Electrochemical and thermal characteristics of aging lithium-ion cells after long-term cycling at abusive-temperature environments

Abstract

This work prepares five kinds of cell samples, i.e. the fresh cell, the cell degrades to 90% SOH (state of health) after high-temperature cycling, the cell degrades to 80% SOH after high-temperature cycling, the cell degrades to 90% SOH after low-temperature cycling and the cell degrades to 80% SOH after low-temperature cycling to reveal the electrochemical and thermal characteristics of the aging cells induced by abusive-temperature cycling. The cells under abusive-temperature environments show severe degradation behaviors over cycling, which may be mainly attributed to lithium inventory loss, anode material loss and electrode interface deterioration. Besides that, abusive-temperature cycling affects the thermal stability of positive electrode materials and single cells, and this is related with environmental temperatures. By comparison to the fresh cell, the thermal stability of the positive electrode materials and single cells after high-temperature cycling is improved, which is different from that of the low-temperature cycled ones who illustrate deteriorated thermal safety at elevated temperatures. Therefore, the thermal risk of aging cells after long-term low-temperature cycling is worthy of more concern, the according monitor and/or management of these cells during operation, transportation, storage and recycle, etc. should be valued.