Zong-huai Liu

Synthesis of lithium-rich LixMn2O4 spinels by lithiation and heat-treatment of defective spinels

Single-phase lithium manganese oxide spinels were synthesized in two steps: (1) the preparation of defective spinel precursors with different Li ∶ Mn ratios through lithium insertion into Li-birnessite manganese oxide in a LiNO3 flux at 400 °C, followed by (2) heat-treatment of the precursors at 750 °C in air. Depending upon the Li ∶ Mn ratio, the precursors yielded three types of single-phase spinels: a lithium-deficient type with lithium and oxygen deficiencies, stoichiometric LiMn2O4, and a lithium-rich type with lithium in the 16d-site of space group Fdm but with oxygen deficiency. The electrochemical measurements showed that good rechargeability on cycling between 3–4.3 V could be obtained in all the lithium-rich spinels Li[LixMn2 − x]O4 − δ, where 0 < x < 0.33 and δ < 0.2.

Intercalation of cobaltammine complex ions into layered manganese oxide

The intercalation of Co(2+), [Co(NH(3))(6)](3+), and [Co(NH(3))(5)Cl](2+) ions into layered manganese oxide (birnessite) was studied by chemical, XRD, SEM, IR, and DTA-TG analyses. The intercalation reaction progressed by a 2:1 or 3:1 ion-exchange mechanism depending on the valence of the starting ions. The oxidation state of cobalt did not change with the intercalation reaction. The intercalation of [Co(NH(3))(6)](3+) ions resulted in an increase of basal spacing from 0.716 to 0.956 nm, giving a layered structure material consisting mainly of platelike particles. The chemical analysis results showed that the structure of [Co(NH(3))(6)](3+) ions was maintained in the interlayer. On the other hand, an H(2)O/NH(3) ligand exchange reaction progressed for the intercalation of [Co(NH(3))(5)Cl](2+) ions, resulting in an increase in the basal spacing from 0.716 to 0.956 nm.

Co-Precipitation Synthesis of Acetylene Black/Li-Birnessite Composite Suitable for a Li-Rechargeable Battery

Binary composites of acetylene black/Li-birnessite manganese oxide were synthesized through the co-precipitation of Li-bimessite with acetylene black. The galvanostatic charge/discharge tests showed that the composites had a higher discharge capacity than their corresponding physical mixture.