title: Radially aligned hierarchical columnar structure as a cathode material for high energy density sodium-ion batteries.
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.
authors.affiliation: Department of Energy Engineering, Hanyang University, Seoul 133-791, South Korea.
authors.forename: Jang-Yeon
authors.initials: JY
authors.lastname: Hwang
authors.affiliation: Department of Energy Engineering, Hanyang University, Seoul 133-791, South Korea.
authors.forename: Seung-Min
authors.initials: SM
authors.lastname: Oh
authors.affiliation: Department of Nano Engineering, Sejong University, Seoul 143-747, South Korea.
authors.forename: Seung-Taek
authors.initials: ST
authors.lastname: Myung
authors.affiliation: Center for Energy Convergence Research, Korea Institute of Science and Technology, Seoul 136-791, South Korea.
authors.forename: Kyung Yoon
authors.initials: KY
authors.lastname: Chung
authors.affiliation: Qatar Environment and Energy Research Institute, Qatar Foundation, PO Box 5825, Doha, Qatar.
authors.forename: Ilias
authors.initials: I
authors.lastname: Belharouak
authors.affiliation: Department of Energy Engineering, Hanyang University, Seoul 133-791, South Korea.
authors.forename: Yang-Kook
authors.initials: YK
authors.lastname: Sun