Lithiation and delithiation behavior of sodium lithium titanate anode

•The suitable solid formation temperature for Na2Li2Ti6O14 is 800 °C.•The lithiation behavior in Na2Li2Ti6O14 is firstly studied by in-situ method.•Na2Li2Ti6O14 reveals high structural and electrochemical reversibility.

Na2Li2Ti6O14 is synthesized by a simple solid state method between 500 and 900 °C. It is found that pure Na2Li2Ti6O14 is only formed at 800 °C or above. The tap density of as-prepared Na2Li2Ti6O14 is about 1.52 g cm−3. Particle morphology analysis shows that the size of Na2Li2Ti6O14 gradually increases with the increase of sintering temperature. Calcined at 900 °C, Na2Li2Ti6O14 shows slight particle aggregation and melting. As a result, Na2Li2Ti6O14 formed at 800 °C reveals higher electrochemical activity than the sample obtained at 900 °C. Therefore, the suitable preparation temperature for Na2Li2Ti6O14 by solid state reaction is 800 °C. Charge–discharge results show that Na2Li2Ti6O14 prepared at 800 °C can deliver a reversible capacity of 89.9 mAh g−1 at 100 mA g−1, 81.3 mAh g−1 at 200 mA g−1, 75.2 mAh g−1 at 300 mA g−1, 69.6 mAh g−1 at 400 mA g−1 and 65.5 mAh g−1 at 500 mA g−1. Besides, the lithium storage mechanism in Na2Li2Ti6O14 is also studied by various in-situ and ex-situ methods, which prove that the structural evolution is highly reversible for Na2Li2Ti6O14 during lithiation/delithiation process.

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