Boron clusters are proposed as a new concept for the design of magnesium-battery electrolytes that are magnesium-battery-compatible, highly stable, and noncorrosive. A novel carborane-based electrolyte incorporating an unprecedented magnesium-centered complex anion is reported and shown to perform well as a magnesium-battery electrolyte. This finding opens a new approach towards the design of electrolytes whose likelihood of meeting the challenging design targets for magnesium-battery electrolytes is very high.

Five heteroleptic Cu(i)bis(phenanthroline) chromophores with distinct variation in the steric bulk at the 2,9-phenanthroline position were synthesized using the HETPHEN method, and their ground and excited state properties are described. Analysis of the crystal structures reveals a significant distortion from tetrahedral geometry around the Cu(i) centre which is attributed to favourable aromatic interactions between the two phenanthroline ligands. Ultrafast and nanosecond transient optical spectroscopies reveal that the excited state lifetime can be tuned across two orders of magnitude up to 74 nanoseconds in acetonitrile by changing the 2,9-substituent from hydrogen to sec-butyl. X-ray transient absorption spectroscopy at the Cu K-edge confirmed Cu(i) oxidation to Cu(ii) and revealed a decrease of the Cu-N bond lengths in the excited state. The ground and excited state characterization presented here will guide the integration of CuHETPHEN chromophores into complex electron donor-acceptor architectures.

Boron clusters are proposed as a new concept for the design of magnesium-battery electrolytes that are magnesiumbattery-compatible, highly stable, and noncorrosive. A novel carborane-based electrolyte incorporating an unprecedented magnesium-centered complex anion is reported and shown to perform well as a magnesium-battery electrolyte. This finding opens a new approach towards the design of electrolytes whose likelihood of meeting the challenging design targets for magnesium-battery electrolytes is very high.The possibility of developing a rechargeable magnesium battery has been a topic of great interest for several decades. [1] Magnesium batteries are particularly attractive owing to their high theoretical capacity (3832 mA h cm À3 ) as well as the low cost and high abundance of Mg metal as compared to Li. [1,2] Additionally, Mg possesses an important safety advantage over Li in that Mg metal is not prone to dendrite formation. [3] However, before Mg batteries can see practical application, several challenges must be overcome, including the identification of a suitable solvent/electrolyte combination.[2] It has proven particularly challenging to identify such a system for magnesium-based batteries owing to the tendency of many common electrolytes to form nonconductive ion-blocking layers at the electrode surface.[4] Thus, any solvent/electrolyte combination used in a Mg battery must be stable across the entire potential window at which the battery operates.This requirement is particularly problematic for the design of high-voltage battery systems, for which an electrolyte candidate must be stable to both Mg metal (À2.37 V versus the normal hydrogen electrode, NHE) and the cathode-active material selected, which should ideally operate near + 1 V (vs. NHE). Furthermore, previous research has suggested that Mg metal is reactive toward many common polar solvents and electrolyte anions.[5] In fact, the majority of previously reported electrolyte systems have been limited to highly inert ethereal solvents, such as tetrahydrofuran (THF).[6] This limitation makes the design of electrolyte materials quite difficult, as a successful candidate must be highly soluble in these nonpolar solvents in addition to being electrochemically robust. As a result, only a handful of potential electrolytes are known to be compatible with Mg anodes. [6] Recent studies at the Toyota Research Institute of North America have demonstrated Mg(BH 4 ) 2 to be a highly competent electrolyte for magnesium-battery applications. [7] This electrolyte was the first non-organomagnesium electrolyte compatible with Mg metal and provided excellent electrochemical performance in glyme. In tandem with further research into this system, we sought to pursue potential routes to materials with enhanced oxidative stability as compared to the observed oxidation onset potential of 1.7 V (vs. Mg on Pt) for Mg(BH 4 ) 2 .High oxidative stability is crucial for the development of Mg batteries for operation with future high-voltage cathodes. Although organo...