Production Environment Requirements for Lithium-Ion Polymer Small Batteries

Introduction

With the widespread adoption of portable electronic devices, lithium-ion polymer (Li-Polymer) batteries have become the mainstream power 

source for modern electronics due to their high energy density, lightweight design, and flexibility. However, the production of such batteries 

requires extremely stringent environmental conditions, which not only affect product quality but also directly impact production safety. This 

article provides a detailed explanation of the key environmental control factors in the production process of small lithium-ion polymer batteries, 

helping readers understand the critical aspects of this precision manufacturing field.

1. Temperature and Humidity Control: Fundamental Elements of the Production Environment

Lithium-ion polymer batteries are highly sensitive to temperature and humidity, necessitating precise control.

1.1 Temperature Requirements

The ideal production environment temperature should be maintained at 20±2°C. Excessively high temperatures accelerate electrolyte 

evaporation, affecting battery performance, while excessively low temperatures may increase electrolyte viscosity, leading to uneven 

coating. Special attention is required in the following processes:

Electrode Preparation Area: Temperature fluctuations must not exceed ±1°C to ensure slurry viscosity stability.

Assembly Area: A constant temperature of 22°C should be maintained to prevent thermal expansion and contraction of metal components.

Aging Test Area: Requires a high-precision environment of 25±0.5°C.

1.2 Humidity Management

Relative humidity in the production environment must be strictly controlled below 30%, with the optimal range being 20±5%. High humidity 

can cause:

Electrode materials to absorb moisture, degrading electrochemical performance.

Hydrolysis of lithium salts (LiPF6) in the electrolyte, producing corrosive HF.

Moisture absorption in separators, reducing ionic conductivity.

It is recommended to use rotary dehumidifiers combined with air conditioning systems. In critical processes such as electrode drying and 

battery sealing, humidity control precision should reach ±2%.

2. Cleanliness Requirements: The Art of Particulate Control

The cleanliness requirements for lithium-ion battery production are comparable to those of the semiconductor industry. Particulate contamination 

can directly cause micro-shorts, compromising battery safety.

2.1 Air Cleanliness Standards

According to the ISO 14644-1 standard, different production areas must meet the following cleanliness levels:

2.2 Particulate Control Measures

Use Fan Filter Unit (FFU) laminar flow systems.

Personnel must wear anti-static cleanroom suits and pass through air showers.

Raw materials must undergo surface cleaning before entering production areas.

Equipment should be made of stainless steel to minimize particle generation from wear.

3. Electrostatic Discharge (ESD) Protection: An Invisible Hazard

Electrostatic buildup in lithium-ion battery production can lead to serious safety incidents, necessitating a comprehensive ESD protection system.

3.1 ESD Control Standards

The production environment must comply with ANSI/ESD S20.20 standards, with surface resistance maintained between 10^6 and 10^9 ohms. 

Key measures include:

Installing anti-static flooring with a grounding resistance <1×10^6 ohms.

Using conductive work surfaces with proper grounding.

Operators must wear anti-static wrist straps and shoes.

Maintaining humidity above 20% (but not exceeding 30%).

3.2 ESD Protection in Critical Processes

Additional precautions are required for processes prone to electrostatic generation, such as electrode slitting and stacking:

Localized ionizers to neutralize static charges.

Installing static eliminators on equipment.

Reducing material handling speeds to minimize friction-induced charging.

4. Atmosphere Control: The Enemies of Oxygen and Moisture

Lithium-ion batteries are highly sensitive to oxygen and moisture, requiring inert atmospheres for critical processes.

4.1 Dry Room Requirements

Dew point ≤-40°C (equivalent to moisture content <120 ppm).

Oxygen content <100 ppm.

Double airlock design to maintain pressure gradients.

4.2 Electrolyte Filling Process Control

Electrolyte filling must be performed in a glove box with the following conditions:

Argon or nitrogen atmosphere with purity ≥99.999%.

Real-time monitoring of oxygen (<10 ppm) and moisture (<10 ppm).

Slightly positive pressure (50-100 Pa) inside the glove box.

5. Safety Environment: Prevention First

Lithium-ion battery production involves flammable and explosive risks, requiring multiple layers of safety protection.

5.1 Explosion-Proof Design

Use explosion-proof electrical equipment (Ex dⅡBT4 or higher).

Install combustible gas detection and alarm systems.

Equip critical machinery with automatic fire suppression (recommended: FM-200).

5.2 Emergency Measures

Keep safety exits clear and emergency lighting functional.

Install emergency ventilation systems capable of full air exchange within 30 seconds.

Provide specialized firefighting equipment (water-based extinguishers are prohibited).

6. Environmental Monitoring and Data Traceability

Modern lithium-ion battery factories should implement comprehensive environmental monitoring systems:

Deploy multi-point temperature and humidity sensors with real-time data logging.

Conduct regular particle counting for cleanliness verification.

Store critical parameter records for at least three years for full traceability.

Implement automatic alarm systems for out-of-spec conditions.

Conclusion

Controlling the production environment for small lithium-ion polymer batteries is a precise science, requiring careful consideration of 

temperature, humidity, cleanliness, ESD protection, and atmospheric conditions. As battery energy densities continue to rise, environmental 

requirements will become even stricter. Only by establishing a scientific environmental management system can manufacturers ensure 

high-quality, safe battery products that meet growing market demands. In the future, with advancements in smart manufacturing, intelligent 

environmental control will become an industry trend.