Discharge Products Research Articles

Stabilizing Lithium Superoxide Formation in Lithium-Air Batteries by Janus Chalcogenide Catalysts

Solid lithium peroxide (Li2O2) is the major discharge product in Li-air batteries. However, the electronically insulating nature of Li2O2 tends to affect the battery’s performance such as the polarization gap and cyclability. On the other hand, lithium superoxide (LiO2), generated through a one-electron transfer process, offers greater electronic conductivity, lower charge transfer resistance, and thus reduced charge potential. Nevertheless, LiO2 long-term stabilization as a final product remains a significant challenge. In this study, we present the molybdenum (Mo)-based Janus chalcogenide family featuring asymmetric structures as a new generation of cathode catalysts for Li-air batteries. These catalysts demonstrate remarkable efficacy in stabilizing LiO2 discharge products, even under high current densities of 5000mA/g (corresponding to 0.5mA/cm2). Our density functional calculations provide an understanding of why the asymmetric Mo-Janus chalcogenides result in LiO2 formation whereas the symmetric Mo-dichalcogenides produce Li2O2 as the discharge product. These results pave the way to explore a new generation of advanced catalysts for superoxide-based Li-air batteries.

Magnetic field and photon co-enhanced S-scheme MXene/In2S3/CoFe2O4 heterojunction for high-performance lithium-oxygen batteries

Under the spotlight for their potential to reduce over-potential, photo-assisted Li–O2 batteries still face a key challenge: the rapid recombination of photo-generated electron-hole pairs, which limits their efficiency. In this study, we address this limitation by designing a Li–O2 battery that integrates both photo and magnetic field assistance, using an S-scheme MXene/In2S3/CoFe2O4 heterojunction photocathode. This unique combination enhances visible light absorption and generates a strong built-in electric field, facilitating effective charge separation and boosting photocatalytic activity. During discharge, photo-generated electrons participate in the oxygen reduction reaction, while photo-induced holes contribute to the decomposition of discharge products during charging. Furthermore, the introduction of a magnetic field, confirmed through vibrating sample magnetometer, Mössbauer spectroscopy, X-ray absorption near edge structure, and cyclic voltammetry analyses, enhances electron-hole separation via Lorentz forces and spin–orbit coupling, accelerating the formation and decomposition of Li2O2. With this synergistic approach, the battery achieves a high specific capacity of 26500 mAh g−1, ultra-low oxygen reduction/evolution reaction over-potentials of 0.08 V/0.17 V, and a long cycle life of 2000 cycles with energy efficiency of 98.11 %. This work demonstrates the promising potential of combining photo and magnetic field effects to improve the electrochemical performance of Li–O2 batteries, opening new avenues for high-performance energy storage systems.

MOF Nanosheet Enable Accelerated Redox Kinetics and Ultralow Overpotential for Light-Assisted Li-CO2 Battery.

Lithium-carbon dioxide (Li-CO₂) batteries have attracted much attention due to their high energy density, low cost, and carbon sequestration. However, the sluggish conversion kinetics between CO₂ and the discharge product lithium carbonate (Li₂CO₃) have hindered their practical applications. Herein, a flower-like photosensitive metal-organic framework (FJU-115-NS) has been employed as a cathodic electrocatalyst for Li-CO₂ batteries. The FJU-115-NS with well-ordered micropores and abundant exposed catalytic sites can effectively facilitate lithium ion transport and catalyze the Li₂CO₃ formation/decomposition, leading to improved battery performance. At a current density of 200mA g⁻¹, the FJU-115-NS battery exhibits a substantial discharge capacity of 31579.34mA h g⁻¹, a low overpotential of 1.31V, and stable operation over 3200 h. Importantly, under light irradiation, the charging voltage significantly dropped from 4.45V (without light) to 3.43V at a high current density of 2 A g⁻¹. Additionally, the cell demonstrated an exceptionally low overpotential of just 0.45V at a current density of 200mA g⁻¹, highlighting its enhanced efficiency under light-assisted conditions. This work provides valuable guidance for developing light-assisted MOF catalysts to upgrade the longevity and energy efficiency of Li-CO₂ batteries.

Hydroxysilylene (HSi-OH) in the gas phase.

The hydroxysilylene (HSiOH) molecule has been spectroscopically identified in the gas phase for the first time. This highly reactive species was produced in a twin electric discharge jet using separate precursor streams of 16O2/18O2 and Si2H6/Si2D6, both diluted in high pressure argon. The strongest and most stable laser induced fluorescence (LIF) signals were obtained by applying an electric discharge to each of the precursor streams and then merging the discharge products just prior to expansion into vacuum. Bands of the Ã1A-X~1A' electronic transition of HSiOH were found in the 455-420nm region, and single vibronic level emission spectra showed only transitions attributable to the trans-hydroxysilylene ground state isomer. High resolution, rotationally resolved spectra were obtained for the 0-0 bands of HSi16OH and HSi18OH. The rotational constants were used to obtain ground and excited state molecular structures of HSiOH, with some necessary constraints. The derived ground state structure is trans-HSiOH, with geometric parameters similar to theoretical predictions from the literature. In the excited state, a skew-HSiOH structure was obtained with a dihedral angle of 102°. Our own CASSCF/aug-cc-pVTZ calculations predict a similar excited state skew geometry. The lack of odd quantum number changes in the torsional mode in emission and our difficulties in obtaining DSiOD spectra, despite considerable effort, all suggest that further experimental and theoretical efforts will be necessary to thoroughly understand the electronic spectrum of hydroxysilylene.

Atomically Dispersed Ta-O-Co Sites Capable of Mitigating Side Reaction Occurrence for Stable Lithium-Oxygen Batteries.

The side reactions accompanying the charging and discharging process, as well as the difficulty in decomposing the discharge product lithium peroxide, have been important issues in the research field of lithium-oxygen batteries for a long time. Here, single atom Ta supported by Co3O4 hollow sphere was designed and synthesized as a cathode catalyst. The single atom Ta forms an electron transport channel through the Ta-O-Co structure to stabilize octahedral Co sites, forming strong adsorption with reaction intermediates and ultimately forming a film-like lithium peroxide that is highly dispersed. More importantly, the formation of the Ta-O-Co structure can reduce the vacancy formation energy on the catalyst surface, accelerate oxygen activation and conversion into superoxide anions, promote the rapid conversion of strong oxidizing intermediate lithium superoxide into lithium peroxide, avoid the oxidation of lithium superoxide to the electrode and electrolyte, reduce the occurrence of side reactions, and mitigate the production of byproduct lithium carbonate. The overpotential of the battery is reduced significantly, and the reversibility and cycling stability of the battery are improved. This study provides a practical and feasible direction for mitigating the side reaction and improving the performance of the battery.

On the Source of Conductivity in Alkaline Zn Anodes: Zn Percolation and ZnO Bridging

Abstract Alkaline Zn anodes are fundamental to commercial Zn-MnO2 batteries as well as emerging rechargeable designs. In these electrodes, Zn particles are both the active material and source of electronic conduction. However, there are known cases in which electronic connectivity between Zn particles or the current collecting pin is lost even though the battery continues to function. Here we use X-ray computed tomography (CT) of AA batteries to demonstrate several examples of Zn particle-to-particle connectivity breakdown, which is observed even in cases at relatively high discharge rate. This indicates maintenance of the electronic network through the less-conductive ZnO discharge product. We introduce a new equation for electronic conductivity maintained through bridges of ZnO formed between percolating Zn particles. This necessitates discarding the Bruggeman correlation and instead redefining effective electronic conductivity using percolation theory. We demonstrate that such a model for conduction enables prediction of an inverted reaction zone, which is an experimentally observed case in which significant Zn dissolution and ZnO formation occurs heavily near the current collecting pin. Current computational Zn-MnO2 models never predict an inverted reaction zone, and thus the updated conductivity enables models to accurately explain a wider range of experimental conditions.

Tuning Dual Catalytic Active Sites of Pt Single Atoms Paired with High-Entropy Alloy Nanoparticles for Advanced Li-O2 Batteries.

To achieve a long cycle life and high-capacity performance for Li-O2 batteries, it is critical to rationally modulate the formation and decomposition pathway of the discharge product Li2O2. Herein, we designed a highly efficient catalyst containing dual catalytic active sites of Pt single atoms (PtSAs) paired with high-entropy alloy (HEA) nanoparticles for oxygen reduction reaction (ORR) in Li-O2 batteries. HEA is designed with a moderate d-band center to enhance the surface adsorbed LiO2 intermediate (LiO2(ads)), while PtSAs active sites exhibit weak adsorption energy and promote the soluble LiO2 pathway (LiO2(sol)). An optimal ratio between LiO2(ads) and LiO2(sol) pathway was realized to modulate PtSAs and HEA active sites via regulating the etching conditions in the dealloying synthesis process for obtaining high-performance Li-O2 batteries. The ORR kinetics are accelerated, and the parasitic reactions are restrained in the Li-O2 batteries. As a result, Li-O2 batteries based on the HEA@Pt-PtSAs catalyst demonstrate an ultralow overpotential (0.3 V) and ultralong cycling performance of 470 cycles at 1000 mA g-1. The insights into the synthetic strategies and the importance of balancing the ORR pathways will offer guidance for devising multisite synergistic catalysts to accelerate redox-reaction kinetics for Li-O2 batteries.

A Bifunctional Imidazolyl Iodide Mediator of Electrolyte Boosts Cathode Kinetics and Anode Stability Towards Low Overpotential and Long‐Life Li‐O2 Batteries

AbstractThe addition of a redox mediator as soluble catalyst into electrolyte can effectively overcome the bottlenecks of poor energy efficiency and limited cyclability for Li‐O2 batteries caused by passivation of insulating discharge products and unfavorable byproducts. Herein we report a novel soluble catalyst of bifunctional imidazolyl iodide salt additive, 1,3‐dimethylimidazolium iodide (DMII), to successfully construct highly efficient and durable Li‐O2 batteries. The anion I− can effectively promote the charge transport of Li2O2 and accelerate the redox kinetics of oxygen reduction/oxygen evolution reactions on the cathode side, thereby significantly decreasing the charge/discharge overpotential. Simultaneously, the cation DMI+ forms an ultrathin stably solid‐electrolyte interphase film on Li metal, greatly inhibiting the shuttle effect of I− and improving the stability of anode. Using this DMII additive, our Li‐O2 batteries achieve an extremely low voltage of 0.52 V and ultra‐long cycling stability over 960 h. Notably, up to 95.8 % of the Li2O2 yield further proves the reversible generation/decomposition of Li2O2 without the occurrence of side reactions. Both experimental and theoretical results disclose that DMII enables Li+ easily solvated, testifying the dominance of the solution‐induced reaction mechanism. This work provides the possibility to design the soluble catalysts towards high‐performance Li‐O2 batteries.

A Bifunctional Imidazolyl Iodide Mediator of Electrolyte Boosts Cathode Kinetics and Anode Stability Towards Low Overpotential and Long-Life Li-O2 Batteries.

The addition of a redox mediator as soluble catalyst into electrolyte can effectively overcome the bottlenecks of poor energy efficiency and limited cyclability for Li-O2 batteries caused by passivation of insulating discharge products and unfavorable byproducts. Herein we report a novel soluble catalyst of bifunctional imidazolyl iodide salt additive, 1,3-dimethylimidazolium iodide (DMII), to successfully construct highly efficient and durable Li-O2 batteries. The anion I- can effectively promote the charge transport of Li2O2 and accelerate the redox kinetics of oxygen reduction/oxygen evolution reactions on the cathode side, thereby significantly decreasing the charge/discharge overpotential. Simultaneously, the cation DMI+ forms an ultrathin stably solid-electrolyte interphase film on Li metal, greatly inhibiting the shuttle effect of I- and improving the stability of anode. Using this DMII additive, our Li-O2 batteries achieve an extremely low voltage of 0.52 V and ultra-long cycling stability over 960 h. Notably, up to 95.8 % of the Li2O2 yield further proves the reversible generation/decomposition of Li2O2 without the occurrence of side reactions. Both experimental and theoretical results disclose that DMII enables Li+ easily solvated, testifying the dominance of the solution-induced reaction mechanism. This work provides the possibility to design the soluble catalysts towards high-performance Li-O2 batteries.

Phase‐Transfer Catalyst for Lithium‐Oxygen Batteries Based on Bidirectional Coordination Catalysis: 2‐Aminopyridine

AbstractLi‐O2 batteries are considered promising candidates for next generation high energy storage systems due to their exceptionally theoretical energy density. However, the accumulation of insulating discharge product Li2O2 leads to severe cathode passivation, reduced conductivity, and hindered charge transfer, which seriously compromise the battery performance. This work proposes a novel phase‐transfer catalyst with bidirectional coordination functionality, 2‐aminopyridine (AP). The AP molecule contains a nucleophilic pyridine nitrogen and an electrophilic amino hydrogen, which can interact with Li+ and reactive oxygen intermediates through electrostatic attraction and hydrogen bonding, respectively. This dual interaction facilitates the liquid‐phase deposition of Li2O2 while enabling efficient product decomposition. The uneven electrostatic potential distribution within the AP molecule generates an internal electric field that stabilizes reduced oxygen species, shields against nucleophilic attacks, and suppresses Li+ deposition at the anode tips, effectively preventing lithium dendrite growth. Therefore, Li‐O2 batteries with AP exhibit an exceptionally high discharge capacity of 36419 mAh g−1, a significantly reduced charge over‐potential of 0.29 V, and an extended cycle life exceeding 2256 h. Through functional molecular structure design, the bidirectional coordination catalytic effect demonstrated by AP molecules effectively regulates the migration and interaction of substances during reactions, significantly improves the electrochemical performance of Li‐O2 batteries.

Targeted anchoring of Cu sites in imine-based covalent organic frameworks as catalytic centers for efficient Li-CO2 battery

The lithium-carbon dioxide (Li-CO2) batteries have attracted much attention due to their high theoretical energy density and reversible CO2 reduction/precipitation process. However, the wide bandgap insulating discharge product Li2CO3 is...

Sluggish Li2O2 dissolution - a key to unlock high-capacity lithium-oxygen batteries.

While lithium-oxygen batteries have a high theoretical specific energy, the practical discharge capacity is much lower due to the passivation of the solid discharge product, Li2O2, on the electrode surface. Herein, we studied and quantified the deposition and dissolution kinetics of Li2O2 using an electrochemical quartz crystal microbalance (EQCM). It is found that the orientation of the electrode greatly influences the formation path and deposition amount of Li2O2. We identified two distinct dissolution modes: surface dissolution and bulk fragmentation, with the latter 100 times faster than the former. By revealing the underlying factors affecting dissolution, 80% of Li2O2 can dissolve within 3 minutes when a desorption potential of 2.9 V is applied. Consequently, we designed an intermittent-desorption discharge strategy, which increased the discharge capacity by an order of magnitude. This work shows that high practical specific energy of Li-O2 batteries can be achieved once problems of Li2O2 dissolution are addressed.

Optimization of mill discharge product fraction composition to enhance production indices: A semi-theoretical formula for ball diameters

Optimization of mill discharge product fraction composition to enhance production indices: A semi-theoretical formula for ball diameters

Multifunctional Quasi‐Homogeneous Catalysts as a New Catalytic Strategy to Boost the Performance of Li‐O2 Batteries

AbstractLi‐O2 batteries have been considered as a kind of prospective next‐generation batteries due to their ultrahigh energy densities. However, limited capacities, high charge overpotentials, and short lifetime are troubling obstacles for realizing their real‐world implementation. Common strategies, including introducing solid‐state catalysts (SSCs) and redox mediators (RMs), are insufficient to solve these issues. Herein, Ru‐loaded amino‐phenanthroline‐based carbonized polymer dots (RuApCPDs) integrating the catalytic activity of SSCs with the mobility of RMs have been designed to behave as quasi‐homogeneous catalysts in the electrolyte. Their mobile nature can ensure the avoidance of complete coverage of active sites, and the catalytic ability decreases the charge overpotential through co‐deposition with the discharge products. Additionally, the RuApCPDs can also adjust the Li+ solvation structure and well protect the Li metal anodes with high stability. As a result, the introduction of RuApCPDs leads to a fivefold increase in discharge capacity, a low charge voltage of 3.75 V, and a running life of 168 cycles (79 cycles without RuApCPDs). The multifunctional quasi‐homogeneous catalyst developed here demonstrates its advantageous potential as a new catalytic strategy for bringing Li‐O2 batteries to become a viable technology.

Machine Learning Driven Optimization of Electrolyte for Highly Reversible Zn-Air Batteries with Superior Long-Term Cycling Performance.

Aqueous alkaline Zn-air batteries (ZABs) have garnered widespread attention due to their high energy density and safety, however, the poor electrochemical reversibility of Zn and low battery round-trip efficiency strongly limit their further development. The manipulation of an intricate microscopic balance among anode/electrolyte/cathode, to enhance the performance of ZABs, critically relies on the formula of electrolytes. Herein, the Bayesian optimization approach is employed to achieve the effective design of optimal compositions of multicomponent electrolytes, resulting in the remarkable enhancement of ZAB performance. Notably, ethylene glycol has been successfully employed as both electrolyte additive and fuel, playing key roles in changing the reaction pathways of ZABs, especially the storage form of discharge products from ZnO deposition on the anode to Zn2+-based hybrid particle colloids in the electrolyte. As a result, the as-obtained novel ZABs can deliver superior battery reversibility and stability (1700 h at 2 mA cm-2 and 1400 h at 20 mA cm-2), greatly improved round-trip efficiency as high as 76.3%, and even continuous discharge until complete Zn anode depletion. This work has demonstrated enormous potential for long-term energy storage applications and holds promise for bringing new opportunities to the development of ZABs.

Zn and Cl Coregulated MXene Catalyst Enhances Li-CO2 Battery Reversibility.

MXenes are promising cathodes for Li-CO2 batteries owing to their high electrical conductivity and efficient CO2 activation function. However, the effects of adsorption and electronic structures of MXene on the full life cycle of Li-CO2 batteries have been rarely investigated. Here, we employ a coregulation approach to enhance the adsorption-decomposition of lithium carbonate (Li2CO3) by introducing Zn and Cl surface groups onto the Ti3C2 MXene (Zn-Ti3C2Cl2) catalyst. The incorporation of Cl surface groups enhances Li2CO3 adsorption on the MXene catalyst surface, resulting in the formation of small-sized and uniform Li2CO3. Additionally, the introduction of Zn shifts the d-band centers of titanium and promotes CO2 evolution reaction (CO2ER) activity, thereby facilitating the decomposition of discharge products. As a result, the Li-CO2 battery based on the Zn-Ti3C2Cl2 catalyst exhibits an ultralow overpotential (0.72 V) at 200 mA g-1 and stable cycling for up to 1500 h. This work validates the efficacy of promoting reversibility in Li-CO2 batteries by adjusting the adsorption-decomposition process.

Development of a Sealed Rechargeable Li-SO2 Battery.

Rechargeable Li-SO2 batteries offer low-cost, high-energy density benefits and can leverage manufacturing processes for the existing primary version at a commercial scale. However, they have so far only been demonstrated in an "open-system" with continuous gas supply, preventing practical application. Here, the utilization and reversibility of SO2 along with the lithium stability are addressed, all essential for long-life, high-energy batteries. The study discovers that high SO2 utilization is achievable only from SO2 dissolved in electrolytes between the lithium anode and carbon cathode. This results from a unique osmosis phenomenon where SO2 consumption increases salt concentration, driving the influx of organic solvents rather than SO2 from outside the current path. This insight leads to configure a bobbin-cell with all electrolytes between the electrodes, realizing nearly 70% of SO2 utilization, >12x greater than in conventional coin cells. To improve reaction rate and SO2 reversibility, triphenylamine is employed to the electrolyte, creating an electron-rich environment that alleviates the disproportionation of discharge products. Incorporating this additive into a bobbin-cell with a lithium protective layer yields a cell with a projected energy density exceeding 183.2Wh kg-1. The work highlights the potential of Li-SO2 batteries as affordable, sustainable energy storage options.

A Review on Minimization of Polysulfide Shuttle Effect of Lithium–Sulfur Batteries by Using Low‐Dimensional Carbon Composite as the Sulfur Cathode

Owing to the high specific energy density in theories, abundance of resources, and adherence to environmental standards, rechargeable lithium–sulfur batteries (LSB) have drawn an increasing amount of interest. However, the weak conductivity of the sulfur and discharge products, the drastic breakdown and migration of the intermediates of lithium polysulfide (LiPSs) leading to shuttle effect, and the enormous volumetric change of sulfur particles upon cycle substantially hinder their practical uses. Due to the considerable capacity diminishing caused by the shuttle impact corrosion of the lithium metal, LSBs are thought to have significant commercial application challenges. Engineering nanomaterials’ surface structures can increase the affinity between the cathode with the LiPSs while also enabling the redox kinetics of the LiPSs, which results in a low level of LiPSs in the electrolyte that can restrict the shuttle effect. Sulfur and carbon materials, when combined, effectively increase the efficiency of active materials, increase the conductive properties of cathode components, and serve as a barrier against polysulfides. In this review, a thorough analysis is provided on low‐dimensional carbon materials as cathode, by which the electrode modification technique for limiting the shuttle effect of polysulfide in LSBs and forecast future research trends on the same.

Pt-Doped Co3O4 Nanowires as High-Efficiency Cathodic Catalysts for Improved Lithium-Oxygen Batteries and Insights into The Electrochemical Reaction Pathway

Lithium-oxygen batteries (LOBs) have garnered considerable interest as promising energy storage solutions owing to their exceptional theoretical energy density. Nevertheless, their practical implementation is impeded by notable obstacles, involving suboptimal energy efficiency, excessive overpotential and limited cycle life. Tricobalt tetra-oxide (Co3O4) is a promising cathodic bifunctional catalyst for LOBs. With deliberate alien-atom doping, their catalytic performance can even be further improved due to the resulted structural adjustment. In this work, platinum-doped cobalt oxide nanowires have been hydrothermally synthesized on the acid-treated carbon paper substrates. These nanowires, with a thickness of about 150 nm and a length of approximately 1.5 μm, are closely stacked and display an urchin-like morphology. As employed as the cathode for the LOBs, an excellent performance is delivered, including a discharge capacity of 17079.4 mAh g−1, an overpotential of 0.88 V, a cycle stability of over 75 cycles, and an initial coulombic efficiency of 95.71%, which is superior to the batteries based on pure Co3O4 nanowires. Combined with the results of density functional theory (DFT) calculations, it can be deduced from the experimental observation that the nanowires’ adsorption affinity toward the discharge/charge intermediates of lithium superoxide (LiO2), as well as the morphologies and formation/decomposition pathways of the discharge products, are all governed by Pt-doping. The Pt-doping-improved adsorption induces a transition of the discharge products from the solution-pathway grown flake-like morphologies which are randomly stacked in the voids between pure Co3O4 nanowires to the surface-pathway grown film-like morphologies which are tightly wrapped around the Pt-doped Co3O4 nanowires. The close contact between the film-like discharge products and the Pt-doped Co3O4 nanowires is facile for fast oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, hence the lowered overpotential and enlengthened cycle durability of the batteries. Furthermore, the increased amount of the film-like discharge products results in the enhancement of the capacity of the batteries. This work may shed light on approaches for boosting the electrochemical performance of the transition-metal-oxide-based LOBs through the strategy of alien-atom doping.

Engineering and construction of multi-functional Janus separator for high-stability Li-CO2 battery.

Due to the high theoretical energy density, lithium-carbon dioxide (Li-CO2) batteries provide unique advantages when using CO2 to generate electricity. However, the issues with lithium dendrite generated by uneven deposition and quick cathode passivation continue to impede the development of Li-CO2 batteries. In this work, a Janus separator with dual functionalities is created using an in-situ growth and hydrothermal technique. It can be used to expand the cathode to alleviate the quick passivation of the cathode, in addition to inhibiting the growth of lithium dendrite. On the one hand, as an ion transport framework, Prussian blue (PB) nanocubes formed in-situ on the anode side can control the uniform transport of Li-ions and prevent the proliferation of lithium dendrites. The Prussian blue and reduced graphene oxide composite material (PB-rGO) on the cathode side, on the other hand, can be employed as an extension of the cathode, which not only contains more discharge products but also encourages their decomposition, playing a self-cleaning role. Moreover, the Li||Li symmetrical battery with Janus separator exhibits a steady cycle life of more than 1700h. Also, when applied to a Li-CO2 battery, it demonstrates an extremely high discharge capacity of 12100mAh g-1 and an exceptionally long cycle life of 3144h.