Zinc-substituted Li4Ti5O12 as a novel large-capacity and low-voltage titanium-based anode material for Li-ion batteries

Abstract

Metal oxides have high theoretical capacities as anode materials for lithium-ion batteries, but the potential of most of them exceeds 1.0 V, which significantly hinders their practical application in full cells. Li₄Ti₅O₁₂ (LTO) anode exhibits excellent cycling performance due to its “zero strain” characteristics. However, its theoretical capacity is only 175 mAh g⁻¹, coupled with the high potential (1.55 V), it will lead to low energy density and low full-cell voltage. Here, we use a partial Zn substitution strategy to tune the potential of LTO to improve its electrochemical performance. LTO with optimal Zn substitution (ZT2) exhibits greatly enhanced battery performance with low working potential (0.62 V) and high capacity (238.4 mAh g⁻¹ after 200 cycles at 2 A g⁻¹). The ultra-low potential of Zn-substituted ZT2 is due to the fact that the reaction process of Li⁺ intercalation has changed from mainly occurring at the 16c octahedral sites to occurring at the 8a site due to the addition of Zn. The specific energy density of the ZT2//LCO (LiCoO₂) full cell is 96.9 Wh kg⁻¹, which is much higher than that of the LTO//LCO full cell. In addition, the ZT2//LCO full cell still maintains a high stability of 78.7 mAh g⁻¹ after 3500 cycles at a current density of 0.5 A g⁻¹. Our results demonstrate that Zn-substituted LTO exhibits high capacity and low voltage advantages, indicating great significance for promoting the practical application of titanium-based anode materials.