The Role of Modified Graphene in Cathode Formulations for Lithium-Ion Batteries

One of the main challenges in the development of lithium-ion batteries is to increase their specific energy by the use of high-voltage and high-capacity cathode materials. LiNi_0.5Mn_1.5O₄ (LNMO) is one of the most promising materials with a theoretical specific capacity of 147 mAh/g and a Li⁺ deinsertion/insertion potential of 4.7-4.8 V vs Li⁺/Li. However, the use of LNMO raises the question of electrolyte decomposition at such a high potential with the consequent formation of a surface layer that affects the cathode and, hence, the cell performance. Interface stability issues are overcome by LiM_xM_1-xPO₄ (LMP, with M=Fe, Mn) and Li₃V₂(PO₄)₃ (LVP) olivines, with Li⁺ deinsertion/insertion at potential ranging from 3.4 V to 4.5 V vs Li⁺/Li, that are widely investigated for their high specific capacity, near 170 mAh/g, and their intrinsic safety and environmental compatibility. However, the electronic and ionic conductivity of olivines need improvements.

We explored the effect of partially reduced graphene oxide on LNMO performance in conventional electrolyte [1] and here we investigate the role of modified graphene in LNMO- and LMP/LVP-composite materials. Morphological and structural characterization of the cathode materials and electrochemical tests of the corresponding electrodes will be reported and discussed.

[1] S. Monaco, F. De Giorgio, L. Da Col, M. Riché, C. Arbizzani, M. Mastragostino, J. Power Sources, submitted

Acknowledgments

The authors wish to thank ENEA and Italy’s Ministero dello Sviluppo Economico for financial support under the Program 2013 “Ricerca di sistema elettrico, Materiali catodici per batterie litio ione ad elevata energia”.