Synthesis and characterization of spinel Li_4Ti_5O_(12) anode material by oxalic acid-assisted sol-gel method

摘要

Anode material Li_4Ti_5O_(12) for lithium-ion batteries has been prepared by a novel sol-gel method with oxalic acid as a chelating agent and Li_2CO_3 and tetrabutyl titanate [Ti(OC_4H_9)_4] as starting materials. Various initial conditions were studied in order to find the optimal conditions for the synthesis of Li_4Ti_5O_(12) Oxalic acid used in this method functioned as a fuel, decomposed the metal complexes at low temperature and yielded the free impurity Li_4Ti_5O_(12) compounds. Thermal analyses (TG-DTA) and XRD data show that powders grown with a spinel structure (Fd3m space group) have been obtained at 800 deg C for 16 h. SEM analyses indicated that the prepared Li_4Ti_5O_(12) powders had a uniform cubic morphology with average particle size of 200 nm. The influence of synthesis conditions on the electrochemical properties was investigated and discussed. The discharge capacity of Li_4Ti_5O_(12) synthesized with an oxalic acid to titanium ratio R = 1.0 was 171 mAh g~(-1) in the first cycle and 150 mAh g~(-1) after 35 cycles under an optimal synthesis condition at 800 deg C for 20h. The very fiat discharge and charge curves indicated that the electrochemical reaction based on Ti~(4+)/Ti~(3+) redox couple was a typical two-phase reaction.