Spin-State Manipulation of Two-Dimensional Metal-Organic Framework with Enhanced Metal-Oxygen Covalency for Lithium-Oxygen Batteries

Aprotic Li-O 2 battery has attracted extensive attention in the past decade owing to the high theoretical energy density, however it is obstructed by the sluggish reaction kinetics at cathodes and large voltage hysteresis. Herein, we regulate the spin state of partial Ni 2+ metal centers ( t 2g 6 e g 2 ) of conductive nickel catecholate framework (Ni II -NCF) nanowire arrays to high-valence Ni 3+ ( t 2g 6 e g 1 ) for Ni III -NCF. The spin-state modulation enables enhanced nickel-oxygen covalency in Ni III -NCF, which facilitates electron exchange between the Ni sites and oxygen adsorbates and accelerates the oxygen redox kinetics. The high affinity of Ni 3+ sites with the intermediate LiO 2 promotes formation of nanosheet-like Li 2 O 2 in the void space among Ni III -NCF nanowires upon discharging. These merit the Li-O 2 battery based on Ni III -NCF with remarkably reduced discharge/charge voltage gaps, superior rate capability, and long cycling stability of over 200 cycles. This work highlights the domination of electron spin state on the redox kinetics and will shed insights into electronic structure regulation of electrocatalysts for Li-O 2 battery and beyond.

Lewis-Acidic PtIr Multipods Enable High-Performance Li-O2 Batteries

The sluggish oxygen reaction kinetics concomitant with the high overpotentials and parasitic reactions from cathodes and solvents is the major challenge in aprotic lithium-oxygen (Li-O₂ ) batteries. Herein, PtIr multipods with a low Lewis acidity of the Pt atoms are reported as an advanced cathode for improving overpotentials and stabilities. DFT calculations disclose that electrons have a strong disposition to transfer from Ir to Pt, since Pt has a higher electronegativity than Ir, resulting in a lower Lewis acidity of the Pt atoms than that on the pure Pt surface. The low Lewis acidity of Pt atoms on the PtIr surface entails a high electron density and a down-shifting of the d-band center, thereby weakening the binding energy towards intermediates (LiO₂ ), which is the key in achieving low oxygen-reduction-reaction (ORR) and oxygen-evolution-reaction (OER) overpotentials. The Li-O₂ cell based on PtIr electrodes exhibits a very low overall discharge/charge overpotential (0.44 V) and an excellent cycle life (180 cycles), outperforming the bulk of reported noble-metal-based cathodes.

A high-capacity cathode for rechargeable K-metal battery based on reversible superoxide-peroxide conversion

As a promising low-cost energy storage device, the development of a rechargeable potassium-ion battery (KIB) is severely hindered by the limited capacity of cathode candidates. Regarded as an attractive capacity-boosting strategy, triggering the O-related anionic redox activity has not been achieved within a sealed KIB system. Herein, in contrast to the typical gaseous open K-O₂ battery (O₂/KO₂ redox), we originally realize the reversible superoxide/peroxide (KO₂/K₂O₂) interconversion on a KO₂-based cathode. Controlled within a sealed cell environment, the irreversible O₂ evolution and electrolyte decomposition (induced by superoxide anion (O₂⁻) formation) are effectively restrained. Rationally controlling the reversible depth-of-charge at 300 mAh/g (based on the mass of KO₂), no obvious cell degradation can be observed during 900 cycles. Moreover, benefitting from electrolyte modification, the KO₂-based cathode is coupled with a limited amount of K-metal anode (merely 2.5 times excess), harvesting a K-metal full-cell with high energy efficiency (∼90%) and long-term cycling stability (over 300 cycles).

Enhancing the Reduction Kinetics of LiSF6 Batteries by Dispersed Cobalt Phthalocyanines on Porous Carbon

Reducing SF₆ (as gas cathode) in Li batteries is a promising concept for the double benefit of mildly converting greenhouse SF₆ and providing a high theoretical energy density of 3922 Wh kg^-1 . However, the reduction process is hampered by its sluggish kinetics. Here, cobalt phthalocyanine (CoPc) molecules immobilized on porous carbon matrix are, for the first time, introduced to the LiSF₆ chemistry to deliver an enhanced energy density. It is revealed that the high redox potential of Co(II)Pc/[Co(I)Pc]^- (≈2.85 V) facilitates the formation of Co(I)N₄ sites to catalyze the SF₆ electrochemical reduction. By using highly porous holey nitrogen-doped carbon nanocages as carbon matrix, the LiSF₆ cells deliver a high discharge voltage of 2.82 V at 50 mA g_C+CoPc ^-1 and an unprecedented areal capacity of 25 mAh cm^-2 at 0.1 mA cm^-2 , much superior to previous results. This work opens up new possibilities for high-efficiency conversion of SF₆ in lithium batteries.

Nitrate Molten Salt Electrolytes with Iron Oxide Catalysts for Open and Sealed Li-O2 Batteries

Li-O₂ batteries with nitrate molten salt electrolytes are attracting considerable attention owing to their various electrochemical pathways to form a discharge product upon the open and sealed systems. Here, we investigate nitrate molten salt electrolyte-based open and sealed Li-O₂ batteries with pristine and iron oxide catalysts. Through the systematic analysis of various Li-O₂ battery characteristics, we observe the irreversible electrochemical reactions of the open Li-O₂ battery with an iron oxide catalyst that erodes the battery performance due to the detrimental parasitic reaction of H₂ gas evolution from the Li anode. In contrast, the sealed Li-O₂ system with cathodes containing the iron oxide catalyst exhibits the formation and decomposition of Li₂O discharge products without significant side reactions, which guarantees long cycle endurance, high-rate performance, and a gravimetric energy density. Thus, promising electrochemical results from the sealed Li-O₂ system with the iron oxide catalyst provide a viable strategy for the high-performance molten salt-based Li-O₂ battery.

Oxygen Vacancy-Rich RuO2-Co3O4 Nanohybrids as Improved Electrocatalysts for Li-O2 Batteries

Lithium oxygen (Li-O₂) batteries have shown great potential as new energy-storage devices due to the high theoretical energy density. However, there are still substantial problems to be solved before practical application, including large overpotential, low energy efficiency, and poor cycle life. Herein, we have successfully synthesized a RuO₂-Co₃O₄ nanohybrid with a rich oxygen vacancy and large specific surface area. The Li-O₂ batteries based on the RuO₂-Co₃O₄ nanohybrid shown obviously reduced overpotential and improved circulatory property, which can cycle stably for more than 100 cycles at a current density of 200 mA g^-1. Experimental results and density function theory calculation prove that the introduction of RuO₂ can increase oxygen vacancy concentration of Co₃O₄ and accelerate the charge transfer. Meanwhile, the hollow and porous structure leads to a large specific surface area about 104.5 m² g^-1, exposing more active sites. Due to the synergistic effect, the catalyst of the RuO₂-Co₃O₄ nanohybrid can significantly reduce the adsorption energy of the LiO₂ intermediate, thereby reducing the overpotential effectively.

Biphasic Electrolyte Inhibiting the Shuttle Effect of Redox Molecules in Lithium-Metal Batteries

Redox molecules (RMs) as electron carriers have been widely used in electrochemical energy-storage devices (ESDs), such as lithium redox flow batteries and lithium-O₂ batteries. Unfortunately, migration of RMs to the lithium (Li) anode leads to side reactions, resulting in reduced coulombic efficiency and early cell death. Our proof-of-concept study utilizes a biphasic organic electrolyte to resolve this issue, in which nonafluoro-1,1,2,2-tetrahydrohexyl-trimethoxysilane (NFTOS) and ether (or sulfone) with lithium bis(trifluoromethane)sulfonimide (LiTFSI) can be separated to form the immiscible anolyte and catholyte. RMs are extracted to the catholyte due to the enormous solubility coefficients in the biphasic electrolytes with high and low polarity, resulting in inhibition of the shuttle effect. When coupled with a lithium anode, the Li-Li symmetric, Li redox flow and Li-O₂ batteries can achieve considerably prolonged cycle life with biphasic electrolytes. This concept provides a promising strategy to suppress the shuttle effect of RMs in ESDs.

Surface plasmon mediates the visible light-responsive lithium-oxygen battery with Au nanoparticles on defective carbon nitride

Aprotic lithium-oxygen (Li-O₂) batteries have gained extensive interest in the past decade, but are plagued by slow reaction kinetics and induced large-voltage hysteresis. Herein, we use a plasmonic heterojunction of Au nanoparticle (NP)-decorated C₃N₄ with nitrogen vacancies (Au/N_V-C₃N₄) as a bifunctional catalyst to promote oxygen cathode reactions of the visible light-responsive Li-O₂ battery. The nitrogen vacancies on N_V-C₃N₄ can adsorb and activate O₂ molecules, which are subsequently converted to Li₂O₂ as the discharge product by photogenerated hot electrons from plasmonic Au NPs. While charging, the holes on Au NPs drive the reverse decomposition of Li₂O₂ with a reduced applied voltage. The discharge voltage of the Li-O₂ battery with Au/N_V-C₃N₄ is significantly raised to 3.16 V under illumination, exceeding its equilibrium voltage, and the decreased charge voltage of 3.26 V has good rate capability and cycle stability. This is ascribed to the plasmonic hot electrons on Au NPs pumped from the conduction bands of N_V-C₃N₄ and the prolonged carrier life span of Au/N_V-C₃N₄ This work highlights the vital role of plasmonic enhancement and sheds light on the design of semiconductors for visible light-mediated Li-O₂ batteries and beyond.

Operando Synchrotron XRD of Bromide Mediated Li-O2 Battery

Li-O₂ battery technology offers large theoretical energy density, considered a promising alternative energy storage technology for a variety of applications. One of the main advances made in recent years is the use of soluble catalysts, known as redox mediators (RM), decreasing the charge overpotential and improving cyclability. Despite its potential, much is still unknown regarding its dynamic, especially over higher loading electrodes, where mass transport may be an issue and the interplay with common impurities in the electrolyte, like residual water. Here we perform for the first time an operando XRD characterization of a DMSO-based LiBr mediated Li-O₂ battery with a high loading electrode based on CNTs aiming to reveal these dynamics and track chemical changes in the electrode. Our results show that, depending on the electrode architecture, the system's issue can move from catalytic to a mass transfer. We also assess the effect of residual water in the system to better understand the reaction routes. As a result, we observed that with DMSO, the system is even more sensitive to water contamination compared to glyme-based studies reported in the literature. Despite the activity of LiBr on the Li-peroxide oxidation and its contribution to cyclability, with the system and electrode configuration used in this study, we verified that a mass transfer limitation caused a cell "sudden death" caused by clogging after cycling.

A novel strategy for improving performance of lithium-oxygen batteries

Although the theoretical energy density of lithium-oxygen batteries is extremely high, pulverization of lithium metal anode obviously influences batteries cycling performance. In this work, the cathode was coated with a membrane to protect the lithium anode from moisture attacking and avoid the pulverization. The membrane is composed of polyethylene oxide and poly tetra fluoroethylene, which improves the cycle life of the lithium-oxygen batteries cycles to 230 times, with a limited specific capacity of 1000 mAh·g^-1, at a current density of 100 mA·g^-1. Furthermore, the batteries perform stable charge and discharge cycles for 55 times in the air atmosphere, with the relative humidity greater than 50%. It demonstrates this strategy provides a new direction for the development of high-performance lithium-oxygen batteries.

Electrode Protection in High-Efficiency Li-O2 Batteries

The aprotic Li-O2 battery possessing the highest theoretical energy density, approaching that of gasoline, has been regarded as one of the most promising successors to Li-ion batteries. Before this kind of battery can become a viable technology, a series of critical issues need to be conquered, like low round-trip efficiency and short cycling lifetime, which are closely related to the continuous parasitic processes happening at the cathode and anode during cycling. With an aim to promote the practical application of Li-O2 batteries, great effort has been devoted to identify the reasons for oxygen and lithium electrodes degradation and provide guidelines to overcome them. Thus, the stability of cathode and anode has been improved a lot in the past decade, which in turn significantly boosts the electrochemical performances of Li-O2 batteries. Here, an overlook on the electrode protection in high-efficiency Li-O2 batteries is presented by providing first the challenges of electrodes facing and then the effectiveness of the existing approaches that have been proposed to alleviate these. Moreover, new battery systems and perspectives of the viable near-future strategies for rational configuration and balance of the electrodes are also pointed out. This Outlook deepens our understanding of the electrodes in Li-O2 batteries and offers opportunities for the realization of high performance and long-term durability of Li-O2 batteries.

An insight into the electro-chemical properties of halogen (F, Cl and Br) doped BP and BN nanocages as anodes in metal-ion batteries

Here, electro-chemical properties of BN and BP nanocages as anodes in metal-ion batteries are examined. The effect of halogens adoption of BN and BP-NCs on electro-chemical properties of M-IBs are investigated. Results showed that the BP nanocages as anode electrode in M-IBs has higher efficiency than BN nanocages and the K-IB has higher cell voltage than N-IBs. Results indicated that the halogens adoption of BN and BP-NCs are improved the cell voltage of M-IBs. Results proved that the F-doped M-IBs have higher cell voltage than M-IBs. Finally, F-B17P18 as anodes in K-IB is proposed as suitable electrodes.

One-pot synthesis of N,S-doped pearl chain tube-loaded Ni3S2 composite materials for high-performance lithium-air batteries

To improve the high reversibility of lithium-air batteries, an air electrode needs to have excellent electrochemical performance and spatial structure. Ni3S2 nanoparticles are loaded onto an N,S-doped pearl chain tube (N,S-PCT) by a method called quasi-chemical vapor deposition (Q-CVD). Additionally, N and S are doped during the synthesis process, thereby forming an ideal pipe rack-like structure. The large amount of space in the tube rack can provide sufficient storage to act as a buffer for the discharge products, and the interconnected tubes can effectively promote the dispersion of O2 and electrolyte. The addition of Ni3S2 nanoparticles effectively reduces the charge transfer resistance, thereby increasing the electron mobility of the cathode. Ni3S2@N,S-PCT cathodes effectively improve the cycling and high-rate performance of lithium-air batteries, demonstrating an ultrahigh discharge capacity of 16 733.7 mA h g-1 at a current density of 400 mA g-1 and an ultrahigh discharge capacity of 5088.1 mA h g-1 at a current density of 1000 mA g-1. When the cut-off capacity is 1000 mA h g-1, the battery with the Ni3S2@N,S-PCT-800 electrode can achieve cycling stability for 148 cycles. This research provides a new solution for the design of lithium-air batteries with high electrocatalytic performance.

Porous Materials Applied in Nonaqueous Li-O2 Batteries: Status and Perspectives

Porous materials possessing high surface area, large pore volume, tunable pore structure, superior tailorability, and dimensional effect have been widely applied as components of lithium-oxygen (Li-O₂ ) batteries. Herein, the theoretical foundation of the porous materials applied in Li-O₂ batteries is provided, based on the present understanding of the battery mechanism and the challenges and advantageous qualities of porous materials. Furthermore, recent progress in porous materials applied as the cathode, anode, separator, and electrolyte in Li-O₂ batteries is summarized, together with corresponding approaches to address the critical issues that remain at present. Particular emphasis is placed on the importance of the correlation between the function-orientated design of porous materials and key challenges of Li-O₂ batteries in accelerating oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) kinetics, improving the electrode stability, controlling lithium deposition, suppressing the shuttle effect of the dissolved redox mediators, and alleviating electrolyte decomposition. Finally, the rational design and innovative directions of porous materials are provided for their development and application in Li-O₂ battery systems.

Efficient separation of photoexcited carriers in a g-C3N4-decorated WO3 nanowire array heterojunction as the cathode of a rechargeable Li-O2 battery

Utilization of solar energy is very important for alleviating the global energy crisis; however, solar-to-electric energy conversion in a compact battery is a great challenge. High charging overpotential of conventional aprotic Li-O₂ batteries still restricts their practical application. Herein, we propose a photo-involved rechargeable Li-O₂ battery to not only realize direct solar-to-electric energy conversion/storage but also address the overpotential issue. In this photo-involved battery system, the g-C₃N₄-decorated WO₃ nanowire array (WO₃@g-C₃N₄ NWA) heterojunction semiconductor is used as both the photoelectrode and oxygen electrode. Upon charging under visible-light irradiation, the photoexcited holes and electrons are in situ generated on the WO₃@g-C₃N₄ NWA heterojunction cathode. The fabrication of the heterojunction can distinctly reduce the recombination rate between electrons and holes, while photon-generated carriers are effectively and quickly separated and then migrate under a large current density. The discharge product (Li₂O₂) can be oxidized to O₂ and Li⁺ with a reduced charging voltage (3.69 V) by the abundant photoexcited holes, leading to high energy efficiency, good cycling stability and excellent rate capability. This newly photo-involved reaction scheme could open new avenues toward the design of advanced solar-to-electric energy conversion and storage systems.

Surface Mechanism of Catalytic Electrodes in Lithium-Oxygen Batteries: How Nanostructures Mediate the Interfacial Reactions

The use of catalysts is the key to boost electrode reactions in lithium-oxygen (Li-O₂) batteries. In-depth understanding of the nanoscale catalytic effect at electrode/electrolyte interfaces is of great significance for guiding a design of functionally optimized catalyst. Here, using electrochemical atomic force microscopy, we present the real-time imaging of interfacial evolution on nanostructured Au electrodes in a working battery, revealing that the nanostructure of Au is directly related to the catalytic activity toward oxygen reduction reaction (ORR)/oxygen evolution reaction (OER). In situ views show that nanoporous Au with a size of ∼14 nm for ligaments and ∼5 nm for nanopores promote the nucleation and growth of discharge product Li₂O₂ with large size at a high discharge voltage, yet densely packed Au nanoparticles with a diameter of ∼15 nm could catalyze Li₂O₂ to fully decompose via the top-bottom approach at a low charge potential. In addition, the difference in the nucleation potential of Li₂O₂ on the electrode with hybrid nanostructures could result in an uneven distribution of discharge products, which is alleviated at a large discharge rate and the capacity of the battery is improved significantly. These observations provide deep insights into the mechanisms of Li-O₂ interfacial reaction catalyzed by nanostructured catalysts and strategies for improving Li-O₂ batteries.

Insights into Ion Occupancy Manipulation of Fe-Co Oxide Free-Standing Cathodes for Li-O2 Batteries with Enhanced Deep Charge Capability and Long-Term Capability

The merits of Li-O₂ batteries due to the huge energy density are shadowed by the sluggish kinetics of oxygen redox and massive side reactions caused by conductive carbon and a binder. Herein, Fe-Co inverse spinel oxide nanowires grown on Ni foam are fabricated as carbon-free and binder-free cathodes for Li-O₂ batteries. Superior high rate cycle durability and deep charge capability are obtained. For example, 300 cycles with a low overpotential under a fixed capacity of 500 mAh g^-1 are achieved at a high current density of 500 mA g^-1. In the deep discharge/charge mode at 500 mA g^-1, the optimized Fe-Co oxide cathode can stably work for more than 30 cycles with the capacity maintained at about 2100 mAh g^-1. Owing to the appreciable incorporation of Fe³⁺ into the surface of stable inverse spinel oxides, the regulated Fe-Co oxide cathodes possess a more stable and higher ratio of Co³⁺/Co²⁺, which offers improved adsorption ability of reactive oxygen intermediates and thus achieves the enhanced electrocatalytic performance in the higher current density. In addition, the morphology evolution from array to pyramid-like structure of nanowires further provides assurance in the superior cycle capability. By coupling pyramid-shaped nanowires with binary inverse spinel, the obtained Fe-Co oxide becomes a promising material for practical applications in Li-O₂ batteries. This work offers a general strategy to design efficient mixed metal oxide-based electrodes for the critical energy storage fields.

Electrodeposition Technologies for Li-Based Batteries: New Frontiers of Energy Storage

Electrodeposition induces material syntheses on conductive surfaces, distinguishing it from the widely used solid-state technologies in Li-based batteries. Electrodeposition drives uphill reactions by applying electric energy instead of heating. These features may enable electrodeposition to meet some needs for battery fabrication that conventional technologies can rarely achieve. The latest progress of electrodeposition technologies in Li-based batteries is summarized. Each component of Li-based batteries can be electrodeposited or synthesized with multiple methods. The advantages of electrodeposition are the main focus, and they are discussed in comparison with traditional technologies with the expectation to inspire innovations to build better Li-based batteries. Electrodeposition coats conformal films on surfaces and can control the film thickness, providing an effective approach to enhancing battery performance. Engineering interfaces by electrodeposition can stabilize the solid electrolyte interphase (SEI) and strengthen the adhesion of active materials to substrates, thereby prolonging the battery longevity. Lastly, a perspective of future studies on electrodepositing batteries is provided. The significant merits of electrodeposition should greatly advance the development of Li-based batteries.

A Facile Surface Preservation Strategy for the Lithium Anode for High-Performance Li-O2 Batteries

Protecting an anode from deterioration during charging/discharging has been seen as one of the key strategies in achieving high-performance lithium (Li)-O₂ batteries and other Li-metal batteries with a high energy density. Here, we describe a facile approach to prevent the Li anode from dendritic growth and chemical corrosion by constructing a SiO₂/GO hybrid thin layer on the surface. The uniform pore-preserving layer can conduct Li ions in the stripping/plating process, leading to an effective alleviation of the dendritic growth of Li by guiding the ion flux through the microstructure. Such a preservation technique significantly enhances the cell performance by enabling the Li-O₂ cell to cycle up to 348 times at 1 A·g^-1 with a capacity of 1000 mA·h·g^-1, which is several times the cycles of cells with pristine Li (58 cycles), Li-GO (166 cycles), and Li-SiO₂ (187 cycles). Moreover, the rate performance is improved, and the ultimate capacity of the cell is dramatically increased from 5400 to 25,200 mA·h·g^-1. This facile technology is robust and conforms to the Li surface, which demonstrates its potential applications in developing future high-performance and long lifespan Li batteries in a cost-effective fashion.

Fabrication of carbon cloth supporting MnO x and its application in Li-O2 batteries

High-efficiency and low-cost electrocatalysts are generally believed to be the critical factor and have been highly researched to catalyze the oxygen reduction reaction (ORR) during the operation of Li-O₂ battery (LOB). The catalysts with better ORR performance are essential for high-performance LOBs. Herein, a binder-free MnO _x @carbon cloth cathode composed of Mn₃O₄ nanoparticles and Mn₂O₃ nanosheets were directly synthesized on the carbon cloth by electrodeposition and subsequently heat treatment at different temperature (from 200 °C to 400 °C). With the increase of temperature, the Mn₃O₄ nanospheres gradually transformed into Mn₂O₃ nanosheets. The MnO _x obtained at 350 °C exhibited the best ORR performance. And MnO _x -350 °C could operate more than 80 cycles at 340 mA g^-1 with a limiting specific capacity of 1000 mAh g^-1, and its first discharge specific capacity could nearly achieve 8000 mAh g^-1 at 200 mA g^-1.

Inhibition of Discharge Side Reactions by Promoting Solution-Mediated Oxygen Reduction Reaction with Stable Quinone in Li-O2 Batteries

Aprotic lithium-oxygen (Li-O₂) batteries with an ultrahigh theoretical energy density have great potential in rechargeable power supply, while their application still faces several challenges, especially poor cycle stability. To solve the problems, one of the effective strategies is to inhibit the generation of the LiO₂ intermediate produced via a surface-mediated oxygen reduction reaction (ORR) pathway, which is an important species inducing byproduct generation and low cell cyclic stability. Herein, a series of quinones and solid materials serve as the solution-mediated and surface-mediated ORR catalysts, and it was found that the generation of LiO₂ and byproducts from solid catalysts was inhibited by quinones. Among the studied quinones, benzo[1,2-b:4,5-b']dithiophene-4,8-dione, a quinone molecule with the advantage of a highly symmetrical planar and conjugated structure and without α-H, exhibits high redox potential, diffusion coefficient, and electrochemical stability, and consequently the best ORR activities and the capability to inhibit byproduct generation. It indicated that the increase of the solution-mediated ORR pathway plays an important role in restraining the discharging side reaction, substantially improving cell cycle stability and capacity. This study provides the theoretical and experimental basis for better understanding the ORR process of Li-O₂ batteries.

Electrochemical Oxidation of Li2O2 Surface-Doped with Li2CO3

Electrochemical oxidation of Li₂O₂, i.e., the charging reaction of the aprotic lithium-oxygen batteries (Li-O₂ batteries), is significantly influenced by its surface chemistry. Here, the surface species of Li₂CO₃, widely identified together with Li₂O₂ at the end of discharge, is investigated to understand its implication for the oxidation of Li₂O₂. In situ doping Li₂O₂ with various amounts of Li₂CO₃ has been obtained by reacting with CO₂ gas in a controlled way, and the electrochemical oxidation of the doped Li₂O₂ is studied with a quantitative differential electrochemical mass spectrometer (DEMS). Instead of a single charging potential plateau and one O₂ gas evolution stage for the pristine Li₂O₂, Li₂CO₃-doped Li₂O₂ exhibits two O₂/CO₂ gas evolution stages and three charging plateaus characterized with the larger overpotential for the initial and final stages. The conductivity of Li₂CO₃ dopant is invoked to explain the different oxidation behaviors of Li₂CO₃-doped Li₂O₂. The DEMS study of the electrochemical oxidation of isotope-labeled Li₂¹³CO₃ is also conducted to identify the origins of O₂ and CO₂ evolution during the oxidation of Li₂CO₃-doped Li₂O₂. The results reported here provide an improved understanding of the Li₂O₂ oxidation in the presence of parasitic Li₂CO₃ species and will contribute to the future development of Li-O₂ batteries.

Defect Engineering on Electrode Materials for Rechargeable Batteries

The reasonable design of electrode materials for rechargeable batteries plays an important role in promoting the development of renewable energy technology. With the in-depth understanding of the mechanisms underlying electrode reactions and the rapid development of advanced technology, the performance of batteries has significantly been optimized through the introduction of defect engineering on electrode materials. A large number of coordination unsaturated sites can be exposed by defect construction in electrode materials, which play a crucial role in electrochemical reactions. Herein, recent advances regarding defect engineering in electrode materials for rechargeable batteries are systematically summarized, with a special focus on the application of metal-ion batteries, lithium-sulfur batteries, and metal-air batteries. The defects can not only effectively promote ion diffusion and charge transfer but also provide more storage/adsorption/active sites for guest ions and intermediate species, thus improving the performance of batteries. Moreover, the existing challenges and future development prospects are forecast, and the electrode materials are further optimized through defect engineering to promote the development of the battery industry.

Guidelines and trends for next-generation rechargeable lithium and lithium-ion batteries

This review article summarizes the current trends and provides guidelines towards next-generation rechargeable lithium and lithium-ion battery chemistries.

Facet-dependent activity of hematite nanocrystals toward the oxygen evolution reaction

Hematite showed facet-dependent OER activity and its origin was investigated based on in situ UV-vis absorption measurements and theoretical calculations.