Tunable Interfacial Electric Field‐Mediated Cobalt‐Doped FeSe/Fe<sub>3</sub>Se<sub>4</sub> Heterostructure for High‐Efficiency Potassium Storage
Lili Song, Shilin Zhang, Liping Duan, Ren‐Ke Li, Yifan Xu, Jiaying Liao, Liang Sun, Xiaosi Zhou, Xiaosi Zhou, Zaiping Guo
Abstract
Abstract The interfacial electric field (IEF) in the heterostructure can accelerate electron transport and ion migration, thereby enhancing the electrochemical performance of potassium‐ion batteries (PIBs). Nevertheless, the quantification and modulation of the IEF for high‐efficiency PIB anodes currently remains a blank slate. Herein, we achieve for the first time the quantification and tuning of IEF via amorphous carbon‐coated undifferentiated cobalt‐doped FeSe/Fe 3 Se 4 heterostructure (denoted UN‐CoFe 4 Se 5 /C) for efficient potassium storage. Co doping can increase the IEF in FeSe/Fe 3 Se 4 , thereby improving the electron transport, promoting the potassium adsorption capacity, and lowering the diffusion barrier. As expected, the IEF magnitude in UN‐CoFe 4 Se 5 /C is experimentally quantified as 62.84 mV, which is 3.65 times larger than that of amorphous carbon‐coated FeSe/Fe 3 Se 4 heterostructure (Fe 4 Se 5 /C). Benefiting from the strong IEF, UN‐CoFe 4 Se 5 /C as a PIB anode exhibits superior rate capability (145.8 mAh g −1 at 10.0 A g −1 ) and long cycle lifespan (capacity retention of 95.1 % over 3000 cycles at 1.0 A g −1 ). Furthermore, this undifferentiated doping strategy can universally regulate the IEF magnitude in CoSe 2 /Co 9 Se 8 and FeS 2 /Fe 7 S 8 heterostructures. This work can provide fundamental insights into the design of advanced PIB electrodes.