Rational design of FeF₂‐based cathode to realize high‐performance potassium storage

Abstract

The poor electronic conductivity of conversion‐type materials (CMs) and the dissolution/diffusion loss of transition metal (TM) ions in electrodes seriously hinder the practical applications of potassium ion batteries. Simply optimizing the electrode materials or designing the electrode components is no longer effective in improving the performance of CMs. Binders, as one of the electrode components, play a vital role in improving the electrochemical performance of batteries. Here we rationally designed FeF2 electrodes for the first time by optimizing electrode materials with the introduction of carbon nanotubes (CNTs) and combined with a sodium alginate (SA) binder based on strong interactions. We show that the FeF2@CNTs‐SA cathode does not suffer from TM ion dissolution and delivers a high capacity of 184.7 mAh g−1 at 10 mA g−1. Moreover, the capacity of FeF2@CNTs‐SA is as high as 99.2 mAh g−1 after 100 cycles at 100 mA g−1, which is a twofold increase compared to FeF2@CNTs‐PVDF. After calculating the average capacity decay rate per cycle of them, we find that FeF2@CNTs‐SA is about one‐third lower than FeF2@CNTs‐PVDF. Therefore, the SA binder can be broadly used for electrodes comprising several CMs, providing meaningful insights into mechanisms that lead to their improved electrochemical performances.