本文選題：γ-丁內(nèi)酯　切入點(diǎn)：戊二腈　出處：《華東理工大學(xué)》2017年碩士論文

【摘要】：目前,鋰離子電池(LIBs)憑借其高能量密度,高放電平臺和長循環(huán)壽命已廣泛應(yīng)用于眾多領(lǐng)域,鋰離子電池在手機(jī)、筆記本電腦、數(shù)碼產(chǎn)品等電子通訊產(chǎn)品中得到廣泛應(yīng)用并占據(jù)了主導(dǎo)地位。鋰電池現(xiàn)使用電解質(zhì)多為液體狀態(tài)的有機(jī)電解質(zhì),它在較高電壓下會持續(xù)氧化分解,從而引起正極中過渡金屬的溶解,加速電池比容量的衰減。本文從提高電解液在高電壓下的穩(wěn)定性入手,通過電解液溶劑及添加劑的選擇,使其在4.35 V和5 V以上的高電壓下也正常工作而不發(fā)生分解。首先,在商業(yè)化的由EC、EMC、DEC和LiPF6組成的基礎(chǔ)電解液體系中,分別加入Y-丁內(nèi)酯(GBL)和戊二腈(GLN)、1%和2%的氟代碳酸乙烯酯(FEC)作為添加劑,改善基礎(chǔ)電解液體系在高電壓下的性能。研究結(jié)果表明,由于Y-丁內(nèi)酯(GBL)作為電解液添加劑,能在LiNi_(0.5)Mn_(1.5)O_4表面優(yōu)先氧化分解形成一層穩(wěn)定的保護(hù)膜,有效阻止了電解液的不斷氧化分解,能夠改善基于LiNi0.5Mn1.504正極的鋰離子電池的性能;而戊二腈(GLN)雖然有一個較寬的電化學(xué)窗口,能維持電池在低倍率下的循環(huán)穩(wěn)定性,但它與低電位的Li負(fù)極間的兼容性隨著電流密度的增加而變差,嚴(yán)重影響了LiNi0.5Mn1.504正極材料性能的發(fā)揮。另外本文還研究了 1%和2%氟代碳酸乙烯酯(FEC)對LiNi_(0.5)Mn_(1.5)O_4(LNMO)電化學(xué)性能的影響,實(shí)驗(yàn)結(jié)果表明:FEC顯著提高了 LiNi0.5Mn1.504的循環(huán)性能和比容量。150圈后,1%FEC作為電解液的半電池比容量為106.7 mA h g~(-1),容量保持率為91.1%。2%FEC作為電解液的半電池比容量為113.5 mAh g~(-1),容量保持率為96.2%。并且,2%FEC體系能夠在2 C倍率下維持105.7 mAh g~(-1)的比容量。而只含有基礎(chǔ)電解液的LiNi_(0.5)Mn_(1.5)O_4/Li半電池,1 C循環(huán)150圈后比容量僅為91.3 mAh g~(-1),容量保持率為82.3%。測試研究表明:FEC的優(yōu)先氧化有利于形成高導(dǎo)電性能的膜,該膜由少量低電導(dǎo)率的物質(zhì)組成。另外,2%FEC比1%FEC更有利于形成一層均一且致密的膜。
[Abstract]:Li-ion battery has been widely used in many fields because of its high energy density, high discharge platform and long cycle life. Electronic communications products, such as digital products, are widely used and dominate. Lithium batteries now use organic electrolytes in liquid state, which continue to be oxidized and decomposed at higher voltages. Therefore, the solution of transition metal in the positive electrode and the attenuation of the specific capacity of the battery are accelerated. In this paper, the stability of the electrolyte under high voltage is improved, and the selection of solvent and additive is carried out. It works normally at a high voltage of 4.35 V and over 5 V without decomposing. First, in a commercial basic electrolyte system composed of EMC DEC and LiPF6, Y-Butyrolactone (GBL) and pentanilonitrile (GLN) (1% and 2%) were added as additives to improve the performance of the basic electrolyte system at high voltage. The results showed that because Y-Butyrolactone (GBL) was used as electrolyte additive, It can preferentially oxidize and decompose on the surface of LiNi_(0.5)Mn_(1.5)O_4 to form a stable protective film, which effectively prevents the continuous oxidation decomposition of electrolyte and improves the performance of lithium-ion battery based on LiNi0.5Mn1.504 positive electrode, while glutaric nitrile GLN) has a wide electrochemical window. It can maintain the cycle stability of the battery at low rate, but its compatibility with the Li negative electrode with low potential becomes worse with the increase of current density. In addition, the effects of 1% and 2% ethylfluorocarbonate on the electrochemical properties of LiNiNiLi-0.5MnM / Mn-Mn-MOS have been studied, and the effects of 1% and 2% ethylfluorocarbonate on the electrochemical properties of LNMOs have also been studied. The experimental results show that the cycle performance and specific capacity of LiNi0.5Mn1.504 were significantly improved by 1: FEC. The specific capacity of 1 C as electrolyte was 106.7 Ma / h / g ~ (-1) / L ~ (-1), and the capacity retention ratio was 91. 1 路2 ~ (2) C as electrolyte. The specific capacity of half cell was 113.5 mAh / L ~ (-1). The specific capacity of LiNi_(0.5)Mn_(1.5)O_4/Li semilayer containing only basic electrolyte was 91.3 mAh / g ~ (-1), and the specific capacity was 91.3 mAh / g ~ (-1) after 150 cycles. The specific capacity of 2C system could maintain 105.7 mAh / g ~ (-1) at the rate of 2 C. The measurement showed that the specific capacity of LiNi_(0.5)Mn_(1.5)O_4/Li half-cell containing basic electrolyte was only 91.3 mAh / g ~ (-1) / L ~ (-1), and the capacity retention was 82.3%. The experimental results show that the preferential oxidation of the FEC is beneficial to the formation of films with high conductivity. The film is composed of a small amount of materials with low conductivity. In addition, 2C is more favorable than 1C to form a uniform and compact film.
【學(xué)位授予單位】：華東理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O646;TM912

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