Li-air Research Articles

Atomically Dispersed Ruthenium Catalysts with Open Hollow Structure for Lithium–Oxygen Batteries

HighlightsThe open hollow structure enhances the accessibility of atomically dispersed Ru sites and improves the diffusion efficiency of catalytic moleculesThe abundant atomically dispersed Ru sites on the surface of catalyst provide a large number of oxygen adsorption and Li2O2 nucleation sitesThe lithium–oxygen battery assembled with h-RuNC could catalyze the production of Li2O2 with better dispersion and improve the cycling stability.

Exploring the Potential of Hierarchical Zeolite-Templated Carbon Materials for High-Performance Li-O2 Batteries: Insights from Molecular Simulations.

The commercialization of ultrahigh capacity lithium-oxygen (Li-O2) batteries is highly dependent on the cathode architecture, and a better understanding of its role in species transport and solid discharge product (i.e., Li2O2) formation is critical to improving the discharge capacity. Tailoring the pore size distribution in the cathode structure can enhance the ion mobility and increase the number of reaction sites to improve the formation of solid Li2O2. In this work, the potential of hierarchical zeolite-templated carbon (ZTC) structures as novel electrodes for Li-O2 batteries was investigated by using reactive force field molecular dynamics simulation (reaxFF-MD). Initially, 47 microporous zeolite-templated carbon morphologies were screened based on microporosity and specific area. Among them, four structures (i.e., RHO-, BEA-, MFI-, and FAU-ZTCs) were selected for further investigation including hierarchical features in their structures. Discharge product cluster analysis, self-diffusivities, and density number profiles of Li+, O2, and dimethyl sulfoxide (DMSO) electrolyte were obtained to find that the RHO-type ZTC exhibited enhanced mass transfer compared to conventional microporous ZTC (approximately 31% for O2, 44% for Li+, and 91% for DMSO) electrodes. This is due to the promoted formation of small-sized product clusters, creating more accessible sites for oxygen reduction reaction and mass transport. These findings indicate how hierarchical ZTC electrodes with micro- and mesopores can enhance the discharge performance of aprotic Li-O2 batteries, providing molecular insights into the underlying phenomena.

An Efficient and Stable Lithium‐Oxygen Battery Based on Metal‐Organic Framework Separator Operating at 160 °C

AbstractA lithium oxygen battery (LOB) with molten salt electrolyte operating at elevated temperature has aroused great interest because it enables fast reaction kinetics. However, there is still a lack of open literature on the separator (membrane) of this kind of LOB. Metal‐organic framework (MOF) materials are widely used as components of separators in many kinds of energy storage devices, due to their regular crystalline and well‐defined pore structures. In this work, a MOF material, zirconium (II) 1,4‐benzenedicarboxylate after lithiation (UiO‐66‐SO3Li) with a narrow pore size (6 Å), is used as a key component of the separator for LOB operating at elevated temperature. A “rolling dough” method is adopted to prepare the separator, which achieves 100% material utilization. The LOB with this membrane operates at 160 °C and delivers a specific capacity of 5.1 mAh cm−2 with an overpotential as low as 40 mV at 0.1 mA cm−2 and a prolonged cycle life, 180 cycles with a high coulombic efficiency of 99.9% at 0.5 mA cm−2. This MOF‐based membrane provides efficient Li+ transfer and restricts discharge product migration during battery operation, which is promising for the development of LOB in large‐scale practical applications.

Hierarchically Porous and Minimally Stacked Graphene Cathodes for High‐Performance Lithium–Oxygen Batteries

AbstractAlthough lithium–oxygen batteries have attracted attention due to their extremely high energy densities, rational design, and critical evaluation of high‐energy‐density cathode for practical Li–O2 batteries is still urgently needed. Herein, the multiscale, angstrom‐to‐millimeter, precisely controllable synthesis of binder‐free cathodes with minimally stacked graphene free from edge sites is demonstrated. The proposed Li–O2 battery, based on a hierarchically porous cathode with a practical mass loading of >4.0 mg cm−2, simultaneously exhibits an unprecedented specific areal (>30.0 mAh cm−2), mass (>6300 mAh g−1), and volumetric (>480 mAh cm−3) capacities. The battery displays the optimal energy density of 793 Wh kg−1 critically normalized to the total mass of all active materials including electrolytes and even discharge products Li2O2. Comprehensive in situ characterizations demonstrate a unique discharge mechanism in hierarchical pores which contributes to competitive battery performance. Superior rate performance in a current density range of 0.1 to 0.8 mA cm−2 and long‐cycle stability (>260 cycles) at a current density of 0.4 mA cm−2, outperforming state‐of‐the‐art carbon cathodes. This study yields insight into next‐generation carbon cathodes, not only for use in practical Li–O2 batteries, but also in other metal–gas batteries with high energy densities.

Orbital Coupling of PbO7 Node in Single-Crystal Metal-Organic Framework Enhances Li-O2 Battery Electrocatalysis.

Optimizing the local coordination environment of metal centers in metal-organic frameworks (MOFs) is crucial yet challenging for regulating the overpotential of lithium-oxygen (Li-O2) batteries. Herein, we report the synthesis of a class of PbO7 nodes in a single crystal MOF (naphthalene-lead-MOF, known as Na-Pb-MOF) to significantly enhance the kinetics of both discharge and charge processes. Compared to the PbO6 node in the single-crystal tetramethoxy-lead-MOF (4OMe-Pb-MOF), the bond length between Pb and O in the PbO7 node of Na-Pb-MOF increases, resulting in weaker Pb 5d-O 2p orbital coupling, which optimizes the adsorption interaction toward intermediates, and thereby promotes the rate-determining steps of both the reduction of LiO2 to Li2O2 and the oxidation of LiO2 to O2 for reducing the activation energy of the overall reaction. Consequently, Li-O2 batteries based on Na-Pb-MOF electrocatalysts exhibit a low total charge-discharge overpotential of 0.52 V and an excellent cycle life of 140 cycles.

Manipulating Li2O2 deposition morphology by surface spin modulation of cobalt-based spinel oxide catalysts in lithium−oxygen batteries

The lithium peroxide (Li2O2) morphology manipulated by the distribution of Li2O2 nucleation sites dramatically affects the electrochemical performance of lithium − oxygen batteries (LOBs). Cathode surface spin modulation engineering is adopted to obtain ideal Li2O2 deposition morphology, as it can effectively manipulate the nucleation site distribution. Herein, Cu1-ZnCo2O4 (Cu0.15Zn0.85Co2O4) electrocatalysts are elaborately constructed by introducing an appropriate amount of Cu2+ into the ZnCo2O4 tetrahedral sites, which successfully regulates the spin state of Co sites under the action of co-top oxygen connection. Density functional theory calculations reveal that the moderate Co dz2 orbital occupancy is obtained via spin regulation, causing the optimum adsorption capability of Cu1-ZnCo2O4 towards oxygen-containing intermediate. On the basis, the distribution of Li2O2 nucleation sites is modulated to promote the uniform deposition of small-size Li2O2 agglomerates, which possess a large contact area with the cathodic surface and a certain void structure, greatly improving reversible deposition and decomposition kinetics. As a result, LOBs catalyzed by Cu1-ZnCo2O4 offer a large specific capacity of 12984.9 mAh/g and an extended cycle stability of over 400 cycles. This work emphasizes that spin regulation engineering efficiently affects the distribution of Li2O2 nucleation sites, achieving the Li2O2 morphology modulation in LOBs.

Application of nanomaterials in lithium-sulfur batteries and lithium-air batteries

Because of its high voltage, high specific energy, and other good qualities, lithium-ion batteries have recently become one of the most popular studies. In the context of nanomaterials, this research investigates the function of nanomaterials in the application of lithium-sulfur and lithium-air batteries. In addition to examining the classification, benefits and drawbacks, uses and advances of nanomaterials, this essay also examines the fundamentals of two batteries, as well as the uses of nanomaterials in both types of batteries. The results show that nanomaterials have a very large surface area and a sudden change in material properties because of their arrival at the nanoscale, and have very good mechanical and optical properties, which have a very good contribution to the performance of the batteries. However, it was discovered that nanomaterials in lithium-ion battery applications still have issues, such as high cost and challenging synthesis procedures, through the investigation of several nanomaterials in two batteries. In addition to offering fresh perspectives for society, this study seeks to better understand the economic and safety issues associated with two batteries used in practical production.

Bimetallic MXene with tailored vanadium d-band as highly efficient electrocatalyst for reversible lithium-oxygen battery

Lithium-oxygen (Li-O2) battery possesses high theoretical energy density of ∼ 3500 Wh kg−1, yet the sluggish kinetics of oxygen redox reactions hinder its practical application. Herein, TiVC bimetallic MXene solid solution is prepared as the efficient electrocatalyst for Li-O2 battery. The results of experiment and theoretical calculations reveal that through the formation of Ti-C-V bond in TiVC, electrons transfer from V site to Ti site enhances electron delocalization of V sites, which causes the upshift of d band center of V site and strengthens the adsorption of intermediate products (LiO2) on TiVC electrode surface. Due to the strong adsorption of intermediates, the film-like Li2O2 can be formed on TiVC electrode via the surface-adsorbed pathway, which ensures the full contact between the electrode and discharged product and thus facilitates the charge transfer between TiVC electrode and oxygen species during charge process. As a consequence, the TiVC based Li-O2 battery exhibits superior electrochemical performance including large discharge capacity (12780 mAh/g) and extended cycling stability (422 cycles) at the current density of 300 mA g−1.

RuCo Alloy Drilling into Graphene for Ultrahigh-Capacity Lithium–Oxygen Batteries

RuCo Alloy Drilling into Graphene for Ultrahigh-Capacity Lithium–Oxygen Batteries

Microwave assisted synthesis for ϵ-MnO2 nanostructures on Ni foam as for rechargeable Li–O2 battery applications

Lithium-air batteries exhibits high practical energy densities ranging from 1000 to 4000 Wh Kg−1, rendering them appealing for applications in portable electronic devices and electric vehicles. Nevertheless, they grapple with challenges like low charge–discharge efficiency, limited stability over multiple cycles, and electrode degradation stemming from undesirable side reactions, thus impeding their commercial market. In this study, ϵ-MnO2 petal-like nanostructures were synthesized on Ni foam via simple, microwave-assisted synthesis approach. The resulting ϵ-MnO2/Ni electrode demonstrated storage capacities (1982 mAh g−1 discharge capacity at 200 mA g−1) alongside enhanced cyclability and stability over 100 cycles, independent of discharge depth. This electrochemical performance can be attributed to its 3D morphology, oxygen defects, and the absence of side reactions from carbon-based additives. Overall, ϵ-MnO2/Ni electrode catalysts hold potential for realizing cost-effective Li-O2 based energy storage technologies.

Recent Advances in the Development of Li‐Air Batteries, Experimental and Predictive Approaches – Prospective, Challenges, and Opportunities

AbstractThe significance of lithium‐air batteries (LABs) has recently increased as they are a highly competitive alternative to lithium‐ion batteries (LIBs) for powering electric automobiles. The reason behind this is their excessive theoretical energy density. The advancement, breakthroughs, and drawbacks of LABs are examined. A comprehensive evaluation of various energy storage devices is provided, followed by an evaluation of several electrochemical storage technologies, their advantages, and drawbacks. Also, recent advances in LABs are reviewed and potential machine learning techniques are explored to address the existing obstacles hindering the widespread adoption of LABs.

Regulating the 4d-band center of Mo atoms in β-Mo2C to promote lithium-oxygen reactions

Lithium-air batteries have attracted much attention because of their high energy density. However, the sluggish kinetics of the Li-O reaction leads to high charge/discharge overpotentials and poor reversibility. Therefore, exploring efficient and low-cost cathode catalysts in promoting the Li-O reaction is crucial. Herein, the first principles calculation method, for the first time, is used to study the catalytic performance based on Pt-like β-Mo2C by modifying the C sites with B, N, and O. The N modification decreases the d-band center of Mo atoms from 0.11 eV (β-Mo2C) to −0.23 eV, resulting in optimal adsorption energy and charge transfer. In comparison, B and O have a negative effect. The N modification changes the rate-determining step of the entire catalytic process from the decomposition of LiO2 (β-Mo2C, B-β-Mo2C, O-β-Mo2C) to the decomposition of Li2O2. The electronic structure and Bader charge analysis show that N-modified β-Mo2C has a significantly lower work function than other structures, which increases the charge transfer ability between the catalyst and LiO2. This work provides a valuable scheme for adjusting the transition metal electronic structure in low-cost MXene for lithium-air batteries.

Raman Spectrum of the Li2SO4-MgSO4-H2O System: Excess Spectrum and Hydration Shell Spectrum.

Lithium, as a green energy metal used to promote world development, is an important raw material for lithium-ion, lithium-air, and lithium-sulfur batteries. It is challenging to directly extract lithium resources from brine with a high Mg/Li mass ratio. The microstructure study of salt solutions provides an important theoretical basis for the separation of lithium and magnesium. The changes in the hydrogen bond network structure and ion association of the Li2SO4 aqueous solution and Li2SO4-MgSO4-H2O mixed aqueous solution were studied by Raman spectroscopy. The SO42- fully symmetric stretching vibration peak at 940~1020 cm-1 and the O-H stretching vibration peak at 2800~3800 cm-1 of the Li2SO4 aqueous solution at room temperature were studied by Raman spectroscopy and excess spectroscopy. According to the peak of the O-H stretching vibration spectrum, with an increase in the mass fraction of the Li2SO4 solution, the proportion of DAA-type and DDAA-type hydrogen bonds at low wavenumbers decreases gradually, while the proportion of DA-type hydrogen bonds at 3300 cm-1 increases. When the mass fraction is greater than 6.00%, this proportion increases sharply. Although the spectra of hydrated water molecules and bulk water molecules are different, the spectra of the two water molecules seriously overlap. The spectrum of the anion hydration shell in a solution can be extracted via spectrum division. By analyzing the spectra of these hydration shells, the interaction between the solute and water molecules, the structure of the hydration shell and the number of water molecules are obtained. For the same ionic strength solution, different cationic salts have different hydration numbers of anions, indicating that there is a strong interaction between ions in a strong electrolytic solution, which will lead to ion aggregation and the formation of ion pairs. When the concentration of salt solution increases, the hydration number decreases rapidly, indicating that the degree of ion aggregation increases with increasing concentration.

Molecular cleavage strategy enabling optimized local electron structure of Co-based metal-organic framework to accelerate the kinetics of oxygen electrode reactions in lithium-oxygen battery

Metal-organic frameworks (MOFs) are considered as promising oxygen electrode materials for lithium-oxygen (Li-O2) batteries. However, their structure-activity relationship in catalyzing oxygen electrode reactions in Li-O2 battery is currently overlooked. Herein, molecular cleavage strategy is adopted to optimize local coordination structure of Co-MOF via introducing missing linkers. Theoretical calculation certifies that the introduction of monodentate ligand-benzoic acid (BA) as the missing linker causes the generation of defect state. Moreover, asymmetrically coordinated cobalt with surrounding oxygen caused by the introduction of BA optimizes electron coupling between Co 3d orbits and oxygen adsorbents, eventually promoting oxygen electrode reactions in Li-O2 batteries. However, excessive missing linkers can lead to the collapse of framework, covering active sites and thus deteriorating the catalytic activity of MOF. As a result, Li-O2 battery with Co-MOF containing 10 mol% BA (named as Co-MOF-BA0.1) delivers low overpotential of 0.86 V and large discharge capacity of 14011 mAh g−1.

A Quantitative Understanding of Electron and Mass Transport Coupling in Lithium–Oxygen Batteries

AbstractThe lithium–oxygen battery has the highest theoretical specific energy among all battery systems, while the actual value falls significantly short. The hindered oxygen and/or electron transport result(s) in limited utilization of the porous air electrode, while achieving a quantitative understanding of the electrochemistry and mass transport coupling is challenging. Herein, a porous electrode with highly consistent and controllable channel units is pioneered that excludes the randomness of disordered pores and consequently enables the investigation of control mechanisms. A three‐dimensional dynamic heterogeneous model is developed, providing the first spatio‐temporal distribution of LiO2 and revealing its reversed diffusion trajectories at limited electron transport. The synergistic combination of experiments and models identifies the crucial role of channel sizes on mechanisms that are divided into mass, hybridization, and electron transport control. For macropores, improving Li2O2 conductivity and mitigating solid‐liquid interface damage are urgent compared to enhancing oxygen diffusion. The unit model offers a promising approach to quantitatively understand the reaction and transport mechanisms in other battery systems with porous electrodes. This work represents a break through in knowledge of control mechanisms and guides the design of disordered electrodes for high‐performance lithium–oxygen batteries.

Study on evolution process and electrochemical behavior of porous cathode in discharge process of the solid-state lithium-oxygen battery

Solid-state lithium‑oxygen battery is one of the lithium-metal batteries with high theoretical specific capacity and strong safety. In order to explore the evolution process and electrochemical behavior of the battery, a study of combination of simulation and experiment is conducted in this paper. Firstly, solid-state lithium‑oxygen batteries with quartz tubes as the battery shell are designed for the experiment. FTIR and Raman results show that the lithium peroxide is produced as discharge products and SEM images show the product is accumulated on the surface of carbon particles and bound the carbon particles into blocks during the cathode evolution process. Then, a 1D multi-physics coupling field model referred to the experiment is established to investigate the electrochemical behavior of the battery. The calculated discharge curves are compared with the experimental discharge curves to verify the accuracy of the model. Using the model, the electrochemical behaviors, such as discharge product volume fraction, active three-phase interface, LATP phase potential and carbon phase potential, are analyzed. At last, the reasons for discharge termination are attributed to the accumulation of lithium peroxide and the decline of active three-phase interface.

Probing interfacial electrochemistry by in situ atomic force microscope for battery characterization

AbstractLithium‐ion batteries (LIBs) have been widely used in electric vehicles and energy storage industries. An understanding of the reaction processes and degradation mechanism in LIBs is crucial for optimizing their performance. In situ atomic force microscopy (AFM) as a surface‐sensitive tool has been applied in the real‐time monitoring of the interfacial processes within lithium batteries. Here, we reviewed the recent progress of the application of in situ AFM for battery characterizations, including LIBs, lithium–sulfur batteries, and lithium–oxygen batteries. We summarized advances in the in situ AFM for recording electrode/electrolyte interface, mechanical properties, morphological changes, and surface evolution. Future directions of in situ AFM for the development of lithium batteries were also discussed in this review.

The initial stages of Li2O2 formation during oxygen reduction reaction in Li-O2 batteries: The significance of Li2O2 in charge-transfer reactions within devices

Lithium-oxygen batteries are a promising technology because they can greatly surpass the energy density of lithium-ion batteries. However, this theoretical characteristic has not yet been converted into a real device with high cyclability. Problems with air contamination, metallic lithium reactivity, and complex discharge and charge reactions are the main issues for this technology. A fast and reversible oxygen reduction reaction (ORR) is crucial for good performance of secondary batteries’, but the partial knowledge of its mechanisms, especially when devices are concerned, hinders further development. From this perspective, the present work uses operando Raman experiments and electrochemical impedance spectroscopy (EIS) to assess the first stages of the discharge processes in porous carbon electrodes, following their changes cycle by cycle at initial operation. A growth kinetic formation of the discharge product signal (Li2O2) was observed with operando Raman, indicating a first-order reaction and enabling an analysis by a microkinetic model. The solution mechanism in the evaluated system was ascribed for an equivalent circuit with three time constants. While the time constant for the anode interface reveals to remain relatively constant after the first discharge, its surface seemed to be more non-uniform. The model indicated that the reaction occurs at the Li2O2 surface, decreasing the associated resistance during the initial discharge phase. Furthermore, the growth of Li2O2 forms a hetero-phase between Li2O2/electrolyte, while creating a more compact and homogeneous on the Li2O2/cathode surface. The methodology here described thus offers a way of directly probing changes in surface chemistry evolution during cycling from a device through EIS analysis.

Rechargeable Lithium-Air Batteries with Practically High Energy Density

Rechargeable Lithium-Air Batteries with Practically High Energy Density

Heme-Based Composites as Cathode Catalysts for Lithium-Oxygen Batteries and Analysis of the Reaction Mechanism

Despite the high theoretical energy density of lithium-oxygen (Li-O2) batteries, the charge/discharge efficiency is unsatisfactory. To overcome this critical problem, we synthesized heme-graphene composites (HEME-GO) as catalysts for Li-O2 batteries. The introduction of graphene produced π-π interactions with the heme matrix, resulting in a composite with enhanced ORR/OER catalytic activity. The free energy diagram of the redox reaction was calculated using density functional theory (DFT) for HEME-GO based on the four-electron reaction pathway, and it was demonstrated that HEME-GO has the lowest ORR overpotential (0.67 V) and OER overpotential (0.53 V). The catalytic mechanism of HEME-GO was also quantitatively described by calculating the adsorption energy of intermediates in the rate determining step (RDS). In addition, the Li-O2 batteries with the composite catalyst exhibited better cycling performance, discharge capacity (7770 mAh g−1), and lower overpotential due to the ability of heme to scavenge superoxide radicals and thus protect the electrode. The results in this paper contribute to the understanding of the redox process of Li-O2 batteries for organic systems and suggest innovative ideas for the design of environmentally friendly batteries.