Study on degradation behavior of commercial 18650 LiAlNiCoO₂cells in over‐charge conditions

Abstract

Summary From the battery life and safety perspective, an investigation was conducted to analyze the degradation behavior of 18650 LiAlNiCoO2 (NCA/C) cells with different cut‐off voltages (4.30, 4.50, 4.80 and 5.00 V) and different cycle numbers. Electrochemical Impedance Spectroscopy (EIS) and Incremental Capacity (IC) analysis were employed to identify the fading mechanism for overcharged NCA/C cells. Key insights were that major side reactions for the overcharged NCA cells are the oxidation and decomposition of electrolyte, the thickening of the passivation layer, the deposition of lithium and the structure change of cathode. These side reactions accounted for the increase of impedance for the cells with the cut‐off voltages and the cycle numbers, especially for the charge transfer impedance. An EIS‐distribution of relaxation time (DRT) method was applied to identify and quantify the influences of various degradation modes during overcharging process. The loss of lithium inventory (LLI) was more pertinent to the degradation than the conductivity loss (CL) and the loss of active material (LAM). Conspicuous variations in the cell can assist in self‐test and failure warning, such as the rapid rise of the temperature change rate, the evident transformation of peaks in IC results and the irreversible increase of CL.

Analysis of the effect of resistance increase on the capacity fade of lithium ion batteries

“…The degradation of lithium ion batteries occurs due to various chemical degradation mechanisms such as electrolyte decomposition and reduction resulting in solidelectrolyte interphase (SEI) formation, active material dissolution, and gas evolution and mechanical degradation mechanisms such as formation of cracks in active materials and loss of contact from current collector. [9][10][11][12] This degradation behavior is typically studied by cycling the batteries with a fixed protocol for a long duration. A typical protocol consists of charging the battery in the constant current constant voltage (CCCV) mode till a specified current cutoff is reached, resting the battery for a fixed time, discharging at a fixed current till a voltage cutoff is reached and further resting the battery for a fixed duration.…”

“…The degradation of lithium ion batteries occurs due to various chemical degradation mechanisms such as electrolyte decomposition and reduction resulting in solid‐electrolyte interphase (SEI) formation, active material dissolution, and gas evolution and mechanical degradation mechanisms such as formation of cracks in active materials and loss of contact from current collector . This degradation behavior is typically studied by cycling the batteries with a fixed protocol for a long duration.…”

Thermal safety study of Li‐ion batteries under limited overcharge abuse based on coupled electrochemical‐thermal model

“…However, due to the poor thermal stability of materials in LIBs, serious hazards may be induced when LIBs are under unexpected abuse conditions such as extrusion, penetration, overheat, and overcharge . Thermal runaway caused by the above abuse conditions can be attributed to a series of side reaction heat generation inside the battery.…”

“…[1][2][3][4][5] However, due to the poor thermal stability of materials in LIBs, serious hazards may be induced when LIBs are under unexpected abuse conditions such as extrusion, penetration, overheat, and overcharge. [6][7][8][9][10] Thermal runaway caused by the above abuse conditions can be attributed to a series of side reaction heat generation inside the battery. The internal heat of the battery continues to accumulate when the heat generation rate is much higher than the heat dissipation rate, eventually causing uncontrollable chemical reactions of battery.…”

A comparative study on the degradation behaviors of overcharged lithium‐ion batteries under different ambient temperatures

“…6,7 To date, the failure mechanisms of overcharged LIBs have been widely investigated. [11][12][13][14][15][16][17] Xu et al 11 announced that during the overcharge process, Fe (iron) dendrites continued growing upon both electrodes, which might penetrate through the separator and induce short circuiting eventually, leading to the failure of a battery. [11][12][13][14][15][16][17] Xu et al 11 announced that during the overcharge process, Fe (iron) dendrites continued growing upon both electrodes, which might penetrate through the separator and induce short circuiting eventually, leading to the failure of a battery.…”