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KVOPO 4 : A New High Capacity Multielectron Na‐Ion Battery Cathode
Author(s) -
Ding Jia,
Lin YuhChieh,
Liu Jue,
Rana Jatinkumar,
Zhang Hanlei,
Zhou Hui,
Chu IekHeng,
Wiaderek Kamila M.,
Omenya Fredrick,
Chernova Natasha A.,
Chapman Karena W.,
Piper Louis F. J.,
Ong Shyue Ping,
Whittingham M. Stanley
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201800221
Subject(s) - cathode , materials science , sodium , ion , lithium (medication) , ionic bonding , battery (electricity) , sodium ion battery , density functional theory , energy storage , formula unit , anode , chemistry , thermodynamics , electrode , crystallography , computational chemistry , physics , crystal structure , medicine , power (physics) , organic chemistry , faraday efficiency , metallurgy , endocrinology
Sodium ion batteries have attracted much attention in recent years, due to the higher abundance and lower cost of sodium, as an alternative to lithium ion batteries. However, a major challenge is their lower energy density. In this work, we report a novel multi‐electron cathode material, KVOPO 4 , for sodium ion batteries. Due to the unique polyhedral framework, the V 3+ ↔ V 4+ ↔ V 5+ redox couple was for the first time fully activated by sodium ions in a vanadyl phosphate phase. The KVOPO 4 based cathode delivered reversible multiple sodium (i.e. maximum 1.66 Na + per formula unit) storage capability, which leads to a high specific capacity of 235 Ah kg −1 . Combining an average voltage of 2.56 V vs. Na/Na + , a high practical energy density of over 600 Wh kg −1 was achieved, the highest yet reported for any sodium cathode material. The cathode exhibits a very small volume change upon cycling (1.4% for 0.64 sodium and 8.0% for 1.66 sodium ions). Density functional theory (DFT) calculations indicate that the KVOPO 4 framework is a 3D ionic conductor with a reasonably, low Na + migration energy barrier of ≈450 meV, in line with the good rate capability obtained.