Lithium‐ion batteries (LIBs) are promising candidates within the context of the development of novel battery concepts with high energy densities. Batteries with high operating potentials or high voltage (HV) LIBs (>4.2 V vs Li+/Li) can provide high energy densities and are therefore attractive in high‐performance LIBs. However, a variety of challenges (including solid electrolyte interface (SEI), lithium plating, etc.) and related safety issues (such as gas formation or thermal runaway effects) must be solved for the practical, widespread application of HV‐LIBs. Most of these challenges arise in the region between the electrodes: the electrolyte region. This review provides an overview of recent development and progress on the electrolyte region, including liquid electrolytes, ionic liquids, gel polymer electrolytes, separators, and solid electrolytes for HV‐LIBs applications. A focus on improving the safety of these systems, with some perspectives on their relative cost and environmental impact, is given. Overall, the new information is encouraging for the development of HV‐LIBs, and this review serves as a guide for potential strategies to improve their safety, allowing the development of HV‐LIBs, including solid‐state batteries, to be accelerated to practical relevance.

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resistance), is suitable for a wide range of industrial applications, depending on its form. [1] The world has consumed resources exceeding 800 million tons of recoverable Gr. Although more than 20 countries are producing natural graphite (NGr), in 2019, as shown in Figure 1a, the world production was controlled by China, Mozambique, and Brazil. [4] Total production of NGr in 2019 was estimated to be 1 130 000 tons, and China is the largest producer of Gr with 62% (about 700 000 tons). The NGr products contain both amorphous Gr (microcrystalline) and flake Gr (crystalline), however, about 1% of NGr is vein (lump) Gr (interlocking aggregates of flake Gr crystals), which is produced in Sri Lanka. [1,[5][6][7][8] Another type of Gr is synthetic (artificial) Gr (SGr), which is synthesized by heat treatment of a coke-based precursor at very high temperature of more than 2500 °C. [9,10] The production of SGr is costly from both an energy and a time perspective. The process of preparation, heating and cooling takes several weeks to several months. [11] Table 1 reports the characteristics of different types of NGr and SGr. Although the chemical structure is similar for both NGr and SGr, they differ in electrochemical behavior and price. In 2018, the price for the NGr and SGr as anode material were between 4 and 8 $ kg −1 , and 12 and 13 $ kg −1 , respectively. [12] Due to the high melting point of 3900 °C, [13] the largest amount of Gr produced is used in the reactors and furnaces of steel and refractory industries. [14] However, emerging Li-ion battery (LIBs) industries could substantially increase world demand for Gr (forecasted to rise by 10-12% per year). [2] Gr is the state-of-the-art anode material in both primary (non-rechargeable), and secondary (rechargeable) batteries with approximately 18% of flake NGr worldwide used in batteries. [15] The market shares of various anode materials are illustrated in Figure 1b,c for years of 1995 and 2010, which mainly is dominated by Gr-based materials. Despite its higher price, the market share of SGr for automotive batteries is growing over time, as the quality fluctuates less than for NGr, and SGr demonstrates extremely high levels of purity. [12,16] In 2018, the SGr had a market share of about 56% in comparison to 35% for NGr as an anode material (which are almost similar to percentages of 2010 (Figure 1c), and the rest consisted of amorphous carbon, silicon composites or lithium titanate. [12] The Gr market, in general, is growing fast due to the replacement of fuel-driven cars by electric vehicles (EVs) (the number of EVs cars produced in 2020 was about 3.24 million cars) [18] and The number of lithium-ion batteries (LIBs) from hybrid and electric vehicles that are produced or discarded every year is growing exponentially, which may pose risks to supply lines of limited resources. Thus, recycling and regeneration of end-of-life LIBs (EoL-LIBs) is becoming an urgent and critical task for a sustainable and environmentally friendly future. In this regard, much attention, esp...

Sono-dispersion of Ni, Co and Ni-Co over Al2O3-MgO with Al/Mg ratio of 1.5 was prepared and tested for dry reforming of methane. The samples were characterized by XRD, FESEM, PSD, EDX, TEM, BET and FTIR analyses. In order to assess the effect of ultrasound irradiation, Ni-Co/Al2O3-MgO with Co content of 8% prepared via sonochemistry and impregnation methods. The sono-synthesized sample showed better textural properties and higher activity than that of impregnated one. Comparison of XRD patterns indicated that the NiO peaks became broader by increasing Co content over the support. The FESEM images displayed the particles are small and well-dispersed as a result of sonochemistry method. Also, EDX analysis demonstrated better dispersion of Ni and Co as a result of sonochemistry method in confirmation of XRD analysis. The sono-synthesized Ni-Co/Al2O3-MgO as a superior nanocatalyst with Co content of 3% illustrates much higher conversions (97.5% and 99% for CH4 and CO2 at 850 °C), yields (94% and 96% for H2 and CO at 850 °C) and 0.97 of H2/CO molar ratio in all samples using an equimolar feed ratio at 850 °C. During the 1200 min stability test, H2/CO molar ratio remained constant for the superior nanocatalyst.