Non-aqueous Lithium-oxygen Batteries Research Articles

Carbon electrode with NiO and RuO2 nanoparticles improves the cycling life of non-aqueous lithium-oxygen batteries

Abstract Carbon has been regarded as one of the most attractive cathode materials for non-aqueous lithium-oxygen batteries due to its excellent conductivity, high specific area, large porosity, and low cost. However, a key disadvantage of carbon electrodes lies in the fact that carbon may react with Li2O2 and electrolyte to form irreversible side products (e.g. Li2CO3) at the active surfaces, leading to a high charge voltage and a short cycling life. In this work, we address this issue by decorating NiO and RuO2 nanoparticles onto carbon surfaces. It is demonstrated that the NiO-RuO2 nanoparticle-decorated carbon electrode not only catalyzes both the oxygen reduction and evolution reactions, but also promotes the decomposition of side products. As a result, the battery fitted with the novel carbon cathode delivers a capacity of 3653 mAh g−1 at a current density of 400 mA g−1, with a charge plateau of 4.01 V. This performance is 440 mV lower than that of the battery fitted with a pristine carbon cathode. The present cathode is also able to operate for 50 cycles without capacity decay at a fixed capacity of 1000 mAh g−1, which is more than twice the cycle number of that of the pristine carbon cathode.

Improving Metal Anode Stability in Potassium Oxygen Batteries with Concentrated Electrolyte

In recent years, metal-oxygen batteries, especially non-aqueous lithium-oxygen batteries (or Li-O2 batteries), have drawn considerable research attention for future energy storage applications due to high theoretical specific energy densities. Compared to conventional lithium-oxygen batteries, potassium-oxygen (K-O2) batteries are based on a reversible O2/KO2 redox chemistry, resulting in much better round-trip efficiencies (higher than 90%) without using electrocatalysts. While the reversibility of the cathode reactions is improved, the cycling performance of K-O2 batteries is greatly limited by the K metal anode stability. The highly reducing K anode would react with electrolyte molecules and degrade seriously during cycling. Moreover, the oxygen crossover to the anode further accelerate the degradation process. Here, we report our studies about the improved K metal anode stability in K-O2 batteries with concentrated electrolytes. It is shown that in this class of electrolytes, a stable Solid Electrolyte Interface (SEI) layer is critical for protecting the K anode and suppressing the undesired side reactions. As a result, the metal anode cycling efficiency and the cycle life of K-O2 batteries can be largely increased.

In-Situ Growth of CeO2 Nanoparticles on N-doped Reduced Graphene Oxide for Anchoring Li2O2 Formation in Lithium-Oxygen Batteries

The large overpotentials during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are still big challenges for the non-aqueous lithium-oxygen batteries. In this paper, CeO2 nanoparticles on N-doped reduced graphene oxide (CeO2@N-RGO) are in-situ synthesized through a one-step hydrothermal process as binder-free cathode catalyst. The battery with CeO2@N-RGO cathode delivers a capacity of 11,900mAhg−1 at current density of 400mAg−1, and can cycle up to 40 times without obvious degradation at the capacity limitation of 1000mAhg−1. The performance enhancement of the battery can be attributed to the synergetic effect of N-RGO and CeO2 nanoparyicles anchoring the formation of Li2O2. The study confirms that CeO2@N-RGO can be a potential excellent cathode catalyst for ORR and OER for rechargeable lithium-oxygen batteries.

Cost-effective carbon supported Fe2O3 nanoparticles as an efficient catalyst for non-aqueous lithium-oxygen batteries

In this work, we synthesize inexpensive Vulcan XC-72 carbon supported Fe2O3 nanoparticles (Fe2O3/XC) as an oxygen evolution reaction (OER) catalyst for non-aqueous lithium-oxygen batteries. It is demonstrated that the battery with the Fe2O3/XC cathode exhibits a charge voltage plateau of 4.01V at a current density of 200mAg−1, which is 0.43V lower than that with the pure XC carbon cathode. The battery also presents an outstanding rate capability, giving a charge voltage plateau of 3.99, 4.01 and 4.15V at the current density of 100, 200 and 400mAg−1, respectively. Furthermore, the battery can be operated for 50 cycles at a fixed capacity of 500mAhg−1 without obvious degradation, showing its superior cycling stability. The results suggest that the iron oxide is a cost-effective catalyst for non-aqueous lithium-oxygen batteries.

Bimetallic MPt (M: Co, Cu, Ni) alloy nanoparticles assembled on reduced graphene oxide as high performance cathode catalysts for rechargable lithium-oxygen batteries

In this work, the performance of bimetallic MPt (M: Co, Cu, Ni) alloy nanoparticles (NPs) assembled on reduced graphene oxide (rGO) as cathode catalysts for rechargable nonaqueous lithium-oxygen (Li-O2) batteries was investigated. Monodisperse MPt alloy NPs were prepared by using one-pot protocol comprising the thermal decomposition of metal acetylacetonates in the presence of oleylamine (OAm) serving as surfactant, reducing agent and solvent. As-synthesized MPt alloy NPs were then assembled on reduced graphene oxide (rGO) via liquid self-assembly method. Both colloidal MPt alloy NPs and rGO assembled ones were characterized by TEM, XRD and ICP-MS. Next, the cathode performance of rGO-MPt catalysts were evaluated by studying the galvanostatic discharge-charge profiles that were carried out in a Li-O2 cells using a solution of 0.5 M LiTFSI in DMSO as an electrolyte at an applied current density of 0.05 mA cm−2. The Li-O2 cells with rGO-MPt cathode catalysts provide the discharge capacities reaching up to about 9.0 mAh cm−2. Among three rGO-MPt catalysts tested for the Li-O2 battery, rGO-Co48Pt52 provided the highest discharge capacity of 9898 mAh g−1 and 80 cycles at the curtailed capacity of 0.75 mAh cm−2 whereas the rGO-Ni47Pt53 catalyst showed the most stable cycle-life.

The Decomposition Mechanism of Crystalline Lioh on Ruthenium in Non-Aqueous Lithium-Oxygen Batteries: A First-Principles Study

Non-aqueous lithium-oxygen (Li-O2) batteries are considered as the potential energy storage system for electric vehicles due to its comparable energy density (11682 W h kg-1) with gasoline (13000 W h kg-1) [1]. However, the development of Li-O2 batteries is still at its early stage and suffers from some critical issues, such as short cycle life, poor electrolyte and electrode stabilities, and low energy efficiency [2], most of which are related to the high charge overpotential during the oxygen evolution reaction (OER). One widely applied approach to decrease the high charge overpotential is using catalyst, such as carbon-based materials, noble metals, metal oxides and so on. Even with this effort, however, it is still difficult to lower the charge voltage as much as possible (e.g. 3.5 V) to ensure the stabilities of electrolyte and electrode materials when Li2O2 is the discharge product [3]. Recently, an alternative strategy that achieves an ultra-low charge ovepotential and excellent stability has been reported, which is to form solid-state LiOH rather than Li2O2in the discharge process [4, 5]. However, the mechanism of crystalline LiOH decomposition on catalysts is still unknown, and the possible catalysts that can promote the decomposition of solid-state LiOH are also limited. In this regard, a first-principles study was used to investigate the OER process in non-aqueous Li-O2batteries via LiOH formation and decomposition. We developed an interfacial model to study the decomposition mechanism of LiOH on different surfaces of ruthenium, and the charge overpotentials among different surfaces were compared. Moreover, the decomposition path of crystalline LiOH and the rate determining step (RDS) were investigated. Our results demonstrate the activity of ruthenium towards the decomposition of crystalline LiOH, and different surfaces can lead to the different decomposition paths. Further analysis of the decomposition mechanism of crystalline LiOH will be presented at the meeting. Our investigations give new insight into the future catalyst design in non-aqueous Li-O2batteries.

Fe2O3/Carbon Nanocomposite As Cathode Catalyst for Non-Aqueous Lithium-Air Batteries

Thanks to the highest capacity of lithium metal (3.86 × 103 mA h g-1) and inexhaustible oxygen in the atmosphere, lithium-air battery offers the promise of a remarkably high theoretical specific energy density up to ~11 kW h g-1, which is comparable to that of conventional fuels [1]. However, the development of lithium-air batteries is hindered by the high overpotential, low rate capacity, and poor cycling performance. The cathode has been shown to be the bottle-neck of rechargeable lithium-air batteries, wherein the sluggish oxygen reduction/evolution reaction (ORR/OER, especially OER) kinetics not only results in a large overpotential, but also causes the poor rechargeability. Thus, it is of great significance and urgency to enhance the electrochemical performances of the cathode. One effective way is to design high efficient catalysts to reduce the charge overpotential. Despite the precious Ru based catalysts have shown promising results as a catalyst for lithium-air batteries, its scarcity and high price will restrict the wide application. As a result, other non-noble transition metal/metal oxides (e.g., MnOx, CoOx) with activities for ORR and/or OER have drawn great interests for lithium-air batteries [2, 3]. Oxides of iron, which in the same group of Ru in the periodic table, however, is less investigated. Herein, we proposed a facile method to fabricate Fe2O3/carbon nanocomposite cathode materials in which Fe2O3 nanoparticles with a diameter of 4-6 nm are deposited onto the carbon surface, as shown in Figure 1. The electro-catalytic activities were investigated by linear sweeping voltammetry (LSV) and discharge-charge profiles. The results show a lower onset potential and a larger OER current density, suggesting that Fe2O3 is an effective OER catalyst. Moreover, a non-aqueous lithium-oxygen battery with this cathode demonstrates a remarkably 430 mV lower charge overpotential and a dramatically improved cycling life. More detailed experimental results will be presented in the meeting. And some possible mechanisms of the catalytic effect will also be discussed. Figure 1

A NiO-RuO2 Nanoparticle-Decorated Carbon Powder Cathode for Non-Aqueous Lithium-Oxygen Batteries

Non-aqueous lithium-oxygen batteries have been considered as one of the most promising power sources for electric vehicles and portable devices, due to the high theoretical capacity (3.86×103 mAh g-1) and energy density (1.14×104 Wh kg-1) [1]. The electrochemical reactions in the discharge and charge processes involve the formation and decomposition of the solid product Li2O2 in the cathode. Carbon has been regarded as one of the most attractive cathode materials, due to its good conductivity, high specific area, proper pore volume, and low cost. However, it has been shown that both the highly oxidizing environment (O2 -) and Li2O2 can lead to the decomposition of carbon materials to form a thin Li2CO3 film at the carbon interface [2]. Besides, carbon can promote decomposition of the electrolyte to form side products (e.g. lithium carbonate and carboxylates) [3]. These irreversible side products accumulate on the cathode surface, leading to a high overpotential during charge, resulting in a short cycle life. A new strategy to solve these issues is to promote the decomposition of side products. In this regard, we here developed a NiO-RuO2 nanoparticle-decorated carbon powder cathode. As NiO has been reported to have activity in the oxidation of carbonate and carboxylate species [4], we used NiO nanoparticles to decorate the carbon powder with two features: i) protect the surface defects, alleviating the decomposition of the electrolyte; and ii) promote the oxidation of side products, retaining the activate surfaces. To further lower the charge overpotential, we meanwhile decorated RuO2 nanoparticles on the carbon powder surface. As a result, this NiO-RuO2 nanoparticle-decorated carbon powder cathode can enable a non-aqueous lithium-oxygen battery with a low charge overpotential and long cycle life. Further analysis and electrochemical characterizations will be presented at the meeting. The lithium-oxygen battery performance employing this type of cathode will also be presented at the meeting.

Three-dimensional Co3O4/CNTs/CFP composite as binder-free cathode for rechargeable Li-O2 batteries

A novel cobalt oxide/carbon nanotubes/carbon fiber composite for high-performance rechargeable lithium-oxygen batteries oxygen electrode is synthesized. The CNTs are deposited on the surface of CFP via a simple chemical vapor deposition (CVD) and Co3O4 nanosheets are directly coated on CNTs by electrochemical deposition. The unique three-dimensional network structural of the composite can facilitate the wetting of electrolyte and diffusion of oxygen. When applied as a self-supporting, binder-free cathode material for rechargeable nonaqueous lithium-oxygen batteries (LOBs), the novel Co3O4/CNTs/CFP electrode exhibited excellent performance (with a specific capacity of 7196.5mAh/g(CNTs+Co3O4) at a current density of 200mA/g and 25 stable cycles with 1000mAh/g(CNTs+Co3O4)). The superior performance is proposed to be associated with the 3D nanoporous structures and the absence of side reactions related to binders.

RuO2Monolayer: A Promising Bifunctional Catalytic Material for Nonaqueous Lithium–Oxygen Batteries

Rutile RuO2 has been widely regarded as an excellent catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in nonaqueous lithium–oxygen batteries and achieved superior performance, but the catalytic activity of RuO2’s polymorph, RuO2 monolayer, has been less studied. In this work, we study the catalytic activities of both rutile RuO2 and RuO2 monolayer for ORR and OER in the battery using density functional theory method. Computational results show that the RuO2 monolayer exhibits a higher catalytic activity than the rutile RuO2 does. More interestingly, it is found that during discharge a similar lattice structure between RuO2 monolayer and Li2O2 {0001} surface can induce the formation of crystallized Li2O2 with the conductive {0001} surface exposed, whereas during charge the RuO2 monolayer can attract the remaining Li2O2 to its surface spontaneously, thus maintaining the solid–solid reaction interface. Our results suggest that the RuO2 monolayer is a promising catalytic material for nonaqueous lithium–oxygen batteries.

Ethylene sulfite based electrolyte for non-aqueous lithium oxygen batteries

Abstract Non-aqueous lithium–oxygen (Li–O 2 ) batteries have been considered as the superior energy storage system due to their high-energy density, however, some challenges limit the practical application of Li–O 2 batteries. One of them is the lack of stable electrolyte. In this communication, a novel electrolyte with ethylene sulfite (ES) used as solvent for Li–O 2 batteries was reported. ES solvent showed low volatility and high electrochemical stability. Without a catalyst in the air-electrode of Li–O 2 batteries, the batteries showed high specific capacity, good round-trip efficiency and cycling stability.

Hierarchical Cr2O3@OPC composites with octahedral shape for rechargeable nonaqueous lithium-oxygen batteries

The development of catalyst materials is the most significant issue that hinders the practical applications of Li-O2 batteries. Herein we show the design and synthesis of the hierarchical chromic oxide-octahedral porous carbon (Cr2O3@OPC) composites catalyst with octahedral shape that derived from Cr-based metal-organic frameworks (MIL-101(Cr)) precursor. When applied as cathode catalysts in rechargeable Li-O2 batteries, the electrode with Cr2O3@OPC composites catalyst exhibits a low charge and discharge over-potential, high discharge capacity and excellent cycling stability. What's more, the electrode with Cr2O3@OPC composite shows a discharge capacity up to ∼4800 mAh g(catalyst + carbon)−1 at a current density of 0.1 mA cm−2, and exhibits a very stable discharge voltage plateau of 2.7 V and a charge voltage plateau of ∼3.9 V. With the addition of Cr2O3@OPC composite, the Li-O2 batteries can obtain good cycle performance over 50 cycles at a fixed capacity of 800 mAh g(catalyst + carbon)−1. These results indicating that the Cr2O3@OPC composite derived from MIL-101(Cr) would be a promising catalyst for Li-O2 batteries.

Improving the Performance of Perovskite in Nonaqueous Oxygen Electrocatalysis.

Nanoparticle (NP) aggregates of lanthanum cobalt oxide perovskite (LCO) were compounded with reduced graphene oxide (rGO) nanosheets and used as the cathode catalyst for nonaqueous lithium-oxygen batteries (LOBs). The LCO NP aggregates were completely surrounded by rGO nanosheets in the composite with 10.5 wt % of rGO (LCO-rGO-10.5) but were partially exposed in the composite with 7.5 wt % of rGO (LCO-rGO-7.5). Both composites performed better than pristine LCO NPs and rGO nanosheets in nonaqueous oxygen electrocatalysis. The LCO-rGO-7.5 composite excelled at capacity and rate performance, while the LCO-rGO-10.5 composite was better at cycle stability. The good performance of the LCO-rGO composites was due to the synergy of functions of LCO and rGO.

In situ real-time and quantitative investigation on the stability of non-aqueous lithium oxygen battery electrolytes

Differential electrochemical mass spectrometry (DEMS) results clearly show that dimethylacetamide (DMA) is more stable and exhibits better performance than tetraethylene glycol dimethyl ether (TEGDME), suggesting that DMA is a more favorable electrolyte for Li–O2 battery applications.

MnO2-x nanosheets on stainless steel felt as a carbon- and binder-free cathode for non-aqueous lithium-oxygen batteries

Manganese dioxide (MnO2) has been recognized as an effective catalyst for the oxygen reduction and oxygen evolution reactions in non-aqueous lithium-oxygen batteries. However, a further improvement in battery performance with the MnO2 catalyst is limited by its low electronic conductivity and catalytic activity, which strongly depend on the morphology and composition. In this work, we develop a carbon- and binder-free MnO2-x nanosheets/stainless steel (SS) cathode via a simple and effective electrodeposition-solvothermal route. The created Mn(III) and oxygen vacancy in MnO2-x nanosheets allows an significant increase in the electronic conductivity and catalytic activity. It is experimentally shown that the use of the present nanostructure MnO2-x/SS cathode in a non-aqueous lithium-oxygen battery results in a rechargeable specific capacity of 7300 mAh g−1 at a current density of 200 mA g−1, which is 39% higher than that with the MnO2/SS cathode. In addition, the specific capacities at 400 mA g−1 and 800 mA g−1 reach 5249 mAh g−1 and 2813 mAh g−1, respectively, which are over 30% higher than that with the MnO2/SS cathode. Furthermore, the discharge/charge cycle test shows no degradation for 120 cycles. All the results show that the present nanostructure MnO2-x/SS cathode is a promising candidate for high-performance lithium-oxygen batteries.

Integrated Porous Cathode made of Pure Perovskite Lanthanum Nickel Oxide for Nonaqueous Lithium–Oxygen Batteries

AbstractThe development of non‐carbon electrodes for nonaqueous lithium–oxygen batteries has become a recent focus as carbon electrodes were found to be unstable. Conventional non‐carbon electrodes are typically formed with a substrate/current collector, which will decrease the practical capacity. Here, we propose an integrated porous electrode made of LaNiO3 that does not require a substrate/current collector. The porous structure allows the formation of nanosized pores on the walls of microsized pores, which facilitates the transport of both oxygen and lithium ions. Importantly, all the surfaces of the porous structure are catalytically active for electrochemical reactions. Experimental results show that the adoption of the electrode in the battery enables a capacity of 1.064 mAh cm−2 at a current density of 0.05 mA cm−2. Furthermore, it is demonstrated that the battery can be cycled for at least 25 cycles at a fixed capacity of 0.3 mAh cm−2, and the electrode shows no degradation after the cycles.

Electrical Circuit-Based Modeling of a Non-Aqueous Lithium-Oxygen Battery for High Accuracy State-of-Charge Estimation

With the increased interest in electric-powered transportation such as electric vehicle (EV) and hybrid electric vehicle (HEV) application, lithium-ion cell and large-format lithium-polymer cell were taken it for granted that they have become more preferable selection. Unfortunately, they are still limited to the application that requires much higher specific energy density. As a result, in order to overcome an aforementioned problem, non-aqueous lithium-oxygen (Li-O2) batteries have attracted substantial attention because of their high energy density. Moreover, the need for accurate and reliable state-of-charge (SOC) information which is considered as one of the key factors in battery management system (BMS) is significantly increased for supporting optimal battery performance and safety. So far, no definitive solution has been provided to this question. Therefore, this research gives insight to the design and implementation of the electrical circuit-based modeling of a non-aqueous lithium-oxygen battery for high accuracy SOC estimation. Four experimental tests including discharge capacity/impedance tests with cycling, open-circuit voltage (OCV) test and discharging/charging cycling test were priorly implemented for a detailed analysis of electrochemical characteristic analysis and parameters identification of a non-aqueous lithium-oxygen battery. Through these tasks, it can be completely succeeded in constructing a finalized electrical circuit-based model that consists of the OCV, one series resistance and one RC-ladder with dynamic characteristic. This model enables us to provide appropriate information for high accuracy and reliable SOC estimation based on the extended Kalman filter (EKF). This research has been extensively validated by additional experimental results conducted on a non-aqueous lithium-oxygen battery that had a rated capacity of 1700mAh/g by the ‘Materials and Electro-Chemistry Laboratory in Inha University’. Consequently, it can be well known that all verification results clearly indicate the robustness of the proposed research.

One-dimensional porous La0.5Sr0.5CoO2.91 nanotubes as a highly efficient electrocatalyst for rechargeable lithium-oxygen batteries

The electrochemical performance of one-dimensional porous La0.5Sr0.5CoO2.91 nanotubes as a cathode catalyst for rechargeable nonaqueous lithium-oxygen (Li-O2) batteries is reported here for the first time. In this study, one-dimensional porous La0.5Sr0.5CoO2.91 nanotubes were prepared by a simple and efficient electrospinning technique. These materials displayed an initial discharge capacity of 7205mAhg−1 with a plateau at around 2.66V at a current density of 100mAg−1. It was found that the La0.5Sr0.5CoO2.91 nanotubes promoted both oxygen reduction and oxygen evolution reactions in alkaline media and a nonaqueous electrolyte, thereby improving the energy and coulombic efficiency of the Li-O2 batteries. The cyclability was maintained for 85 cycles without any sharp decay under a limited discharge depth of 1000mAhg−1, suggesting that such a bifunctional electrocatalyst is a promising candidate for the oxygen electrode in Li-O2 batteries.

Exploring metal nanoclusters for lithium-oxygen batteries.

α-MnO2 nanowires modified with dispersed poly(3,4-ethylenedioxythiophene)-protected Au and Ag nanoclusters (Au-MnO2 and Ag-MnO2) were used for the first time as hybrid oxygen electrocatalysts for nonaqueous lithium-oxygen batteries. The Au-MnO2 and Ag-MnO2 hybrid catalysts surpassed the performance of pristine α-MnO2 nanowires in full-cell tests in the following order: Au-MnO2 > Ag-MnO2 > pristine α-MnO2. Specifically, cells with the Au-MnO2 catalyst could reduce the discharge/charge overpotentials at 100 mA g(-1) to 0.23/1.02 V and deliver discharge/charge capacities of 5784/5020 mAh g(-1). They could also be cycled for at least 60 times at the depth of discharge of 1000 mAh g(-1). The good full cell performance demonstrated the effectiveness of Au/Ag nanoclusters in promoting oxygen electrocatalysis on α-MnO2; forming discharge products with more reactive morphologies. It is therefore worthwhile to explore the use of Au and Ag nanoclusters in other catalyst systems for oxygen electrocatalysis in nonaqueous solutions.

A Metal‐Free, Free‐Standing, Macroporous Graphene@g‐C3N4 Composite Air Electrode for High‐Energy Lithium Oxygen Batteries

The nonaqueous lithium oxygen battery is a promising candidate as a next-generation energy storage system because of its potentially high energy density (up to 2-3 kW kg(-1)), exceeding that of any other existing energy storage system for storing sustainable and clean energy to reduce greenhouse gas emissions and the consumption of nonrenewable fossil fuels. To achieve high energy density, long cycling stability, and low cost, the air electrode structure and the electrocatalysts play important roles. Here, a metal-free, free-standing macroporous graphene@graphitic carbon nitride (g-C3N4) composite air cathode is first reported, in which the g-C3N4 nanosheets can act as efficient electrocatalysts, and the macroporous graphene nanosheets can provide space for Li2O2 to deposit and also promote the electron transfer. The electrochemical results on the graphene@g-C3N4 composite air electrode show a 0.48 V lower charging plateau and a 0.13 V higher discharging plateau than those of pure graphene air electrode, with a discharge capacity of nearly 17300 mA h g(-1)(composite) . Excellent cycling performance, with terminal voltage higher than 2.4 V after 105 cycles at 1000 mA h g(-1)(composite) capacity, can also be achieved. Therefore, this hybrid material is a promising candidate for use as a high energy, long-cycle-life, and low-cost cathode material for lithium oxygen batteries.