RESEARCH ARTICLES report on original research from a study or experiment ("We had a hypothesis, we did something to test the hypothesis, and these are the results.")
Lee, DH., Xu, J., and Meng YS. An advanced cathode for Na-ion batteries with high rate and excellent structural stability. Physical Chemistry Chemical Physics 2013, 15 (9), 3304-3312.
Layered P2-Na-x[Ni1/3Mn2/3]O-2 (0 < x < 2/3) is investigated as a cathode material for Na-ion batteries. A combination of first principles computation, electrochemical and synchrotron characterizations is conducted to elucidate the working mechanism for the improved electrochemical properties. The reversible phase transformation from P2 to O2 is observed. New configurations of Na-ions and vacancy are found at x = 1/3 and 1/2, which correspond to the intermediate phases upon the electrochemical cycling process. The mobility of Na-ions is investigated using the galvanostatic intermittent titration technique (GITT) and the Na diffusion barriers are calculated by the Nudged Elastic Band (NEB) method. Both techniques prove that the mobility of Na-ions is faster than Li-ions in the O3 structure within the 1/3 < x < 2/3 concentration region. Excellent cycling properties and high rate capability can be obtained by limiting the oxygen framework shift during P2-O2 phase transformation, suggesting that this material can be a strong candidate as a sustainable low-cost Na-ion battery cathode. (55 references)
REVIEW ARTICLES summarize research in a given field of study by looking at the research articles. These articles do not contain original research, though may draw additional conclusions. These articles can serve as excellent summaries on a research topic, as well as point you to key research articles.
Islam, MS. and CAJ Fisher. Lithium and sodium battery cathode materials: computational insights into voltage, diffusion and nanostructural properties. Chemical Society Reviews 2014, 43 (1), 184-205.
Energy storage technologies are critical in addressing the global challenge of clean sustainable energy. Major advances in rechargeable batteries for portable electronics, electric vehicles and large-scale grid storage will depend on the discovery and exploitation of new high performance materials, which requires a greater fundamental understanding of their properties on the atomic and nanoscopic scales. This review describes some of the exciting progress being made in this area through use of computer simulation techniques, focusing primarily on positive electrode (cathode) materials for lithium-ion batteries, but also including a timely overview of the growing area of new cathode materials for sodium-ion batteries. In general, two main types of technique have been employed, namely electronic structure methods based on density functional theory, and atomistic potentials-based methods. A major theme of much computational work has been the significant synergy with experimental studies. The scope of contemporary work is highlighted by studies of a broad range of topical materials encompassing layered, spinel and polyanionic framework compounds such as LiCoO2, LiMn2O4 and LiFePO4 respectively. Fundamental features important to cathode performance are examined, including voltage trends, ion diffusion paths and dimensionalities, intrinsic defect chemistry, and surface properties of nanostructures. (216 references)