正确评估锂氧气电池的电化学性能
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- 英文论文题名：Correctly Evaluating the Performance of Lithium-oxygen Battery
- 论文作者：沈越 ; 张旺 ; 黄云辉
- 英文论文作者：Yue Shen ; Wang Zhang ; Yunhui Huang ; School of Material Science and Technology ; Huazhong University of Science and Technology
- 年：2016
- 作者机构：华中科技大学材料科学与工程学院;
- 论文关键词：锂氧气电池 ; 限容循环 ; 过氧化锂-石墨
- 会议召开时间：2016-07-01
- 会议录名称：中国化学会第30届学术年会摘要集-第三十分会：化学电源
- 语种：中文
- 分类号：TM911.41
- 学会代码：ZGHY
- 会议名称：中国化学会第30届学术年会-第三十分会 ; 化学电源
- 会议地点：中国辽宁大连
- 主办单位：中国化学会
- 学会名称：中国化学会
- 页数：2
- 文件大小：159k
- 原文格式：D
- 会议级别：全国
摘要
锂氧气电池是一个非常有争议的研究领域。许多研究人员认为其拥有电池体系中最高的理论能量密度,必将具有广阔的发展前景。而也有其他研究者认为锂氧气电池目前远被高估。一些研究论文中已报道的锂氧气电池正极材料比容量可以达到数千毫安时每克,并且其循环寿命超过一百圈,更有甚者可以达到数千循环~1。然而,当前已报道的电化学性能最优异的锂氧气电池真的好吗?为此,我们对锂氧气电池测试中常用的限制容量循环(金属锂过量)测试方法进行了探讨,发现这种测试手段可能会对电池性能的评估带来误导,原因如下:1.在锂氧气电池中,正极和负极的电化学活性材料分别是氧气和金属锂,两者都是远远过量的。采用限制容量循环的测试方法实际上是在测试催化剂的可重复利用性,而并非电化学活性材料的循环性能。2.锂氧气电池的充放电过程中往往会伴随一些不可逆副反应产物的生成,例如氢氧化锂、碳酸锂、甲酸锂、硫酸锂等。但只要这些副反应产物溶解在电解液中或者沉积在远离电极的位置,使得电化学活性位点没有被堵塞或覆盖,电池就能够继续正常运行。3.锂氧气电池中正极材料与电解液的质量比往往非常小,仅仅基于正极材料质量的比容量是没有任何意义的~2。基于以上几个原因,我们提出了一种新型的过氧化锂-石墨的电池组合来评估正极的循环性能。与传统的金属锂过量的电池结构相比,在过氧化锂-石墨电池体系中,锂离子的含量是有限的。电池循环过程中,任何可能消耗锂离子的副反应的发生都会以容量衰减的形式客观地反映在充放电曲线上。利用这种电池结构,我们对一些电解液体系进行了对比,同时还发现特定氧化还原介质的加入可以有效地提高电池的循环性能~(3,4)。总的来说,锂氧气电池仍然具有的应用前景,但我们必须直面其存在的各种问题并尽可能地解决。
The lithium-oxygen battery(LOB) is quite a controversial topic.A lot of people believe it will have a brilliant future because it has the highest theoretic energy density.But there are also other people believing it is largely overestimated.Some papers have reported LOB cathodes with specific capacity of several thousand mAh g~(-1),and cycle life longer than 100 cycles or even several thousand cycles~1.But is the state-of-art LOB really that good? We looked into the conventional limited capacity cycling tests with unlimited lithium anode,and found the testing result may be misleading due to the following reasons:1.The electrochemically active reactant at the cathode side is oxygen,which is unlimited.The active material at the anode side is lithium,also unlimited.In such a test,we are actually testing the reusability of the catalyst instead of the cyclability of the active electrode material.2.The LOB cathode discharge and charge is accompanied with irreversible formation of side-products such as LiOH,Li_2CO_3,HCOOLi,Li_2SO_4,et al.But as long as these side-products are dissolved or simply accumulated away from the cathode and do not hinder the discharge,the cycling can still go on.3.The cathode/electrolyte weight ratio is usually extremely small,which makes the cathodic weight based specific capacity meaningless.~2Because of the above reasons,we propose a novel Li_2O_2-graphite set-up to evaluate the cathodic cyclability.Unlike the conventional set-up with unlimited lithium metal anode,the total amount of lithium ion in the Li_2O_2-graphite battery is limited.If any side reactions consumed the lithium-ion,the capacity lose would be objectively reflected to the charge/discharge curves.Based on this set-up,several electrolyte recipes were compared and we found the positive effect of redox mediates to improve the cycling performance is very obvious~(3,4).On the whole,the LOB still has a future,but we must face the challenge before overcome it.
The lithium-oxygen battery(LOB) is quite a controversial topic.A lot of people believe it will have a brilliant future because it has the highest theoretic energy density.But there are also other people believing it is largely overestimated.Some papers have reported LOB cathodes with specific capacity of several thousand mAh g~(-1),and cycle life longer than 100 cycles or even several thousand cycles~1.But is the state-of-art LOB really that good? We looked into the conventional limited capacity cycling tests with unlimited lithium anode,and found the testing result may be misleading due to the following reasons:1.The electrochemically active reactant at the cathode side is oxygen,which is unlimited.The active material at the anode side is lithium,also unlimited.In such a test,we are actually testing the reusability of the catalyst instead of the cyclability of the active electrode material.2.The LOB cathode discharge and charge is accompanied with irreversible formation of side-products such as LiOH,Li_2CO_3,HCOOLi,Li_2SO_4,et al.But as long as these side-products are dissolved or simply accumulated away from the cathode and do not hinder the discharge,the cycling can still go on.3.The cathode/electrolyte weight ratio is usually extremely small,which makes the cathodic weight based specific capacity meaningless.~2Because of the above reasons,we propose a novel Li_2O_2-graphite set-up to evaluate the cathodic cyclability.Unlike the conventional set-up with unlimited lithium metal anode,the total amount of lithium ion in the Li_2O_2-graphite battery is limited.If any side reactions consumed the lithium-ion,the capacity lose would be objectively reflected to the charge/discharge curves.Based on this set-up,several electrolyte recipes were compared and we found the positive effect of redox mediates to improve the cycling performance is very obvious~(3,4).On the whole,the LOB still has a future,but we must face the challenge before overcome it.
引文
[1]Liu,T.;Leskes,M.;Yu,W.;Moore,A.J.;Zhou,L.;Bayley,P.M.;Kim,G.;Grey,C.P.Science 2015,350:530.
[2]Shen,Y.;Zhang,W.;Chou,S.-L.;Dou,S.-X.Science 2016,352:667.
[3]Sun,D.;Shen,Y.;Zhang,W.;Yu,L.;Yi,Z.;Yin,W.;Wang,D.;Huang,Y.;Wang,J.;Wang,D.;Goodenough,J.B.J.Am.Chem.Soc.2014,136:8941.
[4]Chen,Y.H.;Freunberger,S.A.;Peng,Z.Q.;Fontaine,O.;Bruce,P.G.Nat.Chem.2013,5:489.
[2]Shen,Y.;Zhang,W.;Chou,S.-L.;Dou,S.-X.Science 2016,352:667.
[3]Sun,D.;Shen,Y.;Zhang,W.;Yu,L.;Yi,Z.;Yin,W.;Wang,D.;Huang,Y.;Wang,J.;Wang,D.;Goodenough,J.B.J.Am.Chem.Soc.2014,136:8941.
[4]Chen,Y.H.;Freunberger,S.A.;Peng,Z.Q.;Fontaine,O.;Bruce,P.G.Nat.Chem.2013,5:489.