Apr 23, 2024
2:00pm - 2:15pm
Terrace Suite 1, Level 4, Summit
Yueyue He1,Sören Dreyer1,Yin-Ying Ting2,Yang Hu3,Thomas Diemant3,Maximilian Fichtner3,Horst Hahn1,Jasmin Aghassi-Hagmann1,Torsten Brezesinski1,Yanjiao Ma4,Ben Breitung1
Karlsruhe Institute of Technology1,RWTH Aachen University2,Helmholtz Institute Ulm (HIU) for Electrochemical Energy Storage3,Nanjing Normal University4
Yueyue He1,Sören Dreyer1,Yin-Ying Ting2,Yang Hu3,Thomas Diemant3,Maximilian Fichtner3,Horst Hahn1,Jasmin Aghassi-Hagmann1,Torsten Brezesinski1,Yanjiao Ma4,Ben Breitung1
Karlsruhe Institute of Technology1,RWTH Aachen University2,Helmholtz Institute Ulm (HIU) for Electrochemical Energy Storage3,Nanjing Normal University4
The high-entropy approach is applied to monoclinic Prussian White (PW) cathode materials for sodium-ion batteries to address the issue of unfavorable multilevel phase transitions, leading to structural degradation and poor cycling stability. A series of Mn-based PWs was prepared, composed of up to six metal atoms sharing the N-coordinated positions (with Mn predominating), endowing the materials with unique structural properties. The high-entropy PW material of composition Na<sub>1.65</sub>Mn<sub>0.4</sub>Fe<sub>0.12</sub>Ni<sub>0.12</sub>Cu<sub>0.12</sub>Co<sub>0.12</sub>Cd<sub>0.12</sub>[Fe(CN)<sub>6</sub>]<sub>0.92</sub>■<sub>0.08</sub> was found to exhibit superior cyclability over medium-entropy, low-entropy and conventional single-metal PWs. In addition to the promising electrochemical performance, we report, to our knowledge for the first time, that the high-symmetry crystal structure (cubic form in this study) is favorable for high-entropy PWs during battery operation. Computational comparisons of the formation enthalpy of high-, medium- and low-entropy materials show that the compositionally less complex samples are prone to phase transitions that negatively affect the cyclability, especially in the deep de-/sodiated state. Based on data from complementary <i>operando</i> and <i>ex-situ</i> characterization techniques, an intrinsic mechanism for the stability improvement of the disordered PW structure during Na<sup>+</sup> insertion/extraction is proposed, namely the dual effect of suppression of phase transitions and gas evolution.