本文選題：鋰離子電池 + 錳基正極材料��； 參考：《河南師范大學(xué)》2017年碩士論文

【摘要】：鋰離子電池憑借體積小、壽命長等優(yōu)勢(shì)廣泛應(yīng)用于智能手機(jī)、便攜式筆記本電腦等電子設(shè)備。隨著純電動(dòng)汽車、混合型電動(dòng)汽車的快速發(fā)展,人們對(duì)鋰離子電池的能量密度提出了更高的要求。由于商用石墨類負(fù)極材料的比容量通常高于現(xiàn)有正極材料,所以正極材料成為影響電池能量密度的直接因素之一。目前,已經(jīng)商業(yè)化的正極材料有LiCoO2(層狀)、Ni-Co-Mn三元材料(層狀)、LiFePO_4(橄欖石型)以及LiMn2O_4(尖晶石型),其中LiMn2O_4以其成本低、制備簡便、無污染以及三維鋰離子通道等優(yōu)勢(shì),得到了科研工作者們的密切關(guān)注。但同樣也存在一些問題,比如在充放電過程中容易發(fā)生姜-泰勒(Jahn-Teller)效應(yīng),導(dǎo)致其立方結(jié)構(gòu)出現(xiàn)晶格畸變,阻礙鋰離子傳輸,造成材料循環(huán)性能較差。一般地,可以在電極材料或電極外表層包覆氧化物或非氧化物,減少M(fèi)n2+的不可逆溶解,改善材料的循環(huán)性能。除此之外,還可以在LiMn2-xMxO_4(0≤x≤1)錳基體系里通過摻雜Ni、Co、Cr、Ti等金屬離子,改變Mn的整體化合價(jià),抑制Jahn-Teller變形,延長材料的循環(huán)壽命。本文主要是以尖晶石型錳基材料為基體,通過Ti摻雜以及導(dǎo)電高分子和金屬氧化物包覆的途徑來改善錳基正極材料的循環(huán)穩(wěn)定性。具體內(nèi)容包括如下幾個(gè)方面:(1)以丙烯酰胺單體為軟模板劑來源,原位聚合形成聚丙烯酰胺(PAM)軟模板,采用PAM軟模板法來制備不同Ti含量摻雜的LiMn_(2-x)Ti_xO_4(x=0,0.25,0.5,0.75,1)前驅(qū)。通過考察Ti的摻雜量,優(yōu)化出電化學(xué)性能最佳的實(shí)驗(yàn)條件。結(jié)果表明,當(dāng)Ti的摻雜量x=0.75時(shí),材料的首次放電比容量為286.1 mA h g~(-1),經(jīng)過100次循環(huán)后,可逆比容量仍然能保持在122.9 mA h g~(-1),具有良好的循環(huán)穩(wěn)定性。(2)LiNi_(0.5)Mn_(1.5)O_4為原材料,采用化學(xué)氧化聚合法,在LiNi_(0.5)Mn_(1.5)O_4材料的表面原位聚合包覆導(dǎo)電高分子聚苯胺(以下簡稱PANI),成功地制備了鋰離子電池高壓正極復(fù)合材料LNMO-PANI,并全面地探究了PANI包覆層的質(zhì)量、厚度、均勻性以及對(duì)材料電化學(xué)性能的影響。結(jié)果表明,當(dāng)加入5%的苯胺單體時(shí),被包覆在LNMO顆粒上的質(zhì)量大約為1%,其厚度大約20 nm。常溫下,復(fù)合材料的首次放電比容量為123.8 mA h g~(-1),循環(huán)200次后,仍有123.4 mA h g~(-1)的可逆容量,容量保持率高達(dá)99.7%。同時(shí)也表現(xiàn)出了良好的倍率性能和優(yōu)異的高溫性能。(3)以LiNi_(0.5)Mn_(1.5)O_4為原材料,按照活性物質(zhì):導(dǎo)電炭黑:粘結(jié)劑為8:1:1的質(zhì)量比制備極片,之后在極片表面進(jìn)行納米Al_2O_3的涂敷,并系統(tǒng)地研究了Al_2O_3的涂敷層對(duì)LNMO電極的結(jié)構(gòu)和電化學(xué)性能的影響。尤其是Al_2O_3涂敷層對(duì)電極在電化學(xué)反應(yīng)過程中不良界面反應(yīng)的抑制。結(jié)果表明,常溫下,復(fù)合電極的首次放電比容量為123.7 mA h g~(-1),200次循環(huán)后可逆比容量為129.1 mA h g~(-1)。同時(shí)該復(fù)合電極也表現(xiàn)出了良好的高溫性能以及較小的極化電阻和界面內(nèi)阻。
[Abstract]:Lithium-ion batteries are widely used in smart phones, laptop computers and other electronic devices by virtue of their small size and long life. With the rapid development of pure electric vehicles (EV) and hybrid electric vehicles (HEVs), the energy density of lithium-ion batteries has been put forward higher requirements. Because the specific capacity of commercial graphite anode materials is usually higher than that of existing cathode materials, cathode materials become one of the direct factors that affect the energy density of batteries. At present, commercial cathode materials include LiCoO _ 2 (layered Ni-Co-Mn ternary material) and limn _ 2O _ 4 (spinel type), in which LiMn2O_4 has the advantages of low cost, simple preparation, no pollution and three-dimensional lithium ion channel. The researchers pay close attention to it. However, there are also some problems, such as the effect of Jahn-Teller, which leads to lattice distortion of the cubic structure, hinders the lithium ion transport, and results in poor cycling performance of the materials. In general, oxide or non-oxide can be coated on the electrode material or electrode surface to reduce the irreversible dissolution of Mn2 and improve the cycling performance of the material. In addition, in the system of LiMn2-xMxO_4(0 鈮，

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