March 14, 2024
What causes lithium battery internal short circuit? Full guide to risks and fixes
Lithium-ion batteries have become an indispensable energy core in modern electronic devices, electric vehicles and energy storage systems due to their excellent energy density (explore energy density lithium battery), long cycle life and excellent charge and discharge performance.
However, lithium batteries are not perfect. Internal short circuit is a major safety hazard they face, which may lead to battery performance degradation, thermal runaway, and even serious accidents such as fire or explosion. This article will explore the causes and effects of lithium battery internal short circuit, and elaborate on how to prevent and respond to this problem, aiming to provide reference for lithium battery practitioners and users.
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What is lithium battery internal short circuit?
Internal short circuit of lithium battery refers to an abnormal conductive path between the positive and negative electrodes inside the battery. Under normal circumstances, lithium ions shuttle between the positive and negative electrodes in an orderly manner through the electrolyte during the charge and discharge process, and the diaphragm, as a key component, plays an insulating role to prevent direct contact between the positive and negative electrodes and avoid direct conduction of electrons.
However, when an internal short circuit occurs, the insulation between the positive and negative electrodes is destroyed, and electrons can bypass the normal circuit and flow directly from the positive electrode to the negative electrode, forming a low-resistance short circuit. This abnormal current path will cause a large amount of heat to be generated inside the battery, accelerate battery aging, and even cause thermal runaway.
Common causes of internal short circuits in lithium batteries
The occurrence of lithium battery internal short circuit is not accidental, but the result of the combined action of multiple factors. The following is an analysis of common causes:
Manufacturing defects
Metal impurities mixed in
During the production of lithium batteries, the environmental cleanliness is not strictly controlled or there are metal impurities in the raw materials, which may be mixed into the battery. Once the metal impurity particles penetrate the diaphragm and contact the positive and negative electrodes, they will form a conductive path between the positive and negative electrodes, causing an internal short circuit.
Electrode burrs
If the shearing, stamping and other process links in the electrode manufacturing process are improperly operated or the equipment is not accurate enough, tiny burrs may be generated on the edge of the electrode. These burrs may gradually pierce the diaphragm during use, eventually causing an internal short circuit.
Diaphragm defects
Defects in the diaphragm itself, such as uneven thickness, excessive porosity, and insufficient strength, may lead to a decrease in its insulation ability and make it easier to be pierced by metal impurities or electrode burrs, thus causing internal short circuits.
Welding defects
If there are defects such as false welding and false welding in the welding points inside the battery, it will lead to increased resistance (find lithium ion battery internal resistance), local overheating, accelerated battery aging, and increased risk of internal short circuits.
Damage during use
Mechanical stress
In daily use, lithium batteries are inevitably subjected to various mechanical stresses, such as mobile phone drops and electric vehicles driving on bumpy roads. These impacts and extrusions may cause deformation and damage to the electrodes, diaphragms and other structures inside the battery. Diaphragm rupture will cause direct contact between the positive and negative electrodes, causing internal short circuits.
Temperature influence
Temperature is crucial to the performance and safety of lithium batteries. Under high temperature conditions, the chemical reaction rate inside the battery is accelerated, which may lead to problems such as electrolyte decomposition and changes in the structure of electrode materials.
Extreme high temperatures may cause the diaphragm to melt, the isolation between the positive and negative electrodes to fail, and cause internal short circuits. Under low temperature environment, the internal resistance of the battery increases, and the migration rate of lithium ions slows down, which may cause excessive local current inside the battery and cause internal short circuit.
Overcharge and over-discharge
Overcharging may cause the structure of the positive electrode material to be unstable, release oxygen, and damage the internal structure of the battery; battery over-discharge may cause the negative electrode copper collector to dissolve, form copper dendrites, pierce the diaphragm, and cause internal short circuit.
Battery aging
SEI film growth
As the number of battery charge and discharge cycles increases, a layer of solid electrolyte interface (SEI) film will gradually form on the surface of the negative electrode. The growth of the SEI film may cause the activity of the negative electrode material to decrease and cracks to form. Crack expansion may cause the contact between the negative electrode and the electrolyte to deteriorate, causing local current concentration and internal short circuit (explore what is battery aging).
Changes in the structure of the positive electrode material
The increase in the number of cycles will cause changes in the crystal structure of the positive electrode material, reduce the stability of the material, and indirectly increase the risk of internal short circuit.
Lithium dendrite growth
After long-term use, especially under low temperature or high rate charge and discharge conditions, lithium dendrites are easily formed on the surface of the negative electrode. These metal lithium dendrites will continue to grow, pierce the diaphragm, and eventually cause an internal short circuit.
Impacts caused by lithium battery internal short circuits
Lithium battery internal short circuits are not trivial, and their impact is wide-ranging, which may cause the following serious consequences:
Battery capacity decay
Internal short circuits can cause self-discharge inside the battery, and a large amount of electrical energy is consumed in the battery without reason, and cannot be output to the outside for use by the device. This will reduce the actual available capacity of the battery and significantly reduce the endurance of the device.
Increased internal resistance of the battery
When an internal short circuit occurs, the current distribution inside the battery becomes uneven, and high current density will appear in local areas. The increase in the internal resistance of the battery will not only increase the energy loss of the battery during charging and discharging, reduce the energy conversion efficiency of the battery, but also cause the battery to heat up during charging and discharging. If the battery is in a high internal resistance state for a long time, the life of the battery will be further shortened, accelerating the failure process of the battery.
Increased risk of thermal runaway
Thermal runaway is one of the most serious consequences that may be caused by lithium battery internal short circuits. When an internal short circuit occurs, a large amount of electrical energy is converted into heat energy in a short period of time, causing the internal temperature of the battery to rise sharply.
As the temperature rises, the chemical reaction inside the battery will further intensify, generating more heat and forming a vicious cycle. If the heat cannot be dissipated in a timely and effective manner, when the temperature reaches a certain threshold, the battery will experience thermal runaway. In the thermal runaway state, the battery may smoke, catch fire or even explode, posing a great threat to personal safety and property safety.
How to prevent lithium battery internal short circuit
Prevention is better than cure, and it is crucial to prevent the occurrence of lithium battery internal short circuit. The following are some effective preventive measures:
Optimize the manufacturing process
- Strictly control the production environment
Battery manufacturers should attach great importance to the cleanliness of the production environment, use advanced air purification equipment, and ensure that the air in the production workshop meets strict cleanliness standards. At the same time, strict quality inspections are carried out on raw materials to prevent raw materials containing metal impurities and other undesirable substances from entering the production process.
- Improve electrode manufacturing accuracy
In the electrode manufacturing process, continuously optimize the process parameters such as shearing and stamping, and use high-precision equipment to ensure smooth electrode edges and reduce the generation of burrs.
- Use high-quality diaphragms
Select diaphragm materials with high mechanical strength, high temperature resistance and good chemical stability, and strictly control the thickness uniformity and porosity of the diaphragm.
- Improve welding process
Use advanced welding technology to ensure the quality of welding points and avoid defects such as cold welding and false welding.
Battery design and use
- Software design
Set reasonable battery warning and battery safety control strategies through the battery management system (BMS) to achieve real-time monitoring of battery cell status, timely detect the location of internal short-circuit battery cells and eliminate safety hazards in time. Reduce the risk of internal short circuit caused by high battery load through redundant and balanced design of battery cell charging and discharging.
- Hardware design
The battery fuse is layered and refined into battery cell fuse, module fuse, battery pack fuse, vehicle power load fuse, etc. Through layered management, the internal short-circuit battery cell circuit can be cut off in time to prevent the continuous development of internal short circuit.
Reasonably design the internal cooling system of the battery to increase thermal conductivity and prevent thermal runaway caused by decomposition reactions of positive and negative electrodes, electrolytes and diaphragms caused by overheating.
Reasonably design the internal heating system of the battery, preheat the battery to a suitable working temperature when charging at low temperature, and avoid thermal runaway caused by dendrites piercing the diaphragm during low-temperature charging.
Strengthen usage management
- Avoid mechanical damage: When using lithium battery equipment, be careful to avoid severe impact and extrusion of the battery.
- Reasonably control the use temperature: Try to control the use temperature of the lithium battery within the appropriate range to avoid high or low temperature environments.
- Avoid overcharging and over-discharging: Use original or certified chargers, and avoid charging for a long time or running out of battery power.
Regular inspection and maintenance
- Establish a battery monitoring system
For equipment that uses lithium batteries on a large scale, such as electric vehicles, energy storage power stations, etc., a complete battery monitoring system should be established. By real-time monitoring of battery voltage, current, temperature and other parameters, possible abnormal conditions of the battery can be discovered in time. When abnormal fluctuations in battery parameters are detected, the system can issue an alarm in time to remind staff to check and handle.
- Regular battery inspection
Regularly conduct comprehensive inspections of lithium batteries, including capacity testing, internal resistance measurement, etc. Through the detection data, it is possible to timely discover whether the battery capacity is attenuated, whether the internal resistance is increased, and other issues, so as to determine whether the battery has the hidden danger of internal short circuit.
Conclusion
The lithium battery internal short circuit is an important factor affecting the safety and reliability of batteries. By deeply understanding the causes and effects of internal short circuits and taking effective prevention and response measures, the risk of internal short circuits can be minimized to ensure the safe and stable operation of lithium batteries. In the process of battery research and development, production, use and maintenance, we should attach great importance to the problem of internal short circuits, and constantly explore new technologies and methods to improve the lithium battery safety.
FAQ
Will lithium battery internal short circuit definitely lead to explosions?
Not all internal short circuits of lithium batteries will lead to explosions. Whether an internal short circuit will cause an explosion depends on many factors, including the severity of the internal short circuit, the heat dissipation capacity of the battery, and the protection mechanism inside the battery. A slight internal short circuit may only cause battery capacity attenuation and performance degradation, while a severe internal short circuit may cause thermal runaway, resulting in smoke, fire, or even explosion.
How to determine whether a lithium battery has an internal short circuit?
To determine whether a lithium battery has an internal short circuit, you can observe the following phenomena:
- Battery abnormal heating: The surface temperature of the battery rises abnormally when it is not charged or discharged.
- Battery capacity decays rapidly: The available capacity of the battery is significantly reduced and the battery life is reduced.
- Battery self-discharge accelerates: The capacity of the battery decreases rapidly during storage.
- Battery voltage abnormality: The open circuit voltage of the battery is low, and it cannot be fully charged or fully discharged during charging.
- Battery swelling and deformation: The battery shell swells or even breaks.
If the above situation occurs, stop using the battery immediately and seek professional inspection and repair.
My mobile phone battery has been heating up recently. Is it an internal short circuit?
There are many reasons for the heating of mobile phone batteries, not necessarily an internal short circuit. For example, running large applications for a long time, using the phone while charging, and mismatching the charger can all cause the battery to heat up.
It is recommended that you check these common reasons first. If other factors are confirmed to be excluded, and the battery heats up abnormally and is accompanied by capacity decay and other phenomena, it may be an internal short circuit. It is recommended to replace the battery as soon as possible.
What is BMS? What role does it play in preventing lithium battery internal short circuit?
BMS (Battery Management System) is a battery management system used to monitor and manage the operating status of lithium battery packs. BMS plays an important role in preventing internal short circuits in lithium batteries:
- Real-time monitoring: BMS can monitor the voltage, current, temperature and other parameters of each single cell in the battery pack in real time, and detect abnormal conditions in time.
- Overcharge and over-discharge protection: BMS can prevent the battery from overcharging and over-discharging, and avoid battery damage and internal short circuits caused by overcharging and over-discharging.
- Overtemperature protection: BMS can monitor the battery temperature and start the protection mechanism when the temperature is too high to prevent thermal runaway of the battery.
- Balance function: BMS can balance the power of each single cell in the battery pack, avoid local overcharge and over-discharge caused by differences in single cells, and reduce the risk of internal short circuits.
- Fault diagnosis: BMS can diagnose battery faults, such as internal short circuits, open circuits, etc., and issue an alarm to remind users to deal with them in time.
How to safely handle lithium batteries with internal short circuits?
Lithium batteries with internal short circuits are dangerous and should be handled with extreme caution. Recommendations:
- Stop using the battery immediately and place it in a safe area away from flammable materials.
- Do not attempt to disassemble or repair the battery yourself.
- If the battery smokes or catches fire, use a fire extinguisher or sand to put it out immediately.
- Submit the battery to a professional recycling agency for disposal to avoid environmental pollution.
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Willow
Willow is a materials engineer with a Master’s degree in Materials Science and Engineering, specializing in lithium-ion battery materials and energy storage technologies.
Her work focuses on EV battery swapping solutions, battery innovation, and new energy industry trends, aiming to translate research insights into practical applications for sustainable transportation.
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