RESUMEN
During the continuous charge and discharge process in lithium-sulfur batteries, one of the next-generation batteries, polysulfides are generated in the battery's electrolyte, and impact its performance in terms of power and capacity by involving the process. The amount of polysulfides in the electrolyte could be estimated by the change of the Gibbs free energy of the electrolyte, [Formula: see text] in the presence of polysulfide. However, obtaining [Formula: see text] of the diverse mixtures of components in the electrolyte is a complex and expensive task that shows itself as a bottleneck in optimization of electrolytes. In this work, we present a machine-learning approach for predicting [Formula: see text] of electrolytes. The proposed architecture utilizes (1) an attention-based model (Attentive FP), a contrastive learning model (MolCLR) or morgan fingerprints to represent chemical components, and (2) transformers to account for the interactions between chemicals in the electrolyte. This architecture was not only capable of predicting electrolyte properties, including those of chemicals not used during training, but also providing insights into chemical interactions within electrolytes. It revealed that interactions with other chemicals relate to the logP and molecular weight of the chemicals.
RESUMEN
Lithium-Sulfur (Li-S) batteries are one of the most promising next-generation batteries due to their ultrahigh energy density up to 500 W h kg-1. However, despite the steady progress during the last several decades, there have been significant challenges for practical applications and commercialization. One of the major issues is controlling the lithium polysulfide (LiPS) shuttling process, which causes premature cell failure. To better understand the mechanism of the LiPS shuttling chemistry, a qualitative and quantitative analysis on polysulfide species in Li-S cell has profound significance for realizing highly efficient sulfur electrochemistry. Here we report a qualitative determination of the derivatized polysulfides in the electrolyte of a custom-made Li-S pouch cell with a high-resolution liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry method for the first time. The ionization efficiency of the methylated polysulfides was affected by the tune parameters such as the corona discharge current, the vaporizer temperature, and the source capillary temperature. It was found that the source capillary temperature was the dominant parameter to increase the peak intensity of CH3S7- ion, which was the smallest peak in the spectrum. An unusual and unique ionization pattern for methylated polysulfides detected in atmospheric pressure chemical ionization negative mode was elucidated by using first-principles calculations.
RESUMEN
LiMn2O4 (LMO) spinel cathode materials suffer from severe degradation at elevated temperatures because of Mn dissolution. In this research, monobasic sodium phosphate (NaH2PO4, P2) is examined as an electrolyte additive to mitigate Mn dissolution; thus, the thermal stability of the LMO cathode material is improved. The P2 additive considerably improves the cyclability and storage performances of LMO/graphite and LMO/LMO symmetric cells at 60 °C. We explain that P2 suppresses the hydrofluoric acid content in the electrolyte and forms a protective cathode electrolyte interphase layer, which mitigates the Mn dissolution behavior of the LMO cathode material. Considering its beneficial role, the P2 additive is a useful additive for spinel LMO cathodes that suffer from severe Mn dissolution.
RESUMEN
Silicon (Si) is one of the most attractive anode materials for lithium secondary batteries because of its large theoretical capacity, high safety, low cost and environmental benignity. However, Si-based anode material needs to overcome the structural change of the solid-electrolyte interphase due to the large volume change during cycling. To resolve these problems of composites by exploiting the superior conductivity, large specific surface area and flexibility of graphene, we have synthesized reduced graphene oxide (rGO)/Si composite electrode via a simple dip-coating method. Nickel foam is used as a current collector and template for the electrode fabrication. At 0.03 wt%, Si concentration, the rGO/Si composite anode presented the excellent cycle performance with large reversible capacity (778 mAh g-1 after 100 cycles). The characteristics of the rGO/Si composites were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman and X-ray photoelectron spectroscopy (XPS). The improved anode performance of the rGO/Si composite anode is ascribed to the rGO serving as a buffer layer, thereby preventing the volume expansion of Si nanoparticles, and provide facile electron pathways.
RESUMEN
Despite two decades of commercial history, it remains very difficult to simultaneously achieve both high rate capability and thermal stability in the graphite anodes of Li-ion batteries because the stable solid electrolyte interphase (SEI) layer, which is essential for thermal stability, impedes facile Li(+) ion transport at the interface. Here, we resolve this longstanding challenge using a mussel-inspired polydopamine (PD) coating via a simple immersion process. The nanometer-thick PD coating layer allows the formation of an SEI layer on the coating surface without perturbing the intrinsic properties of the SEI layer of the graphite anodes. PD-coated graphite exhibits far better performances in cycling test at 60 °C and storage test at 90 °C than bare graphite. The PD-coated graphite also displays superior rate capability during both lithiation and delithiation. As evidenced by surface free energy analysis, the enhanced performance of the PD-coated graphite can be ascribed to the Lewis basicity of the PD, which scavenges harmful hydrofluoric acid and forms an intermediate triple-body complex among a Li(+) ion, solvent molecules, and the PD's basic site. The usefulness of the proposed PD coating can be expanded to various electrodes in rechargeable batteries that suffer from poor thermal stability and interfacial kinetics.