We have recently characterized three classes of peroxodicopper(II) complexes, which are formed reversibly from the reaction of Cu(I) precursors (1-3) with 02 at -80 °C in solution. Here, we detail and compare the reactivities of [Cu2(XYL-O-)(02)]+ (4, a phenoxo-bridged peroxodicopper(II) species having terminal Cu-02 coordination), [|Cu-(TMPA)|2(02)]2+ (5, a trans µ-1,2-peroxo-bridged complex with a tetradentate ligand on each copper(II) atom), and [Cu2(N4)(02)]2+ (6, which contains a bridging peroxo moiety with tridentate groups at both copper atoms). Complexes 4 and 5 possess a basic or nulceophilic peroxo group, but 6 behaves differently, possessing a nonbasic or electrophilic peroxodicopper(II) moiety. Thus, reaction of PPh3 with 4 and 5 readily causes the stoichiometric displacement of the bound 02 ligad, producing Cu(I)-PPh3 complexes. With 6, slow but complete oxygen atom transfer occurs, giving triphenylphosphine oxide. Protonation (or acylation) reactions are particularly striking, as addition of HBF4 or HPF6 to 4 and 5 gives nearstoichiometric yields of H202 (from excess H+; iodometric titration), but 6 is relatively insensitive to protons. Carbon dioxide reacts with 4 and 5 to give peroxycarbonato complexes at -80 °C, which decompose to carbonato compounds; 6 does not react with C02. All three complexes 4-6 react with sulfur dioxide to give sulfato products. Trityl cation (Ph3C+) reacts with all the complexes to give benzophenone, but the relative yields again support the notion that the peroxo group in 6 is a poorer nucleophile. 2,4-Di-Zert-butylphenol acts as a protic acid toward 4 and 5, but in the presence of 6, hydrogen atom abstraction leads to oxidatively coupled biphenol products. The reactions of 4-X-C6H4MgBr (X = CH3, F) with 4-6 produce mixtures of 4-X-C6H4OH and substituted biphenyls; product ratios again support the view that 6 is a better one-electron oxidant and electrophilic reagent. The relationship of the observed reactivity patterns and structures of 4-6 is discussed, and it suggested that the µ-;2: )2^ ^proposed for 6 confers its unique reactivity. The relationship of the structure and reactivity of 6 to a related and previously described monooxygenase model system is discussed, as well as the relevance to the active site chemistry of copper proteins involved in 02 utilization.

Identifying positive electrode materials capable of reversible multivalent electrochemistry in electrolytes containing divalent ions such as Mg2+, Ca2+, and Zn2+ at high operating potentials remains an ongoing challenge in “beyond lithium-ion” research. Herein, we explore the Zn2+ charge-storage mechanism of a vanadium-based Na+ superionic conductor (NASICON), Na3V2(PO4)3. By using X-ray synchrotron techniques to unravel potential-dependent structure–property relationships, we ascribe the reversible electrochemical behavior of Na3V2(PO4)3 to a quasi-two-stage intercalation process that involves both Na+ and Zn2+. Initial charging of Na3V2(PO4)3 leads to a Na+-extracted phase corresponding to NaV2(PO4)3, whereas subsequent discharge results predominantly in Na+ intercalation followed by Zn2+ intercalation. Operando X-ray diffraction of Na3V2(PO4)3 was used to study the phase changes associated with the first charge/discharge process, and ex situ measurements were used to precisely link the changes in the crystal structure to a quasi-two-stage intercalation of Na+ and Zn2+. The corresponding changes in the V-oxidation state, V-O coordination, and the presence of Zn2+ were confirmed by X-ray absorption spectroscopy. The results of this work present a comprehensive understanding of the charge-storage properties for a well-established NASICON structure that confers both the high capacity (∼100 mA h g–1) and high potential (1.35 and 1.1 V vs Zn/Zn2+).

Elemental sulfur (S8) was found to react with [(TMPA)CuI(CH3CN)]+ to form the trans-mu-1,2 end-on disulfide complex [(TMPA)Cu-S-S-Cu(TMPA)]2+. The X-ray structure of this centrosymmetric disulfide complex shows a Cu(1)-S(1) bond length of 2.280(2) A and a S(1)-S(1A) bond length of 2.044(4) A.

Whether attempting to eliminate parasitic Li metal plating on graphite (and other Li-ion anodes) or enabling stable, uniform Li metal formation in 'anode-free' Li battery configurations, the detection and characterization (morphology, microstructure, chemistry) of Li that cannot be reversibly cycled is essential to understand the behavior and degradation of rechargeable batteries. In this review, various approaches used to detect and characterize the formation of Li in batteries are discussed. Each technique has its unique set of advantages and limitations, and works towards solving only part of the full puzzle of battery degradation. Going forward, multimodal characterization holds the most promise towards addressing two pressing concerns in the implementation of the next generation of batteries in the transportation sector (viz. reducing recharging times and increasing the available capacity per recharge without sacrificing cycle life). Such characterizations involve combining several techniques (experimental-and/or modeling-based) in order to exploit their respective advantages and allow a more comprehensive view of cell degradation and the role of Li metal formation in it. It is also discussed which individual techniques, or combinations thereof, can be implemented in real-world battery management systems on-board electric vehicles for early detection of potential battery degradation that would lead to failure.

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Realization of extreme fast charging (XFC, ≤15 minutes) of lithium-ion batteries is imperative for the widespread adoption of electric vehicles. However, dramatic capacity fading is associated with XFC, limiting its...

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