Analyze the causes of common lithium ion problems, decomposition and solutions

1. The voltage is inconsistent, and the individual is too low. Large self-discharge constitutes a low voltage. The battery has a large self-discharge, which makes its voltage drop faster than others. The low voltage can be eliminated by checking the voltage after storage. 2. Uneven charging constitutes a low-voltage battery. When the battery is charged after a test, because the touch resistance or the charging current of the test cabinet is inconsistent, it constitutes the uneven charging of the cells. In the short-term storage (12 hours), the measured voltage has a small difference, but the long-term storage has a large voltage difference. This low voltage has no quality problems and can be solved by charging. Store the voltage for more than 24 hours after charging during processing. 2. The internal resistance is too large. If the test equipment is of different composition, if the test accuracy is not enough, the touch panel may not be eliminated, and the internal resistance will be too large. The AC bridge method principle should be used to test the internal resistance. 2. The storage time is too long. The storage time of the lithium battery is too long, the component capacity loss is too large, the internal passivation, and the internal resistance becomes large, which can be solved by charging and discharging activation. 3. Abnormal heating constitutes a large internal resistance battery cell is produced (spot welding, ultrasonic, etc.), which makes the battery abnormally heated, causing thermal closure of the barrier, and severely increasing the internal resistance. 3. Lithium battery swelling Lithium battery swells when charging. Lithium battery will swell naturally when charging, but generally does not exceed 0.1mm, but overcharge will cause electrolyte differentiation, internal pressure will increase, and lithium battery will swell. 2. The swelling during production is generally due to abnormal production (such as short-circuit, overheating, etc.), which constitutes the internal electrolyte differentiation due to excessive heating, and the lithium battery swells. 3. When the battery is swollen during cycling, the thickness will be added as the number of cycles is added, but it will not be added at all after more than 50 cycles. Generally, the normal addition amount is 0.3~0.6mm, and the aluminum shell is more severe. This phenomenon is attributed to the normal battery response. constitute. However, if the thickness of the shell is increased or the internal materials are reduced, the swelling phenomenon can be appropriately reduced. 4. The battery loses power after spot welding. The voltage of the aluminum shell cell after spot welding is lower than 3.7V, which is generally caused by the excessive current of the spot welding, which causes the internal barrier of the cell to break down and short-circuit, which constitutes a rapid voltage drop. Generally, it is caused by the incorrect spot welding position. The correct spot welding position should be spot welded on the bottom or marked A or side surface. Spot welding is not allowed on the side and large surface without marking. Others are that the weldability of spot-welded nickel tape is too poor, so it is necessary to use a large current for spot welding, so that the internal high-temperature-resistant tape cannot be effective, which constitutes an internal short circuit of the battery. Part of the battery power loss after spot welding is due to the large self-discharge of the battery itself. V. Battery blasting. Battery blasting generally has the following situations: 1. The overcharge blasting maintenance circuit is out of control or the test cabinet is out of control to cause the charging voltage to be greater than 5V, which constitutes electrolyte differentiation. There is a violent response inside the battery, the internal pressure of the battery rises rapidly, and the battery bursts. 2. The overcurrent blasting maintenance circuit is out of control or the test cabinet is out of control, so that the charging current is too large to form lithium ions too late to be embedded, and lithium metal is formed on the surface of the pole piece, penetrating the barrier, and the positive and negative poles are directly short-circuited to form a blast (rarely). 3. When blasting the plastic shell in ultrasonic welding, the ultrasonic energy is transferred to the battery core because of the device's original reason. The large ultrasonic energy melts the internal barrier of the battery, and the positive and negative electrodes are directly short-circuited and blasting occurs. 4. Blasting during spot welding. Excessive current during spot welding constitutes a severe internal short-circuit and blasting. In addition, during spot welding, the positive electrode connecting piece is directly connected to the negative electrode, so that the positive and negative poles are directly short-circuited and then blasted. 5. Over-discharge blasting battery over-discharge or over-current discharge (above 3C) simply dissolve and deposit the negative electrode copper foil on the barrier, causing the positive and negative poles to be directly short-circuited and blasting occurs (rarely). 6. When oscillating and falling, the blasting cell constitutes the internal pole piece of the battery when it oscillates or falls violently, and it blasts in a straight and severe short circuit (rarely). 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