非水溶剂锂-空气电池中的氧气电极反应

基于锂-氧气反应的锂-空气电池在所有的锂电池体系中具有最大的理论容量和能量密度,认识锂-空气电池中的氧气电极反应对锂-空气电池的研发具有指导意义.本文以金电极/乙腈电解液为模型体系,介绍了锂-空气电池在放电和充电过程中的氧气电极反应机理.电池放电时,氧气还原成超氧自由基,超氧自由基与锂离子结合生成不稳定的超氧化锂;通过歧化反应,超氧化锂生成放电反应最终产物过氧化锂.电池充电时,过氧化锂通过一步两电子直接氧化生成氧气,不经过超氧化锂中间态.在阐述氧气电极反应机理的同时,还对研究氧气反应的各种电化学方法作了介绍.     

热处理温度对锂氧气电池用Co-N/C催化剂催化性能的影响(英文)

开发低成本、高效的空气电极催化剂是发展锂空气电池的关键课题之一.采用邻菲咯啉(phen)为配体制备Co(phen)2配合物,负载于BP2000碳载体上,并分别在600、700、800和900°C的温度下进行热处理,制备得到碳支撑的Co-N催化剂(Co-N/C).对催化剂的氧还原反应/析氧反应(ORR/OER)活性进行了表征,并且与典型的CoTMPP/C催化剂进行了比较.同时研究了煅烧温度对Co-N/C催化剂的组成和结构的影响.电化学测试结果表明,热处理温度为700-800°C时催化剂具有较好的电化学性能.Co-N/C催化剂具有电化学性能优良与低成本的特点,是一种良好的锂氧气电池催化剂.     

热处理温度对锂氧气电池用Co-N/C催化剂催化性能的影响

开发低成本、高效的空气电极催化剂是发展锂空气电池的关键课题之一. 采用邻菲咯啉(phen)为配体制备Co(phen)₂配合物,负载于BP2000 碳载体上,并分别在600、700、800 和900 ℃的温度下进行热处理,制备得到碳支撑的Co-N催化剂(Co-N/C). 对催化剂的氧还原反应/析氧反应(ORR/OER)活性进行了表征,并且与典型的CoTMPP/C催化剂进行了比较. 同时研究了煅烧温度对Co-N/C催化剂的组成和结构的影响. 电化学测试结果表明,热处理温度为700-800 ℃时催化剂具有较好的电化学性能. Co-N/C催化剂具有电化学性能优良与低成本的特点,是一种良好的锂氧气电池催化剂.     

锂-氧气电池:正极催化剂的最新进展与挑战（英文）

非质子锂-氧气电池具有高理论能量密度,在过去几年里受到了广泛关注。然而,动力学缓慢的氧还原反应(ORR)/氧析出反应(OER)和放电产物Li₂O₂导电性差导致锂-氧气电池过电位大,放电容量有限,循环寿命短。开发有效的锂-氧气电池正极催化剂可以调控放电与充电过程中Li₂O₂的形成和可逆分解,减小放电/充电极化。尽管提升ORR/OER动力学的正极催化剂已经取得了一系列重要进展,但是对正极在放电和充电中Li₂O₂生成和分解过程的理解依然是不足的。这篇综述聚焦于锂-氧气电池正极催化剂的最新进展,总结了催化剂与Li₂O₂生成/分解的作用关系,本文首先指出了锂-氧气电池正极面临的科学问题,包括动力学缓慢的ORR/OER过程和导电性差的反应产物Li₂O₂钝化电极,并提出了锂-氧气电池正极设计准则。通过对最近报道的正极催化剂进行分类讨论,明晰调控催化剂活性位点策略,理解在正极反应过程中...     

可充锂空气电池多孔纳米催化剂

可充锂空气电池是当前化学电源研究热点和重点, 近年来取得了重要进展. 简要介绍了该领域在空气电极多孔纳米催化材料的设计与应用方面的最新研究成果, 讨论了碳、贵金属、氧化物三类催化材料的特征及性能, 展望了新型高效氧还原/氧析出双功能阴极纳米催化剂的发展方向.     

碱性溶液中空气电极催化剂Co-N/C的研究

采用简单热处理方式制备了空气电极用氧还原电催化剂Co-N/C(800),利用线性电位扫描、控电流极化曲线及单电池测试等方法评价Co-N/C(800)的氧还原反应(ORR)催化活性。结果表明:该催化剂在碱性溶液中(1 mol/LNaOH)对ORR有很好的催化活性,起始氧还原电位约为0.04 V(vs.Hg/HgO);在室温及空气气氛条件下,以Co-N/C(800)制备的空气电极在7 mol/L NaOH溶液中时性能最佳,在电极电位为-0.6 V(vs.Hg/HgO)时电流密度达100 mA/cm2;自制的空气电极与纯锌片所组装的锌-空气电池,以7 mol/L NaOH为电解液,在电池过电位为0.8 V时,电流密度超过了100 mA/cm2,催化性能优于常规MnO2催化剂;同时进行了单电池放电测试,放电平台保持在1.25～1.30 V且性能稳定。     

CoOOH用作阴极催化剂对非水性锂-氧气电池性能的影响

利用工艺简单,成本低廉的共沉淀法制得CoOOH,并用作非水性锂-氧气电池阴极催化剂。通过恒流充放电、线性伏安扫描（LSV）和电化学阻抗（EIS）测试研究了电极的电化学性能。结果表明：由于CoOOH能够明显提高氧气还原反应（ORR）的催化活性,与未使用CoOOH的电极相比较,使用CoOOH为催化剂的电极首次放电容量高达5 093 mAh·g^-1,提高了1.7倍。电池的充电过电压降低了约460 mV,充电可逆性得到增强,充放电可逆性提高,使得循环性能得到显著改善。     

CoOOH用作阴极催化剂对非水性锂-氧气电池性能的影响

利用工艺简单,成本低廉的共沉淀法制得CoOOH,并用作非水性锂-氧气电池阴极催化剂。通过恒流充放电、线性伏安扫描（LSV）和电化学阻抗（EIS）测试研究了电极的电化学性能。结果表明：由于CoOOH能够明显提高氧气还原反应（ORR）的催化活性,与未使用CoOOH的电极相比较,使用CoOOH为催化剂的电极首次放电容量高达5 093 mAh·g^-1,提高了1.7倍。电池的充电过电压降低了约460 mV,充电可逆性得到增强,充放电可逆性提高,使得循环性能得到显著改善。     

基于废旧锂电池回收制备LixMO (x=0.79, 0.30, 0.08; M=Ni/Co/Mn)材料作为锂-氧气电池正极催化剂的电化学性能研究

锂-氧气电池因其超高的理论比容量而受到科研界的广泛关注, 但其存在较为严重的充放电极化和较差的循环稳定性等问题, 从而极大地限制其商业化进程. 因此设计出有效的正极催化剂是解决锂-氧气电池面临的这些棘手问题的必要手段. 通过对不同充电状态的废旧锂电池正极进行回收制得三种不同锂含量的多元金属氧化物Li_xMO (x=0.79, 0.30, 0.08; M=Ni/Co/Mn), 并分别用作锂-氧气电池正极催化剂. 系统研究了Li_xMO材料中锂含量及晶体结构对其电化学性能的影响. 电化学测试结果表明, 与Li_0.79MO和Li_0.08MO催化剂相比, 基于Li_0.30MO为正极催化剂的锂-氧气电池在电流密度100 mA•g^–1和限定容量800 mAh•g^–1的条件下具有较高的放电比容量(14655.9 mAh•g^–1)、较低的充电电压(3.83 V)和较高的能量转换效率(72.2%). 而且该电池体系在充放电循环140圈后充电终止电压仍低于4.3 V. 最终认为制得的Li_0.30MO材料具有优异的催化性能归因于其稳定的层状-岩盐相复合结构以及结构中富含的氧化镍相和氧空位之间的协同作用. 这些优点能够促进放电产物的可逆形成与分解, 从而提高锂-氧气电池循环性能.     

CoOOH用作阴极催化剂对非水性锂-氧气电池性能的影响（英文）

利用工艺简单,成本低廉的共沉淀法制得Co OOH,并用作非水性锂-氧气电池阴极催化剂。通过恒流充放电、线性伏安扫描(LSV)和电化学阻抗(EIS)测试研究了电极的电化学性能。结果表明:由于Co OOH能够明显提高氧气还原反应(ORR)的催化活性,与未使用Co OOH的电极相比较,使用Co OOH为催化剂的电极首次放电容量高达5 093 m Ah·g~(-1),提高了1.7倍。电池的充电过电压降低了约460 m V,充电可逆性得到增强,充放电可逆性提高,使得循环性能得到显著改善。     

The potential for long-term operation of a lithium-oxygen battery using a non-carbonate-based electrolyte

Herein we demonstrate the feasibility of extended cycle operation of a Li-O(2) battery by simple control of the discharge/charge protocol. By avoiding electrolyte decomposition and the deep discharge state of the air electrode, we were able to construct a Li-O(2) cell capable of efficiently cycling over 50 times with high energy density.     

Li-O2 battery with a dimethylformamide electrolyte

Stability of the electrolyte toward reduced oxygen species generated at the cathode is a crucial challenge for the rechargeable nonaqueous Li-O(2) battery. Here, we investigate dimethylformamide as the basis of an electrolyte. Although reactions at the O(2) cathode on the first discharge-charge cycle are dominated by reversible Li(2)O(2) formation/decomposition, there is also electrolyte decomposition, which increases on cycling. The products of decomposition at the cathode on discharge are Li(2)O(2), Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li, NO, H(2)O, and CO(2). Li(2)CO(3) accumulates in the electrode with cycling. The stability of dimethylformamide toward reduced oxygen species is insufficient for its use in the rechargeable nonaqueous Li-O(2) battery.     

Screening for superoxide reactivity in Li-O2 batteries: effect on Li2O2/LiOH crystallization

Unraveling the fundamentals of Li-O(2) battery chemistry is crucial to develop practical cells with energy densities that could approach their high theoretical values. We report here a straightforward chemical approach that probes the outcome of the superoxide O(2)(-), thought to initiate the electrochemical processes in the cell. We show that this serves as a good measure of electrolyte and binder stability. Superoxide readily dehydrofluorinates polyvinylidene to give byproducts that react with catalysts to produce LiOH. The Li(2)O(2) product morphology is a function of these factors and can affect Li-O(2) cell performance. This methodology is widely applicable as a probe of other potential cell components.     

Electrical conductivity in Li2O2 and its role in determining capacity limitations in non-aqueous Li-O2 batteries

Non-aqueous Li-air or Li-O(2) cells show considerable promise as a very high energy density battery couple. Such cells, however, show sudden death at capacities far below their theoretical capacity and this, among other problems, limits their practicality. In this paper, we show that this sudden death arises from limited charge transport through the growing Li(2)O(2) film to the Li(2)O(2)-electrolyte interface, and this limitation defines a critical film thickness, above which it is not possible to support electrochemistry at the Li(2)O(2)-electrolyte interface. We report both electrochemical experiments using a reversible internal redox couple and a first principles metal-insulator-metal charge transport model to probe the electrical conductivity through Li(2)O(2) films produced during Li-O(2) discharge. Both experiment and theory show a "sudden death" in charge transport when film thickness is ~5 to 10 nm. The theoretical model shows that this occurs when the tunneling current through the film can no longer support the electrochemical current. Thus, engineering charge transport through Li(2)O(2) is a serious challenge if Li-O(2) batteries are ever to reach their potential.     

多孔Fe_2O_3纳米纤维用于高容量长寿命锂空气电池催化剂

采用静电纺丝技术,以乙酰丙酮铁[Fe(C5H7O2)3]、聚乙烯吡咯烷酮(PVP)和二甲基甲酰胺(DMF)为原料,制备了由Fe2O3纳米颗粒组成的高比表面积的多孔纳米纤维,并成功应用于锂氧气电池用催化剂.Fe2O3纳米颗粒为反应提供了充足的活性位点,提高了电池容量;而三维网状结构为反应物及产物提供了足够的反应及储存空间,避免了对电极孔道堵塞的问题,从而达到了锂空气电池长循环的目的.     

Novel DMSO-based electrolyte for high performance rechargeable Li-O2 batteries

A dimethyl sulfoxide (DMSO) based electrolyte is first proposed for rechargeable lithium-O(2) (Li-O(2)) batteries. Superior battery performances, including high discharge capacity and low charge potential, are successfully obtained.     

Catalytic activity trends of oxygen reduction reaction for nonaqueous Li-air batteries

We report the intrinsic oxygen reduction reaction (ORR) activity of polycrystalline palladium, platinum, ruthenium, gold, and glassy carbon surfaces in 0.1 M LiClO(4) 1,2-dimethoxyethane via rotating disk electrode measurements. The nonaqueous Li(+)-ORR activity of these surfaces primarily correlates to oxygen adsorption energy, forming a "volcano-type" trend. The activity trend found on the polycrystalline surfaces was in good agreement with the trend in the discharge voltage of Li-O(2) cells catalyzed by nanoparticle catalysts. Our findings provide insights into Li(+)-ORR mechanisms in nonaqueous media and design of efficient air electrodes for Li-air battery applications.     

Stable isotope natural abundance of nitrous oxide emitted from Antarctic tundra soils: effects of sea animal excrement depositions

Nitrous oxide (N2O), a greenhouse gas, is mainly emitted from soils during the nitrification and denitrification processes. N2O stable isotope investigations can help to characterize the N2O sources and N2O production mechanisms. N2O isotope measurements have been conducted for different types of global terrestrial ecosystems. However, no isotopic data of N2O emitted from Antarctic tundra ecosystems have been reported although the coastal ice-free tundra around Antarctic continent is the largest sea animal colony on the global scale. Here, we report for the first time stable isotope composition of N2O emitted from Antarctic sea animal colonies (including penguin, seal and skua colonies) and normal tundra soils using in situ field observations and laboratory incubations, and we have analyzed the effects of sea animal excrement depositions on stable isotope natural abundance of N2O. For all the field sites, the soil-emitted N2O was 15N- and 18O-depleted compared with N2O in local ambient air. The mean delta values of the soil-emitted N2O were delta15N = -13.5 +/- 3.2 per thousand and delta18O = 26.2 +/- 1.4 per thousand for the penguin colony, delta15N = -11.5 +/- 5.1 per thousand and delta18O = 26.4 +/- 3.5 per thousand for the skua colony and delta15N = -18.9 +/- 0.7 per thousand and delta18O = 28.8 +/- 1.3 per thousand for the seal colony. In the soil incubations, the isotopic composition of N2O was measured under N2 and under ambient air conditions. The soils incubated under the ambient air emitted very little N2O (2.93 microg N2O--N kg(-1)). Under N2 conditions, much more N2O was formed (9.74 microg N2O--N kg(-1)), and the mean delta15N and delta18O values of N2O were -19.1 +/- 8.0 per thousand and 21.3 +/- 4.3 per thousand, respectively, from penguin colony soils, and -17.0 +/- 4.2 per thousand and 20.6 +/- 3.5 per thousand, respectively, from seal colony soils. The data from in situ field observations and laboratory experiments point to denitrification as the predominant N2O source from Antarctic sea animal colonies.     

A Long‐Life Lithium–Air Battery in Ambient Air with a Polymer Electrolyte Containing a Redox Mediator

Lithium–air batteries when operated in ambient air generally exhibit poor reversibility and cyclability, because of the Li passivation and Li₂O₂/LiOH/Li₂CO₃ accumulation in the air electrode. Herein, we present a Li–air battery supported by a polymer electrolyte containing 0.05 m LiI, in which the polymer electrolyte efficiently alleviates the Li passivation induced by attacking air. Furthermore, it is demonstrated that I⁻/I₂ conversion in polymer electrolyte acts as a redox mediator that facilitates electrochemical decomposition of the discharge products during recharge process. As a result, the Li–air battery can be stably cycled 400 times in ambient air (relative humidity of 15 %), which is much better than previous reports. The achievement offers a hope to develop the Li–air battery that can be operated in ambient air.     

A Long-Life Lithium–Air Battery in Ambient Air with a Polymer Electrolyte Containing a Redox Mediator

Lithium–air batteries when operated in ambient air generally exhibit poor reversibility and cyclability, because of the Li passivation and Li₂O₂/LiOH/Li₂CO₃ accumulation in the air electrode. Herein, we present a Li–air battery supported by a polymer electrolyte containing 0.05 m LiI, in which the polymer electrolyte efficiently alleviates the Li passivation induced by attacking air. Furthermore, it is demonstrated that I⁻/I₂ conversion in polymer electrolyte acts as a redox mediator that facilitates electrochemical decomposition of the discharge products during recharge process. As a result, the Li–air battery can be stably cycled 400 times in ambient air (relative humidity of 15 %), which is much better than previous reports. The achievement offers a hope to develop the Li–air battery that can be operated in ambient air.