Enhancing the Stability of LiNi0.5Mn1.5O4 by Coating with LiNbO3 Solid-State Electrolyte: Novel Chemically Activated Coating Process versus Sol-Gel Method.

Valeriu Mereacre,Ahmad Ghamlouche,Joachim R. Binder,Pirmin Stüble

doi:10.3390/nano11020548

Valeriu Mereacre, Ahmad Ghamlouche + Show 2 more

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https://doi.org/10.3390/nano11020548

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Abstract

LiNbO3-coated LiNi0.5Mn1.5O4 spinel was fabricated by two methods: using hydrogen-peroxide as activating agent and sol-gel method. The structure of the obtained cathode materials was investigated using a scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and the electrochemical properties of the prepared cathodes were probed by charge-discharge studies. The morphology of the coating material on the surface and the degree of coverage of the coated particles were investigated by SEM, which showed that the surface of LiNi0.5Mn1.5O4 particles is uniformly encapsulated by lithium innovate coating. The influence of the LiNbO3 coating layer on the spinel’s properties was explored, including its effect on the crystal structure and electrochemical performance. XRD studies of the obtained coated active materials revealed very small expansion or contraction of the unit cell. From the capacity retention tests a significant improvement of the electrochemical properties resulted when a novel chemically activated coating process was used. Poorer results, however, were obtained using the sol-gel method. The results also revealed that the coated materials by the new method exhibit enhanced reversibility and stability compared to the pristine and reference ones. It was shown that the morphology of the coating material and possible improvement of communication between the substrates play an important role.

Highlights

One of the most promising candidates for cathode material in high-voltage rechargeable lithium-ion batteries is LiNi0.5 Mn1.5 O4 spinel (LNMO) [1,2,3,4]
In order to overwhelm the dissolution of manganese ions [12] and increase the electrochemical performance of such cathode materials, their surface is covered with a coating layer [13,14,15,16], which acts as a passivation layer, preventing the active material from direct contact with electrolyte
One can produce a large number of materials of different shapes and morphologies, which are difficult to obtain by conventional methods, due to their high melting temperatures

Summary

Introduction

One of the most promising candidates for cathode material in high-voltage rechargeable lithium-ion batteries is LiNi0.5 Mn1.5 O4 spinel (LNMO) [1,2,3,4]. The low interfacial stability between the cathode and the electrolyte slows down the widespread practical use of these materials [7,8]. Because of the disproportionation reaction of Mn3+ , the Mn2+ ions are obtained These ions have the tendency to dissolve into the electrolyte, in this way accelerating the capacity fade of the cell [9,10,11]. In order to overwhelm the dissolution of manganese ions [12] and increase the electrochemical performance of such cathode materials, their surface is covered with a coating layer [13,14,15,16], which acts as a passivation layer, preventing the active material from direct contact with electrolyte

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