rational design of porous carbon matrices to enable efficient lithiated silicon sulfur full cell

Abstract Lithium sulfur technology is a promising near-future battery owing to its high theoretical capacity and low cost materials; nonetheless, its commercial viability is hindered owing to the use of lithium anode. Reactive Li is prone to dendritic growth, causing short-circuits and aggravating electrolyte depletion. Here, lithiated silicon sulfur (SLS) full cells are realized by opting all-designs integrated strategy to rationally architecture the carbon matrices for both electrodes. For cathode, N/S- doped high surface area hierarchical porous carbons are designed to host sulfur and its redox species. Anodes are constructed by electrospinning using nano-silicon@void@carbon nanofibers (SVCNF) cross-linked with alginate-citric acid binder network. As-prepared anodes are reversibly alloyed and dealloyed with high reversible capacity of 2132 mAh g S i − 1 (427 mAh g S i / C N F − 1 ) after 150 cycles at 716 mA g S i − 1 in ether-based electrolyte. At cathode, polypyrrole activated hierarchical carbon sulfur (PPyr_C/S) exhibits very stable performance with capacity retention around 767 mAh g S − 1 after 250 at C/5. After balancing with low Li excess, lithiated SVCNF anodes are coupled with PPyr_C/S cathodes, with initial capacity of 972 mAh g S − 1 and 50% capacity retention after 100 cycles at 225 mA g S − 1 . Full SLS cells have been appreciated by opting rational architecture of carbon matrices in individual electrodes even at low lithium excess

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

Influence of binders and solvents on stability of Ru/RuOx nanoparticles on ITO nanocrystals as Li–O2 battery cathodes

Fundamental research on Li–O2 batteries remains critical, and the nature of the reactions and stability are paramount for realising the promise of the Li–O2 system. We report that indium tin oxide (ITO) nanocrystals with supported 1–2 nm oxygen evolution reaction (OER) catalyst Ru/RuOx nanoparticles (NPs) demonstrate efficient OER processes, reduce the recharge overpotential of the cell significantly and maintain catalytic activity to promote a consistent cycling discharge potential in Li–O2 cells even when the ITO support nanocrystals deteriorate from the very first cycle. The Ru/RuOx nanoparticles lower the charge overpotential compared with those for ITO and carbon-only cathodes and have the greatest effect in DMSO electrolytes with a solution-processable F-free carboxymethyl cellulose (CMC) binder (<3.5 V) instead of polyvinylidene fluoride (PVDF). The Ru/RuOx/ITO nanocrystalline materials in DMSO provide efficient Li2O2 decomposition from within the cathode during cycling. We demonstrate that the ITO is actually unstable from the first cycle and is modified by chemical etching, but the Ru/RuOx NPs remain effective OER catalysts for Li2O2 during cycling. The CMC binders avoid PVDF-based side-reactions and improve the cyclability. The deterioration of the ITO nanocrystals is mitigated significantly in cathodes with a CMC binder, and the cells show good cycle life. In mixed DMSO–EMITFSI [EMITFSI=1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide] ionic liquid electrolytes, the Ru/RuOx/ITO materials in Li–O2 cells cycle very well and maintain a consistently very low charge overpotential of 0.5–0.8 V

MoS2/PANI composite as suitable functional interlayer for lithium polysulfides trapping in Li-S batteries

Lithium-sulfur (Li-S) battery technology promises much higher energy storage capacity compared to common Li-ion commercial batteries. Li-S batteries have high theoretical capacity of 1672 mAh g-1, thanks to conversion reaction from solid sulfur (S8) to lithium polysulfides (LiPS) [1]. At the same time, sulfur allows for a wide range of operation temperature, being non-toxic abundant and low-cost element. Instead of mentioned advantages, few issues are still hindering the commercialization of Li-S battery. The main problem afflicting lithium sulfur batteries is the shuttle phenomenon, due to soluble long chain lithium polysulfides (LiPSs) generated at the cathode, which are soluble and able to migrate to the anode were they directly react with lithium, by a parasitic passivation reactions [2]. In the last years most interlayer separators are based on materials showing a great physical blocking of PS, like graphene. Unfortunately, many of these materials are still not effective enough in preserving long life performance. Recently was demonstrated that metal sulfides and conductive polymers can directly interact with lithium polysulfides through electrostatic or chemical bonds, inhibiting the dissolution of LiPSs. In particular, MoS2 and PANI separately showed strong adsorption capability, preventing polysulfides dissolution and accelerating the redox reaction kinetics of polysulfides conversion [3][4]. In the present work we rationally designed some binary materials based on PANI and MoS2 at different ratio, with the aim to evaluate the different role of the two components and their synergy as PS blocking agent. By the implementation of a second layer containing the MoS2/PANI composite directly on the top of the standard S/KjB electrode. The systematic study confirms that double-layer containing the composite remarkably improves the performance of the sulfur cathode, showing a final specific capacity close to 600 mAh g-1, 25% higher than the standard sulfur cathode, after 500 cycles [5]. [1] A. N. Mistry and P. P. Mukherjee, J. Phys. Chem. C, 122-42, (2018) 23845–23851. [2] L. Tan, X. Li, Z. Wang, H. Guo, and J. Wang, ACS Appl. Mater. Interfaces, 10-4, (2018) 3707–3713. [3] Y. Liu, C. Cui, Y. Liu, W. Liu, and J. Wei, RSC Adv, 10-13, (2020) 7384–7395. [4] Y. Yao, H. Zhang, and X. Wang, J. Solid State Electrochem, 23-8, (2019) 2559–2567. [5] D. Versaci, I. Canale, S. Goswami, J. Amici, C. Francia, E. Fortunato, R. Martins, L. Pereira, S. Bodoardo, Journal of Power Sources 521 (2022) 230945