Rational Design of Phosphorus Abundant Co2P Nanoparticles Encapsulated by Nitrogen-doped Carbon Nanotubes for Superior Lithium Ion Capacitors with 4.5 Voltage

The sluggish reaction kinetics and aggregation of volume during lithiation/delithiation process are the main obstacles of anode for li-ion capacitors (LICs). Here, we use the “three bird one stone” strategy to design the anode of phosphorus abundant Co2P nanoparticles encapsulated by N-doped CNTs rationally. The Co2P nanoparticles contribute to shorten the Li+ diffusion length, while abundant phosphorus guaranteeing the high electrical conductivity and N-CNTs providing stable structure protecting layers. Hence, Co2P/N-CNTs electrode reveals a large specific capacity of 807 mAh g-1 at 0.1 A g-1 over 200 cycles and excellent rate performance of 395 mAh g-1 at 3.2 A g-1. Extraordinary, the capacitive contribution of Co2P/N-CNTs electrode at 1 mV s-1 is 80.73%, contributing to the enhanced reaction kinetics and rate capacity. The LICs comprising of Co2P/N-CNTs anode and activated carbon (AC) cathode demonstrate an outstanding energy density of 130 Wh kg-1 at 625 W kg-1 along with 90.24% capacity retention over 10000 cycles at 5 A g-1 within 4.5 V. The proposed strategy can be applied to develop promising electrode materials for promising energy storage systems.