Improvement of La0.8Sr0.2MnO3−δ Cathode Material for Solid Oxide Fuel Cells by Addition of YFe0.5Co0.5O3

The high efficiency of solid oxide fuel cells with La0.8Sr0.2MnO3−δ (LSM) cathodes working in the range of 800–1000 °C, rapidly decreases below 800 °C. The goal of this study is to improve the properties of LSM cathodes working in the range of 500–800 °C by the addition of YFe0.5Co0.5O3 (YFC). Monophasic YFC is synthesized and sintered at 950 °C. Composite cathodes are prepared on Ce0.8Sm0.2O1.9 electrolyte disks using pastes containing YFC and LSM powders mixed in 0:1, 1:19, and 1:1 weight ratios denoted LSM, LSM1, and LSM1, respectively. X-ray diffraction patterns of tested composites reveal the presence of pure perovskite phases in samples sintered at 950 °C and the presence of Sr4Fe4O11, YMnO3, and La0.775Sr0.225MnO3.047 phases in samples sintered at 1100 °C. Electrochemical impedance spectroscopy reveals that polarization resistance increases from LSM1, by LSM, to LSM2. Differences in polarization resistance increase with decreasing operating temperatures because activation energy rises in the same order and equals to 1.33, 1.34, and 1.58 eV for LSM1, LSM, and LSM2, respectively. The lower polarization resistance of LSM1 electrodes is caused by the lower resistance associated with the charge transfer process.

Biomass-Derived Carbon/Sulfur Composite Cathodes with Multiwalled Carbon Nanotube Coatings for Li-S Batteries

Lithium sulfur (Li-S) batteries stand out among many new batteries for their high energy density. However, the intermediate charge–discharge product dissolves easily into the electrolyte to produce a shuttle effect, which is a key factor limiting the rapid development of Li-S batteries. Among the various materials used to solve the challenges related to pure sulfur cathodes, biomass derived carbon materials are getting wider research attention. In this work, we report on the fabrication of cathode materials for Li-S batteries based on composites of sulfur and biomass-derived porous ramie carbon (RC), which are coated with multiwalled carbon nanotubes (MWCNTs). RC can not only adsorb polysulfide in its pores, but also provide conductive channels. At the same time, the MWCNTs coating further reduces the dissolution of polysulfides into the electrolyte and weakens the shuttle effect. The sulfur loading rate of RC is 66.3 wt.%. As a result, the initial discharge capacity of the battery is 1325.6 mAh·g−1 at 0.1 C long cycle, and it can still maintain 812.5 mAh·g−1 after 500 cycles. This work proposes an effective double protection strategy for the development of advanced Li-S batteries.

Aluminum metal anode rechargeable batteries with sulfur-carbon composite cathodes and inorganic chloroaluminate ionic liquid

Promising sulfurized polyethylene glycol (SPEG) composite cathodes with a high-rate capability over 3000 mA g-1 at 393 K are fabricated for Al metal anode rechargeable batteries with a 61.0-26.0-13.0 mol%...

Multiscale Understanding of High-Energy Cathodes in Solid-State Batteries: from Atomic Scale to Macroscopic Scale

In the crucial area of sustainable energy storage, solid-state batteries (SSBs) with nonflammable solid electrolytes stand out due to their potential benefits of enhanced safety, energy density, and cycle life. However, the complexity within the composite cathode determines that fabricating an ideal electrode needs to link chemistry (atomic scale), materials (microscopic/mesoscopic scale), and electrode system (macroscopic scale). Therefore, understiang solid-state composite cathodes covering multiple scales is of vital importance for the development of practical SSBs. In this review, the challenges and basic knowledge of composite cathodes from the atomic scale to the macroscopic scale in SSBs are outlined with a special focus on the interfacial structure, charge transport, and mechanical degradation. Based on these dilemmas, emerging strategies to design a high-performance composite cathode and advanced characterization techniques are summarized. Moreover, future perspectives toward composite cathodes are discussed, aiming to facilitate the develop energy-dense solid-state batteries.

BiFeO3 Coupled Polysulfide Trapping in C/S Composite Cathode Material for Li-S Batteries as Large Efficiency and High Rate Performance

We demonstrated the efficient coupling of BiFeO3 (BFO) ferroelectric material within the carbon–sulfur (C-S) composite cathode, where polysulfides are trapped in BFO mesh, reducing the polysulfide shuttle impact, and thus resulting in an improved cyclic performance and an increase in capacity in Li-S batteries. Here, the built-in internal field due to BFO enhances polysulfide trapping. The observation of a difference in the diffusion behavior of polysulfides in BFO-coupled composites suggests more efficient trapping in BFO-modified C-S electrodes compared to pristine C-S composite cathodes. The X-ray diffraction results of BFO–C-S composite cathodes show an orthorhombic structure, while Raman spectra substantiate efficient coupling of BFO in C-S composites, in agreement with SEM images, showing the interconnected network of submicron-size sulfur composites. Two plateaus were observed at 1.75 V and 2.1 V in the charge/discharge characteristics of BFO–C-S composite cathodes. The observed capacity of ~1600 mAh g−1 in a 1.5–2.5 V operating window for BFO30-C10-S60 composite cathodes, and the high cyclic stability substantiate the superior performance of the designed cathode materials due to the efficient reduction in the polysulfide shuttle effect in these composite cathodes.

An Improved Cycling Performance of Different Types of Composite Sulfur-Carbon Cathodes with the Use of Lithium Polysulfides Containing Electrolyte Solutions

We report on stabilization of Li-S cells with different types of composite sulfur cathodes using ethereal LiTFSI/LiNO3/DOL/DME electrolyte solutions containing a-priori 0.1M Li2S8. These electrolyte solutions enable an improved cycling behavior for Li-S cells compared to Li2S8-free electrolyte solutions, thanks to the presence of LiSx species from the beginning of operation. We show that Li anodes cycled in Li|S cells with solutions containing Li2S8 possess flatter and more uniform surface, higher dimensions of the surface structures in average and, as a result, a lower surface area. This surface morphology ensures a low rate of parasitic surface reactions of the electrolyte components on the Li anodes’ surface, slower depletion of the electrolyte solution in the cells and stabilization of the cells cycling. Besides, the presence of Li2S8 maintains a better integrity of composite sulfur/carbon/PVdF cathodes, ensuring a better electronic contact between the particles in the composite cathodes. We believe that we outline herein a logical approach for practical Li-S batteries, emphasizing high energy density, cost effectiveness and relatively simple production procedures.

Monitoring electrode/electrolyte interfaces of Li-ion batteries under working conditions: A surface-enhanced Raman spectroscopic study on LiCoO2 composite cathodes

Lithium-ion batteries are commonly used for electrical energy storage in portable devices and are promising systems for large-scale energy storage. However, their application is still limited due to electrode degradation and stability issues. To enhance the fundamental understanding of electrode degradation we report on the Raman spectroscopic characterization of LiCoO2 cathode materials of working Li-ion batteries. To facilitate the spectroscopic analysis of the SEI (solid electrolyte interface) we apply surface-enhanced Raman spectroscopy by using Au nanoparticles coated with a thin SiO2 layer (Au@SiO2). We observe a surface-enhanced Raman signal of Li2CO3 at 1090 cm-1 during electrochemical cycling as an intermediate. Its formation/decomposition highlights the role of Li2CO3 as a component of the SEI on LiCoO2 composite cathodes. Our results demonstrate the potential of Raman spectroscopy to monitor electrode/electrolyte interfaces of lithium-ion batteries under working conditions thus allowing relations between electrochemical performance and structural changes to be established.