Lattice doping regulated interfacial reactions in cathode for enhanced cycling stability

Lianfeng Zou,Arumugam Manthiram,Guofeng Wang,Chongmin Wang,Jianyu Li,Zhenyu Liu

doi:10.1038/s41467-019-11299-2

Abstract

Interfacial reactions between electrode and electrolyte are critical, either beneficial or detrimental, for the performance of rechargeable batteries. The general approaches of controlling interfacial reactions are either applying a coating layer on cathode or modifying the electrolyte chemistry. Here we demonstrate an approach of modification of interfacial reactions through dilute lattice doping for enhanced battery properties. Using atomic level imaging, spectroscopic analysis and density functional theory calculation, we reveal aluminum dopants in lithium nickel cobalt aluminum oxide are partially dissolved in the bulk lattice with a tendency of enrichment near the primary particle surface and partially exist as aluminum oxide nano-islands that are epitaxially dressed on the primary particle surface. The aluminum concentrated surface lowers transition metal redox energy level and consequently promotes the formation of a stable cathode-electrolyte interphase. The present observations demonstrate a general principle as how the trace dopants modify the solid-liquid interfacial reactions for enhanced performance.

Highlights

Interfacial reactions between electrode and electrolyte are critical, either beneficial or detrimental, for the performance of rechargeable batteries
Given the pulverization processes are often accompanied with disintegration inside secondary particles and well-recognized to deteriorate the battery performance[12,18,35,36], several randomly picked secondary particles are sliced into halves using focused ion beam (FIB) and the assembly features inside the buried bulk are examined
The processes start with the phase transitions on the primary particles surfaces in which the layered structure gradually transforms into the disordered rock salt phase, termed as the surface reconstruction, accompanied with the formation of reduced transition metals (TMs) ions, e.g., Ni2+ on the primary particle surfaces

Summary

Introduction

Interfacial reactions between electrode and electrolyte are critical, either beneficial or detrimental, for the performance of rechargeable batteries. We demonstrate an approach of modification of interfacial reactions through dilute lattice doping for enhanced battery properties. The present observations demonstrate a general principle as how the trace dopants modify the solid-liquid interfacial reactions for enhanced performance. We use two Ni-rich cathodes, one with the formula of LiNi0.94Co0.06O2 (NC) and the other with an addition of 2 at% Al in the NC materials (LiNi0.92Co0.06Al0.02O2, termed as NCA), to elucidate the enhanced interfacial and cycling stability of NCA by Al doping. We reveal that the Al dopant enhances cycling performance from two aspects: improve the electrode structural stability and modify the cathode electronic property and reactivity. The atomistic simulations reveal that the Al-concentrated shell facilities the formation of phosphate-containing cathode electrolyte interface (CEI) layers as a consequence of the dopant induced down shift of Fermi level. The CEI layers, coupled with the sparsely scattered Al2O3 nano-islands, plays a dominant role for enhancing the battery performance

Methods

Results

Conclusion