Traditional lithium-based batteries feature an intercalated lithium compound, such as lithium cobalt oxide as one electrode, and graphite as the second, along with an organic solvent electrolyte. This electrochemical combination provides a high energy-density and importantly, a slow loss of charge when not in use.
During the charging process lithium ions move through the electrolyte from the positive lithium cobalt oxide electrode to the negative graphite electrode. When discharging or in use the ions move back through the electrolyte, from negative to positive. This process can be repeated hundreds, if not thousands of times before the quality of the cell begins to truly degrade.
This, combined with the higher operating voltage of lithium-based batteries – 3.7 volts compared to an alkaline battery at 1.5 volts – has made it the portable battery of choice for most consumer electronics.
Lithium-air batteries will work slightly differently. Instead of storing an oxidising chemical internally, the battery will oxidise lithium at the anode, whilst restricting the flow of oxygen to a graphite cathode. This process will induce the flow of electricity and enable the Li-Air battery to measure an energy density similar to petrol. The recharge process will see the same process reversed.
Research into Li-Air batteries is currently driven by increased interest in advanced battery power for vehicles, as more consumers begin to make the switch to greener forms of transportation.
Unfortunately there is still a vast amount of research to be completed, in several key areas, before the Li-Air battery will be commercially or even chemically viable.
Lithium is extremely volatile to aqueous products and, drawing oxygen as a key component for energy-production will need extremely efficient chemical isolation practices to ensure a stable cell. Research terms are also contending with external contaminants entering the cell during the oxidisation process, with similar, volatile results.
Researchers have also encountered problems preventing the anode reacting with the electrolyte required in the cell, causing degradation of the electrochemical process and in some cases producing lithium-carbonate – an unwanted chemical (in this process).
Screening the required chemicals looks an obvious solution with suggestions of lithium-conductive glass-ceramics mooted as a potential separator. However, developing a sufficiently strong glass-ceramic solution will also take time due to the fragility of the material. Other researchers are investigating potential graphene solutions due to the materials strength and conductive nature, but it seems we are still some way off a complete battery.
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