Mesoscale Elucidation of Surface Passivation in the Li–Sulfur Battery Cathode

The cathode surface passivation caused by Li₂S precipitation adversely affects the performance of lithium–sulfur (Li–S) batteries. Li₂S precipitation is a complicated mesoscale process involving adsorption, desorption and diffusion kinetics, which are affected profoundly by the reactant concentration and operating temperature. In this work, a mesoscale interfacial model is presented to study the growth of Li₂S film on carbon cathode surface. Li₂S film growth experiences nucleation, isolated Li₂S island growth and island coalescence. The slow adsorption rate at small S^2– concentration inhibits the formation of nucleation seeds and the lateral growth of Li₂S islands, which deters surface passivation. An appropriate operating temperature, especially in the medium-to-high temperature range, can also defer surface passivation. Fewer Li₂S nucleation seeds form in such an operating temperature range, thereby facilitating heterogeneous growth and potentially inhibiting the lateral growth of the Li₂S film, which may ultimately result in reduced surface passivation. The high specific surface area of the cathode microstructure is expected to mitigate the surface passivation

Theoretical Evaluation of MBenes as Catalysts for the CO₂ Reduction Reaction

Electrochemical reduction of carbon dioxide (CO2) to high-value-added products is a promising strategy for mitigating the greenhouse effect and energy shortage. Designing a high-performance electrocatalyst with a low limit potential and tunable reaction path is a critical challenge for CO2 reduction. Two-dimensional (2D) nanostructured materials are considered as competitive catalysts for electrochemical reduction due to their large specific surface area and rich active sites. The current work theoretically evaluates four 2D MBene nanosheets as potential catalysts for CO2 reduction. It is found that Mo2B2 and Cr2B2 show good catalytic selectivity due to their poor hydrogen evolution reaction (HER) performance and low limit potential for CO2 reduction. We found that the Gibbs energy increase for CHO formation is the highest on all MBenes. Among them, Mo2B2 and Cr2B2 maintain a lower limit potential with values of −0.45 and −0.5 eV, respectively. The electronic structure analysis demonstrates that the electron migration from MBene substrates to the antibonding states of adsorbates can lower the Gibbs free energy of hydrogenation reactions of intermediate products

Revealing Charge Transport Mechanisms in Li₂S₂ for Li–Sulfur Batteries

Besides lithium sulfide (Li₂S), lithium persulfide (Li₂S₂) is another solid discharge product in lithium–sulfur (Li–S) batteries. Revealing the charge transport mechanism in the discharge products is important for developing an effective strategy to improve the performance of Li–S batteries. Li₂S₂ cannot transport free electrons due to its wide bandgap between the valence band maximum (VBM) and conduction band minimum (CBM). However, electron polarons (<i>p</i>^<i>–</i>) and hole polarons (<i>p</i>^<i>+</i>) can appear in solid Li₂S₂ due to the unique molecular orbital structure of the S₂^2– anion. The thermodynamic and kinetic properties of native defects are investigated. It is found that negatively charged Li vacancies (V_Li^–) and <i>p</i>^<i>+</i> are the main native defects with a low formation energy of 0.77 eV. The predominant charge carrier is <i>p</i>^<i>+</i> because <i>p</i>^<i>+</i> has a high mobility. The electronic conductivity related to <i>p</i>^<i>+</i> diffusion is dependent on temperature, and high temperatures are preferred to increase the conductivity

Mesoscale Understanding of Lithium Electrodeposition for Intercalation Electrodes

Stringent performance and operational requirements in electric vehicles can push lithium-ion batteries toward unsafe conditions. Electroplating and possible dendritic growth are a cause for safety concern as well as performance deterioration in such intercalation chemistry-based energy storage systems. There is a need for better understanding of the morphology evolution because of electrodeposition of lithium on the graphite anode surface and the interplay between material properties and operating conditions. In this work, a mesoscale analysis of the underlying multimodal interactions is presented to study the evolution of morphology due to lithium deposition on typical graphite electrode surfaces. It is found that electrodeposition is a complex interplay between the rate of reduction of Li ions and the intercalation of Li in the graphite anodes. The morphology of the electrodeposited film changes from dendritic to mossy structures because of the surface diffusion of lithium on the electrodeposited film

Theoretically Evaluating Two-Dimensional Tetragonal Si₂Se₂ and SiSe₂ Nanosheets as Cathode Catalysts for Alkali Metal–O₂ Batteries

Nonaqueous alkali metal (AM)–O2 batteries are promising next-generation energy storage devices due to their outstanding specific capacity and energy density. However, the high charge–discharge overpotential and slow electrochemical reactions limit their development. Highly active cathode catalysts can solve this problem. Based on first-principles calculations, we theoretically explore the application potential of Si2Se2 and SiSe2 nanosheets as potential cathode electrocatalysts. Different electrochemical reduction paths are proposed for understanding the discharge process. For example, for Li–O2 battery, the main products on the electrocatalyst surface are LiO2 and Li2O2, and the charge/discharge overpotential of SiSe2 is less than 0.46 V. The main products are NaO2 and Na2O2 for Na–O2 battery, and the charge/discharge overpotentials are less than 0.73 V. There is only one catalytic product of K–O2 battery, which is KO2. Specially, the charge/discharge overpotential of Si2Se2 is significantly low, only 0.31 V for K–O2 battery. In addition, we found that neither Si2Se2 nor SiSe2 promoted the formation of the side product Li2CO3/Na2CO3 or caused the decomposition of the dimethyl sulfoxide electrolyte, suggesting that Si2Se2 and SiSe2 can effectively improve the reversible cycle life of AM–O2 batteries

Table_1_Coevolutionary analysis of the Philopteroides Mey, 2004 (Phthiraptera: Ischnocera) parasitizing bulbuls (Passeriformes: Pycnonotidae).docx

IntroductionAvian head lice comprise a diverse group of distantly related genera of lice that exhibit a strongly convergent morphology. Due to their lack of free-living stages, their strong morphological adaptations to living on the host’s head, and the limited opportunities for transfer between hosts during mating or nesting, the lateral transmission of head lice between non-conspecific hosts may be presumed to be restricted. Despite this, many species of head lice are ostensibly host generalists. We here examine lice of the head louse genus Philopteroides Mey, 2004, from bulbuls (Passeriformes: Pycnonotidae).MethodsWe use two different methods, ParaFit and Jane, to get insights on the co-evolutionary history of Philopteroides species and their bulbul hosts. Jane was run with a variation of event costs.ResultsOur phylogenetic analysis indicate that several morphologically cryptic species can be found in this group, most of which appear to be host specific. However, co-phylogenetic analyses indicate that host-switching has been common in the history of these lice, and co-speciation events have been rarer than expected. Moreover, lowest-cost co-evolutionary reconstructions under a variety of event costs are indistinguishable from random. An expanded dataset with more Philopterus-complex lice was found to be evenly balanced between host-switching and co-speciation events.DiscussionThe transfer of avian head lice between host species is poorly understood, but evidently fairly common. Several potential routes are discussed, but direct evidence is missing. Potentially, the presence of multiple bulbul species at fruiting trees may be an important factor in this transfer. However, such transfer routes also do not explain why Philopteroides lice on bulbuls appear to be distinct from those of other hosts. Moreover, as many of the species recovered in our analysis are morphologically indistinguishable, cryptic speciation appears to be common in this group.</p

Unraveling TM Migration Mechanisms in LiNi_1/3Mn_1/3Co_1/3O₂ by Modeling and Experimental Studies

Electrochemical cycling induces transition-metal (TM) ion migration and oxygen vacancy formation in layered transition-metal oxides, thus causing performance decay. Here, a combination of ab initio calculations and atomic level imaging is used to explore the TM migration mechanisms in LiNi1/3Mn1/3Co1/3O2 (NMC333). For the bulk model, TM/Li exchange is an favorable energy pathway for TM migration. For the surface region with the presence of oxygen vacancies, TM condensation via substitution of Li vacancies (TMsub) deciphers the frequently observed TM segregation phenomena in the surface region. Ni migrates much more easily in both the bulk and surface regions, highlighting the critical role of Ni in stabilizing layered cathodes. Moreover, once TM ions migrate to the Li layer, it is easier for TM ions to diffuse and form a TM-enriched surface layer. The present study provides vital insights into the potential paths to tailor layered cathodes with a high structural stability and superior performance

Revealing the Reaction Mechanism of Sodium Selenide Confined within a Single-Walled Carbon Nanotube: Implications for Na–Se Batteries

The sodium–selenium (Na–Se) battery is a competitive candidate as the practical next-generation energy storage device. A Na16Se8 cluster confined within a (10, 10) single-walled carbon nanotube is constructed to reveal the nanoconfinement effect on the reaction mechanism of the Na–Se battery cathode. It is found that the nanoconfinement can enhance the electronic conductivity of Nax≥12Se8 nanostructures because itinerant electrons appear under this condition. During desodiation, polyselenide chains grow longer and the intermediate products become insulators for transferring electrons. However, hole polarons have the potential to act as charge carriers in Nax≤10Se8 nanostructures. The open-circuit voltage profile is plotted, and the voltage window is 1.67 ≤ U ≤ 1 V. After the first charge cycle, the cathode cannot discharge to Na16Se8, but the reversible specific capacity can still arrive at 302 mA h/g of the cathode composite

Resist-Dyed Textile Alkaline Zn Microbatteries with Significantly Suppressed Zn Dendrite Growth

The progress of electronic textiles relies on the development of sustainable power sources without much sacrifice of convenience and comfort of fabrics. Herein, we present a rechargeable textile alkaline Zn microbattery (micro-AZB) fabricated by a process analogous to traditional resist-dyeing techniques. Conductive patterned electrodes are realized first by resist-aided electroless/electrodeposition of Ni/Cu films. The resulting coplanar micro-AZB in a single textile, with an electroplated Zn anode and a Ni0.7Co0.3OOH cathode, achieves high energy density (256.2 Wh kg–1), high power density (10.3 kW kg–1), and stable cycling performances (82.7% for 1500 cycles). The solid-state micro-AZB also shows excellent mechanical reliability (bending, twisting, tailoring, etc.). The improved reversibility and cyclability of textile Zn electrodes over conventional Zn foils are found to be due to the significantly inhibited Zn dendrite growth and suppressed undesirable side reactions. This work provides a new approach for energy-storage textile with high rechargeability, high safety, and aesthetic design versatility