Lithium-ion rechargeable (secondary) batteries are based on a pair of intercalation electrodes. On charging, lithium ions move from the cathode through the electrolyte and insert into the anode; discharging reverses the process. One major element in the efforts to improve the capacity and performance of lithium-ion batteries is a focus on the design and synthesis of new intercalation electrode materials and their optimized manufacturing. Other elements include work on electrolytes, separators and cell design and assembly.

Lithium-air batteries dispense with the intercalation cathode, instead using a catalytic air cathode in combination with an electrolyte and a lithium anode. Oxygen from the air is the active material for the cathode and is reduced at the cathode surface—the lithium reacts directly with the oxygen. Theoretically, with oxygen as essentially an unlimited cathode reactant source, the capacity of the battery is limited only by the lithium anode. The theoretical specific energy of the Li-air cell is 13.0 kWh/kg—the highest of any metal-air battery system.

In addition to this very high energy density, the Li-air battery offers a flat discharge profile and long storage life, and is more environmentally friendly than some Li-ion systems.

Original lithium-air batteries—aqueous batteries, or with an aqueous electrolyte/air interface—were primary cells—i.e., not rechargeable. However, researchers have developed and continue to refine non-aqueous electrolyte rechargeable Li-air systems (earlier post).

There are numerous challenges for the non-aqueous rechargeable Li-air systems, such as low rates of oxygen diffusion in the porous air cathode and the accumulation of solid reaction products on the electrode, which blocks the contact between electrolyte and air. As with Li-ion batteries, there are many factors controlling the performance of a lithium-air battery, including cathode structure, anode morphology, electrolyte composition and cell assembly.

IBM’s focus on exploring battery technologies stems from IBM’s Big Green Innovations initiative. Announced in November 2006, as part of IBM’s investment in 10 new businesses generated by InnovationJam, Big Green Innovations has concentrated its efforts on water management, alternative energy and carbon management.

Almaden Institute. IBM Research will explore the next frontier of electrical energy storage and advanced battery systems at its annual Almaden Institute in San Jose, California, 26-27 August. The goal of the 2009 Almaden Institute is to catalyze long-term, concerted efforts to create next-generation rechargeable batteries capable of storing ten times more energy than today’s most powerful Lithium-ion batteries. Speakers include Nobel Laureate and energy expert Burton Richter; Marc Tarpenning, co-founder of Tesla Motors; and Deborah Gordon, co-author of 2 Billion Cars.

Previous Almaden Institutes have launched major research projects in cognitive computing, service science and healthcare informatics.

Resources

• Seyed Reza Younesi, Katarzyna Ciosek, Kristina Edström (2008) Lithium oxygen batteries; challenges and possibilities (paper at EVS 214)

• Takeshi Ogasawara et al. (2006) Rechargeable Li₂O₂ Electrode for Lithium Batteries. J. Am. Chem. Soc., 128 (4), pp 1390–1393 doi: 10.1021/ja056811q

• Dobley et al. Non-aqueous Lithium-Air Batteries with an Advanced Cathode Structure