Coating plus doping improves performance of promising material for lithium-ion batteries

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).

LiMn_1.5Ni_0.5O₄ (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.