Effects of Mg Doping at Different Positions in Li-Rich Mn-Based Cathode Material on Electrochemical Performance.

Elena Makhonina,Igor Eremenko,Yury Koshtyal,Alexander Goloveshkin,Vyacheslav Volkov,Aleksander Rumyantsev,Yury Politov,Lidia Pechen,Anna Medvedeva

doi:10.3390/nano12010156

Abstract

Li-rich Mn-based layered oxides are among the most promising cathode materials for next-generation lithium-ion batteries, yet they suffer from capacity fading and voltage decay during cycling. The electrochemical performance of the material can be improved by doping with Mg. However, the effect of Mg doping at different positions (lithium or transition metals) remains unclear. Li1.2Mn0.54Ni0.13Co0.13O2 (LR) was synthesized by coprecipitation followed by a solid-state reaction. The coprecipitation stage was used to introduce Mg in TM layers (sample LR-Mg), and the solid-state reaction (st) was used to dope Mg in Li layers (LR-Mg(st)). The presence of magnesium at different positions was confirmed by XRD, XPS, and electrochemical studies. The investigations have shown that the introduction of Mg in TM layers is preferable in terms of the electrochemical performance. The sample doped with Mg at the TM positions shows better cyclability and higher discharge capacity than the undoped sample. The poor electrochemical properties of the sample doped with Mg at Li positions are due to the kinetic hindrance of oxidation of the manganese-containing species formed after activation of the Li2MnO3 component of the composite oxide. The oxide LR-Mg(st) demonstrates the lowest lithium-ion diffusion coefficient and the greatest polarization resistance compared to LR and LR-Mg.

Highlights

Lithium-ion batteries (LIBs) dominate in portable electronic devices such as mobile phones, computers, cameras, etc., and the portable electronics market constantly grows
We studied Mg-doped Li-rich layered cathode materials synthesized by different procedures with the aim to introduce Mg ions at different positions, namely, in transition metal (TM)- and Li layers, and compare their electrochemical properties
Li-rich layered oxide Li1.2 Mn0.54 Ni0.13 Co0.13 O2 was doped with magnesium at different positions (TM and Li) using different procedures for Mg introduction

Summary

Introduction

Lithium-ion batteries (LIBs) dominate in portable electronic devices such as mobile phones, computers, cameras, etc., and the portable electronics market constantly grows. By 2030, the stationary and transportation energy storage markets combined are estimated to grow 2.5–4 terawatt-hours annually, approximately three to five times the current 800-gigawatt-hour market [1]. LIBs are considered to capture the majority of energy storage growth in all markets over at least the 10 years. To meet those needs, especially for their use in batteries for electrical grids and hybrid and electric vehicles, current LIBs need first of all a higher energy density, cycling stability and safety. Among the wide variety of positive electrode materials for LIBs, only a few show enough potential for commercialization, and Li-rich and Ni-rich materials are clearly the most promising of those [2,3]

Methods

Results

Conclusion