Analysis of Lithium-Ion Battery Failure Issues
In commercial lithium-ion batteries, certain failure phenomena often occur during use or storage, significantly reducing the performance, reliability, and safety of lithium-ion batteries.
These failure phenomena result from the interaction of a series of complex chemical and physical mechanisms within the battery.
Correctly analyzing and understanding these failure phenomena play a crucial role in improving the performance and technological advancements of lithium-ion batteries.
This article will introduce the reasons for the failure of lithium-ion batteries.
The lithium-ion battery system is complex and involves aspects of thermodynamics, kinetics, microstructures, interactions, and reactions between components, as well as interfacial reactions.
1. Lithium-Ion Battery Failure Symptoms and Mechanisms
(1) Capacity Degradation
The capacity degradation of lithium-ion batteries can be categorized into reversible capacity degradation and irreversible capacity degradation.
- Reversible capacity degradation can be restored by adjusting the battery’s charging and discharging regimen and improving the battery’s operating conditions.
- Irreversible capacity degradation results from irreversible changes occurring within the battery, leading to unrecoverable capacity loss.
The root cause of battery capacity degradation lies in material failures, closely related to objective factors such as battery manufacturing processes and usage environments.
From a material perspective, the main causes of failure include structural failures in the positive electrode material, excessive growth of the solid-electrolyte interphase (SEI) on the negative electrode surface, electrolyte decomposition and degradation, corrosion of current collectors, and trace impurities in the system.
(2) Increase in Internal Resistance
The internal resistance of lithium-ion batteries is related to the internal electron and ion transfer processes within the battery system and is mainly divided into Ohmic resistance and polarization resistance.
Polarization resistance, in particular, is mainly caused by electrochemical polarization and includes both electrochemical polarization and concentration polarization.
The primary factors leading to an increase in the internal resistance of lithium-ion batteries are related to critical battery materials and battery usage environments.
Researchers such as Que Yongchun from the University of Science and Technology of China have proposed that the jump mechanism of transition elements is the reason for potential lag and voltage decay using synchrotron radiation technology.
This explains that within the battery system, abnormalities in critical materials are the fundamental influencing factors for increased internal resistance and battery polarization.
(3) Internal Short Circuit
The manifestations of a short circuit can be divided into:
① Short circuit between copper/aluminum current collectors.
② Membrane failure leads to the loss of electronic insulation or an increase in gaps, allowing partial contact between the positive and negative electrodes, resulting in severe local heating. During subsequent charging and discharging processes, this heat may spread to the surroundings, leading to thermal runaway.
③ Impurities of transition metals in the positive electrode slurry were not completely removed, causing penetration of the membrane or promoting the generation of lithium dendrites in the negative electrode, resulting in internal short circuits.
④ The occurrence of internal short circuits caused by lithium dendrites.
Furthermore, in the battery design, manufacturing, or battery pack assembly processes, unreasonable designs and excessive localized pressure can also lead to internal short circuits. For example, as reported by the South Korean media SBS in the case of the Samsung Note7 explosions, it was pointed out that internal compression led to the contact between the positive and negative electrodes, causing an internal short circuit, which in turn resulted in thermal runaway of the battery. Under the induction of overcharging and over-discharging of the battery, internal short circuits can also occur, mainly due to corrosion of the current collector, leading to deposition on the electrode surfaces. In severe cases, it can result in the direct connection of the positive and negative electrodes through the membrane, as shown in Figure 1.
Figure 1: Internal Short Circuit Induced by Over-Discharging
(4) Gas Generation
Gas generation in lithium-ion batteries can be divided into normal gas generation and abnormal gas generation.
- Normal gas generation occurs during the formation of the battery’s chemistry when electrolyte is consumed to form a stable SEI (Solid Electrolyte Interphase) film. The gas generated during the formation stage includes H2, CO2, C2H2, and others through ester-type single/double electron reactions.
- Abnormal gas generation, on the other hand, occurs during the battery cycling process when there is excessive consumption of electrolyte, leading to gas release, or when the positive electrode material releases oxygen. This phenomenon is more common in pouch-type batteries, and it can result in increased internal pressure, deformation, rupturing of the aluminum packaging film, and internal cell contact issues.
(5) Thermal Runaway
Thermal runaway refers to the rapid increase in temperature, either locally or throughout the entire lithium-ion battery, where heat cannot dissipate quickly enough. This results in the accumulation of a large amount of heat internally and triggers further secondary reactions. For more common behaviors of thermal runaway inside lithium-ion batteries, please refer to Analysis and Prevention of Lithium Battery Thermal Runaway.
To prevent serious safety issues caused by thermal runaway in lithium-ion batteries, measures such as PTC (Positive Temperature Coefficient) devices, safety valves, and thermal conductive films are often employed. Additionally, a systematic approach is required in battery design, manufacturing processes, battery management systems, and battery usage environments.
(6) Lithium Plating
Lithium plating is a common aging failure phenomenon in lithium-ion batteries. The main manifestation is the appearance of a gray, gray-white, or gray-blue substance on the surface of the negative electrode sheet, which is metallic lithium plated on the surface of the negative electrode. Figure 2 shows a common lithium plating phenomenon.
Researchers at Tsinghua University, led by Zhang Qiang, pointed out that the main factors affecting dendrite growth are current density, temperature, and charge capacity. Measures to inhibit dendrite growth include the addition of electrolyte additives, artificial solid electrolyte interface (SEI), high salt concentration electrolytes, structured negative electrodes, and optimized battery configuration design.
Figure 2: Common lithium plating phenomenon
The failure of lithium-ion batteries mainly stems from the following three aspects: component materials, design and manufacturing, and usage environment. From the perspective of component materials, various failure phenomena can be attributed to the battery’s component materials.