Overcharge durability of Li4Ti5O12 based lithium-ion batteries at low temperature

• Published in: Journal of energy storage Vol. 19; pp. 302 - 310
• Main Authors: Wang, Yu, Chu, Zhengyu, Feng, Xuning, Han, Xuebing, Lu, Languang, Li, Jianqiu, Ouyang, Minggao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2018
• Subjects: Aging mechanism; Lithium-ion battery; Low temperature; LTO; Overcharge; Lithium-ion battery; Overcharge; Aging mechanism; LTO; Low temperature
• ISSN: 2352-152X; 2352-1538
• DOI: 10.1016/j.est.2018.08.012

•A novel approach to compensating the capacity loss of LTO batteries at low temperature is introduced.•The charging capacity of the LTO batteries can be enlarged by 9.5% at -20℃ with slight degradation.•The degradation behavior and mechanisms of LTO batteries overcharged at low temperature are studied.•The potential drop of the LTO anode mainly causes the battery degradation when overcharged. The decrease in capacity at low temperature limits further application of lithium-ion batteries. This paper introduces an approach to compensating the capacity loss of Li4Ti5O12 (LTO) based lithium-ion batteries at low temperature by increasing the charging cut-off voltage. The impact of this approach on battery durability is examined afterwards, and a “tipping point” voltage for degradation is observed. Cut-off voltages over the tipping point (3.2 V) cause severe degradation, while those beneath the tipping point do not. The degradation mechanisms are studied with incremental capacity (IC) curve analysis, a prognostic and mechanistic (P&M) model and Scanning Electron Microscope/X-Ray Energy Dispersive Spectrometer (SEM/EDS) tests. Analysis show that the potential of the LTO anode first drops below 1 V when the battery is overcharged to 3.2 V. The electrolyte exceeds the reduction potential and decomposes on the LTO surface, forming Solid Electrolyte Interface (SEI) film with gas generation. The anode potential then gradually rises to above 1 V as we continue to charge the battery. However, the cathode potential exceeds 4.6 V, resulting in electrolyte oxidation and active material loss in the cathode. Overall, enhancing the cut-off voltage from 2.7 V to 3.2 V is effective to enlarge the charging capacity (9.5%) of the LTO batteries at −20℃ with slight degradation.