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.

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...

In this work, the low temperature one-step electrochemical deposition of arrayed ZnO nanowires (NWs) decorated by Au nanoparticles (NPs) with diameters ranging between 10-100 nm is successfully reported for the first time. The AuNPs and ZnO NWs were grown simultaneously in the same growth solution in consideration of the HAuCl4 concentration. Optical, chemical and structural characterization were performed in detail, showing high crystallinity of the NWs, as well as the distribution of Au NP on the surface of ZnO NWs demonstrated by transmission electron microscopy (TEM). Individual Au NPs-functionalized ZnO NWs (Au-NP/ZnO-NWs) were incorporated into sensor nanodevices using a FIB/SEM system. The gas sensing measurements demonstrated excellent selectivity to hydrogen gas at room temperature with a gas response, Igas/Iair, as high as 7.5 to 100 ppm for Au-NP/ZnO-NWs possessing a AuNP surface coverage of ~ 6.4%. The concentration of HAuCl4 in the growth solution was observed to have no impact on the gas sensing performances. This highlights the significant influence of the total Au/ZnO interfacial area establishing Schottky contacts for the achievement of high performances. The most significant performance of H2 response was observed for gas concentrations higher than 500 ppm of H2 in the environment, which was attributed to surface metallization of ZnO NW during exposure to hydrogen. For this case an ultra-high response of 32.9 and 47 to 1000 and 5000 ppm of H2 was obtained, respectively. Spin-polarized periodic density functional theory calculations were performed on Au/ZnO bulk and surface functionalized models, validating the experimental hypothesis. The combination of H2 gas detection at room temperature, ultra-low power consumption and small size, make these devices ideal candidates for hydrogen gas leakage detection, as well as hydrogen gas monitoring (down to 1 ppm).

This work presents the impact of surface decoration on the VOC sensing properties of ZnO:Ag columnar films by AgPt and AgAu bimetallic alloy nanoparticles.