High-performance Li-O2 Batteries Research Articles

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

The free-standing N-CoO matrix towards optimizing dual-electrodes for high-performance Li-O2 batteries

Lithium-oxygen batteries (LOBs) have been developed because of their high theoretical energy density. However, both the dendrite/passivation problem of the anode and the sluggish ORR/OER kinetics of the cathode impede the improvement of batteries. Herein, N-doped CoO nanoarrays grown on carbon cloth (N-CoO/CC) are developed as a free-standing matrix for both improved anode and cathode of LOBs. The superior lithiophilicity and unique three-dimensional structure of the lithium-infused N-CoO/CC composite anode (Li@N-CoO/CC) can regulate Li plating/stripping behavior and suppress lithium dendrite, achieving a cycle lifespan of more than 2500 h in a symmetrical Li metal battery (1 mA cm−2, 1 mAh cm−2). In addition, the Li@N-CoO/CC anode alleviates it from corrosion of water/oxygen to some extent in Li-O2 batteries due to the Li2CO3-riched SEI formed after cycling. Moreover, N-doped CoO nanoarrays can catalyze the formation/decomposition of amorphous Li2O2, featuring a decreased overpotential. Based on the optimized dual electrodes, the resultant Li-O2 battery can maintain 200 cycles at 0.1 mA cm−2 within 0.25 mAh cm−2.

Bifunctional Photoassisted Li-O2 Battery with Ultrahigh Rate-Cycling Performance Based on Siloxene Size Regulation.

Directly integrating the bifunctional photoelectrode into Li-O2 batteries has been considered an effective way to reduce the overpotential and promote electric energy saving. However, more regular investigations on various bifunctional photocatalysts have still been desired for high-performance photoassisted Li-O2 batteries. Herein, a systematic exploration of various-sized siloxene photocatalysts affected by Li-O2 batteries has been introduced. Compared with the utilization of larger-sized siloxene nanosheets (SNSs), the photoassisted Li-O2 battery with a siloxene quantum dot (SQD) photoelectrode delivers a superior round-trip efficiency of 230% based on the highest discharge potential up to 3.72 V and lowest charge potential of 1.60 V and enables the maintenance of a long-term cycling life with only 13% efficiency attenuation after 200 cycles at 0.075 mA/cm2. Furthermore, this system exhibits a record-high rate-cycling performance (162% round-trip efficiency, even at 3 mA/cm2) and a high discharge capacity of 2212 mAh/g at 1 mA/cm2. These ground-breaking performances could be attributed to the synergistic effect of the photocatalytic and electrocatalytic activities of SQD photocatalysts with the ideal conduction band/valence band values, the abundant defective sites, and the stronger O2 and lower LiO2 adsorption strengths of SQD photocatalysts. These systematic research studies highlight the significance of SQD bifunctional photocatalysts and could be extended to other photocatalysts for further high-efficiency photoelectric conversion and storage.

Trifunctional imidazolium bromide: a high-efficiency redox mediator for high-performance Li-O2 batteries.

In this work, 1-aminopropyl-3-methylimidazolium bromide (APMImBr) is introduced in dimethyl sulfoxide-based Li-O2 batteries. The Br- functions as a redox mediator to catalyze the decomposition of the Li2O2 products. Meanwhile, the APMIm+ serves as a scavenging agent for superoxide radicals as well as protects the lithium metal anodes via an in situ formed Li3N-rich solid electrolyte interface layer. As a result, the Li-O2 batteries containing APMImBr delivered an enlarged discharge capacity, a reduced charge overpotential of around 0.61 V and a prolonged cyclic life of over 200 cycles.

Boosting the kinetics with graphene quantum dots (GQDs)-decorated NiCo2O4 nanosheets towards high-performance Li-O2 batteries

The performance of energy-dense lithium-oxygen batteries depend primarily on the electrocatalytic activity and architecture of the oxygen electrodes. However, highly catalytically active cathode materials such as metal oxides suffer from insufficient electronic conductivity, resulting in restricted kinetics and O2/e−/Li+ three-phase reaction regions. In this study, we design and fabricate a free-standing and lightweight cathode with graphene quantum dots (GQDs) modified NiCo2O4 (NCO) nanosheets array anchored on 3D graphene foam (GF). The potential electrocatalytic activity of metal oxide materials can be fully excited by electronic conductivity compensation, and the triple-phase reaction regions are expanded from the NCO/GF interface to the entire surface of NCO. As a result, the cathode can deliver a discharge capacity as high as 7672 mAh g−1, cacaulated based on the whole mass of the entire cathode, and can sustain more than 500 cycles with a high energy efficiency of over 78.5%. These findings demonstrate that the GQDs@NCO@GF cathode has remarkable potential for applications in lithium-oxygen batteries, and the cathode structure design scheme and GQDs modification strategy can be further applied to other high-efficiency catalysts.

Spin-State Regulation of Nickel Cobalt Spinel toward Enhancing the Electron Transfer Process of Oxygen Redox Reactions in Lithium–Oxygen Batteries

The development of a high-energy-density lithium–oxygen (Li–O2) battery is mainly determined by highly efficient electrocatalysts with excellent activity and stability, facilitating reversible oxygen redox reactions. Engineering the electron spin state provides a novel strategy to enhance the electrocatalytic activity of electrode materials. In this work, sulfur vacancy-enriched spinel NiCo2S4 (Vs-NiCo2S4) with high spin polarization is designed as an effective electrocatalyst for high-performance Li–O2 batteries. Subtle lattice distortion is induced by sulfur vacancy in spinel Vs-NiCo2S4, which strongly contributes to the formation of high spin states of Co3+ (HS, t2g4eg2) from the low spin states of Co3+ (LS, t2g6eg0) at active octahedral sites. The electron transitions of Co3+ from low to high spin enable the increase of the spin polarization and produce abundant unpaired electrons in the 3d orbital of Co3+, enhancing the adsorption of oxygen intermediates and boosting the electron transfer process of oxygen redox reactions. Density functional theory calculations indicate that the spin magnetic moment of Co3+ in Vs-NiCo2S4 is raised in comparison to that in NiCo2S4, which improves the catalytic activity of the material via lowering the energy barrier for electron transfer. Experimentally, Vs-NiCo2S4-based Li–O2 batteries exhibit a large specific capacity of 8707.0 mAh g–1 and long cycling life of 487 h. Furthermore, in situ differential electrochemical mass spectrometry results show that the ratio of electron to oxygen during oxygen redox reactions is close to 2, demonstrating the favorable formation and decomposition of Li2O2 on Vs-NiCo2S4 in a Li–O2 battery. This work presents a powerful strategy to rationally design efficient electrocatalysts via spin engineering to boost oxygen redox reaction kinetics in Li–O2 batteries.

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

Low-cost iron-based electrocatalysts for high-performance Li–O2 batteries

Li–O2 batteries have garnered considerable attention as demands for better energy storage systems continue to increase rapidly. Notably, Li–O2 batteries possess a substantially higher theoretical specific energy than that of conventional Li-ion batteries. However, for Li–O2 batteries to be utilized in various applications, highly efficient cathode catalysts must be developed. This study demonstrates the direct introduction of iron-based catalysts on carbon paper using a simple method, namely, by immersing carbon paper in a Fe precursor-melted solution; this immersed carbon paper is then dried and heated. In a nonaqueous Li–O2 cell, a carbon cathode containing Fe2O3 as a catalyst shows a ∼7% overpotential reduction on average during 40 cycles. Herein, we demonstrate that even introducing approximately 1% Fe2O3 catalyst material could reduce the charging overpotential in a rechargeable Li–O2 cell.

Electronic structure modulation of Ru/W20O58 catalyst via interfacial Ru–O–W bridging bond for high-performance Li–O2 batteries

The development of advanced catalysts with high activity is crucial to addressing the issues of sluggish reaction kinetics at the cathode of Li–O2 batteries. Herein, the authors propose a facile strategy to synthesize Ru nanoparticles anchored on non-stoichiometric tungsten oxide nanosheets (Ru/W20O58) hybrids. The non-stoichiometric lattice structure of W20O58 provides abundant surface nucleation sites, and the defects-induced restriction effect inhibits the agglomeration of Ru nanoparticles. The interfacial covalent coupling between Ru and W20O58 facilitates charge transfer at the interface via Ru–O–W bridging bond and optimizes the electronic structure of catalysts surface. As the obtained Ru/W20O58 employed as cathode catalysts, Li–O2 batteries exhibit high specific discharge capacity of 6346.4 mAh g−1, improved rate performance and a cycling life of 260 cycles. The density functional theory calculation demonstrate that the interfacial coupling enhances the adsorption energy of intermediates on the surface and regulates the discharge reaction pathway, leading to the restraint of O2– nucleophilic attack and the formation of amorphous and decomposable discharge products. This work provides an insight on the correlation between electrochemical activity and interfacial coupling, shedding lights on a promising cathode catalyst for advanced Li–O2 batteries.

3D foam-like P, N, S-codoped NCP@CNS as cathode for high-performance Li–O2 battery

3D foam-like P, N, S-codoped NCP@CNS as cathode for high-performance Li–O2 battery

Platinum Nanocrystals Embedded in Three-Dimensional Graphene for High-Performance Li-O2 Batteries.

Graphene is considered as a promising cathode candidate for Li-O2 batteries because of its excellent electronic conductivity and oxygen adsorption capacity. However, for Li-O2 batteries, the self-stacking effect caused by two-dimensional (2D) structural properties of graphene is not conducive to the rapid oxygen transport and mass transfer process, thereby affecting the electrode kinetics. Here, we successfully prepared three-dimensional (3D) graphene with different scales by plasma-enhanced chemical vapor deposition and physical pulverization strategies, in which CH4 is the carbon source and H2/Ar mixed gas is the etching gas. Meanwhile, we fabricated 3D graphene-based Pt nanocatalysts by an ultraviolet-assisted construction strategy and then applied them in Li-O2 batteries. Systematic studies reveal a special relevance between electrochemical performance and graphene particle size, and the smaller-sized 3D graphene can better maintain the microstructure distribution in both the Pt embedding process and electrochemical applications, which is beneficial to the transport of oxygen and Li ions, lowering the decomposition energy barrier of Li2O2, and further obtaining reduced charge overpotential (0.22 V) and prolonged cycle life for Li-O2 batteries. Finally, we anticipate that this work could promote the practical application of 2D materials and larger-sized 3D materials in Li-O2 batteries.

A self-assembled nanoflower-like Ni5P4@NiSe2 heterostructure with hierarchical pores triggering high-efficiency electrocatalysis for Li–O2 batteries

The remarkably high theoretical energy densities of Li–O2 batteries have triggered tremendous efforts for next-generation conversion devices. Discovering efficient oxygen reduction reaction and oxygen evolution reaction (ORR/OER) bifunctional catalysts and revealing their internal structure-property relationships are crucial in developing high-performance Li–O2 batteries. Herein, we have prepared a nanoflower-like Ni5P4@NiSe2 heterostructure and employed it as a cathode catalyst for Li–O2 batteries. As expected, the three-dimensional biphasic Ni5P4@NiSe2 nanoflowers facilitated the exposure of adequate active moieties and provide sufficient space to store more discharge products. Moreover, the strong electron redistribution between Ni5P4 and NiSe2 heterojunctions could result in the built-in electric fields, thus greatly facilitating the ORR/OER kinetics. Based on the above merits, the Ni5P4@NiSe2 heterostructure catalyst improved the catalytic performance of Li–O2 batteries and holds great promise in realizing their practical applications as well as inspiration for the design of other catalytic materials.

Constructing Bimetallic ZIF‐Derived Zn,Co‐Containing N‐Doped Porous Carbon Nanocube as the Lithiophilic Host to Stabilize Li Metal Anodes in Li−O2 Batteries

Li metal, because of its ultrahigh theoretical capacity, has attracted extensive attention. However, uncontrollable dendritic Li formation and infinite electrode dimensional variation hinder application of Li anodes. Herein, Zn,Co bimetallic zeolitic imidazolate frameworks (ZIFs) were synthesized and further pyrolyzed to obtain Zn,Co-containing N-doped porous carbon nanocube (Zn/Co-N@PCN), which was further applied as lithiophilic host to construct the lithiated Zn/Co-N@PCN (Li-Zn/Co-N@PCN). Zn vapor produced many pores on the carbon framework during calcination process that could store enough Li and thus inhibit the huge electrode volume change. Additionally, there were abundant lithiophilic groups in Zn/Co-N@PCN, such as N- or Co/Zn-based species, which were beneficial to uniform Li deposition. Moreover, the stable and conductive carbon-based matrix could ensure superior and reproducible Li plating/stripping behavior in Zn/Co-N@PCN over cycling. As a result, the Li-Zn/Co-N@PCN anode showed a steady and high columbic efficiency of around 99.0 % for 600 cycles at 0.5 mA cm-2 . The Li-Zn/Co-N@PCN-based Li-O2 battery could continuously work beyond 200 cycles, superior to a cell with a Li-Cu anode. These results in this work provide a novel way for construction of the advanced Li-based anodes and the corresponding high-performance Li-O2 batteries.

Engineering eg Orbital Occupancy of Pt with Au Alloying Enables Reversible Li-O2 Batteries.

Constructing well-designed catalysts to accelerate OER catalytic activity and alleviate the charge overpotential is prevailing for achieving sophisticated Li-O2 batteries. Herein, we report a concept for engineering the eg occupancy of Pt with M alloying (M=Au, Ru) to tune the charge overpotentials for achieving high-performance Li-O2 batteries. The X-ray photoelectron spectroscopy results coupled with density functional theory (DFT) calculations reveal that the highly electronegative Au can capture more eg electrons from Pt, leading to less eg electrons of Pt in PtAu than that in PtRu. The lower eg occupancy of Pt atoms in PtAu alloys entails the upward shift of the Pt d band, which causes a strong binding strength towards the intermediates (LiO2 ), thereby decreasing the OER energy barrier. As a consequence, the Li-O2 battery with a PtAu cathode delivers a low charge overpotential of 0.36 V and superior cycle life of 220 cycles at a cutoff capacity of 1000 mAh g-1 , which is among the best in the reported noble metal-based cathodes.

Tuning the nucleation and decomposition of Li2O2 by fluorine-doped carbon vesicles towards high performance Li-O2 batteries

Li-O2 batteries provide an attractive and potential strategy for energy conversion and storage with high specific energy densities. However, large over-potential in oxygen evolution reactions (OER) caused by the decomposition obstacles of Li2O2 seriously impedes its electrochemical performances. Herein, a novel N, O, S and F co-doping vesicular carbon was prepared by self-template pyrolysis method and used in Li-O2 battery to tune the nucleation and decomposition of Li2O2. The introduction of F in the carbon matrix with suitable content can regulate the adsorption of intermediates, through which the morphology of Li2O2 can be controlled to film, favorable to its decomposition in charge process. The cathode based on the optimized F doped carbon vesicle exhibits improved electrochemical performances including a low over-potential, large capacity and a long-term stability. Density functional theory (DFT) results show that F and C in C–F bond hasve a strong interaction to Li and O in Li2O2, respectively, which can enhance the transfer of electrons from Li2O2 to the carbon matrix to generate hole polaron and thus accelerate the delithiation and decomposition of Li2O2. This work provides a new sight into understanding the mechanism of nucleation and decomposition of Li2O2 for the development of high-performance Li-O2 batteries.

Soluble and Perfluorinated Polyelectrolyte for Safe and High-Performance Li-O2 Batteries.

The severe performance degradation of high-capacity Li-O2 batteries induced by Li dendrite growth and concentration polarization from the low Li+ transfer number of conventional electrolytes hinder their practical applications. Herein, lithiated Nafion (LN) with the sulfonic group immobilized on the perfluorinated backbone has been designed as a soluble lithium salt for preparing a less flammable polyelectrolyte solution, which not only simultaneously achieves a high Li+ transfer number (0.84) and conductivity (2.5 mS cm-1 ), but also the perfluorinated anion of LN produces a LiF-rich SEI for protecting the Li anode from dendrite growth. Thus, the Li-O2 battery with a LN-based electrolyte achieves an all-round performance improvement, like low charge overpotential (0.18 V), large discharge capacity (9508 mAh g-1 ), and excellent cycling performance (225 cycles). Besides, the fabricated pouch-type Li-air cells exhibit promising applications to power electronic equipment with satisfactory safety.

Flower-like three-dimensional bifunctional cathode catalyst for high-performance Li–O2 batteries: ZIF-67@3D-N/rGO

To accelerate the practical application of Li–O2 batteries. A catalyst with outstanding oxygen reduction reaction and oxygen evolution reaction catalytic activity is required. Here, in-situ growth ZIF-67 within three-dimensional nitrogen-doped reduced graphene oxide (3D-N/rGO) layers was used to investigate a bifunctional catalyst. The inner space is supported by ZIF-67 particles, while 3D-N/rGO extends a suitable three-phase reaction interface and enhances O2 adsorbability. When assembled battery with normal electrolyte, it delivered a high specific capacity of 12028 mAh g−1, and stabilised for 203 cycles at 200 mA g−1 with a limited capacity of 500 mAh g−1. When LiBr-gel polymer electrolyte (GPE) was used instead of electrolyte the lithium metal anode, the polarisation value of LiBr-GPE in Li/Li batteries was only about 0.0384 V after continuous working for 1600 h. When used as a cathode catalyst in Li–O2 batteries, the electrode performance was doubled compared with using the normal electrolyte. These findings pave the way for developing of all-encompassing battery materials with high capacity and long cycle life.

A long-life lithium-oxygen battery via a molecular quenching/mediating mechanism.

The advancement of lithium-oxygen (Li-O2) batteries has been hindered by challenges including low discharge capacity, poor energy efficiency, severe parasitic reactions, etc. We report an Li-O2 battery operated via a new quenching/mediating mechanism that relies on the direct chemical reactions between a versatile molecule and superoxide radical/Li2O2. The battery exhibits a 46-fold increase in discharge capacity, a low charge overpotential of 0.7 V, and an ultralong cycle life >1400 cycles. Featuring redox-active 2,2,6,6-tetramethyl-1-piperidinyloxy moieties bridged by a quenching-active perylene diimide backbone, the tailor-designed molecule acts as a redox mediator to catalyze discharge/charge reactions and serves as a reusable superoxide quencher to chemically react with superoxide species generated during battery operation. The all-in-one molecule can simultaneously tackle issues of parasitic reactions associated with superoxide radicals, singlet oxygen, high overpotentials, and lithium corrosion. The molecular design of multifunctional additives combining various capabilities opens a new avenue for developing high-performance Li-O2 batteries.

Boosting the Kinetics with Graphene Quantum Dots (Gqds)-Decorated Nico2o4 Nanosheets Towards High-Performance Li-O2 Batteries

Boosting the Kinetics with Graphene Quantum Dots (Gqds)-Decorated Nico2o4 Nanosheets Towards High-Performance Li-O2 Batteries