During Whittingham's absence from battery research, Japanese companies surged ahead with the development of lithium ion batteries. Sony, in particular, developed lithium-ion rechargeable batteries with lithium cobalt dioxide and carbon electrodes. They obtained important strategic patents and have since dominated the market for batteries in portable electronics. Whittingham turned to other substances, such as manganese and vanadium oxides and to the technique of hydrothermal synthesis.
In the 1990s, researchers sought for alternatives to TiS2. The Goodenoough group at the University of Texas, for instance, has investigated cathodes based on phosphates, such as LiFePO4. Whittingham has focused upon manganese. Manganese is cheap and well-known to battery researchers; it has higher emf than TiS2 and low toxicity. In contrast with TiS2, manganese oxides exhibit several phases, for instance depending upon the degree of lithium intercalation. A phase (and process of synthesis) was sought for that exhibits the most desired characteristics. Potassium-pillared and cobalt-substituted manganese dioxides showed promise. In the second half of the 1990s, Whittingham's group at SUNY have increasingly turned to vanadium oxides, such as that used in Hydro-Québec/3M's lithium polymer battery. Vanadium species used as pillars between manganese dioxide layers should theoretically improve both the stability and the conductivity of the lattice.
Whittingham is now optimistic about the prospect of making the desired 250Ah/kg cells operating around 3.5V within the next decade.
This page was written and last updated on 16-Feb-2001 by Arne Hessenbruch.