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Fast Potassium Storage in Hierarchical Ca 0.5 Ti 2 (PO 4 ) 3 @C Microspheres Enabling High‐Performance Potassium‐Ion Capacitors
Author(s) -
Zhang Zhongyu,
Li Malin,
Gao Yu,
Wei Zhixuan,
Zhang Meina,
Wang Chunzhong,
Zeng Yi,
Zou Bo,
Chen Gang,
Du Fei
Publication year - 2018
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201802684
Subject(s) - materials science , anode , potassium , energy storage , cathode , power density , ion , chemical engineering , electrode , nanotechnology , chemistry , thermodynamics , power (physics) , metallurgy , physics , engineering , organic chemistry
Hybrid potassium‐ion capacitors (KICs) show great promise for large‐scale storage on the power grid because of cost advantages, the weaker Lewis acidity of K + and low redox potential of K + /K. However, a huge challenge remains for designing high‐performance K + storage materials since K + ions are heavier and larger than Li + and Na + . Herein, the synthesis of hierarchical Ca 0.5 Ti 2 (PO 4 ) 3 @C microspheres by use of the electrospraying method is reported. Benefiting from the rich vacancies in the crystal structure and rational nanostructural design, the hybrid Ca 0.5 Ti 2 (PO 4 ) 3 @C electrode delivers a high reversible capacity (239 mA h g −1 ) and superior rate performance (63 mA h g −1 at 5 A g −1 ). Moreover, the KIC employing a Ca 0.5 Ti 2 (PO 4 ) 3 @C anode and activated carbon cathode, affords a high energy/power density (80 W h kg −1 and 5144 W kg −1 ) in a potential window of 1.0–4.0 V, as well as a long lifespan of over 4000 cycles. In addition, in situ X‐ray diffraction is used to unravel the structural transition in Ca 0.5 Ti 2 (PO 4 ) 3 , suggesting a two‐phase transition above 0.5 V during the initial discharge and solid solution processes during the subsequent K + insertion/extraction. The present study demonstrates a low‐cost potassium‐based energy storage device with high energy/power densities and a long lifespan.