title: Understanding the influence of Mg doping for the stabilization of capacity and higher discharge voltage of Li- and Mn-rich cathodes for Li-ion batteries.
abstract: Although Li- and Mn-rich layered cathodes exhibit high specific capacity, the cathode materials of the general formula Li1+x[NiyMnzCow]O2(x + y + z + w = 1) suffer from capacity fading and discharge-voltage decay during prolonged cycling, due to the layered-to-spinel transformation upon cycling to potentials higher than 4.5 V vs. Li. In this paper, we study the effect of Mg doping (by partial replacement of Mn ions) on the electrochemical performance of Li- and Mn-rich cathodes in terms of specific capacity, capacity retention and discharge voltage upon cycling. Mg-doped Li- and Mn-rich Li1.2Ni0.16Mn0.54Mg0.02Co0.08O2and Li1.2Ni0.16Mn0.51Mg0.05Co0.08O2cathode materials were synthesized by a self-combustion reaction (SCR), and their electrochemical performance in Li-ion batteries was tested. The replacement of a small amount of Mn ions by Mg ions in these materials results in a decrease in their specific capacity. The doping of a small amount of Mg (x = 0.02) resulted only in the stabilization of the capacity, whereas a greater amount (x = 0.05) resulted in improved capacity retention and discharge voltage upon cycling. Li1.2Ni0.16Mn0.51Mg0.05Co0.08O2exhibits a low specific capacity of about 160 mA h g-1, which increases and then stabilizes at about 230 mA h g-1, and finally decreases to 210 mA h g-1during 100 cycles. The substitution of Mg for Mn (x = 0.05) results in a higher discharge voltage than the other two cathode materials examined in this study. Structural analysis of the cycled electrodes suggests that Mg suppresses the activation of Li2MnO3during the initial cycling, and hence, partially prevents layered-to-spinel transformation, resulting in a better electrochemical performance of the Mg-doped cathode material as compared to the undoped material.
authors.affiliation: Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel. aurbach@biu.ac.il.
authors.forename: Prasant Kumar
authors.identifier: http://orcid.org/0000-0001-5179-6369
authors.initials: PK
authors.lastname: Nayak
authors.affiliation: Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel. aurbach@biu.ac.il.
authors.forename: Judith
authors.initials: J
authors.lastname: Grinblat
authors.affiliation: Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel. aurbach@biu.ac.il.
authors.forename: Elena
authors.initials: E
authors.lastname: Levi
authors.affiliation: Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel. aurbach@biu.ac.il.
authors.forename: Mikhael
authors.initials: M
authors.lastname: Levi
authors.affiliation: Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel. aurbach@biu.ac.il.
authors.forename: Boris
authors.initials: B
authors.lastname: Markovsky
authors.affiliation: Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel. aurbach@biu.ac.il.
authors.forename: Doron
authors.initials: D
authors.lastname: Aurbach