I. Internal Factors of the BatteryProblems with Electrode MaterialsQuality flaws in the positive and negative electrode materials may lead to a short - circuit. For example, during the preparation of the lithium - iron - phosphate positive - electrode material, if impurities are mixed in, these impu...
Quality flaws in the positive and negative electrode materials may lead to a short - circuit. For example, during the preparation of the lithium - iron - phosphate positive - electrode material, if impurities are mixed in, these impurities may form a conductive path inside the battery. During the operation of the battery, especially in a parallel connection state, when current passes through, these impurities may trigger a short - circuit.
Structural defects in the positive and negative electrode materials can also be a reason. For example, if there are cracks or holes in the crystal structure of the positive - electrode material, the insertion and extraction of lithium ions may lead to a local electric - field concentration, which in turn may cause dendrite growth. Once the lithium dendrites grow to a certain extent, they may penetrate the separator and cause the positive and negative electrodes to come into direct contact, resulting in a short - circuit.
Separator Failure
The separator is a crucial component that prevents the direct contact of the positive and negative electrodes of the battery. If the quality of the separator is poor, such as having oversized micropores or an uneven thickness, after the battery is subjected to vibration, compression, or long - term use, it is possible for the positive and negative electrodes to come into contact through these defective parts, thus triggering a short - circuit.Additionally, when the battery is used in a high - temperature environment or due to the heat accumulation caused by an internal short - circuit, the separator may melt, losing its function of separating the positive and negative electrodes and then causing a short - circuit. For example, when the separator of a certain battery in a parallel battery pack is damaged due to local overheating, it may affect the entire parallel battery pack and lead to a short - circuit fault.
Abnormal Electrolyte
If the electrolyte contains metallic impurities, these impurities may undergo an electrochemical reaction inside the battery and form a conductive path. For example, when metallic impurities are deposited between the positive and negative electrodes, they will act like a "wire" and short - circuit the positive and negative electrodes.
Electrolyte leakage can also lead to a short - circuit. During the battery encapsulation process, if the sealing is not good, the electrolyte may seep out of the battery or come into contact with conductive parts that it should not touch inside the battery, thus triggering a short - circuit. Especially in a parallel battery pack, the electrolyte leakage of one battery may affect other batteries.
II. External Factors
Improper Connection
When lithium - iron - phosphate batteries are connected in parallel, if the connection tabs or terminals are not installed properly, such as the connection tabs having burrs or the connection screws not being tightened, it may lead to loose or poor - contact connection points between the batteries. During the battery operation, due to the passage of current, these poorly - contacted parts may generate electric sparks, which can burn through the battery casing or the separator and trigger a short - circuit.
Moreover, if the specifications of the connecting wires do not meet the requirements and the wires are too thin, it may lead to excessive resistance. According to Ohm's law (), in a parallel circuit, when the total current is large, the excessive resistance will generate too much heat at the connection parts, which may also trigger a short - circuit.
External Physical Damage
During the transportation, installation, or use of the battery, if it is subjected to severe impact, compression, or puncture, it may lead to the deformation or rupture of the battery casing. Once the battery casing is damaged, the internal positive and negative electrodes may come into direct contact, or the separator may be damaged, thus triggering a short - circuit. In a parallel battery pack, the damage of one battery may affect the normal operation of the entire battery pack.
For example, in some application scenarios, such as the battery pack of an electric vehicle, if the vehicle is involved in a collision accident, the lithium - iron - phosphate batteries in the battery pack are prone to external physical damage, which may then lead to a short - circuit and cause a safety accident.
External Electrical Interference
When the battery is in a complex electrical environment, it may be subject to external electromagnetic interference. For example, in some industrial environments with strong magnetic fields or high - frequency electromagnetic fields, these external electromagnetic fields may induce an electromotive force in the conductive parts inside the battery. If the induced electromotive force is large enough, it may cause the insulation material inside the battery to be broken down and thus trigger a short - circuit.
In addition, electrostatic discharge may also damage the battery. In a dry environment, static electricity may accumulate on the human body or other objects. When an object with static electricity touches the battery, the electrostatic discharge may damage the insulation layer of the battery or the electronic components inside the battery and then trigger a short - circuit.
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