Environmentally stable interface of layered oxide cathodes for sodium-ion batteries

Shaohua Guo,Haoshen Zhou,Pan Liu,Mingwei Chen,Qi Li

doi:10.1038/s41467-017-00157-8

Abstract

Sodium-ion batteries are strategically pivotal to achieving large-scale energy storage. Layered oxides, especially manganese-based oxides, are the most popular cathodes due to their high reversible capacity and use of earth-abundant elements. However, less noticed is the fact that the interface of layered cathodes always suffers from atmospheric and electrochemical corrosion, leading to severely diminished electrochemical properties. Herein, we demonstrate an environmentally stable interface via the superficial concentration of titanium, which not only overcomes the above limitations, but also presents unique surface chemical/electrochemical properties. The results show that the atomic-scale interface is composed of spinel-like titanium (III) oxides, enhancing the structural/electrochemical stability and electronic/ionic conductivity. Consequently, the interface-engineered electrode shows excellent cycling performance among all layered manganese-based cathodes, as well as high-energy density. Our findings highlight the significance of a stable interface and, moreover, open opportunities for the design of well-tailored cathode materials for sodium storage.

Highlights

Sodium-ion batteries are strategically pivotal to achieving large-scale energy storage
The bulk structures of the two samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), selected area electron diffraction (SAED), and electron energy-loss spectroscopy (EELS)
Titanium/nickel doping causes the biphasic coexistence of hexagonal P2 and monoclinic O′3 in the bulk materials, according to XRD (Supplementary Fig. 2b) and SAED (Supplementary Fig. 2c) analyses

Summary

Introduction

Sodium-ion batteries are strategically pivotal to achieving large-scale energy storage. Among the various cathode materials, layered oxides of NaxTMO2 (x ≤ 1, TM = Mn, Ni et al.) based on abundant materials have been mostly studied as cathodes for SIBs19, 20, and in particular, Mn-based materials meet requirements for low-cost stationary batteries without sacrificing energy density or safety[12, 21,22,23,24,25]. Their low cost and high performance makes layered manganese-based oxides very promising cathode candidates for SIBs, which are potentially competitive with LiCoO2, i.e., the system most widely used in LIBs26. This facile strategy will contribute to the development of room-temperature SIB technology to achieve high-energy and high-power density

Methods

Results

Conclusion