High edge-nitrogen-doped porous carbon nanosheets with rapid pseudocapacitive mechanism for boosted potassium-ion storage

Abstract

Currently, the development of carbonaceous materials for potassium ion batteries (PIBs) with ultrafast rate performance is limited by the huge volume expansion and sluggish electrochemical kinetics derived from the insertion/de-insertion of large radius of K+. Herein, the high edge-nitrogen-doped porous carbon nanosheets (EN-PCNs) were obtained via a simple and scalable pyrolysis strategy. The synergistic effect of two-dimensional (2D) porous nanosheet structure and ultrahigh content of edge-nitrogen (79.6 at%) provide the EN-PCNs with multiple advantages including rich defect sites, enlarge interlayer spacing (0.378 nm) and high specific surface area (417.0 m2 g−1), which can enhance the K+ storage. As excepted, the as-prepared EN-PCNs electrode delivers a high reversible capacity of 345.2 mA h g−1 at 0.7 C, ultrafast rate capacity of 108.4 mA h g−1 at 7 C and good cycling stability of 121.4 mA h g−1 with a retention of 72% after 1000 cycles at 3.5 C. Moreover, in-depth electrochemical kinetic analysis further verifies that the boosted potassium ion storage of EN-PCNs electrode is attributed to the rapid pseudocapacitance mechanism. This work not only demonstrates a simple and scalable strategy for the construction of advanced high edge N-doped porous nanosheet carbon materials, but also provides a new reference for adjusting the pseudocapacitance mechanism to achieve enhanced potassium storage capacity.