Causes of bulging in polymer lithium-ion battery packs
1. Issues with the manufacturing quality of lithium-ion battery packs, including uneven electrode coating and relatively rough production processes;
2. The violent reaction of a short circuit generates a large amount of heat, which in turn causes the electrolyte to decompose and vaporize, causing the lithium-ion battery to swell.
3. Additionally, polymer lithium-ion battery packs can also bulge if left unused for a long time. This is because air is conductive to some extent, so leaving them unused for too long is equivalent to the positive and negative terminals of the battery coming into direct contact, resulting in a slow short circuit.
4. Reasons for poor quality lithium-ion battery chargers. Chargers using inferior boards, refurbished or substandard components can cause overheating, inaccurate parameter drift, and uncontrolled charging voltage limiting. This can lead to internal gas compression in the lithium-ion battery, resulting in battery casing deformation, bulging, cracking, or even explosion.
5. Overcharging. Overcharging can cause a large amount of gas to flush the plates, leading to the shedding of active materials inside the lithium-ion battery pack, shortening battery life, accelerating water loss, affecting electrolyte decomposition, and increasing battery temperature, causing it to swell!
Repair Techniques for Bulging Polymer Lithium-ion Battery Packs
I. Preparatory Work
Find a well-ventilated location and prepare the polymer lithium-ion battery pack to be processed, scissors, a receipt holder, toothpicks, 705 transparent silicone rubber, transparent tape, a syringe, and an IV needle with a section of plastic tubing attached (it must be the smallest size).
II. Preparation for Vacuuming
Connect the syringe to the infusion needle, hold the needle and find a suitable position to insert it into the seal of the lithium-ion battery pack, then use tape to fix the needle in place and keep it from moving. Use a toothpick to apply a small amount of 705 silicone rubber near the needle to prevent air leakage.
III. Gas Extraction
Pull the syringe to draw out the gas from the battery. After filling the syringe, use a clip to hold the plastic tube of the needle and separate the syringe from the needle to release the gas (although the gas inside the battery is non-toxic, it has a very unpleasant smell, so find a well-ventilated place). Then reconnect the syringe to the needle and repeat the operation.
IV. Sealing
After repeated operations, the aluminum foil encapsulation of the battery will gradually tighten and adhere tightly to the battery body, and the polymer lithium-ion battery pack will become very rigid. After the gas cannot be extracted and the battery is in a near-vacuum state, clamp the plastic tube behind the needle with a clamp, cut a small piece (1 cm square) of transparent tape with scissors, stick it to the needle hole, press it firmly, and then pull the needle out. The operation is complete.
V. Quality Inspection
Because the pinhole is extremely small and sealed with silicone rubber and transparent tape, gas will no longer enter the battery. After a few hours, once the silicone rubber has cured, test the lithium-ion battery pack. First, fully charge and discharge it several times with a small current. If the bulging problem no longer occurs, the treatment is complete. If gas still appears, repeat the above procedure. If the problem persists, the battery is considered unusable. I purchased over ten bulging polymer lithium-ion batteries at a low price online, and after this treatment, all of them have returned to normal use with excellent results.
