AsianScientist (Jun. 16, 2015) – By tweaking the chemical composition of lithium-based electrodes, scientists have developed high-capacity rechargeable batteries. Their findings have been published in the Proceedings of the National Academy of Sciences.
Although much progress has been made in developing alternative power sources such as solar power, the problem of energy storage remains a major concern, particularly for sources that do not allow continuous and consistent energy harvesting.
Existing storage solutions are largely based on lithium (Li-ion) batteries. These rechargeable batteries have become increasingly sophisticated over the years, using different combinations of elements in their electrodes and crystals to extend the life and increase the capacities of the batteries. Despite such advancements, oxidation and decomposition of the electrodes are still a concern and affect the performance of the batteries as a whole.
A recent collaborative effort between scientists from Tokyo Denki University, Tokyo University of Science, Nagoya Institute of Technology, Japan Science and Technology Agency and Ritsumeikan University, has revealed a new material for use as electrodes in Li-batteries–introducing pentavalent niobium (Nb) ions into the cubic-close packed (CCP) crystal structure.
Starting with the electrochemically inactive Li3NbO4 crystal structure, researchers partially substituted lithium and niobium with different transition metals. The new compounds showed varying degrees of effectiveness, with the manganese-substituted sample (Li1.3Nb0.3Mn0.4O2), delivering the largest reversible capacity out of the various substitutes (Co, Ni, Fe, Mn).
The novel electrodes were also tested on various attributes: cyclability was found to improve when charged under constant capacity mode, but was insufficient under galvanostatic charge/discharge. The rate capability, on the other hand, performed much better than expected, given that the lithium migration was anticipated to slow at 50˚C and was proven to be acceptable as electrode materials. It is thought that it may even be possible to further improve the rate capacity by optimizing particle morphology, chemical composition and surface energy, among other factors.
The study impacts energy storage on two fronts: firstly, increased capacities and varied operating conditions have been uncovered, opening the possibility of implementing such energy storage solutions for more applications–either those that operate under currently undesirable conditions, or those that require much higher capacities than what is currently available.
The second impact may be much deeper: by successfully substituting and synthesizing element in the lithium oxide electrodes, the team has shown that oxides that were “previously thought to be electrochemically inactive can actually be used as potential host structures for high-capacity electrode materials,” leading to potential material innovations for batteries.
The article can be found at: Yabuuchi et al. (2015) High-capacity Electrode Materials For Rechargeable Lithium Batteries: Li3NbO4-based System With Cation-disordered Rocksalt Structure .
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