In theory, lithium and oxygen are the ingredients for something close to the perfect battery. Unfortunately, attempts to build them in practice have so far led to something that loses performance very fast. New research suggests an answer to this, but with a twist.
The need for better ways to store electricity, whether to recharge your phone or to power a country at night, is so great that dozens of potential technologies are being explored. Lithium-oxygen combinations look unbeatable on many measures: They are theoretically capable of storing at least five times the amount of charge per volume of the lithium-ion batteries that now dominate the small-to-medium scale market. Lithium and oxygen are also so light that their combination will beat any alternative on weight, which is important for portable uses. And it is not like oxygen is in short supply.
The problem has been that batteries need electrodes, and lithium-oxide anodes have decomposed the electrolytes and corroded the cathodes of laboratory versions far too quickly to consider mass market applications. Professor Linda Nazar of Canada’s University of Waterloo believes the answer is to move away from lithium peroxide (Li2O2) and lithium superoxide (LiO2) in favor of lithium oxide (Li2O).
“In comparison with the peroxide and superoxide, lithium oxide (Li2O) is much less chemically reactive with organic solvents,” Nazar writes in Science. This idea has occurred to people before, but the batteries have refused to play ball, producing lithium peroxide when discharged rather than something more harmless.
Nazar calculated that room temperatures favor lithium-peroxide production, so she ran a battery at 150ºC (302ºF). It not only worked but was almost 100 percent efficient in terms of the ratio of discharge to charge.
Maintaining such high temperatures imposes an energy cost on the system. Certainly no one is going to want something that hot in their pocket, or even their laptop, so many applications are out. Besides those obvious problems, Nazar’s battery faces all the usual obstacles in getting from the lab bench to prototype stage.
However, with an energy density already four times as high as lithium-ion batteries, the potential for Nazar’s product in electric vehicles is huge. Moreover, the cathode in the model tested was made from nickel – a widely abundant metal. The high cobalt content in most existing battery cathodes is becoming a problem as the price spirals and demand for the metal fuels wars and environmental destruction.