Pr-modified Li4Ti5O12 nanofibers as an anode material for lithium-ion batteries with outstanding cycling performance and rate performance

Pr-doped Li4Ti5O12 in the form of Li4-x/3Ti5-2x/3PrxO12 (x = 0, 0.01, 0.03, 0.05, and 0.07) was synthesized successfully by an electrospinning technique. ICP shows that the doped samples are closed to the targeted samples. XRD analysis demonstrates that traces of Pr3+ can enlarge the lattice parameter of Li4Ti5O12 from 8.3403 to 8.3765 without changing the spinel structure. The increase of lattice parameter is beneficial to the intercalation and de-intercalation of lithium-ion. XPS results identify the existence form of Ti is mainly Ti4+ and Ti3+ in minor quantity in Li4-x/3Ti5-2x/3PrxO12 (x = 0.05) samples due to the small amount of Pr3+. The transition from Ti4+ to Ti3+ is conducive to the electronic conductivity of Li4Ti5O12. FESEM images show that all the nanofibers are well crystallized with a diameter of about 200 nm and distributed uniformly. The results of electrochemical measurement reveal that the 1D Li4-x/3Ti5-2x/3PrxO12 (x = 0.05) nanofibers display enhanced high-rate capability and cycling stability compared with that of undoped nanofibers. The high-rate discharge capacity of the Li4-x/3Ti5-2x/3PrxO12 (x = 0.05) samples is excellent (101.6 mAh g(-1) at 50 A degrees C), which is about 58.48 % of the discharge capacity at 0.2 A degrees C and 4.3 times than that of the bare Li4Ti5O12 (23.5 mA g(-1)). Even at 10 A degrees C (1750 mA g(-1)), the specific discharge capacity is still 112.8 mAh g(-1) after 1000 cycles (87.9 % of the initial discharge capacity). The results of cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) illustrate that the Pr-doped Li4Ti5O12 electrodes possess better dynamic performance than the pure Li4Ti5O12, further confirming the excellent electrochemical properties above.