Ti3+-free three-phase Li4Ti5O12/TiO2 for high-rate lithium ion batteries: Capacity and conductivity enhancement by phase boundaries

Abstract Ti-based nanoplates with abundant phase boundaries have been synthesized via partial lithiation reaction and optimized heat treatment. Using phase boundaries (rather than free surfaces) to keep the crystalline domains small might have significant advantages, such as improved tap density (therefore volumetric energy density) and reduced loss of live Lithium to the solid electrolyte interphase (SEI) which only coats the free surfaces. As lithium ion battery anode, the obtained Li 4 Ti 5 O 12 /TiO 2 (Anatase)/TiO 2 (Rutile) three-phase mixture shows a capacity of about 170 mA h g −1 at 4000 mA g −1 (fully charged in ~150 s), and undergoes more than one thousand cycles with capacity fade of only 0.02% per cycle. It also demonstrates excellent cycling stability even after 4000 cycles at 500 mA g −1 in a Li-matched full cell vs. LiFePO 4 cathode in large pouch cell format, with tolerable gassing behavior. Rather than relying on Ti 3+ defects or excessively large surface area, the present material is prepared in fully oxidizing environment, with abundant phase boundaries as the main capacity enhancement mechanism, which simplify its industrial production.