Synthesis, crystal and electronic structure of Li8Zn2Ge3, a compound displaying an open layered anionic network

A better interpretation of the electrochemical behavior of the compound Li2ZnGe as a negative electrode material for lithium batteries has forged the need to revisit the pseudo binary Li(Zn,Ge) system. The crystal structure of Li2ZnGe was found ordered in the cubic F4¯3m space group (a=6.123(1)Å), it was refined both from ambient temperature powder pattern, using the Rietveld method and from single crystal intensities recorded at −100 °C−100 °C. The new compound Li8Zn2Ge3 has been discovered in the Li-rich domain and its structure determined from single crystal in the trigonal R3c space group (a=7.555(1),c=24.449(3)Å). The originality of the compound Li8Zn2Ge3 arises from its hexagonal ZnGe anionic layer in which the 1/3 vacancy on the Zn site is compensated by two lithium atoms. Theoretical analysis on the basis of EHT and DFT periodic calculations has provided informations on the electronic properties and bonding within the planar hexagon-based ZnGe network in Li8Zn2Ge3.

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