Cathode For Li-O2 Batteries Research Articles

UIO-66-NH2 as Photo-Assisted Li-O2 Battery Cathode for High-Current Discharge.

Li-O2 batteries (LOBs) have garnered significant attention in recent years due to high theoretical specific capacity, however, the sluggish charge-discharge reaction kinetics and rapid failure under high current densities have hindered their further application. This work presents a photo-responsive catalyst (UIO-66-NH2) supported on carbon cloth, which could enhance the reaction kinetics of LOBs and improve the discharge capacity under high current densities. It demonstrates that under light, the overpotential decreases by 0.9 V, and the discharge capacity reaches an impressive 4.8 mAh cm-2 at a current density of 0.5 mA cm-2. This finding is expected to inspire the development of various novel MOF-based photoelectrodes for LOBs.

First Principles Study of the Structure-Performance Relation of Pristine Wn+1Cn and Oxygen-Functionalized Wn+1CnO2 MXenes as Cathode Catalysts for Li-O2 Batteries.

Li-O2 batteries are considered a highly promising energy storage solution. However, their practical implementation is hindered by the sluggish kinetics of the oxygen reduction (ORR) and oxygen evolution (OER) reactions at cathodes during discharging and charging, respectively. In this work, we investigated the catalytic performance of Wn+1Cn and Wn+1CnO2 MXenes (n = 1, 2, and 3) as cathodes for Li-O2 batteries using first principles calculations. Both Wn+1Cn and Wn+1CnO2 MXenes show high conductivity, and their conductivity is further enhanced with increasing atomic layers, as reflected by the elevated density of states at the Fermi level. The oxygen functionalization can change the electronic properties of WC MXenes from the electrophilic W surface of Wn+1Cn to the nucleophilic O surface of Wn+1CnO2, which is beneficial for the activation of the Li-O bond, and thus promotes the Li+ deintercalation during the charge-discharge process. On both Wn+1Cn and Wn+1CnO2, the rate-determining step (RDS) of ORR is the formation of the (Li2O)2* product, while the RDS of OER is the LiO2* decomposition. The overpotentials of ORR and OER are positively linearly correlated with the adsorption energy of the RDS LixO2* intermediates. By lowering the energy band center, the oxygen functionalization and increasing atomic layers can effectively reduce the adsorption strength of the LixO2* intermediates, thereby reducing the ORR and OER overpotentials. The W4C3O2 MXene shows immense potential as a cathode catalyst for Li-O2 batteries due to its outstanding conductivity and super-low ORR, OER, and total overpotentials (0.25, 0.38, and 0.63 V).

An integrally bilayered flexible cathode woven from CNTs for homogeneous hosting and fast electrocatalytic conversion of Li2O2 in Li-O2 battery

Due to the ultrahigh theoretical energy density, Li-O2 batteries are considered as potential candidates for power accessories for wearable electronic devices. An effective oxygen-breathing cathode is essential to enable high cyclic stability in Li-O2 batteries. Herein, an integrally bilayered, freestanding flexible Li-O2 battery cathode is constructed by in-situ growth of a layer of microflowers (which is an assembly of nitrogen-doped carbon nanotubes embedded with cobalt nanoparticles) on the surface of a CNT-interwoven film. Owing to the integrally bilayered structural feature and its compositional merits, such three-dimensionally conductive network provides a large space and surface area for homogeneous hosting and also enables efficient electrocatalytic conversion of the insulating Li2O2 solids. Thus obtained cathode delivers a large full capacity of 8.03 mAh cm−2; it also exhibits a low charge potential of approximately 3.6 V and excellent cyclic stability for stable operation up to nearly 2 months at a capacity of 0.1 and 1 mAh cm−2. Moreover, being flexible and binder-free, the cathode is highly robust, which can withstand repetitive folding and unfolding. A co-axial Li-air battery was fabricated accordingly, which exhibits excellent tolerance to bending deformation, showing great potential for application in flexible and wearable electronics.

Lattice Boltzmann Simulations of Non-Homogeneous Li–O2 Battery Cathode: The Effect of Spatial and Temporal Porosity Variations

Abstract The porosity of the cathode in a lithium–oxygen battery is a crucial parameter that influences oxygen transport and active surface area availability. This study explores various cathode models with different initial porosity distributions and analyzes the porosity evolution during discharge. The objective is to maximize the active surface area utilization of the cathode and increase the battery’s discharge capacity. The simulations employ a recently developed lattice Boltzmann method (LBM) model proposed by Chen et al. (2017, “Simulation of Double Diffusive Convection in Fluid-Saturated Porous Media by Lattice Boltzmann Method,” Int. J. Heat Mass Transfer, 108, pp. 1501–1510), which is capable of handling spatial and temporal variations in diffusion coefficient values. The results demonstrate that a hierarchical porous cathode provides a better specific capacity than a uniform porous cathode with the same average initial porosity. The specific capacity increases as the magnitude of initial porosity variation in the domain increases. Furthermore, incorporating oxygen channels improves oxygen transport in the cathode and offers a better specific capacity than the hierarchical porous cathode. A combination of hierarchical porous media and oxygen channels delivers the best specific capacity among all the other cathode models, as it efficiently balances oxygen transport and active surface area.

Air activation enhances the porosity and N,O synergistic effect towards an efficient metal free carbon cathode for Li-O2 battery

The achievement of Li-O2 batteries with high energy density and extended cycle life is often hindered by the disorderly growth of solid discharge product Li2O2 on the cathode and its sluggish decomposition reaction kinetics. Herein, under the guidance of DFT simulations, the N,O co-doped carbon was identified as a potential efficient metal free cathode catalyst to remit these problem in Li-O2 batteries. Then, a spherical shell-like N,O co-doped carbon was prepared through the direct pyrolysis of guanosine 5′-monophosphate disodium salt (5′-GMP, 2Na). After a further activation process in air, the carbon shells exhibit a finer porous surface with greatly enhanced specific surface area and surface N,O contents. As a result, the morphology of Li2O2 changed from large toroidal to film by using the activated carbon as a cathode catalyst due to its tailored surface structure with improved N and O synergistic effect. What's more, the film-like Li2O2 with Li vacancy can not only form an increased interfacial contact and interaction with the active sites on carbon, but also be conducive to the transfer of Li+/electrons during the decomposition of Li2O2, thus accelerating the electrochemical performances of the battery.

Theoretical study of catalytic performance of WN MXenes as cathodes for Li-O2 batteries: Effects of surface functionalization and atomic layers

Promising Li–O2 batteries suffer from high overpotentials of the oxygen evolution reaction (ηOER)/oxygen reduction reaction (ηORR) at cathodes during charging/discharging. Herein, the first-principles calculations were performed to investigate WN MXenes, including the pristine Wn+1Nn and oxygen − functionalized Wn+1NnO2 (n = 1, 2, and 3), as the potential cathode catalysts for Li − O2 batteries. Both Wn+1Nn and Wn+1NnO2 exhibit high electrical conductivity. Compared to the electrophilic W surfaces of Wn+1Nn, the nucleophilic O surfaces of Wn+1NnO2 can not only bind to Li of LixO2 to activate the Li − O bond, but also promote electron transfer to form Li+, which facilitates to the delithiation of LixO2 in the OER, thus lowering ηOER on Wn+1NnO2. Moreover, the O-functionalized surfaces can also reduce the adsorption energies of LixO2, thereby lowering ηORR and ηOER. On the other hand, reducing atomic layers of Wn+1Nn and Wn+1NnO2 can further lower ηORR and ηOER, because WN MXenes with fewer atomic layers have lower d-/p- band centers, which can weaken the adsorption of LixO2. The W2NO2 MXene not only has a high electrical conductivity but also exhibits ultra-low ORR, OER, and total overpotentials (0.12, 0.17, and 0.29 V), indicating it possesses an ultra-high catalytic performance as cathodes for Li-O2 batteries.

NiCoP based carbon nanotube heterostructure for improved oxygen redox reaction kinetics in Li-O2 batteries

The design of ultra-stable cathode materials of Li-O2 batteries with excellent catalytic performance is very important and desirable. However, some problems such as sluggish electrochemical reaction kinetics and unwanted side reactions still remain challenging. Carbon materials own hierarchical porous structure which facilitates mass transport and accommodates discharge products but are not stable enough as cathode of Li-O2 batteries. Here in, we fabricated a unique NiCo bimetallic phosphide combined with carbon nanotube heterostructure (abbreviated as NiCoP/CNT) by hydrothermal method. Density functional theory (abbreviated as DFT) calculation demonstrates that bimetallic phosphide NiCoP/CNT delivered much better electrical conductivity, greater adsorption to reactants, and more electron transfer with discharge products Li2O2, compared to monometallic phosphides CoP and Ni2P. Therefore, NiCoP/CNT based cathode displayed low overpotential of 0.87 V at current of 100 mA g−1 with a fixed specific capacity of 1000 mAh g−1 and run steadily over 150 cycles under high current of 500 mA g−1 with a fixed specific capacity of 1000 mAh g−1. Furthermore, Ex-situ X-ray Photoelectron Spectroscopy and in-situ differential electrochemical mass spectroscopy proved the existence of intermediate products Li2-xO2. This approach provides a reference for designing and synthesis of bimetallic cathode in Li-O2 batteries.

CeO2 Supported on Reduced Graphene Oxide as Li-O2 Battery Cathode

CeO2 Supported on Reduced Graphene Oxide as Li-O2 Battery Cathode

Nitrogen-doped expanded graphite derived from spent graphite induce uniform growth of lithium peroxide for high-performance Li-oxygen battery

Clean treatment and recycling of retired graphite are of great significance to void environmental pollution and resource waste. For this reason, a simple chemical intercalation process combined melamine-assisted expansion strategy is used to prepare nitrogen-doping expanded graphite (N-EG) with a worm-like structure from waste graphite as an ideal lithium-oxygen (Li-O2) battery cathode. The pyrolysis of melamine during annealing can realize the reduction and nitrogen-doping of the expanded graphite in one step, so as to improve the conductivity and electrocatalytic activity of expanded graphite. Moreover, the continuous multilayer hierarchical porous structure of worm-like expanded graphite can not only provide sufficient free-space for the storage of discharge products but also facilitate the mass transfer for battery reactions. As a proof of concept, the as-prepared N-EG have been used as the cathode in Li-O2 battery and achieve excellent electrochemical performances, including high specific capacity, excellent rate performance and long cycle stability. Furthermore, by combining density functional theory (DFT) calculations with experimental data, we demonstrate that the introduction of N-doping in expanded graphite can induce surface combine solution-mediated growth of Li2O2 on the cathode. Such a universal method provides an environmentally friendly approach for the reuse of waste graphite to construct high-performance Li-O2 battery cathode.

Edge‐Site‐Free and Topological‐Defect‐Rich Carbon Cathode for High‐Performance Lithium‐Oxygen Batteries (Adv. Sci. 16/2023)

Carbon Cathodes In article number 2300268, Wei Yu, Hirotomo Nishihara, and co-workers proposed an edge-site-free and topological-defect-rich graphene mesosponge (GMS) as a carbon cathode for Li-O2 batteries. GMS exhibits high discharge capacity, low charge plateau, and enhanced electrochemical stability, which is attributed to the formation of easily decomposable Li2O2 at the topological defects on the GMS.

Pyrochlore LaSrSn2O7 nanoparticles anchored on carbon nanofibers as bifunctional catalysts for an efficient Li-O2 battery

The slow reaction kinetics of oxygen reduction reaction for Li2O2 formation and oxygen evolution reaction for Li2O2 decomposition with poor electrocatalytic activities have been a problem to be solved for the commercialization of lithium-oxygen (Li-O2) batteries. Bifunctional catalysts composed with pyrochlore LaSrSn2O7 nanoparticles (LSSO NPs) and one-dimensional (1D) carbon nanofibers (NFs) were prepared and their catalytic performances were investigated for Li-O2 batteries. As-obtained 1D carbon@LaSrSn2O7 (C@LSSO) NFs composites in Li-O2 battery cathode delivered excellent initial specific capacity (ca. 8067.3 mAh g−1). In addition, decent cycle durability of the C@LSSO cathode was accomplished over 54 cycles with a low overpotential gap of 1.01 V at a rate of 200 mA g−1 with a specific capacity limit of 500 mAh g−1, in comparison to the LSSO NPs and ketjen black carbon. The enhanced properties suggest that these composite structures of pyrochlore LSSO NPs with 1D carbon NFs backbones could be a prospective bifunctional catalyst in the development of the high-performance Li-O2 battery.

Edge-Site-Free and Topological-Defect-Rich Carbon Cathode for High-Performance Lithium-Oxygen Batteries.

The rational design of a stable and catalytic carbon cathode is crucial for the development of rechargeable lithium-oxygen (LiO2 ) batteries. An edge-site-free and topological-defect-rich graphene-based material is proposed as a pure carbon cathode that drastically improves LiO2 battery performance, even in the absence of extra catalysts and mediators. The proposed graphene-based material is synthesized using the advanced template technique coupled with high-temperature annealing at 1800°C. The material possesses an edge-site-free framework and mesoporosity, which is crucial to achieve excellent electrochemical stability and an ultra-large capacity (>6700 mAh g-1 ). Moreover, both experimental and theoretical structural characterization demonstrates the presence of a significant number of topological defects, which are non-hexagonal carbon rings in the graphene framework. In situ isotopic electrochemical mass spectrometry and theoretical calculations reveal the unique catalysis of topological defects in the formation of amorphous Li2 O2 , which may be decomposed at low potential (∼ 3.6V versus Li/Li+ ) and leads to improved cycle performance. Furthermore, a flexible electrode sheet that excludes organic binders exhibits an extremely long lifetime of up to 307 cycles (>1535h), in the absence of solid or soluble catalysts. These findings may be used to design robust carbon cathodes for LiO2 batteries.

High-Conductive Multilayer TiOX-Ti3C2TX Electrocatalyst for Longevous Metal-Oxygen Battery under a High Rate

Metal-oxygen batteries (especially Li-O2 battery) with ultrahigh theoretical energy density are of great promise for long-range vehicle electrification. However, the limited enduring stability and low-rate property further restricted the large-scale commercial application of metal-oxygen batteries. We firstly report the fabrication of a TiOX@Ti3C2TX with multilayer structure and its utilization as cathode for Li-O2 batteries. The TiOX protective layer was fabricated in situ to directly optimize surface properties of Ti3C2TX, as well as to strengthen surface active functional groups. The initial discharge capacity of as-prepared TiOX@Ti3C2TX cathode reaches 7100 mAh g−1 at 2500 mA g−1, as well as delivers impressive cycling stability (>100 cycles) at 2500 mA g−1. Experimental analysis reveals that the in situ TiOX protective layer enhanced active functional-groups and the improved complete decomposition of discharge products Li2O2 are three critical factors for promoting the electrochemical performance of LOBs. This work exhibits a new insight into the design of MXene electrocatalysts for metal-oxygen batteries.

Turn "Waste" Into Wealth: MoO2 @coal Gangue Electrocatalyst with Amorphous/Crystalline Heterostructure for Efficient Li-O2 Batteries.

Unreasonable accumulation of coal gangue in mining area has become the major source of global pollution. Probing the high-valued utilization of coal gangue has become a key approach to address the problem. Herein, a promising catalyst of MoO2 @coal gangue with amorphous/crystalline heterostructure derived from mine solid waste, which acts as an efficient cathode for Li-O2 batteries is first reported. Impressively, the as-prepared catalyst exhibits a favorable initial discharge capacity of 9748mAh g-1 and promising long-term cyclic stability over 2200h. Experimental results coupled with density functional theory (DFT) analysis reveal that the synergistic interaction between high-activity MoO2 and stable SiO2 , unique amorphous/crystalline heterostructure and the modified interfacial adsorption of LiO2 intermediate are critical factors in promoting the electrochemical performance. This work provides a new insight to design marked electrocatalysts by mine solid waste for Li-O2 batteries.

Tailoring the nucleation and growth routes of discharge products for lithium-oxygen batteries through the facet engineering of Ni2P catalysts

Li-O2 batteries (LOBs) with high theoretic energy densities are regarded as potential energy storage devices. However, the insulative discharge product, Li2O2, would accumulate on the cathode, restricting the depth of discharge and raising barriers for charge. The rational catalyst design is proposed as an efficient strategy to tailor growth routes and morphology of Li2O2, and consequently address the above issue. Herein, porous Ni2P nanorods with exposed (0001) or (101¯0) facets are prepared on Ni foams through the heat treatment of Ni2P2O7 arrays in a PH3 atmosphere. The exposed facets of Ni2P nanorods could be well controlled through the variation of the hydrothermal reaction time for Ni2P2O7. Employed as free-standing cathodes for LOBs, Ni2P nanorods with exposed (0001) facets exhibit superior electrochemical performance than those nanorods with exposed (101¯0) facets due to the interaction between exposed facets and the nucleation, growth of LiO2 or Li2O2, consequently tuning the morphology of discharge products. The high electron transfer rate and weak adsorption energy of LiO2 on exposed (0001) facets could promote the generation rate of the (solvated) LiO2, inducing the formation of large Li2O2 sheets (over 30 μm) and further growth of flower-like nanoflake assemblies (∼500 nm) on the surface of Li2O2 sheets assignable to the variation of the surface environment of the cathode during the discharge process, exhibiting more Li2O2 deposited at full coverage of cathode surface. It is proposed that the facet engineering is a feasible way to improve the electrochemical performance of cathode catalysts for LOBs.

An atomic/molecular-level strategy for the design of a preferred nitrogen-doped carbon nanotube cathode for Li-O2 batteries

The formation and growth of Li2O2, the primary discharge product with extremely low conductivity, will cause the passivation of the cathode and the failure or even death of Li-O2 batteries. In this paper, by means of molecular dynamics and density functional theory, we systematically investigated the morphology evolution and electron transport pathway of (Li2O2)n on the surface of nitrogen-doped carbon nanotubes (NCNTs) and the effects of the possible N configuration on the growth stability of (Li2O2)n. Our results demonstrated that the morphology of (Li2O2)n on the surface of NCNTs undergos a process from scattered small-sized clusters to film-like (axial) and toroidal (circumferential) large clusters, and finally completely surrounded the NCNTs. Compared with graphitic N1 and graphitic N2, Li2O2 tends to aggregate stably on the surface of pyridinic N3 and pyridinic N4, which can effectively reduce the capacity loss caused by Li2O2 branches and free state Li2O2. In addition, a stable gap exists between Li2O2 and NCNTs, which is attributed to the Coulomb force and van der Waals interaction. Importantly, (Li2O2)n with p-type semiconductor characteristics acts as a bridge between NCNTs, and electrons are mainly transferred along the surface of (Li2O2)n clusters. Moreover, increasing the wall number of NCNTs and using NCNT bundles were found to be beneficial to improving the deposition stability of (Li2O2)n. Notably, pyrrolic N3 with unstable structure is not recommended for practical application. These results offer general guidelines for designing highly active catalysts for Li-O2 batteries in terms of the optimization of the NCNT-based cathode, and the unique research methods also shed more light on the analysis of the discharge product behavior of other potential metal-air batteries.

A synthetic strategy for graphitized carbon hollow nanospheres with nano-punched holes decorated with bimetallic selenide as efficient bifunctional electrocatalysts for rechargeable Li–O2batteries

Porous graphitized carbon hollow nanospheres with defects and minimal amorphous carbon content are synthesizedviagraphitization with catalyst and post-treatment. As Li–O2battery cathodes, they demonstrate excellent electrochemical performances.

MnFe phosphides doped in hollow Prussian blue analogues with Ru modification as an efficient cathode for Li-O2 batteries.

A highly efficient catalyst for Li-O2 batteries based on Ru and MnFe phosphides nanoparticles entrapped in a MnFe Prussian blue analogue (PBA) substrate (Ru-MnFeP/PBA) was explored. Synergy between homogeneous Ru and MnFe phosphides nanoparticles improved the catalytic activity and alleviated side reactions. The Li-O2 battery based on Ru-MnFeP/PBA exhibited excellent performance.

RuO2-Incorporated Co3O4 Nanoneedles Grown on Carbon Cloth as Binder-Free Integrated Cathodes for Tuning Favorable Li2O2 Formation.

Developing ideal Li-O2 batteries (LOBs) requires the discharge product to have a large quantity, have large contact area with the cathode, and not passivate the porous surface after discharge, which put forward high requirement for the design of cathodes. Herein, combining the rational structural design and high activity catalyst selection, minor amounts of RuO2-incorporated Co3O4 nanoneedles grown on carbon cloth are successfully synthesized as binder-free integrated cathodes for LOBs. With this unique design, plenty of electron-ion-oxygen tri-phase reaction interface is created, the side reaction from carbon is isolated, and oxygen reduction reaction/oxygen evolution reaction (OER) kinetics are significantly facilitated. Upon discharge, film-like Li2O2 is observed growing on the needle surface first and eventually ball-like Li2O2 particles form at each tip of the needle. The cathode surface remains porous after discharge, which is beneficial to the OER and is rare in the previous reports. The battery exhibits a high specific discharge capacity (7.64 mAh cm-2) and a long lifespan (500 h at 0.1 mA cm-2). Even with a high current of 0.3 mA cm-2, the battery achieves a cycling life of 200 h. In addition, punch-type LOBs are fabricated and successfully operated, suggesting that the cathode material can be utilized in ultralight, flexible electronic devices.

Designing a photo-assisted Co-C3N4 cathode for high performance Li-O2 batteries

Designing a photo-assisted Co-C3N4 cathode for high performance Li-O2 batteries