Fast Potassium Storage in Hierarchical Ca0.5Ti2(PO4)3@C Microspheres Enabling High‐Performance Potassium‐Ion Capacitors |
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Authors: | Zhongyu Zhang Malin Li Yu Gao Zhixuan Wei Meina Zhang Chunzhong Wang Yi Zeng Bo Zou Gang Chen Fei Du |
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Affiliation: | 1. Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, P. R. China;2. College of Materials Science and Engineering, Key Laboratory of Automobile Materials (Ministry of Education), and State Key Laboratory of Superhard Materials, Jilin University, Changchun, P. R. China |
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Abstract: | 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 Ca0.5Ti2(PO4)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 Ca0.5Ti2(PO4)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 Ca0.5Ti2(PO4)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 Ca0.5Ti2(PO4)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. |
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Keywords: | excellent performance hybrid potassium‐ion capacitors in situ X‐ray diffraction NASICON structures |
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