Preparation of Tough, Binder‐Free, and Self‐Supporting LiFePO4 Cathode by Using Mono‐Dispersed Ultra‐Long Single‐Walled Carbon Nanotubes for High‐Rate Performance Li‐Ion Battery

Abstract

Abstract Low‐contents/absence of non‐electrochemical activity binders, conductive additives, and current collectors are a concern for improving lithium‐ion batteries' fast charging/discharging performance and developing free‐standing electrodes in the aspects of flexible/wearable electronic devices. Herein, a simple yet powerful fabricating method for the massive production of mono‐dispersed ultra‐long single‐walled carbon nanotubes (SWCNTs) in N‐methyl‐2‐pyrrolidone solution, benefiting from the electrostatic dipole interaction and steric hindrance of dispersant molecules, is reported. These SWCNTs form a highly efficient conductive network to firmly fix LiFePO4 (LFP) particles in the electrode at low contents of 0.5 wt% as conductive additives. The binder‐free LFP/SWCNT cathode delivers a superior rate capacity of 161.5 mAh g−1 at 0.5 C and 130.2 mAh g−1 at 5 C, with a high‐rate capacity retention of 87.4% after 200 cycles at 2 C. The self‐supporting LFP/SWCNT cathode shows excellent mechanical properties, which can withstand at least 7.2 MPa stress and 5% strain, allowing the fabrication of high mass loading electrodes with thicknesses up to 39.1 mg cm−2. Such self‐supporting electrodes display conductivities up to 1197 S m−1 and low charge‐transfer resistance of 40.53 Ω, allowing fast charge delivery and enabling near‐theoretical specific capacities.

Keywords

• binder‐free
• lithium‐ion batteries
• lithium iron phosphate
• mono‐dispersed single‐walled carbon nanotubes
• self‐supporting