Besides the Capacitive and Diffusion Control: Inner-Surface Controlled Bismuth Based Electrode Facilitating Potassium-Ion Energy Storage

One of the major challenges of potassium-ion hybrid capacitors (PIHCs) is to explore favorable anode materials with fast reaction kinetics to match the cathodes. Here, an "inner-surface" controlled electrochemistry mechanism based on bismuth electrode is proposed and in-depth studied, which is different from the capacitive or diffusion controlled electrode. Such inner-surface controlled electrochemistry performance gives a high K ion diffusion ability under not only room temperature (RT) but also low temperature (LT). In this study, a kind of conjunct-like bismuth nanoparticle (CBN) is fabricated to model such an advantage. The CBN anode for PIBs displays ultra-long cycling stability and excellent rate capability, especially with a reversible capacity of 212.9 mAh g(-1) at 30 A g(-1) after 5000 cycles under RT. At -20 degrees C, the CBN anode achieves a capacity of 191.9 mAh g(-1) at 10 A g(-1) after 10 000 cycles. Coupling with activate carbon cathode, the as-assembled PIHCs deliver high energy/power densities (111.8 Wh kg(-1)/412.8 W kg(-1) and 29 Wh kg(-1)/14 312.6 W kg(-1)), which outperforms those of previously reported PIHCs and other hybrid capacitors. The study provides a new understanding of the energy storage mechanism for bismuth-based electrodes and accelerates the development of advancing potassium ion storage devices, especially at LT.