Synthesis, Structure, and Magnetic Properties of [Li(H₂O)M(N₂H₃CO₂)₃]·0.5H₂O (M = Co,Ni) as Single Precursors to LiMO₂ Battery Materials

[Li(H 2 O)M(N 2 H 3 CO 2 ) 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, N 2 H 3 CO 2 -, prepared by mixing N 2 H 4 ·H 2 O and dry ice. Both the compounds crystallized in the chiral space group P 2 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 μ B for 1 and 2, respectively. These two compounds have been investigated as single precursors for layered materials LiMO 2, M = Ni and Co. Pyrolysis of 1 and 2 yields LiNiO 2 and LiCoO 2 at 700 °C in an oxygen atmosphere and at T > 700 °C in air, respectively. They were characterized by powder XRD, Rietveld refinement, and SEM. Cathodic properties of LiMO 2 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.