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Hybrid materials (HMs) combine the high diversity of functionalities of organic compounds with properties typical for inorganic materials, such as high mechanical strength or high thermal stability. Herein, HMs combining organic pigment molecules and TiO2 as inorganic component, with covalently linked components, i.e., so‐called class II HMs, are reported. The synthesis of such HMs is intrinsically challenging, as the apolar organic pigment component and the inorganic polar TiO2 component require different conditions for their respective formation. Herein, we circumvent this issue by employing solvothermal synthesis in superheated isopropanol, which through temperature tunability of the solvent properties allows for both generating and linking both components in one‐pot. First, it is shown that an organic benzimidazole‐based pigment molecule designed for readily binding to Ti can be synthesized solvothermally. Second, new class II titanium‐based HMs are generated from Ti(OiPr)4 and pigment precursors in a solvothermal reaction. The pigment@TiO2 HMs feature significant porosity and are structurally identified as layered structures of lepidocrocite‐like TiO2 linked via pigment molecules. These layered HMs assemble into hierarchical nanoflowers, and depending on the pigment segments, different interlayer spacings in between inorganic layers are observed. Third, the pigment@TiO2 materials are shown to be usable as electrode materials in lithium‐ion batteries.

Modern batteries are highly complex devices. The cells contain many components—which in turn all have many variations, both in terms of chemistry and physical properties. A few examples: the active materials making the electrodes are coated on current collectors using solvents, binders and additives; the multicomponent electrolyte, contains salts, solvents, and additives; the electrolyte can also be a solid ceramic, polymer or a glass material; batteries also contain a separator, which can be made of glass fibres, polymeric, ceramic, composite, etc. Moving up in scale all these components are assembled in cells of different formats and geometries, coin cells and Swagelok cells for funamental testing and understanding, and pouch, prismatic and cylindrical cells for application. Given this complexity dictated by so many components and variations, there is no wonder that addressing the crucial issue of true sustainability is an extremely challenging task. How can we make sure that each component is sustainable? How can the performance can be delivered using more sustainable battery components? What actions do we need to take to address battery sustainability properly? How do we actually qualify and quantify the sustainability in the best way possible? And perhaps most importantly; how can we all work—academia and battery industry together—to enable the latter to manufacture more sustainable batteries for a truly cleaner future? This Roadmap assembles views from experts from academia, industry, research institutes, and other organisations on how we could and should achieve a more sustainable battery future. The palette has many colours: it discusses the very definition of a sustainable battery, the need for diversification beyond lithium-ion batteries (LIBs), the importance of sustainability assessments, the threat of scarcity of raw materials and the possible impact on future manufacturing of LIBs, the possibility of more sustainable cells by electrode and electrolyte chemistries as well as manufacturing, the important role of new battery chemistries, the crucial role of AI and automation in the discovery of the truly sustainable batteries of the future and the importance of developimg a circular battery economy.

Battery technologies based in multivalent charge carriers with ideally two or three electrons transferred per ion exchanged between the electrodes have large promises in raw performance numbers, most often expressed as high energy density, and are also ideally based on raw materials that are widely abundant and less expensive. Yet, these are still globally in their infancy, with some concepts (e.g. Mg metal) being more technologically mature. The challenges to address are derived on one side from the highly polarizing nature of multivalent ions when compared to single valent concepts such as Li ^+ or Na ^+ present in Li-ion or Na-ion batteries, and on the other, from the difficulties in achieving efficient metal plating/stripping (which remains the holy grail for lithium). Nonetheless, research performed to date has given some fruits and a clearer view of the challenges ahead. These include technological topics (production of thin and ductile metal foil anodes) but also chemical aspects (electrolytes with high conductivity enabling efficient plating/stripping) or high-capacity cathodes with suitable kinetics (better inorganic hosts for intercalation of such highly polarizable multivalent ions). This roadmap provides an extensive review by experts in the different technologies, which exhibit similarities but also striking differences, of the current state of the art in 2023 and the research directions and strategies currently underway to develop multivalent batteries. The aim is to provide an opinion with respect to the current challenges, potential bottlenecks, and also emerging opportunities for their practical deployment.

Mg metal anode‐based battery is a more sustainable, lower cost, and higher energy density alternative to Li‐ion. However, this battery chemistry also faces several challenges associated with the high charge density of Mg2+, including achieving high reversibility and low voltage hysteresis for Mg metal plating/stripping. While significant improvements are achieved in last decades, they involve rather complex electrolyte formulations and/or Mg salts difficult to produce, and the use of unpractical substrates such as platinum. Here, significant improvement in terms of Mg plating kinetics is achieved in electrolytes containing commercial magnesium bis(trifluoromethanesulfonyl)imide salt (Mg(TFSI)2) by using titanium substrate with similar crystal structure and lattice parameter as Mg leading to lower nucleation overpotential. Low salt concentration electrolyte and addition of dibutyl magnesium (Mg(butyl)2) also enable the formation of thinner interphase, richer in solvent based decomposition products, further improving Mg plating kinetics. This work highlights the complex role of Mg(butyl)2, often considered as a simple drying agent, and how it impacts ion solvation favoring the mobility of electroactive cationic species, paving the way toward better electrolyte design with improved cation transference number. [ABSTRACT FROM AUTHOR]

The crystal structure of the co-crystal of aquatrifluoridoboron with two ethylene carbonate (systematic name: 1,3-dioxolan-2-one) molecules, BF3H2O·2OC(OCH2)2, was determined by low-temperature single-crystal X-ray diffraction. The co-crystal crystallizes in the orthorhombic space group P212121 with four formula units per unit cell. The asymmetric unit consists of an aquatrifluoridoboron molecule and two ethylene carbonate molecules, connected by O—H...O=C hydrogen bonds. This crystal structure is an interesting example of a superacidic BF3H2O species co-crystallized with an organic carbonate.

Hybrid materials (HMs) combine the high diversity of functionalities of organic compounds with properties typical for inorganic materials, such as high mechanical strength or high thermal stability. Herein, HMs combining organic pigment molecules and TiO2 as inorganic component, with covalently linked components, i.e., so‐called class II HMs, are reported. The synthesis of such HMs is intrinsically challenging, as the apolar organic pigment component and the inorganic polar TiO2 component require different conditions for their respective formation. Herein, we circumvent this issue by employing solvothermal synthesis in superheated isopropanol, which through temperature tunability of the solvent properties allows for both generating and linking both components in one‐pot. First, it is shown that an organic benzimidazole‐based pigment molecule designed for readily binding to Ti can be synthesized solvothermally. Second, new class II titanium‐based HMs are generated from Ti(OiPr)4 and pigment precursors in a solvothermal reaction. The pigment@TiO2 HMs feature significant porosity and are structurally identified as layered structures of lepidocrocite‐like TiO2 linked via pigment molecules. These layered HMs assemble into hierarchical nanoflowers, and depending on the pigment segments, different interlayer spacings in between inorganic layers are observed. Third, the pigment@TiO2 materials are shown to be usable as electrode materials in lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

In recent years, several organic electrolytes have been reported allowing calcium metal electrodeposition. In all cases, some degree of passivation on the surface of the calcium electrode was reported. Following a recent report on borate-based passivation layer playing a crucial role for Ca plating in electrolyte solutions containing Ca(BF4)2, here we report the use of a boron-containing additive. The presence of this additive allows Ca plating and stripping using a Ca(TFSI)2 containing electrolyte, which otherwise lead to the formation of a fully Ca2+ blocking passivation layer.

Calcium-metal-anode based batteries have recently gained much attention owing to their higher theoretical capacity when compared to the commercial lithium-ion cells. However, electrodeposition of metallic calcium is challenging and currently there is only a few reported organic electrolytes allowing reversible plating/stripping, including Ca(BF4)2 in carbonate solvents. Many of the commercial salts are sold as hydrates, which is the case of Ca(BF4)2, however the drying of a divalent-metal cation organic electrolyte is not trivial. Herein, several procedures for drying BF4−-based electrolytes are explored and discussed. It is shown that the tetrafluoroborate anion can easily get hydrolyzed during some drying protocols producing impurities, and thus, it is necessary to prepare the salt in anhydrous conditions to ensure low water and contaminant contents. Two different synthetic routes are presented as alternatives to the commercial hydrated salt.

Batteries based on Ca hold the promise to leapfrog ahead regarding increases in energy densities and are especially attractive as Ca is the 5th most abundant element in the Earth's crust. The viability of Ca metal anodes has recently been shown by approaches that either use wide potential window electrolytes at moderately elevated temperatures or THF-based electrolytes at room temperature. This paper provides realistic estimates of the practical energy densities for Ca-based rechargeable batteries at the cell level, calculated using open source models for several concepts. The results from the Ca metal anode batteries indicate that doubled or even tripled energy density as compared to the state-of-the-art Li-ion batteries is viable if a practical proof-of-concept can be achieved.