本文選題：高分子絡(luò)合 + 納米NiO�。� 參考：《河南科技大學(xué)》2011年碩士論文

【摘要】：NiO是典型的過渡金屬氧化物,在電致變色、催化劑、熱/氣敏傳感等方面的研究已相對成熟,但關(guān)于納米NiO作為鋰離子電池新型高性能負極材料的報道較少。溶膠-凝膠法具有化學(xué)計量容易控制、設(shè)備簡單、成本低等優(yōu)點,受到廣泛關(guān)注。本文以鎳鹽為鎳源,高分子聚合物為螯合劑,去離子水為溶劑在一定溫度下合成溶膠,采用旋轉(zhuǎn)涂布法在基體上沉積薄膜,結(jié)合熱處理工藝制備NiO薄膜�？疾烊苣z粘度、干燥條件、升溫速率和燒結(jié)溫度對NiO薄膜表面形貌的影響。研究了燒結(jié)過程中前驅(qū)體的熱分解行為,并考察了燒結(jié)溫度對薄膜結(jié)構(gòu)和電化學(xué)性能的影響。通過電化學(xué)阻抗技術(shù)初步探討了NiO與Li的反應(yīng)機理。此外,進一步采用溶膠凝膠法獲得了納米NiO粉體,考察了燒結(jié)溫度對NiO粉體形貌、結(jié)構(gòu)和電化學(xué)性能的影響。主要得到以下結(jié)論: 1.以聚丙烯酸(PAA)為螯合劑,醋酸鎳為鎳源,加入去離子水通過高分子絡(luò)合過程在一定溫度下合成了均勻穩(wěn)定的溶膠。干凝膠前驅(qū)體在450℃時有機物基本分解完全并逐步形成NiO晶體結(jié)構(gòu)。隨著燒結(jié)溫度升高,晶粒尺寸逐漸增大且晶體結(jié)構(gòu)趨于完整。 2.隨著溶膠粘度降低、干燥溫度升高和升溫速率降低,溶膠中的水分和有機物揮發(fā)更加充分,薄膜表面形貌更加致密、光滑。以粘度為5.45cst的溶膠沉積的溶膠薄膜,經(jīng)200℃干燥后以0.5℃/min的升溫速率至燒結(jié)溫度獲得了表面光滑致密,無氣孔和裂紋NiO薄膜。 3.隨著燒結(jié)溫度升高,薄膜表面顆粒逐漸長大,晶體結(jié)構(gòu)趨于完善。500℃燒結(jié)2h得到的NiO晶體結(jié)構(gòu)完整,薄膜表面粒徑分布均勻,光滑致密。該薄膜在0.01mA/cm~2的電流密度下,首次放電比容量達1174mAh/g,且在循環(huán)過程中容量損失率低于0.1%,經(jīng)100次循環(huán)后比容量仍有500mAh/g,表現(xiàn)出良好的循環(huán)穩(wěn)定性。當(dāng)充放電電流密度增大時,NiO薄膜比容量和循環(huán)性能逐漸略有降低,表現(xiàn)出良好的大電流充放電承受能力。 4.通過電化學(xué)阻抗分析,提出了等效電路R_S(Q_(dl)(R_(Ct)Z_W))(Q_(SEI)R_(SEI)),擬合誤差小于10%,合理解釋了Li與NiO電極的電化學(xué)反應(yīng)機理。首次放電過程中,固體電解質(zhì)薄膜(SEI膜)隨著極化電位的降低逐漸生長,在0.6V時基本形成。Li~+穿過SEI膜與NiO反應(yīng),形成Ni和Li_2O。充電過程中,SEI膜部分分解且Ni與Li_2O可逆的形成NiO和Li。 5.利用上述溶膠,通過溶膠凝膠法,獲得了納米NiO粉體。隨著燒結(jié)溫度升高,NiO粉體晶體粒徑逐漸長大并趨于完善。燒結(jié)溫度700℃時獲得的NiO顆粒尺寸約34nm,隨著燒結(jié)時間的延長,顆粒尺寸變大,團聚現(xiàn)象加劇。經(jīng)600℃燒結(jié)8h制備的納米NiO首次比容量能達800mAh/g左右,在0.01mA/cm~2的電流密度下進行恒電流充放電循環(huán)20次后比容量保持率高,約為500mAh/g,在0.2mA/cm~2電流密度下仍具有良好的循環(huán)性能,表現(xiàn)出良好的大電流承受能力。
[Abstract]:NiO is a typical transition metal oxide. The research on electrochromism, catalyst, thermal / gas sensing and so on has been relatively mature. However, there are few reports on nanometer NiO as a new type of high performance anode material for lithium ion batteries. The sol-gel method has many advantages, such as easy control of stoichiometry, simple equipment and low cost. In this paper, the sol was synthesized by nickel salt as nickel source, polymer as chelating agent, deionized water as solvent at a certain temperature. The thin films were deposited on the substrate by rotating coating method, and NiO thin films were prepared by heat treatment. The effects of sol viscosity, drying conditions, heating rate and sintering temperature on the surface morphology of NiO films were investigated. The thermal decomposition behavior of the precursor during sintering was studied, and the effect of sintering temperature on the structure and electrochemical properties of the film was investigated. The reaction mechanism between NiO and Li was studied by electrochemical impedance technique. In addition, nanocrystalline NiO powders were obtained by sol-gel method. The effects of sintering temperature on the morphology, structure and electrochemical properties of NiO powders were investigated. The main conclusions are as follows: 1. Using polyacrylic acid PAA) as chelating agent and nickel acetate as source, the homogeneous and stable sol was synthesized by adding deionized water through high molecular complexation process at a certain temperature. At 450 鈩，

本文編號：1789549