Materials for high energy Li-ion and post Li-ion batteries

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Materials for high energy Li-ion and post Li-ion batteries

Lithium-ion batteries (LIBs) are well established energy storage devices for electronic, transportation and renewable-energy applications. Nevertheless, to meet the ever-increasing energy storage demand for electrical mobility and smart grid, future batteries have to guarantee higher energy density and, at the same time, sustainable and cheaper solutions. In this frame anode and cathode materials with higher specific capacity are required. From the cathode side, according to preliminary DFT calculations, carbon nitride (g-C3N4) was selected and investigated as lithium polysulfides trapping agent in Li-S battery, using a double-layer approach. Carbon nitride was synthetized by a simple thermal condensation route using different precursors, with the aim of evaluating the polysulfides trapping ability in relation with morphology and surface chemistry of different g-C3N4 materials. In a second step, g-C3N4 was synthetized from urea at different temperatures showing variations in specific surface area and surface functionalities. In particular, different amounts of pyridinic nitrogen, directly interacting with lithium polysulfides, were detected. In conclusion, carbon nitride obtained from urea at 550 °C resulted to be the best candidate as trapping agent in the double-layer sulphur cathode and the electrode containing carbon nitride demonstrated long cycling performances, for more than 500 cycles, as well as better electrochemical performances at higher C-rates. Concerning the anode electrode, tin oxide-based materials were investigated. Two different strategies were presented in order to limit the rapid capacity fading of tin oxide anode, increasing the reversibility of the conversion reaction and at the same time containing the huge volume expansion. The first strategy was a simple and scalable wet impregnation synthesis, where tin oxide was directly grown on the surface of a commercial carbon black. The final hybrid compound, containing a particularly high amount of SnO2 (30 wt.%), showed a specific capacity higher than 500 mAh g-1 for more than 500 cycles, with a coulombic efficiency of about 99.9 %. These outstanding electrochemical results were correlated to an optimal distribution of small tin oxide nanoparticles directly anchored to C45 surface. The second strategy adopted g-C3N4, already used for the cathode material, as high surface support for tin dioxide growth. In this case, a simple solid-state synthesis was selected, and the SnO2 precursors were directly mixed with carbon nitride. The final hybrid compound showed a final amount of SnO2 of about 90 wt.% and a huge specific surface area able to contain the volume expansion of tin oxide particles during the alloying process. The final compound showed good electrochemical results, presenting a specific capacity of about 500 mAh g-1 for 100 cycles at 1C, and interesting results at higher current regimes. Last but not least all the synthesis approaches studied in this work resulted valid strategies to increase the electrochemical performances while being simple, sustainable and easily up-scalable. References [1] Versaci et al. Solid State Ion. 2020, 346, 115210 [2] Versaci et al. Electrochim. Acta 2021, 367, 137489 [3] Versaci et al. Appl. Mater. Today 2021, 25, 10116

Chitosan and its char as fillers in cement-base composites: A case study

Abstract The continuous research of new functional materials combining both advanced properties and increased sustainability has dramatically risen up in the last decades. Instead of searching for new solutions, composites (formed by a combination of already present materials) are subject of different studies due to their capability of merging the advantages of components. Hence, chitosan, a biowaste-derived biopolymer, has been thermally-converted into chars by pyrolysis treatment. Subsequently, both chitosan and its char are introduced into cementitious matrix forming cement-based composites. The analysis of the mechanical properties of these materials evidenced that char-containing composites show an incipient fracture toughness capability, very appealing for possible structural applications

Tragacanth, an Exudate Gum as Suitable Aqueous Binder for High Voltage Cathode Material

he improvements in future-generation lithium-ion batteries cannot be exclusively focused on the performance. Other aspects, such as costs, processes, and environmental sustainability, must be considered. Research and development of new active materials allow some fundamental aspects of the batteries to be increased, such as power and energy density. However, one of the main future challenges is the improvement of the batteries’ electrochemical performance by using “non-active” materials (binder, current collector, separators) with a lower cost, lower environmental impact, and easier recycling procedure. Focusing on the binder, the main goal is to replace the current fluorinated compounds with water-soluble materials. Starting from these considerations, in this study we evaluate, for the first time, tragacanth gum (TG) as a suitable aqueous binder for the manufacturing process of a cobalt-free, high-voltage lithium nickel manganese oxide (LNMO) cathode. TG-based LNMO cathodes with a low binder content (3 wt%) exhibited good thermal and mechanical properties, showing remarkably high cycling stability with 60% capacity retention after more than 500 cycles at 1 C and an outstanding rate capability of 72 mAh g−1 at 15 C. In addition to the excellent electrochemical features, tragacanth gum also showed excellent recycling and recovery properties, making this polysaccharide a suitable and sustainable binder for next-generation lithium-ion batteries

Innovative hybrid high voltage electrodes based on LMNO/LFP materials for lithium ion batteries

Nowadays the markets of electric vehicles (EV) and energy storage devices are fast increasing pushing a constant increase in the demand for greener and more sustainable power sources. In particular, for EVs applications, batteries guaranteeing long cycle life combined with high specific energy and high power density are needed. To increase the specific energy, one solution is to increase the cell voltage and the capacity. For this reason, combine high voltage cathode, i.e. LMNO (Lithium Manganese Nickel Oxide), together with high capacity anodes, i.e silicon, can be an interesting solution. Unfortunately, LNMO suffers easy cation leaching during cycling, in particular at high C-rates. The present work shows results achieved within HYDRA H2020 project based on the synthesis of new blended materials combining LMNO and LFP (Lithium Iron Phosphate) in order to match their inherent positive characteristic to get better performing electrodes. LFP was chosen because of its outstanding thermal and electrochemical stability, as well as its Li-redox activity at a relatively high voltage [1][2][3]. Therefore, the presence of the LFP should increase the cycling stability of the LMNO, especially at higher current rates. In order to get a homogeneous coating of LFP particles on the LMNO surface, we used ball milling treatments modifying all parameters, such as frequency, time, and weight percent of LFP. The blended active materials were thus characterized from a morphological and structural point of view with FESEM and XRD analysis, and electrochemical characterization: galvanostatic cycling and cyclic voltammetry studies. The results obtained are showing that the mixing through ball milling does not significantly damage the structure of the two pristine materials and ensures a homogeneous dispersion of LFP particles which partially cover the LMNO particles. The electrochemical data confirm that both materials actively contribute to the capacity of the blended electrodes. Authors kindly acknowledge Hydra project (Horizon 2020 innovation programme under Grant agreement number: 875527) for funding. References [1] Martha et al., Journal of The Electrochemical Society, 2011, 158 (10) A1115. [2] Jang et al., Journal of Alloys and Compounds, 2014, 612. 51. [3] Liu et al., Journal of Power Sources, 2012, 204, 127

Ultrasmall SnO2 directly grown on commercial carbon black: a versatile composite material for Li-based energy storage

Herein, we propose a hassle-free approach to prepare SnO2/C composite using a simple, fully sustainable, and economic synthesis process, in which tin oxide is in situ nucleated on commercial carbon black C-NERGYTM Super C45 (Imerys Graphite & Carbon) in form of homogenously distributed nanoparticles. The synthesis is carried out by wet impregnation without any acid treatment or high temperature process. We focused on the presence of the existing oxygen species on the carbon surface that are accessible for tin and promote Sn–O–C interactions, suggesting synergies between the two components, with an active role of the carbon support in the SnO2 conversion reaction. On one hand, in Li-ion technology, development of high-performance SnO2 anodes is hampered by its peculiar electrochemical behavior, characterized by two processes: conversion and alloying reactions. The conversion reaction being irreversible leads to specific capacities lower than theoretical, however rational design of nanosized SnO2 can mitigate this issue, though SnO2 low conductivity and electrode pulverization justify the need of carbon matrices. Some carbon structures proved to be strongly effective at laboratory-scale, but most are too expensive or complicated to obtain for scaling-up. Presence of oxygen species on C45 surface, accessible to tin, prevent fast formation of Li2O, allowing to achieve high capacity and extreme electrode stability. The assembled cells with SnO2 /C45 exhibit for more than 400 cycles the reversible capacity of 560 mA h g−1 per pure SnO2 (after subtracting C45 contribution) at 1C, demonstrating prolonged cycling operation thus providing an interesting opportunity for scalable production of stable and high-capacity battery anodes alternatively to graphite [1]. On the other hand, developing efficient and low cost electrocatalysts for ORR is fundamental to bring the Li-O2 technology closer to practical applications. The obtained composite material shows an optimal ORR activity with a final reduction mechanism following the 4 electrons pathway. This is confirmed in Li-O2 cells, indeed compared to pure C45 air-cathodes, the composite cathodes lead to the formation of much more reversible film-like discharge products, allowing for reduced overvoltage and therefore improved cycling performances both at the high current density of 0.5 mA cm-2 with more than 70 cycles and in prolonged discharge/charge conditions with over 1250 h of operation at the fixed capacity of 2.5 mAh cm-2 [2]. Considering the fast and inexpensive method used to prepare SnO2/C45, these results, in terms of reversible capacities and long cycling stability, are competitive among others obtained for SnO2-based materials synthetized by other methods such as hydrothermal, sonochemical, solvothermal, etc. All these considerations make the synthetic route reported a suitable and interesting approach for large scale production. References 1. D