本文選題：鋰二次電池 + 聚合物電解質�。� 參考：《上海交通大學》2014年博士論文

【摘要】：本文從新型聚合物電解質的結構設計和聚合物的負極表面修飾兩方面著手，以圖改善鋰二次電池的綜合性能。傳統(tǒng)的鋰二次電池采用碳酸酯為電解液溶劑和聚烯烴微孔薄膜為隔膜。碳酸酯溶劑易揮發(fā)和燃燒，安全性差。而所用的隔膜對電解液不具有良好的潤濕性和保液性，易造成電解液泄漏，同時其高溫熱穩(wěn)定性比較差，這些因素易導致嚴重的安全隱患。另一方面，鋰二次電池負極在充電的強還原條件下易與電解液發(fā)生副反應。例如，雖然鈦酸鋰（LTO）被認為是下一代鋰離子電池負極材料的有力競爭者，特別適合于高功率和長壽命鋰離子動力電池。不幸的是，，鈦酸鋰作負極的鋰離子電池不能廣泛應用是因為該材料會與電解液發(fā)生副反應，尤其在高溫環(huán)境下（高于50℃）會出現(xiàn)嚴重的氣脹現(xiàn)象。針對上述二次鋰電池安全性的關鍵問題，本文主要開展下列研究工作。（1）設計、制備了一種全固態(tài)聚合物電解質和二種凝膠聚合物電解質（多孔的凝膠和純凝膠）代替液態(tài)電解液，測定了聚合物電解質的離子電導率、力學性能、電化學穩(wěn)定窗口、聚合物電解質/金屬鋰的界面穩(wěn)定性，并考察了Li/聚合物電解質/Li對稱電池的循環(huán)性能，進而用LiFePO4和pPAN-S正極組成全電池，測試其循環(huán)穩(wěn)定性和倍率性能。（2）在LTO顆粒表面包覆一層均勻的聚酰亞胺（PI）保護層，在55℃下系統(tǒng)地探索該保護層抑制LTO與液態(tài)電解液的副反應的可行性。具體研究結果如下： 1.用溶劑揮發(fā)法首次制備以高含量的聚砜-聚環(huán)氧乙烷（PSF-PEO）嵌段共聚物為基體，含低含量的雙三氟甲烷磺酰亞胺鋰（LiTFSI）和固態(tài)增塑劑丁二腈（SN）的新型全固態(tài)復合聚合物電解質。研究結果表明：PSF-PEO35+LiTFSI+SN全固態(tài)聚合物電解質的室溫和80℃下的離子電導率分別為1.6×104S cm1和1.14×103S cm1，在80℃下的電化學穩(wěn)定窗口為4.2V（對Li/Li+），與金屬鋰有良好的界面穩(wěn)定性。另外，該固態(tài)電解質在寬的溫度范圍內表現(xiàn)出良好的力學性能和熱穩(wěn)定性。Li/PSF-PEO35+LiTFSI+SN/Li對稱電池在65℃下比Li/PEO+LiTFSI/Li有更長的循環(huán)壽命及更低的極化電壓。Li/PSF-PEO35+LiTFSI+SN/LiFePO4電池在80℃具有良好的循環(huán)穩(wěn)定性和倍率性能。 2.采用原位交聯(lián)的方法制備了新型的親水性聚四氟乙烯膜（PTFE）支撐的交聯(lián)聚乙二醇-聚甲基丙烯酸甘油酯嵌段共聚物（PEG-b-PGMA）凝膠電解質（GPE），系統(tǒng)地研究了優(yōu)化的GPE-3的物理性能和電化學性能。研究結果表明：優(yōu)化的GPE-3中交聯(lián)共聚物PEG-b-PGMA和孔隙可以吸附的大量電解液，而親水性的PTFE微孔膜為GPE-3膜提供良好的力學支撐。該電解質的室溫最高離子電導率為1.3×103Scm1，能夠應用于鋰二次電池。其電化學穩(wěn)定窗口為4.5V（對Li/Li+），并與金屬鋰有良好的相容性。另外該凝膠電解質膜表現(xiàn)出優(yōu)秀的潤濕性、熱尺寸穩(wěn)定性和不易燃燒性。Li/GPE-3/LiFePO4電池在25℃具有與傳統(tǒng)液態(tài)電解液組裝的電池相近的循環(huán)穩(wěn)定性和倍率性能。Li/GPE-3/pPAN-S電池同樣擁有良好的循環(huán)穩(wěn)定性，但比容量高于Li/PE-liquid electrolyte/pPAN-S電池。 3.采用紫外光固化（UV-cured）首次合成了含有聚乙二醇二甲基丙烯酸酯-碳酸亞乙烯酯交聯(lián)共聚物（PEGDA-co-PVC）和線性聚偏氟乙烯-六氟丙烯（PVDF-HFP）的新型半互穿網(wǎng)絡聚合物（Semi-IPN）凝膠電解質，并研究其優(yōu)化的半互穿網(wǎng)絡聚合物凝膠電解質的物理和電化學性能。研究結論如下：該凝膠電解質膜沒有孔隙，可避免漏液。其室溫離子電導率為1.49×103S cm1，電化學穩(wěn)定窗口為4.2V（對Li/Li+），與金屬鋰有優(yōu)異的界面穩(wěn)定性。此外，該電解質表現(xiàn)出良好的力學性能和熱穩(wěn)定性，較好的實現(xiàn)了離子電導率和機械性能之間的平衡。Li/Semi-IPN GPE/Li比Li/PE-liquidelectrolyte/Li對稱電池在放置和循環(huán)過程中具有更低且更穩(wěn)定的界面阻抗，表現(xiàn)出更低的極化電壓。另外，Li/Semi-IPN GPE/LiFePO4電池在25℃具有與傳統(tǒng)液態(tài)電解液組裝的電池相似的循環(huán)與倍率性能。 4.鑒于改變電解液組分和在LTO表面包碳的方法對抑制LTO與液態(tài)電解液的副反應并未取得明顯的效果。本研究通過熱亞胺化反應將聚酰亞胺（PI）均勻包覆在LTO表面，并系統(tǒng)研究了該保護層在55℃下抑制LTO與液態(tài)電解液的界面副反應的效果。紅外光譜和TEM及EDS分析確認PI納米層均勻地包覆在LTO表面；PI-LTO在55℃下的循環(huán)穩(wěn)定性和倍率性能要比未包覆的LTO更好，比容量也更高；由循環(huán)前后LTO極片的SEM圖對比可知，PI包覆可以減少副反應發(fā)生；PI-LTO首次循環(huán)后的界面阻抗略大于LTO的，但是50次循環(huán)后，明顯小于LTO的界面阻抗。同時PI包覆的LTO與電解液產(chǎn)生的副反應放熱焓明顯大于未包覆的LTO。而且PI包覆后的LTO的放熱反應溫度從未包覆LTO的263℃提高到276.6℃，提高了材料的熱穩(wěn)定性。上述結果說明，PI保護層可有效地抑制LTO與電解液的副反應，提高了LTO作負極的鋰二次電池的安全性。
[Abstract]:In this paper, two aspects of the structure design of the polymer electrolyte and the surface modification of the negative electrode of the polymer are made in order to improve the comprehensive performance of the lithium two battery. The traditional lithium two battery uses carbonate as the electrolyte solvent and the polyolefin microporous membrane as the diaphragm. The carbonate solvent is easy to volatilize and burn, and the safety is poor. The electrolyte does not have good wettability and liquid retention, and it is easy to cause electrolyte leakage, and its thermal stability is poor at the same time. These factors easily lead to serious safety problems. On the other hand, the lithium two battery anode is liable to react with the electrolyte under the condition of strong reduction. For example, lithium titanate (LTO) is considered as the next generation. A strong competitor for anode materials for lithium ion batteries is particularly suitable for high power and long life lithium ion batteries. Unfortunately, lithium titanate as a negative lithium ion battery can not be widely used because the material will react with the electrolyte, especially in high temperature environment (higher than 50 degrees C). The key problems of the safety of the two lithium battery are discussed. The following research work is carried out in this paper. (1) a all solid polymer electrolyte and two kinds of gel polymer electrolytes (porous gel and pure gel) are prepared instead of liquid electrolyte. The ionic conductivity, mechanical properties and electrochemical stability window of the polymer electrolysis are measured. The interfacial stability of polymer electrolyte / lithium metal was investigated and the cycling performance of Li/ polymer electrolyte /Li symmetric battery was investigated. The cycle stability and multiplying performance of the battery were made up of LiFePO4 and pPAN-S positive electrodes. (2) a uniform polyimide (PI) protective layer was coated on the surface of LTO particles, and the protection was systematically explored at 55 degrees C. The feasibility of inhibiting the side reaction between LTO and liquid electrolyte is shown.
1. a new all solid state composite polymer electrolyte with high content of polysulfone polyepoxide (PSF-PEO) block copolymer with low content of double three fluoranimimide lithium (LiTFSI) and solid plasticizer Ding Erjing (SN) was first prepared by solvent evaporation method. The results showed that the solid state polymer electrolyte of PSF-PEO35+LiTFSI+SN was all solid. The ionic conductivity at room temperature and 80 C is 1.6 x 104S CM1 and 1.14 x 103S CM1 respectively. The electrochemical stability window at 80 C is 4.2V (Li/Li+) and has good interfacial stability with metal lithium. In addition, the solid electrolyte shows good mechanical properties and thermal stability.Li/PSF-PEO35+LiTFSI+SN/Li symmetry in a wide temperature range. The battery has longer cycle life and lower polarization voltage than Li/PEO+LiTFSI/Li at 65 C. The.Li/PSF-PEO35+LiTFSI+SN/LiFePO4 battery has good cycling stability and multiplying performance at 80.
2. a new type of hydrophilic polytetrafluoroethylene membrane (PTFE) supported polyethylene glycol polyglyceryl methacrylate block copolymer (PEG-b-PGMA) gel electrolyte (GPE) supported by a hydrophilic polytetrafluoroethylene membrane was prepared by in-situ crosslinking method. The physical properties and electrochemical properties of the optimized GPE-3 were systematically studied. The results showed that the optimized Crosslinking Copolymerization in GPE-3 was carried out. PEG-b-PGMA and pores can adsorb a large amount of electrolyte, and the hydrophilic PTFE microporous membrane provides good mechanical support for the GPE-3 membrane. The electrolyte has the highest ionic conductivity of 1.3 x 103Scm1 at room temperature and can be applied to the lithium two battery. The electrochemical stability window is 4.5V (Li/Li +), and it has good compatibility with the metal lithium. The gel electrolyte membrane exhibits excellent wettability, thermal stability and non combustibility of.Li/GPE-3/LiFePO4 batteries at 25 degrees centigrade, which have similar cyclic stability and multiplex performance with conventional liquid electrolytes..Li/GPE-3/pPAN-S batteries have good cyclic stability, but the specific capacity is higher than Li/PE-liquid electrolyte/. PPAN-S battery.
3. a new semi interpenetrating polymer (Semi-IPN) gel electrolysis containing polyethylene glycol two methacrylate ethylene carbonate crosslinked copolymer (PEGDA-co-PVC) and linear polyvinylidene fluoride (PVDF-HFP) was synthesized by UV curing (UV-cured) for the first time, and its optimized semi interpenetrating network polymer gel electrolysis was studied. The results are as follows: the gel electrolyte membrane has no pores and can avoid leakage. The ionic conductivity at room temperature is 1.49 x 103S CM1, the electrochemical stability window is 4.2V (to Li/Li+), and it has excellent interfacial stability with the metal lithium. In addition, the electrolyte shows good mechanical properties and thermal stability, and is better. The equilibrium.Li/Semi-IPN GPE/Li between the ionic conductivity and the mechanical properties has a lower and more stable interface impedance in the placement and circulation process than the Li/PE-liquidelectrolyte/Li symmetric cell, showing a lower polarization voltage. In addition, the Li/Semi-IPN GPE/LiFePO4 battery has the electricity assembled with the traditional liquid electrolyte at 25. The pool is similar to the cycle and multiplying performance.
4. in view of the change of the electrolyte component and the side reaction of the carbon in the LTO surface to inhibit the side reaction of the LTO and the liquid electrolyte, the polyimide (PI) was uniformly coated on the LTO surface by the thermo amamination reaction, and the effect of the protective layer at the interface of the LTO and the liquid electrolyte at 55 centigrade was studied. The infrared spectrum and TEM and EDS analysis confirmed that the PI nano layer was uniformly coated on the LTO surface; the cyclic stability and multiplying performance of PI-LTO at 55 C was better than that of the uncoated LTO and higher than that of the uncoated LTO; the PI encapsulation could reduce the occurrence of the side reaction and the interfacial resistance after the first cycle of PI-LTO. The resistance is slightly greater than LTO, but after 50 cycles, it is obviously less than the interface impedance of LTO. At the same time, the enthalpy of the side reaction of the PI coated LTO and the electrolyte is obviously greater than that of the uncoated LTO., and the exothermic reaction temperature of the LTO after the PI coating has never been raised to 276.6 degrees C, and the thermal stability of the material is raised. The above results indicate that PI is guaranteed. The protective layer can effectively inhibit the side reaction of LTO and electrolyte, and improve the safety of lithium secondary batteries with LTO as negative electrode.
【學位授予單位】：上海交通大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TM912

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