【摘要】：鋰離子電池如今被認(rèn)為是未來(lái)混合電動(dòng)和全電動(dòng)汽車以及抑制溫室效應(yīng)的技術(shù)層面的選擇。尖晶石錳酸鋰作為一種正極材料,因其成本低、毒性小和相對(duì)較高的能量密度等優(yōu)勢(shì)而受到廣泛的關(guān)注。然而,尖晶石結(jié)構(gòu)的錳酸鋰材料仍然存在其本身固有的Jahn-Teller效應(yīng)和錳離子溶解等問(wèn)題,高溫下其容量衰減較為嚴(yán)重。為了改進(jìn)錳酸鋰正極材料的能量密度,通過(guò)制備鎳錳酸鋰的二元復(fù)合物材料,可以提高其充放電電壓,也是改進(jìn)其性能的一種方法。對(duì)于電極材料而言,形貌可控,大小均一的材料能夠防止局部極化,增加鋰離子的擴(kuò)散作用。因而,我們首先通過(guò)沉淀法研究空心球形錳酸鋰材料的制備及電化學(xué)性能;進(jìn)而通過(guò)原位摻雜鎳離子進(jìn)入錳酸鋰的晶格中,研究LiNi_(0.33)Mn_(1.67)O_4空心微球材料晶體結(jié)構(gòu)、離子擴(kuò)散、電化學(xué)性能的影響;在此基礎(chǔ)上制備了高電壓LiNi_(0.5)Mn_(1.5)O_4空心微球正極材料,對(duì)其進(jìn)行了電化學(xué)性能研究。主要的研究工作如下:1.通過(guò)碳酸鹽沉淀和固相燒結(jié)法,制備了空心球形結(jié)構(gòu)的尖晶石錳酸鋰正極材料。SEM結(jié)果顯示該空心球粒徑在3.0-4.0μm之間,具有多孔結(jié)構(gòu),其表面較為光滑。鋰錳配比為0.53得到的樣品具有優(yōu)越的電化學(xué)性能,在首次充放電循環(huán)中,0.2 C下首次放電比容量為134.58 mAh g~(-1),首次充放電庫(kù)倫效率達(dá)96.6%,在0.2 C下100次循環(huán)后容量保持率達(dá)95.1%,具有較好的循環(huán)穩(wěn)定性。2.通過(guò)碳酸鹽共沉淀法將鎳離子原位摻雜制備Ni_(0.17)Mn_(0.83)CO_3空心球,固相燒結(jié)后制備了空心球形結(jié)構(gòu)的尖晶石LiNi_(0.33)Mn_(1.67)O_4材料,使少量的鎳離子取代錳酸鋰結(jié)構(gòu)中部分的Mn3+,利用鎳離子的靜電作用穩(wěn)定錳酸鋰的晶體結(jié)構(gòu),進(jìn)而改善其循環(huán)穩(wěn)定性。SEM結(jié)果顯示該空心球粒徑在2.0-4.0μm之間,反應(yīng)條件研究結(jié)果表明在55℃進(jìn)行共沉淀反應(yīng)制備的產(chǎn)品形貌更為均一。該材料在0.5 C下的首次放電比容量為134.49 mAh g~(-1),在1.0 C下200次循環(huán)后容量保持率可達(dá)97.2%,在5.0 C倍率下放電比容量達(dá)124.11 mAh g~(-1),200次循環(huán)后的容量衰減在6.4%以內(nèi),具有較好的循環(huán)穩(wěn)定性。與沉淀法制備的錳酸鋰相比,該材料表現(xiàn)出更好的倍率性能。3.第二部分的研究發(fā)現(xiàn),LiNi_(0.33)Mn_(1.67)O_4材料是錳酸鋰和高電壓LiNi_(0.5)Mn_(1.5)O_4的微晶混合形成的空心球結(jié)構(gòu)。進(jìn)一步在LiNi_(0.33)Mn_(1.67)O_4增加鎳離子的含量,制備了純相的LiNi_(0.5)Mn_(1.5)O_4空心微球。SEM結(jié)果顯示該空心球粒徑在3.5-4.5μm之間,具有多孔結(jié)構(gòu)。EDS結(jié)果顯示鎳離子和錳離子在材料中分布很均勻。所得材料在0.5 C下首次放電比容量為135.21 mAh g~(-1),300次循環(huán)后容量保持率達(dá)92.0%,具有較高的比容量和較好的循環(huán)性能。其在2.0 C下放電比容量達(dá)124.47 mAh g~(-1),200次循環(huán)后的容量衰減在1.5%以內(nèi),說(shuō)明其具有很優(yōu)異的倍率性能。
[Abstract]:Lithium-ion batteries are now seen as the future technical options for hybrid electric and all-electric vehicles and for suppressing Greenhouse Effect. As a kind of cathode material, spinel lithium permanganate has attracted wide attention because of its advantages of low cost, low toxicity and relatively high energy density. However, the spinel LiMnO _ 4 material still has its inherent Jahn-Teller effect and manganese ion dissolution problems, and its capacity attenuation is serious at high temperature. In order to improve the energy density of lithium permanganate cathode material, the charge and discharge voltage of lithium nickel manganese oxide binary composite material can be increased by preparing it, and it is also a method to improve its performance. For electrode materials, the materials with controllable morphology and uniform size can prevent local polarization and increase the diffusion of lithium ions. Therefore, the preparation and electrochemical properties of hollow spherical lithium manganese oxide materials were studied by precipitation method, and then the crystal structure and ion diffusion of LiNi0.33 Mn1.67 O4 hollow microspheres were studied by in-situ doping of nickel ions into the lattice of lithium manganese oxide. The electrochemical properties of high voltage LiNi0.5 Mn1.5 O4 hollow microspheres cathode materials were prepared, and the electrochemical properties of the hollow microspheres were studied. The electrochemical properties of Lini _ (0.5) mn _ (1.5) O _ 4 hollow microspheres were investigated. The main research work is as follows: 1: 1. The hollow spherical spinel lithium manganese oxide cathode material was prepared by carbonate precipitation and solid phase sintering. The SEM results show that the hollow sphere has a porous structure and a smooth surface with a particle size ranging from 3.0 渭 m to 4.0 渭 m. The sample with Li / mn ratio of 0.53 has excellent electrochemical performance. In the first charge / discharge cycle, the first discharge specific capacity is 134.58 mAh g ~ (-1), the first charge / discharge Coulomb efficiency is 96. 6, and the capacity retention rate is 95. 1 after 100 cycles at 0. 2 C. it has good cycle stability. Ni _ (0.17) mn _ (0.83) CO _ 3 hollow spheres were prepared by in-situ doping of nickel ions by carbonate coprecipitation method. After solid phase sintering, spinel LiNi0.33 Mn1.67 O4 with hollow spherical structure was prepared. The crystal structure of lithium permanganate was stabilized by the electrostatic action of nickel ion, and the cyclic stability was improved. SEM results showed that the diameter of the hollow sphere was between 2.0 渭 m and 4.0 渭 m. The results of reaction conditions show that the morphology of the products prepared by coprecipitation at 55 鈩，

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