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Comparative Electrochemical Study of Metal Oxalate As Anode for Lithium Batteries
Several metals based oxalates with different aspect ratios have been synthesized by hydrothermal reaction of metals (= Ni, Co, Mn) with Na2C2O4 and H2O in the presence of ethylene glycol (EG). Control over the aspect ratios of oxalates were achieved by adjusting the hydrothermal reaction temperature and time.
The electrode was fabricated by mixing 70 wt% active material, 10 wt% carbon black (electronic conductive additive) and polyacrylic acid (PAA, binder) in N-methylpyrrolidinone (20 wt%). A solution of 1 M LiPF6 dissolved in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (3 : 7 weight ratio) was used as the electrolyte in the cell. Electrochemical test was carried out in coin type cell. Galvanostatic electrochemical charge and discharge test were made between 0V and 3.0V at 100 mAg-1 current at room temperature.
The hydrothermal method is useful to synthesize metal oxalate with particles and crystallization. Nickel and manganese oxalate crystallize in the monoclinic phase, while the cobalt compound adopts the orthorhombic phase.
The as-prepared metal oxalates demonstrate a high performance as anode material for LIB. Among them, nickel oxalate showed a high initial discharge capacity of 1321 mAhg-1. The first charge capacity of the as-prepared electrode at a current density of 100 mAg-1 reach 786 mAhg-1 with good capacity retention.