抑制锂枝晶的锂硫电池电解液添加剂研究

STUDY ON ADDITIVES IN ELECTROLYTE OF LITHIUM SULFUR BATTERY FOR INHIBITING LITHIUM DENDRITE

李阳阳

11930433

硕士

材料工程

邓永红

2021-05-15

2021-06-07

南方科技大学

深圳

锂硫电池因具备高能量密度而被研究者和企业家们关注。但是，它在具备较高的能量密度的同时也有许多弊端。其中，锂枝晶生长是影响锂硫电池商业化的主要问题。研究电解液对锂枝晶生长的抑制作用是锂硫电池开发的最主要途径。因而，为了得到能抑制锂枝晶生长的长寿命的锂硫电池, 本论文主要从锂硫电池电解液添加剂着手，探究其对锂枝晶生长的抑制效果和对电池性能的影响效果。经过各种测试，证明了所使用的添加剂能有效地抑制锂硫电池中的锂枝晶生长。主要研究内容包括以下两个方面：1、对酯类电解液进行研究，通过在酯类电解液中加入新型添加剂抑制锂电池锂枝晶。本章使用电解液六氟磷酸锂（LiPF6）/ 碳酸乙烯酯（EC）-碳酸二甲酯（DMC）和二氟草酸硼酸锂（LiODFB）/EC-DMC-氟代碳酸乙烯酯（FEC），在其中加入未被报道过的新型的阳离子表面活性剂四甲基六氟磷酸铵（CNPF），研究CNPF应用于酯类电解液时对电解液性能的影响，结果发现CNPF应用于酯类电解液时，LiODFB/EC-DMC-FEC+CNPF的锂硫电池首圈放电比容量可达1415 mAh g-1，锂锂对称电池的短路时间超过600 h，锂铜电池的库伦效率达到98.7%；LiPF6/ EC-DMC+CNPF的锂硫电池首圈放电比容量可达1476 mAh g-1；CNPF的加入可以在一定程度上抑制高负载锂硫电池的放电比容量的剧烈衰减现象。通过表征证实了CNPF具有很好的抑制锂枝晶的作用，研究表明该添加剂在酯类电解液中具有很好的应用前景。2、对醚类电解液进行研究，本研究开发了一种新型添加剂四甲基四氟硼酸铵（CNBF）应用于醚类电解液体系 双三氟甲烷磺酰亚胺锂（LiTFSI）/氯代环烷烃（DOL）-乙二醇二甲醚（DME）+硝酸锂（LiNO3）中。我们对加入不同含量CNBF的锂-铜电池锂沉积/剥离进行测试，测试表明CNBF含量为3 wt.%时电解液性能最好。该电解液应用于锂硫电池时，电池的循环性能能得到极大地改善。在2C倍率下的循环，其首圈放电比容量为793 mAh g-1，在100圈后容量保持率在77%左右，1000圈后容量保持率在64%左右；在0.5C倍率下的循环，其首圈放电比容量为1014 mAh g-1，在100圈后容量保持率在80%左右，400圈时容量保持率在70%左右。

Lithium-sulfur batteries have attracted attention from researchers and entrepreneurs because of their high energy density. However, it has many disadvantages along with its high energy density. Among them, lithium dendrite growth is the main problem affecting the commercialization of lithium-sulfur batteries. The inhibition of lithium dendrite growth by electrolyte is the most important way to develop lithium-sulfur batteries. Therefore, in order to obtain a long-life lithium sulfur battery that can inhibit the growth of lithium dendrite, this paper mainly starts from the electrolyte additive of lithium sulfur battery to explore its inhibition effect on the growth of lithium dendrite and its influence on the performance of the battery. It has been proved by various tests that the additive can effectively inhibit the growth of lithium dendrite in lithium-sulfur batteries. The main research contents include the following two aspects: 1. The ester electrolyte was studied, and the lithium dendrite of lithium battery was inhibited by adding new additives into the ester electrolyte. In this chapter, electrolyte lithium hexafluorophosphate (LIPF6)/vinyl carbonate (EC) -dimethyl carbonate (DMC) and lithium difluoroxalate borate (LIODFB)/EC-DMC-vinyl fluorocarbonate (FEC) were used, and a novel cationic surfactant tetramethylammonium hexafluorophosphate (CNPF) was added to it. The effect of CNPF on the performance of ester electrolyte was studied. The results showed that when CNPF was applied to ester electrolyte, the discharge specific capacity of the first cycle of LiODFB/EC-DMC-FEC+CNPF lithium-sulfur battery could reach 1415 mAh g-1, and the short circuit time of the lithium-lithium symmetric battery was more than 600h. The coulomb efficiency of lithium-copper battery reached 98.7%; The discharge specific capacity of the LiPF6/ EC-DMC+CNPF lithium-sulfur battery can reach 1476 mAh g-1 in the first cycle. The addition of CNPF can suppress the severe attenuation of discharge specific capacity of high load lithium sulfur batteries to a certain extent. It was confirmed by characterization that CNPF has a good effect on inhibiting lithium dendrite, and the study shows that CNPF has a good application prospect in ester electrolyte. 2. The ether electrolyte was studied. In this study, a new additive tetramethylammonium tetrafluoroborate (CNBF) was developed and applied to the ether electrolyte system of lithium bis trifluoromethane sulfimide (LITFSI)/chlorinated cycloalkane (DOL) -ethylene glycol dimethyl ether (DME) + lithium nitrate (LINO3). We tested lithium deposition/stripping of lithium-copper batteries with different CNBF content, and the results showed that the electrolyte with 3 wt% CNBF content had the best performance. The cycle performance of lithium-sulfur batteries can be greatly improved when the electrolyte is applied to the batteries. The specific discharge capacity of the first cycle is 793 mAh g-1 at 2C multiplicity, and the capacity retention rate is about 77% after 100 and 64% after 1000 cycles. The discharge specific capacity is 1014 mAh g-1 in the first cycle at the rate of 0.5C, and the capacity retention rate is about 80% after 100 and 70% after 400 cycles.

锂金属电池 锂金属负极 电解液添加剂 锂枝晶 锂硫电池

Lithium metal batteries Lithium metal anode Electrolyte additive Lithium dendrite Lithium sulfur batteries

中文

独立培养

南方科技大学

李阳阳. 抑制锂枝晶的锂硫电池电解液添加剂研究[D]. 深圳. 南方科技大学,2021.