An α-MnSe nanorod as anode for superior potassium-ion storage via synergistic effects of physical encapsulation and chemical bonding

Abstract

Conversion mechanism anode materials have been widely employed for potassium ion batteries (PIBs) due to high theoretical specific capacities. However, large volume expansion and poor electrochemical kinetics have become the key bottlenecks hindering its further development. Herein, α-MnSe nanorods wrapped by N-doped carbon and graphene (α-MnSe@NC@graphene) are constructed as anode materials for PIBs. The architecture can not only provide superior electrode integrity to buffer volume variation and maintain structure stability via synergistic effects of physical encapsulation and Mn-C chemical bonding, but also serve as conductive network to accelerate the electron transfer and K-ion diffusion. As a result, α-MnSe@NC@graphene composite delivers high initial charge specific capacity of 307.9 mAh·g−1 and great cycling stability over 250 cycles with the capacity retention of 232.8 mAh·g−1 at 50 mA·g−1. Besides, superior rate capability (91.1 mAh·g−1 at 2.0 A·g−1) and long lifespan over 700 cycles at 1.0 A·g−1 with the low capacities decay rate of 0.064% per cycle can be acquired. Ex situ TEM and XPS results verify that K-ion insert into/extract from α-MnSe@NC@graphene through a conversion mechanism based on the Mn-ion redox site (MnSe + 2 K+ + 2e- ↔ Mn + K2Se).