Ionic liquid-based electrolytes for sodium-ion batteries : tuning properties to enhance the electrochemical performance of manganese-based layered oxide cathode

Ionic liquids (ILs) are considered as appealing alternative electrolytes for application in rechargeable batteries, including the next-generation sodium-ion batteries, because of their safe and eco-friendly nature, resulting from their extremely low volatility. In this work, two groups of advanced pyrrolidinium based ILs electrolytes are concerned, made by mixing sodium bis(fluorosulfonyl)imide (NaFSI) or sodium tri(fluoromethanesulfonyl)imide (NaTFSI) salts with N-Methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI), N-Butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr14FSI) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI). The characterization of eight different electrolytes, including single anion electrolytes and binary anions mixtures, in terms of thermal properties, density, viscosity and conductivity as well as electrochemical stability window and cycling performance in room temperature sodium cells is reported here. Among all the blends, those containing Pyr14FSI outperform the others in terms of cell performance enabling the layered P2-Na0.6Ni0.22Al0.11Mn0.66O2 cathode to deliver about 140 mAh g-1 for more than 200 cycles

High performance Na0.5[Ni0.23Fe0.13Mn0.63]O2 cathode for sodium-ion battery

The synthesis of a new layered cathode material, Na0.5[Ni0.23Fe0.13Mn0.63]O2, and its characterization in terms of crystalline structure and electrochemical performance in a sodium cell, is reported. X-ray diffraction studies and high resolution SEM images reveal a well-defined P2-type layered structure, while the electrochemical tests evidence excellent characteristics in terms of high capacity, extending up to 200 mAh g-1, and cycle life, up to 70 cycles. This performance, in addition to the low cost and environmental compatibility of its component, poses Na0.5[Ni0.23Fe0.13Mn0.63]O2 among the best promising materials for the next generation of sodium ion batteries

Challenges and Strategies for High‐Energy Aqueous Electrolyte Rechargeable Batteries

Aqueous rechargeable batteries are becoming increasingly important to the development of renewable energy sources, because they promise to meet cost‐efficiency, energy and power demands for stationary applications. Over the past decade, efforts have been devoted to the improvement of electrode materials and their use in combination with highly concentrated aqueous electrolytes. Here the latest ground‐breaking advances in using such electrolytes to construct aqueous battery systems efficiently storing electrical energy, i.e., offering improved energy density, cyclability and safety, are highlighted. This Review aims to timely provide a summary of the strategies proposed so far to overcome the still existing hurdles limiting the present aqueous batteries technologies employing concentrated electrolytes. Emphasis is placed on aqueous batteries for lithium and post‐lithium chemistries, with potentially improved energy density, resulting from the unique advantages of concentrated electrolytes

Effect of Electrolyte Additives on the LiNi0.5_{0.5}Mn0.3_{0.3}Co0.2_{0.2}O2_{2} Surface Film Formation with Lithium and Graphite Negative Electrodes

The effect of various electrolyte additives (fluoroethylene carbonate (FEC), vinylene carbonate (VC), and propane sultone (PS)) on the performance of LiNi0.5Mn0.3Co0.2O2 (NMC532) electrodes in combination with lithium (half‐cell) and graphite (full‐cell) negative electrodes, is herein reported. The cathode/electrolyte interface (CEI) layer formed on the NMC532 electrode cycled up to 4.5 V versus Li+/Li is investigated by X‐ray photoelectron spectroscopy and scanning electron microscopy. This allows correlating the electrochemical performance of the electrodes to the CEI chemical composition, thickness, and morphology. All the investigated electrolyte additives exhibit beneficial effects in half‐ and full‐cell systems, confirming the effective passivation layer formation protecting the electrolyte from further decomposition at high voltages. It is found that the thickness of the CEI layer forming on the NMC532 electrodes in half‐ and full‐cell configuration is different. VC and PS are found to be the best additives to enhance the performance mainly due to their positive contribution to the CEI formation. The solid/electrolyte interphase (SEI) formed on the graphite electrode is also investigated and compared to the CEI layer formed on the cathode. The detection of typical SEI reduction products on the positive electrode surface confirms the occurrence of cross‐talking between the two electrodes

Elucidating Gas Evolution of Prussian White Cathodes for Sodium‐ion Battery Application: The Effect of Electrolyte and Moisture

As global energy storage demand increases, sodium-ion batteries are often considered as an alternative to lithium-ion batteries. Hexacyanoferrate cathodes, commonly referred to as Prussian blue analogues (PBAs), are of particular interest due their low-cost synthesis and promising electrochemical response. However, because they consist of ~50 wt% cyanide anions, a possible release of highly toxic cyanide gases poses a significant safety risk. Previously, we observed the evolution of (CN)2 during cycling via differential electrochemical mass spectrometry (DEMS), but were unable to determine a root cause or mechanism. In this work, we present a systematical investigation of the gas evolution of Prussian white (PW) with different water content via DEMS. While H2 is the main gas detected, especially in hydrated PW and during overcharge (4.6 V vs. Na+/Na), the evolution of CO2 and (CN)2 depends on the electrolyte conductive salt. The use of oxidative NaClO4 instead of NaPF6 is the leading cause for the formation of (CN)2. Mass spectrometric evidence of trace amounts of HCN is also found, but to a much lower extent than (CN)2, which is the dominant safety risk when using NaClO4-containing electrolyte, which despite being a good model salt, is not a viable option for commercial applications

Ensuring accurate Key Performance Indicators for Battery applications by implementing consistent Reporting Methodologies

Batteries have been identified as a key technology enabling the transition to a low-carbon economy. To achieve the EU decarbonization target by 2050, the demand for high-performance, low-cost, and sustainable batteries is rapidly growing. Several battery technologies have been proposed for different applications, e.g., automotive, aviation, maritime, etc. In this rapidly evolving field, while key performance indicators can be readily accessed, the performance evaluation and comparison of battery technologies remain a challenging task, due to the huge variation in the quality and quantity of data reported and the lack of a common methodology. To address this challenge, Batteries Europe stakeholders have suggested reporting methodology guidelines which, if implemented, will facilitate the identification of the most promising cell technologies while highlighting areas for improvement.publishedVersio

Challenges and strategies for high‐energy aqueous electrolyte rechargeable batteries

Aqueous rechargeable batteries are becoming increasingly important to the development of renewable energy sources, because they promise to meet cost-efficiency, energy and power demands for stationary applications. Over the past decade, efforts have been devoted to the improvement of electrode materials and their use in combination with highly concentrated aqueous electrolytes. Here the latest ground-breaking advances in using such electrolytes to construct aqueous battery systems efficiently storing electrical energy, i.e., offering improved energy density, cyclability and safety, are highlighted. This Review aims to timely provide a summary of the strategies proposed so far to overcome the still existing hurdles limiting the present aqueous batteries technologies employing concentrated electrolytes. Emphasis is placed on aqueous batteries for lithium and post-lithium chemistries, with potentially improved energy density, resulting from the unique advantages of concentrated electrolytes

Elucidating gas evolution of Prussian white cathodes for sodium‐ion battery application : the effect of electrolyte and moisture

As global energy storage demand increases, sodium-ion batteries are often considered as an alternative to lithium-ion batteries. Hexacyanoferrate cathodes, commonly referred to as Prussian blue analogues (PBAs), are of particular interest due their low-cost synthesis and promising electrochemical response. However, because they consist of ~50 wt% cyanide anions, a possible release of highly toxic cyanide gases poses a significant safety risk. Previously, we observed the evolution of (CN)2 during cycling via differential electrochemical mass spectrometry (DEMS), but were unable to determine a root cause or mechanism. In this work, we present a systematical investigation of the gas evolution of Prussian white (PW) with different water content via DEMS. While H2 is the main gas detected, especially in hydrated PW and during overcharge (4.6 V vs. Na+/Na), the evolution of CO2 and (CN)2 depends on the electrolyte conductive salt. The use of oxidative NaClO4 instead of NaPF6 is the leading cause for the formation of (CN)2. Mass spectrometric evidence of trace amounts of HCN is also found, but to a much lower extent than (CN)2, which is the dominant safety risk when using NaClO4-containing electrolyte, which despite being a good model salt, is not a viable option for commercial applications