本文關(guān)鍵詞：共沉淀控制結(jié)晶法制備富鋰錳基鋰離子電池正極材料的技術(shù)研究　出處：《浙江大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 鋰離子電池 正極材料 富鋰錳 共沉淀 前驅(qū)體 表面包覆

【摘要】：本文主要以富鋰錳基層狀正極材料為研究對象,針對其倍率性能差、循環(huán)穩(wěn)定性差等缺點(diǎn),提出表面包覆高密度球形顆粒的結(jié)構(gòu)設(shè)計(jì),并通過化學(xué)沉積法對所制備的材料進(jìn)行表面包覆改性。主要研究結(jié)果如下：通過解析晶體形核經(jīng)驗(yàn)公式,理論分析了共沉淀過程。得出原料溶液濃度、攪拌速度、氨水濃度、加料速度和pH值等參數(shù)對沉淀過程影響,為實(shí)際工作提供了方法論和方向性指導(dǎo)。通過對不加入絡(luò)合劑的共沉淀反應(yīng)體系進(jìn)行熱力學(xué)分析,因體系存在大量金屬自由離子,在不加入絡(luò)合劑體系中生成堿式鹽沉淀物的概率將大幅增加,從而論證了引入絡(luò)合劑的必要性。在加入絡(luò)合劑的共沉淀反應(yīng)體系中,共沉淀反應(yīng)的最佳pH值范圍為8左右,pH值大于8時(shí)出現(xiàn)堿式鹽沉淀雜相,pH值小于8時(shí)出現(xiàn)金屬離子的大量損失。分別研究了溫度、攪拌速度、氨水濃度和pH值等單因素條件對前驅(qū)體制備過程的影響。在以Na2CO3為沉淀劑的沉淀反應(yīng)體系Ni2+-Co2+-Mn2+-C032--NH3-H20中,共沉淀制備前驅(qū)體的最優(yōu)條件為：溫度15℃、攪拌轉(zhuǎn)速800 r·min-1、pH=8.0、氨水濃度0.4mol·L-1。在該最優(yōu)條件下所制備的前軀體,顆粒形貌球形規(guī)整、粒徑分布均勻一致(D50=8.69 μm)。在本文研究的沉淀體系中,所制備前驅(qū)體的振實(shí)密度主要取決于顆粒的形貌、粒徑及其分布。因此,為獲得高的振實(shí)密度,應(yīng)當(dāng)在保證顆粒形貌球形規(guī)整的前提下,優(yōu)化粒徑大小及其分布狀態(tài),以盡可能實(shí)現(xiàn)顆粒自由緊密堆積。以過量7 wt%的碳酸鋰作為鋰源,在850-C燒結(jié)20h后所獲得的電極材料表現(xiàn)出最優(yōu)的電化學(xué)性能,放電比容量可達(dá)263mAh·g-1。采用氟化鋁對富鋰錳基材料進(jìn)行表面包覆改性,改性后電極材料的首次庫倫效率和充放電循環(huán)穩(wěn)定性明顯提升,經(jīng)過100次循環(huán),包覆氟化鋁的電極容量保持率達(dá)到86%,而未包覆的僅有64.5%。
[Abstract]:This paper mainly in lithium rich manganese layered cathode material as the research object, for its rate performance is poor, its poor cycling stability, the structure design of surface coating of high density spherical particles, and the prepared materials were surface modified by chemical deposition method. The main results are as follows: through the analysis of crystal nucleation the empirical formula, the theoretical analysis of the co precipitation process. The raw material concentration, stirring speed, the concentration of ammonia, influence on the precipitation process parameters of feeding speed and pH value, provides the methodology and direction for practical work. According to the addition of complexing agent co precipitation reaction system of thermodynamic analysis, due to the existence of a large number of system the free metal ion, without adding salt precipitate a probability generating complexing agent system will increase, which demonstrates the necessity of introducing the complexing agent. The complexing agent is added The precipitation reaction system, the optimum pH co precipitation reaction range is about 8, the pH value is greater than 8 when salt precipitation phase, the pH value of a large loss of metal ions appear less than 8 respectively. The effects of temperature, stirring speed, effect of ammonia concentration and pH value of the single factor conditions the preparation process of the precursor preparation. In the Na2CO3 Ni2+-Co2+-Mn2+-C032--NH3-H20 precipitation reaction system as precipitating agent in the optimal preparation conditions of co precipitation precursor is 15 degrees Celsius temperature, stirring speed of 800 R / min-1, pH=8.0, prepared by precursor 0.4mol - L-1. ammonia concentration in the optimal conditions, particle morphology, spherical shape, particle size distribution uniform (D50=8.69 m). In the precipitation system in this study, the morphology of the tap density of the precursors prepared mainly depends on the particle, the particle size and distribution. Therefore, in order to obtain high tap density, should guarantee spherical particle morphology Regular under the premise of optimizing the particle size and distribution, as far as possible to achieve free particles closely packed. In excess of 7 wt% lithium carbonate as lithium source electrode materials obtained in the sintering of 850-C after 20h showed the best electrochemical performance. The discharge capacity of 263mAh g-1. using aluminium fluoride on lithium rich manganese base material surface modification, modified electrode material for the first time in Kulun efficiency and cycling stability improved significantly, after 100 cycles, the capacity of electrodes coated aluminum fluoride retention rate reached 86%, but not coated with only 64.5%.

【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM912
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本文編號：1386800