Presentation Title: Single-Crystalline Niobium Titanium Oxide Anode: A Pathway to High-Power and High-Safety Lithium-Ion Batteries

Abstract: 

The Wadsley-Roth phase TiNb₂O₇ material exhibits rapid Li⁺ insertion/extraction kinetics, a moderately high specific capacity, and a working potential of approximately 1.5 V versus Li⁺/Li. The substitution of the dominant graphite anode material with the TiNb₂O₇ anode material can address the current lithium-ion batteries' limitations under fast-charging condition, such as low capacity, rapid performance degradation, and safety concerns, thereby emerging as an optimal anode material for fast-charging, high-safety lithium-ion batteries. This presentation will report a micrometer-scale single-crystal TiNb₂O₇ material developed by our team. Its low crystal defects and high crystallinity contribute to maintaining structural stability during the charge/discharge process. Additionally, its small specific surface area, coupled with the in situ electrochemically generated ionic conductive Li-Nb-O interphase layer, can enhance ionic conductivity while suppressing side reactions with the electrolyte.The correlation between the electrode microstructure and the electrochemical properties of the micrometer-scale single-crystal TiNb₂O₇ material was examined through experimental analysis and theoretical modeling. The fabricated TiNb₂O₇ material delivered a reversible specific capacity of 291.9 mAh g⁻¹ at a current density of 0.5 C. The Ah-level LiFePO₄||TiNb₂O₇ pouch cell achieved a high capacity retention of 74.7% at a current density of 6 C (relative to 0.2 C). An 8 Ah-level LiFePO₄||TiNb₂O₇ pouch cell demonstrated a capacity retention rate of 91.1% over 500 cycles at a current density of 0.5 C. The LiFePO₄||TiNb₂O₇ pouch cell exhibited stabilized electrochemical performance under hazardous test conditions, including fast charging (10 C), fast discharging (8 C), and low temperature (-60 ºC). Moreover, we elucidate the thermal stability of the fully charged (fully lithiated) TiNb₂O₇ material/electrode and the thermal safety of the LiFePO₄||TiNb₂O₇ pouch cell under extreme test conditions, such as continuous floating charge, overcharge, short circuit, thermal shock, adiabatic accelerated calorimetry, and needle test.

Yongming Sun, a professor and doctoral supervisor of Huazhong University of Science and Technology, was selected as one of the National High-level Young Talents Project, and one of the first "TR35 Innovators Under 35" China region list of MIT Technology Review. He was selected as the 2021-2023 Clarivate Global Highly Cited Scientist and the "Lifetime Achievement List of the World's Top 2% of Top Scientists" published by Stanford University in 2022-2023. Yongming Sun has been engaged in fundamental and applied research on high specific energy lithium secondary battery materials for a long time. He has published more than 80 correspondence/one-author papers in well-known international journals such as Nature Energy (3), Nature Communications (2), and Advanced Materials (5), and obtained 15 Chinese authorized patents. He has led over more than 10 national, provincial and ministerial level and enterprise projects related to lithium secondary battery materials.