LiNi0.5Mn0.5O2正極材料具有成本低、低毒性等優點,使它有可能取代LiCoO2正極材料。本研究是改善固相法合成的缺點,利用溶膠凝膠法製備高穩定性、低成本之LiNi0.5Mn0.5O2正極材料。因溶膠凝膠法具有下列特性:(1)原料混合均勻; (2)能以比較低溫的環境合成;(3)較好的化學純度。 在溶膠凝膠的過程中,採用不同的鋰源、錳源、鎳源進行合成。選取合適的原料後,經由溶膠凝膠的反應,合成出LiNi0.5Mn0.5O2前驅物,再進行煅燒。並研究鋰源使用的量、一段煅燒、二段煅燒、反應時間、檸檬酸添加的量、pH值的改變、合成所需溫度探討之間的關係。並藉由X光繞射分析、SEM/EDX、TGA、DLS及恆電位電流儀觀察合成物的結晶構造、表面形態、熱穩定性、顆粒大小及電化學性能的鑑定。 由實驗結果可知,可利用氫氧化鋰、硝酸鎳、醋酸錳和檸檬酸為原料進行合成,並選擇石英管煅燒爐、pH6、Li:Ni:Mn=2.6:1:1、檸檬酸0.05 mole、二段煅燒(第一段溫度450℃、時間5小時,第二段溫度900℃、時間10小時)合成出LiNi0.5Mn0.5O2正極材料。
LiNi0.5Mn0.5O2 cathode materials has been consider to replace LiCoO2 cathode materials because its low cost and low toxicity. The study will improve the disadvantage of solid phase synthesis method to prepare LiNi0.5Mn0.5O2 cathode materials of higher stability and lower cost by sol-gel method. We use sol-gel method to prepare because it has some of the advantages: (1) the material mixing uniformity, (2) the cathode materials can synthesis at low temperature, (3) higher chemical yield. In sol-gel process, we use the different of lithium source, nickel source and manganese source for synthesis. After we chose the appropriate materials ,then through sol-gel reaction can synthesis LiNi0.5Mn0.5O2 precursor and the precursor conduct to calcination furnace. We study the relationship between the amount of lithium source, one step calcination, two step calcinations, reaction time, the amount of citric acid, pH value, temperature. We explore the crystalline phases, the morphology, thermal stability , the particle size and electrochemical performance by XRD, SEM/EDX, TGA, DLS and Potentiostat Autolab. According to the experiments, we could use lithium hydroxide, nickel nitrate, manganese acetate and citric acid to synthesis. And we selected quartz tube calciner, pH =6, Li:Ni:Mn= 2.6:1:1, citric acid= 0.05 mole, two step calcination(first temperature= 450℃,time5 hours, second temperature= 900℃、time=10 hours)to synthesis LiNi0.5Mn0.5O2 cathode material.
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