Lithium-sulfur batteries are considered one of the most appealing technologies for next-generation energy-storage devices. However, the main issues impeding market breakthrough are the insulating ...property of sulfur and the lithium-polysulfide shuttle effect, which cause premature cell failure. To face this challenge, we employed an easy and sustainable evaporation method enabling the encapsulation of elemental sulfur within carbon nanohorns as hosting material. This synthesis process resulted in a morphology capable of ameliorating the shuttle effect and improving the electrode conductivity. The electrochemical characterization of the sulfur-carbon nanohorns active material revealed a remarkable cycle life of 800 cycles with a stable capacity of 520 mA h/g for the first 400 cycles at C/4, while reaching a value around 300 mAh/g at the 750th cycle. These results suggest sulfur-carbon nanohorn active material as a potential candidate for next-generation battery technology.
Abstract The Nobel Prize in Chemistry 2019 recognized the importance of Li-ion batteries and the revolution they allowed to happen during the past three decades. They are part of a broader class of ...electrochemical energy storage devices, which are employed where electrical energy is needed on demand and so, the electrochemical energy is converted into electrical energy as required by the application. This opens a variety of possibilities on the utilization of energy storage devices, beyond the well-known mobile applications, assisting on the decarbonization of energy production and distribution. In this series of reviews in two parts, two main types of energy storage devices will be explored: electrochemical capacitors (part I) and rechargeable batteries (part II). More specifically, we will discuss about the materials used in each type of device, their main role in the energy storage process, their advantages and drawbacks and, especially, strategies to improve their performance. In the present part, electrochemical capacitors will be addressed. Their fundamental difference to batteries is explained considering the process at the electrode/electrolyte surface and the impact in performance. Materials used in electrochemical capacitors, including double layer capacitors and pseudocapacitive materials will be reviewed, highlighting the importance of electrolytes. As an important part of these strategies, synthetic routes for the production of nanoparticles will also be approached (part I).
Abstract In the second part of the review on electrochemical energy storage, the devolvement of batteries is explored. First, fundamental aspects of battery operation will be given, then, different ...materials and chemistry of rechargeable batteries will be explored, including each component of the cell. In negative electrodes, metallic, intercalation and transformation materials will be addressed. Examples are Li or Na metal batteries, graphite and other carbonaceous materials (such as graphene) for intercalation of metal-ions and transition metal oxides and silicon for transformation. In the positive electrode section, materials for intercalation and transformation will be reviewed. The state-of-the-art on intercalation as lithium cobalt oxide and nickel containing oxides will be approached for intercalation materials, whereas sulfur and metal-air will also be explored for transformation. Alongside, the role of electrolyte will be discussed concerning performance and safety, with examples for the next generation devices. Finally, a general future perspective will address both electrochemical capacitors and batteries.
Spinel-type Li1-xMn2O4 material is a promising positive electrode material for lithium-ion batteries. This material presents 3D diffusion channels through the structure, allowing for the rapid ...diffusion of lithium ions during charge/discharge processes. Given its relevant properties, such as a theoretical specific capacity of 149 mA h g−1 and high working potential, we propose LixMn1.8Ti0.2O4@N-doped graphene oxide (x ≤ 1) as a superior positive electrode material for lithium-ion battery applications. In organic media, the spinel showed excellent Li storage performance due to the incorporation of a conductive carbonaceous matrix (using 1,10 phenanthroline as a graphene precursor). We obtained a specific capacity of 139 mA h g–1, which represented 81% charge retention after 70 cycles. Furthermore, taking advantage of the high working potential of this material, we studied the Li storage capacity using ionic liquids as electrolyte solvents. High rate cycling at high temperatures is essential for their practical applications in extreme environments. In this work, we performed rate capability experiments at different temperatures, obtaining the best response at 40 °C with a specific capacity of 117 mA h g–1 at an applied current density of 1 C.
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Understanding the processes in lithium–sulfur (Li–S) batteries is critical to advancing this promising energy storage technology. To this end, a 3D polypyrrole-based sponge (PPY) was synthesized as a ...sulfur host for positive electrodes in (Li–S). Through optimization, the PPY:S8 composite showed interesting electrochemical performance, including a cycle lifetime of over 200 cycles and remarkable specific capacitances at 0.2 A g−1. Electrochemical impedance spectroscopy (EIS) data provided valuable insights. In addition to the unchanged solution resistance indicating a minimal shuttle effect, the capacitance of the PPY film remains robust due to its bipolaronic state and shows strong sulfur retention, especially at the LiPSs/S8 potential. Operando Raman spectroscopy revealed the stability of the bipolaronic state and the “neutralization” of the lithium polysulfides (LiPSs) by the incorporation of sulfur. Moreover, UV–vis analysis confirmed the efficient absorption of LiPS within the PPY matrix. These results highlight the potential of PPY as an effective sulfur host that minimizes the shuttle effect and improves the charge storage capability of Li–S batteries. This research contributes to the development of advanced materials for energy storage systems and highlights the importance of using positively charged materials as carriers for sulfur in Li–S batteries.
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As one of the most promising energy storage devices, lithium-sulfur batteries (LSBs or Li-S batteries) are still facing obstacles due to the notorious shuttling of soluble polysulfide intermediates, ...accompanied by low S utilization, corrosion of the lithium anode, and rapid capacity fading, leading to a short cycling life. To overcome these issues and achieve high-performance LSBs, we introduce a modified separator composed of multi-walled carbon nanotubes/lithium lanthanum titanium oxide (MWCNTs/LLTO). The proposed MWCNTs/LLTO-modified separator improves the redox reaction kinetics from soluble higher-order lithium polysulfides to insoluble lower-order ones and ultimately to Li2S, thereby reducing the polysulfides dissolved in the electrolyte. It also serves as a physical barrier to adsorb polysulfides, efficiently preventing their diffusion from the cathode to the anode. LSBs adopting the MWCNTs/LLTO-modified separator exhibit higher ionic and electronic conductivity than their un-modified counterparts, leading to an initial specific capacity of 1496 mA/h/g (∼90% of the theoretical capacity) at 0.1 C, excellent rate capability performance, and a remarkable capacity retention of 80% after 200 cycles. Furthermore, the cells with S loading reaching up to 4.18 mg/cm2 further confirmed the beneficial impact of the MWCNTs/LLTO-modified separator.
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•Co-conductive MWCNTs/LLTO coating accelerates the redox reaction within LSB.•MWCNTs/LLTO show both physical adsorption and chemisorption towards LiPSs.•Improving the specific capacity and rate capability of LSB through separator modification.
The increasing demand for high performance lithium ion batteries is pushing the research toward the development of new materials for electrodes. Our study focuses on the usage of Germanium as the ...active material for the negative electrode since it has a higher theoretical specific capacity than standard graphite-based electrodes. This research article provides insight into the electrochemical performance of thin films of Germanium deposited on metallic substrates and then nanostructured via electrochemical etching. Molybdenum and stainless steel are investigated as substrates and compared with regard to the performance of the resulting electrodes. The nanostructured Germanium electrodes show promising results, demonstrating a stable and high specific capacity for hundreds of cycles. The long-term stability of the cell together with a high rate capability proves the reliability of the cell engineered.
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•Mechanochemical approaches for the preparation of ZIF-8 carbon composites.•Mechanochemical preparation of ZIF-8-related structures by Zn2+ replacement.•Different approaches for ...incorporation of conductive carbon in all ZIF structures.•ZIF-8/carbon/S8 composite presented initial capacities of 772 mA h g−1.•Lithium Polysulfides are better incorporated by the ZIF-8 carbon material.
The application of lithium-sulfur (Li-S) batteries is still limited by their rapid capacity fading. The pulverization of the sulfur positive electrode after the lithiation and the consequence dissolution of long chain polysulfides in organic solvents lead to the shuttle effect. To address these issues, here we report the mechanochemical preparation of ZIF-8 (Zeolitic Imidazole Framework-8)-based composites as sulfur hosts for positive electrodes in Li-S batteries. We studied different methods for the incorporation of conductive carbon. Also, the replacement of Zn2+ metal centers by other bivalent metals (Cu2+, Co2+ and Ni2+), enabled the preparation of other ZIF-8-based materials. The positive electrode ZIF-8/C/S8 showed initial discharges of 772 mA h g−1 while the pristine one, ZIF-8/S8, displayed 502 mA h g−1. The enhanced performance of 54% for ZIF-8/C/S8 indicates that the direct mechanochemical synthesis of ZIF-8 with conductive carbon is beneficial at initials charge/discharge process in comparison to traditional slurry preparation (ZIF-8/S8). Also, the Li2S6 absorption tests shows 87% of discoloration with ZIF-8/C/S8, confirming the better polysulfides absorption.
•CeO2100-x-S8x nanohybrids are prepared by a simple and rapid synthetic approach.•The CeO270-S830 nanohybrid presents a capacity of 600 mA h g–1 over 160 cycles.•CeO270-S830 promotes fast redox ...reactions, making the shuttle effect negligible.•DFT results reveal strong interactions between the CeO2 surface and sulfur species.
An in-depth investigation of the physical and chemical parameters that affect Li-sulfur batteries is imperative to optimize their performances. Here, we report promising CeO2100-x-S8x nanohybrids for anchoring lithium polysulfides (LiPSs) that are generated during cycling. The composition of CeO2100- x-S8x (x = 30, 50 and 70%) could be simply controlled by varying the CeO2/S8 mass ratio added in each reaction. Our results indicated that the CeO2100- x-S8x nanohybrids displayed a crystalline structure composed of both phases (CeO2 and S8), indicating an efficient impregnation process of S8 on the CeO2 nanowire surface. The surface area of CeO2 nanowires decreased as the amount of S8 was increased, and the CeO270-S830 nanohybrid maintained a uniform distribution of S8 over the entire CeO2 nanowires. Remarkably, the CeO270-S830 nanohybrid showed the best Li-storage performance, leading to specific capacities of approximately 600 mA h g–1 over 160 cycles and a Coulombic efficiency of approximately 100%. Moreover, this sample showed excellent rate capability performance (even discharging at 10 A g–1). Additionally, the chemical interaction of CeO2 with LiPS was demonstrated by a visual experiment through the addition of pure CeO2 in a solution of Li2S6. The solution containing CeO2 nanowires became completely colorless after 30 min. To further investigate these improvements, density functional theory (DFT) calculations revealed the formation of strong interactions between the CeO2 nanowire surface and different sulfur species. For instance, the adsorption energies between the CeO2 nanowires and S8, Li2S4, and Li4S8 were –3.95, –5.84 and –7.31 eV, respectively, suggesting that the CeO270-S830 nanohybrid provided an appropriate surface to anchor LiPS by electrostatic interactions, leading to faster redox kinetics in Li-sulfur battery applications.
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