Comparison of LiVPO₄F to Li₄Ti₅O₁₂ as Anode Materials for Lithium-Ion Batteries

Abstract

In\nthis paper, we reported on a comparison of LiVPO₄F to Li₄Ti₅O₁₂ as anode materials\nfor lithium-ion batteries. Combined with powder X-ray diffraction,\nscanning electron microscopy, high-resolution transmission electron\nmicroscopy, galvanostatic discharge/charge tests and in situ X-ray\ndiffraction technologies, we explore and compare the insertion/extraction\nmechanisms of LiVPO₄F based on the V³⁺/V²⁺/V⁺ redox couples and Li₄Ti₅O₁₂ based on the Ti⁴⁺/Ti³⁺ redox\ncouple cycled in 1.0–3.0 V and 0.0–3.0 V. The electrochemical\nresults indicate that both LiVPO₄F and Li₄Ti₅O₁₂ are solid electrolyte interphase free materials\nin 1.0–3.0 V. The insertion/extraction mechanisms of LiVPO₄F and Li₄Ti₅O₁₂ are similar\nwith each other in 1.0–3.0 V as proved by in situ X-ray diffraction.\nIt also demonstrates that both samples possess stable structure in\n0.0–3.0 V. Additionally, the electrochemical performance tests\nof LiVPO₄F and Li₄Ti₅O₁₂ indicate that both samples cycled in 0.0–3.0 V exhibit much\nhigher capacities than those cycled in 1.0–3.0 V but display\nworse cycle performance. The rate performance of Li₄Ti₅O₁₂ far exceeds that of LiVPO₄F in the\nsame electrochemical potential window. In particular, the capacity\nretention of Li₄Ti₅O₁₂ cycled in\n1.0–3.0 V is as high as 98.2% after 20 cycles. By contrast,\nLi₄Ti₅O₁₂ is expected to be a candidate\nanode material considering its high working potential, structural\nzero-strain property, and excellent cycle stability and rate performance.