Li4−xNaxTi5O12 with low operation potential as anode for lithium ion batteries

In this work, the unique effect of the substitution of lithium ions by sodium ions in Li4Ti5O12 on the structure, crystalline size and electrochemical performance is investigated in details. The Li4−xNaxTi5O12 materials are by high temperature calcination of titania, anhydrous lithium carbonate and anhydrous sodium carbonate. It is shown from the structure analysis that the phase structure transformation is found with gradually increasing the molar ratio of sodium ions to lithium ions in the as-prepared Li4−xNaxTi5O12 samples, accompanied with the evident growth of the crystallites. Because of the phase structure transformation from a cubic structure to an orthorhombic structure whose open relatively tunnel structure along the b-axis makes for the lithium ion insertion/extraction, the Li2Na2Ti5O12 sample presents the low and sloped potential plateau as expected, distinguished from the high and flat potential plateau of Li4Ti5O12. Meanwhile, the Li2Na2Ti5O12 sample delivers the good high-rate capability and cycle stability during cycling. The results clarify the positive effect of the suitable substitution of lithium ions by sodium ions in Li4Ti5O12 anode material with the low operation potential for insuring the high working voltage of lithium ion batteries.