Researchers Missouri University of Science and Technology are working to solve the problem of short-life of lithium-ion batteries like those used in laptops and cellphones, making them reliable and longer-lasting using a atomic layer deposition. This study was carried out using a fluidized bed reactor.
Science Daily reports the following:
"Dr. Xinhua Liang, assistant professor of chemical and biochemical engineering at Missouri S&T, leads the study to dope and coat lithium magnesium nickel oxygen (LMNO) with iron oxide through ALD -- at the same time. Doping means adding an element or compound into the crystalline structure, or lattice, filling in the gaps in the LMNO. Coating is what it sounds like, putting ultra-thin layers of iron oxide around the whole compound. Rajankumar Patel, a Missouri S&T Ph.D. candidate in chemical engineering who will graduate next week, did the majority of the experimental work in the project
TEM images of (a) clean edge of an uncoated LiMn1.5Ni0.5O4 particle, and (b) ~3 nm of conformal iron oxide film coated on one LiMn1.5Ni0.5O4 particle after 160 cycles of iron oxide ALD, (c) cross sectional TEM image of one LiMn1.5Ni0.5O4 particle with 160 cycles of iron oxide ALD, (d) Fe element mapping of cross-sectioned surface by EDS, and (e) Fe EDS line scanning along the red line as shown in (c). TEM image indicates that conformal iron oxide films were coated on primary LiMn1.5Ni0.5O4 particle surface. EDS mapping and EDS element line scanning indicates that Fe was doped in the lattice structure of LiMn1.5Ni0.5O4. (From Open Source - Scientific Reports 6, Article number: 25293 (2016), doi:10.1038/srep25293)
The operating voltage window of LMNO makes it a potential candidate for use in hybrid electric vehicles (HEV). However, it has not gained commercial usability in HEV because of high-capacity fade during cycling at elevated temperatures and manganese(3+) dissolution by hydrogen fluorine.
"Unlike current research practice that either covers the particles' surface with insulating film or dopes the particles to improve the performance of the battery," Liang says, "this ALD process combines the coating and doping processes into one, and applying this technique makes rechargeable lithium-ion batteries last longer."
"This is the first report for a unique phenomenon of ionic iron entering the lattice structure of LMNO during the ALD coating process," Patel says.
Full story:
https://www.sciencedaily.com/releases/2016/05/160505105220.htm and Open Source article below published in Scientific Reports.
Employing Synergetic Effect of Doping and Thin Film Coating to Boost the Performance of Lithium-Ion Battery Cathode Particles
Rajankumar L. Patel, Ying-Bing Jiang, Amitava Choudhury & Xinhua Liang
Atomic layer deposition (ALD) has evolved as an important technique to coat conformal protective thin films on cathode and anode particles of lithium ion batteries to enhance their electrochemical performance. Coating a conformal, conductive and optimal ultrathin film on cathode particles has significantly increased the capacity retention and cycle life as demonstrated in our previous work. In this work, we have unearthed the synergetic effect of electrochemically active iron oxide films coating and partial doping of iron on LiMn1.5Ni0.5O4 (LMNO) particles. The ionic Fe penetrates into the lattice structure of LMNO during the ALD process. After the structural defects were saturated, the iron started participating in formation of ultrathin oxide films on LMNO particle surface. Owing to the conductive nature of iron oxide films, with an optimal film thickness of ~0.6 nm, the initial capacity improved by ~25% at room temperature and by ~26% at an elevated temperature of 55 °C at a 1C cycling rate. The synergy of doping of LMNO with iron combined with the conductive and protective nature of the optimal iron oxide film led to a high capacity retention (~93% at room temperature and ~91% at 55 °C) even after 1,000 cycles at a 1C cycling rate.
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