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. Issue 8 (13th February 2017)

• Record Type: Journal Article
• Authors: Nayak, Prasant Kumar; Grinblat, Judith; Levi, Elena; Levi, Mikhael; Markovsky, Boris; Aurbach, Doron
• Is Part Of: Physical chemistry chemical physics. Volume 19:Issue 8(2017)
• Page Start: 6142
• Page End: 6152
• Publication Date: 2017-02-13
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp07383b
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Mg doping into Li- and Mn-rich cathode materials results in the stabilization of capacity and higher discharge voltage as compared to undoped materials. Abstract : Although Li- and Mn-rich layered cathodes exhibit high specific capacity, the cathode materials of the general formula Li1+ x [Ni y Mn z Co w ]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 Li1.2 Ni0.16 Mn0.54 Mg0.02 Co0.08 O2 and Li1.2 Ni0.16 Mn0.51 Mg0.05 Co0.08 O2 cathode 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. Li1.2 Ni0.16 Mn0.51 Mg0.05 Co0.08 O2 exhibits 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 −1 during 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 Li2 MnO3 during 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.