Electrochemical and Electronic Charge Transport Properties of Ni-Doped LiMn₂O₄ Spinel Obtained from Polyol-Mediated Synthesis.

Shuo Yang,Michael Noyong,Hans Kungl,Rüdiger-Albert Eichel,Simon Jakobi,Dirk Schmidt,Melanie Homberger,Anja Paulus,Abhishek Khetan,Heinz Pitsch,Ulrich Simon,Felix Schrader

doi:10.3390/ma11050806

Shuo Yang, Michael Noyong + Show 10 more

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https://doi.org/10.3390/ma11050806

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Abstract

LiNi0.5Mn1.5O4 (LNMO) spinel has been extensively investigated as one of the most promising high-voltage cathode candidates for lithium-ion batteries. The electrochemical performance of LNMO, especially its rate performance, seems to be governed by its crystallographic structure, which is strongly influenced by the preparation methods. Conventionally, LNMO materials are prepared via solid-state reactions, which typically lead to microscaled particles with only limited control over the particle size and morphology. In this work, we prepared Ni-doped LiMn2O4 (LMO) spinel via the polyol method. The cycling stability and rate capability of the synthesized material are found to be comparable to the ones reported in literature. Furthermore, its electronic charge transport properties were investigated by local electrical transport measurements on individual particles by means of a nanorobotics setup in a scanning electron microscope, as well as by performing DFT calculations. We found that the scarcity of Mn3+ in the LNMO leads to a significant decrease in electronic conductivity as compared to undoped LMO, which had no obvious effect on the rate capability of the two materials. Our results suggest that the rate capability of LNMO and LMO materials is not limited by the electronic conductivity of the fully lithiated materials.

Highlights

The need to involve renewable energy sources to fulfill the global energy demand necessitates the development of large-scale energy storage systems [1,2]
We present the polyol-mediated synthesis of LNMO and its characterization by means of powder X-Ray diffraction, scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX) as well as electrochemical measurements
As the impurity phase is electrochemically inactive within the potential window investigated in this paper, the presence of this phase would lead to lower specific capacity of the as-prepared LNMO, as it was included in the calculation of the active material [58]

Summary

Introduction

The need to involve renewable energy sources to fulfill the global energy demand necessitates the development of large-scale energy storage systems [1,2]. A significant challenge posed to the usage of this material is the capacity-fading during cycling, especially at elevated temperature [5,6,7,8,9]. To overcome this challenge, several bi- or trivalent cations, such as Co [10], Ni [11], and Fe [12], have been investigated in their role as dopants to partially substitute the Mn in LMO.

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