Spherical Carbon Coated Li4Ti5O12 Materials with Stable Interface

Spinel Li₄Ti₅O₁₂ has become an alternative material to replace electrode in terms of solving these safety issues and improving the life time. Compared with carbon-based anode materials, Li₄Ti₅O₁₂ exhibits a flatter operation potential plateau and higher operating voltage of about 1.55 V versus Li/Li⁺, which can make the issue of lithium dendrite deposition on the surface of anode materials entirely resolved. Unfortunately, as Li₄Ti₅O₁₂ is an insulator, the low electrical conductivity becomes a major drawback which is unfavorable to higher rate capability. Besides the low electronic conductivity, severe gassing during charge/discharge cycles is a critical but often-overlooked problem of Li₄Ti₅O₁₂ batteries. To date, this issue is at present unsettled but will clearly bear heavily on electrode materials, electrolyte and battery system. Gassing is not always occurs, the most serious swelling occurs only in Mn-contained cathode battery system, such as LiMn₂O₄ and LiNi_1/3Mn_1/3Co_1/3O₂ cathode based battery system. Stable cycle performance is more likely to occur when the cathode has high stability in electrolyte, such as LiCoO₂. In this paper, our main goal is to synthesize Li₄Ti₅O₁₂ materials with high rate electrochemical performance and stable interface, which can effectively suppress gassing in LiMn₂O₄/ Li₄Ti₅O₁₂ battery system. For these purposes, the micro-spherical Li₄Ti₅O₁₂ were prepared by clustering the nano-sized Li₄Ti₅O₁₂ (100~200nm) without carbon and with carbon respectively. It was found that the spherical clusters of nano-Li₄Ti₅O₁₂ assembled with carbon (SCN-LTO/C) exhibits significantly improved rate capability and cycling performance compared with that of non-carbon spherical clusters of nano-Li₄Ti₅O₁₂ (SCN-LTO). More important, it also shows stable interface in LiMn₂O₄/Li₄Ti₅O₁₂ system. This stable interface can significantly suppress the gas generation reaction during charging/discharging processes in LiMn₂O₄/Li₄Ti₅O₁₂ system. In this paper, gas generation mechanisms in LiMn₂O₄/Li₄Ti₅O₁₂ battery system are also discussed. For SCN-LTO, gassing phenomenon in the LMO/LTO batteries is ascribable to the manganese deposition in the anode materials, while for SCN-LTO/C materials, carbon coating can effectively cause the inhibition of manganese deposition and side-reactions, highlighting the importance of the stable interface for Li₄Ti₅O₁₂ materials in high-performance LIBs.