structural and electrochemical characterisitics of layered manganese bronze synthesizes using a sol-gel

Abstract

Recently proposed layered Li-Mn oxide-based materials(Li2/3[NixMn1-x]O2, x=1/6 - 1/30 have shown promising properties as a positive electrode active material for lithium secondary batteries � 새 their low cost, large theoretical capacity, and environmental safety. In this work, O2-Li2/3[Li1/6Mn5/6]O2 was prepared by ion exchange of Li for Na from precursor P2-Na2/3[Li1/6Mn5/6]O2 synthesized by a sol-gel method as functions of chelating agent and calcination temperature. In order to clearly understand the influence of the temperature on the synthesis of O2-Li2/3[Li1/6Mn5/6]O2, P2-Na2/3[Li1/6Mn5/6]O2 precursor was synthesized in the calcinations temperature range of 700 - 1000℃ using slycolic and adipic acids as chelating agent, respectively. The effect of Ni doping in the synthesized material was investigated to increase the discharge capacity and suppress the capacity fading. Powder X-ray diffraction(XRD) was used to characterize the purity and structure of the prepared samples. Ion exchange in hexanol was almost completed for Li ion with 1/6 and the sample had O2 structure with faults. The structural and electrochemical characteristics of Li2/3[Li1/6Mn5/6]O2 prepared at 800℃ for 10h using glycolic acid. But it was found that the Ni doped sample included T2 structure. The electrochemical test was performed using CR2032 coin-type cells fabricated with the samples prepared for 10h at 800℃ using adipic acids(sample B) and glycolic acid(sample F) as chelating agent. the sample B delivered the intial discharge capacities fo sample F at the 1st and 30th cycles were 187 and 169 mAh/g, respectively. The capacity fading rate was 0.42% per a cycle. The discharge capacity of No-doped O2-Li2/3[Ni1/6Mn5/6]O2 delivered 198 mAh/g at the first cycle with the capacity retention rate of 98% after 30 cycle. The discharge capacity of Ni doped Li2/3[Li1/6Mn5/6]O2 increased and the capacity retention rate was significantly improved. The merits of cation doping in O2 structure has been intensively discussed in this work.