Performance Of Li-O2 Batteries Research Articles

In situ construction of a P-doped TiO2/Ti3C2Tx heterostructure with local site optimization to improve Li-O2 battery performance

The performance of Li-O2 batteries is seriously limited by the sluggish kinetics of the mass transition in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). To explore a useful strategy to overcome these limitations, herein, we constructed a P-doped TiO2/Ti3C2Tx heterostructure (PTT) with local active site optimization, in which the highly conductive substrate anchored the P-TiO2 nanoparticles with a selective adsorption and conversion of LiOx. In contrast to the TiO2/Ti3C2Tx heterostructure with a relatively uniform active site inducing typical toroidal Li2O2, the introduction of P-doping generates a unique nanosheet array Li2O2 on the PTT surface as a discharge product. This unique structure is endowed with a shorter Li+ diffusion path and benefits mass transfer in ORR and OER, facilitating the reaction kinetics. It presents obviously enhanced battery performance with a high specific capacity of 13,482 mAh g−1 and decreased discharge–charge overpotential, as well as superior cycling stability of 190 cycles. Furthermore, this novel and efficient electrocatalyst can stably operate for more than 650 cycles at 1000 mA g−1 with the addition of a LiI redox mediator. This study provides new insight into high-performance electrocatalyst design in Li2O2 related battery system.

Constructing Built-In Electric Field in NiCo2 O4 -CeO2 Heterostructures to Regulate Li2 O2 Formation Routes at High Current Densities.

Developing catalysts with suitable adsorption energy for oxygen-containing intermediates and elucidating their internal structure-performance relationships are essential for the commercialization of Li-O2 batteries (LOBs), especially under high current densities. Herein, NiCo2 O4 -CeO2 heterostructure with a spontaneous built-in electric field (BIEF) is designed and utilized as a cathode catalyst for LOBs at high current density. The driving mechanism of electron pumping/accumulation at heterointerface is studied via experiments and density functional theory (DFT) calculations, elucidating the growth mechanism of discharge products. The results show that BIEF induced by work function difference optimizes the affinity for LiO2 and promotes the formation of nano-flocculent Li2 O2 , thus improving LOBs performance at high current density. Specifically, NiCo2 O4 -CeO2 cathode exhibits a large discharge capacity (9546mAhg-1 at 4000mAg-1 ) and high stability (>430 cycles at 4000mAg-1 ), which are better than the majority of previously reported metal-based catalysts. This work provides a new method for tuning the nucleation and decomposition of Li2 O2 and inspires the design of ideal catalysts for LOBs to operate at high current density.

The effect of water admixture on aprotic Mg-O2 battery performance

Generally, aprotic Li-O2 batteries performance is significantly influenced by water impurity in electrolyte/gas via promotion of Li2O2 mesocrystallization. In the case of promising alkali-earth metals this issue remains unexplored. Here we have studied the role of water content in DMSO-based electrolyte in discharge process of Mg-O2 cells with metallic magnesium anode and carbon cathode. We found that water impurity in the electrolyte is not a key factor determining the discharge capacity for a Mg-O2 battery, at least in a single-compartment cell. Morphology of discharge product does not change upon addition 8000 ppm of water. Discharge products contain major amount of electrolyte byproducts and negligible concentration of magnesium peroxide. Under high water content (more than 8000 ppm) Mg(OH)2 is also formed as discharge product, but content of by-products still remains high.

Regulating d-orbital electronic configuration of Ni-based chalcogenides to enhance the oxygen electrode reactions in Li-O2 batteries

Transition metal chalcogenides based electrocatalysts with regulable d-orbital electronic configuration by various chalcogen anions can exhibit excellent oxygen electrode reaction kinetics in Li-O2 batteries (LOBs). In this work, an electron rearrangement strategy to improve the catalytic activity of hexagonal NiS microsheets for LOBs has been developed via introducing Se anion as a substitution of S. With the as-prepared NiS0.67Se0.33 as cathode catalyst, LOB could achieve evidently lower overpotentials, larger discharge capacity, and ultralong cycling life than that using NiS. With the help of physicochemical techniques and theoretical calculations, the performance enhancement of NiS0.67Se0.33 could be elucidated with its suitable d-orbital electronic configuration. Specifically, Se anion substitution can modulate metal–chalcogen interactions with increased charge density and positively shifted d-band center of Ni metal cation, thereby promoting the d-p orbitals hybridization with increased binding strength to LiO2 intermediates and promoting oxygen reduction/evolution reaction kinetics. Moreover, small amount of Ni dissolution from NiS0.67Se0.33 to the electrolyte because of the rearranged electronic configuration also contributes to the enhanced oxygen electrochemistry and improved LOB performance by serving as a redox mediate catalyst. This work provides a facile anion doping engineering to facilitate the oxygen electrode reactions in LOBs by modulating d-orbital electronic configuration.

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.

Coupling MoSe2 with Non-Stoichiometry Ni0.85 Se in Carbon Hollow Nanoflowers for Efficient Electrocatalytic Synergistic Effect on Li-O2 Batteries.

Li-O2 batteries could deliver ultra-high theoretical energy density compared to current Li-ion batteries counterpart. The slow cathode reaction kinetics in Li-O2 batteries, however, limits their electrocatalytic performance. To this end, MoSe2 and Ni0.85 Se nanoflakeswere decorated in carbon hollow nanoflowers, whichwere served as the cathode catalysts for Li-O2 batteries. The hexagonal Ni0.85 Se and MoSe2 show good structural compatibility with the same space group, resulting in a stable heterogeneous structure. The synergistic interaction of the unsaturated atoms and the built-in electric fields on the heterogeneous structure exposes abundant catalytically active sites, accelerating ion and charge transport and imparting superior electrochemical activity, including high specific capacities and stable cycling performance. More importantly, the lattice distances of the Ni0.85 Se (101) plane and MoSe2 (100) plane at the heterogeneous interfaces are highly matched to that of Li2 O2 (100) plane, facilitating epitaxial growth of Li2 O2 , as well as the formation and decomposition of discharge products during the cycles. This strategy of employing nonstoichiometric compounds to build heterojunctions and improve Li-O2 battery performance is expected to be applied to other energy storage or conversion systems.

A "Trinity" Design of Li-O2 Battery Engaging the Slow-Release Capsule of Redox Mediators.

Nonaqueous Li-O2 battery (LOB) represents one of the promising next-gen energy storage solutions owing to its ultrahigh energy density but suffers from problems such as high charging overpotential, slow redox kinetics and Li anode corrosion etc., calling for a systemic optimization of the battery configuration and structural components. Herein, an ingenious "trinity" design of LOB is initiated by implementing a hollowed cobalt metal organic framework (MOF) impregnating iodized polypyrrole simultaneously as the cathode catalyst, anode protection layer and slow-release capsule of redox mediators, so as to systemically address issues of impeded mass transport and redox kinetics on the cathode, dendrite growth and surface corrosion on the anode, as well as limited intermediate solubility in the low donor-number (DN) solvent. As a result of the systemic effort, the LOB constructed demonstrates an ultralow discharge/charge polarization of 0.2V, prolonged cycle life of 1200h and total discharge capacity of 28.41 mAh cm-2 . Mechanistic investigations attribute the superb LOB performance to the redox-mediated solution growth mechanism of crystalline Li2 O2 with both enhanced reaction kinetics and reversibility. This study offers a paradigm in designing smart materials to raise the performance bar of Li-O2 battery towards realistic applications. This article is protected by copyright. All rights reserved.

Binder-Free Cnt Cathodes for Li-O2 Batteries with More Than One Life.

Li-O2 batteries (LOB) performance degradation ultimately occurs through the accumulation of discharge products and irreversible clogging of the porous electrode during the cycling. Electrode binder degradation in the presence of reduced oxygen species can result in additional coating of the conductive surface, exacerbating capacity fading. Herein, a facile method to fabricate free-standing is established, binder-free electrodes for LOBs in which multi-wall carbon nanotubes form cross-linked networks exhibiting high porosity, conductivity, and flexibility. These electrodes demonstrate high reproducibility upon cycling in LOBs. After cell death, efficient and inexpensive methods to wash away the accumulated discharge products are demonstrated, as reconditioning method. The second life usage of these electrodes is validated, without noticeable loss of performance. These findings aim to assist in the development of greener high energy density batteries while reducing manufacturing and recycling costs.

Effects of Operating Temperature on Li-O2 Battery with Ionic Liquid-Based Binary Electrolyte

The progress of rechargeable Li-O2 battery (LOB) is hampered due to the number of challenges its components present. Among various critical challenges, the choice of electrolyte has always been a bottleneck impeding the breakthrough in the development of LOB. Various electrolytes, including organic solvents and room-temperature ionic liquids (RTILs) have been developed and studied. Each electrolyte comes with various limitations, which restrict its application in the LOB. These include thermal and electrochemical stability, volatility, viscosity, flammability, capability to dissolve incoming oxygen, diffusivity, and ionic conductivity. Consequently, no electrolyte could be regarded as an ideal electrolyte. Nonetheless, efforts have been made to tune the physiochemical properties of the electrolyte by blending two or more miscible solvents. High thermal and electrochemical stability and negligible volatility of RTILs can be combined with high diffusivity and ionic conductivity of organic solvents by merely blending them with optimized volume ratios.In this study, we comprehensively investigated the effects of operating temperature (20°C, 40°C and 60°C) on the electrochemical performance of LOBs incorporated with RTIL and organic solvent binary electrolyte. We designed and investigated, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2C1im][Tf2N]) RTIL and dimethyl sulfoxide (DMSO) organic solvent at various volume ratios ((4:1), (1:1), (1:4)). Among the binary electrolytes, ([C2C1im][Tf2N]/DMSO (1:4)) delivered the highest discharge capacities of 3.70 Ah g-1 (20°C), 4.0 Ah g-1 (40°C) and 3.65 Ah g-1 (60°C) as compared with pure [C2C1im][Tf2N] and DMSO. Cycling stability tests showed superior stability of the binary electrolyte ([C2C1im][Tf2N]/DMSO (1:4)) irrespective of the operating temperature. From viscosity and ionic conductivity measurements (at 20-60°C), [C2C1im][Tf2N]/DMSO (1:4) exhibited the highest ionic conductivity and the lowest viscosity compared with other binary electrolytes and pure RTIL at any given temperature. Cyclic voltammetry (CV) tests revealed a higher reaction rate with [C2C1im][Tf2N]/DMSO (1:4) binary electrolytes than pure electrolytes. The superior performance of [C2C1im][Tf2N]/DMSO (1:4) binary electrolyte was ascribed to enhanced stability against reactive intermediate species during oxygen reduction reaction (ORR), increased ionic conductivity, low viscosity (comparable with organic electrolytes), improved oxygen solubility, and relatively low evaporation rates. The detailed results and discussion will be presented during the presentation.

Quasi-solid-state composite polymer electrolyte with NASICON-type nanofillers for high performance lithium-oxygen batteries

This study designs a quasi-solid-state composite polymer electrolyte (QSCPE) to improve the performance of LiO2 batteries by integrating a composite solid framework and liquid electrolyte. The solid framework, containing poly(vinylidene difluoride-co-hexafluoropropylene) (PVDF-HFP) and sodium superionic conductor (NASICON)-type lithium aluminum germanium phosphate (LAGP) filler, is prepared using a conventional solution casting method. The framework is then activated using a liquid electrolyte to fabricate the QSCPE. The optimized electrolyte exhibits a high ionic conductivity and wide electrochemical stability. The Li/QSCPE/Li symmetric cell shows an overpotential of below 100 mV and a cycle life of >250 cycles at 1 mA cm−2 at a capacity of 2 mA h cm−2, ensuring electrochemical stability. The LiO2 cell fabricated using the optimized electrolyte exhibits significantly improved cyclability with a cycle life of 152. The QSCPE effectively prevents contamination of Li and suppresses the growth of Li dendrites. These results suggest that the LAGP nanofillers-containing QSCPE is a promising approach for further improving the performance of LiO2 batteries.

The Role of Self-Catalysis Induced by Co Doping in Nonaqueous Li-O2 Batteries.

This work systematically studies the product self-catalysis of in situ electrochemical cobalt doping of Li2O2 and reveals its potential mechanism for improving the performance of lithium-oxygen (Li-O2) batteries. Theoretical calculations demonstrate that the discharge products contain substituted and interstitial Co impurities, which serve as active sites to promote the formation of Li3O4 crystallization, thus switching the nucleation mechanism from the main discharge product Li2O2 to Li3O4. This Co-doping behavior leads to the thermodynamically favorable and dynamically stable formation of Li3O4 crystals during the discharge process. Through systematic investigation of the structural, energetic, electronic, diffusive, and catalytic properties of the Co-doped Li2O2 and Li3O4 compounds, we found that Li3O4 has better charge/mass transport and a lower overpotential for the Li3O4 formation/decomposition reaction. Consequently, this work elucidates that Co doping provides a simple and effective approach for increasing the proportion of Li3O4, which can significantly improve the Li-O2 battery performance.

Tuning solid electrolyte interface against oxygen/superoxide-derived attack on Li-metal anode in Li-O2 battery

Practical working environment (O2-saturated base electrolyte), architecture and operation mechanism/processes of Li-O2 batteries (LOBs) endows severe O2 and superoxide (O2-)-derived attack on Li-metal and solid electrolyte interface (SEI) at Li/electrolyte interface, limiting stability of Li anodes and LOBs. Herein, how O2/O2--derived attack on Li-metal and structure/composition of SEI are revealed by cryogenic transmission electron microscopy (cryo-TEM) and comprehensive spectroscopic characterizations. Specifically, generated from O2-reduction on Li-anode, the Li2O-induced nucleophilic attack on base electrolyte decomposition and Li corrosion especially during long-term aging, and more aggressive O2- created in cycling aggravates Li anodes and SEI. Moreover, to address O2/O2--derived attack on Li-metal, 1, 2-difluorobenzene (F-ben) was introduced as cosolvent in base electrolyte to make an F-ben electrolyte, in which F-ben preferentially reacted with Li-metal to form dual-functional SEI. Tuned SEI not only separate Li2O from bulk electrolyte thus suppresses O2-derived chemical attack, also acts as protective film protecting Li-metal against O2- attack. Eventually, electro-stability/reversibility of Li-metal in practical working environment of LOBs and battery performance of LOBs are significantly enhanced with help of F-ben cosolvent. This work sheds light on behavior of O2/O2--derived attack on Li-metal and SEI, sets an effective and practicable path towards practical applications of LOBs.

Li–O2/Air Batteries Using Ionic Liquids – A Comprehensive Review

AbstractThe remarkable surge in energy demand has compelled the quest for high‐energy‐density battery systems. The Li–O2 battery (LOB) and Li–air battery (LAB), owing to their extremely high theoretical energy density, have attracted extensive research in the past two decades. The commercial development of LOB is hampered due to the numerous challenges its components present. Ionic liquids (ILs) are considered potential electrolyte solvents of LOBs and LABs due to their excellent electrochemical stability, thermal stability, non‐flammability, low flammability, and O2 solubility. In addition to electrolyte solvents, ILs also have other applications in LOB and LAB systems. This review reports the progress of IL‐based LOBs and LABs over the years since treported for the first time in 2005. The impact of the physiochemical properties of ILs on the performance of LOB and LAB at various operating conditions is thoroughly discussed. The various methodologies are also summarized that are employed to tune ILs’ physiochemical properties to render them more favorable for rechargeable lithium batteries. Tunable properties of ILs create the possibility of designing cost‐effective batteries with excellent safety, high energy density and high power density, and long‐term stability.

Facile construction of a water-defendable Li anode protection enables rechargeable Li-O2 battery operating in humid atmosphere

The rechargeable Li-O2 battery endowed with high theoretical specific energy density has sparked intense research interest as a promising energy storage system. However, the intrinsic high activity of Li anode, especially to moisture, usually leads to inferior electrochemical performance of Li-O2 battery in humid environments, hindering its widespread application. To settle the trouble of poor moisture tolerance, fabricating a water-proof layer on the Li-metal anode could be an effective tactic. Herein, a facile strategy for constructing an ibuprofen-based protective layer on the Li anode has been proposed to realize highly rechargeable Li-O2 battery in humid atmosphere. Due to the in-situ reaction between ibuprofen reagent and metallic Li, the protective layer with a thickness of ∼30 µm has been uniformly deposited on the surface of Li anode. Particularly, the protective layer, consisting of a large amount of hydrophobic alkyl group and benzene ring, can significantly resist water ingress and enhance the electrochemical stability of Li anode. As a result, the Li-O2 battery based on the protected Li anode achieves a long cycle life of 210 h (21 cycles at 1000 mAh/g, 200 mA/g) in highly moist atmosphere with relative humidity (RH) of 68%. This convenient and efficient strategy offers novel design concept of water-resistant metal anode, and paves the way to the promising future prospect for the high-energy Li-O2 battery implementing in the ambient atmosphere.

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.

The Double-Edged Effect of Water on Li-O2 Aprotic Batteries

Storing larger amounts of energy is becoming critical as more renewable and intermittent energy sources emerge in our society. Li-O2 batteries have the highest theoretical energy density, but there are still barriers to overcome. The presence of water in atmospheric air makes studying its effects on battery performance necessary if ambient oxygen ought to be used in such devices. This paper investigates the effect of different concentrations of water in the electrolyte of Li-O2 aprotic batteries, on deep discharge capacity and cyclability. Batteries were prepared with a metallic lithium anode, glass microfiber membrane, 0.1 M LiClO4/DMSO electrolyte with various water concentrations (15–144,000 ppm), and carbon paper cathode. An increase in discharge capacity of >300% was achieved with 550 ppm of water; however, a gradual reduction in cyclability was observed increasing water concentration. We show that it occurs due to changes in the reaction mechanism, composition, and morphology of the discharge products, incomplete decomposition, and formation of a passivating film on the metallic lithium anode. Moreover, this article elucidates the causes underlying the involved mechanism and highlights the double-edged effect of water on the electrochemical performance of Li-O2 batteries, causing improvements in deep discharge capacity at the cost of reduced cyclability.

Optimal geometrical configuration and oxidation state of cobalt cations in spinel oxides to promote the performance of Li-O2 battery

Optimal geometrical configuration and oxidation state of cobalt cations in spinel oxides to promote the performance of Li-O2 battery

Tailoring the p-Band Center of NS Pair for Accelerating High-Performance Lithium-Oxygen Battery.

The local coordination environment of catalytical moieties directly determines the performance of electrochemical energy storage and conversion devices, such as Li-O2 batteries (LOBs) cathode. However, understanding how the coordinative structure affects the performance, especially for non-metal system, is still insufficient. Herein, a strategy that introduces S-anion to tailor the electronic structure of nitrogen-carbon catalyst (SNC) is proposed to improve the LOBs performance. This study unveils that the introduced S-anion effectively manipulates the p-band center of pyridinic-N moiety, substantially reducing the battery overpotential by accelerating the generation and decomposition of intermediate products Li1-3 O4 . The lower adsorption energy of discharging product Li2 O2 on NS pair accounts for the long-term cyclic stability by exposing the high active area under operation condition. This work demonstrates an encouraging strategy to enhance LOBs performance by modulating the p-band center on non-metal active sites.

Construction of Co-NC@Mo2C hetero-interfaces for improving the performance of Li-O2 batteries

Lithium-oxygen batteries (LOBs) are becoming the rising stars of a new generation of energy storage devices due to high theoretical energy density. The crucial factor of its high performance and stability is developing efficient cathode electro-catalysts. In this work, the Zn3[Co (CN)6]2 Prussian Blue analog (Zn-CoPBA) was used as the precursor, then ammonium molybdate tetrahydrate was incorporated by hydrothermal treatment, and finally Mo2C-modified Co-NC was prepared by one-step pyrolysis. The mesoporous hetero-interfaces of N-doped carbon matrix embedded by Mo2C/Co nano-heterostructures facilitate the transport of substances, provide more catalytic active sites and storage space for the discharge product Li2O2 due to the characteristic electronic structure and catalytic properties of Mo2C with d-orbital state distribution near the noble metal-like Fermi level. The composite Co-NC@Mo2C was used for LOBs cathode catalyst, it presents wonderful charge-discharge specific capacities (21,930 mA h g − 1), stable cycling performance.

Boosting Li-O2 Battery Performance via Coupling of P-N Site-Rich N, P Co-Doped Graphene-Like Carbon Nanosheets with Nano-CePO4.

Development of efficient and robust cathode catalysts is critical for the commercialization of Li-O2 batteries (LOBs). Herein, a well-designed CePO4 @N-P-CNSs cathode catalyst for LOBs via coupling P-N site-rich N, P co-doped graphene-like carbon nanosheets (N-P-CNSs) with nano-CePO4 via a novel "in situ derivation" coupling strategy by in situ transforming the P atoms of P-C sites in N-P-CNSs to CePO4 is reported. The CePO4 @N-P-CNSs exhibit superior bifunctional ORR/OER activity relative to commercial Pt/C-RuO2 with an overall overpotential of 0.64V (vs RHE). Moreover, the LOB with CePO4 @N-P-CNSs as the cathode catalyst delivers a low charge overpotential of 0.67V (vs Li/Li+ ), high discharge capacity of 29774 mAh g-1 at 100mA g-1 and long cycling stability of 415 cycles, respectively. The remarkably enhanced LOB performance is attributable to the in situ derived CePO4 nanoparticles and the P-N sites in N-P-CNSs, which facilitate increased bifunctional ORR/OER activity, promote the rapid and effective decomposition of Li2 O2 and inhibit the formation of Li2 CO3 . This work may provide new inspiration for designing efficient, durable, and cost-effective cathode catalysts for LOBs.