High-performance Li-O2 Batteries Research Articles

Promoted Reaction Reversibility by Dual-Effect 15-Crown-5 Ether Additive for High-Performance Li-O2 Batteries.

The practical application of lithium-oxygen batteries (LOBs) with ultrahigh theoretical energy density faces the problems of poor kinetics and deficient reversibility. The electrolyte is of vital significance to the electrochemical stability and reaction pathway of LOBs due to the formation of soluble products. Here, a 15-crown-5 ether (15C5) is employed to regulate the solvation structure of Li+ and manipulate the reaction mechanism through regulating the binding ability toward Li+. The promoted dissociation of LiNO3 by 15C5 increases the catalytical active anions in the electrolyte and stabilizes the Li-containing reduced oxygen species to promote the solution pathway of discharge product growth. Besides, 15C5 also facilitates the kinetics of the electrochemical decomposition of Li2O2 and prolongs the cycle life to 178 cycles. This work inspires a novel approach to improve the battery performance through electrolyte component design.

Dual-type atomic Ru promoted bifunctional catalytic process realizing ultralow overpotential for Li-O2 batteries

Developing well-defined catalysts to ameliorate overpotential and cycling capability is imperative for high-performance Li-O2 batteries. However, conventional catalysts face fundamental challenges that ORR and OER with different rate-determining steps are catalyzed by the same active center, inevitably weakening the selectivity and activity. Herein, we report a cross-scale catalyst with ultrafine RuPt nanoparticles and surrounding RuPt pairs on porous carbon (RuPt NPs@RuPt-N-C). The planted Ru single atoms within Pt nanoparticles and carbon matrix contribute to a fresh bifunctional catalytic mechanism for enhancing ORR/OER catalytic kinetics. As a proof-of-concept application in Li-O2 batteries, this catalyst realizes extremely low overpotentials of only 0.43 V and superior cyclic stability of 209 cycles at 200 mA g−1. Experimental and computational results disclose that for Pt NPs@Pt-N-C without Ru functionalization, only Pt-N-C works as ORR/OER active centers. By contrast, for RuPt NPs@RuPt-N-C, due to downshifted d-band center and enhanced charge transfer with LiO2 intermediate, the Pt nanocrystals are fully activated by Ru atoms, making RuPt nanocrystals as preferable ORR kinetics promoter for the formation of easily-decomposed nanoflower Li2O2. Moreover, adjacent RuPt pairs with weakened O2 affinity can work as major OER center, contributing to accelerating the following Li2O2 decomposition. This work expands the frontier of cross-scale electrocatalysts with tailored bifunctional catalysis properties for other electrocatalytic fields.

Reducing Overpotential of Lithium-Oxygen Batteries by Diatomic Metal Catalyst Orbital Matching Strategy.

Aprotic Li-O2 batteries have sparked attention in recent years due to their ultrahigh theoretical energy density. Nevertheless, their practical implementation is impeded by the sluggish reaction kinetics at the cathode. Comprehending the catalytic mechanisms is pivotal to developing efficient cathode catalysts for high-performance Li-O2 batteries. Herein, the intrinsic activity map of Li-O2 batteries is established based on the specific adsorption mode of O2 induced by diatomic catalyst orbital matching and the transfer-acceptance-backdonation mechanism, and the four-step screening strategy based on the intrinsic activity map is proposed. Guided by the strategy, FeNi@NC and FeCu@NC promising durable stability with a low overpotential are screened out from 27 Fe-Metal diatomic catalysts. Our research not only provides insights into the fundamental understanding of the reaction mechanism of Li-O2 batteries but also accelerates the rational design of efficient Li-O2 batteries based on the structure-activity relationship.

Integrated platinum-fullerene nanocatalyst as efficient cathode kinetic promoter for advanced lithium−oxygen batteries

Efficient and robust platinum-carbon electrocatalysts are of great significance for long-term service of high-performance Li–O2 batteries. Herein we developed an ultra-low platinum loading platinum-fullerene electrocatalyst by ultraviolet-assisted method. The catalyst features crystalline platinum nanodots integrated into C60 nano-fullerene matrices (Pt–C60), which demonstrates excellent mass-activity, 28.8 times higher than that of commercial Pt/C catalysts, exhibiting an ultra-low cell overpotential of 0.43 V while maintaining an excellent cycle stability over 150 cycles. XPS and Raman spectra disclose the integrated nature of Pt–C bonding interaction, and computational modeling reveal the improved electrocatalytic activity and cathode reaction kinetics. Comprehensive investigations demonstrate that the synergistic contribution of component and structure in integrated Pt–C60 catalyst is responsible for high-efficiency and long-life of Li–O2 batteries. Notably, Pt–C covalent integrated design provides a paradigm of catalyst engineering for developing high-activity and low-cost Pt/C catalysts, and easy synthesis method allows them to be mass-produced and potentially-used in catalyst fields.

Hierarchically Interconnected 3D Catalyst Structure of Porous Multi-Metal Oxide Nanofibers for High-Performance Li-O2 Batteries.

Non-aqueous lithium-oxygen batteries (LOBs) have emerged as a promising candidate due to their high theoretical energy density and eco-friendly cathode reaction materials. However, LOBs still suffer from high overpotential and poor cycling stability resulting from difficulties in the decomposition of discharge reaction Li2 O2 products. Here, a 3D open network catalyst structure is proposed based on highly-thin and porous multi-metal oxide nanofibers (MMONFs) developed by a facile electrospinning approach coupled with a heat treatment process. The developed hierarchically interconnected 3D porous MMONFs catalyst structure with high specific surface area and porosity shows the enhanced electrochemical reaction kinetics associated with Li2 O2 formation and decomposition on the cathode surface during the charge and discharge processes. The uniquely assembled cathode materials with MMONFs exhibit excellent electrochemical performance with energy efficiency of 82% at a current density of 50mAg-1 and a long-term cycling stability over 100 cycles at 200mAg-1 with a cut-off capacity of 500 mAhg-1 . Moreover, the optimized cathode materials exhibit a remarkable energy density of 1013Whkg-1 at the 100th discharge and charge cycle, which is nearly four times higher than that of C/NMC721, which has the highest energy density among the cathode materials currently used in electric vehicles.

Double-phase electrolyte enabling the long-lasting redox mediation in Li–O2 batteries

The achievement of practical Li–O2 batteries is impeded by their low discharge capacity, large charge overpotential, and short lifespan. In general, the use of electrolyte with a high-donor-number solvent such as dimethyl sulfoxide (DMSO) is able to drive the solution-mediated pathway, alleviating the premature passivation of cathode from the surface-mediated Li2O2 film growth, gaining large Li2O2 toroidal particles, and extending the discharge lifetime. However, direct electrochemical decomposition of Li2O2 toroidal products typically occurs at a high charge potential owing to the poor solid-solid contact between cathode catalysts and Li2O2 toroids. Besides, DMSO-based electrolytes are unstable to Li anode, leading to undesired parasitic reactions. To overcome above issues, herein, a double-phase electrolyte composed of 10-methylphenothiazine (MPT)-dissolved DMSO-based catholyte and octyltrimethoxysilane (TOOS)-based anolyte is designed taking advantages of the immiscibility of DMSO and TOOS solvents and the insolubility of MPT in TOOS. Benefiting from the rapid liquid-solid reaction between MPT+ and Li2O2 products, the blocked MPT shuttling in TOOS, and the good compatibility of TOOS-based electrolyte to Li anode, the assembled Li–O2 battery delivers a reduced charge overpotential and a robust cyclability over 250 cycles. This study provides a promising strategy for electrolyte design towards next-generation high-performance Li–O2 batteries.

Electron Localization in Rationally Designed Pt1Pd Single-Atom Alloy Catalyst Enables High-Performance Li-O2 Batteries.

Li-O2 batteries (LOBs) are considered as one of the most promising energy storage devices due to their ultrahigh theoretical energy density, yet they face the critical issues of sluggish cathode redox kinetics during the discharge and charge processes. Here we report a direct synthetic strategy to fabricate a single-atom alloy catalyst in which single-atom Pt is precisely dispersed in ultrathin Pd hexagonal nanoplates (Pt1Pd). The LOB with the Pt1Pd cathode demonstrates an ultralow overpotential of 0.69 V at 0.5 A g-1 and negligible activity loss over 600 h. Density functional theory calculations show that Pt1Pd can promote the activation of the O2/Li2O2 redox couple due to the electron localization caused by the single Pt atom, thereby lowering the energy barriers for the oxygen reduction and oxygen evolution reactions. Our strategy for designing single-atom alloy cathodic catalysts can address the sluggish oxygen redox kinetics in LOBs and other energy storage/conversion devices.

Coupling interface constructions of hollow Co-Mo mixed multiple oxidation states heterostructure for high-performance aprotic Li-O2 battery

Coupling interface constructions of hollow Co-Mo mixed multiple oxidation states heterostructure for high-performance aprotic Li-O2 battery

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.

Evaluating the functions of the key dopant elements in multi-metal oxide electrocatalysts for high-performance Li-O2 batteries

Multi-metal oxides (MMOs) have emerged as promising electrocatalysts for high-performance Li-O2 batteries (LOBs) because of their tailored intrinsic properties. However, the complex nature of MMOs, with multiple elements involved, has made it challenging to fully comprehend the electrochemical behaviour of MMOs in relation to the metal composition. Herein, we systematically synthesized a series of spinel MMOs, including Ni-Co-Fe, Mn-Co-Fe, and Ni-Mn-Fe oxides, by doping Ni, Co, or Mn into spinel Fe3O4 via a hydrothermal method. The properties of the obtained MMOs, including metal element cooperation, oxygen vacancy, and substitution positions of the metal cations, are carefully examined. We further evaluated the obtained MMOs as electrocatalysts in LOBs to investigate the dependency between their metal composition and electrocatalytic properties. Interestingly, we found the ratio of Fe3+/Fe2+ in the MMOs can be changed by matching different doping elements, affecting the cycling stability of LOBs with Fe-based MMOs. It is also revealed that Ni-Co-Fe oxides have stronger adsorption of O2 and LiO2 and better electrical conductivity than Mn-Co-Fe and Ni-Mn-Fe oxides. In addition, more oxygen vacancy in the crystal structure of MMOs can be obtained by doping more Ni and Co atoms, which facilitates electron/Li+ transportation and oxygen adsorption. With the increased amount of the doped Ni and Co in the Ni-Co-Fe oxides, the LOBs demonstrated an improved specific capacity from 8120 mAh g−1 to 10698 mAh g−1 at the same current density of 200 mA g−1. This systematic investigation of the MMO composition has provided a profound understanding of MMOs electrocatalysts, offering valuable insights for designing and optimizing MMO-based electrocatalysts for advanced LOBs.

Orthogonal-Channel, Low-Tortuosity Carbon Nanotube Platforms for High-Performance Li-O2 Batteries.

Aerogels and foams are promising electrode materials owing to their lightweight, high porosity, and large surface area for creating abundant active/catalytic sites. Tailoring their porous structure is essential toward maximum electrode performance yet remains challenging in the field. Here, by modifying a pristine carbon nanotube (CNT) sponge with random internal distribution, we present a CNT platform consisting of regular, orthogonally intercrossed through-channels centered at a suitable lateral size (around 5 μm), with low tortuosity and enhanced electrochemical kinetics under predefined compression. Our CNT platforms, grafted by bifunctional transitional metal hydroxide catalyst, overcome considerable challenges of both long cycle life and high rates simultaneously, serving as Li-O2 cathodes and achieving lifetime of 500 cycles at 0.5 mA cm-2 (275 cycles even at 1 mA cm-2) and also displaying high areal capacity (27 mA h cm-2), which are superior to most of the recently reported porous electrodes based on various materials. The mechanism involving fast triple-phase transport and reversible discharge product deposition, enabled by catalyst-loaded orthogonal channels, has been disclosed. Such structure-tailored robust CNT platforms could find many applications in electrochemical catalysis and energy storage systems.

In-situ imaging electrocatalysis in a solid-state Li-O2 battery with CuSe nanosheets as air cathode

The development of highly efficient catalysts in the cathodes of rechargeable Li-O2 batteries is a considerable challenge. To enhance the electrochemical performance of the Li-O2 battery, it is essential to choose a suitable catalyst material. Copper selenide (CuSe) is considered as a more promising cathode catalyst material for Li-O2 battery due to its better conductivity and rich electrochemical active sites. However, its electrochemical reaction and fundamental catalytic mechanism remain unclear till now. Herein, in-situ environmental transmission electron microscopy technique was used to study the catalysis mechanism of the CuSe nanosheets in Li-O2 batteries during discharge and charge processes. It is found that Li2O was formed and decomposed around the ultrafine-grained Cu during the discharge and charge processes, respectively, demonstrating excellent cycling. This indicate that the freshly formed ultrafine-grained Cu in the conversion reaction catalyzed the latter four-electron-transfer oxygen reduction reaction, leading to the formation of Li2O. Our study provides important understanding of the electrochemistry of the Li-O2 nanobatteries, which will aid the development of high-performance Li-O2 batteries for energy storage applications.

Spatially confined sub-nanometer Pt in RuO2 nanosheet as robust bifunctional oxygen electrocatalyst for stabilizing Li-O2 batteries

Developing a highly active and durable bifunctional oxygen catalyst is the key to boosting lithium-oxygen batteries, but it remains a grand challenge. Herein, we demonstrate a remarkably active and durable bifunctional electrocatalyst (Pt/RuO2/G) with highly exposed active sites for stabilizing Li-O2 batteries by synergistically coupling the advanced oxygen reduction reaction (ORR) catalyst Pt with the oxygen evolution reaction (OER) catalyst RuO2, strongly anchored on graphene. The combined merits, including 2D porous morphology, ultrathin thickness (∼2.5 nm), and a well-dominated (110) plane of ultrasmall RuO2, originating from the efficient spatial confinement, provide the bifunctional Pt/RuO2/G electrocatalyst an extremely narrow OER/ORR voltage gap of only 0.633 V. Moreover, the as-designed Pt/RuO2/G-based Li-O2 batteries deliver a low initial charge-discharge mid-capacity overpotential (0.78 V) and remarkable lifetime (2,200 h) at 200 mA g−1, outperforming most Ru-based catalysts for Li-O2 batteries. This work provides a reliable practical approach for high-performance Li-O2 batteries.

Constructing in-situ SOCl2-induced protective layer on Li anode for high-performance Li–O2 batteries containing LiI redox mediator

Li–O2 batteries have attracted wide attention on account of the ever-increasing demand of high energy density systems. However, their practical application is still facing many critical problems, especially the slurry reaction rate/serious side reactions on cathodes and the fast growth of Li dendrites/passivating layers on anodes. Therefore, we design an in-situ formed coating layer on Li metal anode by introducing thionyl chloride (SOCl2) additives into the Li–O2 system with a redox mediator (RM), LiI. The robust and uniform SOCl2-derived layer can effectively prevent the attack of O2/O2–, which inhibits the surface passivation of Li metal anode and greatly supresses the infinite dendrite growth. Additionally, the SOCl2 additive also contributes to a certain specific capacity of the Li–O2 cells at full discharge/charge conditions. Moreover, the SOCl2-derived coating layer can almost completely stop the diffusion of the soluble I-based RM on Li metal anode to eliminate contiunous side reactions between them. The symmetrical batteries containing SOCl2 display lower overpotentials and longer cycling life than those of cells without SOCl2. More importantly, the SOCl2 based Li–O2 batteries with LiI exhibit the extra-high capacity (31000 mAh g−1), ultra-small voltage polarization (∼1.4 V), and extended operation life (190 cycles).

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.

Intelligently tuning the electronic structure of solid catalyst for bidirectional electrode process in lithium-oxygen batteries

In lithium–oxygen (Li–O2) batteries, catalytic conversion of lithium superoxide (LiO2) is a critical step to enhance kinetics. However, it is challenging for catalysts to be both highly efficient in the charging and discharging processes owing to the varying electrochemical environments. Here, we have achieved the desirable catalysis for the bidirectional electrode process by intelligently tuning the electronic structure of platinum/vanadium oxide (Pt/VOx). Due to changes in the internal electric field, the structure of Pt/VOx dynamically evolves during cycling (Pt/V2O3 or Pt/V2O5). The different redox states of the VOx can dynamically tune the electron density of Pt due to the strong metal-support interaction (SMSI), resulting in desirable adsorption behavior for LiO2 in the bidirectional electrode process. Consequently, Li–O2 batteries with Pt/VOx electrodes show ultra-low charge overpotential (0.14 V) and higher capacity (13,270 mAh g−1), indicating the great potential of catalyst reconstruction for high-performance Li–O2 batteries.

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.

Modulating Electronic Structure with Copper Doping to Promote the Electrocatalytic Performance of Cobalt Disulfide in Li-O2 Batteries.

Introducing heteroatom into catalyst lattice to modulate its intrinsic electronic structure is an efficient strategy to improve the electrocatalytic performance in Li-O2 batteries. Herein, Cu-doped CoS2 (Cu-CoS2 ) nanoparticles are fabricated by a solvothermal method and evaluated as promising cathode catalysts for Li-O2 batteries. Based on physicochemical analysis as well as density functional theory calculations, it is revealed that doping Cu heteroatom in CoS2 lattice can increase the covalency of the CoS bond with more electron transfer from Co 3d to S 3p orbitals, thereby resulting in less electron transfer from Co 3d to O 2p orbitals of Li-O species, which can weaken the adsorption strength toward Li-O intermediates, decrease the reaction barrier, and thus improve the catalytic performance in Li-O2 batteries. As a result, the battery using Cu-CoS2 nanoparticles in the cathode exhibits superior kinetics, reversibility, capacity, and cycling performance, as compared to the battery based on CoS2 catalyst. This work provides an atomic-level insight into the rational design of transition-metal dichalcogenide catalysts via regulating the electronic structure for high-performance Li-O2 batteries.

Ionic Liquid Electrolyte with Weak Solvating Molecule Regulation for Stable Li Deposition in High-Performance Li-O2 Batteries.

Li-O2 batteries with bis(trifluoromethanesulfonyl)imide-based ionic liquid (TFSI-IL) electrolyte are promising because TFSI-IL can stabilize O2 - to lower charge overpotential. However, slow Li+ transport in TFSI-IL electrolyte causes inferior Li deposition. Here we optimize weak solvating molecule (anisole) to generate anisole-doped ionic aggregate in TFSI-IL electrolyte. Such unique solvation environment can realize not only high Li+ transport parameters but also anion-derived solid electrolyte interface (SEI). Thus, fast Li+ transport is achieved in electrolyte bulk and SEI simultaneously, leading to robust Li deposition with high rate capability (3 mA cm-2 ) and long cycle life (2000 h at 0.2 mA cm-2 ). Moreover, Li-O2 batteries show good cycling stability (a small overpotential increase of 0.16 V after 120 cycles) and high rate capability (1 A g-1 ). This work provides an effective electrolyte design principle to realize stable Li deposition and high-performance Li-O2 batteries.

Hollow catalysts through different etching treatments to improve active sites and oxygen vacancies for high-performance Li-O2 battery

Hollow catalysts through different etching treatments to improve active sites and oxygen vacancies for high-performance Li-O2 battery