Hydrogen release and absorption in mixed anion lithiumudamide/lithium ternary nitride systems

摘要

In this work, reactions of either LiBH(_4), ZnCl(_2) or Zn(_3)N(_2) with LiNH(_2) have been studied.ud udThe presence of CoO significantly affected the products and hydrogen release on heating mixtures ofudχLiBH(_4)-γLiNH(_2). The ratios of the l4(_1)/amd and the P2(_1)/c polymorphs of Li(_3)BN(_2) in the products have been changed under different conditions studied. On addition of CoO, the temperature of hydrogen release from the χLiBH(_4)-γLiNH(_2) systems was greatly reduced, starting from 100°C and peaking around 250°C, much lower than 240°C and 330°C without catalyst. Ball-milling helped to improve the amounts of hydrogen desorbed from 3–4 wt% up to ≥10 wt%.ududIn the reactions of ZnCl(_2) + nLiNH(_2) (where (extit n) = 2–6), main products were LiCl, Zn(_3)N(_2), and LiZnN. NH(_3) was the main gas released from these reactions and the addition of LiH changed NH(_3) into H(_2), which was released around 90°C, much lower than in the absence of LiH. A mixture of LiZnN and LiCl obtained from this reaction was partly rehydrogenated to form Li(_2)NH and Zn.ududThe reaction of Zn(_3)N(_2) and LiNH(_2) was found to produce pure LiZnN without LiCl. Neither pure LiZnN nor Zn(_3)N(_2) could be hydrogenated under the conditions tried, but a mixture resulting from the reaction could react with H(_2) to form LiNH(_2) and Zn. The cyclability of the Li–Zn–N system showed an ability to release and take up gases under different pressure conditions. Mg-doping in LiZnN was examined to improve reversibility of the Li–Zn–N system but was not successful.