Studies on LiMn1.5Ni0.4Cr0.1O4 Cathode Spinel Combined with Graphene for Lithium Ion Batteries

The low-cost development of rechargeable lithium ion batteries is of considerable technological importance.  In this context, the use of active cathode LiMn_1.5Ni_0.4Cr_0.1O₄ material has attracted much attention due to its stable structure while intercalation and de-intercalation of lithium ions. The necessity of such battery material is that the energy density stored electrochemically in the electrodes is quite high. They combine high theoretical energy storage capability with low weight and good mechanical strength. Here we report the development of a rechargeable lithium ion battery with homogeneous mixing of graphene powder (with 10, 15 and 20%) in active cathode materials for high energy applications. The reduced graphene oxide was synthesized using modified Hummers method with high purity concentrated of H₂SO₄ (50 ml), oriented pyrolytic graphite, KMnO₄ (7 g) and H₂O₂ (30 wt %). The resultant mixture was stirred well and then filtered with the help of a glass filter. The obtained precipitates were dried for 30 h in a vacuum oven at room temperature. Highly conducting reduced graphene powder was obtained using hydrazine treatment. The redox behavior of the cell, which is normally too slow for practical applications, is accelerated with highly conductive powder of the graphene (which itself functions as an active cathode material). Intimate mixing of the two materials is achieved by a slurry maker using an organic solution for a cathode paste. The resulting electrode can be repeatedly charged to near its theoretical limit and discharged. The gravimetric energy density of our composite cathode materials exceeds that of the LiMn_1.5Ni_0.4Cr_0.1O₄ oxide electrodes in lithium-ion batteries, a feature that is likely to prove advantageous in applications where weight, rather than volume, is a critical factor. The aforementioned results will be discussed.