Unveiling the potential of low-strain nanoporous Li0.33La0.55TiO3 nanofibers as a promising anode for Li-ion batteries: exploring the influence of carbon additives and binders

Abstract

Low-strain intercalation-type anodes are crucial for developing efficient, long-lasting, safe, and reliable lithium-ion batteries. Li_0.33La_0.55TiO₃ (LLTO) is one such anode gaining popularity; nevertheless, its preparation often involves long-term, high-temperature procedures. In this work, LLTO nanofibers were synthesized by electrospinning at different calcination temperatures (700 °C, 800 °C, and 900 °C) and compared with LLTO nanoparticles obtained by a sol–gel method. X-ray diffraction and Raman spectroscopic measurements revealed the presence of LLTO and electrochemically active La₂Ti₂O₇ and Li₂TiO₃ phases in the nanofibers. The interconnected LLTO nanoparticles form a porous structure within the fiber, which enhances the Li-ion (de)intercalation kinetics. Among the prepared samples, the LLTO nanofibers prepared at 800 °C exhibit better electrochemical properties than other variants, combining the conventional binder (PVDF) and carbon additives (carbon black). Furthermore, LLTO NFs calcined at 800 °C with the combination of Ketjenblack and sodium alginate (LLKS) provide a higher discharge capacity of 317 mAh g⁻¹ than the Ketjenblack and PVDF (LLKB) (180 mAh g⁻¹) and conventional carbon black and PVDF (LLCP) (263 mAh g⁻¹) combinations at 0.1 A g⁻¹ due to their low polarization and slightly increased pseudocapacitive contribution. Moreover, the carbon additive of Ketjenblack and the water-soluble sodium alginate binder improved the ionic conductivity, electrochemical activity, and reversibility. The diffusion kinetics of this electrode were examined using the GITT and EIS techniques, revealing a lower reaction resistance (0.85 Ohm g) and higher diffusion coefficient (∼10⁻⁶ cm² s⁻¹). Ex situ XRD indicated that the unit cell volumes of the cycled LLCP, LLKP, and LLKS electrodes are comparable to those of the as-prepared LLTO nanofibers, with less than 1% volume expansion even after 1000 cycles, substantiating the strain-free nature and stability of the LLTO nanofibers.