Compositions of Co-doped LiMn2O4 spinel with MCNT for Lithium Batteries

摘要

Much attention is payed to doping of LiMn2O4 spinel by different chemical elements for the improvement of discharge spinel characteristics in redox reactions with lithium [1]. Cobalt as one from these elements improves specific discharge characteristics and cycling ability of LiMri2O4 spinel in lithium recharged power sources at volume and superficial doping [2, 3]. According to Guohua et al. LiCo_(1/6)Mn_(11/6)O4 showed good cycle performance with energy density of 370 Wh/kg at the 300 cycle [4]. Previously we reported the superiority of electrochemical characteristics of the mechanical mixtures of LiMn2O4 spinel with multiwall carbon nanotubes (MCNT) over those of spinel compositions with natural graphite in the prototypes of the Li-ion battery [5, 6]. Carbon conductive fillers, their nature and particle size plays the key role in the efficiency of the electrochemical transformation of spinel in Li-ion batteries. Electrodes based on the composition of the spinel and MCNT show a good cycling stability and efficiency at the discharge rate of 2C. The resistance of charge transport (R_(ct)) through the film/spinel composite surface is depends on the conductive filler. Value of R_(ct) decreases in spinel electrode in the presence of carbon filler (by the factor of thousand). Exchange current of spinel electrode increases under the influence of MCNT (from the order of 10~(-7) to 10~(-4) A cm~(-2)). The value of R_(ct) depends on the resistance in contacts between spinel particles and also between particles and current collectors. Contact resistance decreases under influence of MCNT with more efficiency than under influence of graphite because of small size of the particles with high surface area of the MCNT.