Advanced Materials for Rechargeable Lithium-Sulfur Batteries

Rechargeable batteries are essential power supplies for our daily life, and they are widely used in portable electronics, hybrid electric vehicles, and grid energy storage. Lithium-ion (Li-ion) batteries, which have the highest energy density among rechargeable batteries, have reached the capacity limits of current electrode materials, such as transition metal oxides (e.g., LiCoO2, LiMn2O4, and LiFePO4). To meet the increasing demand of high energy density batteries, rechargeable lithium-sulfur (Li-S) batteries are considered as one of the most promising systems with significant potential for many practical applications. Sulfur has a theoretical capacity of 1,672 mAh/g by taking two electrons per atom, which is an order of magnitude higher than those of transition metal oxides. However, several challenges impede practical application of Li-S batteries, such as high resistivity of sulfur, dissolution of intermediate polysulfides, and shuttle of these polysulfides from cathode to anode in Li-S batteries. Significant improvements have been achieved over the past years, but further improvements and better understanding of Li-S batteries are still needed. This poster will present several strategies that have been developed including sulfur-conductive polymer nanocomposites, lithium/dissolved polysulfide cells, sandwiched Li2S electrodes, and in situ formed Li2S cathodes. A nanolayer of conductive polypyrrole was fabricated on sulfur particles, which can enhance electrical conductivity and reduce dissolution of polysulfides. Binder-free carbon nanotube current collector was used in lithium/dissolved polysulfide cells, which exhibit unprecedented capaciteis of 1,600 mAh/g in the first cycle and over 1,400 mAh/g after 50 cycles. Lithium metal anode is used in current Li-S batteries since the sulfur cathodes do not have any lithium in the initial stage, which is a safety hazard. Lithium-rich sulfur cathode materials such as Li2S can allow a variety of non-lithium metal anodes to be used, which can advance the Li-S battery technology to an unprecedented level. However, the high reactivity of Li2S results in limited approaches that have been explored. A sandwiched Li2S electrode consisting of two layers of carbon nanotube paper has been developed which shows high capacities and high rate capabilities. In addition, a novel in situ formed Li2S cathode is developed, which utilizes lithiated graphite as a lithium donor to convert lithium polysulfide Li2S6 to the end discharge product Li2S. These materials and strategies are promising for practical applications

A Rechargeable Lithium Battery with Li2O2 Cathode in Closed Systems

poster abstractLi-O2 batteries have one of the highest theoretical specific energy of 3,458 Wh/kg when the weight of the primary discharge product, i.e., Li2O2, is considered. Thus, this BIL (Beyond Lithium Ion) battery technology, if made practical, will find extensive usage especially in the successful electrification of vehicles. However, there are many challenges. Current Li-O2 batteries demonstrated in labs have been limited to “open systems”, i.e., batteries that have a porous carbon cathode that “breathes” pure oxygen. The limitations of these systems are the requirement of pure oxygen. In addition, the consensus among researchers on specific capacity (mAh/g) calculations based on active materials is lacking because extra oxygen is continuously supplied to cells upon cycling. One solution to these limitations is the use of closed systems, i.e., storage and reuse of O2 within the cell. Recently, our group has demonstrated a closed and rechargeable lithium battery with Li2O2 cathode for the first time. This platform is unique as it shows, for the first time in literature, capacites and rate capability based on mass of Li2O2. The cell shows a close-to-theoretical capacity over 18 cycles and shows 50 cycles when the charge capacity is limited to 50% of theoretical. It allows other studies on the stability of electrolyte, electrode kinetics, and oxygen storage materials. This system can eleminate the issues of open systems such as impurities oxygen gas and evaporation of electrolyte. Unstable electrolytes are a major bottleneck in Li-O2 batteries. Such a system provides a suitable medium to optimize electrolytes and other cell components

I-WAS: a Data Augmentation Method with GPT-2 for Simile Detection

Simile detection is a valuable task for many natural language processing (NLP)-based applications, particularly in the field of literature. However, existing research on simile detection often relies on corpora that are limited in size and do not adequately represent the full range of simile forms. To address this issue, we propose a simile data augmentation method based on \textbf{W}ord replacement And Sentence completion using the GPT-2 language model. Our iterative process called I-WAS, is designed to improve the quality of the augmented sentences. To better evaluate the performance of our method in real-world applications, we have compiled a corpus containing a more diverse set of simile forms for experimentation. Our experimental results demonstrate the effectiveness of our proposed data augmentation method for simile detection.Comment: 15 pages, 1 figur

A Graphite-Polysulfide Full Cell with DME-Based Electrolyte

Over the last decade, vast improvements have been made in the field of lithium-sulfur batteries bringing it a step closer to reality. In this field of research, deep understanding of the polysulfide shuttle phenomenon and their affinity with carbons, polymers and other hosts have enabled the design of superior cathodes with prolonged life. However, the anode side has undergone comparatively less transformation. In this work, we have developed a new electrolyte based on 1,2-dimethoxyethane (DME) solvent that enables reversible intercalation of lithium ions in graphite. A novel method to introduce solid lithium polysulfide into a carbon current collector as the cathode has been demonstrated and the electrode shows stable cycling with the new electrolyte. A full cell consisting of a lithiated graphitic anode and lithium polysulfide cathode is constructed, which exhibits an initial capacity as high as 1,500 mAh g−1 (based on the sulfur in the cathode) and a reversible capacity of 700 mAh g−1 for 100 cycles. This full cell is capable of delivering over 460 mAh g−1 at rates as high as 2C. The cell degradation over prolonged cycles could be due to the polysulfide shuttle which results in instability of the SEI layer on the graphitic anode

Geometric and Electrochemical Characteristics of NMC Electrodes with Different Calendering Conditions

poster abstractThe energy and power capabilities of Li ion batteries (LIBs) have been considered critical factors to determine the commercial values of the LIB powered applications. Many efforts have been done to improve the energy density and rate capability of LIBs. In addition to intrinsic material properties of anode and cathode active materials, the structure of electrode at micro and nano scales also plays a critical role in determining the energy density and rate capability of a LIB [1-3]. Calendering is a process in battery manufacturing to lower the porosity of the electrode and increase electrical contact. Increased calendering can increase the packing density of active materials in LIB electrodes, thereby increasing the volumetric energy density. The specific energy density is also increased by calendering via decreasing the percentage of inactive materials, such as current collector and separator. However, higher fraction of active materials in LIB electrodes can change electrodes’ structural properties significantly, such as porosity, specific surface area, pore size distribution and tortuosity [4]. To this end, there are few reports on the geometric characteristics and their impact on the electrochemical performance of LIB electrodes with different calendering conditions due to the inhomogeneity, complexity, and three-dimensional (3D) nature of the electrode’s microstructure [5-6]. Recently, porous electrode microstructures have been reconstructed by advanced tomography techniques such as X-ray nano-computed tomography (nano-CT) and focused ion beam scanning electron microscope (FIB-SEM)[7-8]. The reconstructed microstructures have been employed to investigate the geometric characteristics and spatial inhomogeneity of porous electrodes. In this study, we investigated real 3D Li[Ni1/3Mn1/3Co1/3]O2 (NMC) electrode microstructures under different calendering conditions and the effect of calendering on the performance of LIBs[4]. To investigate geometric characteristics of porous microstructures, cathode electrodes were fabricated from a 94:3:3 (weight %) mixture of NMC, PVDF, and super-P carbon black. To change the calendering condition, initial thickness of the electrodes was set 50μm, 80um, 90um, 100um. Then all electrodes were pressed down to 50 μm by using a rolling press machine. A synchrotron X-ray nano-CT at the Advanced Photon Source of Argonne National Lab was employed to obtain morphological data of the electrodes, with voxel size of 58.2 × 58.2 × 58.2 nm3. The morphology data sets were quantitatively analyzed to characterize their geometric properties. The geometric analysis showed that high packing density can result in smaller pore size and more uniform pore size distribution. The specific surface area and tortuosity of different electrodes will be reported. The charge/discharge experiments were also conducted for these electrodes. The geometric properties and cell testing results will be analyzed and reported

The unique chemistry of thiuram polysulfides enables energy dense lithium batteries

Organosulfur compounds are cheap and abundant cathode materials that can offer high specific energies. Herein, we explore for the first time, the common vulcanization accelerators viz. thiuram polysulfides embedded in carbon nanotubes as binder-free cathodes in lithium batteries that show 3 highly reversible redox reactions (3 discharge plateaus) and high material utilization (up to 97%). We use electrochemical characterization techniques, first-principles calculations, XPS, XRD, FTIR, and SEM to gain insight into the chemical transformations occurring during battery cycling. We identify that the mesomeric form of lithium pentamethylene dithiocarbamate with a positive nitrogen center, formed in the discharge, can act as polysulfide and sulfide anchors through strong coulombic interactions thus enabling a capacity retention of 87% after 100 cycles at C/5 rate. A high loading cathode with an areal capacity of 5.3 mA h cm−2 tested under a low electrolyte to active material ratio of 3 μL mg−1 yields an active material specific energy of 1156 W h kg−1 thus demonstrating the potential of this class of compounds in high specific energy lithium batteries

Sudowoodo: a Chinese Lyric Imitation System with Source Lyrics

Lyrics generation is a well-known application in natural language generation research, with several previous studies focusing on generating accurate lyrics using precise control such as keywords, rhymes, etc. However, lyrics imitation, which involves writing new lyrics by imitating the style and content of the source lyrics, remains a challenging task due to the lack of a parallel corpus. In this paper, we introduce \textbf{\textit{Sudowoodo}}, a Chinese lyrics imitation system that can generate new lyrics based on the text of source lyrics. To address the issue of lacking a parallel training corpus for lyrics imitation, we propose a novel framework to construct a parallel corpus based on a keyword-based lyrics model from source lyrics. Then the pairs \textit{(new lyrics, source lyrics)} are used to train the lyrics imitation model. During the inference process, we utilize a post-processing module to filter and rank the generated lyrics, selecting the highest-quality ones. We incorporated audio information and aligned the lyrics with the audio to form the songs as a bonus. The human evaluation results show that our framework can perform better lyric imitation. Meanwhile, the \textit{Sudowoodo} system and demo video of the system is available at \href{https://Sudowoodo.apps-hp.danlu.netease.com/}{Sudowoodo} and \href{https://youtu.be/u5BBT_j1L5M}{https://youtu.be/u5BBT\_j1L5M}.Comment: 7 pages,3 figures, submit to emnlp 2023 demo trac

Analysis of four achaete-scute homologs in Bombyx mori reveals new viewpoints of the evolution and functions of this gene family

<p>Abstract</p> <p>Background</p> <p><it>achaete-scute </it>complexe (<it>AS-C</it>) has been widely studied at genetic, developmental and evolutional levels. Genes of this family encode proteins containing a highly conserved bHLH domain, which take part in the regulation of the development of central nervous system and peripheral nervous system. Many <it>AS-C </it>homologs have been isolated from various vertebrates and invertebrates. Also, <it>AS-C </it>genes are duplicated during the evolution of Diptera. Functions besides neural development controlling have also been found in <it>Drosophila AS-C </it>genes.</p> <p>Results</p> <p>We cloned four <it>achaete-scute </it>homologs (<it>ASH</it>) from the lepidopteran model organism <it>Bombyx mori</it>, including three proneural genes and one neural precursor gene. Proteins encoded by them contained the characteristic bHLH domain and the three proneural ones were also found to have the C-terminal conserved motif. These genes regulated promoter activity through the Class A E-boxes <it>in vitro</it>. Though both <it>Bm-ASH </it>and <it>Drosophila AS-C </it>have four members, they are not in one by one corresponding relationships. Results of RT-PCR and real-time PCR showed that <it>Bm-ASH </it>genes were expressed in different larval tissues, and had well-regulated expressional profiles during the development of embryo and wing/wing disc.</p> <p>Conclusion</p> <p>There are four <it>achaete-scute </it>homologs in <it>Bombyx mori</it>, the second insect having four <it>AS-C </it>genes so far, and these genes have multiple functions in silkworm life cycle. <it>AS-C </it>gene duplication in insects occurs after or parallel to, but not before the taxonomic order formation during evolution.</p