Lithium - Ion Polymer Battery Bulging: In - depth Analysis of Causes, Daily Usage Mistakes and Prevention 

Measures

Introduction

Lithium - ion polymer batteries power daily essentials like smartphones, tablets, wireless earbuds, and portable chargers. Yet bulging remains a 

common, risky issue—It impairs device performance (e.g., unresponsive smartphone screens, shortened portable charger runtime) and poses 

severe safety hazards, including leakage, overheating, and even explosion. Thus, understanding bulging causes, identifying usage mistakes, 

and adopting prevention measures is critical to protecting devices and users.

In - depth Analysis of the Causes of Bulging

1. Chemical Reactions Inside the Battery

Gas generation inside the battery is the primary cause of bulging. Normal charging and discharging trigger minor side reactions, such as 

electrolyte (a mix of lithium salts and organic solvents) decomposition, producing small amounts of carbon dioxide, methane, and hydrogen. 

The battery’s flexible polymer packaging typically handles this gas without visible deformation. However, improper use (e.g., overcharging) or 

aging amplifies these side reactions, leading to excessive gas accumulation that stretches the packaging and causes bulging.

2. Physical Damage

Physical harm to the battery also fuels bulging. Dropping a smartphone, squeezing a laptop in a backpack, or colliding devices can damage the 

battery’s internal structure. The thin, porous polymer separator between positive and negative electrodes—designed to prevent direct contact—

may puncture, causing an internal short circuit. This short circuit generates instant heat, accelerating electrolyte decomposition and triggering 

violent electrode material reactions. The result is rapid gas production and quick bulging, often within minutes of damage.

3. Manufacturing Defects

In some cases, bulging stems from manufacturing flaws. Uneven electrode coating (a layer of active material on metal foils) leads to local over - 

current during charging and discharging, sparking excessive local reactions (e.g., concentrated electrolyte decomposition) and gas formation in 

specific areas. Poor sealing—from flawed heat - sealing or low - quality adhesive—lets air or moisture enter over time. These substances react 

with internal lithium - rich materials (e.g., moisture forms lithium hydroxide with lithium), generating gas and causing bulging even with normal use.

Daily Usage Mistakes That Cause Bulging

1. Overcharging

Overcharging is a top daily mistake. Many users charge devices overnight, leaving smartphones or tablets plugged in for 8–10 hours—far longer 

than the 2–3 hours needed for a full charge. This keeps the battery at 100% State of Charge (SOC) for extended periods. Once fully charged, 

continued charging pushes voltage beyond the safe range (typically 4.2V for consumer batteries), accelerating electrolyte decomposition and 

lithium dendrite growth (thin, needle - like deposits on the negative electrode). Over time, dendrites may pierce the separator, causing short 

circuits and massive gas production that leads to bulging.

2. Using Unauthorized Chargers

Unauthorized chargers—often cheap, uncertified products from unregulated markets—are another major culprit. They fail to meet battery 

charging standards, with unstable voltage (e.g., fluctuating 4V–5V) or excessive current (e.g., a 2A charger labeled 1A). Forcing the battery to 

accept irregular current/voltage disrupts normal electrochemical reactions, triggers severe side effects (e.g., abnormal lithium plating on 

electrodes), and produces large amounts of gas, resulting in bulging. Even uncertified "compatible" third - party chargers carry this risk.

3. Exposing the Battery to Extreme Temperatures

Extreme temperatures—both high and low—harm batteries. High - temperature environments, like leaving a device in a sun - baked car 

(interior temps can exceed 60°C) or placing a laptop near a hot stove, speed up internal chemical reactions. This causes massive electrolyte 

decomposition and faster electrode degradation, generating excess gas and bulging. In low temperatures (below 0°C, such as winter outdoors), 

battery performance drops sharply. Forced charging in this state hinders smooth lithium ion insertion into the electrode, forming lithium dendrites. 

These dendrites lie dormant until temperatures rise, then pierce the separator, causing short circuits and bulging.

Effective Prevention Measures

1. Avoid Overcharging

Unplug chargers promptly when batteries reach full charge (indicated by 100% or device prompts). For overnight charging, use devices with 

smart features like Apple’s Optimized Battery Charging or Android’s Adaptive Charging—these slow charging after 80% and top up to 100% 

right before use, avoiding prolonged full charge. Also, avoid charging while running high - power apps (e.g., gaming, video editing), as they 

increase battery temperature and stress, raising overvoltage risks.

2. Use Authorized Chargers

Stick to original chargers or authorized ones meeting international standards (e.g., USB - IF certification for USB chargers). These are tailored 

to the battery’s voltage and current needs, with built - in protection circuits that cut power or reduce current when fully charged (e.g., an original 

smartphone charger may drop current from 2A to 0.1A at 100%). Steer clear of cheap, unbranded chargers from street vendors or untrusted 

online stores—they lack essential safety features.

3. Protect the Battery from Physical Damage and Extreme Temperatures

Prevent device drops, squeezes, or collisions. Use shock - absorbing cases for smartphones and padded bags for laptops, and avoid stacking 

heavy objects on laptops. Keep devices away from extreme temperatures: never leave them in hot cars or near heaters in summer, and store 

them in inner pockets (close to body heat) in cold weather. If a device is exposed to extreme cold, let it warm to 20–25°C for 30 minutes before 

charging to avoid dendrite formation.

4. Replace Aging Batteries in Time

Lithium - ion polymer batteries have a 300–500 charge - discharge cycle lifespan. Beyond this, capacity drops to 70–80% of the original, and 

bulging risks rise sharply. Check battery health via device settings (e.g., iPhone’s "Battery Health") or third - party apps (e.g., AccuBattery for 

Android). If signs of aging appear—rapid power loss (e.g., a smartphone dropping from 50% to 20% in 10 minutes), shortened runtime, or slight 

bulging (visible when the device back cover lifts)—replace it with a genuine battery at a professional maintenance point. Avoid self - replacement, 

as improper installation may damage the new battery or cause short circuits.

Conclusion

Lithium - ion polymer battery bulging threatens device safety and lifespan. By understanding its causes—from internal chemical reactions to 

external physical damage—avoiding mistakes like overcharging or using unauthorized chargers, and taking preventive steps (e.g., temperature 

protection, timely battery replacement), users can significantly reduce risks. These practices not only extend device life but also safeguard 

personal and property safety in daily life.