Improving the oxygen redox reversibility of Li-rich battery cathode materials via Coulombic repulsive interactions strategy

Qingyuan Li,Dong Zhou,Götz Schuck,Nian Zhang,Deniz Wong,Zhenhua Chen,De Ning,Ke An,Yuxin Tang,Xiangfeng Liu

doi:10.1038/s41467-022-28793-9

Abstract

The oxygen redox reaction in lithium-rich layered oxide battery cathode materials generates extra capacity at high cell voltages (i.e., >4.5 V). However, the irreversible oxygen release causes transition metal (TM) dissolution, migration and cell voltage decay. To circumvent these issues, we introduce a strategy for tuning the Coulombic interactions in a model Li-rich positive electrode active material, i.e., Li1.2Mn0.6Ni0.2O2. In particular, we tune the Coulombic repulsive interactions to obtain an adaptable crystal structure that enables the reversible distortion of TMO6 octahedron and mitigates TM dissolution and migration. Moreover, this strategy hinders the irreversible release of oxygen and other parasitic reactions (e.g., electrolyte decomposition) commonly occurring at high voltages. When tested in non-aqueous coin cell configuration, the modified Li-rich cathode material, combined with a Li metal anode, enables a stable cell discharge capacity of about 240 mAh g−1 for 120 cycles at 50 mA g−1 and a slower voltage decay compared to the unmodified Li1.2Mn0.6Ni0.2O2.

Highlights

4, Yuxin Tang[5], Dong Zhou[2], Götz Schuck[2], Zhenhua Chen[6], The oxygen redox reaction in lithium-rich layered oxide battery cathode materials generates extra capacity at high cell voltages (i.e., >4.5 V)
We report that the softened crystal structure is favorable to the reversible distortion of TMO6 octahedra in transition metal (TM) layers rather than the migration of TMs caused by a broken rigid octahedral structure; the voltage fade can be mitigated
We can find that the lattice parameters and TM–O bond length are increased for Li1.2Mn0.6Ni0.2O2-δ due to the reduction expansion[16,17], which indicates the existence of crystal distortion

Summary

Introduction

4, Yuxin Tang[5], Dong Zhou[2], Götz Schuck[2], Zhenhua Chen[6], The oxygen redox reaction in lithium-rich layered oxide battery cathode materials generates extra capacity at high cell voltages (i.e., >4.5 V). The irreversible oxygen release causes transition metal (TM) dissolution, migration and cell voltage decay To circumvent these issues, we introduce a strategy for tuning the Coulombic interactions in a model Li-rich positive electrode active material, i.e., Li1.2Mn0.6Ni0.2O2. We tune the Coulombic repulsive interactions to obtain an adaptable crystal structure that enables the reversible distortion of TMO6 octahedron and mitigates TM dissolution and migration This strategy hinders the irreversible release of oxygen and other parasitic reactions (e.g., electrolyte decomposition) commonly occurring at high voltages. The band position is determined by the introduction of the d–d Coulomb interaction term U and charge transfer (CT) term Δ from solid-state physics[12,14,15] According to this theory, electrons are extracted from the filled lower-Hubbard bands (LHB) caused by Mott-Hubbard splitting in many oxides and fluorides due to U

Methods

Results

Conclusion