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

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 700^oC 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 paper

Cycling 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.

References:

1. Shouli Li, et al, “In-situ controllable synthesis and performance investigation of carbon-coatedmonoclinic and hexagonal LiMnBO₃ composites as cathode materials inlithium-ion batteries” - Journal of Power Sources, 236 (2013) 54e60
2. Yong –Suk Leeet al, “Structural and electrochemical behaviour of LiMnBO₃ synthesised at various temperature” - Electronic Material Letters (accepted for publication)