High C-Rate Performant Electrospun LiFePO₄/Carbon Nanofiber Self-Standing Cathodes for Lithium-Ion Batteries

Abstract

In the present study, LiFePO4/CNF self-standing cathodes for LIBs are synthesized by electrospinning. A lower active material amount (12.3 and 34.5 wt%) is used, compared to the conventional tape-casted cathodes (70–85 wt%). The characterization techniques (XRPD, SEM, TEM, EDS, Raman spectroscopy, and thermogravimetry) confirm that the olivine-type structure of LiFePO4 is maintained in the binder-free electrodes, and the active material is homogeneously dispersed into and within the carbon nanofibers. The electrochemical investigation demonstrates that higher Li+ diffusion coefficients (1.36 × 10−11 cm2/s) and improved reversibility are reached for free-standing electrodes, compared to the LiFePO4 tape-casted cathode (80 wt% of active material) appositely prepared for comparison. The 34.5 wt% LiFePO4 self-standing cathode displays a lower capacity fading, good reversibility and stability, enhanced capacity values at C-rates higher than 5C, and a good lifespan when cycled 1000 cycles at 1C and further cycled up to 20C, compared to the tape-casted counterpart. Notably, the improved electrochemical performances are obtained by only the 34.5 wt% of active material. The results evidence the relevant role of the CNF matrix suitable to host LiFePO4, to promote electrolyte permeation and contact with the active material, and to increase the electronic conductivity.

Keywords

• LiFePO₄
• olivine
• self-standing electrode
• carbon nanofibers
• cathode
• electrospinning