Synthesis, structure, and magnetic properties of [Li(H2O)M(N2H3CO2)3]•0.5H2O (M = Co,Ni) as single precursors to LiMO2 battery materials

[Li(H2O)M(N2H3CO2)(3)].0.5H(2)O, M = Ni (1) and Co (2), has been synthesized in moderate yield from the corresponding metal salts and hydrazinecarboxylate anion, N2H3CO2-, prepared by mixing N2H4. H2O and dry ice. Both the compounds crystallized in the chiral space group P2(1) and have interesting 2D bilayer network structures in the solid state comprising fused helical coordination polymers with extensive hydrogen bonding. Samples 1 and 2 exhibited paramagnetism, as shown by the variable temperature magnetic measurements. The calculated magnetic moments were 2.82 and 4.39 mu(B) for 1 and 2, respectively. These two compounds have been investigated as single precursors for layered materials LiMO2, M = Ni and Co. Pyrolysis of 1 and 2 yields LiNiO2 and LiCoO2 at 700 degrees C in an oxygen atmosphere and at T > 700 degrees C in air, respectively. They were characterized by powder XRD, Rietveld refinement, and SEM. Cathodic properties of LiMO2 have been evaluated by cyclic voltammetry and galvanostatic charge-discharge cycling up to 20 cycles in the voltage ranges, 2.5-4.3 and 2.5-4.5 V vs Li metal. Results are in tune with those reported in the literature, thereby indicating that 1 and 2 are excellent single-source precursors for obtaining electrochemically active battery materials.