Atomic layer deposition (ALD), a well-studied layer-by-layer method for depositing thin films on solids, is prized for its ability to form ultrathin films that conform perfectly to oddly shaped and tough-to-coat solid surfaces. A study finds that not only does ALD coat materials with a film-forming compound, but also it can penetrate the solid, doping the material. This combination of coating and doping can improve lithium-ion battery materials (Sci. Rep. 2016, DOI: 10.1038/srep25293).
LiMn1.5Ni0.5O4 (LMNO) has drawn significant attention as a candidate Li-ion battery cathode material because of its low cost, high theoretical charge capacity, and high operating voltage relative to other commonly studied cathode materials, including LiMn2O4, which has been used in plug-in hybrid electric vehicle batteries. In practice, however, unwanted electrochemical reactions cause LMNO’s charge capacity to diminish quickly.
A team led by Xinhua Liang of Missouri University of Science & Technology reasoned that treating LMNO with iron oxide, an electrochemically active compound, via high-temperature ALD would coat and dope LMNO and improve its properties. It worked.
Compared with naked LMNO, the ALD-treated samples exhibited 25% higher charge capacity and retained roughly 93% of their capacity even after 1,000 charging cycles.