Synthesis and Morphological Influence on High Capacity LiMnBO3 Cathode Material for New Generation Lithium Ion Batteries

Abstract

In search of new cathode material, Borate based electrode, LiMBO3 (M= Fe, Mn and Co) for lithium ion battery offer several attractive features, such as low molar mass, abundant, environmental friendliness and relatively high theoretical capacities (222 mAh/g) [1]. In this view,an effort towards improvement in electronic conductivity of LiMnBO3material via reduction in particle size and appropriate synthesis condition is reported in this paper.A simplified Sol gel method was adopted for the synthesis of LiMnBO3cathode material. High Purity, analytical grade LiNO3, Mn(NO3)2. 6H2O and H3BO3 were used as precursors. The synthesized powders were annealed at 700oC for 3 hrs under different atmosphere.Powder X –ray diffraction pattern of the LiMnBO3 revealed the presence of mixed phases of hexagonal and monoclinic in which hexagonal phase is dominant in both Ar and N2atm. [2]. The crystallite size (Debye –Scherrer) calculation indicated nanoparticle formation (~ 38 nm).The SEM images of LiMnBO3 (Fig.1a) showed elongated spherical shaped particle in Ar atmosphere whereas peculiar tetragonal rod shaped particles was observed for N2atmosphere (fig.1b). The influence of morphological changes on the electrochemical performance is reported in this paperCycling profile of LiMnBO3 cells are given in fig.2. The cells were cycled between 1.5 to 4.8V at room temperature at a C rate of C/20. Fig.2, revealed that the capacity was maintained at 198mAh g-1for the first three cycles followed by a good capacity retention upto 35 cycles with a capacity deliverance of 190mAh/g (figure not shown).From the results, we report a sol gel derived LiMnBO3 that delivers a first discharge capacity of 198mAh g-1 at C/20 rate, the best result reported so far for LiMnBO3to our knowledge.