Improved lithium storage performance of lithium sodium titanate anode by titanium site substitution with aluminum

Li2Na2Ti6O14 and its Ti-site substitution Li2Na2Ti5.9M0.1O14 (M = Al, Zr, V) are prepared by a solid-state reaction method and used as anode materials for lithium-ion batteries. It is found that metal doping can effectively enhance the electronic conductivity and ionic diffusion coefficient of Li2Na2Ti6O14. Especially for Li2Na2Ti5.9Al0.1O14, it reveals the highest electronic conductivity (1.02 x 10(-9) S cm(-1)) and lithium ion diffusion coefficient (8.38 x 10(-15) cm(2) s(-1)) among all the samples. As a result, Li2Na2Ti5.9Al0.1O14 reveals the best electrochemical performance. It can deliver a charge specific capacity of 270.3 mAh g(-1) at 50 mA g(-1). Even cycled at 1000 mA g(-1), it still can present a charge capacity of 180.7 mAh g(-1). All these enhanced lithium storage capabilities of Li2Na2Ti5.9Al0.1O14 should be attributed to the increased electronic/ionic conductivities and the decreased charge transfer resistance induced by Al doping. Besides, in-situ X-ray diffraction observation also confirms that the structural change of Li2Na2Ti5.9Al0.1L14 is highly reversible process for lithium storage. (C) 2015 Elsevier B.V. All rights reserved.