Research Article pubs.acs.org/journal/ascecg
Y‑Doped Na2ZrO3: A Na-Rich Layered Oxide as a High-Capacity Cathode Material for Sodium-Ion Batteries Shufeng Song,*,† Masashi Kotobuki,‡ Feng Zheng,‡ Chaohe Xu,† Ning Hu,*,†,§ Li Lu,‡,∥ Yu Wang,⊥ and Wei-Dong Li⊥ †
College of Aerospace Engineering, Chongqing University, 174 Shazhengjie, Shapingba, Chongqing 400044, P. R. China Materials Science Group, Department of Mechanical Engineering, National University of Singapore, 21 Lower Kent Ridge Road, Singapore 117575 § Key Disciplines Lab of Novel Micro-nano Devices and System Technology, International R & D Center of Micro-nano Systems and New Materials Technology, Chongqing University, 174 Shazhengjie, Shapingba, Chongqing 400044, P. R. China ∥ National University of Singapore Suzhou Research Institute, 377 Linquan Street, Suzhou 215123, P. R. China ⊥ School of Chemistry and Chemical Engineering, Chongqing University, 174 Shazhengjie, Shapingba, Chongqing 400044, P. R. China ‡
ABSTRACT: The renewed interest in sodium-ion batteries reflects the persistent concern about the lithium resources that have widespread applications but an uneven distribution, and the overwhelming need for large-scale energy storage. Most exploration has focused on the conventional layered oxides NaxMO2 that stem from lithium-ion cathodes. However, exploring cathode materials with high capacities, long cycle lives, and low costs because of the large ionic radius and high atomic weight of sodium is a great challenge. Here we report a Na-rich layered oxide, yttrium-doped Na2ZrO3, that serves as a cathode material in sodiumion batteries. This material delivers a large reversible capacity of ∼180 mAh g−1 and a good cycle life with no sign of obvious capacity decay over 1500 cycles along with a low cost. The redox reactivity of oxygen is shown to be involved in the sodium extraction−insertion processes. This work not only provides a cathode contender to conventional layered oxides NaxMO2 but also suggests that broad classes of defective Na-rich layered oxides could be discovered. KEYWORDS: Sodium-ion batteries, Cathodes, Na-rich layered oxide, Capacity, Cycle life
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INTRODUCTION Rechargeable lithium-ion batteries commerciallized in the early 1990s played a part in the success of portable electronics and are now regarded as energy storage technologies for electric vehicles and electrical grids. However, the potential applications of lithium-ion batteries for transportation and grids suffer from issues of the skyrocketing price of lithium mining and limited lithium resources.1 Under these considerations, sodium-ion batteries are a more attractive alternative than their lithium counterparts, currently, in particular in grid-scale applications because sodium is abundant worldwide, inexpensive, and the second lightest alkali element and has a low redox potential and electrochemistry similar to that of lithium.2 It is urgent to explore Na-ion electrode materials possessing large capacities, long lifespans, and low costs.3 In this pursuit, numerous © 2017 American Chemical Society
research efforts have been devoted to sodium-layered oxides NaxMO2 (0 < x < 1; M is an electrochemically active transition metal), originating in lithium electrode materials.4 Typical sodium-layered oxides can be classified as O3 and P2 types, where Na ions are in octahedral and prismatic sites, respectively. O3-type NaCoO 2 , NaVO 2 , NaCrO 2 , Na0.8Ni0.4Ti0.6O2, etc., typically show specific capacities of
