Copper-doped Li4Ti5O12/carbon nanofiber composites as anode for high-performance sodium-ion batteries

• Cu-doped Li4Ti5O12/CNF was first introduced as anode for sodium-ion batteries.
• The particle size of Li4Ti5O12 was reduced in Cu-doped Li4Ti5O12/CNF.
• Rate capability of Li4Ti5O12/CNF was improved by copper doping and carbon coating.
• High capacity retention of Cu-doped Li4Ti5O12/CNF was achieved after 150 cycles.

Lithium titanium oxide (Li4Ti5O12) is a promising anode material, owing to its superior safety and reliability. However, the main challenge of Li4Ti5O12 is the low material conductivity which restricts its electrochemical performance. In order to use Li4Ti5O12 in practical sodium-ion batteries, copper-doped Li4Ti5O12 (Li4−xCuxTi5O12, x = 0, 0.05, 0.1) nanoparticles were prepared to enhance the electronic conductivity. Copper-doped Li4Ti5O12 nanoparticles were then embedded in continuous carbon nanofibers (CNFs), which gave rise to fast electron transfer along the fiber direction. After copper-doping and CNF embedding, the resultant copper-doped Li4Ti5O12/CNFs achieved excellent reversible capacity (158.1 mAh g−1) at 30 mA g−1, high coulombic efficiency (99.87%), and good capacity retention (91%) after 150 cycles. In addition, copper-doped Li4Ti5O12/CNFs also exhibited good rate capability. It is, therefore, demonstrated that copper-doped Li4Ti5O12/CNFs are promising anode candidate.