Preparation of spherical spinel LiMn_2O_4 cathode material for lithium ion batteries

摘要

A novel process is proposed for synthesis of spinel LiMn_2O_4 with spherical particles from the inexpensive materials MnSO_4,NH_4HCO_3,and NH_3centre dotH_2O.The successful preparation started with carefully controlled crystallization of MnCO_3,leading to particles of spherical shape and high tap density.Thermal decomposition of MnCO_3 was investigated by both DTA and TG analysis and XRD analysis of products.A precursor of product,spherical Mn_2O_3,was then obtained by heating MnCO_3.A mixture of Mn_2O_3 and Li_2CO_3 was then sintered to produce LiMn_2O_4 with retention of spherical particle shape.It was found that if lithium was in stoichiometric excess of 5% in the calcination of spinel LiMn_2O_4,the product had the largest initial specific capacity.In this way spherical particles of spinel LiMn_2O_4 were of excellent fluidity and dispersivity,and had a tap density as high as 1.9 g cm~(-3) and an initial discharge capacity reaching 125 mAh g~(-1).When surface-doped with cobalt in a 0.01 Co/Mn mole ratio,although the initial discharge capacity decreased to 118 mAh g~(-1),the 100th cycle capacity retention reached 92.4% at 25degC.Even at 55degC the initial discharge capacity reached 113 mAh g~(-1) and the 50th cycle capacity retention was in excess of 83.8%.