@NC復(fù)合材料表現(xiàn)出如此優(yōu)異的電化學(xué)性能可歸因于Fe2O3@NC復(fù)合材料的介孔結(jié)構(gòu)以及氮摻雜的碳材料,這可以提高鋰離子脫嵌過程中γ-Fe2O3的導(dǎo)電性和結(jié)構(gòu)穩(wěn)定性。采用EDTA-Co為前驅(qū)體制備出碳包囊金屬鈷及氧化鈷復(fù)合材料(CoOx@C)。電化學(xué)測試結(jié)果表明,該復(fù)合電極材料在100 mA/g的電流密度下,經(jīng)過50次循環(huán),庫侖效率高達(dá)99%,可逆比容量保持為407 mAh/g,容量保持率為86%;在1600mA/g的電流密度下,復(fù)合電極的可逆比容量高達(dá)120 mAh/g,當(dāng)電流密度恢復(fù)至50 mA/g時(shí),放電比容量仍然可以迅速恢復(fù)至411 mAh/g。CoOx@C表現(xiàn)出如此優(yōu)異的電化學(xué)性能,這可以歸因于以下特性:一、高導(dǎo)電性金屬Co顆粒不僅作為導(dǎo)電劑增加復(fù)合材料的導(dǎo)電性,也作為有效催化劑促使SEI膜組分可逆轉(zhuǎn)化,從而提高復(fù)合電極的儲(chǔ)鋰能力和倍率性能。二、氮摻雜的碳材料增大了復(fù)合材料的導(dǎo)電性,抑制了氧化鈷納米顆粒的團(tuán)聚,從而提高了復(fù)合材料的循環(huán)性能。
[Abstract]:Due to its high theoretical specific capacity, abundant source and environment-friendly characteristics, cobalt oxide and iron trioxide have become a hot spot in the research of cathode materials for lithium ion batteries. However, due to their poor conductivity, low efficiency of the first Coulomb and poor cycle performance, their wide applications are limited. Therefore, under the condition of maintaining high capacity, the electrical conductivity of cobalt oxide and ferric oxide is improved, and the volume expansion of cobalt oxide and ferric oxide is restrained in the process of charging and discharging. The agglomeration of particles and the pulverization of active materials are effective ways to solve these defects. In this paper, EDTA-2Na is used as carbon source and nitrogen source to synthesize cathode materials for lithium ion batteries with good cycling performance and rate performance. The main contents of this study are as follows: using EDTA-Fe as precursor, nano-sized 緯 -Fe _ 2O _ 3 nanoparticles were prepared. The results show that 緯 -Fe _ 2O _ 3 grains of about 23nm size are uniformly dispersed in carbon matrix. The electrochemical test results show that the Coulomb efficiency is up to 98 at 100 mA/g current density, the reversible specific capacity is 1600 mg / g, the capacity retention is 71%, and at 1600 mA/g current density, the Coulomb efficiency is as high as 98%, and the reversible specific capacity is 487mAh-1 路g, and the capacity retention is 71g at the current density of 1600 mA/g. The reversible specific capacity remains at 100mAh / g, and when the current density returns to 50 mA/g, The discharge specific capacity can still be rapidly recovered to 585 mAh/g.Fe2O3@NC composites. The excellent electrochemical performance can be attributed to the mesoporous structure of Fe2O3@NC composites and nitrogen doped carbon materials. This can improve the conductivity and structural stability of 緯 -Fe _ 2O _ 3 in the process of lithium ion deintercalation. Carbon capsule cobalt and cobalt oxide composites were prepared by using EDTA-Co as precursor. The electrochemical test results show that the Coulomb efficiency is as high as 99mh / g, the reversible specific capacity is 407mAh/ g and the capacity retention rate is 86g under the current density of 100 mA/g, and at the current density of 1600mA/g, the Coulomb efficiency is as high as 99mg / g, and the reversible specific capacity is 407mAh/ g. The reversible specific capacity of the composite electrode is as high as 120mAh/ g. When the current density is restored to 50 mA/g, the discharge specific capacity can still be rapidly recovered to 411 mAh/g.CoOx@C, showing such excellent electrochemical performance, which can be attributed to the following characteristics: 1. High conductivity Co particles not only increase the conductivity of composite materials as conductive agents, but also promote the reversible conversion of SEI film components as effective catalysts, thus improving the lithium-storage capacity and the performance of the composite electrodes. Secondly, nitrogen doped carbon increases the electrical conductivity of the composites and inhibits the agglomeration of cobalt oxide nanoparticles, thus improving the cyclic properties of the composites.
【學(xué)位授予單位】：天津工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB332;TM912

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本文編號(hào)：1779643