Direct electrodeposition of lithium titanate as a lithium-ion battery anode active material in propylene carbonate solution containing titanyl compounds

Abstract

Lithium titanium oxide (LTO) type materials for lithium-ion (Li-ion) batteries have become an alternative to the typically used graphitic-based materials as anode materials due to their better safety performance and longer life cycles. In the literature, LTO structures such as Li₄Ti₅O₁₂, Li₂Ti₃O₇ and Li₂Ti₃O₇/Li₂TiO₃ composites with different Li/Ti ratios have been synthesized by solution and solid phase methods such as sol–gel, spray drying, spray pyrolysis and, ultrasonic spray pyrolysis at elevated temperatures using TiO₂ and Li₂CO₃ as starting materials, and their electrochemical performances have been tested. This study demonstrated that electrochemical deposition can directly deposit LTO anode electrode materials using TiOSO₄ and TiO(ClO₄)₂ precursor compounds in Propylene Carbonate (PC) solvent containing LiClO₄ supporting electrolyte at room temperature. TiO(OH)₂ and TiOOH, which are formed by the reactions of the unstable TiO⁺ ion formed by electrochemical reduction with TiO²⁺ in solution and adsorbed on the electrode surface and the OH⁻ ion formed by the electroreduction of water, and TiO(OH)₂ and TiOOH precipitated on the electrode surface, interact with the excessive amount of Li⁺ ions in solution to form lithium titanate. Since electrochemical reduction occurs between 2.4 V and 1.2 V, lithium can be incorporated during electrodeposition, resulting in the formation of various lithium titanate phases (Li₄Ti₅O₁₂, Li₂Ti₃O₇ and Li₂Ti₃O₇/Li₂TiO₃ composite). Electrodeposited Lithium Titanate (ED-LTO) obtained in this way has been characterized using cyclic voltammetry, chronopotentiometry, EIS, XRD, XPS, Raman spectroscopy, and FESEM-EDX techniques. A full cell was fabricated using ED-LTO/LiFePO₄.