锂硫电池隔膜修饰及正极改性研究
发布时间：2018-07-23 09:58
【摘要】：与传统的锂离子电池相比,锂硫二次电池凭借其高比容量(1675 mAh/g)、高能量密度(2600 Wh/kg)、低成本以及环境友好的优点具有更高的经济利益和发展前景。然而,锂硫电池自身的一些物化特性阻碍了其商业化应用:(1)单质硫及放电产物Li_2S_2/Li_2S具有电子绝缘性;(2)单质硫与Li_2S_2/Li_2S密度不同导致体积膨胀;(3)多硫化锂在电解液中的溶解和穿梭效应。本论文以KB@Ir复合材料作为隔膜修饰层,利用金属Ir纳米颗粒的极性吸附和催化特性,提高了锂硫电池的电化学性能。此外还通过将KB@Cu复合材料作为载体对电极的电化学性能进行提升。通过优化粘结剂种类对锂硫电池电化学性能及电极活性物质载量进行优化和提升。在此基础上本论文还成功制备了软包锂硫电池。本论文通过微波还原法将金属Ir纳米颗粒均匀沉积在活化后的KB材料表面,成功制备了KB@Ir复合材料,采用吸附实验、XPS、CV及Tafel等测试手段对KB@Ir复合材料的吸附特性和催化特性进行了表征和分析。研究结果表明KB@Ir复合材料对多硫化锂能够产生强烈的化学吸附作用,同时金属Ir纳米颗粒能够加速多硫化锂的转换过程。通过将其作为隔膜修饰层应用在锂硫电池当中,显著提高了电池的电化学性能。在0.2 C下首次放电容量为1508 mAh/g,即使在2 C的大电流下仍具有653 mAh/g的可逆容量。在1 C倍率下循环500次后,电池仍具有452mAh/g的放电比容量,每圈容量衰减率为0.105%。通过高温固相还原法合成了KB@Cu复合材料,将其作为活性物质载体显著提升了锂硫电池的电化学性能,金属Cu作为极性材料能起到固定硫和多硫化锂的作用,热处理过程中金属Cu会与单质硫反应生成CuSx,金属Cu与单质硫之间的强相互作用使得锂化过程中CuSx能够直接生成Li2S和单质Cu而避免生成可溶性多硫化锂,同时金属Cu能够提高电极的电子电导率。电化学测试结果表明KB@Cu/S复合材料在0.2 C的倍率下首次放电容量为1003 mAh/g,循环100次后仍具有508 mAh/g的可逆容量;即使在2 C的倍率下仍具有499 mAh/g的放电比容量。分析PVDF、PEO和GA作为粘结剂时对锂硫电池的电化学性能的影响,研究发现GA作为粘结剂时能够显著提高锂硫电池的循环性能,这是由于GA具有很强的粘结能力,起到很好的固硫作用,同时能够抑制电极在循环过程中的收缩变形,同时GA中有很多的含氧官能团,能够对多硫化锂起到化学固定作用,从而提高活性物质利用率。在此基础上利用GA优异的粘结能力成功制备了硫载量为3.4mg/cm~2的电极极片。本文还在现有工作基础上成功制备了2 Ah的软包锂硫电池,其首次放电容量达到1784 mAh,并能够持续工作超过7000 min。这为锂硫电池商业化进程的可行性进行了初步探索。
[Abstract]:Compared with the traditional lithium-ion battery, the lithium sulfur secondary battery has higher economic benefits and development prospects because of its advantages of high specific capacity (1675 mAh/g), high energy density (2600 Wh-1 / kg), low cost and environmental friendliness. However, some physical and chemical characteristics of lithium sulfur batteries have hindered their commercial applications: (1) simple sulfur and its discharge product Li _ 2S _ 2 / Li _ 2S have electronic insulation; (2) the density of simple sulfur and Li2S _ 2 / Li _ 2S leads to volume expansion; (3) the dissolving and shuttling effect of lithium polysulfide in electrolyte. In this paper, the electrochemical performance of lithium-sulfur battery was improved by using the polar adsorption and catalytic properties of metal ir nanoparticles as the membrane modification layer. In addition, the electrochemical properties of the electrode were improved by using KBbile-Cu composite as the carrier. The electrochemical performance and electrode active material load of lithium sulfur battery were optimized and enhanced by optimizing the binder types. On this basis, the soft-clad lithium-sulfur battery has been successfully fabricated. In this paper, the metal ir nanoparticles were uniformly deposited on the surface of activated KB materials by microwave reduction method, and KBBIL ir composites were successfully prepared. The adsorption and catalytic properties of KBBP ir composites were characterized and analyzed by means of adsorption experiments, XPS CV and Tafel. The results show that the chemical adsorption of lithium polysulfide on KBbilis ir composite is strong, and the metal ir nanoparticles can accelerate the conversion process of lithium polysulfide. The electrochemical performance of lithium-sulfur battery was improved by using it as a membrane modification layer. The initial discharge capacity is 1508 mg / g at 0.2C, and the reversible capacity is 653 mAh/g even at a high current of 2 C. After 500 cycles at 1 C rate, the specific discharge capacity of 452mAh/g is still present, and the attenuation rate of capacity per cycle is 0.105. The high temperature solid state reduction method was used to synthesize KBIL Cu composite, which was used as active material carrier to improve the electrochemical performance of lithium-sulfur battery significantly. Metal Cu as polar material can play the role of fixed sulfur and lithium polysulfide. During heat treatment, Cu reacts with elemental sulfur to form CuSx.The strong interaction between metallic Cu and elemental sulfur makes CuSx produce Li2S and elemental Cu directly, thus avoiding the formation of soluble lithium polysulfide. At the same time, Cu can improve the electronic conductivity of the electrode. The electrochemical test results show that the initial discharge capacity of KBDB-Cu / S composite is 1003 mg / g at the rate of 0.2C, and the reversible capacity of the composite is 508 mAh/g after 100 cycles, and the specific capacity of discharge is 499 mAh/g even at the rate of 2 C. The effect of PVDF PEO and GA as binder on the electrochemical performance of lithium sulfur battery was analyzed. It was found that GA as binder could significantly improve the cycle performance of lithium sulfur battery, which was due to the strong bonding ability of GA. At the same time, there are many oxygen-containing functional groups in GA, which can fix lithium polysulfide chemically and improve the utilization rate of active substances. On this basis, the electrode with sulfur load of 3.4mg/cm~2 was successfully prepared by using the excellent bonding ability of GA. On the basis of the existing work, a 2 Ah soft-coated lithium-sulfur battery has been successfully prepared. The initial discharge capacity of the battery is 1784 mAhh, and it can work continuously for more than 7000 mins. The feasibility of commercial process of lithium-sulfur battery is preliminarily explored.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912;TB33
本文编号：2139038
[Abstract]:Compared with the traditional lithium-ion battery, the lithium sulfur secondary battery has higher economic benefits and development prospects because of its advantages of high specific capacity (1675 mAh/g), high energy density (2600 Wh-1 / kg), low cost and environmental friendliness. However, some physical and chemical characteristics of lithium sulfur batteries have hindered their commercial applications: (1) simple sulfur and its discharge product Li _ 2S _ 2 / Li _ 2S have electronic insulation; (2) the density of simple sulfur and Li2S _ 2 / Li _ 2S leads to volume expansion; (3) the dissolving and shuttling effect of lithium polysulfide in electrolyte. In this paper, the electrochemical performance of lithium-sulfur battery was improved by using the polar adsorption and catalytic properties of metal ir nanoparticles as the membrane modification layer. In addition, the electrochemical properties of the electrode were improved by using KBbile-Cu composite as the carrier. The electrochemical performance and electrode active material load of lithium sulfur battery were optimized and enhanced by optimizing the binder types. On this basis, the soft-clad lithium-sulfur battery has been successfully fabricated. In this paper, the metal ir nanoparticles were uniformly deposited on the surface of activated KB materials by microwave reduction method, and KBBIL ir composites were successfully prepared. The adsorption and catalytic properties of KBBP ir composites were characterized and analyzed by means of adsorption experiments, XPS CV and Tafel. The results show that the chemical adsorption of lithium polysulfide on KBbilis ir composite is strong, and the metal ir nanoparticles can accelerate the conversion process of lithium polysulfide. The electrochemical performance of lithium-sulfur battery was improved by using it as a membrane modification layer. The initial discharge capacity is 1508 mg / g at 0.2C, and the reversible capacity is 653 mAh/g even at a high current of 2 C. After 500 cycles at 1 C rate, the specific discharge capacity of 452mAh/g is still present, and the attenuation rate of capacity per cycle is 0.105. The high temperature solid state reduction method was used to synthesize KBIL Cu composite, which was used as active material carrier to improve the electrochemical performance of lithium-sulfur battery significantly. Metal Cu as polar material can play the role of fixed sulfur and lithium polysulfide. During heat treatment, Cu reacts with elemental sulfur to form CuSx.The strong interaction between metallic Cu and elemental sulfur makes CuSx produce Li2S and elemental Cu directly, thus avoiding the formation of soluble lithium polysulfide. At the same time, Cu can improve the electronic conductivity of the electrode. The electrochemical test results show that the initial discharge capacity of KBDB-Cu / S composite is 1003 mg / g at the rate of 0.2C, and the reversible capacity of the composite is 508 mAh/g after 100 cycles, and the specific capacity of discharge is 499 mAh/g even at the rate of 2 C. The effect of PVDF PEO and GA as binder on the electrochemical performance of lithium sulfur battery was analyzed. It was found that GA as binder could significantly improve the cycle performance of lithium sulfur battery, which was due to the strong bonding ability of GA. At the same time, there are many oxygen-containing functional groups in GA, which can fix lithium polysulfide chemically and improve the utilization rate of active substances. On this basis, the electrode with sulfur load of 3.4mg/cm~2 was successfully prepared by using the excellent bonding ability of GA. On the basis of the existing work, a 2 Ah soft-coated lithium-sulfur battery has been successfully prepared. The initial discharge capacity of the battery is 1784 mAhh, and it can work continuously for more than 7000 mins. The feasibility of commercial process of lithium-sulfur battery is preliminarily explored.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912;TB33
【参考文献】
相关期刊论文 前1条
1 刁岩;谢凯;洪晓斌;熊仕昭;;Li-S电池硫正极性能衰减机理分析及研究现状概述[J];化学学报;2013年04期
，本文编号：2139038
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