Lithium-ion insertion kinetics of Na-doped Li2TiSiO5 as anode materials for lithium-ion batteries

Li2TiSiO5 receives much interest recently in lithium-ion battery anodes because of its attractive Li-insertion/extraction potential at 0.28 V (vs. Li+/Li), which bridges the potential gap between graphite and Li4Ti5O12. However, Li2TiSiO5 suffers from the low intrinsic electronic conductivity and sluggish Li-ion transfer kinetics. In this work, we report lithium-ion insertion kinetics of Li2TiSiO5 by Na doping, achieving high-rate capability. Rietveld refinement of X-ray diffraction results reveals that Na doping can enlarge the space of Li slabs, thus reducing the Li-ion transfer barrier and enhancing the Li-ion diffusion kinetics. According to first-principles calculations, Na doping can tune the band structure of Li2TiSiO5 from indirect to direct band, leading to improved electronic conductivity and electrochemical performance. In particular, the Na-doped Li2TiSiO5 (Li1.95Na0.05TiSiO5) electrode exhibits outstanding rate capability with a high capacity of 101 mA h g−1 at 5 A g−1 and superior cyclability with a reversible capacity of 137 mA h g−1 under 0.5 A g−1 over 150 cycles.