电解液中痕量水和金属离子杂质对电池性能影响的研究
发布时间：2019-01-02 11:39
【摘要】：目前,从微电子技术到交通运输,可充电电池的使用越来越广泛,要求也越来越苛刻,锂离子电池已经成为能量存储和转换设备中使用最广泛的电池。但随之而来的问题也不断凸显,其中,容量衰减成为限制锂离子电池进一步发展的主要瓶颈。研究发现,痕量水和过渡金属离子的溶蚀对电池性能破坏非常严重。在锂离子电池的生产制备过程中痕量水的存在是不可避免的,这会导致电池的不可逆容量损失,影响固体电解质界面膜的形成,且会引起集流体和阴极材料的腐蚀。过渡金属离子在正极的溶蚀,不仅导致正极可用活性材料损失,且溶蚀的金属离子在电解液中迁移并沉积在负极,致使固体电解质界面膜严重损害,还有部分金属离子插入石墨层导致负极容量衰减。因此,探究痕量水和过渡金属离子对电池性能破坏的机理和提出相对应的抑制措施成为目前研究的重点。本论文主要进行以下三方面的研究。第一,以六氟磷酸锂-碳酸乙烯酯/碳酸二乙酯电解液和双草酸硼酸锂-环丁砜/碳酸二乙酯电解液为研究对象,通过调节电解液中痕量水的含量,系统地研究电解液中不同含量的痕量水对锂离子电池综合性能的影响。若以100个循环后的容量保持率低于85%为电池失效的衡量标准,则六氟磷酸锂-碳酸乙烯酯/碳酸二乙酯和双草酸硼酸锂-环丁砜/碳酸二乙酯电解液中痕量水的临界值分别为0.2113‰和0.5391‰。第二,采用商用电解液六氟磷酸锂-碳酸乙烯酯/碳酸二乙酯作为参比电解液,研究双草酸硼酸锂作为电解质锂盐对负极锰沉积的抑制作用。双草酸硼酸锂-环丁砜/碳酸二乙酯电解液体系具有优异的成膜性,能在石墨电极表面形成致密的保护膜,可有效地抑制锰沉积。但当电解液中锰浓度过高时由于存在电化学吸附的作用,所以固体电解质界面膜表面仍有少量锰离子被检测到。这些锰离子会催化电解液的分解,分解产物沉积在固体电解质界面膜表面上,增加了电池阻抗,从而降低电池的循环稳定性。通过前两部分的研究,明确痕量水和金属离子破坏电池性能的机理,并构建新型的电解液体系来抑制电解液中痕量水和过渡金属离子对电池造成的破坏。第三,利用喷雾沉积技术,采用硫酸锂水溶液对石墨电极表面进行预处理。经硫酸锂预处理的石墨电极组装的半电池,不仅表现出优异的循环性能和较高的容量保持率,还具有较低的界面阻抗。这种修饰处理对锂离子电池性能改善有重要意义,同时从负极材料和固体电解质界面膜的角度出发,为抑制电解液中痕量水和过渡金属离子对电池性能的破坏提供了一个新思路。
[Abstract]:At present, from microelectronics technology to transportation, rechargeable batteries are more and more widely used and demanding. Li-ion batteries have become the most widely used batteries in energy storage and conversion devices. However, the following problems have become increasingly prominent, among which capacity attenuation is the main bottleneck restricting the further development of lithium-ion batteries. It was found that the corrosion of trace water and transition metal ions seriously damaged the performance of the battery. The existence of trace water in the preparation of lithium-ion batteries is inevitable, which will lead to the irreversible loss of the battery capacity, affect the formation of solid electrolyte interfacial films, and cause the corrosion of the collector and cathode materials. The dissolution of transition metal ions at the positive electrode not only results in the loss of the active materials available for the positive electrode, but also the migration of the dissolved metal ions in the electrolyte and deposition in the negative electrode, resulting in serious damage to the solid electrolyte boundary film, Some of the metal ions inserted into the graphite layer lead to negative electrode capacity attenuation. Therefore, exploring the mechanism of trace water and transition metal ions destroying the performance of the battery and putting forward corresponding inhibition measures have become the focus of current research. This paper mainly carries on the following three aspects of research. Firstly, the lithium hexafluorophosphate-vinyl carbonate / diethyl carbonate electrolyte and the lithium oxalate borate-sulfolane / diethyl carbonate electrolyte were used as the research objects, and the content of trace water in the electrolyte was adjusted. The effect of trace water in electrolyte on the comprehensive performance of lithium ion battery was studied systematically. If the capacity retention rate of 100 cycles is less than 85%, The critical values of trace water in lithium-hexafluorophosphate-vinyl carbonate / diethyl carbonate and lithium borate bisoxalate / diethyl carbonate electrolyte are 0.2113 鈥，
本文编号：2398434
[Abstract]:At present, from microelectronics technology to transportation, rechargeable batteries are more and more widely used and demanding. Li-ion batteries have become the most widely used batteries in energy storage and conversion devices. However, the following problems have become increasingly prominent, among which capacity attenuation is the main bottleneck restricting the further development of lithium-ion batteries. It was found that the corrosion of trace water and transition metal ions seriously damaged the performance of the battery. The existence of trace water in the preparation of lithium-ion batteries is inevitable, which will lead to the irreversible loss of the battery capacity, affect the formation of solid electrolyte interfacial films, and cause the corrosion of the collector and cathode materials. The dissolution of transition metal ions at the positive electrode not only results in the loss of the active materials available for the positive electrode, but also the migration of the dissolved metal ions in the electrolyte and deposition in the negative electrode, resulting in serious damage to the solid electrolyte boundary film, Some of the metal ions inserted into the graphite layer lead to negative electrode capacity attenuation. Therefore, exploring the mechanism of trace water and transition metal ions destroying the performance of the battery and putting forward corresponding inhibition measures have become the focus of current research. This paper mainly carries on the following three aspects of research. Firstly, the lithium hexafluorophosphate-vinyl carbonate / diethyl carbonate electrolyte and the lithium oxalate borate-sulfolane / diethyl carbonate electrolyte were used as the research objects, and the content of trace water in the electrolyte was adjusted. The effect of trace water in electrolyte on the comprehensive performance of lithium ion battery was studied systematically. If the capacity retention rate of 100 cycles is less than 85%, The critical values of trace water in lithium-hexafluorophosphate-vinyl carbonate / diethyl carbonate and lithium borate bisoxalate / diethyl carbonate electrolyte are 0.2113 鈥，
本文编号：2398434
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