Inhibition of transition metals dissolution in cobalt-free cathode with ultrathin robust interphase in concentrated electrolyte

Wei Liu,Xinping Qiu,Chao Zhang,Jinxing Li,Wenting Li,Hanying Xu

doi:10.1038/s41467-020-17396-x

Abstract

The low Coulombic efficiency during cycling hinders the application of Cobalt-free lithium-rich materials in lithium-ion batteries. Here we demonstrated that the dissolution of iron, rather than traditionally acknowledged manganese, is mainly responsible for the low Coulombic efficiency of the iron-substituted cobalt-free lithium-rich material. Besides, we presented an approach to inhibit the dissolution of transition metal ions by using concentrated electrolytes. We found that the cathode electrolyte interphase (CEI) layer formed in the concentrated electrolyte is a uniform and robust LiF-rich CEI, which is a sharp contrast with the uneven and fragile organic-rich CEI formed in the dilute electrolyte. The LiF-rich CEI not only effectively inhibits the dissolution of TMs but also stabilizes the cathode structure. The Coulombic efficiency, cycling stability, rate performance, and safety of the Fe-substituted cobalt-free lithium-rich cathode material in the concentrated electrolyte have been improved tremendously.

Highlights

The low Coulombic efficiency during cycling hinders the application of Cobalt-free lithiumrich materials in lithium-ion batteries
The dissolution of transition metals, especially iron, seriously affects the performance of Li1.2Ni0.15Fe0.1Mn0.55O2, whereas the cathode electrolyte interphase (CEI) layer formed on the surface has a profound effect on the dissolution of transition metals
The CEI layer has a direct relationship with cycling stability, coulombic efficiency, rate performance, and safety

Summary

Introduction

The low Coulombic efficiency during cycling hinders the application of Cobalt-free lithiumrich materials in lithium-ion batteries. The Coulombic efficiency, cycling stability, rate performance, and safety of the Fe-substituted cobalt-free lithium-rich cathode material in the concentrated electrolyte have been improved tremendously. Lithium-rich materials, normally denoted as xLi2MnO3·(1 − x) LiMO2 (M = Ni, Co, Mn, Fe, Al, Cr, etc.), can deliver high discharge-specific energy (250 mAh g−1) and have attracted much attention in recent years[5,9,10,11]. Some drawbacks, such as poor cycle performance, fast voltage fade, undesirable rate performance, and low coulombic efficiency (CE), still hinder the practical application of Li-rich materials[11,12]. In our previous works[35,36], we found that the substitution of

Methods

Results

Conclusion