Comprehensive Investigation of a Slight Overcharge on Degradation and Thermal Runaway Behavior of Lithium-Ion Batteries

Abstract

Overcharge is a hazardous abuse condition that has dominant influences on cell performance and safety. This work, for the first time, comprehensively investigates the impact of different overcharge degrees on degradation and thermal runaway behavior of lithium-ion batteries. The results indicate that single overcharge has little influence on cell capacity, while it severely degrades thermal stability. Degradation mechanisms are investigated by utilizing the incremental capacity–differential voltage and relaxation voltage analyses. During the slight overcharge process, the conductivity loss and the loss of lithium inventory always occur; the loss of active material starts happening only when the cell is overcharged to a certain degree. Lithium plating is the major cause for the loss of lithium inventory, and an interesting phenomenon that the arrival time of the dV/dt peak decreases linearly with the increase of the overcharge degree is found. The cells with different degrees of overcharge exhibit a similar behavior during adiabatic thermal runaway. Meanwhile, the relationship between sudden voltage drop and thermal runaway is further established. More importantly, the characteristic temperature of thermal runaway, especially the self-heating temperature (T 1), decreases severely along with overcharging, which means that a slight overcharge severely decreases the cell thermal stability. Further, post-mortem analysis is conducted to investigate the degradation mechanisms. The mechanism of the side reactions caused by a slight overcharge on the degradation performance and thermal runaway characteristics is revealed.

Revealing the Impact of Slight Electrical Abuse on the Thermal Safety Characteristics for Lithium-Ion Batteries

“…In this work, four peaks of IC curve appear. Generally, the loss of lithium inventory (LLI) will cause the area of peak ① to decrease, while the loss of active material (LAM) will decrease the areas of other peaks. , Besides, conductivity loss (CL) will cause the IC curve to shift to a lower voltage.…”

“…Phase transition, transition-metal dissolution and electrode oxidation for the cathode, 28,29 and lithium plating for the anode will happen during the overcharge process, 30 which seriously deteriorates the thermal stability of the lithium-ion battery. 23 From the above analysis, it can be concluded that electrical abuse has a severe impact on the life and safety of lithium-ion batteries. Previous research mainly focused on the impact caused by overcharge or over-discharge, respectively, and did not compare the effects of overcharge and over-discharge on lithium-ion batteries.…”

“…Similarly, overcharge also has a severe impact on lithium-ion batteries. Slight overcharge will not only accelerate battery capacity degradation but also reduce battery safety . Further, deep overcharge will directly trigger battery thermal runaway.…”

“…In addition, complex side reactions occur inside the lithium-ion battery. Phase transition, transition-metal dissolution and electrode oxidation for the cathode, , and lithium plating for the anode will happen during the overcharge process, which seriously deteriorates the thermal stability of the lithium-ion battery …”

“…Slight overcharge will not only accelerate battery capacity degradation but also reduce battery safety. 23 Further, deep overcharge will directly trigger battery thermal runaway. Qian et al 24 found that slight overcharge would seriously affect the cycling performance of lithium-ion batteries, and the cycle life was severely reduced.…”