Battery expansion and deformation (commonly known as "bulging") is a common problem for users of mobile phones, laptops, and electric vehicles. It not only affects the appearance of the equipment, but also hides the risk of short circuit and combustion. Starting from the principle, this article reveals the cause of bulging and provides user-level prevention tips and industry-level technical solutions.
I. Why do batteries bulge?
1. Chemical gas production:
- Overcharging or high temperature causes the electrolyte to decompose, producing gases such as CO and CH₄;
- Lithium (Li metal) is deposited at the negative electrode and reacts with the electrolyte to produce H₂.
2. Material expansion:
- The volume change of silicon-based negative electrodes during charging and discharging is as high as 300% (traditional graphite is only 10%);
- After long-term cycling, the electrode becomes powdered, and the loose structure "enlarges" the battery cell.
3. Physical damage:
- Dropping and squeezing cause the internal diaphragm to rupture, causing local short circuit and gas production.
II. Five preventive tips that users can use
1. Avoid "full charge for a long time":
When storing for a long time, keep the power at 40%~60% (such as discharging the drone to 50% before stopping in winter).
2. Control the charging temperature:
Remove the phone case when charging and avoid direct sunlight (higher than 45℃ accelerates gas production).
3. Reject inferior chargers:
Non-original chargers may have unstable output voltage, resulting in overcharging (such as charging a 4.2V battery to 4.5V).
4. Replace aging batteries in time:
If the battery life of the device drops by more than 30% or the screen is lifted by the battery, send it for repair immediately.
5. Shallow charging and shallow discharge are healthier:
Keep the power range of 20%~80% in daily use to reduce electrode stress (you can turn on the "optimized charging" mode of the phone).
III. How can the industry solve the problem from the root?
1. Material upgrade:
- Silicon-carbon composite negative electrode: Use carbon skeleton to constrain silicon expansion (such as Tesla 4680 battery silicon content increased to 10%);
- Solid electrolyte: Replace liquid electrolyte to prevent gas production (Toyota plans to mass-produce solid-state batteries in 2027).
2. Structural design optimization:
- Reserve expansion space: CATL CTP3.0 technology adds elastic glue layer between battery cells;
- Flexible packaging: Apple MacBook battery adopts wavy folding structure, which can withstand 5% volume change.
3. Intelligent monitoring system:
- Pressure sensor: implanted inside the battery, real-time detection of deformation and triggering BMS voltage reduction;
- AI prediction model: predict bulging risk through charging and discharging data (such as Weilai battery cloud early warning system).
IV. Emergency treatment of bulging batteries
- Immediate deactivation: Puncture of bulging batteries may cause explosion, do not continue to charge or use.
- Professional recycling: Contact brand after-sales or certified recycling points, do not discard at will (electrolyte is hazardous waste).
Summarize: From Passive Response to Active Defense
With breakthroughs in material science (such as pre-lithiation technology for lithium metal anodes) and the popularization of smart BMS, battery expansion problems will be greatly reduced. Users only need to develop scientific usage habits to keep the battery "slim" and safely escort every day.
