Silver Cyanoguanidine Nitrate Hydrate: Ag(C2N4H4)NO3·½ H2O, a Cyanoguanidine Compound Coordinating by an Inner Nitrogen Atom

Silver(I) cyanoguanidine nitrate hydrate, Ag(C2N4H4)NO3·½H2O, was synthesized as the first cyanoguanidine solid-state complex in which monovalent Ag is coordinated through inner nitrogen N atoms. Its structure was characterized by single-crystal X-ray diffraction, crystallizing in the acentric orthorhombic space group P21212 with a = 10.670(3) Å, b = 18.236(5) Å, and c = 3.5078(9) Å. The differing chemical bondings of Ag(C2N4H4)NO3·½H2O and Ag(C2N4H4)3NO3 were compared on the basis of first-principle calculations

Reversible High Capacity and Reaction Mechanism of Cr 2 (NCN) 3 Negative Electrodes for Li‐Ion Batteries

International audienceA detailed study of the electrochemical reaction mechanism between lithium and the trivalent transition-metal carbodiimide Cr2(NCN)3, which shows excellent performance as a negative electrode material in Li-ion batteries, is conducted combining complementary operando analyses and state-of-the-art density functional theory (DFT) calculations. As predicted by DFT, and evidenced by operando X-ray diffraction and Cr K-edge absorption spectroscopy, a two-step reaction pathway involving two redox couples (Cr3þ/Cr2þ and Cr2þ/Cr0) and a concomitant formation of Cr metal nanoparticles is apparent, thus indicating that the conversion reaction of this carbodiimide upon lithiation occurs only after a preliminary intercalation step involving two Li per unit formula. This mechanism, evidenced for the first time in transition-metal carbodiimides, is likely behind its outstanding electrochemical performance as Cr2(NCN)3 can maintain more than 600 mAh g1 for 900 cycles at a high rate of 2 C