發(fā)布時間：2018-03-02 21:20

  本文選題：鋰離子二次電池　切入點：隔膜　出處：《南京大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：當(dāng)今世界,能源問題和環(huán)境問題已經(jīng)成為人類發(fā)展所必須面臨的重要問題。隨著傳統(tǒng)一次能源的不斷消耗,可再生清潔能源的開發(fā)和利用顯得十分重要。由于鋰離子二次電池具有能量密度大、工作電壓高、無記憶效應(yīng)、環(huán)境友好、自放電率低、循環(huán)性能好等優(yōu)點,鋰離子二次電池正成為目前研究熱點之一。組成鋰離子二次電池的關(guān)鍵材料有正極、負(fù)極、隔膜和電解液四種材料,本文以隔膜材料作為研究對象。傳統(tǒng)的隔膜制備方法主要有干法濕法兩種,干法制得的孔徑多為狹長孔,且孔徑和孔隙率難以控制,孔徑不均勻,對鋰離子二次電池一致性無明顯幫助；濕法包含相分離過程,需要用到溶劑,對環(huán)境污染嚴(yán)重。隔膜作為鋰離子二次電池的重要組成部分,在鋰離子二次電池中發(fā)揮著重要的作用。商業(yè)的聚烯烴隔膜雖然能滿足大部分鋰離子二次電池的使用,但是其材料本身特有的性質(zhì)導(dǎo)致其親液性差、熱穩(wěn)定性能差等缺點制約了它在鋰離子二次電池特別是電動汽車領(lǐng)域的發(fā)展。本文發(fā)展了一種新型的制膜方法,通過管道受限濕法腐蝕制備了SiO2尖針陣列模板,然后在聚烯烴熔融溫度下對其進(jìn)行熱壓,制得了均勻的圓形孔洞。研究了不同熱壓壓力對孔洞的影響,發(fā)現(xiàn)孔徑大小同熱壓壓力呈正比關(guān)系。本文分別采用原子層沉積法和涂布法在商業(yè)聚丙烯膜表面涂覆了氧化鋁無機涂層和聚偏氟乙烯-六氟丙烯有機涂層,有效的改善了隔膜的親液性和熱穩(wěn)定性能,從而提高了鋰離子二次電池的安全性。利用原子層沉積技術(shù)制備了氧化鋁無機涂層和聚丙烯的復(fù)合隔膜,分別研究了不同涂層厚度、單雙面涂層對隔膜性能的影響。研究得到雙面涂層在各個方面的性能都優(yōu)于單面涂層。隨著涂層厚度的增加,隔膜的熱穩(wěn)定性能和機械性能、親液性、保液性均有所提高,組裝而成的電池相比原始隔膜表現(xiàn)出了更優(yōu)異的倍率性能和循環(huán)性能。研究表明10nm厚度的雙面氧化鋁涂層對隔膜的性能提升最大,吸液率、保液率均有一倍以上的提高,在160℃環(huán)境下,復(fù)合隔膜沒有任何熱收縮,電池在0.1 C倍率下充放電,其放電比容量達(dá)到了136.68 mAh/g和137.71 mAh/g,1C、2C倍率快速充放電下,其比容量分別為114.48 mAh/g、 95.90 mAh/g和119.77 mAh/g、107.56 mAh/g。在0.5C和1C分別進(jìn)行50次充放電后,容量保持率高達(dá)96.05%和96.92%。采用倒相法制備了聚偏氟乙烯-六氟丙烯／聚丙烯有機涂層復(fù)合隔膜,研究了聚合物本體不同質(zhì)量分?jǐn)?shù)對其孔洞結(jié)構(gòu)的影響,不同鑄膜液配比對孔洞的影響以及不同凝固浴對膜形貌的影響。選取了幾種結(jié)構(gòu)優(yōu)異的復(fù)合隔膜對其進(jìn)行吸液率、保液率、熱收縮性能以及電化學(xué)性能的測試,復(fù)合隔膜表現(xiàn)出了更加優(yōu)異的性能。
[Abstract]:In today's world, energy and environmental problems have become an important issue for human development. With the continuous consumption of traditional primary energy, The development and utilization of renewable clean energy is very important. Because of the advantages of high energy density, high working voltage, no memory effect, friendly environment, low self-discharge rate and good cycling performance, lithium ion secondary battery has many advantages, such as high energy density, high working voltage, no memory effect, etc. Lithium ion secondary battery is becoming one of the research hotspots at present. The key materials of lithium ion secondary battery are positive electrode, negative electrode, diaphragm and electrolyte. In this paper, the membrane material is taken as the research object. The traditional preparation methods of diaphragm are mainly dry and wet process. The pore size obtained by dry method is mostly long and narrow, and the pore size and porosity are difficult to control, and the pore size is not uniform. It has no obvious help to the consistency of lithium ion secondary battery; the wet process includes phase separation process, which requires solvent, which pollutes the environment seriously. Diaphragm is an important part of lithium ion secondary battery. Although commercial polyolefin separators can satisfy most of the use of lithium ion secondary batteries, the unique properties of the materials lead to poor hydrophilicity. The development of lithium ion secondary battery, especially electric vehicle, is restricted by its poor thermal stability. In this paper, a new film making method is developed, and the SiO2 tip needle array template is prepared by pipe limited wet etching. Then the polyolefin was hot-pressed at the melting temperature, and a uniform circular cavity was prepared. The effect of different hot pressing pressure on the pore was studied. It is found that the pore size is proportional to the hot pressing pressure. In this paper, alumina inorganic coating and polyvinylidene fluoride hexafluoropropylene organic coating were coated on commercial polypropylene film by atomic layer deposition and coating method, respectively. The liquid lipophilic and thermal stability of the membrane was improved effectively, and the safety of lithium ion secondary battery was improved. The composite film of alumina inorganic coating and polypropylene was prepared by atomic layer deposition, and the thickness of different coating was studied. The effect of single and double coating on the performance of diaphragm. The results show that the properties of double-sided coating are better than that of single-sided coating in every aspect. With the increase of coating thickness, the thermal stability, mechanical properties, hydrophilicity and liquid-preserving properties of the film are improved. Compared with the original membrane, the assembled battery has better performance of rate and cycle. The results show that the double-sided alumina coating with a thickness of 10 nm can improve the performance of the membrane by more than twice as much as that of the original membrane, and the absorbency and retention rate of the membrane can be increased by more than one time. At 160 鈩，

本文編號：1558093