Feasability of Making a Lithium Ion Cathode using the Layer-by-Layer Process.

Abstract

There has been a renewed interest in secondary lithium ion batteries because of the potential use in various electric and hybrid electric vehicles batteries for automotive applications. These days both high energy and high power density are sought in the same device. Lithium ion batteries are well known for their high energy density. Their power density, however, is relatively low. On the other hand capacitors typically have high power densities but very poor energy densities. It would be ideal to achieve high energy and power densities in the same device. Nano technology could enable the enhancement of both properties in a device. We have shown how using polymer films, a high performance lithium ion battery is made. Using two water soluble polymers, PEO (polyethylene Oxide) and PAH (polyallylamine hydrochloride) we prepare 20 layers of films. Within each pair we introduce Co(OH)2 . This is water -soluble too. Later we do a treatment which produces CoOOH and LiCoO2 . These are the electronic conductor and the active material for the battery respectively. Nano particles are deposited within the films and later treated. Thus we were able to produce a LbL cathode, which demonstrates a very high efficiency, high specific capacity and possibly high capacitance. More detailed testing is proposed to verify the presence of the capacitor. For now it is proposed as a hypothesis. The capacitor in the battery contributes to coulombs or additional current especially at the very high rates. This is all due to the pretreatment done to the electrode prior to constructing the battery. Hence we show that the pretreatment is crucial to developing an electrode showing high capacity and high rate capability. It holds promise of very high energy density and very high power density co-existing in one device. It heralds the beginning of a very important area of investigation and also a direction for future efforts.