面向锂负极的隔膜涂层对锂—硫电池性能的影响研究

发布时间：2018-04-17 16:29

本文选题：锂-硫电池 + 隔膜涂层　；参考：《北京化工大学》2016年硕士论文

【摘要】：锂-硫电池因其高的理论比能量,使它成为满足能源需求的储能材料中最有希望的候选者之一。但金属锂作为锂-硫电池的负极,存在生长枝晶、粉化、多硫化锂“穿梭”造成的锂负极腐蚀等问题,导致低的库伦效率和循环寿命,并存在安全隐患。针对于此,本文创新性的将隔膜涂层改性与锂负极保护有机结合,以期锂负极具有稳定的表面,进而提高锂-硫电池的电化学性能。具体进行了以下研究工作：1、成功地制备了保护锂负极的聚偏氟乙烯(PVDF)隔膜涂层,考察了其对锂-硫电池性能的影响,并揭示了其影响规律。结果表明,PVDF涂层厚度仅为2.5μm时,在200mA/g充放电电流密度下,首次放电比容量可达1173mAh/g,循环80次后仍能保持722mAh/g,平均库伦效率可达99%。SEM测试循环后的锂负极表面发现,硫含量很低,且未见明显腐蚀,进一步证明了面向锂负极的PVDF隔膜涂层可以减少充放电过程中多硫化物的穿梭,抑制锂枝晶生长,从而实现对锂负极的保护。2、首次设计制备了LiNO3/Al2O3/PVDF复合隔膜涂层,通过Al2O3/ PVDF的双重作用及LiNO3的缓释,有效地增强了隔膜涂层对锂负极的保护,进一步提高了锂-硫电池的比容量、循环性能、倍率性能。在200mA/g充放电电流密度下,首次放电比容量提高到1283mAh/g,循环100次后比容量仍有712mAh/g,且锂负极表面形貌保持稳定,元素硫的附着大大减少。且证明了隔膜该涂层可降低了电池内阻和极化现象,减少了电解液与锂负极之间的副反应,抑制了枝晶生长。3、对锂负极保护用有机硅聚二甲基硅氧烷(PDMS)隔膜涂层的制备及性能进行了探索。实现了在200mA/g充放电电流密度下,首次放电比容量为1043mAh/g,100次循环后比容量为818mAh/g,容量保持率提高到78%,有效地提高了电池的循环稳定性。通过充放电测试发现,PDMS涂层可减小极化作用,提高电化学活性,阻隔多硫离子穿梭,抑制锂枝晶生长,进而保护锂负极。这一结果未见文献报道。
[Abstract]:Because of its high theoretical specific energy, lithium-sulfur battery has become one of the most promising candidates for energy storage materials.However, as the negative electrode of lithium-sulfur battery, there are problems such as dendrite growth, pulverization, lithium negative corrosion caused by lithium polysulfide "shuttle", which lead to low Coulomb efficiency and cycle life, and there are hidden dangers of safety.In order to improve the electrochemical performance of lithium-sulfur battery, this paper innovatively combines the membrane coating modification with lithium negative electrode protection to ensure that the lithium anode has a stable surface.In this paper, the following research work was carried out: 1. The PVDF membrane coating was successfully prepared to protect the lithium negative electrode. The effect of PVDF membrane coating on the performance of lithium-sulfur battery was investigated, and the effect of the coating on the performance of lithium-sulfur battery was revealed.The results show that when the thickness of the 200mA/g coating is only 2.5 渭 m, the initial discharge specific capacity can reach 1173 mg / g at the current density of 200mA/g charge / discharge, and the initial discharge specific capacity can be maintained at 722 mg / g after 80 cycles. The average Coulomb efficiency can reach to the surface of the lithium anode after the 99%.SEM test cycle, and the sulfur content is very low.No obvious corrosion was observed, which further proved that the PVDF film coating for lithium anode can reduce the shuttle of polysulfide during charge and discharge, and inhibit the growth of lithium dendrite.The LiNO3/Al2O3/PVDF composite diaphragm coating was designed and fabricated for the first time. By the dual action of Al2O3/ PVDF and the slow release of LiNO3, the protective effect of the diaphragm coating on the lithium negative electrode was effectively enhanced, and the specific capacity of the lithium-sulfur battery was further improved.Cycle performance, rate performance.At 200mA/g charge / discharge current density, the first discharge capacity is increased to 1283 mAh/ g, the specific capacity is still 712mAh/ g after 100 cycles, and the surface morphology of lithium anode remains stable, and the adhesion of elemental sulfur is greatly reduced.It is proved that the coating can reduce the internal resistance and polarization of the battery and reduce the side reaction between the electrolyte and the lithium anode.The dendritic growth was inhibited. The preparation and properties of silicone polydimethylsiloxane (PDMS) membrane coating for lithium negative electrode protection were investigated.Under the charge / discharge current density of 200mA/g, the first discharge specific capacity is 1043mAh/ g / g and the specific capacity is 818mAh/ g after 100 cycles, and the capacity retention rate is increased to 78g, which effectively improves the cycle stability of the battery.By charge-discharge test, it was found that PDMS coating can reduce polarization, improve electrochemical activity, block polysulfide ion shuttle, inhibit the growth of lithium dendrite, and then protect lithium negative electrode.This result is not reported in the literature.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM912

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