Nonaqueous Li-O2 Batteries Research Articles

The Effect of Water on Quinone Redox Mediators in Nonaqueous Li-O2 Batteries.

The parasitic reactions associated with reduced oxygen species and the difficulty in achieving the high theoretical capacity have been major issues plaguing development of practical nonaqueous Li-O2 batteries. We hereby address the above issues by exploring the synergistic effect of 2,5-di-tert-butyl-1,4-benzoquinone and H2O on the oxygen chemistry in a nonaqueous Li-O2 battery. Water stabilizes the quinone monoanion and dianion, shifting the reduction potentials of the quinone and monoanion to more positive values (vs Li/Li+). When water and the quinone are used together in a (largely) nonaqueous Li-O2 battery, the cell discharge operates via a two-electron oxygen reduction reaction to form Li2O2, with the battery discharge voltage, rate, and capacity all being considerably increased and fewer side reactions being detected. Li2O2 crystals can grow up to 30 μm, more than an order of magnitude larger than cases with the quinone alone or without any additives, suggesting that water is essential to promoting a solution dominated process with the quinone on discharging. The catalytic reduction of O2 by the quinone monoanion is predominantly responsible for the attractive features mentioned above. Water stabilizes the quinone monoanion via hydrogen-bond formation and by coordination of the Li+ ions, and it also helps increase the solvation, concentration, lifetime, and diffusion length of reduced oxygen species that dictate the discharge voltage, rate, and capacity of the battery. When a redox mediator is also used to aid the charging process, a high-power, high energy density, rechargeable Li-O2 battery is obtained.

Clean Electrocatalysis in a Li2O2 Redox-Based Li–O2 Battery Built with a Hydrate-Melt Electrolyte

The electrocatalysis of the oxygen reduction reaction and oxygen evolution reaction in nonaqueous Li–O2 batteries suffers from severe side reactions and high charge potential. Herein, we design an unreported hydrate-melt Li–O2 battery without use of an unstable organic solvent. Its redox reaction depends on the formation of Li2O2 in high yield (96%) and its full decomposition. The designed battery shows an ultralow charge potential of ∼3.16 V, a high discharge capacity of 38 mAh cm–2, and stable cycling ability. After careful comparison of the discharge and charge products by XRD, SEM, Raman, FTIR, NMR, and quantitative titration, the great improvement in performance is attributed to the efficient avoidance of side reactions related to organic solvent degradation, which may be the primary cause of the high charge potential in a nonaqueous Li–O2 battery. These results should initiate a deep understanding of Li–O2 batteries and indicate another strategy toward practical Li–air batteries with moisture-proof ...

Ruthenium oxide modified hierarchically porous boron-doped graphene aerogels as oxygen electrodes for lithium-oxygen batteries.

Suitable catalysts and reasonable structures for oxygen electrodes can effectively improve the electrochemical performance of lithium–oxygen batteries. In this work, ruthenium oxide modified boron-doped hierarchically porous reduced graphene aerogels (RuO2-B-HRG) are prepared by a sol–gel and subsequent low temperature annealing method and used as oxygen electrodes. The RuO2 nanoparticles (5–10 nm) are uniformly anchored in the three-dimensional B-HRG continuous electric network. The RuO2-B-HRG aerogel possesses a large specific surface area (287.211 m2 g−1) and numerous mesopores and micropores. The pores facilitate electrolyte impregnation and oxygen diffusion, and they provide greatly increased accommodation space for the discharge products. Electrochemical tests show that the RuO2-B-HRG/KB enables the electrode overpotential to decrease, and the rate capability and the cycling stability are enhanced compared with pure HRG. The enhanced performance is ascribed to the bifunctional catalytic activity of RuO2-B-HRG and its unique three-dimensional porous architecture. The method is proved to be an effective strategy to combine porous carbon materials and nanoscale catalysts as electrodes for Li–O2 batteries.

Cobalt porphyrin and Salcomine as novel redox shuttle species to enhance the oxygen evolution reaction in Li[sbnd]O2 batteries

LiO2 secondary batteries outclass other battery systems in terms of energy density, at least on a theoretical point of view. However, these systems suffer issues from both the metallic lithium electrode and the oxygen electrode. For example, the cathode discharge product (lithium peroxide) is a semiconductor of large bandgap (5 eV), which yields severe cyclability issues, as the re-charge is limited. Using electrolyte additives may be one option to mitigate (if not solve) this issue. Herein, a new redox mediator compound (N,N′-Bis(salicylidene)ethylenediaminocobalt (II), noted Co-salen) is studied with regards to its impact on the oxygen reduction and evolution reactions in non-aqueous medium. Its performances are compared to those of a Cobalt porphyrin (noted Co(II)-Po). Electrochemical experiments in three-electrode setup, Differential Electrochemical Mass Spectrometry (DEMS) and UV–Visible spectroscopy, demonstrate that Co-salen can also greatly improve the oxygen reduction kinetics (the ORR onset potential is positively-shifted by 230 mV in the presence of Co-salen), thanks to the formation of a complex with oxygen in solution. Secondly, Co-salen enables to efficiently transport electrons in the solution, and help to recover the electrode surface (the re-charge of large Li2O2 particles becomes possible). Therefore, enhancing both the oxygen reduction and the oxygen evolution reactions (ORR and OER) with only one additive in the electrolyte is feasible, and places Co-salen among the best compounds to be used as redox shuttles for non-aqueous LiO2 batteries.

Boosting the Cycle Life of Aprotic Li–O2 Batteries via a Photo‐Assisted Hybrid Li2O2‐Scavenging Strategy

AbstractThe development of the nonaqueous Li–O2 battery, a promising candidate for high‐gravimetric‐energy‐storage techniques, is seriously restrained by the high charge overpotential during electrochemical decomposition of insulating Li2O2. Benefiting from the photovoltage, photo‐assisted charging is revealed as a feasible method to reduce the charge potential. However, a long period of illumination will inevitably aggravate the degradation of the electrolyte. Herein, composed of contact‐ion‐pairs (CIPs), a newly introduced superconcentrated electrolyte presents superior stability against parasitic photocatalytic decomposition. More significantly, the conventional and photo‐assisted charging processes are rationally integrated as a unique hybrid strategy, in which the highly polarized charging stage is replaced by the photo‐assisted Li2O2‐scavenging process. By tuning the photocatalysis and Li2O2 electrochemical oxidization, the hybrid Li2O2‐scavenging strategy not only boosts the cycle life of rechargeable Li–O2 batteries but also opens possibilities in designing photocatalysis‐involved rechargeable energy‐storage battery systems.

A powerful Li[sbnd]O2 battery based on an efficient hollow Cu2O cathode catalyst with tailored crystal plane

Issues with the sluggish kinetics of oxygen reduction and oxygen evolution reduction hinder the advance of LiO2 batteries for next-generation energy storage. To alleviate these problems, Cu2O nanoparticles with different crystal planes have been synthesized via a simple solution reaction and characterized as a bi-functional catalyst for non-aqueous LiO2 battery. In this work, catalytic behaviour of Cu2O nanoparticles with different crystal planes are initially explored and it is found that the Cu2O nanoparticles exposing {111} crystal planes exhibit the most catalytic performance compared with other crystal planes, which is further confirmed by using first-principles computations. Inspired by selectively catalytic behaviour of crystal plane, porous Cu2O nanoframes exposed with eight {111} crystal planes and higher surface area derives from all-corner-truncated rhombic dodecahedron Cu2O nanoparticles are synthesized, which can act as highly activity three-dimensional cathode in a typical LiO2 battery after being directly combined with carbon nanotubes by electrostatic interaction. Thanks to the excellent catalytic activity of carbon nanotubes-Cu2O nanoframes and unique cathode structure, batteries with this cathode display an enhanced electrochemical performance including superior round-trip efficiency, excellent cycling performance and high specific capacity.

Two-dimensional siligraphenes as cathode catalysts for nonaqueous lithium-oxygen batteries

The nonaqueous lithium-oxygen (Li-O2) battery is promising as a superior energy storage medium, whose practical applications are limited by the catalytic performance of cathode catalysts. Using density functional theory calculations, we have systematically investigated the catalytic mechanism and catalytic performance of siligraphenes as cathode catalysts in nonaqueous Li-O2 batteries. For the siligraphenes studied here, Li2O is the final discharge product. Among them, the single-layered SiC (SL-SiC) exhibits potential as a suitable cathode catalyst due to the considerably low overpotential values during discharge and charge process. That is, 0.73 V for oxygen reduction reaction (ORR) and 1.87 V for oxygen evolution reaction (OER). The quantitative analysis indicates that the ORR overpotential on siligraphenes is linearly correlated with the ΔEads of the last added Li in Li4O2* (* denotes the adsorbed surface), while the OER overpotential is linearly correlated with the Eads of LiO2 on surface. Our investigations elucidate quantitative correlations between the catalytic performance of siligraphenes and the adsorption performance of Li-contained intermediates on them, which provides promising approach to develop metal-free cathode catalysts with high catalytic activity.

Paramecium‐Like Iron Oxide Nanotubes as a Cost‐Efficient Catalyst for Nonaqueous Lithium‐Oxygen Batteries

AbstractFe2O3‐based catalysts have been developed to achieve a low overpotential and a long cycle life for nonaqueous Li–O2 batteries. However, previous studies focus mainly on nanoparticles or nanoflakes, which have shown limited improvements for battery performance. Here, paramecium‐like Fe2O3 nanotubes (FNTs) are synthesized by a hard‐template method and applied as the catalyst in a nonaqueous Li–O2 battery. The large specific surface area and unique tubular structure of the FNTs allow the nonaqueous Li–O2 battery to deliver a high capacity of 6000 mAh g−1 at a discharge current density of 500 mA g−1 with a low discharge and charge overpotential of approximately 0.19 and 0.85 V, respectively. Moreover, the battery can be operated at a discharge current density as high as 1000 mA g−1 with a capacity of 3940 mAh g−1 and demonstrates an excellent rate capability. The prepared catalyst enables the battery to maintain the discharge capacity and Coulombic efficiency without any degradation for 150 cycles at 500 mA g−1 with a fixed capacity of 500 mAh g−1, which is 110 more cycles than the battery without the catalyst.

Ruthenium dioxide-decorated carbonized tubular polypyrrole as a bifunctional catalyst for non-aqueous lithium-oxygen batteries

Owing to large specific surface area, high electronical conductivity and low mass, carbon materials have been widely used as cathode for non-aqueous lithium-oxygen (Li-O2) batteries. However, carbon cathodes usually present poor catalytic activities toward oxygen reduction and evolution reactions (ORR and OER), resulting in a large charge over-potential and a short cycling life. In this work, a non-aqueous Li-O2 battery with a bifunctional catalyst, ruthenium dioxide (RuO2)-decorated carbonized tubular polypyrrole, is reported. Compared with conventional catalysts, the bifunctional catalyst has two special features: i), a high content of graphitic N, and ii), a large number of RuO2 nanoparticles. The battery with the novel bifunctional catalyst shows a large discharge capacity (10095mAhg−1 at a current density of 200mAg−1), a high rate capacity (6758mAhg−1 at a current density of 1000mAg−1) and a long cycling life (55 cycles at the current density of 500mAg−1). In addition, at the first cycle with a fixed capacity of 1000mAhg−1, the discharge and charge over-potentials are only 0.28 and 0.78V, which are 180 and 360mV lower than those of the batteries fitted with pristine carbonized tubular polypyrrole cathode.

Temperature Dependence of the Oxygen Reduction Mechanism in Nonaqueous Li–O2 Batteries

The temperature dependence of the oxygen reduction mechanism in nonaqueous Li–O2 batteries is investigated within the temperature range of −20 to 40 °C. The discharge capacity of the Li–O2 battery first decreases from 7492 mAh g–1 at 40 °C to 2930 mAh g–1 at 0 °C and then increases sharply with a further decrease in temperature and reaches a very high capacity of 17 716 mAh g–1 at −20 °C at 0.1 mA cm–2. The lifetime of superoxide intermediates and the solution pathway were found to play a dominant role in the discharge of the Li–O2 battery in the temperature range of −20 to 0 °C, but the electrochemical kinetics of oxygen reduction and the surface pathway dominate the discharge behavior of the Li–O2 batteries between 0 and 40 °C. This work will broaden the fundamental understanding of the oxygen reduction process in the Li–O2 battery, especially at different temperatures.

Numerical investigation of a non-aqueous lithium-oxygen battery based on lithium superoxide as the discharge product

It is reported lithium superoxide as the discharge product can largely decrease the charge voltage and enable a high round-trip efficiency of lithium-oxygen (Li-O2) batteries. Here, we conduct a numerical investigation of the discharge behaviors of such batteries with LiO2 as the discharge product. A mathematical model considering the mass transport and electrochemical reaction processes is first developed, which gives good agreement of the simulated discharge voltage with the experimental data. Then, with this model, the effects of electrode and electrolyte properties on the discharge performance are detailedly investigated. It is found that a thin cathode with a large porosity is favorable for a high specific capacity, and a high catalytic activity can lead to a high discharge voltage. For the cathode with different geometrical properties, it is found that the oxygen solubility and diffusivity have similar impacts on discharge capacities, but the oxygen solubility has a larger impact on energy densities. Besides, the limitations and further developments of the present model are also discussed. The results obtained from this work may give useful guidance for the discharge performance improvements of non-aqueous Li-O2 batteries, and provide implications for other energy storage systems with solid product formation such as Na-O2 batteries and Li-S batteries.

Elucidation and Comparison of the Effect of LiTFSI and LiNO3 Salts on Discharge Chemistry in Nonaqueous Li-O2 Batteries.

The role of lithium salts in determining the discharge capacity of Li-O2 batteries has been highlighted in several recent studies; however, questions pertaining to their effect on the cathode surface and in the solution phase still remain unanswered. We conducted galvanostatic discharge experiments with different compositions of a binary mixture of 1 M of LiNO3 and LiTFSI in tetraglyme (TEGDME) as the electrolyte and analyzed the discharge products using techniques such as FT-IR, Raman spectroscopy, and SEM. It was observed that there is a nonlinear correlation between the electrolyte composition and the first discharge capacity, with the highest discharge capacity achieved with the electrolyte composition as 0.75 M LiNO3 and 0.25 M LiTFSI. The ID/IG values obtained from Raman spectroscopy, which represent the degree of order in the carbon cathode surface, were found to be correlated to the measured capacity. Our results indicate that at concentrations of LiNO3 higher than 0.75 M in the electrolyte, nitrogen doping of the carbon surface reaches a critical limit, beyond which it becomes unfavorable for the discharge process. On the other hand, decomposition of the electrolyte and formation of an amorphous layer on the cathode surface was found to intensify with increasing LiTFSI concentration. Our results show that the maximum discharge capacity of the cells is strongly dependent on the surface structure of the carbon cathode, which in turn is heavily influenced by the electrolyte composition. Classical molecular dynamics simulations of the same system indicated no such nonlinearity in the co-ordination of Li+ ions with respect to electrolyte composition, indicating that the ionic association strength of the anion may have only a limited effect.

Boosting the Cycle Life of Li–O2 Batteries at Elevated Temperature by Employing a Hybrid Polymer–Ceramic Solid Electrolyte

With the increasing demands of electric vehicle and grid storage, the solid-state Li–O2 battery is generally considered as an alternative cost-effective energy-storage device because of its high energy density and safety. However, there are several challenges that need to be overcome to meet the stringent requirements imposed by diverse applications, especially at high temperature. In this work, an ion-conducting hybrid solid electrolyte (HSE) integrating polymer electrolyte with ceramic electrolyte (1:1 w/w) has been successfully designed and prepared, which displays high Li+ transference number (0.75) and ionic conductivity (0.32 mS cm–1) at room temperature. The solid-state Li–O2 battery enabled by the as-prepared HSE delivers a superior long life (350 cycles, >145 days) at 50 °C to that of the conventional ether-based nonaqueous Li–O2 battery. The use of a HSE could lead to a new avenue for the development of high-performance solid-state Li–O2 batteries.

New Insights into Parasitic Reactions in Non-Aqueous Alkaline-O2 Batteries

Non-aqueous lithium-oxygen batteries depend critically on the reversible formation and on the decomposition of lithium oxides on cycling [1-3]. The discharge reaction in the cathode of nonaqueous Li-O2 batteries involves the reduction of O2 and the formation of solid Li2O2. The process is reverse on charge. True reversibility of the cathode reaction in the Li-O2 battery requires a set of qualities to obey the stoichiometry and to match each other during discharge and subsequent charge. These are 1) e-/O2 = 2 both on discharge and charge, 2) to produce/consume exactly one mole of Li2O2 and one mole of O2 per 2e- and on discharge/charge, 3) absence of any other gas evolution, e.g. CO2, or generation of solid products other than Li2O2 during discharge and charge, 4) O2 consumed during discharge matches the amount released on subsequent charge. Typically these measures deviate more or less significantly from the ideal due to parasitic reactions, whose source has not been entirely identified. Irreversible parasitic reactions have predominantly been ascribed to the reactivity of reduced oxygen species, e.g., superoxide with cell components [4-6]. These species, however, cannot fully explain these observed side reactions. Only better knowledge of parasitic reactions will allow inhibiting them and reaching towards fully reversible cell reactions. We will discuss recent insights into irreversible parasitic reactions during cycling of a Li-O2 battery, that have so far been overlooked, their detection via newly developed methods and strategies to suppress them effectively [7]. Awareness of these reactions in non-aqueous Li-O2batteries gives a rationale for future research towards achieving highly reversible cell operation.

Electrodeposition of MnO2-Based Nanomaterials As Carbon-Free and Binder-Free Cathodes for Li-O2 Battery

Carbon based nanomaterials have been widely used as cathode materials for Li-O2 batteries because of their high conductivity, large surface area, and good ORR catalytic activity. However, instability of carbon under Li-O2 operation poses problems. During recharge, carbon can decompose to form lithium carbonate at high charging potential1, but also react chemically with the discharge product Li2O2 2. Metal oxides, like MnO2 and RuO2, have been investigated as cathode catalysts in Li-O2 batteries3. In this study, MnO2 nanostructure is electrodeposited on stainless steel mesh and applied as a carbon-free and binder-free cathode for non-aqueous Li-O2 battery. To maintain good adhesion and electrical contact between deposited layer and the substrate, the mesh is pre-treated. Benefiting from enhanced electronic contact and large surface area of MnO2, the electrochemical performance is improved. Material characterization and electrochemical impedance spectroscopy (EIS) technique are also utilized to systematically study the electrochemical processes of these carbon-free MnO2-based electrodes.

Well Dispersed RuO2 Nanoparticle on NiCo2O4 Nanosheet Architectures As Efficient Bifunctional Catalysts for Lithium-oxygen Batteries

The rechargeable nonaqueous Li-O2 battery holds promise to a perfect substitutes for lithium-ion battery for the theoretically high specific energy density (∼3505 Wh·kg-1). 1However, the great challenges facing the Li-O2 battery is still left so far. One of which is a huge energy loss for achieving a reversible Li-O2 electrochemical process, oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) kinetics are critical to the realization of highly efficient lithium-oxygen batteries. 2, 3Rational design of bifunctional catalysts with fast oxygen reduction reaction (ORR) and oxygen reduction reaction (ORR) are valid to work out current problems.4 Here, we first exploit a particular structure of RuO2 nanoparticle and NiCo2O4 nanosheet composite, which RuO2 nanoparticle is uniformly coated on the surface of NiCo2O4 by a simple solution method. We demonstrate that the special design of RuO2/NiCo2O4 nanosheet composite provide excellent bifunctional electrocatalytic activities in Lithium-O2 battery. The air electrodes using RuO2/NiCo2O4 composite show enhanced overpotential characteristics and stable cyclability in our study, demonstrating high potential as efficient OER and ORR catalysts.Referrences 1. D. Xu, Z. L. Wang, J. J. Xu, L. L. Zhang and X. B. Zhang, Chemical communications, 48, 6948 (2012). 2. B. D. McCloskey, A. Speidel, R. Scheffler, D. C. Miller, V. Viswanathan, J. S. Hummelshoj, J. K. Norskov and A. C. Luntz, The journal of physical chemistry letters, 3, 997 (2012). 3. S. S. Zhang, D. Foster and J. Read, Journal of Power Sources, 195, 1235 (2010). 4. V. Viswanathan, K. S. Thygesen, J. S. Hummelshoj, J. K. Norskov, G. Girishkumar, B. D. McCloskey and A. C. Luntz, The Journal of chemical physics, 135, 214704 (2011).

Hierarchical ordered macroporous/ultrathin mesoporous carbon architecture: A promising cathode scaffold with excellent rate performance for rechargeable Li-O2 batteries

In spite of the ultrahigh theoretical energy density, non-aqueous Li-O2 batteries are still constrained by their inefficient cathodes. Here, we report the synthesis of a distinctive hierarchical carbon architecture (HOM-AMUW) for Li-O2 batteries, which consists of highly ordered macropores (250 nm) with abundant mesopores on their ultrathin walls (4–5 nm). This carbon architecture exhibits unprecedented discharge capacity of 37523 mAh g−1 and 12686 mAh g−1 at the current density of 500 mA g−1 and even 2000 mA g−1, respectively. After further functionalization by low crystalline Ru nanoclusters, the resulted Ru-HOM-AMUW architecture presents a much low charge polarization and outstanding cycling stability. The significant performance enhancement is mainly attributed to the unique hierarchical porous structure, wherein the ordered macropores and ultrathin mesoporous walls remarkably enhance the access capability of O2 or Li+ to the numerous active sites, and the large pore volume easily accommodates the discharge products. Moreover, the hierarchical porous structure modulates the morphology of discharge products to three-dimensional porous structure with high charge transport, which also contributes to the striking rate capability. This HOM-AMUW architecture is a promising scaffold to design the gas electrodes with ultrahigh rate performance not only for Li-O2 batteries but also for other metal-air batteries.

The Role of Air-Electrode Structure on the Incorporation of Immiscible PFCs in Nonaqueous Li-O2 Battery.

Perfluorocarbons (PFCs) are considered advantageous additives to nonaqueous Li-O2 battery due to their superior oxygen solubility and diffusivity compared to common battery electrolytes. Up to now, the main focus was concentrated on PFCs-electrolyte investigation; however, no special attention was granted to the role of carbon structure in the PFCs-Li-O2 system. In our current research, immiscible PFCs, rather than miscible fluorinated ethers, were added to activated carbon class air electrode due to their higher susceptibility toward O2•- attack and to their ability to shift the reaction from two-phase to an artificial three-phase reaction zone. The results showed superior battery performance upon PFCs addition at lower current density (0.05 mA cm-2) but unexpectedly failed to do so at higher current density (0.1 and 0.2 mA cm-2), where oxygen transport limitation is best illustrated. The last was a direct result of liquid-liquid displacement phenomenon occurring when the two immiscible liquids were introduced into the porous carbon medium. The investigation and role of carbon structure on the mechanism upon PFCs addition to Li-O2 system are suggested based on electrochemical characterization, wettability behavior studies, and the physical adsorption technique. Finally, we suggest an optimum air-electrode structure enabling the incorporation of immiscible PFCs in a nonaqueous Li-O2 battery.

Mesoporous amorphous binary Ru–Ti oxides as bifunctional catalysts for non-aqueous Li–O2 batteries

Mesoporous amorphous binary Ru–Ti oxides were prepared as bifunctional catalysts for non-aqueous Li–O2 batteries, and their electrochemical performance was investigated for the first time. A Li–O2 battery with mesoporous amorphous binary Ru–Ti oxides exhibited a remarkably high capacity of 27100 mAh g−1 as well as a reduced overpotential. A GITT analysis suggested that the introduction of amorphous TiO2 to amorphous RuO2 was responsible for the enhanced kinetics toward both the oxygen reduction reaction and oxygen evolution reaction. Excellent cyclic stability up to 230 cycles was achieved, confirming the applicability of the new bifunctional catalyst in non-aqueous Li–O2 batteries.

Strontium-doped perovskite oxide La1-xSrxMnO3 (x = 0, 0.2, 0.6) as a highly efficient electrocatalyst for nonaqueous Li-O2 batteries

Strontium (Sr)-doped perovskite oxide La1-xSrxMnO3 (x=0, 0.2, 0.6) composites are prepared by sol-gel process assisted with chelating effect of citric acid, which was used as catalysts for oxygen cathode in rechargeable lithium−air batteries. Sr-doped perovskite oxide La1-xSrxMnO3 composites demonstrate higher catalytic activities than that of the pure LaMnO3. In particular, the La0.4Sr0.6MnO3 had a lower total over potential between the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) than that of the La0.8Sr0.2MnO3 and LaMnO3 .When the Li-O2 cells were tested at the current density of 50mAg−1, the discharge capacities of the oxygen cathode with different La1-xSrxMnO3 (x=0, 0.2, 0.6) catalysts were 3573, 4408, and 5624mAhg−1，respectively. Additionally, the cell employed La0.4Sr0.6MnO3 as catalyst can be cycled at a limited capacity of 200mAhg−1 for about 71cycles, which is much higher than the 42 cycles for LaMnO3 electrode.