本文選題：鋰離子電池 + LiFePO_4/C正極材料��； 參考：《昆明理工大學(xué)》2017年碩士論文

【摘要】：橄欖石型磷酸鐵鋰(LiFePO4)正極材料,因其具有環(huán)境友善、資源豐富、價(jià)格便宜和安全性能好等優(yōu)點(diǎn),被認(rèn)為是極具有發(fā)展前景的鋰離子電池正極材料。但由于本身晶體結(jié)構(gòu)的限制,導(dǎo)致較差的電導(dǎo)性和離子擴(kuò)散性能,導(dǎo)致實(shí)際比容量低且大電流放電性能差,因此提高其材料的電子傳導(dǎo)性和離子擴(kuò)散性已成為研究人員關(guān)注的焦點(diǎn)。本文分別采用了碳熱還原法和混合溶劑熱法來合成LiFePO4材料,并通過碳包覆對(duì)其進(jìn)行改性。運(yùn)用過X射線衍射(XRD)、掃描電鏡(SEM)、透射電鏡(TEM)、元素分析儀、交流阻抗和充放電循環(huán)測(cè)試等對(duì)產(chǎn)物的物相、表面形貌、碳含量和電化學(xué)性能等方面進(jìn)行檢測(cè)和分析。碳熱還原法主要采用磷酸鐵為鐵源和磷源、碳酸鋰為鋰源,研究不同磷酸鐵原料、燒結(jié)溫度、碳源和碳包覆量對(duì)合成材料形貌和電化學(xué)性能的影響。研究發(fā)現(xiàn):當(dāng)采用葡萄糖為碳源,無水FePO4、碳酸鋰、葡萄糖的摩爾比為2:1.03:0.35,燒結(jié)溫度為700 ℃時(shí)為合成LiFePO4/C的最佳條件,所得樣品在0.2 C和10 C倍率下的首次放電比容量分別為160.0和104.9 mAh/g;當(dāng)碳包覆量為0.40時(shí),二者合成的LiFePO4/C材料在10 C的高倍率下的放電比容量分別為106.3 mAh/g,且1 C倍率下200次循環(huán)后的放電比容量保持在99.2%。混合溶劑熱法主要采用磷酸鋰(Li3PO4)、磷酸(H3PO4)和七水硫酸亞鐵(FeSO4·7H2O)為原料制備磷酸鐵鋰,并探討了不同溶劑、溶劑配比和模板劑加入量對(duì)合成材料形貌和電化學(xué)性能的影響。研究發(fā)現(xiàn):當(dāng)以有機(jī)溶劑30 ml聚乙二醇(PEG)和30 ml去離子水混合作為溶劑時(shí)制備的LiFePO4/C材料明顯的(020)晶面衍射峰很強(qiáng),其結(jié)晶性非常好,且顯示出優(yōu)異的電化學(xué)性能;當(dāng)模板劑的加入量為3 mmol時(shí),合成LiFePOO4/C樣品的(020)晶面的結(jié)晶度最高,其在0.2 C倍率下的首次放電比容量為152.3 mAh/g,在10 C倍率下的放電比容量仍能夠達(dá)到 99.2 mAh/g。
[Abstract]:Olivine type lithium ferric phosphate (LiFePO4) cathode material is considered to be a promising cathode material for lithium-ion batteries because of its advantages of friendly environment, abundant resources, low price and good safety performance. However, due to the limitation of crystal structure, it leads to poor conductivity and ion diffusion, which leads to low specific capacity and poor discharge performance of large current. Therefore, improving the electron conductivity and ion diffusion of the materials has become the focus of attention. LiFePO4 materials were synthesized by carbothermal reduction method and mixed solvothermal method, and modified by carbon coating. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis, AC impedance and charge-discharge cycle measurements were used to detect and analyze the phase, surface morphology, carbon content and electrochemical properties of the products. The effects of different raw materials of iron phosphate, sintering temperature, carbon source and amount of carbon coating on the morphology and electrochemical properties of the synthesized materials were studied by using iron phosphate as Tie Yuan and phosphorus source and lithium carbonate as lithium source. The results show that when glucose is used as carbon source, anhydrous FePO _ 4, lithium carbonate, glucose molar ratio is 2: 1.03: 0.35, sintering temperature is 700 鈩，

本文編號(hào)：2080803