The lithium ion battery, which essentially transformed portable electronics, has been a tough act to follow. Last week, researchers from Argonne National Laboratory and the University of Chicago reported in Nature advances suggesting so-called ‘lithium air’ battery technology may be finally easing into position as lithium ion’s successor.
Past lithium air battery efforts have been hobbled by short life cycles and the need to use pure oxygen (hence, referred to as lithium-oxygen batteries); consequently a tank of oxygen gas would have to be part of the battery system, making it prohibitive for use in electric vehicles due to space requirements. A lithium-air battery that uses air from outside eliminates this problem (see paper’s abstract lower in text).
As reported in Nature – “Lithium-Oxygen Batteries with Long Cycle Life in a Realistic Air Atmosphere” – scientists from the University of Illinois at Chicago and the U.S. Department of Energy’s (DOE) Argonne National Laboratory has produced a new design for a beyond-lithium-ion battery cell that operates by running on air (hence, referred to as “lithium-air”) over many charge and discharge cycles.
Key features of the work include a new protective coating for the lithium metal anode, which prevents the anode from reacting with oxygen and hence deteriorating, and a novel electrolyte mixture that allows the cell to operate in an air atmosphere. In tests under an air environment, this cell maintained high performance during 700 cycles, far surpassing previous technology.
“The energy storage capacity was about three times that of a lithium-ion battery, and five times should be easily possible with continued research. This first demonstration of a true lithium-air battery is an important step toward what we call beyond-lithium-ion batteries,” said Amin Salehi-Khojin, co-principal investigator from the UL Chicago, in an account of the work on the ANL web site.
Researchers at the University of Illinois at Chicago built, tested, analyzed and characterized the battery cells, while those at Argonne mainly handled the basic science computational studies to determine how this system operates in air and what factors contribute to the improved cycling stability. The work consisted of tens of ab initio molecular dynamics simulations on systems of size ~500 atoms – such calculations are computationally intensive and entail use of leadership class computing facilities. They used the Center for Nanoscale Materials’ (CNM) high performance computing cluster for initial runs on smaller sizes (~200 atoms); for these they employed ~128 cores for a week according to Badri Narayanan, an assistant materials scientist in Argonne’s Materials Science division and an author on the paper.
Longer production runs on large systems (500 atoms) were performed on Argonne Leadership Computing Facility’s Vesta system. On ALCF, they used 512 compute cores for a period of 3 weeks for each of those runs. All calculations were carried out using the highly parallel density functional theory code (VASP). This new knowledge should prove crucial in scientists’ continued efforts to develop a full-size lithium-air battery.
Here’s a portion of the paper’s abstract:
“So far, however, such systems have been largely restricted to pure oxygen environments (lithium–oxygen batteries) and have a limited cycle life owing to side reactions involving the cathode, anode and electrolyte. In the presence of nitrogen, carbon dioxide and water vapour, these side reactions can become even more complex. Moreover, because of the need to store oxygen, the volumetric energy densities of lithium–oxygen systems may be too small for practical applications. Here we report a system comprising a lithium carbonate-based protected anode, a molybdenum disulfide cathode and an ionic liquid/dimethyl sulfoxide electrolyte that operates as a lithium–air battery in a simulated air atmosphere with a long cycle life of up to 700 cycles.
“We perform computational studies to provide insight into the operation of the system in this environment. This demonstration of a lithium–oxygen battery with a long cycle life in an air-like atmosphere is an important step towards the development of this field beyond lithium-ion technology, with a possibility to obtain much higher specific energy densities than for conventional lithium-ion batteries.”