【作者】 陈静娟；

【导师】 王海辉；

【作者基本信息】 华南理工大学 ， 化学工程， 2013， 博士

【摘要】 隔膜是锂离子电池的重要组成部分，锂离子电池的安全性能很大程度上取决于隔膜的性能，而目前商业化的锂离子电池广泛使用聚合物隔膜，而聚合物隔膜容易被锂枝晶刺穿、在过热时发生形变等引起电池内部短路，从而导致电池损坏甚至短路起火等。另外，由于聚合物隔膜自身的疏水性能，导致其对电解液的浸润和保存性能差，限制了电池大倍率性能，从而影响了锂离子电池在电动汽车上的应用。人们开发了有机-无机复合隔膜、聚合物电解质隔膜等，但是这些隔膜材料仍然存在热稳定性差、离子电导率差等问题。多孔无机膜由于其具有良好的绝缘性能、热稳定性、电解液浸润和保存性能等，被考虑用作锂离子电池隔膜。本论文针对锂离子电池体系，以提高电池的安全性能、倍率性能和低温性能为目的制备了Al₂O₃隔膜、SiO₂隔膜和AAO膜等，并设计基于自支撑隔膜的一体化电池，利用SEM对隔膜的形貌进行分析、采用恒流充放电测试、交流阻抗法等手段对其电化学性能进行了深入系统的研究。首先，通过二次高温烧结纳米Al₂O₃、微米Al₂O₃和造孔剂EDTA制备多孔Al₂O₃膜，对其微观结构、孔隙率、电解液的浸润性能进行了研究，结果表明：相对于聚合物隔膜，多孔Al₂O₃膜具有较高的孔隙率、电解液保存性能；浸润电解液的Al₂O₃膜具有优异的电导率，使用Al₂O₃隔膜的LiFePO₄/石墨电池具有很好的循环性能、倍率性能和低温性能等。因此，多孔Al₂O₃可以用作锂离子电池隔膜。其次，通过高温烧结廉价易得的商业化SiO₂粉制备多孔SiO₂膜，并将其用作LiMn₂O₄/Li电池隔膜。多孔SiO₂膜具有良好的机械性和孔隙率，并且具有很好的电解液浸润和保存性能。由于SiO₂的亲水性和能与电解液中微量的HF反应，从而提高了LiMn₂O₄/Li电池的循环性能、倍率性能和低温性能，并且在一定程度上减缓了LiMn₂O₄的在高温时的容量衰减。这种廉价易得、性能优异的SiO₂隔膜，对锂离子电池性能的提高、价格的降低都有很大作用，为无机隔膜在锂离子电池上的应用提供了有益的选择。再次，利用自制的简单的装置通过二次阳极氧化的方法高效环保地制备了通孔阳极氧化铝膜（AnodicAluminum Oxide，AAO），该通孔AAO膜厚度降至60μm、孔隙率高达72%仍保持足够的机械强度。AAO膜表现出很好的对电解液的吸附和保持性能，同时非水电解液对亲水性的AAO膜的浸润性能优于聚合物隔膜。与聚合物隔膜相比，使用AAO膜作为隔膜的LiFePO₄/石墨电池表现出更好的循环性能、倍率性能和低温性能等。同时利用交流阻抗测试（EIS）分析AAO隔膜对电池性能的影响。实验结果表明，AAO隔膜具有很好的应用前景。最后，通过将电极材料涂覆于二次烧结制备的多孔Al₂O₃膜两侧，制备自支撑的一体化电池，这种自支撑的一体化电池具有良好的电化学性能，简化了电池的制备工艺，省去了将电极材料与隔膜贴合在一起的支撑体和外界压力，同时能够避免电池在运输和撞击过程中隔膜的错位导致的电池内部短路等。更重要的是，这种自支撑的一体化电池可用于设计可插入式的电池堆栈，这种结构的电池易于设计、管理和维护，为大型电池的设计提供有益的参考。更多还原

【Abstract】 Separator is an important part in lithiumion battery, and the safety performanceof the lithium ion battery largely depends on the property of the separator. Up to now,polymer separator are widely used in the commercialized lithium-ion batteries, butsuch separatoror is easy to punctured by lithium dendrites or undergo obviousdimensional changes at elevated temperatures, causing internal short-circuit of thebattery and resulting in the battery damage even firing. Moreover, owning to theintrinsically hydrophobic properties of the polymer separator, it is hard for thepolymer separator to infiltrate and hold the non-aqueous electrolyte, which limits therate performance of the battery, thus adversely affecting the application of thelithium-ion battery for the electric vehicle and hybrid-electric vehicle. Theorganic-inorganic composite separator has been developed, but there are still issues ofthe poor thermal stability, poor ionic conductivity.Because of its insulating property, good thermal stability and excellentelectrolyte retention capacity, the porous inorganic membrane has been taken intoaccount as lithium-ion battery separator for the first time. This dissertation is focuseson lithium-ion battery system, and aim at improving the safety performance and ratecapability of the battery. The porous Al₂O₃, SiO₂and AAO separators have beenprepared. The technique of SEM is adopted to characterize the microstructure andmorphology of the as-prepared membranes. The electrochemical methods includinggalvanostatically charged and discharged test, cyclic voltammetry, and impedancemeasurement were used to systematically investigate their electrochemicalperformances.Firstly, porous Al₂O₃separator has been prepared through twicehigh-temperature sintering of nano-Al₂O₃, micron-sized Al₂O₃and the pore-formingagent of EDTA. The microstructure, porosity and electrolyte-infiltration performancesof porous Al₂O₃separator have been studied. The results demonstrate that: comparingwith the polymer separator, Al₂O₃separator possesses higher porosity and excellentelectrolyte retention performance; after infiltrated with electrolyte of1M LiPF6/EC+DEC （1:1, w/w）, the Al₂O₃separator exhibits an excellent ion conductivity. TheLiFePO₄/graphite cell using the inorganic separator shows higher discharge capacity,rate capability, and better low-temperature performance than that using thecommercialized polymer separator. The LiFePO₄/graphite battery possesses better cycle performance, rate performance, and low temperature performance. Thus, theporous Al₂O₃can be used as a lithium ion battery separator. All the evidences indicatethat the inorganic separator is very promising to be applied in the large-sizedlithium-ion batteries, especially for the long-term energy storage systems.Secondly, the porous SiO₂separator with good mechanical strength has beenprepared by sintering the commercialized raw materials of SiO₂which is cheap andeasy to get. The electrolyte-infltrated SiO₂separator exhibits excellent ionicconductivity even at as low as-20°C and much better electrolyte retentionperformance than polymer at50°C. The LiMn₂O₄/Li cell using the SiO₂separatorshows higher discharge capacity, rate capability and better low-temperatureperformance than that using the commercial polymer separator. Furthermore, the SiO₂separator can alleviate LiMn₂O₄/Li capacity fading at high temperature of55°C. Theexcellent electrochemical performance of the SiO₂separator can be attributed to thefollowing reasons:（1） excellent electrolyte infiltration and retention performance ofhydrophilic SiO₂;（2） capillary force of the porous pores in the SiO₂separator;（3）SiO₂can capture the trace amounts of moisture and acidic impurity in the electrolyte.All these results indicate that the SiO₂separator is very promising to be applied in thelithium-ion batteries, especially for the long-term energy storage systems.Thirdly, through-hole anodic aluminum oxide （AAO） film has been quickly andefficiently prepared within a simple homemade device. The AAO film has a highporosity of72%and good mechanical strength even as thin as60μm. The AAO filmhas excellent performances in electrolyte uptake and retention, and the wettability ofthe electrolyte to the hydrophilic AAO film is much better than that of thecommercialized polymer separator. Compared with the polymer separator, theLiFePO₄/graphite cell using the AAO separator shows better cycling capacity, ratecapability, and low-temperature performance. The effect of the AAO separator onperformance of LiFePO₄/graphite cell has also been investigated by the EIS. It isdemonstrated that the AAO separator is very promising to be applied in thelithium-ion batteries.Finally, an integrative cell with a porous Al₂O₃membrane as both a support anda separator has been fabricated by coating the electrode materiasl on each side of theseparator, while the electrolyte was infltrated inside. The LiFePO₄/graphiteintegrative cells are evaluated in coin-type cells and exhibited good cycle capacity. The self-standing integrative cell is a simple and promising technology to assemblethe battery stacks and meanwhile had an obvious advantage of forming a frmstructure, which could avoid inner short circuit during being moved or crashed. Suchself-standing integrative cell with Al₂O₃porous separator could provide a competitivecandidate to the currently rolling battery assembly, especially for large-sized energystorage device.更多还原