In situ growing Prussian blue nanocrystals on Ti3C2 lamellae as high-performance electrode for potassium-ion storage

Abstract

Surface modification played an important role in tailoring electrode surface chemistry to improve electrochemical performance. More often than not, electrode materials were coated with conductive assistants (e.g. graphite) to enhance their surface electronic conductivity. However, suchlike conductive enclosure was usually not a good ionic conductor in electrolyte. This not only required a lot of strenuous synthetic efforts in thinning surface coatings and avoiding uneven layer thickness, but also retarded surface ionic kinetics in any case. Here, an attempt was made by in situ growing Prussian blue (PB) nanocrystals on well-conductive Ti3C2 lamellae. When used as an electrode, Ti3C2 functioned as an electron bridge to connect current collector with potassium reservoir (viz. PB). Besides, the open-up Ti3C2 framework could buffer volumetric variation of PB during potassiation/depotassiation and also accommodate K+ through electric double-layer capacitive effect. On the other hand, exposed PB nanocrystals were in full contact with electrolyte, so that it would improve the accessibility of K+ by shortening their diffusion path. More strikingly, PB and Ti3C2 components did not operate on their own; instead, they showed great synergy that significantly enhanced the overall performance of the battery. This composite electrode could deliver high K-storage capacity of 355 mAh g−1 after 1000 cycles at 1 A g−1 and exhibit outstanding rate-capacity of 267 mAh g−1 at 10 A g−1.