Robust and Fast Lithium Storage Enabled by Polypyrrole-Coated Nitrogen and Phosphorus Co-Doped Hollow Carbon Nanospheres for Lithium-Ion Capacitors.

Mengdi Zhang,Xuan Zheng,Jiawei Mu,Pengfei Liu,Han Hu,Wenhan Yuan,Tao Xing,Shuli Li,Haiqiu Fang,Haiyan Liu,Xiaobo Wang,Mingbo Wu

doi:10.3389/fchem.2021.760473

Abstract

Lithium-ion capacitors (LICs) have been proposed as an emerging technological innovation that integrates the advantages of lithium-ion batteries and supercapacitors. However, the high-power output of LICs still suffers from intractable challenges due to the sluggish reaction kinetics of battery-type anodes. Herein, polypyrrole-coated nitrogen and phosphorus co-doped hollow carbon nanospheres (NPHCS@PPy) were synthesized by a facile method and employed as anode materials for LICs. The unique hybrid architecture composed of porous hollow carbon nanospheres and PPy coating layer can expedite the mass/charge transport and enhance the structural stability during repetitive lithiation/delithiation process. The N and P dual doping plays a significant role on expanding the carbon layer spacing, enhancing electrode wettability, and increasing active sites for pseudocapacitive reactions. Benefiting from these merits, the NPHCS@PPy composite exhibits excellent lithium-storage performances including high rate capability and good cycling stability. Furthermore, a novel LIC device based on the NPHCS@PPy anode and the nitrogen-doped porous carbon cathode delivers a high energy density of 149 Wh kg−1 and a high power density of 22,500 W kg−1 as well as decent cycling stability with a capacity retention rate of 92% after 7,500 cycles. This work offers an applicable and alternative way for the development of high-performance LICs.

Highlights

In the past decades, electrochemical energy storage devices represented by supercapacitors (SCs) and lithium-ion batteries (LIBs) have gathered global concern and extensive investigation
PPy holds a great application potential in anodes for high-performance Lithium-ion capacitors (LICs), which needs to be further explored. Taking all these considerations into account, we propose a strategy of template-assisted carbonization followed by polymerization to synthesize PPy-coated nitrogen and phosphorus co-doped hollow carbon nanospheres (NPHCS@ PPy) and investigate the electrochemical performances of the composite as the anode material for LIC device
After the removal of silica templates, the spherical structure is preserved and a wealth of mesopores are observed on the surface of spheres (Figure 1B)

Summary

INTRODUCTION

Electrochemical energy storage devices represented by supercapacitors (SCs) and lithium-ion batteries (LIBs) have gathered global concern and extensive investigation. PPy holds a great application potential in anodes for high-performance LICs, which needs to be further explored Taking all these considerations into account, we propose a strategy of template-assisted carbonization followed by polymerization to synthesize PPy-coated nitrogen and phosphorus co-doped hollow carbon nanospheres (NPHCS@ PPy) and investigate the electrochemical performances of the composite as the anode material for LIC device. The LIC device assembled with NPHCS@PPy as the anode and nitrogen-doped porous carbon (NPC) as the cathode achieves high energy density and power density as well as long cycle lifespan. The LIC device was constructed using the NPC cathode and the pre-lithiated NPHCS@PPy anode which was prepared by discharging and charging in the half cell for five cycles at a current density of 0.1 A g−1 and discharging to. Where I is the discharge current (A), t is the discharge time (s), m is the total mass of active materials on anode and cathode (kg), and Vmax and Vmin are the voltage at the beginning and the end of discharge process (V), respectively

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT