Radially aligned hierarchical columnar structure as a cathode material for high energy density sodium-ion batteries.

Jang-Yeon Hwang,Yang-Kook Sun,Kyung Yoon Chung,Seung-Taek Myung,Ilias Belharouak,Seung-Min Oh

doi:10.1038/ncomms7865

Abstract

Delivery of high capacity with good retention is a challenge in developing cathodes for rechargeable sodium-ion batteries. Here we present a radially aligned hierarchical columnar structure in spherical particles with varied chemical composition from the inner end (Na[Ni0.75Co0.02Mn0.23]O2) to the outer end (Na[Ni0.58Co0.06Mn0.36]O2) of the structure. With this cathode material, we show that an electrochemical reaction based on Ni(2+/3+/4+) is readily available to deliver a discharge capacity of 157 mAh (g-oxide)(-1) (15 mA g(-1)), a capacity retention of 80% (125 mAh g(-1)) during 300 cycles in combination with a hard carbon anode, and a rate capability of 132.6 mAh g(-1) (1,500 mA g(-1), 10 C-rate). The cathode also exhibits good temperature performance even at -20°C. These results originate from rather unique chemistry of the cathode material, which enables the Ni redox reaction and minimizes the surface area contacting corrosive electrolyte.

Highlights

Delivery of high capacity with good retention is a challenge in developing cathodes for rechargeable sodium-ion batteries
Through our prior works[36,37], we suggested that the nanorod-structured full concentration gradient materials are beneficial in performing outstanding electrochemical properties and excellent safety in lithium-ion batteries system, because the dense rod assembly could minimize surface area contacting with electrolyte, in which the environment, in turn, renders active materials less exposure in acidic electrolyte due to NaPF6 salt (HF attack)
We anticipate that the linear variation in the Ni concentration towards the surface of the particle leads to high capacity

Summary

Introduction

Delivery of high capacity with good retention is a challenge in developing cathodes for rechargeable sodium-ion batteries. The recent launch of several types of electric vehicles powered by rechargeable lithium batteries has necessitated significant improvements in battery performance including higher capacity and power, longer life cycle and improved safety. Despite their feasibility, the mass production of such large-scale batteries would likely contribute to the future exhaustion of limited lithium resources. Through our prior works[36,37], we suggested that the nanorod-structured full concentration gradient materials are beneficial in performing outstanding electrochemical properties and excellent safety in lithium-ion batteries system, because the dense rod assembly could minimize surface area contacting with electrolyte, in which the environment, in turn, renders active materials less exposure in acidic electrolyte due to NaPF6 salt (HF attack)

Methods

Results

Conclusion