Researchers from Chengdu Development Center of Science and Technology have significantly enhanced the performance of titanium niobium oxides for lithium-ion batteries. This has applications in electric vehicles and mobile electronics. A paper on the work is published in the journal NANO.

Due to its high security and capacity, titanium niobium oxide (TNO) has gained much attention as anode material for lithium-ion batteries. However, its electronic conductivity is too low to have high capability at high rates.

In order to improve the high-rate performance of TNO effectively, a team of researchers from Chengdu Development Center of Science and Technology, China Academy of Engineering Physics, combined utilized crystal structure modification, particle size reduction, porous structure, and conductive-phase compositing. The electrochemical performance, especially high-rate performance, of the material was significantly enhanced.

Ti₂Nb₁₀O_29-x/HRGO hybrid was successfully fabricated by introducing vacancies into Ti₂Nb₁₀O₂₉ (TNO) and hybridizing TNO with holey reduced graphene oxide (HRGO).

Morphology and rate capability of TNO_x/HRGO. TNO_x microspheres are wrapped by gossamer-like HRGO. Capacity is as high as 225 mAh/g and 173 mAh/g at 20 C and 40 C, respectively. Luo et al.

The structure of TNO_x/HRGO is TNO_x microspheres with oxygen vacancies wrapped by gossamer-like HRGO. Electrochemical measurements confirmed that TNO_x/HRGO hybrid exhibited excellent reversible capacity of 316 mAh/g, 278 mAh/g, 242 mAh/g, 225 mAh/g, and 173 mAh/g at 1 C, 5 C, 10 C, 20 C, and 40 C, respectively.

After 300 cycles at 10 C, it still has a high capacity of 238 mAh/g with a high capacity retention of 98%, revealing excellent cycling stability.

The oxygen vacancies of TNO_x and the high conductivity of HRGO can effectively enhance the electronic conductivity of the TNO_x/HRGO hybrid, and the HRGO holes are beneficial for the transmission of lithium-ion (Li⁺). The synergy effect of above features improves the rate performance of the TNO_x/HRGO hybrid.

In addition, the existence of HRGO can buffer volume expansion during the insertion processes of Li+, which can improve cyclic stability of the TNO_x/HRGO hybrid.

This research was supported in part by grants from the National Natural Science Foundation of China (No. 51873240 and 51103141) and Sichuan Science and Technology Program (2019YJ0658).

Resources

• Nan Luo, Guoliang Chen, Yunfan Shang, Suyang Lu, Jun Mei, Changyu Tang, Zhoukun He, Wenwen Zeng and Haoran Zhan (2020) “Porous Ti₂Nb₁₀O_29−𝑥 Microspheres Wrapped by Holey-Reduced Graphene Oxide as Superior Anode Material for High-rate Performance Lithium-ion Storage” NANO doi: 10.1142/S1793292020500952