Design of Pt-Sn-Zn Nanomaterials for Successful Methanol Electrooxidation Reaction

This work highlights the potential for the synthesis of new PtSnZn catalysts with enhanced efficiency and durability for methanol oxidation reaction (MOR) in low-temperature fuel cells. In this research, PtZn and PtSnZn nanoparticles deposited on high surface area Vulcan XC-72R Carbon support were created by a microwave-assisted polyol method. The electrochemical performances of synthesized catalysts were analyzed by cyclic voltammetry and by the electrooxidation of adsorbed CO and the chronoamperometric method. The physicochemical properties of obtained catalysts were characterized by transmission electron microscopy (TEM), thermogravimetric (TGA) analysis, energy dispersive spectroscopy (EDS) and by X-ray diffraction (XRD). The obtained findings showed the successful synthesis of platinum-based catalysts. It was established that PtSnZn/C and PtZn/C catalysts have high electrocatalytic performance in methanol oxidation reactions. Catalysts stability tests were obtained by chronoamperometry. Stability tests also confirmed decreased poisoning and indicated improved stability and better tolerance to CO-like intermediate species. According to activity and stability measurements, the PtSnZn/C catalyst possesses the best electrochemical properties for the methanol oxidation reaction. The observed great electrocatalytic activity in the methanol oxidation reaction of synthesized catalysts can be attributed to the beneficial effects of microwave synthesis and the well-balanced addition of alloying metals in PtSnZn/C catalysts.

CO2 Capture Membrane for Long-Cycle Lithium-Air Battery

Lithium-air batteries (LABs) have attracted extensive attention due to their ultra-high energy density. At present, most LABs are operated in pure oxygen (O₂) since carbon dioxide (CO₂) under ambient air will participate in the battery reaction and generate an irreversible by-product of lithium carbonate (Li₂CO₃), which will seriously affect the performance of the battery. Here, to solve this problem, we propose to prepare a CO₂ capture membrane (CCM) by loading activated carbon encapsulated with lithium hydroxide (LiOH@AC) onto activated carbon fiber felt (ACFF). The effect of the LiOH@AC loading amount on ACFF has been carefully investigated, and CCM has an ultra-high CO₂ adsorption performance (137 cm³ g^-1) and excellent O₂ transmission performance by loading 80 wt% LiOH@AC onto ACFF. The optimized CCM is further applied as a paster on the outside of the LAB. As a result, the specific capacity performance of LAB displays a sharp increase from 27,948 to 36,252 mAh g^-1, and the cycle time is extended from 220 h to 310 h operating in a 4% CO₂ concentration environment. The concept of carbon capture paster opens a simple and direct way for LABs operating in the atmosphere.

Pr6O11: Temperature-Dependent Oxygen Vacancy Regulation and Catalytic Performance for Lithium-Oxygen Batteries

Many challenges still exist in lithium-oxygen batteries (LOBs), particularly exploring an efficient catalyst to optimize the reaction pathway and regulate the Li₂O₂ nucleation. Pr₆O₁₁ has a unique 4f electronic structure and the highest oxygen ion mobility among rare earth oxides, exhibiting superior electronic, optical, and chemical properties. These unique properties might endow it with advanced catalytic activities for LOBs. This work reports two crystal forms of Pr₆O₁₁ as novel catalysts and regulates the oxygen vacancy (V_o) concentrations by feasible calcination. Thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) confirm the conversion from commercial Pr₆O₁₁ to cubic fluorite Pr₆O₁₁ and V_o-rich Pr₆O₁₁. Photographs, high-resolution transmission electron microscopy, selected area electron diffraction, XPS, and electron paramagnetic resonance robustly demonstrate the temperature-dependent evolution of V_o. Ex situ XPS, scanning electron microscopy, and electrochemical techniques are used to study the catalytic mechanism and electrochemical reversibility. It is found that an appropriate V_o concentration can boost O₂ adsorption/desorption, accelerate electron transport, and reduce the reaction energy barrier. V_o-rich Pr₆O₁₁ optimizes the reaction pathway by offering an intermediate Li_2-xO₂ (with metalloid conductivity) and adjusting Li₂O₂ into vertically staggered nanoflakes, effectively avoiding the suffocation of the catalytic surface and presenting excellent capacity, cycling stability, and rate performance.

The key to improving the performance of Li-air batteries: Recent progress and challenges of the catalysts

Li-air batteries are considered to be one of the most promising energy storage devices due to their high energy density and large specific capacity. But the high overpotential, the sluggish...

Li2O-Based Cathode Additives Enabling Prelithiation of Si Anodes

Low first-cycle Coulombic efficiency is especially poor for silicon (Si)-based anodes due to the high surface area of the Si-active material and extensive electrolyte decomposition during the initial cycles forming the solid electrolyte interphase (SEI). Therefore, developing successful prelithiation methods will greatly benefit the development of lithium-ion batteries (LiBs) utilizing Si anodes. In pursuit of this goal, in this study, lithium oxide (Li2O) was added to a LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode using a scalable ball-milling approach to compensate for the initial Li loss at the anode. Different milling conditions were tested to evaluate the impact of particle morphology on the additive performance. In addition, Co3O4, a well-known oxygen evolution reaction catalyst, was introduced to facilitate the activation of Li2O. The Li2O + Co3O4 additives successfully delivered an additional capacity of 1116 mAh/gLi2O when charged up to 4.3 V in half cells and 1035 mAh/gLi2O when charged up to 4.1 V in full cells using Si anodes.

Adjusting the Covalency of Metal-Oxygen Bonds in LaCoO3 by Sr and Fe Cation Codoping to Achieve Highly Efficient Electrocatalysts for Aprotic Lithium-Oxygen Batteries

Developing high-efficiency dual-functional catalysts to promote oxygen electrode reactions is critical for achieving high-performance aprotic lithium-oxygen (Li-O₂) batteries. Herein, Sr and Fe cation-codoped LaCoO₃ perovskite (La_0.8Sr_0.2Co_0.8Fe_0.2O_3-σ, LSCFO) porous nanoparticles are fabricated as promising electrocatalysts for Li-O₂ cells. The results demonstrate that the LSCFO-based Li-O₂ batteries exhibit an extremely low overpotential of 0.32 V, ultrahigh specific capacity of 26 833 mA h g^-1, and superior long-term cycling stability (200 cycles at 300 mA g^-1). These prominent performances can be partially attributed to the existence of abundant coordination unsaturated sites caused by oxygen vacancies in LSCFO. Most importantly, density functional theory (DFT) calculations reveal that codoping of Sr and Fe cations in LaCoO₃ results in the increased covalency of Co 3d-O 2p bonds and the transition of Co³⁺ from an ordinary low-spin state to an intermediate-spin state, eventually resulting in the transformation from nonconductor LCO to metallic LSCFO. In addition, based on the theoretical calculations, it is found that the inherent adsorption capability of LSCFO toward the LiO₂ intermediate is reduced due to the increased covalency of Co 3d-O 2p bonds, leading to the formation of large granule-like Li₂O₂, which can be effectively decomposed on the LSCFO surface during the charging process. Notably, this work demonstrates a unique insight into the design of advanced perovskite oxide catalysts via adjusting the covalency of transition-metal-oxygen bonds for high-performance metal-air batteries.

3D Coral-like LLZO/PVDF Composite Electrolytes with Enhanced Ionic Conductivity and Mechanical Flexibility for Solid-State Lithium Batteries

Composite polymer electrolytes (CPEs) are very promising for high-energy lithium-metal batteries as they combine the advantages of polymeric and ceramic electrolytes. The dimensions and morphologies of active ceramic fillers play critical roles in determining the electrochemical and mechanical performances of CPEs. Herein, a coral-like LLZO (Li_6.4La₃Zr₂Al_0.2O₁₂) is designed and used as a 3D active nanofiller in a poly(vinylidene difluoride) polymer matrix. Building 3D interconnected frameworks endows the as-made CPE membranes with an enhanced ionic conductivity (1.51 × 10^-4 S cm^-1) at room temperature and an enlarged tensile strength up to 5.9 MPa. As a consequence, the flexible 3D-architectured CPE enables a steady lithium plating/stripping cycling over 200 h without a short circuit. Moreover, the assembled solid-state Li|LiFePO₄ cells using the electrolyte exhibit decent cycling performance (95.2% capacity retention after 200 cycles at 1 C) and excellent rate capability (120 mA h g^-1 at 3 C). These results demonstrate the superiority of 3D interconnected garnet frameworks in developing CPEs with excellent electrochemical and mechanical properties.

A 3D free-standing Co doped Ni2P nanowire oxygen electrode for stable and long-life lithium-oxygen batteries

Exploring oxygen electrodes with superior bifunctional catalytic activity and suitable architecture is an effective strategy to improve the performance of lithium-oxygen (Li-O₂) batteries. Herein, the internal electronic structure of Ni₂P is regulated by heteroatom Co doping to improve its catalytic activity for oxygen redox reactions. Meanwhile, magnetron sputtering N-doped carbon cloth (N-CC) is used as a scaffold to enhance the electrical conductivity. The deliberately designed Co-Ni₂P on N-CC (Co-Ni₂P@N-CC) with a typical 3D interconnected architecture facilitates the formation of abundant solid-liquid-gas three-phase reaction interfaces inside the architecture. Furthermore, the rational catalyst/substrate interfacial interaction is capable of inducing a solvation-mediated pathway to form toroidal-Li₂O₂. The results show that the Co-Ni₂P@N-CC based Li-O₂ battery exhibits an ultra-low overpotential (0.73 V), enhanced rate performance (4487 mA h g^-1 at 500 mA g^-1) and durability (stable operation over 671 h). The pouch-type battery based on the Co-Ni₂P@N-CC flexible electrode runs stably for 581 min in air without obvious voltage attenuation. This work verifies that heterogeneous atom doping and interface interaction can remarkably strengthen the performance of Li-O₂ cells and thus pave new avenues towards developing high-performance metal-air batteries.

In Situ Fabricating Oxygen Vacancy-Rich TiO2 Nanoparticles via Utilizing Thermodynamically Metastable Ti Atoms on Ti3C2Tx MXene Nanosheet Surface To Boost Electrocatalytic Activity for High-Performance Li-O2 Batteries

Catalysts with high performance are urgently needed in order to accelerate the reaction kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in lithium-oxygen (Li-O₂) batteries. Herein, utilizing thermodynamically metastable Ti atoms on the Ti₃C₂Tx MXene nanosheet surface as the nucleation site, oxygen vacancy-rich TiO₂ nanoparticles were in situ fabricated on Ti₃C₂Tx nanosheets (V-TiO₂/Ti₃C₂Tx) and used as the oxygen electrode of Li-O₂ batteries. Oxygen vacancy (Vo) can boost the migration rate of electrons and Li⁺ as well as act as the active sites for catalyzing the ORR and OER. Based on the above merits, V-TiO₂/Ti₃C₂Tx-based Li-O₂ battery shows improved performance including the ultralow overpotential of 0.21 V, high specific capacity of 11 487 mA h g^-1 at a current density of 100 mA g^-1, and excellent round-trip efficiency (93%). This work proposes an effective strategy for researching high-performance oxygen electrodes for Li-O₂ batteries via introducing Vo-rich oxides on two-dimensional MXene.

Lithium dendrite-free plating/stripping: a new synergistic lithium ion solvation structure effect for reliable lithium–sulfur full batteries

A new synergistic Li⁺ solvation structure effect is introduced to mitigate the growth of lithium-dendrites and applied for safer Li–S full batteries.

Atomic-Thick TiO2(B) Nanosheets Decorated with Ultrafine Co3O4 Nanocrystals As a Highly Efficient Catalyst for Lithium-Oxygen Battery

Development of highly efficient catalysts based on transition metal oxides (TMOs) is desirable and remains a big challenge for lithium-oxygen (Li-O₂) batteries. In the present work, atomic-thick TiO₂(B) nanosheets decorated with ultrafine Co₃O₄ nanocrystals (Co₃O₄-TiO₂(B)) were synthesized and utilized as cathode catalyst in Li-O₂ batteries by designing a hybrid and inducing oxygen vacancies. The XPS characterization results suggested that the introduction of Co₃O₄ nanocrystals could induce numerous oxygen vacancies in the TiO₂(B) nanosheets through Co doping in the hybrid catalyst. The subsequent electrochemical experiments indicated that the Li-O₂ batteries with the prepared hybrid catalysts showed high specific capacity (11000 mAhg^-1), and good cycling stability (200 cycles at a limited capacity of 1000 mAhg^-1) with low polarization (above 2.7 V for discharge medium voltage and below 4.0 V for charge medium voltage within 80 cycles). Furthermore, a possible working mechanism was proposed for a better understanding of the high performance of Co₃O₄-TiO₂(B) catalysts for the Li-O₂ batteries. This work also provided new insights into designing efficient catalysts through interface engineering between 2D (two-dimensional) TMOs and 0D (zero-dimensional) TMOs for Li-O₂ batteries or other catalysis-related fields.

High-Surface-Area and Porous Co2P Nanosheets as Cost-Effective Cathode Catalysts for Li-O2 Batteries

To enable lithium-oxygen batteries for practical applications, the design and efficient synthesis of nonprecious metal catalysts with high activity and stable structural properties are demanded. The objective is to accelerate the sluggish kinetics of both oxygen reduction reaction and oxygen evolution reaction by facilitating electronic/ionic transport and improving oxygen diffusion in a porous structure. In this study, high-surface-area and porous cobalt phosphide (Co₂P) nanosheets are synthesized via an environmentally safe hydrothermal method, where red phosphorous is used as the phosphorous source. It was found that the as-prepared Co₂P/acetylene black (AB) composite delivered enhanced electrochemical performances, such as high capacities of 2551 mA h g^-1 (based on the total weight of Co₂P and AB) or 5102 mA h g^-1 (based on the weight of Co₂P or AB) and a good cycle life of more than 1800 h (132 cycles) in lithium-oxygen battery. The rational design of the Co₂P/AB porous oxygen electrode structure provides sufficient accessible reaction sites and a short diffusion path for electrolyte penetration and diffusion of O₂.

Quasi-Solid-State Rechargeable Li-O2 Batteries with High Safety and Long Cycle Life at Room Temperature

As interest in electric vehicles and mass energy storage systems continues to grow, Li-O₂ batteries are attracting much attention as a candidate for next-generation energy storage systems owing to their high energy density. However, safety problems related to the use of lithium metal anodes have hampered the commercialization of Li-O₂ batteries. Herein, we introduced a quasi-solid polymer electrolyte with excellent electrochemical, chemical, and thermal stabilities into Li-O₂ batteries. The ion-conducting QSPE was prepared by gelling a polymer network matrix consisting of poly(ethylene glycol) methyl ether methacrylate, methacrylated tannic acid, lithium trifluoromethanesulfonate, and nanofumed silica with a small amount of liquid electrolyte. The quasi-solid-state Li-O₂ cell consisted of a lithium powder anode, a quasi-solid polymer electrolyte, and a Pd₃Co/multiwalled carbon nanotube cathode, which enhanced the electrochemical performance of the cell. This cell, which exhibited improved safety owing to the suppression of lithium dendrite growth, achieved a lifetime of 125 cycles at room temperature. These results show that the introduction of a quasi-solid electrolyte is a potentially new alternative for the commercialization of solid-state Li-O₂ batteries.

O2 selective membranes based on a dextrin-nanosponge (NS) in a PVDF-HFP polymer matrix for Li-air cells

A novel oxygen selective highly hydrophobic membrane is prepared by non-solvent induced phase separation in which a dextrin-based nanosponge is incorporated into a poly(vinylidene fluoride co-hexafluoropropylene) (PVDF-HFP) matrix. The membrane presents high capability to entrap moisture from air as well as good hydrophobic behaviour. The membrane was assembled in a pouch type Li-air cell, which was cycled in a galvanostatic mode at curtailed capacity, in air with 17% relative humidity (RH). Owing to the protection of the membrane, the Li-air cell was able to discharge and re-charge for approximately 145 cycles, which correspond to about 1450 h of cell operation.

Synthesis of porous CoMoO4 nanorods as a bifunctional cathode catalyst for a Li-O2 battery and superior anode for a Li-ion battery

We report the synthesis of porous CoMoO₄ nanorods and their applications in lithium oxygen (Li-O₂) and lithium ion (Li-ion) batteries. The unique porous structures of CoMoO₄ nanorods can promote the permeation of electrolyte and benefit the transport of lithium ion. When employed as the cathode catalyst for a Li-O₂ battery, CoMoO₄ nanorods deliver an improved discharge capacity (4680 mA h g^-1), lower charge potential and better cycle stability (41 cycles at 500 mA h g^-1 capacity limit) compared with the bare carbon. When employed as an anode in Li-ion batteries, CoMoO₄ nanorods can retain a capacity of 603 mA h g^-1 after 300 cycles (400 mA g^-1) and exhibit excellent rate capability.

Influence of Binders and Solvents on Stability of Ru/RuOx Nanoparticles on ITO Nanocrystals as Li-O2 Battery Cathodes

Fundamental research on Li-O₂ batteries remains critical, and the nature of the reactions and stability are paramount for realising the promise of the Li-O₂ system. We report that indium tin oxide (ITO) nanocrystals with supported 1-2 nm oxygen evolution reaction (OER) catalyst Ru/RuO_x nanoparticles (NPs) demonstrate efficient OER processes, reduce the recharge overpotential of the cell significantly and maintain catalytic activity to promote a consistent cycling discharge potential in Li-O₂ cells even when the ITO support nanocrystals deteriorate from the very first cycle. The Ru/RuO_x nanoparticles lower the charge overpotential compared with those for ITO and carbon-only cathodes and have the greatest effect in DMSO electrolytes with a solution-processable F-free carboxymethyl cellulose (CMC) binder (<3.5 V) instead of polyvinylidene fluoride (PVDF). The Ru/RuO_x /ITO nanocrystalline materials in DMSO provide efficient Li₂ O₂ decomposition from within the cathode during cycling. We demonstrate that the ITO is actually unstable from the first cycle and is modified by chemical etching, but the Ru/RuO_x NPs remain effective OER catalysts for Li₂ O₂ during cycling. The CMC binders avoid PVDF-based side-reactions and improve the cyclability. The deterioration of the ITO nanocrystals is mitigated significantly in cathodes with a CMC binder, and the cells show good cycle life. In mixed DMSO-EMITFSI [EMITFSI=1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide] ionic liquid electrolytes, the Ru/RuO_x /ITO materials in Li-O₂ cells cycle very well and maintain a consistently very low charge overpotential of 0.5-0.8 V.

Hydroxylated carbon black as improved deposition support for discharge products in lithium air(oxygen)batteries

The positive roles of the hydroxyls in improving the deposition of Li₂O₂and the performances of the Li–air battery are revealed.

The Use of Spray-Dried Mn₃O₄/C Composites as Electrocatalysts for Li-O₂ Batteries

The electrocatalytic activities of Mn₃O₄/C composites are studied in lithium-oxygen (Li-O₂) batteries as cathode catalysts. The Mn₃O₄/C composites are fabricated using ultrasonic spray pyrolysis (USP) with organic surfactants as the carbon sources. The physical and electrochemical performance of the composites is characterized by X-ray diffraction, scanning electron microscopy, particle size analysis, Brunauer-Emmett-Teller (BET) measurements, elemental analysis, galvanostatic charge-discharge methods and rotating ring-disk electrode (RRDE) measurements. The electrochemical tests demonstrate that the Mn₃O₄/C composite that is prepared using Trition X-114 (TX114) surfactant has higher activity as a bi-functional catalyst and delivers better oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic performance in Li-O₂ batteries because there is a larger surface area and particles are homogeneous with a meso/macro porous structure. The rate constant (k_f) for the production of superoxide radical (O₂^•-) and the propylene carbonate (PC)-electrolyte decomposition rate constant (k) for M₃O₄/C and Super P electrodes are measured using RRDE experiments and analysis in the 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF₆)/PC electrolyte. The results show that TX114 has higher electrocatalytic activity for the first step of ORR to generate O₂^•- and produces a faster PC-electrolyte decomposition rate.

Recent Development of Advanced Electrode Materials by Atomic Layer Deposition for Electrochemical Energy Storage

Electrode materials play a decisive role in almost all electrochemical energy storage devices, determining their overall performance. Proper selection, design and fabrication of electrode materials have thus been regarded as one of the most critical steps in achieving high electrochemical energy storage performance. As an advanced nanotechnology for thin films and surfaces with conformal interfacial features and well controllable deposition thickness, atomic layer deposition (ALD) has been successfully developed for deposition and surface modification of electrode materials, where there are considerable issues of interfacial and surface chemistry at atomic and nanometer scale. In addition, ALD has shown great potential in construction of novel nanostructured active materials that otherwise can be hardly obtained by other processing techniques, such as those solution-based processing and chemical vapor deposition (CVD) techniques. This review focuses on the recent development of ALD for the design and delivery of advanced electrode materials in electrochemical energy storage devices, where typical examples will be highlighted and analyzed, and the merits and challenges of ALD for applications in energy storage will also be discussed.

Influence of electric potential on the apparent viscosity of an ionic liquid: facts and artifacts

According to recent findings, the steady shear viscosity of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][Tf2N]) decreases significantly under the influence of electric potential. This implies a causal connection between nanoscale ordering at the electrified interface and a macroscopic change of transport properties. To study this phenomenon in more detail, we reproduced the above-mentioned measurements; however, we find no evidence that the viscosity of [Emim][Tf2N] is a function of electric potential. Additionally, our results show that steady shear measurements can lead to artifacts that, at first glance, may appear to be potential-induced changes in viscosity. We demonstrate that the artifacts result from a sliding electrical contact at the working electrode of the electrochemical cell and we suggest to consider our findings for future viscosity measurements of ionic liquids.

Facile Synthesis of Boron-Doped rGO as Cathode Material for High Energy Li-O2 Batteries

To improve the electrochemical performance of the high energy Li-O2 batteries, it is important to design and construct a suitable and effective oxygen-breathing cathode. Herein, a three-dimensional (3D) porous boron-doped reduction graphite oxide (B-rGO) material with a hierarchical structure has been prepared by a facile freeze-drying method. In this design, boric acid as the boron source helps to form the 3D porous structure, owing to its cross-linking and pore-forming function. This architecture facilitates the rapid oxygen diffusion and electrolyte penetration in the electrode. Meanwhile, the boron-oxygen functional groups linking to the carbon surface or edge serve as additional reaction sites to activate the ORR process. It is vital that boron atoms have been doped into the carbon lattices to greatly activate the electrons in the carbon π system, which is beneficial for fast charge under large current densities. Density functional theory calculation demonstrates that B-rGO exhibits much stronger interactions with Li5O6 clusters, so that B-rGO more effectively activates Li-O bonds to decompose Li2O2 during charge than rGO does. With B-rGO as a catalytic substrate, the Li-O2 battery achieves a high discharge capacity and excellent rate capability. Moreover, catalysts could be added into the B-rGO substrate to further lower the overpotential and enhance the cycling performance in future.

Why Do Lithium-Oxygen Batteries Fail: Parasitic Chemical Reactions and Their Synergistic Effect

As an electrochemical energy-storage technology with the highest theoretical capacity, lithium-oxygen batteries face critical challenges in terms of poor stabilities and low charge/discharge round-trip efficiencies. It is generally recognized that these issues are connected to the parasitic chemical reactions at the anode, electrolyte, and cathode. While the detailed mechanisms of these reactions have been studied separately, the possible synergistic effects between these reactions remain poorly understood. To fill in the knowledge gap, this Minireview examines literature reports on the parasitic chemical reactions and finds the reactive oxygen species a key chemical mediator that participates in or facilitates nearly all parasitic chemical reactions. Given the ubiquitous presence of oxygen in all test cells, this finding is important. It offers new insights into how to stabilize various components of lithium-oxygen batteries for high-performance operations and how to eventually materialize the full potentials of this promising technology.

A multi-layered Fe2O3/graphene composite with mesopores as a catalyst for rechargeable aprotic lithium-oxygen batteries

Aprotic Li-O2 batteries have attracted a huge amount of interest in the past decade owing to their extremely high energy density. However, identifying a desirable cathodic catalyst for this promising battery system is one of the biggest challenges at present. In this work, a multi-layered Fe2O3/graphene nanosheets (Fe2O3/GNS) composite with sandwich structure was synthesized using an easy thermal casting method, and served as a cathodic catalyst for aprotic Li-O2 batteries. The aprotic Li-O2 cell with the Fe2O3/GNS catalyst demonstrated a better reversibility, lower overpotential for oxygen evolution, and a higher Coulombic efficiency (close to 100%) than those of pure GNS. An excellent rate performance and good cycle stability were also confirmed. The results, characterized by ex and in situ methods, revealed that the dominant discharge product Li2O2 was decomposed below 4.35 V. This superior electrochemical performance is mainly attributed to the unique sandwich structure of the Fe2O3/GNS catalyst with mesopores, which can provide substantially more catalytic sites and prevent direct contact between carbon and Li2O2.

Sodium-Oxygen Batteries: A Comparative Review from Chemical and Electrochemical Fundamentals to Future Perspective

Alkali metal-oxygen (Li-O2 , Na-O2 ) batteries have attracted a great deal of attention recently due to their high theoretical energy densities, comparable to gasoline, making them attractive candidates for application in electrical vehicles. However, the limited cycling life and low energy efficiency (high charging overpotential) of these cells hinder their commercialization. The Li-O2 battery system has been extensively studied in this regard during the past decade. Compared to the numerous reports of Li-O2 batteries, the research on Na-O2 batteries is still in its infancy. Although, Na-O2 batteries show a number of attractive properties such as low charging overpotential and high round-trip energy efficiency, their cycling life is currently limited to a few tens of cycles. Therefore, understanding the chemistry behind Na-O2 cells is critical towards enhancing their performance and advancing their development. Chemical and electrochemical reactions of Na-O2 batteries are reviewed and compared with those of Li-O2 batteries in the present review, as well as recent works on the chemical composition and morphology of the discharge products in these batteries. Furthermore, the determining kinetics factors for controlling the chemical composition of the discharge products in Na-O2 cells are discussed and the potential research directions toward improving Na-O2 cells are proposed.

Color-Coded Batteries - Electro-Photonic Inverse Opal Materials for Enhanced Electrochemical Energy Storage and Optically Encoded Diagnostics

For consumer electronic devices, long-life, stable, and reasonably fast charging Li-ion batteries with good stable capacities are a necessity. For exciting and important advances in the materials that drive innovations in electrochemical energy storage (EES), modular thin-film solar cells, and wearable, flexible technology of the future, real-time analysis and indication of battery performance and health is crucial. Here, developments in color-coded assessment of battery material performance and diagnostics are described, and a vision for using electro-photonic inverse opal materials and all-optical probes to assess, characterize, and monitor the processes non-destructively in real time are outlined. By structuring any cathode or anode material in the form of a photonic crystal or as a 3D macroporous inverse opal, color-coded "chameleon" battery-strip electrodes may provide an amenable way to distinguish the type of process, the voltage, material and chemical phase changes, remaining capacity, cycle health, and state of charge or discharge of either existing or new materials in Li-ion or emerging alternative battery types, simply by monitoring its color change.

Hydroquinone Resin Induced Carbon Nanotubes on Ni Foam As Binder-Free Cathode for Li-O2 Batteries

In this work, hydroquinone resin was used to grow carbon nanotubes directly on Ni foam. The composites were obtained via a simple carbonization method, which avoids using the explosive gaseous carbon precursors that are usually applied in the chemical vapor deposition method. When evaluated as cathode for Li-O2 batteries, the binder-free structure showed enhanced ORR/OER activities, thus giving a high rate capability (12690 mAh g(-1) at 200 mA g(-1) and 3999 mAh g(-1) at 2000 mA g(-1)) and outstanding long-term cycling stability (capacity limited 2000 mAh g(-1), 110 cycles at 200 mA g(-1)). The excellent battery performance provides new insights into designing a low-cost and high-efficiency cathode for Li-O2 batteries.

Using elastin protein to develop highly efficient air cathodes for lithium-O2 batteries

Transition metal-nitrogen/carbon (M-N/C, M = Fe, Co) catalysts are synthesized using environmentally friendly histidine-tag-rich elastin protein beads, metal sulfate and water soluble carbon nanotubes followed by post-annealing and acid leaching processes. The obtained catalysts are used as cathode materials in lithium-O2 batteries. It has been discovered that during discharge, Li2O2 nanoparticles first nucleate and grow around the bead-decorated CNT regions (M-N/C centres) and coat on the catalysts at a high degree of discharge. The Fe-N/C catalyst-based cathodes deliver a capacity of 12,441 mAh g(-1) at a current density of 100 mA g(-1). When they were cycled at a limited capacity of 800 mAh g(-1) at current densities of 200 or 400 mA g(-1), these cathodes showed stable charge voltages of ∼3.65 or 3.90 V, corresponding to energy efficiencies of ∼71.2 or 65.1%, respectively. These results are considerably superior to those of the cathodes based on bare annealed CNTs, which prove that the Fe-N/C catalysts developed here are promising for use in non-aqueous lithium-O2 battery cathodes.

Investigation of MnO₂ and Ordered Mesoporous Carbon Composites as Electrocatalysts for Li-O₂ Battery Applications

The electrocatalytic activities of the MnO₂/C composites are examined in Li-O₂ cells as the cathode catalysts. Hierarchically mesoporous carbon-supported manganese oxide (MnO₂/C) composites are prepared using a combination of soft template and hydrothermal methods. The composites are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, small angle X-ray scattering, The Brunauer–Emmett–Teller (BET) measurements, galvanostatic charge-discharge methods, and rotating ring-disk electrode (RRDE) measurements. The electrochemical tests indicate that the MnO₂/C composites have excellent catalytic activity towards oxygen reduction reactions (ORRs) due to the larger surface area of ordered mesoporous carbon and higher catalytic activity of MnO₂. The O₂ solubility, diffusion rates of O₂ and O₂^•− coefficients (DO2 and DO2•−), the rate constant (k_f) for producing O₂^•−, and the propylene carbonate (PC)-electrolyte decomposition rate constant (k) of the MnO₂/C material were measured by RRDE experiments in the 0.1 M TBAPF₆/PC electrolyte. The values of k_f and k for MnO₂/C are 4.29 × 10⁻² cm·s⁻¹ and 2.6 s⁻¹, respectively. The results indicate that the MnO₂/C cathode catalyst has higher electrocatalytic activity for the first step of ORR to produce O₂^•− and achieves a faster PC-electrolyte decomposition rate.

Facile synthesis of flower-like hierarchical NiCo2O4 microspheres as high-performance cathode materials for Li–O2 batteries

The Li–O₂ battery with flower-like hierarchical NiCo₂O₄ microspheres cathode exhibits a low discharge/charge voltage gap of 0.86 V, much lower than previously reported results for NiCo₂O₄.

Mesoporous boron-doped onion-like carbon as long-life oxygen electrode for sodium–oxygen batteries

Boron-doped onion-like carbon is successfully synthesized by calcination of ultra-dispersed nanodiamond and it exhibits excellent catalytic activity for the oxygen electrode reaction in Na–O₂ batteries.

An urchin-like Ni3ZnC0.7–carbon nanotube-porous carbon composite derived from metal–organic gel as a cathode material for rechargeable Li–O2 batteries

Urchin-like Ni₃ZnC_0.7–carbon nanotubes-porous carbon composites are prepared by one-step carbonization of a metal–organic gel. While applied as the cathode material of Li–O₂ batteries, the composite exhibits an excellent electrochemical performance.

Porous AgPd-Pd Composite Nanotubes as Highly Efficient Electrocatalysts for Lithium-Oxygen Batteries

Porous AgPd-Pd composite nanotubes (NTs) are used as an efficient bifunctional catalyst for the oxygen reduction and evolution reactions in lithium-oxygen batteries. The porous NT structure can facilitate rapid O2 and electrolyte diffusion through the NTs and provide abundant catalytic sites, forming a continuous conductive network throughout the entire energy conversion process, with excellent cycling performance.

Lithium Sulfur Primary Battery with Super High Energy Density: Based on the Cauliflower-like Structured C/S Cathode

The lithium-sulfur primary batteries, as seldom reported in the previous literatures, were developed in this work. In order to maximize its practical energy density, a novel cauliflower-like hierarchical porous C/S cathode was designed, for facilitating the lithium-ions transport and sulfur accommodation. This kind of cathode could release about 1300 mAh g⁻¹ (S) capacity at sulfur loading of 6 ~ 14 mg cm⁻², and showed excellent shelf stability during a month test at room temperature. As a result, the assembled Li-S soft package battery achieved an energy density of 504 Wh kg⁻¹ (654 Wh L⁻¹), which was the highest value ever reported to the best of our knowledge. This work might arouse the interests on developing primary Li-S batteries, with great potential for practical application.