Understanding the electrochemical superiority of 0.6Li[Li_1/3Mn_2/3]O₂-0.4Li[Ni_1/3Co_1/3Mn_1/3]O₂ nanofibers as cathode material for lithium ion batteries

Highlights: •Li-rich 0.6Li[Li_1/3Mn_2/3]O₂-0.4Li[Ni_1/3Co_1/3Mn_1/3]O₂ nanofibers are successfully synthesized by the electrostatic spinning method. •The step-by-step CV tests revealed that nanofibers electrode presents higher discharge voltage platform and increased discharge energy density. •The enhanced electrochemical performance is attributed to the neat ion arrangement in crystal structure and the better electrochemical kinetics of nanofibers electrode. -- Abstract: Solid solution cathode materials 0.6Li[Li_1/3Mn_2/3]O₂-0.4Li[Ni_1/3Co_1/3Mn_1/3]O₂ with different morphologies were synthesized by electrospinning and coprecipitation method respectively. The field-emission scanning electron microscope images verified the successful formation of nanofibers for electrospinning and nanoparticles for coprecipitation and the nanofibers showed larger specific surface area according to the Brurauer Emmerr Teller procedure. The X-ray powder diffraction patterns and the corresponding lattice parameter refinements showed that both samples can be indexed to hexagonal α-NaFeO₂ layered structure with space group of R-3m. And the material prepared by electrostatic spinning method has a tight atomic arrangement in the layer yet the different dimensions do not influence the intercalation and deintercalation of lithium ion through the interlayer. The discharge capacity of nanofibers electrode is 302.3 mAh g⁻¹ at 0.05 C and the initial columbic efficiency is 76.2%, which are higher than 282.7 mAh g⁻¹ and 68.2% of the nanoparticles electrode. The nanofibers electrode also presented better cycleability and rate capability, especially performed capacity of 126.6 mAh g⁻¹ at 5 C, much higher than that of 109.4 mAh g⁻¹ for nanoparticles electrode. The step-by-step cyclic voltammetry revealed that the nanofibers electrode performs higher discharge voltage platform and enhanced discharge energy density. The excellent electrochemical performance of nanofibers electrode is ascribed to the better conductivity and superior lithium ion diffusion ability according to the electrochemical impedance spectrum measurement