Structural insights into the formation and voltage degradation of lithium- and manganese-rich layered oxides

Weibo Hua,Björn Schwarz,Clare P Grey,Steven J Leake,Helmut Ehrenberg,Murat Yavuz,Carsten Richter,Suning Wang,Anatoliy Senyshyn,Joachim R Binder,Michael Knapp,Sylvio Indris

doi:10.1038/s41467-019-13240-z

Abstract

One major challenge in the field of lithium-ion batteries is to understand the degradation mechanism of high-energy lithium- and manganese-rich layered cathode materials. Although they can deliver 30 % excess capacity compared with today’s commercially- used cathodes, the so-called voltage decay has been restricting their practical application. In order to unravel the nature of this phenomenon, we have investigated systematically the structural and compositional dependence of manganese-rich lithium insertion compounds on the lithium content provided during synthesis. Structural, electronic and electrochemical characterizations of LixNi0.2Mn0.6Oy with a wide range of lithium contents (0.00 ≤ x ≤ 1.52, 1.07 ≤ y < 2.4) and an analysis of the complexity in the synthesis pathways of monoclinic-layered Li[Li0.2Ni0.2Mn0.6]O2 oxide provide insight into the underlying processes that cause voltage fading in these cathode materials, i.e. transformation of the lithium-rich layered phase to a lithium-poor spinel phase via an intermediate lithium-containing rock-salt phase with release of lithium/oxygen.

Highlights

One major challenge in the field of lithium-ion batteries is to understand the degradation mechanism of high-energy lithium- and manganese-rich layered cathode materials
The ever-increasing demand for electrical energy storage devices, such as electric vehicles poses challenging requirements on long-cycle life, low-cost, and high-energy density cathode materials used in lithium-ion batteries (LIBs)[1,2]
A series of thermostable oxides (LixNi0.2Mn0.6Oy, 0.00 ≤ x ≤ 1.52) with different contents of lithium and oxygen were obtained by adding different amounts of lithium source (x value) into a hydroxide precursor, details of this synthesis process is in the Supplementary Methods section

Summary

Introduction

One major challenge in the field of lithium-ion batteries is to understand the degradation mechanism of high-energy lithium- and manganese-rich layered cathode materials. They can deliver 30 % excess capacity compared with today’s commercially- used cathodes, the so-called voltage decay has been restricting their practical application. The ever-increasing demand for electrical energy storage devices, such as electric vehicles poses challenging requirements on long-cycle life, low-cost, and high-energy density cathode materials used in lithium-ion batteries (LIBs)[1,2] These Li- and Mn-rich layered oxides (LMLOs) have improved capacities exceeding 250 mA h g−1, much higher than the capacity of conventional cathodes (

Methods

Results

Conclusion