“…Our FeF 3 /graphene product though proves the reaction activity of FeF 3 toward Na, we still have to point out that the electrochemical performance of FeF 3 /graphene in Na system is not as good as in Li system [19][20][21], especially the capacity retention and rate capability. Similar differences haves also been noticed in the cathode applications of layered compounds in Li or Na storage, except the optimized processing, a deeper understanding of the reaction mechanism is needed.…”